Three-dimensional simulation of reactive polymeric flow during microchip encapsulation

A three-dimensional finite element simulation software to predict the plastic encapsulation process of microchips is developed. In the simulation, Stokes flow equations for an inertia-free, incompressible flow are employed. A brick element is used for discretization of the flow domain. Control volume scheme with a fixed finite element mesh is utilized to predict fluid front advancement.; First, the finite element program is used to simulate the plastic melt flow under isothermal conditions. In general, the predicted fluid front advancement and pressure variation in mold cavities similar to those used for microchip encapsulation are in good agreement with the corresponding experimental results. Through the study of the cases with different upper- and lower-cavity thickness combinations, the normalized thickness difference is found to be the main factor affecting the location of the weld line and the pressure spike magnitude near the end of the filling. Then the energy equation is coupled into the isothermal finite element program to simulate the plastic melt flow with thermal and curing effects. The SUPG method was used to solve the convection-dominated energy equation. It is found that oscillations/wiggles in the predicted temperature and curing fields are still significant. To reduce the wiggles, an additional artificial diffusion term is added to the SUPG formulation, and the simulation of the flow in square channels shows significant improvement. The final program is used to simulate spiral flow and the flow in the microchip encapsulation mold. The predicted flow length of spiral flow, pressure history in a mold similar to that used in microchip encapsulation, and fluid front advancement in a microchip encapsulation mold are verified experimentally.