Nanofiber-reinforced polytetrafluoroethylene-based copper-clad plate as well as preparation method and application thereof

Abstract

The invention discloses a nanofiber-reinforced polytetrafluoroethylene-based copper-clad plate as well as a preparation method and application thereof, and relates to the technical field of copper-clad plates. Comprising a metal layer, a nanofiber layer and a bonding layer. According to the copper-clad plate, the nanofiber layer is arranged, and a three-dimensional interconnected nanofiber network structure formed by boron nitride and polytetrafluoroethylene in the nanofiber layer forms a continuous heat conduction path, so that the overall heat conductivity coefficient of the copper-clad plate is remarkably improved, and meanwhile, the problem that a traditional granular filler is easy to agglomerate in a glue solution is avoided; therefore, the heat-conducting property of the copper-clad plate is improved, and the good dielectric property of the copper-clad plate is maintained. In addition, the bonding layer serves as a transition interface between the metal layer and the nanofiber layer, the thermal expansion coefficient matching performance between the metal layer and the nanofiber layer can be effectively improved, and the layering risk caused by thermal stress accumulation is reduced. According to the copper-clad plate provided by the invention, collaborative optimization of heat-conducting property and mechanical bonding property is realized, and the problem that high heat-conducting property, low dielectric loss and high peel strength are difficult to consider in a traditional copper-clad plate is solved.

Description

Technical Field

[0001] This invention relates to the field of copper clad laminate technology, and more specifically, to a nanofiber reinforced polytetrafluoroethylene copper clad laminate, its preparation method, and its application. Background Technology

[0002] With the rapid development of 5G communication, millimeter-wave radar, high-power radio frequency equipment, and aerospace electronic equipment, high-frequency copper-clad laminates (CCLs), as a key basic material, face increasingly stringent performance requirements. In high-speed, high-frequency applications, CCLs must simultaneously possess low dielectric loss, a stable dielectric constant, excellent thermal conductivity, and good mechanical reliability. Polytetrafluoroethylene (PTFE), due to its extremely low dielectric loss and stable dielectric constant, has become the preferred matrix resin material in the field of high-frequency CCLs. However, PTFE itself has inherent defects such as insufficient thermal conductivity and a relatively high coefficient of thermal expansion. This leads to heat accumulation under high-temperature, high-power operating environments, severely affecting signal transmission quality and equipment lifespan.

[0003] To improve the performance defects of PTFE materials, existing technologies commonly employ the method of modifying PTFE by introducing thermally conductive materials. However, these methods have significant limitations in practical applications: thermally conductive materials are prone to agglomeration in the resin matrix, which not only reduces the expected thermal conductivity enhancement effect but also negatively impacts the dielectric properties and mechanical strength of the product. Particularly in copper-clad laminate (CCL) applications, the introduction of thermally conductive materials often leads to a significant decrease in the peel strength between the substrate and the copper foil. Furthermore, some thermally conductive materials possess electrical conductivity, potentially impairing the insulation properties of the substrate. Therefore, current CCL products struggle to simultaneously achieve high thermal conductivity, low dielectric loss, and strong mechanical bonding, which is one of the reasons limiting the development of high-performance CCLs.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a nanofiber-reinforced polytetrafluoroethylene copper-clad laminate, its preparation method, and its application.

[0006] This invention is implemented as follows: In a first aspect, the present invention provides a nanofiber-reinforced polytetrafluoroethylene vinyl clad copper plate, comprising a metal layer, a nanofiber layer and an adhesive layer; both the metal layer and the adhesive layer are two layers, the nanofiber layer is located between the two adhesive layers, and the metal layer is disposed on the surface of the adhesive layer away from the nanofiber layer.

[0007] The nanofiber layer comprises a three-dimensional interconnected nanofiber network structure composed of boron nitride and polytetrafluoroethylene.

[0008] The adhesive layer consists of inorganic fillers, auxiliary additives, and polytetrafluoroethylene.

[0009] In a second aspect, the present invention provides a method for preparing a copper-clad laminate as described in any of the foregoing embodiments, comprising: mixing a boron nitride dispersion and a polytetrafluoroethylene adhesive and then electrospinning the mixture to obtain a nanofiber layer; mixing the adhesive layer material with water to obtain a mixed adhesive solution; preparing the mixed adhesive solution into a wet film; and then heat-treating the wet film to obtain an adhesive layer; and then pressing the nanofiber layer, the adhesive layer, and the metal layer together to form a laminate.

[0010] Thirdly, the present invention provides the application of a copper-clad laminate as described in any of the foregoing embodiments or a copper-clad laminate prepared by any of the foregoing embodiments in electronic devices.

[0011] The present invention has the following beneficial effects: This invention provides a nanofiber-reinforced polytetrafluoroethylene (PTFE) vinyl clad laminate, its preparation method, and its applications. By incorporating a nanofiber layer, a three-dimensional interconnected nanofiber network structure composed of boron nitride and PTFE forms a continuous thermally conductive pathway, significantly improving the overall thermal conductivity of the copper-clad laminate. Furthermore, the boron nitride is uniformly dispersed in the PTFE matrix in nanofiber form, avoiding the problem of easy agglomeration of traditional particulate fillers in the adhesive, thus maintaining good dielectric properties while improving thermal conductivity. In addition, the adhesive layer, as the transition interface between the metal layer and the nanofiber layer, effectively improves the matching of their thermal expansion coefficients, reducing the risk of delamination due to thermal stress accumulation. The copper-clad laminate provided by this invention, through its multi-layer structure and functional design of each layer, achieves synergistic optimization of thermal conductivity and mechanical bonding performance, overcoming the technical challenge of traditional copper-clad laminates that struggle to simultaneously achieve high thermal conductivity, low dielectric loss, and high peel strength. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0013] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0014] In a first aspect, the present invention provides a nanofiber-reinforced polytetrafluoroethylene vinyl clad copper plate, comprising a metal layer, a nanofiber layer and an adhesive layer; both the metal layer and the adhesive layer are two layers, the nanofiber layer is located between the two adhesive layers, and the metal layer is disposed on the surface of the adhesive layer away from the nanofiber layer.

[0015] Therefore, it can be understood that the copper-clad laminate provided by the present invention has a five-layer structure, which consists of an upper metal layer, an upper adhesive layer, a nanofiber layer, a lower adhesive layer, and a lower metal layer from top to bottom.

[0016] The metal layer is copper foil, which can be made of existing materials, such as rolled copper foil or electrolytic copper.

[0017] The nanofiber layer comprises a three-dimensional interconnected nanofiber network structure composed of boron nitride and polytetrafluoroethylene (PTFE).

[0018] The three-dimensional interconnected nanofiber network structure composed of boron nitride and polytetrafluoroethylene in the nanofiber layer forms a continuous thermal conductivity pathway, significantly improving the overall thermal conductivity of the copper clad laminate. Furthermore, the boron nitride is uniformly dispersed in the polytetrafluoroethylene matrix in the form of nanofibers, avoiding the problem of easy agglomeration of traditional particulate fillers in the adhesive, thus maintaining good dielectric properties while improving thermal conductivity.

[0019] Furthermore, to improve the peel strength of the copper clad laminate, an adhesive layer is provided between the nanofiber layer and the metal layer. The adhesive layer is made of inorganic fillers, auxiliary additives, and polytetrafluoroethylene (PTFE). By selecting the materials of the adhesive layer, the matching of the coefficients of thermal expansion between the nanofiber layer and the metal layer can be effectively improved, reducing the risk of delamination caused by thermal stress accumulation, thereby improving the interlayer peel strength of the copper clad laminate.

[0020] The copper-clad laminate provided by this invention achieves synergistic optimization of thermal conductivity and mechanical bonding performance through a multi-layer structure and functional design of each layer, overcoming the technical challenge of traditional copper-clad laminates that are difficult to balance high thermal conductivity, low dielectric loss and high peel strength.

[0021] In an optional embodiment, the mass ratio of boron nitride to polytetrafluoroethylene in the nanofiber layer is 1:2 to 3. By controlling the mass ratio of boron nitride to polytetrafluoroethylene in the nanofiber layer within the above range, a good balance between the thermal conductivity and dielectric properties of the copper clad laminate can be achieved.

[0022] When the mass ratio of boron nitride to polytetrafluoroethylene is too high, the amount of boron nitride added is too large, which can easily affect its dispersibility in the polytetrafluoroethylene body, causing agglomeration and sedimentation. This makes it difficult to form a uniform and continuous three-dimensional interconnected nanofiber network structure, thereby reducing the overall thermal conductivity of the material and potentially causing an increase in dielectric loss.

[0023] When the mass ratio of boron nitride to polytetrafluoroethylene is too low, the amount of boron nitride is insufficient, and a sufficient thermal conductivity path cannot be constructed, resulting in a significant decrease in the thermal conductivity of the copper-clad laminate. At the same time, an excessively high relative content of polytetrafluoroethylene will increase the coefficient of thermal expansion of the material, which is not conducive to dimensional stability under high-temperature operating conditions.

[0024] Therefore, by controlling the mass ratio of boron nitride to polytetrafluoroethylene in the nanofiber layer within a reasonable range, it is possible to ensure that boron nitride is effectively distributed in the matrix in the form of fibers, maintaining good film formation and structural integrity, while also giving full play to the high thermal conductivity of boron nitride, improving the overall heat dissipation capacity of the copper clad laminate, and maintaining the inherent low dielectric loss advantage of polytetrafluoroethylene, thereby obtaining a composite structure with excellent thermal conductivity, stable dielectric properties and good processability.

[0025] Preferably, the boron nitride particle size is 100-200 nm to ensure the formation of a three-dimensional interconnected nanofiber network structure. If the boron nitride particle size is too small, the specific surface area of ​​the particles will increase significantly, making it easy for agglomeration to occur and making it difficult to form a structurally complete three-dimensional interconnected nanofiber network structure; while if the boron nitride particle size is too large, it will be difficult to form a nanoscale fiber network, affecting the thermal conductivity of the nanofiber layer.

[0026] Preferably, the thickness of the nanofiber layer is 100~500 μm. By controlling the thickness of the nanofiber layer within the above range, excellent thermal management and structural durability can be achieved without affecting processing performance.

[0027] When the nanofiber layer is too thin, the effective volume of the three-dimensional interconnected nanofiber network structure is reduced, resulting in insufficient thermal conductivity density. This makes it difficult to fully utilize the high thermal conductivity of boron nitride, thus limiting the improvement of the overall thermal conductivity of the copper clad laminate. On the other hand, if the nanofiber layer is too thick, it will increase the processing difficulty and may also exacerbate the thermal expansion mismatch problem of the copper clad laminate layers, inducing warping or delamination during temperature cycling.

[0028] In an optional embodiment, the mass ratio of inorganic filler, polytetrafluoroethylene (PTFE), and auxiliary additives in the adhesive layer material is 15-25:30-60:0.5-5. The auxiliary additives include coupling agents and thickeners; therefore, in an optional embodiment, the mass ratio of inorganic filler, PTFE, coupling agent, and thickener in the adhesive layer material is 15-25:30-60:0.5-3:0.5-2. By controlling the proportions of each material in the adhesive layer within the above ranges, synergistic optimization of the adhesive layer's peel strength, thermal expansion matching, dielectric properties, and film-forming processability can be achieved.

[0029] In an optional embodiment, the inorganic filler includes at least one selected from silicon dioxide, titanium dioxide, diamond, aluminum nitride, aluminum oxide, graphene oxide, silicon nitride, and magnesium oxide. By selecting the above-mentioned raw materials as inorganic fillers to fill the polytetrafluoroethylene body of the adhesive layer, the thermal expansion coefficient matching, dielectric properties, and mechanical strength of the adhesive layer can be effectively improved.

[0030] Due to the significant difference in thermal expansion coefficients between the metal layer and the polytetrafluoroethylene body, interfacial stress is easily generated during temperature changes, leading to delamination or warping. The aforementioned inorganic filler has a relatively low thermal expansion coefficient. After being uniformly dispersed in the polytetrafluoroethylene body, it can adjust the overall thermal expansion behavior of the composite material, reduce thermal mismatch with the metal layer, and thus improve the structural stability of the copper clad laminate under thermal cycling conditions.

[0031] Furthermore, the inorganic filler material selected in this invention has good insulation properties and a moderate dielectric constant, which can improve the polarization stability of the material system without significantly increasing dielectric loss, and helps maintain the signal integrity of the copper-clad laminate in high-frequency working environments.

[0032] Some fillers, such as diamond, aluminum nitride, and silicon nitride, also have high thermal conductivity, which can form local thermal conduction pathways within the adhesive layer, assisting in the transfer of heat from the metal layer to the nanofiber layer and further optimizing the overall thermal management performance.

[0033] Meanwhile, the presence of these inorganic fillers can also enhance the modulus and cohesive strength of the adhesive layer. During the preparation process, such as the high-temperature pressing process, these inorganic fillers work synergistically with polytetrafluoroethylene to improve the interlayer bonding force, thereby ensuring the high peel strength of the copper clad laminate.

[0034] To further improve the overall thermal conductivity of the copper clad laminate based on the aforementioned embodiments, short nanofibers obtained by mechanical shearing of the nanofiber layer material can be added to the adhesive layer material.

[0035] Since the nanofiber layer is one of the key thermally conductive structures of the copper-clad laminate provided by this invention, the nano-boron nitride filled inside it has excellent thermal conductivity. By mechanically shearing the material of the nanofiber layer to obtain short nanofibers, and then adding the short nanofibers to the adhesive layer material, the thermal conductivity of the adhesive layer can be effectively improved. Both the adhesive layer and the nanofiber layer have the same nanofiber network structure. During the lamination process of the copper-clad laminate, the three-dimensional interconnected nanofiber network structure of adjacent adhesive layers and nanofiber layers achieves partial docking or physical overlap, forming a cross-interface thermal bridge, thereby reducing the interlayer thermal resistance and promoting the efficient transfer of heat from the metal layer through the adhesive layer to the nanofiber layer, which helps to improve the overall thermal conductivity of the copper-clad laminate.

[0036] On the other hand, both the nanofiber layer and the adhesive layer have the same nanofiber network structure, which ensures the structural continuity of the nanofiber layer and the adhesive layer, realizes the intrinsic consistency and functional synergy of the material system, further optimizes the performance matching and interface fusion between the multilayer structures of the copper clad laminate, and improves the peel strength of the copper clad laminate.

[0037] In an optional embodiment, the mass of the nanofibers is 10-20% of the total mass of the adhesive layer material, which imparts a certain nano-thermal conductive network to the adhesive layer while ensuring the dielectric and anti-peel properties of the adhesive layer.

[0038] Preferably, the length of the nanofibers is ≤200μm. When the length of the nanofibers is too long, it can easily lead to entanglement or uneven orientation of the adhesive layer material during subsequent processing, affecting the rheological properties and film uniformity of the adhesive layer material. At the same time, it may form stress concentration points in local areas, weakening the interlayer bonding strength. Therefore, it is more appropriate to control the length of the nanofibers within the above-mentioned range.

[0039] In an optional embodiment, the coupling agent includes at least one of a silane coupling agent and a phthalate coupling agent.

[0040] In an optional embodiment, the thickener includes at least one of hydroxyethyl cellulose, polyvinylpyrrolidone, and fumed silica.

[0041] By adding coupling agents and thickeners, the coating performance of the adhesive layer material can be adjusted, ensuring a smooth structure and uniform dispersion of the raw materials.

[0042] In a second aspect, the present invention provides a method for preparing a copper-clad laminate as described in any of the foregoing embodiments, comprising: mixing a boron nitride dispersion and a polytetrafluoroethylene adhesive and then electrospinning the mixture to obtain a nanofiber layer; mixing the adhesive layer material with water to obtain a mixed adhesive solution; preparing the mixed adhesive solution into a wet film; and then heat-treating the wet film to obtain an adhesive layer; and then pressing the nanofiber layer, the adhesive layer, and the metal layer together to form a laminate.

[0043] By electrospinning a mixture of boron nitride dispersion and polytetrafluoroethylene (PTFE) adhesive, a nanofiber layer can be obtained, enabling the construction of a three-dimensional interconnected nanofiber network structure composed of boron nitride and PTFE at the nanoscale. This structure forms a continuous and dense thermal conductivity pathway in the thickness direction, significantly improving the overall thermal conductivity of the copper clad laminate, while avoiding the problem of decreased thermal conductivity caused by the agglomeration of traditional particulate fillers.

[0044] However, due to the uneven surface morphology of the nanofiber layer formed by electrospinning and its significant performance differences from the metal layer, an adhesive layer needs to be prepared between the nanofiber layer and the metal layer. The adhesive layer material is mixed with water to obtain a mixed adhesive solution, which is then used to prepare a wet film. The wet film is then heat-treated to obtain an adhesive layer with excellent interfacial bonding capabilities. This process effectively controls the uniform distribution of each component in the adhesive layer, achieving initial densification of the polytetrafluoroethylene (PTFE) while removing moisture, ensuring good flowability and wettability during subsequent pressing to enhance the bonding strength with adjacent layers.

[0045] Finally, the nanofiber layer, adhesive layer, and metal layer are stacked and then pressed together to form a copper-clad laminate. This allows the functional layers to achieve tight fusion under high temperature and pressure conditions. The polytetrafluoroethylene (PTFE) in its molten state permeates into the interlayer micropores and fiber gaps, further eliminating interface defects and improving structural density and integrity. This preparation method, by forming different functional layers stepwise and then pressing them together to form a copper-clad laminate, ensures that the high thermal conductivity of the nanofiber layer is fully preserved, while also achieving a strong connection between the adhesive layer and the metal layer and the nanofiber layer. Thus, without sacrificing dielectric properties, a high-performance copper-clad laminate product with high thermal conductivity, low dielectric loss, and high peel strength is obtained.

[0046] In an optional embodiment, the method for preparing copper-clad laminate provided by the present invention includes the following steps: S01. A boron nitride dispersion and a polytetrafluoroethylene (PTFE) adhesive are mixed and then electrospun to obtain a nanofiber layer. This method utilizes electrospinning technology to stretch the mixed solution into ultrafine fibers under an electric field. Solvent evaporation then forms a composite nanofiber membrane of boron nitride coated with PTFE, allowing boron nitride to be stably distributed in the matrix in a fibrous form. This effectively avoids the agglomeration phenomenon caused by excessively high filler concentration in traditional blending processes.

[0047] The nanofiber layer formed by electrospinning has a high specific surface area and pore connectivity, and can retain part of the fiber network structure during subsequent lamination, which is conducive to establishing an efficient heat conduction path in the thickness direction, thereby significantly improving the overall thermal conductivity of the copper clad laminate. At the same time, since polytetrafluoroethylene exists in the fiber as a continuous phase, its excellent dielectric properties are maintained and do not deteriorate significantly due to the introduction of fillers, ensuring the low dielectric loss characteristics of the material under high-frequency applications.

[0048] In an optional embodiment, the mass ratio of boron nitride solid to polytetrafluoroethylene liquid in the boron nitride dispersion is 1:4~6, so as to ensure the fiber-forming performance of the nanofiber layer while achieving synergistic optimization of thermal conductivity and dielectric properties.

[0049] When the relative content of PTFE adhesive is too low, the insufficient polymer concentration in the system leads to a decrease in solution viscosity during electrospinning, making it difficult to form a continuous and uniform fiber structure. This results in bead-like defects or breakage, affecting the integrity and density of the nanofiber layer. Conversely, when the proportion of PTFE adhesive is too high, although it is beneficial for fiber formation, it significantly reduces the boron nitride filling concentration, leading to insufficient thermally conductive filler density in the three-dimensional interconnected nanofiber network structure. This weakens its thermal conductivity in the thickness direction, thus limiting the improvement of the overall thermal conductivity of the copper-clad laminate. Furthermore, excessively high PTFE content also increases the coefficient of thermal expansion of the material, which is detrimental to thermal matching with the metal layer.

[0050] Preferably, the preparation of the boron nitride dispersion includes dispersing boron nitride in an aqueous solution of a silane coupling agent.

[0051] The silane coupling agent in the aqueous solution has a mass percentage of 0.5% to 2% to facilitate the dispersion of boron nitride and its mixing with polytetrafluoroethylene. The silane coupling agent is selected from at least one of KH-550, APTES, KH-560, and GPTMS.

[0052] Preferably, in the boron nitride dispersion, the mass ratio of boron nitride to silane coupling agent is 30~100:1.

[0053] Preferably, the mass percentage of polytetrafluoroethylene in the polytetrafluoroethylene adhesive is 50-60%, more preferably 55%, to facilitate mixing with boron nitride.

[0054] Preferably, the process parameters for electrospinning include: a feed rate of 0.45~0.8 mL / h for the electrospinning equipment, a drum rotation speed of 300~500 r / min, and an applied voltage of 18~25 kV.

[0055] S02. Mix the adhesive layer material with water to obtain a mixed adhesive solution, prepare the mixed adhesive solution into a wet film, and then heat-treat the wet film to obtain the adhesive layer.

[0056] In an optional embodiment, the mass percentage of each raw material in the mixed adhesive is as follows: nano-short fibers: 10-20%, inorganic fillers: 15-25%, polytetrafluoroethylene adhesive: 30-60%, coupling agent: 0.5-3%, thickener: 0.5-2%, and water: 10-30%; the mass concentration of polytetrafluoroethylene in the polytetrafluoroethylene adhesive is 50-60%.

[0057] Preferably, the thickness of the wet film is 100~300μm. Controlling the thickness of the wet film within a suitable range is beneficial for achieving a stable coating process and uniform component distribution. It also allows for sufficient solvent removal and fusion of the polytetrafluoroethylene particles during subsequent heat treatment, forming a dense, continuous adhesive layer with excellent interfacial wettability. This ensures that the adhesive layer flows appropriately during the pressing process to fill the interfacial gaps, enhancing the physical anchoring effect with the metal layer and nanofiber layer. As a result, the interlayer bonding strength and structural stability are significantly improved without affecting the thermal conductivity.

[0058] Preferably, the heat treatment parameters include: a heat treatment temperature of 250~400℃ and a heat treatment time of 15~60min. The heat treatment process can employ conventional drying and sintering processes, as long as the adhesive layer material can be uniformly cured.

[0059] S03. After stacking the nanofiber layer, adhesive layer and metal layer, compress them into shape.

[0060] Preferably, the compression molding can be carried out using existing conventional processes, such as vacuum high-temperature compression molding, with a pressure of 300~600psi, a temperature of 330~380℃, and a compression time of 60~240min.

[0061] Thirdly, the present invention provides the application of a copper-clad laminate as described in any of the foregoing embodiments or a copper-clad laminate prepared by any of the foregoing embodiments in electronic devices.

[0062] Example 1 This embodiment provides a nanofiber-reinforced polytetrafluoroethylene (PTFE) clad copper board, comprising a metal layer, a nanofiber layer, and an adhesive layer. Both the metal layer and the adhesive layer are two layers. Therefore, the clad copper board provided in this embodiment has a total of five layers, which are, from top to bottom, an upper metal layer, an upper adhesive layer, a nanofiber layer, a lower adhesive layer, and a lower metal layer.

[0063] The metal layer is made of copper foil; each copper foil layer is 12 μm thick.

[0064] The nanofiber layer comprises a three-dimensional interconnected nanofiber network structure composed of boron nitride and polytetrafluoroethylene (PTFE); the thickness of the nanofiber layer is 300 μm.

[0065] The adhesive layer consists of inorganic fillers, auxiliary additives, polytetrafluoroethylene, and short nanofibers obtained by mechanical shearing the material from the nanofiber layer; each adhesive layer is 50 μm thick.

[0066] This embodiment also provides a method for preparing the above-mentioned copper-clad laminate, including the following steps: S01. Disperse boron nitride particles and silane coupling agent KH-550 in an aqueous solution. The proportion of silane coupling agent is 0.5 wt%, the particle size of boron nitride is 100 nm, and the mass ratio of boron nitride particles to silane coupling agent is 100:1 to obtain a boron nitride dispersion.

[0067] Boron nitride and 55% polytetrafluoroethylene adhesive were mixed at a weight ratio of 1:5 and then electrospun. The feed rate of the electrospinning equipment was 0.6 mL / h, the drum speed was 400 r / min, and the applied voltage was 22 kV. The nanofiber layer was obtained by electrospinning.

[0068] S02. Take a portion of the nanofiber layer obtained in step S01 and mechanically shear it to obtain short nanofibers with a length of 50 μm.

[0069] The raw materials were mixed evenly according to the following mass percentages: nano-short fiber: 15%, silica: 20%, 55wt% polytetrafluoroethylene adhesive: 45%, KH-550: 2%, hydroxyethyl cellulose: 1%, and deionized water: 17%, to obtain a mixed adhesive.

[0070] A 100 μm wet film was prepared by coating the mixed adhesive solution. The wet film was then dried and sintered at 350 °C for 15 min to obtain the adhesive layer.

[0071] S03. The nanofiber layer obtained in step S01, the adhesive layer obtained in step S02, and the copper foil are stacked in a structure of "upper metal layer, upper adhesive layer, nanofiber layer, lower adhesive layer, and lower metal layer", and then pressed together under a pressure of 300 psi, a temperature of 330 °C, and a time of 60 min.

[0072] Example 2 This embodiment provides a nanofiber-reinforced polytetrafluoroethylene (PTFE) clad copper board, comprising a metal layer, a nanofiber layer, and an adhesive layer. Both the metal layer and the adhesive layer are two layers. Therefore, the clad copper board provided in this embodiment has a total of five layers, which are, from top to bottom, an upper metal layer, an upper adhesive layer, a nanofiber layer, a lower adhesive layer, and a lower metal layer.

[0073] The metal layer is made of copper foil; each copper foil layer is 18 μm thick.

[0074] The nanofiber layer comprises a three-dimensional interconnected nanofiber network structure composed of boron nitride and polytetrafluoroethylene (PTFE); the thickness of the nanofiber layer is 100 μm.

[0075] The adhesive layer is made of inorganic fillers, auxiliary additives, polytetrafluoroethylene, and short nanofibers obtained by mechanical shearing the material of the nanofiber layer; the thickness of each adhesive layer is 100 μm.

[0076] This embodiment also provides a method for preparing the above-mentioned copper-clad laminate, including the following steps: S01. Disperse boron nitride particles and silane coupling agent KH-550 in an aqueous solution. The proportion of silane coupling agent is 0.7 wt%, the particle size of boron nitride is 100 nm, and the mass ratio of boron nitride particles to silane coupling agent is 70:1 to obtain a boron nitride dispersion.

[0077] Boron nitride and 55% polytetrafluoroethylene adhesive were mixed at a weight ratio of 1:4 and then electrospun. The feed rate of the electrospinning equipment was 0.45 mL / h, the drum speed was 300 r / min, and the applied voltage was 18 kV. The nanofiber layer was obtained by electrospinning.

[0078] S02. Take a portion of the nanofiber layer obtained in step S01 and mechanically shear it to obtain short nanofibers with a length of 100 μm.

[0079] The raw materials were mixed evenly according to the following mass percentages: nano-short fiber: 10%, silica: 15%, 55wt% polytetrafluoroethylene adhesive: 44%, KH-550: 0.5%, hydroxyethyl cellulose: 0.5%, and deionized water: 30%, to obtain a mixed adhesive.

[0080] A 150 μm wet film was prepared by coating the mixed adhesive solution. The wet film was then dried and sintered at 375 °C for 45 min to obtain the adhesive layer.

[0081] S03. The nanofiber layer obtained in step S01, the adhesive layer obtained in step S02, and the copper foil are stacked in a structure of "upper metal layer, upper adhesive layer, nanofiber layer, lower adhesive layer, and lower metal layer", and then pressed together under a pressure of 450 psi, a temperature of 350 °C, and a time of 150 min.

[0082] Example 3 This embodiment provides a nanofiber-reinforced polytetrafluoroethylene (PTFE) clad copper board, comprising a metal layer, a nanofiber layer, and an adhesive layer. Both the metal layer and the adhesive layer are two layers. Therefore, the clad copper board provided in this embodiment has a total of five layers, which are, from top to bottom, an upper metal layer, an upper adhesive layer, a nanofiber layer, a lower adhesive layer, and a lower metal layer.

[0083] The metal layer is made of copper foil; each copper foil layer is 35 μm thick.

[0084] The nanofiber layer comprises a three-dimensional interconnected nanofiber network structure composed of boron nitride and polytetrafluoroethylene (PTFE); the thickness of the nanofiber layer is 500 μm.

[0085] The adhesive layer is made of inorganic fillers, auxiliary additives, polytetrafluoroethylene, and short nanofibers obtained by mechanical shearing the material of the nanofiber layer; the thickness of each adhesive layer is 200 μm.

[0086] This embodiment also provides a method for preparing the above-mentioned copper-clad laminate, including the following steps: S01. Disperse boron nitride particles and silane coupling agent KH-550 in an aqueous solution. The silane coupling agent accounts for 1 wt%, the boron nitride particle size is 200 nm, and the mass ratio of boron nitride particles to silane coupling agent is 50:1 to obtain a boron nitride dispersion.

[0087] Boron nitride and 55% polytetrafluoroethylene adhesive were mixed at a weight ratio of 1:6 and then electrospun. The feed rate of the electrospinning equipment was 0.8 mL / h, the drum speed was 500 r / min, and the applied voltage was 25 kV. The nanofiber layer was obtained by electrospinning.

[0088] S02. Take a portion of the nanofiber layer obtained in step S01 and mechanically shear it to obtain short nanofibers with a length of 200 μm.

[0089] The raw materials were mixed evenly according to the following mass percentages: nano-short fiber: 20%, silica: 25%, 55wt% polytetrafluoroethylene adhesive: 40%, KH-550: 3%, hydroxyethyl cellulose: 2%, and deionized water: 10%, to obtain a mixed adhesive.

[0090] A 200 μm wet film was prepared by coating the mixed adhesive solution. The wet film was then dried and sintered at 400℃ for 60 min to obtain the adhesive layer.

[0091] S03. The nanofiber layer obtained in step S01, the adhesive layer obtained in step S02, and the copper foil are stacked in a structure of "upper metal layer, upper adhesive layer, nanofiber layer, lower adhesive layer, and lower metal layer", and then pressed together under the conditions of 600 psi pressure, 380 ℃ temperature, and 240 min time.

[0092] Comparative Example 1 This comparative example provides a nanofiber-reinforced polytetrafluoroethylene (PTFE) clad copper plate and its preparation method. The structure of the clad copper plate is the same as that in Example 1, the only difference being the preparation method, as detailed below: In step S01 of this comparative example, the boron nitride dispersion and polytetrafluoroethylene adhesive were mixed at a volume ratio of 1:2 and then electrospun.

[0093] Comparative Example 2 This comparative example provides a nanofiber-reinforced polytetrafluoroethylene (PTFE) clad copper plate and its preparation method. The structure of the clad copper plate is the same as that in Example 1, the only difference being the preparation method, as detailed below: In step S01 of this comparative example, the boron nitride dispersion and polytetrafluoroethylene adhesive were mixed at a volume ratio of 1:6 and then electrospun.

[0094] Comparative Example 3 This comparative example provides a nanofiber-reinforced polytetrafluoroethylene (PTFE) clad copper plate and its preparation method. The structure of the clad copper plate is the same as that in Example 1, except that the boron nitride used has a particle size of 50 nm.

[0095] Comparative Example 4 This comparative example provides a nanofiber-reinforced polytetrafluoroethylene (PTFE) clad copper plate and its preparation method. The structure of the clad copper plate is the same as that in Example 1, except that the boron nitride used has a particle size of 500 nm.

[0096] Comparative Example 5 This comparative example provides a nanofiber-reinforced polytetrafluoroethylene (PTFE) clad copper plate and its preparation method. The structure of the clad copper plate is the same as that in Example 1, except that in step S02, the materials of the mixed adhesive liquid, by mass percentage, include nanofibers: 5%, silica: 20%, 55wt% PTFE adhesive liquid: 45%, KH-550: 2%, hydroxyethyl cellulose: 1%, and deionized water: 27%.

[0097] Comparative Example 6 This comparative example provides a nanofiber-reinforced polytetrafluoroethylene (PTFE) clad copper plate and its preparation method. The structure of the clad copper plate is the same as that in Example 1, except that in step S02, the materials of the mixed adhesive liquid, by mass percentage, include nanofibers: 30%, silica: 20%, 55wt% PTFE adhesive liquid: 45%, KH-550: 2%, hydroxyethyl cellulose: 1%, and deionized water: 2%.

[0098] Comparative Example 7 This comparative example provides a nanofiber-reinforced polytetrafluoroethylene (PTFE) clad copper plate and its preparation method. The structure of the clad copper plate is similar to that of Example 1, except that it has no nanofiber layer and the adhesive layer is a single layer.

[0099] That is, the copper-clad laminate provided in this comparative example has a three-layer structure, consisting of an upper metal layer, an adhesive layer, and a lower metal layer from top to bottom. The materials of the adhesive layer and the metal layer are the same as those in Example 1.

[0100] Comparative Example 8 This comparative example provides a nanofiber-reinforced polytetrafluoroethylene (PTFE) clad copper plate and its preparation method. The structure of the clad copper plate is similar to that of Example 1, except that there is no adhesive layer.

[0101] That is, the copper-clad laminate provided in this comparative example has a three-layer structure, consisting of an upper metal layer, a nanofiber layer, and a lower metal layer from top to bottom. The materials of the nanofiber layer and the metal layer are the same as those in Example 1.

[0102] Comparative Example 9 This comparative example provides a nanofiber-reinforced polytetrafluoroethylene (PTFE) clad copper plate and its preparation method. The structure of the clad copper plate is similar to that of Example 1, except that in the preparation method, step S01 does not use electrospinning. Instead, boron nitride, inorganic filler, PTFE, coupling agent, thickener, and deionized water are directly mixed evenly in the same amounts as in Example 1, coated, and dried to obtain an insulating substrate. Then, the substrate is laminated with an upper metal layer, an insulating substrate, and a lower metal layer.

[0103] Comparative Example 10 This comparative example provides a nanofiber-reinforced polytetrafluoroethylene (PTFE) clad copper plate and its preparation method. The structure of the clad copper plate is similar to that of Example 1, except that the insulating substrate of Comparative Example 9 is used instead of the adhesive layer.

[0104] That is, the structure of the copper clad laminate provided in this comparative example is: an upper metal layer, an upper insulating substrate, a nanofiber layer, a lower insulating substrate, and a lower metal layer.

[0105] Comparative Example 11 This comparative example provides a nanofiber-reinforced polytetrafluoroethylene (PTFE) clad copper plate and its preparation method. The structure of the clad copper plate is the same as that in Example 1, except that in step S02, the materials of the mixed adhesive liquid, by mass percentage, include nanofibers: 15%, silica: 5%, 55wt% PTFE adhesive liquid: 45%, KH-550: 2%, hydroxyethyl cellulose: 1%, and deionized water: 32%.

[0106] Comparative Example 12 This comparative example provides a nanofiber-reinforced polytetrafluoroethylene (PTFE) clad copper plate and its preparation method. The structure of the clad copper plate is the same as that in Example 1, except that in step S02, the materials of the mixed adhesive liquid, by mass percentage, include nanofibers: 15%, silica: 35%, 55wt% PTFE adhesive liquid: 45%, KH-550: 2%, hydroxyethyl cellulose: 1%, and deionized water: 2%.

[0107] Experimental Example 1 The copper-clad laminates provided in Examples 1-3 and Comparative Examples 1-12 were subjected to performance tests, and the results are shown in Table 1.

[0108] The thermal conductivity was tested using the ASTM D5470 method; the peel strength was tested using the IPC-TM-650 2.4.9 method; the coefficient of thermal expansion was tested using the IPC-TM-650 2.4.24.5 method; and the dielectric loss was tested using the IEC 61189-2-721:2015 method.

[0109] Table 1 Performance of Copper Clad Laminates

[0110] As shown in Table 1, the nanofiber-reinforced polytetrafluoroethylene (PTFE) clad copper laminate provided in this embodiment of the invention exhibits high thermal conductivity, strong peel strength, low coefficient of thermal expansion, and low dielectric loss. This indicates that the clad copper laminate and its preparation method provided by this invention can significantly improve the problem of easy agglomeration of boron nitride during direct mixing with PTFE, which affects the thermal conductivity and electrical properties of the clad copper laminate. The short nanofibers in the adhesive layer and the dense nanofiber network in the nanofiber layer form a 3D network structure, which is beneficial for heat conduction on both sides and in the middle of the clad copper laminate, thus improving the overall thermal conductivity. Simultaneously, the temperature used in the lamination process is higher than the melting point of PTFE but lower than the melting point of boron nitride, allowing the PTFE in the adhesive layer and the nanofiber layer to melt and flow and connect with each other, thereby improving the bonding strength between the adhesive layer and the nanofiber layer.

[0111] In Comparative Example 1, the increased amount of boron nitride resulted in the mixed adhesive solution easily agglomerating and settling, making it impossible to obtain a nanofiber layer through electrospinning. Therefore, no further processing was performed. In Comparative Example 2, the reduced amount of boron nitride led to a significant decrease in the thermal conductivity of the copper-clad laminate, an increase in the coefficient of thermal expansion, an increase in dielectric loss, and a decline in the overall performance of the copper-clad laminate.

[0112] In Comparative Example 3, the small particle size of boron nitride caused a sudden increase in the viscosity of the mixed adhesive, and agglomeration also occurred, making electrospinning impossible. Therefore, no further processing was carried out. In Comparative Example 4, the larger particle size of boron nitride resulted in a larger fiber diameter in the nanofiber layer, and the fiber morphology was also more uneven, leading to a decrease in the overall performance of the copper clad laminate.

[0113] Comparative Example 5 reduced the amount of short nanofibers added to the adhesive layer, resulting in decreased thermal conductivity, increased coefficient of thermal expansion, increased dielectric loss, and overall deterioration of the copper clad laminate (CCL). Comparative Example 6 increased the amount of short nanofibers added, leading to a sharp decrease in peel strength and an excessively low coefficient of thermal expansion, resulting in poor overall performance of the CCL. This may be due to the agglomeration of excessive boron nitride.

[0114] Comparative Example 7 omitted the nanofiber layer, resulting in a decrease in thermal conductivity and an increase in dielectric loss, leading to poor performance of the copper-clad laminate. Comparative Example 8 omitted the adhesive layer, resulting in a significant deterioration in peel strength and thermal expansion properties, poor adhesion between the nanofiber layer and the copper foil, and unsatisfactory performance of the copper-clad laminate.

[0115] Comparative Example 9 did not use electrospinning to prepare the nanofiber layer. Instead, the raw materials were directly mixed in proportion and then coated to prepare the insulating substrate. The copper-clad laminate obtained by Comparative Example 9 had significantly worse performance than that of Example 1. This indicates that the boron nitride with the three-dimensional nanofiber structure provided by the present invention can significantly improve the thermal conductivity of the copper-clad laminate without having a significant negative impact on the peel strength, thermal expansion coefficient and dielectric loss of the copper-clad laminate.

[0116] Comparative Example 10 uses the insulating substrate of Comparative Example 9 to replace the adhesive layer. The performance of Comparative Example 9 is slightly improved, but it is still far from the effect of Example 1. This shows that the boron nitride of the three-dimensional nanofiber structure provided by the present invention can be interconnected to form a network structure after high-temperature pressing, thereby improving the overall thermal conductivity.

[0117] Comparative Example 11 reduced the amount of inorganic filler added, resulting in a significant increase in the coefficient of thermal expansion and dielectric loss of the copper-clad laminate, while the peel strength decreased substantially. This is because the inorganic filler can improve the peel strength, coefficient of thermal expansion, and dielectric loss of the copper-clad laminate. Comparative Example 12 increased the amount of inorganic filler added, resulting in a significant decrease in both the thermal conductivity and peel strength of the copper-clad laminate, while the dielectric loss increased substantially. This is because a large amount of inorganic filler agglomerates and becomes unevenly dispersed, leading to a decrease in overall performance.

[0118] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A nanofiber-reinforced polytetrafluoroethylene (PTFE) clad copper board, characterized in that, It includes a metal layer, a nanofiber layer, and an adhesive layer; both the metal layer and the adhesive layer are two layers, the nanofiber layer is located between the two adhesive layers, and the metal layer is disposed on the surface of the adhesive layer away from the nanofiber layer; The nanofiber layer comprises a three-dimensional interconnected nanofiber network structure composed of boron nitride and polytetrafluoroethylene. The adhesive layer is made of inorganic fillers, auxiliary additives, and polytetrafluoroethylene.

2. The copper-clad laminate according to claim 1, characterized in that, In the nanofiber layer, the mass ratio of boron nitride to polytetrafluoroethylene is 1:2~3; And / or, the boron nitride has a particle size of 100~200 nm; And / or, the thickness of the nanofiber layer is 100~500μm.

3. The copper-clad laminate according to claim 1, characterized in that, The adhesive layer material also includes short nanofibers obtained by mechanical shearing the material of the nanofiber layer. The mass of the nanofibers is 10-20% of the total mass of the adhesive layer material; The length of the nanofibers is ≤200μm.

4. The copper-clad laminate according to claim 1 or 3, characterized in that, In the adhesive layer material, the mass ratio of the inorganic filler, the polytetrafluoroethylene, and the auxiliary additives is 15~25:30~60:0.5~5.

5. The copper-clad laminate according to claim 1, characterized in that, The inorganic filler includes at least one of silicon dioxide, titanium dioxide, diamond, aluminum nitride, aluminum oxide, graphene oxide, silicon nitride, and magnesium oxide. And / or, the auxiliary additives include coupling agents and thickeners; the coupling agents include at least one of silane coupling agents and phthalate coupling agents; the thickeners include at least one of hydroxyethyl cellulose, polyvinylpyrrolidone, and fumed silica.

6. A method for preparing a copper-clad laminate as described in any one of claims 1 to 5, characterized in that, The process includes electrospinning a mixture of boron nitride dispersion and polytetrafluoroethylene adhesive to obtain the nanofiber layer; mixing the adhesive layer material with water to obtain a mixed adhesive solution; preparing the mixed adhesive solution into a wet film; and then heat-treating the wet film to obtain the adhesive layer; and finally pressing the nanofiber layer, the adhesive layer, and the metal layer together to form the adhesive layer.

7. The preparation method according to claim 6, characterized in that, The weight ratio of solid boron nitride to polytetrafluoroethylene adhesive in the boron nitride dispersion is 1:4~6; And / or, the process parameters of the electrospinning include: the feed rate of the electrospinning equipment is 0.45~0.8mL / h, the roller speed is 300~500r / min, and the applied voltage is 18~25kV.

8. The preparation method according to claim 7, characterized in that, The preparation of the boron nitride dispersion includes dispersing boron nitride in an aqueous solution of a silane coupling agent; The mass percentage of silane coupling agent in the aqueous solution is 0.5% to 2%. In the boron nitride dispersion, the mass ratio of boron nitride to the silane coupling agent is 30~100:1; The polytetrafluoroethylene adhesive contains 50-60% polytetrafluoroethylene by mass.

9. The preparation method according to claim 6, characterized in that, The mass percentages of each raw material in the mixed adhesive are as follows: nano-short fibers: 10-20%, inorganic fillers: 15-25%, polytetrafluoroethylene adhesive: 30-60%, coupling agent: 0.5-3%, thickener: 0.5-2%, and water: 10-30%; the mass concentration of polytetrafluoroethylene in the polytetrafluoroethylene adhesive is 50-60%. And / or, the thickness of the wet film is 100~300μm; And / or, the parameters of the heat treatment include: heat treatment temperature of 250~400℃ and heat treatment time of 15~60min.

10. The application of a copper-clad laminate as described in any one of claims 1 to 5 or a copper-clad laminate prepared by any one of claims 6 to 9 in an electronic device.

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