Metal heat-conducting sheet and preparation method and application thereof

Abstract

The invention discloses a metal heat-conducting fin and a preparation method and application thereof.The metal heat-conducting fin is composed of a main body heat-conducting metal sheet and liquid metal, the liquid metal is distributed on the upper side and the lower side of the main body heat-conducting metal sheet, and components of the metal heat-conducting fin are distributed in a non-uniform mode, the linear expansion coefficient ratio D of the main body heat conduction metal sheet to the liquid metal is 0.8 lt; dlt; and 1.2. According to the metal heat-conducting fin, low heat resistance and high heat conductivity are achieved, and meanwhile leakage resistance of metal under high-temperature heating can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of thermally conductive interface materials, and in particular to a metal thermally conductive sheet and a preparation method and application thereof. Background Art

[0002] The heat generation and surface temperature of high-power devices are getting higher and higher. Traditional polymer ceramic composite thermal interface materials are difficult to meet the performance requirements in terms of thermal stability and thermal performance. Therefore, the development of metal-based thermal interface materials with high thermal conductivity, low thermal resistance and high stability is the focus of the current development of the thermal interface material field.

[0003] Metals generally have high thermal conductivity, but these high thermal conductivity metal sheets often have high contact thermal resistance due to their own high hardness. In the prior art, composite thermal conductive paste is often applied on the surface of the metal sheet to eliminate the interface thermal resistance. However, since the composite thermal conductive paste and the metal sheet are physically coated, the stability is poor and the coating layer is prone to fall off. In addition, the composite thermal conductive paste generally has a low thermal conductivity (<10 W / mK), making it difficult to significantly exert the thermal performance of the metal sheet while reducing thermal resistance. There are also literature reports on the solution of compounding two metals to reduce thermal resistance, but this will make one of the metals easy to leak after melting at a very high temperature, increasing the risk of short circuit during the use of electronic equipment.

[0004] Therefore, there is an urgent need to develop a metal heat-conducting sheet that is resistant to leakage and has low thermal resistance and high thermal conductivity to meet the application requirements of high-power devices. Summary of the invention

[0005] In view of the defects in the prior art, the present invention provides a metal heat conductive sheet and a preparation method and application thereof.

[0006] The present invention provides a metal heat conductive sheet, which is composed of a main heat conductive metal sheet and liquid metal, wherein the liquid metal is distributed on the upper and lower sides of the main heat conductive metal sheet, and the components of the metal heat conductive sheet are distributed non-uniformly, wherein the ratio D of the linear expansion coefficients of the main heat conductive metal sheet and the liquid metal satisfies: 0.8 <D<1.2; The linear expansion coefficient measurement method is optical interference method. The linear expansion coefficient between metals can ensure the mechanical stability of the composite structure under heating conditions within a specific range. The difference in linear expansion coefficient between the components is too large, which will cause the metal sheet to delaminate and peel off, and will affect the thermal conductivity of the material. The inventor found that when the ratio of the linear expansion coefficient of the main heat-conducting metal sheet to the liquid metal is not within the specific range of 0.8-1.2, during the temperature change process, due to the degree of expansion of the main heat-conducting metal sheet and the liquid metal, and due to the particularity of the thermal conductive sheet system structure of the present invention, a small gap will be generated at the interface between the two. These gaps will increase the resistance to heat transfer, thereby reducing the thermal conductivity of the thermal conductive sheet, and when heat passes through the thermal conductive sheet, additional heat conduction or heat convection is required at these gaps, which will also reduce the overall heat transfer efficiency. The components of the metal thermal conductive sheet of the present invention are unevenly distributed and have a special heat conduction path. Once a gap appears at the interface, the originally continuous heat conduction path will be interrupted, so that heat cannot be directly and efficiently transferred through the thermal conductive sheet. This causes heat to accumulate inside the thermal conductive sheet, and even causes local overheating, further reducing the thermal conductivity and shortening the service life of the thermal conductive sheet. As for mechanical properties, the difference in linear expansion coefficient between the main thermal conductive metal sheet and the liquid metal is too large, and the thermal expansion of the two will be inconsistent. In the non-uniformly distributed thermal conductive sheet system of the present invention, the connection between the two will produce large thermal stress due to the difference in thermal expansion, causing the main thermal conductive metal sheet to undergo plastic deformation or warping. When the temperature changes frequently or with a large amplitude, it will significantly affect the overall shape and dimensional stability of the thermal conductive sheet, and even cause cracks or looseness at the connection, resulting in a decrease in the overall strength of the thermal conductive sheet and a significant reduction in mechanical properties.

[0007] The main heat-conducting metal sheet and liquid metal are combined. After being heated to a certain temperature, the liquid metal on the surface of the main heat-conducting metal sheet can form a liquid surface layer on the surface of the main heat-conducting metal sheet, thereby better wetting the interface, excluding air, and significantly reducing the interface contact thermal resistance of the main heat-conducting metal sheet.

[0008] Furthermore, the liquid metal is any one or more of gallium, gallium-indium alloy, gallium-indium-tin alloy, indium-bismuth alloy or indium-bismuth-tin alloy, and the liquid metal is a liquid metal with a melting point below 100°C, such as 30°C for gallium, 30°C for gallium-indium alloy, 10°C for gallium-indium-tin alloy, 72°C for indium-bismuth alloy and 60°C for indium-bismuth-tin alloy.

[0009] Further, the main heat-conducting metal sheet is any one of aluminum, indium, tin, bismuth, zinc, silver, and gold, and the main heat-conducting metal sheet is a high thermal conductivity metal with a thermal conductivity of >50 W / mK, for example, aluminum is 228 W / mK, indium is 81 W / mK, tin is 67 W / mK, zinc is 118 W / mK, silver is 414 W / mK, and gold is 315 W / mK; Furthermore, the main heat-conducting metal sheets are all high-melting-point metals, such as 660°C for aluminum, 157°C for indium, 232°C for tin, 271°C for bismuth, 419°C for zinc, 962°C for silver, and 1064°C for gold.

[0010] Furthermore, the surface roughness of the main heat-conducting metal sheet is 10~100μm, such as 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100 μm, and the surface roughness is tested by a 3D profilometer. The surface roughness within this range can maintain a stable combination of the surface liquid metal and the main heat-conducting metal in the metal heat-conducting sheet composite structure. The main heat-conducting metal sheet maintains its surface roughness by means of a surface pattern structure and the like. The pattern structure of the main heat-conducting metal sheet enables it to accommodate low-melting-point liquid metal and avoid metal leakage during application. The pattern structure is any one or more combinations of dot patterns (convex dots / concave dots), diamond patterns, grid patterns or wave patterns, preferably dot patterns. The inventors found that in the thermal conductive sheet system of the present invention, the dot pattern is more conducive to the grain refinement of the liquid metal during the heat treatment process, and by optimizing the microstructure of the material, it can reduce the defects inside the material such as inclusions, pores, etc. and stress concentration points, thereby improving the strength and toughness (fracture tensile properties) of the material.

[0011] Furthermore, the grain size of the main heat-conducting metal sheet is >10 μm, preferably 10 μm-3 mm, and more preferably the grain size is 20-50 μm. The inventors have found that keeping the grain size within this range can significantly improve the overall mechanical properties of the metal heat-conducting sheet, effectively improve the toughness of the metal sheet, and improve thermal properties (such as thermal conductivity), that is, maintain a balance between mechanical properties and thermal properties.

[0012] Furthermore, the thickness of the metal sheet is 0.03-0.5 mm.

[0013] The present invention also provides a method for preparing the metal thermal conductive sheet, comprising the following steps: S1: placing a main heat-conducting metal sheet between two steel plates with a pattern structure and feeding the sheet into a rolling mill to obtain a main heat-conducting metal sheet with a rough surface; the steel plates have a special pattern structure, which can form a special pattern structure on the surface of the main heat-conducting metal sheet, so that the surface of the main heat-conducting metal sheet has a certain degree of roughness; S2: The main heat-conducting metal sheet is subjected to the first heat treatment at a temperature lower than its melting point. The grain size can be controlled by adjusting the heat treatment conditions (such as time, temperature, etc.); S3: attaching the liquid metal to the main heat-conducting metal sheet with a rough surface by brushing or laminating and rolling to form a continuous liquid metal layer, and attaching it to both sides of the main heat-conducting metal sheet to obtain the metal sheet 1; for example, the brushing method is: placing the main heat-conducting metal sheet with a rough surface and the liquid metal in an oven at a temperature above the melting point of the liquid metal (preferably 8-12° C. above the melting point), and then brushing the liquid metal in liquid form (for example, by brushing with a scraper) onto the main heat-conducting metal sheet to form a continuous liquid metal layer, and brushing it to both sides of the main heat-conducting metal sheet to obtain the metal sheet 1; Liquid metal is attached to the rough surface of the main heat-conducting metal, and the pattern structure on the surface can accommodate the low-melting-point liquid metal on the surface to prevent the low-melting-point liquid metal from overflowing under the condition of applying pressure or heating.

[0014] S4: subjecting the metal sheet 1 obtained in S3 to a second heat treatment at a temperature above the melting point of the liquid metal on the surface (preferably 10-50°C above the melting point) (the second heat treatment allows the liquid metal to better fuse with the main thermal conductive metal. At this temperature, although the low-melting-point liquid metal on the surface is in liquid form, it will not aggregate or flow due to the adsorption of the surface pattern structure), thereby obtaining the metal thermal conductive sheet with a non-uniform structure. At this time, the main thermal conductive metal and the liquid metal form a non-layered integral alloy structure.

[0015] Furthermore, the temperature of the first heat treatment in step S2 is 1 / 3 or more of the melting point of the main heat-conducting metal sheet, preferably 1 / 2 or more.

[0016] Furthermore, the time of the first heat treatment in step S2 is 2-12 h.

[0017] The present invention also provides the use of the metal heat conductive sheet in immersion liquid cooling, high-power device thermal management, and laser thermal management, especially as a thermal interface material in high-power and optical devices requiring a large heat flux density.

[0018] In summary, compared with the prior art, the present invention achieves the following technical effects: (1) The metal thermal conductive sheet provided by the present invention has low interface contact thermal resistance and high thermal conductivity; (2) The metal heat conductive sheet provided by the present invention can not only quickly transfer heat under high temperature conditions but also prevent metal from overflowing under high temperature conditions; (3) The metal thermal conductive sheet provided by the present invention has excellent mechanical property stability and excellent toughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention 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 creative work.

[0020] Figure 1 This is a schematic diagram of the structure of the metal heat conductive sheet according to Embodiment 1 of the present invention; Figure 2 This is an appearance diagram of a metal thermal conductive sheet product according to Example 1 of the present invention; Figure 3 This is a surface scanning electron microscope image of the main heat-conducting metal sheet in the metal heat-conducting sheet of Example 1 of the present invention; Figure 4 This is an electron microscope image of a cross section of the metal thermal conductive sheet according to Example 1 of the present invention; Figure 5 This is a leakage test experiment effect diagram of the metal heat conductive sheet of Example 1 of the present invention; Figure 6 This is a leakage test experimental effect diagram of the metal heat conductive sheet of comparative example 2 of the present invention. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only embodiments of a part of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0022] Example The present invention is further described below in conjunction with specific examples and comparative examples. The following specific examples are all preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following examples, and are particularly not limited to the types of the various component raw materials used in the following specific examples.

[0023] 1. The sources of raw materials for the embodiments and comparative examples are as follows: Unless otherwise specified, the raw materials used in the examples and comparative examples of the present invention are commercially available.

[0024] 2. Various performance test methods (1) Metal leakage test: Cut the prepared metal thermal conductive sheet into a square with a side length of 2 cm, clamp it between two metal plates, place a weight of 3 kg on the surface, and place it in an oven at a temperature of 10~100℃ above the melting point of the liquid metal used. Take out the sample after 2 hours, cool it down, and open it to observe whether there is any leakage.

[0025] (2) Thermal resistance test: The test was conducted according to ASTM D5470-17. The metal thermal conductive sheet was cut into sheets with a size of 25.4 mm*25.4 mm. The thermal resistance was tested on a thermal resistance meter with the temperature set to 80°C and the pressure set to 40 PSI.

[0026] (3) Tensile property test: The test is carried out in accordance with ASTM E8 / E8M-22 (before heat treatment refers to the metal sheet that has not undergone the second heat treatment, and after heat treatment refers to the metal sheet that has undergone the second heat treatment).

[0027] (4) Elongation at break test: Tested in accordance with ASTM E8 / E8M-22.

[0028] Example 1 S1: Place an indium sheet with a thickness of 0.1 mm between two stainless steel templates with a thickness of 0.3 mm and diamond patterns, and send the whole into a roller mill. Set the gap of the roller mill to 0.65 mm, and roll it in the roller mill. The thickness of the rolled patterned indium sheet is measured to be 0.15 mm, and cut it into 10*10 cm square indium sheets with a rough surface; S2: placing the cut diamond-shaped indium sheet at 120° C. for a first heat treatment for 5 hours to promote the growth of the grain size in the indium sheet, and obtaining an indium sheet with a grain size of 12 μm; S3: the indium sheet and indium bismuth (InBi, melting point 72°C) alloy obtained in step S2 are placed in an oven at 80°C, the diamond-shaped indium sheet is placed in the oven, clamped vertically with a clip, and the metal sheet is straightened at the lower end with a 1 kg weight, 1 mL of the melted InBi alloy is taken, and the InBi liquid is evenly applied on both sides of the indium sheet with a stainless steel scraper to obtain a metal sheet 1, and the ratio D of the linear expansion coefficient of the diamond-shaped indium sheet and the InBi alloy is 0.9; S4: The metal sheet 1 obtained in S3 is subjected to a second heat treatment at 100° C. for 5 hours to form a non-layered non-uniform structure metal thermal conductive sheet with a product thickness of 0.2 mm; Figure 1 Schematic diagram of the structure of the metal heat conductive sheet of Example 1; Figure 2 This is the appearance diagram of the metal thermal conductive sheet product of Example 1; Figure 3 This is a surface scanning electron microscope image of the main heat-conducting metal sheet in the metal heat-conducting sheet of Example 1; Figure 4 This is an electron microscope image of a cross section of the metal thermal conductive sheet of Example 1; Figure 5 This is a diagram showing the effect of a leakage test experiment of the metal thermal conductive sheet of Example 1.

[0029] Example 2 S1: Place a 0.1 mm thick tin sheet between two 0.3 mm thick stainless steel templates with corrugated patterns, and send the whole into a roller mill. Set the gap of the roller mill to 0.65 mm, and roll it in the roller mill. The thickness of the rolled pattern sheet is measured to be 0.15 mm, and cut it into 10*10 cm square tin sheets with rough surfaces; S2: placing the cut wavy tin sheet at 120° C. for a first heat treatment for 10 hours to promote the growth of the grain size in the tin sheet, thereby obtaining a tin sheet with a grain size of 12 μm; S3: The tin sheet and gallium indium tin (InBiSn, melting point 60°C) alloy obtained in step S2 are placed in an oven at 70°C, the corrugated tin sheet is placed in the oven, clamped vertically with a clip, and the metal sheet is straightened at the lower end with a 1 kg weight, 1 mL of the melted liquid InBiSn alloy is taken, and the InBiSn liquid is evenly applied on both sides of the tin sheet with a stainless steel scraper to obtain a metal sheet 1, and the ratio D of the linear expansion coefficient of the corrugated tin sheet and the InBiSn alloy is 0.95; S4: The metal sheet 1 obtained in S3 is subjected to a second heat treatment at 80° C. for 5 hours to form a non-layered non-uniform structure metal thermal conductive sheet with a product thickness of 0.2 mm.

[0030] Example 3 The only difference from Example 1 is that step S1 is to place the indium sheet with a thickness of 0.1 mm at 135° C. for heat treatment for 5 hours to promote the growth of the grain size in the indium sheet, thereby obtaining an indium sheet with a grain size of 20 μm.

[0031] Example 4 The only difference from Example 1 is that step S1 is to heat treat an indium sheet with a thickness of 0.1 mm at 80° C. for 10 hours to promote the growth of the grain size in the indium sheet, thereby obtaining an indium sheet with a grain size of 7 μm.

[0032] Example 5 S1: Place an indium sheet with a thickness of 0.1 mm between two stainless steel templates with a thickness of 0.3 mm and dot patterns, and send the whole into a roller mill. Set the gap of the roller mill to 0.65 mm, and roll it in the roller mill. The thickness of the rolled patterned indium sheet is measured to be 0.15 mm, and cut it into 10*10 cm square indium sheets with a rough surface; S2: placing the cut dot pattern indium sheet at 120° C. for a first heat treatment for 5 hours to promote the growth of the grain size in the indium sheet, and obtaining an indium sheet with a grain size of 12 μm; S3: the indium sheet and indium bismuth (InBi, melting point 72°C) alloy obtained in step S2 are placed in an oven at 80°C, the dot pattern indium sheet is placed in the oven, clamped vertically with a clip, the lower end of the metal sheet is straightened with a 1 kg weight, 1 mL of the melted liquid InBi alloy is taken, and the InBi liquid is evenly applied on both sides of the indium sheet with a stainless steel scraper to obtain a metal sheet 1, and the ratio D of the linear expansion coefficients of the dot pattern indium sheet and the InBi alloy is 0.9; S4: The metal sheet 1 obtained in S3 is subjected to a second heat treatment at 100° C. for 5 hours to form a non-layered non-uniform structure metal thermal conductive sheet with a product thickness of 0.2 mm.

[0033] Comparative Example 1 An indium sheet with a thickness of 0.1 mm was placed between two diamond-patterned stainless steel templates with a thickness of 0.3 mm, and the whole was sent into a rolling mill. The gap of the rolling mill was set to 0.64 mm, and the rolled in the rolling mill. The thickness of the rolled patterned indium sheet was measured to be 0.15 mm, and the metal sheet was cut into a size of 10*10 cm. The obtained metal thermal conductive sheet was a diamond-patterned indium sheet.

[0034] Comparative Example 2 A smooth indium sheet with a thickness of 0.2 mm was cut into square metal sheets of 10*10 cm, placed in an 80°C oven, clamped vertically with a clamp, and the metal sheet was straightened at the lower end with a 1 kg weight. 1 mL of melted InBi alloy (melting point 72°C) was placed on the indium sheet, and the InBi liquid was evenly applied on both sides with a stainless steel scraper to obtain a metal thermal conductive sheet without a patterned structure. The product thickness was 0.22 mm.

[0035] Comparative Example 3 The only difference from Example 1 is that the second heat treatment in step S4 is not performed.

[0036] Comparative Example 4 S1: Place a 0.1 mm thick tin sheet between two 0.3 mm thick stainless steel templates with diamond patterns, and send the whole into a roller mill. Set the gap of the roller mill to 0.65 mm, and roll it in the roller mill. The thickness of the rolled patterned indium sheet is measured to be 0.15 mm, and cut into 10*10 cm square tin sheets with rough surfaces; S2: placing the cut diamond-patterned tin sheet at 120° C. for a first heat treatment for 5 hours to promote the growth of the grain size in the indium sheet, thereby obtaining an indium sheet with a grain size of 12 μm; S3: The tin sheet and indium bismuth (InBi, melting point 72°C) alloy obtained in step S2 are placed in an oven at 80°C, the diamond-patterned tin sheet is placed in the oven, clamped vertically with a clip, and the metal sheet is straightened at the lower end with a 1 kg weight, 1 mL of the melted InBi alloy is taken, and the InBi liquid is evenly applied on both sides of the tin sheet with a stainless steel scraper to obtain a metal sheet 1, and the ratio D of the linear expansion coefficient of the diamond-patterned tin sheet and the InBi alloy is 0.75; S4: The metal sheet 1 obtained in S3 is subjected to a second heat treatment at 100° C. for 5 hours to form a non-layered non-uniform structure metal thermal conductive sheet with a product thickness of 0.2 mm.

[0037] Comparative Example 5 S1: Place a zinc sheet with a thickness of 0.1 mm between two stainless steel templates with a thickness of 0.3 mm and diamond patterns, and send the whole into a roller mill. Set the gap of the roller mill to 0.65 mm, and roll it in the roller mill. The thickness of the rolled patterned zinc sheet is measured to be 0.15 mm, and cut it into 10*10 cm square zinc sheets with rough surfaces; S2: placing the cut diamond-patterned zinc sheet at 220° C. for a first heat treatment for 5 hours to promote the growth of the grain size in the zinc sheet, thereby obtaining a zinc sheet with a grain size of 12 μm; S3: The zinc sheet and gallium indium (GaIn) alloy obtained in step S2 are placed in an oven at 50°C, the diamond-patterned zinc sheet is placed in the oven, clamped vertically with a clip, and the metal sheet is straightened at the lower end with a 1 kg weight, 1 mL of the melted GaIn alloy is taken, and the GaIn liquid is evenly applied on both sides of the zinc sheet with a stainless steel scraper to obtain a metal sheet 1, and the ratio D of the linear expansion coefficients of the diamond-patterned zinc sheet and the GaIn alloy is 1.45; S4: The metal sheet 1 obtained in S3 is subjected to a second heat treatment at 100° C. for 5 hours to form a non-layered non-uniform structure metal thermal conductive sheet with a product thickness of 0.2 mm.

[0038] Table 1 Technical solutions and effects of embodiments and comparative examples

[0039] In Examples 1-5, the main heat-conducting metal sheet and the liquid metal are combined at the same time, and the linear expansion coefficients of the two are ensured to be within a specific range. In addition, a specific pattern structure is introduced into the main heat-conducting metal sheet, and the thermal resistance of the obtained metal heat-conducting sheet is lower than 0.043 ℃-cm 2 / W, and there will be no metal leakage problem under high-temperature heating, achieving the unity of low thermal resistance, high thermal conductivity and anti-leakage.

[0040] Comparative Examples 1-3 are compared with Example 1. Comparative Example 1 does not combine the main heat-conducting metal with the liquid metal to form a non-uniform structure. In Comparative Example 2, the main heat-conducting metal does not have a pattern structure. In Comparative Example 3, the metal sheet combining the main heat-conducting metal and the liquid metal is not subjected to secondary heat treatment to form a non-layered non-uniform overall structure. In Comparative Examples 4-5, the ratio of the linear expansion coefficient of the main heat-conducting metal sheet to the liquid metal is too small or too large. The above comparative examples cannot simultaneously achieve the unified effects of low thermal resistance, high thermal conductivity and anti-leakage of the metal heat-conducting sheet.

[0041] Based on the test data of thermal resistance, leakage resistance test, tensile properties, and elongation at break in Table 1, the metal thermal conductive sheet prepared by Examples 1-5 has obvious advantages over the comparative example and can effectively meet the high standards of customers and the market.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A metal thermal conductive sheet, characterized in that: The metal heat conductive sheet is composed of a main heat conductive metal sheet and liquid metal. The liquid metal is distributed on the upper and lower sides of the main heat conductive metal sheet. The components of the metal heat conductive sheet are distributed non-uniformly. The ratio D of the linear expansion coefficients of the main heat conductive metal sheet and the liquid metal satisfies: 0.8 <D<1.2。 2. The metal thermal conductive sheet according to claim 1, characterized in that: The liquid metal is any one or more of gallium, gallium-indium alloy, gallium-indium-tin alloy, indium-bismuth alloy or indium-bismuth-tin alloy.

3. The metal thermal conductive sheet according to claim 1, characterized in that: The main heat-conducting metal sheet is any one of aluminum, indium, tin, zinc, silver and gold.

4. The metal thermal conductive sheet according to claim 1, characterized in that: The surface roughness of the main heat-conducting metal sheet is 10-100 μm.

5. The metal thermal conductive sheet according to claim 1, characterized in that: The grain size of the main heat-conducting metal sheet is greater than 10 μm.

6. The metal thermal conductive sheet according to claim 1, characterized in that: The thickness of the metal heat conductive sheet is 0.03-0.5 mm.

7. The method for preparing the metal thermally conductive sheet according to any one of claims 1 to 6, comprising the following steps: S1: placing the main heat-conducting metal sheet between two steel plates with patterned structures and feeding them into a rolling mill to obtain a main heat-conducting metal sheet with a rough surface; S2: subjecting the main heat-conducting metal sheet to a first heat treatment at a temperature lower than its melting point; S3: attaching the liquid metal to the main heat-conducting metal sheet with a rough surface to form a continuous liquid metal layer, and attaching the liquid metal to both sides of the main heat-conducting metal sheet to obtain a metal sheet 1; S4: subjecting the metal sheet 1 obtained in S3 to a second heat treatment at a temperature above the melting point of the liquid metal, thereby obtaining the metal thermal conductive sheet having a non-uniform structure.

8. The preparation method according to claim 7, characterized in that: The temperature of the first heat treatment in step S2 is 1 / 3 or more of the melting point of the main heat-conducting metal sheet.

9. The preparation method according to claim 7, characterized in that: The time of the first heat treatment in step S2 is 2-12 h.

10. Application of the metal heat conductive sheet according to any one of claims 1 to 6 in immersion liquid cooling, thermal management of high power devices, and thermal management of lasers.

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