Insulating heat-conducting composite material with three-dimensional heat-conducting framework and preparation method of insulating heat-conducting composite material

Abstract

The invention discloses an insulating and heat-conducting composite material with a three-dimensional heat-conducting framework and a preparation method of the insulating and heat-conducting composite material. The method comprises the following steps: firstly, carrying out surface modification on hexagonal boron nitride and copper nanowires by utilizing a silane coupling agent; then mixing and dispersing the materials, and constructing a three-dimensional porous heat-conducting framework through vacuum filtration and freeze drying; and finally performing vacuum impregnation epoxy resin curing molding. According to the invention, the one-dimensional copper nanowire is used as a'bridge 'to connect the two-dimensional boron nitride nanosheets, and an efficient three-dimensional long-range heat-conducting network is constructed under the condition of low filler content. The obtained composite material has excellent heat-conducting property and heat stability; the composite material provided by the invention has the advantages of excellent thermal conductivity, excellent dielectric insulation performance, low dielectric constant and dielectric loss, solves the problems of processing difficulty caused by high filling amount and insulation failure caused by metal filler, and is suitable for the field of electronic packaging thermal management.

Description

Technical Field

[0001] This application relates to the field of electronic packaging materials technology, and more specifically, it relates to an insulating and thermally conductive composite material with a three-dimensional thermally conductive skeleton and a method for preparing the same. Background Technology

[0002] Thermally conductive materials are essential for improving heat dissipation in electronic devices. Related organic polymer materials offer advantages such as ease of processing, resistance to chemical corrosion, and excellent electrical insulation. However, due to the amorphous arrangement of their molecular chains and the large amount of phonon scattering generated by vibrations, they are difficult to achieve efficient thermal conductivity, with thermal conductivity typically ranging from 0.1 to 0.5 W·m. -1 ·K -1 Therefore, polymer-based thermally conductive composite materials have become an important development direction. Polymer-based thermally conductive composite materials consist of a polymer matrix and thermally conductive fillers. Their key feature is that they improve upon the insufficient thermal conductivity of polymer materials while retaining the inherent advantages of polymers, achieving a synergistic improvement in the performance of thermally conductive materials.

[0003] To construct an efficient three-dimensional thermally conductive network, patent CN118325287A employs a sacrificial template method, utilizing polyurethane foam as a framework to adsorb filler, followed by sintering at temperatures above 600°C to remove or carbonize the template. Patent CN121021908A, on the other hand, uses an in-situ growth method, growing nanowires on the filler surface through a carbothermal reduction reaction at extremely high temperatures above 1400°C.

[0004] However, the above methods have the following limitations: 1. High energy consumption and complex processes, requiring long-term high-temperature sintering or chemical vapor deposition, high equipment requirements, and difficulty in large-scale mass production; 2. Difficulty in controlling insulation, the organic foam in the template method will form a conductive carbon network after carbonization, and the carbon nanotubes or carbon residues in the in-situ growth method are good conductors, which can easily lead to a decrease in the volume resistivity of the composite material, making it difficult to meet the stringent requirements of high insulation and low dielectric loss for electronic packaging.

[0005] Therefore, developing a preparation technology that is mild, does not require high-temperature sintering, and can stably achieve the dual goals of high thermal conductivity and high insulation is an urgent problem to be solved. Summary of the Invention

[0006] To address the issue that the volume resistivity of composite materials decreases due to the use of polyurethane foam as a skeleton to adsorb filler and the removal or carbonization of the template by high-temperature sintering, making it difficult to meet the requirements of high insulation and low dielectric loss in electronic packaging, this application provides an insulating and thermally conductive composite material with a three-dimensional thermally conductive skeleton and its preparation method.

[0007] In a first aspect, this application provides a method for preparing an insulating and thermally conductive composite material with a three-dimensional thermally conductive framework, employing the following technical solution: A method for preparing an insulating and thermally conductive composite material with a three-dimensional thermally conductive framework includes the following steps: S1. Surface modification of fillers: Hexagonal boron nitride and copper nanowires were modified with silane coupling agents to obtain modified boron nitride and modified copper nanowires. S2, Three-dimensional framework construction: The modified boron nitride and modified copper nanowires obtained in S1 are dispersed in a solvent, a water-soluble polymer binder is added and mixed evenly, and a wet framework is formed by filtration. Then, a three-dimensional porous thermally conductive framework is obtained by directional freeze-drying process. S3. Resin composite curing: Prepare an epoxy resin mixture, fill the pores of the three-dimensional porous thermally conductive skeleton obtained in S2 with the epoxy resin mixture by vacuum impregnation, and cure to obtain the insulating and thermally conductive composite material.

[0008] By employing the above technical solution, the surface modification of hexagonal boron nitride and copper nanowires is first performed to improve their dispersibility in subsequent solvent systems and their interfacial compatibility with the polymer matrix. Then, through vacuum filtration and directional freeze-drying processes, the modified filler self-assembles to form a three-dimensional porous framework with a directional channel structure. This framework constructs a continuous phonon transport pathway. Finally, a low-viscosity epoxy resin mixture is fully filled into the pores of the framework and cured by vacuum impregnation. After curing, the resin becomes a continuous phase, completely fixing the pre-formed three-dimensional thermally conductive network inside the matrix. Therefore, this method can construct a through-type and low-thermal-resistance thermally conductive network in a polymer matrix, obtaining a composite material with high thermal conductivity and excellent electrical insulation properties under relatively low filler load.

[0009] Preferably, in step S1, the silane coupling agent is selected from at least one of amino-based silane coupling agents, epoxy-based silane coupling agents, or vinyl-based silane coupling agents.

[0010] By adopting the above technical solution, the selected type of silane coupling agent molecule contains siloxane groups at one end that can chemically bond or strongly interact with the hydroxyl groups at the edge of the hexagonal boron nitride sheet or the oxide layer on the surface of copper nanowires, and active organic functional groups such as amino, epoxy, or vinyl groups at the other end. When these organic functional groups are subsequently compounded with the epoxy resin matrix, they can participate in the curing and crosslinking reaction of the resin or form strong interactions with the resin molecular chains, thereby constructing a chemical bridge between the inorganic filler and the organic polymer matrix. This strong interfacial bonding helps to reduce the interfacial thermal resistance between the filler and the matrix, promotes phonon transmission, and prevents thermal resistance channel defects caused by interfacial debonding during use. Therefore, composite materials with high interfacial bonding strength and stable thermal conductivity pathways can be obtained.

[0011] Preferably, the silane coupling agent is γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, or N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

[0012] By employing the above technical solution, the primary amino group at the end of the γ-aminopropyltriethoxysilane molecule can undergo a ring-opening addition reaction with the epoxy group of the epoxy resin, covalently bonding to the cured resin network; while the γ-(2,3-epoxypropoxy)propyltrimethoxysilane molecule itself contains epoxy groups, which can participate in the curing and crosslinking of the epoxy resin; the subsequent N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane contains two amino groups, exhibiting higher reactivity and bonding points with the resin; these specific silane coupling agents not only provide interfacial bridging, but their longer alkyl chains or flexible segments also help to introduce a certain flexible buffer layer at the interface, alleviating the internal stress caused by the mismatch between the thermal expansion coefficients of the filler and the matrix; therefore, the above-mentioned silane coupling agents can enhance interfacial adhesion and improve the mechanical and thermal properties of the interfacial layer.

[0013] Preferably, in step S1, the mass ratio of the modified copper nanowires to the modified boron nitride is 1:10 to 1:1.

[0014] By adopting the above technical solution, hexagonal boron nitride, as the dominant thermal filler, has a two-dimensional sheet structure that forms the main body of the three-dimensional framework and the main thermal conduction pathway. Copper nanowires, as one-dimensional connectors, bridge the dispersed boron nitride sheets, forming contacts between the sheet fillers and reducing the contact thermal resistance between the sheets, thereby constructing a three-dimensional thermally conductive network. When the proportion of copper nanowires is too low, its bridging effect is limited, making it difficult to connect all the boron nitride sheets. When the proportion is too high, the network connectivity is enhanced, but excessive metal fillers increase the risk of conductivity in the composite material and impair its insulation performance. Controlling the mass ratio of modified copper nanowires to modified boron nitride to 1:10 to 1:1 achieves a balance between using copper nanowires to improve network connectivity to enhance thermal conductivity and using the insulation properties of boron nitride and the isolation effect of the surface modification layer to maintain high volume resistivity.

[0015] Preferably, in step S2, the water-soluble polymer binder is selected from at least one of sodium carboxymethyl cellulose, polyvinyl alcohol, polyvinylpyrrolidone, or sodium alginate; the amount of water-soluble polymer binder added is 0.5% to 8% of the total mass of the filler.

[0016] By adopting the above technical solution, in the freeze-drying step before constructing the three-dimensional skeleton, the water-soluble polymer binder is dissolved in the dispersion solvent, and its long molecular chains can coat the surface of the modified filler through physical adsorption, entanglement, or hydrogen bonding. In the subsequent filtration process, the polymer chains initially fix the filler particles together to form a wet skeleton with a certain strength, preventing structural collapse in subsequent operations. During freeze-drying, the solvent crystallizes into ice, and the polymer binder is concentrated in the filler interface region between the ice crystals. After drying, it forms bonding points, thereby stabilizing the morphology of the three-dimensional porous skeleton and enabling it to withstand the liquid pressure in the subsequent vacuum impregnation process without deformation. When the addition amount is too low, the binder is insufficient to form a bonding network, resulting in poor skeleton strength. When the addition amount is too high, the excessive binder blocks the pores of the skeleton, affecting the impregnation and filling effect of the subsequent resin, and introducing too much insulating polymer phase into the final composite material, reducing the overall thermal conductivity. Therefore, controlling the addition amount within this range can ensure that the three-dimensional skeleton has sufficient self-supporting strength and a suitable porous structure.

[0017] Preferably, in step S2, the specific conditions of the freeze-drying process are: pre-freezing at -80℃ to -20℃ for 1 to 5 hours, followed by drying under a vacuum of less than 20 Pa for 12 to 48 hours.

[0018] By adopting the above technical solution, the low temperature environment during the pre-freezing stage causes the solvent in the dispersion system to crystallize rapidly. Within the temperature range of -80℃ to -20℃, the lower temperature promotes the formation of finer ice crystals. During the ice crystal growth process, the filler particles are displaced, resulting in a more refined and uniformly distributed porous structure after drying. This is beneficial for the uniform impregnation of the resin and maintaining the structural uniformity of the composite material. The appropriate freezing time ensures that the sample is frozen and solidified from the outside to the inside. Subsequently, sublimation drying is carried out under certain high vacuum conditions. This low-pressure environment lowers the sublimation point of the solvent, allowing the ice crystals to be removed without undergoing a liquid-to-gas transformation. This process avoids the collapse of the pore structure caused by the surface tension of the liquid, and completely preserves the three-dimensional network template formed during freezing. The appropriate drying time ensures the sublimation of ice crystals inside samples of different sizes, resulting in a fully dried and structurally complete three-dimensional porous thermally conductive framework.

[0019] Preferably, in step S3, the epoxy resin mixture is composed of epoxy resin, an anhydride curing agent, and an accelerator; wherein the epoxy resin is selected from one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, or alicyclic epoxy resin.

[0020] By adopting the above technical solution, the selected epoxy resins, such as bisphenol A, bisphenol F, or alicyclic epoxy resins, typically have low viscosity before curing. This facilitates their penetration and filling of the fine pores in the three-dimensional porous skeleton during vacuum impregnation, ensuring the composite material is defect-free. The reaction between anhydride curing agents and epoxy resins is a stepwise polymerization process, with gentle exothermic curing and low shrinkage, which helps reduce curing stress and avoids damage to the brittle three-dimensional skeleton structure. The subsequent addition of an accelerator regulates the rate and onset temperature of the curing reaction, ensuring the resin mixture maintains sufficient working time during impregnation and reacts fully during curing. After curing, this resin system forms a dense, stable polymer matrix with high mechanical properties and insulation, firmly encapsulating and fixing the three-dimensional thermally conductive skeleton, together constituting the final composite material. Therefore, the selection of this resin system balances process operability and the matrix properties of the final product.

[0021] Preferably, in step S3, the curing process is a segmented curing process, including: pre-curing at 80℃~100℃ for 1~3 hours, followed by curing at 150℃~180℃ for 2~6 hours.

[0022] By adopting the above technical solution, the segmented curing process first pre-cures at a lower temperature of 80℃~100℃. During this stage, the resin viscosity further decreases and the fluidity increases, which helps to more fully wet the skeleton and fill the capillary. At the same time, the resin begins to undergo preliminary cross-linking, and the viscosity gradually increases, which initially fixes the filler network and prevents the skeleton from shifting or deforming due to resin flow during subsequent heating. Pre-curing for 1-3 hours ensures the completion of preliminary gelation. Then, the temperature is raised to 150℃~180℃ for post-curing. This high-temperature stage promotes the resin to complete the full cross-linking reaction, achieving high degree of curing and glass transition temperature, thereby obtaining high mechanical strength, thermal stability, and long-term reliability. The appropriate post-curing time ensures that the resin inside samples of different thicknesses can also be completely cured. Therefore, this segmented curing process improves the resin's wetting process of the skeleton and the formation of the final cured network, which is a guarantee for obtaining composite materials with complete internal structure and uniform and stable performance.

[0023] Secondly, this application provides an insulating and thermally conductive composite material with a three-dimensional thermally conductive skeleton, employing the following technical solution: An insulating and thermally conductive composite material with a three-dimensional thermally conductive framework includes a polymer matrix and a three-dimensional thermally conductive framework distributed therein; the three-dimensional thermally conductive framework is composed of surface-modified hexagonal boron nitride and copper nanowires; the filler volume fraction in the composite material is 5%~20%, and the thermal conductivity is ≥1.35 W·m. -1 ·K -1 Volume resistivity > 10 9 Ω·cm.

[0024] By employing the above technical solution, a continuous three-dimensional interpenetrating network framework composed of surface-modified hexagonal boron nitride and copper nanowires is pre-constructed in the composite material. This framework forms an efficient phonon transport pathway within the material. The insulating hexagonal boron nitride sheets form the main body of the framework, providing basic thermal conductivity and insulation properties. The copper nanowires modified with silane coupling agents bridge the boron nitride sheets, reducing the contact thermal resistance between the sheets and enhancing the network connectivity. The surface-modified layer ensures the bonding between the filler and the epoxy resin matrix, reducing interfacial thermal resistance. When the total filler content is 5% to 20%, this pre-constructed three-dimensional continuous network structure can improve the thermal conductivity of the composite material, making its thermal conductivity reach or exceed 1.35 W·m. -1 ·K -1 The thermal conductivity is higher than that of composite materials prepared by blending; at the same time, the insulating boron nitride and the surface modified layer isolate the direct electrical contact between copper nanowires, ensuring the extremely high insulation of the composite material; therefore, this composite material achieves a synergistic improvement in thermal conductivity and insulation performance with low filler content.

[0025] Preferred applications of insulating and thermally conductive composite materials with a three-dimensional thermally conductive framework in electronic packaging thermal management systems, thermal interface materials, or high-frequency copper-clad laminates.

[0026] By adopting the above technical solutions, this composite material possesses high planar and spatial thermal conductivity, excellent electrical insulation, good mechanical strength, and a thermal expansion coefficient similar to that of electronic components. In electronic packaging thermal management systems, it can be used for components such as packaging shells and heat sinks to efficiently dissipate heat generated by chips, ensuring device reliability. As a thermal interface material, it can be filled between the heat source and the heat sink to reduce contact thermal resistance and improve heat dissipation efficiency; its high insulation avoids short-circuit risks. When used as the insulating dielectric layer in high-frequency copper-clad laminates, its high thermal conductivity helps dissipate Joule heat generated during signal transmission, reducing dielectric loss; its high insulation and low dielectric constant meet the electrical performance requirements of high-frequency signal transmission. Therefore, this composite material can meet the comprehensive performance requirements of modern high-performance electronic equipment for heat dissipation and insulation, and has clear application value in the aforementioned fields.

[0027] In summary, this application has the following beneficial effects: 1. This invention uses a freeze-drying-self-assembly physical process to construct a three-dimensional skeleton, avoiding the high energy consumption required by high-temperature carbonization or in-situ growth processes. This allows the preparation process to be completed at a lower temperature, thereby reducing energy consumption and equipment costs. The process is gentle, energy-saving, environmentally friendly, and easy to industrialize.

[0028] 2. This invention uses freeze-drying for direct molding, avoiding the electrical conductivity risks caused by organic template carbonization. At the same time, it utilizes an insulating silane coupling agent modified layer and a boron nitride sheet layer to effectively encapsulate and isolate trace amounts of copper nanowires, effectively blocking electronic pathways while establishing phonon pathways, thereby improving thermal conductivity and volume resistivity, and ultimately enhancing the insulation performance of the composite material.

[0029] 3. This invention utilizes copper nanowires to connect two-dimensional boron nitride and constructs a directional 3D thermally conductive network in a polymer matrix, thereby reducing interfacial thermal resistance and ensuring high structural controllability; thus, it can achieve the effect of improving the thermal conductivity of the composite material while maintaining high dielectric properties with a lower filler content. Attached Figure Description

[0030] Figure 1 This is a process flow diagram for preparing the insulating and thermally conductive composite material according to the present invention; Figure 2 The images show SEM images of the surface morphology of the 3D-(CuNWs / hBNs) / EP thermally conductive composite materials prepared in Examples 1-5 of this invention. The figures are labeled as follows: (a) Example 1; (b) Example 2; (c) Example 3; (d) Example 4; (e) Example 5. Figure 3 The images show cross-sectional SEM images of the 3D-(CuNWs / hBNs) / EP thermally conductive composite materials prepared in Examples 1-5 of this invention. The figures are labeled as follows: (a) Example 1; (b) Example 2; (c) Example 3; (d) Example 4; (e) Example 5. Detailed Implementation

[0031] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0032] The chemical reagents used in the embodiments of this invention are all commercially available analytical grade products and can be used without further purification. In the embodiments of this invention, specific reagents were selected for testing to verify the feasibility of the technical solution, but the scope of protection of this invention is not limited to the following specific models: Epoxy resin: Various electronic-grade epoxy resins can be used in this invention. In the examples, bisphenol A type epoxy resin (E-51) is preferred, but E-44, bisphenol F type epoxy resin, etc. can also be used as substitutes.

[0033] Silane coupling agent: designed to improve the compatibility between inorganic fillers and organic matrix. In the examples, silane coupling agent KH550 (γ-aminopropyltriethoxysilane) containing amino groups is preferred. Those skilled in the art can also select KH560, KH570, etc. for equivalent substitution according to the resin type.

[0034] Binder: Sodium carboxymethyl cellulose (CMC-Na) was selected in the examples, but it can also be replaced with other water-soluble polymers that can assist in molding, such as polyvinyl alcohol (PVA).

[0035] The following examples all use E-51 epoxy resin, KH550 coupling agent, and CMC-Na binder as examples for detailed description. To facilitate the description of subsequent examples, the preparation method of the modified filler will be explained in a unified manner first.

[0036] 1. Preparation of modified hexagonal boron nitride (hBNs-KH550) A mixed solvent was prepared by mixing 10 mL of deionized water and 50 mL of ethanol. 2.5% (by weight) of hexagonal boron nitride (hBNs) silane coupling agent KH550 and 1 mL of dilute hydrochloric acid were added to the mixed solvent. After sonication for 15 min, the mixture was magnetically stirred at 55 °C for 4 h to hydrolyze KH550. Subsequently, 0.5 g of hBNs was added, and magnetic stirring continued for another 4 h. After the reaction was complete, the dispersion was filtered under vacuum and washed repeatedly with deionized water until the pH of the filtrate was approximately 7. The product was dried in a vacuum oven at 90 °C for 5 h and then cooled to room temperature to obtain surface-modified hexagonal boron nitride (hBNs-KH550).

[0037] 2. Synthesis of Copper Nanowires (CuNWs) 75 g of sodium hydroxide was dissolved in 125 mL of deionized water, followed by the addition of 0.1225 g of copper hydroxide and an appropriate amount of ethylenediamine. The mixture was stirred in a water bath at 83 °C until a uniform, transparent blue solution was formed. A suitable amount of 35% hydrazine hydrate solution was added dropwise under a nitrogen atmosphere. After stirring for 3 min, stirring was stopped and the nitrogen atmosphere was turned off, maintaining the reaction at 83 °C for a period of time. After the reaction was complete, the solid product suspended in the upper layer of the solution was collected. The product was ultrasonically dispersed and centrifuged with deionized water and ethanol until the pH value was approximately 7. It was then dried under vacuum at 60 °C for 10 h to obtain copper nanowires (CuNWs).

[0038] 3. Preparation of modified copper nanowires (CuNWs-KH550) In a mixed solution of 10 mL distilled water and 50 mL ethanol, 2.5% KH550 (by mass of copper nanowires) and 1 mL HCl (10 mol / L) were added. After sonication for 10 min, the mixture was magnetically stirred at 60 °C for 4 h to hydrolyze the nanowires. Subsequently, 0.2 g of the prepared copper nanowires were dispersed in the hydrolyzed mixture, sonicated for 2 h, and stirred for another 4 h. After the reaction was complete, the nanowires were repeatedly washed and filtered with anhydrous ethanol to remove residual KH550. Finally, the product was placed in a vacuum oven and dried at 60 °C for 12 h to obtain surface-modified copper nanowires (CuNWs-KH550).

[0039] This invention provides multiple embodiments, the main difference being the different mass ratios of copper nanowires and boron nitride in the thermally conductive framework, as detailed below: Example 1: See Appendix Figure 1 A method for preparing a 3D-(CuNWs / hBNs) / EP thermally conductive composite material includes the following steps: (1) Preparation of dispersion: Weigh the hBNs-KH550 and CuNWs-KH550 prepared above, and disperse them evenly in deionized water at a mass ratio of CuNWs:hBNs=1:5. First, stir magnetically for 1 h, then sonicate for 2 h, and finally mix and stir for 2 h.

[0040] (2) Adding binder: Add CMC-Na to the above mixed dispersion at a rate of 2.3% of the total mass of the fillers (hBNs-KH550 and CuNWs-KH550). Stir magnetically at room temperature for 3 h.

[0041] (3) 3D skeleton construction: The mixed dispersion was filtered and shaped by vacuum filtration to obtain a wet skeleton that supports each other; then the wet skeleton was freeze-dried for 12 h to obtain a dry 3D-(CuNWs / hBNs) thermally conductive skeleton.

[0042] (4) Resin impregnation and curing: E-51 epoxy resin, methyltetrahydrophthalic anhydride and triethanolamine are mixed evenly at a mass ratio of 20:16:0.1 to prepare an epoxy resin mixture. The epoxy resin mixture is filled into the skeleton obtained in step (3) by vacuum impregnation and impregnated for 2 h.

[0043] (5) Curing and molding: The impregnated material is placed in an oven and pre-cured at 90°C for 2 h, and then the temperature is raised to 160°C for 4 h. After natural cooling, the 3D-(CuNWs / hBNs) / EP thermally conductive composite material is obtained.

[0044] Example 2: A method for preparing a 3D-(CuNWs / hBNs) / EP thermally conductive composite material, comprising the following steps: (1) Preparation of dispersion: Weigh the hBNs-KH550 and CuNWs-KH550 prepared above, and disperse them evenly in deionized water at a mass ratio of CuNWs:hBNs=1:5. First, stir magnetically for 1 h, then sonicate for 2 h, and finally mix and stir for 2 h.

[0045] (2) Adding binder: Add CMC-Na to the above mixed dispersion at a rate of 5% of the total mass of the fillers (hBNs-KH550 and CuNWs-KH550). Stir magnetically at room temperature for 3 h.

[0046] (3) 3D skeleton construction: The mixed dispersion was filtered and shaped by vacuum filtration to obtain a wet skeleton that supports each other; then the wet skeleton was freeze-dried for 12 h to obtain a dry 3D-(CuNWs / hBNs) thermally conductive skeleton.

[0047] (4) Resin impregnation and curing: E-51 epoxy resin, methyltetrahydrophthalic anhydride and triethanolamine are mixed evenly at a mass ratio of 20:16:0.1 to prepare an epoxy resin mixture. The epoxy resin mixture is filled into the skeleton obtained in step (3) by vacuum impregnation and impregnated for 2 h.

[0048] (5) Curing and molding: The impregnated material is placed in an oven and pre-cured at 90°C for 2 h, and then the temperature is raised to 160°C for 4 h. After natural cooling, the 3D-(CuNWs / hBNs) / EP thermally conductive composite material is obtained.

[0049] Example 3: A method for preparing a 3D-(CuNWs / hBNs) / EP thermally conductive composite material, comprising the following steps: (1) Preparation of dispersion: Weigh the hBNs-KH550 and CuNWs-KH550 prepared above, and disperse them evenly in deionized water at a mass ratio of CuNWs:hBNs=1:5. First, stir magnetically for 1 h, then sonicate for 2 h, and finally mix and stir for 2 h.

[0050] (2) Adding binder: Add CMC-Na to the above mixed dispersion at a rate of 2.3% of the total mass of the fillers (hBNs-KH550 and CuNWs-KH550). Stir magnetically at room temperature for 3 h.

[0051] (3) 3D skeleton construction: The mixed dispersion was filtered and shaped by vacuum filtration to obtain a wet skeleton that supports each other; then the wet skeleton was freeze-dried for 24 h to obtain a dry 3D-(CuNWs / hBNs) thermally conductive skeleton.

[0052] (4) Resin impregnation and curing: E-51 epoxy resin, methyltetrahydrophthalic anhydride and triethanolamine are mixed evenly at a mass ratio of 20:16:0.1 to prepare an epoxy resin mixture. The epoxy resin mixture is filled into the skeleton obtained in step (3) by vacuum impregnation and impregnated for 2 h.

[0053] (5) Curing and molding: The impregnated material is placed in an oven and pre-cured at 90°C for 2 h, and then the temperature is raised to 160°C for 4 h. After natural cooling, the 3D-(CuNWs / hBNs) / EP thermally conductive composite material is obtained.

[0054] Example 4: A method for preparing a 3D-(CuNWs / hBNs) / EP thermally conductive composite material, comprising the following steps: (1) Preparation of dispersion: Weigh the hBNs-KH550 and CuNWs-KH550 prepared above, and disperse them evenly in deionized water according to the mass ratio of CuNWs:hBNs=4:5. First, stir magnetically for 1 h, then sonicate for 2 h, and finally mix and stir for 2 h.

[0055] (2) Adding binder: Add CMC-Na to the above mixed dispersion at a rate of 2.3% of the total mass of the fillers (hBNs-KH550 and CuNWs-KH550). Stir magnetically at room temperature for 3 h.

[0056] (3) 3D skeleton construction: The mixed dispersion was filtered and shaped by vacuum filtration to obtain a wet skeleton that supports each other; then the wet skeleton was freeze-dried for 12 h to obtain a dry 3D-(CuNWs / hBNs) thermally conductive skeleton.

[0057] (4) Resin impregnation and curing: E-51 epoxy resin, methyltetrahydrophthalic anhydride and triethanolamine are mixed evenly at a mass ratio of 20:16:0.1 to prepare an epoxy resin mixture. The epoxy resin mixture is filled into the skeleton obtained in step (3) by vacuum impregnation and impregnated for 2 h.

[0058] (5) Curing and molding: The impregnated material is placed in an oven and pre-cured at 90°C for 2 h, and then the temperature is raised to 160°C for 4 h. After natural cooling, the 3D-(CuNWs / hBNs) / EP thermally conductive composite material is obtained.

[0059] According to the experimental results, the composite material has good thermal conductivity and maintains high insulation at this ratio.

[0060] Example 5: A method for preparing a 3D-(CuNWs / hBNs) / EP thermally conductive composite material, comprising the following steps: (1) Preparation of dispersion: Weigh the hBNs-KH550 and CuNWs-KH550 prepared above, and disperse them evenly in deionized water according to the mass ratio of CuNWs:hBNs=5:5. First, stir magnetically for 1 h, then sonicate for 2 h, and finally mix and stir for 2 h.

[0061] (2) Adding binder: Add CMC-Na to the above mixed dispersion at a rate of 2.3% of the total mass of the fillers (hBNs-KH550 and CuNWs-KH550). Stir magnetically at room temperature for 3 h.

[0062] (3) 3D skeleton construction: The mixed dispersion was filtered and shaped by vacuum filtration to obtain a wet skeleton that supports each other; then the wet skeleton was freeze-dried for 12 h to obtain a dry 3D-(CuNWs / hBNs) thermally conductive skeleton.

[0063] (4) Resin impregnation and curing: E-51 epoxy resin, methyltetrahydrophthalic anhydride and triethanolamine are mixed evenly at a mass ratio of 20:16:0.1 to prepare an epoxy resin mixture. The epoxy resin mixture is filled into the skeleton obtained in step (3) by vacuum impregnation and impregnated for 2 h.

[0064] (5) Curing and molding: The impregnated material is placed in an oven and pre-cured at 90°C for 2 h, and then the temperature is raised to 160°C for 4 h. After natural cooling, the 3D-(CuNWs / hBNs) / EP thermally conductive composite material is obtained.

[0065] The composite materials prepared in Examples 1-5 above were subjected to performance tests, and the test methods are as follows: The thermal diffusivity was determined using the laser flare method (LFA), and the thermal conductivity was calculated by combining density and specific heat capacity. The volume resistivity was tested using a high insulation resistance meter. The dielectric constant and dielectric loss were tested using a dielectric spectrometer. The thermal decomposition temperature was tested using a thermogravimetric analyzer (TGA) under a nitrogen atmosphere.

[0066] The properties of the insulating and thermally conductive composite materials obtained in Examples 1-5 are shown in Table 1 below: Table 1: Summary of Performance Test Results of Examples ; Test results show that the composite material prepared in Example 4 has the best overall performance, with a thermal conductivity of 1.55 W·m. -1 ·K -1 It has a thermal diffusivity of 1.32 and a volume resistivity higher than 10. 9 Ω·cm, achieving synergistic optimization of high thermal conductivity and electrical insulation. Comparative Example 1: Without adding any thermally conductive fillers or dispersants, pure epoxy resin E-51, curing agent, and accelerator were mixed and cured in the same proportions; the resulting material had a thermal conductivity of 0.19 W·m. -1 ·K -1 The dielectric constant is 7.06 and the dielectric loss is 0.025.

[0067] Comparative Example 2: The raw material ratio was the same as in Example 4, except for the preparation process: the modified boron nitride and copper nanowires were added to an epoxy resin mixture, mechanically stirred at room temperature until homogeneous, and then cast and cured under vacuum without freeze-drying to construct the three-dimensional framework; the resulting material had a thermal conductivity of 0.65 W·m. -1 ·K-1 This indicates that disordered packing cannot form an efficient heat conduction path, confirming the necessity of constructing a three-dimensional heat conduction framework in this invention.

[0068] Comparative Example 3: The preparation method was the same as in Example 4, except that copper nanowires were not added, and boron nitride of the same mass fraction was used to construct the framework; the thermal conductivity of the resulting material was 0.82 W·m. -1 ·K -1 Furthermore, it is relatively brittle in mechanical properties; this indicates that copper nanowires act as a bridge between boron nitrides, effectively reducing interfacial thermal resistance.

[0069] Example 1 Conclusion: Observation Appendix Figure 2 and attached Figure 3 Compared with Comparative Examples 1-3, the thermal conductivity of Examples 1-5 of the present invention is significantly improved, and they have smaller dielectric constants and dielectric losses, indicating that the composite material of the present invention has excellent thermal conductivity, while also possessing high dielectric properties and stability.

[0070] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing an insulating and thermally conductive composite material with a three-dimensional thermally conductive framework, characterized in that, Includes the following steps: S1. Surface modification of fillers: Hexagonal boron nitride and copper nanowires were modified with silane coupling agents to obtain modified boron nitride and modified copper nanowires. S2, Three-dimensional framework construction: The modified boron nitride and modified copper nanowires obtained in S1 are dispersed in a solvent, a water-soluble polymer binder is added and mixed evenly, and a wet framework is formed by filtration. Then, a three-dimensional porous thermally conductive framework is obtained by freeze-drying. S3. Resin composite curing: Prepare an epoxy resin mixture, fill the pores of the three-dimensional porous thermally conductive skeleton obtained in S2 with the epoxy resin mixture by vacuum impregnation, and cure to obtain the insulating and thermally conductive composite material.

2. The method for preparing an insulating and thermally conductive composite material with a three-dimensional thermally conductive framework according to claim 1, characterized in that, In step S1, the silane coupling agent is selected from at least one of amino-based silane coupling agents, epoxy-based silane coupling agents, or vinyl-based silane coupling agents.

3. The method for preparing an insulating and thermally conductive composite material with a three-dimensional thermally conductive framework according to claim 1, characterized in that, The preferred silane coupling agent is γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, or N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

4. The method for preparing an insulating and thermally conductive composite material with a three-dimensional thermally conductive framework according to claim 1, characterized in that, In step S1, the mass ratio of the modified copper nanowires to the modified boron nitride is 1:10 to 1:

1.

5. The method for preparing an insulating and thermally conductive composite material with a three-dimensional thermally conductive framework according to claim 1, characterized in that, In step S2, the water-soluble polymer binder is selected from at least one of sodium carboxymethyl cellulose, polyvinyl alcohol, polyvinylpyrrolidone, or sodium alginate; the amount of water-soluble polymer binder added is 0.5% to 8% of the total mass of the filler.

6. The method for preparing an insulating and thermally conductive composite material with a three-dimensional thermally conductive framework according to claim 1, characterized in that, In step S2, the specific conditions for the freeze-drying process are: pre-freezing at -80℃ to -20℃ for 1 to 5 hours, followed by drying under a vacuum of less than 20 Pa for 12 to 48 hours.

7. The method for preparing an insulating and thermally conductive composite material with a three-dimensional thermally conductive framework according to claim 1, characterized in that, In step S3, the epoxy resin mixture consists of epoxy resin, an anhydride curing agent, and an accelerator; wherein the epoxy resin is selected from one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, or alicyclic epoxy resin.

8. The method for preparing an insulating and thermally conductive composite material with a three-dimensional thermally conductive framework according to claim 1, characterized in that, In step S3, the curing process is a segmented curing process, which includes: pre-curing at 80℃~100℃ for 1~3 hours, followed by curing at 150℃~180℃ for 2~6 hours.

9. An insulating and thermally conductive composite material with a three-dimensional thermally conductive framework, characterized in that, A method for preparing an insulating and thermally conductive composite material with a three-dimensional thermally conductive framework as described in any one of claims 1-8, comprising a polymer matrix and a three-dimensional thermally conductive framework distributed therein; the three-dimensional thermally conductive framework is composed of surface-modified hexagonal boron nitride and copper nanowires; the filler volume fraction in the composite material is 5%~20%, and the thermal conductivity is ≥1.35 W·m. -1 ·K -1 Volume resistivity > 10 9 Ω·cm.

10. The use of the insulating and thermally conductive composite material with a three-dimensional thermally conductive skeleton as described in claim 9 in electronic packaging thermal management systems, thermal interface materials, or high-frequency copper-clad laminates.

Images