Effect of Bi on the kinetics of intermetallics growth in Sn-3Ag-0.5Cu/Cu solder joint

Three lead-free solder alloys, Sn-3Ag-0.5Cu, Sn-3Ag-0.5Cu-1Bi and Sn-3Ag-0.5Cu-3Bi, were used in the current experiments to investigated the microstructural evolution as well as the kinetics of intermetallic compound (IMC) layer growth. The experimental results indicated that the thickness of Cu 6 Sn 5 intermetallic layer at the solder/Cu interface increases with aging temperature, while the growth rate of IMC in Sn-3Ag-0.5Cu-3Bi/Cu joints is slower than that in Sn-3Ag-0.5Cu-1Bi/Cu joints and Sn-Ag-Cu solder joints. The effect of Bi element is attributed to the accumulation of Bi near the joint and the enhancement of the activation energy by the addition of Bi