Composite heat-conducting gasket, preparation method thereof and radiator

Abstract

The invention relates to a composite heat-conducting gasket, a preparation method thereof and a radiator, and belongs to the technical field of thermal interface materials. The composite heat-conducting gasket comprises a graphene layer oriented in the thickness direction, the graphene layer is provided with a first surface and a second surface in the thickness direction, and the first surface is used for being attached to a heat dissipation device; the liquid metal sheet layer is arranged on the second surface of the graphene layer, can be bent towards the side surface of the graphene layer and covers at least part of the side surface of the graphene layer; wherein the liquid metal sheet layer sequentially comprises a first alloy layer, a middle layer and a second alloy layer from top to bottom, the first alloy layer and the second alloy layer are made of the same material, the middle layer is made of a sheet-shaped heat conduction material, and the sheet-shaped heat conduction material comprises a solid metal foil or a third alloy; the melting temperature of the intermediate layer is higher than that of the first alloy layer and the second alloy layer. The composite heat-conducting gasket provided by the invention has high heat-conducting property and also has high compression ratio and high repeatability.

Description

Technical Field

[0001] The present application relates to the technical field of thermal interface materials, and in particular to a composite thermally conductive gasket and a preparation method thereof, and a heat sink. Background Art

[0002] As chip power continues to rise, the requirements for thermal interface materials between the heat sink probe and the chip are getting higher and higher. Thermal interface materials are key components that connect the heat sink and the chip, and their performance directly affects the heat dissipation effect and life of the chip. Before the chip leaves the factory, it needs to be tested for performance, so there are high requirements for thermal conductivity and reusability of thermal interface materials.

[0003] At present, the thermal interface materials used in existing chip testing scenarios mainly include textured indium sheets and carbon fiber gaskets. Although these materials have certain thermal conductivity, their thermal resistance is all within 0.15℃*cm 2 / W or more, which is difficult to meet for high-power chip test scenarios. The strength and reusability of thermal interface materials with good thermal conductivity are currently poor; while for thermal interface materials with high repeatability, their thermal conductivity and compressibility are insufficient. Therefore, many high-performance materials are difficult to meet the requirements for repeatable use, so that the interface material needs to be replaced for each test, which not only increases the test cost, but also wastes time and resources. Summary of the invention

[0004] In view of the deficiencies in the prior art, the purpose of the embodiments of the present application includes providing a composite thermally conductive gasket and a preparation method thereof, and a heat sink, so as to improve the compression rate and repeatability while taking into account the thermal conductivity performance.

[0005] The embodiment of the present application is implemented as follows:

[0006] In a first aspect, an embodiment of the present application provides a composite thermally conductive gasket, comprising: a graphene layer oriented along a thickness direction, the graphene layer having a first surface and a second surface in the thickness direction, the first surface being used to adhere to a heat dissipation device; a liquid metal sheet layer, the liquid metal sheet layer being arranged on the second surface of the graphene layer, and being able to bend toward the side of the graphene layer, and covering at least part of the side of the graphene layer; wherein the liquid metal sheet layer comprises, from top to bottom, a first alloy layer, an intermediate layer, and a second alloy layer, the first alloy layer and the second alloy layer are made of the same material, the intermediate layer is a sheet-like thermally conductive material, and the sheet-like thermally conductive material comprises a solid metal foil or a third alloy; the melting point temperature of the intermediate layer is higher than that of the first alloy layer and the second alloy layer.

[0007] In the above technical scheme, the composite thermally conductive gasket includes a graphene layer and a liquid metal sheet layer oriented in the thickness direction; wherein the graphene layer has a first surface and a second surface in the thickness direction, the first surface is used to fit the heat dissipation device, and the liquid metal sheet layer is arranged on the second surface of the graphene layer. After the graphene layer is oriented in the thickness direction, it forms a unidirectional high thermal conductivity material, and at the same time it has a high compressibility, which can greatly absorb the gap tolerance of the contact surface with the heat dissipation device, thereby achieving efficient heat conduction; the liquid metal sheet layer includes an upper and lower surface alloy layer and an intermediate layer, the intermediate layer has high strength, can play a supporting role, and improves repeatability, and the alloy layer on its surface will melt into a liquid at a certain temperature, and the fluidity and compressibility of the liquid will be much higher than that of the solid state, so it can achieve a close combination with the interface after melting, and play an interface filling role, thereby reducing thermal resistance and better heat conduction; therefore, the present application can improve the compression rate and repeatability while improving the thermal conductivity by combining the graphene layer and the liquid metal sheet layer.

[0008] In some embodiments of the present application, the difference between the melting point temperature of the intermediate layer and the temperature of the first alloy layer is at least 50°C; or, the difference between the melting point temperature of the intermediate layer and the temperature of the second alloy layer is at least 50°C.

[0009] By making the melting point temperature of the surface layer and the middle layer of the liquid metal sheet have a temperature difference of at least 50° C., the atomic diffusion capacity of the alloy in the surface layer and the metal in the middle layer can be weakened, which is beneficial to reducing thermal resistance.

[0010] In some embodiments of the present application, the solid metal foil includes one or more of indium foil, platinum foil, copper foil, silver foil, aluminum foil and zinc foil; and / or the third alloy includes one or more of Cu-Al alloy, Cu-Sn alloy and Cu-In alloy.

[0011] The use of the above-mentioned solid metal foil or the third alloy can provide the liquid metal sheet with good flexibility and a certain strength, so that it can maintain its shape while maintaining its thermal conductivity; therefore, the liquid metal sheet can be bent and punched to be fixed on the heat dissipation device to better conduct heat and reduce thermal resistance.

[0012] In some embodiments of the present application, the material of the first alloy layer or the second alloy layer includes a phase change alloy having a melting point lower than 120°C.

[0013] The material of the first alloy layer or the second alloy layer is a low melting point alloy, that is, a phase change alloy with a melting point temperature below 120°C, which will melt into a liquid at a certain temperature. The fluidity and compressibility of the liquid are much higher than that of the solid state. Therefore, after melting, it can achieve a close combination with the interface and play a role in filling the interface gaps. For example, it can fill the gaps on the surface of the graphene layer, achieve a close combination with the surface of the graphene layer, and better achieve heat conduction, thereby reducing thermal resistance. When in contact with the chip, it can also fill the gaps on the chip surface, achieving better contact between the interface material and the chip surface, thereby reducing thermal resistance and greatly improving the thermal conductivity effect.

[0014] In some embodiments of the present application, the phase change alloy includes one or more of a Ga—In—Sn alloy, an In—Sn—Bi alloy, an In—Bi alloy, and a Ga—In—Sn—Bi alloy.

[0015] The above alloys are all phase change alloys with a melting point below 120°C. Under the binding force of these low-melting-point alloys, the graphene layer and the liquid metal layer can be tightly combined and cannot be easily peeled off. In addition, these alloys can be transformed from solid to liquid or liquid-solid mixed state at a certain temperature to fill the gaps at the interface, thereby reducing the interface impedance. For example, In-Sn-Bi alloy will melt into liquid metal at 60°C, and the liquid metal can be tightly combined with the interface in contact, thereby reducing thermal resistance.

[0016] In some embodiments of the present application, the thickness of the liquid metal sheet layer is 50-100 μm, wherein the thickness of the first alloy layer and the second alloy layer is the same, which is 10-20 μm.

[0017] In the liquid metal sheet, the first alloy layer and the second alloy layer are mainly used to fill the interface gaps. Within the above thickness range, the gaps can be effectively filled to improve the thermal conductivity. The middle layer has high strength and mainly plays a supporting role. Therefore, the thickness of the middle layer is larger than the surface layer, which is more conducive to providing support and thus improving repeatability. Controlling the thickness of the liquid metal sheet to 50-100μm is conducive to reducing thermal resistance. When the thickness of the liquid metal sheet is less than 50μm, the liquid metal sheet is too thin, the surface is not flat and smooth, and wrinkles are easily generated, resulting in poor contact. When the thickness is higher than 100μm, the middle layer will warp due to the high modulus, which will increase thermal resistance.

[0018] In some embodiments of the present application, the thickness of the graphene layer is 0.3-3 mm.

[0019] The thickness of the graphene layer is within the above thickness range, and the graphene layer can not only provide high thermal conductivity for the composite thermal conductive gasket, but also provide high compression rate.

[0020] In the second aspect, an embodiment of the present application provides a method for preparing a composite thermally conductive gasket, comprising: growing graphene on a metal foil using a chemical vapor deposition method, peeling the graphene off the metal foil after the growth is completed and stacking it longitudinally to obtain graphene oriented in the thickness direction; heating and melting the material of the first alloy layer and the material of the second alloy layer to form liquid metal, coating the liquid metal on opposite sides of the intermediate layer of sheet-like thermally conductive material to form a first alloy layer and a second alloy layer, and then rolling the whole to obtain a liquid metal sheet; heating the liquid metal sheet so that the first alloy layer or the second alloy layer on the surface of the liquid metal sheet is in a molten state, and then placing the graphene above the liquid metal sheet, applying pressure to make the graphene and the liquid metal sheet in close contact, and pushing, maintaining the pressure for cooling, to obtain a composite thermally conductive gasket.

[0021] In the above technical solution, the grown graphene is peeled off from the metal foil and stacked longitudinally to form graphene oriented in the thickness direction. This orientation enhances the thermal conductivity path of the graphene and improves the thermal conductivity efficiency. Then, the materials of the first alloy layer and the second alloy layer are heated and melted to form liquid metal, and the liquid metal is applied to the opposite sides of the intermediate layer of sheet-like thermal conductive material. The high fluidity of the liquid metal enables it to penetrate into the microstructure of the sheet-like thermal conductive material, so that the intermediate layer is more firmly bonded to the first alloy layer and the second alloy layer, thereby forming a liquid metal sheet. Furthermore, after the first alloy layer or the second alloy layer on the surface of the liquid metal sheet is heated to a molten state, pressure is applied to bring the graphene into close contact with the liquid metal sheet, and then the graphene is combined by pushing, and then cooled while maintaining the pressure, which helps to form a stable interface structure, thereby improving the stability and durability of the composite thermal conductive gasket.

[0022] In some embodiments of the present application, after coating is completed but before rolling is performed, the thickness of the first alloy layer formed is 10-50 μm, and the thickness of the second alloy layer is 10-50 μm; or / and, the metal foil includes one or more of copper foil, nickel foil, magnesium foil, iron foil, steel foil and titanium foil.

[0023] Setting the coating thickness of the first alloy layer and the second alloy layer to 10-50 μm can achieve a good gap filling effect and is also beneficial to the subsequent rolling process to avoid excessive overflow and affect the thermal conductivity. The use of the above-mentioned metal foil is more conducive to the growth of graphene. For example, copper foil and nickel foil not only have a high thermal conductivity and can effectively conduct heat, but also have high strength and rigidity, and can provide a stable substrate, so that graphene is not easily deformed or damaged during growth and post-processing.

[0024] In some embodiments of the present application, the applied pressure is 20-30 psi, and the pushing speed is 0.8-1.2 mm / s.

[0025] By controlling the pressure to 20-30psi and the pushing speed to 0.8-1.2mm / s, the thickness of the graphene layer and the liquid metal sheet can be effectively controlled, thereby effectively reducing the thermal resistance.

[0026] In a third aspect, an embodiment of the present application provides a heat sink, comprising a heat dissipation device and any of the above-mentioned composite thermally conductive gaskets, wherein a first surface of the composite thermally conductive gasket is attached to the heat dissipation device.

[0027] In the above technical solution, the heat sink and the composite thermally conductive gasket of the present application are bonded to each other, wherein the first surface of the composite thermally conductive gasket is bonded to the heat sink, that is, the graphene side of the composite thermally conductive gasket is closely attached to the heat sink, and the high thermal conductivity of graphene enables heat to be quickly transferred to the heat sink, thereby significantly reducing thermal resistance, improving heat dissipation efficiency, and achieving the purpose of rapid heat dissipation.

[0028] In some embodiments of the present application, in the heat sink, the liquid metal sheet wraps the second surface and the side surface of the graphene layer and extends outward, and the two ends of the extended liquid metal sheet are detachably connected to the opposite sides of the heat sink.

[0029] The liquid metal sheet layer wraps around the second surface and the side surface of the graphene layer and extends outward, that is, the liquid metal sheet layer wraps around the outer portion of the graphene layer, which not only protects the graphene layer, but also improves the interface bonding ability between the graphene layer and the heat dissipation device, thereby reducing thermal resistance and improving heat dissipation efficiency; in addition, the two ends of the extended liquid metal sheet layer are detachably connected to the opposite sides of the heat dissipation device respectively, and due to the high flexibility of the liquid metal sheet, the composite thermally conductive gasket can be bent and perforated, thereby making the composite thermally conductive gasket firmly fixed on the heat dissipation device. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 This is a schematic diagram of the structure of the composite thermally conductive gasket of the present application;

[0032] Figure 2 This is a schematic diagram of the structure of the radiator of this application;

[0033] Figure 3 This is a schematic diagram of the application scenario of the composite thermally conductive gasket of this application.

[0034] Icon: 101 - first alloy layer; 102 - middle layer; 103 - second alloy layer; 200 - graphene layer; 300 - heat sink; 400 - screw; 500 - chip. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0036] The following is a detailed description of a composite thermally conductive gasket, a preparation method thereof, and a heat sink according to an embodiment of the present application.

[0037] The embodiment of the present application provides a composite thermally conductive gasket, comprising: a graphene layer 200 oriented along a thickness direction, the graphene layer 200 having a first surface and a second surface in the thickness direction, the first surface being used to adhere to a heat dissipation device 300; a liquid metal sheet layer, the liquid metal sheet layer being arranged on the second surface of the graphene layer 200, and being able to bend toward the side of the graphene layer 200, and covering at least a portion of the side of the graphene layer 200; wherein the liquid metal sheet layer comprises, from top to bottom, a first alloy layer 101, an intermediate layer 102, and a second alloy layer 103, the first alloy layer 101 and the second alloy layer 103 are made of the same material, the intermediate layer 102 is a sheet-like thermally conductive material, and the sheet-like thermally conductive material comprises a solid metal foil or a third alloy; the melting point temperature of the intermediate layer 102 is higher than that of the first alloy layer 101 and the second alloy layer 103.

[0038] like Figure 1 and Figure 2 As shown, the composite thermally conductive gasket includes a graphene layer 200 and a liquid metal sheet oriented in the thickness direction; wherein the graphene layer 200 has a first surface and a second surface in the thickness direction, the first surface is used to adhere to the heat dissipation device 300, and the liquid metal sheet is arranged on the second surface of the graphene layer 200. The graphene layer 200 is oriented in the thickness direction to form a unidirectional high thermal conductivity material, and at the same time, it has a high compression rate, so that the composite thermally conductive gasket has a high compression rate, which can greatly absorb the gap tolerance of the contact surface with the heat dissipation device 300, thereby achieving efficient heat conduction. Continue to refer to Figure 1It can be seen that the liquid metal sheet can be bent toward the side of the graphene layer 200 and cover at least part of the side of the graphene layer 200, on the one hand, to protect the graphene; on the other hand, since the first surface of the graphene is in contact with the heat sink 300, that is, the heat sink 300 is located below the liquid metal sheet, it can be bent due to the high flexibility of the liquid metal sheet. Therefore, the liquid metal sheet can be made into a bent and perforated shape, so that the liquid metal sheet wraps the second surface and two side surfaces of the graphene, and the end portion extending to the side portion of the graphene is perforated, and then the liquid metal sheet can be fixed on the heat sink 300, which is conducive to better heat conduction. The liquid metal sheet is a sandwich structure, which has the same first alloy layer 101 and second alloy layer 103, and the middle layer 102 is a sheet-like thermal conductive material, which includes a solid metal foil or a third alloy; wherein the middle layer 102 of the sandwich structure has high strength, can play a supporting role, and improve repeatability, and the alloy layer on its surface will melt into a liquid at a certain temperature, and the fluidity and compressibility of the liquid will be much higher than that of the solid state, so it can achieve a close combination with the interface after melting, and play a role in filling the interface, thereby reducing thermal resistance and better heat conduction. Therefore, thanks to the high performance and high strength of the liquid metal sheet sandwich structure, the repeatability of the thermal conductive gasket is improved.

[0039] In the embodiment of the present application, the temperature difference between the melting point of the intermediate layer 102 and the temperature of the first alloy layer 101 is at least 50° C.; or, the temperature difference between the melting point of the intermediate layer 102 and the temperature of the second alloy layer 103 is at least 50° C.

[0040] That is to say, the melting point temperature of the surface layer of the liquid metal sheet must be at least 50°C lower than the melting point temperature of the middle layer 102. Setting such a melting point difference can weaken the atomic diffusion ability of the alloy on the surface layer and the metal in the middle layer 102. If the melting points of the surface layer and the middle layer 102 are close, it is possible that when the atoms in different layers are very active during operation, they are easy to diffuse with each other, resulting in an increase in the melting point of the metal in the surface layer, which in turn leads to an increase in thermal resistance.

[0041] As an example, the temperature difference between the melting point temperature of the intermediate layer 102 and the temperature of the first alloy layer 101 includes but is not limited to 50°C, 55°C, 60°C, 70°C, 80°C, 100°C, 110°C, and 120°C.

[0042] As an example, the solid metal foil includes but is not limited to one or more of indium foil, platinum foil, copper foil, silver foil, aluminum foil and zinc foil; the third alloy includes but is not limited to one or more of Cu-Al alloy, Cu-Sn alloy and Cu-In alloy.

[0043] The material of the first alloy layer 101 or the second alloy layer 103 includes, but is not limited to, a phase change alloy having a melting point lower than 120° C. As an example, the phase change alloy includes, but is not limited to, one or more of Ga-In-Sn alloy, In-Sn-Bi alloy, In-Bi alloy, and Ga-In-Sn-Bi alloy.

[0044] In the present application, the thickness of the liquid metal sheet is 50-100 μm, wherein the thickness of the first alloy layer 101 and the second alloy layer 103 is the same, which is 10-20 μm.

[0045] That is, the thickness of the intermediate layer 102 is 10-80 μm. By way of example, the thickness of the intermediate layer 102 includes but is not limited to 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, and 80 μm.

[0046] Illustratively, the first alloy layer 101 and the second alloy layer 103 have the same thickness, including but not limited to 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, and 20 μm.

[0047] In the present application, the thickness of the graphene layer 200 is 0.3-3 mm.

[0048] By way of example, the thickness of the graphene layer 200 includes, but is not limited to, 0.3 mm, 0.5 mm, 0.8 mm, 1 mm, 1.3 mm, 1.7 mm, 2 mm, 2.2 mm, 2.6 mm, 2.8 mm, and 3 mm.

[0049] The preparation method of the above-mentioned composite thermally conductive gasket is described below.

[0050] A method for preparing a composite thermally conductive pad comprises the following steps:

[0051] (1) Preparation of graphene layer 200

[0052] Graphene is grown on a metal foil using chemical vapor deposition (CVD), and then the graphene is peeled off the metal foil and stacked longitudinally to obtain graphene oriented along the thickness direction.

[0053] The metal foil includes but is not limited to one or more of copper foil, nickel foil, magnesium foil, iron foil, steel foil and titanium foil.

[0054] (2) Preparation of liquid metal sheets

[0055] The material of the first alloy layer 101 and the material of the second alloy layer 103 are heated and melted to form liquid metal, and the liquid metal is coated on the opposite sides of the sheet-shaped thermal conductive material of the middle layer 102 to form the first alloy layer 101 and the second alloy layer 103, and then the whole is pushed to obtain a liquid metal sheet.

[0056] Wherein, after coating and before rolling, the thickness of the formed first alloy layer 101 is 10-50 μm, and the thickness of the second alloy layer 103 is 10-50 μm.

[0057] The first alloy layer 101 and the second alloy layer 103 mainly play a filling role, so if the coating thickness is too thin, it will not have the filling effect. If the coating thickness is too thick, it will overflow during the subsequent rolling process, thereby affecting the thermal conductivity. Therefore, the coating thickness of the first alloy layer 101 and the second alloy layer 103 is set to 10-50μm, which can not only have a filling effect, but also is beneficial to thermal conductivity.

[0058] (3) Combining the graphene layer 200 and the liquid metal sheet

[0059] The liquid metal sheet in step (2) is heated to make the first alloy layer 101 or the second alloy layer 103 on the surface of the liquid metal sheet in a molten state, and then the graphene in step (1) is placed on top of the liquid metal sheet, and pressure is applied to make the graphene and the liquid metal sheet in close contact, and pushed, and the pressure is maintained to cool, so as to obtain a composite thermal conductive gasket.

[0060] In the preparation of the liquid metal sheet, the applied pressure is 20-30 psi, and the pushing speed is 0.8-1.2 mm / s.

[0061] By applying pressure to push, the thickness of graphene and each layer in the liquid metal sheet can be effectively controlled, so that the thickness of graphene is controlled to be 0.3-3mm, and the thickness of the liquid metal sheet is controlled to be 50-100μm, wherein the thickness of the first alloy layer 101 and the second alloy layer 103 are the same, which is 10-20μm. By controlling the pushing pressure and the pushing speed within the above range, the thickness of the composite thermal conductive gasket can be effectively adjusted, thereby effectively reducing the thermal resistance.

[0062] The embodiment of the present application further provides a heat sink, comprising a heat sink 300 and any of the above-mentioned composite thermally conductive gaskets, wherein a first surface of the composite thermally conductive gasket is attached to the heat sink 300 .

[0063] like Figure 2 As shown, the graphene layer 200 is wrapped by the liquid metal sheet layer, the first surface of the graphene layer 200 is attached to the heat dissipation device 300, and the second surface is tightly combined with the liquid metal sheet layer.

[0064] Among them, continue to refer to Figure 2 The liquid metal sheet wraps the second surface and the side surface of the graphene layer 200 and extends outward, and the two ends of the extended liquid metal sheet are detachably connected to the opposite sides of the heat dissipation device 300 respectively.

[0065] The composite thermally conductive gasket of the present application has the advantages of high strength and good flexibility, and therefore, can be bent and punched according to the shape of the heat dissipation device 300 and then fixed with screws or other fixing components, which is simple to operate and takes little time.

[0066] As an example, the liquid metal sheet can be fixed to the heat sink 300 by means of screws 400 or the like (eg Figure 3 ).

[0067] The heat sink of the present application can be used to dissipate heat from the chip 500, and its use schematic diagram is shown in FIG. Figure 3 As shown. Figure 3 It can be seen that the graphene layer 200 at the bottom of the composite thermally conductive gasket is in contact with the heat sink 300, and the liquid metal sheet at the top is in contact with the chip 500. The alloy layer on the surface of the liquid metal sheet will not be easily damaged during the contact and separation process with the chip 500 due to its weak bonding force, and the other side is tightly bonded to the graphene gasket, so it can maintain a low thermal resistance during repeated use, and the graphene can be repeatedly tested without damage due to the support and protection of the liquid metal sheet; however, after repeated testing for many times, the surface of the alloy layer on the surface of the liquid metal sheet will be gradually contaminated by impurities or slightly oxidized, resulting in performance degradation. When it decays to an unusable value, it can be simply replaced.

[0068] The features and performance of the present application are further described in detail below in conjunction with the embodiments.

[0069] Example 1

[0070] This embodiment provides a composite thermally conductive pad, comprising the following steps:

[0071] (1) Preparation of graphene layer 200

[0072] Graphene is grown on copper foil by chemical vapor deposition (CVD), and then the graphene is peeled off from the copper foil and stacked longitudinally to obtain a graphene layer 200 oriented in the thickness direction, and the thickness of the graphene layer 200 is controlled to be 0.3 mm.

[0073] (2) Preparation of liquid metal sheets

[0074] The materials are weighed according to the ratio of In-33.3wt.%, Bi-32wt.%, and Sn-16.5wt.%, and then heated and melted to form liquid metal. The liquid metal is coated on opposite sides of a 0.05mm thick copper foil with a coating thickness of 30μm on one side to form a first alloy layer 101 and a second alloy layer 103 respectively. The whole is then rolled and flattened on a hot roller to achieve uniform thickness of the liquid metal sheet, thereby obtaining a liquid metal sheet with a total thickness of 0.08mm and a single-side thickness of the surface layer of 0.015mm.

[0075] (3) Combining the graphene layer 200 and the liquid metal sheet

[0076] The liquid metal sheet in step (2) is placed on a heating table for heating, so that the first alloy layer 101 or the second alloy layer 103 on the surface of the liquid metal sheet is in a molten state, and then the graphene in step (1) is placed on top of the liquid metal sheet, and a pressure of 30 psi is applied to make the graphene and the liquid metal sheet in close contact, and the pressure is pushed at 1.0 mm / s. After cooling while maintaining the pressure, a composite thermal conductive gasket is obtained.

[0077] Example 2

[0078] This embodiment is substantially the same as the embodiment 1, except that the thickness of the graphene layer 200 is 0.5 mm.

[0079] Example 3

[0080] This embodiment is basically the same as the embodiment 1, except that a 0.12 mm thick copper foil is selected, and the total thickness of the final liquid metal sheet is 0.15 mm.

[0081] Example 4

[0082] This embodiment is substantially the same as the embodiment 1, except that the thickness of the graphene layer 200 is 0.4 mm.

[0083] Example 5

[0084] This embodiment is basically the same as the embodiment 1, except that the total thickness of the liquid metal sheet is 0.11 mm, and a 0.08 mm thick copper foil is selected, that is, the thickness of the intermediate layer 102 is 0.08 mm.

[0085] Example 6

[0086] This embodiment is basically the same as the embodiment 1, except that the total thickness of the liquid metal sheet is 0.06 mm, and a 0.03 mm thick copper foil is selected, that is, the thickness of the intermediate layer 102 is 0.03 mm.

[0087] Example 7

[0088] This embodiment is basically the same as the first embodiment, except that: the liquid metal sheet is copper plated on one side away from the graphene layer 200 .

[0089] Example 8

[0090] This embodiment is basically the same as the first embodiment, except that: the liquid metal sheet is plated with indium on one side away from the graphene layer 200 .

[0091] Comparative Example 1

[0092] This comparative example is basically the same as Example 1, except that the liquid metal sheet is replaced with a copper foil of the same thickness.

[0093] Comparative Example 2

[0094] This comparative example is basically the same as Example 1, except that the liquid metal sheet is replaced with a textured indium sheet of the same thickness.

[0095] Comparative Example 3

[0096] This comparative example is pure graphene with a thickness of 0.3 mm.

[0097] Comparative Example 4

[0098] This comparative example is basically the same as Example 1, except that there is no graphene layer 200 and only a liquid metal sheet is used as a thermal conductive pad.

[0099] This comparative example provides a composite thermally conductive pad, comprising the following steps:

[0100] The materials are weighed according to the ratio of In-33.3wt.%, Bi-32wt.%, and Sn-16.5wt.%, and then heated and melted to form liquid metal. The liquid metal is coated on opposite sides of a 0.05mm thick copper foil with a coating thickness of 30μm on one side to form a first alloy layer 101 and a second alloy layer 103 respectively. The whole is then rolled and flattened on a hot roller to achieve uniform thickness of the liquid metal sheet, thereby obtaining a liquid metal sheet with a total thickness of 0.08mm and a single-side thickness of the surface layer of 0.015mm.

[0101] Some parameters of the above embodiments and comparative examples are shown in Table 1.

[0102] Table 1

[0103]

[0104] Test example

[0105] This test example measures the performance of the materials prepared in Examples 1-8 and Comparative Examples 1-4, including the measurement of contact thermal resistance and cost performance index.

[0106] Among them, the contact thermal resistance measurement method: the materials prepared in Examples 1-8 and Comparative Examples 1-5 are cut into sheets of 30*30 mm in size, and then placed on a thermal resistance meter (Rui Ling Technology LW9389) for testing. The test temperature is 80°C and the pressure is 10-50 psi. The measurement is performed in accordance with ASTM D5470 standard.

[0107] Definition of cost performance index: At the chip test end, performance is prioritized (low thermal resistance), followed by gap tolerance filling and number of repetitions. High-power chip testing requires thermal resistance to be less than 0.15℃*cm 2 / W, the thermal resistance requirement for conventional chip testing is 0.25℃*cm 2 / W. Assuming that for high-power chip test scenarios, the material performance weight is 0.4, with a value lower than 0.15℃*cm 2 / W is 100 points, when the thermal resistance is higher than 0.5℃*cm 2 / W, the score is 0; the compression rate weight is set to 0.3, with 100 points for reaching 50% or more at 50psi, and 0 points for less than 20%; the repetition number weight is 0.3, with 100 times as 100 points, and when the repetition number is less than 10, the weight is 0. The cost performance index of Example 1 is calculated as follows: the performance index score is 40 points, the compression index score is 49.5 / 50*100*0.3=29.7, the repetition index score is 20 / 100*100*0.3=6 points, and the total score is 75.7 points; the cost performance score of Comparative Example 2 is calculated as follows: the performance index is 0.15 / 0.4*100*0.4=15 points, the compression index score is 46.9 / 50*100*0.3=28.1, the repetition index is 80 / 100*100*0.3=24 points, and the total score is 67.1 points; the calculations of other cases are shown in Table 2.

[0108] Table 2

[0109]

[0110]

[0111] As can be seen from Table 2, by comparing Examples 1, 3, 5, and 6, increasing or decreasing the thickness of the liquid metal sheet layer has little effect on repeatability, but will increase thermal resistance. By comparing Example 1 and Comparative Examples 1 and 2, it can be seen that replacing the liquid metal sheet with a copper foil or a textured indium sheet of the same thickness can increase the number of repeatability, but the overall thermal resistance will increase significantly. By comparing Example 1 and Comparative Examples 3 and 4, it can be seen that if only graphene is used, although the thermal resistance is very low, the number of repeatability is only 1-2 times and it cannot be reused; using only liquid metal sheets as thermal pads, the thermal resistance tested on a thermal resistance meter can be very low, but because of its thin thickness and compression rate of less than 20%, it is impossible to fill the contact gap tolerance between the chip and the heat sink, so it is difficult to apply.

[0112] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

Claims

1. A composite thermally conductive pad, characterized in that: include: A graphene layer oriented along a thickness direction, the graphene layer having a first surface and a second surface in the thickness direction, the first surface being used for attaching to a heat dissipation device; a liquid metal sheet layer, the liquid metal sheet layer being disposed on the second surface of the graphene layer and being capable of bending toward the side of the graphene layer and covering at least a portion of the side of the graphene layer; The liquid metal sheet layer includes a first alloy layer, an intermediate layer and a second alloy layer from top to bottom, the first alloy layer and the second alloy layer are made of the same material, the intermediate layer is a sheet-shaped heat-conducting material, and the sheet-shaped heat-conducting material includes a solid metal foil or a third alloy; The melting point temperature of the intermediate layer is higher than that of the first alloy layer and the second alloy layer.

2. The composite thermally conductive pad according to claim 1, characterized in that: The difference between the melting point temperature of the intermediate layer and the temperature of the first alloy layer is at least 50°C; or, the difference between the melting point temperature of the intermediate layer and the temperature of the second alloy layer is at least 50°C.

3. The composite thermally conductive pad according to claim 2, characterized in that: The solid metal foil includes one or more of indium foil, platinum foil, copper foil, silver foil, aluminum foil and zinc foil; And / or, the third alloy includes one or more of a Cu-Al alloy, a Cu-Sn alloy and a Cu-In alloy.

4. The composite thermally conductive pad according to claim 2, characterized in that: The material of the first alloy layer or the second alloy layer includes a phase change alloy having a melting point temperature lower than 120° C.; Optionally, the phase change alloy includes one or more of a Ga-In-Sn alloy, an In-Sn-Bi alloy, an In-Bi alloy and a Ga-In-Sn-Bi alloy.

5. The composite thermally conductive pad according to claim 2, characterized in that: The thickness of the liquid metal sheet is 50-100 μm, wherein the thickness of the first alloy layer and the second alloy layer is the same, which is 10-20 μm; Optionally, the graphene layer has a thickness of 0.3-3 mm.

6. A method for preparing the composite thermally conductive gasket according to any one of claims 1 to 5, characterized in that: include: Growing graphene on a metal foil by chemical vapor deposition, peeling off the graphene from the metal foil after growth is completed and stacking them longitudinally to obtain graphene oriented along the thickness direction; The material of the first alloy layer and the material of the second alloy layer are heated and melted to form liquid metal, and the liquid metal is coated on opposite sides of the sheet-shaped thermal conductive material of the middle layer to form the first alloy layer and the second alloy layer, and then the whole is rolled to obtain a liquid metal sheet; The liquid metal sheet is heated to make the first alloy layer or the second alloy layer on the surface of the liquid metal sheet in a molten state, and then the graphene is placed above the liquid metal sheet, and pressure is applied to make the graphene and the liquid metal sheet in close contact and pushed. After cooling while maintaining the pressure, the composite thermal conductive gasket is obtained.

7. The preparation method according to claim 6, characterized in that: After the coating is completed but before the rolling is performed, the thickness of the first alloy layer formed is 10-50 μm, and the thickness of the second alloy layer is 10-50 μm; Or / and, the metal foil includes one or more of copper foil, nickel foil, magnesium foil, iron foil, steel foil and titanium foil.

8. The preparation method according to claim 6, characterized in that: The applied pressure is 20-30 psi, and the pushing speed is 0.8-1.2 mm / s.

9. A radiator, characterized in that: The invention comprises a heat dissipation device and the composite thermally conductive gasket according to any one of claims 1 to 5, wherein the first surface of the composite thermally conductive gasket is attached to the heat dissipation device.

10. The heat sink according to claim 9, characterized in that In the heat sink, the liquid metal sheet wraps the second surface and the side surface of the graphene layer and extends outward, and two ends of the extended liquid metal sheet are detachably connected to opposite sides of the heat sink.

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