Three dimensional numerical prediction of epoxy flow during the underfill process in flip chip packaging

Abstract

In the present paper, a 3D numerical prediction has been made to study the flip chip underfill process using the epoxy molding compound (EMC). The prediction considered the EMC filling behavior for the flow induced between the tiny gap of silicon die and substrate. Three different arrangements of the solder bump have been tested in this work. The EMC is treated as a generalized Newtonian fluid (GNF). The developed methodology combines the Kawamura and Kawahara technique, and the melt front volume tracking method to solve the two-phase flow field around the solder bumps. The Castro-Macosko rheology model with Arrhenius temperature dependence is adopted in the viscosity model. The predictions are made to investigate the filling patterns at several time intervals. The results show that the underfill process for solder bump with Type A gives minimum filling time and better filling yield. The effect of gap height between the plate and substrate on the underfill process also has been considered. The close agreement between prediction and experimental results from the previous work illustrates the applicability of the present numerical model.