Investigation on properties of Ga to Sn–9Zn lead-free solder

The influences of different Ga content on the properties of Sn–9Zn lead-free solder were investigated. The results indicate that Ga plays an important role not only in the structure and melting behavior, but also in the solderability and mechanical property. Sn–9Zn–0.5Ga shows finer and more uniform microstructure than Sn–9Zn. With the addition of low-melting-point Ga, TL (liquidus temperature) and TS (solidus temperature) of the alloys decreases with increasing of Ga content while △T (liquidus temperature minus solidus temperature) increases. Ga can improve the oxidation resistance and reduce the surface tension of solder, so the solderability of Sn–9Zn–xGa lead-free solder is significantly improved. When the content of Ga is 0.5 wt.%, the pull force of soldered joint is 16.1 N, enhanced by 11% compared to that of Sn–9Zn, and the fracture micrographs show that the joint failed in a ductile manner. The addition of 3 wt.%Ga resulted in a brittle failure. The introduction of 0.5 wt.% Ga into Sn–9Zn alloy improves creep resistance of the solder.