Effect of Underfill Thermomechanical Properties on Thermal Cycling Fatigue Reliability of Flip-Chip Ball Grid Array

Abstract

Plane two-dimensional finite element analysis was applied to study the effect of underfill thermomechanical properties on the potential of thermal fatigue failure for flip-chip ball grid array. Two-stage as well as constant thermomechanical properties of underfills were manipulated to represent extremes of practical underfills. The steady-state creep model was incorporated for the eutectic solder bump to represent its real behavior. It was found from the parametric studies that the underfill with high Young’s modulus, low coefficient of thermal expansion, and high glass transition temperature leads to the longest service life.