Impact of Bi-Content on the High Strain Rate Properties of SnAgCu Solders Under Sustained High-Temperature Operation

In applications such as automotive and aerospace, electronics may require prolonged high-temperature exposure in the range of 150-200°C and random exposure to mechanical shock and vibration. Additionally, electronics may be stored for extended periods in non-climate-controlled enclosures before deployment. To address the negative effects of sustained high-temperature exposure, the industry has experimented with the addition of dopants to SAC solders. There is limited information on new formulations' mechanical performance, reliability, and constitutive models. The research presented in this paper aims to fill a gap in the state of the art by measuring the effect of Bismuth addition on the properties of SAC-Bi alloys at low temperatures, high strain rates, and varying periods of thermal aging of up to 1 year. Various doped alloys have been studied, including SAC-Q, SAC-R, M758, QSAC10, QSAC20, and SAC305 solder, in a strain-rate range of 1-100 per second in the temperature range of -65°C to +200°C after one year of sustained exposure to 50°C and 100°C. The Anand parameters have been computed and used to quantify the accuracy of the Anand model by comparing the experimentally measured data with the predicted data with the computed model constants. The Anand parameters have been integrated into an FE framework to simulate drop events for a ball-grid array package on a printed circuit board assembly, aiming to determine the hysteresis loop and plastic work density. An increase in the bismuth content has been shown to mitigate the UTS degradation and effective modulus at high strain rates under sustained high-temperature operation.