An official website of the United States government
Most research involving resistive field grading materials or nonlinear field-dependent conductivity (FDC) layers has predominantly concentrated on DC or sinusoidal AC voltages, even though (U)WBG power electronic modules typically operate under high-frequency square wave voltages. To bridge this existing research gap, the present study systematically investigates the efficacy of an FDC coating in alleviating electric field stress when subjected to high-frequency, high-slew-rate square wave voltages. The findings indicate that applying a nonlinear FDC layer significantly reduces electric field stress, even under stringent conditions involving elevated operating frequencies. Furthermore, the influence of the square wave voltage type—the distinction between unipolar and bipolar square waveforms—on electric field stress remains inadequately understood despite substantial progress in breakdown and PD experiments related to these phenomena. Consequently, this study undertakes a comparative analysis of nonlinear FDC layers' performance under unipolar (+27.5 kV) and bipolar (±27.5 kV) square wave voltages. In doing so, this investigation contributes valuable insights into the interplay between high-frequency operation, the polarity of square waveforms, and the efficacy of nonlinear FDC layers in mitigating electric field stress within (U)WBG power module packages.
more »
« less
This content will become publicly available on September 14, 2026
3D Simulation of Electric Field Stress Within High Voltage, High Power Density Power Electronic Modules
Partial discharge issues at the triple junctions of the copper-ceramic-silicone gel interfaces in power electronic modules have emerged as a critical barrier to further technological advancement. Therefore, accurately calculating the electric field intensity and optimizing the insulation system are essential to ensure module reliability and performance. In this study, 2D and 3D geometries of a commercial power module were modeled in COMSOL Multiphysics to analyze the electric field distribution around triple points. The results showed a maximum electric field intensity of 22.5 kV/mm in the 3D model, compared to 15.0 kV/mm in the 2D simulation. This finding emphasizes the critical importance of employing 3D modeling to accurately represent the intricate electric field distribution at triple-edge regions. This work lays the foundation for accurate electric field calculations within power electronic modules, which is essential for determining the extent of electric field mitigation required.
more »
« less
- Award ID(s):
- 2306093
- PAR ID:
- 10652872
- Publisher / Repository:
- IEEE
- Date Published:
- Page Range / eLocation ID:
- 249 to 252
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
A vast majority of research on (U)WBG power modules has been going on to implement nonlinear resistive field grading material on metal-brazed substrates in reducing the electric field that is maximum at triple points (TPs). However, nearly all investigations have been conducted under either DC or 50/60 HZ sinusoidal AC voltages, even though the actual operation of envisioned (U)WBG power modules involves high-frequency square voltages with high slew rates. It has been validated by several studies that fast rise times of square voltages rapidly degrade the breakdown strength of insulation materials, leading to premature failure. Therefore, this paper introduces a nonlinear resistive field grading material or field-dependent conductivity (FDC) layer around the TP and metal edges to evaluate the electric field mitigation under a high frequency and high slew rate square voltage. The modeling and simulation of both coated and uncoated (U)WBG substrates were performed in COMSOL Multiphysics to assess the electric field reduction with the nonlinear FDC layer. The improvement of reduction in electric field under 100 kHz high slew rate square voltage is compared with that of 60 Hz. The results reveal a significant decrease in field stress at the TP, even under square voltages with fast rise times and high frequencies, when applying a nonlinear FDC coating, as opposed to the uncoated substrate. The influence of switching field (Eb) and nonlinearity coefficient (α) of nonlinear FDC layer is studied under 100 kHz square voltage, and it is concluded that α and Eb should be more than 10 and less than 8 kV/mm, respectively to achieve effective performance of resistive field grading material.more » « less
-
Within the expanding domain of electrical power demand, the future of power module packaging is entwined with the progress of (ultra) wide bandgap (UWBG) materials. These materials, like silicon carbide (SiC), aluminum nitride (AlN), and diamond, offer advantages with higher power density, decreased weight, and expanded operational abilities regarding temperature, voltage, and frequency. However, the pursuit of pushing these limits confronts challenges within insulation systems, which may struggle to endure the demands of these parameters, potentially resulting in unfavorable conditions like high electric field, space charge accumulation, electrical treeing, and partial discharge (PD), leading to insulation failure. The emphasis of this paper is to review the insulation challenges within (U)WBG power modules and recent research in mitigating the electric field stress at triple points (TPs) and resolving the PD issues. The manuscript first discusses the high electric field stress issue at triple points. Then, ceramic substrate materials, encapsulation materials, and the influence of harsh weather conditions on them are reviewed. The space charge, electrical treeing, and PD issues within encapsulation materials are analyzed under practical operation conditions of (U)WBG power modules like high frequency, temperature, and square wave pulses. Finally, the various strategies to alleviate the associated insulation challenges are meticulously discussed. While the identified mitigation strategies are able to strengthen insulation systems for packaging, their validation under actual operational conditions of (U)WBG power modules remains relatively unexplored, representing a potential avenue for further investigation. This review offers a valuable framework by providing the constraints of the current studies and recommendations for the future that can be utilized as a reference point for future research endeavors.more » « less
-
The future of packaging for power modules hinges on the advancement of (U)WBG) materials like SiC, AlN, and diamond. However, pushing these boundaries faces significant challenges in insulation systems, which must withstand the demanding parameters involved. The repercussions include high electric fields, space charge accumulation, electrical treeing, and partial discharge (PD), all of which can lead to power module failure. This paper delves into reviewing these challenges within insulation materials of (U)WBG power modules and recent research aimed at mitigating electric field stress at triple points (TPs) and addressing PD issues. Beginning with the issue of high electric fields at TPs, the paper explores space charge, electrical treeing, and PD problems within encapsulation materials under practical operating conditions, such as high frequency, and high temperatures. Various strategies to tackle these insulation challenges are thoroughly discussed. While three prevalent mitigation strategies can address electric field issues at TPs, their validation under high-temperature conditions of (U)WBG power modules remains relatively unexplored, suggesting a potential shift towards alternative encapsulation materials. It is observed that the high-temperature dielectric liquids emerge as a promising solution to address thermal stresses for temperatures up to 350 °C with their stable dielectric properties and breakdown strength under repeated tests. Overall, this review provides a valuable framework by outlining the limitations of current mitigation strategies and offering recommendations for future research endeavors, with a particular emphasis on alternative encapsulants.more » « less
-
As power modules based on (U)WBG materials gain attention for their potential to revolutionize high-voltage, high-power density applications, their optimal performance is hindered by current insulation materials. The high electric field stress at triple points (TPs) and encapsulant's diminishing breakdown field strength at high temperatures significantly limit the application of power modules to below 200°C. Therefore, alternative encapsulation materials are essential for hightemperature applications. This paper proposes a novel solution involving replacing standard silicone gel (SG) encapsulant with high-temperature encapsulation composites created by integrating micro- and nano-sized fillers into a silicone elastomer matrix. Additionally, the ceramic structure is redesigned into a mesa configuration, featuring a trench at the base of the metal electrodes. The results from modeling and simulation of COMSOL Multiphysics demonstrate that this combined approach significantly reduces field stress at TPs. Although effective at lower frequencies, further design modifications, such as altering the metalized substrate into a protruding structure, are necessary for optimal electric field mitigation at frequencies above 10 kHz. This research addresses the critical issues of high electric field values at TPs and the limited temperature tolerance of current encapsulation materials, which are challenges exacerbated under high-frequency square pulse operation. By resolving these issues, this work represents a valuable advancement in utilizing highvoltage, high-power density (U)WBG power modules at demanding frequency environments.more » « less
