Deformation Behavior of Two Lead-Free Solders: Indalloy 227 and Castin Alloy

Abstract

The deformation behavior of two commercial lead-free solder alloys, Indalloy 227 (77.2Sn-20.0In-2.8Ag) and Castin alloy (96.2Sn-2.5Ag-0.8Cu-0.5Sb), over a range of strain rates (10−6 s−1 to 10−2 s−1 ), temperatures (–55°C to 125°C), and isothermal and thermomechanical cycling conditions is experimentally determined. The behavior of these two lead-free alloys is compared to that of 60Sn-40Pb solder. In order to minimize the number of experiments, yet capture the significant features of the deformation behavior and obtain the simple Norton power law constants, strain-rate jump tests are successfully used. This minimal test information is also shown to be sufficient to determine a complete set of material parameters for modern unified thermoviscoplastic models that can capture the dominant strain rate and temperature effects including the thermomechanical cycling behavior. As an exercise, the parameters for the Bodner-Partom model are determined for both lead-free alloys and predictions of thermomechanical cycling are shown.