Evaluation and Solderability of Lead‐rich and Eutectic Solder‐coated Component Leads

Abstract

A significant number of integrated circuit (IC) package leads failing solderability tests also had a very thin eutectic solder coating. Poor solderability is attributed to degradation of this coating during various burn‐in times and temperatures. Techniques were developed to pre‐tin IC leads with lead‐rich solder (95Pb‐5Sn) as this finish had been reported in the literature to be particularly effective and superior to the eutectic composition in preserving solderability even after long ageing treatments. The present work has not confirmed those recommendations. In fact, surface analyses and various solderability tests performed on steam‐aged finishes demonstrate that 95Pb‐5Sn is not a viable alternative to 63Sn‐37Pb if standard spacecraft soldering practices are to be followed. Good solder wetting was always achieved if the artifically aged leads had a minimum eutectic coating thickness of 5–7 micrometres.

Citation

Dunn, B.D. and Andrisi, J.‐. (1992), "Evaluation and Solderability of Lead‐rich and Eutectic Solder‐coated Component Leads", Soldering & Surface Mount Technology, Vol. 4 No. 3, pp. 16-20. https://doi.org/10.1108/eb037798