Composite heat conducting material for copper foil substrate

Abstract

The application discloses a composite heat-conducting material of a copper foil substrate. The composite heat-conducting material is a thermal interface material composed of a perforated and roughened copper foil and a liquid metal. The composite thermal interface material is prepared by rolling the roughened copper foil coated with the liquid metal paste on both sides. The liquid metal paste comprises the liquid metal and the cross-linking phase material, and the mass percentage of Bi:In:Sn:Ga in the liquid metal ranges from (25-35):(40-55):(10-18):(3-7) or 0:(15-20):(10-25):(60-80). The roughened copper foil is obtained by perforating and stamping the copper foil. The prepared composite thermal interface material has a high heat-conducting coefficient, which can be up to 50-120 W / m.K, and does not leak after being melted at high temperature, and the liquid metal paste does not agglomerate or deteriorate in stratification.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of heat-conducting materials, and relates to a composite heat-conducting material of a copper foil substrate, in particular to a composite liquid metal interface heat-conducting material and a preparation method thereof. BACKGROUND

[0002] At present, power electronic devices are very dependent on passive cooling systems, and with the improvement of the integration of electronic components, how to achieve a high heat conduction rate has become a research hotspot. Among them, the research on thermal interface materials is the key. The thermal interface material is a material used for coating between the heat-dissipating electronic components and the heat-generating electronic components to reduce the contact thermal resistance between the two electronic components.

[0003] Liquid metal is a low-melting alloy with high thermal conductivity (10-20 W / m.K) near its melting point, and is a common thermal interface material. However, the thermal conductivity of pure liquid metal is still not high enough, and the industry hopes to have an interface heat-conducting material with higher thermal conductivity, and the thermal conductivity thereof is preferably up to 120 W / m.K.

[0004] Generally, high-thermal-conductivity material powders such as micro-nano aluminum oxide powder and copper powder are added to the liquid metal, so that the thermal conductivity thereof can reach up to 120 W / m.K. However, the micro-nano added powder is easy to reduce the thermal conductivity of the heat-conducting material due to delamination and agglomeration during use, and the thermal cycle performance thereof is poor.

[0005] There are also many thermal interface materials in the prior art that composite liquid metal and metal foam (such as foam copper, foam nickel, foam aluminum, etc.). Since the foam metal is completely connected together with through holes, these materials can be well combined with liquid metal and improve the thermal conductivity of the liquid metal interface heat-conducting material.

[0006] The interface heat-conducting material often hopes that the total thickness thereof is not more than 100 um, and the optimal thickness is about 50 um. However, in the actual industry, such thickness of ultra-thin foam copper is very expensive, and the foam copper prepared by the general process is 2 mm thick at most, and cannot solve the actual needs of the interface heat-conducting material at a suitable cost.

[0007] The industry hopes to have a composite liquid metal interface heat-conducting metal material with a suitable cost, a high thermal conductivity (50-120 W / m.K), and a thickness of 20-60 um. SUMMARY

[0008] The purpose of the present application is to provide a low-cost high-thermal-conductivity liquid metal composite thermal interface material.

[0009] The technical solution of the present application is as follows:

[0010] The application provides a composite thermal interface material composed of a roughened copper foil and liquid metal, which is obtained by rolling a copper foil coated with liquid metal paste on both sides.

[0011] Preferably, the liquid metal paste comprises liquid metal and cross-linking phase material; the composition of the liquid metal is Bi, In, Sn, Ga, and the mass percentage ranges are (25-35):(40-55):(10-18):(3-7), or In, Sn, Ga, and the mass percentage ranges are (15-20):(10-25):(60-80).

[0012] Preferably, the content of the cross-linking phase material in the liquid metal paste is 2-8% of the mass of the liquid metal.

[0013] Preferably, the cross-linking phase material is one or more of metal powder, diamond powder, silicone oil, epoxy resin and polyurethane.

[0014] Preferably, the phase transition temperature of the liquid metal thermal paste is 40-70℃, and the latent heat of phase transition is 250-370J / cc.

[0015] Preferably, the thickness of the liquid metal thermal paste coated on each side of the copper foil is 10-30μm.

[0016] Preferably, the copper foil is electrolytic copper foil or rolled copper foil; the roughening treatment of the copper foil is performed by stamping process on both sides of the copper foil; and the thickness of the copper foil is 20-60μm. After stamping, a large number of densely distributed conical openings are formed on the surface of the copper foil, which can provide a channel for bidirectional contact heat conduction of the liquid metal, and artificially divide the liquid metal into numerous independent small areas, so as to reduce the tendency of internal stratification and agglomeration of the liquid metal, and the conical openings can be more closely combined with the liquid metal due to the roughening treatment.

[0017] Preferably, the copper foil is provided with densely distributed one-way or bidirectional openings, and the opening process is stamping; the diameter of the openings is 0.3-3mm, preferably 1mm; and the opening density is 5-20 / cm2.

[0018] The application also provides a preparation method of the composite thermal material, which comprises the following steps:

[0019] (1) heating and smelting Bi, In, Sn and Ga in proportion to obtain the liquid metal;

[0020] (2) adding the cross-linking phase material in 3-8 times, and heating and stirring to obtain the liquid metal thermal paste;

[0021] (3) stamping the copper foil and performing roughening treatment on the copper foil by perforation;

[0022] (4) coating the liquid metal thermal paste on both sides of the punched copper foil;

[0023] (5) rolling the copper foil coated with the liquid metal thermal paste to obtain the composite thermal conductive material;

[0024] (6) cutting the composite thermal conductive material, preferably cutting the size to 40*40mm / piece.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] The composite thermal interface material prepared by the present application has a high thermal conductivity, which can be as high as 50~120W / m.K. In addition, the substrate material is cheap and easy to obtain, and can be directly prepared by punching and perforating the copper foil (typically the electrode copper foil for batteries). The composite thermal interface material is convenient to use, and can be directly used after being cut into the required shape. The copper foil surface is densely covered with conical openings, which can provide a two-way contact thermal conduction channel for the liquid metal, and also divide the liquid metal into countless independent small areas, each of which can reduce the tendency of internal stratification and aggregation of the liquid metal. The conical openings can also be more closely combined with the liquid metal due to the roughening treatment. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The figure is a schematic diagram of the principle of preparing the composite thermal interface material by punching the copper foil substrate for Example 1.

[0028] Figure 2 The composite thermal interface material prepared for Example 1. DETAILED DESCRIPTION

[0029] The embodiments of the present application will be described in detail below by way of examples, so that the implementation process of how to apply technical means to solve technical problems and achieve technical effects can be fully understood and implemented.

[0030] The raw materials and equipment used in the present application, if not specifically stated, are conventional raw materials and equipment in the art, and are all from commercially available products. The methods used in the present application, if not specifically stated, are conventional methods in the art.

[0031] There are still other various implementable technical solutions in the present application, which are not listed one by one, and the technical solutions claimed in the claims of the present application are all implementable.

[0032] "comprising" or "including" is intended to mean that the compositions (e.g., the media) and the methods include the recited elements, but not excluding others. "Consisting essentially of when used to define compositions and methods, means excluding other elements of any importance to the purpose of the compositions. Thus, a composition consisting essentially of the elements as defined herein, does not exclude other materials or steps which do not materially affect the basic and novel characteristic(s) of the claimed application. "Consisting of means excluding other than the element or step specified. Embodiments defined by each of these transition terms are within the scope of this application. The preparation method disclosed in the patent of

[0033] Example 1

[0034] (1) 25-30 parts by weight of Bi, 40-45 parts by weight of In, 10-14 parts by weight of Sn, 3 parts by weight of Ga are heated to 100°C and smelted for 1-2h to obtain a liquid metal;

[0035] (2) 2-8% of cross-linking phase material by weight of the liquid metal is added to the liquid metal in 3-8 times, heated and stirred to obtain the liquid metal thermal paste;

[0036] (3) A copper foil with a thickness of 30um is punched, and roughening treatment is performed on the copper foil with a 1mm diameter perforation, with a hole rate of 5 per cm 2 ;

[0037] (4) The liquid metal thermal paste is coated on both sides of the perforated copper foil, and the single-layer coating thickness is 20um;

[0038] (5) The copper foil coated with the liquid metal thermal paste is rolled to obtain the composite thermal material with a total thickness of 70um;

[0039] (6) The composite thermal material is cut, and the cutting size is preferably 40*40mm / piece.

[0040] After testing, the thermal conductivity of the composite liquid metal thermal paste in this embodiment is 50W / m.K, and there is no degradation phenomenon after multiple thermal cycles.

[0041] Example 2

[0042] (1) 25 parts by weight of Bi, 50 parts by weight of In, 18 parts by weight of Sn, and 7 parts by weight of Ga are heated to 100°C and smelted for 2h to obtain a liquid metal;

[0043] (2) 5% of polyurethane by weight of the liquid metal is added to the liquid metal in 3 times, heated and stirred to obtain the liquid metal thermal paste;

[0044] (3) punching the copper foil with a thickness of 30 um to perform roughening treatment by perforating the copper foil with a diameter of 1 mm, and the hole rate is 5 per cm 2 ;

[0045] (4) coating the liquid metal thermal paste on both sides of the perforated copper foil, and the single-layer coating thickness is 20 um;

[0046] (5) rolling the copper foil coated with the liquid metal thermal paste to obtain the composite thermal conductive material with a total thickness of 70 um;

[0047] (6) cutting the above composite thermal conductive material, and preferably the cutting size is 40*40 mm / piece.

[0048] It is tested that the thermal conductivity of the composite liquid metal thermal paste in the embodiment is 50 W / m.K, and there is no degradation phenomenon after multiple thermal cycles, no liquid metal extrusion phenomenon occurs during use, and no polyurethane powder aggregation is found during disassembly inspection.

[0049] Example 3

[0050] (1) heating 30 parts by weight of Bi, 50 parts by weight of In, 15 parts by weight of Sn and 5 parts by weight of Ga to 100°C to melt for 2 h to obtain a liquid metal;

[0051] (2) adding polyurethane with a weight of 5% of the liquid metal into the liquid metal in three times, heating and stirring to obtain the liquid metal thermal paste;

[0052] (3) punching the copper foil with a thickness of 30 um to perform roughening treatment by perforating the copper foil with a diameter of 1 mm, and the hole rate is 5 per cm 2 ;

[0053] (4) coating the liquid metal thermal paste on both sides of the perforated copper foil, and the single-layer coating thickness is 20 um;

[0054] (5) rolling the copper foil coated with the liquid metal thermal paste to obtain the composite thermal conductive material with a total thickness of 70 um;

[0055] (6) cutting the above composite thermal conductive material, and preferably the cutting size is 40*40 mm / piece.

[0056] It is tested that the thermal conductivity of the composite liquid metal thermal paste in the embodiment is 55 W / m.K, and there is no degradation phenomenon after multiple thermal cycles, no liquid metal extrusion phenomenon occurs during use, and no polyurethane powder aggregation is found during disassembly inspection.

[0057] Example 4

[0058] (1) 35 parts by weight of Bi, 40 parts by weight of In, 18 parts by weight of Sn, and 7 parts by weight of Ga are heated to 100°C and smelted for 2 hours to obtain liquid metal;

[0059] (2) 5% of polyurethane by weight of the liquid metal is added to the liquid metal in three times, and heated and stirred to obtain the liquid metal thermal paste;

[0060] (3) A copper foil with a thickness of 30 um is punched, and roughening treatment is performed on the copper foil with a diameter of 1 mm, and the hole rate is 5 per cm 2 ;

[0061] (4) The liquid metal thermal paste is coated on both sides of the punched copper foil, and the single-layer coating thickness is 20 um;

[0062] (5) The copper foil coated with the liquid metal thermal paste is rolled to obtain the composite thermal material with a total thickness of 70 um;

[0063] (6) The composite thermal material is cut, and the cutting size is preferably 40*40 mm / piece.

[0064] It is tested that the thermal conductivity of the composite liquid metal thermal paste in the embodiment is 58 W / m.K, and there is no degradation phenomenon after multiple thermal cycles, no liquid metal extrusion phenomenon occurs during use, and no polyurethane powder aggregation is found during disassembly inspection.

[0065] Example 5

[0066] (1) 30 parts by weight of Bi, 50 parts by weight of In, 15 parts by weight of Sn, and 5 parts by weight of Ga are heated to 100°C and smelted for 2 hours to obtain liquid metal;

[0067] (2) 1% of polyurethane by weight of the liquid metal is added to the liquid metal in three times, and heated and stirred to obtain the liquid metal thermal paste;

[0068] (3) A copper foil with a thickness of 30 um is punched, and roughening treatment is performed on the copper foil with a diameter of 1 mm, and the hole rate is 5 per cm 2 ;

[0069] (4) The liquid metal thermal paste is coated on both sides of the punched copper foil, and the single-layer coating thickness is 20 um;

[0070] (5) The copper foil coated with the liquid metal thermal paste is rolled to obtain the composite thermal material with a total thickness of 70 um;

[0071] (6) The composite thermal material is cut, and the cutting size is preferably 40*40 mm / piece.

[0072] The thermal conductivity of the composite liquid metal thermal paste in this embodiment is 45 W / m.K after testing, and there is a deterioration phenomenon after multiple thermal cycles. When in use, the liquid metal overflowed from the edge. No polyurethane powder aggregation was found during the disassembly inspection.

[0073] Example 6

[0074] (1) 30 parts by weight of Bi, 50 parts by weight of In, 15 parts by weight of Sn, and 5 parts by weight of Ga were heated to 100°C and smelted for 2h to obtain a liquid metal;

[0075] (2) 9% of polyurethane by weight of the liquid metal was added to the liquid metal in three times, heated and stirred to obtain the liquid metal thermal paste;

[0076] (3) A copper foil with a thickness of 30um was punched, and the copper foil was roughened by punching a hole with a diameter of 1mm, and the hole rate was 5 / cm 2 ;

[0077] (4) The liquid metal thermal paste was coated on both sides of the punched copper foil, and the single-layer coating thickness was 20um;

[0078] (5) The copper foil coated with the liquid metal thermal paste was rolled to obtain the composite thermal material with a total thickness of 70um;

[0079] (6) The composite thermal material was cut, and the preferred cutting size was 40*40mm / piece.

[0080] The thermal conductivity of the composite liquid metal thermal paste in this embodiment is 48 W / m.K after testing, and there is a deterioration phenomenon after multiple thermal cycles. When in use, no liquid metal overflowed from the edge, but the polyurethane powder was found to have a certain degree of aggregation phenomenon during the disassembly inspection.

[0081] Example 7

[0082] (1) 20 parts of In, 20 parts of Sn, and 60 parts of Ga were heated to 60°C to obtain the liquid metal; the smelting time was 1-2h;

[0083] (2) Copper powder with a particle size of about 1um was added in 8 times, heated and stirred, and the weight was 5% of the liquid metal;

[0084] (3) A copper foil with a thickness of 40um was punched, and the copper foil was roughened by punching a hole with a diameter of 0.5mm, and the hole rate was 10 / cm 2 ;

[0085] (4) The liquid metal thermal paste was coated on both sides of the punched copper foil, and the single-layer coating thickness was 30um;

[0086] (5) roll the copper foil coated with the liquid metal thermal paste to obtain the composite thermal material with a total thickness of 90 um;

[0087] (6) cut the composite thermal material, preferably with a size of 40*40 mm / piece.

[0088] It is tested that the thermal conductivity of the composite liquid metal thermal paste in the embodiment is 100 W / m.K, no degradation phenomenon occurs after multiple thermal cycles, no liquid metal overflow phenomenon occurs during use, and no copper powder agglomeration is found during the inspection of the piece.

[0089] Embodiment 8

[0090] (1) heat 17 parts of In, 18 parts of Sn, and 65 parts of Ga to 60°C to obtain the liquid metal; wherein the melting time is 2 h;

[0091] (2) add copper powder with a particle size of about 1 um in 8 times, heat and stir, and the weight is 5% of the liquid metal;

[0092] (3) punch the copper foil with a thickness of 40 um, and perform roughening treatment on the copper foil by perforating a diameter of 0.5 mm, and the hole rate is 10 pieces / cm 2 ;

[0093] (4) coat the liquid metal thermal paste on both sides of the perforated copper foil, and the single-layer coating thickness is 30 um;

[0094] (5) roll the copper foil coated with the liquid metal thermal paste to obtain the composite thermal material with a total thickness of 90 um;

[0095] (6) cut the composite thermal material, preferably with a size of 40*40 mm / piece.

[0096] It is tested that the thermal conductivity of the composite liquid metal thermal paste in the embodiment is 112 W / m.K, no degradation phenomenon occurs after multiple thermal cycles, no liquid metal overflow phenomenon occurs during use, and no copper powder agglomeration is found during the inspection of the piece.

[0097] Embodiment 9

[0098] (1) heat 15 parts of In, 15 parts of Sn, and 70 parts of Ga to 60°C to obtain the liquid metal; wherein the melting time is 2 h;

[0099] (2) add copper powder with a particle size of about 1 um in 8 times, heat and stir, and the weight is 5% of the liquid metal;

[0100] (3) punching the copper foil with a thickness of 40 um to perform roughening treatment by perforating the copper foil with a diameter of 0.5 mm, and the hole rate is 10 per cm 2 ;

[0101] (4) coating the liquid metal thermal paste on both sides of the perforated copper foil, and the single-layer coating thickness is 30 um;

[0102] (5) rolling the copper foil coated with the liquid metal thermal paste to obtain the composite thermal conductive material with a total thickness of 90 um;

[0103] (6) cutting the above composite thermal conductive material, and preferably the cutting size is 40*40 mm / piece.

[0104] It is tested that the thermal conductivity of the composite liquid metal thermal paste in the embodiment is 112 W / m.K, and there is no degradation phenomenon after multiple thermal cycles, no liquid metal overflow phenomenon occurs during use, and no copper powder aggregation is found during disassembly inspection.

[0105] Embodiment 10

[0106] (1) heating 20 parts of In, 20 parts of Sn and 80 parts of Ga to 60°C to obtain the liquid metal, and the melting time is 2 h;

[0107] (2) adding copper powder with a particle size of about 1 um for 8 times, heating and stirring, and the weight of the copper powder is 5% of the liquid metal;

[0108] (3) punching the copper foil with a thickness of 40 um to perform roughening treatment by perforating the copper foil with a diameter of 0.5 mm, and the hole rate is 10 per cm 2 ;

[0109] (4) coating the liquid metal thermal paste on both sides of the perforated copper foil, and the single-layer coating thickness is 30 um;

[0110] (5) rolling the copper foil coated with the liquid metal thermal paste to obtain the composite thermal conductive material with a total thickness of 90 um;

[0111] (6) cutting the above composite thermal conductive material, and preferably the cutting size is 40*40 mm / piece.

[0112] It is tested that the thermal conductivity of the composite liquid metal thermal paste in the embodiment is 98 W / m.K, and there is no degradation phenomenon after multiple thermal cycles, no liquid metal overflow phenomenon occurs during use, and no copper powder aggregation is found during disassembly inspection.

[0113] Embodiment 11

[0114] (1) 17 parts of In, 18 parts of Sn, 65 parts of Ga are heated to 60°C to obtain the liquid metal by smelting; wherein the smelting time is 2h;

[0115] (2) The copper powder with a particle size of about 1 um is added in 8 times, heated and stirred, and the weight is 1% of the liquid metal;

[0116] (3) The copper foil with a thickness of 40 um is punched to roughen the copper foil with a diameter of 0.5 mm, and the hole rate is 10 / cm 2 ;

[0117] (4) The liquid metal thermal paste is coated on both sides of the punched copper foil, and the single-layer coating thickness is 30 um;

[0118] (5) The copper foil coated with the liquid metal thermal paste is rolled to obtain the composite thermal conductive material with a total thickness of 90 um;

[0119] (6) The above composite thermal conductive material is cut, and the cutting size is preferably 40*40 mm / piece.

[0120] After testing, the thermal conductivity of the composite liquid metal thermal paste in the embodiment is 98 W / m.K, there is a deterioration phenomenon after multiple thermal cycles, and the liquid metal appears to overflow from the edge during use. No copper powder agglomeration is found when the piece is checked.

[0121] Example 12

[0122] (1) 17 parts of In, 18 parts of Sn, 65 parts of Ga are heated to 60°C to obtain the liquid metal by smelting; wherein the smelting time is 2h;

[0123] (2) The copper powder with a particle size of about 1 um is added in 8 times, heated and stirred, and the weight is 1% of the liquid metal;

[0124] (3) The copper foil with a thickness of 40 um is punched to roughen the copper foil with a diameter of 0.5 mm, and the hole rate is 10 / cm 2 ;

[0125] (4) The liquid metal thermal paste is coated on both sides of the punched copper foil, and the single-layer coating thickness is 30 um;

[0126] (5) The copper foil coated with the liquid metal thermal paste is rolled to obtain the composite thermal conductive material with a total thickness of 90 um;

[0127] (6) The above composite thermal conductive material is cut, and the cutting size is preferably 40*40 mm / piece.

[0128] The thermal conductivity of the composite liquid metal thermal paste in this embodiment is 98 W / m.K after testing, and there is a deterioration phenomenon after multiple thermal cycles, and there is no liquid metal overflow phenomenon during use. When the piece is checked, it is found that the copper powder is agglomerated.

[0129] Example 13

[0130] (1) 30 parts by weight of Bi, 45 parts by weight of In, 15 parts by weight of Sn, and 5 parts by weight of Ga are heated to 100°C and melted for 2h to obtain a liquid metal;

[0131] (2) Add polyurethane with a weight of 5% of the liquid metal to the liquid metal in 3 times, heat and stir to obtain the liquid metal thermal paste;

[0132] (3) Punch a 30um thick non-punched double-sided roughened copper foil;

[0133] (4) Coat the liquid metal thermal paste on both sides of the copper foil, and the single-layer coating thickness is 20um;

[0134] (5) Roll the copper foil coated with the liquid metal thermal paste to obtain the composite thermal material with a total thickness of 70um;

[0135] (6) Cut the above composite thermal material, preferably the cutting size is 40*40mm / piece.

[0136] The thermal conductivity of the composite liquid metal thermal paste in this embodiment is 35 W / m.K after testing, and there is a deterioration phenomenon after multiple thermal cycles, and there is a small amount of liquid metal extrusion during use. When the piece is checked, it is found that the polyurethane powder is agglomerated.

[0137] Example 14

[0138] (1) 17 parts of In, 18 parts of Sn, and 65 parts of Ga are heated to 60°C and melted to obtain the liquid metal; wherein the melting time is 2h;

[0139] (2) Add copper powder with a particle size of about 1um in 8 times, heat and stir, and the weight is 5% of the liquid metal;

[0140] (3) Coarsely roughen the copper foil with a thickness of 40um on both sides;

[0141] (4) Coat the liquid metal thermal paste on both sides of the copper foil, and the single-layer coating thickness is 30um;

[0142] (5) Roll the copper foil coated with the liquid metal thermal paste to obtain the composite thermal material with a total thickness of 90um;

[0143] (6) The composite heat-conducting material is cut, and preferably the cutting size is 40*40 mm / piece.

[0144] The thermal conductivity of the composite liquid metal heat-conducting paste in the embodiment is 112 W / m.K, and after multiple thermal cycles, deterioration occurs, and a slight overflow of liquid metal from the edge occurs during use. When the piece is removed for inspection, copper powder agglomeration is found.

[0145] The content not described in detail in the specification of the present application is the common knowledge of those skilled in the art.

[0146] As mentioned throughout the specification and claims, "comprising" is an open term, and should be construed to cover "consisting of" as well as "consisting essentially of" unless otherwise noted. "Substantially" means within acceptable limits, and those skilled in the art will recognize the limits of the acceptable range for the specified conditions. The technical problem can be solved within the acceptable range, and the technical effect can be substantially achieved.

[0147] It should also be noted that the terms "comprising", "comprises" or any other variant thereof are intended to cover both non-exclusive and exclusive inclusion, such that the product or system including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or inherent to such product or system. Without more limitations, the element defined by the phrase "comprising a" does not exclude the presence of other identical elements in the product or system including the element.

[0148] The above description shows and describes several preferred embodiments of the present application, but as mentioned above, it should be understood that the present application is not limited to the forms disclosed herein, and should not be considered as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the invention concept described herein, by the above teachings or related art or knowledge. Any modification and change made by those skilled in the art without departing from the spirit and scope of the present application should be within the protection scope of the claims of the present application.

Claims

1. A composite thermal conductive material of a copper foil substrate, characterized by, The copper foil is pressed by two sides coated with liquid metal thermal paste; The liquid metal thermal paste is composed of liquid metal and cross-linking phase material; the mass percentage of each metal in the liquid metal ranges from Bi: In: Sn: Ga = (25-35): (40-55): (10-18): (3-7) or 0: (15-20):(10-25):(60-70); the cross-linking phase material is 2-8% of the weight of the liquid metal; The roughening treatment of the two surfaces of the copper foil is performed by a punching process to form tapered holes; the diameter of the holes is 0.3-3 mm, and the density of the holes is 5-20 per cm 2 ; the thickness of the copper foil is 20-60 μm.

2. The composite thermal conductive material of claim 1, wherein, The cross-linking phase material is one of metal powder, diamond powder, silicone oil, epoxy resin and polyurethane.

3. The composite thermal conductive material of claim 1, wherein, The phase transition temperature of the liquid metal thermal paste is 40-70℃, and the latent heat of phase transition is 250-370J / cc.

4. The composite thermal material of claim 1, wherein, The thickness of the liquid metal thermal paste coated on each side of the copper foil is 10-30μm.

5. The composite thermal material of claim 1, wherein, The copper foil is electrolytic copper foil or rolled copper foil.

6. The composite thermal conductive material of claim 5, wherein, The diameter of the perforation is 0.5-1mm.

7. A method of producing the composite heat conducting material as claimed in any one of claims 1 to 6, characterized in that, The method comprises the following steps: (1) heating and smelting Bi, In, Sn and Ga in proportion to obtain the liquid metal; (2) adding the cross-linking phase material in 3-8 times, heating and stirring to obtain the liquid metal thermal paste; (3) punching the copper foil and performing roughening treatment on the perforated copper foil; (4) coating the perforated copper foil with the liquid metal thermal paste on both sides; (5) rolling the copper foil coated with the liquid metal thermal paste to obtain the composite thermal conductive material; (6) cutting the composite thermal conductive material to obtain a piece with a size of 40*40mm.

8. The preparation method according to claim 7, characterized in that, The smelting temperature in step (1) is 60-100℃, and the smelting time is 1-2h.

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