The tensile properties of Sn–3.5Ag and Sn–3.5Ag–0.75Cu lead-free solders were investigated. The effect of annealing at 100°C for 1 h before the tensile test on mechanical properties was small in both solders. The tensile strength decreased with decreasing strain rate, and with increasing test temperature. However, the ductility of each solder was 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, the strain sensitivity for Sn–3.5Ag and Sn–3.5Ag–0.75Cu were found to be 0.077 and 0.078, respectively.