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This paper reports the performance of an epoxy resin/silicon carbide whisker (EP/SiCw) composite (1–5 wt %) as the field-dependent conductivity (FDC) layer for electric field reduction in the high-voltage power module. The experiments consist of a field emission scanning electron microscope (FESEM), thermal conductivity, Fourier transform infrared (FT-IR) spectroscopy, thermally stimulated discharge current (TSDC), space charge, DC conductivity, and dielectric spectroscopy. The DC conductivity and dielectric spectroscopy are used for DC and AC stationary electric field simulations, respectively. The electric field reduction of EP/SiCw composites in the power module is analyzed, and the void defect in the FDC layer is also identified. The observed percolation threshold of the EP/SiCw composites is 3 wt %, and the DC electric field near the triple point decreases significantly by 74.8% under 10 kV when a 5 wt % EP/SiCw composite is applied for the FDC layer. It was found that the efficient threshold operating frequency of the FDC layer is around 10 kHz. The FDC layer can significantly reduce the electric field under AC voltage below 10 kHz. Although the power loss with the FDC layer increases obviously without the FDC layer, it is still lower than 1 W at 1 MHz, which is negligible for industrial applications. Notably, the void in the FDC layer is identified by the slowly increased dielectric loss with the increase of frequency through dielectric spectroscopy simulation.

This paper reports an enhancement of the nonlinear conductivity, thermal and mechanical properties of micro-silicon carbide/silicone elastomer (m-SiC/SE) composites by adding nano-aluminum nitride (n-AlN) for power module encapsulation applications. The electrical properties (such as nonlinear conductivity characteristics and transient permittivity obtained from polarization current, and trap distributions obtained from thermally stimulated depolarization current) and material properties (including thermo-gravimetric analysis, coefficient of thermal expansion, and thermal conductivity, tensile strength, strain at break and Young’s modulus) of the pure SE, m-SiC/SE microcomposites, m-SiC/n-AlN/SE hybrid composites are investigated. The effect of the m-SiC fillers and n-AlN fillers on physicochemical properties of the SE matrix is analyzed by FT-IR spectroscopy and crosslinking degree. The measured nonlinear conductivity and transient permittivity are used for electric field simulation under DC stationary and square voltages. It is found that the addition of n-AlN fillers in the SE hybrid composite improves the nonlinear conductivity characteristics and mitigates the electric field under DC stationary and square voltages, compared to the SE microcomposite. Furthermore, the m-SiC/n-AlN/SE hybrid composite has a higher thermal degradation temperature, thermal conductivity, tensile strength, Young’s modulus, and crosslinking degree than the SE microcomposite, whereas their CTE and strain at break are lower. It is elucidated that the m-SiC/n-AlN/SE hybrid composite with enhanced nonlinear conductivity and material properties is a promising packaging material for high-voltage power modules.

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