Heat-conducting adhesive with near-zero thermal expansion coefficient as well as preparation method and application of heat-conducting adhesive

Abstract

The invention provides a heat-conducting adhesive with a near-zero thermal expansion coefficient as well as a preparation method and application of the heat-conducting adhesive, and belongs to the technical field of thermal interface materials. A core-shell-shaped adhesive material is designed to solve the triangular contradiction among the heat-conducting property, the thermal expansion coefficient and the adhesive property, a core layer is a liquid metal modified inorganic filler with a low expansion coefficient and has the functions of heat conduction and low thermal expansion, and a shell layer is an ultrathin polymer network and has an adhesive effect; the adhesive material with the core-shell structure can be prepared by extruding through a needle head with a coaxial skin-core structure.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of thermal interface materials, and relates to an adhesive material and a preparation method and application thereof, in particular to a near-zero thermal expansion coefficient thermal conductive adhesive and a preparation method and application thereof. BACKGROUND

[0002] With the wide application of advanced optoelectronic systems such as high-energy lasers, high-power microwaves, high-computing artificial intelligence, and high-density core particle integration in many fields, a large amount of heat is generated during system operation, which seriously affects the performance stability, operation efficiency, and service life of the system. Therefore, developing a material with excellent thermal conductivity and low thermal expansion coefficient has become a research focus.

[0003] Especially in precision optoelectronic devices, thermal stress caused by thermal expansion mismatch between heterogeneous materials can lead to reliability problems such as interface contact failure and optical path deviation. Therefore, it is urgent to develop an adhesive with high thermal conductivity and low thermal expansion to meet the long-term stable application requirements of optoelectronic systems under harsh working conditions.

[0004] In the field of thermal conductive adhesives, for example, CN118617776A discloses a thermal conductive composite material suitable for thermal management of optoelectronic devices. By modifying the inorganic thermal conductive filler in the polymer matrix, the thermal conductivity of the material is significantly improved.

[0005] Although various techniques have been reported to improve the thermal conductivity and thermal resistance of adhesives, the problem of high thermal expansion coefficient of thermal conductive adhesives has not been solved. Even though some strategies can reduce the thermal expansion coefficient of thermal conductive adhesives, they are still far from the near-zero thermal expansion coefficient. The difficulty lies in the fact that the control of thermal conductivity and thermal expansion coefficient depends on the addition of a large amount of different inorganic fillers, and the total amount of fillers is limited. Therefore, high thermal conductivity and low thermal expansion are contradictory. SUMMARY

[0006] To solve the problem of lack of thermal conductive adhesive with near-zero thermal expansion coefficient in the prior art, the present application provides a thermal conductive adhesive with near-zero thermal expansion coefficient and a preparation method and application thereof. The present application solves the triangular contradiction of thermal conductivity, thermal expansion coefficient, and bonding performance by designing a core-shell adhesive material. The core layer is a low-expansion inorganic filler modified by a liquid metal, which plays a role in thermal conductivity and low thermal expansion. The shell layer is an ultrathin polymer network, which plays a role in bonding. This core-shell structure adhesive material can be prepared by a coaxial needle extrusion.

[0007] The technical scheme of the present application is as follows: The thermal conductive adhesive with near-zero thermal expansion coefficient according to the present application is a core-shell adhesive: The core layer is a liquid metal modified inorganic powder material with heat conduction and expansion inhibition functions, and is realized by a unique force-chemical modification treatment method.

[0008] The shell layer is a polymer solution material with bonding function, which is obtained by mixing a polymer matrix with a solvent and an additive according to a specified ratio, and the mixing conditions are vacuum, a mixing time of 1-30 min, a mixing rate of 1000 rpm, and a mixing device of a stirred tank or a homogenizer; the polymer matrix is at least one of epoxy resin, acrylic resin, silicone resin, polyimide resin, and polysilazane resin; the additive is a crosslinking agent and an initiator required for the corresponding polymer matrix, and the solvent is at least one of water, ethanol, acetone, tetrahydrofuran, N-methyl pyrrolidone, ethyl acetate, cyclohexanone, and dimethylbenzene.

[0009] The core-shell structure adhesive provided by the application has the following characteristics: Core layer: liquid metal modified inorganic powder filler, low liquid metal content, thickness: 50-1000 μm; Shell layer: polymer layer, thickness: 0.01-1 μm.

[0010] In particular, theoretically, the core-shell structure adhesive can be blocked in the heat conduction path due to the low thermal conductivity and high thickness of the pure polymer shell layer, and the thermal conductivity is greatly reduced, and the thick shell layer also limits the filling amount of the liquid metal modified inorganic powder filler, so that the thermal expansion performance cannot be sufficiently reduced, but the shell layer of the application has an extremely thin and porous structure, and the thin and porous shell layer makes the surface layer of the core-shell adhesive also permeable to the liquid metal modified inorganic powder, so that the surface layer also has heat conduction, and the core layer can be fully filled with the filler, so that the core-shell structure adhesive can realize an ultra-high filling with a filler mass fraction of up to 99 wt%, and has high thermal conductivity and an ultra-low thermal expansion coefficient which are not possessed by the adhesive in the prior art.

[0011] The object of the application is achieved by the following technical scheme: A near-zero thermal expansion coefficient heat-conducting adhesive is a core-shell structure adhesive, which comprises an adhesive skin layer and an adhesive core layer. The adhesive skin layer comprises a polymer matrix, a solvent and an additive. The thickness of the adhesive skin layer is 0.01 μm to 1 μm; the solid content of the adhesive skin layer, i.e. the ratio of the polymer matrix, is 0.01 wt% to 5 wt%; The thickness of the adhesive core layer is 1 μm to 1000 μm; the adhesive core layer comprises a liquid metal and an inorganic filler; the liquid metal accounts for 0.01 wt% to 6 wt% of the total mass of the adhesive core layer in terms of mass fraction; The physical and chemical property parameters of the near-zero thermal expansion coefficient thermal conductive adhesive include: The thermal conductivity is 2.4 W / (m·K) to 4.0 W / (m·K); The thermal resistance is 27 K mm² W -1 to 40 K mm² W -1 ; The thermal expansion coefficient is 4×10 -6 K -1 to 8×10 -6 K -1 ; The shear strength is 5.0 MPa to 9.9 MPa.

[0012] Further, the polymer matrix is at least one of an epoxy resin, an acrylic resin, a silicone resin, a polyimide resin, and a polysilazane resin; the solvent is at least one of water, ethanol, acetone, N-methyl pyrrolidone, ethyl acetate, cyclohexanone, and dimethylbenzene; and the additive is a crosslinking agent and an initiator required for the corresponding polymer matrix.

[0013] Further, the liquid metal is at least one of metallic mercury, metallic bismuth, metallic gallium, metallic tin, metallic indium, metallic rubidium, and metallic cesium; and the inorganic filler is at least one of low-expansion coefficient fillers or negative-expansion coefficient fillers such as tungsten-zirconium phosphate, zirconium tungstate, fused silica, glass fiber, and bismuth-nickel ferrite.

[0014] Further, the adhesive skin layer has a porous and ultrathin structure after curing.

[0015] The application also relates to a preparation method of the near-zero thermal expansion coefficient thermal conductive adhesive. S1, preparing a raw material of an adhesive core layer: Coating a liquid metal on the surface of an inorganic filler, and then performing mechanochemical treatment to obtain the raw material of the adhesive core layer; The working condition parameters of the mechanochemical treatment include: using a treatment device to perform treatment under the conditions of a temperature of 10 ℃ to 200 ℃, a pressure of 0.1 MPa to 10 MPa, and a time of 1 min to 60 min. S2, preparing raw materials of the adhesive skin layer: The polymer matrix is mixed with the solvent and the additive according to the set proportion, the mixing condition is vacuum, the mixing time is 1 min~30 min, and the mixing rate is 100 rpm~4000 rpm; S3, the adhesive skin layer and the core layer are compounded through a double-layer coaxial needle tube: The raw materials of the adhesive skin layer are fed into the outer layer of the double-layer coaxial needle tube, and the raw materials of the adhesive core layer are fed into the inner layer of the double-layer coaxial needle tube, and the needle tube extrudes the two kinds of raw materials at the same time to obtain the adhesive with a core-shell structure; The double-layer coaxial needle tube has a structure that the skin layer is extremely thin and the core layer is extremely thick, the inner diameter of the inner ring of the needle tube core layer is 50 μm~1000 μm, and the inner diameter of the inner ring of the skin layer is 50.01 μm~1000.01 μm, that is, the thickness (0.01 μm~1 μm) of the skin layer is 1 / 500 or less of the thickness (50 μm~1000 μm) of the core layer.

[0016] Further, the processing equipment in S1 is at least one of a flat press, a ball mill and a grinder.

[0017] Further, the mixing in S2 is performed by using a stirred tank or a homogenizer.

[0018] Further, the shape of the double-layer coaxial needle tube in S3 is one of a circle, a square, a triangle or a special shape.

[0019] Further, the packaging interface of the optoelectronic device involves one of the interface between a silicon-based material and a metal material, the interface between a carbon-based material and a metal material, and the interface between silicon-based materials.

[0020] Further, the packaging interface of the optoelectronic device uses the near-zero thermal expansion coefficient thermal conductive adhesive to be cured by the combination of heating / light irradiation and pressure, on the one hand, the solvent in the polymer of the adhesive surface layer is fully volatilized and fully cured, on the other hand, the thickness of the adhesive skin layer is further reduced by removing the solvent of the adhesive skin layer and applying external pressure, so that the core layer of the adhesive infiltrates the porous structure of the adhesive skin layer, and the liquid metal and the inorganic filler can penetrate through the entire adhesive layer, thereby maximizing the thermal conductivity and reducing the thermal expansion.

[0021] Compared with the prior art, the present application has the following beneficial effects: 1. The near-zero thermal expansion coefficient heat-conducting adhesive of the present application is a core-shell adhesive, the surface polymer layer has the structure characteristics of extremely thin and porous, the extremely thin and porous structure of the surface layer enables the adhesive to achieve good surface bonding strength at extremely low content of high molecular material, and the core layer can be filled with 100% content of liquid metal modified negative expansion coefficient filler, thereby achieving extremely high thermal conductivity and extremely low thermal expansion coefficient. This structure can break the contradiction between low thermal resistance (27K mm2 W -1 40K mm2 W -1 ), low thermal expansion performance (4x10 -6 K -1 8x10 -6 K -1 ) and high bonding performance (i.e. shear strength of 5.0MPa-9.9MPa) of the heat interface material heat-conducting adhesive.

[0022] 2. The preparation method of the near-zero thermal expansion coefficient heat-conducting adhesive of the present application is different from the simple blending preparation method of traditional single-component adhesive and two-component adhesive, but is inspired by the coaxial spinning technology, and a coaxial needle double-layer co-extrusion core-shell adhesive preparation technology is developed. The technology is simple to operate and easy to continuous production, and can simply and quickly produce a large amount of core-shell structure adhesive. More particularly, the core-shell structure has the characteristics of extremely thin and porous surface layer, so that the amount of polymer is extremely low, the amount of functional filler is extremely large, and the functionality (heat conduction and heat expansion inhibition) of the adhesive is very prominent.

[0023] 3. The photoelectric device packaged by the near-zero thermal expansion heat-conducting adhesive provided by the present application not only has the advantages of high efficient heat dissipation of the prior art heat-conducting adhesive, but also has an additional ultra-low thermal expansion coefficient (4x10 -6 K -1 8x10 -6 K -1 ), which can greatly reduce thermal stress and structural deformation and ensure the long-term stability of the photoelectric device under wide temperature variation. DETAILED DESCRIPTION

[0024] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, illustrate the present application together with the embodiments thereof, and explain the present application, and do not constitute a limitation of the present application.

[0025] Figure 1 The process flow chart of the preparation method of the near-zero thermal expansion coefficient heat-conducting adhesive of the present application; Figure 2 The preparation principle and structure schematic diagram of the near-zero thermal expansion heat-conducting adhesive prepared in Example 1 of the present application; Figure 3Device application and performance of the near zero thermal expansion heat conductive adhesive prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0026] The present application will be described in further detail through the following examples. It is necessary to point out that the examples are only used to further illustrate the present application and cannot be understood as limiting the scope of the present application. Those skilled in the art can make some non-essential improvements and adjustments according to the content of the present application.

[0027] In the embodiments of the present application, the near zero thermal expansion coefficient heat conductive adhesive is an adhesive with core-shell structure: the core layer is a liquid metal modified inorganic powder material with heat conduction and expansion inhibition function, which is realized by a unique mechanical chemical modification treatment method. In the embodiments of the present application, the working condition parameters of the mechanical chemical treatment include: using a treatment equipment under the conditions of temperature 10 ℃~200 ℃, pressure 0.1MPa ~10MPa, and time 1min~60min; the treatment equipment is at least one of a flat press, a ball mill, and a grinder. In particular, the inorganic powder filler with negative (low) thermal expansion coefficient in the core layer is treated.

[0028] The shell layer is a polymer solution material with bonding effect, which is obtained by mixing a polymer matrix with a solvent and an additive according to a specified proportion, and the mixing conditions are vacuum, mixing time 1min~30min, mixing rate 1000rpm, and mixing equipment stirring tank or homogenizer; the polymer matrix is at least one of epoxy resin, acrylic resin, silicone resin, polyimide resin, and polysilazane resin; the additive is a crosslinking agent and an initiator required for the corresponding polymer matrix, and the solvent is at least one of water, ethanol, acetone, tetrahydrofuran, N-methyl pyrrolidone, ethyl acetate, cyclohexanone, and dimethylbenzene.

[0029] In the embodiments of the present application, the structure of the core-shell structure adhesive provided has the following characteristics: Core layer: liquid metal modified inorganic powder filler, low liquid metal content, thickness: 50μm ~1000μm; Shell layer: polymer layer, thickness: 0.01μm~1μm.

[0030] The thermal conductivity and thermal resistance of the adhesive thermal interface material are measured according to the material testing association (ASTM) D-5470 standard using the LW-9389 TIM thermal resistance and heat conduction measuring equipment. The temperature is set to 80 ℃ and the pressure is 40psi during the test.

[0031] The thermal expansion performance of the cured adhesive material was tested using a Discovery TMA 450 from TA Instruments, with the test direction being the z-axis thermal expansion coefficient.

[0032] The adhesive material was tested for bonding performance using an INSTRON 5967 universal material testing machine. Before testing, the adhesive was adhered to the interface of two metal plates, and the weighing sensor was 500 N. To ensure the reliability of the data, at least five samples were tested for each experiment.

[0033] Example 1: A preparation method of a near-zero thermal expansion coefficient thermal conductive adhesive, comprising the following three steps, and the preparation process is as shown in Figure 1 : S1, preparing the raw material of the adhesive core layer: 0.1 g of liquid gallium and 9.9 g of tungsten-zirconium phosphate powder (D50 particle size 1.5 μm) were placed in a ball mill at a ball milling speed of 1000 rpm for 50 min, and then the product was placed in a flat plate hot press under the conditions of room temperature and a pressure of 10 MPa for 10 min to obtain the raw material of the adhesive core layer; S2, preparing the raw material of the adhesive skin layer: 10 g of acrylic-modified photocurable silicone resin, 9.9 g of acetone, 0.001 g of 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide, and 0.001 g of triethanolamine were placed in a mixing machine, vacuumized, mixed at a speed of 3600 rpm, and mixed for 3 min in a mode of self-rotation combined with revolution to obtain the raw material of the adhesive skin layer; S3, the adhesive skin layer and the core layer were compounded through a double-layer coaxial needle tube: Figure 2 The preparation principle and structure diagram of the near-zero thermal expansion coefficient thermal conductive adhesive prepared in Example 1 are as shown in Figure 2 The raw material of the adhesive skin layer was introduced into the outer layer of the double-layer coaxial needle tube, and the raw material of the adhesive core layer was introduced into the inner layer of the double-layer coaxial needle tube. The needle tube extruded the two kinds of raw materials at the same time to obtain an adhesive with a core-shell structure. The double-layer coaxial needle tube was made of stainless steel, had the structural characteristics of a very thin skin layer and a very thick core layer, and the inner diameter of the inner ring of the needle tube core layer was 100 μm, and the inner diameter of the inner ring of the skin layer was 102 μm, that is, the thickness (2 μm) of the skin layer was 1 / 50 of the thickness (100 μm) of the core layer.

[0034] The near-zero thermal expansion coefficient thermal conductive adhesive is used for bonding at the interface of a photoelectric device hetero material: Figure 3A schematic diagram of device application and performance of the near zero thermal expansion thermal conductive adhesive prepared in Example 1 is shown in FIG. 1, wherein the core-shell structured adhesive is extruded to the interface between the diamond and the microcrystalline glass of the optoelectronic device, cured using a UV lamp with a power of 125 W and a wavelength of 365-405 nm for 10 s, then the bonded device is fully cured and bonded to the interface of the heterogeneous material by applying a pressure of 0.1 MPa using a flat press and heating to 150 °C for 3 min, the amount of adhesive used depends on the area and thickness of the interface; the optoelectronic device is operated for 30 days, and changes in light path deviation and optoelectronic device performance stability are observed. Figure 3

[0035] Example 2: A preparation method of a near zero thermal expansion coefficient thermal conductive adhesive, which is different from Example 1 in that the inner diameter of the inner ring of the core layer in step S3 is 100 μm, and the inner diameter of the inner ring of the skin layer is 100.5 μm, i.e., the thickness (0.5 μm) of the skin layer is 1 / 500 of the core layer (100 μm), and the remaining conditions and parameters are unchanged.

[0036] Example 3: A preparation method of a near zero thermal expansion coefficient thermal conductive adhesive, which is different from Example 2 in that the content of the liquid metal is increased when preparing the raw material of the adhesive core layer in step S1, and the ratio of the liquid metal to the powder is adjusted to 0.5 g of liquid metal gallium and 9.5 g of zirconium tungsten phosphate powder (D50 particle size 1.5 μm) together in a ball mill for grinding, and the remaining conditions and parameters are unchanged.

[0037] Example 4: A preparation method of a near zero thermal expansion coefficient thermal conductive adhesive, which is different from Example 3 in that the type of liquid metal is changed from liquid metal gallium to liquid metal gallium indium tin when preparing the raw material of the adhesive core layer in step S1, and the remaining conditions and parameters are unchanged.

[0038] Example 5: A preparation method of a near zero thermal expansion coefficient thermal conductive adhesive, which is different from Example 4 in that the raw material for preparing the skin layer of the adhesive is changed in step S2: 10 g of carbamate group modified epoxy resin, 9.9 g of tetrahydrofuran, 0.001 g of phthalic anhydride, and 0.001 g of 2-methyl imidazole are placed in a mixing machine, vacuumized, mixed at a speed of 3600 rpm, mixed in a mode of self-rotation combined with revolution, and mixed for 3 min to obtain the raw material for the skin layer of the adhesive, and the remaining conditions and parameters are unchanged.

[0039] Comparative Example 1: ​A method for preparing an adhesive without a core-shell structure and a filler, which is different from example 1 in that no filler is introduced: 10 g of an acrylic-modified photocurable silicone resin, 9.9 g of acetone, 0.001 g of 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide, and 0.001 g of triethanolamine are placed in a mixing machine, vacuum is drawn, the mixing rate is 3600 rpm, the mixing mode is self-rotation combined with revolution, and the mixing time is 3 min to obtain the adhesive, and the remaining conditions and parameters remain unchanged.

[0040] Comparative example 2: A method for preparing a thermally conductive and low-thermal expansion adhesive without a core-shell structure, which is different from example 1 in that the liquid metal-modified inorganic powder filler is directly physically blended with the adhesive without forming a core-shell structure: 0.1 g of liquid metal gallium and 9.9 g of tungsten-zirconium phosphate powder (D50 particle size 1.5 μm), 10 g of an acrylic-modified photocurable silicone resin, 9.9 g of acetone, 0.001 g of 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide, and 0.001 g of triethanolamine are placed in a mixing machine, vacuum is drawn, the mixing rate is 3600 rpm, the mixing mode is self-rotation combined with revolution, and the mixing time is 3 min to obtain the adhesive, and the remaining conditions and parameters remain unchanged.

[0041] Comparative example 3: A method for preparing an adhesive with a core-shell structure, which is different from example 1 in that when the adhesive skin layer and the core layer are compounded through a double-layer coaxial needle tube, the structure does not have the characteristics of an extremely thin skin layer and an extremely thick core layer: The raw materials of the adhesive skin layer are fed into the outer layer of the double-layer coaxial needle tube, and the raw materials of the adhesive core layer are fed into the inner layer of the double-layer coaxial needle tube. The needle tube simultaneously extrudes the two kinds of raw materials to obtain an adhesive with a core-shell structure. The material of the double-layer coaxial needle tube is stainless steel, has the structure characteristics of an extremely thin skin layer and an extremely thick core layer, the inner diameter of the inner ring of the core layer of the needle tube is 100 μm, the inner diameter of the inner ring of the skin layer is 200 μm, that is, the thickness of the skin layer (100 μm) is consistent with the core layer (100 μm), and the remaining conditions and parameters remain unchanged.

[0042] Results and discussion: The properties of examples 1-6 and comparative examples 1-3 are shown in Table 1: Table 1: Material thermal conductivity, material thermal resistance, material thermal expansion coefficient, interfacial bonding strength, and performance stability of optoelectronic devices

[0043] 1. As can be seen from the comparison of example 1 and comparative example 1 in Table 1, after introducing the liquid metal-modified inorganic powder filler into the polymer matrix of the adhesive in example 1, the thermal conductivity of the material is significantly increased, from 0.3 W m-1 K -1 Increased to 2.4W m -1 K -1 The increase is nearly 7 times; the thermal resistance is significantly reduced, from 120mm in Comparative Example 1. 2 KW -1 The depth decreased to 40 mm in Example 1. 2 KW -1 The coefficient of thermal expansion is 152 mm. 2 KW -1 Dropped to 6mm 2 KW -1 The overall thermal performance improvement significantly enhanced the stability of optoelectronic device performance, and improved the stability of optical path and structure from unstable to stable.

[0044] 2. By comparing Example 1 and Comparative Example 2, it can be seen that the core-shell structure of Example 1 has more outstanding thermal performance than the simple mixed and uniformly dispersed structure of Comparative Example 2. The thermal conductivity is increased by 71%, the thermal resistance is reduced by 44%, the coefficient of thermal expansion is reduced by 47%, and the bonding strength is increased by 100%. The stability of the optoelectronic device is improved from relatively stable to stable. This shows that the special core-shell structure design of the present invention can break through the limits of thermal conductivity, thermal expansion performance and bonding performance of adhesive materials, and achieve a balance among the three and improve the reliability of device performance.

[0045] 3. A comparison between Example 1 and Comparative Example 3 shows that the core-shell structure of Example 1 has more outstanding thermal performance than the core-shell structure adhesive of Comparative Example 3. The thermal conductivity is increased by 71%, the thermal resistance is reduced by 44%, and the coefficient of thermal expansion is reduced by 94%. The stability of the optoelectronic device is improved from unstable to stable. This indicates that the special ultra-thin porous core-shell structure design of the present invention can improve the thermal conductivity and thermal expansion performance of the adhesive material more effectively than the ordinary core-shell structure with uniform thickness, which is beneficial to improving the reliability of optoelectronic device performance.

[0046] 4. A comparison of Example 5 with Examples 1-4 shows that after optimizing the shell thickness, liquid metal content, type of liquid metal, and type of shell polymer material in the core-shell structure of the adhesive, the thermal and adhesive properties can be further improved. For example, the thermal conductivity of Example 1 was 2.4 W / m. -1 K -1 Increased to 4.0 W m in Example 5 -1 K -1 The thermal resistance of Example 1 is 40mm. 2 KW -1 The diameter dropped to 27 mm in Example 5. 2 KW -1, the thermal expansion coefficient is basically unchanged, the interface bonding strength increases from 6.6MPa of example 1 to 9.9MPa of example 5, and the performance stability of the optoelectronic device is steadily improved to very stable.

[0047] In addition, it should be understood that, although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A near-zero thermal expansion coefficient heat conductive adhesive, characterized by, The adhesive is a core-shell structure, comprising an adhesive skin layer and an adhesive core layer; The adhesive skin layer comprises a polymer matrix, a solvent and an additive; The thickness of the adhesive skin layer is 0.01-1 μm; the solid content of the adhesive skin layer, i.e. the ratio of the polymer matrix, is 0.01-5 wt%; The thickness of the adhesive core layer is 1-1000 μm; the adhesive core layer comprises a liquid metal and an inorganic filler; the liquid metal accounts for 0.01-6 wt% of the total mass of the adhesive core layer. The physical and chemical property parameters of the near-zero thermal expansion coefficient thermal conductive adhesive include: The thermal conductivity is 2.4-4.0 W / (m·K); Thermal resistance of 27 K mm2 W -1 ~40 K mm2 W -1 ; coefficient of thermal expansion of 4 x 10 -6 K -1 8 x 10 -6 K -1 ; The shear strength is 5.0-9.9 MPa.

2. A near zero coefficient of thermal expansion, heat-conductive adhesive according to claim 1, characterized in that, The polymer matrix is at least one of epoxy resin, acrylic resin, silicone resin, polyimide resin and polysilazane resin; the solvent is at least one of water, ethanol, acetone, N-methyl pyrrolidone, ethyl acetate, cyclohexanone and dimethylbenzene; and the additive is a crosslinking agent and an initiator required by the corresponding polymer matrix.

3. A near zero coefficient of thermal expansion, heat-conductive adhesive according to claim 1, characterized in that, The liquid metal is at least one of mercury, bismuth, gallium, tin, indium, rubidium and cesium; and the inorganic filler is at least one of low expansion coefficient fillers or negative expansion coefficient fillers such as tungsten-zirconium phosphate, zirconium tungstate, fused silica, glass fiber and bismuth nickel ferrite.

4. A process for the preparation of a near-zero thermal expansion coefficient heat-conducting adhesive according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: S1, preparing raw materials for the adhesive core layer: coating the liquid metal on the surface of the inorganic filler, and then performing mechanochemical treatment to obtain the raw materials for the adhesive core layer; The working condition parameters of the mechanochemical treatment include: using a treatment device to perform treatment under the conditions of a temperature of 10-200 ℃, a pressure of 0.1-10 MPa and a time of 1-60 min; S2, preparing raw materials for the adhesive skin layer: mixing the polymer matrix, the solvent and the additive according to the set proportion, the mixing condition being vacuum, the mixing time being 1-30 min and the mixing rate being 100-4000 rpm; S3, compounding the adhesive skin layer and the core layer through a double-layer coaxial needle tube: passing the raw materials for the adhesive skin layer into the outer layer of the double-layer coaxial needle tube and passing the raw materials for the adhesive core layer into the inner layer of the double-layer coaxial needle tube, and simultaneously extruding the two kinds of raw materials through the needle tube to obtain the adhesive with a core-shell structure; The double-layer coaxial needle tube has a structure with an extremely thin skin layer and an extremely thick core layer, the inner diameter of the inner ring of the core layer of the needle tube is 50-1000 μm, the inner diameter of the inner ring of the skin layer is 50.01-1000.01 μm, and the thickness of the skin layer is less than 1 / 500 of the thickness of the core layer.

5. The method for preparing a near-zero thermal expansion coefficient thermally conductive adhesive according to claim 4, characterized in that, The treatment device in S1 is at least one of a flat press, a ball mill and a grinder.

6. The method for preparing a near-zero thermal expansion coefficient thermally conductive adhesive according to claim 4, characterized in that, The mixing in S2 is performed by using a stirred tank or a homogenizer.

7. The method for preparing a near-zero thermal expansion coefficient thermally conductive adhesive according to claim 4, characterized in that, The shape of the double-layer coaxial needle tube in S3 is one of a circle, a square, a triangle or a special shape.

8. Use of a near-zero thermal expansion coefficient heat-conducting adhesive according to any one of claims 1-3, characterized in that, The photoelectric device is packaged by using the near-zero thermal expansion coefficient thermal conductive adhesive.

9. Use of a near-zero thermal expansion coefficient thermally conductive adhesive according to claim 8, characterized in that, The encapsulation interface of the optoelectronic device is one of an interface between a silicon-based material and a metal material, an interface between a carbon-based material and a metal material, and an interface between silicon-based materials.

10. Use of a near-zero coefficient of thermal expansion thermally conductive adhesive according to claim 9, characterized in that, The encapsulation interface of the optoelectronic device is cured by using the near-zero thermal expansion coefficient thermal conductive adhesive in combination with heat / light and pressure.

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