THERMAL-STRESSES IN LAYERED ELECTRONIC ASSEMBLIES

Thermal stresses in layered electronic assemblies are one of the cause s of the mechanical failure of electronic packages. A simple but accur ate method of estimating these thermal stresses is needed for the desi gn of these packages. A simple approach based on beam theory exists, b ut it suffers from nonequilibrium of the peeling stress distribution. An improved method that overcomes this drawback is proposed here. For layered electronics with thin adhesives, simple analytical expressions are obtained for interfacial shear stress and peeling stress, as well as for other stress components. The finite element method is used to verify these solution. It shows excellent agree- ment between the fini te element results and these simple solutions, especially when the mod uli of adhesive layers are significantly lower than the moduli of the other layers. This method provides an accurate estimate of thermal str esses for use in package design involving thin and compliant interface or adhesive layers.