Composite filler, interlayer prepreg, copper-clad plate and preparation method and application of copper-clad plate

Abstract

The invention discloses a composite filler, an interlayer prepreg, a copper-clad plate and a preparation method and application of the copper-clad plate, and belongs to the technical field of copper-clad plates. The preparation method of the composite filler comprises the following steps: dispersing hexagonal boron nitride nanosheets in a Piranha solution for reaction to obtain surface hydroxylated BNNS; the preparation method comprises the following steps: dispersing Ni-Zn ferrite nanoparticles in nitric acid, and carrying out ultrasonic treatment to obtain activated Ni-Zn ferrite; and carrying out electrostatic self-assembly on the activated Ni-Zn ferrite and the surface hydroxylated BNNS. The Ni-Zn ferrite is a low-magnetic material, so that the dielectric constant and dielectric loss of the copper-clad plate can be reduced, and the copper-clad plate can have relatively high heat conductivity coefficient and relatively low dielectric constant and dielectric loss. The composite filler can form boron nitride nanosheets which are vertically arranged under the condition of a vertical magnetic field, and heat can be quickly transferred to the outside of the surface from the inside of the copper-clad plate, so that the heat is transferred to the external environment, and the problem of heat accumulation of the 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 composite filler, an intermediate layer prepreg, a copper clad laminate, and their preparation methods and applications. Background Technology

[0002] With the rapid development of 5G communication, artificial intelligence, and the Internet of Things, high-frequency and high-speed copper-clad laminates, as a core material for electronic devices, are facing performance challenges. In the millimeter-wave band, signal transmission is particularly sensitive to the dielectric properties of the material, requiring a high dielectric constant (Dk). k Stable and dielectric loss (D) f Extremely low thermal conductivity. Meanwhile, as chip power density continues to increase, the thermal conductivity of traditional PTFE copper-clad laminates is insufficient to meet the demands for good heat dissipation.

[0003] The current technological bottleneck in the industry mainly stems from the interrelationships between material properties. There is a fundamental conflict between improving thermal conductivity and maintaining excellent dielectric properties: high thermal conductivity fillers (such as graphene and carbon nanotubes) often lead to increased dielectric loss while enhancing heat dissipation; while low dielectric fillers (such as SiO2), although beneficial for signal transmission, struggle to meet the ever-increasing heat dissipation demands. Furthermore, the introduction of fillers presents challenges to dielectric uniformity; randomly distributed fillers can cause material anisotropy, leading to signal integrity issues during high-frequency signal transmission. This trade-off between multiple performance indicators makes it difficult for traditional copper-clad laminate materials to simultaneously meet the requirements of high frequency, high speed, and efficient heat dissipation, urgently necessitating the development of novel composite materials or innovative structural designs to overcome existing limitations.

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

[0005] The purpose of this invention is to provide a composite filler, an intermediate layer prepreg, a copper-clad laminate, and their preparation methods and applications, so as to solve or improve the above-mentioned technical problems.

[0006] This invention can be implemented as follows: In a first aspect, the present invention provides a composite packing material, the preparation method of which includes the following steps: Hexagonal boron nitride nanosheets (BNNS) were dispersed in Piranha solution and reacted to obtain surface-hydroxylated BNNS; Ni-Zn ferrite nanoparticles were dispersed in nitric acid and ultrasonically treated to obtain activated Ni-Zn ferrite. The activated Ni-Zn ferrite was electrostatically self-assembled with surface-hydroxylated BNNS.

[0007] In an optional embodiment, the preparation of surface-hydroxylated BNNS includes at least one of the following characteristics: Feature 1: The particle size of the hexagonal boron nitride nanosheets is 0.5 μm to 2 μm; Feature 2: The Piranha solution consists of concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 3:1 to 5:1; Feature 3: The reaction is carried out at 75℃~85℃ for 10min~30min.

[0008] In an optional embodiment, the preparation of the activated Ni-Zn ferrite includes at least one of the following characteristics: Feature 4: The particle size of Ni-Zn ferrite nanoparticles is 25nm~35nm; Feature 5: The concentration of nitric acid is 0.1 mol / L to 0.15 mol / L; Feature 6: Ultrasound time is 15 min to 25 min.

[0009] In an optional embodiment, electrostatic self-assembly includes: dispersing surface-hydroxylated BNNS in a buffer solution to form a suspension; adding activated Ni-Zn ferrite dropwise into the suspension, followed by the addition of NaCl for reaction.

[0010] In an optional implementation, electrostatic self-assembly includes at least one of the following features: Feature 7: The buffer solution is an acetate buffer solution with a pH of 4.8~5.2; Feature 8: Dropping rate is 0.8 mL / min to 1.2 mL / min; Feature 9: The mass ratio of surface-hydroxylated BNNS to activated Ni-Zn ferrite is 10:1 to 30:1, preferably 15:1 to 25:1; Feature 10: The concentration of NaCl in the suspension is 1 mol / L to 3 mol / L; Feature 11: The reaction is carried out at 32℃~38℃ and 450rpm~550rpm for 55min~65min.

[0011] Secondly, the present invention provides an intermediate layer semi-cured sheet, which is obtained by coating a first slurry into a film, followed by drying and sintering; wherein the first slurry includes polytetrafluoroethylene (PTFE) and the composite filler of the aforementioned embodiments, and a vertical magnetic field is applied during the sintering process.

[0012] In an optional embodiment, the mass of the composite filler is 10% to 60% of the mass of PTFE.

[0013] In an optional embodiment, the total mass of the composite filler and PTFE is 60% to 70% of the mass of the first slurry.

[0014] In an optional embodiment, the slurry further includes a dispersant and a thickener.

[0015] In an optional embodiment, the drying temperature is 70°C to 150°C.

[0016] In an optional embodiment, the sintering temperature is 375°C to 385°C.

[0017] In an optional embodiment, the magnetic induction intensity of the vertical magnetic field is 0.05T~0.15T, preferably 0.085T.

[0018] Thirdly, the present invention provides a copper-clad laminate, which includes a first copper foil, a first adhesive layer, an intermediate layer, a second adhesive layer, and a second copper foil; The intermediate layer is formed from the intermediate layer semi-cured sheet of the aforementioned embodiment.

[0019] In an optional embodiment, the copper-clad laminate has at least one of the following characteristics: Feature 12: The thickness of the first copper foil and the second copper foil are independently 35 μm; Feature 13: The thicknesses of the first adhesive layer and the second adhesive layer are independently 50 μm to 100 μm; Feature 14: The thickness of the intermediate layer is 200μm~300μm; Feature 15: The thermal conductivity of the copper clad laminate is not less than 5.1 W / (m·K); Feature 16: The peel strength of the copper clad laminate is not less than 1.3 N / mm; Feature 17: The dielectric constant of the copper clad laminate does not exceed 3.85 / 10GHz; Feature 18: The dielectric loss of the copper clad laminate does not exceed 0.00085 / 10GHz; Feature 19: The coefficient of thermal expansion of the copper clad laminate does not exceed 49ppm / K.

[0020] Fourthly, the present invention provides a method for preparing a copper-clad laminate as described in the foregoing embodiments, comprising the following steps: sequentially stacking a first copper foil, a first adhesive layer prepreg, an intermediate layer prepreg, a second adhesive layer prepreg, and a second copper foil, followed by vacuum hot pressing.

[0021] In an optional embodiment, the adhesive layer semi-cured sheet is obtained by coating a second slurry into a film and then drying and sintering it; wherein the second slurry includes PTFE, BN nanowires, and BNNS modified with a fluorinated silane coupling agent.

[0022] In an optional embodiment, the mass ratio of fluorinated silane coupling agent modified BNNS (boron nitride nanosheets) to BN nanowires (boron nitride nanowires) is 2:1 to 4:1.

[0023] In an optional embodiment, the total mass of BN nanowires and BNNS modified with fluorinated silane coupling agent is 5% to 45% of the mass of PTFE.

[0024] In an optional embodiment, the total mass of BN nanowires and BNNS modified with fluorinated silane coupling agent is 60% to 70% of the mass of the second slurry.

[0025] In an optional embodiment, the drying temperature is 70°C to 150°C.

[0026] In an optional embodiment, the sintering temperature is 375°C to 385°C.

[0027] In an optional embodiment, vacuum hot pressing is performed at 280°C to 320°C and 8MPa to 12MPa for 40 to 60 minutes.

[0028] In an optional embodiment, vacuum hot pressing is performed at 320°C and 10 MPa for 60 minutes.

[0029] Fifthly, the present invention provides an electronic device comprising the copper-clad laminate of the foregoing embodiments.

[0030] The beneficial effects of this invention include: The Ni-Zn ferrite in the composite filler provided by this invention is a low-magnetic material, which helps to reduce the dielectric constant and dielectric loss of the copper-clad laminate, enabling the copper-clad laminate to have a high thermal conductivity and low dielectric constant and dielectric loss. Under a vertical magnetic field, the composite filler can form vertically aligned boron nitride nanosheets, which can rapidly transfer heat from the inside of the copper-clad laminate to the outside, thus transferring heat to the external environment and solving the problem of heat accumulation in copper-clad laminates.

[0031] The copper-clad laminate provided by this invention has a vertical BNNS@Ni-Zn thermal conductive path and a horizontal BNNS / BN nanowire thermal conductive network, i.e., it has a dual thermal conductive path. Low-loss vertical thermal conductive path is achieved by modifying BNNS with Ni-Zn ferrite; a highly efficient horizontal thermal conductive network is constructed using a BNNS / BN nanowire hybrid system. This copper-clad laminate exhibits both good thermal conductivity and dielectric properties, and also has high interfacial peel strength. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram illustrating the heat dissipation from the accumulated heat source inside the copper-clad laminate provided by the present invention to the outside surface. Detailed Implementation

[0034] 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.

[0035] The following is a detailed description of the composite filler, intermediate layer prepreg, copper clad laminate, their preparation methods, and applications provided by this invention.

[0036] This invention provides a method for preparing a composite filler, comprising the following steps: S1: Hexagonal boron nitride nanosheets were dispersed in Piranha solution and reacted to obtain surface-hydroxylated BNNS (denoted as "BNNS-OH").

[0037] In some alternative embodiments, the particle size of the hexagonal boron nitride nanosheets can be 0.5 μm to 2 μm, such as 0.5 μm, 1 μm, 1.5 μm or 2 μm, or other values ​​in the range of 0.5 μm to 2 μm.

[0038] In some alternative embodiments, the Piranha solution comprises concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 3:1 to 5:1 (e.g., 3:1, 3.5:1, 4:1, 4.5:1, or 5:1, etc.).

[0039] In some alternative embodiments, the reaction of hexagonal boron nitride nanosheets with Piranha solution can be carried out at 75°C to 85°C (e.g., 75°C, 80°C, or 85°C) for 10 min to 30 min (e.g., 10 min, 15 min, 20 min, 25 min, or 30 min). Preferably, the reaction of hexagonal boron nitride nanosheets with Piranha solution is carried out at 80°C for 10 min to 30 min.

[0040] After the reaction is complete, the mixture is centrifuged and washed until neutral, then dried for later use.

[0041] S2: Ni-Zn ferrite nanoparticles were dispersed in nitric acid and ultrasonically treated to obtain activated Ni-Zn ferrite.

[0042] In some alternative embodiments, the particle size of Ni-Zn ferrite nanoparticles can be 25nm~35nm, such as 25nm, 30nm or 35nm, or other values ​​in the range of 25nm~35nm.

[0043] In some alternative embodiments, the concentration of nitric acid can be 0.1 mol / L to 0.15 mol / L, such as 0.1 mol / L or 0.15 mol / L, or other values ​​within the range of 0.1 mol / L to 0.15 mol / L.

[0044] In some alternative implementations, the ultrasound time can be 15 min to 25 min, such as 15 min, 20 min or 25 min, or other values ​​within the range of 15 min to 25 min.

[0045] After ultrasonic treatment, the sample is washed with water until neutral, and then immediately dispersed in ultrapure water for later use.

[0046] S3: Electrostatic self-assembly of activated Ni-Zn ferrite with surface-hydroxylated BNNS.

[0047] In some alternative embodiments, electrostatic self-assembly may include: dispersing surface-hydroxylated BNNS in a buffer solution to form a suspension; adding activated Ni-Zn ferrite dropwise into the suspension, followed by the addition of NaCl for reaction.

[0048] The buffer solution can be, for example, an acetate buffer with a pH of 4.8–5.2 (e.g., 4.8, 4.9, 5.0, 5.1, or 5.2). A suspension is formed by dispersing surface-hydroxylated BNNS in the buffer solution and sonicating for approximately 30 minutes.

[0049] The dropping rate can be from 0.8 mL / min to 1.2 mL / min, such as 0.8 mL / min, 1 mL / min, or 1.2 mL / min, or other values ​​within the range of 0.8 mL / min to 1.2 mL / min. During the dropping process, the suspension is stirred at a speed of 190 rpm to 210 rpm.

[0050] The mass ratio of surface-hydroxylated BNNS to activated Ni-Zn ferrite can be from 10:1 to 30:1, such as 10:1, 15:1, 20:1, 25:1, or 30:1, or other values ​​within the range of 10:1 to 30:1. In some preferred embodiments, the mass ratio of surface-hydroxylated BNNS to activated Ni-Zn ferrite is from 15:1 to 25:1.

[0051] The concentration of NaCl in the suspension can be from 1 mol / L to 3 mol / L, such as 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, and 3 mol / L, or other values ​​within the range of 1 mol / L to 3 mol / L.

[0052] The reaction after adding NaCl can be carried out at 32℃~38℃ (e.g., 32℃, 35℃, or 38℃) and 450rpm~550rpm (e.g., 450rpm, 500rpm, or 550rpm) for 55min~65min (e.g., 55min, 60min, or 65min). That is, after the dropwise addition is complete, the temperature is raised to 32℃~38℃, the stirring speed is increased to 450rpm~550rpm, and then NaCl is added and the reaction is carried out for 55min~65min. After the reaction is complete, the mixture is centrifuged, washed, and dried to obtain the magnetized composite filler (denoted as BNNS@Ni-Zn).

[0053] Accordingly, the present invention provides a composite filler prepared by the above-described preparation method.

[0054] The Ni-Zn ferrite in this composite filler is a low-magnetic material, which helps reduce the dielectric constant and dielectric loss of the copper-clad laminate (CCL), resulting in a CCL with higher thermal conductivity and lower dielectric constant and dielectric loss. Under a vertical magnetic field, this composite filler can form vertically aligned boron nitride nanosheets, which can rapidly transfer heat from the inside of the CCL to the outside, thus transferring heat to the external environment and solving the problem of heat accumulation in CCLs. In this article, "vertical" refers to a direction perpendicular to the in-plane direction of the prepreg.

[0055] In addition, the present invention also provides an intermediate layer semi-cured sheet, which is obtained by coating a first slurry into a film, and then drying and sintering it; wherein the first slurry includes PTFE and the above-mentioned composite filler, and a vertical magnetic field is applied during the sintering process.

[0056] In some alternative embodiments, the mass of the composite filler can be 10% to 60% of the mass of PTFE, such as 10%, 20%, 30%, 40%, 50% or 60%, or other values ​​within the range of 10% to 60%.

[0057] The total mass of the composite filler and PTFE can be 60% to 70% of the mass of the first slurry, such as 60%, 65%, or 70%, or other values ​​within the range of 60% to 70%. The solvent in the first slurry can be water.

[0058] Furthermore, the aforementioned slurry may also include a dispersant (such as polyvinylpyrrolidone (PVP)) and a thickener (such as alkylphenol polyoxyethylene ether, polyethylene glycol, hydroxyethyl cellulose, methyl cellulose, polyvinyl alcohol, etc.). The mass of the dispersant may be 0.4% to 0.6% of the mass of the first slurry, and the mass of the thickener may be 0.01% to 0.1% of the mass of the first slurry.

[0059] After mixing the above materials, they can be mixed at 400rpm~500rpm for 2 hours and then degassed to obtain the first slurry.

[0060] In some alternative embodiments, the drying temperature of the intermediate layer prepreg can be 70°C to 150°C, such as 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C, or other values ​​within the range of 70°C to 150°C.

[0061] The sintering temperature of the intermediate layer prepreg can be 375℃~385℃, such as 375℃, 380℃ or 385℃, or other values ​​within the range of 375℃~385℃.

[0062] In some optional embodiments, the magnetic flux density of the vertical magnetic field can be 0.05T to 0.15T, such as 0.05T, 0.1T, or 0.15T, or other values ​​within the range of 0.05T to 0.15T. In some preferred embodiments, the magnetic flux density of the vertical magnetic field is 0.085T.

[0063] By applying a vertical magnetic field, the composite filler is oriented vertically, and after sintering, a semi-cured intermediate layer with vertically oriented filler is obtained. In this process, magnetic field orientation and sintering are completed simultaneously.

[0064] In addition, the present invention also provides a copper-clad laminate, which includes a first copper foil, a first adhesive layer, an intermediate layer, a second adhesive layer, and a second copper foil.

[0065] The intermediate layer is formed from the aforementioned intermediate layer semi-cured sheet.

[0066] In some alternative implementations, the thickness of the first copper foil and the second copper foil can be independently 35 μm.

[0067] The thickness of the first adhesive layer and the second adhesive layer can be independently 50μm to 100μm, such as 50μm, 75μm or 100μm, or other values ​​within the range of 50μm to 100μm.

[0068] The thickness of the intermediate layer can be 200μm to 300μm, such as 200μm, 250μm or 300μm, or other values ​​within the range of 200μm to 300μm.

[0069] In some alternative implementations, the thermal conductivity of the copper clad laminate is not less than 5.1 W / (m·k), such as 5.14 W / (m·k) to 7.33 W / (m·k).

[0070] The peel strength of the copper clad laminate shall not be less than 1.3 N / mm, and may be 1.35 N / mm to 2.21 N / mm.

[0071] The dielectric constant of the copper clad laminate shall not exceed 3.85 / 10GHz, but may be 2.75 / 10GHz to 3.84 / 10GHz.

[0072] The dielectric loss of the copper clad laminate shall not exceed 0.00085 / 10GHz, and may be 0.00043 / 10GHz to 0.00082 / 10GHz.

[0073] The coefficient of thermal expansion of copper clad laminates shall not exceed 49ppm / K, and may be 28.53ppm / K to 48.37ppm / K.

[0074] Accordingly, the present invention also provides a method for preparing the above-mentioned copper-clad laminate, comprising the following steps: stacking a first copper foil, a first adhesive layer prepreg, an intermediate layer prepreg, a second adhesive layer prepreg, and a second copper foil in sequence, and then performing vacuum hot pressing.

[0075] In some alternative embodiments, the adhesive layer semi-cured sheet is obtained by coating a second slurry into a film, followed by drying and sintering; wherein the second slurry includes PTFE, BN nanowires, and BNNS modified with a fluorinated silane coupling agent (such as FAS-13 or FAS-17).

[0076] The length of BNNS can be 1μm to 2μm; the diameter of BN nanowires can be 45nm to 55nm, and the length can be 1μm to 1.5μm.

[0077] The mass ratio of BNNS and BN nanowires modified with the above-mentioned fluorinated silane coupling agent can be from 2:1 to 4:1, such as 2:1, 2.5:1, 3:1, 3.5:1 or 4:1, or other values ​​within the range of 2:1 to 4:1.

[0078] The total mass of BN nanowires and BNNS modified with fluorinated silane coupling agents can be 5% to 45% of the mass of PTFE, such as 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40% or 45%, or other values ​​within the range of 5% to 45%.

[0079] The total mass of BN nanowires and BNNS modified with fluorinated silane coupling agents can be 60% to 70% of the mass of the second slurry, such as 60%, 65%, or 70%, or other values ​​within the range of 60% to 70%. The solvent in the second slurry can be water.

[0080] In some alternative embodiments, the drying temperature of the adhesive layer prepreg can be 70°C to 150°C, such as 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C, or other values ​​within the range of 70°C to 150°C.

[0081] The sintering temperature of the prepreg can be 375℃~385℃, such as 375℃, 380℃ or 385℃, or other values ​​within the range of 375℃~385℃.

[0082] In some optional embodiments, vacuum hot pressing can be performed at 280°C to 320°C (e.g., 280°C, 300°C, or 320°C) and 8MPa to 12MPa (e.g., 8MPa, 10MPa, or 12MPa) for 40 to 60 minutes (e.g., 40 minutes, 50 minutes, or 60 minutes). In some preferred embodiments, vacuum hot pressing is performed at 320°C and 10MPa for 60 minutes.

[0083] After hot pressing, PTFE copper-clad laminate is obtained.

[0084] Following on, such as Figure 1 As shown, the copper-clad laminate provided by this invention has a vertical BNNS@Ni-Zn thermal conductive path and a horizontal BNNS / BN nanowire thermal conductive network, that is, it has a dual thermal conductive path. Low-loss vertical thermal conductive path is achieved by modifying BNNS with Ni-Zn ferrite; a highly efficient horizontal thermal conductive network is constructed using a BNNS / BN nanowire hybrid system.

[0085] It should be noted that existing technologies use large-size fillers to improve the in-plane thermal conductivity of copper-clad laminates (CCLs), but the vertical thermal conductivity is insufficient, resulting in significant anisotropy in the material's thermal conductivity. This invention optimizes the filler distribution and designs interconnected thermal conduction pathways, enabling the material to achieve efficient thermal conductivity in both the in-plane and out-of-plane directions. Furthermore, in existing technologies, increasing the proportion of high thermal conductivity fillers to improve thermal conductivity often weakens the interfacial bonding between the resin matrix and the filler, significantly reducing the interlayer peel strength of the CCL and affecting the material's mechanical reliability and processing performance. This invention successfully achieves synergistic optimization of high peel strength and high thermal conductivity in CCLs by introducing a low-filler-proportion adhesive layer and constructing a three-dimensional thermally conductive network structure.

[0086] In addition, the present invention also provides an electronic device comprising the above-mentioned copper-clad laminate, which has better thermal conductivity and dielectric properties.

[0087] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0088] Example 1 This embodiment provides a copper-clad laminate, the preparation method of which includes: Step (1): Preparation of BNNS@Ni-Zn ferrite composite filler.

[0089] S1: Disperse BNNS particles with a diameter of 2 μm in Piranha solution (concentrated H2SO4:H2O2 = 5:1, volume ratio), react at 80℃ for 30 min to hydroxylate the surface of BNNS, then centrifuge and wash until neutral, and dry to obtain BNNS-OH.

[0090] S2: Ni-Zn ferrite nanoparticles with a particle size of 30 nm were dispersed in 0.1 mol / L HNO3, ultrasonicated for 20 min, washed with water until neutral, and then immediately dispersed in ultrapure water to obtain activated Ni-Zn ferrite.

[0091] S3: Disperse BNNS-OH in acetate buffer solution at pH=5 and sonicate for 30 min to form a suspension. Add the activated Ni-Zn ferrite suspension (mass ratio of BNNS-OH to activated Ni-Zn ferrite is 20:1) dropwise at a rate of 1 mL / min, maintaining a stirring speed of 200 rpm. After the addition is complete, raise the temperature to 35℃, increase the stirring speed to 500 rpm, and add NaCl to a final concentration of 2 mol / L. React for 60 min. After the reaction is complete, centrifuge, wash, and dry to obtain the magnetized BNNS@Ni-Zn composite filler.

[0092] Step (2): Preparation of multilayer structure.

[0093] Preparation of the intermediate layer prepreg: BNNS@Ni-Zn composite filler and PTFE were compounded at a mass ratio of 40:100 to obtain a first mixture. The first mixture was dispersed in deionized water at a ratio of 65 wt%, and then a dispersant (PVP) and a thickener (polyethylene glycol) were added. The mixture was stirred at 500 rpm for 2 hours and then degassed to obtain a first slurry. The amount of dispersant added was 0.5 wt% of the first slurry, and the amount of thickener added was 0.1 wt%. The first slurry was coated into a film using a coating machine, dried at 120℃, and sintered at 380℃. During the high-temperature sintering process, a vertical magnetic field of 0.085T was applied to make the BNNS@Ni-Zn vertically oriented. After sintering, the intermediate layer prepreg was obtained.

[0094] Preparation of the adhesive layer semi-cured sheet: BNNS (2 μm in length) modified with fluorosilane coupling agent FAS-13 was mixed with BN nanowires (50 nm in diameter, 1 μm in length) at a mass ratio of 3:1. This mixture was then combined with PTFE at a mass ratio of 25:100 to obtain a second mixture. The second mixture was dispersed in deionized water at a ratio of 65 wt%, and degassed to obtain a second slurry. The second slurry was coated into a film using a coating machine, dried in an oven at 120°C, and then sintered in a high-temperature oven at 380°C to obtain the adhesive layer semi-cured sheet.

[0095] Step (3): Preparation of copper-clad laminate.

[0096] The first copper foil (35μm), the first adhesive layer prepreg (80μm), the intermediate layer prepreg (200μm), the second adhesive layer prepreg (80μm), and the second copper foil (35μm) are stacked in sequence, and then vacuum hot-pressed at 320℃ and 10MPa for 60min to obtain a PTFE copper-clad laminate with vertical BNNS@Ni-Zn thermal conductive pathways and horizontal BNNS / BN nanowire thermal conductive networks.

[0097] Example 2 The difference between this embodiment and Embodiment 1 is that in S3, the mass ratio of BNNS-OH to activated Ni-Zn ferrite is 15:1.

[0098] Example 3 The difference between this embodiment and Embodiment 1 is that in S3, the mass ratio of BNNS-OH to activated Ni-Zn ferrite is 25:1.

[0099] Example 4 This embodiment provides a copper-clad laminate, the preparation method of which includes: (1) Preparation of BNNS@Ni-Zn ferrite composite filler: S1: BNNS particles with a diameter of 0.5 μm were dispersed in Piranha solution (concentrated H2SO4:H2O2 = 3:1, volume ratio) and reacted at 75 °C for 20 min to hydroxylate the surface of BNNS. The particles were then centrifuged and washed until neutral, and dried to obtain BNNS-OH.

[0100] S2: Ni-Zn ferrite nanoparticles with a particle size of 25 nm were dispersed in 0.1 mol / L HNO3, ultrasonicated for 25 min, washed with water until neutral, and then immediately dispersed in ultrapure water to obtain activated Ni-Zn ferrite.

[0101] S3: Disperse BNNS-OH in acetate buffer solution at pH 4.8 and sonicate for 30 min to form a suspension. Add the activated Ni-Zn ferrite suspension (mass ratio of BNNS-OH to activated Ni-Zn ferrite is 10:1) dropwise at a rate of 0.8 mL / min, maintaining a stirring speed of 190 rpm. After the addition is complete, raise the temperature to 32℃, increase the stirring speed to 450 rpm, and add NaCl to a final concentration of 1 mol / L. React for 65 min. After the reaction is complete, centrifuge, wash, and dry to obtain the magnetized BNNS@Ni-Zn composite filler.

[0102] (2) Fabrication of multilayer structures: Preparation of the intermediate layer prepreg: BNNS@Ni-Zn composite filler and PTFE were compounded at a mass ratio of 10:100 to obtain a first mixture. The first mixture was dispersed in deionized water at a ratio of 60 wt%, and then a dispersant (PVP) and a thickener (alkylphenol polyoxyethylene ether) were added. The mixture was stirred at 400 rpm for 2 hours and then degassed to obtain a first slurry. The amount of dispersant added was 0.5 wt% of the first slurry, and the amount of thickener added was 0.01 wt%. The first slurry was coated into a film using a coating machine, dried at 70℃, and sintered at 375℃. During the high-temperature sintering process, a vertical magnetic field of 0.05T was applied to make the BNNS@Ni-Zn vertically oriented. After sintering, the intermediate layer prepreg was obtained.

[0103] Preparation of the adhesive layer semi-cured sheet: BNNS (1 μm in length) modified with fluorosilane coupling agent FAS-13 was mixed with BN nanowires (45 nm in diameter, 1 μm in length) at a mass ratio of 2:1. This mixture was then combined with PTFE at a mass ratio of 5:100 to obtain a second mixture. The second mixture was dispersed in deionized water at a ratio of 60 wt%, and degassed to obtain a second slurry. The second slurry was coated into a film using a coating machine, dried in an oven at 70°C, and then sintered in a high-temperature oven at 375°C to obtain the adhesive layer semi-cured sheet.

[0104] (3) Preparation of copper clad laminate: The first copper foil (35μm), the first adhesive layer prepreg (50μm), the intermediate layer prepreg (250μm), the second adhesive layer prepreg (50μm), and the second copper foil (35μm) are stacked in sequence, and then vacuum hot-pressed at 280℃ and 8MPa pressure for 60min to obtain a PTFE copper-clad laminate with vertical BNNS@Ni-Zn thermal conductive pathways and horizontal BNNS / BN nanowire thermal conductive networks.

[0105] Example 5 This embodiment provides a copper-clad laminate, the preparation method of which includes: (1) Preparation of BNNS@Ni-Zn ferrite composite filler: S1: Disperse BNNS particles with a diameter of 1 μm in Piranha solution (concentrated H2SO4:H2O2 = 4:1, volume ratio), react at 85 °C for 10 min to hydroxylate the surface of BNNS, then centrifuge and wash until neutral, and dry to obtain BNNS-OH.

[0106] S2: Ni-Zn ferrite nanoparticles with a particle size of 35nm were dispersed in 0.15mol / L HNO3, ultrasonicated for 15min, washed with water until neutral, and then immediately dispersed in ultrapure water to obtain activated Ni-Zn ferrite.

[0107] S3: Disperse BNNS-OH in acetate buffer solution at pH 5.2 and sonicate for 30 min to form a suspension. Add the activated Ni-Zn ferrite suspension (mass ratio of BNNS-OH to activated Ni-Zn ferrite is 30:1) dropwise at a rate of 1.2 mL / min, maintaining a stirring speed of 210 rpm. After the addition is complete, raise the temperature to 38℃, increase the stirring speed to 550 rpm, and add NaCl to a final concentration of 3 mol / L. React for 55 min. After the reaction is complete, centrifuge, wash, and dry to obtain the magnetized BNNS@Ni-Zn composite filler.

[0108] (2) Fabrication of multilayer structures: Preparation of the intermediate layer semi-cured sheet: BNNS@Ni-Zn composite filler and PTFE were compounded at a mass ratio of 60:100 to obtain a first mixture. The first mixture was dispersed in deionized water at a ratio of 70 wt%, and then a dispersant (PVP) and a thickener (hydroxyethyl cellulose) were added. The mixture was stirred at 450 rpm for 2 hours and then degassed to obtain a first slurry. The amount of dispersant added was 0.5 wt% of the first slurry, and the amount of thickener added was 0.05 wt%. The first slurry was coated into a film using a coating machine, dried at 150℃, and sintered at 385℃. During the high-temperature sintering process, a 0.15T vertical magnetic field was applied to make the BNNS@Ni-Zn vertically oriented. After sintering, the intermediate layer semi-cured sheet was obtained.

[0109] Preparation of the adhesive layer semi-cured sheet: BNNS modified with fluorosilane coupling agent FAS-17 (1.5 μm in length) was mixed with BN nanowires (55 nm in diameter, 1.5 μm in length) at a mass ratio of 4:1, and then mixed with PTFE at a mass ratio of 45:100 to obtain a second mixture. The second mixture was dispersed in deionized water at a ratio of 70 wt%, and degassed to obtain a second slurry. The second slurry was coated into a film using a coating machine, dried in an oven at 150°C, and then sintered in a high-temperature oven at 385°C to obtain the adhesive layer semi-cured sheet.

[0110] (3) Preparation of copper clad laminate: The first copper foil (35μm), the first adhesive layer prepreg (100μm), the intermediate layer prepreg (300μm), the second adhesive layer prepreg (100μm), and the second copper foil (35μm) are stacked in sequence, and then vacuum hot-pressed at 320℃ and 12MPa for 40min to obtain a PTFE copper-clad laminate with vertical BNNS@Ni-Zn thermal conductive pathways and horizontal BNNS / BN nanowire thermal conductive networks.

[0111] Comparative Example 1 The difference between this comparative example and Example 1 is that in step (1), Fe3O4 is used to magnetize and modify boron nitride.

[0112] The specific steps are as follows: Step (1): Preparation of BNNS@Fe3O4 ferrite composite filler.

[0113] S1: Same as S1 in Example 1.

[0114] S2: Fe3O4 nanoparticles with a particle size of 30 nm were dispersed in a 1 wt% PEI (polyethyleneimine) aqueous solution (pH=9), reacted at 60 °C for 2 h, and then washed, filtered and dried to obtain Fe3O4@PEI hybrid particles with positively charged surfaces.

[0115] S3: Except for using the Fe3O4@PEI hybrid particles mentioned above as magnetizing particles, the other steps are the same as S3 in Example 1, and finally the magnetized BNNS@Fe3O4 composite filler is obtained.

[0116] Comparative Example 2 The difference between this comparative example and Example 1 is that no magnetic field is applied during the sintering process, and the boron nitride nanosheets are not oriented.

[0117] Comparative Example 3 The difference between this comparative example and Example 1 is that no adhesive layer is provided in the copper clad laminate.

[0118] Comparative Example 4 The difference between this comparative example and Example 1 is that in S3, the mass ratio of BNNS-OH to activated Ni-Zn ferrite is 5:1.

[0119] Comparative Example 5 The difference between this comparative example and Example 1 is that in S3, the mass ratio of BNNS-OH to activated Ni-Zn ferrite is 35:1.

[0120] Comparative Example 6 The difference between this comparative example and Example 1 is that the mass of the composite filler in the preparation process of the intermediate layer prepreg is 5% of the mass of PTFE.

[0121] Comparative Example 7 The difference between this comparative example and Example 1 is that the mass of the composite filler in the preparation process of the intermediate layer prepreg is 65% of the mass of PTFE.

[0122] Test case The copper-clad laminates prepared in Examples 1-5 and Comparative Examples 1-7 were subjected to performance tests, and the results are shown in Table 1.

[0123] The thermal conductivity was tested according to ASTM D5470-2006 standard; the peel strength was tested according to IPC. TM 650 2.4.8 standard test; dielectric loss is measured using IPC. TM 650 2.5.5.5 Standard test coefficient of thermal expansion: using IPC TM 650 2.4.24 Method Test.

[0124] Table 1 Test Results

[0125] As can be seen from Table 1, the copper-clad laminates provided in Examples 1 to 5 all have good thermal conductivity and dielectric properties, and also have high peel strength.

[0126] A comparison of Example 1 and Comparative Example 1 shows that using Ni-Zn ferrite can effectively reduce the dielectric constant and dielectric loss of copper clad laminate.

[0127] A comparison of Example 1 and Comparative Example 2 shows that the bidirectional heat conduction path can significantly enhance the thermal conductivity of the copper clad laminate.

[0128] A comparison of Example 1 and Comparative Example 3 shows that the introduction of the adhesive layer significantly improves the peel strength and thermal conductivity of the copper clad laminate.

[0129] A comparison of Example 1 with Comparative Examples 4-5 shows that neither a mass ratio of BNNS-OH to activated Ni-Zn ferrite that is too low nor too high can simultaneously improve the thermal conductivity, dielectric properties, and peel strength of the copper-clad laminate. For example, Comparative Example 4 exhibits poor dielectric properties, while Comparative Example 5 shows poor thermal conductivity.

[0130] A comparison of Example 1 with Comparative Examples 6-7 shows that an improper mass relationship between the composite filler and PTFE during the preparation of the intermediate layer prepreg process cannot simultaneously improve the thermal conductivity, dielectric properties, and peel strength of the copper-clad laminate. For example, Comparative Example 6 exhibits poor thermal conductivity, and Comparative Example 7 shows low peel strength.

[0131] In summary, existing technologies improve in-plane thermal conductivity by constructing multi-layer structures and introducing large-size fillers. However, due to the limitations of interlayer interface thermal resistance, the vertical thermal conduction efficiency is significantly insufficient, making it difficult for heat generated inside the copper-clad laminate to be effectively conducted outwards, ultimately leading to a significant heat accumulation effect. This anisotropic thermal conductivity severely restricts the heat dissipation performance of materials in high-power applications. This invention, through a symmetrical structural design of a first copper foil, a first adhesive layer, an intermediate layer, a second adhesive layer, and a second copper foil, achieves a bidirectional thermal conduction path. This bidirectional thermal conduction path significantly enhances the thermal conductivity of the copper-clad laminate because the structure forms a continuous thermal conduction path. The vertically arranged boron nitride nanosheets in the intermediate layer can rapidly transfer heat from inside the board to the outside, thereby further transferring heat to the external environment and solving the heat accumulation problem. Furthermore, the introduction of the adhesive layer significantly improves the peel strength of the copper-clad laminate. This improvement is mainly due to two key factors: First, the fluorinated boron nitride nanosheets / nanowires in the adhesive layer significantly enhance the interfacial bonding between the filler and the resin matrix; second, compared with the intermediate layer, the adhesive layer adopts a lower filler content design, which increases the relative proportion of resin, thereby forming more effective bonding sites at the copper foil-resin interface. These two aspects ultimately lead to a significant improvement in the peel strength of the copper-clad laminate. In addition, this invention uses low-magnetic Ni-Zn ferrite material, which can reduce the dielectric constant and dielectric loss. Furthermore, by controlling the loading of magnetic particles, it can maintain a low dielectric constant and dielectric loss even with ultra-high thermal conductivity, balancing the issues of high thermal conductivity and low dielectric loss. This allows it to meet the stringent requirements of high-frequency, high-power devices in terms of heat dissipation, mechanical strength, and signal integrity.

[0132] 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 composite filler, characterized in that, The preparation of the composite filler includes the following steps: Hexagonal boron nitride nanosheets were dispersed in Piranha solution and reacted. Ni-Zn ferrite nanoparticles were dispersed in nitric acid and ultrasonically treated to obtain activated Ni-Zn ferrite. The activated Ni-Zn ferrite was electrostatically self-assembled with surface-hydroxylated BNNS.

2. The composite filler according to claim 1, characterized in that, The preparation of the surface-hydroxylated BNNS includes at least one of the following characteristics: Feature 1: The particle size of the hexagonal boron nitride nanosheets is 0.5 μm to 2 μm; Feature 2: The Piranha solution comprises concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 3:1 to 5:1; Feature 3: The reaction is carried out at 75℃~85℃ for 10min~30min.

3. The composite filler according to claim 1, characterized in that, The preparation of the activated Ni-Zn ferrite includes at least one of the following characteristics: Feature 4: The particle size of the Ni-Zn ferrite nanoparticles is 25nm~35nm; Feature 5: The concentration of the nitric acid is 0.1 mol / L to 0.15 mol / L; Feature 6: Ultrasound time is 15 min to 25 min.

4. The composite filler according to claim 1, characterized in that, Electrostatic self-assembly includes: dispersing surface-hydroxylated BNNS in a buffer solution to form a suspension; adding activated Ni-Zn ferrite dropwise into the suspension, followed by the addition of NaCl for reaction; Preferably, electrostatic self-assembly includes at least one of the following features: Feature 7: The buffer solution is an acetate buffer solution with a pH of 4.8 to 5.2; Feature 8: Dropping rate is 0.8 mL / min to 1.2 mL / min; Feature 9: The mass ratio of the surface-hydroxylated BNNS to the activated Ni-Zn ferrite is 10:1 to 30:1, preferably 15:1 to 25:1; Feature 10: The concentration of NaCl in the suspension is 1 mol / L to 3 mol / L; Feature 11: The reaction is carried out at 32℃~38℃ and 450rpm~550rpm for 55min~65min.

5. A semi-cured intermediate layer sheet, characterized in that, The intermediate layer semi-cured sheet is obtained by coating a first slurry into a film, followed by drying and sintering; wherein the first slurry includes PTFE and the composite filler as described in any one of claims 1 to 4, and a vertical magnetic field is applied during the sintering process; Preferably, the mass of the composite filler is 10% to 60% of the mass of the PTFE; Preferably, the total mass of the composite filler and the PTFE is 60% to 70% of the mass of the first slurry; Preferably, the slurry further includes a dispersant and a thickener; Preferably, the drying temperature is 70℃~150℃; Preferably, the sintering temperature is 375℃~385℃; Preferably, the magnetic induction intensity of the vertical magnetic field is 0.05T~0.15T, more preferably 0.085T.

6. A copper-clad laminate, characterized in that, The copper-clad laminate includes a first copper foil, a first adhesive layer, an intermediate layer, a second adhesive layer, and a second copper foil; The intermediate layer is formed from the intermediate layer semi-cured sheet as described in claim 5.

7. The copper-clad laminate according to claim 6, characterized in that, The copper-clad laminate has at least one of the following characteristics: Feature 12: The thickness of the first copper foil and the second copper foil are independently 35 μm; feature 13: The thicknesses of the first adhesive layer and the second adhesive layer are independently 50 μm to 100 μm; feature 14: The thickness of the intermediate layer is 200μm~300μm; feature 15: The thermal conductivity of the copper-clad laminate is not less than 5.1 W / (m·K); Feature 16: The peel strength of the copper-clad laminate is not less than 1.3 N / mm; Feature 17: The dielectric constant of the copper clad laminate does not exceed 3.85 / 10GHz; Feature 18: The dielectric loss of the copper-clad laminate does not exceed 0.00085 / 10GHz; Feature 19: The coefficient of thermal expansion of the copper-clad laminate does not exceed 49 ppm / K.

8. A method for preparing a copper-clad laminate as described in claim 6 or 7, characterized in that, Includes the following steps: The first copper foil, the first adhesive layer semi-cured sheet, the intermediate layer semi-cured sheet, the second adhesive layer semi-cured sheet, and the second copper foil are stacked in sequence, and then vacuum hot pressing is performed. Preferably, the adhesive layer semi-cured sheet is obtained by coating a second slurry into a film and then drying and sintering it; wherein the second slurry includes PTFE, BN nanowires and BNNS modified with a fluorinated silane coupling agent; Preferably, the mass ratio of the fluorinated silane coupling agent-modified BNNS to the BN nanowires is 2:1 to 4:1; Preferably, the total mass of the BN nanowires and the BNNS modified with the fluorinated silane coupling agent is 5% to 45% of the mass of the PTFE; Preferably, the total mass of the BN nanowires and the BNNS modified with the fluorinated silane coupling agent is 60% to 70% of the mass of the second slurry; Preferably, the drying temperature is 70℃~150℃; Preferably, the sintering temperature is 375℃~385℃.

9. The preparation method according to claim 8, characterized in that, Vacuum hot pressing was performed at 280℃~320℃ and 8MPa~12MPa for 40min~60min; More preferably, vacuum hot pressing is performed at 320°C and 10MPa for 60 minutes.

10. An electronic device, characterized in that, The electronic device includes the copper-clad laminate as described in claim 6 or 7.

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