High Strain Rate Properties and Evolution of Plastic-Work for Doped Solder SAC-Q for Isothermal Aging Up to 240-Days at 100°C

Abstract

In automotive, aerospace, and defense applications – electronic parts can often be exposed to high strain loads during shocks, vibrations and drop-impact conditions. Electronic parts can often face extreme low and high temperatures ranging from −65°C to 200°C. Additionally, these electronic devices can be subjected to strain rates of 1 to 100 per second in a critical environment. Numerous doped solder alloys have emerged to mitigate the effects of sustained high-temperature operation. The mechanical properties of SAC-Q solder alloy, isothermally aged for prolonged durations and tested at extremely low to high operating temperatures, are not available. In this work, SAC-Q doped solder material is tested and studied for this study at a range of operating temperatures of −65°C to 200°C and at a strain rate up to 75 per second for up to 240 days (i.e. 8 months) of isothermal aging with a storage temperature of 100°C. For the extensive range of strain rates and surrounding test temperatures, stress-strain curves are established for the solder. The measured experimental results and data were fitted to the Anand viscoplasticity model. The Anand constants were calculated by estimating the stress-strain behavior measured for operating temperatures −65°C to 200°C for SAC-Q solder. FE analysis for drop/shock events for BGA package assembly with PCB has been carried out. Hysteresis stress-strain curves and plastic work density curves are generated for various aging conditions for SAC-Q solder ball joints.