Mechanical properties of Sn-Bi-Zn solder/Cu joints

This study examined the effects of 0.5 mass%Zn addition to a Sn-57 mass%Bi solder on the interfacial and mechanical properties of the solder joint with Cu substrate. The shear strength was measured by modified double lap shear joint model. Creep tests were performed at 10 MPa and 80degreesC. The shear stength of the solder/Cu joint was found to decrease with aging treatment. Rapid decrease in shear strength of the Sn-57 mass%Bi/Cu joint was noticed in the aged specimen. This seems to be caused by crack growth between a reaction layer and a Cu substrate. At the tension test after aging treatment, the failure of joint was dependent upon existence of crack in the intermetallic compound layer. When the crack existed in the intermetellic compound layer, fracture occurred at the interface of Cu and intermetallic compound. By Zn addition in the Sn-Bi system, the fracture occurred at the interface of the solder and the inermetallic compound. In the Sn-Bi system, however, the crack under creep test was popagated in the solder with regardless existence of crack in the intermetallic compound. In the Sn-Bi-Zn system, the crack was popagated through the interface of the solder and the reaction layer.