Wettability of Sn-9Zn-xAg lead-free solder and mechanical properties of soldered joints

The effects of Ag on the wettability of Sn-9Zn lead-free solder and the mechanical properties of soldered joints are investigated respectively. The results indicate that when the content of Ag is 0.3wt.%, the solder gets the best wettability; when the content of Ag is from 0.5wt.% to 1wt.%, the wettability decreases. The best mechanical property of soldered joint is obtained when the content of Ag is 0.3wt.%. Moreover, the fracture micrographs show that plenty of dimples are found on the Sn-9Zn-0.3Ag soldered joints fractures. When the content of Ag is 1wt.%, some Cu-Zn and Ag-Zn intermetallic compounds appear on the bottom of dimples, and the mechanical property of the soldered joint decreases. In general, the optimum additive amount of Ag in Sn-9Zn solder is about 0.3wt.%.