Prediction of Void-Induced Crack Propagation within Underfill Using the Meshless Material Point Method

Abstract

Underfill has an important role in the reliability of flip-chips, but voids formed during manufacturing can initiate fractures. Simulations can be used to predict when and where the fracture takes place. However, traditional mesh-based methods suffer from mesh distortions, require remeshing, and have long preprocessing times. In this work, the Material Point Method (MPM) is used to study the effect of the void size and relative distance on fracturing in the underfill. We find MPM can predict crack propagation without prior knowledge of the path, reduce preprocessing time, and eliminate remeshing. Therefore, this work aims to show MPM makes for an effective and efficient alternative to traditional simulation methods. Simulations are performed with MPM to investigate the effect of void size and distance between voids on crack propagation in the underfill. The results show that fractures occur later when the distance between voids is larger, but the rate of damage is significantly faster once a crack is formed. Larger void sizes increase the rate of damage, but no significant effect on crack initiation was found. These results show that the meshless material point method is a promising alternative for simulating fractures in the underfill.