Investigating effect of unfilled underfills on board level solder joint reliability of area array packages under drop test and thermal cycling test

The work reported here explores the effect of underfill encapsulants on drop test and thermal cycle reliability of area array packages, such as BGAs, CSPs, and WL-CSPs. An unfilled underfill was found to provide superior drop test performance. Silica filled underfill, with lower CTE, was found to provide superior thermal cycle performance. However, if the unfilled underfill provides adequate thermal cycle performance, its use yields substantial process benefits