A model for thermal fatigue of large area adhesive joints between materials with dissimilar thermal expansion

A model describing thermal fatigue of large area adhesive joints such as die bonds, has been developed. It is based on equations for crack growth rate and stress distribution in large area joints. The basic assumption of the model is that cracks grow from the edges of the area towards the center. The thermal resistance of the bond layer was calculated by assuming the cracked part of the layer had infinite thermal resistance. The thermal resistance as a function of the number of thermal cycles was predicted to be different for adhesives with low and high modulus of elasticity. Good agreement with previously reported experiments was obtained. The thermal resistance in silver filled die bond adhesives as a function of the number of thermal cycles was measured in these experiments