Abstract
Although gold remains a preferred surface finish for components used in high-reliability electronics, rapid developments in this area have left a gap in the fundamental understanding of solder joint gold (Au) embrittlement. Furthermore, as electronic designs scale down in size, the effect of Au content is not well understood on increasingly smaller solder interconnections. As a result, previous findings may have limited applicability. The current study focused on addressing these gaps by investigating the interfacial microstructure that evolves in 63Sn-37Pb solder joints as a function of Au layer thickness. Those findings were correlated to the mechanical performance of the solder joints. Increasing the initial Au concentration decreased the mechanical strength of a joint, but only to a limited degree. Kirkendall voids were the primary contributor to low-strength joints, while brittle fracture within the intermetallic compounds (IMC) layers is less of a factor. The Au embrittlement mechanism appears to be self-limiting, but only once mechanical integrity is degraded. Sufficient void evolution prevents continued diffusion from the remaining Au.
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Acknowledgments
Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525. This article has been authored by an employee of National Technology & Engineering Solutions of Sandia, LLC under Contract No. DE-NA0003525 with the U.S. Department of Energy (DOE). The views expressed in this article do not necessarily represent the views of the U.S. Department of Energy or the United States Government. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this article or allow others to do so, for United States Government purposes. The DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan https://www.energy.gov/downloads/doe-public-access-plan. Authors would like to extend thanks to the members of the Sandia Metallography Lab (Christina Profazi, Jeier Yang, and Alex Hickman) for always delivering high quality metallographic samples that enable the analyses discussed above as well as to Dr. Don Susan for providing a thorough review. Authors would also like to thank Somuri Prasad for providing initial guidance.
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Wheeling, R., Vianco, P., Williams, S. et al. Impact of Gold Thickness on Interfacial Evolution and Subsequent Embrittlement of Tin–Lead Solder Joints. J. Electron. Mater. 51, 7337–7352 (2022). https://doi.org/10.1007/s11664-022-09891-2
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DOI: https://doi.org/10.1007/s11664-022-09891-2