Dynamic Mechanical Analysis and Viscoelastic Behavior of Epoxy Molding Compounds Used in Fan-Out Wafer-Level Packaging

In decades of microelectronic devices manufacturing, a few generations of epoxy molding compounds (EMCs) have been developed and applied successfully in different packaging processes. Up to date, minimizing the warpage of the cured molding compound is still a hot topic in the microelectronics industry, as the warpage has significant impact on devices' reliability and process yield. In this work, five commercial EMCs, which are the main stream packaging materials used in FOWLP process, were selected and investigated. Differential scanning calorimetry (DSC) was used to determine the degree of cure (DoC) of the EMCs. The results show that the DoCs of the EMCs are from 97% to 99.2% after post-cure process. The viscoelastic properties of the EMCs were determined in terms of Prony coefficients. The Williams-Landel-Ferry (WLF) equation was used to describe the time-temperature superposition (TTS), in order to predict the mechanical behaviors of the EMCs beyond the experimental timescale. All these data were used in predictions of the relaxation behavior of the molding compounds. Meanwhile, other thermo-mechanical properties of all the EMCs were also characterized.