Tin pest in lead‐containing solders

Abstract

PurposeThe purpose of this paper is to describe the effects of mechanical testing and thermal treatment prior to storage at either −18 or −40°C, for periods in excess of ten years on the Sn‐37Pb alloy.Design/methodology/approachFor over a decade, The Solder Research Group at The Open University has studied tin pest development in several of the new lead‐free solders. Bulk samples, employed for mechanical testing, are laid down at −18 and −40°C, and inspected periodically.FindingsIn a previous examination in 2006, there was no evidence of tin pest formation in this alloy. On re‐examination of the same specimens in 2008, about one in ten of the samples stored at −18°C, both “as cast” and “tested”, exhibited warts of tin pest. Storage at −40°C increased this ratio to about one in three following treatment.Originality/valueThe paper's findings demonstrate that, even with high concentrations of lead present, eventually tin pest will form. So, for interconnections used in long‐term applications, whether lead‐free or lead‐bearing solders are employed, performance and structural integrity considerations should not ignore tin pest.