A gradient adhesive layer-based polytetrafluoroethylene-based high-thermal-conductivity high-frequency copper-clad plate based on interface adaptation and a preparation method thereof

Abstract

This invention discloses a high thermal conductivity, high-frequency copper-clad laminate (CCL) based on a gradient adhesive layer with interface compatibility, belonging to the field of CCL manufacturing technology. The CCL includes a reinforcing substrate, a gradient adhesive layer, and a metal conductive layer. The gradient adhesive layer ensures that the adhesive material near the metal conductive layer has high adhesion strength to the metal, while the adhesive material near the reinforcing substrate has interfacial compatibility matching the reinforcing substrate. Furthermore, the adhesive material exhibits a certain gradient distribution along the thickness direction from the metal conductive layer to the reinforcing substrate. This invention effectively solves the heat dissipation problem in high-frequency applications while maintaining the inherent excellent high-frequency dielectric properties of the PTFE substrate, achieving a harmonious balance between high thermal conductivity and low loss.

Description

Technical Field

[0001] This invention belongs to the field of copper clad laminate manufacturing technology, and specifically relates to a high thermal conductivity, high frequency copper clad laminate with a gradient adhesive layer of polytetrafluoroethylene based on interface adaptation and its preparation method. Background Technology

[0002] With the rapid development of high-frequency and high-speed electronic technologies such as 5G communication, millimeter-wave radar, high-speed computing, and satellite communication, increasingly stringent requirements are being placed on high-frequency substrate materials. Polytetrafluoroethylene (PTFE), due to its excellent dielectric properties, chemical stability, and heat resistance, has become one of the preferred substrate materials for high-frequency copper-clad laminates (CCLs). However, PTFE itself has poor thermal conductivity (approximately 0.25 W / (m·K)), making it difficult to meet the urgent heat dissipation requirements of high-power, highly integrated devices. Simultaneously, its high surface inertness typically results in insufficient bonding strength with copper foil, affecting the long-term reliability of CCLs under harsh environments such as thermal cycling and humidity.

[0003] Currently, the industry commonly improves the thermal conductivity of composite materials by adding high thermal conductivity fillers (such as boron nitride, aluminum nitride, and alumina) to the polytetrafluoroethylene (PTFE) vinyl matrix. However, simple physical blending can easily lead to uneven filler dispersion and poor interfacial compatibility, which not only limits the effective construction of thermal conductivity pathways but may also introduce interfacial thermal stress due to the mismatch between the thermal expansion coefficients of the filler and the matrix, reducing the material's mechanical properties and dimensional stability. In addition, traditional processes typically use a single adhesive layer to bond the PTFE-based dielectric layer to the copper foil. This adhesive layer often struggles to simultaneously achieve high bond strength, high thermal conductivity, and thermal expansion properties that match both. Under drastic temperature changes, it is prone to delamination, warping, and other problems due to thermal mismatch, affecting the reliability of the final circuit assembly.

[0004] In summary, how to provide a copper-clad laminate with high bonding strength, high thermal conductivity and low loss is a key problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the technical problems in existing technologies, this invention provides a high thermal conductivity, high-frequency copper-clad laminate based on an interface-adaptive gradient adhesive layer of polytetrafluoroethylene (PTFE), and its preparation method. This invention effectively solves the heat dissipation problem in high-frequency applications while maintaining the inherent excellent high-frequency dielectric properties of the PTFE substrate, achieving a harmonious balance between high thermal conductivity and low loss.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: a high thermal conductivity, high-frequency copper-clad laminate based on an interface-adaptive gradient adhesive layer, comprising a reinforcing substrate, a gradient adhesive layer, and a metal conductive layer; the gradient adhesive layer enables the adhesive material on the side near the metal conductive layer to have high adhesion strength to the metal, and the adhesive material on the side near the reinforcing substrate to have interfacial compatibility matching the reinforcing substrate, and exhibits a certain gradient distribution along the thickness direction from the metal conductive layer to the reinforcing substrate.

[0007] Furthermore, the residual slurry mass fraction on the surface of the reinforcing substrate after deslurry pretreatment is ≤0.1 wt%; the reinforcing substrate is electronic grade or higher alkali-free glass cloth.

[0008] Furthermore, the conductive metal layer is an electrolytic copper foil or a rolled copper foil; the surface roughness of the conductive metal layer after roughening treatment is 0.5μm~2.0μm; and the thickness of the conductive metal layer is 12μm~70μm.

[0009] Further, the gradient adhesive layer comprises the following components by weight: 100-400 parts hexagonal boron nitride, 0-140 parts agglomerated boron nitride, 30-600 parts alumina, 300-400 parts PTFE emulsion, 0-70 parts surfactant, and 5-30 parts coupling agent. By adjusting the amount of polytetrafluoroethylene (PTFE) in the adhesive layer at different locations, the adhesive material near the metal conductive layer has higher adhesion strength to the metal, while the adhesive material near the reinforcing substrate has interfacial compatibility matching the reinforcing substrate, thereby achieving synergistic adaptation of the gradient adhesive layer at the interface between the metal conductive layer, the adhesive layer, and the reinforcing substrate. Because boron nitride has a regular crystal structure and strong surface inertness, it bonds with the polytetrafluoroethylene (PTFE) polymer matrix mainly through van der Waals forces and mechanical interlocking, resulting in weak chemical bonding. This easily forms a weak interfacial layer, often a sheet-like structure, which tends to align parallel to the base plane in the adhesive layer or matrix, forming a "barrier layer" that hinders the perpendicular crosslinking and interlocking between the adhesive layer and the copper foil. Therefore, the adhesive layer in contact with the copper foil needs to reduce the boron nitride content and increase the alumina content. Utilizing the polar groups such as hydroxyl groups on the surface of alumina, stronger chemical bonds (covalent / hydrogen bonds) can be formed with the resin matrix through coupling agents (such as silanes), thereby strengthening the filler-matrix interface. Increasing the alumina ratio results in stronger interfacial bonding of the overall composite material, more effective stress transfer to the copper foil interface, and increased peel strength.

[0010] Furthermore, the average particle size of the hexagonal boron nitride is 10~20μm; the average particle size of the agglomerated boron nitride is 20~30μm; and the average particle size of the alumina is 3~5μm. In the gradient adhesive layer, the alumina filler and the boron nitride filler form a synergistic thermal conductive network. The use of fillers with different particle sizes improves the continuity of the thermal conductive path, and the thermal conductivity can reach more than 1.9W / m·K.

[0011] Furthermore, the surfactant is α-[3,5-dimethyl-1-(2-methylpropyl)ethyl]-ω-hydroxy poly(oxo-1,2-ethylenedimethyl); the coupling agent is a phenyltrimethoxysilane coupling agent.

[0012] Furthermore, the solid content of the PTFE emulsion is 55-65 wt%, and the D50 particle size of the PTFE emulsion is 0.2-0.3 μm.

[0013] Another object of the present invention is to provide a method for preparing the aforementioned interface-adaptive gradient adhesive layer polytetrafluoroethylene high thermal conductivity high frequency copper-clad laminate, comprising the following steps: Step (1): The reinforcing substrate is continuously passed through a high-temperature treatment furnace at a temperature of 300~450℃ for 10~30 minutes. The surface of the heat-treated glass cloth is modified with a coupling agent solution and then dried for later use. Step (2): Gradient adhesive layer preparation: After the surfactant is fully dissolved in deionized water, the coupling agent is added and the solution is continued to dissolve. Then, alumina is added and the mixture is stirred at a speed of 1000 r / min. After it is fully dispersed, PTFE emulsion is added and the mixture is stirred at a speed of 200 r / min. Then, hexagonal boron nitride and agglomerated boron nitride are slowly added and stirred at a speed of 150 r / min. After the mixture is fully stirred and dispersed, a stable adhesive solution is obtained, which is the gradient adhesive layer. Gradient adhesive layer 1 and gradient adhesive layer 2 are prepared according to this method for later use. The gradient adhesive layer 1 has a good bond with the reinforcing substrate, and the gradient adhesive layer 2 has a good bond with the metal conductive layer.

[0014] Step (3): Gradient adhesive layer film preparation: The reinforced substrate treated in step (1) is immersed in the gradient adhesive layer 1 obtained in step (2), dried and sintered to obtain a semi-finished film, and then the semi-finished film is immersed in the gradient adhesive layer 2, dried and sintered to obtain a gradient adhesive layer film. Step (4): Copper-clad laminate production: According to the required thickness, several gradient adhesive films obtained in step (3) are stacked, copper foil is applied to the top and bottom surfaces, hot-pressed and sintered, and finally cooled to room temperature to obtain copper-clad laminate.

[0015] Furthermore, in step (3), the time for impregnating the substrate with the adhesive is 10~60s; in the drying and sintering process, the drying temperature range is 50~100℃, the drying time is 10~20min, and the sintering temperature range is 370~400℃.

[0016] Furthermore, in step (4), the hot pressing sintering type is vacuum hot pressing sintering, which includes three stages: heating, holding and cooling. In the heating stage, the temperature is raised to 250-300°C at a heating rate of 5-15°C / min. In the holding stage, the temperature is raised to 360-400°C at a heating rate of 1°C / min and the holding time is 2-4 hours. In the cooling stage, the temperature is lowered to 250-300°C at a cooling rate of 1°C / min. The cooling method is natural air cooling or water cooling.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention constructs a continuous and efficient heat conduction pathway within the substrate by directionally introducing surface-modified thermally conductive fillers such as boron nitride into a high-frequency polytetrafluoroethylene (PTFE) substrate, combined with a gradient-distributed adhesive layer design. This not only increases the thermal conductivity in the thickness direction of the copper-clad laminate to over 1.9 W / (m·K), effectively solving the heat dissipation problem in high-frequency applications, but also maintains the inherent excellent high-frequency dielectric properties of the PTFE substrate, achieving a harmonious balance between high thermal conductivity and low loss.

[0018] 2. This invention employs a gradient adhesive layer structure composed of two adhesive liquids, with its thermal conductivity exhibiting a continuous transition between the copper foil and the dielectric layer, significantly reducing interfacial stress caused by material thermal mismatch. Simultaneously, combined with micro-roughening treatment of the copper foil surface, it greatly improves the long-term reliability and service life of the copper-clad laminate under harsh environments such as high temperature and humidity, and thermal cycling.

[0019] 3. The preparation method described in this invention adopts a process path of stepwise pretreatment, adhesive mixing, layer-by-layer impregnation and sintering, and hot pressing. The parameters of each step are clear and precisely controlled. In particular, by optimizing the formulation ratio of different adhesive layers, the interfacial bonding force between the gradient adhesive layer and the glass cloth and copper foil is effectively improved. The entire process can be operated continuously and in batches, the raw material cost is controllable, and the product quality is stable and consistent. It has good prospects for industrialization and can meet the growing market demand for high-performance copper-clad laminates in fields such as 5G communication, automotive radar, and satellite communication. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Example 1

[0021] A high thermal conductivity, high-frequency copper-clad laminate based on interface-adaptive gradient adhesive layer polytetrafluoroethylene (PTFE) is wrapped with 104 electronic-grade glass cloth, a gradient adhesive layer, and 12μm electrolytic copper foil. The gradient adhesive layer includes gradient adhesive layer 1 and gradient adhesive layer 2.

[0022] The formulation of gradient adhesive layer 1 is as follows: Square boron nitride, 360 parts, D50 particle size 15μm; Aggregate boron nitride, 100 parts, D50 particle size 25 μm; Alumina, 200 parts, D50 particle size 5μm; PTFE emulsion, 340 parts, solid content 60 wt.%, D50 particle size 0.25 μm; Surfactant, 60 parts, α-[3,5-dimethyl-1-(2-methylpropyl)ethyl]-ω-hydroxy poly(oxo-1,2-ethylenedimethyl) surfactant; Coupling agent, 10 parts, phenyltrimethoxysilane coupling agent.

[0023] The formulation of gradient adhesive layer 2 is as follows: Square boron nitride, 100 parts, D50 particle size 15 μm; Aggregate boron nitride, 0 parts, D50 particle size 25 μm; Alumina, 600 parts, D50 particle size 5μm; PTFE emulsion, 300 parts, solid content 60 wt.%, D50 particle size 0.25 μm; Surfactant, 60 parts, α-[3,5-dimethyl-1-(2-methylpropyl)ethyl]-ω-hydroxy poly(oxo-1,2-ethylenedimethyl) surfactant; Coupling agent, 10 parts, phenyltrimethoxysilane coupling agent.

[0024] A method for preparing a high thermal conductivity, high-frequency copper-clad laminate with a gradient adhesive layer based on interface adaptation of polytetrafluoroethylene includes the following steps: (1) Desizing and surface treatment of glass cloth: The glass cloth was continuously passed through a high-temperature treatment furnace at 400℃ for 20 minutes to completely remove the surface slurry. Subsequently, the surface of the heat-treated glass cloth was modified with a phenyltrimethoxysilane coupling agent solution and then dried for later use.

[0025] (2) Gradient adhesive layer preparation: An α-[3,5-dimethyl-1-(2-methylpropyl)ethyl]-ω-hydroxy poly(oxo-1,2-ethylenedimethyl) surfactant was dissolved in an appropriate amount of deionized water. Then, a phenyltrimethoxysilane coupling agent was added and the solution was further dissolved. Alumina was then added and the mixture was stirred rapidly (1000 rpm). After thorough dispersion, polytetrafluoroethylene emulsion was added and stirred at low speed (150 rpm). Hexagonal boron nitride and agglomerated boron nitride were then slowly added and stirred at low speed until a stable adhesive solution was obtained, which is the gradient adhesive layer. This method was continued to prepare stable gradient adhesive layer 1 and gradient adhesive layer 2 for later use. (3) Gradient adhesive layer film preparation: The prepared 104 electronic grade glass cloth was immersed in gradient adhesive 1 for 60 seconds according to the design, then dried at 100℃ and sintered at 400℃. It was then immersed in gradient adhesive 2, dried and sintered to obtain a gradient adhesive film with a thickness of 5mil and an adhesive content of 95%, which was then set aside. (4) Made of copper clad laminate: Six sheets of PTFE copper-clad laminate with a designed thickness of 30 mil were stacked, and copper foil was applied to both sides. The laminate was then hot-pressed and sintered. During the heating phase, the temperature was increased at a rate of 10°C / min to 300°C, then increased at a lower rate of 1°C / min to 385°C, held at that temperature for 3 hours, and then decreased at a lower rate of 1°C / min to 300°C, before being allowed to cool naturally to room temperature. This yielded a 30 mil thick high thermal conductivity PTFE copper-clad laminate.

[0026] The copper-clad laminate prepared in this embodiment was tested for thermal, dielectric, and mechanical properties according to the national standards GB / T36476-2018 and GB4722-2017. The test results are shown in Table 1. Example 2

[0027] A high thermal conductivity, high-frequency copper-clad laminate based on interface-adaptive gradient adhesive layer polytetrafluoroethylene (PTFE) is wrapped with 104 electronic-grade glass cloth, a gradient adhesive layer, and 12μm electrolytic copper foil. The gradient adhesive layer includes gradient adhesive layer 1 and gradient adhesive layer 2.

[0028] The formulation of gradient adhesive layer 1 is as follows: Square boron nitride, 360 parts, D50 particle size 15μm; Aggregate boron nitride, 100 parts, D50 particle size 25 μm; Alumina, 200 parts, D50 particle size 5μm; PTFE emulsion, 340 parts, solid content 60 wt.%, D50 particle size 0.25 μm; Surfactant, 60 parts, α-[3,5-dimethyl-1-(2-methylpropyl)ethyl]-ω-hydroxy poly(oxo-1,2-ethylenedimethyl) surfactant; Coupling agent, 10 parts, phenyltrimethoxysilane coupling agent.

[0029] The formulation of gradient adhesive layer 2 is as follows: Square boron nitride, 120 parts, D50 particle size 15μm; Aggregate boron nitride, 0 parts, D50 particle size 25 μm; Alumina, 580 parts, D50 particle size 5μm; PTFE emulsion, 300 parts, solid content 60 wt.%, D50 particle size 0.25 μm; Surfactant, 60 parts, α-[3,5-dimethyl-1-(2-methylpropyl)ethyl]-ω-hydroxy poly(oxo-1,2-ethylenedimethyl) surfactant; Coupling agent, 10 parts, phenyltrimethoxysilane coupling agent.

[0030] A method for preparing a high thermal conductivity, high-frequency copper-clad laminate with a gradient adhesive layer based on interface adaptation of polytetrafluoroethylene includes the following steps: (1) Desizing and surface treatment of glass cloth: The glass cloth was continuously passed through a high-temperature treatment furnace at 400℃ for 20 minutes to completely remove the surface slurry; then the surface of the heat-treated glass cloth was modified with a phenyltrimethoxysilane coupling agent solution, and dried for later use. (2) Gradient adhesive layer preparation: An α-[3,5-dimethyl-1-(2-methylpropyl)ethyl]-ω-hydroxy poly(oxo-1,2-ethylenedimethyl) surfactant was dissolved in an appropriate amount of deionized water. Then, a phenyltrimethoxysilane coupling agent was added and the solution was further dissolved. Alumina was then added and the mixture was stirred rapidly (1000 rpm). After thorough dispersion, polytetrafluoroethylene emulsion was added and stirred at low speed (150 rpm). Hexagonal boron nitride and agglomerated boron nitride were then slowly added and stirred at low speed until a stable adhesive solution was obtained, which is the gradient adhesive layer. This method was continued to prepare stable gradient adhesive layer 1 and gradient adhesive layer 2 for later use. (3) Gradient adhesive layer film preparation: The prepared 104 electronic grade glass cloth was immersed in gradient adhesive 1 for 60 seconds according to the design, then dried at 100℃ and sintered at 400℃. The same process was repeated to immerse it in gradient adhesive 2, then dried and sintered to obtain a gradient adhesive film with a thickness of 5mil and an adhesive content of 95%, which was then ready for use. (4) Made of copper clad laminate: Six sheets of PTFE copper-clad laminate with a designed thickness of 30 mil were stacked, and copper foil was applied to both sides. The laminate was then hot-pressed and sintered. During the heating phase, the temperature was increased at a rate of 10°C / min to 300°C, then increased at a lower rate of 1°C / min to 385°C, held at that temperature for 3 hours, and then decreased at a lower rate of 1°C / min to 300°C, before being allowed to cool naturally to room temperature. This yielded a 30 mil thick high thermal conductivity PTFE copper-clad laminate.

[0031] The copper-clad laminate prepared in this embodiment was tested for thermal, dielectric, and mechanical properties according to the national standards GB / T36476-2018 and GB4722-2017. The test results are shown in Table 1. Example 3

[0032] A high thermal conductivity, high-frequency copper-clad laminate based on interface-adaptive gradient adhesive layer polytetrafluoroethylene (PTFE) is wrapped with 104 electronic-grade glass cloth, a gradient adhesive layer, and 12μm electrolytic copper foil. The gradient adhesive layer includes gradient adhesive layer 1 and gradient adhesive layer 2.

[0033] The formulation of gradient adhesive layer 1 is as follows: Square boron nitride, 320 parts, D50 particle size 15μm; Boron nitride aggregates, 140 parts, D50 particle size 25 μm; Alumina, 200 parts, D50 particle size 5μm; PTFE emulsion, 340 parts, solid content 60 wt.%, D50 particle size 0.25 μm; Surfactant, 60 parts, α-[3,5-dimethyl-1-(2-methylpropyl)ethyl]-ω-hydroxy poly(oxo-1,2-ethylenedimethyl) surfactant; Coupling agent, 10 parts, phenyltrimethoxysilane coupling agent.

[0034] The formulation of gradient adhesive layer 2 is as follows: Square boron nitride, 140 parts, D50 particle size 15μm; Aggregate boron nitride, 0 parts, D50 particle size 25 μm; Alumina, 560 parts, D50 particle size 5 μm; PTFE emulsion, 300 parts, solid content 60 wt.%, D50 particle size 0.25 μm; Surfactant, 60 parts, α-[3,5-dimethyl-1-(2-methylpropyl)ethyl]-ω-hydroxy poly(oxo-1,2-ethylenedimethyl) surfactant; Coupling agent, 10 parts, phenyltrimethoxysilane coupling agent.

[0035] A method for preparing a high thermal conductivity, high-frequency copper-clad laminate with a gradient adhesive layer based on interface adaptation of polytetrafluoroethylene includes the following steps: (2) Desizing and surface treatment of glass cloth: The glass cloth was continuously passed through a high-temperature treatment furnace at 400℃ for 20 minutes to completely remove the surface slurry; then the surface of the heat-treated glass cloth was modified with a phenyltrimethoxysilane coupling agent solution, and dried for later use. (2) Gradient adhesive layer preparation: An α-[3,5-dimethyl-1-(2-methylpropyl)ethyl]-ω-hydroxy poly(oxo-1,2-ethylenedimethyl) surfactant was dissolved in an appropriate amount of deionized water. Then, a phenyltrimethoxysilane coupling agent was added and the solution was further dissolved. Alumina was then added and the mixture was stirred rapidly (1000 rpm). After thorough dispersion, polytetrafluoroethylene emulsion was added and stirred at low speed (150 rpm). Hexagonal boron nitride and agglomerated boron nitride were then slowly added and stirred at low speed until a stable adhesive solution was obtained, which is the gradient adhesive layer. This method was continued to prepare stable gradient adhesive layer 1 and gradient adhesive layer 2 for later use. (3) Gradient adhesive layer film preparation: The prepared 104 electronic grade glass cloth was immersed in gradient adhesive 1 for 60 seconds according to the design, then dried at 100℃ and sintered at 400℃. The same process was repeated to immerse it in gradient adhesive 2, then dried and sintered to obtain a gradient adhesive film with a thickness of 5mil and an adhesive content of 95%, which was then ready for use. (4) Made of copper clad laminate: Six sheets of PTFE copper-clad laminate with a designed thickness of 30 mil were stacked, and copper foil was applied to both sides. The laminate was then hot-pressed and sintered. During the heating phase, the temperature was increased at a rate of 10°C / min to 300°C, then increased at a lower rate of 1°C / min to 385°C, held at that temperature for 3 hours, and then decreased at a lower rate of 1°C / min to 300°C, before being allowed to cool naturally to room temperature. This yielded a 30 mil thick high thermal conductivity PTFE copper-clad laminate.

[0036] The copper-clad laminate prepared in this embodiment was tested for thermal, dielectric, and mechanical properties according to the national standards GB / T36476-2018 and GB4722-2017. The test results are shown in Table 1.

[0037] Comparative Example 1: A high thermal conductivity, high-frequency copper-clad laminate based on interface-adaptive gradient adhesive layer polytetrafluoroethylene includes 104 electronic-grade glass cloth, a gradient adhesive layer, and 12μm electrolytic copper foil.

[0038] The gradient adhesive layer formulation is as follows: Square boron nitride, 360 parts, D50 particle size 15μm; Aggregate boron nitride, 100 parts, D50 particle size 25 μm; Alumina, 200 parts, D50 particle size 5μm; PTFE emulsion, 340 parts, solid content 60 wt.%, D50 particle size 0.25 μm; Surfactant, 60 parts, α-[3,5-dimethyl-1-(2-methylpropyl)ethyl]-ω-hydroxy poly(oxo-1,2-ethylenedimethyl) surfactant; Coupling agent, 10 parts, phenyltrimethoxysilane coupling agent.

[0039] A method for preparing a high thermal conductivity, high-frequency copper-clad laminate with a gradient adhesive layer based on interface adaptation of polytetrafluoroethylene includes the following steps: (1) Desizing and surface treatment of glass cloth: The glass cloth was continuously passed through a high-temperature treatment furnace at 400℃ for 20 minutes to completely remove the surface slurry; then the surface of the heat-treated glass cloth was modified with a phenyltrimethoxysilane coupling agent solution, and dried for later use. (2) Gradient adhesive layer preparation: α-[3,5-dimethyl-1-(2-methylpropyl)ethyl]-ω-hydroxy poly(oxo-1,2-ethylenedimethyl) surfactant was dissolved in an appropriate amount of deionized water. Then, phenyltrimethoxysilane coupling agent was added and the solution was dissolved. Alumina was then added and stirred rapidly (1000 r / min). After the solution was fully dispersed, polytetrafluoroethylene emulsion was added and stirred at low speed (150 r / min). Then, hexagonal boron nitride and agglomerated boron nitride were slowly added and stirred at low speed until the solution was fully dispersed to obtain a stable adhesive solution, which is the gradient adhesive layer, for later use. (3) Gradient adhesive layer film preparation: The prepared 104 electronic grade glass cloth was immersed in a gradient adhesive solution for 60 seconds according to the design, then dried at 100℃ and sintered at 400℃. This process was repeated several times to finally obtain a film with a thickness of 5mil and an adhesive content of 95%, which was then set aside for later use. (4) Made of copper clad laminate: Six sheets of PTFE copper-clad laminate with a designed thickness of 30 mil were stacked, and copper foil was applied to both sides. The laminate was then hot-pressed and sintered. During the heating phase, the temperature was increased at a rate of 10°C / min to 300°C, then increased at a lower rate of 1°C / min to 385°C, held at that temperature for 3 hours, and then decreased at a lower rate of 1°C / min to 300°C, before being allowed to cool naturally to room temperature. This yielded a 30 mil thick high thermal conductivity PTFE copper-clad laminate.

[0040] The copper-clad laminate prepared in this embodiment was tested for thermal, dielectric, and mechanical properties according to the national standards GB / T36476-2018 and GB4722-2017. The test results are shown in Table 1.

[0041] Comparative Example 2: A high thermal conductivity, high-frequency copper-clad laminate based on interface-adaptive gradient adhesive layer polytetrafluoroethylene includes 104 electronic-grade glass cloth, a gradient adhesive layer, and 12μm electrolytic copper foil.

[0042] The gradient adhesive layer formulation is as follows: Hexagonal boron nitride, 100 parts, D50 particle size 15 μm; Aggregate boron nitride, 0 parts, D50 particle size 25 μm; Alumina, 600 parts, D50 particle size 5μm; PTFE emulsion, 300 parts, solid content 60 wt.%, D50 particle size 0.25 μm; Surfactant, 60 parts, α-[3,5-dimethyl-1-(2-methylpropyl)ethyl]-ω-hydroxy poly(oxo-1,2-ethylenedimethyl) surfactant; Coupling agent, 10 parts, phenyltrimethoxysilane coupling agent.

[0043] A method for preparing a high thermal conductivity, high-frequency copper-clad laminate with a gradient adhesive layer based on interface adaptation of polytetrafluoroethylene includes the following steps: (1) Desizing and surface treatment of glass cloth: The glass cloth was continuously passed through a high-temperature treatment furnace at 400℃ for 20 minutes to completely remove the surface slurry; then the surface of the heat-treated glass cloth was modified with a phenyltrimethoxysilane coupling agent solution, and dried for later use. (2) Gradient adhesive layer preparation: Dissolve α-[3,5-dimethyl-1-(2-methylpropyl)ethyl]-ω-hydroxy poly(oxo-1,2-ethylenedimethyl) surfactant in an appropriate amount of deionized water. Then add phenyltrimethoxysilane coupling agent and continue dissolving. Next, add alumina and stir rapidly (1000 r / min). After it is fully dispersed, add polytetrafluoroethylene emulsion and stir at low speed (150 r / min). Then slowly add hexagonal boron nitride and stir at low speed until it is fully dispersed to obtain a stable adhesive solution, which is the gradient adhesive layer, for later use. (3) Gradient adhesive layer film preparation: The prepared 104 electronic grade glass cloth was immersed in a gradient adhesive solution for 60 seconds according to the design, then dried at 100℃ and sintered at 400℃. This process was repeated several times to finally obtain a film with a thickness of 5mil and an adhesive content of 95%, which was then set aside for later use. (4) Made of copper clad laminate: Six sheets of PTFE copper-clad laminate with a designed thickness of 30 mil were stacked, and copper foil was applied to both sides. The laminate was then hot-pressed and sintered. During the heating phase, the temperature was increased at a rate of 10°C / min to 300°C, then increased at a lower rate of 1°C / min to 385°C, held at that temperature for 3 hours, and then decreased at a lower rate of 1°C / min to 300°C, before being allowed to cool naturally to room temperature. This yielded a 30 mil thick high thermal conductivity PTFE copper-clad laminate.

[0044] The copper-clad laminate prepared in this embodiment was tested for thermal, dielectric, and mechanical properties according to the national standards GB / T36476-2018 and GB4722-2017. The test results are shown in Table 1.

[0045] Performance verification: Performance tests were performed on Examples 1-3 and Comparative Examples 1-2, and the results are as follows: Table 1. Performance test results of Examples 1-3 and Comparative Examples 1-2 The copper-clad laminates prepared in Examples 1, 2, and 3 exhibit excellent thermal conductivity (thermal conductivity > 1.9 W / m K) and dielectric properties. Furthermore, the copper foil peel strength of the copper-clad laminates is greater than 6 lb / inch.

[0046] The biggest difference between Comparative Example 1 and Example 1 is that there is only a single high thermal conductivity adhesive layer with a relatively large thermal conductivity of 2.3 W / m·K, but the adhesion between the copper foil and the adhesive layer is insufficient, and the peel strength is only 2.31 lb / inch.

[0047] The biggest difference between Comparative Example 2 and Example 1 is that there is only a single thermally conductive adhesive layer. This adhesive layer has a good interface bond with the copper foil and a peel strength of up to 6.21 lb / inch, but its thermal conductivity is poor, only 0.67 W / m K.

[0048] Therefore, this invention not only maintains the inherent excellent high-frequency dielectric properties of polytetrafluoroethylene (PTFE) substrate, but also achieves a balance between high thermal conductivity and low loss.

[0049] The embodiments described above are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications, substitutions, and improvements without departing from the concept of the present invention, and these should all be considered within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A high thermal conductivity, high-frequency copper-clad laminate with a gradient adhesive layer based on interface adaptation, characterized in that, It includes a reinforcing substrate, a gradient adhesive layer, and a metal conductive layer; the gradient adhesive layer enables the adhesive material on the side near the metal conductive layer to have high adhesion strength to the metal, and the adhesive material on the side near the reinforcing substrate to have interfacial compatibility matching the reinforcing substrate, and is distributed in a certain gradient along the thickness direction from the metal conductive layer to the reinforcing substrate.

2. The high thermal conductivity, high-frequency copper-clad laminate with a gradient adhesive layer based on interface adaptation of polytetrafluoroethylene as described in claim 1, characterized in that, The residual slurry mass fraction on the surface of the reinforcing substrate after deslurry pretreatment is ≤0.1 wt%; the reinforcing substrate is electronic grade or higher alkali-free glass cloth.

3. The high thermal conductivity, high-frequency copper-clad laminate with a gradient adhesive layer based on interface adaptation of polytetrafluoroethylene as described in claim 1, characterized in that, The conductive metal layer is an electrolytic copper foil or a rolled copper foil; the surface roughness of the conductive metal layer after roughening treatment is 0.5μm~2.0μm; the thickness of the conductive metal layer is 12μm~70μm.

4. The high thermal conductivity, high-frequency copper-clad laminate with a gradient adhesive layer based on interface adaptation of polytetrafluoroethylene as described in claim 1, characterized in that, The gradient adhesive layer comprises the following components in parts by weight: 100-400 parts hexagonal boron nitride, 0-140 parts agglomerated boron nitride, 30-600 parts alumina, 300-400 parts PTFE emulsion, 0-70 parts surfactant, and 5-30 parts coupling agent.

5. The high thermal conductivity, high-frequency copper-clad laminate with a gradient adhesive layer based on interface adaptation of polytetrafluoroethylene as described in claim 4, characterized in that, The average particle size of the hexagonal boron nitride is 10~20μm; the average particle size of the agglomerated boron nitride is 20~30μm; and the average particle size of the alumina is 3~5μm.

6. The high thermal conductivity, high-frequency copper-clad laminate with a gradient adhesive layer based on interface adaptation of polytetrafluoroethylene as described in claim 4, characterized in that, The surfactant is α-[3,5-dimethyl-1-(2-methylpropyl)ethyl]-ω-hydroxy poly(oxo-1,2-ethylenedimethyl); the coupling agent is a phenyltrimethoxysilane coupling agent.

7. The high thermal conductivity, high-frequency copper-clad laminate with a gradient adhesive layer based on interface adaptation of polytetrafluoroethylene as described in claim 4, characterized in that, The solids content of the PTFE emulsion is 55-65 wt%, and the D50 particle size of the PTFE emulsion is 0.2-0.3 μm.

8. The interface-adaptive gradient adhesive layer polytetrafluoroethylene high thermal conductivity high-frequency copper-clad laminate according to any one of claims 4-7, characterized in that, The method for preparing the interface-adaptive gradient adhesive layer polytetrafluoroethylene high thermal conductivity high frequency copper clad laminate includes the following steps: Step (1): The reinforcing substrate is continuously passed through a high-temperature treatment furnace at a temperature of 300~450℃ for 10~30 minutes. The surface of the heat-treated glass cloth is modified with a coupling agent solution and then dried for later use. Step (2): Gradient adhesive layer preparation: After the surfactant is fully dissolved in deionized water, the coupling agent is added and the solution is continued to dissolve. Then, alumina is added and the mixture is stirred at a speed of 1000 r / min. After it is fully dispersed, PTFE emulsion is added and the mixture is stirred at a speed of 200 r / min. Then, hexagonal boron nitride and agglomerated boron nitride are slowly added and stirred at a speed of 150 r / min. After the mixture is fully dispersed, a stable adhesive solution is obtained, which is the gradient adhesive layer. Gradient adhesive layer 1 and gradient adhesive layer 2 are prepared according to this method for later use. The gradient adhesive layer 1 has a good bond with the reinforcing substrate, and the gradient adhesive layer 2 has a good bond with the metal conductive layer. Step (3): Gradient adhesive layer film preparation: The reinforced substrate treated in step (1) is immersed in the gradient adhesive layer 1 obtained in step (2), dried and sintered to obtain a semi-finished film, and then the semi-finished film is immersed in the gradient adhesive layer 2, dried and sintered to obtain a gradient adhesive layer film. Step (4): Copper-clad laminate production: According to the required thickness, several gradient adhesive films obtained in step (3) are stacked, copper foil is applied to the top and bottom surfaces, hot-pressed and sintered, and finally cooled to room temperature to obtain copper-clad laminate.

9. The high thermal conductivity, high-frequency copper-clad laminate with a gradient adhesive layer based on interface adaptation of polytetrafluoroethylene as described in claim 8, characterized in that, In step (3), the impregnation time of the reinforcing substrate with the adhesive is 10~60s; During the drying and sintering process, the drying temperature range is 50~100℃, the drying time is 10~20min, and the sintering temperature range is 370~400℃.

10. The high thermal conductivity, high-frequency copper-clad laminate with a gradient adhesive layer based on interface adaptation of polytetrafluoroethylene as described in claim 8, characterized in that, In step (4), the hot pressing sintering type is vacuum hot pressing sintering, which includes three stages: heating, holding and cooling. In the heating stage, the temperature is raised to 250-300℃ at a heating rate of 5-15℃ / min. In the holding stage, the temperature is raised to 360-400℃ at a heating rate of 1℃ / min and the holding time is 2-4h. In the cooling stage, the temperature is lowered to 250-300℃ at a cooling rate of 1℃ / min. The cooling method is natural air cooling or water cooling.

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