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 a-T-3 (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.