Effects of aging treatment on mechanical properties and microstructure of Sn–8.5Zn–0.5Ag–0.01Al–0.1Ga Solder

The aging effect on mechanical properties of Sn–8.5Zn–0.5Ag–0.01Al–0.1Ga solder was investigated. The specimens were treated at four different temperatures (−10 °C, room temperature, 80, 150 °C) for five different durations (0, 75, 150, 300, 1000 h). The corresponding microstructural variation was also investigated. The results showed that the microstructure of the solder did not change prominently when aging at −10 °C, although the tensile strength slightly increases. On the other hand, the solder underwent age-softening at room temperature, 80 and 150 °C. It appears that the age-softening of the solder was associated with the coarsening of Sn–Zn eutectic structure and grain growth of Sn matrix of the solder. The tensile strengths of the specimens aged at 150 °C were greater than those at 80 °C. This observation was explained by the solid solution hardening of greater Zn dissolution at higher temperature.