Influence of Bi and P additions on microstructure and mechanical properties of Sn-Zn-RE solder

The Sn-9Zn0.05Ce lead-free solder with Bi and P additions were prepared, and microstructure, tensile strength, elongation and Vickers hardness of the lead-free solders were studied. Experimental results show that the tensile strength and hardness increase with more Bi addition in Sn-9Zn0.05Ce lead-free solder, while the elongation decreases with Bi addition. P addition in Sn-9Zn0.05Ce lead-free solder does not obviously affect the tensile strength and hardness. In addition, either Bi or P addition in Sn-9Zn0.05Ce lead-free solder would make Zn separate out from Sn-9Zn0.05Ce lead-free solder more easily, and needle-like or grain-like Zn-rich phase can be found in the solder. Moreover, Zn-rich phase increases with more Bi or P additions in the solder, and accordingly has a great effect on the mechanical properties of Sn-9Zn0.05Ce solder.