Effect of unfilled underfill on drop test and thermal cycle reliability

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