Viscoplastic deformation of lead-free solder alloy - Experiments and simulations

In this paper, viscoplastic deformations of Sn-3.5Ag-0.75Cu solder alloy are discussed. First, the following experiments are conducted: (1) Pure tension at several strain rates. (2) Cyclic tension-compression loading with several strain amplitudes at several strain rates. (3) Creep tests at several stress levels. The test results show that the Sn-3.5Ag-0.75Cu solder alloy has large strain rate and temperature effects, and that there is a noticeable transient creep region in the creep curves. A viscoplastic constitutive model for the solder alloy is also discussed. The model is constructed based on the dislocation density based constitutive model proposed by Estrin [6]. The constitutive model well simulates both the time and temperature dependences on the deformation of the lead free solder alloy. Finally, the constitutive model is incorporated into a general purpose FEM program (Marc) to clarify the applicability of the model to the structural analysis.