Comparative Analysis of Flow Capability of Epoxy Molding Compound between Spiral Structure and Actual Mold by Mold Flow Simulation

Plastic package usually requires the epoxy molding compound (EMC) to be filled in mold by transfer molding method. In order to achieve better filling results, the selected EMC needs to have good flow capability at molding temperature to avoid insufficient filling or voids during molding process. At present, a commonly used method for evaluating flow capability of EMC is spiral flow test, and the spiral flow length, i.e., the length that EMC could fill in the spiral structure at molding temperature, is regarded as the key index of flow capability. However, due to the significant difference in structure, whether the spiral flow length can fully reflect the filling results of EMC in real mold is worth paying attention. In this paper, we use mold flow simulation to simulate the EMC with similar physical properties to fill in the spiral pattern and actual mold structure respectively, to verify the differences in flow capability. The key material properties of EMC and the influence of the main process parameters on the filling results of these two structures are further studied. For material properties, we mainly focus on the zero shear viscosity, gel point and curing kinetics of EMC, while for process conditions, we focus on molding temperature and filling time. It shows that the spiral flow length is much more sensitive than the filling results in actual mold structure, so the spiral flow length could not fully represent the flow capacity in actual mold. The mechanism of flow results of EMC in spiral flow mold and actual mold is analyzed in detail based on the principles of fluid mechanics and material properties of EMC.