Thermal and mechanical finite element analysis of a VLSI package including spatially varying thermal contact resistance

Abstract

Pressure-dependent thermal contact resistance has been simulated using numerical finite element models (FEMs) of representative plastic VLSI packages with and without interfacial delamination. Delamination at various material interfaces in the FEMs of these packages was modeled using gap finite elements. FEM results show that delamination redistributes mechanical stresses associated with encapsulation and operating conditions so that local stress concentrations are elevated in regions of the plastic where cracks have been observed. During chip operating conditions thermal flux and temperature fields were altered when pressuredependent thermal contact resistance was introduced in the FEMs. Maximum chip operating temperatures were also increased significantly. These increases were magnified when delamination occurs or the thickness of the plastic in the package was reduced in the FEMs. Debonding (interfacial separation) was predicted at delaminated material surfaces during operating conditions.Further analytical and experimental research should be carried out in order to more fully understand the coupled effects of thermal contact resistance in VLSI packages.