The effect of strain rate and temperature on the tensile properties of Sn–3.5Ag solder

The tensile response of Sn–3.5% Ag solder was investigated and compared with that of a Sn–37% Pb eutectic solder at various strain rates from 2.38×10−6 s−1 to 2.38×10−3 s−1 over the temperature range from −50 °C to 150 °C. The relationship between tensile strength, σUTS, and strain rate, ɛ´, for Sn–3.5Ag can be expressed by the equation σUTS=Aɛ´m. The influence of temperature on the strain rate sensitivity index m was very slight for Sn–3.5Ag, whereas the m values of Sn–37Pb increased strongly with increasing temperature. The relationship between the tensile strength of the Sn–3.5Ag alloy and temperature follows an Arrhenius law, and the activation energy for creep was found to be 78 kJ/mol, close to that for the pipe diffusion controlled creep of tin. The microstructure and fracture morphologies of both solders were observed with a scanning electron microscope. Ag3Sn particles were observed in the primary β-Sn in the Sn–3.5Ag solder by transmission electron microscope.