Flexible copper-clad plate with high thermal conductivity and low dielectric property and preparation method of flexible copper-clad plate

Abstract

The invention discloses a flexible copper-clad plate with high thermal conductivity and low dielectric property and a preparation method of the flexible copper-clad plate. The flexible copper-clad plate comprises an insulating substrate, the composite film is a thermoplastic polyimide / heat-conducting low-dielectric ePTFE / thermoplastic polyimide insulating composite film which is composed of a middle layer ceramic / boron nitride-expanded polytetrafluoroethylene functional hybrid membrane and thermoplastic polyimide layers on the two sides of the middle layer ceramic / boron nitride-expanded polytetrafluoroethylene functional hybrid membrane. And the flexible conductive metal foil is compounded with the single surface, double surfaces or multiple layers of the insulating substrate through a thermal forming compounding process. Through the mode, the flexible copper-clad plate can have excellent peel strength under the adhesive-free condition through structure optimization and process innovation, low dielectric constant and low dielectric loss tangent value can be realized under the high-frequency condition, and meanwhile, the heat conductivity coefficient is remarkably improved. And through continuous production, the efficiency is greatly improved, and a high-reliability base material is provided for the high-end electronic fields such as new energy vehicles, 5G / 6G communication and wearable equipment.

Description

Technical Field

[0001] This invention relates to the field of electronic materials, and in particular to a flexible copper-clad laminate with high thermal conductivity and low dielectric properties and its preparation method. Background Technology

[0002] Flexible copper clad laminate (FCCL), as a key basic material for electronic interconnection, is widely used in flexible printed circuits (FPC). Its high wiring density, thinness, bendability, and three-dimensional assembly capabilities have driven the development of electronic products towards thinner, lighter, shorter, and smaller designs. With the rapid development of high-tech fields such as new energy and intelligent connected vehicles, 5G / 6G communications, metaverse, optoelectronic information, wearable devices, medical devices, aerospace, AI supercomputing, and military applications, data transmission throughput is increasing dramatically, and operating frequencies are constantly rising (e.g., 10 GHz and above). This has led to an increasing demand for miniaturization, high speed, low heat generation, and low latency in electronic devices and products. In high-frequency signal transmission, signal loss and distortion mainly occur at the circuit surface (i.e., the contact area between the metal layer and the insulating layer). Therefore, the dielectric properties of the insulating layer material have become a core challenge. High-frequency equipment requires insulating materials with extremely low dielectric constants and dielectric loss tangents to reduce signal transmission delays and energy losses. Simultaneously, they must possess high thermal conductivity for effective heat dissipation, a low coefficient of linear expansion to match the metal layers, and excellent flexibility (such as bending and flexural strength) to meet the needs of flexible applications. Against this backdrop, the market demand for flexible copper-clad laminates with high thermal conductivity and low dielectric properties has grown dramatically, becoming a key development direction for future electronic printed circuit board materials.

[0003] Existing flexible copper-clad laminate (CCL) technology has significant drawbacks when dealing with high-frequency applications. First, traditional structures often employ a "copper foil-low-dielectric epoxy adhesive-insulating base film" design, but this structure frequently results in rigid products lacking sufficient flexibility to meet the needs of bendable or dynamically mounted electronic devices. Second, while specialty engineering plastics such as polytetrafluoroethylene (PTFE) are used for low-dielectric applications (with a dielectric constant of approximately 2.5), filling with large amounts of ceramic powder to reduce dielectric loss introduces a series of new problems: for example, while high filler content can reduce the dielectric loss tangent, it sacrifices the overall material performance, leading to decreased mechanical strength (e.g., embrittlement), extremely low thermal conductivity (ineffective heat dissipation), and severely compromised flexibility (poor bending and flexural strength). Furthermore, the manufacturing process requires complex filtration, drying, and sintering processes, resulting in low production efficiency.

[0004] Furthermore, the introduction of coupling agents, binders, or water-based additives in existing technologies introduces polar groups, increasing dielectric loss and further deteriorating high-frequency performance. These issues collectively prevent existing flexible copper-clad laminates from balancing low dielectric strength, high thermal conductivity, and good flexibility under high-frequency conditions, limiting their expanded applications in high-end electronics fields such as 5G base stations and wearable sensors. Summary of the Invention

[0005] The main technical problem solved by this invention is to provide a flexible copper-clad laminate with high thermal conductivity and low dielectric properties and its preparation method. It can have a low dielectric constant and dielectric loss tangent under high frequency conditions, significantly reducing signal loss, and has excellent thermal conductivity, low linear expansion coefficient, and excellent mechanical properties, which can meet the needs of flexible electronic dynamic applications.

[0006] To solve the above-mentioned technical problems, one technical solution adopted by the present invention is: to provide a flexible copper-clad laminate with high thermal conductivity and low dielectric properties, comprising: The insulating substrate with no adhesive bonding on both sides is a thermoplastic polyimide / thermally conductive low dielectric ePTFE / thermoplastic polyimide insulating composite film composed of a middle layer ceramic / boron nitride-expanded polytetrafluoroethylene functional hybrid film and thermoplastic polyimide layers on both sides. The intermediate ceramic / boron nitride-expanded PTFE functional hybrid film provides low dielectric constant, low loss, and high thermal conductivity. The thermoplastic polyimide layers on both sides enable adhesive-free bonding and offer excellent flexibility, flexural strength, and high peel strength to metal foils (>1.5 N / mm). This three-layer composite structure works synergistically to simultaneously meet the conflicting requirements of low dielectric constant, high thermal conductivity, and high flexibility.

[0007] Flexible conductive metal foil is laminated to an insulating substrate on one side, two sides, or multiple layers via a thermoforming composite process. This thermoforming composite process requires no additional adhesives and allows for single-sided, double-sided, or multi-layer lamination, meeting the needs of various application scenarios and offering high flexibility.

[0008] In a preferred embodiment of the present invention, the conductive metal foil is electrolytic copper foil or rolled copper foil. Alternatively, common and mature copper foil materials in the industry can be used, which reduces the manufacturing threshold and cost.

[0009] In a preferred embodiment of the present invention, the thickness of the thermoplastic polyimide / thermally conductive low-dielectric ePTFE / thermoplastic polyimide insulating composite film is 12.5 μm to 150 μm, which can meet the needs of different applications and ensure the practicality and mass production feasibility of the solution.

[0010] To solve the above-mentioned technical problems, another technical solution adopted by the present invention is: a method for preparing a flexible copper-clad laminate with high thermal conductivity and low dielectric properties, comprising the following steps: (1) Mix polytetrafluoroethylene dispersion resin, ceramic powder and multi-size boron nitride evenly, and atomize and spray aviation kerosene to achieve material homogenization. Multi-size boron nitride is beneficial for optimizing filler stacking density, thereby forming a more effective thermal conduction path in the composite material; atomized spraying of aviation kerosene is a key process to achieve uniform mixing with low resin content, ensuring smooth subsequent processing and uniform performance of the final product.

[0011] (2) The mixture from step (1) is molded, extruded, calendered, biaxially stretched and sintered at high temperature to form a ceramic / boron nitride-expanded polytetrafluoroethylene hybrid film with a three-dimensional micro-nano porous structure. The three-dimensional micro-nano porous structure is the key. On the one hand, it can further reduce the overall dielectric constant of the material. On the other hand, it provides anchoring points for the subsequent wetting and embedding of thermoplastic polyimide solution, which is the basis for achieving adhesive-free bonding.

[0012] In steps (1) and (2), polytetrafluoroethylene (PTFE) micropowder, ceramic powder, and boron nitride of different particle sizes are directly and uniformly mixed, then molded, extruded, and calendered without adding any coupling agents, binders, or water-based additives, thus reducing the introduction of polar groups at the source. A biaxially stretched expanded PTFE hybrid functional membrane is then prepared, introducing a porous structure during film formation, further reducing the dielectric constant and dielectric loss of the ceramic / boron nitride-expanded PTFE membrane.

[0013] (3) A thermoplastic polyimide precursor solution is coated on both sides of the hybrid membrane, and after gradient drying and dehydration ring-closed imidization, a thermoplastic polyimide layer is formed on the surface of the ceramic / boron nitride-expanded polytetrafluoroethylene hybrid membrane, thus obtaining a thermoplastic polyimide / thermally conductive low dielectric ePTFE / thermoplastic polyimide insulating composite film with adhesive-free bonding function on both sides; Thermoplastic polyimide precursor solution impregnates and fills the micropores of ePTFE membrane, and after curing, forms a mechanically interlocking structure, thereby achieving excellent peel strength (>1.5 N / mm) without the use of additional adhesives, realizing a strong bond between the two materials, and giving the final product excellent flexibility.

[0014] (4) The composite film obtained in step (3) is laminated with conductive metal foil on one, two or multiple sides to obtain a flexible copper-clad laminate, which makes full use of the thermal bonding characteristics of the thermoplastic polyimide layer on the surface of the insulating film to achieve reliable lamination.

[0015] In a preferred embodiment of the present invention, the complementary boron nitride described in step (1) includes at least two different particle sizes, with particle sizes of 900 nm, 2 μm, 10 μm, or 15 μm. The boron nitride fillers of different particle sizes can complement each other, with the smaller particle size filler filling the voids between the larger particle size fillers, thereby maximizing the formation of a dense thermally conductive network in the matrix and significantly improving the thermal conductivity of the composite material.

[0016] In a preferred embodiment of the present invention, during step (1), while the aviation kerosene is atomized and sprayed, the uniformly mixed particles undergo three-dimensional motion. This three-dimensional motion ensures that there are no dead corners in the mixing process, enabling the PTFE resin, ceramic powder, and boron nitride of different particle sizes to achieve uniform dispersion at the molecular level, preventing uneven product performance or defects due to agglomeration.

[0017] In a preferred embodiment of the present invention, the amount of ceramic powder added in the ceramic / boron nitride-expanded polytetrafluoroethylene membrane in step (2) is 8 to 25 wt%, and the amount of boron nitride added is 3 to 25 wt%. Within this range, various properties can be balanced: ensuring low dielectric and high thermal conductivity while avoiding serious damage to the mechanical properties and processability of the material due to excessive filler.

[0018] In a preferred embodiment of the present invention, in step (3), the coating adopts a high-precision surface controllable coating technology, so that the thermoplastic polyimide precursor solution is immersed in the surface of the ceramic / boron nitride-expanded polytetrafluoroethylene membrane and embedded in the pore structure of the microporous membrane, forming an integral structure in which the thermoplastic polyimide layer is connected to the ceramic / boron nitride-expanded polytetrafluoroethylene membrane.

[0019] "High-precision surface controllable coating technology" is used to precisely control the thickness and uniformity of the coating and ensure that the solution can fully and deeply penetrate into the micropores. This is a prerequisite for forming a robust mechanical interlocking structure, which directly determines the interlayer bonding strength of the insulating film and the reliability of the final product.

[0020] In a preferred embodiment of the present invention, the composite film obtained in step (3) has a dielectric constant of <2.5, a dielectric loss tangent of <0.002, and a thermal conductivity of >0.25 W / m·K at a high frequency of 10 GHz, and its performance meets the requirements of high-end high-frequency applications.

[0021] In a preferred embodiment of the present invention, in step (4), under adhesive-free conditions, the insulating composite film and the conductive metal foil are composited on one, two or more sides to form a symmetrical or asymmetrical copper-clad laminate by a continuous roll-to-roll thermoforming composite process. This is suitable for large-scale industrial production and has the advantages of high efficiency and low cost, solving the problem of low efficiency in traditional processes.

[0022] The beneficial effects of this invention are as follows: Through structural optimization and process innovation, this invention enables a flexible copper-clad laminate with high thermal conductivity and low dielectric properties to achieve excellent peel strength (>1.5 N / mm) under adhesive-free conditions, and to achieve low dielectric constant (<2.5) and low dielectric loss tangent (<0.002) under high-frequency conditions (10 GHz), while significantly improving thermal conductivity (>0.25 W / m·K). The preparation process does not add coupling agents or binders, reducing polar groups at the source and lowering dielectric loss. The material also exhibits a low coefficient of linear expansion (CTE, <25 ppm / ℃ in both X and Y directions) and excellent overall reliability. Continuous production significantly improves efficiency, solving the bottlenecks of existing technologies in high-frequency signal transmission, heat dissipation efficiency, and flexibility, providing a highly reliable basic material for high-end electronic fields such as new energy vehicles, 5G / 6G communications, and wearable devices. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 This is a schematic diagram of a preferred embodiment of the flexible copper-clad laminate with high thermal conductivity and low dielectric properties of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0025] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0026] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0027] In the description of this invention, it should be noted that the terms "front," "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is conventionally placed during use. These terms are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0028] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0029] In this invention, unless otherwise expressly specified and limited, "above or below" a first feature may include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on" the first feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the first feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0030] Please see Figure 1 The embodiments of the present invention include: A flexible copper-clad laminate with high thermal conductivity and low dielectric properties, comprising: The insulating substrate with no adhesive bonding on both sides is a thermoplastic polyimide / thermally conductive low dielectric ePTFE / thermoplastic polyimide insulating composite film 6 composed of a middle layer ceramic / boron nitride-expanded polytetrafluoroethylene functional hybrid film 5 and thermoplastic polyimide layers 3 on both sides. The ceramic / boron nitride-expanded polytetrafluoroethylene functional hybrid membrane 5 comprises a framework layer 1 and a filler layer 2. The framework layer is prepared from polytetrafluoroethylene dispersed resin micropowder, and the filler layer consists of ceramic powder and complementary boron nitride. The amount of ceramic powder added is 8–25 wt%, and the amount of boron nitride added is 3–25 wt%. The complementary boron nitride includes at least two different particle sizes: 900 nm, 2 μm, 10 μm, or 15 μm.

[0031] The flexible conductive metal foil 4 is laminated with the insulating substrate on one side, two sides, or multiple layers through a thermoforming composite process.

[0032] The conductive metal foil 4 is either electrolytic copper foil or rolled copper foil. Different conductive metal foil materials are selected according to different application scenarios.

[0033] Electrolytic copper foil has the advantage of high bonding strength: when the rough surface is melted and bonded with the thermoplastic polyimide layer, a mechanical interlocking structure is formed, which significantly improves the peel strength (>1.5 N / mm); it is suitable for consumer electronics products (such as mobile phone battery boards) with moderate bending requirements (<50,000 times).

[0034] Rolled copper foil possesses high ductility (elongation > 15%) and low roughness, reducing stress concentration during bending and supporting > 100,000 dynamic bends (bending diameter 2.5mm). It maintains high-frequency signal fidelity: the smooth surface reduces skin effect loss, making it suitable for high-end applications and extreme environments such as 5G millimeter-wave radar.

[0035] The thickness of the thermoplastic polyimide / thermally conductive low-dielectric ePTFE / thermoplastic polyimide insulating composite film 6 is 12.5 μm to 150 μm. This allows it to meet the needs of various application scenarios and offers high flexibility.

[0036] This invention also includes a method for preparing a flexible copper-clad laminate with high thermal conductivity and low dielectric properties, specific embodiments of which include: Example 1

[0037] (1) Mix 88 wt% polytetrafluoroethylene dispersion resin micro powder, 10 wt% ceramic powder and 2 wt% mutually matched boron nitride evenly (wherein, the boron nitride powder is a mixture of 15 μm and 2 μm particle sizes), and then spray aviation kerosene onto the surface of the three-dimensional moving polytetrafluoroethylene dispersion resin / functional particles in an atomized manner to achieve high homogeneity of the mixed materials.

[0038] (2) A ceramic / boron nitride-expanded polytetrafluoroethylene functional hybrid membrane with a thickness of 25 μm and a three-dimensional network micro-nano pore structure was prepared by molding, extrusion, calendering, biaxial stretching and high-temperature sintering.

[0039] (3) A composite thermoplastic polyimide precursor solution is coated on both sides of the ceramic / boron nitride-expanded polytetrafluoroethylene functional hybrid film 5 using high-precision surface controllable coating technology. After gradient drying, dehydration and ring-closed imidization, a thermoplastic polyimide layer 3 with a single-sided thickness of 12.5 μm is formed, and a thermoplastic polyimide / thermal conductive low dielectric ePTFE / thermoplastic polyimide insulating composite film 6 with a total thickness of 50 μm is prepared.

[0040] (4) The 50 μm composite dielectric layer 6 prepared above is laminated with electrolytic or rolled copper foil 4 in a single-sided, double-sided or multi-layer manner through a continuous roll-to-roll thermoforming process to obtain a flexible copper-clad laminate 7. The dielectric and thermal conductivity properties of the obtained copper-clad laminate 7 are tested. Example 2

[0041] (1) Mix 88 wt% polytetrafluoroethylene dispersion resin micro powder, 10 wt% ceramic powder and 2 wt% mutually matched boron nitride evenly (wherein, the boron nitride powder is a mixture of 10 μm and 900 nm particle sizes), and then spray aviation kerosene onto the surface of the three-dimensional moving polytetrafluoroethylene dispersion resin / functional particles in an atomized manner to achieve high homogeneity of the mixed materials.

[0042] (2) A ceramic / boron nitride-expanded polytetrafluoroethylene functional hybrid membrane with a thickness of 25 μm and a three-dimensional network micro-nano pore structure was prepared by molding, extrusion, calendering, biaxial stretching and high-temperature sintering.

[0043] (3) A composite thermoplastic polyimide precursor solution is coated on both sides of the ceramic / boron nitride-expanded polytetrafluoroethylene functional hybrid film 5 using high-precision surface controllable coating technology. After gradient drying, dehydration and ring-closed imidization, a thermoplastic polyimide layer 3 with a single-sided thickness of 12.5 μm is formed, and a thermoplastic polyimide / thermal conductive low dielectric ePTFE / thermoplastic polyimide insulating composite film 6 with a total thickness of 50 μm is prepared.

[0044] (4) The 50 μm composite dielectric layer 6 prepared above is laminated with electrolytic or rolled copper foil 4 in a single-sided, double-sided or multi-layer manner through a continuous roll-to-roll thermoforming process to obtain a flexible copper-clad laminate 7. The dielectric and thermal conductivity properties of the obtained copper-clad laminate 7 are tested. Example 3

[0045] (1) Mix 80 wt% polytetrafluoroethylene dispersion resin micro powder, 15 wt% ceramic powder and 5 wt% mutually matched boron nitride evenly (wherein, the boron nitride powder is a mixture of 10 μm and 900 nm particle sizes), and then spray aviation kerosene onto the surface of the three-dimensional moving polytetrafluoroethylene dispersion resin / functional particles in an atomized manner to achieve high homogeneity of the mixed materials.

[0046] (2) A ceramic / boron nitride-expanded polytetrafluoroethylene functional hybrid membrane with a thickness of 25 μm and a three-dimensional network micro-nano pore structure was prepared by molding, extrusion, calendering, biaxial stretching and high-temperature sintering.

[0047] (3) A composite thermoplastic polyimide precursor solution is coated on both sides of the ceramic / boron nitride-expanded polytetrafluoroethylene functional hybrid film 5 using high-precision surface controllable coating technology. After gradient drying, dehydration and ring-closed imidization, a thermoplastic polyimide layer 3 with a single-sided thickness of 12.5 μm is formed, and a thermoplastic polyimide / thermal conductive low dielectric ePTFE / thermoplastic polyimide insulating composite film 6 with a total thickness of 50 μm is prepared.

[0048] (4) The 50 μm composite dielectric layer 6 prepared above is laminated with electrolytic or rolled copper foil 4 in a single-sided, double-sided or multi-layer manner through a continuous roll-to-roll thermoforming process to obtain a flexible copper-clad laminate 7. The dielectric and thermal conductivity properties of the obtained copper-clad laminate 7 are tested. Example 4

[0049] (1) Mix 80 wt% polytetrafluoroethylene dispersion resin micro powder, 15 wt% ceramic powder and 5 wt% mutually matched boron nitride evenly (wherein, the boron nitride powder is a mixture of 10 μm and 900 nm particle sizes), and then spray aviation kerosene onto the surface of the three-dimensional moving polytetrafluoroethylene dispersion resin / functional particles in an atomized manner to achieve high homogeneity of the mixed materials.

[0050] (2) A ceramic / boron nitride-expanded polytetrafluoroethylene functional hybrid membrane with a thickness of 50 μm and a three-dimensional network micro-nano pore structure was prepared by molding, extrusion, calendering, biaxial stretching and high-temperature sintering.

[0051] (3) A composite thermoplastic polyimide precursor solution is coated on both sides of the ceramic / boron nitride-expanded polytetrafluoroethylene functional hybrid film 5 using high-precision surface controllable coating technology. After gradient drying, dehydration and ring-closed imidization, a thermoplastic polyimide layer 3 with a single-sided thickness of 12.5 μm is formed, and a thermoplastic polyimide / thermal conductive low dielectric ePTFE / thermoplastic polyimide insulating composite film 6 with a total thickness of 75 μm is prepared.

[0052] (4) The 75 μm composite dielectric layer 6 prepared above is laminated with electrolytic or rolled copper foil 4 in a single-sided, double-sided or multi-layer manner through a continuous roll-to-roll thermoforming process to obtain a flexible copper-clad laminate 7. The dielectric and thermal conductivity properties of the obtained copper-clad laminate 7 are tested. Example 5

[0053] (1) Mix 80 wt% polytetrafluoroethylene dispersion resin micro powder, 15 wt% ceramic powder and 5 wt% mutually matched boron nitride evenly (wherein, the boron nitride powder is a mixture of 10 μm and 900 nm particle sizes), and then spray aviation kerosene onto the surface of the three-dimensional moving polytetrafluoroethylene dispersion resin / functional particles in an atomized manner to achieve high homogeneity of the mixed materials.

[0054] (2) A ceramic / boron nitride-expanded polytetrafluoroethylene functional hybrid membrane with a thickness of 75 μm and a three-dimensional network micro-nano pore structure was prepared by molding, extrusion, calendering, biaxial stretching and high temperature sintering.

[0055] (3) A composite thermoplastic polyimide precursor solution is coated on both sides of the ceramic / boron nitride-expanded polytetrafluoroethylene functional hybrid film 5 using high-precision surface controllable coating technology. After gradient drying, dehydration and ring-closed imidization, a thermoplastic polyimide layer 3 with a single-sided thickness of 12.5 μm is formed, and a thermoplastic polyimide / thermal conductive low dielectric ePTFE / thermoplastic polyimide insulating composite film 6 with a total thickness of 100 μm is prepared.

[0056] (4) The 100 μm composite dielectric layer 6 prepared above is laminated with electrolytic or rolled copper foil 4 in a single-sided, double-sided or multi-layer manner through a continuous roll-to-roll thermoforming process to obtain a flexible copper-clad laminate 7. The dielectric and thermal conductivity properties of the obtained copper-clad laminate 7 are tested.

[0057] Compare with Example 1 (1) Mix 85 wt% polytetrafluoroethylene dispersion resin micro powder and 15 wt% ceramic powder evenly, and then spray aviation kerosene onto the surface of the three-dimensional moving polytetrafluoroethylene dispersion resin / functional particles in an atomized manner to achieve high homogeneity of the mixed materials.

[0058] (2) A ceramic / boron nitride-expanded polytetrafluoroethylene functional hybrid membrane with a thickness of 25 μm and a three-dimensional network micro-nano pore structure was prepared by molding, extrusion, calendering, biaxial stretching and high-temperature sintering.

[0059] (3) A composite thermoplastic polyimide precursor solution is coated on both sides of the ceramic / boron nitride-expanded polytetrafluoroethylene functional hybrid film 5 using high-precision surface controllable coating technology. After gradient drying, dehydration and ring-closed imidization, a thermoplastic polyimide layer 3 with a single-sided thickness of 12.5 μm is formed, and a thermoplastic polyimide / thermal conductive low dielectric ePTFE / thermoplastic polyimide insulating composite film 6 with a total thickness of 50 μm is prepared.

[0060] (4) The 50 μm composite dielectric layer 6 prepared above is laminated with electrolytic or rolled copper foil 4 in a single-sided, double-sided or multi-layer manner through a continuous roll-to-roll thermoforming process to obtain a flexible copper-clad laminate 7. The dielectric and thermal conductivity properties of the obtained copper-clad laminate 7 are tested.

[0061] The dielectric performance testing methods and standards for the flexible copper-clad laminates prepared in Examples 1-5 and Comparative Example 1 are as follows: IEC 61189-2-721-2015 Test methods for electrical materials, printed boards and other interconnection structures and assemblies - Part 2-721. The thermal conductivity testing methods and standards for the insulating layers prepared in Examples 1-5 and Comparative Example 1 are as follows: ASTM E1461 Standard Test Method for Thermal Diffusivity by the Flash Method.

[0062] Table 1. Performance Comparison Table of Examples 1-5 and Comparative Example 1 Serial Number Insulation layer thickness (μm) Boron nitride particle size (μm) Dielectric constant (10 GHz) Dielectric loss tangent (10 GHz) Thermal conductivity (W / m·K) Example 1 50 15 / 2 2.1 0.0030 0.25 Example 2 50 10 / 0.9 2.2 0.0025 0.31 Example 3 50 10 / 0.9 2.3 0.0018 0.40 Example 4 75 10 / 0.9 2.3 0.0018 0.41 Example 5 100 10 / 0.9 2.3 0.0017 0.40 Compare with Example 1 50 —— 2.2 0.0036 0.037 Table 1 compares the core performance of six groups of samples (Examples 1-5 are the schemes of the present invention, and Control Example 1 is the traditional scheme without boron nitride). The data shows that the embodiments of the present invention are significantly superior to the traditional scheme in terms of low dielectric and high thermal conductivity. The specific analysis is as follows: 1. All embodiments of the present invention achieve low dielectric properties at high frequencies (10 GHz): Dielectric constant stability: All examples have a dielectric constant of ≤2.3 (target <2.5) and are not affected by thickness (e.g., Examples 3, 4, and 5 all have a dielectric constant of 2.3 at a thickness of 50~100 μm).

[0063] Dielectric loss optimization: The loss value decreases as the boron nitride particle size decreases. For example: Example 1 (15 / 2 μm) loss was 0.0030. Example 2 (10 / 0.9 μm) decreased to 0.0025 Examples 3-5 (10 / 0.9 μm) were further reduced to 0.0017-0.0018.

[0064] Compared with Control Example 1 (loss 0.0036), the present invention effectively reduces signal loss by combining boron nitride and microporous structure (such as biaxial stretching process).

[0065] 2. The improved thermal conductivity is the core advantage of this invention: The direct effect of adding boron nitride: The thermal conductivity of Examples 1 to 5 is all >0.25 W / m·K, while that of Control Example 1 (without boron nitride) is only 0.037 W / m·K, a difference of 6 to 11 times.

[0066] Particle size blending effect: Small-sized boron nitride particles (e.g., 0.9 μm) significantly improve thermal conductivity. For example: Example 1 (15 / 2 μm) Thermal conductivity: 0.25 W / m·K Example 2 (10 / 0.9 μm) increased to 0.31 W / m·K Examples 3-5 (10 / 0.9 μm) achieved 0.40-0.41 W / m·K.

[0067] 3. The effect of thickness is negligible: The thermal conductivity of both Example 3 (50 μm) and Example 5 (100 μm) is 0.40 W / m·K, indicating that the change in thickness does not weaken the thermal conductivity.

[0068] By comparing Examples 1-5 with Comparative Example 1, the significant progress of the present invention can be seen: 1. The present invention fully meets the target: the high-frequency dielectric constant (<2.3), dielectric loss (≤0.0030) and thermal conductivity (≥0.25 W / m·K) of all embodiments are better than the target values ​​and significantly exceed the control examples.

[0069] 2. The key to the optimization of this invention lies in the compound boron nitride: small particle size compounding (e.g., 10 / 0.9 μm) is the core of improving thermal conductivity (thermal conductivity increased by 56%~64% in Examples 2~5 vs. Example 1), while maintaining low dielectric loss.

[0070] 3. The present invention has the flexibility of thickness: the insulating layer can be increased from 50 μm to 100 μm (Examples 3-5), the dielectric properties are stable, the thermal conductivity does not decrease, and it meets the needs of different applications.

[0071] 4. This invention solves the industry bottleneck of balancing high frequency, low dielectric constant, and high thermal conductivity through compound filler and structural innovation, providing a reliable material basis for scenarios such as 5G / new energy vehicles.

[0072] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A flexible copper-clad laminate with high thermal conductivity and low dielectric properties, characterized in that, include: The insulating substrate with no adhesive bonding on both sides is a thermoplastic polyimide / thermally conductive low dielectric ePTFE / thermoplastic polyimide insulating composite film composed of a middle layer ceramic / boron nitride-expanded polytetrafluoroethylene functional hybrid film and thermoplastic polyimide layers on both sides. Flexible conductive metal foil is laminated with the insulating substrate on one side, two sides, or multiple layers through a thermoforming composite process.

2. The flexible copper-clad laminate with high thermal conductivity and low dielectric properties according to claim 1, characterized in that, The conductive metal foil is an electrolytic copper foil or a rolled copper foil.

3. The flexible copper-clad laminate with high thermal conductivity and low dielectric properties according to claim 1, characterized in that, The thickness of the thermoplastic polyimide / thermally conductive low-dielectric ePTFE / thermoplastic polyimide insulating composite film is 12.5 μm ~ 150 μm.

4. The method for preparing the flexible copper-clad laminate with high thermal conductivity and low dielectric properties according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Mix polytetrafluoroethylene dispersion resin, ceramic powder and multi-size boron nitride evenly, and atomize and spray aviation kerosene to achieve material homogenization. (2) The mixture in step (1) is molded, extruded, rolled, biaxially stretched and sintered at high temperature to form a ceramic / boron nitride-expanded polytetrafluoroethylene hybrid film with a three-dimensional micro-nano porous structure. (3) A thermoplastic polyimide precursor solution is coated on both sides of the hybrid membrane, and after gradient drying and dehydration ring-closed imidization, a thermoplastic polyimide layer is formed on the surface of the ceramic / boron nitride-expanded polytetrafluoroethylene hybrid membrane, thus obtaining a thermoplastic polyimide / thermally conductive low dielectric ePTFE / thermoplastic polyimide insulating composite film with adhesive-free bonding function on both sides; (4) The composite film obtained in step (3) is combined with conductive metal foil in one, two or more layers to obtain a flexible copper-clad laminate.

5. The method for preparing the flexible copper-clad laminate with high thermal conductivity and low dielectric properties according to claim 4, characterized in that, The intermatched boron nitride described in step (1) includes at least two different particle sizes, with particle sizes of 900 nm, 2 μm, 10 μm or 15 μm.

6. The method for preparing the flexible copper-clad laminate with high thermal conductivity and low dielectric properties according to claim 4, characterized in that, In step (1), while the aviation kerosene is atomized and sprayed, the uniformly mixed particles are undergoing three-dimensional motion.

7. The method for preparing the flexible copper-clad laminate with high thermal conductivity and low dielectric properties according to claim 4, characterized in that, In step (2), the amount of ceramic powder added to the ceramic / boron nitride-expanded polytetrafluoroethylene membrane is 8 to 25 wt%, and the amount of boron nitride added is 3 to 25 wt%.

8. The method for preparing the flexible copper-clad laminate with high thermal conductivity and low dielectric properties according to claim 4, characterized in that, In step (3), the coating adopts a high-precision surface controllable coating technology, so that the thermoplastic polyimide precursor solution is immersed in the surface of the ceramic / boron nitride-expanded polytetrafluoroethylene membrane and embedded in the pore structure of the microporous membrane, forming an integral structure in which the thermoplastic polyimide layer is connected to the ceramic / boron nitride-expanded polytetrafluoroethylene membrane.

9. The method for preparing the flexible copper-clad laminate with high thermal conductivity and low dielectric properties according to claim 4, characterized in that, The composite film obtained in step (3) has a dielectric constant of <2.5, a dielectric loss tangent of <0.002, and a thermal conductivity of >0.25 W / m·K at a high frequency of 10 GHz.

10. The method for preparing the flexible copper-clad laminate with high thermal conductivity and low dielectric properties according to claim 4, characterized in that, In step (4), under adhesive-free conditions, the insulating composite film is laminated with the conductive metal foil on one, two or more sides through a continuous roll-to-roll thermoforming composite process to form a symmetrical or asymmetrical copper-clad laminate.

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