A high-performance carbon-based thermal conductive film and its preparation method

Abstract

The present invention discloses a carbon-based thermally conductive film and a preparation method thereof, the steps comprising pre-treating carbon nanofibers and graphene oxide → preparing a composite slurry → coating the composite slurry on the surface of a substrate layer → drying → peeling off the film → roller pressing → magnetron sputtering copper plating → multi-layer lamination. The present invention uses graphene oxide and carbon fiber as raw materials, and adopts plasma treatment to modify the surface of carbon nanofibers so that graphene oxide and carbon nanofibers are fully dispersed in deionized water. A high-performance (thermal conductivity>1900W / mK) carbon-based thermally conductive film is prepared by roller pressing combined with low-temperature drying and cold isostatic pressing. The carbon nanofibers are modified by plasma, and argon plasma can introduce a large number of active groups on the surface of the carbon fiber to improve the surface polarity of the carbon fiber, thereby increasing the hydrophilicity of the carbon fiber surface and better dispersing it in water.

Description

Technical Field

[0001] The present invention relates to the field of coating materials and surface science technology, and in particular to a high-performance carbon-based thermal conductive film and a preparation method thereof. Background Art

[0002] With the rapid development of modern electronic technology, various semiconductors and electronic devices are moving towards miniaturization, high integration, and high power density, resulting in a sharp increase in chip heat generation. Failure to dissipate heat in a timely manner can lead to premature aging of semiconductor chips or accelerated thermomechanical damage to electronic components and devices. Studies have shown that for every 10°C increase in temperature, the failure rate of Si or GaAs semiconductors due to shortened lifespan increases threefold. This is due to thermal fatigue and thermal stress caused by thermal expansion coefficient mismatches between materials in microelectronic integrated circuits or high-power rectifier devices. Therefore, the development of efficient heat dissipation materials is urgently needed.

[0003] Traditional thermally conductive materials include ceramics, epoxy glass, diamond, metals, and their composites. While some have mature applications in electronic packaging, they often have drawbacks. For example, Cu has the highest thermal conductivity of any metal at 380 W / mK, but its high density significantly limits its practical applications.

[0004] Graphene is a single-atom-thick layer of graphite with a two-dimensional honeycomb grid structure. Its thermal conductivity is 5300 W / m·K, exceeding that of diamond and carbon nanotubes. It is the strongest known substance, stronger than diamond and 100 times stronger than the finest steel. Its Young's modulus is 1100 GPa and its tensile strength is 130 GPa. Carbon nanofibers (CNFs) offer high strength, low density, and a large surface area, resulting in excellent thermal and electrical conductivity. They possess the strong tensile strength of carbon materials while also offering the flexibility of flexible fabrication. With diameters typically ranging from 10 nm to 500 nm and lengths of approximately 0.5 μm to 100 μm, they are one-dimensional carbon materials intermediate between conventional carbon fibers and carbon nanotubes. Currently, the common method of preparing composite paper from chopped carbon fibers and graphene oxide using vacuum filtration is followed by reduction. The resulting graphene composite paper has an in-plane thermal conductivity of up to 977 W / m·K. However, the vacuum filtration method has a small product area, is not suitable for industrial production, and is difficult to prepare large-area graphene films. Therefore, it is necessary to find a simple, energy-saving, cycle-saving, and easy-to-scale production method for preparing thermal conductive films. Summary of the Invention

[0005] In view of this, the present invention provides a carbon-based thermally conductive film and a preparation method thereof to solve the problems raised in the above-mentioned background technology. Graphene oxide and carbon fiber are used as raw materials, and after surface plasma treatment, a high thermal conductivity carbon-based thermally conductive film is prepared by a roller coating method combined with low-temperature drying, magnetron sputtering copper plating, and cold isostatic pressing.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] In one aspect, the present invention discloses a method for preparing a carbon-based thermally conductive film, comprising the following steps:

[0008] (1) firstly using plasma to modify the surface of carbon nanofibers and graphene oxide, then dispersing graphene and carbon nanotubes in water by magnetic stirring combined with ultrasound, and mixing them evenly to obtain a pretreated slurry;

[0009] (2) heating the pretreated slurry to evaporate water so that its concentration is controlled at 2-8 mg / mL to obtain a composite slurry;

[0010] (3) coating the composite slurry on the surface of the base layer by a coating method to obtain a thermal conductive coating substrate with the composite slurry attached to the surface;

[0011] (4) drying the thermal conductive coating substrate at 30-60° C., peeling the film formed after the composite slurry is dried from the substrate layer, and rolling the film at a pressure of 20-30 MPa;

[0012] (5) Soaking the rolled film in an acid solution for at least 3 hours, taking out the film, and plating a copper film on the upper and lower surfaces thereof using a magnetron sputtering method, with a copper film thickness of 3-5 μm, to obtain a copper-plated film;

[0013] (6) The multi-layer copper-plated films are laminated by cold isostatic pressing and dried to obtain a carbon-based thermal conductive film.

[0014] As a further solution of the present invention: in step (1), the magnetic stirring speed is 1000-8000 rpm.

[0015] As a further solution of the present invention: in step (1), the ultrasonic treatment power is 30-80W, and the ultrasonic dispersion time is 1-3 hours.

[0016] As a further solution of the present invention: in step (1), the mass ratio of the carbon nanofibers to the graphene oxide is 1:19-1:4.

[0017] As a further solution of the present invention: in step (1), the plasma treatment is specifically: using nitrogen as the medium, using DC pulse plasma to treat the carbon nanofibers, the power is 100-300W, the working pressure is 0.05MPa~0.5MPa, and the time is 1-6min.

[0018] As a further solution of the present invention: in step (3), the coating thickness is 100-150 μm.

[0019] As a further solution of the present invention: in step (5), the acid solution is a HI solution with a concentration of ≥45%.

[0020] As a further solution of the present invention: in step (6), the pressure of the cold isostatic pressing treatment is at least 80 MPa, and the time is 20-40 minutes.

[0021] As a further solution of the present invention: in step (6), the carbon-based thermally conductive film comprises 3-5 layers of copper-plated films.

[0022] Another aspect of the present invention discloses a carbon-based thermally conductive film, which is prepared by any of the preparation methods described above. The thermally conductive film has a thickness of 32-45 μm and a thermal conductivity of 1925 W / mK or more.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention uses graphene oxide and carbon fiber as raw materials, adopts plasma treatment to modify the surface of carbon nanofibers, so that the graphene oxide and carbon nanofibers are fully dispersed in deionized water, and uses a roller pressing method combined with low-temperature drying and cold isostatic pressing to prepare a high-performance (thermal conductivity >1900W / mK) carbon-based thermal conductive film.

[0025] Carbon nanofibers are modified by plasma. Argon plasma can introduce a large number of active groups on the surface of carbon fibers to improve the surface polarity of carbon fibers, increase the hydrophilicity of the carbon fibers, and disperse better in water.

[0026] Graphene thermally conductive film has a layered structure with gaps between the layers. As the film dries, the solvent evaporates into gas. If the temperature is too high, the solvent inside the film will evaporate too quickly, preventing it from diffusing out quickly and accumulating inside the film. This creates numerous voids and bubbles, and can even cause the film to crack during drying. Low-temperature drying can reduce the voids within the film, resulting in better forming results (excessively high temperatures prevent the film from forming).

[0027] Cold isostatic pressing can provide great pressure and ensure uniform force at all points of the film. After the film is treated with cold isostatic pressing, the air inside the film (the thermal conductivity of air is extremely low, only 0.026W / mK) is compressed out, its internal structure becomes denser, and both mechanical properties and thermal conductivity can be improved. The use of cold isostatic pressing for multi-layer lamination technology gives the film a laminated structure, which increases its electromagnetic shielding performance. A layer of metallic copper film is plated on the surface of the graphene film using magnetron sputtering. The copper film has high thermal and electrical conductivity as well as good electromagnetic shielding performance, which can effectively improve the electromagnetic shielding performance and tensile strength of the film. DETAILED DESCRIPTION

[0028] To facilitate understanding of the present invention, the present invention will be described more fully below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0030] The specific information of the raw materials used in the following examples and comparative examples is as follows:

[0031] The manufacturer of carbon fiber is Jiangsu Xianfeng Nanomaterial Technology Co., Ltd., with diameter of 200-600nm and length of 5-50μm;

[0032] The graphene oxide is produced by Shenzhen Guoheng Qihang Technology Co., Ltd., and its flake size is 5-50 μm;

[0033] The concentration of hydroiodic acid (HI) is 45%;

[0034] The thermal conductivity of the films in the following examples was determined according to the following formula:

[0035] K=p×λ×Cp

[0036] K is thermal conductivity; Cp is specific heat; λ is thermal diffusion coefficient; ρ is film density.

[0037] The test standard for thermal diffusivity λ is GB / T 22588-2008, using the laser flash method with a NETZSCHLFA 467 laser flash spectrometer (Germany).

[0038] Cp was determined by differential scanning calorimetry (DSC) using a DSC240, Netzsch, Selb, Germany. Density was calculated using the formula ρ = m / V (mass m was measured using an analytical balance, and V was calculated as film area × film thickness).

[0039] The test temperature was room temperature (25° C.), and the film was peeled off from the substrate before testing.

[0040] EMI stands for electromagnetic interference, and its full name is Electromagnetic Interference; SE stands for shielding efficiency, and its full name is Shielding efficiency.

[0041] It is understood that the above raw materials and reagents are only examples of some specific embodiments of the present invention, which make the technical solution of the present invention clearer, and do not mean that the present invention can only adopt the above reagents. The specific scope in the claims shall prevail. In addition, the "parts" described in the examples and comparative examples, unless otherwise specified, refer to parts by weight.

[0042] Any range described in the present invention includes the end value and any numerical value between the end values ​​and any sub-range formed by the end value or any numerical value between the end values.

[0043] Example 1

[0044] (1) First, carbon nanofibers and graphene oxide were surface modified by argon plasma. Then, graphene and carbon nanotubes were dispersed in water by magnetic stirring (5000 rpm) combined with ultrasound (40 W). After mixing, a pretreated slurry was obtained. In the pretreated slurry, the mass ratio of carbon nanofibers to graphene oxide was 1:19. The plasma treatment parameters were: DC pulse power of 100 W, working pressure of 0.1 MPa, and time of 3 min.

[0045] (2) heating the pretreated slurry to evaporate water until the concentration reaches 5 mg / mL to obtain a composite slurry;

[0046] (3) coating the composite slurry on the surface of the base layer by a coating method to obtain a thermal conductive coating substrate with the composite slurry attached to the surface; the coating thickness is 100 μm;

[0047] (4) drying the thermal conductive coating substrate at 40° C., peeling the film formed after the composite slurry is dried from the substrate layer, and rolling the film at a pressure of 30 MPa;

[0048] (5) soaking the rolled film in a HI acid solution for 3 hours to completely reduce the graphene oxide in the film to graphene, taking out the film, and plating copper films on its upper and lower surfaces using a magnetron sputtering method to obtain a copper-plated film;

[0049] (6) The three layers of the copper-plated films are stacked, packaged in a plastic bag, placed in oil, and subjected to cold isostatic pressing. After drying, a carbon-based thermal conductive film is obtained; wherein the cold isostatic pressing pressure is 100 MPa and the time is 20 minutes.

[0050] After testing, the carbon-based thermal conductive film has a thickness of 32μm, a thermal conductivity of 2400W / mK, an electromagnetic shielding performance EMI SE of 69dB, and a tensile strength of 34MPa.

[0051] Example 2

[0052] (1) First, carbon nanofibers and graphene oxide were surface modified by argon plasma. Then, graphene and carbon nanotubes were dispersed in water by magnetic stirring (5000 rpm) combined with ultrasound (40 W). After mixing, a pretreated slurry was obtained. In the pretreated slurry, the mass ratio of carbon nanofibers to graphene oxide was 1:18. The plasma treatment parameters were: DC pulse power of 100 W, working pressure of 0.1 MPa, and time of 3 min.

[0053] (2) heating the pretreated slurry to evaporate water until the concentration reaches 5 mg / mL to obtain a composite slurry;

[0054] (3) coating the composite slurry on the surface of the base layer by a coating method to obtain a thermal conductive coating substrate with the composite slurry attached to the surface; the coating thickness is 150 μm;

[0055] (4) drying the thermal conductive coating substrate at 50° C., peeling the film formed after the composite slurry is dried from the substrate layer, and rolling the film at a pressure of 20 MPa;

[0056] (5) soaking the rolled film in a HI acid solution for 3 hours to completely reduce the graphene oxide in the film to graphene, taking out the film, and plating copper films on its upper and lower surfaces using a magnetron sputtering method to obtain a copper-plated film;

[0057] (6) The three layers of the copper-plated films are stacked, packaged in a plastic bag, placed in oil, and subjected to cold isostatic pressing. After drying, a carbon-based thermal conductive film is obtained; wherein the cold isostatic pressing pressure is 100 MPa and the time is 20 minutes.

[0058] After testing, the thickness of the carbon-based thermal conductive film is 40μm, the thermal conductivity is 2310W / mK; the tensile strength is 30MPa; and the electromagnetic shielding performance EMI SE is 78dB.

[0059] Example 3

[0060] (1) First, carbon nanofibers and graphene oxide were surface modified by argon plasma. Then, graphene and carbon nanotubes were dispersed in water by magnetic stirring (5000 rpm) combined with ultrasound (40 W). After mixing, a pretreated slurry was obtained. In the pretreated slurry, the mass ratio of carbon nanofibers to graphene oxide was 1:18. The plasma treatment parameters were: DC pulse power of 100 W, working pressure of 0.1 MPa, and time of 3 min.

[0061] (2) heating the pretreated slurry to evaporate water until the concentration reaches 5 mg / mL to obtain a composite slurry;

[0062] (3) coating the composite slurry on the surface of the base layer by a coating method to obtain a thermal conductive coating substrate with the composite slurry attached to the surface; the coating thickness is 150 μm;

[0063] (4) drying the thermal conductive coating substrate at 60° C., peeling the film formed after the composite slurry is dried from the substrate layer, and rolling the film at a pressure of 25 MPa;

[0064] (5) soaking the rolled film in a HI acid solution for 3 hours to completely reduce the graphene oxide in the film to graphene, taking out the film, and plating copper films on its upper and lower surfaces using a magnetron sputtering method to obtain a copper-plated film;

[0065] (6) The three layers of the copper-plated films are stacked, packaged in a plastic bag, placed in oil, and cold isostatically pressed. After drying at 90°C in a vacuum box, a carbon-based thermal conductive film is obtained. The cold isostatic pressing pressure is 100 MPa and the time is 20 minutes.

[0066] After testing, the thickness of the thermal conductive film is 35μm, the thermal conductivity is 2260W / mK; the tensile strength is 29MPa; and the electromagnetic shielding performance EMI SE is 75dB.

[0067] Example 4

[0068] (1) First, carbon nanofibers and graphene oxide were surface modified by argon plasma. Then, graphene and carbon nanotubes were dispersed in water by magnetic stirring (5000 rpm) combined with ultrasound (40 W). After mixing, a pretreated slurry was obtained. In the pretreated slurry, the mass ratio of carbon nanofibers to graphene oxide was 1:4. The plasma treatment parameters were: DC pulse power of 100 W, working pressure of 0.1 MPa, and time of 3 min.

[0069] (2) heating the pretreated slurry to evaporate water until the concentration reaches 5 mg / mL to obtain a composite slurry;

[0070] (3) coating the composite slurry on the surface of the base layer by a coating method to obtain a thermal conductive coating substrate with the composite slurry attached to the surface; the coating thickness is 150 μm;

[0071] (4) drying the thermal conductive coating substrate at 60° C., peeling the film formed after the composite slurry is dried from the substrate layer, and rolling the film at a pressure of 20 MPa;

[0072] (5) soaking the rolled film in a HI acid solution for 3 hours to completely reduce the graphene oxide in the film to graphene, taking out the film, and plating copper films on its upper and lower surfaces using a magnetron sputtering method to obtain a copper-plated film;

[0073] (6) The three layers of the copper-plated films are stacked, packaged in a plastic bag, placed in oil, and cold isostatically pressed. After drying at 90°C in a vacuum box, a carbon-based thermal conductive film is obtained. The cold isostatic pressing pressure is 100 MPa and the time is 20 minutes.

[0074] After testing, the thickness of the thermal conductive film is 45μm, the thermal conductivity is 1925W / mK; the tensile strength is 37MPa; and the electromagnetic shielding performance EMI SE is 56dB.

[0075] Comparative Example 1

[0076] The difference between Comparative Example 1 and Example 2 is that the pressure used in the cold isostatic pressing in Comparative Example 1 is 30 MPa.

[0077] After testing, the thickness of the thermal conductive film is 53μm, the thermal conductivity is 1613W / mK; the tensile strength is 24MPa; and the electromagnetic shielding performance EMI SE is 80dB.

[0078] Comparative Example 2

[0079] The difference between Comparative Example 2 and Example 2 is that in Comparative Example 2, five layers of copper-plated films are stacked and cold isostatically pressed.

[0080] After testing, the thickness of the thermal conductive film is 64μm, the thermal conductivity is 1825W / mK; the tensile strength is 32MPa; and the electromagnetic shielding performance EMI SE is 92dB.

[0081] Comparative Example 3

[0082] The difference between Comparative Example 3 and Example 2 is that no carbon nanofibers are added in Comparative Example 3.

[0083] After testing, the thickness of the thermal conductive film is 37μm, the thermal conductivity is 2107W / mK; the tensile strength is 26MPa; and the electromagnetic shielding performance EMI SE is 76dB.

[0084] Although this specification is described according to implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0085] Therefore, the above description is only a preferred embodiment of the present application and is not intended to limit the scope of implementation of the present application; that is, all equivalent modifications made according to the scope of the claims of the present application are within the scope of protection of the claims of the present application.

Claims

1. A method for preparing a high-performance carbon-based thermally conductive film, characterized in that: The following steps are involved: (1) First, the carbon nanofibers and graphene oxide are surface modified by plasma, and then the graphene oxide and carbon nanofibers are dispersed in water by magnetic stirring combined with ultrasound, and after being mixed evenly, a pretreated slurry is obtained; (2) heating the pretreated slurry to evaporate water so that its concentration is controlled at 2-8 mg / mL to obtain a composite slurry; (3) coating the composite slurry on the surface of the base layer by a coating method to obtain a thermal conductive coating substrate with the composite slurry attached to the surface; (4) drying the thermal conductive coating substrate at 30-60°C, peeling off the film formed after the composite slurry is dried from the substrate layer, and rolling the film at a pressure of 20-30 MPa; (5) Soaking the rolled film in an acid solution for at least 3 hours, taking out the film, and plating a copper film on its upper and lower surfaces using a magnetron sputtering method. The copper film has a thickness of 3-5 μm to obtain a copper-plated film; (6) The three layers of the copper-plated films are stacked by cold isostatic pressing and dried to obtain a carbon-based thermal conductive film; the pressure of the cold isostatic pressing treatment is at least 80 MPa, and the treatment time is 20-40 minutes.

2. The preparation method according to claim 1, characterized in that In step (1), the magnetic stirring speed is 1000-8000 rpm.

3. The preparation method according to claim 1, characterized in that In step (1), the ultrasonic treatment power is 30-80W, and the ultrasonic dispersion time is 1-3 hours.

4. The preparation method according to claim 1, characterized in that In step (1), the mass ratio of the carbon nanofibers to the graphene oxide is 1:19-1:

4.

5. The preparation method according to claim 1, characterized in that In step (1), the plasma treatment is specifically as follows: using nitrogen as the medium, using direct current pulse plasma to treat the carbon nanofibers, with a power of 100-300W, a working pressure of 0.05MPa to 0.5MPa, and a time of 1-6min.

6. The preparation method according to claim 1, characterized in that In step (3), the coating thickness is 100-150µm.

7. A high-performance carbon-based thermally conductive film, prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The high-performance carbon-based thermally conductive film has a thickness of 32-45 μm and a thermal conductivity of more than 1925 W / mK.