Comprehensive Study on the Interactions of Multiple Die Shift Mechanisms During Wafer Level Molding of Multichip-Embedded Wafer Level Packages

Comprehensive numerical and experimental analyses were performed to investigate the issue of die shift during the 12-in wafer level molding process of multichip-embedded wafer level packages. The proposed modeling methodology considers the major mechanical and mold flow mechanisms in the phenomenon. Experimental characterization of the adhesion behavior of a die attached on mold tape at molding temperature suggests that mold tape behavior is an important contributing factor to die shift and the mold tape behavior at high temperature needs to be considered for improved die shift prediction. Incorporating the characteristics of the mold tape adhesion behavior, the die shift obtained from the improved numerical model is compared with the experimental observations and a good correlation is observed. From the investigation, it was found that mechanical effects such as coefficient of thermal expansion of the mold plate and chemical shrinkage can contribute up to 85% of the die shift while fluidic force accounts for the rest.