Tensile properties of Sn–Ag based lead-free solders and strain rate sensitivity

The tensile properties of Sn-3.5 mass%Ag, Sn-3.5 mass%Ag-0.75 mass%Cu and Sn-3 mass%Ag-2 mass%Bi lead-free solders were investigated and compared with those of a Sn–Pb eutectic solder. The tensile strength of each solder decreases with decreasing strain rate, and with increasing test temperature. The ductility of each lead-free solder is relatively constant in the strain rate ranging from 1.67×10−4 s−1 to 1.67×10−2 s−1 and in the test temperature ranging from −40 to 120 °C. From the results of the strain-rate-change tests, stress exponents were investigated. The stress exponents for the lead-free solders are higher than those of the Sn–Pb eutectic solder at 25, 80 and 120 °C, and are relatively stable at these temperatures. The activation energies for the creep of the lead-free solders were also investigated.