Solderability and microstructure of Sn-9Zn-xPr lead-free solder

The effects of Pr on the wettability of Sn-9Zn lead-free solder and the mechanical properties of soldered joints are investigated and the results indicate that with the addition of rare earth Pr into Sn-9Zn solder, the microstructure is refined obviously, Zn-rich phrase is decreased and mechanical properties improved. The best wettability and mechanical property of soldered joint is obtained when the content of Pr is 0.05 wt.%. Moreover, when the content of Pr is exceeded 0.1 wt.%, plenty of Sn-Pr compounds are found in the Sn-9Zn solder, which lead to the growth of whiskers.