A graphite heat conducting sheet and its preparation, and semiconductor heat dissipation device

Abstract

The present invention provides a graphite thermally conductive sheet, a preparation method thereof, and a semiconductor heat dissipation device. The preparation method comprises the following steps: (1) performing array drilling on a graphite sheet to obtain a graphite sheet having an array hole arrangement; (2) performing plasma treatment on the graphite sheet having an array hole arrangement obtained in step (1), and then chemically grafting the graphite sheet using a vinyl-containing silane coupling agent to obtain a graphite sheet having a surface coated with a coupling agent layer; (3) coating the outer surface of the graphite sheet having a surface coated with a coupling agent layer obtained in step (2) with a polymer layer by chemical vapor deposition to obtain the graphite thermally conductive sheet. The graphite thermally conductive sheet provided by the present invention has good heat dissipation effect, good thermal uniformity, and good structural stability, and is suitable for heat conduction and heat dissipation of semiconductor chips in electronic products.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor heat dissipation materials, and in particular relates to a graphite heat conductive sheet and a preparation method thereof, and a semiconductor heat dissipation device. Background Art

[0002] With the rapid advancements in AI, 5G, and big data, the demand for high-performance thermally conductive sheet materials is increasing. Graphite, as an excellent thermal conductor, is often used as a thermally conductive material in mobile phones, laptops, medical devices, LED screens, and more. However, due to its unique grain orientation, graphite thermally conductive sheets are quite brittle, and their use as thermally conductive sheets can lead to localized breakage and powder loss. Furthermore, graphite powder's excellent electrical conductivity poses the risk of short-circuiting electronic devices. Therefore, graphite sheets often need to be coated before use to prevent conductivity and powder loss.

[0003] CN204031699U discloses a graphite thermally conductive sheet for electronic products. The sheet comprises a graphite sheet with a metal layer coated on both its upper and lower surfaces; a release paper layer coated with a thermally conductive adhesive layer and bonded to the metal layer on the lower surface of the graphite layer; a polyester film layer with an adhesive layer coated on its lower surface, adhered to the upper surface of the graphite sheet; and a release paper layer adhered to the other surface of the thermally conductive adhesive layer. The release paper layer is longer and wider than the graphite sheet, and the length and width of the polyester film layer are equal to those of the release paper layer. In this technical solution, the design of a release paper layer and a polyester film layer coated with an adhesive layer ensures that the prepared graphite thermal conductive sheet has good insulation properties and can prevent the shedding of graphite powder and graphite particles in the ink sheet from affecting the electrical performance of electronic products. However, since the length and width of the release paper layer and the polyester film layer are greater than the length and width of the graphite sheet, the edge width of the prepared thermal conductive sheet is large, which greatly reduces the effective heat dissipation area of ​​the graphite sheet, and the heat dissipation effect of the graphite thermal conductive sheet prepared in this way is poor.

[0004] CN207842213U discloses a thermally conductive sheet composed of a graphite sheet and a metal layer. The thermally conductive sheet includes a graphite layer, a flexible thermally conductive layer, an edge seal, release paper, a tooth groove, an aluminum sheet, and a silver sheet. Copper foil is provided below the graphite layer, a flexible thermally conductive layer is provided above the graphite layer, a release paper is provided above the flexible thermally conductive layer, the interior of the flexible thermally conductive layer is filled with silicone rubber below, and the interior of the flexible thermally conductive layer is filled with aluminum oxide above. An edge seal is provided on the left side of the graphite layer, a silver sheet is provided on the left side of the edge seal, and an aluminum sheet is provided on the right side of the edge seal. The aluminum sheet is fixed to the silver sheet with an adhesive, an adhesive is provided on the right side of the outer edge seal, and a tooth groove is provided at the bottom of the release paper. The thermally conductive sheet prepared by this technical solution has poor insulation performance.

[0005] CN103037669A discloses a graphite thermally conductive sheet. The sheet comprises a graphite sheet and a backing layer, the graphite sheet and backing layer being bonded and fixed via a double-sided adhesive layer. The upper surface of the graphite sheet is covered with a film layer, and the edges of the graphite sheet, double-sided adhesive layer, and film layer are aligned. While this technical solution can avoid undesirable phenomena such as graphite sheet powder shedding through the design of the backing layer and film layer, the resulting thermally conductive sheet suffers from poor heat dissipation.

[0006] As can be seen from the above content, single / double-sided tape is currently commonly used to bond and coat graphite sheets. However, the thicker adhesive layer (usually 3 to 15 μm) seriously affects the thermal conductivity of the graphite sheet, and the edge width is often larger, resulting in a significant reduction in the effective heat dissipation area of ​​the graphite sheet after being coated. At the same time, since the graphite material is relatively brittle, the prepared graphite thermal conductive sheet is generally bonded to the semiconductor chip through the backing adhesive when used. The adhesive not only plays an insulating and protective role, but also helps the graphite to fit tightly with the heat source or other semiconductor heat dissipation devices. However, the graphite surface itself is uneven and has a certain degree of roughness. Therefore, when the backing adhesive is applied, there will be certain bubbles inside, and the interface thermal resistance will increase, resulting in a decrease in the heat dissipation capacity of the final product.

[0007] Therefore, how to provide a graphite heat conducting sheet and heat dissipation device that has both good heat dissipation effect and good structural stability has become a technical problem that needs to be solved urgently. Summary of the Invention

[0008] To address the shortcomings of the existing technology, the present invention aims to provide a graphite thermally conductive sheet, a method for its preparation, and a semiconductor heat dissipation device. The present invention treats graphite sheets through a series of processes, including array punching, plasma treatment, chemical grafting with a silane coupling agent, and polymer coating. This utilizes the dual effects of physical structural fastening and chemical covalent bonding to enhance the polymer coating of the graphite sheet. The resulting graphite thermally conductive sheet exhibits excellent heat dissipation, thermal uniformity, and structural stability, making it suitable for heat conduction and heat dissipation of semiconductor chips in electronic products.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a method for preparing a graphite thermally conductive sheet, the method comprising the following steps:

[0011] (1) performing array punching on a graphite sheet to obtain a graphite sheet having an array hole arrangement;

[0012] (2) After the graphite sheet with arrayed holes obtained in step (1) is subjected to plasma treatment, it is chemically grafted using a vinyl-containing silane coupling agent to obtain a graphite sheet with a coupling agent layer coated on the surface;

[0013] (3) The outer surface of the graphite sheet coated with the coupling agent layer obtained in step (2) is coated with a polymer layer by chemical vapor deposition to obtain the graphite thermal conductive sheet.

[0014] In the present invention, by performing array drilling on the graphite sheet, the polymer layer can not only be attached to the front and back sides of the graphite sheet, but also the polymer layers on the front and back sides of the graphite sheet can be connected through the holes on the graphite sheet to form a physical interlocking structure, thereby improving the structural stability of the graphite thermal conductive sheet.

[0015] In the present invention, graphite sheets are subjected to plasma treatment to impart hydroxyl functional groups to the surface of the graphite sheets. Vinyl groups are then introduced into the surface of the graphite sheets through a chemical reaction between a vinyl-containing silane coupling agent and the hydroxyl groups, thereby obtaining graphite sheets with carbon-carbon double bonds on the surface. A dimer of a polymer layer is then formed through a vapor deposition method. During the formation of the polymer layer, free radicals are first cracked to form free radicals, which are then deposited on the surface of the graphite sheets through a reaction between the free radicals and the carbon-carbon double bonds, ultimately forming the polymer layer.

[0016] In the present invention, a coupling agent layer is coated on the surface of a graphite sheet, and the polymer layer and the graphite sheet are further connected by a chemical covalent bond through the vinyl groups in the coupling agent layer, thereby improving the adhesion between the polymer layer and the graphite sheet, thereby improving the coating stability of the polymer layer on the graphite sheet, and making the graphite sheet less likely to shed powder.

[0017] In the present invention, the graphite thermal conductive sheet is treated through a series of processes such as array punching, plasma treatment, chemical grafting of silane coupling agent, and polymer coating. The dual effects of physical structure fastening and chemical covalent bond bonding are adopted to improve the structural stability of the polymer-coated graphite sheet and avoid the occurrence of the problem of graphite sheet powder falling. The graphite thermal conductive sheet prepared in this way has good heat dissipation effect, good thermal uniformity and good structural stability.

[0018] It should be noted that the present invention does not impose any special limitation on the shape of the hole, and illustrative examples include but are not limited to cylindrical shapes.

[0019] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the objectives and beneficial effects of the present invention can be better achieved and realized.

[0020] As a preferred technical solution of the present invention, the graphite sheet is selected from natural single-layer graphite sheet, synthetic graphite sheet, multi-layer composite graphite sheet, graphene sheet or foamed graphite sheet.

[0021] Preferably, the array is punched by a laser punching method or a mechanical punching method.

[0022] Preferably, based on the volume of the graphite sheet as 100%, the total volume of the pores is 0.01 to 10%, more preferably 0.01 to 2.5% (for example, it can be 0.01%, 0.02%, 0.05%, 0.1%, 0.3%, 0.7%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc.), and further preferably 0.01 to 2.5%.

[0023] In the present invention, by controlling the total pore volume within a specific range, the graphite thermally conductive sheet produced has both good heat dissipation and good structural stability. If the total pore volume is too large, the resulting graphite thermally conductive sheet will have poor thermal uniformity; if the total pore volume is too small, the resulting graphite thermally conductive sheet will have poor structural stability.

[0024] Preferably, based on an area of ​​50 mm×50 mm of the graphite sheet, the number of holes on the graphite sheet is ≥20, for example, 20, 40, 60, 80, 100, 120, 150 or 200.

[0025] As a preferred technical solution of the present invention, the power of the plasma treatment is 50 to 1500 W, for example, it can be 50 W, 100 W, 300 W, 500 W, 700 W, 900 W, 1100 W, 1300 W or 1500 W.

[0026] Preferably, the plasma treatment time is 30 to 60 min, for example, it can be 30 min, 33 min, 36 min, 39 min, 42 min, 46 min, 50 min, 52 min, 55 min, 57 min or 60 min.

[0027] Preferably, the plasma used in the plasma treatment is selected from any one of oxygen, helium, neon or argon, or a combination of at least two thereof, more preferably a combination of oxygen and helium or a combination of oxygen and neon.

[0028] Preferably, the volume percentage of oxygen in the combination of oxygen and helium or the combination of oxygen and neon is independently selected from 99 to 99.5%, for example, it can be 99%, 99.1%, 99.2%, 99.3%, 99.4% or 99.5%.

[0029] Preferably, the volume percentage of helium in the combination of oxygen and helium is 0.5-1%, for example, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%.

[0030] Preferably, the volume percentage of neon in the combination of oxygen and neon is 0.5-1%, for example, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%.

[0031] As a preferred technical solution of the present invention, the vinyl-containing silane coupling agent is selected from any one of γ-methacryloxypropyltrimethoxysilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxyethoxy)silane, vinyltri-tert-butyloxysilane, vinyltri-tert-butylperoxysilane or vinyltriacetoxysilane, or a combination of at least two thereof.

[0032] As a preferred technical solution of the present invention, the polymer layer is prepared from a dimer.

[0033] Preferably, the dimer is selected from any one of p-xylene dimer, dichlorop-xylene dimer, tetrachlorop-xylene dimer, tetrafluorop-xylene dimer and octafluorop-xylene dimer, or a combination of at least two thereof.

[0034] In the present invention, the polymer in the formed polymer layer is selected from N-type polyparaxylene, C-type polyparaxylene, D-type polyparaxylene, F-type polyparaxylene, and HT-type polyparaxylene. The dimer forming N-type polyparaxylene is p-xylene dimer, the dimer forming C-type polyparaxylene is dichlorop-xylene dimer, the dimer forming D-type polyparaxylene is tetrachlorop-xylene dimer, the dimer forming F-type polyparaxylene is octafluorop-xylene dimer, and the dimer forming HT-type polyparaxylene is tetrafluorop-xylene dimer.

[0035] Preferably, the thickness of the polymer layer is 1 to 3 μm, for example, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm or 3 μm.

[0036] The present invention controls the thickness of the polymer layer within a specific range, so that the graphite thermal conductive sheet prepared has good structural stability. If the thickness of the polymer layer is too large or too small, the structural stability of the graphite thermal conductive sheet prepared is poor.

[0037] As a preferred technical solution of the present invention, the preparation method specifically comprises the following steps:

[0038] (1) punching a graphite sheet in an array to obtain a graphite sheet having an array of holes, wherein the total volume of the holes is 0.01 to 10% based on the volume of the graphite sheet as 100%, and the number of holes on the graphite sheet is ≥20 based on an area of ​​50 mm×50 mm;

[0039] (2) subjecting the graphite sheet with arrayed holes obtained in step (1) to plasma treatment for 30 to 60 minutes at a power of 50 to 1500 W, and then chemically grafting the graphite sheet with a vinyl-containing silane coupling agent to obtain a graphite sheet coated with a coupling agent layer;

[0040] (3) Using the dimer, the outer surface of the graphite sheet coated with the coupling agent layer obtained in step (2) is coated with a polymer layer by chemical vapor deposition to obtain the graphite thermal conductive sheet, wherein the thickness of the polymer layer is 1 to 3 μm.

[0041] In a second aspect, the present invention provides a graphite thermally conductive sheet prepared by the preparation method described in the first aspect.

[0042] The graphite heat conductive sheet prepared by the preparation method provided by the present invention comprises a graphite sheet, a coupling agent layer and a polymer layer arranged in sequence radially from the inside to the outside; the coupling agent layer is prepared from a vinyl-containing silane coupling agent.

[0043] In a third aspect, the present invention provides a semiconductor heat dissipation device, comprising the graphite heat conductive sheet as described in the second aspect;

[0044] The graphite heat conductive sheet is clamped between the packaged semiconductor chip and the first heat sink.

[0045] As a preferred technical solution of the present invention, the first heat sink includes heat dissipation fins and a heat dissipation fan.

[0046] As a preferred technical solution of the present invention, the heat dissipation device further includes a second heat sink, and the second heat sink is located between the packaged semiconductor chip and the graphite heat conducting sheet.

[0047] Preferably, the second heat sink includes a heat pipe and a heat spreader.

[0048] The preparation method provided by the present invention provides a graphite thermally conductive sheet having excellent heat dissipation performance and structural stability, thereby avoiding the problem of graphite sheet powder shedding. When a semiconductor heat dissipation device is prepared using the graphite thermally conductive sheet provided by the present invention, a first heat sink or a second heat sink can be directly pressed together with the graphite thermally conductive sheet to form a semiconductor heat dissipation device. During direct pressing, the graphite thermally conductive sheet does not experience problems such as detachment of the polymer coating or cracking of the graphite sheet, thereby blocking the graphite thermally conductive sheet's electrical conductivity. Furthermore, the direct pressing process effectively reduces the interfacial thermal resistance between the semiconductor heat dissipation devices, thereby improving the overall heat dissipation capability of the device.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] In the present invention, a graphite thermal conductive sheet prepared by a specific preparation method and by controlling the thickness of the polymer layer and the total volume of the pores on the graphite sheet within a specific range has good heat dissipation effect and good thermal uniformity. After a heat dissipation test, the temperature of the simulated heat source is 76.9-79.4°C, and the temperature difference between the graphite thermal conductive sheet at one end away from the simulated heat source and the temperature of the graphite thermal conductive sheet directly above the simulated heat source is 2.3-3.9°C. At the same time, the prepared graphite thermal conductive sheet has good structural stability. Under the conditions of a curvature radius of 5mm and a bending angle of 180°, no creases will appear after 500 bendings. After 50 cycles of cold and hot shocks, no delamination will appear, and the sheet is suitable for heat conduction and heat dissipation of semiconductor chips in electronic products. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 Schematic diagram of the cross section of the graphite thermal conductive sheet provided in Examples 1-4 of the present invention at a location containing a hole;

[0052] Figure 2 Schematic diagram of the cross section of the graphite heat conductive sheet provided in Examples 1-4 of the present invention without holes;

[0053] Figure 3 Schematic top view of the graphite thermal conductive sheet provided in Examples 1-4 of the present invention;

[0054] Figure 4 This is a schematic structural diagram of a heat dissipation device prepared from the graphite heat conductive sheet provided in Example 2 of the present invention;

[0055] Figure 5 This is a schematic structural diagram of the side surface of a heat dissipation device prepared using the graphite heat conductive sheet provided in Example 2 of the present invention;

[0056] Figure 6 This is a schematic structural diagram of a graphite heat conductive sheet provided in Example 3 of the present invention for heat conduction and heat dissipation of semiconductor chips in electronic products;

[0057] Figure 7 This is a schematic structural diagram of the side surface of a graphite heat conductive sheet provided by Example 3 of the present invention for heat conduction and heat dissipation of a semiconductor chip in an electronic product;

[0058] Figure 8 This is a schematic structural diagram of the heat dissipation test of the graphite heat conductive sheet provided by the present invention;

[0059] Among them, 1-graphite thermal conductive sheet, 11-graphite sheet, 12-coupling agent layer, 13-polymer layer, 14-hole, 2-semiconductor chip, 3-heat pipe, 4-heat fin, 5-housing, 6-test base, 7-simulated heat source. DETAILED DESCRIPTION

[0060] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0061] The sources of some components in the following examples and comparative examples are as follows:

[0062] Synthetic graphite sheet: thermal conductivity is 1200W / (m·K);

[0063] Graphene sheet: thermal conductivity is 1500W / (m·K);

[0064] Foamed graphite sheet: thermal conductivity is 1000W / (m·K).

[0065] Example 1

[0066] This embodiment provides a graphite heat conducting sheet and a preparation method thereof. The cross-sectional structural diagram of the graphite heat conducting sheet 1 is shown in FIG. Figure 1 and Figure 2 As shown, the preparation method is as follows:

[0067] (1) punching an array of holes in a synthetic graphite sheet of 40 mm × 60 mm and 25 μm in thickness by mechanical punching to obtain a graphite sheet 11 having an array of circular holes, wherein the diameter of the circular holes is 3.90 mm and the number of the circular holes is 20. Based on the volume of the graphite sheet 11 being 100%, the total volume of the circular holes is 10%;

[0068] (2) subjecting the graphite sheet 11 having an array of circular holes obtained in step (1) to plasma treatment for 60 min at a power of 1000 W, and then immersing it in vinyltrimethoxysilane for 1 min for chemical grafting to obtain a graphite sheet 11 having a surface coated with a coupling agent layer 12, wherein the plasma is oxygen;

[0069] (3) Using paraxylene dimer, the outer surface of the graphite sheet 11 with the surface-coated coupling agent layer 12 obtained in step (2) is coated with a polymer layer 13 by chemical vapor deposition to obtain the graphite thermal conductive sheet 1, wherein the thickness of the polymer layer 13 is 1 μm.

[0070] Example 2

[0071] This embodiment provides a graphite heat conducting sheet and a preparation method thereof, and a semiconductor heat dissipation device. The cross-sectional structural diagram of the graphite heat conducting sheet 1 is shown in FIG. Figure 1 and Figure 2 As shown, the preparation method is as follows:

[0072] (1) punching an array of holes in a synthetic graphite sheet of 40 mm × 60 mm and 25 μm in thickness by mechanical punching to obtain a graphite sheet 11 having an array of circular holes, wherein the diameter of the circular holes is 1.95 mm and the number of the circular holes is 20. Based on the volume of the graphite sheet 11 being 100%, the total volume of the circular holes is 2.5%;

[0073] (2) After the graphite sheet 11 with an array of circular holes obtained in step (1) is subjected to plasma treatment for 60 minutes at a power of 1500 W, vinyl tris(β-methoxyethoxy)silane is added dropwise to any surface of the graphite sheet 11 to completely wet the surface of the graphite sheet 11, and the surface is allowed to stand for 30 minutes. After drying for 1 minute, the above operation is performed on the other surface of the graphite sheet 11 to obtain a graphite sheet 11 coated with a coupling agent layer 12, wherein the plasma is oxygen and helium (volume ratio is 99:1);

[0074] (3) Using octafluoroparaxylene dimer, the outer surface of the graphite sheet 11 with the surface-coated coupling agent layer 12 obtained in step (2) is coated with a polymer layer 13 by chemical vapor deposition to obtain the graphite thermal conductive sheet 1, wherein the thickness of the polymer layer 13 is 1 μm.

[0075] A heat dissipation device for semiconductor chips is prepared from the graphite heat conductive sheet, and its structural diagram is shown in FIG. Figure 4-5 As shown, the semiconductor chip 2 is offset to a certain extent, so a heat pipe 3 is used at the bottom of the heat dissipation device to quickly transfer the heat generated by the semiconductor chip 2 to the middle position of the graphite thermal conductive sheet 1. A heat dissipation fin 4 is installed on the top of the graphite thermal conductive sheet 1 to assist in heat dissipation by increasing the contact area with the air. The heat pipe 3, the graphite thermal conductive sheet 1, and the heat dissipation fin 4 are all assembled by direct pressing.

[0076] Example 3

[0077] This embodiment provides a graphite heat conducting sheet and a preparation method thereof. The cross-sectional structural diagram of the graphite heat conducting sheet 1 is shown in FIG. Figure 1 and Figure 2 As shown, the preparation method is as follows:

[0078] (1) punching a 40 mm × 60 mm, 25 μm thick graphene sheet into an array of holes by mechanical punching to obtain a graphite sheet 11 having an array of circular holes, wherein the diameter of the circular holes is 0.50 mm and the number of the circular holes is 40. Based on the volume of the graphite sheet 11 being 100%, the total volume of the circular holes is 0.3%;

[0079] (2) Under a power of 500 W, the graphite sheet 11 with an array of circular holes obtained in step (1) is subjected to plasma treatment for 60 minutes, the treated graphite sheet 11 is hung, and γ-methacryloxypropyltrimethoxysilane is sprayed on any surface of the graphite sheet 11 using a spray valve to completely wet the surface of the graphite sheet 11. After standing for 30 minutes, it is dried, and the above operation is performed on the other surface of the graphite sheet 11 to obtain a graphite sheet 11 coated with a coupling agent layer 12, wherein the plasma is oxygen and helium (volume ratio is 99:1);

[0080] (3) Using dichloroparaxylene dimer, the outer surface of the graphite sheet 11 with the surface-coated coupling agent layer 12 obtained in step (2) is coated with a polymer layer 13 by chemical vapor deposition to obtain the graphite thermal conductive sheet 1, wherein the thickness of the polymer layer 13 is 2 μm.

[0081] The graphite heat conducting sheet provided in this embodiment can be directly used for heat conduction and heat dissipation of semiconductor chips in electronic products. Its structural diagram is shown in FIG. Figure 6-7 As shown, one side of the graphite heat conductive sheet 1 is directly bonded to the semiconductor chip 2 , and the other side is directly bonded to the housing 5 .

[0082] Example 4

[0083] This embodiment provides a graphite heat conducting sheet and a preparation method thereof. The cross-sectional structural diagram of the graphite heat conducting sheet 1 is shown in FIG. Figure 1 and Figure 2 As shown, the preparation method is as follows:

[0084] (1) A 40 mm × 60 mm, 25 μm thick foamed graphite sheet was punched with an array of holes by mechanical punching to obtain a graphite sheet 11 having an array of circular holes. The diameter of the circular holes was 0.10 mm, and the number of the circular holes was 200. Based on the volume of the graphite sheet 11 being 100%, the total volume of the circular holes accounted for 0.06%;

[0085] (2) Plasma-treating the graphite sheet 11 with the arrayed circular holes obtained in step (1) for 60 min at a power of 50 W, placing the treated graphite sheet 11 in a vapor deposition apparatus, and vapor-depositing vinyltriethoxysilane to chemically graft the graphite sheet 11 onto the surface, thereby obtaining a graphite sheet 11 coated with a coupling agent layer 12, wherein the plasma is composed of oxygen and neon (volume ratio of 99:1);

[0086] (3) Tetrachloroparaxylene dimer is used to coat the outer surface of the graphite sheet 11 coated with the coupling agent layer 12 obtained in step (2) with a polymer layer 13 by chemical vapor deposition to obtain the graphite thermal conductive sheet 1, wherein the thickness of the polymer layer 13 is 3 μm.

[0087] Example 5

[0088] This embodiment provides a graphite thermally conductive sheet and a preparation method thereof. The difference from Example 2 is that the diameter of the circular holes is 0.14 mm, the number is 20, the volume of the graphite sheet is 100%, and the total volume of the circular holes is 0.01%. Other conditions are the same as those in Example 2.

[0089] Example 6

[0090] This embodiment provides a graphite thermally conductive sheet and a preparation method thereof. The difference from Example 2 is that the diameter of the circular holes is 1.75 mm, the number is 20, the volume of the graphite sheet is 100%, the total volume of the circular holes is 2%, and other conditions are the same as Example 2.

[0091] Example 7

[0092] This embodiment provides a graphite thermally conductive sheet and a preparation method thereof. The difference from Example 2 is that the diameter of the circular holes is 3.90 mm, the number is 20, the volume of the graphite sheet is 100%, and the total volume of the circular holes is 10%. Other conditions are the same as Example 2.

[0093] Example 8

[0094] This embodiment provides a graphite thermally conductive sheet and a preparation method thereof. The difference from Example 2 is that the diameter of the circular holes is 4.63 mm, the number is 20, the volume of the graphite sheet is 100%, and the total volume of the circular holes is 14%. Other conditions are the same as Example 2.

[0095] Example 9

[0096] This embodiment provides a graphite thermally conductive sheet and a preparation method thereof. The difference from Example 2 is that the thickness of the polymer layer is 2 μm, and other conditions are the same as those of Example 1.

[0097] Example 10

[0098] This embodiment provides a graphite thermally conductive sheet and a preparation method thereof. The difference from Example 2 is that the thickness of the polymer layer is 3 μm, and other conditions are the same as those of Example 1.

[0099] Example 11

[0100] This embodiment provides a graphite thermally conductive sheet and a preparation method thereof. The difference from Example 2 is that the thickness of the polymer layer is 0.5 μm, and other conditions are the same as those of Example 1.

[0101] Example 12

[0102] This embodiment provides a graphite thermally conductive sheet and a preparation method thereof. The difference from Example 2 is that the thickness of the polymer layer is 4 μm, and other conditions are the same as those of Example 1.

[0103] Comparative Example 1

[0104] This comparative example provides a graphite thermal conductive sheet and a preparation method thereof, which differs from Example 2 in that step (1) is not performed, and other conditions are the same as those in Example 2.

[0105] Comparative Example 2

[0106] This comparative example provides a graphite thermally conductive sheet and a preparation method thereof. The difference from Example 2 is that the graphite thermally conductive sheet does not contain a coupling agent layer, and other conditions are the same as those in Example 2.

[0107] Comparative Example 3

[0108] This comparative example provides a graphite thermal conductive sheet and a preparation method thereof, which differs from Example 2 in that plasma treatment is not performed in step (2), and other conditions are the same as those in Example 2.

[0109] The performance of the graphite thermal conductive sheet provided in the above embodiments and comparative examples was tested using the following test methods:

[0110] Heat dissipation: The graphite heat conductive sheet prepared in the above examples and comparative examples was directly pressed on the surface of a simulated heat source device to test the heat dissipation effect. Figure 8 As shown, the simulated heat source includes a test base 6 and a simulated heat source 7. The temperature of the simulated heat source 7 (T1), the temperature of the graphite heat conductive sheet 1 directly above the simulated heat source 7 (T2), and the temperature of the graphite heat conductive sheet 1 directly above the test base 6 away from the simulated heat source 7 (T3) are recorded;

[0111] Bending resistance: The test standard is a bending angle of 180° and a curvature radius of 5mm;

[0112] Thermal shock test: GB / T 2423 "Basic environmental testing procedures for electrical and electronic products".

[0113] The performance test results of the graphite thermal conductive sheets provided in the above examples and comparative examples are shown in Tables 1-3 below:

[0114] Table 1

[0115]

[0116]

[0117] As can be seen from the contents of Table 1, the present invention adopts a specific preparation method and controls the total volume of the holes on the graphite sheet within the range of 0.01 to 10%. The graphite thermal conductive sheet prepared has a good heat dissipation effect. After the heat dissipation test, the temperature of the simulated heat source is 76.9 to 79.4°C, and the prepared graphite thermal conductive sheet has good thermal uniformity. The temperature difference between the graphite thermal conductive sheet at one end away from the simulated heat source and the temperature of the graphite thermal conductive sheet directly above the simulated heat source is 2.3 to 3.9°C. Further, by controlling the total volume of the holes on the graphite sheet within the range of 0.01 to 2.5%, the temperature difference between the graphite thermal conductive sheet at one end away from the simulated heat source and the temperature of the graphite thermal conductive sheet directly above the simulated heat source is 2.3 to 3.1°C.

[0118] Compared with Example 2, if the total volume of the holes on the graphite sheet is larger (Example 7), the heat dissipation effect and thermal uniformity of the prepared graphite thermal conductive sheet are poor; if the total volume of the holes on the graphite sheet is too large (Example 7), the thermal uniformity of the prepared graphite thermal conductive sheet is poor, and the temperature difference between the graphite thermal conductive sheet at one end away from the simulated heat source and the temperature of the graphite thermal conductive sheet directly above the simulated heat source is 4.3°C; if the total volume of the holes on the graphite sheet is too small, or even no holes are set (Comparative Example 1), the prepared graphite thermal conductive sheet has good heat dissipation and thermal uniformity, but its structural stability is poor.

[0119] Table 2

[0120]

[0121]

[0122] Table 3

[0123]

[0124]

[0125] As can be seen from the contents of Table 2-3, the graphite thermal conductive sheet prepared by the present invention through a specific preparation method and by controlling the thickness of the polymer layer within a specific range has good structural stability. The prepared graphite thermal conductive sheet will not be delaminated after 50 cycles of hot and cold shock. Under the conditions of a curvature radius of 5 mm and a bending of 180°, no crease will appear after 500 bendings. It has a long service life and is suitable for preparing heat dissipation devices for electronic products.

[0126] Compared with Example 2, if the thickness of the polymer layer is too small (Example 11), the structural stability of the prepared graphite thermal conductive sheet is poor, and the membrane will break when it is bent 500 times; if the thickness of the polymer layer is too large (Example 12), the structural stability of the prepared graphite thermal conductive sheet is poor, and creases will appear when it is bent 500 times.

[0127] Compared with Example 2, if no holes are provided on the graphite sheet (Comparative Example 1) or no coupling agent layer is provided in the graphite thermal conductive sheet (Comparative Example 2) or the graphite sheet is not treated with plasma (Comparative Example 3), the structural stability of the prepared graphite thermal conductive sheet is poor and creases are easily formed after bending.

[0128] In summary, through a specific preparation method and by controlling the thickness of the polymer layer and the total volume of the pores on the graphite sheet within a specific range, the prepared graphite thermal conductive sheet has good heat dissipation effect and good thermal uniformity. At the same time, the prepared graphite thermal conductive sheet has good structural stability and is suitable for heat conduction and heat dissipation of semiconductor chips in electronic products.

[0129] The applicant declares that the present invention uses the above-described embodiments to illustrate the detailed process flow of the present invention, but the present invention is not limited to the above-described detailed process flow, that is, it does not mean that the present invention must rely on the above-described detailed process flow to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for various raw materials in the products of the present invention, addition of auxiliary ingredients, and selection of specific methods, etc., are all within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing a graphite thermal conductive sheet, characterized in that: The preparation method comprises the following steps: (1) Punching holes in an array on a graphite sheet to obtain a graphite sheet having an array hole arrangement; (2) After the graphite sheet with arrayed holes obtained in step (1) is subjected to plasma treatment, it is chemically grafted using a vinyl-containing silane coupling agent to obtain a graphite sheet with a coupling agent layer coated on the surface; (3) coating the outer surface of the graphite sheet coated with the coupling agent layer obtained in step (2) with a polymer layer by chemical vapor deposition to obtain the graphite thermal conductive sheet; Based on the volume of the graphite sheet as 100%, the total volume of the pores is 0.01-10%; The polymer layer is prepared from a dimer; The dimer is selected from any one of p-xylene dimer, dichlorop-xylene dimer, tetrachlorop-xylene dimer, tetrafluorop-xylene dimer and octafluorop-xylene dimer, or a combination of at least two thereof; The thickness of the polymer layer is 1-3 μm.

2. The preparation method according to claim 1, characterized in that The graphite sheet is selected from natural single-layer graphite sheet, synthetic graphite sheet, multi-layer composite graphite sheet, graphene sheet or foamed graphite sheet.

3. The preparation method according to claim 1, characterized in that The array punching method is a laser punching method or a mechanical punching method.

4. The preparation method according to claim 1, characterized in that Based on the volume of the graphite sheet being 100%, the total volume of the pores is 0.01-2.5%.

5. The preparation method according to claim 1, characterized in that Based on the graphite sheet area of ​​50 mm×50 mm, the number of holes on the graphite sheet is ≥20.

6. The preparation method according to claim 1, characterized in that The power of the plasma treatment is 50~1500W.

7. The preparation method according to claim 1, characterized in that The plasma treatment time is 30 to 60 minutes.

8. The preparation method according to claim 1, characterized in that The plasma used in the plasma treatment is selected from any one of oxygen, helium, neon or argon, or a combination of at least two of them.

9. The preparation method according to claim 8, characterized in that The plasma used in the plasma treatment is a combination of oxygen and helium or a combination of oxygen and neon.

10. The preparation method according to claim 9, characterized in that The volume percentage of oxygen in the combination of oxygen and helium or the combination of oxygen and neon is independently selected from 99 to 99.5%.

11. The preparation method according to claim 9, characterized in that The volume percentage of helium in the combination of oxygen and helium is 0.5-1%.

12. The preparation method according to claim 9, characterized in that The volume percentage of neon in the combination of oxygen and neon is 0.5-1%.

13. The preparation method according to claim 1, characterized in that The vinyl-containing silane coupling agent is selected from any one of γ-methacryloxypropyltrimethoxysilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxyethoxy)silane, vinyltri-tert-butyloxysilane, vinyltri-tert-butylperoxysilane or vinyltriacetoxysilane, or a combination of at least two thereof.

14. The preparation method according to claim 1, characterized in that The preparation method specifically comprises the following steps: (1) Punching a graphite sheet in an array to obtain a graphite sheet having an array of holes, wherein the total volume of the holes is 0.01-10% based on the volume of the graphite sheet as 100%, and the number of holes on the graphite sheet is ≥20 based on the area of ​​the graphite sheet of 50 mm×50 mm; (2) Plasma-treating the graphite sheet with arrayed holes obtained in step (1) for 30 to 60 minutes at a power of 50 to 1500 W, chemically grafting the sheet with a vinyl-containing silane coupling agent to obtain a graphite sheet coated with a coupling agent layer; (3) Using the dimer, the outer surface of the graphite sheet coated with the coupling agent layer obtained in step (2) is coated with a polymer layer by chemical vapor deposition to obtain the graphite thermal conductive sheet, wherein the thickness of the polymer layer is 1 to 3 μm.

15. A graphite thermally conductive sheet prepared by the preparation method according to any one of claims 1 to 14.

16. A semiconductor heat dissipation device, characterized in that: The semiconductor heat dissipation device comprises the graphite heat conductive sheet as claimed in claim 15; The graphite heat conductive sheet is clamped between the packaged semiconductor chip and the first heat sink.

17. The semiconductor heat dissipation device according to claim 16, wherein: The first heat sink includes heat dissipation fins and a heat dissipation fan.

18. The semiconductor heat dissipation device according to claim 16 or 17, characterized in that: The heat dissipation device further includes a second heat sink, which is located between the packaged semiconductor chip and the graphite heat conducting sheet.

19. The semiconductor heat dissipation device according to claim 18, wherein: The second heat sink includes a heat pipe and a heat spreader.

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