Composite heat-conducting rubber mat based on gallium-based liquid metal and surface metallized diamond and preparation method of composite heat-conducting rubber mat

Abstract

The invention discloses a composite heat-conducting rubber mat based on gallium-based liquid metal and surface metallized diamond and a preparation method of the composite heat-conducting rubber mat. The problems that an existing heat-conducting rubber mat is poor in interface bonding performance, poor in structural stability, complex in process, high in cost and the like are solved. The preparation method comprises the steps that firstly, gallium-based liquid metal is dissolved in absolute ethyl alcohol, a silane coupling agent is added, ultrasonic treatment is conducted in an ice-water bath, and silane coupling agent modified liquid metal is obtained; 2, performing ultrasonic cleaning on the surface metallized diamond micro powder; 3, mixing and grinding the two materials obtained in the step 1, and adding bi-component polyurethane to obtain composite slurry; and 4, injecting the composite slurry into a mold, and carrying out vacuum curing treatment. The surface-modified gallium indium alloy and the surface-metallized diamond micro-powder are adopted to construct a phonon-electron continuous heat conduction channel, the phonon-electron continuous heat conduction channel is combined with a polyurethane matrix to prepare the composite heat conduction material, the volume fraction of diamond can reach 20%-50%, the cross section of the material is free of obvious pores, internal interface bonding is good, and the material has excellent heat conductivity.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite heat-conducting materials, and particularly relates to a composite heat-conducting gasket based on gallium-based liquid metal and surface-metallized diamond and a preparation method thereof. Background Art

[0002] With the rapid development of modern electronic technology, electronic devices are evolving towards high performance, high integration and miniaturization, and the heat generated during their operation has increased sharply. Efficient heat-dissipating materials and technologies have become crucial for ensuring the stable operation of electronic devices, extending their service life and improving their overall performance.

[0003] Gallium-based liquid metal is a metal alloy that is liquid at room temperature (such as the Ga-In-Sn system), with both the high thermal conductivity (>20 W / m·K), electrical conductivity of metals and the deformability of fluids. Its unique wettability and low melting point have made it a research hotspot in the fields of flexible electronics, thermal management, etc. However, the existing technology still faces bottlenecks such as easy oxidation of liquid metal, uneven dispersion of fillers, and poor binding performance with other heat-conducting components, and there is an urgent need to achieve breakthroughs through interface collaborative design and low-temperature forming processes.

[0004] Diamond, with its excellent thermal conductivity (>2000 W / m·K), has become a highly potential heat-dissipating material. It not only has extremely high thermal conductivity, but also has excellent mechanical properties such as high hardness and high wear resistance, as well as good chemical stability. Currently, the synthesis technology of artificial diamond has been relatively mature, and the cost has gradually decreased, and it has been widely used in many fields. However, diamond itself has some limitations. Its interfacial compatibility with most matrix materials is poor, and it is difficult to fully exert its heat-dissipating efficiency when directly applied. Surface metallization treatment is one of the effective ways to improve the binding performance between diamond and the matrix. By plating metals such as titanium, chromium, tungsten, etc. on the surface of diamond, its surface activity and wettability can be improved, and the interfacial binding force with other materials can be enhanced, thereby improving the comprehensive performance of the overall composite material.

[0005] Polyurethane, as a polymer material, has good flexibility, adhesiveness and processing performance, can adapt to the heat-dissipating requirements of different shapes and structures, and has a wide application basis in the field of heat-conducting gaskets. However, the thermal conductivity of polyurethane itself is relatively low, and it is difficult to meet the application scenarios with high heat-dissipating requirements when used alone.

[0006] Traditional heat dissipation materials often struggle to meet the performance requirements in multiple aspects such as high thermal conductivity, good interfacial bonding, and flexibility. Patent CN116606636A discloses a composite thermal interface material based on liquid metal enhanced heat transfer and its preparation method, preparing a composite material composed of a gallium-based liquid metal enhanced thermal conductive gasket and a packaging gasket arranged around it. The thermal conductive gasket includes gallium-based liquid metal, thermal conductive filler, and polymer, and the packaging gasket includes thermal conductive filler and polymer, which can prevent the leakage of liquid metal and further contact with the metal substrate, effectively inhibiting the corrosion of the substrate. In its examples, surface metallized diamond is selected as the thermal conductive filler, which improves the wettability to a certain extent. However, only relying on simple mixing of the filler does not form a stable interfacial bonding, resulting in uneven distribution of the thermal conductive filler, discontinuous thermal conduction paths, high thermal resistance, and no inhibition of liquid metal oxidation. After long-term use, filler agglomeration and performance decay are likely to occur. At the same time, this patent only provides pictures of the bendable thermal conductive gasket without verifying the number of bending times, and the flexibility is not fully demonstrated. Moreover, the processing steps for each part of the raw materials are cumbersome, the curing temperature is high, and the process is complex, restricting the reliability and large-scale production of the material. The interfacial compatibility problem between liquid metal and diamond has not been solved, especially the chemical bonding mechanism between the surface of metallized diamond and liquid metal has not been explored. Summary of the Invention

[0007] The present invention aims to solve the problems of poor interfacial bonding performance, poor structural stability, high process complexity and high cost of existing thermal conductive pads, and provides a composite thermal conductive pad based on gallium-based liquid metal and surface metallized diamond and its preparation method.

[0008] The preparation method of the composite thermal conductive pad based on gallium-based liquid metal and surface metallized diamond of the present invention is realized according to the following steps:

[0009] I. Preparation of silane coupling agent modified liquid metal:

[0010] Dissolve gallium-based liquid metal in absolute ethanol, then add silane coupling agent, perform ultrasonic treatment in an ice-water bath, centrifugal treatment, and vacuum drying treatment to obtain silane coupling agent modified liquid metal;

[0011] II. Pretreatment of metallized diamond micropowder:

[0012] Use absolute ethanol to ultrasonically clean the surface metallized diamond micropowder, and obtain pretreated diamond micropowder after drying;

[0013] III. Preparation of composite slurry:

[0014] Mix and grind the silane coupling agent modified liquid metal and pretreated diamond micropowder at room temperature, add two-component polyurethane and perform vacuum stirring to obtain composite slurry;

[0015] IV. Curing and forming of the composite slurry:

[0016] Inject the composite slurry into a mold, and perform vacuum curing treatment at a curing temperature of 60 - 80 °C to obtain a composite thermal conductive gasket based on gallium-based liquid metal and surface metallized diamond.

[0017] The surface metallized diamond micropowder described in step II is titanium-plated diamond micropowder, chromium-plated diamond micropowder or tungsten-plated diamond micropowder.

[0018] The composite thermal conductive gasket based on gallium-based liquid metal and surface metallized diamond of the present invention first uses a silane coupling agent to modify the surface of the gallium-based liquid metal, and obtains surface-modified gallium-based liquid metal under an ice-water bath. The surface-modified gallium-based liquid metal and surface metallized diamond micropowder are mixed and ground, and then two-component polyurethane is added to form a composite slurry. Finally, the composite slurry is subjected to vacuum curing treatment.

[0019] The gallium-based liquid metal used in the present invention usually has a thermal conductivity in the range of 20 - 40 W / m·K, has good fluidity and self-healing ability, and can efficiently fill and conduct heat in micro-gaps and complex structures. Using a silane coupling agent to modify the gallium-based liquid metal to construct a flexible thermal conductive path for liquid metal. Taking KH550 as an example, the amino group at one end of its molecular structure can chemically react with the metal atoms on the surface of the liquid metal to form a stable chemical bond, inhibiting the oxidation of the liquid metal surface; the organic functional group at the other end can react with the active groups in the polyurethane matrix. In this way, a stable covalent bond connection is constructed between the liquid metal and the polyurethane matrix, significantly enhancing the interfacial bonding force, thereby effectively preventing the leakage of the liquid metal and ensuring the structural stability and long-term use performance of the composite thermal conductive gasket. In addition, a rigid thermal conductive path of diamond is constructed, that is, titanium / platinum / tungsten-plated diamond is combined with the liquid metal through chemical bonds to form a high-thermal-conductivity skeleton. At the same time, the gallium-based liquid metal has strong fluidity, can adhere to the surface of the diamond, has good wettability with the coating metal, and forms a phonon-electron continuous liquid thermal conductive path, reducing the interfacial thermal resistance. The polyurethane matrix has the functions of wrapping the thermal conductive filler and reducing the density, and also endows the composite gasket with a certain flexibility.

[0020] The preparation process of the composite thermal conductive gasket of gallium-based liquid metal and surface metallized diamond of the present invention has low requirements for equipment, simple process, and can realize mass production. The composite thermal conductive gasket prepared by combining the phonon-electron continuous thermal conductive path constructed by the silane coupling agent-modified gallium-indium alloy and the surface metallized diamond micropowder with the polyurethane matrix has a liquid metal volume fraction of 20% - 30% and a diamond volume fraction of 20% - 50%. The material cross-section has no obvious pores, good internal interfacial bonding, low density, good deformation ability and high thermal conductivity. Description of the Drawings

[0021] Figure 1 SEM cross-sectional view of the composite thermal conductive gasket prepared in Example 1;

[0022] Figure 2 Magnified SEM cross-sectional view of the composite thermal conductive gasket;

[0023] Figure 3 Physical photos of the composite thermal conductive gaskets prepared in Example 1 and Example 2, where the left figure represents the thermal conductive gasket of Example 1 and the right figure represents the thermal conductive gasket of Example 2;

[0024] Figure 4 Physical photos of the bent composite thermal conductive gaskets prepared in Example 1 and Example 2, where the left figure represents the thermal conductive gasket of Example 1 and the right figure represents the thermal conductive gasket of Example 2;

[0025] Figure 5 Physical photos of the composite thermal conductive gaskets after being bent in Example 1 and Example 2, where the left figure represents the thermal conductive gasket of Example 1 and the right figure represents the thermal conductive gasket of Example 2. Detailed implementation manners

[0026] Detailed implementation manner 1: The preparation method of the gallium-based liquid metal / diamond composite thermal conductive gasket is implemented according to the following steps:

[0027] I. Preparation of silane coupling agent modified liquid metal:

[0028] Dissolve the gallium-based liquid metal in absolute ethanol, then add the silane coupling agent, perform ultrasonic treatment in an ice-water bath, perform centrifugation treatment, and then perform vacuum drying treatment to obtain the silane coupling agent modified liquid metal;

[0029] II. Pretreatment of metallized diamond micropowder:

[0030] Use absolute ethanol to perform ultrasonic cleaning on the surface metallized diamond micropowder, and obtain the pretreated diamond micropowder after drying;

[0031] III. Preparation of composite slurry:

[0032] Mix and grind the silane coupling agent modified liquid metal and the pretreated diamond micropowder at room temperature, add two-component polyurethane, and perform vacuum stirring to obtain the composite slurry;

[0033] IV. Curing and forming of the composite slurry:

[0034] Inject the composite slurry into a mold, and perform vacuum curing treatment at a curing temperature of 60-80°C to obtain a composite thermal conductive gasket based on gallium-based liquid metal and surface metallized diamond;

[0035] Among them, the surface metallized diamond micropowder described in step two is titanium-plated diamond micropowder, chromium-plated diamond micropowder or tungsten-plated diamond micropowder.

[0036] In step four of this embodiment, the air pressure after vacuum pumping for vacuum stirring is lower than 100 Pa.

[0037] In this embodiment, the liquid metal is modified by a silane coupling agent and forms a covalent bond with the metallized diamond coating to achieve a phonon-electron synergistic heat conduction path, breaking through the performance bottleneck of traditional materials.

[0038] Specific Embodiment 2: The difference between this embodiment and Specific Embodiment 1 is that the gallium-based liquid metal described in step one is gallium-indium alloy liquid metal, and the melting point of the gallium-indium alloy liquid metal is 16 °C to 25 °C, and the density is 6 to 7 g / cm 3 。

[0039] Specific Embodiment 3: The difference between this embodiment and Specific Embodiment 1 or 2 is that the silane coupling agent described in step one is KH550, KH560, KH570 or KH580.

[0040] Specific Embodiment 4: The difference between this embodiment and any one of Specific Embodiments 1 to 3 is that the dosage of the silane coupling agent in step one is 1% to 10% of the mass of the liquid metal.

[0041] Specific Embodiment 5: The difference between this embodiment and any one of Specific Embodiments 1 to 4 is that the particle size of the surface metallized diamond micropowder in step two is 10 to 100 μm.

[0042] Specific Embodiment 6: The difference between this embodiment and any one of Specific Embodiments 1 to 5 is that the volume ratio of the silane coupling agent-modified gallium-based liquid metal and the pretreated diamond micropowder in step three is 2:5 to 5:2.

[0043] Specific Embodiment 7: The difference between this embodiment and Specific Embodiment 6 is that the volume ratio of the silane coupling agent-modified gallium-based liquid metal and the pretreated diamond micropowder in step three is (2 - 3):(4 - 5).

[0044] Specific Embodiment 8: The difference between this embodiment and any one of Specific Embodiments 1 to 7 is that the volume ratio of the two-component polyurethane and the mixture of the silane coupling agent-modified gallium-based liquid metal and the pretreated diamond micropowder in step three is (5 - 8):(1 - 5).

[0045] Specific Embodiment 9: The difference between this embodiment and any one of Specific Embodiments 1 to 8 is that the vacuum stirring time in step three is 10 to 30 min.

[0046] Embodiment 10: The difference between this embodiment and any one of Embodiments 1 to 9 is that in Step 4, it is cured at 60 - 80°C and a vacuum degree ≤ 100 Pa for 2 - 4 h.

[0047] Embodiment 11: The difference between this embodiment and any one of Embodiments 1 to 10 is that in Step 4, the thickness of the composite thermal conductive gasket based on gallium-based liquid metal and surface-metallized diamond is 2 - 6 mm.

[0048] Example 1: The preparation method of the gallium-based liquid metal / diamond composite thermal conductive gasket in this example is implemented according to the following steps:

[0049] I. Preparation of silane coupling agent-modified liquid metal:

[0050] Dissolve the gallium-indium alloy liquid metal with a melting point of 16°C in absolute ethanol, add KH560 silane coupling agent according to the mass ratio of silane coupling agent to gallium-indium alloy liquid metal of 1:100, mix, and perform ultrasonic treatment in an ice-water bath for 30 min. After centrifuging three times, collect the solid phase, and obtain the silane coupling agent-modified liquid metal after vacuum drying at 60°C.

[0051] II. Pretreatment of tungsten-plated diamond micropowder:

[0052] Use absolute ethanol to perform ultrasonic cleaning on the tungsten-plated diamond micropowder for 30 min, and place it in a vacuum drying oven to dry at 80°C for 4 h.

[0053] III. Preparation of composite slurry:

[0054] Add the pretreated tungsten-plated diamond micropowder to the silane coupling agent-modified liquid metal according to a volume ratio of 2:5, mix, and mix at a high speed of 1500 revolutions per minute for 10 minutes. Then add two-component polyurethane (A:B = 1:1), and the volume ratio of two-component polyurethane to the diamond / modified gallium-based liquid metal mixture is 7:3. Stir in vacuum for 10 minutes to obtain the composite slurry.

[0055] IV. Curing and forming of the composite slurry

[0056] Pour the composite slurry into a mold, and cure it in a vacuum oven with a vacuum degree of 0.08 MPa at a curing temperature of 60°C for 4 hours to obtain a gallium-based liquid metal / diamond composite thermal conductive gasket with a thickness of 1 mm.

[0057] Among them, the metallized diamond micropowder described in Step II is tungsten-plated diamond powder (commercially available) with a particle size of 40 - 50 μm; the model of the polyurethane described in Step III is two-component LN-3005A / B (commercially available).

[0058] Example 2: The preparation method of the gallium-based liquid metal / diamond composite thermal conductive gasket in this example is implemented according to the following steps:

[0059] I. Preparation of silane coupling agent modified liquid metal:

[0060] Dissolve the gallium-indium alloy liquid metal with a melting point of 20 °C in absolute ethanol. Add KH550 silane coupling agent according to the mass ratio of silane coupling agent to gallium-indium alloy liquid metal of 1:100. After mixing, perform ultrasonic treatment in an ice-water bath for 30 min, and centrifuge three times to collect the solid phase. After vacuum drying at 60 °C, obtain the silane coupling agent modified gallium-based liquid metal;

[0061] II. Pretreatment of chromium-plated diamond micropowder:

[0062] Use absolute ethanol to ultrasonically clean the chromium-plated diamond micropowder for 30 min, and place it in a vacuum drying oven to dry at 70 °C for 3 h;

[0063] III. Preparation of composite slurry:

[0064] Add the pretreated chromium-plated diamond micropowder to the silane coupling agent modified liquid metal according to a volume ratio of 3:4, mix under high-speed stirring at 2000 revolutions per minute for 10 minutes, add two-component polyurethane (A:B = 1:1), and the volume ratio of two-component polyurethane to the diamond / modified gallium-based liquid metal mixture is 6:4. Stir in vacuum for 10 minutes to obtain the composite slurry;

[0065] IV. Curing and molding of the composite slurry

[0066] Pour the composite slurry into a mold, and cure it in a vacuum oven with a vacuum degree of 0.05 MPa at a curing temperature of 80 °C for 3 hours to obtain a gallium-based liquid metal / diamond composite thermal conductive gasket with a thickness of 3 mm;

[0067] The metallized diamond micropowder described in step II is chromium-plated diamond powder with a particle size of 10 - 30 μm (commercially available); the model of the polyurethane described in step III is two-component LN-3005A / B (commercially available).

[0068] Comparative example: The preparation method of the composite thermal conductive gasket in this example is as follows:

[0069] I. Take liquid metal gallium-indium alloy and chromium-coated diamond powder as thermal conductive filler and mix them according to a volume ratio of 2:5. Place them in a mortar and stir repeatedly until a fully mixed material in which the thermal conductive filler is completely wetted by the liquid metal is obtained; place the obtained mixed material in a constant temperature furnace and keep it at 200 °C for 2 h to form a firm metallurgical bond between the liquid metal and the thermal conductive filler;

[0070] II. The mixture of liquid metal and heat-conducting filler is pulverized and granulated, and classified and separated through standard sieves with different pore diameters to obtain fine-particle heat-conducting filler particles with liquid metal coated on the surface, and the particle diameter is below 100 μm. After the selected fine-particle powder is paved flat, it is compacted for 30 min to form a three-dimensional network structure material of heat-conducting filler interconnected by liquid metal coating.

[0071] III. The obtained three-dimensional network structure material with continuous voids is placed in a refrigerator or a low-temperature environment of liquid nitrogen to solidify the liquid metal gallium. Then the obtained material is immersed in liquid silicone resin and placed in a vacuum furnace (vacuum degree: 10 Pa), and the liquid polymer silicone resin is filled into the pores of the obtained material through a vacuum impregnation process.

[0072] IV. The excess residual resin on the surface of the three-dimensional network structure material filled with liquid silicone resin is removed, and the sample is placed in an incubator and crosslinked and cured at a temperature of 120 °C for 40 min. After curing, the thickness is limited to 1.5 mm with a cutter, and finally a gallium-based liquid metal enhanced heat-conducting gasket is obtained.

[0073] The liquid metal described in Step I is a gallium-indium alloy with a melting point of 20 °C, and the diamond micropowder is chromium-plated diamond powder with an average particle size of 40 μm.

[0074] The performance tests of the gallium-based liquid metal / diamond composite heat-conducting rubber gaskets obtained in Example 1 and Example 2 are shown in Table 1 below.

[0075] The density of the sample is measured by the Archimedes drainage method; the thermal conductivity of the sample is measured according to ASTM D5470 (steady state method); the sample is bent tested according to the standard IPC-TM-650 2.4.3 (bending radius 1 mm, rate 60 times / min); the tensile shear test is carried out by using a universal material testing machine, and the strength is calculated.

[0076] Table 1

[0077]

Claims

1. A method for preparing a composite thermally conductive adhesive pad based on gallium-based liquid metal and surface metallized diamond, characterized in that The preparation method of the composite thermally conductive adhesive pad is achieved by following the steps:

1. Preparation of liquid metal modified by silane coupling agent: The gallium-based liquid metal is dissolved in anhydrous ethanol, and a silane coupling agent is added, and the mixture is ultrasonically treated in an ice-water bath, centrifuged, and then vacuum dried to obtain a silane coupling agent-modified liquid metal; 2. Pretreatment of metallized diamond powder: Ultrasonic cleaning of the surface metallized diamond micropowder was performed using anhydrous ethanol, and pre-treated diamond micropowder was obtained after drying; 3. Preparation of composite slurry: The silane coupling agent-modified liquid metal and pre-treated diamond powder are mixed and ground at room temperature, and two-component polyurethane is added and vacuum stirred to obtain a composite slurry; 4. Curing and molding of composite slurry: The composite slurry is injected into a mold, and vacuum cured at a curing temperature of 60 to 80° C. to obtain a composite thermal conductive adhesive pad based on gallium-based liquid metal and surface metallized diamond; The surface metallized diamond micropowder described in step 2 is titanium-plated diamond micropowder, chrome-plated diamond micropowder or tungsten-plated diamond micropowder.

2. The method for preparing a composite thermally conductive adhesive pad based on gallium-based liquid metal and surface metallized diamond according to claim 1, characterized in that The gallium-based liquid metal described in step 1 is a gallium-indium alloy liquid metal, the melting point of which is 16°C to 25°C and the density is 6 to 7 g / cm 3 .

3. The method for preparing a composite thermally conductive adhesive pad based on gallium-based liquid metal and surface metallized diamond according to claim 1, characterized in that The silane coupling agent described in step 1 is KH550, KH560, KH570 or KH580.

4. The method for preparing a composite thermally conductive adhesive pad based on gallium-based liquid metal and surface metallized diamond according to claim 1, characterized in that The dosage of the silane coupling agent in step 1 is 1% to 10% of the mass of the liquid metal.

5. The method for preparing a composite thermally conductive adhesive pad based on gallium-based liquid metal and surface metallized diamond according to claim 1, characterized in that The particle size of the surface metallized diamond powder in step 2 is 10 to 100 μm.

6. The method for preparing a composite thermally conductive adhesive pad based on gallium-based liquid metal and surface metallized diamond according to claim 1, characterized in that In step 3, the volume ratio of the silane coupling agent modified liquid metal and the pre-treated diamond powder is (2-3): (4-5).

7. The method for preparing a composite thermally conductive adhesive pad based on gallium-based liquid metal and surface metallized diamond according to claim 1, characterized in that In step three, the volume ratio of the mixture of two-component polyurethane and silane coupling agent modified liquid metal and pre-treated diamond micropowder is (5-8): (1-5).

8. The method for preparing a composite thermally conductive adhesive pad based on gallium-based liquid metal and surface metallized diamond according to claim 1, characterized in that In step 4, the curing is carried out at 60-80° C. and vacuum degree ≤100 Pa for 2-4 hours.

9. The method for preparing a composite thermally conductive adhesive pad based on gallium-based liquid metal and surface metallized diamond according to claim 1, characterized in that In step 4, the thickness of the composite thermal conductive adhesive pad based on gallium-based liquid metal and surface metallized diamond is 2 to 6 mm.

10. A composite thermal conductive adhesive pad based on gallium-based liquid metal and surface metallized diamond, characterized in that The composite thermal conductive adhesive pad based on gallium-based liquid metal and surface metallized diamond is prepared by firstly using a silane coupling agent to perform surface modification on the gallium-based liquid metal, obtaining the silane coupling agent-modified liquid metal in an ice water bath, mixing and grinding the silane coupling agent-modified liquid metal and the surface metallized diamond micropowder, and then adding two-component polyurethane to mix into a composite slurry, and finally subjecting the composite slurry to vacuum curing treatment.

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