Modeling, simulation and calibration of the chip encapsulation molding process

The transient process of filling the mold cavity in microelectronics packaging has been simulated applying the finite element method (FEM). The results have been compared to those of so-called 'short shot' experiments, in which the molding process is interrupted at predefined points in time. After determining the quantitative discrepancies between the simulation and the experimental results, conventional model calibration was performed covering the full dimensional, material, and load parameter space, in which the actual test conditions could have deviated from the target values considered in the first simulation run. This way, parameter deviations could be ruled out as main reason as most of the simulation inaccuracy persisted. Instead, a subsequent investigation revealed the following additional effects having caused the discrepancies: the effect of cavity vacuum, the systematic concentration of filler particles on top of the dies, the gas bubbles formed at the mold front by the chemical reactions, and the coasting flow of mold material after process interruption. Accounting for these effects as well, the simulation accuracy was improved substantially. It now allows the virtual design optimization of the microelectronics packages and the molding tool as well as that of process conditions and material selection prior to experimental tests boosting both, manufacturing efficiency and product reliability.