Ultrathin liquid metal thermal interface material based on dynamic infiltration regulation and preparation method

Abstract

The invention provides an ultrathin liquid metal thermal interface material based on dynamic infiltration regulation and a preparation method, the ultrathin liquid metal thermal interface material is composed of a high-purity liquid metal main body and liquid metal dynamic infiltration adhesion layers connected to the two sides of the high-purity liquid metal main body, the material of the liquid metal dynamic infiltration adhesion layer is the same as that of the high-purity liquid metal main body, and the liquid metal dynamic infiltration adhesion layer is spread on the surface of the heating substrate and the surface of the heat dissipation substrate respectively. According to the method, the ultrathin metal liquid layer formed through dynamic infiltration is directly used as a heat transfer medium, molecular-level seamless attachment between the liquid metal and the substrate material interface is achieved, the ultrathin thermal interface with the minimum thickness of only nanoscale 1-1000 nm can be obtained, the contact thermal resistance is greatly reduced, the actually measured interface thermal conductivity can reach 25.9-47.1 W / m <-1 >. K <-1 >, and the thermal conductivity of the interface is greatly improved. The measured value far exceeds the measured value of the current commercial thermal interface material; the dynamic infiltration regulation and control means provided by the invention has universality and can be widely applied to various different heating and heat dissipation substrate materials.

Description

Technical Field

[0001] The invention relates to the field of chemistry and chemical engineering, and in particular to an ultra-thin liquid metal thermal interface material based on dynamic wetting control and a preparation method thereof. Background Art

[0002] With the rapid development of new generation electronic information technologies such as 5G, AI, big data, cloud computing, and industrial Internet, the demand for cooling and heat dissipation of highly integrated and heat-generating electronic components is increasing rapidly, which puts more stringent requirements on the contact heat transfer between heat-generating devices and heat-dissipating devices. Thermal interface materials are a general term for materials that are specially arranged between the two to improve thermal conductivity and reduce contact thermal resistance. Common thermal interface materials include thermal grease, thermal gaskets, thermal adhesives, phase change materials, liquid metals, and graphene thermal conductive sheets. Among them, thermal grease, thermal gaskets, thermal adhesives, phase change materials, and other materials are mainly organic or polymer, and their thermal conductivity is relatively low (0.5~8.0W / m -1 ·K -1 ); Graphene thermal conductive sheets have higher thermal conductivity (greater than 1200W / m -1 ·K -1 ), but it is expensive and complicated to produce, and as a solid material, it is difficult to fully fill the interface gap according to the irregular shape of the device itself, which in turn increases the contact thermal resistance. Liquid metal has a higher thermal conductivity (10-40W / m -1 ·K -1 ), as well as good fluidity and shape adaptability, showing a wider range of application value in the field of cooling and heat dissipation of electronic devices.

[0003] At present, the main form of commercial liquid metal thermal interface material is liquid metal-based thermal conductive paste, which is a paste-like thermal conductive medium prepared by adding nano-scale metal particles (such as copper, iron, aluminum, zinc, gold, silver, tin, bismuth, tungsten, vanadium, etc.) to liquid metal (patent application numbers: 201710155296.8, 202110465028.2, 202310528723.8). Although it has considerable thermal conductivity, the thickening effect brought by doping increases the coating thickness. The difficulty of coating (patent application number: 200510112867.7) inevitably increases the thickness of the paste (patent application number: 201711269950.4, 201911292500.6, 202011013195.5), which indirectly restricts the depth reduction of the contact thermal resistance. At the same time, the uneven distribution and flow failure of doped particles in long-term use (patent application number: 202210558818.X) will also reduce the heat dissipation quality. Therefore, it is urgent to develop ultra-thin thermal interface materials based on non-doped high-purity liquid metal.

[0004] However, the inherent high surface tension of liquid metal (greater than 600mN / m) greatly limits its wetting into the surface of the heating or heat dissipation base material. At the same time, the high surface chemical activity makes it easy to react with oxygen in the air to form an oxide layer, which not only interferes with the fluidity, but also affects the thermal conductivity to a certain extent (patent application number: 202110798209.7). When preparing ultra-thin high-purity liquid metal thermal interface materials, it is necessary to promote the full wetting of liquid metal through simple and efficient control means, while ensuring that the interface oxidation is strictly prevented. Existing technical solutions involving liquid metal infiltration control (patent application numbers: 202110767759.2, 202210463706.6) are all dedicated to filling liquid metal into other materials (such as heat dissipation device main material or porous polymer film). The contact thermal resistance is limited by the size of the filled material and it is difficult to obtain further reduction.

[0005] Therefore, there is a need for a new type of thermal interface material that directly utilizes ultra-thin liquid metal with dynamic wetting as a heat transfer medium, breaks through the limitation of the size of the filled material, and significantly reduces the contact thermal resistance. Summary of the invention

[0006] The present invention is to solve the problem of contact thermal resistance, and provides an ultra-thin liquid metal thermal interface material and preparation method based on dynamic infiltration regulation. The ultra-thin high-purity liquid metal thermal interface includes a high-purity liquid metal body and a liquid metal dynamic infiltration adhesion layer; the liquid metal dynamic infiltration adhesion layer includes a heating substrate adhesion layer that is closely attached to the surface of the heating substrate and a heat dissipation substrate adhesion layer that is closely attached to the surface of the heat dissipation substrate. The high-purity liquid metal body is between the heating substrate adhesion layer and the heat dissipation substrate adhesion layer, and is squeezed and fused by the heating substrate and the heat dissipation substrate to form an ultra-thin thermal interface material. The preparation method of the ultra-thin high-purity liquid metal thermal interface includes the following steps: surface pretreatment of the substrate material, dynamic infiltration of liquid metal, pressure fusion and extrusion redundancy, packaging and shaping. The method for using the ultra-thin high-purity liquid metal thermal interface includes the following steps: the coupled packaged ultra-thin high-purity liquid metal thermal interface can be used directly, and the split packaged ultra-thin high-purity liquid metal thermal interface needs to remove the surface oxide layer first, and then the heating substrate and the heat dissipation substrate are coupled and connected before use. It is widely used in the enhanced heat conduction of various application terminals in the field of microelectronics, including but not limited to 5G base stations, AI chips, high-performance PCs, data center servers, smart charging piles, power batteries, LED lighting, IGBT equipment and other scenarios. The present invention realizes molecular-level seamless bonding between interfaces, greatly reduces contact thermal resistance, and is low-cost and easy to operate.

[0007] The present invention provides an ultra-thin liquid metal thermal interface material based on dynamic wetting control, which is composed of a high-purity liquid metal main body and a liquid metal dynamic wetting adhesion layer connected to both sides of the high-purity liquid metal main body. The material of the liquid metal dynamic wetting adhesion layer is the same as that of the high-purity liquid metal main body. The liquid metal dynamic wetting adhesion layer is spread on the surface of a heating substrate and the surface of a heat dissipation substrate respectively.

[0008] The liquid metal dynamic infiltration adhesion layer includes a heating substrate adhesion layer seamlessly bonded to the surface of the heating substrate and a heat dissipation substrate adhesion layer seamlessly bonded to the surface of the heat dissipation substrate. The high-purity liquid metal main body, the heating substrate adhesion layer and the heat dissipation substrate adhesion layer constitute an ultra-thin liquid metal thermal interface material. The ultra-thin thermal interface material, the heating substrate and the heat dissipation substrate are seamlessly fused by extrusion, and the pressure range is 0 to 5 MPa.

[0009] The main body of high-purity liquid metal is a metal and its alloy that is liquid at room temperature, a doped mixture of metal and other metals, other metal oxides, non-metals, and non-metal oxides; the metal is gallium or indium or tin or bismuth or mercury or lithium or sodium or potassium, the other metal is any one of the following: copper, aluminum, gold, silver, tungsten, platinum, rhodium, iridium, vanadium, zinc, magnesium, lead, nickel, chromium and cadmium, and the non-metal is carbon or silicon;

[0010] The heating substrate surface connected to the heating substrate adhesive layer is pretreated so that the heating substrate and the heating substrate adhesive layer are connected through interface interaction; the heat dissipation substrate surface connected to the heat dissipation substrate adhesive layer is pretreated so that the heat dissipation substrate and the heat dissipation substrate adhesive layer are connected through interface interaction;

[0011] The interfacial interaction is hydrogen bonding, coordination, complexation, dipole bonding, π bonding or alloying reaction.

[0012] The ultra-thin liquid metal thermal interface material based on dynamic wetting control described in the present invention, as a preferred embodiment, the static contact angles of the pretreated heat-generating substrate, the pretreated heat-dissipating substrate and the high-purity liquid metal body are all less than 10°;

[0013] The heating substrate and the heating substrate adhesive layer are seamlessly bonded at the molecular level, the thickness of the liquid metal dynamic infiltration adhesive layer under normal pressure is 10 to 200 μm, and the thickness of the high-purity liquid metal body and the liquid metal dynamic infiltration adhesive layer after pressure fusion is no more than 200 μm;

[0014] The material of the heating substrate is any one of the following: silicon, silicon oxide, silicon-doped semiconductor, silicon carbide, silicon carbide-doped semiconductor, gallium nitride and gallium nitride-doped semiconductor;

[0015] The material of the heat dissipation substrate is any one of the following: copper, copper alloy, copper oxide, aluminum, aluminum alloy, aluminum oxide, iron, iron alloy, iron oxide, carbon steel and stainless steel.

[0016] The ultra-thin liquid metal thermal interface material based on dynamic wetting control described in the present invention, as a preferred embodiment, both the heating substrate and the heat dissipation substrate can be provided with a surface coating or packaging material;

[0017] The surface coating is any of the following: nickel, nickel alloy, nickel oxide, chromium, chromium alloy, chromium oxide, zinc, zinc alloy, zinc oxide, copper, copper alloy, copper oxide, iron, iron alloy, iron oxide, tin, tin alloy, tin oxide, carbon steel, stainless steel, gold, silver, platinum, rhodium and iridium;

[0018] The packaging material includes any one of the following: polyethylene, polypropylene, polyvinyl alcohol, polyethylene terephthalate, polyimide, polyphenylene sulfide, polyetheretherketone, polyvinylidene fluoride, polytetrafluoroethylene, silicone and epoxy resin.

[0019] The present invention provides a method for preparing an ultra-thin liquid metal thermal interface material based on dynamic wetting control, comprising the following steps:

[0020] S1, performing surface pretreatment on a heating substrate and a heat dissipation substrate to obtain a pretreated heating substrate and a pretreated heat dissipation substrate;

[0021] S2, subjecting the pretreated heating substrate and the pretreated heat dissipation substrate to dynamic infiltration of liquid metal, destroying the initial oxide layer on the surface of the liquid metal, promoting the interface interaction between the liquid metal and the pretreated heating substrate and the pretreated heat dissipation substrate, spreading and infiltrating to obtain the heating substrate adhesion layer and the heat dissipation substrate adhesion layer;

[0022] The method of dynamic wetting operation includes any one of the following: droplet rolling, droplet sliding, droplet impact, liquid film scraping, liquid film spin coating, liquid flow spraying, liquid immersion pulling and liquid immersion stirring;

[0023] S3, introducing a high-purity liquid metal body between a heating substrate with a heating substrate adhesive layer and a heat dissipation substrate with a heat dissipation substrate adhesive layer, applying pressure to the heating substrate and the heat dissipation substrate to seamlessly fuse the high-purity liquid metal body, the heating substrate adhesive layer, and the heat dissipation substrate adhesive layer, thinning the ultra-thin thermal interface material and squeezing out excess liquid metal;

[0024] S4, the packaging method includes coupling packaging and split packaging. In coupling packaging, after applying pressure for a specified time in step S3, a coupling package based on an ultra-thin liquid metal thermal interface material is obtained; in split packaging, the heating substrate and the heat dissipation substrate after applying pressure for a specified time in step S3 are split to obtain a heating substrate bonded to the metal liquid layer and a heat dissipation substrate bonded to the metal liquid layer;

[0025] The heating substrate bonded to the metal liquid layer includes a metal liquid layer, a heating substrate adhesion layer, and a heating substrate that are seamlessly bonded in sequence; the heat dissipation substrate bonded to the metal liquid layer includes a metal liquid layer, a heat dissipation substrate adhesion layer, and a heat dissipation substrate that are seamlessly bonded in sequence; the metal liquid layer includes a high-purity liquid metal main body and an oxide layer of the high-purity liquid metal; a preparation method for an ultra-thin liquid metal thermal interface material based on dynamic infiltration regulation is completed.

[0026] The method for preparing an ultra-thin liquid metal thermal interface material based on dynamic wetting control described in the present invention is, as a preferred embodiment, in step S1, the surface pretreatment method includes any one of the following: chemical modification, metal deposition, plasma treatment, ozone treatment and ultraviolet irradiation;

[0027] The interface interaction obtained by the chemical improvement pretreatment method is hydrogen bond, coordination, complexation, dipole or π bond; the interface interaction obtained by the metal deposition pretreatment method is coordination, complexation or alloying reaction; the interface interaction obtained by plasma treatment, ozone treatment and ultraviolet light irradiation is hydrogen bond, coordination or complexation;

[0028] Chemical modification reagents include acid-base reagents, reducing reagents, and chemical reagents that can bring about hydrogen bonds, coordination, complexation, dipole or π bonds through chemical modification.

[0029] The method for preparing an ultra-thin liquid metal thermal interface material based on dynamic wetting control described in the present invention, as a preferred embodiment, the chemically modified reagent includes any one of the following: hydrofluoric acid, sulfuric acid, nitric acid, hydrochloric acid, acetic acid, sodium hydroxide, potassium hydroxide, hydrogen peroxide, sodium persulfate, polydopamine, rosin antioxidant, silane coupling agent and ionic liquid;

[0030] The metal deposition method includes any one of the following: chemical vapor deposition, physical vapor deposition, vacuum evaporation and atomic layer deposition, and the deposited metal includes any one of the following: copper, aluminum, gold, silver, platinum, rhodium, iridium, vanadium, tungsten, zinc, magnesium, lead, nickel, chromium and cadmium.

[0031] The method for preparing an ultra-thin liquid metal thermal interface material based on dynamic wetting control described in the present invention is, as a preferred mode, in step S1, the surface pretreatment method also includes selective confinement, and only the target area of ​​the heating substrate and the heat dissipation substrate is pretreated, so that the target area and the non-target area form a differentiated liquid metal affinity to prevent the high-purity liquid metal body from leaking during use;

[0032] The target area is the central area of ​​the heat-generating substrate and the heat-dissipating substrate.

[0033] The present invention describes a method for preparing an ultra-thin liquid metal thermal interface material based on dynamic wetting control, as a preferred embodiment, in step S3, the seamless fusion method includes any one of the following: natural infiltration fusion, vacuum or pressure assisted fusion, light or electrical or magnetic induced fusion.

[0034] The method for preparing an ultra-thin liquid metal thermal interface material based on dynamic infiltration control described in the present invention is, as a preferred mode, in step S4, when the heating substrate attached to the metal liquid layer and the heat dissipation substrate attached to the metal liquid layer are used, the oxide layer of the high-purity liquid metal is first removed, and then the heating substrate attached to the metal liquid layer and the heat dissipation substrate attached to the metal liquid layer are coupled and connected for use by infiltration and fusion of the high-purity liquid metal body;

[0035] The method for removing the oxide layer of the high-purity liquid metal is to chemically react the oxide layer of the high-purity liquid metal with an acidic, alkaline or reducing agent;

[0036] The acidic, alkaline or reducing agent is any one of the following: hydrofluoric acid, sulfuric acid, nitric acid, hydrochloric acid, acetic acid, citric acid, sodium hydroxide, potassium hydroxide, hydrogen peroxide, sodium persulfate and rosin antioxidant.

[0037] The present invention discloses a method for preparing an ultra-thin liquid metal thermal interface material based on dynamic wetting control. As a preferred method, the ultra-thin liquid metal thermal interface material is suitable for enhancing heat conduction of application terminals in the field of microelectronics, including any one of the following: 5G base stations, AI chips, PCs, data center servers, smart charging piles, power batteries, LED lighting, and IGBT equipment;

[0038] The heating substrate is any of the following: 5G base station chip or chip shell coating or packaging, AI chip or chip shell coating or packaging, PC chip or chip shell coating or packaging, data center server chip or chip shell coating or packaging, smart charging pile chip or chip shell coating or packaging, power battery or battery shell coating or packaging, LED lighting chip or chip shell coating or packaging, IGBT equipment chip or chip shell coating or packaging;

[0039] The heat dissipation substrate is any one of the following: 5G base station radiator or coating or package, AI chip radiator or coating or package, PC radiator or coating or package, data center server radiator or coating or package, smart charging pile radiator or coating or package, power battery radiator or coating or package, LED lighting radiator or coating or package, IGBT equipment radiator or coating or package.

[0040] The present invention provides an ultra-thin liquid metal thermal interface based on dynamic infiltration control and a preparation method and a use method thereof, which significantly improves the wettability of liquid metal by pre-treating the surface of the substrate material, directly uses the ultra-thin metal liquid layer formed by dynamic infiltration as a heat transfer medium, realizes seamless bonding at the molecular level of the interface, greatly reduces the contact thermal resistance, and has low cost and convenient operation, and can be widely adapted to various different heating and heat dissipation substrate materials. The ultra-thin liquid metal thermal interface of the present invention is an ultra-thin high-purity liquid metal thermal interface.

[0041] The ultra-thin high-purity liquid metal thermal interface of the present invention comprises a high-purity liquid metal main body and a liquid metal dynamic infiltration adhesion layer; the liquid metal dynamic infiltration adhesion layer comprises a heating substrate adhesion layer that is closely attached to the surface of the heating substrate and a heat dissipation substrate adhesion layer that is closely attached to the surface of the heat dissipation substrate, and the high-purity liquid metal main body is between the heating substrate adhesion layer and the heat dissipation substrate adhesion layer, and is squeezed and fused by the heating substrate and the heat dissipation substrate to form an ultra-thin thermal interface material. The preparation method of the ultra-thin high-purity liquid metal thermal interface comprises the following steps: pretreatment of the surface of the substrate material, dynamic infiltration of liquid metal, pressure fusion and extrusion redundancy, packaging and shaping. The method for using the ultra-thin high-purity liquid metal thermal interface includes the following steps: the coupled packaged ultra-thin high-purity liquid metal thermal interface can be used directly, and the split packaged ultra-thin high-purity liquid metal thermal interface needs to remove the surface oxide layer first, and then the heating substrate and the heat dissipation substrate are coupled and connected before use. It is widely used in the enhanced heat conduction of various application terminals in the field of microelectronics, including but not limited to 5G base stations, AI chips, high-performance PCs, data center servers, smart charging piles, power batteries, LED lighting, IGBT equipment and other scenarios. The present invention realizes molecular-level seamless bonding between interfaces, greatly reduces contact thermal resistance, and is low-cost and easy to operate.

[0042] The present invention has the following advantages:

[0043] (1) The present invention directly utilizes the ultra-thin metal liquid layer formed by dynamic infiltration as a heat transfer medium, achieving molecular-level seamless bonding between the interface of the liquid metal and the substrate material. The lowest ultra-thin thermal interface with a thickness of only 1 to 1000 nm can be obtained, which greatly reduces the contact thermal resistance. The measured interface thermal conductivity can reach 25.9 to 47.1 W / m -1 ·K -1 , far exceeding the measured values ​​of current commercial thermal interface materials;

[0044] (2) Compared with the current commercial thermal interface materials rich in various doped particles, the present invention has fluidity and adaptability closer to liquid, while avoiding problems such as reduced thermal quality control caused by non-uniform doping, and has better long-term stability;

[0045] (3) Compared with the complex material preparation process of the current commercial thermal interface, the key is that the present invention significantly improves the wettability of liquid metal through simple surface pretreatment of the substrate material, which is low-cost and easy to operate;

[0046] (4) The dynamic wetting control method of the present invention is universal and can be widely adapted to various types of heating and heat dissipation substrate materials by relying on different forms of interface interactions, greatly broadening the terminal application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a schematic diagram of the overall structure of an ultra-thin liquid metal thermal interface material based on dynamic wetting control;

[0048] Figure 2 A statistical diagram of the natural thickness of the liquid metal dynamic infiltration adhesion layer on the surface of different substrate materials at normal pressure in an embodiment of an ultra-thin liquid metal thermal interface material based on dynamic infiltration control and a preparation method thereof;

[0049] Figure 3 It is a flow chart of a preparation method of ultra-thin liquid metal thermal interface material based on dynamic wetting control;

[0050] Figure 4 It is an ultra-thin liquid metal thermal interface material based on dynamic wetting control and a preparation method embodiment, the pretreatment means of different substrate material surfaces and the corresponding interface interaction forms;

[0051] Figure 5 The long-term leak-proof performance of the ultra-thin high-purity liquid metal thermal interface in an ultra-thin liquid metal thermal interface material and preparation method embodiment based on dynamic wetting control;

[0052] Figure 6 A cryo-electron microscopic photograph of a liquid metal dynamic wetting adhesion layer in an ultra-thin liquid metal thermal interface material based on dynamic wetting control and a preparation method embodiment;

[0053] Figure 7 The present invention is a comparison of the thermal conductivity of the ultra-thin high-purity liquid metal thermal interface and the traditional thermal interface material in an ultra-thin liquid metal thermal interface material and a preparation method embodiment based on dynamic wetting control.

[0054] Reference numerals:

[0055] 1. High-purity liquid metal main body; 2. Liquid metal dynamic infiltration adhesion layer; 23. Heat-generating base adhesion layer; 24. Heat-dissipating base adhesion layer; 3. Heat-generating base; 4. Heat-dissipating base. DETAILED DESCRIPTION

[0056] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0057] Example 1

[0058] An ultra-thin liquid metal thermal interface material and preparation method based on dynamic wetting control, combined with Figures 1 to 7 As shown, the ultra-thin liquid metal thermal interface material includes: a high-purity liquid metal body 1 and a liquid metal dynamic infiltration adhesion layer 2; the liquid metal dynamic infiltration adhesion layer 2 includes a heating substrate adhesion layer 23 that is closely attached to the surface of the heating substrate 3 and a heat dissipation substrate adhesion layer 24 that is closely attached to the surface of the heat dissipation substrate 4, and the high-purity liquid metal body 1 is between the heating substrate adhesion layer 23 and the heat dissipation substrate adhesion layer 24, and is squeezed and fused by the heating substrate 3 and the heat dissipation substrate 4 to form an ultra-thin thermal interface material (such as Figure 1 shown).

[0059] The composition of the high-purity liquid metal body 1 is a metal or its alloy that is liquid at room temperature, or a trace-doped mixture of it with other metals, other metal oxides, non-metals or non-metal oxides; metals include but are not limited to gallium or indium or tin or bismuth or mercury or lithium or sodium or potassium, etc., other metals include but are not limited to copper, aluminum, gold, silver, tungsten, platinum, rhodium, iridium, vanadium, zinc, magnesium, lead, nickel, chromium and cadmium, etc., and non-metals are carbon or silicon.

[0060] The object to which the liquid metal dynamic infiltration adhesion layer 2 is attached is any surface of the heating substrate 3 or the heat dissipation substrate 4, and the material includes the heating substrate 3 material, the heat dissipation substrate 4 material, or the surface coating or packaging material thereof.

[0061] The material of the heating substrate 3 includes but is not limited to silicon or its oxide or its doped semiconductor, silicon carbide or its doped semiconductor, gallium nitride or its doped semiconductor, etc.

[0062] The material of the heat dissipation substrate 4 includes, but is not limited to, copper or its alloy or oxide, aluminum or its alloy or oxide, iron or its alloy or oxide, carbon steel, stainless steel and the like.

[0063] Surface coatings include but are not limited to nickel or its alloys or oxides, chromium or its alloys or oxides, zinc or its alloys or oxides, copper or its alloys or oxides, tin or its alloys or oxides, iron or its iron alloys or iron oxides, carbon steel, stainless steel, and precious metals such as gold, silver, platinum, rhodium or iridium; packaging materials include but are not limited to polyethylene (PE), polypropylene (PP), polyvinyl alcohol (PVA), polyethylene terephthalate (PET), polyimide (PI), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), silicone and epoxy resin (EP) and other polymer materials.

[0064] The natural thickness of the single liquid metal dynamic infiltration adhesion layer 2 under normal pressure is 10-200 μm, and it is fused with the high-purity liquid metal body 1 under pressure to form an ultra-thin thermal interface material with a thickness not higher than 200 μm.

[0065] The natural thickness of the single liquid metal dynamic infiltration adhesion layer 2 under normal pressure is 10-100 μm, and it is pressurized and fused with the high-purity liquid metal body 1 to form an ultra-thin thermal interface material with a thickness not higher than 100 μm.

[0066] Furthermore, the natural thickness of the single liquid metal dynamic infiltration adhesion layer 2 under normal pressure is 10-50 μm, and it is pressurized and fused with the high-purity liquid metal body 1 to form an ultra-thin thermal interface material with a thickness not higher than 50 μm.

[0067] The thickness of the ultra-thin high-purity liquid metal thermal interface can be as low as nanometer level, reaching 1nm to 1000nm, and the lower limit is mainly determined by the surface roughness of the heating substrate 3 and the heat dissipation substrate 4.

[0068] In a specific embodiment, the natural thickness of the liquid metal dynamic wetting adhesion layer 2 formed on the surface of the heating substrate 3 made of silicon, the heat dissipation substrate 4 made of copper and stainless steel, and the packaging materials polyvinyl alcohol and epoxy resin (gallium-indium mass ratio 75:25) can reach 13.2±2.8μm, 19.9±5.2μm, 23.0±5.1μm, 32.7±4.0μm and 37.0±3.7μm respectively (e.g. Figure 2 shown).

[0069] The present invention also provides a method for preparing the ultra-thin liquid metal thermal interface based on dynamic wetting control (such as Figure 3 As shown), it includes the following steps: S1, surface pretreatment of substrate material, S2, dynamic infiltration of liquid metal, S3, pressure fusion and extrusion redundancy, S4, packaging and shaping.

[0070] The purpose of the surface pretreatment of the substrate material is to increase the functional chemical bonds or metal deposition layers on the surfaces of the heating substrate 3 and the heat dissipation substrate 4 materials, and obtain super liquid metal affinity (the static contact angle of the liquid metal after infiltration is less than 10°) properties through interface interactions, so that it is easy to form a molecular-level seamless adhesion layer; interface interactions include but are not limited to hydrogen bonds, coordination, complexation, dipoles, π bonds or alloying reactions.

[0071] The means of surface pretreatment of the substrate material include but are not limited to chemical modification, metal deposition, plasma treatment, ozone treatment or ultraviolet light, etc.; the reagents for chemical modification include but are not limited to hydrofluoric acid, sulfuric acid, nitric acid, hydrochloric acid, acetic acid, sodium hydroxide, potassium hydroxide, hydrogen peroxide, sodium persulfate, polydopamine, rosin antioxidants, silane coupling agents, ionic liquids, etc.; the methods of metal deposition include but are not limited to chemical vapor deposition, physical vapor deposition, vacuum evaporation or atomic layer deposition, etc., and the types of deposited metals include but are not limited to copper, aluminum, gold, silver, platinum, rhodium, iridium, vanadium, tungsten, zinc, magnesium, lead, nickel, chromium or cadmium, etc.

[0072] In a specific embodiment, the surface of a single-crystal silicon wafer with a thickness of 0.5 mm is pretreated by chemical modification, metal deposition, plasma treatment, ozone treatment or ultraviolet light irradiation, and combined with X-ray photoelectron spectroscopy (XPS) analysis, various corresponding interface interaction forms are summarized (as shown in the following table).

[0073]

[0074] Specific methods for pretreating the surface of the substrate material also include selective confinement, which is to pretreat the surface of the substrate material only in a specific target area (usually the central area of ​​the heating substrate 3 and the heat dissipation substrate 4), while non-target areas (usually the peripheral areas of the heating substrate 3 and the heat dissipation substrate 4) are masked; its purpose is to form differentiated liquid metal affinity differences to prevent leakage during use.

[0075] In one embodiment, by a fixture (such as Figure 4 As shown in the figure, a gallium-indium alloy (gallium-indium mass ratio of 75:25) is placed between the silicon of the heating substrate 3 and the copper of the heat dissipation substrate 4 to form an ultra-thin high-purity liquid metal thermal interface to simulate the pressure conditions of the heating substrate 3, the heat dissipation substrate 4 and the thermal interface material in a real application scenario. The side of the fixture in contact with the heating substrate 3 and the heat dissipation substrate 4 is a plane, and the size of the fixture is larger than the heating substrate 3 and the heat dissipation substrate 4. The two fixtures are detachably connected to the heating substrate 3 and the heat dissipation substrate 4 inside by screws. The pressure is about 1.5 MPa. There is no leakage when it is placed upright for a long time for 6 months, and the total weight of the clamping device tested every half a month remains almost unchanged.

[0076] The purpose of dynamically infiltrating liquid metal is to destroy the initial oxide layer on the surface of the liquid metal through dynamic operation, promote the interface interaction between the liquid metal and the surface of the heating substrate 3 and the heat dissipation substrate 4, so that it spreads and infiltrates to form an ultra-thin adhesion layer; the specific methods of dynamic operation include but are not limited to droplet rolling, droplet sliding, droplet impact, liquid film scraping, liquid film spin coating, liquid flow spraying, liquid immersion pulling or liquid immersion stirring, etc.

[0077] Pressurized fusion and extrusion redundancy utilize the heat-generating substrate 3 and the heat-dissipating substrate 4 to apply pressure to promote seamless fusion between the high-purity liquid metal body 1 and the heat-generating substrate adhesion layer 23 and the heat-dissipating substrate adhesion layer 24, while squeezing out excess liquid metal to achieve deep thinning of the thermal interface; the pressure applied between the heat-generating substrate 3 and the heat-dissipating substrate 4 ranges from 0 to 5 MPa; specific methods of seamless fusion include but are not limited to natural infiltration fusion, vacuum or pressure-assisted fusion, optical, electrical or magnetic induced fusion, etc.

[0078] The packaging and shaping modes include coupling packaging and split packaging. Coupling packaging is to couple the high-purity ultra-thin liquid metal thermal interface with the heating substrate 3 and the heat dissipation substrate 4 as a whole, and directly push it to the application terminal in the form of a shaped product; split packaging is to split the heating substrate 3 and the heat dissipation substrate 4 again after the ultra-thin metal liquid layer is formed by pressure fusion and extrusion redundancy, so as to be continued for use; under the traction of the heating substrate adhesion layer 23 and the heat dissipation substrate adhesion layer 24, the liquid metal after splitting will form a metal liquid layer on the surface of the heating substrate 3 and the heat dissipation substrate 4 respectively, and at the same time rely on the oxide layer formed quickly on its surface to shape.

[0079] In a specific embodiment, the gallium-indium alloy (gallium-indium mass ratio 75:25) liquid metal can be dynamically infiltrated on the surface of the plasma-treated hydroxyl-rich silicon heating substrate 3, and only needs to be simply scraped and fused under pressure below 0.1MPa to form a stable and adherent ultra-thin liquid metal thermal interface; at the same time, the cryo-electron microscopy results (such as Figure 5 As shown in the figure, it is shown that the liquid metal dynamic infiltration adhesion layer 2 and the heating substrate 3 achieve seamless bonding at the molecular level, and no interface gap is visible at the nanoscale.

[0080] In another specific embodiment, gallium-indium alloy (gallium-indium mass ratio 75:25) liquid metal can be dynamically infiltrated on the surface of the copper heat dissipation substrate 4 modified by hydrochloric acid. Only a few times of liquid dipping and pulling are required to form an ultra-thin liquid metal dynamic infiltration adhesion layer 2, and the liquid metal maintains a large area of ​​uniform and stable adhesion with the surface of the heat dissipation substrate 4 (such as Figure 6 shown).

[0081] The present invention also provides a method for using the above-mentioned ultra-thin liquid metal thermal interface based on dynamic wetting control, comprising the following steps: the coupled packaged ultra-thin liquid metal thermal interface can be used directly, and the split packaged ultra-thin liquid metal thermal interface needs to first remove the surface oxide layer, and then couple and connect the heating substrate 3 and the heat dissipation substrate 4 before use.

[0082] The specific method for removing the surface oxide layer is to rely on acidic, alkaline or reducing reagents to chemically react with the oxide layer; when the surface oxide layer is removed, the metal liquid layer on the surface of the heating substrate and the metal liquid layer on the surface of the heat dissipation substrate can quickly and spontaneously infiltrate and fuse to complete the coupling connection.

[0083] Acidic, alkaline or reducing agents include, but are not limited to, hydrofluoric acid, sulfuric acid, nitric acid, hydrochloric acid, acetic acid, citric acid, sodium hydroxide, potassium hydroxide, hydrogen peroxide, sodium persulfate, rosin-based antioxidants, and the like.

[0084] The ultra-thin high-purity liquid metal thermal interface based on dynamic wetting control provided by the present invention can be widely used in enhanced heat conduction of various application terminals in the field of microelectronics, including but not limited to 5G base stations, AI chips, high-performance PCs, data center servers, smart charging piles, power batteries, LED lighting, IGBT equipment and other scenarios.

[0085] In a specific embodiment, a silicon sheet and a copper sheet with a thickness of 0.5 mm are used to simulate the heating substrate 3 and the heat dissipation substrate 4, and the thermal conductivity of the "silicon-thermal interface-copper" system within 5 minutes under different interface contact states is tested under a fixed pressure of 0.1 MPa (e.g. Figure 7 As shown), including no thermal interface material (i.e. direct contact between silicon wafer and copper wafer (current commercial situation), sample 1), filling with thermal conductive silicone grease (thickness 100μm, sample 2), filling with liquid metal thermal conductive paste (thickness 100μm, sample 3), placing a thermal conductive indium sheet (thickness 100μm, sample 4) and filling with ultra-thin high-purity liquid metal thermal interface with thickness of 200μm, 100μm and 50μm respectively, i.e. sample 5, sample 6 and sample 7.

[0086] Figure 7 The results show that the measured thermal conductivity of the ultra-thin high-purity liquid metal thermal interface of the present invention is higher than that of the current commercial thermal interface materials, and as the thickness decreases, the thermal conductivity of the interface continues to increase.

[0087] Sample 5, Sample 6 and Sample 7 adopt different specific implementation methods, specifically:

[0088] (1) The preparation method of 200 μm ultra-thin high-purity liquid metal thermal interface (sample 5) is as follows: 2The silicon wafer substrate 3 is chemically modified by the end group silane coupling agent to provide hydrogen bonds and coordination bonds, and the surface of the copper wafer substrate 4 is treated with 0.1mol / L hydrochloric acid to promote the gallium-copper alloying reaction; the liquid metal is dynamically infiltrated by liquid film coating, so that the surfaces of the silicon wafer 3 and the copper wafer 4 obtain dynamic infiltration adhesion layers 23 and 24 respectively; under a load of 0.1MPa, it is pressurized and fused with 200μL liquid metal body 1, and the redundancy is squeezed out and the package is disassembled; before the thermal conductivity test, a trace amount of 0.5mol / L potassium hydroxide solution is added to remove the oxide layer, and it is re-coupled and connected before use.

[0089] (2) The preparation method of 100 μm ultra-thin high-purity liquid metal thermal interface (sample 6) is as follows: copper nanoparticles are coated on the surface of the silicon wafer substrate 3 by metal deposition, and 1.0 mol / L sodium hydroxide is used to treat the silicon wafer substrate surface 3 and the copper wafer substrate 4 surface coated with copper nanoparticles to promote the gallium-copper alloying reaction; the liquid metal is dynamically infiltrated by liquid immersion and pulling to obtain dynamic infiltration adhesion layers 23 and 24 on the surfaces of the silicon wafer 3 and the copper wafer 4, respectively; the liquid metal is pressurized and fused with a 200 μL liquid metal body 1 under a load of 0.5 MPa, and the redundancy is squeezed out and the package is disassembled; before the thermal conductivity test, a small amount of 0.5 mol / L sulfuric acid solution is added to remove the oxide layer, and the sample is recoupled and connected for use.

[0090] (3) The preparation method of 50μm ultra-thin high-purity liquid metal thermal interface (sample 7) is as follows: the silicon wafer substrate 3 and the copper wafer substrate 4 are treated with 200W plasma and ultraviolet light respectively to provide hydrogen bonds and coordination bonds; the liquid metal is dynamically infiltrated by repeatedly sliding 500μL droplets to form uniformly distributed dynamic infiltration adhesion layers 23 and 24; the 200μL liquid metal body 1 is pressurized and fused under a load of 1.0MPa to squeeze out the redundancy, and then the silicon wafer-liquid metal-copper sheet coupling package is maintained under normal pressure; before the thermal conductivity test, the coupled silicon wafer-liquid metal-copper sheet is directly placed in the instrument.

[0091] In this application, the terms "packaging", "lamination", "forming" and the like should be understood in a broad sense. For example, "packaging" can be direct packaging or indirect packaging through an intermediate medium, and "lamination" can be direct lamination or lamination assisted by an external component. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0092] Thermal interface material: A general term for materials placed between heat dissipation devices and heat generation devices to improve thermal conductivity and reduce contact thermal resistance.

[0093] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. An ultra-thin liquid metal thermal interface material based on dynamic wetting control, characterized in that: The device comprises a high-purity liquid metal body (1) and a liquid metal dynamic infiltration and adhesion layer (2) connected to both sides of the high-purity liquid metal body (1), wherein the material of the liquid metal dynamic infiltration and adhesion layer (2) is the same as that of the high-purity liquid metal body (1), and the liquid metal dynamic infiltration and adhesion layer (2) is spread on the surface of a heating substrate (3) and the surface of a heat dissipation substrate (4) respectively; The liquid metal dynamic infiltration adhesion layer (2) comprises a heating substrate adhesion layer (23) seamlessly bonded to the surface of the heating substrate (3) and a heat dissipation substrate adhesion layer (24) seamlessly bonded to the surface of the heat dissipation substrate (4); the high-purity liquid metal body (1), the heating substrate adhesion layer (23) and the heat dissipation substrate adhesion layer (24) constitute an ultra-thin liquid metal thermal interface material; the ultra-thin thermal interface material, the heating substrate (3) and the heat dissipation substrate (4) are seamlessly fused by extrusion, and the pressure range is 0 to 5 MPa; The high-purity liquid metal body (1) is a metal and its alloy that is liquid at room temperature, a metal and other metals, other metal oxides, non-metals, and a doped mixture of non-metal oxides; the metal is gallium or indium or tin or bismuth or mercury or lithium or sodium or potassium; the other metal is any one of the following: copper, aluminum, gold, silver, tungsten, platinum, rhodium, iridium, vanadium, zinc, magnesium, lead, nickel, chromium and cadmium; the non-metal is carbon or silicon; The surface of the heating substrate connected to the heating substrate adhesive layer (23) is pre-treated so that the heating substrate (3) and the heating substrate adhesive layer (23) are connected through interface interaction; the surface of the heat dissipation substrate connected to the heat dissipation substrate adhesive layer (24) is pre-treated so that the heat dissipation substrate (4) and the heat dissipation substrate adhesive layer (24) are connected through interface interaction; The interface interaction is hydrogen bond, coordination, complexation, dipole, π bond or alloying reaction.

2. The ultra-thin liquid metal thermal interface material based on dynamic wetting control according to claim 1, characterized in that: The static contact angles of the pretreated heat-generating substrate (3), the pretreated heat-dissipating substrate (4) and the high-purity liquid metal body (1) are both less than 10°; The heating substrate (3) and the heating substrate adhesive layer (23) are seamlessly bonded at the molecular level, the thickness of the liquid metal dynamic infiltration adhesive layer (2) at normal pressure is 10 to 200 μm, and the thickness of the high-purity liquid metal body (1) and the liquid metal dynamic infiltration adhesive layer (2) after being fused under pressure is no more than 200 μm; The material of the heating substrate (3) is any one of the following: silicon, silicon oxide, silicon-doped semiconductor, silicon carbide, silicon carbide-doped semiconductor, gallium nitride and gallium nitride-doped semiconductor; The material of the heat dissipation substrate (4) is any one of the following: copper, copper alloy, copper oxide, aluminum, aluminum alloy, aluminum oxide, iron, iron alloy, iron oxide, carbon steel and stainless steel.

3. The ultra-thin liquid metal thermal interface material based on dynamic wetting control according to claim 1, characterized in that: The heating substrate (3) and the heat dissipation substrate (4) may both be provided with a surface coating or packaging material; The surface coating is any one of the following: nickel, nickel alloy, nickel oxide, chromium, chromium alloy, chromium oxide, zinc, zinc alloy, zinc oxide, copper, copper alloy, copper oxide, iron, iron alloy, iron oxide, tin, tin alloy, tin oxide, carbon steel, stainless steel, gold, silver, platinum, rhodium and iridium; The packaging material includes any one of the following: polyethylene, polypropylene, polyvinyl alcohol, polyethylene terephthalate, polyimide, polyphenylene sulfide, polyetheretherketone, polyvinylidene fluoride, polytetrafluoroethylene, silica gel and epoxy resin.

4. A method for preparing an ultra-thin liquid metal thermal interface material based on dynamic wetting control according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1, performing surface pretreatment on the heating substrate (3) and the heat dissipation substrate (4) to obtain a pretreated heating substrate and a pretreated heat dissipation substrate; S2, subjecting the pretreated heating substrate and the pretreated heat dissipation substrate to dynamic infiltration of liquid metal, destroying the initial oxide layer on the surface of the liquid metal, promoting the liquid metal to interact with the pretreated heating substrate and the pretreated heat dissipation substrate at the interface, spreading and infiltrating to obtain the heating substrate adhesion layer (23) and the heat dissipation substrate adhesion layer (24); The method of the dynamic wetting operation includes any one of the following: droplet rolling, droplet sliding, droplet impact, liquid film scraping, liquid film spin coating, liquid flow spraying, liquid immersion pulling and liquid immersion stirring; S3, introducing a high-purity liquid metal body (1) between a heating substrate (3) with the heating substrate adhesion layer (23) and a heat dissipation substrate (4) with the heat dissipation substrate adhesion layer (24), applying pressure to the heating substrate (3) and the heat dissipation substrate (4) to allow the high-purity liquid metal body (1), the heating substrate adhesion layer (23) and the heat dissipation substrate adhesion layer (24) to be seamlessly integrated, thinning the ultra-thin thermal interface material and squeezing out excess liquid metal; S4, the packaging method includes coupling packaging and split packaging. In coupling packaging, after applying pressure for a specified time in step S3, a coupling package based on an ultra-thin liquid metal thermal interface material is obtained; in split packaging, after applying pressure for a specified time in step S3, the heating substrate (3) and the heat dissipation substrate (4) are split to obtain a heating substrate bonded to the metal liquid layer and a heat dissipation substrate bonded to the metal liquid layer; The heating substrate bonded to the metal liquid layer comprises a metal liquid layer, a heating substrate adhesive layer (23), and a heating substrate (3) which are bonded seamlessly in sequence; the heat dissipation substrate bonded to the metal liquid layer comprises a metal liquid layer, a heat dissipation substrate adhesive layer (24), and a heat dissipation substrate (4) which are bonded seamlessly in sequence; the metal liquid layer comprises the high-purity liquid metal main body (1) and an oxide layer of the high-purity liquid metal; and a preparation method for an ultra-thin liquid metal thermal interface material based on dynamic wetting control is completed.

5. The method for preparing an ultra-thin liquid metal thermal interface material based on dynamic wetting control according to claim 4, characterized in that: In step S1, the surface pretreatment method includes any one of the following: chemical modification, metal deposition, plasma treatment, ozone treatment and ultraviolet irradiation; The interface interaction obtained by the chemical improvement pretreatment method is hydrogen bond, coordination, complexation, dipole or π bond; the interface interaction obtained by the metal deposition pretreatment method is coordination, complexation or alloying reaction; the interface interaction obtained by plasma treatment, ozone treatment, and ultraviolet light irradiation is hydrogen bond, coordination or complexation; Chemical modification reagents include acid-base reagents, reducing reagents, and chemical reagents that can bring about hydrogen bonds, coordination, complexation, dipole or π bonds through chemical modification.

6. The method for preparing an ultra-thin liquid metal thermal interface material based on dynamic wetting control according to claim 5, characterized in that: The chemical modification reagent includes any one of the following: hydrofluoric acid, sulfuric acid, nitric acid, hydrochloric acid, acetic acid, sodium hydroxide, potassium hydroxide, hydrogen peroxide, sodium persulfate, polydopamine, rosin antioxidant, silane coupling agent and ionic liquid; The metal deposition method includes any one of the following: chemical vapor deposition, physical vapor deposition, vacuum evaporation and atomic layer deposition, and the deposited metal includes any one of the following: copper, aluminum, gold, silver, platinum, rhodium, iridium, vanadium, tungsten, zinc, magnesium, lead, nickel, chromium and cadmium.

7. The method for preparing an ultra-thin liquid metal thermal interface material based on dynamic wetting control according to claim 5, characterized in that: In step S1, the surface pretreatment method further comprises selective confinement, where only the target area of ​​the heat-generating substrate (3) and the heat-dissipating substrate (4) is pretreated, so that the target area and the non-target area form a differentiated affinity of liquid metal to prevent the high-purity liquid metal body (1) from leaking during use; The target area is the central area of ​​the heat-generating substrate (3) and the heat-dissipating substrate (4).

8. The method for preparing an ultra-thin liquid metal thermal interface material based on dynamic wetting control according to claim 5, characterized in that: In step S3, the seamless fusion method includes any one of the following: natural infiltration fusion, vacuum or pressure assisted fusion, light or electrical or magnetic induced fusion.

9. The method for preparing an ultra-thin liquid metal thermal interface material based on dynamic wetting control according to claim 4, characterized in that: In step S4, when the heating substrate bonded to the metal liquid layer and the heat dissipation substrate bonded to the metal liquid layer are used, the oxide layer of the high-purity liquid metal is first removed, and then the heating substrate bonded to the metal liquid layer and the heat dissipation substrate bonded to the metal liquid layer are coupled and connected for use by infiltration and fusion of the high-purity liquid metal body; The method for removing the oxide layer of the high-purity liquid metal is to chemically react the oxide layer of the high-purity liquid metal with an acidic, alkaline or reducing agent; The acidic, alkaline or reducing agent is any one of the following: hydrofluoric acid, sulfuric acid, nitric acid, hydrochloric acid, acetic acid, citric acid, sodium hydroxide, potassium hydroxide, hydrogen peroxide, sodium persulfate and rosin antioxidant.

10. The method for preparing an ultra-thin liquid metal thermal interface material based on dynamic wetting control according to claim 4, characterized in that: Ultra-thin liquid metal thermal interface materials are suitable for enhanced heat conduction in application terminals in the field of microelectronics, including any of the following: 5G base stations, AI chips, PCs, data center servers, smart charging piles, power batteries, LED lighting, IGBT equipment; The heating substrate (3) is any one of the following: a chip or chip shell coating or packaging for a 5G base station, an AI chip or chip shell coating or packaging, a PC chip or chip shell coating or packaging, a data center server chip or chip shell coating or packaging, a smart charging pile chip or chip shell coating or packaging, a power battery or battery shell coating or packaging, an LED lighting chip or chip shell coating or packaging, an IGBT equipment chip or chip shell coating or packaging; The heat dissipation substrate (4) is any one of the following: a 5G base station heat sink or coating or package, an AI chip heat sink or coating or package, a PC heat sink or coating or package, a data center server heat sink or coating or package, a smart charging pile heat sink or coating or package, a power battery heat sink or coating or package, an LED lighting heat sink or coating or package, an IGBT equipment heat sink or coating or package.

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