Evolution of Anand Parameters for SAC-Q Solder Alloy after Prolonged Storage up to 1-Year at High Strain Rate at Very High Operating Temperature

摘要

Solder joints in electronics installed in downhole, automotive and avionics applications may be exposed to high temperatures (> 150°C) and high strain rates (1-100 per sec) during storage, operation and handling. The microstructure for SAC lead free solder alloys constantly evolves when subject to thermal aging for longer period, which can cause degradation in mechanical properties of solder alloys. In order to improve the survivability of leadfree alloys, industry has used doping of the SAC alloys to mitigate aging effects. Several doped SAC solder alloys have emerged. Examples include SAC-Q, and SAC-R. However, there are very little data available for SAC-Q solder alloys at high strain rate and sustained operation at high operating temperatures. In this study, high strain-rate material behavior for 1-year thermal aged SAC-Q during operation at high operating temperature has been characterized. High strain-rate tensile tests were performed to extract the mechanical properties at high strain rates of 10, 35, 50 and 75 per sec at high operating temperatures up to 200°C for thermal aged samples. SAC-Q samples were subjected to thermal aging at 50 °C up to 1-year before testing. In addition, the evolution of Anand model parameters has been explored when the alloy is subjected to thermal aging. Stress-Strain measurement at each test condition has been fit to the ANAND's viscoplastic model to compute the nine-Anand parameters. A good correlation was found between experimental data and Anand predicted data. Finite Element Analysis (FEA) based method has been used to simulate the drop events using Anand constitutive model.