Living With PB-Free in High Performance Engineering Design
As Pb-free technology increasingly becomes the standard for electronic interconnects and finishes, engineers must cope with the various challenges posed by this material.
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Authored By:
Anthony J. Rafanelli
Raytheon Company
Integrated Defense Systems
Portsmouth, RI, USA
Summary
As Pb-free technology increasingly becomes the standard for electronic interconnects and finishes, engineers must cope with the various challenges posed by this material. Summarizing at a high level, these challenges represent risks associated with 1) durability of the interconnection and 2) deleterious effects of tin whiskers. Subsequently, IPC Task Group 8-81D (Research Coordination and Technical Guidance), of the IPC PERM COUNCIL, has undertaken an assignment to generate an industry-wide guide to aid engineers in designing with Pb-free technology. The focus is to provide insight and information such that the design will maintain performance requirements for aerospace, defense, and high-performance (ADHP) products and systems.
Having started out as a "laundry list" of Pb-free concerns and challenges identified by the ADHP industry, the guide is structured such that those "delta" considerations, i.e. technical knowledge gaps with Pb-free technology are brought to the designer's attention. Furthermore, the guide highlights Pb-free concerns, as they are encountered in the phases which generally reflect the product development cycle used by Aerospace, Defense, and High-Performance systems industries. This paper presents a summary of efforts from document inception to document release.
Conclusions
While the Pb-free movement may appear ominous and challenging, there are tools and resources available to the designer. These have been developed over the past several years thanks to the efforts of the IPC Pb-free Electronics Risk Mitigation (PERM) Council [12]. Some key resources include the following set of standards and handbooks developed for working with Pb-free materials in various electronics applications:
1. GEIA-STD-0005-1, Revision A, "Performance Standard for Aerospace and High Performance Electronic Systems Containing Pb-free Solder"
2. GEIA-STD-0005-2, Revision A, "Standard for Mitigating the Effects of Tin in Aerospace and High Performance Electronic Systems"
3. GEIA-STD-0005-3, Revision A,"Performance Testing for Aerospace and High Performance Electronics Containing Pb-free
Solder and Finishes"
4. GEIA-HB-0005-1, Revision A, "Program Management / Systems Engineering Guidelines for Managing the Transition to Pbfree Electronics"
5. GEIA-HB-0005-2 "Technical Guidelines for Aerospace and High Performance Electronic Systems Containing Pb-free Solder"
6. GEIA-HB-0005-3 "Rework and Repair Handbook To Address the Implications of Pbfree Electronics and Mixed Assemblies in Aerospace and High Performance Electronic Systems"
Each of these is now owned and administered by the G-24 Committee of the Society of Automotive Engineers (SAE).
Other resources include work performed in 2009 to benchmark the Pb-free technical knowledge base as well as develop a roadmap and plan to close those technical data gaps [13, 14]. The plan included a list of tasks necessary to provide ADHP engineers sufficient information to minimize risks associated with Pb-free solders and finishes. Upon reviewing these plans, several research consortiums and organizations embraced the plan and, to date, have addressed many of the technical needs although the significant effort of obtaining sufficient data to develop Pbfree reliability models still remains unanswered [15]. Finally, a good number of texts and a continuously increasing amount of data is now available in the open literature. Engineers will need to "act like engineers" in order to comprehend this information and apply it to their needs.
In conclusion, the Aerospace, Defense, and High Performance (ADHP) industries are at a technology crossroads. With a heavy dependence on COTS to maintain a competitive edge, the industry is heavily influenced by the commercial supply chain and its increasing use of Pb-free materials. While considerable progress has been made in closing Pb-free knowledge gaps, the challenge of characterizing performance and reliability still needs to be addressed. It will take a combination of high-level design strategies and an effective set of guidelines to enable the ADHP engineer to develop mission-successful products and systems.
Initially Published in the SMTA Proceedings
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