Liquid metal-based composite heat-conducting silicone grease, preparation method and application thereof

Abstract

The application belongs to the technical field of heat-conducting materials, and provides a liquid metal-based composite heat-conducting silicone grease, a preparation method and application thereof. The modified silicone oil, liquid metal, heat-conducting auxiliary filler and hydrophobic fumed silica with specific proportions are used as main components of the liquid metal-based composite heat-conducting silicone grease. The prepared liquid metal-based composite heat-conducting silicone grease has high heat-conducting coefficient (6.05-10.0 W / mk), low thermal resistance (0.01-0.03 DEG C*cm / W), and can maintain good appearance in double 85 and high-temperature 125 DEG C tests and temperature cycle aging tests, and thus is suitable for the assembly interface of power modules and heat sinks with high-power heat dissipation requirements, and improves the heat dissipation efficiency. 2 / W), and can maintain good appearance in double 85 and high-temperature 125 DEG C tests and temperature cycle aging tests, and thus is suitable for the assembly interface of power modules and heat sinks with high-power heat dissipation requirements, and improves the heat dissipation efficiency.

Description

Technical Field

[0001] This invention relates to the field of thermal conductive materials technology, and more specifically, to a liquid metal-based composite thermal conductive grease, its preparation method, and its application. Background Technology

[0002] In recent years, with the development of communication and computing products, the integration and power consumption of chips have increased significantly. Thermal management of power devices has gradually become a research hotspot and a key competitive indicator for products. Thermal interface materials play an indispensable role in improving heat dissipation efficiency, and the requirements for their thermal conductivity are becoming increasingly stringent. Furthermore, with the increasing number of application scenarios, the reliability requirements for thermal interface materials are also rising.

[0003] Common thermal interface materials mainly include thermal grease, thermal gel, thermal pads, and thermally conductive phase change materials. Among these, thermal grease is widely used due to its excellent processability and heat dissipation efficiency. However, thermal grease still falls short in heat dissipation efficiency for high-power devices, failing to effectively balance high thermal conductivity (≥6W / mK) and low thermal resistance (≤0.03℃·cm). 2 The appearance reliability requirements (e.g., 85°C and 85% RH, simultaneously meeting the requirements of 85°C and 85% RH), 125°C, and temperature cycling aging tests all failed to maintain a good appearance.

[0004] Liquid metals possess high thermal conductivity due to their unique physical properties, significantly improving heat dissipation efficiency. However, they also present potential problems such as electrical conductivity, corrosiveness, and complex manufacturing processes, requiring high standards for manufacturing and installation maintenance. This has limited the widespread adoption of liquid metals in interfacial heat dissipation. To address these issues, two main approaches are currently being explored: one is to use liquid metal as the liquid phase, combined with other thermally conductive fillers (metal powder or inorganic thermally conductive fillers) to create a liquid metal paste. This improves thixotropy and alleviates the wetting problem at the heat dissipation interface, reducing the risk of leakage. However, this approach cannot address the corrosion issues at certain interfaces (such as aluminum). Furthermore, the lack of surface coating on liquid metals (primarily gallium and its alloys) prevents the resolution of continuous oxidation under 85°C conditions. Secondly, silicone grease is made by compounding silicone oil, liquid metal and other thermally conductive auxiliary fillers. Currently, methyl silicone oil is mainly used as the auxiliary liquid phase. This method can improve the corrosion problem of liquid metal. However, the surface coating structure of the formed liquid metal has poor stability. In the scraping operation, vibration test and appearance reliability test (double 85, high temperature 125℃ and temperature cycling aging test), liquid metal precipitation, hydrolysis and cracking are very likely to occur.

[0005] Therefore, there is an urgent need to develop a liquid metal-based thermal conductive material that combines high thermal conductivity, low thermal resistance, and excellent reliability. Summary of the Invention

[0006] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a liquid metal-based composite thermal grease, its preparation method, and its application. The liquid metal-based composite thermal grease provided by this invention has a high thermal conductivity (reaching 6.05–10.0 W / mK) and low thermal resistance (as low as 0.01–0.03 °C·cm). 2 / W), thixotropic index 3.3~4.2, high reliability (under the conditions of double 85, high temperature 125℃ and temperature cycling aging test, the appearance is well maintained, without cracking or slippage).

[0007] The first aspect of the present invention provides a liquid metal-based composite thermal grease.

[0008] Specifically, a liquid metal-based composite thermal grease, by weight, comprises the following components:

[0009] 100 parts modified silicone oil, 2000-5000 parts liquid metal, 0-500 parts thermally conductive auxiliary filler, and 0.2-10 parts hydrophobic fumed silica;

[0010] The modified silicone oil includes single-terminated alkoxy-capped silicone oil containing ethylene short chains and branched silicone oil;

[0011] The structure of the single-ended alkoxy-terminated silicone oil containing ethylene short chains is shown in formula (Ⅰ):

[0012]

[0013] Wherein, R1 is an alkoxy group containing 1 to 3 carbons, R2 is CH3— or CH2=CH—, and n represents the average degree of polymerization, which is an integer from 10 to 50;

[0014] The structure of the branched silicone oil is shown in formula (Ⅱ):

[0015]

[0016] Where the sum of α + β + γ represents the average degree of polymerization, the sum of α + β + γ is an integer from 2 to 30, and 1 ≤ β ≤ 2, α, β, and γ are all integers, and R3 is... m represents the average degree of polymerization, and m is an integer from 10 to 50.

[0017] Unlike the Si-O-Si main chain structure of silicone oil, the ethylene short-chain single-ended alkoxy-terminated silicone oil used in this invention has a higher bond energy in its main chain structure than the Si-O-Si chain, resulting in better thermal stability. When surface-treated with liquid metal, it improves the stability of the coating structure and mitigates the problem of liquid metal precipitation. The silicon-oxygen-silicon chains in the branched silicone oil are flexible segments. This invention enhances the cohesiveness of the liquid metal-based composite thermal grease by increasing its branching degree, thereby improving its crack resistance and appearance reliability. This invention uses two different modified silicone oils in combination: the ethylene short-chain single-ended alkoxy-terminated silicone oil is linked to the liquid metal at one end, while the other end is embedded in the branched silicone oil, effectively ensuring the stability of the liquid metal in the modified silicone oil system.

[0018] Preferably, the liquid metal-based composite thermal grease comprises, by weight, the following components: 100 parts modified silicone oil, 3000-4500 parts liquid metal, 0-300 parts thermally conductive auxiliary filler, and 5-10 parts hydrophobic fumed silica.

[0019] More preferably, the liquid metal-based composite thermal grease comprises, by weight, the following components: 100 parts modified silicone oil, 3200-4500 parts liquid metal, 60-200 parts thermally conductive auxiliary filler, and 8-10 parts hydrophobic fumed silica.

[0020] Preferably, the viscosity of the ethylene short-chain single-ended alkoxy-terminated silicone oil at 25°C is 10–40 mPa·s.

[0021] More preferably, the viscosity of the ethylene short-chain single-ended alkoxy-terminated silicone oil at 25°C is 15–30 mPa·s.

[0022] Preferably, the branched silicone oil has a viscosity of 50–10000 mPa·s at 25°C.

[0023] More preferably, the branched silicone oil has a viscosity of 100–5000 mPa·s at 25°C.

[0024] More preferably, the branched silicone oil has a viscosity of 100–400 mPa·s at 25°C.

[0025] Preferably, the mass ratio of the ethylene-short-chain, single-ended alkoxy-terminated silicone oil to the branched silicone oil is 1:1 to 9. This invention combines the two silicone oils in a suitable ratio to coat liquid metal, thereby achieving excellent anti-aging properties and appearance reliability. If the mass of the ethylene-short-chain, single-ended alkoxy-terminated silicone oil accounts for less than 10% of the total mass of the modified silicone oil, the coating effect of the modified silicone oil on the liquid metal will be poor, affecting appearance reliability. If the mass of the ethylene-short-chain, single-ended alkoxy-terminated silicone oil accounts for more than 50% of the total mass of the modified silicone oil, problems such as aging cracks and slippage will also occur.

[0026] Preferably, the ethylene short-chain-containing single-ended alkoxy-terminated silicone oil is at least one of the structures shown in formulas (III) to (V):

[0027]

[0028]

[0029] Where a represents the average degree of polymerization, and a is an integer from 10 to 30.

[0030] More preferably, the ethylene short-chain-containing single-ended alkoxy-terminated silicone oil has at least one of the structures shown in Formulas 1 to 4 below:

[0031]

[0032] Preferably, the sum of α+β+γ is an integer from 10 to 30, and m is an integer from 20 to 50.

[0033] More preferably, the branched silicone oil has a structure of at least one of the structures shown in Formulas 5 to 7:

[0034]

[0035] Preferably, the preparation method of the ethylene short-chain-containing single-ended alkoxy-terminated silicone oil includes the following steps:

[0036] Vinyl-terminated silicone oil, trialkoxysilane (or trimethoxyhydrosilane, triethoxysilane) and caster platinum catalyst are mixed and reacted at 60-110°C for 30-60 min. Byproducts are removed under vacuum and the mixture is cooled to obtain the single-terminated alkoxy silicone oil containing ethylene short chains.

[0037] Preferably, the vinyl-terminated silicone oil is a vinyl-terminated silicone oil with an average degree of polymerization of 5 to 40.

[0038] More preferably, the vinyl-terminated silicone oil is a vinyl-terminated silicone oil with an average degree of polymerization of 10 to 30.

[0039] Preferably, the vacuum degree of the vacuum removal is -0.095 to -0.098 MPa, and / or the vacuum removal temperature is 100 to 190°C, and / or the vacuum removal time is 30 to 120 min.

[0040] Preferably, the method for preparing the branched silicone oil includes the following steps:

[0041] A single-end alkenyl-terminated silicone oil, a side-containing hydrogen polysiloxane, and a caster platinum catalyst are mixed and reacted at 60–110 °C for 30–60 min until the alkenyl groups are completely reacted. Then, the alkenyl groups are removed under vacuum and the mixture is cooled to obtain the branched silicone oil.

[0042] Preferably, the single-end alkenyl-terminated silicone oil is a single-end vinyl-terminated silicone oil.

[0043] More preferably, the single-end alkenyl-terminated silicone oil is a single-end vinyl-terminated silicone oil with an average degree of polymerization of 10 to 60.

[0044] More preferably, the single-end alkenyl-terminated silicone oil is a single-end vinyl-terminated silicone oil with an average degree of polymerization of 20 to 50.

[0045] Preferably, the side-hydrogenated polysiloxane is a side-hydrogenated polysiloxane with a hydrogen content of 0.1% to 0.3%.

[0046] Preferably, the vacuum degree of the vacuum removal is -0.095 to -0.098 MPa, and / or the vacuum removal temperature is 100 to 190°C, and / or the vacuum removal time is 30 to 120 min.

[0047] Preferably, the melting point of the liquid metal is -20 to 50°C.

[0048] Preferably, the liquid metal is at least one of gallium, gallium-indium alloy, gallium-indium-tin, and gallium-indium-bismuth alloy.

[0049] Preferably, the average particle size of the thermally conductive auxiliary filler is 0.1–5 μm, and / or the particle size D of the thermally conductive auxiliary filler is… 100 ≤15μm, and / or, the thermally conductive auxiliary filler is spherical or near-spherical in shape. Spherical or near-spherical thermally conductive auxiliary fillers help increase the filler volume and help reduce viscosity and thermal resistance.

[0050] Preferably, the thermally conductive auxiliary filler is at least one selected from zinc oxide, aluminum oxide, aluminum nitride, silver, copper, and nickel.

[0051] Preferably, the hydrophobic fumed silica is at least one of silazane-modified hydrophobic fumed silica, polydimethylsiloxane-modified hydrophobic fumed silica, and chlorosilane-modified hydrophobic fumed silica.

[0052] More preferably, the hydrophobic fumed silica is at least one of Cabot's TS-720, Cabot's TS-530, Tokuyama's KS-20SC, and Tokuyama's DM-20S.

[0053] A second aspect of the present invention provides a method for preparing liquid metal-based composite thermal grease.

[0054] A method for preparing a liquid metal-based composite thermal grease includes the following steps:

[0055] Modified silicone oil and liquid metal were added sequentially to obtain a paste, and then the remaining components were added to prepare the liquid metal-based composite thermal grease.

[0056] Preferably, the liquid metal is melted to a liquid state at 30-40°C before use.

[0057] Preferably, modified silicone oil and liquid metal are added sequentially, and then stirring is started at a speed of 1400-2000 r / min and / or for a time of 1-20 min.

[0058] Preferably, the stirring is carried out in a planetary gravity stirred tank.

[0059] Preferably, after obtaining the paste, thermally conductive auxiliary filler and hydrophobic fumed silica are added sequentially to prepare the liquid metal-based composite thermally conductive grease.

[0060] More preferably, after obtaining the paste, the paste is transferred to a planetary reactor, and then thermally conductive auxiliary filler and hydrophobic fumed silica are added in sequence, and stirred at a stirring speed of 10-15 Hz, and / or the vacuum degree of the planetary reactor is -0.09 MPa to -0.1 MPa, until a uniform paste is formed.

[0061] A third aspect of the present invention provides an application of liquid metal-based composite thermal grease.

[0062] Application of a liquid metal-based composite thermal grease in the fields of communication networks, new energy vehicles, electronic products, or artificial intelligence devices.

[0063] A fourth aspect of the present invention provides a thermal interface material.

[0064] A thermal interface material, comprising the liquid metal-based composite thermally conductive silicone grease.

[0065] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0066] This invention uses a specific ratio of modified silicone oil, liquid metal, thermally conductive auxiliary filler, and hydrophobic fumed silica as the main components of a liquid metal-based composite thermal grease. The modified silicone oil includes ethylene-short-chain, single-ended alkoxy-terminated silicone oil and branched silicone oil. The ethylene-short-chain, single-ended alkoxy-terminated silicone oil has a higher bond energy than the Si-O-Si chain, exhibiting better thermal stability. Furthermore, the ethylene-short-chain alkoxy-terminated silicone oil can improve the stability of the coating structure and mitigate liquid metal precipitation during surface treatment. The branched silicone oil contains flexible Si-O-Si segments with a high degree of branching, thereby improving the crack resistance and appearance reliability of the liquid metal-based composite thermal grease. The liquid metal-based composite thermal grease prepared by this invention possesses both high thermal conductivity (reaching 6.05–10.0 W / mK) and low thermal resistance (down to 0.01–0.03 °C·cm). 2 With good reliability, it maintains a good appearance (no cracking or slippage) under high temperature (125℃), high temperature and high humidity (dual 85) and temperature cycling conditions, making it suitable for the assembly interface of power modules and heat sinks with high power heat dissipation requirements, thus improving heat dissipation efficiency. Attached Figure Description

[0067] Figure 1 The images show the appearance of the liquid metal-based composite thermal grease prepared in Example 1 of this invention after being tested under three different conditions: dual 85°C, 125°C, and cyclic aging.

[0068] Figure 2 The images show the appearance of the liquid metal-based composite thermal grease prepared in Example 2 of this invention after being tested under three different conditions: dual 85°C, 125°C, and cyclic aging.

[0069] Figure 3 The images show the appearance of the liquid metal-based composite thermal grease prepared in Example 3 of this invention after being tested under three different conditions: dual 85°C, 125°C, and cyclic aging.

[0070] Figure 4 The images show the appearance of the liquid metal-based composite thermal grease prepared in Example 4 of this invention after being tested under three different conditions: dual 85°C, 125°C, and cyclic aging.

[0071] Figure 5 The images show the appearance of the liquid metal-based composite thermal grease prepared in Example 5 of this invention after being tested under three different conditions: dual 85°C, 125°C, and cyclic aging.

[0072] Figure 6 The images show the appearance of the liquid metal-based composite thermal grease prepared in Example 6 of this invention after being tested under three different conditions: dual 85°C, 125°C, and cyclic aging.

[0073] Figure 7 The images show the appearance of the liquid metal-based composite thermal grease prepared in Example 7 of this invention after being tested under three different conditions: dual 85°C, 125°C, and cyclic aging.

[0074] Figure 8 The images show the appearance of the liquid metal-based composite thermal grease prepared in Example 8 of this invention after being tested under three different conditions: dual 85°C, 125°C, and cyclic aging.

[0075] Figure 9 The images show the appearance of the liquid metal-based composite thermal grease prepared in Example 9 of this invention after being tested under three different conditions: dual 85°C, 125°C, and cyclic aging.

[0076] Figure 10 The images show the appearance of the liquid metal-based composite thermal grease prepared in Comparative Example 1 after testing under three different conditions: dual 85°C, 125°C, and cyclic aging.

[0077] Figure 11 The images show the appearance of the liquid metal-based composite thermal grease prepared in Comparative Example 2 after testing under three different conditions: dual 85°C, 125°C, and cyclic aging.

[0078] Figure 12 The images show the appearance of the liquid metal-based composite thermal grease prepared in Comparative Example 3 after testing under three different conditions: dual 85°C, 125°C, and cyclic aging.

[0079] Figure 13 The images show the appearance of the liquid metal-based composite thermal grease prepared in Comparative Example 5 after testing under three different conditions: dual 85°C, 125°C, and cyclic aging.

[0080] Figure 14 This is an optical microscope image of the liquid metal-based composite thermal grease prepared in Example 1 of the present invention;

[0081] Figure 15 An optical microscope image of the liquid metal-based composite thermal grease prepared in Example 2 of this invention;

[0082] Figure 16 This is an optical microscope image of the liquid metal-based composite thermal grease prepared in Example 3 of the present invention;

[0083] Figure 17 This is an optical microscope image of the liquid metal-based composite thermal grease prepared in Example 4 of the present invention. Detailed Implementation

[0084] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0085] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0086] The main raw materials involved in the various embodiments and comparative examples of this invention are as follows:

[0087] 1. Preparation of silicone oils with ethylene short chains and single-ended alkoxy groups

[0088] Formula 1: 100g of vinyl-terminated silicone oil with an average degree of polymerization of 30, 5.52g of trimethoxysilane, and 0.1g of caster platinum catalyst were added to a reaction vessel and mixed evenly. The mixture was stirred and slowly heated to 80℃ and reacted for 60min. After the vinyl reaction was confirmed to be complete, the mixture was vacuum-removed for 60min under a vacuum of -0.098MPa and a temperature of 150℃, and then cooled to obtain Formula 1.

[0089] The structural formula of Equation 1 is shown below:

[0090]

[0091] Formula 2: 100g of vinyl-terminated silicone oil with an average degree of polymerization of 20, 8.11g of trimethoxysilane and 0.1g of caster platinum catalyst were added to a reaction vessel, mixed evenly, and the mixture was slowly heated to 80℃ while stirring, and reacted for 60min; under vacuum conditions of -0.098MPa and 150℃, the mixture was vacuum desorbed for 60min, cooled, and Formula 2 was obtained.

[0092] The structural formula of Equation 2 is shown below:

[0093]

[0094] Formula 3: 100g of vinyl-terminated silicone oil with an average degree of polymerization of 10, 15.25g of trimethoxysilane and 0.1g of caster platinum catalyst were added to a reaction vessel, mixed evenly, and the mixture was slowly heated to 80℃ while stirring, and reacted for 60min; under vacuum conditions of -0.098MPa and 150℃, the mixture was vacuum desorbed for 60min, cooled, and Formula 3 was obtained.

[0095] The structural formula of Equation 3 is shown below:

[0096]

[0097] Formula 4: 100g of vinyl-terminated silicone oil with an average degree of polymerization of 15, 14.23g of triethoxysilane, and 0.1g of caster platinum catalyst were added to a reaction vessel and mixed evenly. The mixture was stirred and slowly heated to 80°C and reacted for 60min. After the vinyl reaction was confirmed to be complete, the mixture was vacuum-removed for 60min under a vacuum of -0.098MPa and a temperature of 150°C. The mixture was then cooled to obtain Formula 4.

[0098] The structural formula of Formula 4 is shown below:

[0099]

[0100] 2. Preparation of branched silicone oil

[0101] Formula 5: 100g of single-end vinyl-terminated silicone oil with an average degree of polymerization of 50, 30g of side-containing hydrogen polysiloxane with a hydrogen content of 0.1%, and 0.1g of caster platinum catalyst are added to a reaction vessel and mixed evenly. While stirring, the temperature is slowly raised to 80℃ and reacted for 60min. After the vinyl reaction is complete, the mixture is vacuum-removed for 60min under a vacuum of -0.098MPa and a temperature of 150℃. The mixture is then cooled to obtain Formula 5.

[0102] The structural formula of Formula 5 is shown below:

[0103]

[0104] Formula 6: 100g of single-end vinyl-terminated silicone oil with an average degree of polymerization of 30, 44g of side-containing hydrogen polysiloxane with a hydrogen content of 0.1%, and 0.01g of caster platinum catalyst are added to a reaction vessel and mixed evenly. The mixture is stirred and slowly heated to 80℃ and reacted for 60min. Vacuum removal is carried out for 60min under the conditions of vacuum degree of -0.098MPa and temperature of 150℃. The mixture is then cooled to obtain Formula 6.

[0105] The structural formula of Formula 6 is shown below:

[0106]

[0107] Formula 7: 100g of single-end vinyl-terminated silicone oil with an average degree of polymerization of 20, 32.3g of side-containing hydrogen polysiloxane with a hydrogen content of 0.2%, and 0.1g of caster platinum catalyst are added to a reaction vessel and mixed evenly. The mixture is stirred and slowly heated to 80℃ and reacted for 60min. Vacuum removal is carried out for 60min under the conditions of vacuum degree of -0.098MPa and temperature of 150℃. The mixture is then cooled to obtain Formula 7.

[0108] The structural formula of Formula 7 is shown below:

[0109]

[0110] Formula 8: 100g of single-end vinyl-terminated silicone oil with an average degree of polymerization of 20, 21.5g of side-containing hydrogen polysiloxane with a hydrogen content of 0.3%, and 0.1g of caster platinum catalyst are added to a reaction vessel and mixed evenly. While stirring, the temperature is slowly raised to 80℃ and reacted for 60min. Under vacuum conditions of -0.098MPa and 150℃, the reaction is vacuum-removed for 60min. After cooling, the branched silicone oil of Formula 8 is obtained.

[0111] The structural formula of Formula 8 is shown below:

[0112]

[0113] 3. Preparation of single-ended alkoxy-terminated silicone oils without ethylene short chains

[0114] Formula 9: 100g of single-terminated hydroxymethyl silicone oil with an average degree of polymerization of 20, 10.1g of methyl orthosilicate, and 0.2g of dibutylamine formate are added to a reaction vessel, mixed evenly, and the mixture is slowly heated to 80℃ while stirring, and reacted for 60min; under vacuum conditions of -0.098MPa and 150℃, the mixture is vacuum-removed for 60min, cooled, and Formula 9 is obtained.

[0115] The structural formula of Formula 9 is shown below:

[0116]

[0117] 4. Thermally conductive auxiliary filler:

[0118] The average particle size of zinc oxide is 0.6 μm, D 100 It is 5μm;

[0119] The average particle size of the silver powder is 3 μm, D 100 It is 12μm;

[0120] The average particle size of alumina is 2.5 μm, D 100 It is 8μm;

[0121] The average particle size of aluminum nitride is 2.6 μm, D 100 It is 10μm.

[0122] 5. Hydrophobic fumed silica: Manufacturer: Cabot, Model: TS-720.

[0123] Example 1

[0124] A liquid metal-based composite thermal grease, comprising the components shown in Table 1 below.

[0125] The preparation method of the above-mentioned liquid metal-based composite thermal grease includes the following steps:

[0126] (1) Place the liquid metal in a 35°C oven to melt it into a liquid state. The average particle size of the dispersed liquid metal is 30-60 μm. Set aside for later use.

[0127] (2) Add ethylene short-chain single-ended alkoxy-terminated silicone oil (Formula 1), branched silicone oil (Formula 6) and liquid metal sequentially to a planetary gravity stirred tank. Disperse at high speed for 10 minutes at a speed of 1600 r / min until a uniform paste is obtained.

[0128] (3) Transfer the paste to the planetary reactor, add the thermally conductive auxiliary filler and hydrophobic fumed silica in sequence, and stir thoroughly under the conditions of stirring frequency of 12Hz and vacuum degree of -0.098MPa until a uniform paste product is formed, which is the liquid metal-based composite thermally conductive grease.

[0129] Examples 2-9

[0130] Examples 2-9 provide liquid metal-based composite thermal greases, which differ from Example 1 in that they have different components, as shown in Table 1. The preparation method is the same as in Example 1.

[0131] Comparative Examples 1-5

[0132] Comparative Examples 1-5 provide liquid metal-based composite thermal greases, the specific components of which are shown in Table 1. Comparative Examples 1-3 and 5 differ from Example 1 in composition, but are prepared using the same method as Example 1. Comparative Example 4 has the same composition as Example 1, but is prepared using a different method, as detailed below:

[0133] (1) Place the liquid metal in a 35°C oven to melt it into a liquid state and set aside;

[0134] (2) Add ethylene short-chain single-ended alkoxy-terminated silicone oil, branched silicone oil, thermally conductive auxiliary filler, and hydrophobic fumed silica to a planetary gravity stirred tank in sequence. Set the rotation speed to 1600 r / min and disperse at high speed for 10 min until a uniform paste is formed.

[0135] (3) Transfer the paste to a planetary reactor, add liquid metal, and stir thoroughly at a stirring frequency of 12 Hz and a vacuum degree of -0.098 MPa until a uniform paste product is formed, which is the liquid metal-based composite thermal grease.

[0136] Product effectiveness test

[0137] 1. Testing Method

[0138] (1) Thermal conductivity: The thermal conductivity of each paste was tested at 80℃ @ 30psi using an interface material thermal resistance and thermal conductivity meter (model: LW-9389).

[0139] (2) Viscosity@25℃: The viscosity of each paste was tested under the conditions of 4#@5r using a CAP 2000 viscometer.

[0140] (3) Thixotropic index: The viscosity of each paste under low shear (7#@1rpm) and high shear (7#@10rpm) was tested using an HA type rotational viscometer, and then the viscosity ratio under low shear and high shear was calculated.

[0141] (4) Thermal resistance: The thermal resistance of each paste was tested at 80℃ @ 30psi using an interface material thermal resistance and thermal conductivity meter (model: LW-9389).

[0142] (5) Appearance reliability:

[0143] The sample was uniformly coated between two glass slides and assembled. After assembly, the sample was kept as centered as possible, with a thickness of 0.1–0.15 mm and a diameter of 26–30 mm. The sample fabrication was then completed. Three parallel samples were then tested under the following three different aging test conditions:

[0144] Condition ①—Double 85: Under the relative conditions of 80℃ temperature and 80% humidity, the appearance fixture is kept vertical throughout the process, and the appearance of the sample is observed after 1000h aging test.

[0145] Condition ②—125℃: Under the condition of 125℃, the appearance fixture is kept vertical throughout the process, and the appearance of the sample is observed after 1000h aging test.

[0146] Condition ③—Temperature Cycling: Under conditions of -40 to 125℃ (temperature change rate: 11℃ / min, holding time: 30min), the appearance fixture is kept vertical throughout the process, and the appearance of the sample is observed after 200 cycles of aging test.

[0147] 2. Test Results

[0148] Table 1. Components and their amounts (parts by weight) of each embodiment and comparative example.

[0149]

[0150]

[0151] As shown in the table above, the liquid metal-based composite thermal greases prepared in Examples 1-9 have thermal conductivity of 6.05-10.0 W / mk, viscosity of 80,000-127,000 mPa·s, thixotropic index of 3.3-4.2, and thermal resistance as low as 0.01-0.03 °C·cm. 2 / W, exhibiting good thermal conductivity. Furthermore, the liquid metal-based composite thermal greases of Examples 1-9, after undergoing aging tests under three different conditions—double 85°C, 125°C high temperature, and temperature cycling—showed the following results: Figure 1 AC, Figure 2 AC, Figure 3 AC, Figure 4 AC, Figure 5 AC, Figure 6 AC, Figure 7 AC, Figure 8 AC, Figure 9 As shown in AC, even after different aging tests, the appearance remains intact, without obvious cracks or slippage, indicating good appearance reliability and excellent stability.

[0152] The results of Comparative Example 1 show that when the branching degree of the branched silicone oil is high (i.e., more than 3 branches), the viscosity of the composite silicone grease increases significantly, reducing its wetting performance with the heatsink surface and increasing the difficulty of stencil printing. Simultaneously, the degree of branching greatly affects the cohesive strength of the composite silicone grease; a high degree of branching results in poor system toughness. After aging treatment, Comparative Example 1 exhibits obvious cracking, such as… Figure 10 AC.

[0153] Comparative Example 2 reduced the amount of liquid metal used. Due to the reduction in the effective heat transfer channels, the contact thermal resistance increased, leading to a decrease in thermal conductivity and thixotropic index. The appearance was as follows: Figure 11 AC.

[0154] Comparative Examples 3 and 5 show that Comparative Example 3 uses a single-ended alkoxy silicone oil without ethylene short chains, while Comparative Example 5 does not use a single-ended alkoxy silicone oil containing ethylene short chains. Although Comparative Example 3 exhibits better thermal conductivity, its thixotropic index is lower than 3, resulting in insufficient binding ability for liquid metal and a tendency for liquid metal precipitation and oxidation, leading to poor reliability. This indicates that the ethylene short chains in the single-ended alkoxy silicone oil of this invention have a significant promoting effect on improving the thixotropic effect of the composite silicone grease. The appearances of Comparative Examples 3 and 5 are as follows: Figure 12 AC and Figure 13 AC.

[0155] Comparative Example 4 involved adjusting the preparation process of the composite silicone grease, resulting in a layering phenomenon. This is because liquid metal has a very high surface tension, and the process in Comparative Example 4 easily leads to the formation of an incompatible phase between the thermally conductive auxiliary filler and the liquid metal, causing the stability of the silicone grease to deteriorate. Consequently, some liquid metal cannot be well dispersed in the silicone grease, resulting in layering. Therefore, no related performance tests were conducted.

[0156] In summary, the preparation method of this invention is simple and easy to operate. The liquid metal is first dispersed at high speed with modified silicone oil, and then the liquid metal is uniformly cut into droplets of uniform particle size through high-speed shearing (the average particle size of the liquid metal in the liquid metal-based composite thermal grease is 30–60 μm, such as…). Figures 14-17 Then, it reacts with modified silicone oil to form a stable coating structure, thus ensuring the stability of the structure when thermally conductive auxiliary materials are added. With the cooperation of other thermally conductive auxiliary fillers, it achieves the characteristics of high thermal conductivity and low thermal resistance, with the thermal resistance even as low as 0.01℃·cm. 2 / W. It exhibits excellent stability during dual 85℃ and 125℃ temperature cycling tests, with no liquid metal precipitation, resulting in high process and appearance reliability. It can be further applied to stencil printing operations where liquid metal is less likely to precipitate.

Claims

1. A liquid metal matrix composite thermal conductive silicone grease, characterized in that, By weight parts, comprising the following components: Modified silicone oil 100 parts, liquid metal 2000~5000 parts, heat-conducting auxiliary filler 0~500 parts, hydrophobic fumed silica 0.2~10 parts; The modified silicone oil comprises a single-end alkoxy-terminated silicone oil containing an ethylene short chain and a branched structure silicone oil; The single-end alkoxy-terminated silicone oil containing an ethylene short chain has the following formula (I): Formula (I); Wherein, R1 is an alkoxy containing 1~3 carbons, R2 is CH3— or CH2=CH—, n represents the average polymerization degree, n is an integer of 10~50; The branched structure silicone oil has the following formula (II): Formula (II); wherein the sum of α+β+γ represents the average polymerization degree, the sum of α+β+γ is an integer of 2 to 30, and 1≤β≤2, α, β, and γ are each an integer, R3is , m represents the average polymerization degree, and m is an integer of 10 to 50.

2. The liquid metal matrix composite thermal conductive silicone grease according to claim 1, wherein, By weight parts, comprising the following components: modified silicone oil 100 parts, liquid metal 3000~4500 parts, heat-conducting auxiliary filler 0~300 parts, hydrophobic fumed silica 5~10 parts.

3. The liquid metal-based composite thermal grease according to claim 1, characterized in that, The single-end alkoxy-terminated silicone oil containing an ethylene short chain is at least one of the following structures of formula (III)~formula (V): Formula (III); Formula (IV); Formula (V); Wherein, a represents the average polymerization degree, a is an integer of 15~30.

4. The liquid metal matrix composite thermal conductive silicone grease of claim 1, wherein the liquid metal matrix composite thermal conductive silicone grease is characterized by, The sum of α+β+γ is an integer of 10~30, and m is an integer of 20~50.

5. The liquid metal matrix composite thermal conductive silicone grease of claim 1, wherein the liquid metal matrix composite thermal conductive silicone grease is characterized by, The liquid metal is at least one of gallium, gallium-indium alloy, gallium-indium-tin, gallium-indium-bismuth alloy.

6. The liquid metal-based composite thermal grease according to claim 1, characterized in that, The average particle diameter of the heat conductive auxiliary filler is 0.1 to 5 μm, and / or the particle diameter D 100 ≤ 15 μm, and / or the shape of the heat conductive auxiliary filler is spherical or spheroidal.

7. The liquid metal-based composite thermal grease according to claim 1, characterized in that, The hydrophobic fumed silica is at least one of a silazane-modified hydrophobic fumed white carbon, a polydimethylsiloxane-modified hydrophobic fumed white carbon, and a chlorosilane-modified hydrophobic fumed white carbon.

8. The method of claim 1-7, wherein the liquid metal matrix composite thermal conductive silicone grease is prepared by the steps of: Comprising the following steps: The modified silicone oil and the liquid metal are added in sequence to obtain a paste, and then the remaining components are added to prepare the liquid metal-based composite heat-conducting silicone grease.

9. The application of the liquid metal-based composite heat-conducting silicone grease according to any one of claims 1-7 in the field of communication networks, new energy vehicles, electronic products, or artificial intelligence devices.

10. A thermal interface material, characterized by, The liquid metal-based composite heat-conducting silicone grease according to any one of claims 1-7.

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