Some remarks on finite element modeling of electromigration in solder joints

This paper investigates several issues in finite element modeling of electromigration in solder joints: current density and thermal stress singularities; negative divergences of atomic fluxes due to electron current and thermal stresses; and submodeling accuracy. A copper post wafer level package is used as a test vehicle for simulation. Coupled electrical-, thermal-, and mechanical finite element modeling is performed. Results show that the values of maximum current density in solder balls significantly depend on finite element mesh sizes, indicating a singularity exists. Negative values of the divergences of atomic fluxes due to electron current and thermal stresses are obtained under certain loading conditions. Submodeling presents accurate results if cut boundary is appropriately chosen.