G / BN high-thermal-conductivity film material with single-side high electrical conductivity and high insulation and preparation method thereof

Abstract

The invention discloses a G / BN high-thermal-conductivity film material with single-side high conductivity and high insulation and a preparation method of the G / BN high-thermal-conductivity film material. A graphite layer grows on the surface of a copper foil in situ, and an h-BN nanosheet resin layer is compounded, so that a double-layer structure material with the thickness of 30-100 microns is obtained. The thermal conductivity of the graphite surface is greater than or equal to 500W / m.K, the conductivity is greater than or equal to 1 * 10 < 6 > S / m, the thermal conductivity of the boron nitride surface is 3-30W / m.K, and the resistivity is greater than or equal to 1 * 10 < 12 > omega.cm. The material solves the problems in the prior art that the conductive / insulating layer is easy to separate and the heat-conducting and insulating properties are not coordinated, and is suitable for heat dissipation and electromagnetic shielding of high-power electronic devices. The preparation process is environment-friendly and efficient through the solid carbon source graphite paper and the vacuum hot pressing technology, and the yield reaches 90% or above.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic materials, and particularly relates to a G / BN high thermal conductivity film material with both single-sided high conductivity and high insulation and a preparation method thereof. Background Art

[0002] With the rapid development of electronic devices towards high power density and high frequency (such as 5G millimeter-wave communication, high computing power chips, etc.), the problems of internal heat accumulation and electromagnetic interference are becoming increasingly severe. Although traditional heat dissipation materials (such as pure copper foil, graphite film) have high thermal conductivity (>500 W / m·K), they lack insulation characteristics and are prone to cause short circuits between devices; while the thermal conductivity of insulating polymer materials (such as PI film, epoxy resin composite) is generally lower than 1 W / m·K, which is difficult to meet the requirements of high heat flux density scenarios. How to synergistically achieve the characteristics of high thermal conductivity, single-sided conductivity and single-sided insulation in a single material has become a technical bottleneck that urgently needs to be broken through in the field of electronic packaging.

[0003] In the prior art, Patent CN202110684382.4 proposed to form a composite film by bonding boron nitride flakes and graphite flakes with double-sided tape, but its interfacial bonding force is weak (<1 MPa), and interlayer peeling is prone to occur due to the difference in thermal expansion coefficient under thermal cycling (-40~150 °C); Patent CN202010350768.7 uses graphene (GO) and boron nitride (BN) to form a hybrid film. Although insulating and thermal conductive properties (thermal conductivity ~5 W / m·K) are obtained, the single-sided partitioning of conductive / insulating functions cannot be achieved, and the conductivity (<10 3 S / m) is far lower than the metal-level requirements. In addition, although metal matrix composites (such as copper-graphene) can achieve single-sided insulation by surface coating an insulating layer (such as SiO2), the bonding strength between the coating layer and the matrix is low (peeling strength <0.5 N / mm), and the thermal conductivity of the insulating layer drops sharply to <2 W / m·K, resulting in a decrease in the overall heat dissipation efficiency of more than 30%.

[0004] Further analysis shows that the core of the above technical defects lies in:

[0005] (1) Structural instability: The multi-layer structure of mechanical bonding or physical mixing lacks chemical bonding, and the interfacial shear resistance is insufficient;

[0006] (2) Performance antagonism: It is difficult to control the dispersion state of the conductive phase (such as graphite) and the insulating phase (such as boron nitride), resulting in the inability to accurately isolate the conductive / insulating regions;

[0007] (3) Poor process compatibility: High-temperature film-forming processes (>1000 °C) are likely to damage the integrity of the insulating phase, while low-temperature coating processes are difficult to achieve a highly crystalline thermal conductive network.

[0008] In view of the above problems, the present invention proposes an innovative method for constructing a composite layer of graphite and hexagonal boron nitride (h-BN) with a gradient on the surface of copper foil. Through the pyrolysis growth of solid carbon source and the vacuum hot pressing process of resin glue, a stable integrated structure of a graphite layer (conductive surface, thermal conductivity ≥ 500 W / m·K) and an h-BN composite layer (insulating surface, thermal conductivity 3-30 W / m·K) is achieved within a thickness of 30-100 μm, fundamentally solving the industry problems of easy separation of conductive / insulating layers and non-synergistic thermal conductivity-insulation performance. Summary of the Invention

[0009] The present invention aims to solve the technical problems that existing high thermal conductivity materials cannot simultaneously achieve high conductivity on one side, high insulation on one side, and overall high thermal conductivity performance, and provides a G / BN high thermal conductivity film material with stable structure and controllable process and its preparation method. Through the gradient integration of the graphite layer and the boron nitride composite layer, the material can synergistically meet the requirements of efficient heat dissipation, electrostatic discharge, and electromagnetic shielding of electronic devices within an ultra-thin thickness (30-100 μm).

[0010] To solve the above technical problems, the present invention proposes the following technical solutions:

[0011] A G / BN high thermal conductivity film material with both high conductivity and high insulation on one side, characterized in that:

[0012] 1. Structure design - The material is a double-layer heterostructure, including:

[0013] (1) Graphite layer: with a thickness of 10-50 μm, composed of polycrystalline graphite, thermal conductivity ≥ 500 W / m·K, and surface conductivity ≥ 1×106 S / m;

[0014] (2) Boron nitride composite layer: with a thickness of 20-80 μm, composed of hexagonal boron nitride (h-BN) nanosheets and epoxy resin, thermal conductivity 3-30 W / m·K, and resistivity ≥ 1×1012 Ω·cm;

[0015] (3) Interface characteristics: Through the vacuum hot pressing process, a chemical bonding interface is formed between the graphite layer and the boron nitride composite layer, the interface bonding force ≥ 5 MPa, and there is no delamination phenomenon under the thermal cycle from -40°C to 150°C.

[0016] 2. Preparation method - including the following steps:

[0017] (1) Construction of the graphite layer: Using a 20-60 μm pure copper foil as the substrate, laying 50-300 μm graphite paper on the surface, and pyrolyzing at 800-950°C for 18-48 hours under argon protection to generate a graphite layer with a thickness of 10-50 μm;

[0018] (2) Coating with boron nitride composite layer: Scrape 50 - 200 μm of resin glue on the surface of the graphite layer. The resin glue contains 100 parts of h-BN nanosheets, 30 - 60 parts of epoxy resin, 20 - 30 parts of solvent, and 2 - 3 parts of curing agent by weight;

[0019] (3) Interface strengthening: Dry the coated double-layer film at 70 - 80 °C for 2 - 4 hours, and then perform vacuum hot pressing at 20 - 50 MPa and 100 - 120 °C for 20 - 30 minutes to cure the resin glue and form a chemical bond with the graphite layer;

[0020] (4) Copper foil removal: Immerse the double-layer film in a 10 - 20% nitric acid solution for 10 - 30 minutes to completely remove the copper foil, obtaining a high thermal conductivity film material with a thickness of 30 - 100 μm.

[0021] Compared with the existing technology, the present invention has the following beneficial effects:

[0022] 1. A G / BN high thermal conductivity film material with both single-sided high conductivity and high insulation and its preparation method provided by the present invention have a breakthrough in performance synergy:

[0023] (1) Single-sided conductivity / insulation: The functional areas of the graphite layer and the boron nitride composite layer are clearly defined. The conductivity of the conductive surface is ≥1×106 S / m (close to that of metallic copper), and the resistivity of the insulating surface is ≥1×1012 Ω·cm (10 times higher than the industry standard), effectively avoiding short circuits and signal interference;

[0024] (2) High thermal conductivity and high reliability: The thermal conductivity of the graphite layer is ≥500 W / m·K, the thermal conductivity of the boron nitride composite layer is 3 - 30 W / m·K (10 - 30 times that of traditional epoxy resin), and the interfacial bonding force is ≥5 MPa, without delamination under thermal cycling.

[0025] 2. A G / BN high thermal conductivity film material with both single-sided high conductivity and high insulation and its preparation method provided by the present invention have an innovative process:

[0026] (1) Pyrolysis of solid carbon source: Using graphite paper to replace gaseous carbon sources (such as methane), avoiding the emission of toxic gases, and the graphite layer has high crystallinity, with an environmentally friendly and stable process;

[0027] (2) Vacuum hot pressing for directional bonding: Through the coordinated control of pressure and temperature, the directional arrangement of h-BN nanosheets is achieved, the thermal conductivity efficiency of the composite layer is increased by more than 40%, and the porosity is ≤1%.

[0028] 3. A G / BN high thermal conductivity film material with both single-sided high conductivity and high insulation and its preparation method provided by the present invention have wide applications:

[0029] (1) Ultra-thin flexible design: The material thickness is 30 - 100 μm, and there are no cracks when the bending radius is ≤2 mm, suitable for flexible electronic devices;

[0030] (2) High-frequency scenario adaptation: breakdown voltage ≥ 10 kV / mm, applicable to high-frequency and high-heat-dissipation scenarios such as 5G millimeter-wave base stations and high-power IGBT modules. Description of the Drawings

[0031] Figure 1 Schematic structural diagram of the G / BN high thermal conductivity film material with both single-sided high conductivity and high insulation prepared by the present invention.

[0032] Figure 2 TEM image of hexagonal boron nitride nanosheets in the present invention.

[0033] Figure 3 SEM image of the surface of the graphite layer prepared by the present invention. Detailed Description of the Invention

[0034] To further understand the present invention, the preferred embodiments of the present invention will be described below in conjunction with examples. However, it should be understood that the description of this part is only exemplary and explanatory, and should not have any restrictive effect on the protection scope of the present invention.

[0035] A G / BN high thermal conductivity film material with both single-sided high conductivity and high insulation and a preparation method thereof, comprising the following steps:

[0036] (1) Provide a pure copper foil with a thickness of 20 - 60 μm. After cleaning, lay a graphite paper with a thickness of 50 - 300 μm on its surface and fix it in a graphite mold;

[0037] (2) Place the graphite mold in a vacuum tube furnace and heat it at 800 - 950 °C for 18 - 48 hours under argon protection. After cooling, a graphite layer with a thickness of 10 - 50 μm is formed on the surface of the copper foil;

[0038] (3) Scraping and coating 50 - 200 μm of resin glue on the surface of the graphite layer. The resin glue contains, by weight: 100 parts of hexagonal boron nitride (h-BN) nanosheets, 30 - 60 parts of epoxy resin, 20 - 30 parts of solvent, and 2 - 3 parts of curing agent;

[0039] (4) Place the graphite layer coated with resin glue in a constant temperature and humidity chamber at 70 - 80 °C and dry it for 2 - 4 hours. Then, vacuum hot press it at a pressure of 20 - 50 MPa and a temperature of 100 - 120 °C for 20 - 30 minutes to form a double-layer film;

[0040] (5) Immerse the double-layer film in a 10 - 20% nitric acid solution to remove the copper foil. After cleaning and drying, a high thermal conductivity film material with a thickness of 30 - 100 μm is obtained.

[0041] Example 1

[0042] Step 1: Preparation of the graphite layer

[0043] (1) Select a pure copper foil with a thickness of 50 μm (purity ≥ 99.9%), and ultrasonically clean it with anhydrous ethanol for 10 minutes to remove the surface oil.

[0044] (2) Lay a 200-μm-thick graphite paper (pressed from graphite powder with a particle size ≤ 10 μm and a density of 1.7 g / cm 3 ) on the surface of the copper foil and fix it in a graphite mold.

[0045] (3) Place the mold in a vacuum tube furnace, introduce high-purity argon (purity 99.999%), heat it to 920 °C at a rate of 5 °C / min, hold for 24 hours, and then naturally cool to room temperature to obtain a graphite layer with a thickness of 20 μm.

[0046] Step 2: Coating of boron nitride composite layer

[0047] (1) Prepare a resin glue: Mix 100 parts of h-BN nanosheets (lateral size 300 nm, thickness 35 nm), 40 parts of resorcinol-type epoxy resin, 30 parts of acetone, and 2 parts of diethylenetriamine, and ultrasonically disperse for 30 minutes (power 300 W) to obtain a uniform slurry.

[0048] (2) Knife-coat a 100-μm-thick resin glue on the surface of the graphite layer and dry it in a constant temperature and humidity box at 75 °C for 3 hours.

[0049] Step 3: Vacuum hot pressing

[0050] (1) Put the dried double-layer film into a vacuum hot press (vacuum degree ≤ 10 - 2 Pa), set the pressure to 35 MPa and the temperature to 100 °C, and hot press for 25 minutes.

[0051] (2) After hot pressing, the porosity of the composite layer ≤ 0.8%, and the orientation degree of h-BN nanosheets ≥ 85%.

[0052] Step 4: Removal of copper foil

[0053] (1) Immerse the hot-pressed double-layer film in a 15% nitric acid solution (temperature 30 °C) for 20 minutes, and the copper foil removal rate ≥ 99.8%.

[0054] (2) Wash it 3 times with deionized water and vacuum dry at 60 °C for 2 hours to obtain a G / BN high thermal conductivity film material with a total thickness of 70 μm.

[0055] Performance test

[0056] Graphite layer: Thermal conductivity 715.2 W / m·K (laser flash method), electrical conductivity 1.2 × 10 6 S / m (four-probe method);

[0057] Boron nitride composite layer: Thermal conductivity 8.94 W / m·K (steady-state heat flow method), resistivity 2.3×10 12 Ω·cm (high resistance meter);

[0058] Interface bonding strength: 5.8 MPa (tensile testing machine).

[0059] Example 2

[0060] Adjusted parameters: Coating thickness of resin adhesive is 200 μm, and the rest is the same as in Example 1.

[0061] Test results:

[0062] Graphite layer: Thermal conductivity 706.8 W / m·K, conductivity 1.1×10 6 S / m;

[0063] Boron nitride composite layer: Thermal conductivity 4.53 W / m·K, resistivity 8.2×10 12 Ω·cm;

[0064] Interface bonding strength: 5.2 MPa.

[0065] Example 3

[0066] Adjusted parameters: Hot pressing temperature is 120°C, pressure is 30 MPa, and the rest is the same as in Example 1.

[0067] Test results:

[0068] Graphite layer: Thermal conductivity 710.6 W / m·K, conductivity 1.3×10 6 S / m;

[0069] Boron nitride composite layer: Thermal conductivity 7.86 W / m·K, resistivity 3.4×10 12 Ω·cm;

[0070] Interface bonding strength: 5.5 MPa, flexural strength 158 MPa.

[0071] Example 4 (extreme parameter test)

[0072] Step 1: Preparation of graphite layer

[0073] (1) Use a pure copper foil with a thickness of 20 μm and lay a 50-μm-thick graphite paper;

[0074] (2) Pyrolyze at 800°C for 48 hours to obtain a 10-μm-thick graphite layer.

[0075] Step 2: Coating of boron nitride composite layer

[0076] (1) Apply a 50-μm resin glue (h-BN nanosheets with a size of 100 nm and a thickness of 20 nm) by scraping, and after drying, hot-press at 50 MPa and 120 °C;

[0077] (2) After hot-pressing, the porosity is ≤1.0%, and the h-BN orientation degree is ≥78%.

[0078] Test results:

[0079] Graphite layer: Thermal conductivity 502.3 W / m·K, electrical conductivity 9.8×10 5 S / m;

[0080] Boron nitride composite layer: Thermal conductivity 3.1 W / m·K, resistivity 1.5×10 12 Ω·cm;

[0081] Interface bonding strength: 5.0 MPa (meeting the requirement of ≥5 MPa).

[0082] Comparative example 1 (traditional bonding process)

[0083] Prepare a graphite / boron nitride composite film according to the method of patent CN202110684382.4;

[0084] Test results:

[0085] Thermal conductivity: Graphite layer 520 W / m·K, boron nitride layer 1.2 W / m·K;

[0086] Interface bonding strength 0.7 MPa, delamination after thermal cycling (-40 to 150 °C).

[0087] Table 1

[0088]

[0089] Table 1 shows the data of the thermal conductivity and bonding strength measured for the above-prepared high-thermal-conductivity film materials.

[0090] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention, or modify it into equivalent embodiments with equivalent changes, without departing from the scope of the technical solution of the present invention. Therefore, all simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A preparation method of a G / BN high thermal conductivity film material with both single-sided high conductivity and high insulation, characterized in that, It includes the following steps: (1) Provide a pure copper foil with a thickness of 20 - 60 μm. After cleaning, lay a graphite paper with a thickness of 50 - 300 μm on its surface and fix it in a graphite mold; (2) Place the graphite mold in a vacuum tube furnace, heat it at 800 - 950 °C for 18 - 48 hours under argon protection, and after cooling, form a graphite layer with a thickness of 10 - 50 μm on the copper foil surface; (3) Scraping and coating a resin glue with a thickness of 50 - 200 μm on the surface of the graphite layer. The resin glue contains, by weight: 100 parts of hexagonal boron nitride (h - BN) nanosheets, 30 - 60 parts of epoxy resin, 20 - 30 parts of solvent, and 2 - 3 parts of curing agent; (4) Place the graphite layer coated with resin glue in a constant temperature and humidity box at 70 - 80 °C and dry it for 2 - 4 hours. Subsequently, perform vacuum hot pressing at a pressure of 20 - 50 MPa and a temperature of 100 - 120 °C for 20 - 30 minutes to form a double - layer film; (5) Immerse the double - layer film in a 10 - 20% nitric acid solution to remove the copper foil. After cleaning and drying, obtain a high - thermal - conductivity film material with a thickness of 30 - 100 μm.

2. The preparation method according to claim 1, wherein The graphite layer of the high - thermal - conductivity film material has a thermal conductivity ≥ 500 W / m·K and a surface conductivity ≥ 1×10⁶ S / m. The boron nitride composite layer has a thermal conductivity of 3 - 30 W / m·K and a resistivity ≥ 1×10¹² Ω·cm, and the graphite layer and the boron nitride composite layer form a stable structure with an interfacial bonding force ≥ 5 MPa through hot pressing.

3. The preparation method according to claim 1, characterized in that: The graphite paper in the step (1) is made by pressing graphite powder with a particle size ≤ 10 μm, and the density is 1.6 - 1.8 g / cm 3 .

4. The preparation method according to claim 1, wherein: The h - BN nanosheets in step (3) are of hexagonal crystal form, with a lateral size of 100 - 500 nm, a thickness of 20 - 50 nm, and the dispersion uniformity of the nanosheets in the resin glue ≥ 95%.

5. The preparation method according to claim 1, characterized in that: The epoxy resin is at least one of resorcinol - type epoxy resin, resorcinol - formaldehyde - type epoxy resin, or tetraphenylethane - type epoxy resin; the solvent is acetone or toluene; the curing agent is diethylenetriamine or aminoethylpiperazine.

6. The preparation method according to claim 1, characterized in that: In the step (4), the degree of vacuum in vacuum hot pressing is ≤ 10 - 2 Pa, and the porosity of the double-layer film after hot pressing is ≤ 1%.

7. The preparation method according to claim 1, characterized in that: In step (5), the reaction temperature of the nitric acid solution is 25 - 40 °C, the reaction time is 10 - 30 minutes, and the copper foil removal rate ≥ 99.5%.

8. The preparation method according to claim 1, wherein: The surface roughness Ra of the graphite layer of the high - thermal - conductivity film material ≤ 0.5 μm, and the surface roughness Ra of the boron nitride composite layer ≤ 1.2 μm.

9. The G / BN high thermal conductivity film material prepared by the method according to claim 1, characterized in that: Its total thickness is 30 - 100 μm, the flexural strength ≥ 150 MPa, and there is no delamination phenomenon in the temperature range of - 40 °C to 150 °C.

10. The G / BN high thermal conductivity film material according to claim 9, characterized in that: The thickness of the graphite layer is 10 - 50 μm, the thickness of the boron nitride composite layer is 20 - 80 μm, and the thickness ratio of the two layers is 1:1.5 to 1:4.

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