Effects of Filler Configuration and Moisture on Dissipation Factor and Critical Electric Field of Epoxy Composites for HV-ICs Encapsulation

Molding compounds (MCs) are widely used as an encapsulation material for integrated circuits; however, traditional MCs are susceptible to moisture and charge spreading over time. The increase in dissipation factor due to the increase of parasitic electrical conductivity ( $\sigma$ ) and the decrease in dielectric strength $(E_{\mathrm {MC}}^{\mathrm {Crit}})$ restrict their applications. Thus, a fundamental understanding of moisture transport as a function of MC parameters is essential to suppress moisture diffusion and broaden their applications. In this article, we: 1) propose a generalized effective medium and solubility (GEMS) Langmuir model by identifying a set of parameters that control water uptake as a function of filler configuration and relative humidity; 2) investigate the dominant impact of reacted-water on $\sigma $ through numerical simulations, mass-uptake, and dc conductivity measurements; 3) investigate electric field distribution to explain how moisture ingress reduces $E_{\mathrm {MC}}^{\mathrm {Crit}}$ ; and finally 4) optimize the filler configuration to lower the dissipation factor, and enhance $E_{\mathrm {MC}}^{\mathrm {Crit}}$ . The GEMS-Langmuir model can be used for any application (e.g., photovoltaics, biosensors) where moisture ingress leads to reliability challenges.