Thermal interface material and preparation method thereof, and electronic equipment

Abstract

The present application relates to a thermal interface material and a preparation method thereof, and an electronic device, and belongs to the technical field of thermal interface materials. A thermal interface material comprises a partially oxidized liquid metal material and an unoxidized liquid metal material mixed with each other; the volume fraction of the partially oxidized liquid metal material in the liquid metal layer is 0.1-10%. The liquid metal layer on the thermal interface material has a uniform thickness, a small proportion of the oxidation layer, and good thermal conductivity.

Description

Technical Field

[0001] The present application relates to the technical field of thermal interface materials, and in particular to a thermal interface material, a preparation method thereof, and an electronic device. Background Art

[0002] In the field of material surface treatment technology, especially in the field of metal materials and liquid metal applications, the uniform adhesion of liquid metal to solid metal surfaces is a key technology. This technology not only significantly improves the thermal conductivity of metal materials, but also plays a vital role in electronic equipment and heat dissipation systems. However, ensuring the uniform adhesion of liquid metal to solid metal surfaces faces many technical challenges, especially in high-temperature and high-pressure environments, where preventing the flow and leakage of liquid metal becomes a major issue.

[0003] Existing technologies primarily use a brush coating method to apply liquid metal to solid metal surfaces. While this method is simple to operate, it struggles to ensure uniform adhesion of the liquid metal, often resulting in uneven coating thickness and an excessively high surface oxide layer, which compromises thermal conductivity. Furthermore, under high temperature and pressure conditions, the risk of liquid metal flowing and leaking increases, posing safety risks.

[0004] Therefore, the existing technology has the following major problems: First, the liquid metal has poor adhesion uniformity, uneven thickness and large tolerance, which directly affects the thermal conductivity of the interface; second, the proportion of the oxide layer on the surface of the liquid metal is too high, which reduces the thermal conductivity efficiency; third, in extreme environments, the liquid metal is prone to flow and leakage, increasing safety risks. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the purpose of the embodiments of the present application includes providing a thermal interface material and its preparation method, and electronic equipment to improve the uniformity of liquid metal adhesion, reduce thickness tolerance, and reduce the proportion of the oxide layer on the liquid metal surface, thereby improving the thermal conductivity effect.

[0006] In a first aspect, an embodiment of the present application provides a thermal interface material, comprising a solid metal layer and a liquid metal layer in close contact with the surface of the solid metal layer; wherein the liquid metal layer comprises a partially oxidized liquid metal material and an unoxidized liquid metal material mixed with each other; the volume fraction of the partially oxidized liquid metal material in the liquid metal layer is 0.1-10%.

[0007] The thermal interface material comprises a solid metal layer and a liquid metal layer in close contact with the surface of the solid metal layer; wherein the liquid metal layer comprises a mixture of partially oxidized liquid metal material and unoxidized liquid metal material, wherein the partially oxidized liquid metal material forms a good mechanical bond when in contact with the solid metal surface. This bond not only increases the contact area between the materials, but also effectively reduces bubbles and defects at the interface, thereby improving thermal conductivity; this good contact allows heat to be more effectively conducted from the solid metal to the liquid metal layer, thereby reducing contact thermal resistance. Unoxidized liquid metal has a low thermal resistance, so in this thermal interface material, the presence of the unoxidized liquid metal material (unoxidized layer) significantly improves the overall thermal conductivity, and the structure of the material enables heat to spread rapidly within the liquid metal layer. In addition, setting the volume fraction of the partially oxidized liquid metal material (oxide layer) between 0.1-10% can not only significantly reduce the proportion of the oxide layer, but also enable the oxide layer to maintain good adhesion while still achieving excellent thermal conductivity.

[0008] In some embodiments of the present application, the oxidation fraction of the partially oxidized liquid metal material is 20-50%, and the oxidation fraction of the unoxidized liquid metal material is ≤5%.

[0009] The partially oxidized liquid metal material is able to form a good mechanical bond when in contact with solid metal.

[0010] Liquid metal materials with an oxidation fraction of 20-50% can destroy the surface energy of the solid metal surface and increase the surface roughness. On the one hand, it facilitates the subsequent coating of unoxidized liquid metal materials; on the other hand, it improves the adhesion between the liquid metal and the solid metal and reduces the risk of peeling and delamination.

[0011] In some embodiments of the present application, the total thickness of the liquid metal layer is 5-15 μm.

[0012] Controlling the total thickness of the liquid metal layer within the range of 5-15μm can optimize thermal conductivity efficiency, enhance adhesion, reduce oxidation risk, maintain good fluidity and stability, and have strong adaptability and flexibility.

[0013] In some embodiments of the present application, the material of the solid metal layer includes any one of gold, silver, copper, aluminum and indium; or / and the material of the liquid metal layer includes Ga 6.5 In 48.3 Sn 15.2 Bi 30 、In 51 Sn 32 Bi 17 and In 66.7 Bi 33.3Any of the alloys.

[0014] Metals such as gold, silver, copper, and aluminum have very good electrical and thermal conductivity. The high electron mobility of these metals enables them to conduct current and heat quickly, thus achieving efficient thermal management in electronic devices and cooling systems. Moreover, these metals are not easily oxidized under air and humidity conditions, which helps maintain the long-term stability and performance of the thermal interface and reduces the impact of the oxide layer on thermal conductivity. 6.5 In 48.3 Sn 15.2 Bi 30 The alloy has a moderate melting point and good wettability, which can effectively fill tiny defects on the surface of solid metals, enhance interfacial contact, and thus reduce contact thermal resistance. In addition, the alloy has high thermal conductivity in the liquid state, which can effectively enhance the thermal conductivity efficiency of the thermal interface, especially in high-temperature environments, and can achieve rapid heat transfer.

[0015] In second aspect, an embodiment of the present application provides a method for preparing the above-mentioned thermal interface material, comprising: performing surface treatment on a solid metal layer; coating a partially oxidized liquid metal material on the surface of the surface-treated solid metal layer to form an oxidized metal material layer; and coating an unoxidized liquid metal material on the surface of the oxidized metal material layer to obtain a liquid metal layer.

[0016] The present application can achieve a close combination of liquid metal and solid metal by brushing liquid metal on the surface of solid metal and covering it with a thin film, and pushing it with a scraper; this method effectively reduces the problem of uneven thickness, and the tolerance can be controlled within 5μm, effectively improving the adhesion uniformity of the liquid metal, thereby improving the thermal conductivity of the interface contact. Among them, after brushing the partially oxidized liquid metal to achieve infiltration, it is covered with pure liquid metal (unoxidized liquid metal material), that is, a layer of unoxidized liquid metal material is covered on the surface of the oxidized metal material layer; then through the pushing step, the partially oxidized liquid metal material and the unoxidized liquid metal material are mixed together, and the pushing can take away the excess oxidized liquid metal on the one hand, which can effectively reduce the proportion of the oxide layer on the surface of the liquid metal, thereby improving the thermal conductivity; on the other hand, it can also effectively prevent the flow and leakage of liquid metal under extreme conditions, significantly reducing the safety hazards during use.

[0017] In some embodiments of the present application, the above-mentioned preparation method also includes: covering the surface of the liquid metal layer with a thin film, heating to melt the metal, pushing the surface of the film while keeping the liquid metal molten so that the film and the liquid metal layer are in close contact; then cooling, and tearing off the film after cooling to obtain a thermal interface material.

[0018] Liquid metal has excellent fluidity when heated, allowing for a tight bond between the film and the liquid metal. Therefore, pressing in the hot melt state effectively optimizes the heat conduction path, creating a better heat conduction channel and improving overall thermal conductivity. Pressing also expels excess liquid metal, preventing it from leaking under high-temperature, high-pressure conditions. When the film is removed after cooling, the liquid metal will have solidified, so it won't stick to it, preventing it from affecting the uniformity of the liquid metal layer.

[0019] In some embodiments of the present application, the thickness of the coated oxidized metal material layer is 5-10 μm, and the thickness of the coated unoxidized liquid metal material is 30-100 μm.

[0020] During the coating process, the thickness of the coated oxidized metal material layer is controlled to be 5-10μm, and the thickness of the coated unoxidized liquid metal material is controlled to be 30-100μm. Among them, the 5-10μm oxidized metal material layer can be well infiltrated into the solid metal surface to form a more uniform interface contact, reducing the risk of peeling and failure; it can also effectively reduce the contact thermal resistance and improve the thermal conductivity efficiency; the 30-100μm unoxidized liquid metal material can effectively store and conduct heat, so that it can adapt to higher heat flux density, thereby providing better thermal conductivity.

[0021] In some embodiments of the present application, the pushing pressure is 30-50 psi.

[0022] The pushing pressure is set at 30-50psi, which can eliminate bubbles and gaps between the liquid metal and the film, effectively promoting the close bonding between the film and the liquid metal layer, thereby improving the consistency of the coating thickness and improving the interface uniformity.

[0023] In some embodiments of the present application, the thickness of the film is 10-100 μm.

[0024] Controlling the thickness of the film within the range of 10-100 μm is beneficial to maintaining the thickness uniformity of the liquid metal layer during the pushing process and reducing the generation of bubbles.

[0025] In a third aspect, an embodiment of the present application provides an electronic device, comprising a device body and any of the above-mentioned thermal interface materials, wherein the surface of the device body is in contact with the liquid metal layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. 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 relevant drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 This is a flow chart of a preparation process for uniformly adhering liquid metal to a solid metal surface according to an embodiment of the present application;

[0028] Figure 2 A thermal interface material prepared using the preparation method of the present application;

[0029] Figure 3 It is a thermal interface material prepared using a conventional brush coating process;

[0030] Figure 4 This is a diagram showing the vertical flow leakage of the thermal interface material prepared using the preparation method of the present application at high temperature;

[0031] Figure 5 This is a diagram showing the vertical leakage of thermal interface materials prepared using a conventional brush coating process at high temperatures. DETAILED DESCRIPTION

[0032] To make the purpose, technical solutions and advantages of the examples of the present application clearer, the technical solutions in the examples of the present application will be described clearly and completely below. Where specific conditions are not specified in the examples, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0033] The following is a detailed description of a thermal interface material, a preparation method thereof, and an electronic device according to an embodiment of the present application.

[0034] An embodiment of the present application provides a thermal interface material, comprising a solid metal layer and a liquid metal layer in close contact with the surface of the solid metal layer; wherein the liquid metal layer comprises a partially oxidized liquid metal material and an unoxidized liquid metal material mixed with each other; the partially oxidized liquid metal material; and the volume fraction of the partially oxidized liquid metal material in the liquid metal layer is 0.1-10%.

[0035] The thermal interface material of the present application is prepared by first coating a layer of partially oxidized liquid metal material, i.e., an oxide layer, on the surface of a metal substrate; and then coating a layer of unoxidized liquid metal material on the surface of the oxide layer; wherein the partially oxidized liquid metal material and the unoxidized liquid metal material are mixed with each other, and the liquid metal layer is in direct contact with the surface of the metal substrate, forming a good mechanical bond. This bond not only increases the contact area between the materials, but also effectively reduces bubbles and defects at the interface, thereby improving thermal conductivity; this good contact allows heat to be more effectively transferred from the solid metal to the liquid metal layer, thereby reducing contact thermal resistance; the unoxidized layer can further improve thermal conductivity. This layered structure can also effectively prevent the flow and leakage of liquid metal, thereby improving safety during use.

[0036] The oxidation fraction of the partially oxidized liquid metal material is 20-50%, and the oxidation fraction of the unoxidized liquid metal material is ≤5%.

[0037] Partially oxidized liquid metal materials can form a good mechanical bond when in contact with solid metal, thereby improving the adhesion between the liquid metal and the solid metal and reducing the risk of peeling and delamination. In addition, an oxidation fraction between 20-50% helps maintain the fluidity of the liquid metal and has certain thermal conductivity. Unoxidized liquid metal materials with an oxidation fraction of ≤5% can have higher thermal conductivity, which facilitates providing better thermal conductivity, reducing thermal resistance, and optimizing the heat transfer effect of the thermal interface.

[0038] In the embodiment of the present application, the total thickness of the liquid metal layer is 5-15 μm. As an example, the total thickness of the liquid metal layer includes but is not limited to 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, and 15 μm.

[0039] The liquid metal layer within this thickness range can reduce heat loss during conduction, allowing heat to be quickly transferred from the solid metal to the liquid metal layer. Furthermore, the 5-15μm thickness allows the liquid metal to maintain good fluidity within the layer while not being too thin. This reduces leakage or loss due to excessive fluidity, thereby maintaining a good thermal interface effect. Furthermore, within this thickness range, the liquid metal can fully infiltrate the solid metal surface, forming a good mechanical bond, improving interfacial contact, and reducing the risk of peeling.

[0040] In the embodiment of the present application, the material of the solid metal layer includes any one of gold, silver, copper, aluminum and indium; or / and, the material of the liquid metal layer includes Ga 6.5 In 48.3 Sn 15.2 Bi 30 、In51 Sn 32 Bi 17 and In 66.7 Bi 33.3 Any of the alloys.

[0041] The preparation method of the above thermal interface material is described below.

[0042] A method for preparing the above-mentioned thermal interface material comprises the following steps:

[0043] (1) Surface treatment

[0044] The metal substrate is placed in a sodium hydroxide solution and its surface is cleaned and degreased to make the metal surface of the substrate clean and free of oil. The clean surface can increase the contact area between the liquid metal and the solid metal and promote better adhesion of the liquid metal.

[0045] (2) Liquid metal infiltration

[0046] The surface of the solid metal layer after surface treatment is brushed with partially oxidized liquid metal material to form an oxidized metal material layer. The liquid metal material includes Ga 6.5 In 48.3 Sn 15.2 Bi 30 、In 51 Sn 32 Bi 17 and In 66.7 Bi 33.3 Any of the alloys.

[0047] During this process, the thickness of the oxidized metal layer applied by brushing is controlled within 10μm. By brushing the partially oxidized liquid metal material on the surface of the surface-treated solid metal layer, the liquid wettability of the substrate surface can be improved, achieving good contact between the liquid metal and the solid metal.

[0048] (3) Covered with pure liquid metal

[0049] On the basis of step (2), a dropper or a brush is used to apply unoxidized liquid metal material to cover the surface of the oxidation metal material layer to form a liquid metal layer.

[0050] During this process, the thickness of the brushed unoxidized liquid metal material is controlled to be 30-100 μm.

[0051] (4) Film covering

[0052] Cover the surface of the liquid metal with a 10-100μm thick PET film and heat it to melt the metal. It should be noted that the heating temperature should be about 10℃ higher than the melting point of the alloy. For example, for Ga65 In 483 Sn 152 Bi 30 The alloy is heated to 70° C., which is not limited in this application.

[0053] The thickness of PET film is 10-100μm. PET film with a thickness of more than 100μm is too thick, which will cause large contact bubbles when laminating and affect the surface; PET film with a thickness of less than 10μm is too thin and will easily wrinkle when pushed, affecting the thickness uniformity.

[0054] (5) Pushing, cooling and film tearing to obtain thermal interface material

[0055] While keeping the liquid metal molten, a scraper is used to push the surface of the film to make the film and the liquid metal layer in close contact; then the film is cooled, and after cooling, the film is torn off to obtain a thermal interface material.

[0056] Pushing the surface of the film while keeping the liquid metal molten can maintain the fluidity of the liquid metal so that it can better combine with the PET film. After the pushing is completed, the metal substrate is moved to the cooling area to cool it to room temperature. Finally, the PET film is torn off to obtain the thermal interface material, in which the volume fraction of the partially oxidized liquid metal material in the liquid metal layer is 0.1-10%, that is, the oxide layer accounts for a low proportion in the liquid metal layer. By pushing and cooling, a liquid metal layer with uniform thickness and less oxidation can be obtained.

[0057] The pushing pressure is controlled at 30-50 psi. This pressure control not only ensures a tight bond between the PET film and the liquid metal and discharges excess liquid metal, but also keeps the total thickness of the liquid metal layer within 5-15 μm.

[0058] By way of example, the pushing pressure includes but is not limited to 30 psi, 35 psi, 40 psi, 45 psi, and 50 psi.

[0059] The features and performance of the present application are further described in detail below with reference to the embodiments.

[0060] Example 1

[0061] Figure 1 For the process flow chart of preparing liquid metal uniformly attached to the surface of solid metal according to the embodiment of the present application, please refer to Figure 1 .

[0062] This embodiment provides a thermal interface material, and the preparation method thereof includes the following steps:

[0063] (1) Surface treatment

[0064] A 0.1 mm thick copper foil substrate is placed in a sodium hydroxide solution to clean and degrease its surface so that the metal surface of the copper foil is clean and free of oil stains.

[0065] (2) Liquid metal infiltration

[0066] The surface of the copper foil after surface treatment is brushed with partially oxidized Ga 6.5 In 48.3 Sn 15.2 Bi 30 alloy (oxidation fraction is 30%) to form an oxidized metal material layer, and the thickness of the oxidized metal material layer applied by brushing is controlled to be 7 μm.

[0067] (3) Covered with pure liquid metal

[0068] On the basis of step (2), unoxidized liquid metal material (oxidation fraction of 1%) is applied by a dropper or brush to cover the surface of the oxidized metal material layer to form a liquid metal layer. In this process, the thickness of the unoxidized liquid metal material applied by brush is 80 μm.

[0069] (4) Film covering

[0070] The surface of the liquid metal layer is covered with a 50 μm thick PET film and heated to 70°C to melt the metal.

[0071] (5) Pushing, cooling and film tearing to obtain thermal interface material

[0072] While keeping the liquid metal molten, a scraper is used to push the surface of the film at a pressure of 40 psi to ensure close contact between the film and the liquid metal layer; the film is then cooled, and after cooling, the film is torn off to obtain a thermal interface material.

[0073] Example 2

[0074] This embodiment provides a thermal interface material, and the preparation method thereof includes the following steps:

[0075] (1) Surface treatment

[0076] A 0.1 mm thick copper foil substrate is placed in a sodium hydroxide solution to clean and degrease its surface so that the metal surface of the copper foil is clean and free of oil stains.

[0077] (2) Liquid metal infiltration

[0078] The surface of the copper foil after surface treatment is brushed with partially oxidized Ga 6.5 In 48.3 Sn 15.2 Bi 30alloy (oxidation fraction is 30%) to form an oxidized metal material layer, and the thickness of the oxidized metal material layer applied by brushing is controlled to be 7 μm.

[0079] (3) Covered with pure liquid metal

[0080] On the basis of step (2), unoxidized liquid metal material (oxidation fraction of 1%) is applied by a dropper or brush to cover the surface of the oxidized metal material layer to form a liquid metal layer. In this process, the thickness of the unoxidized liquid metal material applied by brush is 80 μm.

[0081] (4) Film covering

[0082] The surface of the liquid metal layer is covered with a 50 μm thick PET film and heated to 70°C to melt the metal.

[0083] (5) Pushing, cooling and film tearing to obtain thermal interface material

[0084] While keeping the liquid metal molten, a scraper is used to push the surface of the film at a pressure of 20 psi to ensure close contact between the film and the liquid metal layer; the film is then cooled, and after cooling, the film is torn off to obtain a thermal interface material.

[0085] Example 3

[0086] This embodiment provides a thermal interface material, and the preparation method thereof includes the following steps:

[0087] (1) Surface treatment

[0088] A 0.1 mm thick copper foil substrate is placed in a sodium hydroxide solution to clean and degrease its surface so that the metal surface of the copper foil is clean and free of oil stains.

[0089] (2) Liquid metal infiltration

[0090] The surface of the copper foil after surface treatment is brushed with partially oxidized Ga 6.5 In 48.3 Sn 15.2 Bi 30 alloy (oxidation fraction is 30%) to form an oxidized metal material layer, and the thickness of the oxidized metal material layer applied by brushing is controlled to be 7 μm.

[0091] (3) Covered with pure liquid metal

[0092] On the basis of step (2), unoxidized liquid metal material (oxidation fraction of 1%) is applied by a dropper or brush to cover the surface of the oxidized metal material layer to form a liquid metal layer. In this process, the thickness of the unoxidized liquid metal material applied by brush is 80 μm.

[0093] (4) Film covering

[0094] The surface of the liquid metal layer is covered with a 50 μm thick PET film and heated to 70°C to melt the metal.

[0095] (5) Pushing, cooling and film tearing to obtain thermal interface material

[0096] While keeping the liquid metal molten, a scraper is used to push the surface of the film at a pressure of 70 psi to ensure close contact between the film and the liquid metal layer; the film is then cooled, and after cooling, the film is torn off to obtain a thermal interface material.

[0097] Example 4

[0098] This embodiment provides a thermal interface material, and the preparation method thereof includes the following steps:

[0099] (1) Surface treatment

[0100] A 0.1 mm thick copper foil substrate is placed in a sodium hydroxide solution to clean and degrease its surface so that the metal surface of the copper foil is clean and free of oil stains.

[0101] (2) Liquid metal infiltration

[0102] The surface of the copper foil after surface treatment is brushed with partially oxidized Ga 6.5 In 48.3 Sn 15.2 Bi 30 alloy (oxidation fraction is 30%) to form an oxidized metal material layer, and the thickness of the oxidized metal material layer applied by brushing is controlled to be 3.5 μm.

[0103] (3) Covered with pure liquid metal

[0104] On the basis of step (2), unoxidized liquid metal material (oxidation fraction of 1%) is applied by a dropper or brush to cover the surface of the oxidized metal material layer to form a liquid metal layer. In this process, the thickness of the unoxidized liquid metal material applied by brush is 80 μm.

[0105] (4) Film covering

[0106] The surface of the liquid metal layer is covered with a 50 μm thick PET film and heated to 70°C to melt the metal.

[0107] (5) Pushing, cooling and film tearing to obtain thermal interface material

[0108] While keeping the liquid metal molten, a scraper is used to push the surface of the film at a pressure of 40 psi to ensure close contact between the film and the liquid metal layer; the film is then cooled, and after cooling, the film is torn off to obtain a thermal interface material.

[0109] Example 5

[0110] This embodiment provides a thermal interface material, and the preparation method thereof includes the following steps:

[0111] (1) Surface treatment

[0112] A 0.1 mm thick copper foil substrate is placed in a sodium hydroxide solution to clean and degrease its surface so that the metal surface of the copper foil is clean and free of oil stains.

[0113] (2) Liquid metal infiltration

[0114] The surface of the copper foil after surface treatment is brushed with partially oxidized Ga 6.5 In 48.3 Sn 15.2 Bi 30 alloy (oxidation fraction is 30%) to form an oxidized metal material layer, and the thickness of the oxidized metal material layer applied by brushing is controlled to be 13 μm.

[0115] (3) Covered with pure liquid metal

[0116] On the basis of step (2), unoxidized liquid metal material (oxidation fraction of 1%) is applied by a dropper or brush to cover the surface of the oxidized metal material layer to form a liquid metal layer. In this process, the thickness of the unoxidized liquid metal material applied by brush is 80 μm.

[0117] (4) Film covering

[0118] The surface of the liquid metal layer is covered with a 50 μm thick PET film and heated to 70°C to melt the metal.

[0119] (5) Pushing, cooling and film tearing to obtain thermal interface material

[0120] While keeping the liquid metal molten, a scraper is used to push the surface of the film at a pressure of 40 psi to ensure close contact between the film and the liquid metal layer; the film is then cooled, and after cooling, the film is torn off to obtain a thermal interface material.

[0121] Example 6

[0122] This embodiment provides a thermal interface material, and the preparation method thereof includes the following steps:

[0123] (1) Surface treatment

[0124] A 0.1 mm thick copper foil substrate is placed in a sodium hydroxide solution to clean and degrease its surface so that the metal surface of the copper foil is clean and free of oil stains.

[0125] (2) Liquid metal infiltration

[0126] The surface of the copper foil after surface treatment is brushed with partially oxidized Ga 6.5 In 48.3 Sn 15.2 Bi 30 alloy (oxidation fraction is 30%) to form an oxidized metal material layer, and the thickness of the oxidized metal material layer applied by brushing is controlled to be 7 μm.

[0127] (3) Covered with pure liquid metal

[0128] Based on step (2), unoxidized liquid metal material (oxidation fraction of 1%) is applied by a dropper or brush to cover the surface of the oxidized metal material layer to form a liquid metal layer. In this process, the thickness of the unoxidized liquid metal material applied by brush is 22 μm.

[0129] (4) Film covering

[0130] The surface of the liquid metal layer is covered with a 50 μm thick PET film and heated to 70°C to melt the metal.

[0131] (5) Pushing, cooling and film tearing to obtain thermal interface material

[0132] While keeping the liquid metal molten, a scraper is used to push the surface of the film at a pressure of 40 psi to ensure close contact between the film and the liquid metal layer; the film is then cooled, and after cooling, the film is torn off to obtain a thermal interface material.

[0133] Example 7

[0134] This embodiment provides a thermal interface material, and the preparation method thereof includes the following steps:

[0135] (1) Surface treatment

[0136] A 0.1 mm thick copper foil substrate is placed in a sodium hydroxide solution to clean and degrease its surface so that the metal surface of the copper foil is clean and free of oil stains.

[0137] (2) Liquid metal infiltration

[0138] The surface of the copper foil after surface treatment is brushed with partially oxidized Ga 6.5 In 48.3 Sn 15.2 Bi 30 alloy (oxidation fraction is 30%) to form an oxidized metal material layer, and the thickness of the oxidized metal material layer applied by brushing is controlled to be 7 μm.

[0139] (3) Covered with pure liquid metal

[0140] On the basis of step (2), a dropper or brush is used to apply unoxidized liquid metal material (oxidation fraction is 1%) to the surface of the oxidized metal material layer to form a liquid metal layer. In this process, the thickness of the unoxidized liquid metal material applied by brush is 120 μm.

[0141] (4) Film covering

[0142] The surface of the liquid metal layer is covered with a 50 μm thick PET film and heated to 70°C to melt the metal.

[0143] (5) Pushing, cooling and film tearing to obtain thermal interface material

[0144] While keeping the liquid metal molten, a scraper is used to push the surface of the film at a pressure of 40 psi to ensure close contact between the film and the liquid metal layer; the film is then cooled, and after cooling, the film is torn off to obtain a thermal interface material.

[0145] Comparative Example

[0146] In this comparative example, the conventional brushing method was adopted to brush oxidized liquid metal on the metal substrate to prepare the thermal interface material.

[0147] This comparative example provides a thermal interface material, the preparation method of which comprises the following steps:

[0148] (1) Surface treatment

[0149] Place a 0.1 mm thick copper foil substrate in a sodium hydroxide solution, clean and degrease its surface to make the metal surface of the copper foil clean and free of oil stains, then rinse with pure water and dry.

[0150] (2) Liquid metal brushing

[0151] The surface of the copper foil after surface treatment is brushed with partially oxidized Ga 6.5 In 48.3 Sn 15.2 Bi 30 alloy (oxidation fraction is 30%), forming a liquid metal layer with a brush coating thickness of 40 μm.

[0152] Some parameters of the above examples and comparative examples are detailed in Table 1.

[0153] Table 1

[0154]

[0155]

[0156] Test Example 1

[0157] This test example measured the performance of the thermal interface materials prepared in Examples 1-7 and the comparative example, including the liquid metal layer thickness tolerance, contact thermal resistance, and high-temperature leakage.

[0158] Liquid metal layer thickness tolerance determination method: tear off the surface film of each thermal interface material, use a digital deep throat thickness gauge to randomly select 5 points for thickness measurement, and analyze the measurement data to obtain the tolerance.

[0159] Contact thermal resistance measurement method: Each thermal interface material was cut into 30*30mm sheets and then placed on a thermal resistance meter (Rui Ling Technology LW9389) for testing at a test temperature of 80°C and a pressure of 50 psi, in accordance with ASTM D5470.

[0160] High temperature leakage: Place each thermal interface material vertically under pressure on two pieces of glass at 125°C for 2 hours, and observe whether sag and overflow occur. If so, it is a leakage.

[0161] Figure 2 A thermal interface material prepared using the preparation method of the present application; Figure 3 It is a thermal interface material prepared using a conventional brush coating process; Figure 4 This is a diagram showing the vertical flow leakage of the thermal interface material prepared using the preparation method of the present application at high temperature; Figure 5 This is a diagram showing the vertical leakage of thermal interface materials prepared using conventional brush coating technology at high temperatures; please refer to Figure 2-Figure 5 ; Please see Table 2 for the measurement results of the above items.

[0162] Table 2

[0163]

[0164] Table 2 and Figure 2 and Figure 3 It can be seen that the preparation method of the present application can achieve uniform adhesion of liquid metal on the surface of solid metal, thereby improving thermal conductivity; at the same time, it can also prevent the flow and leakage of liquid metal in high temperature and high pressure environments (such as Figure 4 and Figure 5 ), which improves security.

[0165] 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 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 efforts are within the scope of protection of this application.

Claims

1. A thermal interface material, characterized in that: The invention comprises a solid metal layer and a liquid metal layer in close contact with a surface of the solid metal layer; wherein the liquid metal layer comprises a partially oxidized liquid metal material and an unoxidized liquid metal material mixed with each other; The volume fraction of the partially oxidized liquid metal material in the liquid metal layer is 0.1-10%.

2. The thermal interface material according to claim 1, characterized in that: The oxidation fraction of the partially oxidized liquid metal material is 20-50%, and the oxidation fraction of the unoxidized liquid metal material is ≤5%.

3. The thermal interface material according to claim 1, characterized in that: The total thickness of the liquid metal layer is 5-15 μm.

4. The thermal interface material according to any one of claims 1 to 3, characterized in that: The material of the solid metal layer includes any one of gold, silver, copper, aluminum and indium; Or / and, the material of the liquid metal layer includes Ga 6.5 In 48.3 Sn 15.2 Bi 30 、In 51 Sn 32 Bi 17 andIn 66.7 Bi 33.3 Any of the alloys.

5. A method for preparing a thermal interface material according to any one of claims 1 to 4, characterized in that: include: performing surface treatment on the solid metal layer; The partially oxidized liquid metal material is coated on the surface of the solid metal layer after the surface treatment to form an oxidized metal material layer; and the unoxidized liquid metal material is coated on the surface of the oxidized metal material layer to obtain the liquid metal layer.

6. The preparation method according to claim 5, characterized in that: Also includes: After the unoxidized liquid metal material is coated on the surface of the oxidized metal material layer, a film is covered on the surface of the unoxidized liquid metal material, and the metal is heated to melt the metal, and the surface of the film is pushed while the liquid metal is kept molten, so that the film and the liquid metal layer are in close contact; Then the film is cooled, and after cooling, the film is torn off to obtain the thermal interface material.

7. The preparation method according to claim 6, characterized in that: The thickness of the coated oxidized metal material layer is 5-10 μm, and the thickness of the coated unoxidized liquid metal material is 30-100 μm.

8. The preparation method according to claim 7, characterized in that: The pushing pressure is 30-50 psi.

9. The preparation method according to claim 7, characterized in that: The film has a thickness of 10-100 μm.

10. An electronic device, characterized in that: The thermal interface material comprises a device body and the thermal interface material according to any one of claims 14, wherein a surface of the device body is in contact with the liquid metal layer.

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