A metal heat conducting sheet, its preparation method and application

Abstract

The present invention discloses a metal heat-conducting sheet, a preparation method and an application thereof. The metal heat-conducting sheet is composed of a main heat-conducting metal sheet and a liquid metal. The liquid metal is distributed on the upper and lower sides of the main heat-conducting metal sheet, and the components of the metal heat-conducting sheet are non-uniformly distributed. Among them, the ratio D of the linear expansion coefficients of the main heat-conducting metal sheet and the liquid metal satisfies: 0.8 < D < 1.2. The metal heat-conducting sheet of the present invention can not only achieve low thermal resistance and high heat conduction, but also achieve anti-leakage of the metal under high-temperature heating.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal interface materials, and particularly relates to a metal heat conducting sheet, a preparation method thereof, and an application thereof. Background Art

[0002] The heat generation amount 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 both 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 development in the field of thermal interface materials at present.

[0003] Metals generally have high thermal conductivity characteristics. However, due to their relatively high hardness, these high-thermal-conductivity metal sheets often have high contact thermal resistance. In the prior art, a composite thermal conductive paste is often applied to 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 not good, the coating layer is prone to falling off, and the composite thermal conductive paste generally has a low thermal conductivity coefficient (<10 W / mK), and it is difficult to significantly exert the thermal performance of the metal sheet on the basis of reducing the thermal resistance. At present, there are also literature reports on a scheme of compounding two metals to reduce the thermal resistance, but this will cause one of the metals to easily leak after melting at a very high temperature, increasing the risk of short circuit during the use of electronic devices.

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

[0005] Aiming at the defects in the prior art, the present invention provides a metal heat conducting sheet, a preparation method thereof, and an application thereof.

[0006] The present invention provides a metal heat conducting sheet, which is composed of a main body heat conducting metal sheet and a liquid metal. The liquid metal is distributed on the upper and lower sides of the main body heat conducting metal sheet, and the components of the metal heat conducting sheet are non-uniformly distributed. Among them, the ratio D of the linear expansion coefficients of the main body heat conducting metal sheet and the liquid metal satisfies: 0.8 < D < 1.2;

[0007] The method for measuring the coefficient of linear expansion is the optical interference method. The coefficient of linear expansion of the intermetallic can ensure the mechanical stability of the composite structure under heating conditions within a specific range. A too large difference in the coefficient of linear expansion between the components will cause delamination and peeling of the metal sheet, and at the same time will affect the thermal conductivity of the material. The inventor found that when the ratio of the coefficient of linear expansion 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 inconsistent degree of expansion between the main heat-conducting metal sheet and the liquid metal, and due to the special structure of the heat-conducting sheet system of the present invention, tiny gaps 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 heat-conducting sheet. And when heat passes through the heat-conducting 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 heat-conducting sheet of the present invention are non-uniformly distributed and have a special heat conduction path. Once gaps appear at the interface, the originally continuous heat conduction path will be interrupted, making it impossible for heat to be directly and efficiently transferred through the heat-conducting sheet. This leads to the accumulation of heat inside the heat-conducting sheet, even causing local overheating phenomena, further reducing the thermal conductivity and also reducing the service life of the heat-conducting sheet. For mechanical properties, if the difference in the coefficient of linear expansion between the main heat-conducting metal sheet and the liquid metal is too large, the thermal expansion amounts of the two will be inconsistent. In the non-uniformly distributed heat-conducting sheet system of the present invention, large thermal stresses will be generated at the connection between the two due to the difference in thermal expansion amounts, resulting in plastic deformation or warping of the main heat-conducting metal sheet. When the temperature changes frequently or by a large amplitude, it will significantly affect the overall shape and dimensional stability of the heat-conducting sheet, and even cause cracks or looseness at the connection, leading to a decrease in the overall strength of the heat-conducting sheet and significantly reducing the mechanical properties.

[0008] The combination of the main heat-conducting metal sheet and the liquid metal can form a liquid surface layer on the surface of the main heat-conducting metal sheet after heating to a certain temperature, so as to better wet the interface, exclude air, and significantly reduce the interfacial contact thermal resistance of the main heat-conducting metal sheet.

[0009] Further, 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. The liquid metal is a liquid metal with a melting point below 100 °C. For example, the melting point of gallium is 30 °C, that of gallium-indium alloy is 30 °C, that of gallium-indium-tin alloy is 10 °C, that of indium-bismuth alloy is 72 °C, and that of indium-bismuth-tin alloy is 60 °C.

[0010] Further, the main heat-conducting metal sheet is any one of aluminum, indium, tin, bismuth, zinc, silver, gold. The main heat-conducting metal sheets are all high thermal conductivity metals with a thermal conductivity > 50 W / mK. For example, the thermal conductivity of aluminum is 228 W / mK, that of indium is 81 W / mK, that of tin is 67 W / mK, that of zinc is 118 W / mK, that of silver is 414 W / mK, and that of gold is 315 W / mK;

[0011] Furthermore, the main heat-conducting metal sheets are all high-melting-point metals. For example, the melting point of aluminum is 660 °C, indium is 157 °C, tin is 232 °C, bismuth is 271 °C, zinc is 419 °C, silver is 962 °C, and gold is 1064 °C.

[0012] Furthermore, the surface roughness of the main heat-conducting metal sheets is 10 - 100 μm, such as 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100 μm. The surface roughness is measured by a 3D profilometer. The surface roughness within this range can maintain the stable combination of the liquid metal in the surface layer and the main heat-conducting metal in the composite structure of the metal heat-conducting sheet. The main heat-conducting metal sheet maintains its surface roughness through means such as surface pattern structures. The pattern structure of the main heat-conducting metal sheet enables it to accommodate low-melting-point liquid metal and prevent metal leakage during application. The pattern structure is any one or a combination of dot patterns (convex dots / concave dots), diamond patterns, grid patterns, or wavy patterns, preferably dot patterns. The inventor found that in the heat-conducting sheet system of the present invention, dot patterns are more conducive to the grain refinement of liquid metal during the heat treatment process, and by optimizing the microstructure of the material, internal defects such as inclusions and pores and stress concentration points in the material can be reduced, thereby improving the strength and toughness (fracture tensile properties) of the material.

[0013] Furthermore, the grain size of the main heat-conducting metal sheets > 10 μm, preferably 10 μm - 3 mm, more preferably the grain size is 20 - 50 μm. The inventor found that maintaining 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 enhance the thermal properties (such as thermal conductivity), that is, maintain the balance between mechanical properties and thermal properties.

[0014] Furthermore, the thickness of the metal sheet is 0.03 - 0.5 mm.

[0015] The present invention also provides a method for preparing the metal heat-conducting sheet, including the following steps:

[0016] S1: Place the main heat-conducting metal sheet between two steel plates with pattern structures and send it into a rolling mill to obtain a main heat-conducting metal sheet with a rough surface; the steel plates have special pattern structures that can form special pattern structures on the surface of the main heat-conducting metal, making the surface of the main metal heat-conducting sheet have a certain roughness;

[0017] S2: Conduct the first heat treatment on the main heat-conducting metal sheet at a temperature below its melting point, and control the heat treatment conditions (such as time, temperature, etc.) to control the grain size;

[0018] S3: Attach the liquid metal to the rough-surfaced main body heat-conducting metal sheet by brushing or laminated roll pressing to form a continuous liquid metal layer. When attached to both sides of the main body heat-conducting metal sheet, metal sheet 1 is obtained. For example, the brushing method is as follows: Place the rough-surfaced main body heat-conducting metal sheet 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 brush (e.g., by a squeegee) the liquid metal in liquid form onto the main body heat-conducting metal sheet to form a continuous liquid metal layer. When brushed onto both sides of the main body heat-conducting metal sheet, metal sheet 1 is obtained.

[0019] Attach the liquid metal to the rough surface of the main body heat-conducting metal. The pattern structure on its surface can hold the low-melting-point liquid metal on its surface, preventing the low-melting-point liquid metal from overflowing under the conditions of applied pressure or heating.

[0020] S4: Perform a second heat treatment on the metal sheet 1 prepared in S3 at a temperature above the melting point of the surface liquid metal (preferably 10 - 50 °C above the melting point). (Through the second heat treatment, the liquid metal can better fuse with the main body heat-conducting metal. At this temperature, although the surface low-melting-point liquid metal is in a liquid state, due to the adsorption of the surface pattern structure, it will not aggregate or flow), and then the metal heat-conducting sheet with a non-uniform structure is obtained. At this time, the main body heat-conducting metal and the liquid metal form an integral alloy structure without delamination.

[0021] Further, the temperature of the first heat treatment in step S2 is 1 / 3 or more of the melting point of the main body heat-conducting metal sheet, preferably 1 / 2 or more.

[0022] Further, the time of the first heat treatment in step S2 is 2 - 12 h.

[0023] The present invention also provides the application of the metal heat-conducting 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.

[0024] In summary, compared with the prior art, the present invention achieves the following technical effects:

[0025] (1) The metal heat-conducting sheet provided by the present invention has a low interface contact thermal resistance and a high thermal conductivity.

[0026] (2) The metal heat-conducting sheet provided by the present invention can not only transfer heat quickly under high-temperature conditions but also avoid the overflow of the metal under high heat.

[0027] (3) The metal heat-conducting sheet provided by the present invention has excellent mechanical property stability and excellent toughness. Description of the Drawings

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0029] Figure 1 Schematic diagram of the metal heat-conducting sheet structure of Embodiment 1 of the present invention;

[0030] Figure 2 Appearance diagram of the metal heat-conducting sheet product of Embodiment 1 of the present invention;

[0031] Figure 3 Surface scanning electron microscope image of the main heat-conducting metal sheet in the metal heat-conducting sheet of Embodiment 1 of the present invention;

[0032] Figure 4 Cross-sectional electron microscope image of the metal heat-conducting sheet of Embodiment 1 of the present invention;

[0033] Figure 5 Effect diagram of the leakage test experiment of the metal heat-conducting sheet of Embodiment 1 of the present invention;

[0034] Figure 6 Effect diagram of the leakage test experiment of the metal heat-conducting sheet of Comparative Example 2 of the present invention. Specific implementation manners

[0035] In order to enable those skilled in the art to better understand the solutions of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0036] Embodiment

[0037] The following will further illustrate the present invention in combination with specific embodiments and comparative embodiments. The following specific embodiments are all preferred implementation manners of the present invention, but the implementation manners of the present invention are not limited by the following embodiments, especially not limited to the models of the various component raw materials used in the following specific embodiments.

[0038] I. The sources of raw materials for the embodiments and comparative examples are as follows:

[0039] Unless otherwise specified, the raw material substances used in the embodiments and comparative examples of the present invention are all commercially available.

[0040] II. Various performance test methods

[0041] (1) Metal anti-leakage test: Cut the prepared metal heat-conducting sheet into a square with a side length of 2 cm, clamp it in the middle of two metal plates, place a weight of 3 kg on the surface, put it in an oven, and the oven temperature is 10 - 100 °C above the melting point of the used liquid metal. Take out the sample after 2 hours, and observe whether there is leakage after cooling.

[0042] (2) Thermal resistance test: Conduct the test according to ASTM D5470-17. Cut the metal heat-conducting sheet into sheets with dimensions of 25.4 mm * 25.4 mm, and test its thermal resistance on a thermal resistance tester. Set the temperature to 80 °C and the pressure to 40 PSI.

[0043] (3) Tensile property test: Conduct the test according to 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).

[0044] (4) Elongation at break test: Conduct the test according to ASTM E8 / E8M-22.

[0045] Example 1

[0046] 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 a diamond pattern, send the whole into a rolling mill, set the gap of the rolling mill to 0.65 mm, roll in the rolling mill, and after measurement, the thickness of the rolled indium sheet with a pattern is 0.15 mm. Cut it into a rough-surfaced square indium sheet with a size of 10 * 10 cm;

[0047] S2: Place the cut indium sheet with a diamond pattern in a first heat treatment at 120 °C for 5 hours to promote the growth of the grain size in the indium sheet, and obtain an indium sheet with a grain size of 12 μm;

[0048] S3: Place the indium sheet obtained in step S2 and indium-bismuth (InBi, melting point 72 °C) alloy in an oven at 80 °C. Place the indium sheet with a diamond pattern in the oven, clamp it vertically with a clip, and use a 1-kg weight at the lower end to straighten the metal sheet. Take 1 mL of melted InBi alloy, and use a stainless-steel scraper to evenly brush the InBi liquid on both sides of the indium sheet to obtain metal sheet 1. The ratio D of the linear expansion coefficients of the indium sheet with a diamond pattern and the InBi alloy is 0.9;

[0049] S4: Conduct a second heat treatment on the metal sheet 1 prepared in S3 at 100 °C for 5 hours to form a non-uniform structure metal heat-conducting sheet without delamination, and the product thickness is 0.2 mm;

[0050] Figure 1 is a schematic diagram of the structure of the metal heat-conducting sheet for Example 1;

[0051] Figure 2 Appearance diagram of the metal heat conducting sheet product of Example 1;

[0052] Figure 3 Surface scanning electron microscope image of the main heat conducting metal sheet in the metal heat conducting sheet of Example 1;

[0053] Figure 4 Cross-sectional electron microscope image of the metal heat conducting sheet of Example 1;

[0054] Figure 5 Effect diagram of the leakage test experiment of the metal heat conducting sheet of Example 1.

[0055] Example 2

[0056] S1: Place a tin sheet with a thickness of 0.1 mm between two corrugated stainless steel templates with a thickness of 0.3 mm, send the whole into a rolling mill, set the gap of the rolling mill to 0.65 mm, roll in the rolling mill, and after measurement, the thickness of the rolled patterned sheet is 0.15 mm, and cut it into a square tin sheet with a surface roughness of 10*10 cm;

[0057] S2: Place the cut corrugated tin sheet at 120 °C for the first heat treatment for 10 hours to promote the growth of the grain size in the tin sheet, and obtain a tin sheet with a grain size of 12 μm;

[0058] S3: Place the tin sheet obtained in step S2 and gallium indium tin (InBiSn, melting point 60 °C) alloy in an oven at 70 °C. Place the corrugated tin sheet in the oven, clamp it vertically with a clip, and straighten the metal sheet with a 1 kg weight at the lower end. Take 1 mL of melted InBiSn alloy, and use a stainless steel scraper to evenly brush the InBiSn liquid on both sides of the tin sheet to obtain metal sheet 1. The ratio D of the linear expansion coefficients of the corrugated tin sheet and the InBiSn alloy is 0.95;

[0059] S4: Heat-treat the metal sheet 1 obtained in S3 at 80 °C for 5 hours to form a non-uniform structure metal heat conducting sheet without delamination, and the product thickness is 0.2 mm.

[0060] Example 3

[0061] The difference from Example 1 is only that in step S1, an indium sheet with a thickness of 0.1 mm is heat-treated at 135 °C for 5 hours to promote the growth of the grain size in the indium sheet, and an indium sheet with a grain size of 20 μm is obtained.

[0062] Example 4

[0063] The difference from Example 1 is only that in step S1, an indium sheet with a thickness of 0.1 mm is placed at 80 °C for heat treatment for 10 hours to promote the growth of the grain size in the indium sheet, and an indium sheet with a grain size of 7 μm is obtained.

[0064] Example 5

[0065] 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, send the whole into a rolling mill, set the gap of the rolling mill to 0.65 mm, roll in the rolling mill. After measurement, the thickness of the rolled indium sheet with patterns is 0.15 mm, and it is cut into a square indium sheet with a surface roughness of 10*10 cm;

[0066] S2: Place the cut indium sheet with dot patterns at 120 °C for the first heat treatment for 5 hours to promote the growth of the grain size in the indium sheet, and obtain an indium sheet with a grain size of 12 μm;

[0067] S3: Place the indium sheet obtained in step S2 and indium-bismuth (InBi, melting point 72 °C) alloy in an oven at 80 °C. Place the indium sheet with dot patterns inside the oven, clamp it vertically with a clip, and straighten the metal sheet with a 1-kg weight at the lower end. Take 1 mL of melted InBi alloy in liquid state, and use a stainless-steel scraper to evenly brush the InBi liquid on both sides of the indium sheet to obtain Metal Sheet 1. The ratio D of the linear expansion coefficients of the indium sheet with dot patterns and the InBi alloy is 0.9;

[0068] S4: Heat-treat Metal Sheet 1 obtained in S3 at 100 °C for the second heat treatment for 5 hours to form a non-uniform structure metal heat-conducting sheet without delamination, and the product thickness is 0.2 mm.

[0069] Comparative Example 1

[0070] Place an indium sheet with a thickness of 0.1 mm between two rhombus-pattern stainless-steel templates with a thickness of 0.3 mm, send the whole into a rolling mill, set the gap of the rolling mill to 0.64 mm, roll in the rolling mill. After measurement, the thickness of the rolled indium sheet with patterns is 0.15 mm, and cut it into a metal sheet with a size of 10*10 cm. The obtained metal heat-conducting sheet is a rhombus-pattern indium sheet.

[0071] Comparative Example 2

[0072] Cut a smooth indium sheet with a thickness of 0.2 mm into a square metal sheet with a size of 10*10 cm, place it in an 80 °C oven, clamp it vertically with a clip, and straighten the metal sheet with a 1-kg weight at the lower end. Take 1 mL of melted InBi alloy (melting point 72 °C) and place it on the indium sheet, and use a stainless-steel scraper to evenly brush the InBi liquid on both sides to obtain a metal heat-conducting sheet with a non-patterned structure, and the product thickness is 0.22 mm.

[0073] Comparative Example 3

[0074] The difference from Example 1 is only that the second heat treatment in step S4 is not carried out.

[0075] Comparative Example 4

[0076] S1: Place a tin sheet with a thickness of 0.1 mm between two stainless - steel templates with a thickness of 0.3 mm and having diamond patterns, send the whole into a rolling mill, set the gap of the rolling mill to 0.65 mm, roll in the rolling mill, measure that the thickness of the rolled indium sheet with patterns is 0.15 mm, and cut it into a rough - surfaced square tin sheet with a size of 10 * 10 cm;

[0077] S2: Place the cut diamond - patterned tin sheet at 120 °C for the first heat treatment for 5 hours to promote the growth of grain size in the indium sheet, and obtain an indium sheet with a grain size of 12 μm;

[0078] S3: Place the tin sheet obtained in step S2 and indium - bismuth (InBi, melting point 72 °C) alloy in an oven at 80 °C. Place the diamond - patterned tin sheet in the oven, clamp it vertically with a clip, straighten the metal sheet with a 1 - kg weight at the lower end. Take 1 mL of melted InBi alloy, and evenly brush the InBi liquid on both sides of the tin sheet with a stainless - steel scraper to obtain Metal Sheet 1. The ratio D of the linear expansion coefficients of the diamond - patterned tin sheet and the InBi alloy is 0.75;

[0079] S4: Heat - treat Metal Sheet 1 obtained in S3 at 100 °C for 5 hours to form a non - delaminated non - uniform - structure metal heat - conducting sheet, and the product thickness is 0.2 mm.

[0080] Comparative Example 5

[0081] 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 having diamond patterns, send the whole into a rolling mill, set the gap of the rolling mill to 0.65 mm, roll in the rolling mill, measure that the thickness of the rolled zinc sheet with patterns is 0.15 mm, and cut it into a rough - surfaced square zinc sheet with a size of 10 * 10 cm;

[0082] S2: Place the cut diamond - patterned zinc sheet at 220 °C for the first heat treatment for 5 hours to promote the growth of grain size in the zinc sheet, and obtain a zinc sheet with a grain size of 12 μm;

[0083] S3: The zinc sheet and gallium-indium (GaIn) alloy obtained in step S2 are placed in a 50°C oven. The diamond-patterned zinc sheet is placed in the oven and clamped vertically with a clamp. A 1 kg weight is used to straighten the metal sheet at the lower end. 1 mL of the melted GaIn alloy is taken and evenly applied to both sides of the zinc sheet using a stainless steel scraper to obtain metal sheet 1. The ratio of the linear expansion coefficients of the diamond-patterned zinc sheet and the GaIn alloy is 1.45.

[0084] 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 structured metal thermal conductive sheet with a product thickness of 0.2 mm.

[0085] Table 1 Technical solutions and effects of the embodiments and comparative examples

[0086]

[0087] In Examples 1-5, the main heat-conducting metal sheet is combined with the liquid metal, and the linear expansion coefficient of the two is ensured to be within a specific range. In addition, a specific pattern structure is introduced into the main heat-conducting metal sheet. 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.

[0088] Comparative Examples 1-3 are compared with Example 1. In Comparative Example 1, the main heat-conducting metal and the liquid metal are not combined to form a non-uniform structure. In Comparative Example 2, the main heat-conducting metal does not have a patterned structure. In Comparative Example 3, the metal sheet combined with the main heat-conducting metal and the liquid metal is not subjected to a 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 and the liquid metal is too small or too large. None of the above comparative examples can simultaneously achieve the unified effects of low thermal resistance, high thermal conductivity and anti-leakage of the metal heat-conducting sheet.

[0089] Based on the test data of thermal resistance, leakage resistance test, tensile properties, and elongation at break in Table 1, the metal thermal conductive sheets prepared by Examples 1-5 have obvious advantages over the comparative examples and can effectively meet the high standards of customers and the market.

[0090] 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 heat conducting sheet, characterized in that, The metal heat-conducting sheet is composed of a main body heat-conducting metal sheet and a liquid metal. The liquid metal is distributed on the upper and lower sides of the main body heat-conducting metal sheet, and the components of the metal heat-conducting sheet are non-uniformly distributed. Among them, the ratio D of the linear expansion coefficients of the main body heat-conducting metal sheet and the liquid metal satisfies: 0.8 < D < 1.2; 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; The grain size of the main body heat-conducting metal sheet > 10 μm; The preparation method of the metal heat-conducting sheet includes the following steps: S1: Place the main body heat-conducting metal sheet between two steel plates with a pattern structure and send it into a rolling mill to obtain a main body heat-conducting metal sheet with a rough surface; S2: Perform the first heat treatment on the main body heat-conducting metal sheet at a temperature below its melting point; S3: Attach the liquid metal to the main body heat-conducting metal sheet with a rough surface to form a continuous liquid metal layer, and attach it to both sides of the main body heat-conducting metal sheet to obtain Metal Sheet 1; S4: Perform the second heat treatment on Metal Sheet 1 prepared in S3 at a temperature above the melting point of the liquid metal to obtain the metal heat-conducting sheet with a non-uniform structure.

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

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

4. The metal heat-conducting sheet according to claim 1, wherein The thickness of the metal heat-conducting sheet is 0.03 - 0.5 mm.

5. The metal heat conducting sheet according to claim 1, 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 body heat-conducting metal sheet.

6. The metal heat-conducting sheet according to claim 1, wherein The time of the first heat treatment in step S2 is 2 - 12 h.

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

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