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.