The properties of Sn-9Zn lead-free solder alloys doped with trace rare earth elements

The Sn-Zn alloys have been considered as lead-free solders. It is well known that their poor properties of wetting and oxidation resistance are the main problems to prevent them from becoming commercially viable solders. In this paper, trace rare earth (RE) elements of mainly Ce and La have been used as alloying elements into the Sn-9Zn alloy. The results indicated that with the RE addition the originally coarse beta-Sn grains in the microstructure of the alloy were refined. The tensile strength significantly increased with only a slight decrease in ductility. The surface tension was decreased, resulting in great improvement in wetting properties with rosin-based active flux.