Underfill flow as viscous flow between parallel plates driven bycapillary action

摘要

Epoxy underfill is often required to enhance the reliability offlip-chip interconnects. This study evaluates the flow of filled epoxyunderfill materials between parallel plates driven by capillary action.An exact model was developed to understand the functional relationshipbetween flow distance, flow time, separation distance, surface tension,and viscosity for quasi-steady laminar flow between parallel plates. Themodel was verified experimentally with a typical underfill material. Themeasured values of flow distance agreed well with the exact model. A newmaterial parameter, the coefficient of planar penetrance, is introduced.This parameter measures the penetrating power of a liquid betweenparallel plates driven by capillary action. The effectiveness of gravityand vacuum as flow rate enhancements are explored