Heat-conducting and insulating silica gel fabric as well as preparation method and application thereof

Abstract

The invention discloses a heat-conducting insulating silica gel fabric as well as a preparation method and application thereof, and relates to the technical field of high-performance electronic functional composite materials. The heat-conducting insulating silica gel fabric sequentially comprises a controllable self-permeation oil layer, a first insulating barrier layer, a central anti-puncture reinforcing layer, a second insulating barrier layer and a high heat-conducting layer from inside to outside, the high-thermal-conductivity layer is formed by compounding a multi-element heterostructure insulating thermal-conductivity filler and a silicone rubber matrix, and the multi-element heterostructure insulating thermal-conductivity filler comprises a compound filler of spherical aluminum oxide and flaky boron nitride, surface-passivated zinc oxide whiskers and high-length-diameter-ratio boron nitride nanosheets which are directionally arranged in the in-plane direction through flow field induction. The heat-conducting insulating silica gel fabric can realize low thermal resistance and high voltage resistance under the condition of ultrathin thickness, and has excellent dynamic puncture resistance and long-term reliability.

Description

Technical Field

[0001] This invention relates to the field of high-performance electronic functional composite materials, and in particular to a thermally conductive insulating silicone cloth for heat dissipation of high-voltage, high-power-density power semiconductor devices (such as MOSFETs), which has ultra-low thermal resistance, high voltage resistance, high strength, puncture resistance and self-oiling properties, as well as its preparation method and application. Background Technology

[0002] In high-voltage power electronic equipment, heat dissipation and insulation of power MOSFETs are crucial for ensuring system reliability. Thermally conductive insulating silicone cloth, as an important interfacial thermally conductive and insulating material, is widely used in the packaging and heat dissipation of power devices. Currently, mainstream thermally conductive insulating silicone cloths on the market typically employ a composite structure with thermally conductive fillers (such as alumina and boron nitride) added to a silicone rubber matrix, and glass fiber cloth or polyimide (PI) film as the reinforcing substrate. However, in high-voltage, high-reliability applications, existing technologies have significant limitations: on the one hand, glass fiber cloth, as the reinforcing substrate, is relatively brittle, and while polyimide film has good flexibility, its resistance to dynamic impact puncture is limited. During actual installation or use, sharp metal foreign objects, component leads, or installation stress can easily cause the substrate to be punctured, resulting in permanent insulation failure and posing a significant safety hazard; on the other hand, to achieve low thermal resistance, a high filler content is required, but this often leads to excessive thickness of the thermally conductive insulating silicone cloth material, while simultaneously reducing flexibility and worsening interfacial contact. Summary of the Invention

[0003] In order to solve the problems existing in the prior art, the purpose of this invention is to provide a thermally conductive, fully insulating, and highly reliable thermally conductive insulating silicone cloth and its preparation method, thereby solving the problem that it is difficult to simultaneously achieve thermal conductivity, insulation, mechanical protection, and thinness in the prior art.

[0004] This invention provides the following technical solution: This invention provides a thermally conductive and insulating silicone cloth, which comprises five layers from the inside out: a controllable self-permeable oil layer, a first insulating barrier layer, a central puncture-resistant reinforcing layer, a second insulating barrier layer, and a high thermal conductivity layer; The high thermal conductivity layer is composed of a multi-component heterogeneous insulating thermally conductive filler and a silicone rubber matrix. The multi-component heterogeneous insulating thermally conductive filler includes: A composite filler consisting of spherical alumina and plate-shaped boron nitride; Zinc oxide whiskers with surface passivation treatment; High aspect ratio boron nitride nanosheets (BN nanosheets) are oriented in the in-plane direction by flow field induction.

[0005] Preferably, the thickness of the controllable self-permeable oil layer is 0.015-0.045 mm.

[0006] Preferably, the thickness of the first insulating barrier layer is 0.02-0.040 mm.

[0007] Preferably, the thickness of the central puncture-resistant reinforcing layer is 0.02-0.05 mm.

[0008] Preferably, the thickness of the second insulating barrier layer is 0.02-0.040 mm.

[0009] Preferably, the thickness of the high thermal conductivity layer is 0.045-0.12 mm.

[0010] Furthermore, in the composite filler of spherical alumina and plate boron nitride, the particle size of spherical alumina is 1-10 μm, the particle size of plate boron nitride is 10-30 μm, and the mass ratio of spherical alumina to plate boron nitride is (1-3):1.

[0011] Furthermore, the zinc oxide whiskers with surface passivation treatment have a tetrapter structure, and their surface is passivated using a silane coupling agent. Preferably, the passivation treatment involves placing the zinc oxide whiskers in an ethanol solution of the silane coupling agent and ultrasonically treating them for 30 minutes. Preferably, the concentration of the ethanol solution of the silane coupling agent is 2 wt%.

[0012] Preferably, the aspect ratio of the high aspect ratio boron nitride nanosheet is ≥150.

[0013] Preferably, the surface of the high aspect ratio boron nitride nanosheets is dispersed using a silane coupling agent to improve their dispersibility; the dispersion treatment involves immersing the high aspect ratio boron nitride nanosheets in an ethanol solution of the silane coupling agent. Preferably, the concentration of the ethanol solution of the silane coupling agent is 1.5-2.5 wt%.

[0014] Furthermore, the raw materials for the silicone rubber matrix include vinyl silicone oil, crosslinking agent, and catalyst.

[0015] Preferably, the raw materials of the silicone rubber matrix, by weight, include 100 parts vinyl silicone oil, 1.2-1.8 parts crosslinking agent, 0.08-0.12 parts catalyst and 0.01 parts inhibitor.

[0016] Furthermore, the mass of the multi-component heterostructure insulating thermally conductive filler accounts for 70%-91% of the total mass fraction of the high thermal conductivity layer, and the mass ratio of the spherical alumina and plate boron nitride composite filler, the surface passivated zinc oxide whiskers, and the high aspect ratio boron nitride nanosheets is (60-75):(10-20):(15-25).

[0017] Furthermore, both the first and second insulating barrier layers are made of ceramizable silicone rubber composite material.

[0018] Preferably, the raw materials of the ceramicizable silicone rubber composite material include ceramicizable silicone rubber raw rubber in the ratio of 100:(3-6):(35-45):(20-30):(3-6), hydroxyl silicone oil, mica powder, glass powder and sintering aids.

[0019] The ceramicized silicone rubber raw material is methyl vinyl silicone rubber; the mica powder has a particle size of 800-1250 mesh; the glass powder has a softening point of 500-600℃; and the sintering aid is boron-containing glass powder.

[0020] Furthermore, the central puncture-resistant reinforcing layer is formed by impregnating and curing a blended mesh of aramid 1414 and ultra-high molecular weight polyethylene (UHMWPE) fibers with a shear-thickening adhesive. Preferably, the blended mesh of aramid 1414 and UHMWPE fibers has an areal density of 100-150 g / m². 2 The plain-weave mesh, wherein the blending ratio of aramid 1414 and high molecular weight polyethylene fiber is 60:40. The shear thickening adhesive is a composite material with polyethylene glycol as the dispersion medium and silica nanoparticles as the dispersion phase, and the solid content in the shear thickening adhesive is 60-70%.

[0021] Preferably, the soaking time is 5-10 minutes.

[0022] Further, by weight, the controllable self-permeable oil layer comprises the following raw materials: 100 parts vinyl silicone oil, 10 parts microencapsulated silicone oil, 30 parts spherical alumina thermally conductive filler, 2.0 parts crosslinking agent, 0.1 parts platinum catalyst, 0.03 parts inhibitor, and 10 parts pore-forming agent. Preferably, the vinyl content of the vinyl silicone oil is 1.0 mol%, the particle size of the microencapsulated silicone oil is 5-10 μm, the medium particle size of the spherical alumina is 3 μm, the hydrogen content of the hydrogen-containing silicone oil is 1.0 wt%, the Pt content of the platinum catalyst is 5000 ppm, the inhibitor is ethynylcyclohexanol, and the pore-forming agent is water-soluble polyvinyl alcohol (PVA) microspheres with a medium particle size of 30 μm.

[0023] Under the action of the pore-forming agent, the interior of the controllable self-permeable oil layer contains oil-storing microcavities, which can form a "dual-mode oil supply system" together with microencapsulated silicone oil. The working principle of their synergistic operation is as follows: Short-term / initial lubrication: Under installation pressure, the microencapsulated silicone oil on the material surface breaks first, releasing the silicone oil and quickly filling the microscopic gaps at the interface, achieving low initial contact thermal resistance.

[0024] Long-term / dynamic replenishment: When the interfacial silicone oil decreases due to high-temperature volatilization or migration, the free silicone oil stored in the microcavity (from the low-viscosity silicone oil component in the formulation) continuously and slowly migrates towards the interface to replenish the silicone oil through a three-dimensional interconnected pore network driven by capillary action and thermal expansion.

[0025] Meanwhile, the controllable self-permeating oil layer can also achieve pressure / temperature response. When the temperature rises, the silicone oil in the cavity expands, enhancing the seepage force; when the interface pressure increases (such as when screws are tightened), the microcavity is locally deformed under pressure, pumping out more silicone oil. This achieves "on-demand supply" and avoids ineffective leakage.

[0026] Furthermore, the thickness of the thermally conductive insulating silicone cloth is 0.15-0.3 mm, and the thermal resistance is <0.25℃·in. 2 / W, withstand voltage ≥6kV.

[0027] Secondly, the present invention also provides a method for preparing the above-mentioned thermally conductive and insulating silicone cloth, comprising the following steps: S1: Prepare a preform of a controllable self-permeable oil layer slurry, a first insulating barrier layer slurry, a second insulating barrier layer slurry, a high thermal conductivity layer slurry, and a central puncture-resistant reinforcing layer; S2: The controllable self-permeable oil layer slurry and the first insulating barrier layer slurry are applied sequentially. Then, the central puncture-resistant reinforcing layer preform is assembled on the applied first insulating barrier layer slurry. Next, the second insulating barrier layer slurry and the high thermal conductivity layer slurry are applied sequentially on the central puncture-resistant reinforcing layer preform to form the uncured preform of the five-layer structure. During the application of the high thermal conductivity layer slurry, the shear flow field generated by the scraping process induces the boron nitride nanosheets to align in the in-plane direction. S3: The uncured preform is hot-pressed and cured to obtain thermally conductive and insulating silicone cloth.

[0028] Preferably, the preparation method of the controllable self-permeable oil layer slurry is as follows: Vinyl silicone oil, microencapsulated silicone oil, and spherical alumina are mixed uniformly under vacuum conditions. Then, hydrogen-containing silicone oil, platinum catalyst, and inhibitor are added sequentially and stirred until uniform. Finally, a pore-forming agent is added and dispersed uniformly at low speed to obtain the slurry. After coating the slurry, it is pre-cured at 80℃ for 3 minutes, followed by treatment in a 60℃ water vapor environment for 2 minutes to dissolve and remove the PVA microspheres, forming three-dimensional interconnected pores, i.e., oil-storing microcavities, with a size and shape basically consistent with the microspheres. Finally, primary curing is performed at 170℃ for 15 minutes.

[0029] Preferably, the first insulating barrier layer slurry is the same as the second insulating barrier layer slurry, and its preparation method is as follows: ceramicized silicone rubber raw rubber, hydroxyl silicone oil, mica powder, glass powder and sintering aid are mixed in proportion; after mixing in an internal mixer at 80-100℃ for 20 minutes, it is transferred to a two-roll mill for thin passing 5 times to form a uniform sheet rubber material, and then dissolved in a solvent (xylene) to prepare a coating slurry with a solid content of 65-75%.

[0030] Preferably, the preparation method of the central puncture-resistant reinforcing layer preform is as follows: aramid 1414 and UHMWPE fiber are blended at a mass ratio of 60:40 and woven into a fabric with an areal density of 100-150 g / m². 2 Plain weave mesh. Immerse the plain weave mesh in a silica nanoparticle / polyethylene glycol 200-based shear thickener (STF, solid content 60-70%) for 5-10 minutes, ensuring complete wetting. After removal, pre-dry in an oven at 80-100℃ for 10-20 minutes to allow the STF to initially gel, forming a flexible pre-reinforced sheet.

[0031] Preferably, the method for preparing the high thermal conductivity layer slurry includes the following steps: d1. Filler pretreatment: Four-needle zinc oxide whiskers were placed in an ethanol solution of 2 wt% silane coupling agent, ultrasonically treated for 30 minutes, filtered, and dried to obtain surface passivated ZnO whiskers. High aspect ratio (≥150) boron nitride nanosheets were dispersed in an ethanol solution containing silane coupling agent.

[0032] d2. Slurry Mixing: Using 100 parts by weight of vinyl silicone oil as the precursor for the silicone rubber matrix, a composite filler of spherical alumina and lamellar boron nitride (total mass parts: 50-70, mass ratio: 1:1 to 3:1), surface passivated ZnO whiskers (10-15 parts), and pretreated BN nanosheets (15-25 parts) are added sequentially. After pre-dispersing in a high-speed disperser at 2000-3000 rpm for 15 minutes, the mixture is transferred to a planetary mixer and stirred at 500-800 rpm for 60-90 minutes under a vacuum of -0.098 MPa to form a uniform, high-viscosity slurry. Finally, inhibitors and catalysts are added, and after thorough mixing, a crosslinking agent is added and stirred at low speed for 10 minutes.

[0033] Preferably, in step S2, the controllable self-permeable oil layer slurry is first coated onto the release film with a wet film thickness of 15-45 μm. Then, it is treated in a 60°C steam environment for 2 minutes to dissolve and remove the PVA microspheres, forming three-dimensional interconnected pores, i.e., oil-storing microcavities, with a size and shape basically consistent with the microspheres. Finally, it undergoes primary curing at 170°C for 15 minutes. Next, a first insulating barrier layer slurry (wet film thickness controlled to 20-40 μm after drying) is coated onto it. The central puncture-resistant reinforcing layer preform is then laid flat on the uncured first insulating barrier layer. Subsequently, a second insulating barrier layer slurry (wet film thickness controlled to 20-40 μm after drying) and a high thermal conductivity layer slurry (wet film thickness controlled to 45-120 μm after drying) are sequentially coated. During the coating of the high thermal conductivity layer, by adjusting the doctor blade angle and coating speed (1-3 m / min), the strong shear flow field generated by the slurry flowing through the doctor blade induces the BN nanosheets to align in the in-plane direction. Finally, a release film is applied to form a laminated preform of "release film / five-layer functional material / release film".

[0034] Preferably, in step S3, the hot-press curing is a stepped hot-press curing method, which includes: The first stage (pre-curing and interface fusion): hot-pressing for 3-5 minutes at a temperature of 80-100℃ and a pressure of 0.1-0.5 MPa. This stage aims to initially cross-link the layers of the slurry, initially fuse the interfaces, fix the orientation structure of the BN nanosheets, and remove residual air bubbles.

[0035] The second stage (primary curing and structural densification): hot pressing for 10-20 minutes at a temperature of 150-170℃ and a pressure of 1-5MPa. This stage achieves complete vulcanization and cross-linking of the silicone rubber, with strong chemical and physical bonds formed between the layers through molecular diffusion, resulting in a final dense structure.

[0036] Preferably, in step S3, the hot-press curing process further includes a post-treatment process and a surface treatment process. The post-treatment process includes a curing and cooling process, specifically as follows: the hot-pressed cured silicone cloth roll is passed through a drying tunnel at 120-130°C at a uniform speed for 2-4 hours under normal pressure to eliminate internal stress and further improve the degree of crosslinking. It is then cooled to room temperature by a cooling roller.

[0037] The surface treatment is a surface corona treatment, with the following conditions: voltage 10-15kV, frequency 20-30kHz, electrode spacing 1-2mm, and processing speed 5-10m / min. This treatment aims to slightly increase the surface polarity and improve its instantaneous wettability with the metal casing of the MOSFET without damaging the surface structure.

[0038] Thirdly, the present invention also provides an application of the above-mentioned thermally conductive insulating silicone cloth in heat dissipation and insulation protection of power MOSFETs with operating voltages higher than 600V.

[0039] Through the above design, the present invention has the following effects: This invention utilizes a tightly packed spherical alumina structure to reduce phonon scattering interfaces; interspersed lamellar boron nitride provides a two-dimensional thermal conductivity path, and the combination of these two forms a stable, low-thermal-resistance thermal conductivity base; ZnO whiskers interlock within a silicone rubber matrix to form a three-dimensional thermal conductivity framework, significantly improving thermal diffusion efficiency; and highly oriented in-plane BN nanosheets with high aspect ratios construct an ultra-efficient in-plane thermal conductivity pathway, rapidly dispersing hotspots. Thus, through a multi-component heterogeneous filler system of "spherical alumina + lamellar boron nitride + zinc oxide whiskers + high aspect ratio boron nitride nanosheets," a multi-dimensional, high-efficiency thermal conductivity pathway is constructed under the premise of complete insulation. Simultaneously, the aforementioned fillers exhibit stable chemical properties, strong aging resistance, and low performance degradation throughout the product's lifespan.

[0040] Meanwhile, the thermally conductive insulating silicone cloth of the present invention absorbs and disperses impact energy through the central puncture-resistant reinforcing layer, avoiding insulation failure caused by puncture, ensures low and stable interfacial contact thermal resistance through the self-permeable oil layer, achieves insulation protection through the double-layer insulating barrier layer, and combines the high thermal conductivity layer to achieve the technical effects of full insulation, ultra-low thermal resistance, high pressure resistance, high strength, puncture resistance and self-permeable oil properties. Attached Figure Description

[0041] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a schematic diagram of the thermally conductive and insulating silicone cloth structure provided in Embodiment 1 of the present invention.

[0043] The markings in the diagram are as follows: 1-Controllable self-permeable oil layer; 2-First insulating barrier layer; 3-Central puncture-resistant reinforcing layer; 4-Second insulating barrier layer; 5-High thermal conductivity layer. Detailed Implementation

[0044] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] It should be understood that, when used in this specification and the appended claims, the terms “comprising” and “including” indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0046] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0047] Example 1 A thermally conductive and insulating silicone cloth comprises a five-layer structure from the inside out, such as... Figure 1 As shown, the layers are, in order: a controllable self-permeable oil layer 1, a first insulating barrier layer 2, a central puncture-resistant reinforcing layer 3, a second insulating barrier layer 4, and a high thermal conductivity layer 5.

[0048] Raw material formulation for controllable self-permeable oil layer 1 (by weight): Vinyl silicone oil (vinyl content 1.0 mol%): 100 parts; Microencapsulated silicone oil (particle size 5-10μm): 10 parts; Spherical alumina filler (medium particle size 3μm): 30 parts; Hydrogen-containing silicone oil crosslinking agent (hydrogen content 1.0 wt%): 2.0 parts; Platinum catalyst (calculated as platinum element, accounting for 50 ppm of the total mass of silicone oil): 0.1 parts; Inhibitor (ethynylcyclohexanol): 0.03 parts; Water-soluble polyvinyl alcohol microspheres (medium particle size 30 μm, used as a porogen): 10 parts.

[0049] Raw material formula for first insulating barrier layer 2 / second insulating barrier layer 4 (by weight): Ceramicized silicone rubber raw material (methyl vinyl silicone rubber): 100 parts; Hydroxy silicone oil: 5 parts; Mica powder (800 mesh): 40 parts; Glass powder (softening point 550℃): 25 parts; Boron-containing glass powder (sintering aid): 5 parts; Vulcanizing agent (Double 24): 0.5 parts.

[0050] Central puncture-resistant reinforcing layer 3: Plain weave mesh woven from a blend of aramid 1414 fiber and ultra-high molecular weight polyethylene fiber at a mass ratio of 60:40.

[0051] Surface density: 120 g / m³ 2 .

[0052] Impregnation material: silica nanoparticles / polyethylene glycol 200-based shear thickener (STF), solid content 65%.

[0053] High thermal conductivity layer 5 formulation: Silicone rubber matrix: 100 parts vinyl silicone oil, 1.6 parts crosslinking agent (hydrogen-containing silicone oil), 0.10 parts catalyst (platinum catalyst) and 0.01 parts inhibitor (ethynylcyclohexanol).

[0054] Multi-component heterogeneous insulating and thermally conductive filler (accounting for 82% of the total mass of the high thermal conductivity layer): The compound filler consists of spherical alumina (3μm particle size) and plate-shaped boron nitride (15μm particle size) in a 1:1 mass ratio, accounting for 60% of the total mass of the multi-element heterogeneous insulating and thermally conductive filler.

[0055] Three-dimensional reinforced filler: Four needle-shaped zinc oxide whiskers with surface passivation treatment by silane coupling agent KH-550 account for 15% of the total mass of multi-element heterogeneous insulating and thermally conductive filler.

[0056] In-plane oriented filler: High aspect ratio boron nitride nanosheets (aspect ratio 200) dispersed by silane coupling agent KH-560 account for 25% of the total mass of multi-element heterostructure insulating and thermally conductive filler.

[0057] A method for preparing the above-mentioned thermally conductive and insulating silicone cloth includes the following steps: S1. Preparation of a preform containing a controllable self-permeable oil layer slurry, a first insulating barrier layer slurry, a second insulating barrier layer slurry, a high thermal conductivity layer slurry, and a central puncture-resistant reinforcing layer: a. Preparation of controllable self-exuding oil slurry: Vinyl silicone oil, microencapsulated silicone oil, and spherical alumina were mixed uniformly under vacuum in a planetary mixer (vacuum degree -0.095MPa). Then, hydrogen-containing silicone oil crosslinking agent, platinum catalyst, and inhibitor were added sequentially and stirred uniformly (400 rpm). Finally, water-soluble polyvinyl alcohol microspheres were added as pore-forming agents and dispersed uniformly at low speed (100 rpm) to obtain the slurry.

[0058] b. Preparation of the first insulating barrier layer slurry and the second insulating barrier layer slurry: Ceramicized silicone rubber raw rubber, hydroxyl silicone oil, mica powder, glass powder and sintering aid are mixed in proportion; after mixing in an internal mixer at 90°C for 20 minutes, it is transferred to a two-roll mill for thin passing 5 times to form a uniform sheet rubber material, which is then dissolved in a solvent (xylene) to prepare a coating slurry with a solid content of 70%.

[0059] c. Preparation of the central puncture-resistant reinforcement layer preform: Aramid 1414 and UHMWPE fiber are blended at a mass ratio of 60:40 and woven into a preform with an areal density of 120 g / m². 2 Plain weave mesh. Immerse the plain weave mesh in a silica nanoparticle / polyethylene glycol 200-based shear thickener (STF, 65% solids content) for 8 minutes to ensure complete wetting. After removal, pre-dry in a 90°C oven for 15 minutes to allow the STF to initially gel, forming a flexible pre-reinforced sheet.

[0060] d. Preparation of high thermal conductivity slurry: d1. Filler pretreatment: Four-needle zinc oxide whiskers were placed in an ethanol solution containing 2 wt% silane coupling agent, ultrasonically treated for 30 minutes, filtered, and dried to obtain surface passivated ZnO whiskers. High aspect ratio (≥150) boron nitride nanosheets were dispersed in an ethanol solution containing 2 wt% silane coupling agent.

[0061] d2. Slurry Mixing: Using 100 parts by weight of vinyl silicone oil as the precursor for the silicone rubber matrix, a composite filler of spherical alumina and lamellar boron nitride (total mass parts: 50-70, mass ratio: 1:1 to 3:1), surface passivated ZnO whiskers (10-15 parts), and pretreated BN nanosheets (15-25 parts) are added sequentially. After pre-dispersing in a high-speed disperser at 2000-3000 rpm for 15 minutes, the mixture is transferred to a planetary mixer and stirred at 500-800 rpm for 60-90 minutes under a vacuum of -0.098 MPa to form a uniform, high-viscosity slurry. Finally, inhibitors and catalysts are added, and after thorough mixing, a crosslinking agent is added and stirred at low speed for 10 minutes.

[0062] S2. First, a controllable self-permeable oil layer slurry is coated onto the release film with a wet film thickness of 30 μm. Then, it is treated in a 60℃ steam environment for 2 minutes to dissolve and remove the PVA microspheres, forming three-dimensional interconnected pores, i.e., oil-storing microcavities, with a size and shape basically consistent with the microspheres. Finally, it undergoes primary curing at 170℃ for 15 minutes. Next, a first insulating barrier layer slurry (wet film thickness controlled to 30 μm after drying) is coated on top. The central puncture-resistant reinforcement preform is then laid flat on the uncured first insulating barrier layer. Subsequently, a second insulating barrier layer slurry (wet film thickness controlled to 30 μm after drying) and a high thermal conductivity layer slurry (wet film thickness controlled to 80 μm after drying) are coated sequentially. During the coating of the high thermal conductivity layer, the blade angle and coating speed (2 m / min) are adjusted, utilizing the strong shear flow field generated by the slurry flowing through the blade to induce the BN nanosheets to align in the in-plane direction. Finally, a release film is applied to form a laminated preform consisting of "release film / five-layer functional material / release film".

[0063] S3, Hot-press curing: The first stage (pre-curing and interface fusion): hot-pressing for 3 minutes at 90℃ and 0.3MPa. This stage aims to achieve initial cross-linking and interface fusion of the slurry layers, fix the orientation structure of the BN nanosheets, and remove residual air bubbles.

[0064] The second stage (primary curing and structural densification): hot pressing for 15 minutes at 160℃ and 3MPa. This stage achieves complete vulcanization and cross-linking of the silicone rubber, with strong chemical and physical bonds formed between the layers through molecular diffusion, resulting in a final dense structure.

[0065] S4. Post-treatment: The hot-pressed and cured silicone cloth is heat-cured in a 125℃ oven for 3 hours. After cooling, the surface of the controllable self-permeable oil layer is subjected to corona treatment (voltage 12 kV, frequency 25 kHz, processing speed 8 m / min) to obtain thermally conductive and insulating silicone cloth.

[0066] Example 2 The difference between this embodiment and Embodiment 1 lies in the adjustment of the proportion of the multi-component heterogeneous insulating thermally conductive filler in the high thermal conductivity layer: the mass is increased to 91% of the total mass of the high thermal conductivity layer, of which the proportion of high aspect ratio BN nanosheets (aspect ratio ~200) is increased to 18% (accounting for the total mass of the multi-component heterogeneous insulating thermally conductive filler), the proportion of spherical Al2O3 and plate-like BN composite filler is adjusted to 62% of the total mass of the multi-component heterogeneous insulating thermally conductive filler, and the surface passivated ZnO whiskers account for 20% of the total mass of the multi-component heterogeneous insulating thermally conductive filler. The remaining formulation, structure, and process are the same as in Embodiment 1.

[0067] Example 3 The difference between this embodiment and Embodiment 1 lies in the adjustment of the proportion of the multi-component heterogeneous insulating thermally conductive filler in the high thermal conductivity layer: the mass is 75% of the total mass of the high thermal conductivity layer, wherein the proportion of spherical Al2O3 and sheet-like BN composite filler is increased to 75% (accounting for 10% of the total mass of the multi-component heterogeneous insulating thermally conductive filler), surface passivated ZnO whiskers account for 10% of the total mass of the multi-component heterogeneous insulating thermally conductive filler, and high aspect ratio BN nanosheets (aspect ratio ~200) account for 15% of the total mass of the multi-component heterogeneous insulating thermally conductive filler. The remaining formulation, structure, and process are the same as in Embodiment 1.

[0068] Example 4 The difference between this embodiment and Embodiment 1 is that BN nanosheets with an aspect ratio of approximately 100 are used in the high thermal conductivity layer, and the mass fraction (of the total mass of the high thermal conductivity layer) of the multi-component heterostructure insulating thermally conductive filler is reduced to 70%. The remaining formulation, structure, and process are the same as in Embodiment 1.

[0069] Comparative Example 1 The only difference between this comparative example and Example 1 is that the high thermal conductivity layer uses raw tetra-needle zinc oxide whiskers without any surface passivation treatment. The rest of the formulation, structure, and process are the same as in Example 1.

[0070] Comparative Example 2 The only difference between this comparative example and Example 1 is that, in preparing the high thermal conductivity layer, all fillers (including BN nanosheets) were not subjected to a flow field-induced orientation step; instead, conventional stirring was used to randomly distribute the fillers in the matrix. The remaining formulation, structure, and process are the same as in Example 1.

[0071] Comparative Example 3 The difference between this comparative example and Example 1 is that the "central puncture-resistant reinforcing layer" (an aramid / UHMWPE hybrid woven mesh impregnated with STF) is replaced with a single-layer polyimide film of similar thickness (approximately 0.04 mm). This film is laminated to the upper and lower insulating barrier layers using an adhesive. The materials and processes for the remaining layers are consistent with those in Example 1.

[0072] Performance Tests and Results The samples prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to performance tests, including tests on their thickness, thermal resistance, withstand voltage, puncture resistance, and dynamic impact performance. The test standards for each indicator are as follows.

[0073] Testing standards: Thermal resistance: ASTM D5470.

[0074] Withstand voltage strength: ASTM D149.

[0075] Puncture resistance: GB / T 37841-2019.

[0076] Dynamic shock: ASTM D3763 (simulating accidental drop impact on MOSFET pins).

[0077] The test results are shown in Table 1 below: Table 1 Performance Test Results As shown in Table 1, the thermally conductive and insulating silicone cloths provided in Examples 1-4 of the present invention, with a thickness of 0.25 mm, all achieved a temperature below 0.25°C / in. 2 It exhibits ultra-low thermal resistance of / W and a withstand voltage of over 6kV, along with excellent dynamic impact resistance. In contrast, Comparative Example 1, which uses unpassivated ZnO whiskers, suffers a severe decrease in insulation reliability; Comparative Example 2, lacking the flow-induced directional alignment of BN nanosheets, shows a significant increase in thermal resistance, failing to meet the core performance indicators; and Comparative Example 3, which uses a traditional polyimide film as a reinforcing layer, has acceptable static puncture resistance but is extremely prone to breakage and failure under dynamic impact.

[0078] In summary, this invention, through the synergistic design of a "five-layer composite structure" and a "multi-element heterogeneous thermally conductive filler system," successfully overcomes the technical bottleneck of simultaneously achieving high thermal conductivity, high insulation, and high mechanical reliability at ultra-thin scales. This thermally conductive and insulating silicone cloth is suitable for heat dissipation and insulation protection of high-voltage semiconductor devices such as power MOSFETs operating at voltages above 600V, providing a novel material solution for improving the long-term operational reliability of high-power-density power electronic equipment, and possesses significant industrial application value.

[0079] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A heat-conducting, insulating silicone rubber sheet, characterized by comprising: From inside to outside, it comprises five layers of structure, in turn: controllable self-permeable oil layer, first insulating barrier layer, central anti-puncture reinforcing layer, second insulating barrier layer and high thermal conductivity layer; The high thermal conductivity layer is composed of a multi-heterostructure insulating thermal conductive filler and a silicone rubber matrix, and the multi-heterostructure insulating thermal conductive filler comprises: A compounded filler of spherical alumina and flaky boron nitride; Oxide zinc whiskers with surface passivation treatment; High aspect ratio boron nitride nanosheets oriented in the in-plane direction by flow field induction.

2. The heat-conducting insulating silicone rubber sheet according to claim 1, wherein In the compounded filler of spherical alumina and flaky boron nitride, the particle size of the spherical alumina is 1-10 μm, the particle size of the flaky boron nitride is 10-30 μm, and the mass ratio of the spherical alumina to the flaky boron nitride is (1-3):

1.

3. The heat-conducting insulating silicone sheeting of claim 1, wherein, The oxide zinc whiskers with surface passivation treatment are in a four-needle structure, and the surface is passivated by a silane coupling agent.

4. The heat-conducting insulating silicone sheeting of claim 1, wherein, The high aspect ratio boron nitride nanosheets have an aspect ratio of ≥150.

5. The heat-conducting, insulating silicone sheeting of claim 1, wherein, The mass of the multi-heterostructure insulating thermal conductive filler accounts for 70%-91% of the total mass of the high thermal conductivity layer, and the mass ratio of the compounded filler of spherical alumina and flaky boron nitride, the oxide zinc whiskers with surface passivation treatment, and the high aspect ratio boron nitride nanosheets is (60-75):(10-20):(15-25).

6. The heat-conducting insulating silicone sheeting of claim 1, wherein, The central anti-puncture reinforcing layer is formed by impregnating a shear thickening gel into a mixed net of aramid 1414 and ultra-high molecular weight polyethylene fibers and then curing.

7. The heat-conducting insulating silicone sheeting of claim 1, wherein the silicone sheeting has a thickness of 0.1 to 1.0 mm. The controllable self-permeable oil layer comprises, by mass fraction, the following raw materials: 90-110 parts of vinyl silicone oil, 8-12 parts of microencapsulated silicone oil, 20-40 parts of spherical alumina thermal conductive filler, 1-2.5 parts of crosslinking agent, 0.05-0.3 parts of platinum gold catalyst, 0.01-0.04 parts of inhibitor, and 8-12 parts of pore former.

8. The heat-conducting insulating silicone sheeting of claim 1, wherein, The thickness of the heat-conducting insulating silicone rubber cloth is 0.15-0.3mm, and the thermal resistance is less than 0.25℃.in 2 / W, and the voltage resistance is greater than or equal to 6kV.

9. A process for the production of the heat-conducting and insulating silicone rubber sheeting as claimed in any one of claims 1 to 8, characterized in that, The method comprises the following steps: S1: preparing controllable self-permeable oil layer slurry, first insulating barrier layer slurry, second insulating barrier layer slurry, high thermal conductivity layer slurry, and central anti-puncture reinforcing layer preform; S2: sequentially coating the controllable self-permeable oil layer slurry and the first insulating barrier layer slurry, then combining the central anti-puncture reinforcing layer preform on the coated first insulating barrier layer slurry, and then sequentially coating the second insulating barrier layer slurry and the high thermal conductivity layer slurry on the central anti-puncture reinforcing layer preform to form an uncured embryo of the five-layer structure; wherein, when the high thermal conductivity layer slurry is coated, the shear flow field generated by the doctor blade coating process induces the boron nitride nanosheets to be oriented in the in-plane direction; S3: heat pressing and curing the uncured embryo to obtain the thermal conductive and insulating silicone rubber cloth.

10. The thermal conductive and insulating silicone rubber cloth according to any one of claims 1-8 is used in the heat dissipation and insulation protection of power MOS tubes with a working voltage higher than 600 V.

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