Comparative Drop Shock Reliability Study of SAC-Based Alloys in BGA Assemblies

The reliability of SnAgCu (SAC)-based alloys has attracted considerable attention following the restrictions on lead-based alloys in the electronics industry due to their toxic nature. Considering the tendency of portable electronic devices to experience drop events during typical usage, ensuring a robust board-level drop shock reliability is crucial for the optimal performance and to safeguard the performance and overall lifespan of these devices. This study investigates the drop shock reliability of ball grid array (BGA) assemblies utilizing various SAC-based alloys and compares their performance with the established SnPb alloy benchmark. Drop tests were conducted at different acceleration levels and pulse widths for each alloy, enabling the determination of input energy for each specific condition. Additionally, a drop life prediction model has been developed for each alloy at different energy levels. In parallel, hardness tests have been performed on each alloy under pristine conditions, and the results have been correlated with the corresponding drop life performance. Furthermore, comprehensive microscopy analysis has been performed to ascertain the failure modes and identify trends in failure patterns as a function of acceleration levels. The study findings revealed that SAC-bismuth (Bi) alloys exhibit superior performance compared to both SAC305 and SnPb alloys at lower energy levels. Moreover, the failure mode for SAC-Bi alloys and SnPb remains independent and constant across all energy levels, while SAC305 exhibits variability in its failure mode. The study outcomes contribute to a deeper understanding of drop shock reliability in lead-free electronic devices, emphasizing the potential benefits of SAC-Bi alloys as a promising alternative.