Heat-conducting electromagnetic shielding composite material with orientation structure as well as preparation method and application of heat-conducting electromagnetic shielding composite material

Abstract

The invention provides a heat-conducting electromagnetic shielding composite material with an orientation structure as well as a preparation method and application of the heat-conducting electromagnetic shielding composite material. The heat-conducting electromagnetic shielding composite material comprises surface metallized carbon fibers, a low-melting-point alloy and an organic silicon material, the surface metallized carbon fiber has orientation parallel to the thickness direction of the heat-conducting electromagnetic shielding composite material, and the surface metallized carbon fiber penetrates through the thickness direction of the heat-conducting electromagnetic shielding composite material; the low-melting-point alloy and the organic silicon material are dispersed in gaps among the surface metallized carbon fibers. Through screening and synergistic compounding of specific components, electromagnetic wave interference can be effectively reduced, and the electromagnetic shielding effectiveness and heat-conducting property of the composite material are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic packaging materials, and relates to a thermally conductive electromagnetic shielding composite material with an oriented structure, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of 5G communication and high-density integrated circuit technologies, the heat accumulation and electromagnetic interference generated by electronic components severely limit the improvement of their performance, which makes the demand for heat dissipation and electromagnetic shielding of electronic components gradually increase. Therefore, it is crucial to explore new types of highly efficient and multifunctional high-thermal-conductivity electromagnetic shielding materials.

[0003] Current research shows that by constructing an efficient conductive / thermal network, optimizing the filler system, and adopting a multi-layer structure design, etc., the thermal conductivity and electromagnetic shielding performance of composite materials can be improved. The prior art discloses a flexible cellulose / boron nitride / MXene "sandwich" structure composite film and a preparation method and application thereof. Using cellulose, boron nitride solution, and MXene colloidal solution, a "sandwich" structure composite film composed of a thermally conductive and electrically insulating cellulose / boron nitride outer layer and a conductive MXene interlayer is prepared by layer-by-layer self-assembly through an alternating vacuum-assisted filtration method, which has both thermal conductivity and electromagnetic shielding performance. However, its preparation method is complex, and the thickness of the obtained composite film is relatively thick.

[0004] However, most current electromagnetic shielding composite materials do not have excellent thermal conductivity. Therefore, developing a composite material with lightweight, high thermal conductivity, and high electromagnetic shielding performance is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a thermally conductive electromagnetic shielding composite material with an oriented structure, a preparation method thereof, and an application thereof. Through the screening and synergistic compounding of specific components, it can effectively reduce electromagnetic wave interference and improve the electromagnetic shielding efficiency and thermal conductivity of the composite material.

[0006] To achieve the purpose of this invention, the following technical solutions are adopted by the present invention:

[0007] In the first aspect, the present invention provides a thermally conductive electromagnetic shielding composite material with an oriented structure, and the thermally conductive electromagnetic shielding composite material includes surface metallized carbon fibers, a low-melting-point alloy, and a silicone material;

[0008] The surface metallized carbon fibers have an orientation parallel to the thickness direction of the thermally conductive electromagnetic shielding composite material, and the surface metallized carbon fibers penetrate through the thickness direction of the thermally conductive electromagnetic shielding composite material;

[0009] The low-melting-point alloy and the silicone material are both dispersed in the voids between the surface metallized carbon fibers.

[0010] In the present invention, the oriented structure of the surface metallized carbon fiber is oriented and arranged in a single direction.

[0011] The thermally conductive electromagnetic shielding composite material provided by the present invention includes a combination of surface metallized carbon fiber, low melting point alloy and silicone material. By dispersing the low melting point alloy and silicone material in the gaps between the surface metallized carbon fibers, it can effectively reduce electromagnetic wave interference and improve the electromagnetic shielding efficiency and thermal conductivity of the composite material.

[0012] It should be noted that using surface metallized carbon fiber with an oriented structure is beneficial to the construction of a continuous thermal conduction path, and the metal layer on the surface of the thermally conductive carbon fiber enhances the electrical conductivity and electromagnetic shielding performance of the composite material; in addition, by dispersing the low melting point alloy in the gaps between the surface metallized carbon fibers, when the composite material is placed between the chip and the radiator, under the condition of applying pressure or heating, the fluidity of the low melting point alloy enables it to fill the interfaces between the composite material and the chip and the heat dissipation device, thereby reducing the contact thermal resistance and preventing electromagnetic waves from leaking from the interfaces. Through the synergistic effect of the two, the heat dissipation and electromagnetic shielding performance of the electronic device or chip are improved.

[0013] As a preferred technical solution of the present invention, by mass percentage, the thermally conductive electromagnetic shielding composite material includes the following components: 10wt%-60wt% of surface metallized carbon fiber, 10wt%-40wt% of low melting point alloy, and the balance is silicone material.

[0014] As a preferred technical solution of the present invention, the surface metallized carbon fiber is a thermally conductive carbon fiber with a metal layer on its surface.

[0015] Preferably, the thickness of the metal layer is 10-500nm, preferably 50-200nm.

[0016] Preferably, the metal in the metal layer includes any one or a combination of at least two of silver, copper, nickel, gold or tin, preferably silver.

[0017] As a preferred technical solution of the present invention, the diameter of the surface metallized carbon fiber is 5-20μm, preferably 8-15μm.

[0018] As a preferred technical solution of the present invention, the low melting point alloy is also dispersed in the silicone material.

[0019] Preferably, the melting point of the low melting point alloy ≤50°C.

[0020] Preferably, the low melting point alloy includes gallium-based alloy and / or indium-based alloy.

[0021] Preferably, the average particle size of the low-melting-point alloy is 0.1-50 μm, preferably 1-10 μm.

[0022] As a preferred technical solution of the present invention, the silicone material includes any one or a combination of at least two of addition-cured silicone rubber, condensation-cured silicone rubber, or polydimethylsiloxane.

[0023] As a preferred technical solution of the present invention, the thermally conductive electromagnetic shielding composite material is in a sheet structure.

[0024] Preferably, the thickness of the thermally conductive electromagnetic shielding composite material is 0.1-3 mm.

[0025] In a second aspect, the present invention provides a method for preparing the thermally conductive electromagnetic shielding composite material as described in the first aspect. The preparation method includes the following steps:

[0026] (1) Orient the surface-metallized carbon fibers in a single direction and fill them into a mold, and then pour a mixture of the low-melting-point alloy and the silicone material into the mold. After curing, a strip-shaped composite material is obtained;

[0027] (2) Cut the strip-shaped composite material obtained in step (1) to obtain the thermally conductive electromagnetic shielding composite material.

[0028] In the present invention, when placing the surface-metallized carbon fibers, their orientation is perpendicular to the bottom surface of the mold.

[0029] The preparation method provided by the present invention has an orientation structure formed by orienting the surface-metallized carbon fibers in a single direction in the mold, then pouring the low-melting-point alloy and the silicone material and curing them under vacuum, and finally cutting perpendicular to the orientation direction to obtain a thermally conductive electromagnetic shielding composite material with an orientation structure. The overall process operation is simple and suitable for large-scale industrial applications.

[0030] As a preferred technical solution of the present invention, the length of the surface-metallized carbon fibers in step (1) is 5-200 mm, preferably 50-100 mm.

[0031] Preferably, the mixing method of the mixture in step (1) includes the following situations:

[0032] (a) When the melting point of the low-melting-point alloy ≤ room temperature, the low-melting-point alloy is microsphere-treated and then first mixed with the silicone material; or

[0033] (b) When the melting point of the low-melting-point alloy > room temperature, the low-melting-point alloy is second mixed with the silicone material.

[0034] Preferably, after pouring into the mold in step (1), vacuum pumping is performed before curing.

[0035] Preferably, the curing temperature in step (1) ≥ 80°C.

[0036] Preferably, the curing time in step (1) ≥ 2 h.

[0037] Preferably, the cutting direction in step (2) is perpendicular to the orientation of the surface metallized carbon fiber.

[0038] In a third aspect, the present invention provides an application of the thermally conductive electromagnetic shielding composite material as described in the first aspect in the field of electronic packaging.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] (1) For the thermally conductive electromagnetic shielding composite material provided by the present invention, through the screening and synergistic compounding of specific components, and by dispersing a low-melting-point alloy and a silicone material in the voids between the surface metallized carbon fibers, it can effectively reduce electromagnetic wave interference and improve the electromagnetic shielding efficiency and thermal conductivity of the composite material; among them, the thermal conductivity of the obtained composite material > 7 W / m - 1 K -1 , and the near-field shielding efficiency within 1 - 6 GHz > 54 dB;

[0041] (2) For the thermally conductive electromagnetic shielding composite material provided by the present invention, the regulation of the thermal conductivity and electromagnetic shielding performance of the composite material can be achieved by adjusting the proportions of the respective components and the material and thickness of the metal layer. Specific Embodiments

[0042] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0043] The specific embodiments of the present invention provide a thermally conductive electromagnetic shielding composite material with an oriented structure, and the thermally conductive electromagnetic shielding composite material includes surface metallized carbon fibers, a low-melting-point alloy, and a silicone material;

[0044] The surface metallized carbon fibers have an orientation parallel to the thickness direction of the thermally conductive electromagnetic shielding composite material, and the surface metallized carbon fibers penetrate through the thickness direction of the thermally conductive electromagnetic shielding composite material;

[0045] The low-melting-point alloy and the silicone material are both dispersed in the voids between the surface metallized carbon fibers.

[0046] In some embodiments of the present invention, by mass percentage, the thermally conductive electromagnetic shielding composite material includes the following components: 10 wt% - 60 wt% of surface metallized carbon fibers, 10 wt% - 40 wt% of low-melting-point alloy, and the balance is silicone material.

[0047] It should be noted that by controlling the addition amount range of the surface metallized carbon fiber, it helps to improve the electromagnetic shielding effectiveness and thermal conductivity of the composite material.

[0048] In the present invention, the total mass of each component in the thermally conductive electromagnetic shielding composite material is 100 wt%. The mass content of the surface metallized carbon fiber in the thermally conductive electromagnetic shielding composite material is 10 wt% - 60 wt%, for example, it can be 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt% or 55 wt% etc., and preferably 20 wt% - 50 wt%. The mass content of the low melting point alloy in the thermally conductive electromagnetic shielding composite material is 10 wt% - 40 wt%, for example, it can be 12 wt%, 15 wt%, 16 wt%, 18 wt%, 20 wt%, 22 wt%, 25 wt%, 26 wt%, 28 wt%, 30 wt%, 32 wt%, 35 wt%, 36 wt% or 38 wt% etc., and preferably 25 wt% - 35 wt%.

[0049] In some embodiments of the present invention, the surface metallized carbon fiber is a thermally conductive carbon fiber with a metal layer on its surface.

[0050] In the present invention, the metal layer is formed on the surface of the carbon fiber by electroless plating, electroplating or magnetron sputtering.

[0051] In some embodiments of the present invention, the thickness of the metal layer is 10 - 500 nm, for example, it can be 20 nm, 50 nm, 60 nm, 80 nm, 100 nm, 120 nm, 150 nm, 160 nm, 180 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm or 450 nm etc., and preferably 50 - 200 nm.

[0052] It should be noted that by controlling the metal layer thickness range of the surface metallized carbon fiber, it also helps to improve the electromagnetic shielding effectiveness and thermal conductivity of the composite material.

[0053] In some embodiments of the present invention, the metal in the metal layer includes any one or a combination of at least two of silver, copper, nickel, gold or tin, and preferably silver.

[0054] In some embodiments of the present invention, the diameter of the surface metallized carbon fiber is 5 - 20 μm, for example, it can be 6 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm or 19 μm etc., and preferably 8 - 15 μm.

[0055] In some embodiments of the present invention, the low-melting-point alloy is also dispersed in the silicone material.

[0056] In the present invention, the low-melting-point alloy is distributed in the voids between the surface-metallized carbon fibers and in the silicone material.

[0057] In some embodiments of the present invention, the melting point of the low-melting-point alloy is ≤ 50 °C, and for example, it can be 48 °C, 46 °C, 45 °C, 42 °C, 40 °C, 38 °C, 35 °C, 32 °C, 30 °C, 28 °C, 25 °C, 22 °C, 20 °C or 15 °C, etc.

[0058] In some embodiments of the present invention, the low-melting-point alloy includes a gallium-based alloy and / or an indium-based alloy.

[0059] In the present invention, the gallium-based alloy includes, but is not limited to, gallium-indium alloy, gallium-indium-tin alloy or gallium-tin-zinc alloy.

[0060] In some embodiments of the present invention, the average particle size of the low-melting-point alloy is 0.1 - 50 μm, and for example, it can be 0.5 μm, 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm or 45 μm, etc., and preferably it is 1 - 10 μm.

[0061] In some embodiments of the present invention, the silicone material includes any one or a combination of at least two of addition-curing silicone rubber, condensation-curing silicone rubber or polydimethylsiloxane.

[0062] It should be noted that if the silicone material is selected as polydimethylsiloxane, a corresponding curing agent needs to be used to form a silicone rubber through crosslinking.

[0063] In some embodiments of the present invention, the thermally conductive electromagnetic shielding composite material is in a sheet structure.

[0064] In some embodiments of the present invention, the thickness of the thermally conductive electromagnetic shielding composite material is 0.1 - 3 mm, and for example, it can be 0.2 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.8 mm, 1 mm, 1.2 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.8 mm, 2 mm, 2.2 mm, 2.4 mm, 2.5 mm, 2.6 mm or 2.8 mm, etc.

[0065] It should be noted that by controlling the thickness range of the thermally conductive electromagnetic shielding composite material, it is ensured that the surface-metallized carbon fibers can penetrate through the thickness direction of the sheet-shaped thermally conductive electromagnetic shielding composite material, thereby ensuring the construction of a continuous thermal conduction path.

[0066] The specific implementation manner of the present invention further provides a preparation method of the foregoing thermally conductive electromagnetic shielding composite material, and the preparation method includes the following steps:

[0067] (1) Orient the surface metallized carbon fibers in a single direction and fill them into a mold, and then pour a mixture of a low melting point alloy and an organosilicon material into the mold. After curing, a strip-shaped composite material is obtained;

[0068] (2) Cut the strip-shaped composite material obtained in step (1) to obtain the thermally conductive electromagnetic shielding composite material.

[0069] In some embodiments of the present invention, the length of the surface metallized carbon fibers is 5-200 mm, for example, it can be 10 mm, 20 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm, 160 mm, 170 mm, 180 mm or 190 mm, etc., and preferably 50-100 mm.

[0070] In some embodiments of the present invention, the mixing method of the mixture in step (1) includes the following situations:

[0071] (a) When the melting point of the low melting point alloy ≤ room temperature, the low melting point alloy is subjected to microsphere treatment and then first mixed with the organosilicon material; or

[0072] (b) When the melting point of the low melting point alloy > room temperature, the low melting point alloy is second mixed with the organosilicon material.

[0073] It should be noted that if the low melting point alloy is in a liquid state at room temperature, the low melting point alloy needs to be subjected to microsphere treatment to increase the contact area between the alloy and the organosilicon material and improve the dispersion of the alloy in the organosilicon matrix. The microsphere treatment includes mixing the low melting point alloy and an alcohol solvent and then ultrasonic dispersion, and obtaining liquid metal alloy microspheres after drying.

[0074] In some embodiments of the present invention, after the pouring into the mold in step (1), vacuum pumping is also performed before curing.

[0075] In the present invention, the purpose of vacuum pumping is to remove the bubbles in the mold materials and avoid affecting the quality of the product.

[0076] In some embodiments of the present invention, the curing temperature in step (1) ≥ 80 °C, for example, it can be 85 °C, 90 °C, 95 °C, 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, 150 °C or 160 °C, etc.

[0077] In some embodiments of the present invention, the curing time in step (1) is ≥ 2 h, for example, it can be 2.2 h, 2.5 h, 2.6 h, 2.8 h, 3 h, 3.2 h, 3.5 h, 3.6 h, 3.8 h, 4 h, etc.

[0078] In some embodiments of the present invention, the cutting direction in step (2) is perpendicular to the orientation of the surface metallized carbon fiber.

[0079] The specific embodiments of the present invention also provide an application of the aforementioned thermally conductive electromagnetic shielding composite material in the field of electronic packaging.

[0080] In the present invention, the thermally conductive electromagnetic shielding composite material is placed between the chip and the heat dissipation device. After applying pressure, due to the fluidity of the liquid metal inside the composite material, it will fill the interface between the thermally conductive electromagnetic shielding composite material gasket and the chip and the heat dissipation device, thereby greatly reducing the contact thermal resistance at the interface and preventing electromagnetic waves from leaking from the interface, so as to improve the heat dissipation and electromagnetic shielding performance of the electronic device or chip.

[0081] The numerical ranges described in the present invention not only include the above-listed point values, but also include any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, the specific point values included in the described ranges are not exhaustively listed in the present invention.

[0082] Unless otherwise defined, the technical terms used in the following examples and comparative examples have the same meanings as commonly understood by those skilled in the art to which the present invention belongs. The raw materials, instruments, and equipment used in the following examples and comparative examples can all be obtained through market purchases or can be obtained by existing methods; the experimental methods, unless otherwise specified, are all conventional methods.

[0083] The preparation of the silicone materials used in the following examples and comparative examples is as follows:

[0084] Preparation Example 1

[0085] This preparation example provides a preparation method of an addition-cured silicone rubber. The preparation method includes: mixing component A and component B of methyl vinyl silicone (purchased from DOW, brand SYLGARD TM 527A&B Silicone DielectricGel) in a mass ratio of 1:1, and then dispersing them evenly through a vacuum mixer to obtain an addition-cured silicone rubber.

[0086] Preparation Example 2

[0087] This preparation example provides a preparation method of a polydimethylsiloxane matrix. The preparation method includes: mixing polydimethylsiloxane and a curing agent (purchased from DOW, brand SYLGARD in a mass ratio of 20:1TM (184Silicone Elastomer Kit), and then it is evenly dispersed by a vacuum mixer to obtain a polydimethylsiloxane matrix.

[0088] Example 1

[0089] This example provides a thermally conductive electromagnetic shielding composite material with an oriented structure and a preparation method thereof. By mass percentage, the thermally conductive electromagnetic shielding composite material includes the following components: 40wt% of surface metallized carbon fiber, 30wt% of low melting point alloy, and 30wt% of silicone material.

[0090] The surface metallized carbon fiber has an orientation parallel to the thickness direction of the thermally conductive electromagnetic shielding composite material, and the surface metallized carbon fiber penetrates through the thickness direction of the thermally conductive electromagnetic shielding composite material; the surface metallized carbon fiber is a thermally conductive carbon fiber plated with a 100nm thick silver layer on the surface; the diameter of the surface metallized carbon fiber is 10μm;

[0091] The low melting point alloy is a gallium-indium alloy, the gallium content in the gallium-indium alloy is 75wt%, the melting point is 15.7°C, and the average particle size is 5μm; the low melting point alloy is dispersed in the voids between the surface metallized carbon fibers and the silicone material;

[0092] The silicone material is an addition-cured silicone rubber provided by Preparation Example 1; the silicone material is dispersed in the voids between the surface metallized carbon fibers;

[0093] The thermally conductive electromagnetic shielding composite material is in a sheet structure with a thickness of 1mm;

[0094] The preparation method includes the following steps:

[0095] (1) Mix the gallium-indium alloy and ethanol, and sequentially perform ultrasonic dispersion and drying to obtain spherical gallium-indium alloy droplets; then blend the spherical gallium-indium alloy droplets and the addition-cured silicone rubber, and after stirring and ultrasonic dispersion, obtain a gallium-indium alloy-addition-cured silicone rubber blend;

[0096] (2) Orient and arrange surface metallized carbon fibers with a length of 100mm in a single direction and fill them into a mold (length × width × height is 30×30×100mm 3 ) with the orientation perpendicular to the bottom surface of the mold, then pour the gallium-indium alloy-addition-cured silicone rubber blend described in step (1) into the mold, and then transfer the mold to a vacuum oven, evacuate and cure at a temperature of 130°C for 2h to obtain a strip-shaped composite material;

[0097] (3) Cut the strip-shaped composite material described in step (2) ultrasonically perpendicular to the orientation direction of the surface-metallized carbon fiber to obtain the thermally conductive electromagnetic shielding composite material (length × width × thickness: 30 × 30 × 1 mm 3 ).

[0098] Examples 2-8 and Comparative Examples 1-4

[0099] Except for changing the components or dosages in the thermally conductive electromagnetic shielding composite material, the formulations of the thermally conductive electromagnetic shielding composite material are shown in Tables 1 and 2; other conditions are all carried out with reference to Example 1.

[0100] Perform performance tests on the thermally conductive electromagnetic shielding composite materials prepared in the examples and comparative examples of the present invention. The test methods are as follows:

[0101] (1) Thermal conductivity: Test according to the method provided by ASTM D5470;

[0102] (2) Near-field shielding effectiveness: Test using a near-field scanning system. The distance between the test probe and the electromagnetic wave radiation source is ≤ λ / 2π (λ is the wavelength corresponding to the test frequency). Provide an excitation source for the chip or device through a vector network analyzer, and test the radiation field strength of the chip or device in the presence of the shielding material. The near-field shielding effectiveness is obtained through calculation. The specific test method can refer to the relevant literature (IEEE Transactions on Electromagnetic Compatibility, 2022, 64(5), 1622-1631).

[0103] The above performance test results are shown in Tables 1 and 2.

[0104] Table 1

[0105]

[0106]

[0107] Table 2

[0108]

[0109]

[0110] As can be seen from Tables 1 and 2:

[0111] (1) For the composite materials provided in Examples 1-4 of the present invention, through the screening and synergistic compounding of specific components, the composite materials have both high thermal conductivity and electromagnetic shielding performance, and the thermal conductivity and electromagnetic shielding performance of the composite materials can also be regulated by adjusting the proportions of each component and the material and thickness of the metal layer; among them, the thermal conductivity of the obtained composite material > 7 W / m-1 K -1 The near-field shielding effectiveness within 1 - 6 GHz > 54 dB;

[0112] (2) By comparing Example 1, Examples 5 - 6, and Comparative Example 1 comprehensively, it can be seen that when the thickness of the metal layer in the surface metallized carbon fiber is too thin, the conductivity of the composite material decreases, resulting in a decline in the electromagnetic shielding performance of the obtained composite material; when the thickness of the metal layer in the surface metallized carbon fiber is too thick, since the metal layer blocks some of the heat conduction paths, the thermal conductivity of the obtained composite material decreases, but the conductivity of the composite material is increased, improving the near-field electromagnetic shielding performance; when conventional heat-conducting carbon fiber is used to replace the surface metallized carbon fiber, due to the decrease in conductivity, the near-field electromagnetic shielding performance of the obtained composite material decreases.

[0113] (3) By comparing Example 1 and Examples 7 - 8 comprehensively, it can be seen that when the ratio of the low-melting-point alloy to the silicone material remains the same as in Example 1, when the amount of the surface metallized carbon fiber is too small, due to too few heat conduction paths, the thermal conductivity of the obtained composite material decreases significantly, and a small amount of the metal layer is difficult to provide a rich conductive network for the composite material, and the near-field electromagnetic shielding performance of the composite material also decreases; when the amount of the surface metallized carbon fiber is too large, due to the large volume fraction of the carbon fiber, it is difficult for the silicone rubber to infiltrate between the carbon fibers, which may cause bubbles or pores inside the composite material, reducing the mechanical properties of the material, and allowing electromagnetic waves to leak from the pores, resulting in a decrease in the near-field electromagnetic shielding performance of the obtained composite material.

[0114] (4) By comparing Example 1 and Comparative Examples 2 - 4 comprehensively, it can be seen that when the low-melting-point alloy is not added, the contact thermal resistance between the composite material and the chip cannot be reduced, and it is also impossible to effectively prevent electromagnetic waves from leaking from the interface, resulting in a decrease in both the thermal conductivity and the near-field electromagnetic shielding performance of the obtained composite material; when a high-melting-point alloy is used to replace the low-melting-point alloy, the high-melting-point alloy will not melt during actual use, and it is impossible to form a liquid phase filling at the interface, and further reduce the contact thermal resistance and electrical connectivity between the composite material and the chip, resulting in a decrease in both the thermal conductivity and the near-field electromagnetic shielding performance of the obtained composite material.

[0115] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A thermally conductive electromagnetic shielding composite material with an oriented structure, characterized in that: The thermal conductive electromagnetic shielding composite material comprises surface metallized carbon fiber, low melting point alloy and organic silicon material; The surface metallized carbon fibers have an orientation parallel to the thickness direction of the thermal conductive electromagnetic shielding composite material, and the surface metallized carbon fibers penetrate the thickness direction of the thermal conductive electromagnetic shielding composite material; The low melting point alloy and the organic silicon material are both dispersed in the gaps between the surface metallized carbon fibers.

2. The thermal conductive electromagnetic shielding composite material according to claim 1, characterized in that: The thermal conductive electromagnetic shielding composite material comprises the following components in percentage by mass: 10wt%-60wt% of surface metallized carbon fiber, 10wt%-40wt% of low melting point alloy, and the remainder of organic silicon material.

3. The thermal conductive electromagnetic shielding composite material according to claim 1 or 2, characterized in that: The surface metallized carbon fiber is a thermally conductive carbon fiber having a metal layer on the surface; Preferably, the thickness of the metal layer is 10-500 nm, preferably 50-200 nm; Preferably, the metal in the metal layer includes any one of silver, copper, nickel, gold or tin, or a combination of at least two thereof, preferably silver.

4. The thermal conductive electromagnetic shielding composite material according to any one of claims 1 to 3, characterized in that: The diameter of the surface metallized carbon fiber is 5-20 μm, preferably 8-15 μm.

5. The thermal conductive electromagnetic shielding composite material according to any one of claims 1 to 4, characterized in that: The low melting point alloy is also dispersed in the organosilicon material; Preferably, the melting point of the low melting point alloy is ≤50°C; Preferably, the low melting point alloy comprises a gallium-based alloy and / or an indium-based alloy; Preferably, the average particle size of the low melting point alloy is 0.1-50 μm, preferably 1-10 μm.

6. The thermal conductive electromagnetic shielding composite material according to any one of claims 1 to 5, characterized in that: The organic silicon material includes any one of addition silicone rubber, condensation silicone rubber or polydimethylsiloxane or a combination of at least two thereof.

7. The thermal conductive electromagnetic shielding composite material according to any one of claims 1 to 6, characterized in that: The thermally conductive electromagnetic shielding composite material is a sheet structure; Preferably, the thickness of the thermally conductive electromagnetic shielding composite material is 0.1-3 mm.

8. A method for preparing the thermally conductive electromagnetic shielding composite material according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: (1) aligning the surface metallized carbon fibers in a single direction and filling them into a mold, and then filling a mixture of a low melting point alloy and an organic silicon material into the mold, and obtaining a strip composite material after curing; (2) Cutting the strip-shaped composite material described in step (1) to obtain the thermal conductive electromagnetic shielding composite material.

9. The preparation method according to claim 8, characterized in that: The length of the surface metallized carbon fiber in step (1) is 5-200 mm, preferably 50-100 mm; Preferably, the mixing method of the mixture in step (1) includes the following: (a) when the melting point of the low melting point alloy is less than or equal to room temperature, the low melting point alloy is subjected to microspheroidization treatment and then first mixed with the organosilicon material; or (b) when the melting point of the low melting point alloy is greater than room temperature, secondly mixing the low melting point alloy with the organic silicon material; Preferably, after the filling into the mold in step (1), vacuuming is performed before curing; Preferably, the curing temperature in step (1) is ≥80°C; Preferably, the curing time in step (1) is ≥ 2 h; Preferably, the cutting direction in step (2) is perpendicular to the orientation of the surface metallized carbon fibers.

10. Use of the thermally conductive electromagnetic shielding composite material according to any one of claims 1 to 7 in the field of electronic packaging.

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