The doping of SZC solders with bismuth to improve their thermal and tensile characteristics for microelectronic applications

Sn–Zn–Cu is one of the most popular soldering alloys, especially when it has been doped with Bi, which has proved very effective. The Sn–6.5Zn–0.3Cu (SZC–0.0Bi) stress–strain characteristics have been tested and compared to the SZC–1.0 Bi and SZC–3.0 Bi solder alloys. The results of the differential scanning calorimeter confirmed that the melting temperatures, pasty ranges, and undercooling levels would significantly reduce with Bi addition to the SZC solder alloy. Also, it has been found that SZC–3.0 Bi alloy has the highest ultimate tensile stress, yield stress, and Young’s modulus compared to SZC–0.0 Bi and SZC–1.0 Bi alloys. The higher characteristics of stress–strain were caused by the Bi precipitation reinforcing effects as well as solid solution mechanism. The rush of these Bi atoms or particles will greatly improve the microstructure, block dislocation mobility, and raise of percent of Bi to 3.0 wt% enhanced the hardening parameters.