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.