Liquid metal composite heat conduction paste, preparation method, thermal interface material and electronic product

Abstract

The invention relates to the technical field of equipment heat dissipation, and provides a liquid metal composite heat-conducting paste, a preparation method, a thermal interface material and an electronic product, the thermal interface material obtained after the liquid metal composite heat-conducting paste provided in the method is heated is of a packaging structure with two layers of polysiloxane networks, liquid metal can be better packaged and protected, and the service life of the liquid metal is prolonged. The contact between water vapor and liquid metal is isolated, the liquid metal is prevented from leaking, the liquid metal is not prone to leaking for a long time under the environment that the temperature is 85 DEG C and the humidity is 85%, and the long-term stability is good. And the second polysiloxane network is not easy to pump out and dry up, so that the long-term stability of the thermal interface material is further improved. According to the liquid metal composite heat-conducting paste provided by the embodiment of the invention, a thermal interface material obtained after heating is relatively good in long-term stability, and liquid metal is not liable to leak for a long time in an environment with the temperature of 85 DEG C and the humidity of 85%.

Description

Technical Field

[0001] This application relates to the field of equipment heat dissipation technology, and in particular to a liquid metal composite thermal conductive paste, its preparation method, thermal interface material, and electronic products. Background Technology

[0002] With the increasing integration of electronic products, heat dissipation performance has become a core issue restricting the improvement of electronic product performance. This challenge can usually be addressed by applying thermal interface materials such as thermal paste or thermal gel to the tiny gaps between heat-generating and heat-dissipating components in electronic products. Liquid metals, due to their strong deformation capacity and excellent thermal conductivity at room temperature, have been frequently used as thermally conductive fillers in recent years as novel advanced thermal interface materials.

[0003] Currently, liquid metal composite thermal pastes prepared using liquid metal as a thermally conductive filler can be used directly as thermal interface materials, or they can be heated and cured to form a thermal interface material. However, these thermal interface materials have low long-term stability and are prone to liquid metal leakage in a short period of time under conditions of 85°C and 85% humidity, posing a short-circuit risk to electronic products. Therefore, there is an urgent need for a thermal interface material with better long-term stability, so that it is not prone to liquid metal leakage for extended periods under conditions of 85°C and 85% humidity. Summary of the Invention

[0004] This application provides a liquid metal composite thermal conductive paste, a preparation method, a thermal interface material, and an electronic product. The liquid metal composite thermal conductive paste provides a thermal interface material with good long-term stability after heating and curing, and is not prone to liquid metal leakage for a long time in an environment with a temperature of 85°C and a humidity of 85%.

[0005] To achieve the above objectives, this application adopts the following technical solution:

[0006] In a first aspect, a liquid metal composite thermal conductive paste is provided, comprising: liquid metal, a first polysiloxane network, and a macroscopic encapsulant; the first polysiloxane network encapsulates the liquid metal, the first polysiloxane network being formed by a condensation reaction of the microscopic encapsulant under the catalysis of the liquid metal, the microscopic encapsulant being a compound containing hydrolyzable silicon functional groups; the macroscopic encapsulant comprises component A, component B, and an initiator, component A and component B being polysiloxane compounds having crosslinkable functional groups, and component A and component B, when heated, polymerize under the action of the initiator to form a second polysiloxane network, the second polysiloxane network encapsulating the first polysiloxane network.

[0007] The thermal interface material obtained by heating the liquid metal composite thermal conductive paste provided in this application has a two-layer polysiloxane network encapsulation structure. Because the polysiloxane network is hydrophobic and thermally conductive, it can both protect the liquid metal from contact with external moisture and provide good thermal conductivity. Therefore, the two-layer polysiloxane network encapsulation structure can better encapsulate and protect the liquid metal, isolate moisture from contact with the liquid metal, and prevent liquid metal leakage. The thermal interface material is not prone to liquid metal leakage for extended periods under conditions of 85°C and 85% humidity, exhibiting good long-term stability. Furthermore, since the second polysiloxane network is formed by the polymerization of two polysiloxane compounds with crosslinkable functional groups under the action of an initiator, the polymer molecular weight in the second polysiloxane network is relatively large, and the molecular chains are fixed within the polysiloxane network through crosslinking or entanglement. Therefore, the second polysiloxane network is less prone to pumping out and drying out, further improving the long-term stability of the thermal interface material. The present application provides a liquid metal composite thermal grease, which provides a thermal interface material with good long-term stability after heating, and is less prone to liquid metal leakage in an environment with a temperature of 85°C and a humidity of 85%.

[0008] In one possible implementation of the first aspect, the liquid metal composite thermal paste further includes a small molecule blocking agent, which is a polysiloxane compound; the small molecule blocking agent has a viscosity at room temperature between 10 and 100 mPa·s and a molecular weight between 5000 and 10000, and the small molecule blocking agent does not react with the microencapsulating agent and the macroencapsulating agent.

[0009] In this embodiment, the small molecule blocking agent is a polysiloxane compound. Therefore, the small molecule blocking agent has good compatibility with both micro and macro encapsulating agents. Furthermore, its small molecular weight and low flow resistance allow it to flow back into the pores of the second polysiloxane network during the heating and curing process of the liquid metal composite thermal conductive paste to form a thermal interface material. This blocks the pores of the second polysiloxane network, preventing moisture from entering through these channels and reacting with the liquid metal. Simultaneously, the small molecule blocking agent can also flow back into the cracks caused by the thermal interface material's thermal cycling stress during use, blocking drainage channels and preventing moisture from entering through these channels and contacting the liquid metal. Therefore, the small molecule blocking agent in this embodiment can further improve the long-term stability of the thermal interface material.

[0010] In one possible implementation of the first aspect, the small molecule blocking agent is one of dimethyl silicone oil, ethyl silicone oil, phenyl silicone oil, and epoxy silicone oil. Various small molecule blocking agents that meet the above-mentioned viscosity and molecular weight requirements are provided in the embodiments of this application.

[0011] In one possible implementation of the first aspect, the liquid metal comprises 92 to 97 parts by weight, the total number of the micro-encapsulating agent and the macro-encapsulating agent comprises 3 to 8 parts by weight, and the small molecule blocking agent comprises 0.03 to 0.08 parts by weight.

[0012] In this embodiment, liquid metal is used as the main thermally conductive filler in the liquid metal composite thermal conductive paste, accounting for the largest proportion, while the small molecule blocker accounts for the smallest proportion. A trace amount of the small molecule blocker can flow back into the pores of the second polysiloxane network during the heating and curing process of the liquid metal composite thermal conductive paste to form a thermal interface material. This blocks the pores of the second polysiloxane network, preventing moisture from entering through these channels and reacting with the liquid metal, thus preventing liquid metal leakage. Simultaneously, a trace amount of the small molecule blocker can also flow back into the cracks caused by the thermal cycle stress of the thermal interface material during use, blocking drainage channels and preventing moisture from entering through these channels and reacting with the liquid metal, thus preventing liquid metal leakage. Unlike the current practice of using small molecule blockers as diluents or leveling agents (0.5–20 parts), excessive use of small molecule blockers can lead to overflow of the encapsulation structure, causing oil seepage from the thermal interface material and affecting its normal use.

[0013] In one possible implementation of the first aspect, the mass ratio of the small molecule blocking agent to the macroscopic encapsulating agent is between 1:99 and 5:95.

[0014] Within this ratio range, the small molecule blocking agent will not be used in excessive amounts, causing an overflow of excessive small molecule blocking agent into the encapsulation structure; nor will it be used in insufficient amounts, failing to effectively block the pores and cracks of the second polysiloxane network. For example, the mass ratio of small molecule blocking agent to macroscopic encapsulant can be: 1:99, 2:98, 3:97, 4:96, or 5:95, etc.

[0015] In one possible implementation of the first aspect, component A comprises at least one polysiloxane compound, the polysiloxane compound comprising a functional group selected from vinyl, hydrogen, alkoxy, silanol, acyloxy, and amino groups; component B comprises at least one polysiloxane compound, the polysiloxane compound comprising a functional group selected from vinyl, hydrogen, alkoxy, silanol, acyloxy, and amino groups. This example provides several possible implementations of components A and B, which can be selected according to actual needs.

[0016] In one possible implementation of the first aspect, component A comprises at least one of side-chain hydrogen-based polysiloxane and terminal hydrogen-based polysiloxane, component B comprises at least one of side-chain vinyl polysiloxane and terminal vinyl polysiloxane, and the initiator is a caster catalyst.

[0017] In this embodiment, all polysiloxane molecules in component A include hydrogen groups, i.e., silicon-hydrogen bonds (-Si-H), while all polysiloxane molecules in component B include vinyl groups. Under heating conditions, the silicon-hydrogen bonds (-Si-H) of the polysiloxane molecules in component A can undergo an addition reaction with the vinyl groups (-CH=CH2) of the polysiloxane molecules in component B in the presence of a castor catalyst. The hydrogen atom adds to one carbon atom of the vinyl group, while the silicon atom forms a new silicon-carbon bond with the other carbon atom of the vinyl group, resulting in cross-linking between the molecular chains and ultimately forming a three-dimensional network structure of polysiloxane.

[0018] Furthermore, the hydrogen groups in component A are located on the side chains or end groups of the polysiloxane molecules, and the vinyl groups in component B are also located on the side chains or end groups of the polysiloxane molecules. Thus, during the reaction to form silicon-carbon bonds, the hydrogen groups on the side chains of component A react with the vinyl groups on the side chains or end groups of component B, and the hydrogen groups on the end groups of component A react with the vinyl groups on the side chains or end groups of component B. In other words, the original polysiloxane molecules in components A and B will not break during the reaction, but new molecules will be added to the side chains and end groups of the original polysiloxane molecules. Therefore, the polymer molecular weight in the second polysiloxane network formed by the reaction of components A and B is relatively large, and the molecular chains are fixed in the polysiloxane network through cross-linking or entanglement. Therefore, the second polysiloxane network is not easy to be pumped out or dried out, which further improves the long-term stability of the thermal interface material.

[0019] In one possible implementation of the first aspect, the component A comprises 80 to 92 parts by weight, the component B comprises 7 to 15 parts by weight, and the initiator comprises 0.1 to 0.3 parts by weight.

[0020] In this embodiment, component A includes at least one of side-chain hydrogen-based polysiloxane and terminal hydrogen-based polysiloxane, component B includes at least one of side-chain vinyl polysiloxane and terminal vinyl polysiloxane, and the initiator is a caster catalyst. By weight, the amount of component A is between 80 and 92, the amount of component B is between 7 and 15, and the amount of initiator is between 0.1 and 0.3. The amount of component A is excessive, and there is still some component A remaining after the reaction of component A and component B is completed. This avoids the problem of excessive crosslinking of the second polysiloxane network, which would lead to large shrinkage and easy cracking when heated, and further improves the long-term stability of the thermal interface material.

[0021] Furthermore, the viscosity of the macro-encapsulant at room temperature is between 10 and 500 mPa·s. In this embodiment, if the viscosity of the macro-encapsulant at room temperature is greater than 500 mPa·s, the resulting thermal interface material after heating will have poor fluidity and will be unable to fill the tiny gaps in the electronic product. If the viscosity of the macro-encapsulant at room temperature is less than 10 mPa·s, the resulting thermal interface material after heating will have excessive fluidity and will not easily adhere to the electronic product. However, if the viscosity of the macro-encapsulant at room temperature is between 10 and 500 mPa·s, the resulting thermal interface material after heating will have appropriate fluidity, which allows it to deform and fill the tiny gaps in the electronic product without being too fluid and flowing out of the tiny gaps.

[0022] In one possible implementation of the first aspect, the microencapsulating agent is one of a mercaptosilane coupling agent, 3-chloropropyltriethoxysilane, 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane, and triethoxyfluorosilane. Several alternative implementations of the microencapsulating agent are provided in this embodiment.

[0023] In one possible implementation of the first aspect, the liquid metal is metallic gallium or gallium-based liquid metal, wherein the gallium-based liquid metal is one of gallium-indium alloy and gallium-indium-tin alloy. Because metallic gallium or gallium-based liquid metals have low melting points, good stability, and are non-toxic, they are often used as one of the main thermally conductive fillers in liquid metal composite thermal pastes.

[0024] In a second aspect, a thermal interface material is provided, comprising: a liquid metal, a first polysiloxane network encapsulating the liquid metal, and a second polysiloxane network encapsulating the first polysiloxane network; the first polysiloxane network is formed by a condensation reaction of a micro-encapsulating agent under the catalysis of the liquid metal, wherein the micro-encapsulating agent is a compound containing hydrolyzable silicon functional groups; the second polysiloxane network is formed by the polymerization of a macro-encapsulating agent upon heating, wherein the macro-encapsulating agent comprises component A, component B, and an initiator, wherein component A and component B are polysiloxane compounds having crosslinkable functional groups, and component A and component B undergo a polymerization reaction under the action of the initiator upon heating.

[0025] The thermal interface material in this embodiment comprises a liquid metal and a two-layer polysiloxane network encapsulation structure. Due to the hydrophobicity and thermal conductivity of the polysiloxane network, it can both protect the liquid metal from contact with external moisture and provide good thermal conductivity. Therefore, the two-layer polysiloxane network encapsulation structure can better encapsulate and protect the liquid metal, isolate moisture from contact with the liquid metal, and prevent liquid metal leakage. The thermal interface material is not prone to liquid metal leakage for extended periods at 85°C and 85% humidity, exhibiting good long-term stability. Furthermore, since the second polysiloxane network is formed by the polymerization of two polysiloxane compounds with crosslinkable functional groups under the action of an initiator, the polymer molecular weight in the second polysiloxane network is relatively large, and the molecular chains are fixed within the polysiloxane network through crosslinking or entanglement. Therefore, the second polysiloxane network is less prone to pumping out and drying out, further improving the long-term stability of the thermal interface material.

[0026] In one possible implementation of the second aspect, the thermal interface material further includes a small molecule blocking agent, which is a polysiloxane compound; the small molecule blocking agent has a viscosity at room temperature between 10 and 100 mPa·s and a molecular weight between 5000 and 10000, and the small molecule blocking agent does not react with the micro-encapsulating agent and the macro-encapsulating agent.

[0027] In this embodiment, the small molecule blocking agent is a polysiloxane compound. Therefore, the small molecule blocking agent has good compatibility with both micro and macro encapsulating agents. Furthermore, its small molecular weight and low flow resistance allow it to flow back into the pores of the second polysiloxane network during the heating and curing process of the liquid metal composite thermal conductive paste to form a thermal interface material. This blocks the pores of the second polysiloxane network, preventing moisture from entering through these channels and reacting with the liquid metal. Simultaneously, the small molecule blocking agent can also flow back into the cracks caused by the thermal interface material's thermal cycling stress during use, blocking drainage channels and preventing moisture from entering through these channels and contacting the liquid metal. Therefore, the small molecule blocking agent in this embodiment can further improve the long-term stability of the thermal interface material.

[0028] In one possible implementation of the second aspect, the thermal interface material has a thermal conductivity between 5 and 18 W / m·K, exhibiting good thermal conductivity.

[0029] In one possible implementation of the second aspect, the thermal interface material does not leak liquid metal for 48 to 216 hours under the double 85 test, indicating good long-term stability.

[0030] Thirdly, a method for preparing a liquid metal composite thermal conductive paste is provided, comprising: adding liquid metal to a micro-encapsulating agent and heating to disperse it evenly, wherein the micro-encapsulating agent is a compound containing hydrolyzable silicon functional groups; adding a macro-encapsulating agent and dispersing it evenly, wherein the macro-encapsulating agent comprises component A, component B and an initiator, wherein component A and component B are polysiloxane compounds having crosslinkable functional groups, wherein, when heated, component A and component B form a second polysiloxane network under the action of the initiator.

[0031] Using the preparation method and preparation parameters in the embodiments of this application, the liquid metal droplets in the thermal interface material obtained by heating and curing the liquid metal composite thermal conductive paste have a particle size between 100 nm and 400 μm and a thermal conductivity between 5 and 18 W / m·K. Moreover, it can maintain a liquid metal leakage rate of ~216 h at a temperature of 85℃ and a humidity of 85%, exhibiting good thermal conductivity and good long-term stability.

[0032] Fourthly, an electronic product is provided, comprising a heat-generating element and a heat-dissipating element, and a thermal interface material located between the heat-generating element and the heat-dissipating element, as described in the second aspect or any possible implementation thereof. Examples of electronic products include transistors, CPU assemblies, thermistors, temperature sensors, automotive electronic components, car refrigerators, power modules, and printer heads. The thermal interface material, applied to these electronic products, functions as a heat transfer medium while also providing moisture-proof, dust-proof, corrosion-proof, and shock-proof functions, exhibiting significant application value and economic benefits.

[0033] Based on the implementation methods provided in the above aspects, this application can be further combined to provide more implementation methods. Attached Figure Description

[0034] Figure 1 This is an exemplary flowchart of the preparation method of the liquid metal composite thermal conductive paste provided in the embodiments of this application;

[0035] Figure 2 This is a bar chart showing the thermal conductivity of the thermal interface materials obtained by the preparation methods of Examples 1 to 13 provided in this application.

[0036] Figure 3 This is a bar chart showing the double 85 leakage time of the thermal interface material obtained by the preparation methods of Examples 1 to 13 provided in this application;

[0037] Figure 4 This is a bar chart showing the double 85 leakage time of the thermal interface material obtained by the preparation methods of Example 6 and Comparative Examples 1 to 4 provided in this application. Detailed Implementation

[0038] The technical solutions in this application will now be described with reference to the accompanying drawings.

[0039] In the description of the embodiments of this application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. "And / or" in this document is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone.

[0040] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this embodiment, unless otherwise stated, "a plurality of" means two or more.

[0041] To facilitate understanding of the technical solutions of the embodiments of this application, some terms involved in the embodiments of this application will be briefly explained below.

[0042] As the integration of electronic products increases, heat dissipation performance has become a core issue restricting the improvement of electronic product performance. This challenge can typically be addressed by applying thermal interface materials such as thermal paste or thermal gel to the tiny gaps between the heat-generating and heat-dissipating components of electronic products. The thermal interface materials required for heat dissipation in electronic products should possess high thermal conductivity, low contact thermal resistance, high insulation, and a certain degree of flowability, thereby helping to extend the lifespan of electronic products.

[0043] Liquid metals, due to their strong deformability and excellent thermal conductivity at room temperature, have been frequently used as thermally conductive fillers in novel advanced thermal interface materials in recent years. For example, a composite thermal grease uses liquid metal as the main thermally conductive filler, supplemented with a small amount of organic material for shaping, and can also incorporate various reinforcing materials to further enhance the composite material's performance. Furthermore, because liquid metals can freely deform, compared to other types of traditional composite thermal greases, composite thermal greases using liquid metal as the main thermally conductive filler can better fill the tiny gaps between chips and heat sinks in highly integrated electronic devices such as mobile phones, further reducing interfacial thermal resistance and achieving relatively higher thermal conductivity.

[0044] Currently, liquid metal composite thermal conductive pastes prepared using liquid metal as the thermally conductive filler can be used directly as thermal interface materials, or the liquid metal composite thermal conductive paste can be heated and cured to form a thermal interface material. However, these thermal interface materials with liquid metal as the main thermally conductive filler are less stable in actual use and have unique long-term stability issues. For example, liquid metal easily reacts with water in the air under heating conditions to generate gas, causing the thermal interface material to expand in volume. This phenomenon can cause leakage of liquid metal in the thermal interface material, creating a short-circuit risk for electronic devices. In addition, similar to other thermal interface materials, thermal interface materials containing liquid metal can also experience pumping out and drying of the encapsulation layer (such as the polymer matrix) during use, leading to separation of the liquid metal from the encapsulation layer, specifically manifested as the thermal interface material becoming powdery. Due to its extremely high surface tension, the liquid metal separated from the encapsulation layer will rapidly agglomerate into larger liquid metal droplets, and then be squeezed out onto the surface of the encapsulation layer through the gaps formed by the thermal cycle stress of the thermal interface material, exacerbating the leakage of liquid metal. Meanwhile, moisture in the air can also seep into the encapsulation layer through the gaps, reacting with the liquid metal filler to generate hydrogen gas, which can further break through the encapsulation layer and accelerate the leakage of liquid metal. Therefore, the long-term stability of thermal interface materials with liquid metal as the main thermally conductive filler has always been a key issue hindering their large-scale application in actual production.

[0045] Currently, thermal interface materials using liquid metal as the primary thermally conductive filler exhibit low long-term stability. In the 85°C / 85% RH accelerated aging test, slight drying of the encapsulation layer within a short time, coupled with the high temperature and humidity environment, can lead to liquid metal leakage, posing a short-circuit risk to electronic products. The 85°C / 85% RH test for thermal interface materials measures how long it takes for the material to fail. For thermal interface materials using liquid metal as the primary thermally conductive filler, the main form of failure is liquid metal leakage. This test can be used to assess the stability of thermal interface materials during long-term use and their stability under extreme environments such as high temperature and high humidity.

[0046] Therefore, there is an urgent need for a thermal interface material with good long-term stability, using liquid metal as the main thermally conductive filler, so that the thermal interface material is not prone to liquid metal leakage for a long time in an environment with a temperature of 85℃ and a humidity of 85%.

[0047] In view of this, embodiments of this application provide a liquid metal composite thermal conductive paste, comprising: liquid metal, a first polysiloxane network, and a macroscopic encapsulant; the first polysiloxane network encapsulates the liquid metal, the first polysiloxane network being formed by a condensation reaction of the microscopic encapsulant under the catalysis of the liquid metal, the microscopic encapsulant being a compound containing hydrolyzable silicon functional groups; the macroscopic encapsulant comprising component A, component B, and an initiator, component A and component B being polysiloxane compounds having crosslinkable functional groups, and component A and component B, when heated, polymerize under the action of the initiator to form a second polysiloxane network, the second polysiloxane network encapsulating the first polysiloxane network.

[0048] The thermal interface material obtained by heating the liquid metal composite thermal conductive paste provided in this application has a two-layer polysiloxane network encapsulation structure. Because the polysiloxane network is hydrophobic and thermally conductive, it can both protect the liquid metal from contact with external moisture and provide good thermal conductivity. Therefore, the two-layer polysiloxane network encapsulation structure can better encapsulate and protect the liquid metal, isolate moisture from contact with the liquid metal, and prevent liquid metal leakage. The thermal interface material is not prone to liquid metal leakage for extended periods under conditions of 85°C and 85% humidity, exhibiting good long-term stability. Furthermore, since the second polysiloxane network is formed by the polymerization of two polysiloxane compounds with crosslinkable functional groups under the action of an initiator, the polymer molecular weight in the second polysiloxane network is relatively large, and the molecular chains are fixed within the polysiloxane network through crosslinking or entanglement. Therefore, the second polysiloxane network is less prone to pumping out and drying out, further improving the long-term stability of the thermal interface material. The present application provides a liquid metal composite thermal grease, which makes the thermal interface material obtained after heating have good long-term stability and is not prone to liquid metal leakage for a long time in an environment with a temperature of 85°C and a humidity of 85%.

[0049] In a first aspect, the liquid metal composite thermal paste provided in the embodiments of this application includes liquid metal, a first polysiloxane network, and a macroscopic encapsulant, wherein the first polysiloxane network is formed by the microscopic encapsulant undergoing a condensation reaction under the catalytic action of the liquid metal.

[0050] The raw materials used to form the liquid metal composite thermal paste in the embodiments of this application will be described in detail below.

[0051] (1) Liquid metal

[0052] In the embodiments of this application, the liquid metal may be metallic gallium or gallium-based liquid metal, and the gallium-based liquid metal may be one of gallium-indium alloy and gallium-indium-tin alloy.

[0053] Liquid metals are generally defined as single-element or alloy compositions that have low melting points and a liquid phase at room temperature. The classification of liquid metals is extremely rich, including elemental metals and alloys. A well-known liquid metal is mercury (Hg), with a melting point of -38.86°C, which has been used in the electronics and medical industries; however, its use is highly regulated due to its extreme toxicity. Unlike traditional metals such as mercury, the liquid metals in this application primarily refer to metallic gallium (Ga) or gallium-based liquid metals, which are stable and non-toxic metallic materials. Pure gallium has a melting point of 29.78°C, and its related alloys (i.e., gallium-based liquid metals) often have even lower melting points. Gallium-based liquid metals can be either gallium-indium alloys or gallium-indium-tin alloys. The known lowest melting point of a gallium-based liquid metal (where the mass percentages of the components are Ga: 61%, In: 25%, Sn: 13%, Zn: 1%) is 8°C. Because gallium or gallium-based liquid metals have low melting points, good stability, and are non-toxic, they are often used as one of the main thermal fillers in composite thermal pastes.

[0054] In one feasible approach, the melting point of gallium-based liquid metal is 10–15°C. This allows the gallium-based liquid metal to remain liquid at room temperature and during use, freely deforming. Composite thermal pastes using gallium-based liquid metal as a thermally conductive filler can better fill the tiny gaps between chips and heat sinks in highly integrated electronic devices such as mobile phones. The thermal conductivity of gallium-based liquid metal is 25.4–26.4 W / m·K, exhibiting good thermal conductivity; therefore, composite thermal pastes using gallium-based liquid metal as a thermally conductive filler also possess good thermal conductivity.

[0055] (2) Microencapsulant

[0056] The microencapsulant is a compound containing hydrolyzable silicon functional groups. Upon heating, it undergoes a hydrolysis reaction catalyzed by liquid metal to generate silanols (Si-OH). These silanol groups can then form silicon-oxygen bonds (Si-O-Si) through dehydration condensation, thus constructing a polysiloxane network. This polysiloxane network is a three-dimensional network structure formed by chemical bonds between polysiloxane molecules. It possesses good mechanical strength, heat resistance, chemical stability, and sealing properties, effectively encapsulating the liquid metal to form the first layer of encapsulation. Because the polysiloxane network is hydrophobic and thermally conductive, it protects the liquid metal from contact with external moisture and provides excellent thermal conductivity.

[0057] The aforementioned hydrolyzable silicon functional group can be a silaneoxy group (Si-O-Alkyl). In silaneoxy (Si-O-Alkyl), "Alkyl" refers to an alkyl chain composed of carbon and hydrogen atoms, which is a group formed when an alkane molecule loses a hydrogen atom. The alkyl chain can be straight or branched, and its length can be arbitrary, ranging from the simplest methyl (-CH3) to longer groups such as ethyl (-C2H5) and propyl (-C3H7). For example, if "Alkyl" is methyl, then the alkoxy group is methoxy (Si-O-CH3); if "Alkyl" is ethyl, then the alkoxy group is ethoxy (Si-O-C2H5), and so on.

[0058] For example, the microencapsulating agent may be one of mercaptosilane coupling agents, 3-chloropropyltriethoxysilane, 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane, and triethoxyfluorosilane.

[0059] Among the various compounds provided above, mercaptosilane coupling agents typically contain a mercapto group (-SH) and a silaneoxy group (such as -Si-O-Alkyl); 3-chloropropyltriethoxysilane typically contains a silaneoxy group (such as -Si-O-Alkyl) and a chloro group (-Cl); 3-aminopropyltriethoxysilane typically contains an amino group (-NH) and a silaneoxy group (such as -Si-O-Alkyl); vinyltriethoxysilane typically contains a vinyl group (-CH=CH2) and a silaneoxy group (such as -Si-O-Alkyl); heptadecafluorodecyltrimethoxysilane typically contains a long-chain perfluoroalkyl group and a trimethoxysilyl group (-Si(OCH3)3), where the trimethoxysilyl group is a type of silaneoxy group; and triethoxyfluorosilane typically contains one fluorosilyl group (Si-F) and three ethoxy groups (Si-O-C2H5), where the ethoxy groups are a type of silaneoxy group.

[0060] (3) Macro encapsulant

[0061] The macroscopic encapsulant comprises component A, component B, and an initiator. Components A and B are polysiloxane compounds with crosslinkable functional groups. During the heating and curing process of the liquid metal composite thermal conductive paste to form a thermal interface material, when heated, the two crosslinkable functional groups in components A and B react under the action of the initiator to form new chemical bonds, thereby crosslinking to form a network structure. Since components A and B are both polysiloxane compounds, their molecular structures contain repeating silicon-oxygen bond (Si-O) units. Therefore, the polymer generated by the reaction of components A and B has a large molecular weight, and the molecular chains are fixed in the polysiloxane network through crosslinking or entanglement. Thus, the second polysiloxane network is less prone to pumping out and drying. In the thermal interface material obtained after heating the liquid metal composite thermal conductive paste, the second polysiloxane network encapsulates the first polysiloxane network. The two encapsulation layers work together to improve the long-term stability of the thermal interface material.

[0062] Examples of crosslinkable functional groups include vinyl and hydrogen groups. Polysiloxane compounds containing hydrogen groups have silane-hydrogen bonds (-Si-H). These bonds can undergo addition reactions with vinyl groups (-CH=CH2), where the hydrogen atom adds to one carbon atom of the double bond, while the silicon atom forms a new silicon-carbon bond with the other carbon atom. Another example is alkoxy and silanol groups. Alkoxy groups (-OR) hydrolyze in water to form silanol groups (-SiOH). These silanol groups can condense with each other or with an alkoxy or silanol group on another molecule to form a siloxane bond. Yet another example is acyloxy and amino groups. Acyloxy groups can undergo amidation reactions with amino groups to form amide bonds (-CONH-).

[0063] For example, component A includes at least one polysiloxane compound, which includes a functional group selected from vinyl, hydrogen, alkoxy, silanol, acyloxy, and amino; component B includes at least one polysiloxane compound, which includes a functional group selected from vinyl, hydrogen, alkoxy, silanol, acyloxy, and amino.

[0064] For example: If component A is a polysiloxane compound containing vinyl groups, then component B can be a polysiloxane compound containing hydrogen groups; conversely, if component A is a polysiloxane compound containing hydrogen groups, then component B can be a polysiloxane compound containing vinyl groups. If component A is a polysiloxane compound containing alkoxy groups, then component B can be a polysiloxane compound containing silanol groups; conversely, if component A is a polysiloxane compound containing silanol groups, then component B can be a polysiloxane compound containing alkoxy groups. If component A is a polysiloxane compound containing acyloxy groups, then component B can be a polysiloxane compound containing amino groups; conversely, if component A is a polysiloxane compound containing amino groups, then component B can be a polysiloxane compound containing acyloxy groups. This example provides several possible implementations of components A and B. In this case, different initiators can be selected based on the choice of components A and B.

[0065] For example, component A includes at least one of side-chain hydrogen-based polysiloxane and terminal hydrogen-based polysiloxane, component B includes at least one of side-chain vinyl polysiloxane and terminal vinyl polysiloxane, and the initiator is a caster catalyst.

[0066] In this embodiment, all polysiloxane molecules in component A include hydrogen groups, i.e., silicon-hydrogen bonds (-Si-H), while all polysiloxane molecules in component B include vinyl groups. Under heating conditions, the silicon-hydrogen bonds (-Si-H) of the polysiloxane molecules in component A can undergo an addition reaction with the vinyl groups (-CH=CH2) of the polysiloxane molecules in component B in the presence of a castor catalyst. The hydrogen atom adds to one carbon atom of the vinyl group, while the silicon atom forms a new silicon-carbon bond with the other carbon atom of the vinyl group, resulting in cross-linking between the molecular chains and ultimately forming a three-dimensional network structure of polysiloxane. Furthermore, the hydrogen groups in component A are located on the side chains or end groups of the polysiloxane molecules, and the vinyl groups in component B are also located on the side chains or end groups of the polysiloxane molecules. Thus, during the reaction to form silicon-carbon bonds, the hydrogen groups on the side chains of component A react with the vinyl groups on the side chains or end groups of component B, and the hydrogen groups on the end groups of component A react with the vinyl groups on the side chains or end groups of component B. In other words, the original polysiloxane molecules in components A and B will not break during the reaction, but new molecules will be added to the side chains and end groups of the original polysiloxane molecules. Therefore, the polymer molecular weight in the second polysiloxane network formed by the reaction of components A and B is relatively large, and the molecular chains are fixed in the polysiloxane network through cross-linking or entanglement. Therefore, the second polysiloxane network is not easy to be pumped out or dried out, which further improves the long-term stability of the thermal interface material. Among them, cascade catalysts are transition metal catalysts used to catalyze organic synthesis reactions. They mainly refer to composite catalysts formed by transition metals such as palladium, platinum or rhodium and organic ligands (such as biphenyl, phenanthrene, indene, etc.).

[0067] For example, by weight, component A is between 80 and 92 parts, component B is between 7 and 15 parts, and the initiator is between 0.1 and 0.3 parts.

[0068] In this embodiment, with component A comprising at least one of side-chain hydrogen-based polysiloxane and terminal hydrogen-based polysiloxane, component B comprising at least one of side-chain vinyl polysiloxane and terminal vinyl polysiloxane, and the initiator being a caster catalyst, the weight percentages of component A are between 80 and 92, component B between 7 and 15, and the initiator between 0.1 and 0.3. The excess of component A, with some remaining after the reaction of components A and B, avoids excessive crosslinking of the second polysiloxane network, which could lead to excessive shrinkage and cracking under heat, thus further improving the long-term stability of the thermal interface material.

[0069] In one example, 82 parts of component A, 15 parts of component B, and 0.1 parts of initiator can react fully, wherein the mass ratio of side-chain hydrogen-based polysiloxane to terminal hydrogen-based polysiloxane in component A is 10:7, and the mass ratio of side-chain vinyl polysiloxane to terminal vinyl polysiloxane in component B is 10:5.

[0070] In another example, 88 parts of component A, 10 parts of component B, and 0.2 parts of initiator can react fully, wherein the mass ratio of side-chain hydrogen-based polysiloxane to terminal hydrogen-based polysiloxane in component A is 12:76, and the mass ratio of side-chain vinyl polysiloxane to terminal vinyl polysiloxane in component B is 5:5.

[0071] In another example, 81 parts of component A, 7 parts of component B, and 0.25 parts of initiator can react fully, wherein the mass ratio of side-chain hydrogen-based polysiloxane to terminal hydrogen-based polysiloxane in component A is 10:81, and the mass ratio of side-chain vinyl polysiloxane to terminal vinyl polysiloxane in component B is 2:5.

[0072] It is worth noting that the viscosity of macroscopic encapsulants at room temperature ranges from 10 to 500 mPa·s. If the viscosity of the macroscopic encapsulant at room temperature is greater than 500 mPa·s, the resulting thermal interface material after heating will have poor fluidity and will be unable to fill the tiny gaps in electronic products. If the viscosity of the macroscopic encapsulant at room temperature is less than 10 mPa·s, the resulting thermal interface material will have excessive fluidity after heating and will not easily adhere to the electronic product. A viscosity between 10 and 500 mPa·s at room temperature allows the resulting thermal interface material to have appropriate fluidity after heating, enabling it to deform and fill the tiny gaps in the electronic product without being too fluid and flowing out of them. For example, the viscosity of macroscopic encapsulants at room temperature can be 10 mPa·s, 50 mPa·s, 100 mPa·s, 500 mPa·s, etc.

[0073] The following examples illustrate the liquid metal composite thermal conductive paste described in the above embodiments.

[0074] Example 1: The raw materials of the liquid metal composite thermal conductive paste include: 96.2 parts of liquid metal (gallium indium alloy), 1.15 parts of micro-encapsulation agent (thiol silane coupling agent), and 2.65 parts of macro-encapsulation agent. The macro-encapsulation agent includes 82 parts of component A, 15 parts of component B, and 0.1 parts of initiator. In component A, the mass ratio of side-chain hydrogen-based polysiloxane to terminal hydrogen-based polysiloxane is 10:7. In component B, the mass ratio of side-chain vinyl polysiloxane to terminal vinyl polysiloxane is 10:5. The initiator is a caster catalyst.

[0075] Example 2: The raw materials of the liquid metal composite thermal paste include: 94.3 parts of liquid metal (gallium indium alloy), 1.0 part of micro-encapsulation agent (3-chloropropyltriethoxysilane), and 4.7 parts of macro-encapsulation agent. The macro-encapsulation agent includes 86 parts of component A, 10 parts of component B, and 0.2 parts of initiator. Component A is a side-chain hydrogen-based polysiloxane and a terminal hydrogen-based polysiloxane in a mass ratio of 12:74. Component B is a side-chain vinyl polysiloxane and a terminal vinyl polysiloxane in a mass ratio of 8:2. The initiator is a Castells catalyst.

[0076] Example 3: The raw materials of the liquid metal composite thermal paste include: 92 parts of liquid metal (gallium indium tin alloy), 1.24 parts of micro-encapsulation agent (vinyltrimethoxysilane), and 6.76 parts of macro-encapsulation agent. The macro-encapsulation agent includes 89 parts of component A, 10 parts of component B, and 0.2 parts of initiator. Component A is a side-chain hydrogen-based polysiloxane and a terminal hydrogen-based polysiloxane in a mass ratio of 7:82. Component B is a side-chain vinyl polysiloxane and a terminal vinyl polysiloxane in a mass ratio of 8:2. The initiator is a Castells catalyst.

[0077] Example 4: The raw materials of the liquid metal composite thermal paste include: 97 parts of liquid metal (gallium indium tin alloy), 1.15 parts of micro-encapsulation agent (heptadecyltrimethoxysilane), and 1.95 parts of macro-encapsulation agent. The macro-encapsulation agent includes 86 parts of component A, 12 parts of component B, and 0.2 parts of initiator. Component A is a side-chain hydrogen-based polysiloxane and a terminal hydrogen-based polysiloxane in a mass ratio of 10:76. Component B is a side-chain vinyl polysiloxane and a terminal vinyl polysiloxane in a mass ratio of 8:4. The initiator is a Castells catalyst.

[0078] Example 5: The raw materials of the liquid metal composite thermal paste include: 96.2 parts of liquid metal (gallium indium tin alloy), 1.15 parts of micro-encapsulation agent (triethoxyfluorosilane), and 2.65 parts of macro-encapsulation agent. The macro-encapsulation agent includes 82 parts of component A, 15 parts of component B, and 0.1 parts of initiator. Component A is a side-chain hydrogen-based polysiloxane and a terminal hydrogen-based polysiloxane in a mass ratio of 7:75. Component B is a side-chain vinyl polysiloxane and a terminal vinyl polysiloxane in a mass ratio of 10:5. The initiator is a cassiterite catalyst.

[0079] Example 6: The raw materials of the liquid metal composite thermal paste include: 93.2 parts of liquid metal (gallium indium tin alloy), 1.17 parts of micro-encapsulation agent (3-aminopropyltriethoxysilane), and 5.63 parts of macro-encapsulation agent. The macro-encapsulation agent includes 85 parts of component A, 10 parts of component B, and 0.2 parts of initiator. Component A is a side-chain hydrogen-based polysiloxane and a terminal hydrogen-based polysiloxane in a mass ratio of 10:75. Component B is a side-chain vinyl polysiloxane and a terminal vinyl polysiloxane in a mass ratio of 8:2. The initiator is a Castells catalyst.

[0080] The liquid metal composite thermal paste provided in this application includes not only the liquid metal, the first polysiloxane network, and the macroscopic encapsulant mentioned above, but also a small molecule blocking agent.

[0081] Among them, the small molecule blocking agent is a polysiloxane compound. Thus, the small molecule blocking agent has similar chemical structure and properties to the micro-encapsulation agent (containing hydrolyzable silicon functional groups) and the macro-encapsulation agent (including polysiloxane compounds), and has good compatibility. The small molecule blocking agent does not react with the micro-encapsulation agent and the macro-encapsulation agent.

[0082] For example, the viscosity of small molecule blocking agents at room temperature is between 10 and 100 mPa·s, and the molecular weight is between 5,000 and 10,000.

[0083] Currently, small-molecule substances in thermal interface material systems are mostly used as diluents and leveling agents. They can adjust the viscosity and thixotropy of the material during mixing and processing, balance the surface tension of the matrix, and improve the smoothness of the system surface. In the embodiments of this application, the small-molecule blocking agent exhibits good compatibility with both micro- and macro-encapsulating agents. Furthermore, its small molecular weight and low flow resistance allow it to flow back into the pores of the second polysiloxane network during the heating of the liquid metal composite thermal conductive paste to form the thermal interface material. This blocks the pores of the second polysiloxane network, preventing moisture from entering through these channels and reacting with the liquid metal. Simultaneously, the small-molecule blocking agent can also flow back into the cracks caused by the thermal interface material's thermal cycling stress during use, blocking drainage channels and preventing moisture from entering through these channels and contacting the liquid metal. Therefore, the small-molecule blocking agent in the embodiments of this application can further improve the long-term stability of the thermal interface material.

[0084] For example, the small molecule blocking agent is one of dimethyl silicone oil, ethyl silicone oil, phenyl silicone oil, and epoxy silicone oil. This application provides various small molecule blocking agents that meet the above viscosity and molecular weight requirements.

[0085] For example, by weight, the liquid metal is between 92 and 97 parts, the total number of micro-encapsulants and macro-encapsulants is between 3 and 8 parts, and the number of small molecule blocking agents is between 0.03 and 0.08 parts.

[0086] In this embodiment, liquid metal is used as the main thermally conductive filler in the liquid metal composite thermal conductive paste, accounting for the largest proportion, while the small molecule blocker accounts for the smallest proportion. A trace amount of the small molecule blocker can flow back into the pores of the second polysiloxane network during the heating process of the liquid metal composite thermal conductive paste to form the thermal interface material, blocking the pores of the second polysiloxane network and preventing moisture from entering through these channels and reacting with the liquid metal, thus preventing liquid metal leakage. Simultaneously, a trace amount of the small molecule blocker can also flow back into the cracks caused by the thermal interface material's thermal cycle stress during use, blocking drainage channels and preventing moisture from entering through these channels and reacting with the liquid metal, thus preventing liquid metal leakage. Unlike the current practice of using small molecule blockers as diluents or leveling agents (0.5–20 parts), excessive use of small molecule blockers can lead to overflow of the encapsulation structure, causing oil seepage from the thermal interface material and affecting its normal use.

[0087] For example, the mass ratio of the small molecule blocking agent to the macroscopic encapsulant is between 1:99 and 5:95. Within this range, the small molecule blocking agent is not used in excessive amounts, causing an overflow of excess small molecule blocking agent into the encapsulation structure; nor is it used in insufficient amounts, failing to effectively block the pores and cracks of the second polysiloxane network. For example, the mass ratio of the small molecule blocking agent to the macroscopic encapsulant can be 1:99, 2:98, 3:97, 4:96, or 5:95, etc.

[0088] First, a general description of the liquid metal composite thermal paste containing small molecule blocking agents in the above embodiments is given.

[0089] The main raw materials of liquid metal composite thermal paste containing small molecule blocking agents include: liquid metal, micro-encapsulating agent, macro-encapsulating agent and small molecule blocking agent.

[0090] The liquid metal can be metallic gallium or gallium-based liquid metal, with gallium-based liquid metal being either gallium-indium alloy or gallium-indium-tin alloy. The melting point of gallium-based liquid metal is between 10 and 15 °C, and its thermal conductivity is between 25.4 and 26.4 W / m·K.

[0091] The microencapsulating agent may be one of the following: mercaptosilane coupling agent, 3-chloropropyltriethoxysilane, 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane, and triethoxyfluorosilane.

[0092] The macroscopic encapsulant comprises component A, component B, and an initiator. Component A may be at least one of side-chain hydrogen-based polysiloxane and terminal hydrogen-based polysiloxane, component B may be at least one of side-chain vinyl polysiloxane and terminal vinyl polysiloxane, and the initiator is a caster catalyst. Specifically, by weight, component A comprises 80–92 parts, component B comprises 7–15 parts, and the initiator comprises 0.1–0.3 parts. The viscosity of the macroscopic encapsulant at 25°C is 10–500 mPa·s.

[0093] The small molecule blocking agent can be one of dimethyl silicone oil, ethyl silicone oil, phenyl silicone oil, or epoxy silicone oil. These small molecule blocking agents are low molecular weight polysiloxane compounds that can flow in the first polysiloxane network and the second polysiloxane network. The viscosity of the small molecule blocking agent at 25°C is 10–100 mPa·s, and the molecular weight of the small molecule blocking agent is 5000–10000.

[0094] The amounts of the above raw materials can be as follows: by weight, the liquid metal is 92-97 parts, the total amount of micro-encapsulating agent and macro-encapsulating agent is 3-8 parts, and the small molecule blocking agent is 0.03-0.08 parts.

[0095] Secondly, specific examples are used to illustrate the liquid metal composite thermal conductive paste containing small molecule blocking agents in the above embodiments.

[0096] Example 1: The raw materials of the liquid metal composite thermal paste include: 96.2 parts of liquid metal (gallium indium alloy), 1.15 parts of micro-encapsulation agent (thiol silane coupling agent), and 2.65 parts of small molecule blocking agent and macro-encapsulation agent in total, with a mass ratio of small molecule blocking agent to macro-encapsulation agent of 3:97. The macro-encapsulation agent includes 82 parts of component A, 15 parts of component B, and 0.1 parts of initiator. In component A, the mass ratio of side-chain hydrogen-based polysiloxane to terminal hydrogen-based polysiloxane is 10:7; in component B, the mass ratio of side-chain vinyl polysiloxane to terminal vinyl polysiloxane is 10:5; and the initiator is a Castrol catalyst.

[0097] Example 2: The raw materials of the liquid metal composite thermal paste include: 94.3 parts of liquid metal (gallium indium alloy), 1.0 part of micro-encapsulating agent (3-chloropropyltriethoxysilane), and 4.7 parts of small molecule blocking agent and macro-encapsulating agent in a mass ratio of 4:96. The macro-encapsulating agent comprises 86 parts of component A, 10 parts of component B, and 0.2 parts of initiator. Component A consists of side-chain hydrogen-based polysiloxane and terminal hydrogen-based polysiloxane in a mass ratio of 12:74, component B consists of side-chain vinyl polysiloxane and terminal vinyl polysiloxane in a mass ratio of 8:2, and the initiator is a caster catalyst.

[0098] Example 3: The raw materials of the liquid metal composite thermal paste include: 92 parts of liquid metal (gallium indium tin alloy), 1.24 parts of micro-encapsulating agent (vinyltrimethoxysilane), and 6.76 parts of small molecule blocking agent and macro-encapsulating agent in a mass ratio of 1:99. The macro-encapsulating agent comprises 89 parts of component A, 10 parts of component B, and 0.2 parts of initiator. Component A consists of side-chain hydrogen-based polysiloxane and terminal hydrogen-based polysiloxane in a mass ratio of 7:82, component B consists of side-chain vinyl polysiloxane and terminal vinyl polysiloxane in a mass ratio of 8:2, and the initiator is a Castrol catalyst.

[0099] Example 4: The raw materials of the liquid metal composite thermal paste include: 97 parts of liquid metal (gallium indium tin alloy), 1.15 parts of micro-encapsulating agent (heptadecyltrimethoxysilane), and 1.95 parts of small molecule blocking agent and macro-encapsulating agent in a mass ratio of 2:98. The macro-encapsulating agent includes 86 parts of component A, 12 parts of component B, and 0.2 parts of initiator. Component A consists of side-chain hydrogen-based polysiloxane and terminal hydrogen-based polysiloxane in a mass ratio of 10:76, ​​component B consists of side-chain vinyl polysiloxane and terminal vinyl polysiloxane in a mass ratio of 8:4, and the initiator is a Castrol catalyst.

[0100] Example 5: The raw materials of the liquid metal composite thermal paste include: 96.2 parts of liquid metal (gallium indium tin alloy), 1.15 parts of micro-encapsulating agent (triethoxyfluorosilane), and 2.65 parts of small molecule blocking agent and macro-encapsulating agent in total, with a mass ratio of 3:97. The macro-encapsulating agent includes 82 parts of component A, 15 parts of component B, and 0.1 parts of initiator. Component A consists of side-chain hydrogen-based polysiloxane and terminal hydrogen-based polysiloxane in a mass ratio of 7:75, component B consists of side-chain vinyl polysiloxane and terminal vinyl polysiloxane in a mass ratio of 10:5, and the initiator is a caster catalyst.

[0101] Example 6: The raw materials of the liquid metal composite thermal paste include: 93.2 parts of liquid metal (gallium indium tin alloy), 1.17 parts of micro-encapsulation agent (3-aminopropyltriethoxysilane), and 5.63 parts of small molecule blocking agent and macro-encapsulation agent in total, with a mass ratio of 5:95. The macro-encapsulation agent includes 85 parts of component A, 10 parts of component B, and 0.2 parts of initiator. Component A consists of side-chain hydrogen-based polysiloxane and terminal hydrogen-based polysiloxane in a mass ratio of 10:75, component B consists of side-chain vinyl polysiloxane and terminal vinyl polysiloxane in a mass ratio of 8:2, and the initiator is a caster catalyst.

[0102] The degradation of existing thermal interface materials during long-term use is mainly due to the extrusion of organic molecular chains and the volatilization of small molecules, which leads to the pumping out and drying of the encapsulation structure (such as the polymer matrix). For thermal interface materials with liquid metal as the main thermally conductive filler, in addition to the pumping out and drying of the encapsulation structure (such as the polymer matrix), the liquid metal filler will not only agglomerate due to surface tension, but will also react with water in the air to release hydrogen gas, which will break through the encapsulation structure (such as the polymer matrix), causing the liquid metal to leak and bringing a greater risk of short circuit.

[0103] In the above embodiments of this application, liquid metal, micro-encapsulating agent, macro-encapsulating agent, and small molecule blocking agent are mixed and dispersed uniformly to obtain a liquid metal composite thermal conductive paste. Heating and curing the liquid metal composite thermal conductive paste then yields a thermal interface material. Under the catalysis of the liquid metal, the micro-encapsulating agent undergoes a condensation reaction to form a first polysiloxane network that facilitates heat transfer and possesses a certain degree of hydrophobicity, forming a first encapsulation layer on the surface of the liquid metal filler. The polysiloxane structure can hinder the mutual contact between liquid metal droplets, preventing their aggregation. Simultaneously, due to the hydrophobic nature of the siloxane structure, this first encapsulation layer can also hinder the contact between liquid metal and water vapor, preventing the reaction to generate hydrogen gas and causing liquid metal leakage.

[0104] The macroscopic encapsulant acts as the polymer matrix of the thermal interface material. Components A and B undergo polymerization under the action of a caster catalyst to generate a stable second polysiloxane network with cross-linking and entanglement effects, forming a second encapsulation layer. This second encapsulation layer can further coat and protect the liquid metal filler, further isolating water vapor from contact with the liquid metal and preventing liquid metal leakage. Furthermore, because the polymer molecules in the second polysiloxane network have a large molecular weight, and the molecular chains are fixed within the polysiloxane network through cross-linking or entanglement, the polymer molecules in the second polysiloxane network are not easily pumped out or dried out. Therefore, the liquid metal composite thermal conductive paste, including liquid metal, microscopic encapsulant, and macroscopic encapsulant, can form a thermal interface material with good long-term stability after heating, and it is not prone to liquid metal leakage for extended periods at 85°C and 85% humidity.

[0105] Furthermore, the small-molecule blocking agent can flow back into the pores of the second polysiloxane network when the liquid metal composite thermal conductive paste is heated to form a thermal interface material, blocking the pores of the second polysiloxane network and preventing moisture from entering through these channels and reacting with the liquid metal. Moreover, during use, under the long-term action of thermal cycling stress, the thermal interface material will develop cracks, forming drainage channels. The small-molecule blocking agent can also flow back into these cracks when the thermal interface material is heated, blocking the drainage channels and preventing moisture from entering the matrix and contacting the liquid metal, thereby preventing liquid metal leakage and further improving the long-term stability of the thermal interface material.

[0106] On the other hand, small molecule blocking agents can also act as lubricants to control the viscosity of the matrix, thereby controlling the particle size of the liquid metal filler and keeping the particle size within a range that can maintain the high thermal conductivity of the thermal interface material.

[0107] Secondly, embodiments of this application also provide a thermal interface material, obtained by heating and curing the liquid metal composite thermal conductive paste described in the above embodiments. The thermal interface material includes: liquid metal, a first polysiloxane network encapsulating the liquid metal, and a second polysiloxane network encapsulating the first polysiloxane network. The first polysiloxane network is formed by a condensation reaction of a micro-encapsulating agent under the catalysis of the liquid metal. The micro-encapsulating agent is a compound containing hydrolyzable silicon functional groups. The second polysiloxane network is formed by the polymerization of a macro-encapsulating agent upon heating. The macro-encapsulating agent includes component A, component B, and an initiator. Component A and component B are polysiloxane compounds with crosslinkable functional groups. Component A and component B undergo a polymerization reaction under the action of the initiator upon heating.

[0108] In this embodiment, the thermal interface material comprises a liquid metal and a two-layer polysiloxane network encapsulation structure. Due to the hydrophobicity and thermal conductivity of the polysiloxane network, it protects the liquid metal from reaction with external moisture while providing excellent thermal conductivity. Therefore, the two-layer polysiloxane network encapsulation structure effectively encapsulates and protects the liquid metal, preventing moisture contact and leakage. The thermal interface material exhibits good long-term stability, showing minimal liquid metal leakage even under prolonged conditions of 85°C and 85% humidity. Furthermore, since the second polysiloxane network is formed by the polymerization of two polysiloxane compounds with crosslinkable functional groups under the action of an initiator, the polymers in the second polysiloxane network have a larger molecular weight, and the molecular chains are fixed within the polysiloxane network through crosslinking or entanglement. Therefore, the second polysiloxane network is less prone to pumping out and drying out, further improving the long-term stability of the thermal interface material.

[0109] For example, the thermal interface material also includes a small molecule blocking agent, which is a polysiloxane compound; the viscosity of the small molecule blocking agent at room temperature is between 10 and 100 mPa·s, the molecular weight is between 5000 and 10000, and the small molecule blocking agent does not react with the micro-encapsulating agent and the macro-encapsulating agent.

[0110] In this embodiment, the small molecule blocking agent is a polysiloxane compound. Therefore, the small molecule blocking agent has good compatibility with both micro and macro encapsulating agents. Furthermore, its small molecular weight and low flow resistance allow it to flow back into the pores of the second polysiloxane network during the heating and curing process of the liquid metal composite thermal conductive paste to form a thermal interface material. This blocks the pores of the second polysiloxane network, preventing moisture from entering through these channels and reacting with the liquid metal. Simultaneously, the small molecule blocking agent can also flow back into the cracks caused by the thermal interface material's thermal cycling stress during use, blocking drainage channels and preventing moisture from entering through these channels and contacting the liquid metal. Therefore, the small molecule blocking agent in this embodiment can further improve the long-term stability of the thermal interface material.

[0111] For example, the curing temperature is 55–65°C and the time is 1–6 hours.

[0112] For example, the thermal interface material obtained by heating and curing the liquid metal composite thermal conductive paste in the above embodiments has a thermal conductivity between 5 and 18 W / m·K, and has good thermal conductivity.

[0113] For example, the thermal interface material obtained by heating and curing the liquid metal composite thermal conductive paste in the above embodiments does not leak liquid metal for 48 to 216 hours under the double 85 test, indicating good long-term stability.

[0114] For example, the small molecule blocking agent is one of dimethyl silicone oil, ethyl silicone oil, phenyl silicone oil, and epoxy silicone oil.

[0115] For example, by weight, the liquid metal is between 92 and 97 parts, the total number of parts of the micro-encapsulant and the macro-encapsulant is between 3 and 8 parts, and the number of parts of the small molecule blocking agent is between 0.03 and 0.08 parts.

[0116] For example, the mass ratio of small molecule blocking agent to macroscopic encapsulant is between 1:99 and 5:95.

[0117] For example, component A includes at least one polysiloxane compound, which includes a functional group selected from vinyl, hydrogen, alkoxy, silanol, acyloxy, and amino; component B includes at least one polysiloxane compound, which includes a functional group selected from vinyl, hydrogen, alkoxy, silanol, acyloxy, and amino.

[0118] For example, component A includes at least one of side-chain hydrogen-based polysiloxane and terminal hydrogen-based polysiloxane, component B includes at least one of side-chain vinyl polysiloxane and terminal vinyl polysiloxane, and the initiator is a caster catalyst.

[0119] For example, by weight, component A is between 80 and 92 parts, component B is between 7 and 15 parts, and the initiator is between 0.1 and 0.3 parts; the viscosity of the macro-encapsulating agent at room temperature is between 10 and 500 mPa·s.

[0120] For example, the microencapsulating agent is one of mercaptosilane coupling agent, 3-chloropropyltriethoxysilane, 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane, and triethoxyfluorosilane.

[0121] For example, the liquid metal is metallic gallium or gallium-based liquid metal, and the gallium-based liquid metal is one of gallium-indium alloy and gallium-indium-tin alloy.

[0122] It is worth noting that the thermal interface material in this embodiment is not described in detail in relation to the liquid metal composite thermal grease in the above embodiments. For details, please refer to the detailed description of the liquid metal composite thermal grease in the above embodiments.

[0123] Thirdly, this application also provides a method for preparing a thermal interface material, capable of preparing the thermal interface material described in the above embodiments. For example... Figure 1 As shown, the specific steps include S101 to S103.

[0124] Step S101: Add liquid metal to a microencapsulating agent and heat to disperse it evenly. The microencapsulating agent is a compound containing hydrolyzable silicon functional groups.

[0125] In this embodiment, the microencapsulant is a compound containing hydrolyzable silicon functional groups. Upon heating, it undergoes a hydrolysis reaction under the catalysis of liquid metal to generate silanol (Si-OH). The silanol groups can then form silicon-oxygen bonds (Si-O-Si) through a dehydration condensation reaction, thereby constructing the first polysiloxane network. The polysiloxane network is a network structure formed by chemical bonds between polysiloxane molecules. It possesses the characteristics of a three-dimensional network, exhibiting good mechanical strength, heat resistance, chemical stability, and sealing properties, enabling it to encapsulate the liquid metal and form the first encapsulation layer. Because the polysiloxane network is hydrophobic and thermally conductive, it can both protect the liquid metal from contact with external moisture and provide good thermal conductivity.

[0126] For example, adding liquid metal to a microencapsulant and heating it to disperse it evenly includes: adding liquid metal to a microencapsulant and dispersing it at a speed of 300-600 rpm for 1-3 minutes in an environment of 40-60°C; and then dispersing it at a speed of 400-1000 rpm for 1-7 minutes in an environment of 40-60°C.

[0127] As dispersion time increases, the degree of reaction of the micro-encapsulant also increases, and the coating degree of the first polysiloxane network on the liquid metal also improves. In addition, by using a dispersion process of low speed (300-600 rpm) followed by high speed (400-1000 rpm), the micro-encapsulant can react more fully on the surface of the liquid metal, forming a dense first polysiloxane network with better coating effect.

[0128] Step S102: Add macroscopic encapsulant and disperse evenly.

[0129] In this embodiment, the macroscopic encapsulant includes component A, component B, and an initiator. Component A and component B are polysiloxane compounds with crosslinkable functional groups. When heated, components A and B form a second polysiloxane network under the action of the initiator.

[0130] No heating is involved in this step. Therefore, the macro encapsulant does not polymerize to form a second polysiloxane network after this step. Instead, components A, B, and the initiator are evenly dispersed around the first polysiloxane network. As a result, the second polysiloxane network formed during subsequent heating and curing is more evenly distributed.

[0131] For example, adding a macro-encapsulating agent and dispersing it evenly includes: adding the macro-encapsulating agent and stirring at a speed of 800-3000 rpm for 1-10 minutes; and performing ultrasonic treatment after stirring.

[0132] In this embodiment, high-speed stirring at 800–3000 rpm is used to control the minimum particle size of the liquid metal filler, keeping the particle size within a range that maintains the high thermal conductivity of the thermal interface material. After stirring, ultrasonic treatment is performed to make the particle size of the liquid metal filler more uniform.

[0133] According to the above steps S101 and S102, a liquid metal composite thermal paste comprising liquid metal, micro-encapsulant and macro-encapsulant can be prepared.

[0134] In another embodiment, the preparation method may further include step S103: adding a small molecule blocking agent and dispersing it evenly.

[0135] In this embodiment, the small molecule blocking agent is a polysiloxane compound. The viscosity of the small molecule blocking agent at room temperature is between 10-100 mPa·s, and the molecular weight is between 5000 and 10000. The small molecule blocking agent does not react with the micro-encapsulating agent or the macro-encapsulating agent.

[0136] In this embodiment, the small-molecule blocking agent exhibits excellent compatibility with both micro- and macro-encapsulating agents. Its low molecular weight and low flow resistance allow it to flow back into the pores of the second polysiloxane network during the heating of the liquid metal composite thermal conductive paste to form a thermal interface material. This blocks the pores of the second polysiloxane network, preventing moisture from entering through these channels and reacting with the liquid metal. Simultaneously, the small-molecule blocking agent can also flow back into the cracks caused by the thermal interface material's cyclic stress during use, blocking drainage channels and preventing moisture from entering through these channels and contacting the liquid metal. Therefore, the small-molecule blocking agent in this embodiment can further improve the long-term stability of the thermal interface material.

[0137] For example, adding a small molecule blocking agent and dispersing it evenly includes: adding the small molecule blocking agent and stirring at a speed of 300-1000 rpm for 1-5 minutes; and performing ultrasonic treatment after stirring is completed.

[0138] In this embodiment, after adding the small molecule blocking agent, the mixture is stirred at a low speed of 300-1000 rpm. While keeping the minimum particle size of the liquid metal filler unchanged, the liquid metal filler with a larger particle size is dispersed. Then, ultrasonic treatment is performed to make the particle size of the liquid metal filler more uniform, while the small molecule blocking agent is dispersed at the same time.

[0139] Using the preparation method and preparation parameters in the embodiments of this application, the liquid metal droplets in the thermal interface material obtained by heating and curing the liquid metal composite thermal conductive paste have a particle size between 100 nm and 400 μm and a thermal conductivity between 5 and 18 W / m·K. Moreover, it can maintain liquid metal leakage for 48 to 216 hours under an environment of 85°C and 85% humidity.

[0140] The preparation method of the thermal interface material in the embodiments of this application will be described below with reference to specific examples.

[0141] First, the test methods involved in the embodiments and comparative examples of this application should be explained as follows: Thermal conductivity: tested according to ASTM D5470 standard; Double 85 test: tested according to JESD22-A101C standard.

[0142] The manufacturers and grades of the raw materials involved in the embodiments and comparative examples of this application are as follows:

[0143] Gallium-indium alloy: Manufacturer is ALADDIN, grade is G380237;

[0144] Gallium indium tin alloy: Manufacturer is ALADDIN, grade is G466317-1EA;

[0145] Mercaptosilane coupling agent: Manufacturer is MACKLIN, brand name is M887643;

[0146] 3-Chloropropyltriethoxysilane: Manufacturer: Sigma-Aldrich, Grade: 569615;

[0147] 3-Aminopropyltriethoxysilane: Manufacturer: Sigma-Aldrich, Grade: A3648;

[0148] Vinyltrimethoxysilane: Manufacturer: Sigma-Aldrich, Grade: 235768;

[0149] Heptadecafluorodecyltrimethoxysilane: Manufacturer: Huawiray, Product Code: HWG21036;

[0150] Triethoxyfluorosilane: Manufacturer: ALADDIN, Grade: T162285;

[0151] Dimethyl silicone oil: Manufacturer is Myriel, brand name is M22244;

[0152] Ethyl silicone oil: Manufacturer is MACKLIN, grade is P934279;

[0153] Phenyl silicone oil: Manufacturer: Huiyan; Brand: HY-556;

[0154] Epoxy silicone oil: Manufacturer: Qingdao Baisenmao New Materials Co., Ltd., Grade: BSM204;

[0155] Hydrogen-terminated polysiloxane: Manufacturer: ALADDIN, Grade: P304458;

[0156] End-group vinyl polysiloxane: Manufacturer is MACKLIN, brand name is V833863;

[0157] KARSTEDT catalyst: Manufacturer: MACKLIN, Grade: K855033;

[0158] Side-chain hydrogen-based polysiloxane: Manufacturer is Jiangxi Haiduo Organosilicon Materials Co., Ltd., brand name is H-202L;

[0159] Side-chain vinyl polysiloxane: Manufacturer is Zhejiang Runhe Organosilicon New Material Co., Ltd., brand name is RH-Vi306.

[0160] Secondly, specific implementation methods are shown below.

[0161] Example 1:

[0162] (1) Preparation of raw materials

[0163] Liquid metal: gallium-indium alloy;

[0164] Microencapsulation agent: mercaptosilane coupling agent;

[0165] Small molecule blocking agent: epoxy silicone oil;

[0166] Macroscopic encapsulant: by weight, it comprises 82 parts of component A, 15 parts of component B, and 0.1 parts of initiator. Component A consists of side-chain hydrogen-based polysiloxane and terminal hydrogen-based polysiloxane in a mass ratio of 10:72, component B consists of side-chain vinyl polysiloxane and terminal vinyl polysiloxane in a mass ratio of 10:5, and the initiator is a caster catalyst.

[0167] By weight, the amounts of each raw material are as follows: 96.2 parts liquid metal, 1.15 parts micro-encapsulating agent, and 2.65 parts total of small molecule blocking agent and macro-encapsulating agent; the mass ratio of small molecule blocking agent to macro-encapsulating agent is 3:97.

[0168] (2) Add liquid metal to the micro-encapsulating agent and disperse it in a water bath at 40°C at a speed of 400 rpm for 1 min, and then disperse it at a speed of 600 rpm for 2 min.

[0169] (3) Add macroscopic encapsulating agent to the system in step (2), stir at 1200 rpm for 3 min, and after stirring, perform ultrasonic treatment at 40 W power for 3 min.

[0170] (4) Add a small molecule blocking agent to the system in step (3), stir at 600 rpm for 1 min, and after stirring, sonicate at 40 W for 2 min to obtain a liquid metal composite thermal paste that can prepare a thermal interface material with good long-term stability.

[0171] The above-mentioned liquid metal composite thermal conductive paste was applied between the heating element and the heat dissipation element and cured at 60°C for 6 hours to obtain a thermal interface material with long-term double 85 stability. The average particle size of the liquid metal droplets was 30 μm. Figure 2 As shown, the thermal conductivity is 8 W / m·K; Figure 3 As shown, the thermal interface material with long-term double 85 stability can maintain its liquid metal leakage for 169 hours in the double 85 stability test.

[0172] Example 2:

[0173] (1) Preparation of raw materials

[0174] Liquid metal: gallium-indium alloy;

[0175] Microencapsulation agent: mercaptosilane coupling agent;

[0176] Small molecule blocking agent: epoxy silicone oil;

[0177] Macroscopic encapsulant: by weight, it comprises 83 parts of component A, 15 parts of component B and 0.15 parts of initiator. Component A is a side-chain hydrogen-based polysiloxane and a terminal hydrogen-based polysiloxane in a mass ratio of 10:73. Component B is a side-chain vinyl polysiloxane and a terminal vinyl polysiloxane in a mass ratio of 10:5. The initiator is a caster catalyst.

[0178] By weight, the amounts of each raw material are as follows: 96.2 parts liquid metal, 1.15 parts micro-encapsulating agent, and 2.65 parts total of small molecule blocking agent and macro-encapsulating agent; the mass ratio of small molecule blocking agent to macro-encapsulating agent is 2:98.

[0179] (2) Add liquid metal to the micro-encapsulating agent and disperse it in a water bath at 40°C at a speed of 400 rpm for 2 min, and then disperse it at a speed of 600 rpm for 3 min.

[0180] (3) Add macroscopic encapsulating agent to the system in step (2), stir at 800 rpm for 3 min, and after stirring, perform ultrasonic treatment at 40 W power for 4 min.

[0181] (4) Add a small molecule blocking agent to the system in step (3), stir at 550 rpm for 4 min, and after stirring, sonicate at 40 W for 5 min to obtain a liquid metal composite thermal paste that can prepare a thermal interface material with good long-term stability.

[0182] The above-mentioned liquid metal composite thermal conductive paste was applied between the heating element and the heat dissipation element and cured at 60°C for 6 hours to obtain a thermal interface material with long-term double 85 stability. The average particle size of the liquid metal droplets was 50 μm. Figure 2 As shown, the thermal conductivity is 9.5 W / m·K; Figure 3 As shown, the thermal interface material with long-term double 85 stability can maintain its liquid metal leakage for 168 hours in the double 85 stability test.

[0183] Example 3

[0184] (1) Preparation of raw materials

[0185] Liquid metal: gallium-indium alloy;

[0186] Microencapsulation agent: mercaptosilane coupling agent;

[0187] Small molecule blocking agent: epoxy silicone oil;

[0188] Macroscopic encapsulant: by weight, it comprises 88 parts of component A, 10 parts of component B and 0.2 parts of initiator. Component A is a side-chain hydrogen-based polysiloxane and a terminal hydrogen-based polysiloxane in a mass ratio of 12:76. Component B is a side-chain vinyl polysiloxane and a terminal vinyl polysiloxane in a mass ratio of 5:5. The initiator is a caster catalyst.

[0189] By weight, the amounts of each raw material are as follows: 96.2 parts liquid metal, 1.15 parts micro-encapsulating agent, and 2.65 parts total of small molecule blocking agent and macro-encapsulating agent; the mass ratio of small molecule blocking agent to macro-encapsulating agent is 2:98.

[0190] (2) Add liquid metal to the micro-encapsulating agent and disperse it in a water bath at 40°C at a speed of 400 rpm for 2 min, and then disperse it at a speed of 600 rpm for 3 min.

[0191] (3) Add macroscopic encapsulating agent to the system in step (2), stir at 800 rpm for 3.5 min, and after stirring, perform ultrasonic treatment at 40 W power for 8 min.

[0192] (4) Add a small molecule blocking agent to the system in step (3), stir at 550 rpm for 4 min, and after stirring, sonicate at 40 W for 4 min to obtain a liquid metal composite thermal paste that can prepare a thermal interface material with good long-term stability.

[0193] The above-mentioned liquid metal composite thermal conductive paste was applied between the heating element and the heat dissipation element and cured at 60°C for 6 hours to obtain a thermal interface material with long-term double 85 stability. The average particle size of the liquid metal droplets was 40 μm. Figure 2 As shown, the thermal conductivity is 9 W / m·K; Figure 3 As shown, the thermal interface material with long-term double 85 stability can maintain its liquid metal leakage for 144 hours in the double 85 stability test.

[0194] Example 4

[0195] (1) Preparation of raw materials

[0196] Liquid metal: gallium-indium alloy;

[0197] Microencapsulation agent: mercaptosilane coupling agent;

[0198] Small molecule blocking agent: epoxy silicone oil;

[0199] By weight, the macro encapsulant comprises 81 parts of component A, 7 parts of component B, and 0.25 parts of initiator. Component A consists of side-chain hydrogen-based polysiloxane and terminal hydrogen-based polysiloxane in a mass ratio of 10:81, component B consists of side-chain vinyl polysiloxane and terminal vinyl polysiloxane in a mass ratio of 2:5, and the initiator is a caster catalyst.

[0200] By weight, the amounts of each raw material are as follows: 96.2 parts liquid metal, 1.15 parts micro-encapsulating agent, and 2.65 parts total of small molecule blocking agent and macro-encapsulating agent; the mass ratio of small molecule blocking agent to macro-encapsulating agent is 2:98.

[0201] (2) Add liquid metal to the micro-encapsulating agent and disperse it in a water bath at 40°C at a speed of 400 rpm for 2 min, and then disperse it at a speed of 600 rpm for 3 min.

[0202] (3) Add macroscopic encapsulating agent to the system in step (2), stir at 800 rpm for 4.5 min, and after stirring, perform ultrasonic treatment at 40 W power for 10 min.

[0203] (4) Add a small molecule blocking agent to the system in step (3), stir at 550 rpm for 4 min, and after stirring, sonicate at 40 W for 9 min to obtain a liquid metal composite thermal paste that can prepare a thermal interface material with good long-term stability.

[0204] The above-mentioned liquid metal composite thermal conductive paste was applied between the heating element and the heat dissipation element and cured at 60°C for 6 hours to obtain a thermal interface material with long-term double 85 stability. The average particle size of the liquid metal droplets was 400 nm. Figure 2 As shown, the thermal conductivity is 11 W / m·K; Figure 3 As shown, the thermal interface material with long-term double 85 stability can maintain its liquid metal leakage for 144 hours in the double 85 stability test.

[0205] Example 5

[0206] (1) Preparation of raw materials

[0207] Liquid metal: gallium-indium alloy;

[0208] Microencapsulation agent: mercaptosilane coupling agent;

[0209] Small molecule blocking agent: epoxy silicone oil;

[0210] Macroscopic encapsulant: by weight, it comprises 82 parts of component A, 15 parts of component B, and 0.3 parts of initiator. Component A consists of side-chain hydrogen-based polysiloxane and terminal hydrogen-based polysiloxane in a mass ratio of 10:72, component B consists of side-chain vinyl polysiloxane and terminal vinyl polysiloxane in a mass ratio of 10:5, and the initiator is a caster catalyst.

[0211] By weight, the amounts of each raw material are as follows: 96.2 parts liquid metal, 1.15 parts micro-encapsulating agent, and 2.65 parts total of small molecule blocking agent and macro-encapsulating agent; the mass ratio of small molecule blocking agent to macro-encapsulating agent is 3:97.

[0212] (2) Add liquid metal to the micro-encapsulating agent and disperse it in a water bath at 40°C at 400 rpm for 3 min, and then disperse it at 600 rpm for 2 min.

[0213] (3) Add macroscopic encapsulating agent to the system in step (2), stir at 800 rpm for 1.5 min, and after stirring, perform ultrasonic treatment at 40 W power for 13 min.

[0214] (4) Add a small molecule blocking agent to the system in step (3), stir at 600 rpm for 1 min, and after stirring, sonicate at 40 W for 10 min to obtain a liquid metal composite thermal paste that can prepare a thermal interface material with good long-term stability.

[0215] A liquid metal composite thermal conductive paste was applied between the heating element and the heat dissipation element and cured at 60°C for 6 hours to obtain a thermal interface material with long-term double 85 stability. The average particle size of the liquid metal droplets was 200 nm. Figure 2 As shown, the thermal conductivity is 8.8 W / m·K; Figure 3 As shown, the thermal interface material with long-term double 85 stability can maintain its liquid metal leakage for 192 hours in the double 85 stability test.

[0216] Example 6:

[0217] (1) Preparation of raw materials

[0218] Liquid metal: gallium-indium alloy;

[0219] Microencapsulation agent: mercaptosilane coupling agent;

[0220] Small molecule blocking agent: dimethyl silicone oil;

[0221] Macroscopic encapsulant: by weight, it comprises 86 parts of component A, 12 parts of component B, and 0.2 parts of initiator. Component A consists of side-chain hydrogen-based polysiloxane and terminal hydrogen-based polysiloxane in a mass ratio of 10:76, ​​component B consists of side-chain vinyl polysiloxane and terminal vinyl polysiloxane in a mass ratio of 10:2, and the initiator is a caster catalyst.

[0222] By weight, the amounts of each raw material are as follows: 95.1 parts liquid metal, 1.02 parts micro-encapsulating agent, and 3.88 parts total of small molecule blocking agent and macro-encapsulating agent; the mass ratio of small molecule blocking agent to macro-encapsulating agent is 2:98.

[0223] (2) Add liquid metal to the micro-encapsulating agent and disperse it in a water bath at 45°C at a speed of 600 rpm for 1 min, and then disperse it at a speed of 800 rpm for 1 min.

[0224] (3) Add macroscopic encapsulating agent to the system in step (2), stir at 800 rpm for 4 min, and after stirring, perform ultrasonic treatment at 40 W power for 6 min.

[0225] (4) Add a small molecule blocking agent to the system in step (3), stir at 300 rpm for 2 min, and after stirring, sonicate at 40 W for 4 min to obtain a liquid metal composite thermal paste that can prepare a thermal interface material with good long-term stability.

[0226] The above-mentioned liquid metal composite thermal conductive paste was applied between the heat-generating and heat-dissipating components of an electronic product and cured at 55°C for 6 hours to obtain a thermal interface material with long-term double 85 stability. The average particle size of the liquid metal droplets was 200 μm. Figure 2 As shown, the thermal conductivity is 9 W / m·K; Figure 3 As shown, the thermal interface material with long-term double 85 stability can maintain its liquid metal leakage for 48 hours in the double 85 stability test.

[0227] Example 7

[0228] (1) Preparation of raw materials

[0229] Liquid metal: gallium-indium alloy;

[0230] Microencapsulation agent: 3-chloropropyltriethoxysilane;

[0231] Small molecule blocking agent: dimethyl silicone oil;

[0232] Macroscopic encapsulant: by weight, it comprises 86 parts of component A, 10 parts of component B, and 0.2 parts of initiator. Component A consists of side-chain hydrogen-based polysiloxane and terminal hydrogen-based polysiloxane in a mass ratio of 12:74, component B consists of side-chain vinyl polysiloxane and terminal vinyl polysiloxane in a mass ratio of 8:2, and the initiator is a caster catalyst.

[0233] By weight, the amounts of each raw material are as follows: 94.3 parts liquid metal, 1.0 part micro-encapsulating agent, and 4.7 parts total of small molecule blocking agent and macro-encapsulating agent; the mass ratio of small molecule blocking agent to macro-encapsulating agent is 4:96.

[0234] (2) Add liquid metal to the micro-encapsulating agent and disperse it in a water bath at 50°C at a speed of 300 rpm for 1 min, and then disperse it at a speed of 400 rpm for 2 min.

[0235] (3) Add macroscopic encapsulating agent to the system in step (2), stir at 800 rpm for 5 min, and after stirring, perform ultrasonic treatment at 40 W power for 2 min.

[0236] (4) Add a small molecule blocking agent to the system in step (3), stir at 800 rpm for 3 min, and after stirring, sonicate at 40 W for 1 min to obtain a liquid metal composite thermal paste that can prepare a thermal interface material with good long-term stability.

[0237] A liquid metal composite thermal conductive paste was applied between the heating element and the heat dissipation element and cured at 65°C for 6 hours to obtain a thermal interface material with long-term double 85 stability. The average particle size of the liquid metal droplets was 400 μm. Figure 2 As shown, the thermal conductivity is 12 W / m·K; Figure 3 As shown, the thermal interface material with long-term double 85 stability can maintain 96 hours without liquid metal leakage in the double 85 stability test.

[0238] Example 8

[0239] (1) Preparation of raw materials

[0240] Liquid metal: gallium-indium alloy;

[0241] Microencapsulation agent: 3-aminopropyltriethoxysilane;

[0242] Small molecule blocking agent: Ethyl silicone oil;

[0243] Macroscopic encapsulant: by weight, it comprises 85 parts of component A, 10 parts of component B and 0.2 parts of initiator. Component A is a side-chain hydrogen-based polysiloxane and a terminal hydrogen-based polysiloxane in a mass ratio of 10:75. Component B is a side-chain vinyl polysiloxane and a terminal vinyl polysiloxane in a mass ratio of 8:2. The initiator is a caster catalyst.

[0244] By weight, the amounts of each raw material are as follows: 93.2 parts liquid metal, 1.17 parts micro-encapsulating agent, and 5.63 parts total of small molecule blocking agent and macro-encapsulating agent; the mass ratio of small molecule blocking agent to macro-encapsulating agent is 5:95.

[0245] (2) Add liquid metal to the micro-encapsulating agent and disperse it in a water bath at 55°C at a speed of 300 rpm for 2 min, and then disperse it at a speed of 500 rpm for 2 min.

[0246] (3) Add macroscopic encapsulating agent to the system in step (2), stir at 1500 rpm for 1 min, and after stirring, perform ultrasonic treatment at 40 W power for 15 min.

[0247] (4) Add a small molecule blocking agent to the system in step (3), stir at 1000 rpm for 4 min, and after stirring, sonicate at 40 W for 18 min to obtain a liquid metal composite thermal paste that can prepare a thermal interface material with good long-term stability.

[0248] A liquid metal composite thermal conductive paste was applied between the heating element and the heat dissipation element and cured at 60°C for 6 hours to obtain a thermal interface material with long-term double 85 stability. The average particle size of the liquid metal droplets was 200 nm. Figure 2 As shown, the thermal conductivity is 6 W / m·K; Figure 3 As shown, the thermal interface material with long-term double 85 stability can maintain its liquid metal leakage for 72 hours in the double 85 stability test.

[0249] Example 9

[0250] (1) Preparation of raw materials

[0251] Liquid metal: Gallium indium tin alloy;

[0252] Microencapsulation agent: Vinyltrimethoxysilane;

[0253] Small molecule blocking agent: phenyl silicone oil;

[0254] Macroscopic encapsulant: by weight, it comprises 89 parts of component A, 10 parts of component B, and 0.2 parts of initiator. Component A consists of side-chain hydrogen-based polysiloxane and terminal hydrogen-based polysiloxane in a mass ratio of 7:82, component B consists of side-chain vinyl polysiloxane and terminal vinyl polysiloxane in a mass ratio of 8:2, and the initiator is a caster catalyst.

[0255] By weight, the amounts of each raw material are as follows: 92 parts liquid metal, 1.24 parts micro-encapsulating agent, and a total of 6.76 parts small molecule blocking agent and macro-encapsulating agent; the mass ratio of small molecule blocking agent to macro-encapsulating agent is 1:99.

[0256] (2) Add liquid metal to the micro-encapsulating agent and disperse it in a water bath at 60°C at 600 rpm for 2 min, and then disperse it at 1000 rpm for 3 min.

[0257] (3) Add macroscopic encapsulating agent to the system in step (2), stir at 2000 rpm for 2 min, and after stirring, perform ultrasonic treatment at 40W power for 18 min.

[0258] (4) Add a small molecule blocking agent to the system in step (3), stir at 400 rpm for 5 min, and after stirring, sonicate at 40 W for 20 min to obtain a liquid metal composite thermal paste that can prepare a thermal interface material with good long-term stability.

[0259] A liquid metal composite thermal conductive paste was applied between the heating element and the heat dissipation element and cured at 60°C for 6 hours to obtain a thermal interface material with long-term double 85 stability. The average particle size of the liquid metal droplets was 100 nm. Figure 2 As shown, the thermal conductivity is 5 W / m·K; Figure 3 As shown, the thermal interface material with long-term double 85 stability can maintain 120 hours without liquid metal leakage in the double 85 stability test.

[0260] Example 10

[0261] (1) Preparation of raw materials

[0262] Liquid metal: Gallium indium tin alloy;

[0263] Microencapsulation agent: heptadecyltrimethoxysilane;

[0264] Small molecule blocking agent: phenyl silicone oil;

[0265] Macroscopic encapsulant: by weight, it comprises 86 parts of component A, 12 parts of component B and 0.2 parts of initiator. Component A is a side-chain hydrogen-based polysiloxane and a terminal hydrogen-based polysiloxane in a mass ratio of 10:76. Component B is a side-chain vinyl polysiloxane and a terminal vinyl polysiloxane in a mass ratio of 8:4. The initiator is a caster catalyst.

[0266] By weight, the amounts of each raw material are as follows: 97.0 parts liquid metal, 1.15 parts micro-encapsulating agent, and 1.95 parts total of small molecule blocking agent and macro-encapsulating agent; the mass ratio of small molecule blocking agent to macro-encapsulating agent is 2:98.

[0267] (2) Add liquid metal to the micro-encapsulating agent and disperse it in a water bath at 40°C at a speed of 300 rpm for 2 min, and then disperse it at a speed of 400 rpm for 5 min.

[0268] (3) Add macroscopic encapsulating agent to the system in step (2), stir at 2500 rpm for 1 min, and after stirring, perform ultrasonic treatment at 40 W power for 2 min.

[0269] (4) Add a small molecule blocking agent to the system in step (3), stir at 600 rpm for 1 min, and after stirring, sonicate at 40 W for 2 min to obtain a liquid metal composite thermal paste that can prepare a thermal interface material with good long-term stability.

[0270] A liquid metal composite thermal conductive paste was applied between the heating element and the heat dissipation element and cured at 60°C for 6 hours to obtain a thermal interface material with long-term double 85 stability. The average particle size of the liquid metal droplets was 200 μm. Figure 2 As shown, the thermal conductivity is 12 W / m·K; Figure 3 As shown, the thermal interface material with long-term double 85 stability can maintain its liquid metal leakage for 144 hours in the double 85 stability test.

[0271] Example 11

[0272] (1) Preparation of raw materials

[0273] Liquid metal: Gallium indium tin alloy;

[0274] Microencapsulation agent: Triethoxyfluorosilane;

[0275] Small molecule blocking agent: Ethyl silicone oil;

[0276] Macroscopic encapsulant: by weight, it comprises 82 parts of component A, 15 parts of component B and 0.1 parts of initiator. Component A is a side-chain hydrogen-based polysiloxane and a terminal hydrogen-based polysiloxane in a mass ratio of 7:75. Component B is a side-chain vinyl polysiloxane and a terminal vinyl polysiloxane in a mass ratio of 10:5. The initiator is a caster catalyst.

[0277] By weight, the amounts of each raw material are as follows: 96.2 parts liquid metal, 1.15 parts micro-encapsulating agent, and 2.65 parts total of small molecule blocking agent and macro-encapsulating agent; the mass ratio of small molecule blocking agent to macro-encapsulating agent is 3:97.

[0278] (2) Add liquid metal to the micro-encapsulating agent and disperse it in a water bath at 40°C at a speed of 300 rpm for 3 min, and then disperse it at a speed of 400 rpm for 6 min.

[0279] (3) Add macroscopic encapsulating agent to the system in step (2), stir at 3000 rpm for 1 min, and after stirring, perform ultrasonic treatment at 40W power for 1 min.

[0280] (4) Add a small molecule blocking agent to the system in step (3), stir at 400 rpm for 1 min, and after stirring, sonicate at 40 W for 1 min to obtain a liquid metal composite thermal paste that can prepare a thermal interface material with good long-term stability.

[0281] A liquid metal composite thermal conductive paste was applied between the heating element and the heat dissipation element and cured at 60°C for 6 hours to obtain a thermal interface material with long-term double 85 stability. The average particle size of the liquid metal droplets was 100 μm. Figure 2 As shown, the thermal conductivity is 16 W / m·K; Figure 3 As shown, the thermal interface material with long-term double 85 stability can maintain its liquid metal leakage for 169 hours in the double 85 stability test.

[0282] Example 12

[0283] (1) Preparation of raw materials

[0284] Liquid metal: Gallium indium tin alloy;

[0285] Microencapsulation agent: mercaptosilane coupling agent;

[0286] Small molecule blocking agent: epoxy silicone oil;

[0287] Macroscopic encapsulant: by weight, it comprises 83 parts of component A, 15 parts of component B and 0.3 parts of initiator. Component A is a side-chain hydrogen-based polysiloxane and a terminal hydrogen-based polysiloxane in a mass ratio of 8:75. Component B is a side-chain vinyl polysiloxane and a terminal vinyl polysiloxane in a mass ratio of 10:5. The initiator is a caster catalyst.

[0288] By weight, the amounts of each raw material are as follows: 96.2 parts liquid metal, 1.15 parts micro-encapsulating agent, and 2.65 parts total of small molecule blocking agent and macro-encapsulating agent; the mass ratio of small molecule blocking agent to macro-encapsulating agent is 2:98.

[0289] (2) Add liquid metal to the micro-encapsulating agent and disperse it in a water bath at 40°C at a speed of 300 rpm for 3 min, and then disperse it at a speed of 500 rpm for 7 min.

[0290] (3) Add macroscopic encapsulating agent to the system in step (2), stir at 800 rpm for 10 min, and after stirring, perform ultrasonic treatment at 40 W power for 3 min.

[0291] (4) Add a small molecule blocking agent to the system in step (3), stir at 500 rpm for 1 min, and after stirring, sonicate at 40 W for 2 min to obtain a liquid metal composite thermal paste that can prepare a thermal interface material with good long-term stability.

[0292] A liquid metal composite thermal conductive paste was applied between the heating element and the heat dissipation element and cured at 60°C for 6 hours to obtain a thermal interface material with long-term double 85 stability. The average particle size of the liquid metal droplets was 80 μm. Figure 2 As shown, the thermal conductivity is 18 W / m·K; Figure 3 As shown, the thermal interface material with long-term double 85 stability can maintain 96 hours without liquid metal leakage in the double 85 stability test.

[0293] Example 13

[0294] (1) Preparation of raw materials

[0295] Liquid metal: gallium-indium alloy;

[0296] Microencapsulation agent: mercaptosilane coupling agent;

[0297] Small molecule blocking agent: epoxy silicone oil;

[0298] Macroscopic encapsulant: by weight, it comprises 88 parts of component A, 10 parts of component B and 0.2 parts of initiator. Component A is a side-chain hydrogen-based polysiloxane and a terminal hydrogen-based polysiloxane in a mass ratio of 15:73. Component B is a side-chain vinyl polysiloxane and a terminal vinyl polysiloxane in a mass ratio of 8:2. The initiator is a caster catalyst.

[0299] By weight, the amounts of each raw material are as follows: 96.2 parts liquid metal, 1.15 parts micro-encapsulating agent, and 2.65 parts total of small molecule blocking agent and macro-encapsulating agent; the mass ratio of small molecule blocking agent to macro-encapsulating agent is 2:98.

[0300] (2) Add liquid metal to the micro-encapsulating agent and disperse it in a water bath at 40°C at 400 rpm for 1 min, and then disperse it at 600 rpm for 4 min.

[0301] (3) Add macroscopic encapsulating agent to the system in step (2), stir at 1200 rpm for 3 min, and after stirring, perform ultrasonic treatment at 40 W power for 5 min.

[0302] (4) Add a small molecule blocking agent to the system in step (3), stir at 600 rpm for 1 min, and after stirring, sonicate at 40 W for 4 min to obtain a liquid metal composite thermal paste that can prepare a thermal interface material with good long-term stability.

[0303] A liquid metal composite thermal conductive paste was applied between the heating element and the heat dissipation element and cured at 65°C for 6 hours to obtain a thermal interface material with long-term double 85 stability. The average particle size of the liquid metal droplets was 50 μm. Figure 2 As shown, the thermal conductivity is 10 W / m·K; Figure 3 As shown, the thermal interface material with long-term double 85 stability can maintain 216 hours without liquid metal leakage in the double 85 stability test.

[0304] Based on Example 6 above, several comparative examples are given below to demonstrate the importance of the selection of small molecule blocking agents in the embodiments of this application.

[0305] Comparative Example 1

[0306] The preparation method is basically the same as in Example 6, except that the small molecule blocking agent is dibutyl phthalate.

[0307] The final thermal interface material has a liquid metal droplet thermal conductivity of 8.7 W / m·K; the thermal interface material can maintain its liquid metal leakage for 12 hours in the double 85 stability test.

[0308] like Figure 4As shown, comparing Comparative Example 1 and Example 6, it can be found that the double 85 stability of the thermal interface material prepared using dibutyl phthalate as a small molecule blocker is significantly reduced. This is because the small molecule dibutyl phthalate used in Comparative Example 1 is a non-siloxane, which has poor compatibility with the encapsulation layer (polysiloxane network). Moreover, its molecular weight is 278.34, which is not in the range of 5000-10000. It can only be used as a diluent and leveling agent. It can adjust the material to have appropriate viscosity and thixotropy during the mixing process, balance the surface tension of the matrix, and improve the smoothness of the system surface. However, it cannot flow freely in the second polysiloxane network composed of macroscopic encapsulants, block the drainage channels, and cannot isolate the contact between liquid metal and water.

[0309] Comparative Example 2

[0310] The preparation method is basically the same as in Example 6, except that the small molecule blocking agent is vinyl silicone oil, and the viscosity of vinyl silicone oil at 25°C is 500 mPa·s.

[0311] The final thermal interface material has a liquid metal droplet thermal conductivity of 9.6 W / m·K; the thermal interface material can maintain its liquid metal leakage for 12 hours in the double 85 stability test.

[0312] like Figure 4 As shown, comparing Comparative Example 2 and Example 6, it can be found that the double 85 stability of the thermal interface material prepared using vinyl silicone oil as a small molecule blocker is significantly reduced. This is because the vinyl silicone oil used in Comparative Example 2 contains vinyl groups, which will undergo a cross-linking reaction with the macro encapsulant, leading to its over-polymerization. Moreover, its viscosity at 25°C is not in the range of 10-100 mPa·s, so it cannot flow freely in the second polysiloxane network formed by the macro encapsulant, blocking the drainage channels and failing to isolate the contact between liquid metal and water.

[0313] Comparative Example 3

[0314] The preparation method is basically the same as in Example 6, except that the small molecule blocking agent is polyethylene glycol diglycidyl ether, and the viscosity of polyethylene glycol diglycidyl ether at 25°C is 130 mPa·s.

[0315] The final thermal interface material has a liquid metal droplet thermal conductivity of 8.5 W / m·K; the thermal interface material can maintain its liquid metal leakage for 24 hours in the double 85 stability test.

[0316] like Figure 4As shown, comparing Comparative Example 3 and Example 6, it can be found that the double 85 stability of the thermal interface material prepared using polyethylene glycol diglycidyl ether as a small molecule blocking agent is significantly reduced. This is because the polyethylene glycol diglycidyl ether used in Comparative Example 3 is a non-siloxane, which has poor compatibility with the encapsulation layer (polysiloxane network). Moreover, its viscosity at 25°C is not in the range of 10-100 mPa·s. It can only be used as a diluent and leveling agent. It can adjust the material to have appropriate viscosity and thixotropy during the mixing process, balance the surface tension of the matrix, and improve the smoothness of the system surface. However, it cannot flow freely in the second polysiloxane network composed of macroscopic encapsulants, block drainage channels, and cannot isolate the contact between liquid metal and water.

[0317] Comparative Example 4

[0318] The preparation method is basically the same as in Example 6, except that the small molecule blocking agent is polyether-modified silicone oil, and the viscosity of polyether-modified silicone oil at 25°C is 1000 mPa·s.

[0319] The final thermal interface material has a liquid metal droplet thermal conductivity of 9.3 W / m·K; the thermal interface material can maintain its liquid metal leakage for 36 hours in the double 85 stability test.

[0320] like Figure 4 As shown, comparing Comparative Example 4 and Example 6, it can be found that the double 85 stability of the thermal interface material prepared using polyether modified silicone oil as a small molecule blocking agent is significantly reduced. This is because the viscosity of the polyether modified silicone oil used in Comparative Example 4 at 25°C is not in the range of "10-100 mPa·s". It can only be used as a diluent and leveling agent. It can adjust the material to have appropriate viscosity and thixotropy during the mixing process, balance the surface tension of the matrix, and improve the smoothness of the system surface. However, it cannot flow freely in the second polysiloxane network composed of macroscopic encapsulants, block the drainage channels, and cannot isolate the contact between liquid metal and water.

[0321] It should be understood that the above examples are provided to help those skilled in the art understand the embodiments of this application, and are not intended to limit the embodiments of this application to the specific values ​​or scenarios illustrated. Those skilled in the art can obviously make various equivalent modifications or changes based on the above examples, and such modifications or changes also fall within the scope of the embodiments of this application.

[0322] This application also provides an electronic product, which includes a heat-generating element and a heat-dissipating element, as well as a thermal interface material located between the heat-generating element and the heat-dissipating element as described in the above embodiments. The thermal interface material is obtained by heating and curing the liquid metal composite thermal conductive paste described in the above embodiments.

[0323] Electronic products such as transistors, CPU assemblies, thermistors, temperature sensors, automotive electronic components, car refrigerators, power modules, and printer heads utilize thermal interface materials. These materials act as a heat transfer medium while also providing moisture-proof, dust-proof, corrosion-proof, and shock-proof functions, demonstrating significant application value and economic benefits.

[0324] The above description is merely a specific implementation of the embodiments of this application, but the protection scope of the embodiments of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of this application should be included within the protection scope of the embodiments of this application. Therefore, the protection scope of the embodiments of this application should be determined by the protection scope of the claims.

Claims

1. A liquid metal composite thermal conductive paste, characterized in that, The liquid metal composite thermal paste comprises: liquid metal, a first polysiloxane network, and a macroscopic encapsulant; The first polysiloxane network encapsulates the liquid metal. The first polysiloxane network is formed by the condensation reaction of a microencapsulant under the catalysis of the liquid metal. The microencapsulant is a compound containing hydrolyzable silicon functional groups. The macroscopic encapsulant includes component A, component B, and an initiator. Component A and component B are polysiloxane compounds with crosslinkable functional groups. When heated, component A and component B polymerize under the action of the initiator to form a second polysiloxane network, and the second polysiloxane network encapsulates the first polysiloxane network.

2. The liquid metal composite thermal conductive paste according to claim 1, characterized in that, The liquid metal composite thermal conductive paste also includes a small molecule blocking agent, which is a polysiloxane compound. The small molecule blocking agent has a viscosity between 10 and 100 mPa·s at room temperature and a molecular weight between 5,000 and 10,000. The small molecule blocking agent does not react with the micro-encapsulating agent or the macro-encapsulating agent.

3. The liquid metal composite thermal conductive paste according to claim 2, characterized in that, The small molecule blocking agent is one of dimethyl silicone oil, ethyl silicone oil, phenyl silicone oil, and epoxy silicone oil.

4. The liquid metal composite thermal conductive paste according to claim 2 or 3, characterized in that, By weight, the liquid metal comprises 92 to 97 parts, the total number of the micro-encapsulating agent and the macro-encapsulating agent comprises 3 to 8 parts, and the small molecule blocking agent comprises 0.03 to 0.08 parts.

5. The liquid metal composite thermal conductive paste according to claim 4, characterized in that, The mass ratio of the small molecule blocking agent to the macroscopic encapsulating agent is between 1:99 and 5:

95.

6. The liquid metal composite thermal grease according to any one of claims 1 to 5, characterized in that, Component A includes at least one polysiloxane compound, which includes a functional group selected from vinyl, hydrogen, alkoxy, silanol, acyloxy, and amino groups. Component B includes at least one polysiloxane compound, which includes a functional group selected from vinyl, hydrogen, alkoxy, silanol, acyloxy, and amino groups.

7. The liquid metal composite thermal conductive paste according to claim 6, characterized in that, Component A includes at least one of side-chain hydrogen-based polysiloxane and terminal hydrogen-based polysiloxane, and component B includes at least one of side-chain vinyl polysiloxane and terminal vinyl polysiloxane. The initiator is a caster catalyst.

8. The liquid metal composite thermal conductive paste according to claim 7, characterized in that, By weight, the amount of component A is between 80 and 92, the amount of component B is between 7 and 15, and the amount of initiator is between 0.1 and 0.

3. The viscosity of the macroscopic encapsulant at room temperature is between 10 and 500 mPa·s.

9. The liquid metal composite thermal grease according to any one of claims 1 to 8, characterized in that, The microencapsulating agent is one of the following: mercaptosilane coupling agent, 3-chloropropyltriethoxysilane, 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane, and triethoxyfluorosilane.

10. The liquid metal composite thermal grease according to any one of claims 1 to 9, characterized in that, The liquid metal is metallic gallium or gallium-based liquid metal, and the gallium-based liquid metal is one of gallium-indium alloy and gallium-indium-tin alloy.

11. A thermal interface material, characterized in that, include: Liquid metal, a first polysiloxane network encapsulating the liquid metal, and a second polysiloxane network encapsulating the first polysiloxane network; The first polysiloxane network is formed by the condensation reaction of a microencapsulant under the catalysis of the liquid metal, wherein the microencapsulant is a compound containing hydrolyzable silicon functional groups; The second polysiloxane network is formed by the polymerization of a macro-encapsulating agent upon heating. The macro-encapsulating agent includes component A, component B, and an initiator. Component A and component B are polysiloxane compounds with crosslinkable functional groups. When heated, component A and component B undergo a polymerization reaction under the action of the initiator.

12. The thermal interface material according to claim 11, characterized in that, The thermal interface material also includes a small molecule blocking agent, which is a polysiloxane compound. The small molecule blocking agent has a viscosity between 10 and 100 mPa·s at room temperature and a molecular weight between 5,000 and 10,000. The small molecule blocking agent does not react with the micro-encapsulating agent or the macro-encapsulating agent.

13. The thermal interface material according to claim 12, characterized in that, The small molecule blocking agent is one of dimethyl silicone oil, ethyl silicone oil, phenyl silicone oil, and epoxy silicone oil.

14. The thermal interface material according to claim 12 or 13, characterized in that, By weight, the liquid metal comprises 92 to 97 parts, the total number of the micro-encapsulating agent and the macro-encapsulating agent comprises 3 to 8 parts, and the small molecule blocking agent comprises 0.03 to 0.08 parts.

15. The thermal interface material according to claim 14, characterized in that, The mass ratio of the small molecule blocking agent to the macroscopic encapsulating agent is between 1:99 and 5:

95.

16. The thermal interface material according to any one of claims 11 to 15, characterized in that, Component A includes at least one polysiloxane compound, which includes a functional group selected from vinyl, hydrogen, alkoxy, silanol, acyloxy, and amino groups. Component B includes at least one polysiloxane compound, which includes a functional group selected from vinyl, hydrogen, alkoxy, silanol, acyloxy, and amino groups.

17. The thermal interface material according to claim 16, characterized in that, Component A includes at least one of side-chain hydrogen-based polysiloxane and terminal hydrogen-based polysiloxane, and component B includes at least one of side-chain vinyl polysiloxane and terminal vinyl polysiloxane. The initiator is a caster catalyst.

18. The thermal interface material according to claim 17, characterized in that, By weight, the amount of component A is between 80 and 92, the amount of component B is between 7 and 15, and the amount of initiator is between 0.1 and 0.

3. The viscosity of the macroscopic encapsulant at room temperature is between 10 and 500 mPa·s.

19. The thermal interface material according to any one of claims 11 to 18, characterized in that, The microencapsulating agent is one of the following: mercaptosilane coupling agent, 3-chloropropyltriethoxysilane, 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane, and triethoxyfluorosilane.

20. The thermal interface material according to any one of claims 11 to 19, characterized in that, The liquid metal is metallic gallium or gallium-based liquid metal, and the gallium-based liquid metal is one of gallium-indium alloy and gallium-indium-tin alloy.

21. A method for preparing a liquid metal composite thermal conductive paste, characterized in that, The preparation method includes: Liquid metal is added to a microencapsulating agent and heated to disperse it evenly. The microencapsulating agent is a compound containing hydrolyzable silicon functional groups. A macroscopic encapsulating agent is added and dispersed evenly. The macroscopic encapsulating agent includes component A, component B and an initiator. Component A and component B are polysiloxane compounds with crosslinkable functional groups. When heated, component A and component B form a second polysiloxane network under the action of the initiator.

22. The preparation method according to claim 21, characterized in that, After adding the macroscopic encapsulant and dispersing it evenly, the process further includes: A small molecule blocking agent is added and dispersed evenly. The small molecule blocking agent is a polysiloxane compound with a viscosity of 10-100 mPa·s at room temperature and a molecular weight of 5000-10000. The small molecule blocking agent does not react with the micro-encapsulating agent or the macro-encapsulating agent.

23. The preparation method according to claim 22, characterized in that, The addition of the small molecule blocking agent and its uniform dispersion includes: Add the small molecule blocking agent and stir at 300-1000 rpm for 1-5 minutes; After stirring, ultrasonic treatment is performed.

24. The preparation method according to any one of claims 21 to 23, characterized in that, The step of adding liquid metal to a micro-encapsulation agent and heating it to disperse it evenly includes: Liquid metal was added to the microencapsulant and dispersed at 300-600 rpm for 1-3 minutes in an environment of 40-60°C. Disperse for 1 to 7 minutes at a speed of 400 to 1000 rpm in an environment of 40 to 60°C.

25. The preparation method according to any one of claims 21 to 24, characterized in that, The addition of the macroscopic encapsulant and its uniform dispersion includes: Add macro-encapsulating agent and stir at 800-3000 rpm for 1-10 minutes; After stirring, ultrasonic treatment is performed.

26. An electronic product, characterized in that, The electronic product includes a heat-generating element and a heat-dissipating element, as well as a thermal interface material as described in any one of claims 11 to 20 located between the heat-generating element and the heat-dissipating element.

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