Creep behavior of joint-scale Sn1.0Ag0.5Cu solder shear samples

Abstract

This study investigates the creep behavior of joint-scale Sn1.0Ag0.5Cu (SAC105) solder samples under shear loading. The objective of the work is to determine the Anand viscoplastic constitutive model parameters for this low silver content ternary SAC solder alloy. A series of monotonic constant shear stress (5-15MPa) and constant shear strain rate (1E-6-1E-2 (1/s)) tests was conducted at temperatures of 20°C, 50°C, 75°C and 100°C in order to provide data to extract the constitutive model parameters. The predictions of the Anand model are compared graphically with the experimental data in order to illustrate goodness-of-fit. SAC105 was found to be more creep resistant at higher strain rates than at lower strain rates for all temperatures and test conditions. The derived Anand parameters are shown to capture the creep performance of the SAC105 solder under shear loading very well, with the experimental data being tightly bound to the Anand predictions. In addition to the quantification of mechanical characteristics, a preliminary Electron Backscatter Diffraction (EBSD) investigation was conducted to investigate the effect of preconditioning on the grain structure of SAC105 solder joints. Results indicate that the misorientaion of the solder grains increased during preconditioning, signaling grain coarsening due to ageing.