High Strain Rate Materials Characterization at Low Test Temperatures for Thermally Aged SAC-Q Solder Alloys

A number of doped SnAgCu alloys have emerged to mitigate the effects of thermal aging on the property deterioration of the interconnects. Much less is known about the performance of alloys at low temperatures simultaneously with high strain rates which may be encountered in harsh environment applications including automotive, aerospace and defense. Electronics in harsh environments is often used for function critical use. High strain-rate and low temperatures may occur during storage, transport and operation. In this paper, data on the evolution of material properties including the elastic modulus, ultimate tensile strength is presented for SAC-Q solder which includes Bi in addition to SnAgCu. The high strain rate low temperature data has been fit to the Anand Viscoplasticity Model to represent the non-linear constitutive behavior. The evolution of the Anand Constants has been presented with the increase in storage duration for period of upto 1-year at a storage temperature of 50°C. The accuracy of Anand model has been quantified by comparing the experimentally measured data with the predicted data with the computed model constants. The Anand parameters have been implemented in an FE-framework to simulate the drop events for a ball-grid array package on printed circuit board assembly to determine hysteresis loop and plastic work density. Effect of the evolution of the properties on the change in the hysteresis loops has been assessed.