A high-compressibility carbon material thermal conductive pad and preparation method thereof

Abstract

The present invention discloses a highly compressible carbon material thermally conductive gasket and a preparation method thereof, comprising a graphite / graphene thermally conductive layer and a thermally conductive silicone layer. The graphite / graphene thermally conductive layer and the thermally conductive silicone layer are stacked layer by layer to form a stack, and then the stack is formed by a bevel cutting process at a certain angle. The thermally conductive gasket has good thermal conductivity and mechanical properties as well as excellent compressibility, is suitable for promotion in the field of thermally conductive gaskets, and has broad development prospects.

Description

Technical Field

[0001] The invention relates to the field of heat conduction, and in particular to a high-compressibility carbon material heat-conducting gasket and a preparation method thereof. Background Art

[0002] Today, thermal interface materials have undergone decades of development, from low-end products such as thermal oil, thermal grease, and thermal silicone cloth to high-end products such as thermal gaskets, phase change materials, thermal gels, and liquid metals. The technology has also been gradually improved, among which thermal gaskets have developed the fastest and are the most widely used.

[0003] Traditional thermal pads are basically based on silica gel or other polymer materials as the matrix material. By filling thermal conductive powder, the composite material has a thermal conductive channel, which plays a role in the thermal conduction of the material. The more powder is filled, the more reasonable the powder particle size is, the more thermal conductive channels there are, and the higher the corresponding material thermal conductivity. However, with more and more filling materials, the mechanical properties of the product, especially the tensile strength and compressibility, have dropped significantly, thus limiting its application in many occasions. At the same time, the more powder is filled, the higher the density of the material, which is obviously inconsistent with the current trend of pursuing lightweight and user physical examination. The thermal conductivity of existing thermal pads is generally 3-5W / mK, which cannot meet the more urgent needs of industry development.

[0004] However, the inventors of this application found that the prior art has at least the following technical problems in the process of implementing the technical solution of the invention in the embodiments of this application:

[0005] The prior art (201621266385.7) discloses a white graphene thermal pad, which includes a substrate and a white graphene layer; the substrate is used as a base layer, the upper surface of the substrate is coated with a first white graphene layer, and the lower surface of the substrate is coated with a second white graphene layer; a thermal conductive adhesive layer is also adhered below the second white graphene layer, and the substrate is a metal sheet such as a steel sheet or an aluminum sheet. The prepared graphene thermal pad can reduce the working temperature of the LED display from 60°C to below 45°C when the LED display is working, achieving a good heat dissipation effect. However, because the thermal conductive adhesive layer is a double-sided tape, it is easy to have a negative impact on the thermal conductivity and heat dissipation performance of the thermal pad during operation, and the double-sided tape is also easy to lose its bonding effect in a long-term high-temperature environment; and the thermal conductive pad in the patent is simply stacked layer by layer, and has poor compressibility when facing vertical pressure, and cannot be used in some working environments with high external pressure.

[0006] Therefore, it is a very practical task to study a thermally conductive gasket that has excellent thermal conductivity and good compression performance. Summary of the invention

[0007] In order to solve the above problems, a first aspect of the present invention provides a highly compressible carbon material thermally conductive gasket, wherein the thermally conductive gasket comprises a thermally conductive layer and an adhesive layer.

[0008] In some preferred embodiments, the thermally conductive layer is at least one of a graphite sheet and a graphene sheet.

[0009] In some preferred embodiments, the thermally conductive layer is at least one of a hollow graphite sheet and a hollow graphene sheet.

[0010] In some preferred embodiments, the adhesive layer is a thermally conductive silicone layer.

[0011] In some preferred embodiments, the thickness of the adhesive layer is 30 to 50 microns; the thickness of the thermal conductive layer is 15 to 30 microns.

[0012] In some preferred embodiments, the volume fraction of the heat conductive layer is 80-85%.

[0013] The second aspect of the present invention provides a method for preparing the above-mentioned high-compressibility carbon material thermal conductive gasket, and the preparation steps include the following steps: (1) moving the thermal conductive layer flat to a laser cutting platform, using laser cutting to cut the thermal conductive layer horizontally in the middle into parallel long strips, the width of the unretained layer is 0.3 mm, and the width of the retained layer is 0.6 mm. After removing the unretained cut part of the layer, a finished hollow graphite layer or a hollow graphene layer is obtained; (2) then the hollow graphite layer or the hollow graphene layer is flatly transferred to a bonding platform by a robotic arm, and on the layer Evenly spray a layer of thermal conductive silicone layer; then align the second hollow graphite sheet or hollow graphene sheet with the first sheet sprayed with the thermal conductive silicone layer and stack them neatly; repeat the process until the stack reaches a height of 4 to 5 cm, and then place it at room temperature until the thermal conductive silicone layer is completely cured to obtain a stack; (3) tilt the stack at a certain angle with the horizontal line as the reference line and wait for cutting; (4) use a multi-wire cutting machine to vertically cut the tilted stack in the direction perpendicular to the horizontal line, and the thickness of the slice obtained is 0.1 mm to 2 mm, so as to obtain a highly compressible carbon material thermal conductive gasket.

[0014] In some preferred embodiments, the thermal conductive layer has a width of 5 to 6 centimeters and a length of 6 to 7 centimeters.

[0015] In some preferred embodiments, the time of standing at room temperature is 6 to 10 hours.

[0016] In some preferred embodiments, the inclination angle of the stack is 10-80° with the horizontal line as the reference line.

[0017] The present invention adds graphite / graphene sheets and thermally conductive silicone layers during the preparation process of the thermally conductive gasket, and adopts a special multi-wire cutting process. The synergistic effect of the two makes the thermally conductive gasket have excellent thermal conductivity, mechanical properties and compressibility.

[0018] The inventors further discovered that when the graphite / graphene sheet is a hollow graphite / graphene sheet, the mechanical properties of the thermally conductive gasket can be effectively improved; further, when the volume fraction of the hollow graphite / graphene sheet in the stack is 80-85%, the prepared thermally conductive gasket can simultaneously take into account good thermal conductivity and mechanical properties. This may be that when the volume fraction of the hollow graphite / graphene sheet is 80-85%, the gasket can have good thermal conductivity and heat dissipation performance, and at this time, the thermally conductive silicone layer, which mainly acts as a bonding agent, can effectively bond the hollow graphite / graphene sheet tightly, thereby connecting the heat conduction path and serving as a "bridge" between the heat conduction layers; the applicant has concluded through a large number of experiments that when the volume fraction of the hollow graphite / graphene sheet is 80-85%, the thermally conductive gasket still has excellent thermal conductivity while having the most excellent mechanical properties.

[0019] The inventors have also found that the use of an oblique multi-wire cutting process can further improve the thermal conductivity of the thermally conductive gasket, and can effectively improve the compressibility of the thermally conductive gasket; further, when the angle of the oblique multi-wire cutting of the stack is 10 to 80°, the obtained thermally conductive gasket not only has good thermal conductivity in the horizontal and vertical directions, but also obtains excellent gasket compressibility. The reason is: the physical rigidity direction of the gasket obtained by 10 to 80° oblique cutting changes from vertical upward to an oblique angle, and its physical rigidity direction is different from the vertical stress direction received by the gasket. Under the same vertical stress conditions, the oblique gasket will undergo oblique compression, which can reach the physical limit of the compression of the thermally conductive gasket; and after oblique cutting, the graphite / graphene thermal conductive layer has a split direction in both the horizontal and vertical directions. When the bevel angle is less than 10° or greater than 80°, the rigidity direction of the graphite tends to coincide with and be perpendicular to the vertical stress direction, and there is no premise for oblique compression.

[0020] The inventors also unexpectedly discovered that the prepared inclined graphite / graphene thermal gasket, due to the oblique rigid direction and the stacking method of the hollow sheet layers, reduces the breakage of the thermally conductive sheet layer caused by the large angle between the bending direction and the physical rigid direction, thereby greatly improving the flexibility of the thermal gasket.

[0021] The multi-wire cutting machine in the present invention can be commercially available, such as the CF400T multi-wire cutting machine sold by Yantai Likai Intelligent Technology Co., Ltd.

[0022] The heat conductive layer in the present invention can be commercially available, such as the graphite sheet product LD-RG017 sold by Foshan Xinshi Intelligent Technology Co., Ltd.

[0023] The thermally conductive silicone in the present invention may be commercially available, such as the Ecoflex 00-20 product sold by Smooth-On, Inc.

[0024] Beneficial effect: The highly compressible carbon material thermal conductive gasket of the present invention, through the mutual superposition of the hollow thermal conductive sheet layer and the thermal conductive silicone layer and the oblique multi-wire cutting process, makes the prepared graphite / graphene thermal conductive gasket have excellent thermal conductivity while also obtaining excellent mechanical strength and great compressibility, and can adapt to the use environment with large stress in the vertical direction, and has good promotion prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the structure of the hollow heat-conducting sheet layer in the present invention;

[0026] Figure 2 It is a schematic diagram of the beveling process of the stacked blocks in the present application;

[0027] Figure 3 It is a cross-sectional view of the thermally conductive pad obtained in the present application;

[0028] In the figure:

[0029] L1 length of thermal conductive layer; L2 width of thermal conductive layer; L3 width of sheet layer not retained; L4 width of sheet layer retained; 1 thermal conductive layer; 2 adhesive layer; 3 multi-line cutting direction. DETAILED DESCRIPTION

[0030] Example 1

[0031] Embodiment 1 provides a highly compressible carbon material thermally conductive gasket, comprising a graphite sheet layer and a thermally conductive silicone layer.

[0032] The present embodiment also provides a method for preparing a highly compressible carbon material thermal conductive pad, the steps comprising the following steps: (1) a graphite sheet with a thickness of 200 microns (graphite sheet length L16 cm, width L25 cm) is flatly moved to a laser cutting platform, and the graphite sheet is horizontally cut into strips with a length of 4 cm and arranged parallel to the long and wide sides by laser cutting. The width L3 of the unretained sheet is 0.3 mm, and the width L4 of the retained sheet is 0.6 mm. After removing the unretained cut portion of the sheet, a finished hollow graphite sheet 1 is obtained; (2) the hollow graphite sheet 1 is then flatly transferred to a bonding plate by a robotic arm. Form a platform, use a spray system to evenly spray a layer of thermal conductive silicone layer 2 on the hollow graphite sheet 1, the thickness of the thermal conductive silicone layer 2 is 20 microns; then align the second hollow graphite sheet 1 with the first sheet sprayed with the thermal conductive silicone layer 2, and stack them neatly; repeat the process until the stacking height is 4 cm, and then leave it at room temperature for 8 hours to allow the thermal conductive silicone layer to completely solidify; (3) tilt the stacked blocks 45° based on the horizontal line and wait for cutting; (4) use a multi-wire cutting machine to vertically cut the tilted stacked blocks in the vertical direction of the horizontal line, and the thickness of the slices obtained is 1 mm, thus obtaining a highly compressible carbon material thermal conductive gasket.

[0033] In this embodiment, the thermally conductive silicone is the Ecoflex 00-20 product sold by Smooth-On, Inc.

[0034] The multi-wire cutting machine in this embodiment is a CF400T model multi-wire cutting machine sold by Yantai Likai Intelligent Technology Co., Ltd.

[0035] The graphite in this embodiment is the graphite sheet product LD-RG017 sold by Foshan Xinshi Intelligent Technology Co., Ltd.

[0036] The thermally conductive gasket prepared in this embodiment is denoted as R1.

[0037] Example 2

[0038] The specific implementation of this embodiment is the same as that of Embodiment 1, except that the inclination angle of the stacking block is 80°.

[0039] The thermally conductive film prepared in this example is denoted as R2.

[0040] Example 3

[0041] The specific implementation of this embodiment is the same as that of Embodiment 1, except that the inclination angle of the stacking block is 10°.

[0042] The thermally conductive film prepared in this example is recorded as R3.

[0043] Comparative Example 1

[0044] The specific implementation of this comparative example is the same as that of Example 1, except that the inclination angle of the stacking block is 85°.

[0045] The thermally conductive film prepared in this comparative example is recorded as D1.

[0046] Comparative Example 2

[0047] The specific implementation of this comparative example is the same as that of Example 1, except that the inclination angle of the stacking block is 5°.

[0048] The thermally conductive film prepared in this comparative example is recorded as D2.

[0049] Comparative Example 3

[0050] The specific implementation of this comparative example is the same as that of Example 1, except that the thickness of the graphite sheet is 150 microns.

[0051] The thermally conductive film prepared in this comparative example is recorded as D3.

[0052] Comparative Example 4

[0053] The specific implementation of this comparative example is the same as that of Example 1, except that the thickness of the graphite sheet is 300 microns.

[0054] The thermally conductive film prepared in this comparative example is recorded as D4.

[0055] Comparative Example 5

[0056] The specific implementation of this comparative example is the same as that of Example 1, except that the graphite sheet layer is a common graphite sheet layer, and the hollow heat-conducting sheet layer is not produced by laser cutting.

[0057] The thermally conductive film prepared in this comparative example is recorded as D5.

[0058] Performance Evaluation

[0059] 1. Thermal conductivity: The thermal conductivity of the thermally conductive gasket was tested according to ASTM D5470-2006. Five samples were tested for each comparative example. The average value of the measured values ​​was recorded in Table 1.

[0060] 2. Compression rate: Test the compression of thermally conductive gasket samples of the same thickness at 50 psi and express it as a percentage. For each comparative example, five samples are tested and the average value is taken and recorded in Table 1.

[0061] 3. Tensile strength: A universal tensile tester was used to test the tensile strength of thermally conductive gasket samples of the same thickness. Five samples were tested for each comparative example. The measured values ​​were averaged and recorded in Table 1.

[0062] Table 1

[0063] Example Thermal conductivity (W / mk) Compression rate (%) Tensile strength(MPa) R1 39.5 70 17 R2 38.7 60 15 R3 38.8 61 16 D1 21.5 32 11 D2 24.3 33 10 D3 22.7 45 9 D4 23.4 44 9 D5 24.5 47 8

[0064] It can be seen from Examples 1 to 3 and Comparative Examples 1 to 5 that the highly compressible carbon material thermally conductive gasket and its preparation method provided by the present invention have good thermal conductivity and mechanical properties as well as excellent compressibility, and are suitable for promotion in the field of thermally conductive gaskets, and have broad development prospects. Among them, Example 1 obtains the best performance index under the conditions of the best sheet thickness ratio, preparation process and other factors.

[0065] Finally, it is pointed out that the above-described embodiments are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A highly compressible carbon material thermally conductive pad, characterized in that: The invention relates to a method for preparing a highly compressible carbon material thermally conductive gasket, comprising the following steps: (1) moving a graphite layer with a length L1 of 6 cm, a width L25 cm, and a thickness of 200 μm to a laser cutting platform, and using laser cutting to cut the middle of the graphite layer horizontally into strips with a length of 4 cm and arranged parallel to the wide side, wherein the width L3 of the unretained layer is 0.3 mm, and the width L4 of the retained layer is 0.6 mm. After removing the unretained cut portion of the layer, a finished hollow graphite layer 1 is obtained; (2) then the hollow graphite layer 1 is smoothly transferred to a bonding platform by a robotic arm, and a layer of thermally conductive silicone is evenly sprayed on the hollow graphite layer 1 using a spray glue system. Thermal silicone layer 2, the thickness of thermal conductive silicone layer 2 is 20 microns; then align the second hollow graphite sheet 1 with the first sheet sprayed with thermal conductive silicone layer 2, and stack them neatly; repeat the process until the stacking height is 4 cm, and then place it at room temperature for 8 hours to wait for the thermal conductive silicone layer to completely solidify; (3) tilt the stacked blocks 45° based on the horizontal line and wait for cutting; (4) use a multi-wire cutting machine to vertically cut the tilted stacked blocks in the direction perpendicular to the horizontal line, and the thickness of the slices obtained is 1 mm, thus obtaining a highly compressible carbon material thermal conductive gasket.

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