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In the ever-growing landscape of electrical power demand, the future of power electronics module packaging lies in the realm of wide-bandgap (WBG) materials, including silicon carbide (SiC), gallium nitride (GaN), and cutting-edge ultra WBG (UWBG) materials like diamond, aluminum nitride (AlN), and hexagonal-boron nitride (h-BN). These materials offer superior properties to traditional silicon-based devices, promising higher power density, reduced weight, and increased operating temperature, voltage, and frequency. However, pushing the boundaries for power electronics modules presents challenges in insulation systems as the encapsulation material and the ceramic substrate may not withstand the functional parameters, potentially leading to unfavorable conditions like high field stress and partial discharge (PD), ultimately resulting in insulation failure. This paper presents a thorough analysis of the characteristics of the electrical insulation materials used in power electronics devices based on the research in WBG packaging conducted in recent years. The significance of maximum electric field stress at triple points (TPs) is examined. Furthermore, the paper reviews the strategies and techniques employed to mitigate the challenges related to maximum field stress and PDs in both encapsulation and substrate materials. It is concluded that the mitigation strategies are promising in improving insulation systems for packaging, but the studies lack their implementation under actual operating conditions of WBG power modules.
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A Comprehensive Review of Mitigation Strategies to Address Insulation Challenges within High Voltage, High Power Density (U)WBG Power Module Packages
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.
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- Award ID(s):
- 2306093
- PAR ID:
- 10498696
- Publisher / Repository:
- IEEE
- Date Published:
- Journal Name:
- IEEE Transactions on Dielectrics and Electrical Insulation
- ISSN:
- 1070-9878
- Page Range / eLocation ID:
- 1 to 1
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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In the ever-growing landscape of electrical power demand, the future of power electronics module packaging lies in the realm of wide-bandgap (WBG) materials, including silicon carbide (SiC), gallium nitride (GaN), and cutting-edge ultra WBG (UWBG) materials like diamond, aluminum nitride (AlN), and hexagonal-boron nitride (h-BN). These materials offer superior properties to traditional silicon-based devices, promising higher power density, reduced weight, and increased operating temperature, voltage, and frequency. However, pushing the boundaries for power electronics modules presents challenges in insulation systems as the encapsulation material and the ceramic substrate may not withstand the functional parameters, potentially leading to unfavorable conditions like high field stress and partial discharge (PD), ultimately resulting in insulation failure. This paper presents a thorough analysis of the characteristics of the electrical insulation materials used in power electronics devices based on the research in WBG packaging conducted in recent years. The significance of maximum electric field stress at triple points (TPs) is examined. Furthermore, the paper reviews the strategies and techniques employed to mitigate the challenges related to maximum field stress and PDs in both encapsulation and substrate materials. It is concluded that the mitigation strategies are promising in improving insulation systems for packaging, but the studies lack their implementation under actual operating conditions of WBG power modules.more » « less
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null (Ed.)Our previous studies showed that geometrical techniques including (1) metal layer offset, (2) stacked substrate design and (3) protruding substrate, either individually or combined, cannot solve high electric field issues in high voltage high-density wide bandgap (WBG) power modules. Then, for the first time, we showed that a combination of the aforementioned geometrical methods and the application of a nonlinear field-dependent conductivity (FDC) layer could address the issue. Simulations were done under a 50 Hz sinusoidal AC voltage per IEC 61287-1. However, in practice, the insulation materials of the envisaged WBG power modules will be under square wave voltage pulses with a frequency of up to a few tens of kHz and temperatures up to a few hundred degrees. The relative permittivity and electrical conductivity of aluminum nitride (AlN) ceramic, silicone gel, and nonlinear FDC materials that were assumed to be constant in our previous studies, may be frequency- and temperature-dependent, and their dependency should be considered in the model. This is the case for other papers dealing with electric field calculation within power electronics modules, where the permittivity and AC electrical conductivity of the encapsulant and ceramic substrate materials are assumed at room temperature and for a 50 or 60 Hz AC sinusoidal voltage. Thus, the big question that remains unanswered is whether or not electric field simulations are valid for high temperature and high-frequency conditions. In this paper, this technical gap is addressed where a frequency- and temperature-dependent finite element method (FEM) model of the insulation system envisaged for a 6.5 kV high-density WBG power module will be developed in COMSOL Multiphysics, where a protruding substrate combined with the application of a nonlinear FDC layer is considered to address the high field issue. By using this model, the influence of frequency and temperature on the effectiveness of the proposed electric field reduction method is studied.more » « less
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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
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null (Ed.)Emerging applications of compact high-voltage SiC modules pose strong challenges in the module package insulation design. Such SiC module insulations are subjected to both high voltage DC and PWM excitations between different terminals during different switching intervals. High dV/dt strongly interferes with partial discharge (PD) testing as it is hard to distinguish PD pulses and PWM excitation induced interferences. This paper covers both the testing and modeling of PD phenomena in high-voltage power modules. A high dV/dt PD testing platform is proposed, which involves a Super-High-Frequency (SHF, >3GHz) down-mixing PD detection receiver and a high-voltage scalable square wave generator. The proposed method captures SHF PD signatures and determines PDIV for packaging insulation. Using this platform, this paper provides a group of PDIV comparisons of packaging insulation under DC and PWM waveforms and discloses discrepancies in these PDIV results with respect to their excitations. Based on these PD testing results, the paper further provides a model using space charge accumulation to explain the PD difference under DC and PWM waveforms. Both simulation and sample testing results are included in this paper to support this hypothesis. With this new model, the paper includes an updated insulation design procedure for high-voltage power modules.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1109/TDEI.2024.3382070
