Ball Grid Array Solder Joint Reliability Under System-Level Compressive Load

Heatsinks have been widely used in the electronics industry as a thermal solution for high-performance and highpower-density devices. The thermal efficiency of heatsink solutions may be improved by increasing the compressive load applied on the interface between the electronic package and heatsink. Typical approaches for heatsink retention, however, would also lead to high levels of compressive load on the package ball grid array (BGA) solder joints. In this paper, the effect of compressive load on SnPbAg solder joint reliability is investigated by using both experimental and numerical approaches. Accelerated system-level solder joint reliability tests under temperature cycling and isothermal aging conditions, with the presence of compressive loads, are first performed to identify and characterize the critical reliability failure mode. Creep constitutive behavior under compression is then characterized and implemented in numerical finite-element simulations for developing a phenomenological model of the BGA solder joint failure under compressive loading. A life prediction formula for SnPbAg solder joint subject to constant compressive load is also proposed.