IPC-4553

IPC-4553A Specification for Immersion Silver Plating for Printed Boards May 2009 Supersedes IPC-4553 June 2005 A standard developed by IPC ® Association Connecting Electronics Industries The Principles of Standardization In May 1995 the IPC’s Technical Activities Executive Committee (TAEC) adopted Principles of Standardization as a guiding principle of IPC’s standardization efforts. Standards Should: • Show relationship to Design for Manufacturability (DFM) and Design for the Environment (DFE) • Minimize time to market • Contain simple (simplified) language • Just include spec information • Focus on end product performance • Include a feedback 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 Notice IPC Standards and Publications are designed to serve the public interest through eliminating mis- understandings between manufacturers and purchasers, facilitating interchangeability and improve- ment 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 adop- tion 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 them- selves against all claims of liabilities for patent infringement. IPC Position Statement on Specification Revision Change It is the position of IPC’s Technical Activities Executive Committee that the use and implementation of IPC publications is voluntary and is part of a relationship entered into by customer and supplier. When an IPC publication is updated and a new revision is published, it is the opinion of the TAEC that the use of the new revision as part of an existing relationship is not automatic unless required by the contract. The TAEC recommends the use of the latest revision. Adopted October 6, 1998 Why is there a charge for this document? Your purchase of this document contributes to the ongoing development of new and updated industry standards and publications. Standards allow manufacturers, customers, and suppliers to understand one another better. Standards allow manufacturers greater efficiencies when they can set up their processes to meet industry standards, allowing them to offer their customers lower costs. IPC spends hundreds of thousands of dollars annually to support IPC’s volunteers in the standards and publications development process. There are many rounds of drafts sent out for review and the committees spend hundreds of hours in review and development. IPC’s staff attends and par- ticipates in committee activities, typesets and circulates document drafts, and follows all necessary procedures to qualify for ANSI approval. IPC’s membership dues have been kept low to allow as many companies as possible to participate. Therefore, the standards and publications revenue is necessary to complement dues revenue. The price schedule offers a 50% discount to IPC members. If your company buys IPC standards and publications, why not take advantage of this and the many other benefits of IPC membership as well? For more information on membership in IPC, please visit www.ipc.org or call 847/597-2872. Thank you for your continued support. ©Copyright 2009. IPC, Bannockburn, Illinois, USA. All rights reserved under both international and Pan-American copyright conventions. Any copying, scanning or other reproduction of these materials without the prior written consent of the copyright holder is strictly prohibited and constitutes infringement under the Copyright Law of the United States. IPC-4553A Specification for Immersion Silver Plating for Printed Boards Developed by the Plating Processes Subcommittee (4-14) of the Fabrication Processes Committee (4-10) of IPC Users of this publication are encouraged to participate in the development of future revisions. Contact: IPC 3000 Lakeside Drive, Suite 309S Bannockburn, Illinois 60015-1249 Tel 847 615.7100 Fax 847 615.7105 Supersedes: IPC-4553 - June 2005 ® --`,`,`,`,,`,,,,`,,,``,``,,,`,-`-`,,`,,`,`,,`--- This Page Intentionally Left Blank Acknowledgment Any document involving a complex technology draws material from a vast number of sources. While the principal members of the Plating Processes Subcommittee (4-14) of the Fabrication Processes Committee (4-10) are shown below, it is not pos- sible 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. Fabrication Processes Committee Plating Processes Subcommittee Technical Liaisons of the IPC Board of Directors Chair George Milad UIC/Uyemura International Corp. Vice Chair Gary C. Roper One Source Group, Eagle Circuits Inc. Co-Chair George Milad UIC/Uyemura International Corp. Co-Chair Gerard A. O’Brien Photocircuits Corporation Peter Bigelow IMI Inc. Sammy Yi Flextronics International Plating Processes Subcommittee Gail Auyeung, Celestica Martin Bayes, Ph.D., Rohm and Haas Electronic Materials Elizabeth Benedetto, Hewlett-Packard Company Mumtaz Bora, Peregrine Semiconductor Trevor Bowers, Adtran Inc. Peter Bratin, Ph.D., ECI Technology, Inc. Lee Burger, OMG Electronic Chemicals Dennis Cantwell, Printed Circuits Inc. Michael Carano, OMG Electronic Chemicals Peter Marc Carter, Rockwell Collins Phillip Chen, L-3 Communications Electronic Systems Jun Choi, Oxford Instruments America, Inc. Christine Coapman, Delphi Electronics and Safety David Corbett, Defense Supply Center Columbus G. Sidney Cox, Ph.D., E. I. du Pont de Nemours and Co. Donald Cullen, MacDermid, Inc. Gordon Davy, Best Manufacturing Practices Center of Excellence Steve Dunford, Nokia Americas C. Don Dupriest, Lockheed Martin Missiles and Fire Control Richard Edgar, Tec-Line Inc. Theodore Edwards, Dynaco Corp. Dennis Fritz, MacDermid, Inc. Gerald Gagnon, Bose Corporation Hollese Galyon, Merix Corporation Marion Graybeal, Consultant Michael Green, Lockheed Martin Space Systems Company Donald Gudeczauskas, Uyemura International Corp. David Hillman, Rockwell Collins Helen Holder, Hewlett-Packard Company Kuldip Johal, Atotech USA Inc. Jack Josefowicz, Ph.D., Palm International Thomas Kemp, Rockwell Collins James Kenny, Enthone Inc. - Cookson Electronics John Konrad, Endicott Interconnect Technologies Inc. Brigitte Lawrence, Brigitflex Inc. Gary Long, Intel Corporation Joe McGurran, Atotech USA Inc. David McQuinn, Flextronics John Meyers, OMG Electronic Chemicals James Monarchio, TTM Technologies, Inc. Keith Newman, Sun Microsystems Inc. Gary Nicholls, Enthone Inc. - Cookson Electronics Sean Oflaherty, Oxford Instruments America, Inc. Mario Orduz, Consultant J. Lee Parker, Ph.D., JLP Anders Pedersen, Harris Corporation, GCSD Mike Pfeifer, Continental AG Jim Reed, Dell Inc. Randy Reed, Merix Corporation Henry Rekers, Schneider Electric Hugh Roberts, Atotech USA Inc. Gary Roper, Roper Resources, Inc. Andrew Ryzynski, Research In Motion Limited Stan Sappington, S/G Electronics Inc. Daryl Sato, Intel Corporation Karl Sauter, Sun Microsystems Inc. Thomas Saven, Ticer Technologies Michael Schneider, ECI Technology, Inc. Randy Schueller, Ph.D., DfR Solutions Tom Selby, Thermo Fisher Scientific Atamjit Singh, Unitech Industries Inc. Joseph Slanina, Honeywell Inc. May 2009 IPC-4553A iii --`,`,`,`,,`,,,,`,,,``,``,,,`,-`-`,,`,,`,`,,`--- Polina Snugovsky, Ph.D., Celestica Bill Starmann, Raytheon Company Michael Toben, Rohm and Haas Electronic Materials Donald Walsh, Uyemura International Corp. Karl Wengenroth, Enthone Inc. - Cookson Electronics John Williams, Raytheon Company Yung-Herng Yau, Enthone Inc. - Cookson Electronics IPC-4553A May 2009 iv Table of Contents 1 SCOPE ...................................................................... 1 1.1 Statement of Scope .............................................. 1 1.2 Description ........................................................... 1 1.3 Objective .............................................................. 1 1.4 Performance Functions ........................................ 1 1.4.1 Solderability ......................................................... 1 1.4.2 Contact Surface .................................................... 1 1.4.2.1 Membrane Switches ............................................. 1 1.4.2.2 Metallic Dome Contacts ...................................... 1 1.4.3 EMI Shielding ...................................................... 1 1.4.4 Aluminum Wire Bonding .................................... 1 2 APPLICABLE DOCUMENTS .................................... 2 2.1 IPC ....................................................................... 2 2.2 Mil-Standards ....................................................... 2 2.3 Telcordia™ ........................................................... 2 3 REQUIREMENTS ...................................................... 2 3.1 Visual ................................................................... 2 3.2 Finish Thickness .................................................. 2 3.2.1 Immersion Silver (IAg) Thickness ...................... 2 3.3 Porosity ................................................................ 2 3.4 Adhesion .............................................................. 2 3.5 Solderability ......................................................... 4 3.6 Cleanliness ........................................................... 4 3.7 Electrolytic Corrosion Testing ............................. 5 3.8 Packing and Storage ............................................ 5 3.9 Chemical Resistance ............................................ 6 3.10 High Frequency Signal Loss ............................... 6 3.11 Microvoids ........................................................... 6 4 QUALITY ASSURANCE PROVISIONS .................... 6 4.1 Qualification ......................................................... 6 4.1.1 Sample Test Coupons .......................................... 6 4.2 Acceptance Tests .................................................. 6 4.3 Quality Conformance Testing .............................. 6 APPENDIX 1 Chemical Definitions ............................ 7 APPENDIX 2 Process Sequence (Generic) .............. 8 APPENDIX 3 Qualification of IAg Process by the Board Supplier ............................... 9 APPENDIX 4 Standard Developments Efforts of Immersion Silver ............................ 10 APPENDIX 5 X-Ray Fluorescence (XRF) Spectroscopy ...................................... 25 APPENDIX 6 ROUND ROBIN TESTING ................... 28 Figures Figure 3-1 Example of Uniform Plating ........................... 3 Figure 3-2 Example of Staining of the Silver .................. 3 Figure 3-3 Another Example of Surface Staining ............ 4 Figure 3-4 Additional Staining Example .......................... 4 Figure 3-5 Additional Staining Example .......................... 4 Figure 3-6 IPC-2221 Test Speciman M, Surface Mount Solderability Testing, mm [in] .............. 5 Figure 3-7 Improper Packing or Storage Can Result in the Immersion Silver Corroding ................. 5 Figure A-4-1 Immersion Silver Industry Survey Results ... 11 Figure A-4-2 Comparison of Thin Versus Thick Silver Solderability Performance Using Real Time Shelf Life ............................................. 12 Figure A-4-3 XRF Results of Thin IAg Deposit ................. 12 Figure A-4-4 XRF Results of Thick IAg Deposit ............... 13 Figure A-4-5 Wetting Balance Coupon ............................. 13 ...................................................................... 13 Figure A-4-6 Supplied Immersion Silver Deposit for Wetting Balance Testing .............................. 14 Figure A-4-7 Solderability Performance Vendor A - Real Time Storage ....................................... 15 Figure A-4-8 Solderability Performance Vendor D - Real Time Storage ....................................... 15 Figure A-4-9 Solderability Performance Vendor E - Real Time Storage ....................................... 16 Figure A-4-10 Comparison of Vendor D Protected vs Unprotected - Day 709 ................................. 16 Figure A-4-11 Comparison of Vendor A Protected vs Unprotected - Day 763 ................................. 17 Figure A-4-12 Comparison of Vendor E Protected vs Unprotected - Day 709 ................................. 17 Figure A-4-13 IAg Deposit Thickness for TM-650, 2.6.14.1, as Measured by ‘‘Micron X’’ XRF Unit ...................................................... 18 Figure A-4-14 Final Readings in Chamber of First Round of Electrolytic Corrosion Testing at 35°C/92% R.H., Post 500 Hours of 10 Volt DC Bias. NO FAILURES PRODUCED ................................................. 19 Figure A-4-15 SEM Image of Vendor A’s 3X Sample Confirming XRF Measurements ................... 19 Figure A-4-16 Final Readings in Chamber of First Round of Electrolytic Corrosion Testing at 65°C/87% R.H., Post 500 Hours of 10 Volt DC Bias - NO FAILURES PRODUCED ................................................. 20 Figure A-4-17 Comb Patterns After 596 Hours in 65°C / 87% R.H. with 10 Volt Bias Applied - No Failures for Dendritic Growth but Water Spotting Clearly Evident ............................................. 20 Figure A-4-18 Test Protocol Applied Voltages Used for 3-11G Testing .......................................... 20 May 2009 IPC-4553A v Figure A-4-19 Comb Test Pattern and UL Parallel Pattern Used for Testing .............................. 21 Figure A-4-20 SIR Values for the Test at 96 Hours - 35°C/87.5% R.H. All Five IAg Suppliers’ Data are Combined ...................................... 21 Figure A-4-21 Resistance Values at 596 Hours - All Groups Included - Different Spaces/ Bias Voltages ............................................... 22 Figure A-4-22 Resistance Readings at 1344 Hours for IAg as a Function of Applied Volts/mil ......... 22 Figure A-4-23 Evidence of Dendritic Growth on the Electrolytic Silver Sample ............................ 23 Figure A-4-24 SEM/EDX Analysis of Figure 14, Above ...... 23 Figure A-4-25 Contact Resistance for IAg Supplier A ........ 24 Tables Table 3-1 Requirements of IAg ........................................... 3 Table 4-1 Qualification Test Coupons ................................. 6 Table A-6-1 Plating Thicknesses on Test Vehicles [µinches] .......................................................... 28 IPC-4553A May 2009 vi Specification for Immersion Silver Plating for Printed Boards 1 SCOPE 1.1 Statement of Scope This specification sets the requirements for the use of Immersion Silver (IAg) as a surface finish for printed boards. This specification is intended to set requirements for IAg deposit thickness based on performance criteria. It is intended for use by chemical supplier, printed board manufacturer, electronics manufacturing services (EMS) and original equipment manufacturer (OEM). 1.2 Description IAg is a thin immersion deposit over copper. It is a multifunctional surface finish, applicable to soldering. It may also be applicable for some press fit con- nections and as a contact surface. It has the potential to be suitable for aluminum wire bonding. The immersion silver protects the underlying copper from oxidation over its intended shelf life. Exposure to moisture and air contami- nants, such as sulfur and chlorine, may negatively impact the useful life of the deposit. The impact can range from a slight discoloration of the deposit to the pads turning com- pletely black. Proper packaging is a requirement. 1.3 Objective This specification sets the requirements specific to IAg as a surface finish. As other finishes require specifications, they will be addressed by the IPC Plating Processes Subcommittee as part of the IPC-4550 specifica- tion family. As this and other applicable specifications are under continuous review, the subcommittee will add appro- priate amendments and make necessary revisions to these documents. 1.4 Performance Functions 1.4.1 Solderability This primary function of IAg is to provide a solderable surface finish, suitable for all surface mount and through-hole assembly applications and with an appropriate shelf life. The deposit has demonstrated the ability to meet a shelf life of 12 months per IPC J-STD-003 and industry data, when handled per this specification’s requirements. 1.4.2 Contact Surface There is a possibility for using IAg for the following applications. The use of Immersion Silver is acceptable for the IPC-6010 series Class 1 and Class 2 applications, but is NOT currently recommended for the IPC-6010 series Class 3 applications which are for High Reliability Electronic Products where equipment downtime cannot be tolerated, and the circuitry shall func- tion, when required. Examples of such Class 3 applications are for life support items and critical weapons systems. 1.4.2.1 Membrane Switches The IAg surface with as little as 0.1 µm [4 µin] of immersion silver has demon- strated that it is suitable for one million actuations with negligible resistance change. However the end use atmo- sphere (temperature/humidity/contaminants) may degrade this performance. The end user shall determine the impact of use environments on the IAg deposit. 1.4.2.2 Metallic Dome Contacts Data on this topic should be submitted to the IPC 4-14 Plating Processes Subcommittee to be considered for inclusion in upcoming revisions of this standard. 1.4.3 EMI Shielding IAg is one of the surface finishes that may be used as an interface between electromagnetic interference (EMI) shielding and the printed board. A key characteristic for this application is a consistent metal inter- face between the printed board metallization and the shield material. The formation of a highly conductive interface between the two surfaces will ensure excellent EMI shield- ing capability, which should also provide resistance to atmospheric influences on the IAg deposit. The end user shall determine the impact of the end use environment on the reliability of the shield interface. Tarnish of surround- ing areas not in contact directly with the shield is NOT a reason to reject the printed board/deposit but rather an indi- cation of the impact of the atmosphere on an active metal. 1.4.4 Aluminum Wire Bonding IAg meets the require- ments of MIL-STD-883, Method 2011.7. Variables that affect performance include cleanliness, substrate materials, wire thickness and surface topography. IAg is not a surface leveler; the surface topography largely depends on the con- ditions of the underlying copper surface. While producing acceptable wire bonds, silver, unlike the other Noble met- als used for this application, is potentially not stable due to its reactive nature with the atmosphere in which it exists. Total encapsulation of the wire bonded sites is recom- mended in order to ensure consistent and reliable long term bonds. The committee is actively seeking additional data on the use of immersion silver as a suitable wire bonding metallization. May 2009 IPC-4553A 1 2 APPLICABLE DOCUMENTS 2.1 IPC1 IPC