Damage Life-Prediction Model for Doped Lead-Free SnAgCu Solder Electronic Assemblies Under High Strain Rate Vibration After Prolonged Storage

Growing complexity of automotive electronics, particularly those deployed in harsh under-hood environments, necessitates a deep understanding of solder interconnect reliability under combined high temperature and high strain rate vibration. Electronic assemblies, including those mounted on engines, transmissions, and within wheel wells, endure significant vibration loads coupled with extreme temperature fluctuations over extended periods. While doped SAC-X solder alloys have been developed to mitigate temperature-induced property degradation, the damage mechanisms and predictive models for vibration reliability, particularly under high strain rates (1–100 per sec), remain limited. This study addresses this gap by developing energy-based damage relationships for life prediction in doped SAC-Q solder ball grid array (BGA) assemblies, critical for ensuring the viability of high I/O packaging in demanding automotive applications. A standardized CABGA208 board assembly, adhering to JEDEC JESD22-B111A, was designed and fabricated. To simulate realworld conditions, assemblies were subjected to harmonic vibration at their first natural frequency, with acceleration levels of 5g and 10g, and at ambient temperatures ranging up to 150°C. Isothermal aging was also incorporated to assess the impact of prior thermal exposure. Experimental modal analysis and high-speed motion capture techniques were employed to accurately determine the natural frequencies under varying test conditions. Finite element (FE) models were developed to correlate with the experimental data, incorporating viscoplastic constitutive models that accurately capture the non-linear, strain rate-dependent behavior of solder at high strain rates. These models enabled the extraction of critical parameters such as plastic work densities and hysteresis loops from key solder interconnects. By establishing a relationship between accumulated plastic work and time-to-failure, an energy-based life prediction model was formulated. This model addresses the limitations of traditional linear-elastic FE analysis offering a more nuanced understanding of solder joint damage accrual.