Authored By:
Anthony J. Rafanelli, Ph.D., P.E.
Raytheon Missiles & Defense - Raytheon Technologies
RI, USA
Summary
The Aerospace & Defense (A & D) industries maintain a high level of interest in the expansive amount of work performed in developing and qualifying Pb-free solder alloys. The three main areas of interest continue to be thermal cycle, mechanical shock, and vibration. The past twenty years have seen an unprecedented increase in alloy development such that the concepts of “generations of solders and “families of solders” have been coined to help manage the numerous individual alloys on the market today.
The efforts of industry, academia, and the U.S. Department of Defense have resulted in developing standards, handbooks, and guidelines as well as an immense amount of data all benefiting a rigorous risk management framework. This paper will discuss the Pb-free challenges (also considered risks) and the “building blocks” generated which provide a methodology to allow cautious and responsible implementation of Pb-free materials in high performance products.
Conclusions
The A&D industry has impressively advanced in its recognition, acknowledgement, and acclimation with Pb-free materials, i.e., as interconnects and finishes. However, for certain high reliability applications (e.g., space systems, missile systems) total acceptance will still require a considerable amount of verification and validation time. Therefore, during this time, such conditions will continue to require SnPb solder until a suitable replacement material is found.
Yet, the partnership between the DoD and industry (USPAE) provides hope on providing a long-needed approach to responsible and effective selection of solder alloys for high performance conditions. With the anticipation of the USPAE SPRA deliverables, a disciplined evaluation process, for using Pb-free materials, is a valid mid-term goal. Given the body of work completed to date (industry/academic generated data, GEIA suite of tools, etc.), a methodology for risk mitigation has been proposed. The USPAE deliverables should provide a means to enhance this proposed methodology. In addition, the author anticipates and welcomes many variations and revisions to this approach with the ultimate goal of ensuring reliable systems for the warfighter.
Initially Published in the SMTA Proceedings
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