Effect of Zn Addition to Sn-3Ag-5Bi Solder on Joint Strength and Joint Interface

抄録

The mechanical properties and the joint strength of Sn-Ag-Bi solders as replacement solders for Sn-Pb eutectic solder were investigated. The joint strength between Cu sheets and solder decreases when more than 5 mass% Bi is added to Sn-Ag system solders after annealing. Zn addition to Sn-3Ag-5Bi solder is carried out in order to improve the joint strength. The effect of Zn addition to Sn-3Ag-5Bi solder on the joint strength and the joint interface structure was investigated. Zn addition to Sn-3Ag-5Bi solder changes the joint interface structure from solder/Cu-Sn intermetallic compounds/Cu to solder/Cu-Zn intermetallic compound/Cu-Sn intermetallic compound/Cu. Cu-Zn intermetallic compound acts as a barrier layer for inhibiting the growth of Cu-Sn reaction layer. Therefore, the growth of reaction layer and decrease of joint strength are inhibited by Zn addition after annealing.