Nonlinear Stress Modeling Scheme to Analyze Semiconductor Packages Subjected to Combined Thermal and Hygroscopic Loading

A nonlinear finite element modeling (FEM) scheme to analyze the combined effect of thermal and hygroscopic deformation is presented. The scheme employs the conventional moisture diffusion, heat transfer, and stress analysis routines available in the commercial FEM package, but offers a unique way of linking the routines to conduct a nonlinear stress analysis of semiconductor packages subjected to moisture as well as temperature excursions. Strategies to implement the proposed scheme using commercial finite element analysis softwares are discussed. The numerical accuracy of the scheme is confirmed with the analytical solution of elastic/viscoelastic composite cylinder subjected to the combined loading of thermal expansion and hygroscopic swelling.