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IPC-7721 Repair and Modification of PCBA

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THE INSTITUTE FOR INTERCONNECTING AND PACKAGING ELECTRONIC CIRCUITS IPC-7721 Repair and Modification of Printed Boards and Electronic Assemblies IPC-7721 February 1998 Supersedes IPC-R-700C January 1988 A standard developed by the Institute for Interconnecting and Packaging Electronic Circuits 2215 Sanders Road Northbrook, Illinois 60062-6135 Tel 847 509.9700 Fax 847 509.9798 URL: http://www.ipc.org THE INSTITUTE FOR INTERCONNECTING AND PACKAGING ELECTRONIC CIRCUITS IPC-7721 Repair and Modification of Printed Boards and Electronic Assemblies Developed by the Printed Board Repair Task Group (7-34a) of the Institute for Interconnecting and Packaging Electronic Circuits Users of this standard are encouraged to participate in the development of future revisions. Contact: IPC 2215 Sanders Road Northbrook, Illinois 60062-6135 Tel 847 509.9700 Fax 847 509.9798 The Principles of Standardization Notice In May 1995 the IPC’s Technical Activities Executive Committee adopted Principles of Standardization as a guiding principle of IPC’s standardization efforts. Standards Should: • Show relationship to DFM & DFE • Minimize time to market • Contain simple (simplified) language • Just include spec information • Focus on end product performance • Include a feed back system on use and problems for future improvement Standards Should Not: • Inhibit innovation • Increase time-to-market • Keep people out • Increase cycle time • Tell you how to make something • Contain anything that cannot be defended with data IPC Standards and Publications are designed to serve the public interest through eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products, and assisting the purchaser in selecting and obtaining with minimum delay the proper product for his particular need. Existence of such Standards and Publications shall not in any respect preclude any member or nonmember of IPC from manufacturing or selling products not conforming to such Standards and Publication, nor shall the existence of such Standards and Publications preclude their voluntary use by those other than IPC members, whether the standard is to be used either domestically or internationally. Recommended Standards and Publications are adopted by IPC without regard to whether their adoption may involve patents on articles, materials, or processes. By such action, IPC does not assume any liability to any patent owner, nor do they assume any obligation whatever to parties adopting the Recommended Standard or Publication. Users are also wholly responsible for protecting themselves against all claims of liabilities for patent infringement. The material in this standard was developed by the Printed Board Repair Task Group (7-34a) of the Institute for Interconnecting and Packaging Electronic Circuits. Copyright © 1998 by the Institute for Interconnecting and Packaging Electronic Circuits. All rights reserved. Published 1998. Printed in the United States of America. No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher. March 2000 IPC-7721 Acknowledgment Any Standard involving a complex technology draws material from a vast number of sources. While the principal members of the IPC Printed Board Repair Task Group (7-34a) of the Product Assurance Committee are shown below, it is not possible to include all of those who assisted in the evolution of this standard. To each of them, the members of the IPC extend their gratitude. Product Assurance Committee Chairman Mike Hill Viasystems Technologies Corp. Printed Board Repair Task Group Chairman Jeff Ferry Circuit Technology Center, Inc. Vice Chairman Christine Miller FORE Systems, Inc. Technical Liaisons of the IPC Board of Directors Stan Plzak Pensar Corp. Peter Bigelow Beaver Brook Circuits Inc. A Special Note of Appreciation The following core group has volunteered much of their time and have made significant contributions to this document. Blakley, Peggi, NSWC Crane Brock, Ron, NSWC Crane Day, Jennifer, Soldering Technology International Ferry, Jeff, Circuit Technology Center, Inc. Foster, Daniel L., PACE Inc. Hersey, Ralph J., Ralph Hersey & Associates Hopkins, Reed, Metcal Inc. Houghton, F.D. Bruce, Celestica Corporation Miller, Christine A., FORE Systems Inc. Moffitt, James H., Moffitt Consulting Services Norton, John S., Tektronix Inc. Siegel, Eric, PACE, Inc. Printed Board Repair Task Group Anderson, Kari, Hughes Technical Services Co. Aoki, Masamitsu, Toshiba Chemical Corp. Ashaolu, Peter, Cisco Systems Inc. Bates, Timothy E., DSC Communications Corporation Bergum, Erik J., Polyclad Laminates Blakley, Peggi, NSWC Crane Boerdner, Richard W., EJE Research Bogert, G.L., Westinghouse Electric Bradford, Diana, Soldering Technology International Brock, Ron, NSWC Crane Cash, Alan S., Northrop Grumman Corporation Chance, Gary W., Nokia Telecommunications Chen, D. Phillip, Honeywell Canada Cirimele, Ray, Diversified Systems Inc. D’Andrade, Derek, Surface Mount Technology Centre Daugherty, Dale, Siemens Energy & Automation Day, Jennifer, Soldering Technology International Deane, William, Solectron Technology Inc. Dehne, Rodney, O.E.M. Worldwide Dennehy, Charles S., Circuit Technology Center Inc. Dieffenbacher, William C., Lockheed Martin Corporation DiFranza, Michele J., The Mitre Corp. Dutcher, Nancy, U.S. Assemblies Hallstead Inc. Etheridge, Thomas R., McDonnell Douglas Aerospace Falconbury, Gary, Raytheon Technical Services Co. Ferry, Jeff, Circuit Repair Corporation Fieselman, Charles D., IBM Corp. Foster, Daniel L., Pace Inc. Foust, Skip, Solectron Technology Inc. Freeman, Fortunata A., Solectron Technology Inc. Gillespie, Alan L., Boeing/McDonnell A & MS Gonzalez, Constantino, ACME, Inc. Griffiths, William F., Plessey Tellumat South Africa Grim, Edward A., Raytheon Systems Company Hargreaves, Larry, DC. Scientific Inc. Herrberg, Steven A., Hughes Defense Communications Hersey, Ralph J., Ralph Hersey & Associates Hiett, Carol E., Lockheed Martin Astronautics Hill, Michael E., Viasystems Technologies Corp. Ho, David P., Circuit Graphics Ltd. Hopkins, Reed, Metcal Inc. Houghton, F. D. Bruce, Celestica Hymes, Les, Les Hymes Associates Johnson, Kathryn L., Hexacon Electric Company Johnson, Laurence G., General Electric Co. Jones, Sue A., Compaq Computer Corporation Kemp, Cindy A., Evenflo Company Inc. Kennady, Richard, Bahiatech Bahia Technologia Ltda. Kern, Terence, Axiom Electronics, Inc. Konsowitz, Robert J., Glasteel Industrial Laminates Korth, Connie M., Hibbing Electronics Corp. Lambert, Leo P., EPTAC Corporation Lee, Frederic W., Northrop Grumman Norden Systems MacLennan, Karen E., M/A-COM Inc. Maher, Peter E., Kimball Electronics Group A special note of thanks is due to Circuit Technology Center for the preparation of the illustrations in this document. iii IPC-7721 Malewicz, Wesley R., Siemens Medical Systems Inc. Mastorides, John, Lucas Aerospace Power Systems May, William Dean, NSWC - Crane McCormick, Becky, EMD Associates Inc. Meeks, Jr., Stephen, Motorola Computer Group Miller, Christine A., FORE Systems Moffitt, James H., Moffitt Consulting Services Moir, Jim, Hewlett Packard Co. Neumark, Yori, Hadco Corp. Nicol, David, Lucent Technologies Inc. Northam, Riley L., EMPF/ACI Norton, John S., Tektronix Inc. Nunnelley, Benetta, IEC Electronics Corp. Nuppola, Seppo, Nokia Networks, Switching Platform Parrish, Mel, EMPF/ACI Poelking, Monica, Defense Supply Center Columbus Quinn, Paul J., Lockheed Martin Missiles & Space Raby, Jim D., Soldering Technology International Rassal, David, 3COM Corporation Rausch, James E., Delphi Delco Electronics Systems Raye, John F., Defense Supply Center Columbus Robertson, David E., Hexacon Electric Company Rowe, Teresa M., AAI Corporation Sanford, Kelly, Micron Custom Mfg. Services Inc. Scott, Patricia A., Electronic Training Advantage Sherman, Lowell, Defense Supply Center Columbus DSCC March 2000 Siegel, Eric, PACE, Inc. Smith, Rick B., Motorola Inc. Sober, Douglas J., Polyclad Laminates Inc. Steele, David B., Lucent Technologies Inc. Steen, Wayne A., Rockwell International Tevels, John R., Harris Corp. Thompson, Ronald E., NSWC - Crane Torres, Steven, Corlund Electronics Corp. Ventress, Sharon T., U.S. Aviation & Missile Command Woodford, James Walter, Department of Defense Wooldridge, James R., Rockwell International Xiao, Nora, Tektronix Inc. Youngblood, Don, Honeywell Inc. Foreword IPC’s documentation strategy is to provide distinct documents that focus on specific aspects of electronic packaging issues. In this regard document sets are used to provide the total information related to a particular electronic packaging topic. A document set is identified by a four digit number that ends in zero (0) (i.e., IPC-7710). This standard is intended to provide information on the rework, repair and modification of printed boards and electronic assemblies. This information must also be supplemented by a performance specification that contains the requirements for the chosen technology. When used together, these documents should lead both manufacturer and customer to consistent terms of acceptability. These documents supersede the following: IPC-7711 supersedes IPC-R-700C IPC-7721 supersedes IPC-R-700C As technology changes, a performance specification will be updated, or new focus specifications will be added to the document set. The IPC invites input on the effectiveness of the documentation and encourages user response through completion of ‘‘Suggestions for Improvement’’ forms at the end of each document. iv February 1998 Table of Contents IPC-7721 General ................................................................................................................................................................................................... 1 Handling/Cleaning Procedure Description 2.1 Handling Electronic Assemblies Illustration Product Class R, F, C, W Skill Level Intermediate Level of Conformance High 2.2 Cleaning R, F, C, W Intermediate High Coating Removal Procedure 2.3.1 Description Coating Removal, Identification of Conformal Coating Illustration Product Class R, F, W, C Skill Level Advanced Level of Conformance High 2.3.2 Coating Removal, Solvent Method R, F, W, C Advanced High 2.3.3 Coating Removal, Peeling Method R, F, W, C Advanced High 2.3.4 Coating Removal, Thermal Method R, F, W, C Advanced High 2.3.5 Coating Removal, Grinding/ Scraping Method 2.3.6 Coating Removal, Micro Blasting Method R, F, W, C Advanced High R, F, W, C Advanced High v IPC-7721 Coating Replacement Procedure 2.4.1 Description Coating Replacement, Solder Resist February 1998 Illustration Product Class R, F, W, C Skill Level Intermediate Level of Conformance High 2.4.2 Coating Replacement, Conformal Coatings/Encapsulants R, F, W, C Intermediate High Surface Preparation Procedure Description 2.5 Baking and Preheating Illustration Product Class R, F, W, C Skill Level Intermediate Level of Conformance High Epoxy Mixing and Handling Procedure Description 2.6 Epoxy Mixing and Handling Illustration Product Class R, F, W, C Skill Level Intermediate Level of Conformance High Legends/Markings Procedure 2.7.1 Description Legend/Marking, Stamping Method Illustration Product Class R, F, W, C Skill Level Intermediate Level of Conformance High 2.7.2 Legend/Marking, Hand Lettering Method R, F, W, C Intermediate High 2.7.3 Legend/Marking, Stencil Method R, F, W, C Intermediate High vi February 1998 Blisters and Delamination Procedure 3.1 Description Delamination/Blister Repair, Injection Method IPC-7721 Illustration Product Class R Skill Level Advanced Level of Conformance High Bow & Twist Procedure Description 3.2 Bow and Twist Repair Illustration Product Class R, W Skill Level Advanced Level of Conformance Medium Hole Repair Procedure Description 3.3.1 Hole Repair, Epoxy Method Illustration Product Class R, W Skill Level Advanced Level of Conformance High 3.3.2 Hole Repair,Transplant Method R. W Expert High Key and Slot Repair Procedure 3.4.1 Description Key and Slot Repair, Epoxy Method Illustration Product Class R, W Skill Level Advanced Level of Conformance High 3.4.2 Key and Slot Repair, Transplant Method R, W Expert High vii IPC-7721 Base Material Repair Procedure 3.5.1 Description Base Material Repair, Epoxy Method February 1998 Illustration Product Class R, W Skill Level Advanced Level of Conformance High 3.5.2 Base Material Repair, Area Transplant Method R, W Expert High 3.5.3 Base Material Repair, Edge Transplant Method R, W Expert High Lifted Conductors Procedure 4.1.1 Description Lifted Conductor Repair, Epoxy Seal Method Illustration Product Class R, F Skill Level Intermediate Level of Conformance Medium 4.1.2 Lifted Conductor Repair, Film Adhesive Method R, F Intermediate High viii March 2000 Conductor Repair Procedure 4.2.1A Description Conductor Repair, Foil Jumper, Epoxy Method IPC-7721 Illustration Product Class R, F, C Skill Level Advanced Level of Conformance Medium 4.2.2 Conductor Repair, Foil Jumper, Film Adhesive Method R, F, C Advanced High 4.2.3 Conductor Repair, Weld Method R, F, C Advanced High 4.2.4 Conductor Repair, Surface Wire Method R, F, C Intermediate Medium 4.2.5A Conductor Repair Through Board Wire Method R Advanced Medium 4.2.6 Conductor Repair/Modification, Conductive Ink Method R, F, C Expert Medium 4.2.7 Conductor Repair, Inner Layer Method R, F Expert High ix IPC-7721 Conductor Cut Procedure 4.3.1 Description Conductor Cut, Surface Conductors February 1998 Illustration Product Class R, F Skill Level Advanced Level of Conformance High 4.3.2 Conductor Cut, Inner Layer Conductors 4.3.3 Deleting Inner Layer Connection at a Plated Hole, Drill Through Method 4.3.4 Deleting Inner Layer Connection at a Plated Hole, Spoke Cut Method R, F Advanced High R, F Advanced High R, F Advanced High Lifted Land Repair Procedure Description 4.4.1 Lifted Land Repair, Epoxy Method Illustration Product Class R, F Skill Level Advanced Level of Conformance Medium 4.4.2 Lifted Land Repair, Film Adhesive Method R, F Advanced Medium Land Repair Procedure Description 4.5.1 Land Repair, Epoxy Method 4.5.2 Land Repair, Film Adhesive Method Illustration Product Class R, F Skill Level Advanced Level of Conformance Medium R, F Advanced High x February 1998 Edge Contact Repair Procedure 4.6.1 Description Edge Contact Repair, Epoxy Method 4.6.2 Edge Contact Repair, Film Adhesive Method 4.6.3 Edge Contact Repair, Plating Method IPC-7721 Illustration Product Class R, F, W, C Skill Level Advanced Level of Conformance Medium R, F, W, C Advanced High R, F, W, C Advanced High Surface Mount Pad Repair Procedure 4.7.1 Description Surface Mount Pad Repair, Epoxy Method Illustration Product Class R, F, C Skill Level Advanced Level of Conformance Medium 4.7.2 Surface Mount Pad Repair, Film Adhesive Method R, F, C Advanced High Plated Hole Repair Procedure 5.1 Description Plated Hole Repair, No Inner Layer Connection Illustration Product Class R, F, W Skill Level Intermediate Level of Conformance High 5.2 Plated Hole Repair, Double Wall Method R, F, W Advanced Medium 5.3 Plated Hole Repair, Inner Layer Connection R Expert Medium xi IPC-7721 Jumpers Procedure Description 6.1 Jumper Wires April 2001 Illustration Product Class R, F, W, C Skill Level Intermediate Level of Conformance N/A 6.2.1 Jumper Wires, BGA Components, Foil Jumper Method R, F Expert Medium Component Additions Procedure 6.3 Description Component Modifications and Additions Illustration Product Class R, F, W, C Skill Level Advanced Level of Conformance N/A xii February 1998 Repair and Modification of Printed Boards and Electronic Assemblies IPC-7721 1.0 General 1.1 Scope This document covers procedures for repairing and reworking printed board assemblies. It is an aggregate of information collected, integrated and assembled by the Repairability Subcommittee (7-34) of the Product Assurance Committee of the IPC. 1.2 Purpose This document prescribes the procedural requirements, tools and materials and methods to be used in the modification, rework, repair, overhaul or restoration of electronic products. Although this document is based in large part on the Product Class Definitions of ANSI/J-STD001, this document should be considered applicable to any type of electronic equipment. When invoked by contract as the controlling document for the modification, rework, repair, overhaul or restoration of products, the requirements flowdown apply. IPC has identified the most common equipment and process in order to affect a specific repair or rework. It is possible that alternate equipment and processes can be used to make the same repair. If alternate equipment is used, it is up to the user to determine that the resultant assembly is good and undamaged. 1.2.1 Definition of Requirements The words must and shall have no special meaning beyond that commonly used in other IPC standards. 1.2.2 Requirements Flowdown The applicable requirements of this document must be imposed by each manufacturer or supplier on all applicable subcontracts and purchase orders. The manufacturer or supplier must not impose or allow any variation from these requirements on subcontracts or purchase orders other than those that have been approved by the user. Unless otherwise specified, the requirements of this document are not imposed on the procurement of off the shelf assemblies or subassemblies. However, the manufacturer of these items may comply as deemed appropriate. 1.3 Background Today’s PC boards are more complex and microminiaturized than ever before. Despite this, they can be successfully modified, reworked or repaired if the proper techniques are followed. This manual is designed to help you repair, rework and modify PC boards reliably. The procedures in this document have been obtained from end product assemblers, printed board manufacturers and end product users who recognized the need for documenting commonly used rework, repair and modification techniques. These techniques have, in general, been proven to be acceptable for the class of product indicated through testing and extended field functionality. Procedures contained herein were submitted for inclusion by commercial and military organizations too numerous to list individually. The Repairability Subcommittee has, where appropriate, revised procedures to reflect improvements. Rework completed satisfactorily will meet the original specification and requirements of IPC-A-600 and IPC-A610. But, by definition, modifications and repairs do not comply with the initial design or fabrication criteria. For modification and repair, the user must recognize that the criteria in IPC-A-600 Acceptability of Printed Boards and IPC-A-610 Acceptability of Printed Board Assemblies are not necessarily applicable to the procedures herein. Modifications and repairs should not compensate for the lack of proper processes and quality controls. Ultimate cost effectiveness is achieved using appropriate design, fabrication and assembly techniques that minimize the need for modification and repair. 1.4 Controls Although modification, rework and repair procedures may be very similar, the control of such procedures may not be the same, due to the conditions and objectives involved. 1. Modification The revision of the functional capability of a product in order to satisfy new acceptance criteria. Modifications are usually required to incorporate design changes which can be controlled by drawings, change orders, etc. Modifications should only be performed when specifically authorized and described in detail on controlled documentation. 2. Rework The act of reprocessing non-complying articles, through the use of original or equivalent processing, in a manner that assures full compliance of the article with applicable drawings or specifications. 3. Repair The act of restoring the functional capability of a defective article in a manner that precludes compliance of the article with applicable drawings or specifications. 1 IPC-7721 Repairs are generally changes to an unacceptable end product to make it acceptable in accordance with original functional requirements. The control of repaired products should be by means of Material Review Board (MRB), or its equivalent, which may consist of Design Engineering, Quality Assurance, and User representatives. The MRB, with technical support, should define the mutually acceptable repair method to be used and take the action necessary to ensure that all applicable procedures are adhered to. Repair of a failure in the field seldom includes an MRB, and typically is done in accordance with a contract, repair/service order or the user-activity maintenance program requirements. The maximum number of repairs per printed wiring board assembly should be determined by the using activity or agency. 1.4.1 Classification The user of the product is responsible for identifying the Class of Product. The procedure selected for action to be taken (modification, rework, repair, overhaul etc.) must be consistent with the Class identified by the user. The three Classes of Product are: 1. Class 1 – General Electronic Products Includes products for applications where the major requirement is the function of the completed assembly. 2. Class 2 – Dedicated Service Electronic Products Includes products where continued performance and extended life is required, and for which uninterrupted service is desired but not critical. Typically, the end use environment would not cause failures. 3. Class 3 – High Performance Electronic Products Includes products where continued performance or performance-on-demand is critical. Equipment downtime cannot be tolerated, end-use environment may be uncommonly harsh, and the equipment must function where required, such as life support and other critical systems. 1.4.2 Printed Board Types There are a variety of printed board types that the procedures in this document apply to. When selecting the appropriate modification, rework or repair procedure the printed board type being worked should be considered. Select a procedure that applies to the printed board type as listed on the procedure. Printed board types include the following: R. Rigid Printed Boards and Assemblies A printed board or assembly using rigid base materials only. These may be single-sided, double-sided or multilayered, and may be constructed from base laminate material that spans all approved commercial grades of laminate and includes glass fabric reinforced epoxy and polyimide resin laminates. 2 February 1998 F. Flexible Printed Boards and Assemblies A printed board or assembly using flexible or a combination of rigid and flexible materials only. May be partially provided with electrically non-functional stiffeners and/or cover lay. These may be single-sided, double-sided or multilayered. W. Discrete Wiring Boards and Assemblies A printed board or assembly using a discrete wiring technique to obtain electrical interconnections. C. Ceramic Boards and Assemblies A printed board or assembly using ceramic as the base material with interconnections separated by dielectric. The board layers are usually formed by alternate printing or depositing of interconnections and dielectric. The assemblies are either surface mount or die attach. Usually multilayered, these may be single-sided or double-sided. 1.4.3 Level of Conformance Level of Conformance provides the means for selecting an appropriate level of conformance to the original electrical, mechanical, physical, environmental and visual product requirements. Each procedure lists a Level of Conformance that the product will attain when successfully completed. The Level of Conformance rating for each procedure is based on the skill of the technician. The ratings are based on long term industry experience and are not necessarily backed up with testing data. Levels of Conformance include the following: L. Lowest Level – Significant variance with the physical character of the original and may vary with many of the electrical, functional, environmental and serviceability factors. M. Medium Level – Some variance with the physical character of the original and most likely varies with some of the functional, environmental and serviceability factors. H. Highest Level – Most closely duplicates the physical characteristics of the original and most probably complies with all the functional, environmental and serviceability factors. Class 3 Products must use procedures rated Highest level unless it can be demonstrated that a lower level procedure will not adversely affect the product’s functional characteristics. Class 2 and 1 Products should use procedures rated Highest level for assured safety and dependability but Medium and Low Level procedures can be used if it has been determined that they are suitable for the specific product’s functional characteristics. Procedures in this manual are given a ‘‘Level of Conformance’’ rating which is described in Table 1. February 1998 Table 1 Level of Conformance Level of Conformance Functional Consideration L M H Electrical - Resistance No Verify Yes Electrical - Inductance No Verify Yes Electrical - Capacitance No Verify Yes Electrical - Cross Talk No Verify Yes Electrical - High Speed Frequency No Verify Yes Environmental - Shock No Verify Yes Environmental - Vibration No Verify Yes Environmental - Humidity Verify Verify Yes Environmental - Temperature Yes Yes Yes Environmental - Altitude Verify Verify Verify Environmental - Bacteria Verify Verify Yes Environmental - Fungus Verify Verify Yes Serviceability - Future Repair No Yes Yes or Mod. No Verify Yes Procedure may not comply with functional consideration. Procedure should comply with functional consideration but should be tested to verify. Procedure will normally comply with functional consideration. In principle any modification, rework or repair action taken on a product should reestablish the products original character, ‘‘Make it like it was.’’ Physical changes, obvious or otherwise, can adversely affect the products performance or capability factors. 1.4.5 Skill Level To assist you in determining the skill level needed for each procedure a Skill Level indicator is included in each process. The Skill Level recommended should be used as a guide only. Skill levels will vary widely from technician to technician and from company to company. These recommendations come from industry experience and are not necessarily backed up with substantive testing. Skills are separated into three categories. I. Intermediate – Technician with skills in basic soldering and component rework but inexperienced in general repair/rework procedures. A. Advanced – Technician with soldering and component rework skills and exposure to most repair/rework procedures but lacking extensive experience. E. Expert – Technician with advanced soldering and component rework skills and extensive experience in most repair/rework procedures. 1.5 Terms And Definitions For terms and definitions refer to IPC-T-50 Terms And Definitions. 1.6 Training The quality and reliability of modified or repaired printed boards and assemblies is highly dependent upon the skill and competence of the person performing IPC-7721 these tasks. The implementation of proper methods by unqualified personnel can result in a substandard end product. Consequently, achieving successful results with the methods described herein is predicated on the use of properly trained personnel whose skills have been tested and certified to be of a sufficient level of competence. 1. Soldering Skills Many companies have considered assembly personnel who are competent in soldering techniques to be sufficiently trained for rework/repair activities. This has often proven to be erroneous, since proper soldering is only one of the skills required. Also, in order to attain comparable results, there are many instances where component rework requires techniques that are different than those used to originally solder the component. 2. Personnel Selection The proper selection of trainees will contribute significantly toward the success in developing capable repair personnel. Personnel with above average soldering abilities and sound reasoning capabilities often make ideal trainees. However, personnel who have no soldering skills, but possess a good level of eye acuity, manual dexterity, and sound reasoning capability, can be successfully trained. 3. Professional Training Companies should establish and maintain procedures for identifying the training needs and provide for the training of all personnel performing the activities affecting product quality. Personnel performing specific assigned tasks shall be qualified on the basis of appropriate education, training and experience, as required. Appropriate records of training shall be maintained. a. Training for personnel and instructors is commercially available and can be completed by an outside organization specializing in the applicable discipline. b. Modification/rework/repair training employs concepts, techniques, procedures and a vocabulary that distinguishes it from basic soldering training. c. Effective training requires the development of high levels of comprehension and reasoning within the trainee. This necessitates expansive teaching methods and detailed demonstration under close instructor supervision, to help assure the development of proficiency within each trainee. Training to establish a desired level of proficiency can usually be achieved after three to ten days of training, depending on the content of the training program, the complexity of the end product, and the proficiency of the trainee. Testing and certification can be provided for each trainee, as the situation warrants. 3 IPC-7721 1.7 Basic Considerations 1. Appropriate Approvals Appropriate approvals should be obtained before proceeding with PC board modification, rework or repair. Such approvals should include agreements as to acceptance criteria and limitations. 2. Singular Procedures Procedures in this book are presented as individual methods. Multiple procedures may be necessary to complete the task. 3. Quality And Reliability All attempts to modify, rework or repair printed boards and assemblies should seek to equal the quality and reliability of the original, unaltered, end product. 4. Procedure Selection The procedure selected should be on the basis of optimum end product functionality. Test data should be obtained wherever possible. 5. Patience To achieve best results, do not rush the process. Keep in mind that most of the cost for fabrication/assembly has already been spent, but with care and patience, most of this cost can be salvaged. 6. Heat Application Incorrect heat application may cause severe damage to board materials, conductors, components, conformal coatings and solder connections. 7. Removal of Coatings Coating should be removed from affected areas prior to processing. Coatings will inhibit solder removal and adversely affect resoldering operations. 1.8 Tools and Materials Modification, rework and repair of PC boards and assemblies is generally a highly labor intensive operation relying more on individual operator skills than automation. The use of proper tools and supplies will often have a significant impact on the function and reliability of the end product. To enhance the ease of the task at hand and to improve the potential for a successful operation, the following equipment and supplies are recommended. This list should be used as a guide only. 1. Proper Workstations A proper workstation; ESD grounded with acceptable lighting, outlets, and configured for comfort is preferable due to the degree of concentration and dexterity required to perform high reliability PC board modification, rework and repair. 2. High Quality Microscope Precision work generally requires a microscope. Refer to IPC-OI-645 Standard for Visual Optical Inspection Aids for more information. 4 February 1998 3. Lighting Illuminations at the surface of work stations should be 1000 Lm/m2 minimum. 4. Soldering Tools Precision soldering is important in today’s modification, rework and repair operations. Technicians may need an assortment of special use soldering tools appropriate to the variety of tasks at hand. These tools must be temperature controlled, ESD/EOS safe, ergonomically designed and include a selection of tips to suit each particular operation. 5. Preheating (Auxiliary) Heating Preheating printed board assemblies is sometimes recommended to avoid thermal shock to temperature sensitive materials and components. Preheating also elevates the thermal mass of the assembly to allow a rework process to proceed in an acceptable time. Preheating can be accomplished using either an oven, heat lamp, hot plate, infrared or convective style heating system. 6. Fume Extraction Work environments can often expose technicians to potentially hazardous fumes. Disposal and release of certain materials may have a significant environmental impact. The use of localized fume extraction systems, environmental control devices and other personnel protection equipment may be necessary to comply with MSDS requirements and applicable federal, state and local laws. 7. Hand Held Drilling and Grinding Tool PC Board modification, rework and repair procedures often require drilling, milling or grinding operations. The best type of tool for these delicate operations is preferably a lightweight, high quality, EOS/ESD controlled motorized rotary tool. This tool can be used for detailed work (i.e., solder resist and conformal coating removal, grinding out burns or laminate defects, drilling out plated holes, cutting fine pitch conductors etc.). 8. Precision Drill/Mill System Demanding projects often require the need to make very precise holes, slots, groves etc.. Accurate depth control and high speed may be required. A precision drilling/milling system with fixturing to hold the printed board assembly and an attached microscope may be advisable for those unusually demanding projects. 9. Replacement Conductors and Lands There are commercially available replacement conductors and lands that are normally fabricated from copper foil and plated with solder or nickel and gold for edge contact repair. These conductors and lands are available with or without a dry film adhesive on the February 1998 back. Adhesive backed conductors and lands are normally heat bonded to the board surface. Replacement conductors and lands are available in hundreds of different shapes. Compatible replacement conductors and features may also be salvaged from scrap printed wiring boards, if necessary. 10. Gold Plating System Plating gold edge contacts or any metal surface requires the use of materials that may have environmental and safety concerns and must be handled properly. The power applied to the plating surfaces must be controlled accurately to expect reliable results. A good plating systems should include; a DC power supply with voltage and current meters, plating anodes sized for gold edge contact plating, a solution tray to collect the solution runoff, a support for the PC board and a tray to hold and store the various chemicals safely. 11. Epoxy and Coloring Agents Many repair operations require the use of high strength, high temperature epoxies. For high temperature applications two-part epoxies offer the highest strength, thermal resistance and durability. It may also be important to have resists or coloring agents so that you can restore the cosmetic appearance of the board. It is best to cure the epoxies in an oven if possible. 12. Eyelets and Eyelet Press System Solder plated copper eyelets and an eyelet press/setting tool to repair damaged plated through holes may be required. IPC-7721 13. Cleaning Station/System Regardless of the Class of Product serviced, a cleaning system that is chemically matched to the flux system(s) in use will be essential to a satisfactory repair. In organizations that perform procedures on Class 3 Products, it may also be necessary to have a cleanliness test system in order to periodically evaluate the ability of the cleaning system to meet the requirements/expectations of the user. Interim or in-process cleaning at the workstation should be used pending completion of the procedure and the final cleaning. 14. Tools and Supplies Also needed are a wide assortment of hand tools including tweezers, various pliers, files, dental picks, cutting tools and materials such as fluxes, solders, and other common items. 15. Conformal Coating Area The cost, safety concerns and utility services (air pressure/vacuum, power, venting, UV illuminations, etc.) of equipment associated with both the removal and application of conformal coating suggest to many organizations that one central conformal coating and encapsulant area be installed. 5 IPC-7721 February 1998 This Page Intentionally Left Blank 6 Revision: 7721 Repair and Modification of Printed Boards and Electronic Assemblies Date: 2/98 Handling Electronic Assemblies Number: 2.1 Product Class: R, F, C, W Skill Level: Intermediate Level of Conformance: High OUTLINE Electrostatic Discharge (ESD) is the rapid discharge of electrical energy that was created from static sources. When the electrical energy is allowed to come in contact with or even close to a sensitive component it can cause damage to the component. Electrostatic-Discharge Sensitive (ESDS) components are those components that are affected by these high energy surges. The relative sensitivity of a component to ESD is dependent upon its construction and materials. As components become smaller and operate faster, the sensitivity increases. Electrical Overstress (EOS) is the internal result of a unwanted application of electrical energy that results in damaged components This damage can be from many different sources, such as electrically powered process equipment or ESD occurring during handling or processing. ESDS components can fail to operate or change in value as a result of improper handling or processing. These failures can be immediate or latent. The result of immediate failure can be additional testing and rework or scrap. However the consequences of latent failure are the most serious. Even though the product may have passed inspection and functional test, it may fail after it has been delivered to the customer. It’s important to build protection for ESDS components into circuit designs and packaging. However, in the manufacturing and assembly areas, we often work with unprotected electronic assemblies that are attached to the ESDS components. This section will be dedicated to safe handling of these unprotected electronic assemblies. For that purpose, the following subjects are addressed: 2.1.1 2.1.2 2.1.2.1 2.1.2.2 2.1.3 2.1.4 Electrical Overstress (EOS) Damage Prevention Electrostatic Discharge (ESD) Damage Prevention Warning Labels Antistatic Materials Anti-Static Work Station Physical Handling Information in this specification is intended to be general in nature. Additional detailed information can be found in EIA625, Requirements for Handling Electrostatic-DischargeSensitive (ESDS) Devices 2.1.1 Electrical Overstress (EOS) Damage Prevention Electrical components can be damaged by unwanted electrical energy from many different sources. This unwanted electrical energy can be the result of ESD potentials or the result of electrical spikes caused by the tools we work with, such as soldering irons, soldering extractors, testing instruments or other electrically operated process equipment. Some devices are more sensitive than others. The degree of sensitivity is a function of the design of the device. Generally speaking higher speed and smaller devices are more susceptible than their slower, larger predecessors. The purpose or family of the device also plays an important part in component sensitivity. This is because the design of the component can allow it to react to smaller electrical sources or wider frequency ranges. With todays products in mind, we can see that EOS is a more serious problem than it was even a few years ago. It will be even more critical in the future. When considering the susceptibility of the product we must keep in mind the susceptibility of the most sensitive component in the assembly. Applied unwanted electrical energy can be processed or conducted just as an applied signal would be during circuit performance. Before handling or processing sensitive components, tools and equipment need to be carefully tested to ensure that they do not generate damaging energy, including spike voltages. Current research indicates that voltages and spikes less than 0.5 volt are acceptable. However, an increasing number of extremely sensitive components require that soldering irons, solder extractors, test instruments and other equipment must never generate spikes greater than 0.3 volt. As required by most ESD specifications including EIA-625, periodic testing may be warranted to preclude damage as equipment performance may degrade with use over time. Maintenance programs are also necessary for process equipment to ensure the continued ability to not cause EOS damage. EOS damage is certainly similar in nature to ESD damage, since damage is the result of undesirable electrical energy. 2.1.2 Electrostatic Discharge (ESD) Damage Prevention The best ESD damage prevention is a combination of preventing static charges and eliminating static charges if they do Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 8 Number: 2.1 Revision: Date: 2/98 IPC-7721 Subject: Handling Electronic Assemblies occur. All ESD protection techniques and products address one or both of the two issues. ESD damage is the result of electrical energy that was generated from static sources either being applied or in close proximity to ESDS devices. Static sources are all around us. The degree of static generated is relative to the characteristics of the source. To generate energy relative motion is required. This could be contacting, separation, or rubbing of the material. Most of the serious offenders are insulators since they concentrate energy where it was generated or applied rather than allowing it to spread across the surface of the material. Common materials such as plastic bags or Styrofoam containers are serious static generators and as such are not to be allowed in processing areas especially static safe areas. Peeling adhesive tape from a roll can generate 20,000 volts. Even compressed air nozzles which move air over insulating surfaces generate charges. Table 1 Typical Static Charge Sources Work surfaces Waxed, painted or varnished surfaces Untreated vinyl and plastics Glass Floors Sealed concrete Waxed or finished wood Floor tile and carpeting Clothes and personnel Non-ESD smocks Synthetic materials Non-ESD Shoes Hair Chairs Finished wood Vinyl Fiberglass Non-conductive wheels Packaging and handling materials Plastic bags, wraps, envelopes Bubble wrap, foam Styrofoam Non-ESD totes, trays, boxes, parts bins Assembly tools and materials Pressure sprays Compressed air Synthetic brushes Heat guns, blowers Copiers, printers Destructive static charges are often induced on nearby conductors, such as human skin, and discharged into conductors. This can happen when a printed board assembly is touched by a person having a static charge potential. The electronic assembly can be damaged as the discharge passes through the conductive pattern to a static sensitive component. Static discharges may be too low to be felt by humans (less than 3500 volts), and still damage ESDS components. Typical static voltage generation is included in Table 2 Table 2 Typical Static Voltage Generation Source Walking on carpet Walking on vinyl flooring Worker at a bench Vinyl envelopes (Work Instructions) Plastic bag picked up from the bench Work chair with foam pad 10-20% humidity 35,000 volts 12,000 volts 6,000 volts 7,000 volts 20,000 volts 18,000 volts 65-90% humidity 1,500 volts 250 volts 100 volts 600 volts 1,200 volts 1,500 volts 2.1.2.1 Warning Labels Warning labels are available for posting in facilities and placement on devices, assemblies, equipment and packages to alert people to the possibility of inflicting electrostatic or electrical overstress damage to the devices they are handling. An example of frequently encountered labels are shown in Figure 1. Symbol (a) ESD susceptibility symbol. A triangle with a reaching hand and a slash across it. This is used to indicate that an electrical or electronic device or assembly is susceptible to damage from an ESD event. Symbol (b) ESD protective symbol. This differs from the ESD susceptibility symbol in that it has an arc around the outside of the triangle and no slash across the hand. This is used to identify items that are specifically designed to provide ESD protection for ESD sensitive assemblies and devices. Symbols (a) and (b) identify devices or an assembly as containing devices that are ESD sensitive, and that they must be handled accordingly. These symbols are promoted by the ESD association and are described in EOS/ESD standard Page 2 of 8 Number: 2.1 Revision: Date: 2/98 IPC-7721 Subject: Handling Electronic Assemblies S8.1-1992 as well as the Electronic Industries Association (EIA) in EIA standard RS-471. Note that the absence of a symbol does not necessarily mean that the assembly is not ESD sensitive. When doubt exists about the sensitivity of an assembly, it must be handled as a sensitive device until it is determined otherwise. Recommend removing the reference symbols c and d since they were removed from the MIL specs over 10 years ago. Symbol (c) covers not only electrostatic fields, but electromagnetic and magnetic fields as well. The use of this symbol to designate ESD is discouraged since it does not specifically identify EOS/ESD sensitivity. Symbol (d) has been used widely as an ESD symbol. The standard meaning for the lightning bolt symbol is high voltage in the context of electrical utility power, and typically damaging to personnel. For example, UL-1244 (and IEC-348) requires that a lightening bolt label be placed near high voltage terminals on test equipment. Unfortunately, this symbol is encountered quite often to designate static sensitive devices. The use of a lightning bolt to designate ESD is discouraged to avoid possible dangerous confusion. 2.1.2.2 ESD Protective Materials ESDS components and assemblies must be protected from static sources when not being worked on in static safe environments or work stations. This protection could be conductive static-shielding boxes, bags or wraps. ESDS items must be removed from their protective enclosures only at static safe work stations. It is important to understand the difference between the three types of protective enclosure material: (1) static shielding (or barrier packaging), (2) antistatic, and (3) static dissipative materials. Static shielding packaging will prevent an electrostatic discharge from passing through the package and into the assembly causing damage. Antistatic packaging materials are used to provide inexpensive cushioning and intermediate packaging for ESDS items. Antistatic materials do not generate charges when motion is applied. However, if an electrostatic discharge occurs, it could pass through the packaging and into the part or assembly, causing EOS/ESD damage to ESDS components. (a) ESD Susceptibility Symbol (b) ESD Protective Symbol w w w CAUTION SENSITIVE ELECTRONIC DEVICES DO NOT SHIP OR STORE NEAR STRONG ELECTROSTATIC, ELECTROMAGNETIC, MAGNETIC OR RADIOACTIVE FIELDS (c) MIL-STD-129H Symbol CAUTION _ STATIC ECLEOCNTTREINCTITSY_COAPNEDNAOMNALGYE AT STATIC-FREE STATION (d) No Official Status IPC-610-001 Figure 1 Frequently Encountered EOS/ESD Warning Labels Page 3 of 8 Number: 2.1 Revision: Date: 2/98 IPC-7721 Subject: Handling Electronic Assemblies Static dissipative materials have enough conductivity to allow applied charges to dissipate over the surface relieving hot spots of energy. Parts leaving an EOS/ESD protected work area must be overpacked in static shielding materials, which normally also have static dissipative and antistatic materials inside. Do not be misled by the ‘‘color’’ of packaging materials. It is widely assumed that ‘‘black’’ packaging is static shielding or conductive and that ‘‘pink’’ packaging is antistatic in nature. While that may be generally true, it can be misleading. In addition, there are many new clear materials now on the market that may be antistatic and even static shielding. At one time, it could be assumed that clear packing materials introduced into the manufacturing operation would represent an EOS/ ESD hazard. This is not necessarily the case now. Caution: Some static shielding and antistatic materials and some topical antistatic solutions may affect the solderability of assemblies, components, and materials in process. Select only non-contaminating packaging and handling materials for in-process assemblies and use them with regard for the vendors instructions. Solvent cleaning of static dissipative or antistatic surfaces can degrade their ESD performance. Follow the manufacturers recommendations for cleaning. 2.1.3 Anti-Static Work Station An EOS/ESD safe work station prevents damage to sensitive components from spikes and static discharges while operations are being performed. Safe work stations should include EOS damage prevention by avoiding spike generating repair, manufacturing or testing equipment. Soldering irons, solder extractors and testing instruments can generate energy of sufficient levels to destroy extremely sensitive components and seriously degrade others. For ESD protection, a path-to-ground must be provided to neutralize static charges that might otherwise discharge to a device or assembly. ESD safe work stations also have static dissipative or antistatic work surfaces which are connected to a common ground. Provisions are also made for grounding the worker’s skin, preferably via a wrist strap to eliminate charges generated on the skin or clothing. Provision must be made in the grounding system to protect the worker from live circuitry as the result of carelessness or equipment failure. This is commonly accomplished through resistance in line with the ground path, which also slows the charge decay time to prevent sparks or surges of energy from ESD sources. Additionally, a survey must be performed of the available voltage sources that could be encountered at the work station to provide adequate protection from personnel electrical hazards. For maximum allowable resistance and discharge times for static safe operations, see Table 3. Table 3 Maximum Allowable Resistance and Discharge Times for Static Safe Operations Reading from Operator Through Floor mat to ground Table mat to ground Wrist strap to ground Maximum Tolerable Resistance 1000 megohms 1000 megohms 100 megohms Maximum Acceptable Discharge Time Less than 1 sec. Less than 1 sec. Less than 0.1 sec. Note: the selection of resistance values are to be based on the available voltages at the station to ensure personnel safety as well as to provide adequate decay or discharge time for ESD potentials. Examples of static safe work stations are shown in Figures 2 and 3. When necessary, air ionizers may be required for more sensitive applications. The selection, location, and use procedures for ionizers must be followed to ensure their effectiveness. Keep static dissipative or antistatic work station(s) free of static generating materials such as styrofoam, plastic solder removers, sheet protectors, plastic or paper notebook folders, and employees personal items. Periodically check EOS/ESD work stations to make sure they work. EOS/ESD assembly and personnel hazards can be caused by improper grounding methods or by an oxide build-up on grounding connectors. Tools and equipment must be periodically checked and maintained to ensure proper operation. Particular care must be given to ‘‘third wire’’ ground terminations. Frequently, instead of being at workbench or earth potential, the third wire ground may have a ‘‘floating’’ potential of 80 to 100 volts. This 80 to 100 volt potential between an electronic assembly on a properly grounded EOS/ESD work station and a third wire grounded electrical tool may Page 4 of 8 Number: 2.1 Revision: Date: 2/98 IPC-7721 Subject: Handling Electronic Assemblies Personal Wrist Strap EOS Protective Trays, Shunts, etc. 1 M Ohm 10% EOS Protective Table Top 1 M Ohm 10% 1 M Ohm 10% Ground Common Ground Point Building Floor EOS Protective Floor or Mat IPC-610-002 Figure 2 Target condition EOS/ESD Workstation Personal Wrist Strap 1 M Ohm 10% EOS Protective Trays, Shunts, etc. EOS Protective Table Top 1 M Ohm 10% 1 M Ohm 10% Table 4 General Rules for Handling Electronic Assemblies 1. Keep work stations clean and neat. There must not be any eating, drinking, or use of tobacco products in the work area. 2. Minimize the handling of electronic assemblies and components to prevent damage. 3 When gloves are used, they need to be changed as frequently as necessary to prevent contamination from dirty gloves. (See Figure 4). 4. Solderable surfaces are not to be handled with bare hands or fingers. Body oils and salts reduce solderability, promote corrosion and dendritic growth. They can also cause poor adhesion of subsequent coatings or encapsulates. 5. Do not use hand creams or lotions containing silicone since they can cause solderability and conformal coating adhesion problems.. 6. Never stack electronic assemblies or physical damage may occur. Special racks need to be provided in assembly areas for temporary storage. 7. Always assume the items are ESDS even if they are not marked. 8. Personnel must be trained and follow appropriate ESD practices and procedures. 9. Never transport ESDS devices unless proper packaging is applied. Ground Common Ground Point Building Floor EOS Protective Floor or Mat IPC-610-003 Figure 3 Acceptable EOS/ESD Workstation damage EOS sensitive components or could cause injury to personnel. Most ESD specifications also require these potentials to be electrically common. The use of ground fault interrupter (GFI) electrical outlets at EOS/ESD workstations is highly recommended. 2.1.4 Physical Handling Care must be taken during acceptability inspections to ensure product integrity at all times. Table 4 provides general guidance. Physical Damage Improper handling can readily damage components and assemblies (e.g., cracked, chipped or broken components and connectors, bent or broken terminals, badly scratched board surfaces and conductor lands). Physical damage of this type can ruin the entire assembly or attached components. Contamination Contamination by handling with bare hands or fingers without some form of protection causes soldering and coating problems; body salts and oils, and unauthorized hand creams are typical contaminants. Body oils and acids reduce solderability, promote corrosion and dendritic growth. They can also cause poor adhesion of subsequent coatings or encapsulates. Lotion formulated specifically for use in solder assembly areas is available. Normal cleaning procedures will not always Page 5 of 8 Number: 2.1 Revision: Date: 2/98 IPC-7721 Subject: Handling Electronic Assemblies remove such contaminants. The best solution is to prevent contamination. Handling Electronic Assemblies If no ESDS markings are on an assembly, it still needs to be handled as if it were an ESDS assembly. However, ESDS components and electronic assemblies need to be identified by suitable EOS/ESD labels (see Figure 1). Many sensitive assemblies will also be marked on the assembly itself, usually on an edge connector. To prevent ESD and EOS damage to sensitive components, all handling, unpacking, assembly and testing must be performed at a static controlled work station (See Figures 2 & 3). Avoid contaminating solderable surfaces prior to soldering. Whatever comes in contact with these surfaces must be clean. When boards are removed from their protective wrappings, handle them with great care. Touch only the edges away from any edge connector tabs. Where a firm grip on the board is required due to any mechanical assembly procedure, gloves meeting EOS/ESD requirements need to be worn. These principles are especially critical when no-clean processes are employed. Handling After Solder After soldering and cleaning operations, the handling of electronic assemblies still requires great care. Finger prints are extremely hard to remove and will often show up in conformally coated boards after humidity or environmental testing. Gloves or other protective handling devices need to be used to prevent such contamination. Use mechanical racking or baskets with full ESD protection when handling during cleaning operations. Common Tools and Equipment Work environments require tools and equipment to conduct electronic assembly operations. The following information is provided as guidance regarding the use of common equipment. EIA-625 provides more specific information. Gloves and Finger Cots The use of gloves or finger cots may be required under contract to prevent contamination of parts and assemblies. Gloves and finger cots must be carefully chosen to maintain EOS/ESD protection. Figure 4 Target Condition - Class 1,2,3 • Handling with clean gloves and full EOS/ESD protection • Handling during cleaning procedures using solvent resistant gloves meeting all EOS/ESD requirements. Figure 5 Acceptable - Class 1,2,3 • Handling with clean hands by board edges using full EOS/ ESD protection Page 6 of 8 Number: 2.1 Revision: Date: 2/98 IPC-7721 Subject: Handling Electronic Assemblies Figure 6 IPC-2-1-1 NOTE: Any assembly related component if handled without EOS/ESD protection may damage electrostatic sensitive components. This damage could be in the form of latent failures, or product degradation not detectedable during initial test or catastrophic failures found at initial test. Page 7 of 8 Number: 2.1 Revision: Date: 2/98 NOTES IPC-7721 Subject: Handling Electronic Assemblies Page 8 of 8 Revision: 7721 Date: 2/98 Repair and Modification of Cleaning Printed Boards and Electronic Assemblies Number: 2.2 Product Class: R, F, W, C Skill Level: Intermediate Level of Conformance: High OUTLINE Surface contaminants can significantly effect soldering, bonding, coating and the electrical characteristics of printed board and assemblies. This procedure outlines the cleaning methods for printed wiring boards and assemblies. REFERENCES NAWCWPNS Final report for NON-ODS cleaning of electronics and avionics report of October 10, 1995. BACKGROUND In the past few years, the Environmental Protection Agency (EPA) has been actively involved in reducing the production of chlorofluorocarbons (CFC’s). Through their efforts, and the Montreal Protocol, the production of CFC’s have been frozen to 1986 levels with requirements to further decrease to zero production by the year 2000. The London Amendments (June 1990) to the protocol are even more restrictive. Cleaning of the PCB is an important part of any rework/repair process. The different cleaning processes are dependent upon the type of flux used in the soldering process or the type of contaminate to be removed. A general rule of thumb is ‘‘like dissolves like,’’ which is a quick way of saying that usually organic/nonpolar contaminants are best removed by nonpolar solvents and inorganic/polar contaminants are best removed by polar solvents. A desirable cleaning medium should: A. Not be harmful to employees or the environment. B. Possess excellent wetting ability. C. Dissolve and removes both soluble and particulate con- taminants. D. Be compatible with the PCB assembly. E. Be stable during use. INTRODUCTION If rework/repair operations are performed in a facility that has an automated cleaning systems (i.e., batch, in-line, aqueous, semi aqueous, or solvent), then such equipment should be used to clean the assembly. If an automated system is not available, the cleaning method that follows should be used to reduce surface contamination prior to using adhesives, coating materials or soldering. A cleaning step after soldering is used to ensure that surface contaminants are not trapped beneath conformal coatings or encapsulants, nor will they contribute to future functional assembly problems. LIMITATIONS 1. The ability of solvent based cleaning solutions to remove flux residue containing polyglycols should be assessed since not all solvent based cleaning solutions will remove polyglycols. 2. A de-ionized (DI) water rinse should follow IPA/DI cleaning except that a water rinse for double sided printed wiring boards with plated through holes may not be required. 3. Potable (drinking) water should not be used as a final rinse due to the potential of contaminating the printed wiring board assembly with chlorine, fluorine and halides. 4. When automated cleaning is used for assemblies that have been conformally coated, it is important that the cleaning process is compatible with the type of coating used and with any unsealed components. The coating should be checked to ensure that the coating will not be degraded by the cleaning process. TOOLS AND MATERIALS Black Light Brush, Soft Bristles Cleaner, Aqueous or Semi-Aqueous Containers De-ionized Water (DI) Gloves Isopropyl Alcohol (IPA) Oven Wipes, Lint Free PROCEDURE CAUTION Use clean gloves during this entire operation. NOTE To reduce solvent volumes, mixtures of IPA with water and IPA with solvent are available in pressurized containers. The propellants are HFC’s. These containers may be fitted with a bristle brush spray attachments for additional cleaning action. 1. Clean the board in an Aqueous or Semi-Aqueous cleaner, or pour approximately 10 ml per 4 square inches of effected area. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 2.2 Revision: Date: 2/98 IPC-7721 Subject: Cleaning 2. Scrub the board vigorously with a continually wet soft bristle brush for 10 seconds. 3. Rinse the area with 10 ml per 26 square centimeters of clean Isopropyl Alcohol to effectively remove all potentially harmful residues. 4. Handle the board by the edges and blot the excess Isopropyl Alcohol with clean, lint free cloth. 5. Examine board visually for cleanliness. The use of a black light will help detect contaminants that will fluoresce. 6. Dry boards in oven, if desired. 7. If the boards or assemblies are to be stored before use or coating, remove them from the oven and allow to cool until they can be handled. Place the boards or assemblies into self sealing bags with packages of desiccant. EVALUATION 1. Visually examine and test for cleanliness using IPC-TM650, Test Method 2.3.25 or 2.3.26 NOTES Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 2.3.1 Coating Removal, Identifi- Product Class: R, F, W, C Skill Level: Advanced cation of Conformal Coating Level of Conformance: High OUTLINE This procedure covers the techniques for identifying various coatings so that the appropriate coating removal method can be selected. Conformal Coating Types IPC-CC-830 has superseded MIL-I-46058 as the primary specification for printed circuit assembly conformal coatings, and covers the following types of conformal coatings: 1. Type AR – Acrylic resin (includes lacquers and varnishes) 2. Type ER – Epoxy resin 3. Type SR – Silicone resin 4. Type UR – Polyurethane resin 5. Type XY – Paraxylylene REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling IPC - CC-830 TOOLS AND MATERIALS Abrasive Discs Brush Cleaner Cleaner Wipes Cotton Swab Dental Style Drill Heated Blade Knife Solvent Thermal Parting Tool Wood Stick PROCEDURE To determine the appropriate coating removal procedure the coating must first be identified. During original manufacture the specific coating is usually known. Consequently, the coating removal methods can usually be specified and based on the known coatings being used. When identification of the coating is not available, simple observation and testing will help identify the coating characteristics so that the proper removal procedure can be specified. NOTE The generic or commercial identification of the coating material is not necessary to accomplish coating removal. 1. Hardness Penetration test in a non-critical area to determine relative hardness. The harder the coating the more suitable to pure abrasive techniques. The softer and gummier the coatings the more suitable to the brushing removal procedures. 2. Transparency Obviously transparent coatings are usually more suitable for removal than the opaque type. Removal methods used with opaque coatings must be far more controllable and less sensitive to damaging the covered components and printed board surfaces and are usually slower. 3. Solubility Most coatings are soluble; however, the solvent required to dissolve a specific coating may also attack the board and/or components. Unless directed by other maintenance actions, the solubility test and solvent use should be limited to isopropyl alcohol. Test coat the surface in a noncritical area by brushing on a small quantity and observing the solubility action. CAUTION Printed board assemblies should not be immersed in harsh solvents. 4. Thermal Removal Use a thermal parting device with controlled heating and without a cutting edge to determine whether the coating can be thermally removed. Start with a low temperature, approximately 100°C, and increase the temperature until the coating is removed. If the coating flows or gums up, the temperature is too hot or the coating is not suitable for thermal removal. 5. Stripability Carefully slit the coating with a sharp blade in a noncritical area and try to peel back from the surface to determine if this method is feasible. Due to the adhesion required of coating materials, stripable techniques without chemical aids is usually very limited. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 4 Number: 2.3.1 Revision: Date: 2/98 IPC-7721 Subject: Coating Removal, Identification of Conformal Coating 6. Thickness Coating thickness is determined by visual inspection. Thin coatings show sharp outlines of the components and almost no fillet at intersection points of part leads to the circuit board. Thick coatings reduce these sharp outlines and show fillets where part leads intersect with the board. Coatings thinner than 0.064 cm are considered thin. Coatings thicker than 0.064 cm are classed as thick. The specific coating to be removed may have one or more of these characteristics and consequently the removal method selected should consider the composite characteristics. See Figure 1 for Conformal Coating Identification. See Table 1 for Conformal Coating Characteristics. See Table 2 for Conformal Coating Removal Methods. EVALUATION NOTES Page 2 of 4 Number: 2.3.1 Revision: Date: 2/98 IPC-7721 Subject: Coating Removal, Identification of Conformal Coating Figure 1 Conformal Coating Identification IPC-7721-1 Page 3 of 4 Number: 2.3.1 Revision: Date: 2/98 IPC-7721 Subject: Coating Removal, Identification of Conformal Coating Characteristics Hard Medium Hard Soft Heat Reaction Surface Bond - Very Strong Surface Bond - Strong Surface Bond - Medium Surface Bond - Light Solvent Reaction Non-porous Surface Glossy Surface Semi-glossy Surface Dull Surface Rubbery Surface Brittle Chips Peels and Flakes Stretches Scratch, Dent, Bend, Tear Table 1 Conformal Coating Characteristics Epoxy U U U U U U Conformal Coating Type Acrylic Polyurethane Silicone Resin U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U Paraxylylene U U U U U U Table 2 Conformal Coating Removal Methods Removal Method Conformal Coating 2.3.2 2.3.3 Solvent Method Peeling Method 2.3.4 Thermal Method 2.3.5 Grinding Scraping Method 2.3.6 Micro Blasting Method Paraxylyene 1 2 3 Epoxy 1 2 3 Acrylic 1 2 3 4 Polyurethane 3 1 2 4 Silicone Thin 1 2 3 4 Silicone Thick 1 2 NOTE: The preferred order for applying removal methods to specific coatings is numerically indicated. These removal methods are listed in ascending order. More than one method may be required. Page 4 of 4 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 2.3.2 Coating Removal, Solvent Method Product Class: R, F, W, C Skill Level: Advanced Level of Conformance: High OUTLINE This procedure uses a solvent to remove surface coatings. This procedure can be use for spot or overall coating removal of conformal coatings or solder resists. Approved solvents may be used to remove specific soluble type coatings on a spot basis by brushing or swabbing the local area with the controlled application of solvent until the area is free of the coating material. If warranted, all the soluble type coating can be removed by immersing and brushing the entire printed board or printed board assembly. To determine the appropriate coating removal procedure the coating must first be identified. Refer to procedure number 2.3.1. Figure 1 Apply tape to outline for coating removal. NOTE Coating removal may require the use of one or more methods. CAUTION Determine, on a module by module basis, the hazards to parts, etc., by short term immersion in the removal solvents. If chloride based or other harsh solvents are used, extreme care must be exercised to prevent damage to base material, component parts, plated-through holes, and solder joints. Some solvent coating removal methods can cause expansion or swelling of the base material which can degrade the printed board or printed board assembly. Under no circumstances should these solvents be used except in a closely controlled process. It is recommended that the printed board or printed board assembly be inspected to ensure that no damage has occurred. Before using any solvent refer to Material Safety Data Sheets. Figure 2 Apply solvent with foam swab to remove coating. REFERENCES 2.1 2.2 2.3.1 2.4.1 2.4.2 Handling Electronic Assemblies Cleaning Coating Removal, Identification of Conformal Coatings Coating Replacement, Solder Resist Coating Replacement, Conformal Coatings/Encapsulants TOOLS AND MATERIALS Brush Cotton Swab Polyimide Tape Knife Suitable Solvent Thermal Parting Tool Wood Stick Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 2.3.2 Revision: Date: 2/98 IPC-7721 Subject: Coating Removal, Solvent Method PROCEDURE – LOCAL SPOT REMOVAL 1. Apply Polyimide tape to outline the area where the coating needs to be removed. (See Figure 1.) 2. Dip the end of a foam swab in stripping solution and apply a small amount to the area of coating to be removed. (See Figure 2.) As an alternative, a small cotton patch can be cut to the size of the area masked (see Figure 1), saturated with the stripping solution, and pressed into intimate contact with the surface of the coating to be removed. The patch will retard the evaporation of certain solvents and reduce exposure time. NOTE Since various substances may be used as coatings, the time required for a given coating to dissolve or soften will vary. Reapply solvent several times as most solvents evaporate rapidly. 3. Rub the treated surface carefully with a brush or wood stick to dislodge the coating. A wedge shaped applicator tip, knife, or heated blade may be effective in removing some coatings, particularly polyurethanes. 4. Neutralize or clean the stripped area and dry. PROCEDURE – OVERALL REMOVAL 1. A single step for removal of all the coating may be completed by providing a continuous flow of solvent. Alternately, process the board in a series of tanks containing mild solvent, starting with a high contamination tank and progressing sequentially to a final, fresh solvent tank. EVALUATION 1. Visual examination or UV light may be used to verify complete removal of coating. NOTES Coating Removal Required at Outlined Areas Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 2.3.3 Coating Removal, Peeling Method Product Class: R, F, W, C Skill Level: Advanced Level of Conformance: High OUTLINE This peeling removal method for coating can be used only under special circumstances. Normally this method is used to remove RTV silicone or other thick rubberylike coating materials. The coating material is removed using a dull knife or otherwise dull blade to slit the coating material and to peel it off the printed board or printed board assembly. To determine the appropriate coating removal procedure the coating must first be identified. Refer to procedure number 2.3.1. NOTE This method is limited to coatings that are rubbery in nature to allow the coating material to be slit into small sections and peeled off the printed board assembly. Figure 1 Slit and peel off coating using a knife or heated blade. REFERENCES 2.1 2.2 2.3.1 2.4.1 2.4.2 Handling Electronic Assemblies Cleaning Coating Removal, Identification of Conformal Coatings Coating Replacement, Solder Resist Coating Replacement, Conformal Coatings/Encapsulants TOOLS AND MATERIALS Heated Blade Knife Wood Sticks Figure 2 Removal complete. PROCEDURE 1. Slit and peel off the coating material with a dull knife or heated dull blade. (See Figure 1.) 2. Repeat as needed until the required material is removed. EVALUATION 1. Visual examination or UV light may be used to verify complete removal of coating. NOTE Coating Removal Required at Outlined Area Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 2.3.3 Revision: Date: 2/98 NOTES IPC-7721 Subject: Coating Removal, Peeling Method Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 2.3.4 Coating Removal, Thermal Method Product Class: R, F, W, C Skill Level: Advanced Level of Conformance: High OUTLINE This coating removal procedure uses a controlled, low temperature, localized heating method for removing thick coatings by an overcuring or softening means. Two methods are covered. The first method uses various shaped, temperature controlled tips, with dull edges to soften and remove the coating. The second method uses a localized controlled jet of hot air or inert gas to soften the coating material which is pushed away or removed by a non-marring tool. These methods do not burn or char either the coating or printed board. CAUTION Soldering irons should not be used for coating removal as their high operating temperatures will cause the coatings to char and possibly delaminate the printed board base material. The use of thinned down soldering iron tips or soldering iron heated thin cutting blades are not recommended since they do not provide controlled heating and may present dangerous sharp edges to the workpiece surface. To determine the appropriate coating removal procedure the coating must first be identified. Refer to procedure number 2.3.1. REFERENCES 2.1 2.2 2.3.1 2.4.1 2.4.2 Handling Electronic Assemblies Cleaning Coating Removal, Identification of Coatings Coating Replacement, Solder Resist Coating Replacement, Conformal Coatings/Encapsulants Figure 1 Apply thermal tip to soften or granulate the material. Figure 2 Apply hot air to the work area and remove overcured coating. TOOLS AND MATERIALS Brush Heated Blade or Thermal Parting Tool Hot Air Tool Knife Small Cutters Wood Sticks Figure 3 Removal complete. PROCEDURE - THERMAL PARTING METHOD 1. Select an appropriate thermal parting tip to suit the workpiece configuration. Set the nominal tip temperature, using the manufacturer’s recommended procedure. 2. Apply the thermal parting tip to the coating, using a light pressure. The coating material will either soften or granulate. Polyurethanes will soften and epoxies will granulate. The tip temperature should be regulated to a point where it will effectively ‘‘break down’’ the coating without scorching or charring. (See Figure 1.) Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 2.3.4 Revision: Date: 2/98 IPC-7721 Subject: Coating Removal, Thermal Method 3. Gradually reduce the coating thickness around the component body without contacting the board surface. Remove as much coating as possible from around component leads to allow easy removal of the leads. Clip leads of component parts that are known to be faulty, thus permitting removal of the part body separately from leads and solder joints. Low pressure air or a brush should be used to remove the loosened coating. 4. Once sufficient coating has been removed, leaving only a small bonded joint between the part body and printed board, heat the component body with the thermal parting tool or hot air jet to weaken the bond beneath the component. 5. Lift the component body free of the printed board using small pliers. NOTE Twist the component prior to removal to shear any remaining epoxy bond to the printed board surface. 6. Once the component body has been removed from the board surface, the remaining coating material can be removed by additional thermal parting. The remaining leads and solder joints are then removed by appropriate solder extraction means. PROCEDURE - HOT AIR METHOD By control of the gas/air temperature, flow rates and jet shape, the hot air method can be applied to almost any workpiece configuration on both the component and solder side of the printed board without damage. Extremely delicate work can be handled in this manner while permitting direct observation of the heating action. 1. Set up the hot air tool per the manufacturer’s instructions. Adjust flow rate and temperature to suit specific coating removal application. CAUTION Never set the gas/air temperature at a level that will cause scorching or charring of the coating material or reflow the solder connections. 2. Apply the heated air jet to work area. Apply light pressure using a wood stick or other non marring tool to remove the softened or overcured coating. All coating around individual leads, solder joints and component bodies can be removed in this manner. (See Figure 2.) 3. When the coating has been removed, use appropriate solder extraction method to remove components if needed. EVALUATION 1. Visual examination or UV light may be used to verify complete removal of coating. NOTES Coating Removal Required at Outlined Area Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 2.3.5 Coating Removal, Grinding/Scraping Method Product Class: R, F, W, C Skill Level: Advanced Level of Conformance: High OUTLINE This coating removal method uses various grinding and scraping tools, depending on the composition of the coating material. A knife or dental style scraper is normally used when a scraping method is desired. A hand held drill is normally used when a grinding technique is desired. A wide variety of rotary abrasive materials including ball mills may be required. To determine the appropriate coating removal procedure the coating must first be identified. Refer to procedure number 2.3.1. CAUTION Abrasion operations can generate electrostatic charges. Figure 1 Scrape away damaged or unwanted coating. REFERENCES 2.1 2.2 2.3.1 2.4.1 2.4.2 Handling Electronic Assemblies Cleaning Coating Removal, Identification of Conformal Coatings Coating Replacement, Solder Resist Coating Replacement, Conformal Coatings/Encapsulants TOOLS AND MATERIALS Ball Mills Brush Cleaner Cleaning Wipes Hand Held Drill Knife Microscope Rubberized Abrasives Scraper Wood Sticks Rubber Eraser Figure 2 Rubberized abrasives used to remove thin, hard coating. PROCEDURE - SCRAPING 1. Clean the area. 2. Remove the damaged or unwanted coating or solder resist using a knife or scraper. Hold the blade perpendicular to the coating and scrape from side to side until the desired material is removed. (See Figure 1.) 3. Remove all loose material and clean the area. Figure 3 Rotary brushes are best used to remove soft coating. PROCEDURE - GRINDING 1. Clean the area. 2. Insert an abrasive tip into the hand held drill. Abrade away the damaged or unwanted coating. Move the tool from side to side to prevent damage to the printed wiring board surface. (See Figure 2.) 3. Remove all loose material and clean the area. Figure 4 Removal complete. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 2.3.5 Revision: Date: 2/98 IPC-7721 Subject: Coating Removal, Grinding/Scraping Method NOTE Rubberized abrasives of the proper grade and grit are ideally suited for removing thin hard coatings from flat surfaces but not for soft coatings since these would cause the abrasive to ‘‘load up’’ with coating material and become ineffective. Rotary brushes are better suited than rubberized abrasives on contoured or irregular surfaces, such as soldered connections, etc., since the bristles will conform to surface irregularities while removing hard or soft coatings. (See Figure 3.) NOTE The procedure for removing thick coatings is primarily to reduce their thickness to a thin coating and then to remove the remaining thin coating by the scraping method. EVALUATION 1. Visual examination or UV light may be used to verify complete removal of coating. NOTES Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 2.3.6 Coating Removal, Micro Blasting Method Product Class: R, F, W, C Skill Level: Advanced Level of Conformance: High OUTLINE This coating removal method uses a micro abrasive blasting system and a very fine soft abrasive powder. The powder is propelled through a small nozzle toward the area where the coating needs to be removed. To determine the appropriate coating removal procedure the coating must first be identified. Refer to procedure number 2.3.1. CAUTION Micro blasting will generate substantial static charges. The work area should be flooded with ionized air and the printed wiring board assembly should be grounded whenever possible. Figure 1 Apply tape to outline area for coating removal. REFERENCES 2.1 2.2 2.3.1 2.4.1 2.4.2 Handling Electronic Assemblies Cleaning Coating Removal, Identification of Conformal Coatings Coating Replacement, Solder Resist Coating Replacement, Conformal Coatings/Encapsulants TOOLS AND MATERIALS Abrasive Powder Polyimide Tape Micro Blasting System Removable Mask Stencils Figure 2 Remove coating using micro blasting system. PROCEDURE 1. Clean the area. 2. Select the appropriate abrasive blasting powder and nozzle size. Set the air pres- sure at the desired setting per equipment manufacturer’s instructions. 3. Apply polyimide tape or other masking material to protect the printed wiring board surface as needed. (See Figure 1.) Masking materials can consist of tapes, curable liquid masks or reusable stencils. 4. If the printed wiring board has static sensitive components, insert the entire printed wiring board into a shielded bag. Only the area needing rework should be exposed. Ground the printed wiring board to dissipate static charges if needed. 5. Insert the printed wiring board into the blasting chamber and blast away the damaged or unwanted coating or solder resist. Slowly move the nozzle along the area where the coating is to be removed. (See Figure 2.) 6. Blow off the blasting dust and clean the area. Figure 3 Removal complete. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 2.3.6 Revision: Date: 2/98 IPC-7721 Subject: Coating Removal, Macro Blasting Method EVALUATION 1. Visual examination or UV light may be used to verify complete removal of coating. NOTES Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 2.4.1 Coating Replacement, Solder Resist Product Class: R, F, W, C Skill Level: Intermediate Level of Conformance: High OUTLINE This method is used to replace solder resist or coatings on printed wiring boards. Most replacement coatings can be applied by dipping, brushing or spraying. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling TOOLS & MATERIALS Cleaner Cleaning Wipes Color Agent, Various Colors Brush Epoxy or Replacement Coating Foam Swab Heat Lamp Microscope Oven Figure 1 Apply polyimide tape if needed. PROCEDURE 1. Clean the area. CAUTION Surfaces to be coated must be thoroughly cleaned prior to coating to ensure adequate adhesion, minimized corrosion, and optimized electrical properties. 2. If needed, apply Polyimide tape to outline the area where the solder resist will be applied. (See Figure 1.) 3. Mix the epoxy or replacement coating. If desired, add color agent to the mixed epoxy to match the printed wiring board color. 4. Apply the replacement coating to the board surface as required. A brush or foam swab may be used to apply and spread the epoxy or replacement coating. (See Figure 2.) 5. Cure the replacement coating per the manufacturer’s instructions. Figure 2 Apply replacement coating with a foam swab to create a texture. CAUTION Some components may be sensitive to high temperature. EVALUATION 1. Visual examination for texture, color match, adhesion and coverage. 2. Electrical tests to conductors around the repaired area as applicable. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 2.4.1 Revision: Date: 2/98 NOTES IPC-7721 Subject: Coating Replacement, Solder Resist Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 2.4.2 Coating Replacement, Conformal Coatings/ Encapsulants Product Class: R, F, W, C Skill Level: Intermediate Level of Conformance: High OUTLINE This method is used to replace conformal coatings and encapsulants on printed wiring boards. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling TOOLS & MATERIALS Cleaner Cleaning Wipes Brush Epoxy or Replacement Coating Foam Swab Heat Lamp Microscope Oven Figure 1 Apply replacement coating with foam swab to create a texture. PROCEDURE 1. Clean the area. CAUTION Surfaces to be coated must be thoroughly cleaned prior to coating to ensure adequate adhesion, minimized corrosion, and optimized electrical properties. 2. If needed, apply Polyimide tape to outline the area where the coating will be applied. (See Figure 1.) 3. If required, bake the printed wiring board prior to the application of the replacement coating. 4. Mix the replacement coating. 5. Apply the replacement coating to the board surface as required. A brush or foam swab may be used to apply and spread the replacement coating. (See Figure 2.) For large surfaces, apply the replacement coating with a foam swab to create a texture. 6. Cure the replacement coating per the manufacturer’s instructions. Figure 2 Repair complete. CAUTION Some components may be sensitive to high temperature. EVALUATION 1. Visual examination for texture, color match, adhesion and coverage. 2. Electrical tests to conductors around the repaired area as applicable. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 2.4.2 Revision: Date: 2/98 NOTES IPC-7721 Subject: Coating Replacement, Conformal Coatings/Encapsulants Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 2.5 Baking and Preheating OUTLINE This procedure covers baking and preheating of printed boards and printed board assemblies to prepare the product for the subsequent operations. Included are steps for: A. Baking Baking is used to eliminate absorbed moisture. Whenever possible printed wiring boards and printed wiring board assemblies should be baked prior to soldering, unsoldering and coating operation to prevent blistering, measling or other laminate degradation. B. Preheating Preheating is used to promote the adhesion of subsequent materials to the board surfaces and to raise the temperature of the printed wiring board to allow soldering and unsoldering operations to be completed more quickly. CAUTION Baking and preheating procedures must be carefully selected to ensure that temperature and time cycles used do not degrade the product. Environmental conditions must also be carefully considered to ensure that vapors, gases, etc., generated during the heating process do not contaminate the product’s surfaces. CAUTION To prevent fluxes or other contaminates from being baked onto the board surface, thoroughly clean the board or assembly prior to baking or preheating. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning TOOLS & MATERIALS Cleaner Cleaning Wipes Oven EVALUATION Product Class: R, F, W, C Skill Level: Intermediate Level of Conformance: High Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 2.5 Revision: Date: 2/98 NOTES IPC-7721 Subject: Baking and Preheating Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Epoxy Mixing and Handling Number: 2.6 Product Class: R, F, W, C Skill Level: Intermediate Level of Conformance: High OUTLINE This procedure covers epoxy mixing and handling. The epoxy covered by this procedure has multiple uses including solder resist repair, base board repair, circuitry over-coating and delamination repair. NOTE For high strength or high temperature applications two part epoxies will generally have the best properties. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating Figure 1 Mix resin and activator inside package of prepackaged epoxy. TOOLS AND MATERIALS Balance/Scale Cleaner Color Agent, Various Colors Epoxy Foam Swab Heat Lamp Mixing Cup Mixing Stick Oven Wipes PRINTED WIRING BOARD PREPARATION The area where the epoxy is to be applied should be prepared prior to mixing the epoxy. This preparation may include preheating the affected area to improve absorption of the applied epoxy. The entire printed wiring board may also be heated in an oven or with a heat lamp. Figure 2 Apply epoxy. Foam swab may be used to add texture. CAUTION Some components may be sensitive to high temperatures. CAUTION Avoid skin contact with epoxy materials. PROCEDURE - Prepackaged Two Part Epoxy 1. Remove the clip separating the resin and activator. Mix by squeezing both halves together with your fingers. Mix for at least one minute to ensure a complete mix of the resin and activator. (See Figure 1.) 2. Cut open one end of the epoxy tube and squeeze the contents into a mixing cup. Mix again with a mixing stick to ensure a thorough mixture of the resin and activator. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 2.6 Revision: Date: 2/98 IPC-7721 Subject: Epoxy Mixing and Handling NOTE For bubble free epoxy, remove the clip separating the resin and activator. Cut open one end of the Epoxy tube and squeeze the contents into a mixing cup. Slowly stir the mixture with the mixing stick. Be sure to stir the mixture for at least 2 minutes to ensure that all the resin and actuator have completely mixed. 3. If needed, add color agent to the mixed epoxy. Stir slowly to prevent bubbles. CAUTION Be sure the color agent is compatible with the epoxy mixture. 4. Apply or use as needed. (See Figure 2.) 5. Cure the epoxy per the manufacturer’s recommendations. EVALUATION 1. Visual examination of epoxy for texture and color match. 2. Testing of epoxy surface for complete cure. 3. Electrical tests as applicable. NOTES Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 2.7.1 Legend/Marking, Stamping Method Product Class: R, F, W, C Skill Level: Intermediate Level of Conformance: High OUTLINE This method can be used to add, change or replace legend and markings on printed boards or printed board assemblies. This method uses epoxy ink and an ink stamp to place the legends on the printed board surface in much the same manner as taking a ‘‘finger print.’’ REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling Figure 1 Apply legend using a peg stamp. TOOLS & MATERIALS Cleaner Cleaning Wipes Epoxy Ink Ink Plate Ink Roller Knife Microscope Oven Peg Stamps PROCEDURE 1. Clean the area. 2. Scrape off any remaining character or legend with a knife and clean the area. CAUTION Abrasion operations can generate electrostatic charges. 3. Select the appropriate characters from the peg stamp set or have a special stamp made up. 4. Mix the epoxy ink. White is the most common color. Spread a thin even coating of the epoxy ink on the ink plate or on a smooth surface. 5. Gently press the peg stamp into the epoxy coating to coat the character surface. 6. Gently press the peg stamp onto the desired location on the printed wiring board surface. (See Figure 1.) 7. Cure the epoxy ink per the manufacturer’s instructions. Figure 2 Completed legend repair. EVALUATION 1. Visual examination for proper characters, positioning and legibility. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 2.7.1 Revision: Date: 2/98 NOTES IPC-7721 Subject: Legend/Marking, Stamping Method Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 2.7.2 Legend/Marking, Hand Lettering Method Product Class: R, F, W, C Skill Level: Intermediate Level of Conformance: High OUTLINE This method can be used to add, change or replace legend and markings on printed boards or printed board assemblies. This method uses epoxy ink and a pen to hand letter the legends on the printed board surface. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling Figure 1 Apply legend using a wood stick dipped in epoxy ink. TOOLS & MATERIALS Cleaner Cleaning Wipes Epoxy Ink Ink Pen Knife Microscope Oven Wood Stick PROCEDURE 1. Clean the area. 2. Scrape off any remaining character or legend with a knife and clean the area. CAUTION Abrasion operations can generate electrostatic charges. 3. Mix the epoxy ink. White is the most common color. 4. Sharpen a wood stick and dip the pointed end into the epoxy ink. Hand letter the legend or markings as needed. (See Figure 1.) 5. Cure the epoxy ink per the manufacturer’s instructions. Figure 2 Completed legend repair. EVALUATION 1. Visual examination for proper characters, positioning and legibility. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 2.7.2 Revision: Date: 2/98 NOTES IPC-7721 Subject: Legend/Marking, Hand Lettering Method Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 2.7.3 Legend/Marking, Stencil Method Product Class: R, F, W, C Skill Level: Intermediate Level of Conformance: High OUTLINE This method can be used to add, change or replace legend and markings on printed boards or printed board assemblies. This method uses epoxy ink and a brush or roller technique. A stencil is used to outline the characters. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling Figure 1 Replace legend using a stencil. TOOLS & MATERIALS Cleaner Cleaning Wipes Epoxy Ink Ink Plate Ink Roller Knife Microscope Oven Stencil PROCEDURE 1. Clean the area. 2. Scrape off any remaining character or legend with a knife and clean the area. CAUTION Abrasion operations can generate electrostatic charges. 3. Select the appropriate stencil or have a special stencil made up. (See Figure 1.) 4. Mix the epoxy ink. White is the most common color. Spread a thin even coating of the epoxy ink on the ink plate or on a smooth surface. 5. Position the stencil on the printed wiring board surface and hold in place firmly. 6 Roll or brush the ink onto the stencil. Do not smudge characters or apply excess ink. 7. Cure the epoxy ink per the manufacturer’s instructions. Figure 2 Completed legend repair. EVALUATION 1. Visual examination for proper characters, positioning, and legibility. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 2.7.3 Revision: Date: 2/98 NOTES IPC-7721 Subject: Legend/Marking, Stencil Method Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 3.1 Delamination/Blister Repair, Injection Method Product Class: R Skill Level: Advanced Level of Conformance: High OUTLINE This method is used to repair mechanical or thermal blisters or delaminations in printed wiring board laminated base materials. The blister is sealed by injecting a low viscosity epoxy into the blister/delamination void. CAUTION This method can only be used when the laminate base material has separated sufficiently to allow the epoxy to flow throughout the void area. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling Figure 1 Drill into the delamination blister TOOLS & MATERIALS Ball Mill, #1/2 Cleaner Cleaning Wipes Epoxy Epoxy Cartridge with Tip Epoxy Injection System, Optional Hand Held Drill Heat Lamp Oven Scraper Vacuum Source, Optional Figure 2 Inject epoxy into the delamination blister. PROCEDURE 1. Clean the area. 2. Drill into delamination blister with the dental style drill and ball mill. Drill in an area clear of circuitry or components. Drill at least two holes opposite each other around the perimeter of the delamination. (See Figure 1.) Brush away all loose material. CAUTION Be careful not to drill too deep exposing internal conductors or planes. CAUTION Abrasion operations can generate electrostatic charges. 3. Bake the printed wiring board to remove any entrapped moisture. Do not allow the printed wiring board to cool prior to injecting the epoxy. CAUTION Some components may be sensitive to high temperature. 4. Mix the epoxy. See manufacturers instructions on how to mix epoxy without bubbles. Figure 3 Completed Repair. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 3.1 Revision: Date: 2/98 IPC-7721 Subject: Delamination/Blister Repair, Injection Method CAUTION Exercise care to prevent bubbles in the epoxy mixture. 5. Pour the epoxy into the epoxy cartridge. 6. Inject the epoxy into one of the holes in the delamination. (See Figure 2.) The heat retained in the printed wiring board will improve the flow characteristics of the epoxy and will draw the epoxy into the void area filling it completely. 7. If the void does not fill completely, the following procedures may be used: A. Apply light local pressure on the board surface starting at the fill hole, slowly proceeding to the vent hole. B. Apply vacuum to the vent hole to draw the epoxy through the void. 8. Cure the epoxy per the manufacturers recommendation. 9. Scrape away any excess epoxy using a knife or scraper. NOTE If needed, apply additional thin coating to seal any scrapped areas. EVALUATION 1. Visual examination for texture and color match. 2. Electrical tests to conductors around the repaired area as applicable. NOTES Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 3.2 Bow and Twist Repair Product Class: R, W Skill Level: Advanced Level of Conformance: Medium OUTLINE This method is used to eliminate, or reduce the bow and twist, or warping of printed wiring boards. The warping is removed by controlled heating and cooling of the printed wiring board while under restraint. CAUTION This repair method is most suitable for FR-4, GE or GF substrate base materials having glass transition temperatures below 125°C. The bake/time cycle will have to be adjusted depending on the base material glass transistion temperature. CAUTION This process uses high temperatures. Some components may be sensitive to high temperature and should be removed if this procedure will adversely affect them. Figure 1 Check edge deflection for maximum wrap. CAUTION High temperatures will cause oxidation of solderable surfaces. NOTE Bow and twist should not be repaired unless sited as a defect. REFERENCES 2.1 Handling Electronic Assemblies 2.5 Baking and Preheating Figure 2 Clamp restraint bars to edge needing rework. TOOLS & MATERIALS Base Plate Caliper or Pin Gauges Oven Restraint Bars Restraint Clamps PROCEDURE 1. Check the deflection to determine if rework is needed. (See Figure 1.) NOTE Bow and twist after soldering shall not exceed 1.5% for through-hole printed wiring boards and 0.75% for surface mount printed wiring boards. The bow and twist shall not be sufficient to cause difficulties during placement, soldering and testing operations. Before dispositioning printed wiring boards with bow and twist as scrap, keep in mind how the printed wiring board is mounted in it’s final destination. Keep in mind ‘‘form, fit and function’’ without jeopardizing reliability. 2. Place the restraint bars along the edges that require rework. (See Figure 2.) CAUTION Components or parts that will interfere with the restraint bars should be removed. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 3.2 Revision: Date: 2/98 IPC-7721 Subject: Bow and Twist Repair 3. If the printed wiring board is warped along more than one edge or more than one plane, clamp the entire printed wiring board to the base plate. 4. Place the printed wiring board, restraint bars and base plate into the oven. Bake for 1 hour at 125°C. NOTE If possible, after the 1 hour bake cycle, shut off the oven and leave the printed wiring board inside. This will allow the printed wiring board to slowly cool to room temperature improving stress relief. 5. Remove from the oven and allow to cool to room temperature. 6. Remove restraint bars. 7. Check the edges deflection using a caliper or pin gauges. EVALUATION 1. Check for marks or damage along edges. 2. Electrical tests as applicable. NOTES Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Hole Repair, Epoxy Method Number: 3.3.1 Product Class: R, W Skill Level: Advanced Level of Conformance: High OUTLINE This method is used to repair cosmetic defects or minor damage to an unsupported tooling or mounting hole. The hole may have component leads, wires, fasteners, pins, terminals or other hardware run through it. This repair method uses high strength epoxy to restore the damaged surface surrounding the hole. This method can be used on single sided, double sided or multilayer printed wiring boards and assemblies. CAUTION Damaged inner-layer connections may require surface wire adds. Figure 1 Mill away damaged material. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling TOOLS & MATERIALS Ball Mills Cleaner Color Agent, Various Colors Epoxy Hand Held Drill Polyimide Tape Knife Mixing Sticks Oven Wipes Figure 2 Apply epoxy with a small wood stick sharpened at one end. PROCEDURE 1. Clean the area. 2. Mill away the damaged board base material using the hand held drill and ball mill. All damaged base board material and solder resist must be removed. No fibers of laminate material should be exposed at the surface peremiter of the hole. (See Figure 1.) NOTE To clearly see that all damaged material has been removed, flood the area with alcohol or solvent. Damaged internal fibers of the base material will show up clearly. 3. Remove all loose material and clean the area. 4. Where needed, apply Polyimide tape to protect exposed parts of the printed wiring board. Tape may be required inside the hole. If epoxy reduces the inside diameter, the hole may have to be redrilled after the epoxy has cured. NOTE The printed wiring board may be preheated prior to filling the area with epoxy. A preheated printed wiring board will allow the epoxy to easily flow and level out. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 3.3.1 Revision: Date: 2/98 IPC-7721 Subject: Hole Repair, Epoxy Method Epoxy applied to an unheated printed wiring board may settle below the printed wiring board surface as the epoxy cures. CAUTION Some components may be sensitive to high temperatures. 5. Mix the epoxy. If desired, add color agent to the mixed epoxy to match the printed wiring board color. 6. Coat the area with epoxy up to and flush with the printed wiring board surface. A small wood stick may be used to apply and spread the epoxy. (See Figure 2.) NOTE A slight overfill of epoxy may be desired to allow for shrinkage when epoxy cures. 7. Cure epoxy per the manufacturers recommended instructions. 8. After the epoxy has cured, remove the tape. 9. If needed, use the knife or scraper and scrape off any excess epoxy. Scrape until the new epoxy surface is level with the surrounding printed wiring board surface. NOTE Apply surface coating to match prior coating as required. 10. Remove all loose material. Clean the area. EVALUATION 1. Visual examination for texture and color match. 2. Hole size measurement to specification 3. Electrical tests to conductors around the repaired area as applicable. NOTES Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 3.3.2 Hole Repair, Transplant Method Product Class: R, W Skill Level: Expert Level of Conformance: High OUTLINE This method is used to repair severe damage to a hole or to modify the size, shape or location of an unsupported tooling or mounting hole. The hole may have component leads, wires, fasteners, pins, terminals or other hardware run through it. This repair method uses a dowel of matching board material and high strength epoxy to secure the dowel in place. After the new material is bonded in place a new hole can be drilled. This method can be used on single sided, double sided or multilayer printed wiring boards and assemblies. CAUTION Damaged inner-layer connections may require surface wire adds. Figure 1 New hole is milled to encompass entire damaged area. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling TOOLS & MATERIALS Base Material Rod, Various Diameters Cleaner Epoxy Hand Held Drill Polyimide Tape Knife Microscope Mixing Sticks Oven Precision Drill Press Razor Saw Wipes Figure 2 Precision drill press with microscrope attachment. PROCEDURE 1. Clean the area. 2. Drill out the damaged or improperly sized hole using a carbide end mill or drill. Mill the hole using a precision drill press or milling machine for accuracy. The diameter of the cutting tool should be as small as possible yet still encompass the entire damaged area. (See Figures 1 and 2.) Figure 3 Place replacement dowel in position and bond with epoxy. NOTE Abrasion operations can generate electrostatic charges. 3. Cut a piece of replacement base material rod. Base material rod is made from FR-4 dowel stock. Cut the length approximately 12.0 mm longer than needed. 4. Clean the reworked area. 5. Use Polyimide tape to protect exposed parts of the printed wiring board bordering the rework area. 6. Mix the epoxy. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Figure 4 Cut off excess material and redrill holes as required. Page 1 of 2 Number: 3.3.2 Revision: Date: 2/98 IPC-7721 Subject: Hole Repair, Transplant Method 7. Coat both the dowel and the hole with epoxy and fit together. Apply additional epoxy around perimeter of new material. (See Figure 3.) Remove excess epoxy. 8. Cure the epoxy per the manufactures instructions. CAUTION Some components may be sensitive to high temperatures. 9. Remove tape and cut off the excess material using the razor saw. Mill or file the dowel flush with the board surface. 10. Complete the procedure by redrilling holes and adding circuitry as required. (See Figure 4.) NOTE Apply surface coating to match prior coating as required. 11. Clean the reworked area. EVALUATION 1. Visual and dimensional examination of the reworked area for conformance to drawings and specifications. NOTES Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 3.4.1 Key and Slot Repair, Epoxy Method Product Class: R, W Skill Level: Advanced Level of Conformance: High OUTLINE This method is used to repair minor damage to a key slot, or other cutout in a printed board or assembly. The area is repaired using high strength epoxy. CAUTION Care should be taken to limit the application of epoxy to the specific areas desired and to avoid damage to the conductive patterns, contacts and components. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling Figure 1 Mill away the damaged board base material. TOOLS & MATERIALS Cleaner Cleaning Wipes Color Agent, Various Colors Epoxy Hand Held Drill Polyimide Tape Knife Milling Machine Mixing Sticks Oven Precision Drill Press Scraper Figure 2 Apply epoxy to the edges of the key slot. PROCEDURE 1. Clean the area to be filled, including the edges. 2. Mill away the damaged board base material using a hand held drill and ball mill. All damaged base board material must be removed. No fibers of laminate material should be exposed at the surface of the keyslot. (See Figure 1.) NOTE To clearly see that all damaged material has been removed, flood the area with alcohol or solvent. Damaged internal fibers of the base material will show up clearly. CAUTION Abrasion operations can generate electrostatic charges. 3. Remove all loose material and clean the area. 4. Apply Polyimide tape to the surface of the printed wiring board adjacent to the slot. The tape should protect any adjacent contacts or components. NOTE The printed wiring board may be preheated prior to filling the area with epoxy. A preheated printed wiring board will allow the epoxy to easily flow and level out. Epoxy applied to an unheated printed wiring board may settle below the printed wiring board surface as the epoxy cures. Figure 3 Complete key slot repair. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 3.4.1 Revision: Date: 2/98 IPC-7721 Subject: Key and Slot Repair, Epoxy Method 5. Mix the epoxy. If desired, add color agent to the mixed epoxy to match the printed wiring board color. 6. Apply a small amount of epoxy to the edges of the slot. A mixing stick sharpened at the end may be used to apply the epoxy. (See Figure 2.) NOTE A slight overfill of epoxy may be desired to allow for shrinkage when epoxy cures. NOTE The printed wiring board may be turned on its side to keep the epoxy in place while it cures. 7. Cure the epoxy per the manufacturers instructions. CAUTION Some components may be sensitive to high temperature. 8. After the epoxy has cured remove the tape. 9. If needed use the knife or scraper and scrape off any excess epoxy. 10. If precision is required, machine the edges of the slot using a milling machine or precision drill and appropriate milling cutter. Use great care to correctly relocate the slot. NOTE If needed, apply additional thin coating to seal any scrapped areas. 11. Clean the area. EVALUATION 1. Visual examination and measurement of key slot location and dimension. NOTES Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 3.4.2 Key and Slot Repair, Transplant Method Product Class: R, W Skill Level: Expert Level of Conformance: High OUTLINE This method is used to modify or repair a key slot, or other cutout in a printed board or assembly. A replacement piece of matching board material is epoxied into the area needing repair. A new cut is then machined into the repaired area if needed. CAUTION Care should be taken to limit the application of epoxy to the specific areas desired and to avoid damage to the conductive patterns, contacts and components. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling Figure 1 Mill out damaged area using a carbide end mill. TOOLS & MATERIALS Ball Mills, Carbide Base Material, Various Sizes Carbide Saw Cleaner Cleaning Wipes Epoxy End Mills Hand Held Drill Polyimide Tape Knife Milling Machine Mixing Stick Oven Precision Drill Press Scraper Figure 2 Cut a groove into both sides of the key slot. PROCEDURE 1. Clean the area to be filled, including the edges. 2. Mill out the damaged area using a milling machine or precision drill system and carbide end mill. (See Figure 1.) CAUTION Abrasion operations can generate electrostatic charges. 3. Clean the area. Figure 3 Machine a tongue onto both sides of replacement material. 4. Install carbide saw into the hand held drill. Set the speed to maximum and machine a groove in the edge of the printed wiring board where the new base material will be installed. The groove must be centered in the edge to ensure that the new piece will fit properly. The groove width should be approximately 1/3 of the printed wiring board thickness. The groove depth should be be approximately double the groove width. (See Figure 2.) 5. Cut a piece of replacement base board material that is the same thickness and type as the printed wiring board. The replacement piece should be longer than the length of the slot to allow for ease of handling. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Figure 4 Insert the replacement piece into the slot. Page 1 of 2 Number: 3.4.2 Revision: Date: 2/98 IPC-7721 Subject: Key and Slot Repair, Transplant Method 6. Install an end mill into the chuck of the drill press. Machine a tongue onto both sides of the replacement piece. The dimensions of the tongue should match the size of the milled groove. (See Figure 3.) 7. Where required apply tape to protect exposed parts of printed wiring board bordering the prepared area. 8. Carefully check the fit of the replacement piece and then clean both the replacement piece and the slot. The replacement base material should fit firmly into the slot so that it will not move or fall out when epoxied in place. 9. Apply tape to the surface of the printed wiring board adjacent to the slot. The tape should protect any adjacent contacts or components. 10. Mix the epoxy. 11. Apply a small amount of epoxy to the edges of the replacement piece and to the inside edges of the slot. 12. Insert the replacement piece into the slot. Check alignment. Remove excess epoxy. (See Figure 4.) 13. If needed, apply additional epoxy to the edges of the slot. A wood stick sharpened at the end may be used to apply the epoxy. 14. Cure the epoxy per the manufacturers instructions. CAUTION Some components may be sensitive to high temperature. 15. After the epoxy has cured remove the tape. 16. If needed use the knife or scraper and scrape off any excess epoxy. NOTE If needed, apply additional thin coating to seal any scrapped areas. 17. Clean the area. 18. Cut off excess length of replacement material and file to match contour of existing edge. (See Figure 5.) 19. If a new slot is needed, machine using milling machine and appropriate milling cutter. Use great care to correctly relocate the slot. 20. Clean the area. Figure 5 Cut off excess material and file to match edge. EVALUATION 1. Visual examination and measurement of key slot location and dimension. NOTES Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 3.5.1 Base Material Repair, Epoxy Method Product Class: R, W Skill Level: Advanced Level of Conformance: High OUTLINE This procedure is used to repair minor damage to printed wiring board base material. Scrapes and scratches in the board base material may be caused by accidents during handling. Burns in the base material may be caused by improper use of soldering and desoldering tools. CAUTION This method may be used when the damage extends deep into the base material, but not completely through. If the base board material is damaged completely through, see Procedure No. 3.5.2 or 3.5.3. Figure 1 Scrape away damaged base board material with a knife. CAUTION Surface conductors may need to be replaced in the damaged area. Be sure that the appropriate conductor diagrams, or photographs reflecting the original conductors are available so that they may be replaced after repairing the base board material. Damage to internal conductors or planes may have to be restored using surface wires. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling Figure 2 Commercially available hand held drill. TOOLS & MATERIALS Ball Mills, Carbide Cleaner Color Agent, Various Colors Epoxy Hand Held Drill Halogen Light Heat Lamp Polyimide Tape Knife Microscope Oven Scraper Wipes PROCEDURE 1. Clean the damaged area. 2. Scrape away the damaged board base material using a knife. All damaged base board material and solder resist must be removed at the surface. (See Figure 1.) See step 2A for alternate method. NOTE To clearly see that all damaged material has been removed, flood the area with alcohol or solvent. Damaged internal fibers of the base material will show up clearly. Figure 3 An undercut to enhance mechanical strength. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Figure 4 Apply the epoxy with a wood stick sharpened at the end. Page 1 of 2 Number: 3.5.1 Revision: Date: 2/98 IPC-7721 Subject: Base Material Repair, Epoxy Method CAUTION Abrasion operations can generate electrostatic charges. 2A. Mill away the damaged board base material using dental style drill and ball mill. All damaged base board material and solder resist must be removed. (See Figure 2.) NOTE An undercut to enhance mechanical strength may be desired for class 3 product. (See Figure 3.) 3. Remove all loose material and clean the area. 4. Where needed, apply tape to protect exposed parts of printed wiring board. NOTE The printed wiring board may be preheated prior to filling the area with epoxy. A preheated printed wiring board will allow the epoxy to easily flow and level out. Epoxy applied to an unheated printed wiring board may settle below the printed wiring board surface as the epoxy cures. 5. Mix the epoxy. If desired, add color agent to the mixed epoxy to match the printed wiring board color. 6. Fill the area with epoxy up to and flush with the printed wiring board surface. No fibers of laminate material should be exposed. A wood stick sharpened at the end may be used to apply and spread the epoxy. For large areas, apply the epoxy with a foam swab to create a texture in the surface. (See Figures 4 and 5.) NOTE A slight overfill of epoxy may be desired to allow for shrinkage when epoxy cures. NOTE Epoxy may be applied using a foam swab to restore the surface appearance. 7. Cure the epoxy per the manufacturer’s instructions. CAUTION Some components may be sensitive to high temperature. 8. After the epoxy has cured remove the tape. 9. If needed, use a knife or scraper and scrape off any excess epoxy. Scrape until the new epoxy surface is level with the surrounding printed wiring board surface. 10. Remove all loose material. Clean the area. NOTE If needed, apply an additional thin coating to seal any scraped areas. Figure 5 Apply the epoxy with a foam swab to create a texture in the surface. EVALUATION 1. Visual examination for texture and color match. 2. Electrical tests to conductors around the repaired area as applicable. NOTES Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 3.5.2 Base Material Repair, Area Transplant Method Product Class: R, W Skill Level: Expert Level of Conformance: High OUTLINE This procedure is used to repair mechanical or thermal damage to printed wiring board base material. This method is used when extended areas of base material must be completely replaced. This method may be used on single sided, double sided or multilayer printed wiring boards or assemblies. CAUTION Surface conductors may need to be replaced in the damaged area. Be sure that the appropriate conductor diagrams, or photographs reflecting the original conductors are available so that they may be replaced after repairing the base board material. Damage to internal conductors or planes may have to be restored using surface wires. Figure 1 Mill away damaged base material. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling TOOLS & MATERIALS Ball Mills, Carbide Base Board Material Carbide Saw Cleaner Cleaning Wipes Color Agent, Various Colors End Mills, Carbide Epoxy Hand Held Drill Heat Lamp Polyimide Tape Knife Oven Precision Drill Press Razor Saw Scraper Figure 2 Bevel edge using a hand held drill or file. PROCEDURE 1. Clean the area 2. Mill away the damaged board material using a hand held drill and ball mill. Remove all evidence of the damaged material. No fibers of laminate material should be exposed. At the surface file the edges to ensure that the opening is rectangular or uniform in shape. (See Figure 1.) CAUTION Abrasion operations can generate electrostatic charges. 3. Clean the area. 3A. Bevel the edge using a hand held drill and ball mill or using a file. (See Figure 2.) Figure 3 Mill a step into the edge of the PC board. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Figure 4 Mill a step onto the edge of the replacement base material. Page 1 of 2 Number: 3.5.2 Revision: Date: 2/98 IPC-7721 Subject: Base Material Repair, Area Transplant Method CAUTION Exercise care to avoid damage to any internal conductors. If any internal conductors are damaged, surface wires may be required to restore electrical connection. 3B. Install an end mill into the chuck of a precision drill press. Set the speed to maximum and machine a step or lap joint in the edge of the printed wiring board where the new base material will be installed. The depth and width of the step should be approximately 1/2 of the printed wiring board thickness. (See Figure 3.) 4. Cut or machine a piece of replacement base board material that is the same thickness and type as the piece removed. The replacement piece must be precisely the same size and shape of the opening including the step joint. 5. Install an end mill into the chuck of a precision drill press. Machine a step onto the entire mating edge of the replacement base material. The dimensions of the step should match the size of the step in the printed wiring boardmilled groove. (See Figure 4.) 6. Where required apply Polyimide tape to protect exposed parts of printed wiring board bordering the prepared area. 7. Check the fit to be sure the new base material properly mates with the step in the printed wiring board. 8. Mix the epoxy. 9. Coat both the tongue and groove surfaces with epoxy and fit together. (See Figure 5.) Remove excess epoxy. 10. Cure the epoxy per the manufacturers instructions. CAUTION Some components may be sensitive to high temperature. 11. After the epoxy has cured remove the Polyimide tape. 12. If needed scrape off any excess epoxy using a scraper or knife. NOTE If needed, apply additional thin coating to seal any scrapped areas. 13. Clean the area. 14. Complete by drilling holes, slots, etc. or adding circuitry as required. 15. If solder resist replacement or conformal coating is needed see appropriate procedure. Figure 5 Bond replacement piece in place. Figure 6 Completed repair. EVALUATION 1. Dimensions of area replaced should be checked to conform to specifications required. NOTES Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 3.5.3 Base Material Repair, Edge Transplant Method Product Class: R, W Skill Level: Expert Level of Conformance: High OUTLINE This procedure is used to repair mechanical or thermal damage to printed wiring board base material. This method is used when extended areas of base material must be completely replaced. This method may be used on single sided, double sided or multilayer printed wiring boards or assemblies. CAUTION Surface conductors may need to be replaced in the damaged area. Be sure that the appropriate conductor diagrams, or photographs reflecting the original conductors are available so that they may be replaced after repairing the base board material. Damage to internal conductors or planes may have to be restored using surface wires. Figure 1 Cut away damaged base material. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling TOOLS & MATERIALS Ball Mills, Carbide Base Board Material Carbide Saw Cleaner Cleaning Wipes Color Agent, Various Colors End Mills, Carbide Epoxy Hand Held Drill Heat Lamp Polyimide Tape Knife Oven Precision Drill Press Razor Saw Scraper Figure 2 Cut a groove into the edge of the PC board. PROCEDURE 1. Clean the area 2. Cut away the damaged board material using a razor saw or milling cutter. Remove all evidence of the damaged material. No fibers of laminate material should be exposed. File the edge to ensure that the edge is flat. (See Figure 1.) Figure 3 Mill a tongue onto the edge of the replacement base material. CAUTION Abrasion operations can generate electrostatic charges. CAUTION Exercise care to avoid damage to any internal conductors. If any internal conductors are damaged, surface wires may be required to restore electrical connection. 3. Clean the area. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Figure 4 Check fit of new base material. Page 1 of 2 Number: 3.5.3 Revision: Date: 2/98 IPC-7721 Subject: Base Material Repair, Edge Transplant Method 4. Install a carbide saw into the hand held drill. Set the speed to maximum and machine a groove in the edge of the printed wiring board where the new base material will be installed. The groove must be centered in the edge to ensure that the new piece will fit properly. The groove width should be approximately 1/3 of the printed wiring board thickness. The groove depth should be approximately double the groove width. (See Figure 2.) 5. Cut a piece of replacement base board material that is the same thickness and type as the piece removed. The replacement piece may be oversized, the excess material will be removed after the replacement piece has been epoxied in place. 6. Install an end mill into the chuck of a precision drill press. Machine a tongue onto the entire mating edge of the replacement base material. The dimensions of the tongue should match the size of the milled groove. (See Figure 3.) 7. Where required apply Polyimide tape to protect exposed parts of printed wiring board bordering the prepared area. 8. Check the fit to be sure the new base material properly mates with the groove in the printed wiring board. (See Figure 4.) 9. Mix the epoxy. 10. Coat both the tongue and groove surfaces with epoxy and fit together. Remove excess epoxy. 11. Cure the epoxy per the manufacturers instructions. CAUTION Some components may be sensitive to high temperature. 12. After the epoxy has cured remove the Polyimide tape. 13. If needed, scrape off any excess epoxy using a scraper or knife. NOTE If needed, apply additional thin coating to seal any scrapped areas. 14. Saw or mill off excess base material and file flush with existing edge. (See Figure 5.) 15. Clean the area. 16. Complete by drilling holes, slots, etc. or adding circuitry as required. (See Figure 6.) 17. If needed, replace solder resist or conformal coating. Figure 5 Saw off excess new base material. Figure 6 Complete by drilling holes, or adding circuitry as required. EVALUATION 1. Dimensions of area replaced should be checked to conform to specifications required. NOTES Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 4.1.1 Lifted Conductor Repair, Epoxy Seal Method Product Class: R, F Skill Level: Intermediated Level of Conformance: Medium OUTLINE This method is used to rebond a lifted conductor. Liquid epoxy is inserted under and around the conductor to bond it back down to the printed wiring board surface. CAUTION This method should not be used to rebond a conductor that has been stretched or damaged. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling Figure 1 Apply a small amount of epoxy under the lifted conductor. TOOLS AND MATERIALS Cleaner Cleaning Wipes Epoxy Heat Lamp or Oven Knife Pick PROCEDURE 1. Clean the area. 2. Remove any obstructions that prevent the lifted conductor from making contact with the base board surface. CAUTION Be careful while cleaning and removing all obstructions, not to stretch or damage the lifted conductor. 3. Clean the area. 4. Mix the epoxy. 5. Carefully apply a small amount of epoxy under the entire length of the lifted conductor. The tip of a knife may be used to apply the epoxy. (See Figure 1.) 6. Press the lifted conductor down into the epoxy and into contact with the base board material. 7. Apply additional epoxy to the surface of the lifted conductor and to all sides as needed. 8. Cure the epoxy per the manufacturer’s instructions. CAUTION Some components may be sensitive to high temperature. 9. Apply surface coating to match prior coating as required. Figure 2 Completed repair. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 4.1.1 Revision: Date: 2/98 IPC-7721 Subject: Lifted Conductor Repair, Epoxy Seal Method EVALUATION 1. Visual examination and tape test per IPC-TM-650, Test Method 2.4.1. 2. Electrical tests as applicable. NOTES Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 4.1.2 Lifted Conductor Repair, Film Adhesive Method Product Class: R, F Skill Level: Intermediate Level of Conformance: High OUTLINE This method is used to re-bond a lifted conductor. Dry film epoxy is used to re-bond the lifted conductor. CAUTION This method should not be used to re-bond a conductor that has been stretched or damaged REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating Figure 1 Place a piece of dry film epoxy under lifted conductor. TOOLS & MATERIALS Bonding Iron Bonding System Bonding Tips Cleaner Cleaner Wipes Dry Film Epoxy PROCEDURE Polyimide Tape Knife Microscope Scraper Tweezers Figure 2 Place tape over the lifted conductor. 1. Clean the area. 2. Remove any obstructions that prevent the lifted conductor from making contact with the base board surface. CAUTION Be careful while cleaning and removing all obstructions, not to stretch or damage the lifted conductor. 3. Clean the area. 4. Cut out a piece of dry film epoxy that closely matches the size of the lifted conductor. Be careful not to contaminate the dry film epoxy with materials that could reduce the bond strength. (See Figure 1.) NOTE Dry film epoxy thickness should be selected to meet the requirements of the printed wiring board. 5. Place a piece of Polyimide tape over the lifted conductor. Leave the tape in place during the bonding cycle. (See Figure 2.) 6. Position the printed wiring board so that it is flat and stable. Gently place the hot bonding tip onto the tape covering the conductor. Apply pressure and heat per equipment manufacturer’s recommendation. (See Figure 3.) Figure 3 Bond the lifted conductor using a bonding system. Figure 4 Completed repair. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 4.1.2 Revision: Date: 2/98 IPC-7721 Subject: Lifted Conductor Repair, Film Adhesive Method NOTE The bonding tip should be as small as possible but should completely cover the entire surface of the conductor. 7. After the bonding cycle lift the bonding tool and remove the tape used for alignment. The film is fully cured. Carefully clean the area and inspect the conductor. 8. Replace surface coating to match prior coating as required. EVALUATION 1. Visual examination and tape test per IPC-TM-650, Test Method 2.4.1. 2. Electrical tests as applicable. NOTES Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: A Date: 11/99 Number: 4.2.1 Conductor Repair, Foil Jumper, Epoxy Method Product Class: R, F, C Skill Level: Advanced Level of Conformance: Medium OUTLINE This method is used on printed wiring boards to replace damaged or missing conductors on the printed wiring board surface. CAUTION The conductor widths, spacing and current carrying capacity must not be reduced below allowable tolerances. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling Figure 1 Scrape off any coating from the ends of the remaining conductors. TOOLS AND MATERIALS Buffer Cleaner Conductor Foil Jumpers Color Agent Various Colors Epoxy Hand Held Drill Heat Lamp Polyimide Tape Knife Light Liquid Flux Microscope Oven Scraper Solder Solder Iron with Tips Wipes Figure 2 Place the new foil jumper in position, hold in place with tape conductor. PROCEDURE 1. Clean the area. 2 Remove the damaged section of conductor using a knife. The damaged conductor should be trimmed back to a point where the conductor still has a good bond to the printed wiring board surface. NOTE Heat can be applied to the damaged conductor using a soldering iron to allow the conductor to be removed more easily. 3. Use a knife and scrape off any solder resist or coating from the ends of the remaining conductor. (See Figure 1.) 4. Remove all loose material. Clean the area. NOTE It is essential that the board surface be smooth and flat. If the base material is damaged see appropriate procedure. Figure 3 Bend foil jumper using 2 wood sticks. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Figure 4 Wide conductors may be folded over. Page 1 of 4 Number: 4.2.1 Revision: A Date: 11/99 IPC-7721 Subject: Conductor Repair, Foil Jumper, Epoxy Method 5. Apply a small amount of liquid flux to the ends of the remaining conductor. Tin the exposed end of each conductor using solder and a soldering iron. 6. Clean the area. 7. Select a conductor foil jumper to match the width and thickness of the conductor to be replaced. Cut a length approximately as needed. The foil jumper should overlap the existing conductor a minimum of 2 times the conductor width. NOTE The new conductor may be trimmed from copper sheet. 8. Gently abrade the top and bottom surface of the replacement foil jumper with a buffer to remove the protective coating. NOTE A thin protective coating is often applied to the replacement foil jumper to prevent oxidation. 9. Clean the conductor foil jumper. 10. If needed, the ends of the replacement conductor foil jumper may be tinned with solder prior to lap soldering it in place. 11. If the conductor foil jumper is long or has bends, one end may be soldered prior to forming the new shape. Place the foil jumper in position. The foil jumper should overlap the existing conductor a minimum of 2 times the conductor width. The jumper may be held in place with Polyimide tape. (See Figure 2.) 12. Apply a small amount of liquid flux to the overlap joint. 13. Lap solder the foil jumper to the conductor on the printed wiring board surface using solder and a soldering iron. Make sure the foil jumper is properly aligned. NOTE If the configuration permits, the overlap solder joint connection should be a minimum of 3.00 mm from the related termination. This gap will minimize the possibility of simultaneous reflow during soldering operations. 14. Bend the foil jumper as needed to match the shape of the missing conductor. (See Figure 3.) NOTE Two wood sticks can be used to make sharp bends in the replacement foil jumper. Use one stick to hold the new jumper at the bend location and use the other wood stick to form the shape as needed. 15. Wide conductors that cannot be easily formed may be folded over to produce a sharp bend. (See Figure 4.) 16. Form the final shape of the jumper and hold in place with tape. Lap solder the foil jumper to the remaining conductor on the printed wiring board surface using solder and a soldering iron. Remove the tape used to hold the foil jumper. Clean the area. (See Figure 5.) 17. Mix the epoxy. If desired, add color agent to the mixed epoxy to match the printed wiring board color. Figure 5 Form the final shape of the jumper and hold in place with tape. Figure 6 Coat the top and sides of the foil jumper with epoxy. Page 2 of 4 Number: 4.2.1 Revision: A Date: 11/99 IPC-7721 Subject: Conductor Repair, Foil Jumper, Epoxy Method 18. Coat the top and sides of the foil jumper with epoxy. The epoxy bonds the foil jumper to the printed wiring board surface and insulates it. A wooden stick sharpened at one end may be used to apply and spread the epoxy. (See Figure 6.) 19. Cure the epoxy per the manufacturers instructions. CAUTION Some components may be sensitive to high temperature. 20. Apply surface coating to match prior coating as required. EVALUATION 1. Visual examination for alignment and overlap of foil jumper. 2. Visual examination of epoxy coating for texture and color match. 3. Electrical tests as applicable. Page 3 of 4 Number: 4.2.1 Revision: A Date: 11/99 NOTES IPC-7721 Subject: Conductor Repair, Foil Jumper, Epoxy Method Page 4 of 4 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 4.2.2 Conductor Repair, Foil Jumper, Film Adhesive Method Product Class: R, F, C Skill Level: Advanced Level of Conformance: High OUTLINE This method is used to replace damaged or missing conductors on the printed wiring board surface. CAUTION It is essential that the board surface be extremely smooth and flat. If the base board is damaged see appropriate procedure. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling Figure 1 Remove solder mask from the connecting conductor. TOOLS & MATERIALS Bonding Iron Bonding System Bonding Tips Buffer Conductor Foil Jumpers with Film Adhesive Cleaner Cleaner Wipes Heat Lamp Polyimide Tape Knife Liquid Flux Microscope Oven Scraper Solder Soldering Iron Tweezers Figure 2 Replacement conductors with dry film adhesive backing. PROCEDURE 1. Clean the area. 2. Remove the damaged section of conductor using a knife. The damaged con- ductor should be trimmed back to a point where the conductor still has a good bond to the printed wiring board surface. 3. Use the knife and scrape off any epoxy residue, contamination or burned material from the board surface. 4. Scrape off any solder resist or coating from the connecting conductor. (See Figure 1.) 5. Clean the area. 6. Apply a small amount of liquid flux to the connection area on the board surface and tin with solder. Clean the area. The length of the overlap solder connection should be a minimum of 2 times the conductor width. Figure 3 Scrape off epoxy bonding film. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Figure 4 Cut out the new conductor. Cut from the plated side. Page 1 of 4 Number: 4.2.2 Revision: Date: 2/98 IPC-7721 Subject: Conductor Repair, Foil Jumper, Film Adhesive Method 7. Select a replacement conductor with film adhesive backing that most closely matches the size of the conductor to be replaced. If a special size or shape is needed they can be custom fabricated. (See Figure 2.) NOTE New conductors are fabricated from copper foil. The foil is plated on the top side with solder and an epoxy bonding film is applied to the bottom side. 8. Before trimming out the new conductor carefully scrape off the adhesive epoxy film from the solder joint connection area on the back of the new conductor. (See Figure 3.) CAUTION Scrape off the epoxy backing only from the joint connection area. When handling the new conductor avoid touching the epoxy backing with your fingers or other materials that may contaminate the surface and reduce the bond strength. 9. Cut out and trim the new conductor. Cut out from the plated side. Cut the length to provide the maximum allowable conductor overlap for soldering. Minimum 2 times the conductor width. (See Figure 4.) NOTE If the configuration permits, the overlap solder joint connection should be a minimum of 3.00 mm from the related termination. This gap will minimize the possibility of simultaneous reflow during soldering operations. 10. Place a piece of tape over the top surface of the new conductor. Place the new conductor into position on the printed wiring board surface using tape to help in alignment. Leave the tape in place during the bonding cycle. (See Figure 5.) 11. Select a bonding tip with a shape to match the shape of the new conductor. NOTE The bonding tip should be as small as possible but should completely cover the entire width of the new conductor. 12. Position the printed wiring board so that it is flat and stable. Gently place the hot bonding tip onto the tape covering the new pad. Apply pressure as recommended in the manual of the repair system or repair kit. (See Figure 6.) 13. After the bonding cycle lift the bonding iron and remove the tape used for alignment. The new conductor is fully cured. Carefully clean the area and inspect the new conductor for proper alignment. 14. Apply a small amount of liquid flux to the lap solder joint connection area and solder the conductor from the new conductor to the conductor on the printed wiring board surface. Use minimal flux and solder to ensure a reliable connection. Tape may be placed over the top of the new conductor to prevent excess solder overflow. Clean the area. 15 Mix epoxy and coat the lap solder joint connections. Cure the epoxy per the manufacturer’s instructions. CAUTION Some components may be sensitive to high temperature. 16. Apply surface coating to match prior coating as required. Figure 5 Place the new conductor in place using tape. Figure 6 Repair system. Figure 7 Completed repair. Page 2 of 4 Number: 4.2.2 Revision: Date: 2/98 IPC-7721 Subject: Conductor Repair, Foil Jumper, Film Adhesive Method EVALUATION 1. Visual examination 2. Measurement of new pad width and spacing. 3. Electrical continuity measurement. Page 3 of 4 Number: 4.2.2 Revision: Date: 2/98 NOTES IPC-7721 Subject: Conductor Repair, Foil Jumper, Film Adhesive Method Page 4 of 4 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 4.2.3 Conductor Repair, Welding Method Product Class: R, F, C Skill Level: Advanced Level of Conformance: High OUTLINE This procedure is used to repair short breaks or opens in conductors on printed wiring boards. A parallel gap welder is used to weld a jumper ribbon across the damaged conductor. CAUTION Welding current and voltages may affect component reliability on assembled printed wiring boards. CAUTION The repaired section must not reduce the conductor width, spacings or current carrying capacity below the allowable tolerances. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.6 Epoxy Mixing and Handling PREPARATION Prior to using any welding equipment, certain precautions should be taken. The equipment should have electrodes cleaned, aligned and set for the proper board thickness. Test samples that have similar conductor widths, spacing, thickness, surface finish, contour, etc. Observe and test the weld quality, alignment, discoloration, fusion and the appearance of the base material in the area of the weld. Readjust the weld equipment settings and repeat until acceptable results have been achieved. The alignment of the welded ribbon to the conductor pattern should be within 0.050 mm. The weld bond strength should exceed the conductor/base material bond strength. TOOLS & MATERIALS Cleaner Cleaner Wipes Epoxy Knife Kovar Ribbon Liquid Flux Microscope Parallel Gap Welder Ribbon - Gold Plated Kovar Solder Soldering Iron Tweezers Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 4.2.3 Revision: Date: 2/98 IPC-7721 Subject: Conductor Repair, Welding Method PROCEDURE 1. Clean the area. 2. Select a section of Kovar ribbon of the same width as the conductor pattern being repaired ± .050 mm. 3. Cut the ribbon approximately 3.0 mm longer than the section being repaired. 4. Clean the ribbon conductor and base material surrounding the repair area. 5. Place and center the ribbon over the section to be repaired leaving equal ribbon end lengths on each side and parallel to the conductor pattern. 6. Place the printed wiring board under the weld electrodes so that the electrodes are depressed to the area of the weld. 7. Hold the ribbon in place with tweezers until the weld is completed. Weld in place using settings based on the accepted test samples. 8. Clean the area. 9. Carefully inspect the joint for weld quality and alignment. 10. If required, apply a small amount of flux and tin the entire area with solder. 11. Clean the area. 12. Coat the repaired area with epoxy if needed. EVALUATION 1. Visual examination, dimensional measurement of conductor width and spacing, and electrical continuity measurement. NOTES Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 4.2.4 Conductor Repair, Surface Wire Method Product Class: R, F, C Skill Level: Intermediate Level of Conformance: Medium OUTLINE This method is used on printed wiring boards to replace damaged or missing conductors on the printed wiring board surface. A length of standard insulated or noninsulated wire is used to repair the damaged conductor. CAUTION The conductor widths, spacing and current carrying capacity must not be reduced below allowable tolerances. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating Figure 1 Scrap off any coating from the ends of the conductors. TOOLS AND MATERIALS Cleaner Cleaning Wipes Epoxy Heat Lamp Polyimide Tape Knife Light Liquid Flux Microscope Oven Scraper Solder Soldering Iron with Tips Wire Wire Guide Tool Figure 2 Lap solder the wire to one end of the conductor. PROCEDURE 1. Clean the area. 2. Remove the damaged section of conductor using a knife. The damaged con- ductor should be trimmed back to a point where the conductor still has a good bond to the printed wiring board surface. NOTE Heat can be applied to the damaged conductor using a soldering iron to allow the conductor to be removed more easily. 3. Use a knife and scrape off any solder resist or coating from the ends of the remaining conductor. (See Figure 1.) 4. Remove all loose material. Clean the area. 5. Apply a small amount of liquid flux to the ends of the remaining conductor. Tin the exposed end of each conductor using solder and a soldering iron. 6. Clean the area. Figure 3 Form wire using wire guide tools. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Figure 4 Form the final shape of the wire and solder in place. Page 1 of 4 Number: 4.2.4 Revision: Date: 2/98 IPC-7721 Subject: Conductor Repair, Surface Wire Method 7. Select a wire to match the width and thickness of the conductor to be replaced. Cut a length approximately as needed. See Table 1 for Solid Wire Equivalents. Table 1 Solid Wire Equivalents Conductor Width 2 oz. Copper Equivalent Solid Wire Diameter 0.25 mm #34, 0.15 mm 0.38 mm #32, 0.20 mm 0.50 mm #31, 0.23 mm 0.78 mm #29, 0.28 mm 2.08 mm #26, 0.46 mm 3.18 mm #23, 0.58 mm When using solid wire to repair a conductor, there should be no reduction in the cross sectional area. Figure 5 Bond the wire to the surface with adhesive or tape. 8. Strip the wire and tin the ends if needed. Non-insulated wire may be used for short repairs if conductors are not crossed. 9. Clean the wire. 10. If the wire is long or has bends, one end may be soldered prior to forming the new shape. Place the wire in position. The wire should overlap the existing conductor a minimum of 2 times the conductor width. The wire may be held in place with Polyimide tape during soldering. NOTE If the configuration permits, the overlap solder joint connection should be a minimum of 3.00 mm from the related termination. This gap will minimize the possibility of simultaneous reflow during soldering operations. Refer to 7.1 Soldering Basics. 11. Apply a small amount of liquid flux to the overlap joint. 12. Lap solder the wire to one end of the conductor on the printed wiring board surface. Make sure the wire is properly aligned. (See Figure 2.) 13. Bend the wire as needed to match the shape of the missing conductor. (See Figure 3.) NOTE Wire guide tools can be used to form the wire as needed. 14. Lap solder the other wire end to the remaining conductor on the printed wiring board surface using solder and a soldering iron. Make sure the wire is properly aligned. (See Figure 4.) 15. Remove any Polyimide tape and clean the area. NOTE It may be necessary to encapsulate the solder joint connection if electrical spacing is reduced or the connection is beneath a component. 16. If desired bond the wire to the printed wiring board surface with adhesive, epoxy or tape dots. (See Figure 5.) Page 2 of 4 Number: 4.2.4 Revision: Date: 2/98 IPC-7721 Subject: Conductor Repair, Surface Wire Method CAUTION Some components may be sensitive to high temperature. 17. Cure the epoxy per the manufacturers instructions. 18. After the epoxy has cured clean the area. EVALUATION 1. Visual examination for alignment and overlap of wire. 2. Electrical tests as applicable. Page 3 of 4 Number: 4.2.4 Revision: Date: 2/98 NOTES IPC-7721 Subject: Conductor Repair, Surface Wire Method Page 4 of 4 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: A Date: 11/99 Number: 4.2.5 Conductor Repair, Through Board Wire Method Product Class: R Skill Level: Advanced Level of Conformance: Medium OUTLINE This method is used on printed wiring boards to replace damaged or missing conductors on the printed wiring board surface. A length of standard insulated or noninsulated wire is used to repair the damaged conductor. CAUTION The conductor widths, spacing and current carrying capacity must not be reduced below allowable tolerances. CAUTION This method is not acceptable when wire will be subsequently subjected to a mass soldering operation. Figure 1 Scrape off any coating from ends of remaining conductors. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating TOOLS AND MATERIALS Cleaner Knife Liquid Flux Dental Style Drill Microscope Solder Soldering Iron with Tips Wipes Solid Wire Figure 2 Drill through board adjacent to conductor. PROCEDURE 1. Clean the area. 2. Remove the damaged section of conductor using the knife. The damaged con- ductor should be trimmed back to a point where the conductor still has a good bond to the printed wiring board surface. NOTE Heat can be applied to the damaged conductor using a soldering iron to allow the conductor to be removed more easily. 3. Use a knife and scrape off any solder resist or coating from the ends of the remaining conductor. (See Figure 1.) 4. Remove all loose material. Clean the area. 5. Apply a small amount of liquid flux to the ends of the remaining conductor. Tin the exposed end of each conductor using solder and a soldering iron. Figure 3 Drill through board, through conductors. Figure 4 Lap solder wire to conductor. Material in this manual was voluntarily established by Technical Committees of IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by IPC. Page 1 of 4 Number: 4.2.5 Revision: A Date: 11/99 IPC-7721 Subject: Conductor Repair, Through Board Wire Method 6. Clean the area. 7. Select a wire to match the width and thickness of the conductor to be replaced. Cut a length approximately as needed. See Table 1 for Solid Wire Equivalents. Table 1 Solid Wire Equivalents Conductor Width 2 oz. Copper Equivalent Solid Wire Diameter 0.25 mm #34, 0.15 mm 0.38 mm #32, 0.20 mm 0.50 mm #31, 0.23 mm 0.78 mm #29, 0.28 mm 2.08 mm #26, 0.46 mm 3.18 mm #23, 0.58 mm When using solid wire to repair a conductor, there should be no reduction in the cross sectional area. 8. Strip the wire and tin the ends if needed. Non-insulated wire may be used for short repairs if conductors are not crossed. 9. Clean the wire. CAUTION Review conductor diagrams to be sure no surface or internal conductors will be damaged or shorted. 10. Drill through the board, either adjacent to both ends of the remaining conductors or through the conductors. Drill the hole slightly larger than the wire diameter to be used. (See Figure 2.) 11. Position the wire on the opposite side from the repair and insert the stripped ends into the drilled holes. 12. Bend the stripped wire over the prepared conductors in line with the conductors. The wire should overlap the existing conductor a minimum of 2 times the conductor width. (See Figure 3.) NOTE If the configuration permits, the overlap solder joint connection should be a minimum of 3.00 mm from the related termination. This gap will minimize the possibility of simultaneous reflow during soldering operations. 13. Apply a small amount of liquid flux to the overlap joint. 14 Lap solder the wire to the conductors on the printed wiring board surface. Make sure the wire is properly aligned. (See Figure 4.) 15. Form the wire on the opposite side to match the shape of the missing conductor. 16. Clean the area. NOTE It may be necessary to encapsulate the solder joint connection if electrical spacing is reduced. Page 2 of 4 Number: 4.2.5 Revision: A Date: 11/99 IPC-7721 Subject: Conductor Repair, Through Board Wire Method 17. If desired bond the wire to the printed wiring board surface with adhesive, epoxy or Tape Dots. CAUTION Some components may be sensitive to high temperature. 18. Cure the epoxy per Procedure 2.7 Epoxy Mixing and Handling. 19. After the epoxy has cured clean the area. EVALUATION 1. Visual examination for alignment and overlap of wire. 2. Electrical tests as applicable. Page 3 of 4 Number: 4.2.5 Revision: A Date: 11/99 NOTES IPC-7721 Subject: Conductor Repair, Through Board Wire Method Page 4 of 4 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 4.2.6 Conductor Repair/ Modification, Conductive Ink Method Product Class: R, F, C Skill Level: Expert Level of Conformance: Medium OUTLINE This modification/repair conductive pattern is fabricated via a solder/copper composite of screen printable polymer thick film (PTF). The interconnects are established at conductor lands and through hole locations of the original conductor. Electrical continuity is optimized between two or more points of interconnection by solder fusion of the new conductor pattern to the original etched PCB pattern. NOTE This modification/repair method is UL recognized, Type 1 94-V-0. It is compatible with both digital and analog printed wiring board applications and it has resistance of less than 3.0 milliohms/sq. It consists of greater than 90% copper and solder. The resin system employed is thermal setting and adhesion of approximately 1.5 kg on a 6 mm x 0.6 mm wide strip. It is typically applied to either or both sides of printed wiring boards on thru-hole or surface mount PCB’s prior to assembly, without any final solder resist coating. (Line resist coating can be applied and it is considered optional.) Figure 1 Isolation layer. CAUTION This modification/repair method can be employed on a single-sided, double-sided or a multilayer printed wiring board. Its primary application is for signal carrying conductors. New or additional power distribution should be designed into the new conductor pattern on the basis of 0.25 mm of line width 2.6 amps of current required, up to a maximum of 3.4 amps. When applying this method to the wave solder side or a thru-hole printed wiring board, it should be covered with a solder (line) resist. Figure 2 Copper ink is applied. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating TOOLS AND MATERIALS Screen printer/screens with matalizer and IR belt ovens Modification/repair master artwork Conductive Ink, directly solderable SMT compatible solder paste IR solder reflow (fuse) belt oven Flux cleaner, deionized water Electronic multi-point tester Figure 3 Solder ink fused to copper ink. PROCEDURE 1. Convert conductor design revision via CAD to additive layer conductor pattern including vias to be exposed and etch deletes to be performed. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 4.2.6 Revision: Date: 2/98 IPC-7721 Subject: Conductor Repair/Modification, Conductive Ink Method 2. Expose CAD generated additive conductor patterns of new conductor revision in isolation layer, copper and solder screens. 3 Print and cure isolation layer of protective epoxy. 4 Print, metalize and cure the new conductive ink pattern which establishes the modified/repaired conductor. 5. Print the SMT compatible solder paste on to the cured conductive ink pattern, totally encompassing the underlying material. 6 Fuse the printed solder paste to form the electrical optimization of the new con- ductor and the interconnection to the original etched conductor. See reflow soldering (IPC-J-STD-001). CAUTION Care should be taken not to add any solder to any unmodified or un-repaired areas on the printed wiring board. All solder flux residue should be removed to meet IPCTM-650, Test Methods 2.3.25 and 2.3.26, ionic contamination requirements. EVALUATION Visually examine and conduct dimensional measurement of conductor width and spacing. Ring-out for electrical continuity to detect for ‘shorts’ or ‘opens.’ This testing can be affected manually via continuity meter, automated electronic point-topoint tester or via a universal bed of nails electronic tester. NOTE Additive Conductor Modification Operations has become an industry standard for production quantities of PCB modification/repair revisions. NOTE Because of the expert level of workmanship required, qualified vendors of the service should be considered or the acquisition of dedicated in-house systems and personnel to perform this work. NOTES Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 4.2.7 Conductor Repair, Inner Layer Method Product Class: R, F Skill Level: Expert Level of Conformance: High OUTLINE This method is used to replace damaged or missing conductors on internal layers of multilayer printed wiring boards. CAUTION The conductor widths, spacing and current carrying capacity must not be reduced below allowable tolerances. CAUTION The overlap joint used in this method may cause problems with high frequency circuitry. Figure 1 Milling into miltilayer board to expose the damaged conductors. CAUTION This procedure is complicated and should be attempted only by properly skilled repair personnel using the best tools and equipment. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling Figure 2 A high quality, hand held drill. TOOLS AND MATERIALS Ball Mills Buffer Conductor Foil Jumpers Cleaner Cleaning Wipes Color Agent Epoxy Hand Held Drill Heat Lamp Polyimide Tape Knife Liquid Flux Microscope Oven Scraper Solder Soldering Iron Figure 3 Remove the remaining board material with a knife. PROCEDURE 1. Locate and determine the coordinates where the repair is to be made. Use films or master drawings of the board as needed. NOTE Obtain as much information as possible on the conductive and non-conductive layers prior to starting the procedure. 2. Remove components from the immediate area if necessary and clean the area. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Figure 4 Conductor foil jumper in place ready to be soldered. Page 1 of 4 Number: 4.2.7 Revision: Date: 2/98 IPC-7721 Subject: Conductor Repair, Inner Layer Method 3. Use the microscope and hand held drill and cut through the base material, one layer at a time, until the desired inner layer has been reached. (See Figure 1 and 2.) CAUTION Great care should be taken to prevent further damage to internal conductors. 4. Each internal conductor should have a flat section exposed to allow the new conductor to be soldered in place. (See Figure 3.) NOTE To reduce damage to the internal conductor, complete the final exposure of the internal conductor using a knife. (See Figure 3.) 5. Remove all loose material. Clean the area. 6. Apply a small amount of liquid flux to the ends of the internal conductor. Tin the exposed end of each conductor using solder and a soldering iron. 7. Clean the area. 8. Select a replacement conductor foil jumper that most closely matches the size of the conductor to be replaced. Cut length approximately as needed. 9. Gently abrade the top and bottom of the conductor foil jumper with a buffer to remove any protective coating and clean. NOTE If needed, the ends of the conductor foil jumper may be tinned with solder prior to lap soldering in place. 10. Place the conductor foil jumper in position. The conductor foil jumper should overlap the existing conductor a minimum of 2 times the conductor width. (See Figure 4.) NOTE If spacing is critical or the printed wiring board uses high frequency conductors, bevel the joint. (See Figure 5.) CAUTION This bevel joint method may cause problems with printed wiring boards exposed to extreme temperature fluctuations. 11. Apply a small amount of liquid flux to the overlap joint. 12. Lap solder the conductor foil jumper to the exposed internal conductor using solder and a soldering iron. Make sure the new conductor is properly aligned. 13. Clean the area. NOTE The printed wiring board may be preheated prior to filling the area with epoxy. A preheated printed wiring board will allow the epoxy to easily flow and level out. Epoxy applied to an unheated printed wiring board may settle below the printed wiring board surface as the epoxy cures. 14. Mix epoxy. If desired, add color agent to the mixed epoxy to match the printed wiring board color. Figure 5 Bevel end joint. Figure 6 Coat the top and sides of the new conductor with epoxy. Figure 7 Completed repair. Page 2 of 4 Number: 4.2.7 Revision: Date: 2/98 IPC-7721 Subject: Conductor Repair, Inner Layer Method 15. Coat the top and sides of the replaced conductor with epoxy. The epoxy bonds the new conductor to the base board material and insulates the conductor. Continue adding epoxy up to the top surface of the printed wiring board or to the height of the next internal conductor. (See Figure 6.) NOTE A slight overfill of epoxy may be desired to allow for shrinkage when the epoxy cures. 16. Cure the epoxy per the manufacturer’s instructions. CAUTION Some components may be sensitive to high temperature. 17. Add additional conductor foil jumpers if needed and coat with additional epoxy. 18. Continue completing all layers until the top surface of the printed wiring board is reached. (See Figure 7.) 19. Clean the board as required. 20. Apply surface coating to match prior coating as required. EVALUATION 1. Visual examination for alignment and overlap of new conductor. 2. Visual examination of epoxy coating for texture and color match. 3. Electrical tests as applicable. Page 3 of 4 Number: 4.2.7 Revision: Date: 2/98 NOTES IPC-7721 Subject: Conductor Repair, Inner Layer Method Page 4 of 4 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 4.3.1 Conductor Cut, Surface Conductors Product Class: R, F Skill Level: Advanced Level of Conformance: High OUTLINE This method is used to sever a conductor or short. A small section of the conductor is removed forming a break. The width of the break should be at least as wide as the minimum conductor spacing. A knife or high speed, hand held drill is used. This method is recommended for surface conductor cuts only. After cutting, the area is sealed with epoxy. NOTE This method is recommended for surface conductor cuts only. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.6 Epoxy Mixing and Handling Figure 1 Make two small cuts with a knife and remove section of conductor. TOOLS AND MATERIALS Ball Mills, Carbide Cleaner Cleaner Wipes Color Agent Continuity Meter Epoxy Epoxy Dispensing System Hand Held Drill Heat Lamp Knife Microscope Oven Figure 2 A high quality, hand held drill. PROCEDURE 1. Identify the conductor or short to be cut. Determine from the artwork or drawings where the best location is to make the break. The width of the break should at least match the minimum required electrical spacing. 2. Clean the area. 3. Carefully make two small cuts with the knife and remove the short section of conductor. (See Figure 1.) NOTE If desired, remove a second section of the conductor at the opposite end to eliminate the potential of the conductor acting as an antenna. 4. Select the appropriate size ball mill and insert it into the dental style drill. Set the speed to high. (See Figure 2.) The ball mill should be approximately the same width as the conductor to be cut. (See Table 1 for standard ball mill sizes.) CAUTION Abrasion operations can generate electrostatic charges. NOTE Ball mills should be dental grade carbide steel for precision cutting and long life. Figure 3 Make one or two cuts as needed to cut conductor. Figure 4 Completed repair. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 4.3.1 Revision: Date: 2/98 IPC-7721 Subject: Conductor Cut, Surface Conductors Table 1 Standard Ball Mill Sizes 0.50 mm Diameter 0.70 mm Diameter 0.80 mm Diameter 1.00 mm Diameter 1.20 mm Diameter 1.40 mm Diameter 1.60 mm Diameter 1.80 mm Diameter 2.10 mm Diameter 5. Carefully make 1 or 2 cuts as needed. (See Figure 3.) CAUTION Exercise care to avoid damage to adjoining conductors. NOTE If desired, remove a second section of the conductor at the opposite end to eliminate the potential of the conductor acting as an antenna. 6. Check continuity to be sure that the conductor has been cut. 7. Clean the area. 8. Mix epoxy. If desired, add color agent to the mixed epoxy to match the printed wiring board color. 9. Coat the area with epoxy if needed. An epoxy dispenser may be used to accu- rately control the application of epoxy. Remove any excess epoxy. 10. Cure the epoxy per the manufacturer’s instructions. CAUTION Some components may be sensitive to high temperatures. EVALUATION 1. Visual examination of cuts for spacing, and unintended damage to surrounding conductors. 2. Electrical tests as applicable. NOTES Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 4.3.2 Conductor Cut, Inner layer Conductors Product Class: R, F Skill Level: Advanced Level of Conformance: High OUTLINE This method is used to sever a conductor or short. A small section of the conductor is removed forming a break. The width of the break should be at least as wide as the minimum conductor spacing. A precision drill system is used with a carbide end mill. This method is recommended for surface or inner layer conductor cuts. After milling, the area is sealed with epoxy. NOTE This method is recommended for surface or inner layer conductor cuts. CAUTION Extreme care must be taken to prevent damage to adjacent or underlying inner layer conductors. A microscope must be used during milling when extreme accuracy is required. Figure 1 Precision drill press with base plate. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.6 Epoxy Mixing and Handling TOOLS AND MATERIALS Cleaner Cleaner Wipes Color Agent Continuity Meter End Mills, Carbide Epoxy Epoxy Dispensing System Heat Lamp Microscope Precision Drill Press Oven Figure 2 Mill into PC board at proper coordinates. PROCEDURE 1. Identify the conductor or short to be cut. Determine from the artwork or drawings where the best location is to make the break. The width of the break should at least match the minimum required electrical spacing. 2. Clean the area. 3. If the cut is on an inner layer conductor, mark the coordinates on the printed wiring board surface or set up a fixture to precisely locate the board in the precision drill press. (See Figure 1.) 4. Select the appropriate size end mill or ball mill and insert it into the chuck of the precision drill press. The milling cutter should be slightly larger in diameter than the conductor to be cut. Set speed to high. Figure 3 fill the milled hole with epoxy up to and flush with the surface. Figure 4 Completed repair. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 4.3.2 Revision: Date: 2/98 IPC-7721 Subject: Conductor Cut, Inner Layer Conductors CAUTION Abrasion operations can generate electrostatic charges. NOTE End mills are normally single end, two or four flute high grade solid carbide. 5. Mill down into the board at the proper coordinates to cut the inner layer conductors or to break the inner layer short. Do not mill deeper than needed. A microscope should be used for accuracy. (See Figure 2.) 6. Blow away material with air and clean the area. 7. Check continuity to be sure that the conductor has been cut. 8. Mix epoxy. If desired, add color agent to the mixed epoxy to match the printed wiring board color. 9. Fill the milled hole with epoxy up to and flush with the surface. An epoxy dispenser may be used to accurately control the application of epoxy. Remove any excess epoxy. (See Figure 3.) CAUTION Examine milled hole to be sure all material is removed from the hole prior to filling the hole with epoxy. NOTE A slight overfill of epoxy may be desired to allow for shrinkage when epoxy cures. 10. Cure the epoxy per the manufacturer’s instructions. CAUTION Some components may be sensitive to high temperatures. EVALUATION 1. Visual examination of cuts for spacing, and unintended damage to surrounding conductors. 2. Electrical tests as applicable. NOTES Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 4.3.3 Deleting Inner Layer Connection At A Plated Product Class: R, F Skill Level: Advanced Hole, Drill Through Method Level of Conformance: High OUTLINE This method is used on multilayer printed wiring boards or assemblies to disconnect an internal connection at a plated hole. A precision drill press is used with a carbide drill, end mill or ball mill to drill out the hole. The hole may then be filled with epoxy and redrilled to the diameter needed. CAUTION Extreme care must be taken to prevent damage to adjacent conductors. A microscope must be used during milling when extreme accuracy is required. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling Figure 1 Precision drill press with base plate. TOOLS AND MATERIALS Cleaner Cleaner Wipes Color Agent Continuity Meter End Mills, Carbide Epoxy Epoxy Dispensing System Heat Lamp Polyimide Tape Oven Microscope Pin Clamps Precision Drill Press Figure 2 Completely mill through the hole. PROCEDURE 1. Identify the hole that requires rework and clean the area. 2. Mark the coordinates on the board surface and pin the printed wiring board in place on the base plate of the precision drill press. (See Figure 1.) 3. Select the appropriate size end mill, drill or ball mill and insert it into the chuck of the precision drill press. The cutting tool should be approximately 0.50 mm greater than the plated through hole inside diameter. Set speed to high. CAUTION Abrasion operations can generate electrostatic charges. NOTE End mills are normally single end, two or four flute high grade solid carbide. 4. Completely mill through the hole to isolate the internal connection(s). A microscope should be used for accuracy. (See Figure 2.) 5. Blow away material with air and clean the area. 6. Check continuity to be sure that the internal connection has been deleted. Also Figure 3 Fill the hole with epoxy up to and flush with the surface. Figure 4 Repair complete. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 4.3.3 Revision: Date: 2/98 IPC-7721 Subject: Deleting Inner Layer Connection At A Plated Hole, Drill Through Method check the continuity and inspect the neighboring conductors to make sure that none of them have been severed or damaged. If desired complete the following steps 7. Mask the opposite side with Polyimide tape or flexible mask to prevent the epoxy from flowing out the opposite side. 8. Mix the epoxy. 9. Fill the hole with epoxy up to and flush with the surface. Remove excess epoxy. (See Figure 3.) NOTE A slight overfill of epoxy may be desired to allow for shrinkage when epoxy cures. 10. Cure the epoxy per the manufacturer’s instructions. CAUTION Some components may be sensitive to high temperature. 11. Clean the area. 12. Select an end mill or drill as needed. Insert the cutting tool into the precision drill press. Mill directly through the center of the cured epoxy. The surface pad remaining may be used as a target location for accuracy. A microscope should be used during milling for accuracy. (See Figure 4.) CAUTION Be careful not to re-expose the internal layers of the hole when drilling out the epoxy. 13. Clean the area. Inspect the new hole using a microscope. EVALUATION 1. Visual and electrical examination as required. NOTES Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 4.3.4 Deleting Inner Layer Connection At A Plated Hole, Spoke Cut Method Product Class: R, F Skill Level: Advanced Level of Conformance: High OUTLINE This method is used on multilayer printed wiring boards or assemblies to disconnect an internal connection at a plated hole. A precision drill press is used with a carbide end mill to make precise cuts at the spokes or internal conductors extending from the hole. CAUTION Extreme care must be taken to prevent damage to adjacent conductors. A microscope must be used during milling when extreme accuracy is required. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling Figure 1 Precision drill press with base plate. TOOLS AND MATERIALS Cleaner Cleaner Wipes Color Agent Continuity Meter End Mills, Carbide Epoxy Epoxy Dispensing System Heat Lamp Polyimide Tape Oven Microscope Pin Clamps Precision Drill Press Figure 2 Plated-through hole with inner layer spoke connections. PROCEDURE 1. Identify the hole that requires rework and clean the area. 2. Mark the coordinates on the board surface and place the printed wiring board on the base plate of the precision drill press. (See Figure 1.) 3. Select the appropriate size end mill or drill and insert it into the chuck of the precision drill press. The cutting tool should be approximately 0.010 - 0.025 mm greater than the width of the spoke or conductor to be cut. (See Table 1 for Standard End Mill Sizes.) Set speed to high. CAUTION Abrasion operations can generate electrostatic charges. NOTE End mills are normally single end, two or four flute high grade solid carbide. Figure 3 Mill adjacent to the plated hole to sever spoke connections. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 4.3.4 Revision: Date: 2/98 IPC-7721 Subject: Deleting Inner Layer Connection At A Plated Hole, Spoke Cut Method Table 1 Standard End Mill Sizes 0.381 mm Diameter 0.635 mm Diameter 0.812 mm Diameter 1.016 mm Diameter 1.143 mm Diameter 1.397 mm Diameter 1.575 mm Diameter 2.362 mm Diameter 3.175 mm Diameter 4. Mill into the printed wiring board surface adjacent to the plated hole. The milled holes should be aligned directly above the internal spoke connections. Mill down just deep enough to sever the internal spokes connecting the plated hole to the internal plane. A microscope must be used for accuracy. Up to 4 milled holes may be required. Do not drill deeper than needed. (See Figure 3.) 5. Blow away material with air and clean the area. 6. Check continuity to be sure that the internal connection has been deleted. Also check the continuity and inspect the neighboring conductors to make sure that none of them have been severed or damaged. 7. Mix the epoxy. 8. Fill the holes with epoxy up to and flush with the surface. Remove excess epoxy. NOTE A slight overfill of epoxy may be desired to allow for shrinkage when epoxy cures. 9. Cure the epoxy per the manufacturer’s instructions. CAUTION Some components may be sensitive to high temperature. 10. Clean the area. EVALUATION 1. Visual and electrical examination as required. NOTES Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 4.4.1 Lifted Land Repair, Epoxy Method Product Class: R, F Skill Level: Advanced Level of Conformance: Medium OUTLINE This method is used to rebond a lifted land. Liquid epoxy is inserted under and around the land to bond it back down to the printed wiring board surface. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling TOOLS AND MATERIALS Cleaner Epoxy Heat Lamp Polyimide Tape Knife Oven Wipes Figure 1 Apply epoxy under the entire length of the lifted land. PROCEDURE 1. Clean the area. 2. Remove any obstructions that prevent the lifted land from making contact with the base board surface. CAUTION Be careful while cleaning and removing all obstructions, not to stretch or damage the lifted land. 3. Mix the epoxy. 4. Carefully apply a small amount of epoxy under the entire length of the lifted land. The tip of a knife or scraper may be used to apply the epoxy. (See Figure 1.) 5. Place a piece of Polyimide tape over the lifted land and press the land down into the epoxy and into contact with the base board material. (See Figure 2.) 6. Apply additional epoxy to the surface of the lifted land and to all sides as needed. 7. Cure the epoxy per the manufacturer’s instructions. CAUTION Some components may be sensitive to high temperatures. NOTE Double sided and multilayer printed wiring boards, may require an eyelet to restore the through connection. Refer to section 5.0 Plated Hole Procedures. 8. Carefully remove any excess epoxy inside the plated hole using a ball mill or drill bit. Turn the ball mill or drill bit by hand to prevent damage to the wall of the plated through hole. Figure 2 Place tape over the lifted land. Figure 3 Completed repair. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 4.4.1 Revision: Date: 2/98 IPC-7721 Subject: Lifted Land Repair, Epoxy Method 9. Install the proper component and solder in place. NOTE This method is used to repair a lifted lands, but the repaired land may not have an intermetallic connection to the remaining plated hole. The solder joint of the replaced component will restore the integrity of the electrical connection or an eyelet or buss wire may be used. See Plated Hole Repair Procedures. 10. Replace surface coating to match prior coating as required. EVALUATION 1. Visual examination and tape test per IPC-TM-650, Test Method 2.4.1. 2. Electrical tests as applicable. NOTES Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 4.4.2 Lifted Land Repair, Film Adhesive Method Product Class: R, F Skill Level: Advanced Level of Conformance: Medium OUTLINE This method is used to repair damaged and lifted lands. The lifted lands are repaired with dry film epoxy. They are re-bonded to the printed wiring board surface using a bonding press or bonding iron. CAUTION It is essential that the board surface be extremely smooth and flat. If the base board is damaged see appropriate procedure. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning Figure 1 Cut out dry film material to match the area of the lifted land. TOOLS & MATERIALS Ball Mills Bonding Iron Bonding System Bonding Tips Cleaner Dry Film Adhesive Polyimide Tape Knife Microscope Scraper Tweezers Wipes PROCEDURE 1. Clean the area. 2. Remove any obstructions that prevent the lifted land from making contact with the base board material. 3. Use the knife and scrape off any epoxy residue, contamination or burned mate- rial from the board surface. 4. Clean the area. 5. Cut out a piece of bonding film that matches the area of the lifted land. Be careful not to contaminate the dry film epoxy with materials that could reduce the bond strength. NOTE Dry film adhesive thickness should be selected to meet the requirements of the printed wiring board. 6. Place the dry film under the lifted land. (See Figure 1). 7. Place a piece of Polyimide tape over the lifted land and press the land down into contact with the adhesive film. (See Figure 2). Figure 2 Place tape over the lifted land. Figure 3 Bond the land down using a commercially available system. Figure 4 Completed repair. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 2 Number: 4.4.2 Revision: Date: 2/98 IPC-7721 Subject: Lifted Land Repair, Film Adhesive Method 8. Select a bonding tip with a shape to match the shape of the lifted land. NOTE The bonding tip should be as small as possible but should completely cover the entire surface of the new land. 9. Position the printed wiring board so that it is flat and stable. Gently place the hot bonding tip onto the tape covering the new land. Apply pressure and heat as recommended in the manual of the repair system or repair kit. (See Figure 3). 10. After the bonding cycle remove the tape used for alignment. The film is fully cured. Carefully clean the area and inspect the land. NOTE Double sided and multilayer printed wiring boards, may require an eyelet to restore the through connection. Refer to section 5.0 Plated Hole Procedures. 11. Carefully remove any excess bonding film inside the plated hole using a ball mill or drill bit. Turn the ball mill or drill bit by hand to prevent damage to the wall of the plated through hole. 12. Install the proper component and solder in place. NOTE This method is used to repair a lifted land, but the repaired land may not have an intermetallic connection to the remaining plated hole. The solder joint of the replaced component will restore the integrity of the electrical connection or an eyelet or buss wire may be used. See Plated Hole Repair Procedures. 13. Replace surface coating to match prior coating as required. EVALUATION 1. Visual examination and tape test per IPC-TM-650, Test Method 2.4.1. 2. Electrical tests as applicable. NOTES Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Land Repair, Epoxy Method Number: 4.5.1 Product Class: R, F Skill Level: Advanced Level of Conformance: Medium OUTLINE This method is used to replace damaged and lifted lands. The damaged lands are replaced with new lands. The new lands are bonded to the printed wiring board surface using a commercially available epoxy. CAUTION This method is used to replace a damaged or missing land, but the new land will not have an intermetallic connection to the remaining plated hole. The solder joint of the replaced component will restore the electrical connection. If a component is not installed, a wire clinched to both sides of the printed wiring board may be used. Figure 1 Remove the defective land and solder resist from the conductor. CAUTION It is essential that the board surface be smooth and flat. If the base board is damaged see appropriate procedure. NOTE This method uses commercially available replacement lands. The new lands are fabricated from copper foil. They are available in hundreds of sizes and shapes and are generally supplied solder plated. If a special size or shape is needed they can be custom fabricated. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling Figure 2 Select a replacement land that matches the missing land. TOOLS & MATERIALS Ball mills or drills Buffer Cleaner Epoxy Heat Lamp Polyimide Tape Knife Liquid Flux Microscope Replacement Lands Scraper Solder Soldering Iron Tweezers Wipes Figure 3 Cut out the replacement land. PROCEDURE 1. Clean the area. 2. Remove the defective land and a short length of the connecting conductor if any. (See Figure 1.) Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Figure 4 Place the new land in place using tape. Page 1 of 4 Number: 4.5.1 Revision: Date: 2/98 IPC-7721 Subject: Land Repair, Epoxy Method 3. Use the knife and scrape off any epoxy residue, contamination or burned material from the board surface. CAUTION Abrasion operations can generate electrostatic charges. 4. Scrape off any solder resist or coating from the connecting conductor. (See Figure 1.) 5. Clean the area. 6. Apply a small amount of liquid flux to the connection area on the board surface and tin with solder. Clean the area. The length of the overlap solder connection should be a minimum of 2 times the conductor width. 7. The area for the new pad on the board surface must be smooth and flat. If internal fibers of the board are exposed or if there are deep scratches in the surface they should be repaired. Refer to appropriate procedure. 8. Select a replacement land that most closely matches the land to be replaced. (See Figure 2.) 9. Cut out and trim the new land. Cut the length to provide the maximum allowable conductor overlap for soldering. Minimum 2 times the conductor width. (See Figure 3.) NOTE The new replacement land may be trimmed from copper sheet. 10. Mix the epoxy and apply a small amount to the surface where the new land will be placed. 11. Place a piece of Polyimide tape over the top surface of the land. Place the new land into position on the printed wiring board surface using the tape to aid in alignment. (See Figure 4.) 12. Cure the epoxy per the manufacturer’s instructions. 13. After the epoxy has cured, remove the tape used for the alignment. Carefully clean the area and inspect the new land for proper alignment. NOTE If the configuration permits, the overlap solder joint connection should be a minimum of 3.00 mm from the related termination. This gap will minimize the possibility of simultaneous reflow during soldering operations. 14. Remove tape and clean the area. 15. Mix the epoxy and coat the lap solder joint connections. Cure the epoxy per the manufacturer’s recommended instructions. NOTE Additional epoxy can be applied around the perimeter of the new land to provide additional bond strength. CAUTION Some components may be sensitive to high temperature. 16. Carefully remove any excess epoxy inside the plated hole using a ball mill or drill bit. Turn the ball mill or drill bit by hand to prevent damage to the wall of the plated through hole. Figure 5 Completed repair. Page 2 of 4 Number: 4.5.1 Revision: Date: 2/98 IPC-7721 Subject: Land Repair, Epoxy Method 17. Install the proper component and solder in place. NOTE This method is used to replace a damaged or missing lands, but the new land will not have an intermetallic connection to the remaining plated hole. The solder joint of the replaced component will restore the integrity of the electrical connection or an eyelet or clinched buss wire may be used. See Plated Hole Repair Procedures. 18. Apply surface coating to match prior coating as required. EVALUATION 1. Visual examination 2. Measurement of new pad width and spacing. 3. Electrical continuity measurement. Page 3 of 4 Number: 4.5.1 Revision: Date: 2/98 NOTES IPC-7721 Subject: Land Repair, Epoxy Method Page 4 of 4 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 4.5.2 Land Repair, Film Adhesive Method Product Class: R, F Skill Level: Advanced Level of Conformance: High OUTLINE This method is used to replace damaged and lifted lands. The damaged lands are replaced with new dry film, adhesive backed lands. The new lands are bonded to the printed wiring board surface using a bonding press or bonding iron. CAUTION This method is used to replace a damaged or missing land, but the new land will not have an intermetallic connection to the remaining plated hole. The solder joint of the replaced component will restore the integrity of the electrical connection. If a component is not installed, a wire clinched to both sides of the printed wiring board may be used. Figure 1 Remove the defective land and solder resist from the conductor. CAUTION It is essential that the board surface be smooth and flat. If the base board is damaged see appropriate procedure. NOTE This method uses commercially available replacement lands. The new lands are fabricated from copper foil and have a dry film adhesive coating on the back. They are available in hundreds of sizes and shapes and are generally supplied solder plated. If a special size or shape is needed they can be custom fabricated. Figure 2 Select a replacement land that matches the missing land. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling TOOLS & MATERIALS Bonding Iron Bonding System Bonding Tips Buffer Cleaner Epoxy Heat Lamp Polyimide Tape Knife Liquid Flux Microscope Replacement Lands, Adhesive Backed Scraper Solder Soldering Iron Tweezers Wipes Figure 3 Scrape off the adhesive bonding film from solder joint area. Figure 4 Cut out the new land. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 4 Number: 4.5.2 Revision: Date: 2/98 IPC-7721 Subject: Land Repair, Film Adhesive Method PROCEDURE 1. Clean the area. 2. Remove the defective land and a short length of the connecting conductor if any. (See Figure 1.) 3. Use the knife and scrape off any epoxy residue, contamination or burned material from the board surface. CAUTION Abrasion operations can generate electrostatic charges. 4. Scrape off any solder resist or coating from the connecting conductor. (See Figure 1.) 5. Clean the area. 6. Apply a small amount of liquid flux to the connection area on the board surface and tin with solder. Clean the area. The length of the overlap solder connection should be a minimum of 2 times the conductor width. 7. The area for the new pad on the board surface must be smooth and flat. If internal fibers of the board are exposed or if there are deep scratches in the surface they should be repaired. Refer to appropriate procedure. 8. Select a replacement land that most closely matches the land to be replaced. (See Figure 2.) NOTE The new replacement land may be trimmed from copper sheet. 9. Before trimming out the new land carefully scrape off the adhesive film from the solder joint connection area on the back of the new land. (See Figure 3.) CAUTION Scrape off the epoxy backing only from the joint connection area. When handling the replacement land avoid touching the adhesive backing with your fingers or other materials that may contaminate the surface and reduce the bond strength. 10. Cut out and trim the new land. Cut out from the plated side. Cut the length to provide the maximum allowable conductor overlap for soldering. Minimum 2 times the conductor width. (See Figure 4.) 11. Place a piece of tape over the top surface of the new land. Place the new land into position on the printed wiring board surface using the tape to aid in alignment. Leave the tape in place during the bonding cycle. (See Figure 5.) 12. Select a bonding tip with a shape to match the shape of the new land. NOTE The Bonding Tip should be as small as possible but should completely cover the entire surface of the new land. 13. Position the printed wiring board so that it is flat and stable. Gently place the hot bonding tip onto the tape covering the new land. Apply pressure as recommended in the manual of the repair system or repair kit of the manufacturer. (See Figure 6.) Figure 5 Place the new land in place using tape. Figure 6 Bonding systems. Figure 7 Completed land repair. Page 2 of 4 Number: 4.5.2 Revision: Date: 2/98 IPC-7721 Subject: Land Repair, Film Adhesive Method CAUTION Excessive bonding pressure may cause measling in the printed wiring board surface or the new conductor to slide out of position. 14. After the bonding cycle remove the tape used for alignment. The land is fully cured. Carefully clean the area and inspect the new land for proper alignment. 15. If the new land has a connecting conductor apply a small amount of liquid flux to the lap solder joint connection area and solder the conductor from the new land to the conductor on the printed wiring board surface. Use minimal flux and solder to ensure a reliable connection. Tape may be placed over the top of the new land to prevent excess solder overflow. NOTE If the configuration permits, the overlap solder joint connection should be a minimum of 3.00 mm from the related termination. This gap will minimize the possibility of simultaneous reflow during soldering operations. 16. Remove tape and clean the area. 17. Mix epoxy and coat the lap solder joint connections. Cure the epoxy per the manufacturers instructions. NOTE Additional epoxy can be applied around the perimeter of the new pad to provide additional bond strength. CAUTION Some components may be sensitive to high temperature. 18. Carefully remove any excess bonding film inside the plated hole using ball mill or drill bit. Turn the ball mill or drill bit by hand to prevent damage to the wall of the plated through hole. 19. Install the proper component and solder in place. NOTE This method is used to replace a damaged or missing land, but the new land will not have an intermetallic connection to the remaining plated hole. The solder joint of the replaced component will restore the integrity of the electrical connection or an eyelet or buss wire may be used. See Plated Hole Repair Procedures. 20. Apply surface coating to match prior coating as required. EVALUATION 1. Visual examination. 2. Measurement of new pad width and spacing. 3. Electrical continuity measurement. Page 3 of 4 Number: 4.5.2 Revision: Date: 2/98 NOTES IPC-7721 Subject: Land Repair, Film Adhesive Method Page 4 of 4 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 4.6.1 Edge Contact Repair, Epoxy Method Product Class: R, F, W, C Skill Level: Advanced Level of Conformance: Medium OUTLINE This method is used to replace a damaged edge contact with a new edge contact. The new edge contact is bonded to the printed wiring board surface using liquid epoxy. CAUTION It is essential that the board surface be smooth and flat. If the base material is damaged see appropriate procedure. NOTE This method uses commercially available replacement edge contacts. The edge contacts are fabricated from copper foil. They are available in hundreds of sizes and shapes and are generally supplied either plain copper, solder plated or nickel and gold plated. If a special size or shape is needed they can be custom fabricated. Figure 1 Remove the defective edge contact and solder resist. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking And Preheating 2.6 Epoxy Mixing and Handling Figure 2 Select a replacement contact that matches. TOOLS & MATERIALS Cleaner Epoxy File, Finish Grade Heat Lamp Polyimide Tape Knife Liquid Flux Microscope PROCEDURE Oven Replacement Edge Contacts Scraper Solder Soldering Iron Tweezers Wipes Figure 3 Cut out the new edge contact. 1. Clean the area. 2. Remove the defective edge contact and a short length of the connecting conductor. Heat from a soldering iron will allow the old contact to be removed more easily. 3. Use the knife and scrape off any epoxy residue, contamination or burned material from the board surface. CAUTION Abrasion operations can generate electrostatic charges. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Figure 4 Place the new edge contact in place using tape. Page 1 of 4 Number: 4.6.1 Revision: Date: 2/98 IPC-7721 Subject: Edge Contact Repair, Epoxy Method 4. Scrape off any solder resist or coating from the connecting conductor. (See Figure 1.) 5. Clean the area. 6. Apply a small amount of liquid flux to the connection area on the board surface and tin with solder. Clean the area. The length of the overlap solder connection should be a minimum of 2 times the conductor width. 7. The area for the new edge contact on the board surface must be smooth and flat. If internal fibers of the board are exposed or deep scratches exist in the surface they should be repaired. Refer to appropriate procedure. 8. Select a new edge contact that most closely matches the edge contact to be replaced. (See Figure 2.) 9. Cut out and trim the new edge contact. Cut out from the plated side. Cut the length to provide the maximum allowable joint if lap soldering. Minimum 2 times the conductor width. Leave the new edge contact extra long. The excess material will be trimmed after curing. (See Figure 3.) NOTE The new replacement edge contact may be trimmed from copper sheet. 10. Mix the epoxy and apply a small amount to the surface where the new contact will be placed. 11. Place a piece of tape over the top surface of the new edge contact. Position the new edge contact on the printed wiring board surface using the tape to aid in alignment. (See Figure 4.) NOTE Allow the edge contact to overhang the edge of the printed wiring board. Leave the tape in place during the bonding cycle. 12. Cure the epoxy per the manufacturer’s instructions. CAUTION Some components may be sensitive to high temperature. 13. After the epoxy has cured, remove the tape used for alignment. Carefully clean and inspect the new pad for proper alignment. NOTE Additional epoxy can be applied around the perimeter of the new edge contact to provide additional bond strength. 14. If the new edge contact has a connecting conductor apply a small amount of liquid flux to the lap solder joint connection area and solder the conductor from the new edge contact to the conductor on the printed wiring board surface. Use minimal flux and solder to ensure a reliable connection. Tape may be placed over the top of the new edge contact to prevent excess solder overflow. NOTE If the configuration permits, the overlap solder joint connection should be a minimum of 3.00 mm from the related termination. This gap will minimize the possibility of simultaneous reflow during soldering operations. 15. Remove the tape and clean the area. Figure 5 File overhanging piece of new edge contact. Figure 6 Completed repair. Page 2 of 4 Number: 4.6.1 Revision: Date: 2/98 IPC-7721 Subject: Edge Contact Repair, Epoxy Method 16. Trim the extending edge of the new edge contact with a file. File parallel to the beveled edge until the excess material has been removed. (See Figure 5.) 17. If sealing the lap solder joint connection is required, mix epoxy and coat the lap solder joint connections. Cure the epoxy per the manufacturer’s instructions. 18. If plating is required refer to appropriate procedure. 19. Apply surface coating to match prior coating as required. EVALUATION 1. Visual examination, measurement of new pad width and spacing. 2. Electrical continuity measurement. Page 3 of 4 Number: 4.6.1 Revision: Date: 2/98 NOTES IPC-7721 Subject: Edge Contact Repair, Epoxy Method Page 4 of 4 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 4.6.2 Edge Contact Repair, Film Adhesive Method Product Class: R, F, W, C Skill Level: Advanced Level of Conformance: High OUTLINE This method is used to replace a damaged edge contact with a new dry film, adhesive backed edge contact. The new edge contact is hot bonded to the printed wiring board surface. CAUTION It is essential that the board surface be smooth and flat. If the base material is damaged see appropriate procedure. NOTE This method uses commercially available replacement edge contacts. The edge contacts are fabricated from copper foil and have a dry film adhesive coating on the back. They are available in hundreds of sizes and shapes and are generally supplied nickel and gold plated. If a special size or shape is needed they can be custom fabricated. Figure 1 Remove the defective edge contact and solder resist. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling Figure 2 Select a replacement contact that matches. TOOLS & MATERIALS Bonding Iron Bonding System Bonding Tips Cleaner Epoxy File, Finish Grade Heat Lamp Polyimide Tape Knife Liquid Flux Microscope Oven Replacement Edge Contacts, Adhesive Backed Scraper Solder Soldering Iron Tweezers Wipes Figure 3 Scrape off adhesive bonding film from solder joint area. PROCEDURE 1. Clean the area. 2. Remove the defective edge contact and a short length of the connecting con- ductor. Heat from a soldering iron will allow the old contact to be removed more easily. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Figure 4 contact. Cut out the new edge Page 1 of 4 Number: 4.6.2 Revision: Date: 2/98 IPC-7721 Subject: Edge Contact Repair, Film Adhesive Method 3. Use the knife and scrape off any epoxy residue, contamination or burned material from the board surface. CAUTION Abrasion operations can generate electrostatic charges. 4. Scrape off any solder resist or coating from the connecting conductor. (See Figure 1.) 5. Clean the area. 6. Apply a small amount of liquid flux to the connection area on the board surface and tin with solder. Clean the area. The length of the overlap solder connection should be a minimum of 2 times the conductor width. 7. The area for the new edge contact on the board surface must be smooth and flat. If internal fibers of the board are exposed or deep scratches exist in the surface they should be repaired. Refer to appropriate procedure. 8. Select a new edge contact that most closely matches the edge contact to be replaced. (See Figure 2.) NOTE The new replacement edge contact may be trimmed from copper sheet. 9. Before trimming out the new edge contact carefully scrape off the adhesive film from the solder joint connection area on the back of the new edge contact. (See Figure 3.) CAUTION Scrape off the epoxy backing only from the joint connection area. When handling the replacement contact, avoid touching the epoxy backing with your fingers or other materials that may contaminate the surface and reduce the bond strength. 10. Cut out and trim the new edge contact. Cut out from the plated side. Cut the length to provide the maximum allowable joint if lap soldering. Minimum 2 times the conductor width. Leave the new edge contact extra long. The excess material will be trimmed after bonding. (See Figure 4.) 11. Place a piece of tape over the top surface of the new edge contact. Position the new edge contact on the printed wiring board surface using the tape to aid in alignment. (See Figure 5.) NOTE Allow the edge contact to overhang the edge of the printed wiring board. Leave the Tape in place during the bonding cycle. 12. Select a bonding tip with a shape to match the shape of the new edge contact. NOTE The bonding tip should be as small as possible but completely cover the entire surface of the new edge contact. 13. Position the printed wiring board so that it is flat and stable. Gently place the hot bonding tip onto the tape covering the new edge contact. Apply pressure as recommended by the manufacturer. (See Figure 6.) CAUTION Excessive bonding pressure may cause measling in the printed wiring board surface or the new conductor to slide out of position. Figure 5 Place the new edge contact in place using tape. Figure 6 Bonding system. Figure 7 File overhanging piece of the new edge contact. Figure 8 Completed repair. Page 2 of 4 Number: 4.6.2 Revision: Date: 2/98 IPC-7721 Subject: Edge Contact Repair, Film Adhesive Method 14. After the bonding cycle remove the tape used for alignment. The new edge contact is fully cured. Carefully clean the area and inspect the new edge contact for proper alignment. 15. If the new edge contact has a connecting conductor apply a small amount of liquid flux to the lap solder joint connection area and solder the conductor from the new edge contact to the conductor on the printed wiring board surface. Use minimal flux and solder to ensure a reliable connection. Tape may be placed over the top of the new edge contact to prevent excess solder overflow. NOTE If the configuration permits, the overlap solder joint connection should be a minimum of 3.00 mm from the related termination. This gap will minimize the possibility of simultaneous reflow during soldering operations. 16. Remove tape and clean the area. 17. Trim the extending edge of the new edge contact with a file. File parallel to the beveled edge until the excess material has been removed. (See Figure 7.) 18. If sealing the lap solder joint connection is required, mix epoxy and coat the lap solder joint connections. Cure the epoxy per the manufacturer’s instructions. CAUTION Some components may be sensitive to high temperature. NOTE Additional epoxy can be applied around the perimeter of the new edge contact to provide additional bond strength. 19. Apply surface coating to match prior coating as required. EVALUATION 1. Visual examination, measurement of new pad width and spacing. 2. Electrical continuity measurement. Page 3 of 4 Number: 4.6.2 Revision: Date: 2/98 NOTES IPC-7721 Subject: Edge Contact Repair, Film Adhesive Method Page 4 of 4 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 4.6.3 Edge Contact Repair, Plating Method Product Class: R, F, W, C Skill Level: Advanced Level of Conformance: High OUTLINE This method is used to replate edge contacts by selective swab plating. Edge contacts may require replating if they become contaminated with solder or are scratched during handling. Other applications may arise when the plating on the edge contacts does not meet the minimum thickness specification or if the specification changes. This electroplating process uses a DC power supply. One lead is connected to the connector edge contacts that need plating. A second lead is connected to the plating probe. The plating probe has an anode fastened to the tip. The anode has absorbent wrapping. The anode is dipped into high-speed proprietary plating solutions. When the saturated anode is swabbed across the printed wiring board connector edge contacts, the metal contained in the solution is plated wherever electrical contact is made. Prior to replating any solder contamination must be removed. Figure 1 Apply tape. CAUTION This method can be used to replate any metal surface including connector edge contacts, but it is essential that the surface to be plated is free of deep scratches, nicks, pin holes or other defects. If the edge contacts need to be replaced see appropriate procedure. SAFETY A thorough review of this method should be made before repairs are attempted. Technicians should become familiar with the tools included and should practice on scrap printed wiring boards To expect the best results a clean work environment is essential. A smooth work surface and good lighting are recommended. Safety glasses and safety gloves should always be worn when handling hazardous chemicals. The work area should be adequately ventilated. It is particularly important to have adequate ventilation when using gold solution, since gold solution contains a very small percentage of free cyanide. If ventilation is not adequate, use a fan to move fumes away from the operator. CAUTION It is essential to follow the manufacturer’s instructions supplied with the plating equipment. Figure 2 Flow solder. Figure 3 Solder stripping solution. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning Figure 4 Rinse. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 6 Number: 4.6.3 Revision: Date: 2/98 IPC-7721 Subject: Edge Contact Repair, Plating Method TOOLS & MATERIALS Abrasive Pad Board Support Burnisher Cleaner Cleaner Wipes Connector Edge Plating System Conductive Pen Desoldering Braid or Desoldering System Eraser Stick Gloves, Antistatic Polyimide Tape Knife Liquid Flux Peel Testing Tape Pin Fixtures Plating Anodes Plating Cables Plating Probe Plating Solution, Gold Plating Solution, Nickel Plating Solution, Electroclean Plating Solution, Solder Strip Plating Tape Power Supply Probe Clip Rinse Bottle Rinse Tray Safety Glasses Solder Solder Iron Solution Cups Solution Tray Swab Thickness Measuring System, Gold and Nickel Water/Air Sprayer Wire, Buss, 30 AWG Work Sink PREPARATION − Remove Solder Contamination Figure 5 Solder a wire to the edge of the contacts needing plating. Figure 6 Apply conductive paint to the edge of the contacts. CAUTION Safety glasses and safety gloves should always be worn when handling hazardous chemicals. Do not work within a small enclosed room without supplemental ventilation. If ventilation is not adequate, use a fan to move fumes away from the operator. 1. Clean the rework area. 2. Apply plating tape to the printed wiring board surface surrounding the area to be reworked. (See Figure 1.) The plating tape will protect adjacent components and the printed wiring board surface from unwanted exposure to stripping and plating solutions. 3. Flow solder over the entire area of any contacts that have contamination using a soldering iron. This provides a more even surface when plating. Remove the bulk of the solder contamination using desoldering tools or desoldering braid. (See Figure 2.) 4. Clean the area. 5. Place the printed wiring board on the board support so that the leading edge overhangs the rinse tray. 6. Swab the solder stripping solution over the solder contamination using a swab. Swab the surface until all remaining solder has been stripped off. (See Figure 3.) 7. Thoroughly rinse the entire area with water. (See Figure 4.) 8. Mildly buff the contacts using abrasive pad. Mild buffing will prepare the surface for plating and remove any remaining solder contamination. 9. Thoroughly rinse with water to remove any residue. Figure 7 Sample plating anodes shown with fabric wrapping. Figure 8 Brush the surface with the saturated plating probe. Page 2 of 6 Number: 4.6.3 Revision: Date: 2/98 IPC-7721 Subject: Edge Contact Repair, Plating Method PREPARATION − Remove Poor Plating or Surface Defects 1. Clean the rework area. 2. Apply plating tape to the printed wiring board surface surrounding the area to be reworked. The plating tape will protect adjacent components and the printed wiring board surface from unwanted exposure to stripping and plating solutions. 3. Clean the area. 4. Buff the contacts using an abrasive pad. Buff the contacts until all defective or poor plating is removed. 5. Burnish small scratches. Use the tip of the burnisher to work the copper material into the scratch and smooth out the area. Finish by mildly buffing the area to remove any minor burnishing marks. If there are large scratches the contact may need replacement. See Procedure Number 4.6.1 or 4.6.2. 6. Thoroughly rinse the entire area with water to remove any residue. BUSSING A conductive buss must be made to all the contacts that need plating. There are 4 basic connection options. NOTE Making a reliable buss connection is the most important step in plating. All sorts of problems will be eliminated by taking the time to make a reliable buss connection. BUSSING − Wire Soldered to Edge (Option 1) CAUTION When finished, this method will leave a small unplated line along the inner tip of each contact. 1. Apply Polyimide tape to all the contacts to be plated. The tape should cover the entire contact except for a small line along the inboard edge. The tape will prevent further solder contamination. 2. Solder a wire directly to the inboard tip or connecting conductor of each contact to be plated. The smallest amount of solder should be used to prevent further contamination. (See Figure 5.) BUSSING − Conductive Paint Applied to Edge (Option 2) CAUTION When finished, this method will leave a small unplated line along the inner tip of each contact. 1. Apply Polyimide tape to all the contacts to be plated. The tape should cover the entire contact except for a small line along the inboard edge. The tape will prevent the conductive paint from contaminating the contact surface. 2. Apply a thin coating of conductive paint directly to the inboard tip of each contact to be plated. The conductive paint should extend out to one edge so that a clip can be applied to make electrical connection. (See Figure 6.) Page 3 of 6 Number: 4.6.3 Revision: Date: 2/98 IPC-7721 Subject: Edge Contact Repair, Plating Method BUSSING − Mechanical Probe, Individual Contacts (Option 3) 1. Each contact needing plating can be individually probed using the plating probe. Touch the tip of the plating probe to the inboard edge of each contact or to the connecting conductor as each solution is applied during the plating process. BUSSING − Pin Fixture, Multiple Contacts (Option 4) 1. Make a mechanical connection to each contact using a pin fixture. The pin fixture has spring loaded contact pins on centers matching the spacing of the edge contacts to be plated. The contact pins make direct mechanical connection to the inboard tip of each contact, the connecting conductor trace or a connecting plated through hole. PROCEDURE − Plating Process 1. Place the printed wiring board on the board support so that the leading edge overhangs the rinse tray. 2. Make the cathode connection (-) to the printed wiring board by using a plating probe or probe clip. Connect the probe clip directly to the wire buss connection or to the edge where conductive paint has been applied. The cable should be connected to the (-) or black jack on the power supply. 3. Connect the plating probe to the power supply (+) or red jack. (See Figure 7.) 4. Set the output current on the power supply to setting recommended by the equipment manufacturer. 5. Dip the plating probe into the electroclean plating solution. Wait a few seconds for the solution to saturate the absorbent wrapping. 6. Swab the entire surface to be plated by brushing the surface with the saturated plating probe. The plating probe should be moved back and forth briskly to prevent burning and to provide even coverage. (See Figure 8.) Swab the area for the time recommended by the equipment manufacturer. 7. Thoroughly rinse the entire area with water. Any burning or darkening of the contacts may be removed with an abrasive pad. Saturate the abrasive pad and the printed wiring board surface with water and lightly buff the contacts until all evidence of the burning or discoloring is removed. Rinse the entire area with water. CAUTION Do not allow the rework area to dry out between steps. The water coating prevents oxidation. 8. Connect the nickel plating probe to the power supply (+) or red jack. 9. Dip the plating probe into the nickel plating solution. Wait a few seconds for the solution to saturate the absorbent wrapping. 10. Swab the entire surface to be plated by brushing the surface with the saturated plating probe. The plating probe should be moved back and forth briskly to prevent burning and to provide even coverage. Swab the area for the time recommended by the equipment manufacturer. Before rinsing, lightly buff the contacts with an abrasive pad. Page 4 of 6 Number: 4.6.3 Revision: Date: 2/98 IPC-7721 Subject: Edge Contact Repair, Plating Method 11. Thoroughly rinse the entire area with water. 12. Connect the gold plating probe to the power supply (+) or red jack. 13. Dip the plating probe into the gold plating solution. Wait a few seconds for the solution to saturate the absorbent wrapping. 14. Swab the entire surface to be plated by brushing the surface with the saturated plating probe. The plating probe should be moved back and forth briskly to prevent burning and to provide even coverage. Swab the area for the time recommended by the equipment manufacturer. 15. Thoroughly rinse the entire area with water. 16. Remove and discard all plating tape and thoroughly rinse the area with water. Dry the area using a air sprayer or wipes. 17. Remove the wire or conductive paint used to buss the contacts. CAUTION Apply tape to protect the contacts from further contamination while removing the buss connection. 16. Thoroughly rinse the entire area with deionized water or rinse the printed wiring board in an aqueous water cleaning system. EVALUATION 1. The rework area should be checked by measuring the thickness of the nickel and gold to make sure they meet the minimum thickness requirement. 2. The plating bond may also be checked by doing a peel test using peel testing tape. 3. Visually examine the rework area for color and luster. Page 5 of 6 Number: 4.6.3 Revision: Date: 2/98 NOTES IPC-7721 Subject: Edge Contact Repair, Plating Method Page 6 of 6 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 4.7.1 Surface Mount Pad Repair, Epoxy Method Product Class: R, F, C Skill Level: Advanced Level of Conformance: Medium OUTLINE This method is used to replace damaged surface mount pads with commercially available replacement pads. The new pads are bonded to the printed wiring board surface using liquid epoxy. CAUTION It is essential that the board surface be smooth and flat. If the base material is damaged see appropriate procedure. NOTE This method uses commercially available replacement surface mount pads. The new pads are fabricated from copper foil. They are available in hundreds of sizes and shapes and are generally supplied solder plated. If a special size or shape is needed they can be custom fabricated. Figure 1 Remove pad. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling Figure 2 Scrape off solder resist. TOOLS & MATERIALS Buffer Cleaner Epoxy Heat Lamp Knife Polyimide Tape Liquid Flux Microscope Oven Replacement Surface Mount Pads Scraper Solder Soldering Iron Tweezers Wipes PROCEDURE 1. Clean the area. 2. Remove the defective pad and a short length of the connecting conductor. (See Figure 1.) 3. Use a knife and scrape off any epoxy residue, contamination or burned material from the board surface. CAUTION Abrasion operations can generate electrostatic charges. 4. Scrape off any solder resist or coating from the connecting conductor. (See Figure 2.) Figure 3 Cut out new pad. Figure 4 Position pad using tape. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 4 Number: 4.7.1 Revision: Date: 2/98 IPC-7721 Subject: Surface Mount Pad Repair, Epoxy Method 5. Clean the area. 6. Apply a small amount of liquid flux to the connection area on the board surface and tin with solder. Clean the area. The length of the overlap solder connection should be a minimum of 2 times the conductor width. 7. The area for the new pad on the board surface must be smooth and flat. If internal fibers of the board are exposed or if there are deep scratches in the surface they should be repaired. Refer to appropriate procedure. 8. Select a commercially available surface mount pad that most closely matches the surface mount pad to be replaced. If a special size or shape is needed they can be custom fabricated. 9. Cut out and trim the new pad. Cut the length to provide the maximum allowable conductor overlap for soldering. Minimum 2 times the conductor width. (See Figure 3.) NOTE The new replacement surface mount pad may be trimmed from copper sheet. 10. Mix the epoxy and apply a small amount to the surface where the new pad will be placed. 11. Place a piece of Polyimide tape over the top surface of the new pad. Place the new pad into position on the printed wiring board surface using the tape to help in alignment. (See Figure 4.) 12. Cure the epoxy per the manufacturers instructions. CAUTION Some components may be sensitive to high temperature. 13. After the epoxy has cured remove the Polyimide tape used for alignment. Carefully clean the area and inspect the new pad for proper alignment. 14. If the new pad has a connecting conductor apply a small amount of liquid flux to the lap solder joint connection area and solder the conductor from the new pad to the conductor on the printed wiring board surface. Use minimal flux and solder to ensure a reliable connection. Tape may be placed over the top of the new pad to prevent excess solder overflow. NOTE If the configuration permits, the overlap solder joint connection should be a minimum of 3.00 mm from the related termination. This gap will minimize the possibility of simultaneous reflow during soldering operations. 15. Mix epoxy and coat the lap solder joint connections. Cure the epoxy per the manufacturers recommended instructions. NOTE Additional epoxy can be applied around the perimeter of the new pad to provide additional bond strength. 16. Apply surface coating to match prior coating as required. Figure 5 Completed repair. Page 2 of 4 Number: 4.7.1 Revision: Date: 2/98 IPC-7721 Subject: Surface Mount Pad Repair, Epoxy Method EVALUATION 1. Visual examination 2. Measurement of new pad width and spacing. 3. Electrical continuity measurement. Page 3 of 4 Number: 4.7.1 Revision: Date: 2/98 NOTES IPC-7721 Subject: Surface Mount Pad Repair, Epoxy Method Page 4 of 4 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 4.7.2 Surface Mount Pad Repair, Film Adhesive Method Product Class: R, F, C Skill Level: Advanced Level of Conformance: High OUTLINE This method is used to replace damaged surface mount pads with new dry film, adhesive backed pads. The new pads are bonded to the printed wiring board surface using a specially designed bonding press or bonding iron. CAUTION It is essential that the board surface be smooth and flat. If the base material is damaged see appropriate procedure. NOTE This method uses commercially available replacement surface mount pads. The new pads are fabricated from copper foil. They are available in hundreds of sizes and shapes and are generally supplied solder plated. If a special size or shape is needed they can be custom fabricated. Figure 1 Remove the defective surface mount pad and soldermask. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating 2.6 Epoxy Mixing and Handling Figure 2 Scrape off solder resist. TOOLS & MATERIALS Bonding Iron Bonding System Bonding Tips Cleaner Epoxy Heat Lamp Polyimide Tape Knife Liquid Flux PROCEDURE Microscope Oven Replacement Surface Mount Pads Scraper Solder Soldering Iron Tweezers Wipes Figure 3 Scrape off the adhesive bonding film from solder joint area. 1. Clean the area. 2. Remove the defective pad and a short length of the connecting circuit. (See Figure 1.) 3. Use a knife and scrape off any epoxy residue, contamination or burned material from the board surface. CAUTION Abrasion operations can generate electrostatic charges. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Figure 4 Cut out the new surface mount pad. Page 1 of 4 Number: 4.7.2 Revision: Date: 2/98 IPC-7721 Subject: Surface Mount Pad Repair, Film Adhesive Method 4. Scrape off any solder resist or coating from the connecting circuit. (See Figure 2.) 5. Clean the area. 6. Apply a small amount of liquid flux to the connection area on the board surface and tin with solder. Clean the area. The length of the overlap solder connection should be a minimum of 2 times the circuit width. 7. The area for the new pad on the board surface must be smooth and flat. If internal fibers of the board are exposed or if there are deep scratches in the surface, they should be repaired. Refer to appropriate procedure. 8. Select a commercially available surface mount pad that most closely matches the surface mount pad to be replaced. If a special size or shape is needed they can be custom fabricated. NOTE New surface mount pads are fabricated from copper foil. The foil is plated on the top side with solder and an adhesive bonding film is applied to the bottom side. 9. Before trimming out the new pad carefully scrape off the adhesive bonding film from the solder joint connection area on the back of the new pad. (See Figure 3.) CAUTION Scrape off the epoxy backing only from the joint connection area. When handling the replacement contact, avoid touching the epoxy backing with your fingers or other materials that may contaminate the surface and reduce the bond strength. 10. Cut out and trim the new pad. Cut out from the plated side. Cut the length to provide the maximum allowable circuit overlap for soldering. Minimum 2 times the circuit width. (See Figure 4.) 11. Place a piece of Polyimide tape over the top surface of the new pad. Place the new pad into position on the printed wiring board surface using the tape to help in alignment. Leave the tape in place during the bonding cycle. (See Figure 5.) 12. Select a commercially available bonding tip with a shape to match the shape of the new pad. See bonding tip chart in the replacement parts section of the manual provided with the repair system or repair kit. NOTE The tip used for bonding should be as small as possible but should completely cover the entire surface of the new pad. 13. Position the printed wiring board so that it is flat and stable. Gently place the hot bonding tip onto the tape covering the new pad. Apply pressure as recommended in the manual of the repair system or repair kit. (See Figure 6.) CAUTION Excessive bonding pressure may cause measling in the printed wiring board surface or may cause the new pad to slide out of position. Figure 5 Place the new surface mount pad in place using tape. Figure 6 Bonding system. Figure 7 Completed repair. Page 2 of 4 Number: 4.7.2 Revision: Date: 2/98 IPC-7721 Subject: Surface Mount Pad Repair, Film Adhesive Method 14. After the timed bonding cycle lift the bonding iron and remove the tape used for alignment. The pad is fully cured. Carefully clean the area and inspect the new pad for proper alignment. 15. If the new pad has a connecting circuit apply a small amount of liquid flux to the lap solder joint connection area and solder the circuit from the new pad to the circuit on the printed wiring board surface. Use minimal flux and solder to ensure a reliable connection. Tape may be placed over the top of the new pad to prevent excess solder overflow. NOTE If the configuration permits, the overlap solder joint connection should be a minimum of 3.00 mm from the related termination. This gap will minimize the possibility of simultaneous reflow during soldering operations. 16. Mix epoxy and coat the lap solder joint connection. Cure the epoxy per the manufacturers recommended instructions. NOTE Additional epoxy can be applied around the perimeter of the new pad to provide additional bond strength. CAUTION Some components may be sensitive to high temperature. 17. Apply surface coating to match prior coating as required. EVALUATION 1. Visual examination 2. Measurement of new pad width and spacing. 3. Electrical continuity measurement. Page 3 of 4 Number: 4.7.2 Revision: Date: 2/98 NOTES IPC-7721 Subject: Surface Mount Pad Repair, Film Adhesive Method Page 4 of 4 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 5.1 Plated Hole Repair, No Inner Layer Connection Product Class: R, F, W Skill Level: Intermediate Level of Conformance: High OUTLINE This procedure covers the repair of a damaged hole that has no inner layer connection. An eyelet is used to repair the damage to the hole and the eyelet flanges replace the pads on the printed wiring board surface. CAUTION This procedure is used only to restore the integrity of a through connection in a double sided board or a multilayer board where there is no inner layer connection. If there is an inner layer connection see appropriate procedure. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning Figure 1 Drill out the hole using a hand held drill and ball mill. TOOLS & MATERIALS Ball Mills, Carbide Caliper Cleaner Eyelets Eyelet Press System Eyelet Repair Kit Eyelet Setting Tools Hand Held Drill Liquid Flux Knife Microscope Pin Gauges Solder Solder Iron Wipes Figure 2 The eyelet flange can be used to secure a new conductor in place. EYELET SELECTION CRITERIA Figure 3 Set the eyelet using an eyelet press. ID Inside Diameter The eyelet inside diameter should be a 0.075 - 0.500 mm greater than the component lead diameter. LUF Length Under Flange The length of the eyelet barrel under the flange should be 0.630 - 0.890 mm greater than the thickness of the printed wiring board. This added length allows for proper protrusion when setting the eyelet. Figure 4 Completed repair. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 4 Number: 5.1 Revision: Date: 2/98 IPC-7721 Subject: Plated Hole Repair, No Inner Layer Connection FD Flange Diameter The eyelet flange diameter should be small enough to prevent interference with adjacent pads or conductors. OD Outside Diameter The clearance hole should allow the eyelet to be inserted without force but should not exceed 0.125 mm greater than the eyelet outside diameter. NOTE Be sure to select an eyelet meeting the proper criteria. An eyelet with an oversize flange may interfere with adjacent conductors. An eyelet that is too short will not protrude through the printed wiring board for proper setting. PROCEDURE 1. Clean the area. 2. Select an eyelet using the Eyelet Selection Criteria. Use a pin gauge and caliper to measure the existing plated hole dimensions. 3. Insert the appropriate ball mill into the hand held drill. Drill out the hole remov- ing all the plating. The drilled hole should be 0.025 - 0.125 mm larger than the eyelet O.D. (See Figure 1.) CAUTION This procedure may isolate internal connections on multilayer printed wiring boards. 4. Clean the area. 5. Apply a small amount of liquid flux to the pad or conductor on the printed wiring board surface, if any, and tin with solder using a soldering iron and solder. Clean the area. 6. Insert the eyelet into the hole. If a new conductor is required, the new conductor may extend into the drilled hole and the flange of the eyelet will secure the new conductor in place. (See Figure 2.) The eyelet may be inserted from either side. 7. Select the proper setting tools and insert them into an eyelet press system. (See Figure 3.) 8. Turn the printed wiring board over and rest the eyelet flange on the lower setting tool. 9. Apply firm even pressure to form the eyelet barrel. NOTE Inspect the eyelet flange for evidence of damage. Refer to IPC-A-610 Acceptability of Electronic Assemblies. 10. Apply a small amount of liquid flux and solder the eyelet flanges to the pads on the printed wiring board surface if necessary. Clean the area. Inspect for good solder flow and wetting around the eyelet flanges and lands. Page 2 of 4 Number: 5.1 Revision: Date: 2/98 IPC-7721 Subject: Plated Hole Repair, No Inner Layer Connection EVALUATION 1. Visual examination, dimensional requirement of pad diameter and inside diameter. 2. Electrical continuity measurement. Page 3 of 4 Number: 5.1 Revision: Date: 2/98 NOTES IPC-7721 Subject: Plated Hole Repair, No Inner Layer Connection Page 4 of 4 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 5.2 Plated Hole Repair, Double Wall Method Product Class: R, F, W Skill Level: Advanced Level of Conformance: Medium OUTLINE This procedure covers the use of an eyelet for the repair of a damaged pad on a hole that has an inner layer connect. CAUTION This procedure is used to restore the integrity of a through connection on a multilayer PC board, having an inner layer connect, but ONLY if the full barrel of the plated through hole remains intact. If there is barrel damage see appropriate procedure. CAUTION This method will reduce the inside diameter of the hole. The minimum hole size requirement must be checked for acceptance. Figure 1 Insert the eyelet into the hole. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning TOOLS & MATERIALS Ball Mills, Carbide Buffer Caliper Eyelets Eyelet Press System Eyelet Repair Kit Eyelet Setting Tools Hand Held Drill Liquid Flux Knife Microscope Pin Gauges Solder Solder Iron Wipes Figure 2 Set the eyelet using an eyelet press. EYELET SELECTION CRITERIA Figure 3 Completed repair. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Page 1 of 4 Number: 5.2 Revision: Date: 2/98 IPC-7721 Subject: Plated Hole Repair, Double Wall Method ID Inside Diameter The eyelet inside diameter should be a 0.075 - 0.500 mm greater than the component lead diameter. LUF Length Under Flange The length of the eyelet barrel under the flange should be 0.630 - 0.890 mm greater than the thickness of the PC board. This added length allows for proper protrusion when setting the eyelet. FD Flange Diameter The eyelet flange diameter should be small enough to prevent interference with adjacent pads or circuits. OD Outside Diameter The clearance hole should allow the eyelet to be inserted without force but should not exceed 0.125 mm greater than the eyelet outside diameter. NOTE Be sure to select an eyelet meeting the proper criteria. An eyelet with an oversize flange may interfere with adjacent circuits. An eyelet that is too short will not protrude through the PC board for proper setting. PROCEDURE 1. Clean the area. 2. Examine the hole to ensure that there is no damage to the wall of the hole. Check continuity to establish the integrity of the connection. 3. Select an eyelet using the Eyelet Selection Criteria. Use a pin gauge and caliper to measure the existing plated hole dimensions. The eyelet must have an inside diameter sufficient to receive the component lead and an outside diameter that will allow the eyelet to be inserted into the hole without force. 4. Remove oxides from the surface pads where the eyelet is to be installed using a buffer and clean. 5. Apply a small amount of liquid flux to the pad or circuit on the PC board surface, if any, and tin with solder using a soldering iron and solder. Clean the area. 6. Insert the eyelet into the hole. If a new circuit is required, the new circuit may extend into the hole and the flange of the eyelet will secure the new circuit in place. (See Figure 1.) 7. Select the proper setting tools and insert them into an eyelet press system. (See Figure 2.) 8. Turn the PC board over and rest the eyelet flange on the lower setting tool. 9. Apply firm even pressure to form the eyelet barrel. 10. Apply a small amount of liquid flux and solder the eyelet flanges to the pads on the PC board surface if necessary. Clean the area. Inspect for good solder flow and wetting around the eyelet flanges and lands. 11. Clean the area. 12. Install the component lead and solder, if required. Page 2 of 4 Number: 5.2 Revision: Date: 2/98 IPC-7721 Subject: Plated Hole Repair, Double Wall Method EVALUATION 1. Visual examination, dimensional requirement of pad diameter and inside diameter. 2. Electrical continuity measurement. Page 3 of 4 Number: 5.2 Revision: Date: 2/98 NOTES IPC-7721 Subject: Plated Hole Repair, Double Wall Method Page 4 of 4 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 2/98 Number: 5.3 Plated Hole Repair, Inner Layer Connection Product Class: R Skill Level: Expert Level of Conformance: Medium OUTLINE This procedure describes the use of flat set eyelets for the repair of a through connection that has an inner layer connect, no surface wire is used. The inner layer reconnect is established by soldering the barrel of an eyelet to the exposed inner layer and the connection is encapsulated in high strength epoxy. CAUTION This is a complex repair procedure that demands the proper tools and materials. To expect reliable results, repair technicians must have a high level of expertise. Use this method only when alternative methods are unacceptable. Figure 1 Drill press shown with PC board pinned in place. CAUTION This procedure requires very accurate control over the location and depth of a milled hole. It is recommended that a precision drill system be used in combination with a high power stereo microscope. REFERENCES 2.1 Handling Electronic Assemblies 2.2 Cleaning TOOLS & MATERIALS Ball Mills, Carbide Buffer Caliper Cleaner End Mills, Carbide Eyelets Eyelet Press System Eyelet Repair Kit Eyelet Setting Tools Hand Held Drill Liquid Flux Knife Microscope Pin Gauges Precision Drill Press Solder Solder Iron Wipes EYELET SELECTION CRITERIA Figure 2 Mill down to and expose inner layer signal or plane. Figure 3 Solder the eyelet barrel to the exposed inner layer. Material in this manual was voluntarily established by Technical Committees of the IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by the ipc. Figure 4 epoxy. Fill the milled hole with the Page 1 of 4 Number: 5.3 Revision: Date: 2/98 IPC-7721 Subject: Plated Hole Repair, Inner Layer Connection ID Inside Diameter The eyelet inside diameter should be a 0.075 - 0.500 mm greater than the component lead diameter. LUF Length Under Flange The length of the eyelet barrel under the flange should be 0.630 - 0.890 mm greater than the thickness of the printed wiring board. This added length allows for proper protrusion when setting the eyelet. FD Flange Diameter The eyelet flange diameter should be small enough to prevent interference with adjacent pads or conductors. OD Outside Diameter The clearance hole drilled through the printed wiring board should allow the eyelet to be inserted without force but should not exceed 0.125 mm greater than the eyelet outside diameter. Figure 5 Set the eyelet using an eyelet press. NOTE Be sure to select an eyelet meeting the proper criteria. An eyelet with an oversize flange may interfere with adjacent conductors. An eyelet that is too short will not protrude through the printed wiring board for proper setting. PROCEDURE 1. Clean the area. 2. Select an eyelet using the Eyelet Selection Criteria. Use a pin gauge and caliper to measure the existing plated hole dimensions. 3. Pin the printed wiring board to the base of a precision drill press. (See Figure 1.) 4. Insert the appropriate ball mill, end mill or drill into the chuck of the drill press. 5. Mill or drill out the hole. The drilled hole should be approximately 0.030 mm larger than the eyelet O.D. Inspect to ensure no metallic particles or burrs remain. 6. Select the side of the assembly that will have a counterbored hole milled into it. This side preferably would have no surface connection. 7. Select an end mill approximately 0.050 - 0.075 mm larger than the eyelet diameter. Insert into the precision drill press and mill down to and expose the inner layer signal or plane. (See Figure 2.) CAUTION Great care must be taken to control the depth of the milled hole to prevent damage to the inner layer signal or plane. 8. Clean the area. 9. Apply a small amount of flux to the exposed signal or plane and tin with solder. 10. Clean the area. 11. Insert the eyelet into the hole from the side opposite the milled hole, then apply a small amount of flux into the milled hole. Figure 6 Eyelet barrel formed flat to PC board surface. Page 2 of 4 Number: 5.3 Revision: Date: 2/98 IPC-7721 Subject: Plated Hole Repair, Inner Layer Connection 12. Solder the eyelet to the exposed inner layer signal or plane by applying heat from a soldering iron to barrel of the eyelet. (See Figure 3.) 13. Completely remove any solder flux residue by spray rinsing with cleaner. 14. Use a microscope and inspect the solder fillet from the eyelet to the inner con- nection and perform electrical tests as required. 15. Mix epoxy as required. 16. Fill the milled hole with the epoxy up to, and level with, the surface of the board. (See Figure 4.) The epoxy filler material should be free of voids and air bubbles. 17. Cure epoxy per the manufacturer’s recommendations 18. Select the proper setting tools and insert them into the eyelet press. (See Fig- ure 5.) 19. Turn the printed wiring board over and rest the eyelet flange on the lower set- ting tool. 20. Apply firm even pressure to form the eyelet barrel. (See Figure 6.) 21. Install the component lead and solder, if required. 22. Clean the area. EVALUATION 1. Visual examination, dimensional requirement of pad diameter and inside diameter. 2. Electrical continuity measurement. Page 3 of 4 Number: 5.3 Revision: Date: 2/98 NOTES IPC-7721 Subject: Plated Hole Repair, Inner Layer Connection Page 4 of 4 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 11/99 Jumper Wires Number: 6.1 Product Class: R/F/W/C Skill Level: Intermediate Level of Conformance: N/A OUTLINE This procedure covers the repair/modification of printed boards and electronic assemblies by the use of jumper wires to complete electrical continuity between two points. This procedure is meant to provide a foundation for adding jumper wires during the repair/modification process. The techniques and guidelines are based on general commercial and industry practices. Jumper wires fall into three (3) categories 1. Those that are considered wires and are installed during assembly. The routing, termination, and bonding of these jumper wires are documented by engineering instructions or drawing notations. 2. Those that are added after assembly to effect a change or modification. The routing, termination, and bonding of these jumper wires are documented by engineering change notice instructions or drawing notations. 3. Those that are added to correct a defect. This procedure has nine main sections. 1. References 2. Tools and Materials 3. General Rules 4. PC Board Preparation 5. Jumper Wire Selection 6. Jumper Wire Preparation 7. Jumper Wire Termination and Routing 8. Jumper Wire Bonding 9. Jumper Wire Termination Figures Figure 1 Route jumper wires. Figure 2 Use sleeving through PTH. REFERENCES 1.0 Foreword 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating Figure 3 Use insulated wire if required. TOOLS & MATERIALS Adhesive, Hot Melt Solder Adhesive, Quick Set Soldering Iron with Tips Cleaner Tape Dots Cleaning Wipes Wire Flush Cutter Wire, Adhesive Coated Flux, Liquid Wire Stripper Smooth Pliers Figure 4 Bond wires using tape dots or strips. Material in this manual was voluntarily established by Technical Committees of IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by IPC. Page 1 of 10 Number: 6.1 Revision: Date: 11/99 IPC-7721 Subject: Jumper Wires GENERAL RULES 1. Jumper wires should be placed on the component side of the assembly or printed board unless otherwise specified. 2. Jumper wires shall be routed in an XY manner as directly as feasible, making as few bends as possible. (See Figure 1.) 3. Jumper wires shall not be raised more than 3.2 mm [0.125 in] above the board surface or not above components or leads in such a way that they will interfere with PC board mounting. 4. Bare conductor jumper wires longer than 12.7 mm [0.50 in] shall not be used. Bare conductor jumper wires shorter than 12.7 mm [0.50 in] shall not violate the minimum electrical clearance. NOTE The 12.7 mm [0.50 in] dimension refers to the length between terminations. 5. Jumper wires may pass over lands provided sufficient slack is available so that the wire can be moved away from the land for component replacement. Jumper wires shall not pass over pads or vias used as test points. 6. Jumper wires shall not be routed under or over component leads or component bodies. Contact with heat sinks must be avoided. 7. Jumper wires shall not pass through component foot prints unless the layout of the assembly prohibits the routing in other areas. 8. Jumper wires shall have stress relief. 9. Jumper wires may be routed through plated through holes provided the wire is insulated and insulation sleeving is placed in the hole. If a hole is needed, use the following method. (See Figure 2.) A. Drill a hole 0.25 mm [0.010 in] larger than the insulation diameter. B. Inspect the hole for burs or exposed internal circuits. C. Document the added hole on a control drawing. NOTE Be careful that the drilled hole does not interfere with surface and internal conductors. 10. Jumper wires soldered into plated through holes must be discernible on the opposite side. 11. Jumper wires soldered to lifted or clipped component leads may require insulation to prevent shorting. (See Figure 3.) 12. Jumper wires may be terminated by a variety of methods. See illustrations. Figure 5 Bond wires using adhesive. Figure 6 Adhesive coated wires are heat bonded. PC BOARD PREPARATION 1. Clean the area. NOTE When wires are in place cleaning will often be more difficult. 2. Remove coating material or oxidization as necessary from the component leads, pads, or conductors where wire terminations will be soldered. Clean the area. Page 2 of 10 Number: 6.1 Revision: Date: 11/99 IPC-7721 Subject: Jumper Wires 3. Remove solder from the connection point if needed. Clean the area. 4. Measure approximately the length of each wire needed. JUMPER WIRE SELECTION 1. Bare conductor jumper wires longer than 12.7 mm [0.50 in] shall not be used. Bare conductor jumper wires shorter than 12.7 mm [0.50 in] shall not violate the minimum electrical clearance. NOTE The 12.7 mm [0.50 in] dimension refers to the length between terminations. 2. Silver plated wire must not be used; under some conditions corrosion of the wire can occur. 3. The smallest diameter wire that will carry the required current should be selected. 4. Insulation requirements of the wire should withstand soldering temperatures, have some resistance to abrasion, have a dielectric resistance equal to or better than the board insulation material. 5. Recommended wire is solid insulated copper wire, tin lead plated, 22 to 32 AWG with Kynar, Milene, Kapton, Teflon or equivalent insulation. CAUTION Wires with nicked or damaged conductors should not be used. JUMPER WIRE PREPARATION 1. Cut the jumper wires approximately 12.7 mm [0.50 in] longer than the estimated length needed. NOTE The length and gauge of the jumper wire may be critical. All wires have an electrical resistance (impedance) to the flow of electricity. This impedance is important to electronic circuitry. Always refer to wiring lists for specific jumper wire requirements. 2. Strip insulation from each end of the jumper wire. NOTE Strip length is dependent on the termination style. 3. If required, tin the stripped ends with solder. Clean if necessary. JUMPER WIRE TERMINATING AND ROUTING 1. Form the wire as needed and place the wire in position depending on the termination style. Center the wire on the component lead or pad, do not overhang sides. If the wire is soldered to a pin, terminal or component lead, wrap the wire a minimum of 90°. 2. Solder one end of the wire. Clean if necessary. NOTE Solder joint length must meet acceptability requirements. Page 3 of 10 Number: 6.1 Revision: Date: 11/99 IPC-7721 Subject: Jumper Wires CAUTION The insulation shall not be stripped back more than two wire diameters from the solder joint. Wire insulation may touch but not penetrate the solder joint provided proper wetting of the wire is evident. 3. Bend the wire as needed and run the wire along board surface. Route the jumper wire using the shortest route in an XY direction with the fewest possible bends to the second termination point. NOTE Jumper wires shall not be routed under or over component leads or component bodies. Contact with heat sinks must be avoided. CAUTION Do not bend the wire tighter than a radius of three times the conductor diameter. 4. After routing the jumper wire, solder the opposite end. Clean if necessary. CAUTION Wires soldered to lifted or clipped components leads may require insulation to prevent shorting. JUMPER WIRE BONDING 1. After the wire has been soldered at both ends and cleaned if necessary, the wire should be bonded to the board surface. NOTE Bonding is not required if wire is insulated and insulated length is less than 25 mm [1.00 in]. 2. Bond the jumper wire using one of the following methods. A. Tape Dots or Tape Strips. (See Figure 4.) B. Quick Set Adhesive. (See Figure 5.) C. Hot Melt Adhesive. (See Figure 5.) D. Hot Bonding. Some jumper wires are manufactured with a special thermo-set adhesive coating and are thermally bonded to the board surface with a special bonding tool. (See Figure 6.) 3. Bond the jumper wire within 6.0 mm [0.25 in] of each solder joint. 4. Bond the jumper wire within 6.0 mm [0.25 in] of each bend in the wire. 5. Bond the jumper wire at intervals not less than 25 mm [1.00 in] on straight runs. Page 4 of 10 Number: 6.1 Revision: Date: 11/99 IPC-7721 Subject: Jumper Wires Table 1 Jumper Wire Termination Methods Figure Type Wire Termination Method 7 PTH Hole Wire soldered into plated-through hole on component side. * 8 PTH Lead Wire soldered parallel to lead on component side. 9 PTH Hole Wire soldered into plated-through hole on solder side. * 10 PTH Hole Wire wrapped around component lead on solder side. 11 PTH Hole Wire wrapped around lead on component side. 12 PTH Lead Wire soldered to lifted component lead. + 13 PTH Lead Wire soldered to clipped lead on component side. + 14 PTH Lead Wire looped and soldered to adjacent component leads. 15 PTH Lead Wire soldered to lead, wire over component. 16 PTH Lead Soldered perpendicular to component lead. 17 PTH Lead Multiple wires soldered to component lead overhanging edge. 18 Chip Wire soldered to pad, parallel or perpendicular to component. 19 Chip Wire soldered parallel or perpendicular to component. 20 Chip Wire soldered to component end, lifted off pad. 21 Chip Multiple wires overhanging pad edge. 22 PTH Hole Wire soldered into plated-through hole. * 23 PTH Pad Wire soldered across top of PTH pad. 24 PTH Pad Multiple wires soldered to pad overhanging pad edge. 25 Conductor Wire soldered parallel to conductor, contact, SMT pad. 26 Conductor Wire perpendicular to conductor, contact, SMT pad. 27 Conductor Multiple wires soldered to conductor, contact, SMT pad. 28 J Lead Wire soldered parallel to component lead. 29 J Lead Wire soldered to clipped component lead. + 30 J Lead Wire looped and soldered to adjacent component leads. 31 J Lead Wire soldered to component lead, wire running over component. 32 J Lead Wire soldered perpendicular to lead. 33 J Lead Multiple wires soldered to lead overhanging edge. 34 J Lead Wire soldered to lifted component lead. 35 Gull Wing Wire soldered parallel to component lead. 36 Gull Wing Wire soldered to lifted component lead. + 37 Gull Wing Wire soldered to clipped component lead. + 38 Gull Wing Wire looped and soldered to adjacent component leads. 39 Gull Wing Wire soldered to component lead, wire over component. 40 Gull Wing Wire soldered perpendicular to component lead. 41 Gull Wing Multiple wires soldered to lead overhanging edge. * Jumper wires soldered into plated-through holes must be discernible on the opposite side. + Jumper wires soldered to lifted or clipped component leads may require insulation to prevent shorting. Acceptability Acceptable Acceptable Acceptable Acceptable Acceptable Acceptable Acceptable Acceptable Not Recommended Not Recommended Not Recommended Acceptable Acceptable Acceptable Not Recommended Acceptable Acceptable Not Recommended Acceptable Not Recommended Not Recommended Acceptable Acceptable Acceptable Not Recommended Not Recommended Not Recommended Not Recommended Acceptable Acceptable Acceptable Acceptable Not Recommended Not Recommended Not Recommended Page 5 of 10 Number: 6.1 Revision: Date: 11/99 IPC-7721 Subject: Jumper Wires Jumper Wire Termination Figures – Through-Hole Components Figure 7 Acceptable Wire soldered into plated-through hole, component side. * Figure 8 Acceptable Wire soldered parallel to lead on component side. Figure 9 Acceptable Wire soldered into plated-through hole on solder side. * Figure 10 Acceptable Wire wrapped around component lead on solder side. Figure 11 Acceptable Wire wrapped around lead on component side. Figure 12 Acceptable Wire soldered to lifted component lead. + Figure 13 Acceptable Wire soldered to clipped lead on component side. + Figure 14 Acceptable Wire looped and soldered to adjacent component leads. Figure 15 Not Recommended Wire soldered to lead, wire over component. Figure 16 Not Recommended Soldered perpendicular to component lead. Figure 17 Not Recommended Multiple wires soldered to lead overhanging edge. * Jumper wires soldered into plated-through holes must be discernible on the opposite side. + Jumper wires soldered to lifted or clipped component leads may require insulation to prevent shorting. Page 6 of 10 Number: 6.1 Revision: Date: 11/99 IPC-7721 Subject: Jumper Wires Jumper Wire Termination Figures – Chip Components, Pads and Conductors Figure 18 Acceptable Wire soldered to pad, parallel or perpendicular to component. Figure 19 Acceptable Wire soldered parallel or perpendicular to component. Figure 20 Acceptable Wire soldered to component end, lifted off pad. Figure 21 Not Recommmended Multiple wires overhanging pad edge. Figure 22 Acceptable Wire soldered into Figure 23 Acceptable Wire soldered plated-through hole. * across top of PTH pad. Figure 24 Not Recommended Multiple wires soldered to pad overhanging pad edge. Figure 25 Acceptable Wire soldered parallel to conductor, contact, SMT pad. Figure 26 Not Recommended Wire per- Figure 27 Not Recommended Multiple pendicular to conductor; contact, SMT pad. wires soldered to conductor, contact, SMT pad. * Jumper wires soldered into plated-through holes must be discernible on the opposite side. + Jumper wires soldered to lifted or clipped component leads may require insulation to prevent shorting. Page 7 of 10 Number: 6.1 Revision: Date: 11/99 IPC-7721 Subject: Jumper Wires Jumper Wire Termination Figures – J Lead Components Figure 28 Acceptable Wire soldered parallel to component lead. Figure 29 Acceptable Wire soldered to clipped component lead. + Figure 30 Acceptable Wire looped and soldered to adjacent leads. Figure 31 Not Recommended Wire soldered to lead, over component. Figure 32 Not Recommended Wire soldered perpendicular to lead. Figure 33 Not Recommended Multiple wires soldered to lead overhanging edge. Figure 34 Not Recommended Wire soldered to lifted component lead. * Jumper wires soldered into plated-through holes must be discernible on the opposite side. + Jumper wires soldered to lifted or clipped component leads may require insulation to prevent shorting. Page 8 of 10 Number: 6.1 Revision: Date: 11/99 IPC-7721 Subject: Jumper Wires Jumper Wire Termination Figures – Gull Wing Components Figure 35 Acceptable Wire soldered parallel to component lead. Figure 36 Acceptable Wire soldered to lifted component lead. + Figure 37 Acceptable Wire soldered to clipped component lead. + Figure 38 Acceptable Wire looped and soldered to adjacent component leads. Figure 39 Not Recommended Wire sol- Figure 40 Not Recommended Wire dered to component lead, wire over component. soldered perpendicular to component lead. Figure 41 Not Recommended Multiple wires soldered to lead overhanging edge. * Jumper wires soldered into plated-through holes must be discernible on the opposite side. + Jumper wires soldered to lifted or clipped component leads may require insulation to prevent shorting. Page 9 of 10 Number: 6.1 Revision: Date: 11/99 IPC-7721 Subject: Jumper Wires This Page Intentionally Left Blank Page 10 of 10 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 11/99 Number: 6.2.1 Jumper Wires, BGA Components, Foil Jumper Method Product Class: R/F Skill Level: Expert Level of Conformance: Medium OUTLINE This method is used to change a circuit path at a BGA site for engineering changes or modifications. NOTE This procedure requires precision milling equipment and highly trained technicians. CAUTION This procedure is not applicable for ‘‘via in pad’’ applications. REFERENCES 1.0 Foreword 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking And Preheating 2.6 Epoxy Mixing and Handling 4.2.1 Conductor Repair, Foil Jumper, Epoxy Method 4.4.3 Surface Mount, BGA Pad Repair, Film Adhesive Method 6.1 Jumper Wires Figure 1 Cut the connection to the via using a drill system. TOOLS & MATERIALS BGA Rework System Bonding Iron Bonding Tips Bonding System Buffer Circuit Frames, BGA Pads Cleaner Drill System End Mills Epoxy Flux, Liquid Foil Jumpers PROCEDURE Heat Lamp Microscope Milling System Oven Precision Knife Repair System or Repair Kit Scraper Solder Soldering Iron Tape, High Temperature Tweezers Wipes Figure 2 Remove BGA pad & mill shallow channel into solder mask surface. Figure 3 Bond a new BGA pad in place. 1. Clean the area. 2. Remove the BGA component if installed, remove excess solder from the pads, and clean and inspect the site using standard BGA rework equipment. 3. Cut the short conductor (dog bone) connecting the BGA pad to the connecting via using a drill system or milling machine and appropriate size end mill. (See Figure 1 and 6.) 4. Remove the existing BGA pad. Apply heat from a soldering iron if needed. (See Figure 2.) Figure 4 Solder a foil jumper to the tail extending from the new BGA pad. Material in this manual was voluntarily established by Technical Committees of IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by IPC. Page 1 of 2 Number: 6.2.1 Revision: Date: 11/99 IPC-7721 Subject: Jumper Wires, BGA Components, Foil Jumper Method 5. Inspect the proposed path for the foil jumper to ensure proper clearance. Use a milling machine to mill a shallow groove in the solder mask surface from the BGA pad area to the perimeter of the BGA site. Tight spacing may restrict the width of the channel to 0.25 mm [0.010 in] or less. Use a carbide end mill approximately 0.050 mm [0.002 in] wider than the new connecting circuit. (See Figure 3.) NOTE Be sure to mill a shallow groove to prevent damage to internal conductive layers. 6. Bond a replacement BGA pad in place using a bonding system. (See Procedure 4.7.3.) The new BGA pad must have a tail that will align with the foil jumper to be added next. (See Figure 4.) 7. Select a foil jumper to match the width and thickness of the circuit to be replaced. Cut a length approximately as needed. The foil jumper should overlap the BGA tail section a minimum of two times the circuit width. 8. Gently abrade the top and bottom ends of the new foil jumper with the buffer to remove any oxidation and clean. NOTE If needed, the ends of the foil jumper may be tinned with solder prior to lap soldering in place. 9. Position this new foil jumper along the milled groove. The foil jumper should overlap the existing circuit a minimum of two times the circuit width. (See Figure 4.) 10. Apply a small amount of liquid flux to the overlap joint. 11. Lap solder the foil jumper to the BGA tail section using solder and a soldering iron. Make sure the foil jumper is properly aligned. 12. Clean the area. 13. Mix epoxy. If desired, add color agent to the mixed epoxy to match the printed wiring board color. 14. Coat the top and bottom of the foil jumper with epoxy. The epoxy bonds the new circuit to the base board material and insulates the circuit. (See Figure 5.) CAUTION Some components may be sensitive to high temperature. 16. Clean the board as required. 17. Install new BGA per applicable procedures. 18. Solder one end of a fine gauge wire to the end of the extending foil jumper. (The opposite end of the wire will be soldered later.) (See Figure 5.) 19. Route and terminate the other end of the jumper wire. Figure 5 Solder a wire to the foil jumper bond with epoxy. Figure 6 Sample of drill system used to cut the connection from the BGA pad to the via. EVALUATION 1. Visual examination for alignment and overlap of new circuit. 2. Visual examination of epoxy coating for texture and color match. 3. Electrical tests as applicable. Page 2 of 2 7721 Repair and Modification of Printed Boards and Electronic Assemblies Revision: Date: 03/01 Number: 6.3 Component Modifications and Additions Product Class: R,F,W,C Skill Level: Advanced Level of Conformance: N/A OUTLINE This procedure covers the general guidelines for modifications that involve adding components. REFERENCES 1.0 Index 2.1 Handling Electronic Assemblies 2.2 Cleaning 2.5 Baking and Preheating TOOLS & MATERIALS Cleaner Cleaning Wipes Flux Microscope System Soldering Iron with Tips Solder GENERAL RULES 1. Added components may need to be secured with adhesive, or by other means, if the component leads or component body would be subjected to mechanical stress. 2. Leads of added components should not be inserted into plated holes occupied by another component lead. 3. Added components placed on the circuit board surface should be placed on the component side of the assembly or circuit board unless otherwise specified. 4. Added components shall not be raised above the board surface beyond allowable dimensions. 5. Added components shall not cover over pads or vias used as test points. 6. Added components shall not cover other component foot prints unless the lay- out of the assembly prohibits mounting in other areas. 7. Added component leads may require insulation to avoid contact with compo- nent body or other conductors. 8. Removal of existing solder from a connection point may be necessary to avoid bridging, or excess solder, in the final connection. 9. Consider design limitations and product use environments when stacking com- ponents. 10. Do not exceed minimum component lead bend radius. 11. When possible, component identification marking shall be legible. Material in this manual was voluntarily established by Technical Committees of IPC. This material is advisory only and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment referenced is for the convenience of the user and does not imply endorsement by IPC. Page 1 of 4 Number: 6.3 Revision: Date: 03/01 IPC-7721 Subject: Component Modifications and Additions PROCEDURE 1. When required, form the component leads and clean the area. 2. When required, secure the component in place by bending leads or other mechanical means. 3. Apply flux to the connection. 4. Place the soldering iron tip at the connection between both leads. Apply a small amount of solder at the connection of soldering iron tip and lead to form a solder bridge. 5. Immediately feed solder into the joint from the side opposite the soldering iron tip until the proper fillet is achieved. Remove the solder and iron simultaneously. 6. When required, clean the flux residue. 7. Inspect. Page 2 of 4 Number: 6.3 Revision: Date: 03/01 IPC-7721 Subject: Component Modifications and Additions Component Modification Examples Figure 1 Radial lead component soldered to through hole component leads. Note: Leads of the radial component should not need to be inserted into the plated holes. Figure 2 Axial lead component soldered to through hole component leads. Note: Leads of axial component should not be inserted into the plated holes. Figure 3 Axial lead component soldered to adjacent axial lead component. Note: Added component may be stacked vertically or horizontally. Figure 4 Chip component soldered to surface mount component using jumper wires. Note: One lead of surface mount component is shown lifted. Figure 5 DIP component stacked and soldered onto another DIP component. One lead shown clipped. Note: Leads of added component should not be inserted into the plated holes. Figure 6 Chip cap bridging adjacent leads. Page 3 of 4 Number: 6.3 Revision: Date: 03/01 IPC-7721 Subject: Component Modifications and Additions Component Modification Examples (continued) Figure 7 Chip component bridging leads of surface mount component. Figure 8 Chip component stacked onto another chip component. Figure 9 Acceptable Surface mount component mounted upside down with jumper wires attached. Note: One lead is bent outward. Figure 10 DIP component mounted upside down with jumper wires attached. Figure 11 Chip component mounted to one pad only. Page 4 of 4 Figure 12 Radial lead component mounted upside down. Note: Insulate leads to avoid contact with component body. Standard Improvement Form The purpose of this form is to provide the Technical Committee of IPC with input from the industry regarding usage of the subject standard. Individuals or companies are invited to submit comments to IPC. All comments will be collected and dispersed to the appropriate committee(s). 1. I recommend changes to the following: Requirement, paragraph number Test Method number , paragraph number The referenced paragraph number has proven to be: Unclear Too Rigid In Error Other IPC-7721 If you can provide input, please complete this form and return to: IPC 2215 Sanders Road Northbrook, IL 60062-6135 Fax 847 509.9798 2. Recommendations for correction: 3. Other suggestions for document improvement: Submitted by: Name Company Address City/State/Zip Telephone E-mail Date THE INSTITUTE FOR INTERCONNECTING AND PACKAGING ELECTRONIC CIRCUITS ANSI/IPC-T-50 Terms and Definitions for Interconnecting and Packaging Electronic Circuits Definition Submission/Approval Sheet The purpose of this form is to keep current with terms routinely used in the industry and their definitions. Individuals or companies are invited to comment. Please complete this form and return to: IPC 2215 Sanders Road Northbrook, IL 60062-6135 Fax: 847 509.9798 SUBMITTOR INFORMATION: Name: Company: City: State/Zip: Telephone: Date: u This is a NEW term and definition being submitted. u This is an ADDITION to an existing term and definition(s). u This is a CHANGE to an existing definition. Term Definition If space not adequate, use reverse side or attach additional sheet(s). Artwork: u Not Applicable u Required u To be supplied u Included: Electronic File Name: Document(s) to which this term applies: Committees affected by this term: IPC Office Date Received: Comments Collated: Returned for Action: Revision Inclusion: Office Use Committee 2-30 Date of Initial Review: Comment Resolution: Committee Action: u Accepted u Rejected u Accept Modify IEC Classification Classification Code • Serial Number Terms and Definition Committee Final Approval Authorization: Committee 2-30 has approved the above term for release in the next revision. Name: Committee: IPC 2-30 Date: Technical Questions The IPC staff will research your technical question and attempt to find an appropriate specification interpretation or technical response. Please send your technical query to the technical department via: tel 847/509-9700 http://www.ipc.org fax 847/509-9798 e-mail: answers@ipc.org IPC Technical Forums IPC technical forums are opportunities to network on the Internet. It’s the best way to get the help you need today! Over 2,500 people are already taking advantage of the excellent peer networking available through e-mail forums provided by IPC. Members use them to get timely, relevant answers to their technical questions. TechNet@ipc.org TechNet forum is for discussion of technical help, comments or questions on IPC specifications, or other technical inquiries. IPC also uses TechNet to announce meetings, important technical issues, surveys, etc. ChipNet@ipc.org ChipNet forum is for discussion of flip chip and related chip scale semiconductor packaging technologies. It is cosponsored by the National Electronics Manufacturing Initiative (NEMI). ComplianceNet@ipc.org ComplianceNet forum covers environmental, safety and related regulations or issues. DesignerCouncil@ipc.org Designers Council forum covers information on upcoming IPC Designers Council activities as well as information, comment, and feedback on current design issues,local chapter meetings, new chapters forming, and other design topics. Roadmap@ipc.org The IPC Roadmap forum is the communication vehicle used by members of the Technical Working Groups (TWGs) who develop the IPC National Technology Roadmap for Electronic Interconnections. IPCsm840@ipc.org This peer networking forum is specific to solder mask qualification and use. ADMINISTERING YOUR SUBSCRIPTION STATUS: All commands (such as subscribe and signoff) must be sent to listserv@ipc.org. Please DO NOT send any command to the mail list address, (i.e. @ipc.org), as it would be distributed to all the subscribers. Example for subscribing: To: LISTSERV@IPC.ORG Subject: Message: subscribe TechNet Joseph H. Smith Example for signing off: To: LISTSERV@IPC.ORG Subject: Message: sign off DesignerCouncil Please note you must send messages to the mail list address ONLY from the e-mail address to which you want to apply changes. In other words,if you want to sign off the mail list, you must send the signoff command from the address that you want removed from the mail list. Many participants find it helpful to signoff a list when travelling or on vacation and to resubscribe when back in the office. How to post to a forum: To send a message to all the people currently subscribed to the list, just send to @ipc.org Please note, use the mail list address that you want to reach in place of the string in the above instructions. Example: To: TechNet@IPC.ORG Subject: Message: The associated e-mail message text will be distributed to everyone on the list, including the sender. Further information on how to access previous messages sent to the forums will be provided upon subscribing. For more information, contact Dmitriy Sklyar tel 847/509-9700 x311 fax 847/509-9798 e-mail: sklydm@ipc.org http://www.ipc.org/html/forum.htm IPC World Wide Web Page http://www.ipc.org Our home page provides access to information about upcoming events, publications and videos, membership, and industry activities and services. Visit soon and often. Education and Training IPC conducts local educational workshops and national conferences to help you better understand emerging technologies. National conferences have covered Ball Grid Array and Flip Chip/Chip Scale Packaging. Some workshop topics include: Printed Wiring Board Fundamentals Troubleshooting the PWB Manufacturing Process Choosing the Right Base Material Laminate Acceptability of Printed Boards New Design Standards High Speed Design Design for Manufacturability Design for Assembly Designers Certification Preparation IPC video tapes and CD-ROMs can increase your industry know-how and on the job eff ectiveness. For more information on programs, contact John Riley tel 847/509-9700 ext. 308 fax 847/509-9798 e-mail: rilejo@ipc.org http://www.ipc.org For more information on IPC Video/CD Training, contact Mark Pritchard tel 505/758-7937 ext. 202 fax 505/758-7938 e-mail: markp@taos.newmex.com http://www.ipc.org Training and Certification IPC-A-610 Training and Certification Program “The Acceptability of Electronic Assemblies” (ANSI/IPC-A-610) is the most widely used specification for the PWB assembly industry. An industry consensus Training and Certification program based on the IPC-A-610 is available to your company. For more information, contact John Riley tel 847/509-9700 ext. 308 fax 847/509-9798 e-mail: rilejo@ipc.org http://www.ipc.org/html/610.htm IPC Printed Circuits Expo IPC Printed Circuits Expo is the largest trade exhibition in North America devoted to the PWB industry. Over 90 technical presentations make up this superior technical conference. April 28-30, 1998 Long Beach, California March 16-18, 1999 Long Beach, California For more information, contact Kim Behr tel 847/509-9700 ext. 319 fax 847/509-9798 e-mail: behrki@ipc.org http://www.ipc.org How to Get Involved The first step is to join IPC. An application for membership can be found on page 74. Once you become a member, the opportunities to enhance your competitiveness are vast. Join a technical committee and learn from our industry’s best while you help develop the standards for our industry. Participate in market research programs which forecast the future of our industry. Participate in Capitol Hill Day and lobby your Congressmen and Senators for better industry support. Pick from a wide variety of educational opportunities: workshops, tutorials, and conferences. More up-to-date details on IPC opportunities can be found on our web page: http:/www.ipc.org. For information on how to get involved, contact: Jeanette Ferdman, Membership Manager tel 847/509-9700 ext. 309 fax 847/509-9798 e-mail: JeanetteFerdman@ipc.org http://www.ipc.org APPLICATION FOR SITE MEMBERSHIP PLEASE CHECK APPROPRIATE CATEGORY Thank you for your decision to join IPC members on the “Intelligent Path to Competitiveness”! IPC Membership is site specific, which means that IPC member benefits are available to all individuals employed at the site designated on the other side of this application. To help IPC serve your member site in the most efficient manner possible, please tell us what your facility does by choosing the most appropriate member category. s INDEPENDENT PRINTED BOARD MANUFACTURERS Our facility manufactures and sells to other companies, printed wiring boards or other electronic interconnection products on the merchant market. WHAT PRODUCTS DO YOU MAKE FOR SALE? n One-sided and two-sided rigid printed boards n Multilayer printed boards n Flexible printed boards n Flat cable n Hybrid circuits n Discrete wiring devices n Other interconnections Name of Chief Executive Officer/President___________________________________________________________________ s INDEPENDENT PRINTED BOARD ASSEMBLERS EMSI COMPANIES Our facility assembles printed wiring boards on a contract basis and/or offers other electronic interconnection products for sale. n Turnkey n SMT n Chip Scale Technology n Through-hole n Mixed Technology n Consignment n BGA Name of Chief Executive Officer/President ________________________ _ s OEM – MANUFACTURERS OF ANY END PRODUCT USING PCB/PCAS OR CAPTIVE MANUFACTURERS OF PCBS/PCAS Our facility purchases, uses and/or manufactures printed wiring boards or other electronic interconnection products for our own use in a final product. Also known as original equipment manufacturers (OEM). IS YOUR INTEREST IN: n purchasing/manufacture of printed circuit boards n purchasing/manufacturing printed circuit assemblies What is your company’s main product line? __________________________________________________________________ s INDUSTRY SUPPLIERS s GOVERNMENT AGENCIES/ ACADEMIC TECHNICAL LIAISONS Our facility supplies raw materials, machinery, equipment or services used in the manufacture or assembly of electronic interconnection products. What products do you supply?_____________________________________________________________________________ We are representatives of a government agency, university, college, technical institute who are directly concerned with design, research, and utilization of electronic interconnection devices. (Must be a non-profit or not-for-profit organization.) Please be sure both sides of this application are correctly completed APPLICATION FOR SITE MEMBERSHIP Site Information: Company Name Street Address City Main Phone No. Primary Contact Name Title Phone Alternate Contact Name Title Phone State Zip Fax Mail Stop Fax Mail Stop Fax Country e-mail e-mail Please check one: t $1,000.00 Annual dues for Primary Site Membership (Twelve months of IPC membership begins from the time the application and payment are received) t $800.00 Annual dues for Additional Facility Membership: Additional membership for a site within an organization where another site is considered to be the primary IPC member. t $600.00** Annual dues for an independent PCB/PWA fabricator or independent EMSI provider with annual sales of less than $1,000,000.00. **Please provide proof of annual sales. t $250.00 Annual dues for Government Agency/University/not-for-profit organization TMRC Membership t Please send me information on Membership in the Technology Marketing Research Council (TMRC) AMRC Membership t Please send me information for Membership in the Assembly Marketing Research Council (AMRC) Payment Information Enclosed is our check for $ Please bill my credit card: (circle one) MC AMEX VISA DINERS Card No. Authorized Signature Mail application with check or money order to: IPC Dept. 77-3491 Chicago, IL 60678-3491 Fax/Mail application with credit card payment to: IPC 2215 Sanders Road Northbrook, IL 60062-6135 Tel: 847 509.9700 Fax: 847 509.9798 Exp date ____________________ @@@@@@@@@@@@@@@@@@h h h h h h @@@@@@@@@@ee????????@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e?? @@@@@@@@@@@@@@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ PLEASE ATTACH BUSINESS CARD @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ OF OFFICIAL REPRESENTATIVE HERE @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@@@g g g g g g @@@@@@@@@@@@ ??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@??e e@@@@@@@@@@@@@@@@e e??@@@@@@@@@@@@@@@@ ??@@@@@@@@@@??????@@@@@@@@@@@@@@@@@@ ISBN #1-580981-75-5 2215 Sanders Road Northbrook, Illinois 60062-6135 Tel 847 509.9700 Fax 847 509.9798 URL: http://www.ipc.org

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