Digital image correlation analysis of the deformation behavior of Pb-free solders at intermediate strain rates

Digital image correlation (DIC) is a powerful tool for quantifying local stresses and strains. The demand for environmentally benign Pb-free solders and the push toward smaller portable electronics will make it more likely for solder interconnects to encounter mechanical shock through dropping or mishandling. Thus, quantifying the strain rate behavior of Pb-free solders from the quasi-static to the shock regime is essential for developing reliable numerical models of the mechanical shock behavior. In this paper we report on the use of DIC to measure the local strain and strain rate occurring in the neck of Sn-3.5 Ag-0.7 Cu specimens, at the onset of necking. Tensile tests were conducted in the range 10^-3 s^-1 - 30 s^-1. A parametric study was conducted to identify the optimum DIC parameters for the experimental setup. The effect of microstructure and applied strain rate on the local values of strain and strain rate is discussed.