Study on rate-dependent behaviors of underfills based on two-phase composites

Abstract

Underfills' properties are very important for the reliability of flip chip packages. As epoxy based materials, underfills show obvious rate-dependent behaviors under mechanical loading. However, studies on the rate-dependent behavior of underfills have been rarely reported, In this paper, the rate-dependent strain-stress behavior of underfills is studied based on two-phase composite assumption. A micromechanical method is employed to predict the overall strain-stress behavior of underfills. Results show good agreement between the predicted data and experimental data.