The Limited Reliability of Board-Level SAC Solder Joints under both Mechanical and Thermo-mechanical Loads

The trend of miniaturization, light weight, high speed and multifunction are common in electronic assemblies, especially, for portable electronic products. In particular, board-level solder joint reliability, in term of both mechanical (e.g., drop impact) and thermo-mechanical (e.g., thermal cycling) loads is of great concern for portable electronic products. The transition to lead-free solder happened to coincide with a dramatic increase in portable electronic products. Sn-Ag-Cu (SAC) is now recognized as the standard lead-free solder alloy for packaging interconnects in the electronics industry. Hence, this study review the reliability of board-level SAC solders joints when subjected to drop impact and thermal cycling loading conditions from the viewpoints of mechanical and micro-structural properties of the bulk solder. The finding presented in this study indicates that the best SAC composition for drop performance is not necessarily the best composition for optimum thermal cycling reliability, thus the SAC solder alloys are limited in their potential applications in the electronic industries. This contribution has its value in giving information on possible developments and the suitability for the usage of SAC solder in portable electronic devices.