Effects of Ce addition on properties of Sn-0.3Ag-0.7Cu low-Ag lead-free solder

The effects of the rare earth Ce element on melting temperature, wettability of Sn-0.3Ag-0.7Cu low-Ag lead-free solder and the intermetallic compounds morphologies of Sn-0.3Ag-0.7Cu-XCe/Cu were investigated. The addition of the Ce element has an unconspicuous effect on decreasing the melting temperature of Sn-0.3Ag-0.7Cu solder. The results indicate that the addition of Ce element increases the wettability of solder alloy. When the content of Ce is 0.05 wt. %, the spreading area of solder joint is the highest by 50.80 mm² which is 8% higher than that of Sn-0.3Ag-0.7Cu lead-free solder. The 3-D morphology of intermetallic compounds (IMC) shows that the addition of Ce promotes grain refinement. The diameter of the grains decreases continuously as the content of Ce increase. It indicated that the addition of Ce elements suppresses the growth of the thickness of intermetallic compounds layer (IML). The microstructure of Sn-0.3Ag-0.7Cu-0.05Ce/Cu is more stable than that of the Sn-0.3Ag-0.7Cu/Cu and the grains´ microstructure became thick and coarse with the increase of thermal aging time.