A multi-substrate plasma surface modification method for high voltage power supply device potting structure

Abstract

This invention discloses a plasma surface modification method for multi-substrate encapsulation structures in high-voltage power supply devices, belonging to the field of material surface modification technology. This invention significantly enhances the interfacial bonding strength and electrical insulation performance between the encapsulation structure substrate and the silicone gel by plasma activation treatment of the substrate material, introducing oxygen-containing polar functional groups and constructing a nano- to micron-level rough structure. Compared to untreated materials, the adhesive strength of the treated encapsulation structure substrate can be increased by more than 50%, and the surface flashover voltage at an electrode spacing of 5-15 mm is not less than 20 kV. Using this invention, the interfacial bonding strength and surface withstand voltage performance of the multi-component heterogeneous materials and the encapsulating silicone gel can be significantly improved, solving the engineering challenge of integrated treatment of multi-component, cross-material encapsulation interfaces in high-voltage power supplies, and offering the advantage of easy online integration with existing vacuum encapsulation production lines.

Description

Technical Field

[0001] This invention relates to the field of material surface modification technology, and in particular to a multi-substrate plasma surface modification method for potting structures of high-voltage power supply devices. Background Technology

[0002] In high-voltage power supply devices, to ensure electrical insulation performance and thermal management capabilities, potting processes are often used to fill the spaces between internal components with encapsulation materials such as silicone gel. Commonly used substrates or structural materials for internal components include FR4 (flame-retardant epoxy fiberglass board), silicone rubber, ceramics, polytetrafluoroethylene (PTFE), and epoxy resin. While these materials possess excellent dielectric strength, chemical resistance, and ease of processing, their surfaces generally exhibit low surface energy, weak polarity, poor hydrophilicity, and chemical inertness. Especially at the nanoscale, their surfaces are relatively smooth, leading to poor wettability and insufficient interfacial adhesion between them and the silicone potting gel. Therefore, in practical applications, especially under harsh conditions such as temperature cycling and thermal vacuum, the aforementioned potting structure substrate and encapsulation material are prone to interfacial debonding and delamination failures. Moreover, these interfacial defects can induce local electric field concentration under the influence of a high-voltage electric field (usually below 10 kV), causing surface flashover; simultaneously, the increased thermal resistance due to interfacial voids can cause local overheating, accelerating material aging and failure.

[0003] To improve the interfacial bonding performance between low surface energy materials and potting materials, existing technologies often employ surface treatment methods such as wet alkaline etching to increase the surface roughness and activity of the materials. However, this wet treatment method has significant limitations: on the one hand, strongly alkaline solutions can easily corrode sensitive structures such as metal pads and wires in circuits; on the other hand, residual ions may be introduced during the process, affecting the electrical performance of devices; furthermore, wet treatment is usually time-consuming, requires harsh process conditions, and is not suitable for post-processing scenarios where components have already been mounted, making it difficult to meet the demands of high integration, high reliability, and mass production in modern high-voltage power supply products.

[0004] Therefore, it is urgent for those skilled in the art to develop a surface modification method that is applicable to a variety of low surface energy materials, compatible with assembled devices, has controllable processes, and is environmentally friendly, so as to effectively improve the interfacial bonding strength between low surface energy materials and potting materials and ensure the insulation reliability and thermal stability of high voltage power supply devices. Summary of the Invention

[0005] The main objective of this invention is to propose a multi-substrate plasma surface modification method for potting structures of high-voltage power supply devices, aiming to solve the problem of insufficient interfacial bonding strength between potting structure substrates and potting materials of different materials in high-voltage power supply devices.

[0006] To achieve the above objectives, this invention proposes a multi-substrate plasma surface modification method for potting structures of high-voltage power supply devices, comprising the following steps: The potting structural substrate to be treated is placed in a plasma treatment system for plasma treatment; The material of the potting structure substrate is selected from at least one of polytetrafluoroethylene, polyimide, polypropylene, silicone rubber, epoxy resin, polycarbonate, alumina, aluminum nitride, aluminum alloy, and FR4 copper clad laminate.

[0007] In one embodiment, plasma treatment is performed in a mixture of oxygen and an inert gas, wherein the oxygen volume percentage in the mixture is 5% to 80%, and the total gas flow rate of the mixture is 50 to 200 sccm. The radio frequency power of the plasma treatment is 50~150 W, the treatment time is 2~30 min, and the vacuum degree of the plasma treatment is 1~100 Pa.

[0008] In one embodiment, plasma treatment is performed in a mixture of oxygen and an inert gas, wherein the oxygen volume percentage in the mixture is 20% to 50%. The radio frequency power of the plasma treatment is 80~120 W, the treatment time is 5~15 min, and the vacuum degree of the plasma treatment is 1~100 Pa.

[0009] In one embodiment, the method further includes, prior to the step of placing the substrate to be treated in a plasma treatment system for plasma treatment: The substrate of the potting structure to be treated is cleaned.

[0010] In one embodiment, the step of placing the potting structure substrate to be treated in a plasma treatment system for plasma treatment includes: The potting structural substrate to be treated is placed in a plasma treatment system for plasma treatment to obtain a plasma-treated potting structural substrate. A primer is applied to the surface of the plasma-treated potting structure substrate, followed by standing for 1-2 hours and then heat treatment for 4-5 hours.

[0011] In one embodiment, the primer includes an epoxy primer.

[0012] In one embodiment, after the step of coating the plasma-treated potting structure substrate with a primer, followed by standing for 1-2 hours and then heat-treating for 4-5 hours, the method further includes: The substrate of the potting structure, after being coated with a primer, is potted using potting material.

[0013] In one embodiment, the potting material comprises silicone gel.

[0014] In this invention, plasma activation treatment of the surface of the potting structure substrate simultaneously introduces oxygen-containing polar functional groups such as -OH and -C=O and constructs a nano- to micron-level rough structure, significantly enhancing the wettability and intermolecular forces of the silicone gel on the material surface. This significantly enhances the interfacial bonding and electrical insulation performance between the potting structure substrate and the silicone gel, thereby improving the long-term reliability of the equipment under high-voltage conditions. Compared to untreated materials, the adhesive strength of the treated potting structure substrate can be increased by more than 50%, and the surface flashover voltage at an electrode spacing of 5-15 mm is not less than 20 kV. This invention can efficiently treat low surface energy materials with different properties, such as polymers, metals, and ceramics, achieving a significant improvement in both interfacial adhesive strength and surface voltage resistance between multi-component heterogeneous materials and potting silicone gel. It solves the engineering challenge of integrated treatment of multi-component, cross-material potting interfaces in high-voltage power supplies and has the advantage of easy online integration with existing vacuum potting production lines. Furthermore, the plasma treatment employed in this invention is a dry physical method, which eliminates the need for the use and emission of harmful chemical reagents throughout the entire process. This avoids the potential corrosion and damage to precision electronic components caused by wet treatment, resulting in high environmental friendliness and safety. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0016] Figure 1 The graph shows the bond strength test results of the PTFE material without plasma treatment in Example 1; Figure 2 The graph shows the test results of the adhesive strength of the plasma-treated PTFE material in Example 1. Figure 3 The graph shows the bond strength test results of the PI material without plasma treatment in Example 2; Figure 4 This is a graph showing the test results of the adhesive strength of the plasma-treated PI material in Example 2; Figure 5 The graph shows the adhesive strength test results of the PP material without plasma treatment in Example 3; Figure 6 The graph shows the test results of the adhesive strength of the plasma-treated PP material in Example 3. Figure 7 The graph shows the test results of the adhesive strength of the FR4 copper-clad laminate material without plasma treatment in Example 4; Figure 8 The graph shows the test results of the adhesive strength of the plasma-treated FR4 copper-clad laminate material in Example 4. Figure 9 This is a schematic diagram of the flashover voltage testing system provided by the present invention.

[0017] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0020] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0021] To improve the interfacial bonding performance between low surface energy materials and potting materials, existing technologies often employ wet surface treatment methods such as wet alkaline etching or strong reducing organometallic etchants to increase the surface roughness and activity of the materials. However, these methods have significant limitations: on the one hand, strongly alkaline solutions can easily corrode sensitive structures such as metal pads and wires in circuits; on the other hand, residual ions may be introduced during the process, affecting the electrical performance of devices; furthermore, wet processing is usually time-consuming, requires harsh process conditions, and is not suitable for post-processing scenarios involving already mounted components, making it difficult to meet the demands of high integration, high reliability, and mass production in modern high-voltage power supply products.

[0022] Plasma is a fully or partially ionized gaseous substance with high energy, readily reacting with other substances physically or chemically. Plasma treatment in a suitable atmosphere can increase the oxygen content on a material surface, introducing polar groups such as hydroxyl and amino groups. Simultaneously, during plasma treatment, high-energy ions and free radicals bombard the material surface, breaking surface molecular chains and removing or volatilizing some low-molecular-weight fragments; this etching effect can improve surface roughness. Furthermore, plasma treatment only affects the surface of an insulating layer approximately 5-10 μm thick, a thickness far smaller than the overall thickness of the insulating layer inside a high-voltage power supply device, thus not affecting the conductive materials encapsulated within the insulating material. Currently, most research on plasma surface treatment technology is limited to single materials or laboratory settings, lacking systematic process parameter databases and optimization methods for multi-component, multi-material systems.

[0023] Based on the above background, the present invention proposes a multi-substrate plasma surface modification method for potting structures of high-voltage power supply devices, comprising the following steps: The potting structural substrate to be treated is placed in a plasma treatment system for plasma treatment; The material of the potting structure substrate is selected from at least one of polytetrafluoroethylene (PTFE), polyimide (PI), polypropylene (PP), silicone rubber, epoxy resin, polycarbonate (PC), alumina, aluminum nitride, aluminum alloy, and FR4 copper clad laminate.

[0024] In this invention, plasma activation treatment of the surface of the potting structure substrate simultaneously introduces oxygen-containing polar functional groups such as -OH and -C=O and constructs a nano- to micron-level rough structure, significantly enhancing the wettability and intermolecular forces of the silicone gel on the material surface. This significantly enhances the interfacial bonding and electrical insulation performance between the potting structure substrate and the silicone gel, thereby improving the long-term reliability of the equipment under high-voltage conditions. Compared to untreated materials, the adhesive strength of the treated potting structure substrate can be increased by more than 50%, and the surface flashover voltage at an electrode spacing of 5-15 mm is not less than 20 kV. This invention can efficiently treat low surface energy materials with different properties, such as polymers, metals, and ceramics, achieving a significant improvement in both interfacial adhesive strength and surface voltage resistance between multi-component heterogeneous materials and potting silicone gel. It solves the engineering challenge of integrated treatment of multi-component, cross-material potting interfaces in high-voltage power supplies and has the advantage of easy online integration with existing vacuum potting production lines. Furthermore, the plasma treatment employed in this invention is a dry physical method, which eliminates the need for the use and emission of harmful chemical reagents throughout the entire process. This avoids the potential corrosion and damage to precision electronic components caused by wet treatment, resulting in high environmental friendliness and safety.

[0025] In one embodiment of the present invention, the aluminum alloy may be, for example, 5A06 aluminum. "FP4 copper clad laminate" refers to FR4 copper clad laminate, which is a glass fiber epoxy resin copper clad laminate, a polymer composite material composed of glass fiber and epoxy resin.

[0026] It should be noted that the technical solution of this invention does not impose specific limitations on the plasma surface modification system; any conventional plasma surface modification system can be used for plasma treatment. In the embodiments of this invention, the plasma surface modification system for performing plasma treatment includes a vacuum chamber, a gas path system, a radio frequency (RF) power supply, and a control system; wherein, the vacuum chamber is equipped with a sample stage, the gas path system is used to introduce a mixture of oxygen and inert gas, the RF power supply has an adjustable power range of 50~150 W, the RF power supply is used to establish and maintain a vacuum environment of 1~100 Pa, and the control system is used to set and execute process parameters.

[0027] In an embodiment of the present invention, plasma treatment is performed in a mixture of oxygen and an inert gas, wherein the oxygen volume percentage in the mixture is 5% to 80%, the total gas flow rate of the mixture is 50 to 200 sccm, the radio frequency power of the plasma treatment is 50 to 150 W, the plasma treatment time is 2 to 30 min, and the vacuum degree of the plasma treatment is 1 to 100 Pa. For example, the mixed gas can be an oxygen-xenon mixture, an oxygen-argon mixture, a hydrogen-argon mixture, or an oxygen-nitrogen mixture. The volume percentage of oxygen in the mixed gas can be 5%, 15%, 30%, 45%, 60%, 70%, or 80%, and the total gas flow rate of the mixed gas can be 50 sccm, 100 sccm, 150 sccm, or 200 sccm. The radio frequency power of the plasma treatment can be 50 W, 75 W, 100 W, 125 W, or 150 W. The processing time of the plasma treatment is 2 min, 5 min, 10 min, 15 min, or 30 min. The vacuum degree of the plasma treatment can be 1 Pa, 10 Pa, 20 Pa, 30 Pa, 40 Pa, 50 Pa, 60 Pa, 70 Pa, 80 Pa, 90 Pa, or 100 Pa.

[0028] Furthermore, in order to maintain the uniformity and stability of plasma glow while ensuring plasma processing efficiency, the radio frequency power of plasma processing is preferably 80 W to 120 W, the processing time of plasma processing is preferably 5 min to 15 min, and the volume percentage of oxygen in the mixed gas is preferably 20% to 50%.

[0029] Conventional plasma treatment methods, in pursuit of high efficiency, typically employ rapid cleaning at high power. However, the technical solution of this invention, based on a comprehensive consideration of particle transport behavior and ion energy control within the microcavities of the potting structure, avoids the high-efficiency range. Setting the plasma treatment process parameters within the aforementioned range not only satisfies the synergistic parameter window for both the deep accessibility and surface integrity of the substrate, facilitating uniform modification without damage, but also enables a unified dry plasma process to simultaneously and significantly improve both the interfacial adhesion strength and surface pressure resistance of the multi-component heterogeneous materials and the potting silicone gel. This results in a peel strength improvement rate of no less than 50% between the material and the silicone gel after treatment using the plasma surface modification method provided by this invention, and a surface flashover voltage of no less than 20kV at an electrode spacing of 5-15 mm.

[0030] In an embodiment of the present invention, before the step of placing the potting structure substrate to be treated in the plasma treatment system for plasma treatment, the method further includes: cleaning the potting structure substrate to be treated. This is done using a reagent such as ethanol or acetone, followed by drying.

[0031] In an embodiment of the present invention, the step of placing the potting structure substrate to be treated in a plasma treatment system for plasma treatment includes: The potting structural substrate to be treated is placed in a plasma treatment system for plasma treatment to obtain a plasma-treated potting structural substrate. A primer is applied to the surface of the plasma-treated potting structure substrate, followed by standing for 1-2 hours and then heat treatment for 4-5 hours.

[0032] By adding a primer treatment step, the bonding strength is further improved, and the plasma aging problem is solved.

[0033] The purpose of allowing the substrate to stand for 1-2 hours is as follows: plasma treatment constructs a micro-nano rough structure on the substrate surface and introduces oxygen-containing polar groups. The standing process allows the primer to fully wet and penetrate into the micro-nano pores, forming a mechanical interlock; simultaneously, it allows the solvent in the primer to evaporate slowly, preventing direct entry into the subsequent high-temperature stage, which could lead to micropores at the interface between the primer and the substrate due to violent solvent boiling; furthermore, the standing process provides time for the primer molecules to undergo initial hydrogen bonding with the oxygen-containing polar groups on the substrate surface.

[0034] The purpose of high-temperature drying for 4-5 hours is to provide sufficient activation energy, promote the formation of a strong covalent cross-linked network at the interface between the primer and the substrate, and significantly improve adhesion; and to completely remove residual solvents and small molecule byproducts, ensuring the extreme density of the potting interface and the reliability of high-voltage insulation.

[0035] If the resting period is not allowed or the drying time is shortened, the interface requirement of resisting flashover voltage above 20kV in this invention cannot be met.

[0036] In embodiments of the present invention, the primer includes an epoxy primer. Epoxy primers not only exhibit good adhesion to the substrate of the high-voltage power supply device potting structure, but also good compatibility with the silicone gel potting material used.

[0037] In an embodiment of the present invention, after the step of coating the plasma-treated potting structure substrate with a primer, and then allowing it to stand for 1 to 2 hours and then heat-treating it for 4 to 5 hours, the method further includes: potting the potting structure substrate coated with the primer with a potting material.

[0038] In embodiments of the present invention, the potting material comprises silicone gel. The present invention does not specifically limit the type of potting material; for example, silicone gel from Zhonglan Chenguang Chemical Research and Design Institute Co., Ltd. can be used.

[0039] It should be noted that before using silicone gel for potting, the silicone gel can be degassed to reduce the impact of air bubbles in the cured gel on subsequent peel tests. Specifically, during degasing, vacuum degasing can be performed for a period of time, followed by restoring to normal pressure. This breaks down the air bubbles gathered on the surface of the gel and prevents them from blocking the escape of lower-layer air bubbles. Subsequently, a second vacuum degasing can be performed to improve the degasting efficiency.

[0040] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0041] In the following embodiments, the epoxy primer was purchased from Zhonglan Chenguang Chemical Research and Design Institute Co., Ltd., and the product model is DG-2; Organosilicon gels A and B were purchased from Zhonglan Chenguang Chemical Research and Design Institute Co., Ltd., product model GN-522; The PTFE material before treatment came from Polyton Plastics; the PI material before treatment came from Wuxi Chenghao Plastics Co., Ltd.; the PP material before treatment came from Shenzhen Kaisheng Packaging Materials Factory; and the FR4 material before treatment came from Shenzhen Jiadesheng Plastic Products Co., Ltd.

[0042] Example 1 This embodiment provides a multi-substrate plasma surface modification method for potting structures of high-voltage power supply devices, which involves processing polytetrafluoroethylene (PTFE) samples, specifically including the following steps: (1) Cut the PTFE material to the standard sample size (350 mm * 25 mm) according to the requirements of GB / T 2790-1995, and wipe the surface of the PTFE material with anhydrous ethanol to obtain the PTFE material to be treated; (2) Place the PTFE material to be treated on the sample stage of the sample vacuum chamber of the plasma cleaner (with the surface to be treated facing upwards), extract and maintain the vacuum environment, and perform plasma treatment according to the set process parameters to obtain plasma-treated PTFE material; wherein, the specific process parameters are: plasma treatment is carried out in a mixture of oxygen and argon, the oxygen volume percentage in the mixture is 45%, the total gas flow rate of the mixture is 45 sccm; the radio frequency power of the plasma treatment is 150 W, the plasma treatment time is 30 min, and the vacuum degree of the plasma treatment is 60 Pa; (3) Coat the PTFE material surface treated with epoxy primer in step (2) with plasma, and then dry it in an oven at 75°C for 3 h.

[0043] Furthermore, the plasma-treated PTFE material and silicone gel are used to prepare PTFE material-silicone gel potting and bonding samples, specifically including the following steps: Silicone gel A and silicone gel B were mixed in a 1:1 mass ratio to obtain a mixed silicone gel, which was then degassed under vacuum. Subsequently, double-sided tape was used to fix the plasma-treated PTFE material in the mold groove, ensuring the plasma-treated surface of the PTFE material faced upwards. The degassed mixed silicone gel was then poured onto the treated surface, with a pouring thickness of 3 mm and a bonding section length of 150 mm. The entire mold was then placed in an oven for curing (80℃, 7 h) to obtain a PTFE material-silicone gel potting and bonding sample.

[0044] Example 2 Compared with Example 1, the difference is that the PTFE material is replaced with PI material of the same size, and the specific process parameters for plasma treatment are adjusted as follows: plasma treatment is carried out in a mixture of oxygen and argon, wherein the oxygen volume percentage in the mixture is 45%, the total gas flow rate of the mixture is 45 sccm, the radio frequency power of the plasma treatment is 120 W, the plasma treatment time is 5 min, and the vacuum degree of the plasma treatment is 60 Pa.

[0045] Example 3 Compared with Example 1, the difference is that the PTFE material is replaced with PP material of the same size, and the specific process parameters for plasma treatment are adjusted as follows: plasma treatment is carried out in a mixture of oxygen and argon, wherein the oxygen volume percentage in the mixture is 80%, the total gas flow rate of the mixture is 80 sccm, the radio frequency power of the plasma treatment is 75 W, the plasma treatment time is 30 min, and the vacuum degree of the plasma treatment is 60 Pa.

[0046] Example 4 Compared with Example 1, the difference is that the PTFE material is replaced with FP4 material of the same size, and the specific process parameters for plasma treatment are adjusted as follows: plasma treatment is carried out in a mixture of oxygen and argon, wherein the oxygen volume percentage in the mixture is 80%, the total gas flow rate of the mixture is 80 sccm, the radio frequency power of the plasma treatment is 120 W, the plasma treatment time is 15 min, and the vacuum degree of the plasma treatment is 60 Pa.

[0047] Example 5 This embodiment provides an application of a plasma surface modification method in the molding of multi-substrate high-voltage power modules, specifically including the following steps: The high-voltage power module semi-finished product to be potted is prepared. This module includes an FR4 copper-clad laminate substrate, an alumina ceramic high-voltage capacitor soldered onto it, and polytetrafluoroethylene (PTFE) insulating support pillars. The entire surface of the module is sprayed with isopropanol for cleaning and then dried for later use. The high-voltage power module was placed into the plasma treatment system and plasma treatment was carried out in a mixture of oxygen and argon (oxygen volume ratio 60%, total flow rate 150 sccm). The radio frequency power was set to 100 W, the treatment time was 20 min, and the vacuum degree was maintained at 40 Pa. After processing, the module is removed and the degassed mixed silicone gel is directly injected into a vacuum potting equipment. The vacuum degree is maintained below 100 Pa to remove internal air bubbles, and then it is placed in an 80℃ oven to cure for 7 hours.

[0048] Results: Since the molded device could not undergo standard peel testing, the cured potting module was subjected to high and low temperature thermal cycling tests (-40℃ to 80℃, 200 cycles). After the test, the module was dissected. No delamination or debonding was observed at the heterogeneous interfaces (FR4 / silicone gel, ceramic / silicone gel, PTFE / silicone gel) of the plasma-treated module, and the overall partial discharge of the module did not increase significantly. The above demonstrates the effectiveness of the treatment method provided by this invention in complex multi-element potting structures.

[0049] Comparative Example 1 The difference between this comparative example and Example 1 is that a traditional sodium-naphthalene complex chemical etching solution was used instead of plasma treatment to modify the PTFE surface. Specific steps include: Cut PTFE material according to GB / T 2790-1995 requirements, clean with anhydrous ethanol and then dry; (2) Immerse the PTFE sample in a sodium-naphthalene complex treatment solution at room temperature for 3 minutes to cause the surface to undergo a defluorination and carbonization reaction and turn brown. (3) After taking out the sample, quickly put it into acetone and ultrasonically clean it for 5 minutes to wash away the residual reaction liquid on the surface. Then, ultrasonically clean it with deionized water for 10 minutes and finally dry it in an 80°C oven for 1 hour. (4) The subsequent steps of primer coating, silicone gel potting and curing are exactly the same as in Example 1.

[0050] Results: Although the treatment method in Comparative Example 1 can also improve the adhesion and increase the peel force test result after treatment, it is easy to introduce sodium ion residues on the surface, which will significantly reduce the flashover voltage measurement value. Furthermore, immersion in etching solution will cause significant damage to the strength of the material substrate, making the material softer and more likely to break under mechanical stress.

[0051] Comparative Example 2 The difference compared to Example 1 is that the radio frequency power is 20 W.

[0052] Results: Insufficient RF power leads to inadequate plasma density and particle kinetic energy. Due to the high CF bond energy of PTFE, low-energy plasma cannot effectively break the surface chemical bonds, resulting in weak physical bombardment and etching effects. Therefore, insufficient RF power prevents the formation of a sufficiently rough nano- to micro-scale structure on the material surface, and generates very few free radicals. Consequently, the grafting rate of polar oxygen-containing groups is extremely low, failing to effectively improve the adhesion between the substrate and the silicone gel, resulting in minimal changes in peel force test results before and after treatment.

[0053] Comparative Example 3 The difference compared to Example 1 is that the radio frequency power is 200 W.

[0054] Results: Excessive power led to over-etching and thermal damage. The intense bombardment of high-energy particles caused severe breakage and degradation of the polymer chain segments on the substrate surface, forming a "weak boundary layer" composed of low molecular weight debris. This made the surface structure loose and fragile, and under stress, cohesive failure would occur directly from this "weak boundary layer." Compared with the optimal working condition group (Example 1), the effect of improving the adhesion between the substrate and the silicone gel was worse, and the original insulation and withstand voltage performance was destroyed.

[0055] Comparative Example 4 The difference compared to Example 1 is that the plasma treatment time is 1 min.

[0056] Results: The processing time was too short, and the surface etching depth and the amount of polar functional groups introduced did not reach the optimal threshold required for penetration into the primer or silicone gel. As a result, the improvement in interface wettability was not obvious, the peel force test results before and after the treatment did not change significantly, and the flashover voltage measurement value was significantly reduced.

[0057] Comparative Example 5 The difference compared to Example 1 is that the plasma treatment time is 60 min.

[0058] Results: Prolonged exposure to plasma bombardment continuously damages the surface polymer cross-linking network, leading to carbonization or large-area degradation of the material surface. This not only weakens the strength of the substrate, but the appearance of the carbonized layer also drastically increases the leakage current on the surface, resulting in a significant reduction in the surface flashover voltage under high voltage.

[0059] Comparative Example 6 Compared to Example 1, the difference is that the oxygen volume percentage is 0%, and pure inert gas is used for plasma treatment.

[0060] Results: Pure inert gas (such as pure argon) plasma only has a physical bombardment effect, which increases the surface roughness, but lacks chemical reactivity. Since there are no free oxygen atoms or oxygen ions in the environment, it is impossible to build a large number of polar crosslinking sites such as -OH and -C=O on the PTFE surface. As a result, there is a lack of chemical covalent bonding and strong hydrogen bonding between the material and the organosilicon gel, and the improvement in adhesion is extremely limited.

[0061] Comparative Example 7 Compared to Example 1, the difference is that the oxygen volume percentage is 100%, and pure oxygen is used for plasma treatment.

[0062] Results: Oxygen has a high breakdown voltage, the plasma concentration generated in a pure oxygen environment is low, and the oxygen ions are relatively light, lacking a strong physical bombardment effect. Therefore, it is difficult to open enough CF bonds on the inert PTFE surface to generate reactive sites, and it is also impossible to etch an ideal rough microstructure. The lack of physical interlocking effect leads to a significant reduction in the overall interfacial bonding strength.

[0063] Performance testing 1. Interface adhesion test: Potting and bonding samples of substrates treated with plasma and potting materials were prepared according to the methods of Examples 1-4 and Comparative Examples 1-7, and potting and bonding samples of corresponding substrates without plasma treatment and potting materials were prepared according to the methods of Examples 1-4 and Comparative Examples 1-7.

[0064] According to GB / T 2790-1995 standard, a universal tensile testing machine was used to perform peel tests from 0° to 180° on the above-mentioned potting bonded specimens, and the average peel strength was recorded and calculated. The test procedures are as follows: 1) Fixture installation: Attach the mixed silicone gel side of the potting and bonding sample to the acrylic plate and fix it in the lower fixture to ensure stability and no shaking; fix the plasma-treated substrate side of the potting and bonding sample in the upper fixture and bend it 180° in the opposite direction along the bonding interface to ensure that the peel angle is 180°. 2) Equipment settings: Set the peeling speed according to GB / T 2790-1995; set the force value to zero before starting the universal tensile testing machine to ensure that the sample is not preloaded and that there is no external force interference at the start of the test. 3) Perform the peel test: Start the universal tensile testing machine, and gradually separate the upper and lower clamps according to the set peel speed, applying a 180° peel force to the plasma-treated substrate to gradually peel it from the surface of the mixed silicone gel. Maintain the peel angle at 180° throughout the process to avoid lateral displacement or clamp slippage; 4) Data recording and analysis: Record the force-displacement curve during the peeling process, record the force value during the peeling process, calculate the average peel force according to the standard peel strength test method GB / T 2790-1995, and analyze the damage of the adhesive interface.

[0065] Please refer to Table 1 for the test results of average peel force. Figures 1 to 8 ,in, Figure 1 and Figure 2 The results show the bond strength test results of the PTFE material before and after treatment in Example 1. Figure 3 and Figure 4 The results show the bond strength test results of the PI material before and after treatment in Example 2. Figure 5 and Figure 6 The results of the adhesive strength test of the PP material before and after treatment in Example 3 are as follows. Figure 7 and Figure 8 The results show the adhesive strength test results of the FR4 copper clad laminate material in Example 4 before and after treatment.

[0066] 2. Method for testing surface flashover voltage: like Figure 9 As shown, a flashover test platform is prepared, which includes a pair of adjustable-pitch finger electrodes and an insulating support platform; The testing steps are as follows: 1) Sample preparation: Clean and dry the plasma-treated substrate. Cut the dried substrate sample to be tested into rectangular pieces with the following size requirements: the width is slightly larger than the diameter of the finger electrode; the length must be longer than the distance between the two electrodes to ensure that the sample can completely cover and span the two electrodes. 2) Sample installation and electrode adjustment: Loosen the fixing bolts on the test platform; insert the substrate sample to be tested horizontally into the gap between the two finger electrodes; place the sample on the insulating platform and adjust the distance between the two electrodes to match the sample thickness; tighten the clamps to make the electrodes press the sample appropriately to ensure good electrical contact and avoid excessive compression that could cause sample deformation or damage. 3) Electrode sealing and curing: A special mold is placed on the surface of the substrate to be tested and the front end of the finger electrode; mixed silicone gel (organic silicone gel AB glue) is poured into the mold until the contact area and surface between the electrode and the substrate to be tested are completely sealed; the entire device is placed in a vacuum drying oven for curing (80℃, 7 h); after curing, the mold is removed; an electrostatic eliminator is used to remove static electricity from the sample to be tested and the test platform to prevent electrostatic interference with the test results; 4) Test System Connection and Initialization: Connect the finger electrodes to the high-voltage constant voltage source via high-voltage wiring; connect the high-voltage probe to the test circuit, with the probe end connected to the high-voltage circuit and the output end connected to the oscilloscope; ensure that the electric field lines are parallel to the solid (PI) surface to form a uniform electric field along the surface; the experimental setup is as follows. Figure 9 The layout is shown; the high-voltage power supply output is adjusted to 0 kV, and then connected to the mains power to complete the system initialization; 5) Boost and flashover test: Turn on the high-voltage power supply equipment and start from 0 kV. At 1-second intervals, gradually adjust the boost knob according to the set boost rate. Continuously monitor the voltage change waveform with an oscilloscope. When a surface flashover occurs (i.e., discharge breakdown occurs), immediately stop boosting. Record the voltage value at the time of flashover (i.e., flashover voltage). 6) Power off, remove the flashover test platform, remove any remaining test samples from the platform, and clean it.

[0067] The average flashover voltage of the material in Example 1 after plasma treatment was found to be greater than 20 kV under conditions of 5 mm electrode spacing, 10 mm electrode spacing and 15 mm electrode spacing.

[0068] Furthermore, the flashover voltage test results of Examples 2-4 and Comparative Examples 1-7 are shown in Table 1.

[0069] Table 1 Performance test results of the examples and comparative examples

[0070] As can be seen from Table 1, after adopting the plasma surface modification method provided by the present invention in Examples 1-4, the interfacial bonding strength between the substrate and the potting material was significantly improved. Compared with the substrate that has not been treated with plasma, the bonding strength can be increased by more than 50%, and the phenomenon of flashover causing equipment failure or damage during the use of high voltage power supply can be avoided, which greatly enhances the long-term reliability of the equipment in high voltage environment.

[0071] Furthermore, the test results of Example 1 and Comparative Examples 2-7 in Table 1 also show that if the radio frequency power during plasma treatment is too low or too high, the treatment time is too short or too long, or the oxygen volume percentage is too low or too high, the peel force test results after treatment will be worse, and the adhesion between the substrate and the silicone gel will not be effectively improved. In addition, the flashover voltage measurement value will also be reduced.

[0072] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for plasma surface modification of multi-substrate materials for potting structures of high-voltage power supply devices, characterized in that, Includes the following steps: The potting structural substrate to be treated is placed in a plasma treatment system for plasma treatment; The material of the potting structure substrate is selected from at least one of polytetrafluoroethylene, polyimide, polypropylene, silicone rubber, epoxy resin, polycarbonate, alumina, aluminum nitride, aluminum alloy, and FR4 copper clad laminate.

2. The multi-substrate plasma surface modification method for potting structures of high-voltage power supply devices as described in claim 1, characterized in that, Plasma treatment is performed in a mixture of oxygen and an inert gas, wherein the oxygen volume percentage in the mixture is 5% to 80%, and the total gas flow rate of the mixture is 50 to 200 sccm. The radio frequency power of the plasma treatment is 50~150 W, the treatment time is 2~30 min, and the vacuum degree of the plasma treatment is 1~100 Pa.

3. The multi-substrate plasma surface modification method for potting structures of high-voltage power supply devices as described in claim 2, characterized in that, Plasma treatment is performed in a mixture of oxygen and an inert gas, wherein the oxygen volume percentage in the mixture is 20% to 50%. The radio frequency power of the plasma treatment is 80~120 W, the treatment time is 5~15 min, and the vacuum degree of the plasma treatment is 1~100 Pa.

4. The multi-substrate plasma surface modification method for potting structures of high-voltage power supply devices as described in claim 1, characterized in that, The procedure further includes, prior to the step of placing the potting structure substrate to be treated in a plasma treatment system for plasma treatment: The substrate of the potting structure to be treated is cleaned.

5. The multi-substrate plasma surface modification method for potting structures of high-voltage power supply devices as described in claim 1, characterized in that, The step of placing the potting structure substrate to be treated in a plasma treatment system for plasma treatment includes: The potting structural substrate to be treated is placed in a plasma treatment system for plasma treatment to obtain a plasma-treated potting structural substrate. A primer is applied to the surface of the plasma-treated potting structure substrate, followed by standing for 1-2 hours and then heat treatment for 4-5 hours.

6. The multi-substrate plasma surface modification method for potting structures of high-voltage power supply devices as described in claim 5, characterized in that, The primer includes epoxy primers.

7. The multi-substrate plasma surface modification method for potting structures of high-voltage power supply devices as described in claim 5, characterized in that, The step of coating the plasma-treated potting structure substrate with a primer, followed by standing for 1-2 hours and then heat treatment for 4-5 hours, further includes: The substrate of the potting structure, after being coated with a primer, is potted using potting material.

8. The multi-substrate plasma surface modification method for potting structures of high-voltage power supply devices as described in claim 7, characterized in that, The potting material includes silicone gel.

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