Effect of isothermal aging and salt spray tests on reliability and mechanical strength of eutectic Sn-Bi lead-free solder joints

Eutectic Sn-Bi solder has attracted a great deal of interest since it offers good reliability comparable to that of Sn-Pb solders. Additionally, the increasing need for low cost manufacturing processes, particularly in consumer electronics, has made it an interesting alternative. This paper presents reliability and microstructural studies of eutectic 42%Sn-58%Bi (wt.%) lead-free solder alloy. The reliability was investigated using two different accelerated environmental tests. The first test series was subjected to isothermal aging at 100°C, the second series was subjected to salt spray test to analyze corrosion resistance, and the last test series was exposed to a combination of both tests. To study the effect of salt spray and isothermal aging on the mechanical reliability shear test and drop test were performed on the samples. A failure analysis was conducted and different types of failure modes were extracted. In addition, the effect of IMC types and growth on the mechanical strength of the solder joints was investigated.