Abstract
Interfacial insulation degradation remains a critical barrier to the reliability of wide-bandgap power electronic packaging subjected to high-frequency pulse voltages and elevated temperatures. This study systematically investigates the electrical treeing behavior at the silicone gel/ceramic substrate interface. It is found that the interfacial electrical treeing exhibits a characteristic three-stage evolutionary process, transitioning from initial sparse dendritic initiation to the rapid expansion of complex reticular cracks, and finally into a stagnation stage where growth rates approach zero. The final tree length follows a linear positive correlation with the pulse voltage amplitude. Besides, the electrical tree length increases significantly with rising frequency in the low-frequency range, while no obvious change in length occurs with further increase in frequency over 5 kHz. On the other hand, the higher the temperature is, the greater the growth rate of electrical trees in the rapid growth stage, and the length of electrical trees increases with the increase in temperature. These findings provide fundamental insights into the interfacial failure mechanisms of elastomeric encapsulants and offer a theoretical framework for designing high-performance insulation systems for next-generation SiC power devices.
1 Introduction
Silicon carbide (SiC) power devices have promising applications in new energy vehicles, rail transit, smart grids and other fields due to excellent high-voltage and high-temperature performance of SiC chips (; ; ; ; ). However, it has been reported that under operating conditions such as high-frequency repetitive pulse voltages and high temperatures, electric field will distort significantly in the triple points among silicone gel, ceramic, copper inside SiC power devices packaging, which could further initiate partial discharges at silicone gel/ceramic interfaces and probably lead to power devices failure. This seriously restricts the further improvement in the devices performance and their applications in special fields (; ; ; ; ; ). Therefore, it is necessary to study the electrical tree growth behavior at the silicone gel/ceramic substrate interface under pulsed voltage and high-temperature conditions, in order to deepen the understanding of insulation degradation mechanisms and provide a guidance on reliability of the packaging insulation system.
Currently, numerous researchers have investigated the growth behavior of electrical trees at the silicone gel/ceramic substrate interface. Under AC voltage, Masahiro Sato et al. found that electrical trees at the silicone gel/glass substrate interface consist of spherical cavities and filamentary channels. Charges tend to accumulate on the cavity surface via streamers, while cavity movement is driven by changes in their net internal charge (). They also observed that aluminum nitride (AlN) substrates become conductive on the surface due to discharge, leading to a significantly longer final cavity extension compared to other substrates (). Yan et al. proposed a modified ceramic substrate structure to reduce the risk of interfacial discharge (). Under pulsed voltage, it has been reported that electrical tree characteristics differ from those under AC conditions. Nakamura further revealed that the cavity length increases with the frequency from 50 Hz to 1 kHz and is especially long when the rise time is short and discharge tracks under positive impulses have filamentary shapes while discharge tracks under negative impulses have spindle-shape (). Zhang et al. further found that the frequency, rise time, and duty cycle of positive square-wave voltage significantly affect the morphology and growth of electrical trees at the silicone gel/DBC substrate interface (Zhang et al., 2024). For the influence of temperature, Nakamura et al. observed that the magnitude of partial discharges, cavity length, and number of cavities increase significantly with elevated temperature under AC voltages (). Wang et al. also supported that elevated temperature accelerated interfacial electrical-tree growth between silicone elastomer packaging insulation and ceramic substrates (). Zhang et al. further reported that increasing temperature reduced the electrical-tree inception voltage and promoted tree growth in silicone gel under pulsed electric fields (). Most of SiC power devices work under the pulsed voltage with high frequency, while studies on interfacial electrical tree growth behavior under pulsed voltage with higher frequency like 10 kHz is few. Besides, the understanding about interfacial electrical tree growth behavior under pulsed voltage and high temperatures is lacking.
Therefore, this paper conducts a systematic investigation into the electrical tree growth behavior at the silicone gel/ceramic substrate interface under pulsed voltage and elevated temperatures. This work is beneficial to further understanding the insulation failure mechanisms at the interface between encapsulation insulating materials and ceramic substrates, enabling the rational design of packaging structures and materials, which is of great significance for enhancing the insulation performance of next-generation SiC power devices and advancing the development of high-temperature and high-voltage SiC devices.
2 Sample preparation and experimental platform setup
2.1 Material and sample preparation
To investigate the growth and evolution mechanism of electrical trees at the interface of silicone gel/ceramic substrates under pulse voltage and high temperature, this experiment used a needle plate electrode discharge structure to prepare experimental samples. The details of the discharge samples prepared in this experiment are shown in Figure 1, where Figure 1a is the actual image of the prepared sample, which can visually display the overall appearance of the sample, Figure 1b is a schematic diagram of a single sample structure. The setup includes a needle electrode, a Al2O3 ceramic substrate (40 mm × 40 mm × 1 mm), copper foil, and silicone gel. The back side of substrate is coated with copper foil and grounded as the reference electrode. The ceramic substrate was placed in a mold and a tungsten steel needle with a tip curvature radius of 10 μm was placed in tight contact with the upper surface of the ceramic substrate at a 17° angle. The needle electrode and the mold were secured using casting adhesive to prevent any movement of the needle electrode that could affect the experimental results.
FIGURE 1
SEMICOSIL 915HT silicone gel was used as the encapsulation and insulating material for the test samples (). During sample preparation, components A and B were mixed at a mass ratio of 10:1 and stirred homogeneously for 10 min using a magnetic stirrer. Subsequently, the uniformly mixed liquid was poured into the mold, ensuring the needle electrode was completely submerged by the silicone gel to form an effective encapsulation structure. The mold was then placed in a vacuum drying oven and subjected to vacuum degassing for 60 min at room temperature to remove bubbles within the silicone gel. After degassing, the sample was heated at 100 °C for 60 min to cure the silicone gel.
2.2 Platform for electrical tree growth observations
Figure 2 shows the experimental platform for discharge at the interface of silicone gel/ceramic substrate under high-frequency pulse voltage. The high-voltage pulse generation and detection part consists of a high-voltage power supply, a high-voltage probe, a signal generator, a protective resistor, and MOSFET switch tubes. The imaging part includes an optical microscope (MZ62), a computer, and an experimental light source. The temperature control section uses a constant temperature heating table (Bangyuan BY1010).
FIGURE 2
The high-voltage power supply adopts Tasman TD2202 high-voltage power supply, which can stably output DC voltage. Connect a 50 kΩ protective resistor in series between the power supply and the sample to prevent sudden discharge from damaging the circuit. Use the signal generator Tektronix AFG3102C to control the conduction and turn off of two MOSFET switches A and B. By alternately switching between A and B, a positive polarity pulse voltage can be generated. By changing the on/off frequency of switches A and B, the frequency of the positive polarity pulse voltage can be further adjusted. The high voltage (HV) probe monitors the voltage applied to both ends of the sample and is connected to an oscilloscope to obtain the pulse waveform of the applied voltage.
In the electrical tree observation system, use an optical microscope to observe the image of the electrical tree. The microscope adopts a high-power binocular microscope with a maximum resolution of 3072 × 2048 and is equipped with an independent adjustable light source device to clearly observe the internal conditions of the silicone sample. The microscope is connected to a computer, and with the help of video capture software that matches the microscope, the growth process of electrical trees on the interface between the silicone gel/ceramic substrate in the experimental sample is observed in real time. At the same time, photos are taken and recorded at predetermined time intervals, and the length of the electrical tree branches is measured and saved through system software. It should be noted that the annular bright area around the cavity in the image is not the luminescence phenomenon generated by partial discharge of silicone gel, nor represents the boundary of electrical tree or discharge damage area, but the annular halo artifact caused by optical microscopic imaging system.
A Bangyuan BY1010 intelligent constant-temperature heating stage was used for temperature control. To ensure data reliability, the laboratory temperature was maintained as consistently as possible, and strong airflow and mechanical vibration were avoided. The heating stage was preheated for more than 30 min, and the probe of a standard thermometer was positioned as close as possible to the sample location. At least four sets of temperature readings were obtained according to the calibration procedure specified in the product manual, and the measurement error was calculated before equipment calibration. After calibration, the specimen was placed on the temperature-controlled heating stage for 30min to reach thermal equilibrium, and its ambient temperature was controlled by adjusting the real-time temperature setting of the stage.
The growth process of electrical trees at the silicone gel/ceramic substrate interface under different pulse voltage amplitudes, frequencies, and operating temperatures is observed to obtain the influence of pulse voltage parameters and temperature on the interface electrical trees growth. In this experiment, electrical tree images were selected at 0 s, 30 s, 60 s, 120 s, 300 s, 540 s, and 900 s from the start of voltage application, and the electrical tree lengths were measured. The pulse voltage amplitude, frequency, temperature, and other parameters for different experiments are shown in Table 1.
TABLE 1
| Amplitude (kV) | Frequency (kHz) | Temperature (°C) |
|---|---|---|
| 6, 6.5, 7, 7.5, 8 | 0.1 | 40 |
| 7 | 0.1, 0.5, 1, 5, 10 | 20 |
| 6 | 0.1 | 70, 100, 130, 160 |
Experimental parameters of positive polarity pulse voltage.
Additionally, it should be noted that this study conducted multiple sets of repeated experiments under different voltage amplitudes, pulse frequencies, and temperature conditions (three independent experiments were conducted under each condition). The length time curve of the electrical tree branches and corresponding optical images in the original manuscript are not derived from a single accidental result, but from a representative set of complete, continuous, and typical evolution processes selected from the repeated experiments. In addition, in studies related to electrical trees and partial discharge, obtaining statistical results based on repeated experiments and selecting typical samples to demonstrate the continuous morphology evolution process is a commonly used way of presenting results(; Zhang et al., 2024; ; ; ).
3 Influence of pulse waveform parameters and temperature on the growth process of electrical trees at the silicone gel/ceramic substrate interface
3.1 Growth process of electrical trees at the silicone gel/ceramic substrate interfacial under pulse voltage
To more conveniently observe and quantitatively study the growth process of electrical trees at the silicone gel/ceramic substrate interface under positive polarity pulse voltage, this experiment uses the electrical tree length as an index. The electrical tree length is defined as the straight-line distance between the farthest point in the electrical tree channel and the initial initiation point (i.e., the needle tip). The growth process of interface electrical trees under a positive polarity pulse voltage with a working temperature of 40 °C, voltage amplitude of 6 kV, and voltage frequency of 100 Hz are taken as an example, as shown in Figures 3a–d.
FIGURE 3
Under a positive polarity pulsed voltage of 40 °C, 6 kV and 100 Hz, the growth of the interfacial electrical tree exhibits a typical three-stage evolutionary characteristic. At 2 s (Figure 3a), it is in the initial germination stage with a size of 329.5 μm, and only a small number of sparse initial branches are formed near the electrode tip. From 30 s to 120 s (Figures 3b,c), it enters the rapid expansion stage where the size of the electrical tree increases from 732 μm to 969.7 μm. The number and density of branches increase significantly, forming a complex reticular crack structure. At 900 s (Figure 3d), the growth tends to stagnate. The tree size shows only a slight increase to 989.9 μm, whereas the branches become highly dense and fill most of the newly expanded region. At the same time, an extensive yellowish-brown region and several black channels are observed near the electrical tree branches.
This process results from the synergistic effect of electric field concentration and thermally assisted material degradation (; ; ). In the initial stage, the strong electric field concentration at the electrode tip causes local breakdown, forming initial electrical tree branches. During the intermediate stage, continuous space-charge injection under pulsed voltage, together with enhanced molecular chain mobility at 40 °C, accelerates the deterioration of the dielectric properties of the insulating material. As a result, the electrical tree undergoes rapid branching and propagation under the combined action of the electric field and electrostrictive stress. In the final stage, the dense tree structure redistributes the local electric field and weakens the field concentration effect, while the extensive material damage further constrains continued growth, ultimately leading to a pronounced reduction in the propagation rate.
After removing the silicone gel from the surface of the Al2O3 ceramic substrate, direct observation (Figure 3e) revealed obvious discharge damage traces on the ceramic substrate near electrode tip. Numerous small black spots were observed near the electrode tip, spreading radially around the electrode. Extremely fine dendritic residual traces appeared directly above the electrode tip, and the overall discharge-damaged region was distributed approximately symmetrically about the electrode center. The formation of the black etched marks observed above is primarily attributed to the severe thermochemical decomposition of the insulating material under the high local energy density generated by partial discharge. Dominated by dehydrogenation, this process promotes carbon enrichment and subsequent carbonization, ultimately resulting in conductive carbonaceous residues along the inner walls of the discharge channels (). This feature signifies irreversible and permanent damage to the insulating material, indicating severe insulation degradation.
Figure 3f shows the time dependent electrical tree length under a positive polarity pulsed voltage of 40 °C, 6 kV and 100 Hz. The length of the electrical tree first increases and then tends to be flat. It is specifically divided into three stages (rapid growth, slow growth and stagnant growth), which is consistent with the observation in Figures 3a–d. Within the first 60 s after the electrical tree initiation, it grows rapidly, reaching a length of 958.7 μm in a short time with a growth rate of 13.8 μm/s. After 60 s, the growth rate decreases noticeably. By 120 s, the electrical tree length reaches 969.7 μm, only about 11 μm greater than that at 60 s, corresponding to a growth rate of 0.2 μm/s. Thereafter, the tree length shows no significant increase, indicating entry into a stagnant growth stage with a growth rate close to zero, where the electrical tree approaches a relatively stable limit state.
To quantitatively characterize the time-dependent growth kinetics of the interfacial electrical trees, the measured electrical tree length was fitted using the one-phase exponential association function aswhere L(t) is the electrical tree length at time t, Yb is the fitted baseline length at t = TD, A is the growth amplitude, TD is the time offset associated with the beginning of the fitted growth process, and τ is the characteristic growth time. The asymptotic electrical tree length iswhere is the electrical tree length as time approaches infinity. The apparent growth-rate constant is calculated aswhere v is the apparent growth-rate constant. Respectively. Based on the representative time-dependent growth behavior shown in Figure 3, the subsequent sections further analyze the effects of pulse voltage amplitude, frequency, and temperature on interfacial electrical tree growth. For each influencing factor, the electrical tree length as a function of time is first compared, and the final length at 900 s is then used to evaluate the steady-state growth characteristics under different operating conditions.
3.2 Influence of voltage amplitude on the growth behavior of interfacial electrical trees
The length curves of the electrical tree over time under different voltage amplitudes (6 kV, 6.5 kV, 7 kV, 7.5 kV, 8 kV) are shown in Figure 4a. All electrical trees grow rapidly in the first 60 s, and at the same time, the higher the voltage amplitude, the longer the length, and the faster the growth rate. After applying a voltage of about 300 s, the growth of the electrical tree in all samples entered a stagnant stage, and the length of the electrical tree at 8 kV was significantly longer than other voltages under the same voltage application time.
FIGURE 4
Figure 4 (b1–b5) shows the steady-state electrical tree images for 900 s under positive polarity pulse voltages of different amplitudes. These images show a clear trend of voltage-dependent evolution. The length of the electrical tree increases monotonically with voltage, rising from 989.9 μm at 6 kV to 1811.6 μm at 8 kV. From a morphological perspective, under low voltage, the branches of the electrical tree are sparse, while under high voltage, the branches become denser and darker, indicating more severe material damage ().
Figure 4c shows the variation of electrical tree length with pulsed voltage amplitude at 900 s, where the final length of electrical trees increases almost linearly with the rise in pulsed voltage amplitude. When a pulsed voltage is applied to the needle electrode, charges are injected from the needle tip into the insulating material, and a higher pulse amplitude results in greater charge injection into the dielectric. At the same time, increasing the pulse amplitude intensifies the electric field at the needle tip, thereby enhancing the kinetic energy and transport distance of the injected charges. This process aggravates the impact-induced damage to the molecular chains of the silicone gel and promotes more intense partial discharge activity, ultimately accelerating the further growth of electrical trees ().
The differences in the growth behavior of electrical tree branches under different voltage amplitudes can be semi-quantitatively explained by the Schottky barrier lowering mechanism. Specifically, the Schottky emission current density (), J, is expressed aswhere J is the electrode emission current density, A* is a constant (Richardson constant) related to the mass and charge of electrons, T is the thermodynamic temperature, q is the elementary charge, φB is the zero-bias Schottky barrier height, Δφ is the Schottky barrier lowering, kB is the Boltzmann constant, kB = 1.381 × 10−23 J/K. For a fixed needle plate structure, the local electric field near the needle tip can be approximated aswhere Eloc is the local electric field strength near the needle tip, and α is the geometric field enhancement coefficient. The Schottky barrier lowering satisfies:where ε0 is the vacuum dielectric constant of the material; εr is the relative dielectric constant. Therefore, when the temperature and electrode geometry remain unchanged as
Using 6 kV as the reference, the normalized Schottky barrier-lowering parameter is expressed as
Where B(V) is the normalized Schottky barrier-lowering parameter, and V is the voltage applied in the experiment.
The normalized barrier-lowering factors, B(V), calculated at pulse voltages of 6, 6.5, 7, 7.5, and 8 kV were 1.000, 1.041, 1.080, 1.118, and 1.155, respectively. Thus, when the applied voltage increased from 6 to 8 kV, the Schottky barrier-lowering term increased by approximately 15.5%. Correspondingly, the electrical tree length at 900 s increased from 989.9 to 1811.6 μm, representing an increase of approximately 83%. Therefore, as the voltage amplitude increases, the enhanced local electric field at the interface produces a more pronounced Schottky barrier lowering, thereby promoting charge-carrier injection and space-charge accumulation, ultimately accelerating the initiation and propagation of interfacial electrical trees.
3.3 Influence of voltage frequency on the growth behavior of interfacial electrical trees
Figure 5a shows the effect of different voltage frequencies (100 Hz, 500 Hz, 1 kHz, 5 kHz, 10 kHz) on the electrical tree growth behavior at the interface of silicone gel/ceramic substrate under 7 kV positive polarity pulse voltage amplitude at 20 °C. Higher frequencies (≤5 kHz) correspond to faster initial growth rates, earlier saturation, and longer final lengths of electrical trees. Specifically, the electrical trees at 100 Hz, 500 Hz, 1 kHz, 5 kHz stabilized at about 630 μm, 930 μm, 980 μm, and 1100 μm. However, the 5 kHz and 10 kHz electrical trees length nearly overlapping in the late stage.
FIGURE 5
Figure 5 (b1–b5) shows the electrical tree images at different pulse voltage frequencies for a steady state of 900 s, demonstrating a clear frequency-dependent evolution pattern. The length of the electrical tree first increases rapidly, and then tends to saturate with the increase of frequency. At 100 Hz, the electrical tree length is 637.4 μm, which increases to 1,100.8 μm at 5 kHz and only reaches 1,102.1 μm at 10 kHz, indicating a slight increase in length in the high-frequency range. In terms of morphology, the tree exhibits a sparse dendritic structure at 100 Hz. At 500 Hz–1 kHz, coarse main channels accompanied by fine branches were observed. When the frequency further increases to 5–10 kHz, the electrical tree shows obvious multi-directional growth, significantly higher branch density, and a significant expansion of the dielectric damage area.
Figure 5c depicts the variation of electrical tree length with pulse voltage frequency at 900 s, revealing a clear correlation between pulse frequency and electrical tree growth. In the low frequency range, the length of the tree increases significantly with increasing frequency, but once the frequency reaches 5 kHz, there is no significant change in the growth of the electrical tree branch length with further increase in frequency.
This frequency dependence can be explained by analyzing the number of pulses and pulse intervals. The formula for the total number of pulses is:where N is the total number of pulses, f is the frequency, t is the total time of the experiment, t = 900 s. The formula for pulse interval is:where TP is the pulse interval time.
According to formulas 9, 10, during the 900 s experiment, the total number of pulses corresponding to 100 Hz, 500 Hz, 1 kHz, 5 kHz, and 10 kHz were 9.0 × 104, 4.5 × 105, 9.0 × 105, 4.5 × 106, and 9.0 × 106, respectively. The pulse intervals were 10, 2, 1, 0.2, and 0.1 m. Partial discharge predominantly occurs at the rising and falling edges of the voltage pulses. As the pulse repetition frequency increases, the number of voltage transitions per unit time increases, resulting in more frequent partial-discharge events and thereby promoting electrical tree growth. As the frequency increases further, the shorter pulse period prevents the local electric field from fully recovering between adjacent pulses, while the accumulated charges may partially shield the subsequent applied field. Consequently, as charge injection and dissipation approach a periodic dynamic equilibrium, the local electric-field distortion no longer increases significantly. Therefore, when the frequency increases from 5 to 10 kHz, the promoting effect of frequency on the axial growth of electrical trees becomes limited, and the final electrical tree length tends to stabilize.
3.4 Influence of temperature on the growth behavior of interfacial electrical trees
The effect of temperature on the electrical tree under positive polarity pulse voltage of 100 Hz and 6 kV is shown in Figure 6a. Within the first 60 s, electrical trees grew rapidly at all tested temperatures, and high temperatures played a facilitating role in the electrical tree growth process.
FIGURE 6
Figure 6 (b1–b4) shows the electrical tree images at the interface of silicone gel/ceramic substrate at different temperatures for 900 s, exhibiting significant temperature dependence. The length of the electrical tree branch continues to increase with the rise of temperature. From a morphological perspective, the electrical tree formed at 70 °C exhibits sparse branching and obvious directional growth. As the temperature increases, the main channel thickens and the branch density significantly increases (; ).
Figure 6c shows the variation of electrical tree length with temperature at 900 s, where the final length of the electrical tree increases with the increase of increasing temperature. According to the Schottky effect formula 4, an increase in temperature will simultaneously enhance the excitation of electrode hot electrons, reduce the interface barrier, and intensify the distortion of the electric field, resulting in a significant increase in the injection of charge carriers, accelerating local discharge and damage evolution in the medium, and ultimately promoting the initiation and growth of electrical trees.
By Equation 1, the fitting results are shown in Figure 6a. It can be found that the fitting results are excellent, which indicates that the Equation 1 can depict the electrical tree growth behavior well. In addition, the fitted apparent growth-rate constants, v, are extracted, as shown in Figure 7. Therefore, the growth rate increases with the rise in temperature without apparent critical turning point.
FIGURE 7
In the triple-junction region of SiC power modules, electric-field distortion is one of the major factors contributing to insulation degradation and electrical tree initiation. Previous research suggests that the local electric-field strength at the triple junction follows an exponential empirical relationship with temperature ().where E is the local electric field strength at the triple junction, E0 is the electric field strength when the thermodynamic temperature approaches 0 K, and A and B are fitting constants, T is the thermodynamic temperature. Our research team has previously revised Equation 11 to obtain a quantitative formula for electric field temperature that combines physical significance and fitting accuracy ():where A′ is a fitting constant, Ea is the activation energy of the ceramic substrate, Ea‘ is the pseudo-activation energy, T0 is the Vogel temperature of the silicone elastomer and kB is the Boltzmann constant, kB = 1.381 × 10−23 J/K.
According to Equation 12, as the temperature T increases, both the exponential term and T term increase, and the electric field E at the triple junction increases exponentially, According to previous studies, high temperatures significantly intensify the concentration of electric fields in the region, and the enhanced local electric field enhances Schottky barrier lowering, thereby reducing the effective injection barrier required for charge carriers to cross the interface. At the same time, the temperature rise will enhance the thermal excitation of carriers, so that more carriers can cross the reduced interface barrier, causing local electric field distortion and partial discharge enhancement, thus accelerating the deterioration of silicone gel molecular chain and the initiation and expansion of electrical tree.
4 Conclusion
This paper investigated the growth characteristics and mechanisms of electrical trees at the silicone gel/ceramic substrate interface under high-frequency pulse voltage and high temperatures. The interfacial electrical treeing exhibits a characteristic three-stage evolutionary process, transitioning from initial sparse dendritic initiation to the rapid expansion of complex reticular cracks, and finally into a stagnation stage where growth rates approach zero. It is found that the final tree length follows a linear positive correlation with the pulse voltage amplitude, as higher field concentrations at the electrode tip enhance charge injection and accelerate the irreversible carbonization of the insulating matrix. Furthermore, the electrical tree length increases significantly with rising frequency in the low-frequency range, while no obvious change in length occurs with further increase in frequency over 5 kHz. On the other hand, the higher the temperature is, the greater the growth rate of electrical trees in the rapid growth stage, and the length of electrical trees increases with the increase in temperature. These findings provide a robust theoretical foundation for elucidating interfacial insulation failure and offer critical guidance for optimizing the long-term reliability of next-generation SiC power electronic packaging.
Statements
Data availability statement
The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding authors.
Author contributions
YiL: Writing – original draft. YaL: Writing – original draft. YuL: Writing – review and editing. YS: Writing – original draft. TW: Writing – review and editing.
Funding
The author(s) declared that financial support was received for this work and/or its publication. This work was supported by the National Natural Science Foundation of China (Grant No. 52307167), and Fundamental Research Funds for the Central Universities (Grant No. JZ2025HGTB0200), State Key Laboratory of Power System Operation and Control (Grant No. SKLD25KM22).
Conflict of interest
The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Generative AI statement
The author(s) declared that generative AI was not used in the creation of this manuscript.
Any alternative text (alt text) provided alongside figures in this article has been generated by Frontiers with the support of artificial intelligence and reasonable efforts have been made to ensure accuracy, including review by the authors wherever possible. If you identify any issues, please contact us.
Publisher’s note
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.
References
1
ChenM.WangY.FanL.DingY.YinY. (2025). Temperature-dependent local electric-field transient analysis and measurement in high-voltage power module packaging. IEEE Trans. Dielectr. Electr. Insul.32, 2229–2238. 10.1109/TDEI.2024.3495593
2
CherkasovA. (2024). “SiC market,” in Sic Technology (Cham: Springer Nature Switzerland), 287–297. 10.1007/978-3-031-63418-5_8
3
DissadoL. A. (2002). Understanding electrical trees in solids: from experiment to theory. IEEE Trans. Dielectr. Electr. Insulation9, 483–497. 10.1109/TDEI.2002.1024425
4
DonzelL.SchudererJ. (2012). Nonlinear resistive electric field control for power electronic modules. IEEE Trans. Dielectr. Electr. Insulation19, 955–959. 10.1109/TDEI.2012.6215099
5
DuB. X.HanT.SuJ. G. (2015). Electrical tree characteristics in silicone rubber under repetitive pulse voltage. IEEE Trans. Dielectr. Electr. Insulation22, 720–727. 10.1109/TDEI.2015.7076767
6
DuB. X.SuJ. G.HanT. (2017). Temperature-dependent electrical tree in silicone rubber under repetitive pulse voltage. IEEE Trans. Dielectr. Electr. Insulation24, 2291–2298. 10.1109/TDEI.2017.006461
7
FuH.ZhangC.XiangJ.ChengZ.WangS.LiJ. (2020). “Electrical tree characteristics of epoxy resin under bipolar square wave voltage,” in 2020 IEEE 3rd International Conference on Dielectrics (ICD) (IEEE), 142–145. 10.1109/ICD46958.2020.9341976
8
FujishimaN. (2024). Technical trends of SiC power semiconductor devices and their applications in power electronics. IEEJ J. Industry Appl.13, 372–378. 10.1541/ieejjia.23005497
9
HanT.DuB. X.MaT. T.WangF. Y.GaoY.LeiZ. P.et al (2019). Electrical tree in HTV silicone rubber with temperature gradient under repetitive pulse voltage. IEEE Access7, 41250–41260. 10.1109/ACCESS.2019.2907302
10
HeD.ZhangZ.WangG.LiuK.WangH.XuZ.et al (2024). Mechanism analysis of bubble discharge within silicone gels under pulsed electric field. Gels10, 799. 10.3390/gels10120799
11
KimotoT. (2022). High-voltage SiC power devices for improved energy efficiency. Proc. Jpn. Acad. Ser. B98, 161–189. 10.2183/pjab.98.011
12
LiH.MuH.YaoH.YangY. (2024). “Propagation of electrical tree and characteristic of partial discharge at gel-substrate surface in IGBT,” in The Proceedings of the 18th Annual Conference of China Electrotechnical Society. Lecture Notes in Electrical Engineering. Editors YangQ.LiZ.LuoA. (Singapore: Springer), 1165, 853–862. 10.1007/978-981-97-1351-6_89
13
LinY.DongL.DangM.LiP.LiM.LiuY. (2025a). Silicone encapsulants with high thermal stability for SiC power devices under high temperatures. Journal of materials science. Mater. Electron.36, 18. 10.1007/s10854-024-14078-y
14
LinY.HengC.LiuY.XuY.WenT.FacchettiA.et al (2025b). Decoupling of interfacial ionic diffusion from segmental dynamics in silica-filled silicone gel through experiments. Langmuir41, 17875–17884. 10.1021/acs.langmuir.5c01650
15
LinY.LiM.DongL.LiuY.HouT.WenT.et al (2025c). Improving thermal stability and high-temperature performance of silicone gel simultaneously through low-concentration fillers. IEEE Trans. Dielectr. Electr. Insulation33, 869–877. 10.1109/TDEI.2025.3621164
16
MaZ.LiK.LinY.HengC.WenT., (2026). Ceramic-substrate-dependent electric-field distribution at triple points in SiC power modules under pulse waves and high temperatures. IEEE Trans. Dielectr. Electr. Insul., 1. 10.1109/TDEI.2026.3656485
17
NakamuraS.SatoM.KumadaA.HidakaK.TakanoS.HayaseY.et al (2020). “Polarity effect on electrical treeing in silicone gel under repetitive voltage impulses,” in 2020 IEEE 3rd International Conference on Dielectrics (ICD) (IEEE), 122–125. 10.1109/ICD46958.2020.9341954
18
NakamuraS.NakanoR.SatoM.KumadaA.HidakaK.TakanoS.et al (2021). “Effect of temperature on electrical treeing in silicone gel for power modules,” in 2021 IEEE Conference on Electrical Insulation and Dielectric Phenomena (CEIDP), 551–554. (IEEE). 10.1109/CEIDP50766.2021.9705314
19
NakamuraT.NishiokaK.NishimuraY.HanadaT.OkudaT. (2022). “Application of SiC power devices to ultra-high voltage equipment,” in 2022 IEEE CPMT Symposium Japan (ICSJ) (IEEE), 146–149. 10.1109/ICSJ55786.2022.10034706
20
SatoM.KumadaA.HidakaK.YamashiroK.HayaseY.TakanoT. (2014). “On the nature of surface discharges in silicone-gel: prebreakdown discharges in cavities,” in 2014 IEEE Conference on Electrical Insulation and Dielectric Phenomena (CEIDP) (IEEE), 19–22. 10.1109/CEIDP.2014.6995729
21
SatoM.KumadaA.HidakaK.YamashiroK.HayaseY.TakanoT. (2016). Surface discharges in silicone gel on AlN substrate. IEEE Trans. Dielectr. Electr. Insulation23, 494–500. 10.1109/TDEI.2015.005412
22
SemenovI.Grav AakreT.Gunheim FolkestadI.SmisethjellI.NiayeshK.LundgaardL. E. (2024). Partial discharge inception in ceramic substrates embedded in silicone liquid, silicone gel, and mineral oil at fast voltage rise and sinusoidal voltage. IEEE Trans. Dielectr. Electr. Insulation31, 1721–1728. 10.1109/TDEI.2024.3413725
23
ShimizuN.LaurentC. (1998). Electrical tree initiation. IEEE Trans. Dielectr. Electr. Insulation5, 651–659. 10.1109/94.729688
24
SimmonsJ. G. (1967). Poole-frenkel effect and schottky effect in metal-insulator-metal systems. Phys. Rev.155, 657–660. 10.1103/PhysRev.155.657
25
SuJ.ZhangP.LiuZ.HuangX.PangX.ZhengZ.et al (2024). Electrical tree and partial discharge characteristics of silicone rubber under mechanical pressure. Energies (Basel)17, 5645. 10.3390/en17225645
26
VeliadisV.SuM.Di GiovanniF. (2024). “Overview of silicon carbide,” in Sic Technology (Cham: Springer Nature Switzerland), 1–23. 10.1007/978-3-031-63418-5_1
27
WangY.HuangZ.ZhangX.ShangJ. (2022). Characteristics of electrical tree morphological in glass fibre reinforced epoxy resin under power frequency voltage. IET Sci. Meas. and Technol.16, 274–282. 10.1049/smt2.12102
28
WangQ.ChenX.ParamaneA.LiJ.HuangX.RenN. (2024). Design of interfacial electrical tree-resistant packaging insulation using grafted silicone elastomer nanocomposites for high-temperature power modules. IEEE Trans. Power Electron.39 (5), 4933–4946. 10.1109/TPEL.2024.3365304
29
YanF.WangL.GanY.LiK.ZhangB. (2022). A new structure of ceramic substrate to reduce the critical electric field in high voltage power modules. J. Electron. Packag.144 (3), 031016. 10.1115/1.4053891
30
ZhangY.LewinerJ.AlquieC.HamptonN. (1996). Evidence of strong correlation between space-charge buildup and breakdown in cable insulation. IEEE Trans. Dielectr. Electr. Insulation3, 778–783. 10.1109/94.556559
31
ZhangY.ZhouY.ZhangL.ZhouZ.NieQ. (2018). Electrical trees and their growth in silicone rubber at various voltage frequencies. Energies (Basel).11, 327. 10.3390/en11020327
32
ZhangB.YangZ.LiK.JiangX.YaoM.LiX. (2024). Electrical tree failure at DBC substrate-silicone gel interface in high-voltage power module under positive square wave voltage. IEEE J. Emerg. Sel. Top. Power Electron.12 (5), 4967–4978. 10.1109/JESTPE.2024.3407665
33
ZhangY.LinW.ZhouY.XingW.ChengJ.TengC. (2024). Electrical tree degradation of MgO/epoxy resin composites at different voltage frequencies. High. Volt.9, 581–590. 10.1049/hve2.12407
34
ZhangC.AnX.LiQ.WuJ.XuZ.KhaledU.et al (2025). Research on the electrical tree deterioration characteristics of silicone gel and silicone rubber under pulsed electric field. Gels11 (4), 253. 10.3390/gels11040253
Summary
Keywords
electrical tree growth, high temperature, power electronics, pulse voltage, silicone gel/ceramic substrate interface
Citation
Lin Y, Liu Y, Liu Y, Shi Y and Wen T (2026) Electrical tree growth behavior at the silicone gel/ceramic substrate interface under pulse voltage and high temperature. Front. Mater. 13:1855888. doi: 10.3389/fmats.2026.1855888
Received
14 April 2026
Revised
18 June 2026
Accepted
22 June 2026
Published
09 July 2026
Volume
13 - 2026
Edited by
Xiuxun Han, Jiangxi University of Science and Technology, China
Updates
Copyright
© 2026 Lin, Liu, Liu, Shi and Wen.
This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Yuhao Liu, yhliu@fzu.edu.cn; Tao Wen, tao-wen@hfut.edu.cn
Disclaimer
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.