CN116606636A - Composite thermal interface material based on liquid metal enhanced heat transfer and its preparation method - Google Patents

Abstract

The invention discloses a composite thermal interface material based on liquid metal enhanced heat transfer and a preparation method thereof, which consists of a gallium-based liquid metal enhanced heat conduction gasket and packaging gaskets arranged on the upper, lower and surrounding sides of the gallium-based liquid metal enhanced heat conduction gasket; The gallium-based liquid metal enhanced thermal conductivity gasket is obtained by flattening the small particle size mixture material particles, then uniformly filling the high molecular polymer and cross-linking and curing; the packaging gasket is made by stirring the high molecular polymer and the thermal conductivity filler evenly. The mixed material is obtained; the mixed material is fixed on the upper, lower and surrounding areas of the gallium-based liquid metal reinforced thermal conduction pad by using a molding process, and then the high molecular polymer is cross-linked and solidified; the packaging gasket of the present invention can prevent the internal liquid metal from top, bottom and Leakage around prevents direct contact between liquid metal and the heat dissipation substrate, thereby eliminating short circuit and corrosion problems caused by liquid metal, and improving the reliability of heat transfer.

Description

Composite thermal interface material based on liquid metal enhanced heat transfer and its preparation method

technical field

The invention relates to the technical field of thermal interface materials, in particular to a composite thermal interface material based on liquid metal enhanced heat transfer and a preparation method thereof.

Background technique

With the rapid development of microelectronics technology, the power density of the chip has increased sharply, and the heat flux in the local overheated area of the chip has reached 300W/cm ² . Excessive temperature rise will seriously affect the electrical parameters of electronic equipment and restrict its electrical performance. , and even cause the failure of electronic components, reducing the reliability of the device. Therefore, thermal management of electronic devices, especially chips, is becoming more and more important. In a sense, by reducing the thermal resistance of electronic components, especially the interface thermal resistance between different materials, it is possible to effectively prevent overheating problems of chips and electronic components. When the electronic equipment is working, the heat generated by the heat source needs to be dissipated through the heat sink, and the use of thermal interface materials can fill the gap between the heat source and the heat sink to improve the heat dissipation efficiency of the electronic equipment.

Traditional thermal interface materials include thermally conductive silicone grease, phase change materials, and thermally conductive silicone sheets. They are usually composed of polymer materials and thermally conductive fillers. Each thermally conductive filler is isolated by a polymer matrix, and its distribution is similar to an "islands in the sea" structure. Such materials have been widely used in the thermal connection between electronic equipment and heat sinks, but there is a huge thermal resistance between the thermally conductive filler particles, resulting in poor thermal conductivity, which makes it difficult to meet higher heat dissipation requirements.

From the perspective of material mechanics and heat transfer, an ideal thermal interface material must have an elastomeric matrix of polymer material to meet the requirements of softness, compliance, and support strength; while thermally conductive fillers should be connected through continuous channels to Eliminates the effect of the polymer's higher thermal resistance. In addition, the heat transfer channel must have sufficient deformability, otherwise the composite material cannot meet the requirement of good compatibility. Based on the requirements of the above two aspects, considering the advantages of gallium-based liquid metals with high thermal conductivity, excellent fluidity, low viscosity and non-toxicity, it is possible to greatly improve the heat transfer performance of thermal interface materials by using gallium-based liquid metals. However, during the service process, gallium-based liquid metal often has the problem of seepage and overflow, especially when the liquid metal encounters some metal heat dissipation substrates, it will corrode, resulting in the failure of the thermal connection between the device and the heat sink. Seriously affect the reliability of device heat dissipation.

Existing composite thermal interface materials based on liquid metal enhanced heat transfer cannot meet the requirements of high thermal conductivity and anti-leakage at the same time. Chinese invention patent CN108912683B discloses a thermal interface material based on a low-melting-point metal/heat-conducting particle composite heat-conducting network and its preparation method. It is composed of a low-melting-point metal, heat-conducting particles and a high molecular polymer. As a linking agent, each heat-conducting particle is connected by a low-melting-point metal to form a three-dimensional heat-conducting network channel; the pores between the three-dimensional heat-conducting network channels are filled with polymers; the melting point of the low-melting-point metal is lower than 80°C, and its chemical composition is Containing one or more of gallium, bismuth, cadmium, tin, lead, dysprosium and indium elements; the heat-conducting particles are metal heat-conducting fillers and/or inorganic non-metal heat-conducting fillers, and the surface of the inorganic non-metal heat-conducting fillers can be metallized; The metal thermally conductive filler is pure metal or alloy material, and the inorganic non-metallic thermally conductive filler is one or more of diamond, boron nitride, aluminum oxide, aluminum nitride, silicon nitride, graphite, carbon nanotube and graphene. This technology uses gallium-based liquid metal and heat-conducting particles to build an efficient three-dimensional heat-conducting channel, and in the process of use, the interface between the low-melting point metal and the metal substrate forms a metallurgical interconnection, and the high-molecular polymer and the substrate are bonded. Two connection methods The overflow problem of low-melting point alloys is limited, but liquid metal will corrode when it encounters some metal heat dissipation substrates, resulting in the failure of the thermal connection between the device and the heat sink, which seriously affects the reliability of device heat dissipation, so it is not suitable to contain The liquid metal composite thermal interface material makes direct contact with the heat dissipation substrate.

Chinese invention patent CN110643331B discloses a liquid metal heat conduction paste and its preparation method and application. The invention uses a polymer material to wrap the liquid metal in it, and uses a viscosity modifier to increase the viscosity of the composite material to avoid the leakage of the liquid metal. The thermal paste is more stable and safe during use, but the composite thermal interface material is prepared by a blending method, and most of the thermal conductive fillers are isolated by the polymer matrix, resulting in poor thermal conductivity of the material. Therefore, it is urgent to develop a composite thermal interface material based on liquid metal to enhance heat transfer that takes into account the characteristics of high thermal conductivity and anti-leakage.

Contents of the invention

Aiming at the shortcomings of existing thermal interface materials, the purpose of the present invention is to provide a composite thermal interface material based on liquid metal enhanced heat transfer and its preparation method. The prepared thermal interface material has extremely high thermal conductivity, good Excellent flexibility and thermal connection reliability.

In order to achieve the above object, the technical scheme provided by the present invention is as follows:

A composite thermal interface material based on liquid metal enhanced heat transfer, which is composed of a gallium-based liquid metal enhanced thermal conduction gasket and packaging gaskets arranged on the upper, lower and surrounding sides of the gallium-based liquid metal enhanced thermal conduction gasket; the gallium-based liquid metal The metal-reinforced heat-conducting gasket is obtained by flattening the small particle size mixed material particles with a particle size of 1-1000 μm, pressing and forming, and then uniformly filling high molecular polymer and cross-linking and curing; the small particle size mixed material is gallium-based liquid Stir the metal and the heat-conducting filler evenly, pulverize and granulate, and sieve the obtained product; the packaging gasket is obtained by mixing the high-molecular polymer and the heat-conducting filler evenly to obtain a mixed material; the mixed material is fixed on a gallium-based liquid metal-reinforced The upper, lower, and surrounding areas of the thermal pad are obtained by cross-linking and curing high molecular polymers;

The liquid metal is pure gallium, gallium-indium alloy, gallium-tin alloy, gallium-zinc alloy, gallium-indium-tin alloy, gallium-indium-zinc alloy or gallium-indium-tin-zinc alloy; the high molecular polymer is epoxy resin, organic silicon resin or polyurethane resin.

In order to further realize the purpose of the present invention, preferably, in terms of volume percentage, in the said liquid metal enhanced thermal conduction gasket, the gallium-based liquid metal accounts for 5%-40%, the thermally conductive filler accounts for 35%-75%, and the polymer Polymer accounts for 20%-60%.

Preferably, the thermally conductive filler is a metal thermally conductive filler and/or an inorganic non-metallic thermally conductive filler, and the particle size of the thermally conductive filler is 0.1-300 μm; The polymer is filled into the pores of the three-dimensional network structure material formed by pressing the mixed material particles with small particle size after they are flattened. .

Preferably, the metal thermally conductive filler is one or more of copper, nickel, molybdenum, tungsten, copper alloy, nickel alloy, molybdenum alloy or tungsten alloy; the inorganic non-metallic thermally conductive filler is boron nitride, oxide One or more of aluminum, aluminum nitride, silicon nitride, graphite, diamond, graphene and carbon nanotubes; the vacuum degree of the vacuum impregnation process is 1-1000Pa.

Preferably, the molding process is used to fix the mixed material on the upper, lower and surrounding sides of the gallium-based liquid metal enhanced thermal conductivity gasket through the following methods:

Put the high molecular polymer and the thermal conductive filler in the mixer, and stir repeatedly until the high molecular polymer and the thermal conductive filler are fully mixed to obtain the mixed material; the mixed material is coated on the plastic film by the screen printing process; the second A plastic film coated with mixed materials is placed on top of the gallium-based liquid metal enhanced thermal conduction gasket; vacuum press molding realizes the combination of the liquid metal enhanced thermal conduction gasket and the first surface packaging gasket;

The gallium-based liquid metal-enhanced thermal conduction gasket is combined with the opposite side of the packaging gasket on the first side facing up, and an annular groove mold is arranged on the outer periphery of the gallium-based liquid metal-enhanced thermal conduction gasket, and the mixed material is filled in the annular groove mold; the other A plastic film coated with a polymer mixture material is placed on the gallium-based liquid metal-enhanced thermal conduction gasket, vacuum-pressed, and the mixture material is combined with the package gasket on the upper surface and surroundings of the gallium-based liquid metal-enhanced heat conduction gasket.

Preferably, the vacuum pressing is to create a vacuum environment in the vacuum laminating machine first, and paste the mixed material on the gallium-based liquid metal reinforced thermal conductivity gasket under the action of pressure; the hollow annular width of the annular groove is It is 2-5mm.

Preferably, the pressure is 10kPa-500kPa, and the holding time is 0.1min-60min; the vacuum drawn by the vacuum laminating machine is 1-1000Pa.

Preferably, the thickness of the screen in the screen printing process is 0.1-1 mm.

Preferably, the temperature for crosslinking and curing is 20°C-200°C, and the holding time is 0.1min-60min.

The preparation method of the composite thermal interface material based on liquid metal enhanced heat transfer comprises the following steps:

1) Stir the gallium-based liquid metal and the thermally conductive filler evenly; pulverize and granulate, and sieve to obtain mixed material particles with a particle size of 1-1000 μm;

2) Flatten the particles of the mixed material with small particle size and press them into shape to obtain a liquid metal/thermally conductive filler three-dimensional network structure material; fill the liquid high molecular polymer into the liquid metal/thermally conductive filler three-dimensional network structure material through a vacuum infiltration process In the pores of the network structure material; after cross-linking and solidification, a gallium-based liquid metal enhanced thermal conductivity gasket is obtained;

3) Stir the high molecular polymer and the thermally conductive filler evenly to obtain a mixed material of the high molecular polymer and the thermally conductive filler; use a molding process to fix the mixed material of the high molecular polymer and the thermally conductive filler on the upper and lower sides of the gallium-based liquid metal reinforced thermally conductive gasket and Four weeks, the high molecular polymer is cross-linked and solidified to obtain a composite thermal interface material based on liquid metal enhanced heat transfer.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

1) The packaging gasket of the present invention is arranged on the upper, lower and surrounding sides of the gallium-based liquid metal enhanced thermal conduction gasket, and the sealing performance of the gallium-based liquid metal enhanced thermal conduction gasket is ensured through an integral molding process, effectively avoiding the liquid metal The composite heat-conducting thermal interface material is in direct contact with the heat-dissipating substrate, which improves safety, prevents the internal liquid metal from leaking from the upper, lower and surrounding areas of the thermal pad, and acts as an isolation between the liquid metal and the heat-dissipating substrate to prevent The liquid metal corrodes the surface of the radiator.

2) The packaging gasket of the present invention is used as a liquid metal escape blocking medium and is also a heat transfer medium; and the packaging gasket is mainly formed by a high molecular polymer and a thermally conductive filler; and the gallium-based liquid metal enhanced thermally conductive gasket also includes a polymer polymer Materials and thermally conductive fillers, such raw materials effectively ensure the heat transfer between the package gasket and the gallium-based liquid metal-enhanced thermally conductive gasket and avoid the problem of excessive stress after heating, resulting in the combination of the package gasket and the gallium-based liquid metal-enhanced thermally conductive gasket Not tight and heat transfer is not timely.

3) Since the present invention adopts a mold with the function of filling around the thermal pad, the mixture of polymer and thermal filler can be filled around the liquid metal reinforced thermal pad, so the thermal pad can not only prevent the internal liquid metal from heat conduction Leakage from the top and bottom of the gasket avoids the problem of corrosion caused by direct contact between the liquid metal and the heat dissipation substrate, and can effectively prevent the liquid metal from overflowing from around the thermal pad, completely eliminating the risk of short circuit caused by liquid metal.

4) The liquid metal reinforced thermal pad is composed of gallium-based liquid metal, thermally conductive filler and polymer. The efficient three-dimensional heat conduction channel constructed by liquid metal and thermally conductive filler makes the composite material have extremely high thermal conductivity, and the polymer It gives the material good support strength and flexibility;

5) The liquid metal reinforced thermal conductive gasket of the present invention has a three-dimensional skeleton of "liquid metal/thermal conductive filler" and a double continuous phase structure of high molecular polymer. The thermal conductive filler forms a three-dimensional heat conduction network channel after being bridged by liquid metal, and the three-dimensional heat conduction network channel The continuous through pores are filled by flexible polymers.

6) The combination of the packaging gasket and the liquid metal-enhanced heat-conducting material of the present invention adopts screen printing and vacuum bonding technology, which can realize flexible control of the thickness of the heat-conducting gasket, effectively suppress the generation of pores inside it, and greatly reduce the leakage of liquid metal. flow risk.

7) The high-efficiency three-dimensional heat conduction channel constructed by liquid metal and heat conduction filler in the present invention enables the composite material to have extremely high thermal conductivity, and the high molecular polymer endows the material with good support strength and flexibility.

8) The composite thermal interface material based on liquid metal enhanced heat transfer of the present invention has the advantages of high thermal conductivity and anti-leakage, and is suitable for high-power interface heat transfer applications such as high-performance computers, 5G communications, and electronic power.

Description of drawings

Fig. 1 is a schematic diagram of the preparation method of the composite thermal interface material based on liquid metal enhanced heat transfer of the present invention.

Fig. 2 is a photo of the three-dimensional microstructure of the liquid metal-enhanced thermally conductive gasket in the embodiment.

Figure 3 is the mold used for the second vacuum bonding of the ordinary thermal pad and the liquid metal enhanced thermal pad;

Fig. 4 is a physical display of the composite thermal interface material of the present invention.

Figure 5 is a schematic diagram of the structure of the thermal conductivity test platform.

Fig. 6 is the sealing performance test of the composite thermal interface material of the present invention;

Detailed ways

The content of the present invention will be further elaborated below in conjunction with the accompanying drawings and examples. The examples are only used to illustrate the present invention, but not to limit the protection scope of the present invention.

Example 1

As shown in Figure 1, a method for preparing a composite thermal interface material based on liquid metal enhanced heat transfer includes the following steps:

(1) Material preparation: pure gallium (purity 99.99wt%, Northeast Nonferrous Metals Company, China), chromium-coated diamond powder (average particle size 40 μm, HFD-D type, Henan Huanghe Cyclone Company (China), silicone resin ( PDMS, Caster 1010, China).

(2) Take liquid metal gallium and thermally conductive filler chromium-coated diamond powder and mix them according to the volume ratio of 1:1.6, place them in a mortar, and stir repeatedly until the fully mixed material in which the thermally conductive filler is completely wetted by the liquid metal is obtained; the resulting mixed material Place it in a constant temperature furnace and keep it warm at 200°C for 2 hours to form a firm metallurgical bond between the liquid metal and the heat-conducting filler.

(3) Grinding and granulating the mixture of liquid metal and heat-conducting filler, passing through standard sieves with different apertures for fractional separation, to obtain fine-sized heat-conducting filler particles coated with liquid metal on the surface, and the particle diameter is below 100 μm; the screened After the fine-grain particle powder is flattened, it is compacted with a pressure of 1.16×10 ⁶ Pa (holding for 30 minutes) to obtain a three-dimensional network structure material of thermally conductive fillers coated and interconnected by liquid metal.

(4) Place the obtained three-dimensional network structure material with continuous voids in a refrigerator or a liquid nitrogen low-temperature environment to solidify the liquid metal gallium; then immerse the obtained material in liquid silicone resin and place it in a vacuum furnace (vacuum Degree 10Pa), the liquid high molecular polymer silicone resin is filled into the pores of the obtained material through the process of vacuum impregnation.

(5) Clean up excess residual resin on the surface of the three-dimensional network structure material filled with liquid silicone resin, put the sample in a constant temperature box, and cross-link and solidify the high molecular polymer at a temperature of 120°C for 40 minutes; After curing, use a cutter to limit its thickness to 1.5 mm, and finally obtain a gallium-based liquid metal-enhanced thermal pad, and its microstructure photo is shown in Figure 2. It can be seen from the figure that the liquid metal enhanced thermal conduction gasket is composed of a three-dimensional heat conduction network channel constructed by liquid metal gallium and diamond heat conduction fillers, and silicone resin filled in the gaps.

(6) Put the silicone resin and alumina particles in the mortar according to the volume ratio of 1:1, and stir repeatedly until the high molecular polymer and the thermally conductive filler are fully mixed, and then use a 0.2mm thick screen to mix the above mixture The material is coated on the plastic film by screen printing, and two copies are made to meet the combination requirements of the upper and lower sides.

(7) Place the first plastic film coated with a mixture of polymer and thermally conductive filler on the above liquid metal reinforced thermally conductive gasket, and use plasticine to suspend it, and place it in a vacuum laminating machine for vacuuming. Vacuum to 10 Pa, and then press bond them under a pressure of 1.16×10 ⁶ Pa (holding time 30 min).

(8) Put the sample into a constant temperature box and wait for the silicone resin to be cross-linked and cured at a temperature of 120° C., and the curing time is 40 minutes.

(9) Put the uncoated side of the obtained liquid metal reinforced thermal pad facing upwards, place the annular groove mold shown in Figure 3 on the upper surface of the liquid metal reinforced thermal pad, and fill a circle of polymer at a distance of 2 mm from the outer diameter of the pad The mixture of polymer and thermal conductive filler; then remove the mold, place the second plastic film coated with the mixed material of high molecular polymer and thermal conductive filler on the above liquid metal reinforced thermal conductive gasket, and place it in a vacuum laminating machine Vacuum to 10Pa in the center, and press them again under the pressure of 1.16×10 ⁶ Pa (holding time 30min). Under the pressure, the mixed material can cover the surface of the gallium-based liquid metal reinforced thermal pad, and fill to its surroundings; the mixed material forms packaging gaskets on the upper, lower, and surrounding sides of the gallium-based liquid metal enhanced thermal conductivity gasket.

(10) Put the sample into a constant temperature box and wait for the silicone resin to be cross-linked and cured at a temperature of 120°C. The curing time is 40 minutes, and finally a composite thermal interface material as shown in Figure 4 can be obtained.

Example 2

(1) Material preparation: gallium indium tin alloy (mass ratio of gallium, indium, and tin is 7:2:1, Northeast Nonferrous Metals Company, China), boron nitride particles (particle size ≈5 μm, purity 99.9%, Henan Huanghe Cyclone Company (China), epoxy resin (PDMS, Caster1010, China).

(2) Magnetron sputtering technology is used to coat metal chromium film on the surface of boron nitride particles. During this process, the boron nitride powder is freely turned over by an ultrasonic vibration platform to ensure that the surface of the thermally conductive filler is covered with a metal film. In this step, the magnetron sputtering technology can be replaced by vacuum evaporation, electroless plating, electroplating and other processes, which can achieve similar effects.

(3) Take liquid gallium indium tin alloy and boron nitride thermally conductive filler and mix according to the volume ratio of 1:1.6, place it in a mortar, and stir repeatedly until the fully mixed material in which the thermally conductive filler is completely wetted by the liquid metal is obtained; the obtained mixed material Place it in a constant temperature furnace and keep it warm at 200°C for 2 hours to form a firm metallurgical bond between the liquid metal and the heat-conducting filler.

(4) Grinding and granulating the mixture of liquid metal and heat-conducting filler, passing through standard sieves with different apertures for fractional separation, to obtain fine-sized heat-conducting filler particles coated with liquid metal on the surface, and the particle diameter is below 100 μm; the screened After the fine-grain particle powder is flattened, it is compacted with a pressure of 1.16×10 ⁶ Pa (holding for 30 minutes) to obtain a three-dimensional network structure material of thermally conductive fillers coated and interconnected by liquid metal.

(5) Place the obtained three-dimensional network structure material with continuous voids in a refrigerator or a liquid nitrogen low-temperature environment to solidify the liquid gallium indium tin alloy; then immerse the material in liquid epoxy resin and place it in a vacuum furnace ( The vacuum degree is 10Pa), and the liquid polymer is filled into the pores of the material through the process of vacuum impregnation.

(6) Clean up the excess residual resin on the surface of the three-dimensional network structure material filled with liquid epoxy resin, put the sample in a constant temperature box, and cross-link and solidify the high molecular polymer at a temperature of 120°C for 40 minutes; After curing, use a cutter to limit its thickness to 1.5mm, and obtain a gallium-based liquid metal enhanced thermal conduction gasket.

(7) Put the silicone resin and alumina particles in a mortar at a volume ratio of 1:1, and stir repeatedly until a material that is fully mixed with a high molecular polymer and a thermally conductive filler is obtained, and then use a 0.2mm thick screen to mix the above mixture The material is coated on the plastic film by screen printing, and two samples need to be made to meet the combination requirements of the upper and lower parts.

(8) Place the first plastic film coated with a mixture of high molecular polymer and thermal conductive filler on the above liquid metal reinforced thermal conductive gasket, and use plasticine to suspend it, and place it in a vacuum laminating machine to pump it. Vacuum to 10Pa, and then press and bond them under a pressure of 1.16×106Pa (holding time 30min).

(9) Put the sample into a constant temperature box and wait for the epoxy resin to be cross-linked and cured at a temperature of 120° C., and the curing time is 40 minutes.

(10) Place the uncoated side of the obtained liquid metal reinforced thermal pad upwards, place the annular groove mold shown in Figure 3 on the upper surface of the liquid metal reinforced thermal pad, and fill a circle of polymer at a distance of 2mm from the outer diameter of the pad Polymer and thermal conductive filler mixed material; then remove the mold, place the second plastic film coated with high molecular polymer and thermal conductive filler mixed material above the above-mentioned gallium-based liquid metal reinforced thermal conductive gasket, and place it in a vacuum Vacuumize the machine to 10Pa, and press it again under the pressure of 1.16×106Pa (holding time 30min). Under the pressure, the mixed material can cover the surface of the gallium-based liquid metal reinforced thermal pad and fill it to its surroundings; the mixed material forms packaging gaskets on the upper, lower, and surrounding sides of the gallium-based liquid metal enhanced thermal conductivity gasket.

(11) Put the sample into a constant temperature box and wait for the epoxy resin to be cross-linked and cured at a temperature of 120°C. The curing time is 40 minutes, and finally a composite thermal interface material with liquid metal enhanced heat transfer is obtained.

Example 3

(1) Material preparation: pure gallium (purity 99.99wt%, Northeast Nonferrous Metals Company, China), chromium-coated diamond powder (average particle size 40 μm, HFD-D type, Henan Huanghe Cyclone Company (China), silicone resin ( PDMS, Caster 1010, China).

(2) Mix liquid gallium metal and diamond heat-conducting filler according to the volume ratio of 1:1.6, place it in a mortar, and stir repeatedly until the heat-conducting filler is completely wetted by the liquid metal; place the resulting mixture in a constant temperature furnace In the process, heat preservation at 200°C for 2 hours to form a firm metallurgical bond between the liquid metal and the thermally conductive filler.

(3) Grinding and granulating the mixture of liquid metal and heat-conducting filler, passing through standard sieves with different apertures for fractional separation, to obtain fine-sized heat-conducting filler particles coated with liquid metal on the surface, and the particle diameter is below 100 μm; the screened After the fine-grain particle powder is flattened, it is compacted with a pressure of 1.16×10 ⁶ Pa (holding for 30 minutes) to obtain a three-dimensional network structure material of thermally conductive fillers coated and interconnected by liquid metal.

(4) Place the obtained three-dimensional network structure material with continuous voids in a refrigerator or a liquid nitrogen low-temperature environment to solidify the liquid metal gallium; then immerse the material in liquid silicone resin and place it in a vacuum furnace (vacuum degree 10Pa), the liquid polymer is filled into the pores of the material through the process of vacuum impregnation.

(5) Clean up excess residual resin on the surface of the three-dimensional network structure material filled with liquid silicone resin, put the sample in a constant temperature box, and cross-link and solidify the high molecular polymer at a temperature of 120°C for 40 minutes; After curing, use a cutter to limit its thickness to 1.5mm, and obtain a gallium-based liquid metal enhanced thermal conduction gasket.

(6) Put epoxy resin and diamond particles in a mortar with a volume ratio of 1:1, and stir repeatedly until a material that is fully mixed with a polymer and a thermally conductive filler is obtained, and then use a 0.2mm thick screen to mix the above mixed material It is coated on the plastic film by screen printing, and two samples need to be made to meet the combination requirements of the upper and lower sides.

(7) Place the first plastic film coated with a mixture of polymer and thermally conductive filler on the above liquid metal reinforced thermally conductive gasket, and use plasticine to suspend it, and place it in a vacuum laminating machine for vacuuming. Vacuum to 10Pa, and then press and bond them under a pressure of 1.16×106Pa (holding time 30min).

(8) Put the sample into a constant temperature box and wait for the silicone resin to be cross-linked and cured at a temperature of 120° C., and the curing time is 40 minutes.

(9) Put the uncoated side of the obtained liquid metal reinforced thermal pad facing upwards, place the annular groove mold shown in Figure 3 on the upper surface of the liquid metal reinforced thermal pad, and fill a circle of polymer at a distance of 2 mm from the outer diameter of the pad The mixture of polymer and thermal conductive filler; then remove the mold, place the second plastic film coated with the mixed material of high molecular polymer and thermal conductive filler above the above liquid metal reinforced thermal conductive gasket, and place it in a vacuum laminating machine evacuate to 10Pa, and press them again under the pressure of 1.16×106Pa (holding time 30min). Under the pressure, the mixed material can cover the surface of the gallium-based liquid metal reinforced thermal pad and fill it to its Surrounding: The mixed material forms a packaging gasket on the upper, lower and surrounding sides of the gallium-based liquid metal enhanced thermal conductivity gasket.

(10) Put the sample into a constant temperature box and wait for the silicone resin to be cross-linked and cured at a temperature of 120°C. The curing time is 40 minutes, and finally a composite thermal interface material with liquid metal enhanced heat transfer is obtained.

Taking Example 1 as an example, a thermal conductivity tester (DRL-IV thermal resistance tester produced by Xiangtan Xiangyi Company in China) was used for the experiment, and the thermal conductivity of the composite material was mainly evaluated by the ASTM D5470 steady-state heat flow method. During the test, the temperature of the heat source was set to 125°C, and the temperature of the cold source was set to 5°C, so that the average temperature at the sample was 60°C during the test. The computer system will complete data collection, data processing and instrument control to realize fully automatic testing. The structure principle of the test equipment is shown in Fig. 5.

After exporting the test parameter results, the thermal conductivity λ _S can be calculated according to the following formula:

In the formula: λs——the thermal conductivity of the measured sample

λ _cu ——the thermal conductivity of the average temperature of the copper hot pole

A _cu ——The cross-sectional area of the hot pole perpendicular to the direction of heat flow

As—sample cross-sectional area perpendicular to the direction of heat flow

t ₁ , t ₂ ——Temperatures of thermocouples T1 and T2

t ₃ , t ₄ ——Temperatures of thermocouples T3 and T4

Ls - the length of the sample

L ₁ ——The distance between thermocouple 1 and thermocouple 2

L ₂ ——The distance between the thermocouple 2 and the end face of the heat source

After testing, it can be obtained that the overall thermal conductivity of the composite thermal interface material is 23.4W/(m·K).

In the Chinese invention patent CN108912683B, the thermal conductivity of the gallium-based liquid metal enhanced thermal conductivity pad mentioned in Example 1 is 29.28W/(m K). In this embodiment, due to the introduction of both sides of the thermal pad, the compound The overall thermal performance of the material will be reduced; but traditional thermal interface materials include thermal conductive silicone grease, phase change materials and thermal conductive silica gel sheets, etc., and their thermal conductivity is only 1-8W/(m K). Although the thermal conductivity of the interface material is not as good as the direct use of liquid metal to enhance the thermal conductivity of the gasket, its thermal conductivity is much higher than that of the traditional thermal interface material, and the thermal conductivity of the existing composite thermal interface material is not far behind.

Also taking Example 1 as an example, as shown in Figure 6, the anti-leakage test of the composite heat conduction gasket with liquid metal enhanced heat transfer is carried out:

1. The thermal pad was bent more than 45° by hand, and no liquid metal leakage occurred.

2. Use a heavy object to apply a load in the vertical direction of the thermal pad. The weight used is an iron block with a size of 50mm×50mm

×30mm, weight 600g; the sample was placed between two acrylic plates, and an iron block was placed on the top, and the sample did not leak after standing still.

It can be seen from the above embodiments that the packaging gasket of the present invention is arranged on the upper, lower and surrounding sides of the gallium-based liquid metal enhanced thermal conduction gasket, and the sealing performance of the gallium-based liquid metal enhanced thermal conduction gasket is ensured through an integrated molding process, effectively avoiding The composite thermal interface material containing liquid metal is in direct contact with the heat dissipation substrate, which improves safety, prevents the internal liquid metal from leaking from the top, bottom and surroundings of the thermal pad, and serves as an isolation between the liquid metal and the heat dissipation substrate The effect is to prevent liquid metal from corroding the surface of the radiator. Because the present invention adopts the mold with the function of filling the surroundings of the heat-conducting gasket, the mixture of high molecular polymer and heat-conducting filler can be filled around the liquid metal-enhanced heat-conducting gasket, so the heat-conducting gasket can not only prevent the internal liquid metal from flowing from the heat-conducting gasket Leakage from the top and bottom of the heat sink avoids the problem of corrosion caused by direct contact between the liquid metal and the heat dissipation substrate. It can also effectively prevent the liquid metal from overflowing from the surroundings of the thermal pad, completely eliminating the risk of short circuit caused by the liquid metal.

The packaging gasket of the present invention is used as a liquid metal escape flow blocking medium and is also a heat transfer medium; the packaging gasket is mainly formed of a high molecular polymer and a thermally conductive filler; and the gallium-based liquid metal enhanced thermal conductive gasket also includes a high molecular polymer and a Thermally conductive filler, such raw materials effectively ensure the heat transfer between the package gasket and the gallium-based liquid metal enhanced thermal conduction gasket and avoid the problem of excessive stress after heating, resulting in a loose combination of the package gasket and the gallium-based liquid metal enhanced thermal conduction gasket And the heat transfer is not timely.

The gallium-based liquid metal reinforced thermal conduction gasket of the present invention is composed of gallium-based liquid metal, thermally conductive fillers and polymers. The efficient three-dimensional heat conduction channel constructed by liquid metal and thermally conductive fillers makes the composite material have extremely high thermal conductivity, and the polymer Polymers give the material good support strength and flexibility.

The composite thermal interface material based on liquid metal enhanced heat transfer in the present invention takes into account high thermal conductivity and liquid metal anti-leakage function, and effectively solves the problem of direct contact between liquid metal and radiator in Chinese invention patent CN108912683B, and realizes better liquid metal Sealing greatly improves the availability of thermally conductive materials.

Claims (10)

1. The composite thermal interface material based on liquid metal enhanced heat transfer is characterized in that it is composed of a gallium-based liquid metal enhanced thermal conduction gasket and packaging gaskets arranged on the gallium-based liquid metal enhanced thermal conduction gasket and around it; The gallium-based liquid metal reinforced thermal conductivity gasket is obtained by paving the small particle size mixed material particles with a particle size of 1-1000 μm, pressing and forming, and then uniformly filling high molecular polymer and crosslinking and curing; the small particle size mixed material It is obtained by stirring the gallium-based liquid metal and the heat-conducting filler evenly, crushing and granulating, and sieving; the packaging gasket is obtained by stirring the high-molecular polymer and the heat-conducting filler evenly to obtain a mixed material; the mixed material is fixed on the gallium The base liquid metal strengthens the top, bottom and surroundings of the thermal pad, and then cross-links and solidifies the high molecular polymer; The gallium-based liquid metal is pure gallium, gallium-indium alloy, gallium-tin alloy, gallium-zinc alloy, gallium-indium-tin alloy, gallium-indium-zinc alloy or gallium-indium-tin-zinc alloy; the polymer is epoxy resin, Silicone resin or polyurethane resin. 2. The composite thermal interface material based on liquid metal enhanced heat transfer according to claim 1, characterized in that, in terms of volume percentage, gallium-based liquid metal accounts for 5% of the liquid metal enhanced thermal conductivity gasket -40%, thermally conductive fillers account for 35%-75%, and polymers account for 20%-60%. 3. The composite thermal interface material based on liquid metal enhanced heat transfer according to claim 1, wherein the thermally conductive filler is a metal thermally conductive filler and/or an inorganic non-metallic thermally conductive filler, and the particle size of the thermally conductive filler is 0.1 -300 μm; The uniformly filled high molecular polymer is to fill the liquid high molecular polymer into the pores of the three-dimensional network structure material formed by pressing and forming the mixed material particles with small particle size through the vacuum impregnation process. . 4. The composite thermal interface material based on liquid metal enhanced heat transfer according to claim 3, wherein the metal thermally conductive filler is copper, nickel, molybdenum, tungsten, copper alloy, nickel alloy, molybdenum alloy or tungsten One or more of alloys; the inorganic non-metallic thermally conductive filler is one or more of boron nitride, aluminum oxide, aluminum nitride, silicon nitride, graphite, diamond, graphene and carbon nanotubes; The vacuum degree of the vacuum impregnation process is 1-1000Pa. 5. The composite thermal interface material based on liquid metal enhanced heat transfer according to claim 1, characterized in that, the molding process is used to fix the mixed material on the upper, lower and surrounding sides of the gallium-based liquid metal enhanced heat conduction gasket through the following steps Method implementation: Put the high molecular polymer and the thermal conductive filler in the mixer, and stir repeatedly until the high molecular polymer and the thermal conductive filler are fully mixed to obtain the mixed material; the mixed material is coated on the plastic film by the screen printing process; the second A plastic film coated with mixed materials is placed on top of the gallium-based liquid metal enhanced thermal conduction gasket; vacuum press molding realizes the combination of the liquid metal enhanced thermal conduction gasket and the first surface packaging gasket; The gallium-based liquid metal-enhanced thermal conduction gasket is combined with the opposite side of the packaging gasket on the first side facing up, and an annular groove mold is arranged on the outer periphery of the gallium-based liquid metal-enhanced thermal conduction gasket, and the mixed material is filled in the annular groove mold; the other A plastic film coated with a polymer mixture material is placed on the gallium-based liquid metal-enhanced thermal conduction gasket, vacuum-pressed, and the mixture material is combined with the package gasket on the upper surface and surroundings of the gallium-based liquid metal-enhanced heat conduction gasket. 6. The composite thermal interface material based on liquid metal enhanced heat transfer according to claim 5, characterized in that, the vacuum pressing is to create a vacuum environment in the vacuum laminating machine first, and under the action of pressure, the mixed material Pasted on the gallium-based liquid metal reinforced heat conduction gasket; the width of the hollow ring of the annular groove is 2-5 mm. 7. The composite thermal interface material based on liquid metal enhanced heat transfer according to claim 6, characterized in that, the pressure is 10kPa-500kPa, and the holding time is 0.1min-60min; 1-1000Pa. 8 . The composite thermal interface material based on liquid metal enhanced heat transfer according to claim 5 , wherein the thickness of the screen in the screen printing process is 0.1-1 mm. 9 . The composite thermal interface material based on liquid metal enhanced heat transfer according to claim 1 , characterized in that, the crosslinking curing temperature is 20° C.-200° C. and the holding time is 0.1 min-60 min. 10. The preparation method of the composite thermal interface material based on liquid metal enhanced heat transfer according to any one of claims 1-9, characterized in that it comprises the following steps: 1) Stir the gallium-based liquid metal and the thermally conductive filler evenly; pulverize and granulate, and sieve to obtain mixed material particles with a particle size of 1-1000 μm; 2) Flatten the particles of the mixed material with small particle size and press them into shape to obtain a liquid metal/thermally conductive filler three-dimensional network structure material; fill the liquid high molecular polymer into the liquid metal/thermally conductive filler three-dimensional network structure material through a vacuum infiltration process In the pores of the network structure material; after cross-linking and solidification, a gallium-based liquid metal enhanced thermal conductivity gasket is obtained; 3) Stir the high molecular polymer and the thermally conductive filler evenly to obtain a mixed material of the high molecular polymer and the thermally conductive filler; use a molding process to fix the mixed material of the high molecular polymer and the thermally conductive filler on the upper and lower sides of the gallium-based liquid metal reinforced thermally conductive gasket and Four weeks, the high molecular polymer is cross-linked and solidified to obtain a composite thermal interface material based on liquid metal enhanced heat transfer.