Journal of SMT Article
Thermal Preconditioning, Microstructure Restoration and Property Improvement in Bi-Containing Solder Alloys
Company: Celestica, Department of Materials Science & Engineering, University of Toronto, Rockwell-Collins, BAE Systems, Honeywell Aerospace, Curtiss-Wright
Date Published: 1/30/2018 Volume: 31-1
This paper contains details from a recently patented process which allows for the improvement of the properties of the solder joint, either post-reflow, or after some amount of product lifetime. The treatment was analyzed by comparing the creep properties of Violet, an alloy containing 2.25% Ag, 0.5% Cu, and 6.0% Bi, with SAC 305. An above-solvus aging treatment was performed on each alloy, either after solidification, or after below-solvus aging. It was found that the creep resistance of both alloys is reduced after below-solvus aging, but the creep resistance of Violet is significantly improved after above-solvus aging (regardless of prior thermal history). These results show that this aforementioned thermal treatment is a viable method to improve the long-term reliability of solder joints in electronic assemblies.
creep, thermal treatment, bismuth, aging
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