A flexible graphene-diamond composite thermal interface material, a preparation method thereof and application thereof

Abstract

The application discloses a flexible graphene-diamond composite thermal interface material, a preparation method thereof and application thereof, and belongs to the technical field of composite thermal interface materials. The preparation method is as follows: liquid small molecules are used as carbon sources and nitrogen sources, and are deposited on the surface of silicon or graphite by using a microwave plasma chemical vapor deposition method to generate a graphene-diamond composite film, and then organic polymer spin coating is carried out to make the organic polymer penetrate into the internal pores of the graphene-diamond composite film, and thus the graphene-diamond composite thermal interface material is obtained. The graphene-diamond composite thermal interface material has a thermal conductivity of greater than or equal to 90 W / (m*K), the flexible graphene-diamond composite thermal interface material has a thermal conductivity of greater than or equal to 10 W / (m*K), a bending radius of greater than or equal to 3.9 mm, and a hardness reaching the ASTM-D2240 standard 22 level. Through comparison with actual measurement of a commercial thermal interface material, the surface temperature of a smart OLED mobile phone is reduced by greater than or equal to 2 DEG C, and the service life is increased by greater than or equal to 10%.

Description

Technical Field

[0001] This invention relates to the field of composite thermal interface materials technology, and in particular to a flexible graphene-diamond composite thermal interface material, its preparation method and its application. Background Technology

[0002] With the development of the microelectronics industry and the application of 5G technology, electronic components are gradually shifting towards higher integration and higher assembly density. During operation, these components generate a significant amount of heat, causing their operating temperatures to rise rapidly. This reduces the stability and reliability of the electronic components and shortens their lifespan. Research by Bar-Cohen et al. found that for every 2°C increase in temperature, the stability of electronic devices decreases by 10%. To ensure good stability and reliability of electronic components during operation and extend their lifespan, it is essential to prevent the operating temperature of electronic components from rising. Therefore, effectively and promptly transferring the heat generated during electronic component operation to external thermal interface materials has become the focus of electronic device cooling.

[0003] Currently, high-energy-density, high-brightness 5G (and even 6G) flexible OLED smartphones are indispensable electronic products in daily life. With the rapid pace of upgrades, their thermal management issues are becoming increasingly prominent, and their heat dissipation performance has become one of the core issues affecting user experience and the lifespan of the phone. Therefore, developing new high thermal conductivity and highly flexible thermal interface materials is key to solving the heat dissipation problem of electronic products. Summary of the Invention

[0004] One of the objectives of this invention is to provide a method for preparing a flexible graphene-diamond composite thermal interface material to solve the above-mentioned problems.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a flexible graphene-diamond composite thermal interface material includes the following steps: (1) Using microwave plasma chemical vapor deposition, liquid small molecules are used as carbon and nitrogen sources. By changing the type of gas source, graphene-diamond composite films are deposited on the surface of silicon or graphite under heat source. Its principle is as follows Figure 1 As shown, within the annular cavity, liquid sources such as n-butylamine, diethylamine, or acetonitrile react chemically with H2. The liquid small molecules provide carbon and nitrogen sources; the carbon source is the primary raw material for forming the composite film, while the nitrogen source promotes graphene growth. When the liquid source small molecules have a higher N / C ratio, the graphene-diamond composite film can exhibit smaller nanoscale dimensions and a higher growth rate, such as... Figure 3As shown, under the same conditions, graphene-diamond composite films prepared with acetonitrile molecules (N / C=0.5) have smaller graphene nanoparticle sizes and higher growth rates compared to those prepared with diisopropylamine molecules (N / C=0.17).

[0006] (2) The polymer is penetrated into the graphene-diamond composite film obtained in step (1) by spin coating, cured, and then the excess polymer on the surface of the penetrated graphene-diamond composite film is removed to obtain a flexible graphene-diamond composite thermal interface material.

[0007] This invention fully utilizes the ultra-high in-plane thermal conductivity of diamond and graphene, and uses the MPCVD one-step method to prepare vertically grown graphene-diamond array thermal conductive materials. Then, PVA and other materials are infiltrated into the gaps of the graphene-diamond array by spin coating, so that the composite material has flexible properties and is finally applied to chip heat dissipation of flexible high-power electronic devices.

[0008] The graphene-diamond composite array of the present invention can serve as a good medium for heat conduction, while PVA or PDMS endows the graphene-diamond composite array with good flexibility. Ultimately, it can be applied to heat dissipation of high power density flexible electronic devices, and has good heat transfer, tensile and bending properties.

[0009] As a preferred technical solution, the specific process in step (1) is as follows: 1) The silicon substrate is pre-treated by grinding under diamond micro powder, then cleaned in ultrasonic waves, diamond micro powder "seeds" are embedded, and then dried in an oven; 2) The pretreated silicon wafer is placed in a microwave plasma chemical vapor deposition system (MPCVD) with liquid small molecules as carbon and nitrogen sources and auxiliary gas to prepare a graphene-diamond composite film with a vertical array structure.

[0010] As a further preferred technical solution, the microwave plasma chemical vapor deposition system includes a microwave source, a reaction chamber, a vacuum system, a water and electricity protection system, and a gas path system.

[0011] As a further preferred technical solution The microwave source has a rated power of 10 kW and an output frequency of 2.45 GHz. The reaction chamber is a double-layered water-cooled stainless steel type with a maximum diameter of 500 mm, and the sample stage is made of molybdenum with a maximum diameter of 240 mm. The vacuum system mainly consists of a mechanical pump, a turbomolecular pump, a vacuum measuring device, and various valves. The overall system has a base vacuum of 10⁻⁶. -3 Pa; Both the water and electricity protection system and the gas circuit system adopt existing technologies. For example, the water and electricity protection system consists of an electrical control module, a power supply voltage stabilization module, and a cooling water module; the gas circuit system consists of a gas source, a mass flow meter, a mixing tank, and stainless steel gas pipelines.

[0012] As a preferred technical solution, in step (1), the liquid small molecule is selected from one or two of diethylamine, acetonitrile, n-butylamine and diisopropylamine.

[0013] As a preferred technical solution, in step (2), the polymer is PVA, PDMS or other organic polymers that are easy to dry and will not corrode the graphene-diamond composite film.

[0014] As a preferred technical solution, in step (2), the curing temperature is 55-65℃.

[0015] The second objective of this invention is to provide a flexible graphene-diamond composite thermal interface material prepared by the above-described method.

[0016] The third objective of this invention is to provide the application of the above-mentioned flexible graphene-diamond composite thermal interface material in electronic products.

[0017] As a preferred technical solution, the electronic product is a flexible OLED smartphone.

[0018] Compared with the prior art, the advantages of the present invention are as follows: the thermal conductivity of the flexible graphene-diamond composite thermal interface material of the present invention is ≥90 W / (m·K), the bending radius is ≥3.9mm, and the hardness reaches ASTM-D2240 standard level 22; through actual measurement comparison with commercial thermal interface material Laird thermal conductive silicone pad (7.5 W / (m·K)), the surface temperature of smart OLED mobile phones is reduced by ≥2℃, and the service life is increased by ≥10%. Attached Figure Description

[0019] Figure 1 This is a diagram illustrating the growth process of the microwave plasma chemical vapor deposition graphene-diamond composite film of the present invention. Figure 2 This is a morphology image of the graphene-diamond composite film prepared in Example 1 of the present invention; Figure 3 The morphology of graphene-diamond composite films prepared with different liquid source molecules in Example 1 of this invention is shown in the figure. Figure 4 The thermal conductivity values ​​of graphene-diamond composite films prepared at different growth temperatures in Example 1 of the present invention under different temperature conditions. Figure 5This is a physical image of the flexible graphene-diamond composite thermal interface material prepared in Example 1 of the present invention. Implementation

[0020] The invention will now be further described with reference to the accompanying drawings. Example 1:

[0021] A flexible graphene-diamond composite thermal interface material is prepared by the following steps: (1) Graphene-diamond composite films were prepared by microwave plasma chemical vapor deposition. The specific method is as follows: 1) The silicon substrate is pre-treated by grinding with 10,000-mesh diamond powder, then cleaned in an ultrasonic bath, and then embedded with 30,000-mesh diamond powder "seeds" and dried in an oven. 2) The pretreated silicon wafer from step 1) is placed in a microwave plasma chemical vapor deposition system. Using liquid small-molecule n-butylamine as the carbon and nitrogen source and H2 as the auxiliary gas, deposition occurs on the silicon surface under heat source to prepare a graphene-diamond composite film with a vertical array structure, such as... Figure 2 As shown, from Figure 2 The film shows an array structure inside, and the composite film has tiny voids inside.

[0022] In the above process, the growth temperatures of the graphene-diamond composite film at 600℃, 700℃, and 800℃ were controlled by adjusting the power and chamber pressure (corresponding to...). Figure 3 "VDG" 600 “VDG” 700 “VDG” 800 The hydrogen flux was 160 sccm, and the pressure of the MPCVD system after stabilization was approximately 11.5 kPa. After 3 hours of growth, the liquid source inlet channel, microwave input source, and hydrogen generator were shut off, and the system was allowed to cool naturally to room temperature, generating a graphene-diamond composite film. The thermal conductivity values ​​of the obtained graphene-diamond composite film under different test temperature conditions are as follows: Figure 4 As shown, the composite film grown at 700℃ exhibits the highest thermal conductivity under different ambient temperatures, while the composite film grown at 600℃ exhibits the lowest thermal conductivity under different ambient temperatures. Furthermore, ambient temperature has a relatively small impact on the thermal conductivity of different types of composite films, indicating that the composite films possess good stability. (2) Performance test of thermal interface material: According to the standard ASTM E1461 for thermal conductivity testing by laser scintillation thermal conductivity meter, the thermal conductivity of the graphene-diamond composite thermal interface material grown at 700℃ in step (1) of this embodiment is 97 W / (m·K). -1 ; (3) Spin-coating PVA, the specific method is as follows: Using a pipette, 80 mL of PVA adhesive solution was repeatedly dripped onto the surface of the graphene-diamond composite film prepared in step (1). Gravity allowed the PVA to penetrate into the interior of the graphene-diamond composite film. The film was then cured at 60°C. Afterward, excess PVA was removed from the surface of the permeated graphene-diamond composite film, ensuring that the graphene-diamond composite material was not coated. This yielded a flexible graphene-diamond composite thermal interface material. Figure 5 As shown. Example 2:

[0023] This embodiment is based on the graphene-diamond composite film obtained by growing at 700℃ in step (1) of embodiment 1. Flexible graphene-diamond composite thermal interface material is prepared by spin-coating PDMS. The specific steps are as follows: 80 mL of PDMS adhesive solution is taken with a pipette, stirred evenly, and then dropped onto the surface of the graphene-diamond composite film multiple times. PDMS is penetrated into the interior of the graphene-diamond composite film by gravity. The film is cured at 60℃. After that, the excess PDMS on the surface of the graphene-diamond composite film after penetration is removed so that the graphene-diamond composite material is not covered, thus obtaining the flexible graphene-diamond composite thermal interface material. Example 3:

[0024] According to the standard ASTM E1461 for thermal conductivity testing using the laser flash thermal conductivity meter, the specific thermal conductivity value of the thin film grown at 600℃ after spin coating in step (3) of Example 1 is 12 W / (m·K). -1 The thermal conductivity of the thin film grown at 700℃ after spin coating is 30 W / (m·K). -1 The thermal conductivity of the thin film grown at 800℃ after spin coating is 20 W / (m·K). -1 According to NN / J.41.07.08-2022 standard, the bending radius of the film grown at 700℃ after spin coating is 4 mm, and the hardness reaches ASTM-D2240 standard level 22. Example 4:

[0025] According to the ASTM E1461 standard for thermal conductivity testing using the laser flare method, the thermal conductivity of the flexible graphene-diamond composite thermal interface material obtained in Example 2 was 20 W / (m·K). -1 According to NN / J.41.07.08-2022 standard, the bending radius is 4 mm and the hardness reaches ASTM-D2240 standard level 22. Example 5:

[0026] The sample obtained in step (3) of Example 1 or Example 2 was peeled off from the Si substrate and tested for actual heat dissipation effect in OLED smartphones.

[0027] The specific steps are as follows: Disassemble three identical 5G flexible OLED smartphones, and install the target VDG thin film flexible TIM (with heat source attached to the peel-off surface), Shin-Etsu X-23-7921 thermal grease, Laird Tflex HD90000 thermal conductive silicone sheet, and commercial graphite sheet into the thermal channel of the OLED smartphone's 5G chip, respectively. Attach micron-sized thermocouple probes to the top and bottom surfaces of the four types of TIMs, and connect eight thermocouples to the same temperature recorder. Run the Master Lu (or 3DMark11) stress test software on the phone continuously, and record the outer surface temperature of the TIM installation location using an infrared thermal imager (Fluke TIS10+), thereby obtaining the actual heat dissipation performance data of the entire device. Under the same conditions, compared with commercial thermally conductive silicone sheets and commercial graphite sheets, when using the flexible graphene-diamond composite thermal interface material grown at 700°C under the conditions of Example 1, the temperature at the OLED smartphone chip location is 4°C lower, and the lifespan of the phone is increased by more than 20%; when using the flexible graphene-diamond composite thermal interface material of Example 2, the temperature at the OLED smartphone chip location is 2°C lower, and the lifespan of the phone is increased by more than 10%.

[0028] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for preparing a flexible graphene-diamond composite thermal interface material, characterized in that, Includes the following steps: (1) A graphene-diamond composite film is generated by using microwave plasma chemical vapor deposition, with liquid small molecules as carbon and nitrogen sources and auxiliary gas, under heat source. The liquid small molecules are selected from one or two of diethylamine, acetonitrile, n-butylamine and diisopropylamine. (2) The polymer is penetrated into the pores inside the graphene-diamond composite film obtained in step (1) by spin coating, cured, and then the excess polymer on the surface of the graphene-diamond composite film after penetration is removed to obtain a flexible graphene-diamond composite thermal interface material; wherein the polymer is PVA and the curing temperature is 55-65℃.

2. The preparation method according to claim 1, characterized in that, In step (1), the specific process is as follows: 1) The silicon substrate is pre-treated by grinding under diamond micro powder, then cleaned in ultrasonic waves, diamond micro powder "seeds" are embedded, and then dried in an oven; 2) The pretreated silicon wafer was placed in a microwave plasma chemical vapor deposition system, with liquid small molecules as carbon and nitrogen sources, and an auxiliary gas was used to prepare a graphene-diamond composite film with a vertical array structure.

3. The preparation method according to claim 2, characterized in that, The microwave plasma chemical vapor deposition system includes a microwave source, a reaction chamber, a vacuum system, a water and electricity protection system, and a gas path system.

4. The preparation method according to claim 3, characterized in that, The microwave source has a rated power of 10 kW and an output frequency of 2.45 GHz; the reaction chamber is a double-layer water-cooled stainless steel type with a maximum diameter of 500 mm, and the sample stage is made of molybdenum with a maximum diameter of 240 mm. The vacuum system has a base vacuum level of 10. -3 Pa.

5. The flexible graphene-diamond composite thermal interface material prepared by the method according to any one of claims 1 to 4.

6. The application of the flexible graphene-diamond composite thermal interface material according to claim 5, characterized in that, Used in electronic products.

7. The application according to claim 6, characterized in that, The electronic product in question is a flexible OLED smartphone.

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