A viscoplastic constitutive model for 63Sn37Pb eutectic solders

Abstract

Solder joints serve both as electrical and mechanical connections in IC packages and the reliability of solder joints is one of most important issues in electronic packaging. In this study, a new constitutive model for eutectic solders (63Sn37Pb) is proposed. Grain sizes and phase sizes are considered as coarsening is one of the main reasons for solder joint failures. The model has been developed based on the combination of grain boundary sliding and matrix dislocation deformation mechanisms in order to describe the thermo-mechanical behavior of eutectic solders. Internal stress tensors are also introduced to describe the transient behavior during the tensile test and first stage creep. A series of tensile tests, creep and creep recovery tests were conducted over a temperature range from -10 to 100/spl deg/C. Specimens with two different phase sizes were tested. Good agreements were obtained between the experimental results and the model.