Microstructural evolution and tensile properties of Sn-5Sb solder alloy containing small amount of Ag and Cu

The near peritectic Sn-5Sb Pb-free solder alloy has received considerable attention for high temperature electronic applications, especially on step soldering technology, flip-chip connection. In the present study, a separate addition of the same amount of Ag and Cu are added with the near-peritectic Sn-5Sb solder alloy to investigate the effect of a third element addition on the microstructural, thermal and mechanical properties of the newly developed ternary solder alloys. The results indicate that the melting point of Sn-5Sb solder is enhanced by Ag and Cu additions. Besides, the Ag and Cu content refine the microstructure and form new intermetallic compounds (IMCs) with the near-peritectic Sn-5Sb solder alloy. The tensile tests revealed that all alloys exhibit higher mechanical strength with increasing strain rate and/or decreasing testing temperature, suggesting that the tensile behavior of the three alloys is strain rate and temperature dependence. The yield and ultimate tensile strength are higher for Sn-5Sb-0.7Cu alloy compared with Sn-5Sb and Sn-5Sb-0.7Ag alloys. Good mechanical performance of Sn-5Sb-0.7Cu solder is often correlated to a fine β-Sn grain size and more dispersed Cu-Sn IMC particles, which makes the solder exhibit high strength and yield stress.