Characterization of Sn2.4Ag solder viscoplastic behavior under cyclic loading

A series of monotonic and cyclic experiments, including constant strain-rate, creep and cyclic loading tests at isothermal temperatures between 25°C and 150°C, were performed to characterize the viscoplastic behavior of Pb-free Sn2.4Ag solder. The constitutive model of the solder was developed by fitting the monotonic test results to the Anand viscoplastic model. Finite element model based on the Anand constitutive model was then applied to simulate solder responses under various cyclic loading histories, and compared to the experimental results. From the comparison it was observed that the Anand model reproduces the isotropic hardening behavior of the Sn2.4Ag solder; but as a result of lacking tensorial state variable, the model could not capture the kinematic hardening response under load reversal. Nevertheless, the thermal recovery behavior of the Sn2.4Ag solder is limited under cyclic creep loading, and the Anand model is still suitable for predicting the Sn2.4Ag solder response under low-stress cyclic loading conditions.