Solder joint reliability challenges in sub 1.00MM ball pitch for flip chip ball grid array

FCBGA is an electronic package used to achieve a high Inputs/Outputs (I/Os). To continue to achieve a higher I/O count without increasing package size, ball pitch reduction is inevitable. However, ball pitch reduction using smaller ball size has posed substantial challenges to solder joint reliability (SJR). On top of that, rising power dissipation requirement in FCBGA package has created a need for high performance heat sinks. These heat sinks require significant compression loading to ensure good thermal conductance of thermal interface materials. The impact of these loads on SJR has typically not been considered in thermal cycle stressing. Hence, this paper focuses on different types of heat sinks and their compressive load effect on solder joint thermal fatigue performance. It also covers package size and board thickness effect when heat sink compressive load is taken into account during thermal stressing. Lastly, lead free and eutectic solders at sub 1.00mm ball pitch technology were also evaluated.