Effect of Interphase Dielectric Property in Electric Field Distribution in Silicone Elastomer Nanocomposite

The emergence of ultra-wide bandgap (UWBG) devices results in increasing research in high-density and high-temperature power electronic (PE) packaging. Encapsulants are crucial for electronic packaging and are required to be functional at high-density, high temperatures in UWBG-based power electronic devices. Silicone (Si)-based gels and elastomers, popularly used as encapsulations in conventional power electronic packaging, show dielectric issues under high-density and high-temperature systems. The local electric field enhancement at triple points in the high-power density PE devices increases the risk of partial discharge (PD). Adding nano-fillers in Si-based elastomers is one of the approaches to increase the dielectric integrity of high-power density devices. The high-volume fraction of interphase between the nanoparticles and polymers improves the dielectric properties. The interphase power model relates the dielectric constant of polymer composites with the dielectric constant of the interphase layer. In this paper, a numerical study has been conducted to investigate the effect of interphase dielectric constant on the electric field mitigation at the triple points Si-elastomer-based nanocomposites. A numerical model is developed in COMSOL Multiphysics to investigate the effect of interphase dielectric property on electric field distribution in the encapsulant of PE modules. Furthermore, the effect of nano-filler dielectric properties in minimizing the local electric field is compared.

I. Introduction

Global sustainability is strongly impacted by climate change and is irreversibly headed toward political and economic upheaval. The primary objectives are to transition to 100% renewable energy and all-electric mobility to reach net-zero emissions by 2050. Another requirement of modern power and energy systems is to achieve high gravimetric and volumetric power densities. High-voltage and high-power density engineering is emerging in this regard that can address the requirement of high power in reduced weight and volumetric systems as well as achieving clean energy. Using newly developed wide bandgap (WBG) and ultra-wide bandgap (UWBG) based power electronics systems are other trends that offers operating voltages and power density improvements of orders of magnitude[1], [2]. The fact that WBG and UWBG devices have far higher slew rates and switching frequencies than Si-based devices is one of their advantages. However, electric field control is more important in these power modules than in the conventional silicon (Si) based counterparts due to their higher voltage rating, higher dv/dt, fast switching speed, and higher power designs [3]. In PE modules, the insulation systems consist ceramic substrate that isolates chips and encapsulation materials that protects substrate, connections, and semiconductors from moisture, dirt, and vibrations. Under high density, high slew rate, and fast switching speed conditions both ceramic substrate and encapsulation materials experience locally enhanced electric field that initiates PD in the power modules and decreases device lifetime. Si-gels are most commonly used encapsulation materials in power module packaging for their excellent electrical properties, high elasticity, and self-healing properties [3]–[5]. However, their insulation properties experience degradation the operating frequency close to 18 kHz and temperature above 100 °C [3]. One of the approaches of increasing the dielectric integrity of encapsulation materials at high density and high operating temperatures is to adding nano-fillers in the Sielastomers. In [6], it is shown that by adding nano-sized boron nitride (BN) and silicone carbide (SiC) in Si-elastomer the PD inception voltage (PDIV) can be increased.