High strength graphene thermal pad and method for manufacturing same

Abstract

This application relates to high strength graphene thermal pads and methods for making same, and relates to the field of thermal interface materials. [Solution] A high-strength graphene thermal pad includes at least two graphene thermally conductive layers stacked in sequence, with adjacent graphene thermally conductive layers bonded and fixed with a binder. The graphene thermally conductive layer includes multiple graphene films stacked in sequence, with adjacent graphene films bonded with a binder. The stacking directions of the graphene films in two adjacent graphene thermally conductive layers are perpendicular to each other but parallel to the same plane. The stacking direction of the graphene thermally conductive layers is also perpendicular to the stacking direction of the graphene films in any of the graphene thermally conductive layers. In this application, graphene thermally conductive layers manufactured by stacking multiple graphene films are stacked, and the stacking directions of the graphene films in adjacent layers are orthogonal to each other, thereby providing the graphene thermal pad with good mechanical strength in two directions: the graphene stacking direction and the direction perpendicular to the graphene film stacking direction.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION This application relates to the field of thermal interface materials, and more particularly to high strength graphene thermal pads and methods for making same.

[0002] Cross-reference to related applications This application claims priority based on a Chinese application filed with the China Patent Office on January 4, 2023, bearing application number 202310007425.4 and entitled "High-strength graphene thermal pad and manufacturing method thereof," the entire contents of which are incorporated herein by reference. [Background technology]

[0003] With the advent of the 5G era, the operating frequencies of electronic chips continue to increase, and electronic products are gradually becoming lighter and more highly integrated. As a result, the heat generated by devices is increasing significantly. If excess heat is not quickly dissipated, it will have a significant impact on the operating status of electronic components, and in severe cases, it may even cause failure or a shortened lifespan. Thermal interface materials have emerged to solve this problem, but traditional thermal interface materials have low thermal conductivity and are mainly limited to 1-10W, making it difficult to meet the demand for high thermal conductivity.

[0004] Graphene is a new type of carbon material with a single-layer, two-dimensional honeycomb lattice structure formed by the deposition of carbon atoms. It not only possesses excellent mechanical, optical, and electrical properties, but also excellent thermal performance, with a theoretical thermal conductivity of 5300 W / (m·K), more than 10 times that of common metals. Currently, graphene films developed using graphene as a raw material have horizontal thermal conductivity of up to 2000 W / (m·K), providing excellent thermal conductivity and making them suitable as new thermal interface materials for the heat dissipation of chips with high heat flux densities.

[0005] However, the thermal conductivity of graphene films through their thickness is relatively low, typically less than 10 W / (m·K), making it difficult to meet the requirements for longitudinal thermal conductivity. Currently, graphene films are typically stacked to produce graphene blocks, which are then sliced ​​along the stacking direction to produce graphene spacers with high through-thickness thermal conductivity. However, because the graphene film often has a multilayer structure with weak cohesive strength, the resulting graphene thermal pads exhibit strength anisotropy, with good strength perpendicular to the stacking direction but poor strength in the stacking direction, significantly affecting their use. Related technologies use a drilling device to create through-holes in the graphene film and then inject a polymer resin. However, graphene films have poor adhesion to the resin and are prone to overflow when pressure is applied, resulting in a lack of resin remaining in the gaps within the through-holes. Furthermore, the drilling process performed on the surface of the graphene film can damage the graphene film, affecting heat conduction. Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above technical problems, the present application provides a high-strength graphene thermal pad that improves the thermal conductivity performance and mechanical strength of the graphene thermal pad, and a manufacturing method thereof. [Means for solving the problem]

[0007] According to an exemplary embodiment of the present application, the present application provides a high-strength graphene thermal pad, which adopts the following technical features: The high-strength graphene thermal pad includes at least two graphene thermally conductive layers stacked in order, with adjacent graphene thermally conductive layers adhesively fixed together by a binder.

[0008] The graphene thermal conductive layer includes a plurality of graphene films stacked in order, and adjacent graphene films are bonded together by a binder. The stacking directions of the graphene films in two adjacent graphene thermal conduction layers are perpendicular to each other but parallel to the same plane, and the stacking direction of the graphene thermal conduction layers is perpendicular to the stacking direction of the graphene films in any of the graphene thermal conduction layers.

[0009] By adopting the above-described technology, the graphene film has excellent thermal conductivity in its in-layer direction. The graphene thermal conductive layer is manufactured by stacking multiple graphene films and bonding each layer with a binder, thereby fully utilizing the high in-layer horizontal thermal conductivity of the graphene film in the graphene thermal conductive layer. At least two graphene thermal conductive layers are bonded and stacked, with the bonding surfaces of adjacent two graphene thermal conductive layers perpendicular to any one of the graphene films, and the stacking directions of the graphene films in adjacent two graphene thermal conductive layers perpendicular to each other when stacked. In the graphene thermal pad obtained by stacking in this manner, the stacking direction of the graphene film in any one of the graphene thermal conductive layers is perpendicular to the stacking direction of the graphene film in at least one other graphene thermal conductive layer. In other words, by arranging the stacking directions of the graphene films in adjacent graphene thermal conductive layers perpendicular to each other, a graphene thermal pad is manufactured that has higher strength in two mutually perpendicular horizontal X and Y directions.

[0010] The graphene thermal conductive layer obtained by laminating multiple graphene films has high strength in the direction perpendicular to the plane of the graphene film due to the support effect of the adhesive, but has low strength in the stacking direction of the graphene film due to the low cohesive strength of the graphene film. Furthermore, when pressure is applied in this direction, the adhesive between the graphene film layers tends to spill out, affecting mechanical performance. By arranging the stacking direction of the graphene thermal conductive layer perpendicular to the stacking direction of the graphene film when stacking the graphene thermal conductive layer, the resulting graphene thermal pad has excellent strength in the stacking direction of the graphene film and in the other two directions perpendicular to the graphene film.

[0011] Optionally, the graphene film is a film layer prepared by coating a graphene oxide slurry, and a specific preparation method includes the following steps: Step S1: A graphene oxide slurry is applied to produce a graphene oxide coating film, and the graphene oxide coating film is dried to obtain a graphene oxide thin film. Step S2: The graphene oxide thin film is graphitized to produce a graphene film.

[0012] By adopting the above-described technique, graphene oxide has good hydrophilicity and disperses well in water to form a slurry, which can be applied to form a film. During the application process, the graphene oxide layers can be well oriented in the coating plane and can exhibit good bonding between the graphene oxide layers. The formed graphene oxide film has high bonding strength and mechanical strength, as well as good thermal conductivity in the plane direction of the graphene oxide film.

[0013] The graphite treatment of graphene oxide thin films allows the randomly distributed carbon atoms in graphene oxide to be organized at high temperatures, and the carbon material can undergo a structural transformation from a two-dimensional carbon network structure to a three-dimensional structure through "microcrystalline" growth, effectively improving the mechanical properties and strength of the graphene film, significantly reducing the thermal resistance between the layers of the graphene oxide film, and effectively improving the horizontal and vertical thermal conductivity.

[0014] Optionally, in step S1, the graphene oxide slurry is a graphene oxide aqueous slurry, and the solid content of the graphene oxide is 0.1-15 wt%.

[0015] By adopting the above technical form, the solid content of graphene oxide in the graphene oxide slurry is limited to the above range, which improves the coatability of the graphene oxide slurry, facilitates film formation, improves the orientation of the graphene oxide film layer in the film layer, and also improves the thermal conductivity performance of the film layer.

[0016] Optionally, the drying temperature of the graphene oxide coating is 80 to 150°C. More preferably, the drying temperature for the graphene oxide coating film is 100 to 120°C.

[0017] Optionally, in step S2, the graphitization temperature is 2500 to 3200° C., and the graphitization treatment time is 4 to 10 hours.

[0018] More preferably, the graphitization temperature is 2800 to 3000°C. By adopting the above-mentioned technical form, the graphene oxide coating film is heated and dried to remove moisture, forming a film layer with a certain strength, and then graphitized at a high temperature. In the graphitization process, if the graphitization temperature is too low, the degree of graphitization will be affected, resulting in insufficient graphitization within the graphene film and affecting the thermal conductivity performance of the film layer. If the graphitization temperature is too high, the formed graphene film will be too brittle, adversely affecting the mechanical performance of the film layer.

[0019] Optionally, the number of layers of the graphene thermally conductive layer is an even number. By adopting the above-described technical form, the number of layers of the graphene thermal conductive layer is made even, so that the mechanical performance and thermal conductivity performance of the graphene thermal conductive layer can be matched in two mutually perpendicular directions, and the performance in the two directions can be maintained in a balanced manner.

[0020] Optionally, the graphene film has a thickness of 50 to 600 μm. When the above-described technical form is adopted, if the graphene film is too thin, it is difficult to handle and the graphene film is easily torn during the lamination process. Furthermore, if the graphene film itself is too thin, a large amount of binder is required to laminate it to a predetermined thickness, which increases the amount of binder in the graphene thermal pad and affects the thermal conductivity performance of the thermal pad. If the graphene film is too thick, it becomes difficult to coat and the orientation of the graphene flakes in the coated graphene film layer becomes poor.

[0021] Optionally, the binder is any one or combination of polyurethane-based binders, epoxy resin-based binders, phenolic resin-based binders, acrylic resin-based binders, and binders. By adopting the above technical forms, all of the above binders have good adhesive effect with the graphene film, good thermal conductivity performance, and little impact on the thermal conductivity performance of the graphene thermal pad.

[0022] Optionally, the coating thickness of the binder between the layers of the graphene film is 5 to 80 μm. More preferably, the thickness of the binder applied between the layers of the graphene film is 10 to 30 μm.

[0023] In the above technical form, the binder mainly serves to adhere and fix the graphene film, and if the binder is applied too thinly, the adhesive effect is affected, making it difficult to provide good support when extruding the graphene thermal pad and affecting the mechanical strength of the graphene thermal pad.If the binder is applied too thickly, the proportion of the binder in the graphene thermal pad increases, reducing the thermal conductivity of the graphene film in the interlayer direction of the graphene thermal pad and affecting the thermal conductivity performance of the graphene thermal pad.

[0024] Optionally, the thickness of the graphene thermal conductive layer may be 0.1 to 3.5 mm. By adopting the above technical form, the thickness of the graphene thermal conductive layer can be kept within the above range, and the graphene thermal pad manufactured by stacking multiple layers of graphene has better thermal conductivity and mechanical strength.

[0025] According to an exemplary embodiment of the present application, the present application provides a manufacturing method for a high-strength graphene thermal pad, which adopts the following technical form: The manufacturing method for the high strength graphene thermal pad includes the following steps: Step S1: Formation of graphene block by stacking: Using a graphene film, a binder is applied to one layer of graphene film, and another layer of graphene is stacked on top of that. The stacking is repeated until a predetermined height is reached, and the binder is hardened to obtain a graphene block. Step S2: Slicing of graphene block: The graphene block is sliced ​​along the stacking direction of the graphene film to obtain a graphene thermal conductive layer. Step S3: Lamination of graphene flake layers: A binder is applied to the cut surface and / or one side parallel to the cut surface of the sliced ​​graphene thermally conductive layer, and the sliced ​​graphene thermally conductive layer is laminated with another layer of graphene thermally conductive layer, so that the surface where two adjacent graphene thermally conductive layers are bonded to each other is the cut surface or one side parallel to the cut surface, and the stacking direction of the graphene film in the two adjacent graphene layers is perpendicular. Step S4: Curing: Once the graphene thermal conductive layers have been stacked to the predetermined number, the binder is cured to obtain a high-strength graphene thermal pad. Optionally, in step S2, the slicing method is any one of wire cutting, laser cutting, ultrasonic cutting, and circular blade cutting. By adopting the above-described technology, a graphene thermal conduction block is manufactured by stacking multiple graphene films, which are then sliced ​​vertically. The thickness direction of the resulting graphene thermal conduction layer is aligned with the intralayer plane of the graphene film, resulting in extremely high thermal conductivity in the thickness direction of the graphene thermal conduction layer. In the subsequent process of stacking graphene thermal conduction layers to manufacture a graphene thermal pad, multiple graphene thermal conduction layers are sequentially stacked and adhesively fixed along their thickness direction, with the stacking directions of the graphene films in adjacent two graphene thermal conduction layers orthogonal to each other. This results in the graphene thermal pad having high strength in two orthogonal directions, the X and Y directions, in a plane perpendicular to the thickness direction. In other words, because any graphene thermal conduction layer has excellent mechanical performance in the stacking direction of the graphene film, the mechanical performance of the graphene thermal pad is further improved.

[0026] As described above, the present application includes at least one of the following beneficial technical effects. 1. In the technical form of the present application, a graphene thermal pad is manufactured by stacking at least two graphene thermal conductive layers obtained by stacking multiple layers of graphene, and the stacking directions of the graphene films in two adjacent thermal conductive layers in the graphene thermal pad are orthogonal to each other. As a result, the manufactured graphene thermal pad has excellent mechanical performance in two mutually orthogonal directions, the X direction and the Y direction, in the horizontal direction, which significantly improves the drawback of the graphene thermal pad having poor mechanical performance in the stacking direction of the graphene films. 2. In the technical form of the present application, a graphene film is produced by applying a graphene oxide slurry, drying it, and then graphitizing it. The graphene film produced by this method has good intralayer orientation of the graphene oxide layers, high thermal conductivity, high internal bond strength, and superior mechanical properties. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a schematic structural diagram of a graphene thermal pad according to Example 1 of the present application. [Figure 2] FIG. 1 is a schematic structural diagram of a graphene thermal pad according to Example 2 of the present application. [Figure 3] FIG. 1 is a schematic structural diagram of a graphene thermal pad according to Example 4 of the present application. [Figure 4] FIG. 1 is a schematic structural diagram of a graphene thermal pad according to Comparative Example 1 of the present application. [Figure 5] FIG. 1 is a schematic structural diagram of a graphene thermal pad according to Comparative Example 2 of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0028] The present application will be described in more detail below with reference to the drawings and specific examples. In the following examples, although specific conditions are not specified, the processes can be carried out under conventional conditions or under conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following examples can be ordinary commercially available products.

[0029] Example 1 This example provides a high-strength graphene thermal pad. As shown in FIG. 1, the graphene thermal pad includes two graphene thermal conductive layers 2. The graphene thermal conductive layers 2 are fabricated by sequentially stacking multiple graphene films 1. A silicone resin binder with model number KH-505 is applied between adjacent graphene films 1. The graphene thermal conductive layers 2 are stacked in the thickness direction (i.e., the Z direction in the figure), with the stacking direction perpendicular to the stacking direction of the graphene films 1. The high-strength graphene thermal pad is fabricated by the following method. Step S1: Graphene film production: A graphene oxide aqueous slurry with a solid content of 15 wt% was applied using a precision coater to obtain a graphene oxide coating film with a thickness of 100 μm. The graphene oxide coating film was dried at 100°C to remove moisture, obtaining a graphene oxide thin film. The graphene oxide thin film was graphitized at 2500°C for 4 hours to obtain a graphene film. Step S2: Formation of graphene block by lamination: Using graphene film, a binder was uniformly applied to one layer of graphene film with a coating thickness of 10 μm, and another layer of graphene film was laminated on top of it while aligning the position. Lamination was repeated in this manner until the total thickness reached 50 mm, and then the binder was cured to obtain a graphene block with a size of 50 × 50 × 50 mm. Step S3: Slicing of graphene block: The graphene block was sliced ​​by laser cutting along the stacking direction of the graphene film to a slice thickness of 0.2 mm, thereby obtaining a graphene thermally conductive layer. Step S4: Using two graphene thermally conductive layers, a binder was uniformly applied to the cut surface, with each layer having a thickness of 10 μm. The two graphene thermally conductive layers were stacked together with one side of the binder applied so that the stacking directions of the graphene films in the two graphene thermally conductive layers were perpendicular to each other. The binder was then cured to obtain a graphene thermal pad.

[0030] Example 2 The high-strength graphene thermal pad shown in FIG. 2 has four graphene thermal conductive layers 2, and is otherwise the same as in Example 1.

[0031] Example 3 In this example, the number of graphene thermal conduction layers is four, the thickness of a single layer of the graphene thermal conduction layer 2 is 0.1 mm, and the rest is the same as in Example 1.

[0032] Example 4 As shown in FIG. 3, this example is the same as Example 3, except that the graphene thermal conduction layer 2 has three layers.

[0033] Comparative Example 1 As shown in FIG. 4, in this comparative example, the graphene thermal pad is made of a single-layer graphene thermal conductive layer 2 having a thickness of 0.4 mm, and is otherwise the same as in Example 1.

[0034] Comparative Example 2 As shown in FIG. 5, in this comparative example, the stacking directions of the graphene films 1 in the two graphene thermal conduction layers 2 are the same, and the rest is the same as in Example 1.

[0035] Performance Test Using the graphene thermal pads manufactured in the above examples and comparative examples, tests for thermal conductivity and mechanical performance were carried out as follows. Thermal conductivity: The thermal resistance of the graphene thermal pad is tested in the thickness direction (Z direction in the figure). Mechanical performance: The tensile strength of the graphene thermal pad in the horizontal direction (X and Y directions in the figure) is tested.

[0036] The results of the performance tests for Examples 1 to 3 and Comparative Examples 1 and 2 are shown in Table 1 below. [Table 1]

[0037] As can be seen from the data in Table 1, by stacking multiple graphene thermal conductive layers and orthogonally stacking the graphene films in two adjacent graphene thermal conductive layers, the graphene thermal pad manufactured has high strength in two orthogonal directions, the X direction and the Y direction, without affecting the thermal conductivity of the graphene thermal pad. Compared to graphene thermal pads made of a single graphene thermal conductive layer or graphene thermal pads with multiple layers of graphene films arranged in the same direction, the thermal pad according to the technical form of the present application has superior mechanical performance.

[0038] Example 5 In this example, the graphene oxide slurry had a solid content of graphene oxide of 5 wt %, and the other conditions were the same as in Example 1.

[0039] Example 6 In this example, the graphene oxide slurry had a solid content of graphene oxide of 20 wt %, and the other conditions were the same as in Example 5.

[0040] Example 7 In this example, the graphene film was not graphitized during the manufacturing process, and the other steps were the same as in Example 5.

[0041] Example 8 In this example, the thickness of the graphene film is 600 μm, and the other aspects are the same as in Example 5.

[0042] Example 9 In this example, the thickness of the graphene film is 800 μm, and the other aspects are the same as in Example 5.

[0043] Example 10 In this example, the thickness of the slice of the graphene thermal conductive layer is 3.5 mm, and the other aspects are the same as in Example 5.

[0044] Example 11 In this example, the thickness of the slice of the graphene thermal conduction layer is 5 mm, and the other aspects are the same as in Example 5.

[0045] The results of the performance tests for Examples 5 to 11 are shown in Table 2 below. [Table 2]

[0046] As can be seen from the data in Table 2, in the manufacturing process of the graphene thermal pad, by adjusting parameters such as the thickness of the graphene film and the thickness of the graphene thermal conductive layer, the mechanical performance and thermal conductivity of the graphene thermal pad can be further improved. And as can be seen from the data in Table 2, when parameters such as the thickness of the graphene thermal conductive layer and the graphene film are within the preferred ranges of the present application, the manufactured graphene thermal pad has better mechanical performance and thermal conductivity, but when the limited ranges are exceeded, the mechanical performance and / or thermal conductivity of the graphene thermal pad will be reduced to a certain extent.

[0047] The above are preferred embodiments of the present application, and do not limit the scope of protection of the present application. Therefore, any equivalent modifications made according to the structure, shape and principle of the present application shall be included in the scope of protection of the present application.

[0048] Industrial Applicability The present application relates to a high-strength graphene thermal pad and a method for manufacturing the same, which relates to the field of thermal interface materials. The high-strength graphene thermal pad includes at least two graphene thermally conductive layers stacked in sequence, with adjacent graphene thermally conductive layers bonded and fixed by a binder. The graphene thermally conductive layer includes multiple graphene films stacked in sequence, with adjacent graphene films bonded by a binder. The stacking directions of the graphene films in two adjacent graphene thermally conductive layers are perpendicular to each other but parallel to the same plane. The stacking direction of the graphene films in any of the graphene thermally conductive layers is also perpendicular to the stacking direction of the graphene films in any of the graphene thermally conductive layers. In the present application, graphene thermally conductive layers manufactured by stacking multiple graphene films are stacked, and the stacking directions of the graphene films in adjacent layers are orthogonal to each other, thereby providing the graphene thermal pad with good mechanical strength in two directions: the graphene stacking direction and the direction perpendicular to the graphene stacking direction.

[0049] The high-strength graphene thermal pad and its manufacturing method according to the present application are reproducible and applicable to various industrial applications, for example, the high-strength graphene thermal pad according to the present application can be applied in the field of thermal interface materials. [Explanation of symbols]

[0050] 1. Graphene film 2. Graphene thermal conductive layer

Claims

1. The thermal conductive layer (2) includes at least two layers of graphene thermal conductive layers (2) stacked in order, and adjacent graphene thermal conductive layers (2) are bonded and fixed by a binder; The graphene thermal conduction layer (2) includes a plurality of graphene films (1) stacked in order, and adjacent graphene films (1) are bonded together by a binder; In two adjacent graphene thermal conductive layers (2), the stacking directions of the graphene films (1) are perpendicular to each other but parallel to the same plane, and the stacking direction of the graphene thermal conductive layer (2) is perpendicular to the stacking direction of the graphene films (1) in any of the graphene thermal conductive layers (2). High strength graphene thermal pad.

2. The graphene film (1) is a film layer produced by applying graphene oxide slurry, and the specific production method is as follows: a step S1 of applying a graphene oxide slurry to produce a graphene oxide coating film and drying the graphene oxide coating film to obtain a graphene oxide thin film; and a step S2 of graphitizing the graphene oxide thin film to produce a graphene film (1).

2. The high strength graphene thermal pad of claim 1.

3. In step S1, the graphene oxide slurry is a graphene oxide aqueous slurry, and the solid content of the graphene oxide is 0.1 to 15 wt %.

3. The high strength graphene thermal pad of claim 2.

4. In step S2, the graphitization temperature is 2500 to 3200°C, and the graphitization treatment time is 4 to 10 hours.

4. The high-strength graphene thermal pad according to claim 2 or 3.

5. In step S1, the drying temperature of the graphene oxide coating film is 80 to 150°C. A high-strength graphene thermal pad according to any one of claims 2 to 4.

6. The thickness of the graphene film (1) is 50 to 600 μm. A high-strength graphene thermal pad according to any one of claims 1 to 5.

7. The binder is any one or a combination of a polyurethane binder, an epoxy resin binder, a phenolic resin binder, an acrylic resin binder, and a binder. A high-strength graphene thermal pad according to any one of claims 1 to 6.

8. The number of layers of the graphene thermal conduction layer (2) is an even number. A high-strength graphene thermal pad according to any one of claims 1 to 7.

9. The thickness of the graphene thermal conductive layer (2) is 0.1 to 3.5 mm. A high-strength graphene thermal pad according to any one of claims 1 to 8.

10. The thickness of the binder applied between the graphene films (1) is 5 to 80 μm. A high-strength graphene thermal pad according to any one of claims 1 to 9.

11. a graphene block forming step S1 by lamination in which a binder is applied to one layer of the graphene film (1), another layer of graphene is laminated thereon, and the lamination is repeated up to a predetermined height, and the binder is hardened to obtain a graphene block; a graphene block slicing step S2 in which the graphene block is sliced ​​along the stacking direction of the graphene film (1) to obtain a graphene thermal conduction layer (2); a graphene flake layer lamination step S3 in which a binder is applied to the cut surface and / or one side parallel to the cut surface of the sliced ​​graphene thermal conductive layer (2), and the sliced ​​graphene thermal conductive layer (2) is laminated with another layer of graphene thermal conductive layer (2), so that the surfaces where two adjacent graphene thermal conductive layers (2) are bonded to each other are the cut surface or one side parallel to the cut surface, and the lamination directions of the graphene films in the two adjacent graphene layers are perpendicular; and a curing step S4 in which the binder is cured after the graphene thermal conductive layer (2) has been laminated to a predetermined number of layers to obtain a high-strength graphene thermal pad. A method for manufacturing a high-strength graphene thermal pad according to any one of claims 1 to 10.

12. In step S2, the slicing method is any one of wire cutting, laser cutting, ultrasonic cutting, and circular blade cutting. The method for manufacturing a high strength graphene thermal pad according to claim 11.

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