Analytical Thermo-Mechanical Model for Non-Underfilled Area Array Flip Chip Assemblies

Abstract

An analytical model is derived for the calculation of thermo-mechanical induced stresses in area array flip chip assemblies. This analytical model is based on structural mechanics and has the ability to characterize the nature and to estimate the magnitude of the induced stresses. The extension of this model compared to existing procedures is its applicability to area array systems, which behave significantly different from peripheral assemblies. The model is compared to finite element simulations. The model calculates accurately the forces and bending moments acting on the flip chip connections. The transformation of these forces and moments into stresses is less accurate as the model does not include stress concentrations near the corners. The model simulates very well the different parameter trends such as chip size and is therefore well suited for understanding parameter sensitivity studies.