High Strain Rate Mechanical Properties of M758 Solder at Extreme Surrounding Temperatures, with 100°C Isothermal Aging for up to 180 Days

Abstract

In the industries related to automotive, oil and gas, aerospace, medical technologies, electronic parts can often be exposed to high strain loads during shocks, vibrations and drop-impact conditions. Such electronic parts can often face the 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/sec in the critical environment. Lately, numerous doped solder alloys are being introduced in the electronic component e.g. SAC-Q, SAC-R, Innolot, etc. M758 is a novel general purpose, thermal fatigue resistant doped solder alloy, used for surface mount technology. Mechanical characteristic results and data for lead-free solder alloys are extremely important for optimizing electronic package reliability, at high temperature storage and elevated strain rates. Moreover, the mechanical properties of solder alloys can be transformed considerably due to the thermal aging, which is causing alteration of microstructure. Statistics for the mechanical properties of M758 solder alloy with an extreme low to high operating temperatures, with thermal aging effects are not available. In this work, M758 doped solder material is tested and studied for this study at range of operating temperatures of -65°C to 200°C and at a strain rate up to 75/sec for up to 180 days (i.e. 6 months) of isothermal aging with storage temperature of 100°C. For the extensive range of strain rates and surrounding test temperatures, stress-strain curves are established. Additionally, the measured experimental results and data were fitted to the Anand viscoplasticity model and the Anand constants were calculated by estimating the stress-strain behavior measured for operating temperatures -65°C to 200°C. Also, FE analysis has been carried out for drop/shock events for BGA package assembly with PCB. Hysteresis stress-strain curves and plastic work density curves are generated for various aging conditions for M758 solder ball joints.