Microstructure and mechanical properties of Sn-xBi solder alloy

In this study, microstructure and mechanical properties of Sn-xBi solder alloy were investigated. In Sn-3.6Bi and Sn-7.25Bi solder alloys, the particle-shaped Bi phase distributed in Sn-rich phase matrix. In Sn-14.5Bi and Sn-29Bi solder alloys, the shape of Bi phase was irregular. In Sn-58Bi solder alloy, the island-shaped Sn-rich phase distributed in Bi phase uniformly. The hardness of Sn-xBi was improved from 11.36 to 27.04 MPa first and declined to 10.05 MPa then when the Bi fraction was increased form 0 to 100 wt%. The bend fracture energy of Sn-58Bi showed a dependence on the loading speed. Moreover, the bend fracture energy of Sn-29Bi solder alloy was lower than that of Sn-14.5Bi and Sn-58Bi, which was caused by the special microstructure of Sn-29Bi.