Ultra-thin liquid metal thermal interface material based on dynamic wetting regulation and preparation method thereof

Abstract

This invention provides an ultrathin liquid metal thermal interface material based on dynamic wetting control and its preparation method. The ultrathin liquid metal thermal interface material consists of a high-purity liquid metal substrate and a dynamically wetting adhesive layer of liquid metal connected to both sides of the high-purity liquid metal substrate. The material of the dynamically wetting adhesive layer is the same as that of the high-purity liquid metal substrate. The dynamically wetting adhesive layer is spread on both the surface of the heating substrate and the surface of the heat dissipation substrate. This invention directly utilizes the ultrathin liquid metal layer formed by dynamic wetting as a heat transfer medium, achieving seamless molecular-level bonding between the liquid metal and the substrate material interface. It can obtain ultrathin thermal interfaces with a thickness of only 1–1000 nm, significantly reducing contact thermal resistance. The measured interface thermal conductivity can reach 25.9–47.1 W / m. ‑1 ·K ‑1 The measured values ​​far exceed those of currently commercially available thermal interface materials; the dynamic wetting control method of this invention is universal and can be widely adapted to various types of heat-generating and heat-dissipating substrate materials.

Description

Technical Field

[0001] This invention relates to the fields of chemistry and chemical engineering, specifically to an ultrathin liquid metal thermal interface material based on dynamic wetting control and its preparation method. Background Technology

[0002] With the rapid development of next-generation electronic information technologies such as 5G, AI, big data, cloud computing, and the industrial internet, the demand for cooling and heat dissipation of highly integrated, high-heat-generating electronic components is increasing dramatically, placing more stringent requirements on the contact heat transfer between heat-generating and heat-dissipating devices. Thermal interface materials are a general term for materials specifically placed between these two components to improve thermal conductivity and reduce contact thermal resistance. Common thermal interface materials include thermal grease, thermal pads, thermal adhesives, phase change materials, liquid metals, and graphene-based thermal sheets. Among these, thermal grease, thermal pads, thermal adhesives, and phase change materials, due to their organic or polymeric composition, have relatively low thermal conductivity (0.5–8.0 W / m²). -1 ·K -1 ); Graphene-based thermal conductive sheets have higher thermal conductivity (greater than 1200W / m); -1 ·K -1 However, while liquid metals are expensive and complex to manufacture, as solid materials, they are difficult to fully fill the interface gaps to accommodate the irregular shape of the device, which in turn increases the contact thermal resistance. Liquid metals, on the other hand, have high thermal conductivity (10–40 W / m). -1 ·K -1 Its excellent fluidity and shape adaptability make it a widely applicable material in the field of electronic device cooling and heat dissipation.

[0003] Currently, the main form of commercial liquid metal thermal interface materials is liquid metal-based thermal paste. This paste-like thermal conductive medium is prepared by adding nanoscale 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). While it possesses considerable thermal conductivity, the thickening effect caused by doping increases the coating thickness. The increased difficulty in applying the coating (patent application number: 200510112867.7) inevitably leads to a greater thickness of the coating (patent application numbers: 201711269950.4, 201911292500.6, 202011013195.5), indirectly limiting the depth of contact thermal resistance reduction. Furthermore, the uneven distribution and flow failure of doped particles during long-term use (patent application number: 202210558818.X) will also degrade heat dissipation quality. Therefore, there is an urgent need to develop ultrathin thermal interface materials based on undoped high-purity liquid metals.

[0004] However, the inherently high surface tension (greater than 600 mN / m) of liquid metals greatly limits their wetting onto the surface of heat-generating or heat-dissipating substrate materials. Simultaneously, their high surface chemical reactivity makes them prone to reacting with oxygen in the air to form an oxide layer, which interferes with fluidity and also affects thermal conductivity to some extent (Patent Application No.: 202110798209.7). In preparing ultrathin, high-purity liquid metal thermal interface materials, simple and efficient control methods are needed to promote sufficient wetting of the liquid metal while ensuring strict prevention of interface oxidation. Existing technical solutions involving liquid metal wetting control (Patent Application Nos.: 202110767759.2, 202210463706.6) focus on filling the liquid metal into other materials (such as the main body material of heat dissipation devices or porous polymer films). However, the contact thermal resistance is limited by the size of the filled material, making further reduction difficult.

[0005] Therefore, there is a need for a new type of thermal interface material that directly utilizes dynamically wetted ultrathin liquid metal as a heat transfer medium, overcomes the limitations of the size of the filled material, and significantly reduces contact thermal resistance. Summary of the Invention

[0006] This invention addresses the problem of contact thermal resistance by providing an ultrathin liquid metal thermal interface material and its preparation method based on dynamic wetting control. The ultrathin high-purity liquid metal thermal interface comprises a high-purity liquid metal substrate and a dynamically wetting adhesive layer. The dynamically wetting adhesive layer includes a heating substrate adhesive layer tightly bonded to the surface of a heating substrate and a heat dissipation substrate adhesive layer tightly bonded to the surface of a heat dissipation substrate. The high-purity liquid metal substrate is located between the heating substrate adhesive layer and the heat dissipation substrate adhesive layer, and is fused together by the heating and heat dissipation substrates to form the ultrathin thermal interface material. The preparation method of the ultrathin high-purity liquid metal thermal interface includes the following steps: substrate material surface pretreatment, dynamic wetting of liquid metal, pressure fusion and extrusion redundancy, and encapsulation and shaping. The method of using the ultrathin high-purity liquid metal thermal interface includes the following steps: the coupled and packaged ultrathin high-purity liquid metal thermal interface can be used directly; the disassembled and packaged ultrathin high-purity liquid metal thermal interface requires first removing the surface oxide layer, and then coupling and reconnecting the heating substrate and the heat dissipation substrate before use. It is widely applicable to enhancing heat conduction in various application terminals in the microelectronics field, 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. This invention achieves seamless molecular-level bonding between interfaces, significantly reducing contact thermal resistance, and is low in cost and easy to operate.

[0007] This invention provides an ultrathin liquid metal thermal interface material based on dynamic wetting control, which consists of a high-purity liquid metal body and a liquid metal dynamic wetting adhesive layer connected to both sides of the high-purity liquid metal body. The liquid metal dynamic wetting adhesive layer is made of the same material as the high-purity liquid metal body, and the liquid metal dynamic wetting adhesive layer is spread on the surface of the heating substrate and the surface of the heat dissipation substrate respectively.

[0008] The liquid metal dynamic wetting adhesive layer includes a heating substrate adhesive layer that is seamlessly attached to the surface of the heating substrate and a heat dissipation substrate adhesive layer that is seamlessly attached to the surface of the heat dissipation substrate. The high-purity liquid metal body, the heating substrate adhesive layer and the heat dissipation substrate adhesive 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 with a pressure range of 0 to 5 MPa.

[0009] The high-purity liquid metal is mainly composed of metals and their alloys that are liquid at room temperature, including mixtures of metals with other metals, oxides of other metals, non-metals, and oxides of non-metals; the metals are gallium, indium, tin, bismuth, mercury, lithium, sodium, or potassium, and the other metals are any one of the following: copper, aluminum, gold, silver, tungsten, platinum, rhodium, iridium, vanadium, zinc, magnesium, lead, nickel, chromium, and cadmium; the non-metals are carbon or silicon.

[0010] The surface of the heating substrate connected to the heating substrate adhesive layer is pretreated to enable the heating substrate and the heating substrate adhesive layer to be connected through interface interaction; the surface of the heat dissipation substrate connected to the heat dissipation substrate adhesive layer is pretreated to enable the heat dissipation substrate and the heat dissipation substrate adhesive layer to be connected through interface interaction.

[0011] Interfacial interactions can be hydrogen bonds, coordination, complexation, dipoles, π bonds, or alloying reactions.

[0012] In the present invention, an ultrathin liquid metal thermal interface material based on dynamic wetting control is preferred in which the static contact angle between the pretreated heating substrate, the pretreated heat dissipation substrate and the high-purity liquid metal body is 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 wetting adhesive layer under normal pressure is 10-200 μm. The thickness of the high-purity liquid metal body and the liquid metal dynamic wetting adhesive layer after being fused under pressure 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 heat dissipation substrate is made of any of the following materials: copper, copper alloy, copper oxide, aluminum, aluminum alloy, aluminum oxide, iron, iron alloy, iron oxide, carbon steel, and stainless steel.

[0016] The present invention provides an ultrathin liquid metal thermal interface material based on dynamic wetting control. In a preferred embodiment, both the heating substrate and the heat dissipation substrate can be provided with surface coatings or encapsulation materials.

[0017] 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, ferroalloy, iron oxide, tin, tin alloy, tin oxide, carbon steel, stainless steel, gold, silver, platinum, rhodium, and iridium.

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

[0019] This invention provides a method for preparing an ultrathin liquid metal thermal interface material based on dynamic wetting control, comprising the following steps:

[0020] S1. Pre-treat the surface of the heating substrate and the heat dissipation substrate to obtain a pre-treated heating substrate and a pre-treated heat dissipation substrate;

[0021] S2. Dynamically wet the pretreated heating substrate and the pretreated heat dissipation substrate with liquid metal, destroy the initial oxide layer on the surface of the liquid metal, promote the interfacial interaction between the liquid metal and the pretreated heating substrate and the pretreated heat dissipation substrate, and spread and wet to obtain the heating substrate adhesion layer and the heat dissipation substrate adhesion layer.

[0022] Dynamic wetting operations include any of the following: droplet rolling, droplet sliding, droplet impact, liquid film scraping, liquid film spin coating, liquid jet spraying, liquid immersion lifting, and liquid immersion stirring;

[0023] S3. A high-purity liquid metal body is introduced between the heating substrate with a heating substrate adhesive layer and the heat dissipation substrate with a heat dissipation substrate adhesive layer. Pressure is applied to the heating substrate and the heat dissipation substrate to make the high-purity liquid metal body, the heating substrate adhesive layer, and the heat dissipation substrate adhesive layer seamlessly fused, the ultra-thin thermal interface material is thinned, and the excess liquid metal is squeezed out.

[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 ultrathin 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 and a heat dissipation substrate that are attached to the liquid metal layer.

[0025] The heating substrate with the attached liquid metal layer includes a liquid metal layer, a heating substrate adhesive layer, and a heating substrate that are seamlessly attached in sequence. The heat dissipation substrate with the attached liquid metal layer includes a liquid metal layer, a heat dissipation substrate adhesive layer, and a heat dissipation substrate that are seamlessly attached in sequence. The liquid metal layer includes a high-purity liquid metal body and an oxide layer of high-purity liquid metal. A method for preparing an ultrathin liquid metal thermal interface material based on dynamic wetting control has been completed.

[0026] The present invention discloses a method for preparing an ultrathin liquid metal thermal interface material based on dynamic wetting control. 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 interfacial interactions obtained by chemically improved pretreatment methods are hydrogen bonds, coordination, complexation, dipoles, or π bonds; the interfacial interactions obtained by metal deposition pretreatment methods are coordination, complexation, or alloying reactions; the interfacial interactions obtained by plasma treatment, ozone treatment, and ultraviolet irradiation are hydrogen bonds, coordination, or complexation.

[0028] Chemically modified reagents include acid-base reagents, reducing reagents, and chemical reagents that can be chemically modified to form hydrogen bonds, coordination, complexation, dipoles, or π bonds.

[0029] The present invention describes a method for preparing an ultrathin liquid metal thermal interface material based on dynamic wetting control. As a preferred embodiment, 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-based antioxidants, silane coupling agents, and ionic liquids.

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

[0031] The present invention provides a method for preparing an ultrathin liquid metal thermal interface material based on dynamic wetting control. In a preferred embodiment, the surface pretreatment method in step S1 further includes selective confinement, pretreating only the target areas of the heating substrate and the heat dissipation substrate, so that the target areas and non-target areas form a differentiated liquid metal affinity to prevent leakage of the high-purity liquid metal body during use.

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

[0033] The present invention discloses a method for preparing an ultrathin 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 wetting fusion, vacuum or pressure-assisted fusion, or optical, electrical or magnetic induced fusion.

[0034] In the preferred embodiment of the method for preparing an ultrathin liquid metal thermal interface material based on dynamic wetting control described in this invention, in step S4, when the heating substrate and the heat dissipation substrate of the liquid metal layer are used, the oxide layer of the high-purity liquid metal is first removed, and then the heating substrate and the liquid metal layer are coupled and continued to be used by the high-purity liquid metal body through wetting and fusion.

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

[0036] The acidic, alkaline, or reducing reagent 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-based antioxidants.

[0037] The present invention discloses a method for preparing an ultrathin liquid metal thermal interface material based on dynamic wetting control. As a preferred embodiment, the ultrathin liquid metal thermal interface material is suitable for enhancing heat conduction in application terminals in the microelectronics field, 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 heat-generating substrate is any one of the following: 5G base station chip or chip shell plating or packaging, AI chip or chip shell plating or packaging, PC chip or chip shell plating or packaging, data center server chip or chip shell plating or packaging, smart charging pile chip or chip shell plating or packaging, power battery or battery shell plating or packaging, LED lighting chip or chip shell plating or packaging, IGBT equipment chip or chip shell plating or packaging.

[0039] The heat dissipation substrate can be any of the following: 5G base station heat sink or plating or encapsulation, AI chip heat sink or plating or encapsulation, PC heat sink or plating or encapsulation, data center server heat sink or plating or encapsulation, smart charging pile heat sink or plating or encapsulation, power battery heat sink or plating or encapsulation, LED lighting heat sink or plating or encapsulation, IGBT equipment heat sink or plating or encapsulation.

[0040] This invention provides an ultrathin liquid metal thermal interface based on dynamic wetting control, along with its preparation and application methods. By pretreating the substrate material surface, the wettability of the liquid metal is significantly improved. The ultrathin liquid metal layer formed by dynamic wetting is directly used as a heat transfer medium, achieving seamless molecular-level bonding at the interface, greatly reducing contact thermal resistance. Furthermore, it is low-cost, easy to operate, and widely adaptable to various heat-generating and heat-dissipating substrate materials. The ultrathin liquid metal thermal interface of this invention is an ultrathin, high-purity liquid metal thermal interface.

[0041] The ultrathin high-purity liquid metal thermal interface of the present invention comprises a high-purity liquid metal substrate and a liquid metal dynamic wetting adhesive layer; the liquid metal dynamic wetting adhesive layer comprises a heating substrate adhesive layer tightly bonded to the surface of a heating substrate and a heat dissipation substrate adhesive layer tightly bonded to the surface of a heat dissipation substrate, the high-purity liquid metal substrate being located between the heating substrate adhesive layer and the heat dissipation substrate adhesive layer, and being fused together by the heating substrate and the heat dissipation substrate to form an ultrathin thermal interface material. The preparation method of the ultrathin high-purity liquid metal thermal interface comprises the following steps: substrate material surface pretreatment, dynamic wetting of liquid metal, pressure fusion and extrusion redundancy, encapsulation and shaping. The method of using the ultrathin high-purity liquid metal thermal interface includes the following steps: the coupled and packaged ultrathin high-purity liquid metal thermal interface can be used directly; the disassembled and packaged ultrathin high-purity liquid metal thermal interface requires first removing the surface oxide layer, and then coupling and reconnecting the heating substrate and the heat dissipation substrate before use. It is widely applicable to enhancing heat conduction in various application terminals in the microelectronics field, 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. This invention achieves seamless molecular-level bonding between interfaces, significantly reducing contact thermal resistance, and is low in cost and easy to operate.

[0042] The present invention has the following advantages:

[0043] (1) This invention directly utilizes an ultrathin liquid metal layer formed by dynamic wetting as a heat transfer medium, achieving seamless molecular-level bonding between the liquid metal and the substrate material interface. It can obtain ultrathin thermal interfaces with a thickness of only 1–1000 nm, significantly reducing contact thermal resistance. The measured interfacial thermal conductivity can reach 25.9–47.1 W / m. -1 ·K -1 This far exceeds the measured values ​​of currently commercially available thermal interface materials;

[0044] (2) Compared with the current commercial thermal interface materials rich in various doped particles, the present invention has a fluidity and adaptability closer to that of a liquid, while avoiding problems such as decreased 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 pretreatment of the substrate material surface, which is low in cost and easy to operate;

[0046] (4) The dynamic wetting control method of the present invention has universality. Relying on different forms of interface interaction, it can be widely adapted to various heat-generating and heat-dissipating substrate materials, greatly expanding the terminal application scenarios. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the overall structure of an ultrathin liquid metal thermal interface material based on dynamic wetting control.

[0048] Figure 2 This is a statistical chart of the natural thickness of the liquid metal dynamic wetting adhesion layer on the surface of different substrate materials under normal pressure in an embodiment of an ultrathin liquid metal thermal interface material and its preparation method based on dynamic wetting control.

[0049] Figure 3 This is a flowchart of a method for preparing an ultrathin liquid metal thermal interface material based on dynamic wetting control.

[0050] Figure 4 Examples of an ultrathin liquid metal thermal interface material based on dynamic wetting control and its preparation method include pretreatment methods for different substrate materials and corresponding interfacial interaction forms.

[0051] Figure 5 This example illustrates the long-term leak-proof performance of an ultrathin, high-purity liquid metal thermal interface material and its preparation method based on dynamic wetting control.

[0052] Figure 6 This is a cryo-electron microscopy image of the liquid metal dynamically wetted adhesive layer in an embodiment of an ultrathin liquid metal thermal interface material and its preparation method based on dynamic wetting control.

[0053] Figure 7 This paper presents a comparison of the thermal conductivity of an ultrathin high-purity liquid metal thermal interface material and a traditional thermal interface material in an embodiment of a dynamically wetted ultrathin liquid metal thermal interface material and its preparation method.

[0054] Figure label:

[0055] 1. High-purity liquid metal substrate; 2. Liquid metal dynamic wetting adhesive layer; 23. Heating substrate adhesive layer; 24. Heat dissipation substrate adhesive layer; 3. Heating substrate; 4. Heat dissipation substrate. Detailed Implementation

[0056] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0057] Example 1

[0058] An ultrathin liquid metal thermal interface material based on dynamic wetting control and its preparation method, combined with Figures 1 to 7 As shown, the ultrathin liquid metal thermal interface material includes: a high-purity liquid metal body 1 and a liquid metal dynamic wetting adhesive layer 2; the liquid metal dynamic wetting adhesive layer 2 includes a heating substrate adhesive layer 23 that is tightly attached to the surface of the heating substrate 3 and a heat dissipation substrate adhesive layer 24 that is tightly attached to the surface of the heat dissipation substrate 4; the high-purity liquid metal body 1 is located between the heating substrate adhesive layer 23 and the heat dissipation substrate adhesive layer 24, and is fused together by the extrusion of the heating substrate 3 and the heat dissipation substrate 4 to form the ultrathin thermal interface material (e.g., Figure 1 (As shown).

[0059] The high-purity liquid metal body 1 is composed of a metal or its alloy that is liquid at room temperature, or a mixture of it with other metals, oxides of other metals, non-metals or non-metal oxides, etc.; the metals include, but are not limited to, gallium or indium or tin or bismuth or mercury or lithium or sodium or potassium, etc., and the 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 the non-metals are carbon or silicon.

[0060] The liquid metal dynamic wetting adhesive layer 2 is bonded to any surface of the heat-generating substrate 3 or the heat-dissipating substrate 4, and the material includes the material of the heat-generating substrate 3, the material of the heat-dissipating substrate 4, or their surface coating or encapsulation material.

[0061] The heating substrate 3 material 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 heat dissipation substrate 4 materials include, but are not limited to, copper or its alloys or oxides, aluminum or its alloys or oxides, iron or its alloys or oxides, carbon steel, stainless steel, etc.

[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 ferroalloys or iron oxides, carbon steel, stainless steel, and precious metals such as gold, silver, platinum, rhodium or iridium; encapsulation materials include, but are not limited to, high molecular weight materials such as polyethylene (PE), polypropylene (PP), polyvinyl alcohol (PVA), polyethylene terephthalate (PET), polyimide (PI), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), silicone and epoxy resin (EP).

[0064] The natural thickness of the single liquid metal dynamic wetting adhesive layer 2 under normal pressure is 10-200 μm. When it is fused with the high-purity liquid metal body 1 under pressure, the thickness of the ultra-thin thermal interface material is no more than 200 μm.

[0065] The natural thickness of the single liquid metal dynamic wetting adhesive layer 2 under normal pressure is 10-100 μm. When it is pressed and fused with the high-purity liquid metal body 1, the thickness of the ultra-thin thermal interface material is no more than 100 μm.

[0066] The natural thickness of the single liquid metal dynamic wetting adhesive layer 2 under normal pressure is 10-50 μm. It fuses with the high-purity liquid metal body 1 under pressure to form an ultra-thin thermal interface material with a thickness of no more than 50 μm.

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

[0068] In one specific embodiment, the natural thicknesses of the gallium-indium alloy (gallium-indium mass ratio 75:25) liquid metal dynamic wetting adhesive layer 2 formed on the surfaces of the heat-generating substrate 3 (silicon), the heat-dissipating substrate 4 (copper and stainless steel), and the encapsulation materials (polyvinyl alcohol and epoxy resin) under normal pressure 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 (As shown).

[0069] This invention also provides a method for preparing an ultrathin liquid metal thermal interface based on dynamic wetting control (e.g., Figure 3 As shown), it includes the following steps: S1, surface pretreatment of substrate material, S2, dynamic wetting of liquid metal, S3, pressure fusion and extrusion redundancy, S4, encapsulation and shaping.

[0070] The purpose of surface pretreatment of the substrate material is to increase the functional chemical bonds or metal deposition layer on the surface of the heat-generating substrate 3 and the heat-dissipating substrate 4, and to obtain the super-hydrophilic properties of liquid metal (static contact angle after liquid metal wetting is less than 10°) through interfacial interaction, so as to facilitate the formation of a molecular-level seamless adhesive layer; interfacial interaction includes but is not limited to hydrogen bonding, coordination, complexation, dipole, π bond or alloying reaction, etc.

[0071] The methods for surface pretreatment of the substrate material include, but are not limited to, chemical modification, metal deposition, plasma treatment, ozone treatment, or ultraviolet irradiation; 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-based antioxidants, silane coupling agents, ionic liquids, etc.; the methods for metal deposition include, but are not limited to, chemical vapor deposition, physical vapor deposition, vacuum evaporation, or atomic layer deposition, etc.; 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 one specific embodiment, the surface of a 0.5 mm thick single-crystal silicon wafer was subjected to pretreatments such as chemical modification, metal deposition, plasma treatment, ozone treatment, or ultraviolet irradiation. Combined with X-ray photoelectron spectroscopy (XPS) analysis, the corresponding interfacial interaction forms were summarized (as shown in the table below).

[0073]

[0074] The specific methods of substrate material surface pretreatment also include selective confinement. Selective confinement is to perform substrate material surface pretreatment only on specific target areas (usually the central areas 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. The purpose is to create differentiated liquid metal affinity to prevent leakage during use.

[0075] In one specific embodiment, by means of a clamp (such as Figure 4 As shown, a gallium-indium alloy (gallium-indium mass ratio 75:25) is placed between the heating substrate 3 (silicon) and the heat dissipation substrate 4 (copper) to form an ultra-thin high-purity liquid metal thermal interface. This is used to simulate the pressure conditions of the heating substrate 3, the heat dissipation substrate 4, and the thermal interface material in real application scenarios. The side of the fixture that contacts the heating substrate 3 and the heat dissipation substrate 4 is a plane. The size of the fixture is larger than that of 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 after being placed upright for 6 months. The total weight of the clamping device tested every half month remains almost unchanged.

[0076] The purpose of dynamic wetting of liquid metal is to disrupt the initial oxide layer on the surface of liquid metal through dynamic operation, promote the interfacial interaction between liquid metal and the surfaces of heating substrate 3 and heat dissipation substrate 4, and spread and wet to form an ultra-thin adhesive layer. Specific dynamic operation methods include, but are not limited to, droplet rolling, droplet sliding, droplet impact, liquid film scraping, liquid film spin coating, liquid jet spraying, liquid immersion lifting or liquid immersion stirring, etc.

[0077] Pressure-induced fusion and extrusion redundancy utilize the pressure applied to the heating substrate 3 and the heat dissipation substrate 4 to promote seamless fusion between the high-purity liquid metal body 1 and the adhesive layers 23 and 24 of the heating substrate and the heat dissipation substrate, while extruding excess liquid metal to achieve a deep thinning of the thermal interface; the pressure applied between the heating substrate 3 and the heat dissipation substrate 4 ranges from 0 to 5 MPa; specific methods of seamless fusion include, but are not limited to, natural wetting fusion, vacuum or pressure-assisted fusion, and optical, electrical or magnetic induced fusion.

[0078] The packaging and shaping modes include coupled packaging and split packaging. Coupled packaging couples the high-purity ultrathin liquid metal thermal interface with the heat-generating substrate 3 and the heat-dissipating substrate 4 as a whole, and pushes it directly to the application terminal in the form of a shaped product. Split packaging is to split the heat-generating substrate 3 and the heat-dissipating substrate 4 again after the ultrathin liquid metal layer is formed by pressure fusion and extrusion redundancy, so that it can be used again. Under the attraction of the heat-generating substrate adhesive layer 23 and the heat-dissipating substrate adhesive layer 24, the liquid metal will form a liquid metal layer on the surface of the heat-generating substrate 3 and the heat-dissipating substrate 4 respectively after splitting, and the shaping is achieved by the oxide layer that forms rapidly on its surface.

[0079] In one specific embodiment, a gallium-indium alloy (gallium-indium mass ratio 75:25) liquid metal can be dynamically wetted onto a plasma-treated silicon heating substrate 3 rich in hydroxyl groups. Only simple liquid film coating and fusion under pressure below 0.1 MPa are required to form a stable and adherent ultrathin liquid metal thermal interface. Simultaneously, cryo-electron microscopy results (such as...) Figure 5 As shown in the figure, the liquid metal dynamic wetting adhesive layer 2 and the heating substrate 3 achieve a seamless molecular-level bond, and no interface gaps are visible at the nanoscale.

[0080] In another specific embodiment, a gallium-indium alloy (gallium-indium mass ratio 75:25) liquid metal can be dynamically wetted on the surface of a hydrochloric acid-modified copper heat dissipation substrate 4. Only a few liquid immersion and lifting processes are needed to form an ultra-thin liquid metal dynamic wetting adhesion layer 2, maintaining a large-area, uniform, and stable adhesion to the surface of the heat dissipation substrate 4 (e.g., ...). Figure 6 (As shown).

[0081] The present invention also provides a method for using the above-mentioned ultrathin liquid metal thermal interface based on dynamic wetting control, including the following steps: the coupled and packaged ultrathin liquid metal thermal interface can be used directly, and the unpacked ultrathin liquid metal thermal interface needs to have its surface oxide layer removed first, and then the heating substrate 3 and the heat dissipation substrate 4 coupled and connected before use.

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

[0083] Acidic, alkaline, or reducing reagents 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, etc.

[0084] The ultrathin, high-purity liquid metal thermal interface based on dynamic wetting control provided by this invention can be widely used to enhance heat conduction in various application terminals in the microelectronics field, 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 one specific embodiment, a silicon wafer and a copper sheet with a thickness of 0.5 mm were used to simulate the heat-generating substrate 3 and the heat-dissipating substrate 4. The thermal conductivity (e.g., 0.5 mm) of the "silicon-thermal interface-copper" system was tested for 5 minutes under different interface contact states at a fixed pressure of 0.1 MPa. Figure 7 As shown, the samples include those without thermal interface material (i.e., direct contact between silicon wafer and copper sheet (current commercial use), sample 1), filled with thermally conductive silicone grease (100 μm thick, sample 2), filled with liquid metal thermal paste (100 μm thick, sample 3), with thermally conductive indium sheet placed (100 μm thick, sample 4), and filled with ultra-thin high-purity liquid metal thermal interfaces with thicknesses of 200 μm, 100 μm, and 50 μm, respectively, i.e., samples 5, 6, and 7.

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

[0087] Samples 5, 6, and 7 were implemented using different specific methods, as follows:

[0088] (1) The preparation method of the 200μm ultrathin high-purity liquid metal thermal interface (sample 5) is as follows: the silicon substrate 3 is chemically modified with a silane coupling agent containing -NH2 end group to provide hydrogen bonds and coordination bonds, and the surface of the copper substrate 4 is treated with 0.1mol / L hydrochloric acid to promote the gallium-copper alloying reaction; the liquid metal is dynamically wetted by liquid film scraping, so that the surfaces of silicon substrate 3 and copper substrate 4 are dynamically wetted and adhesive layers 23 and 24, respectively; under a load of 0.1MPa, it is fused with the 200μL liquid metal body 1 under pressure, and after extrusion of redundancy, it is disassembled and packaged; before the thermal conductivity test, a small amount of 0.5mol / L potassium hydroxide solution is added to remove the oxide layer, and it is recoupled and reconnected before use.

[0089] (2) The preparation method of the 100μm ultrathin high-purity liquid metal thermal interface (sample 6) is as follows: copper nanoparticles are coated on the surface of silicon substrate 3 by metal deposition. The silicon substrate 3 and the copper substrate 4 coated with copper nanoparticles are treated with 1.0mol / L sodium hydroxide to promote the gallium-copper alloying reaction. Liquid metal is dynamically wetted by liquid immersion and pulling method, so that the surfaces of silicon substrate 3 and copper substrate 4 are dynamically wetted and adhesive layers 23 and 24, respectively. Under a load of 0.5MPa, it is fused with 200μL liquid metal body 1 under pressure, and after extrusion of redundancy, it is disassembled and packaged. Before the thermal conductivity test, a small amount of 0.5mol / L sulfuric acid solution is added to remove the oxide layer, and it is recoupled and reconnected before use.

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

[0091] In this application, the terms "encapsulation," "bonding," and "shaping" should be interpreted broadly. For example, "encapsulation" can refer to direct encapsulation or indirect encapsulation through an intermediate medium, and "bonding" can refer to direct bonding or bonding assisted by external components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0092] Thermal interface materials: 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 embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing an ultrathin liquid metal thermal interface material based on dynamic wetting control, characterized in that: Includes the following steps: S1. The heating substrate (3) and the heat dissipation substrate (4) are subjected to surface pretreatment to obtain a pretreated heating substrate and a pretreated heat dissipation substrate; Surface pretreatment methods include any of the following: chemical modification, plasma treatment, ozone treatment, and ultraviolet irradiation; The interfacial interactions obtained by the chemically improved pretreatment method are hydrogen bonds, coordination, complexation, dipole, or π bonds; the interfacial interactions obtained by plasma treatment, ozone treatment, or ultraviolet irradiation are hydrogen bonds, coordination, or complexation. S2. Dynamically wet the pretreated heating substrate and the pretreated heat dissipation substrate with liquid metal, destroy the initial oxide layer on the surface of the liquid metal, promote the interfacial interaction between the liquid metal and the pretreated heating substrate and the pretreated heat dissipation substrate, and spread and wet to obtain the heating substrate adhesive layer (23) and the heat dissipation substrate adhesive layer (24). The dynamic wetting operation method includes any of the following: droplet rolling, droplet sliding, droplet impact, liquid film scraping, liquid film spin coating, liquid jet spraying, liquid immersion lifting and liquid immersion stirring; S3. A high-purity liquid metal body (1) is introduced between the heating substrate (3) with the heating substrate adhesive layer (23) and the heat dissipation substrate (4) with the heat dissipation substrate adhesive layer (24). The heating substrate (3), the heating substrate adhesive layer (23), the high-purity liquid metal body (1), the heat dissipation substrate adhesive layer (24) and the heat dissipation substrate (4) are pressed by a clamp to make the high-purity liquid metal body (1), the heating substrate adhesive layer (23) and the heat dissipation substrate adhesive layer (24) seamlessly fused, the ultra-thin thermal interface material is thinned and excess liquid metal is extruded. 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 (3) and the heat dissipation substrate (4) after applying pressure for a specified time in step S3 are split to obtain a heating substrate and a heat dissipation substrate with a metal liquid layer. The heating substrate with the attached liquid metal layer includes a liquid metal layer, a heating substrate adhesive layer (23), and a heating substrate (3) that are seamlessly attached in sequence. The heat dissipation substrate with the attached liquid metal layer includes a liquid metal layer, a heat dissipation substrate adhesive layer (24), and a heat dissipation substrate (4) that are seamlessly attached in sequence. The liquid metal layer includes the high-purity liquid metal body (1) and an oxide layer of high-purity liquid metal. The ultrathin liquid metal thermal interface material based on dynamic wetting control consists of the high-purity liquid metal body (1) and the liquid metal dynamic wetting adhesive layer (2) connected to both sides of the high-purity liquid metal body (1). The material of the liquid metal dynamic wetting adhesive layer (2) is the same as that of the high-purity liquid metal body (1). The liquid metal dynamic wetting adhesive layer (2) is spread on the surface of the heating substrate (3) and the surface of the heat dissipation substrate (4), respectively. The liquid metal dynamic wetting adhesive layer (2) includes a heating substrate adhesive layer (23) that is seamlessly attached to the surface of the heating substrate (3) and a heat dissipation substrate adhesive layer (24) that is seamlessly attached to the surface of the heat dissipation substrate (4). The high-purity liquid metal body (1), the heating substrate adhesive layer (23) and the heat dissipation substrate adhesive layer (24) are made of the same material and form an ultra-thin liquid metal thermal interface material. The heating substrate adhesive layer (23) and the heat dissipation substrate adhesive layer (24) are heat transfer media. The ultra-thin thermal interface material, the heating substrate (3) and the heat dissipation substrate (4) are seamlessly fused by extrusion with a pressure range of 0~5 MPa. The high-purity liquid metal body (1) is a metal and its alloy that are liquid at room temperature, and a mixture of the metal with other metals, oxides of other metals, non-metals, and oxides of non-metals; the metal is gallium or indium or tin or bismuth or mercury or lithium or sodium or potassium, and 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; The heating substrate surface connected to the heating substrate adhesive layer (23) is pretreated to make the heating substrate (3) and the heating substrate adhesive layer (23) connected through interface interaction; the heat dissipation substrate surface connected to the heat dissipation substrate adhesive layer (24) is pretreated to make the heat dissipation substrate (4) and the heat dissipation substrate adhesive layer (24) connected through interface interaction. The interfacial interactions are hydrogen bonds, coordination, complexation, dipoles, π bonds, or alloying reactions.

2. The method for preparing an ultrathin liquid metal thermal interface material based on dynamic wetting control according to claim 1, characterized in that: 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 wetting adhesive layer (2) under normal pressure is 10~200 μm. The thickness of the high-purity liquid metal body (1) and the liquid metal dynamic wetting adhesive layer (2) after being fused under pressure is not higher 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 heat dissipation substrate (4) is made of any of the following materials: copper, copper alloy, copper oxide, aluminum, aluminum alloy, aluminum oxide, iron, iron alloy, iron oxide, carbon steel, and stainless steel.

3. The method for preparing an ultrathin liquid metal thermal interface material based on dynamic wetting control according to claim 1, characterized in that: Both the heat-generating substrate (3) and the heat-dissipating substrate (4) can be provided with surface coatings or encapsulation materials; 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, ferroalloy, iron oxide, tin, tin alloy, tin oxide, carbon steel, stainless steel, gold, silver, platinum, rhodium, and iridium. The encapsulation material includes any one of the following: polyethylene, polypropylene, polyvinyl alcohol, polyethylene terephthalate, polyimide, polyphenylene sulfide, polyether ether ketone, polyvinylidene fluoride, polytetrafluoroethylene, silicone, and epoxy resin.

4. The method for preparing an ultrathin liquid metal thermal interface material based on dynamic wetting control according to claim 1, characterized in that: In step S1, the surface pretreatment method further includes metal deposition, wherein the interfacial interaction obtained by the metal deposition pretreatment method is a coordination, complexation, or alloying reaction. Chemically modified reagents include acid-base reagents, reducing reagents, and chemical reagents that can be chemically modified to form hydrogen bonds, coordination, complexation, dipoles, or π bonds.

5. The method for preparing an ultrathin liquid metal thermal interface material based on dynamic wetting control according to claim 4, characterized in that: The chemically modified reagents include 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-based antioxidants, silane coupling agents, and ionic liquids; The metal deposition method includes any of the following: chemical vapor deposition, physical vapor deposition, vacuum evaporation and atomic layer deposition, and the deposited metal includes any of the following: copper, aluminum, gold, silver, platinum, rhodium, iridium, vanadium, tungsten, zinc, magnesium, lead, nickel, chromium and cadmium.

6. The method for preparing an ultrathin liquid metal thermal interface material based on dynamic wetting control according to claim 4, characterized in that: In step S1, the surface pretreatment method also includes selective confinement, which pretreatment is performed only on the target areas of the heating substrate (3) and the heat dissipation substrate (4) to form a differentiated liquid metal affinity between the target area and the non-target area to prevent leakage of the high-purity liquid metal body (1) during use. The target area is the central area of ​​the heating substrate (3) and the heat dissipation substrate (4).

7. The method for preparing an ultrathin liquid metal thermal interface material based on dynamic wetting control according to claim 4, characterized in that: In step S3, the seamless fusion method includes any one of the following: natural immersion fusion, vacuum or pressure-assisted fusion, and light, electricity or magnetism-induced fusion.

8. The method for preparing an ultrathin liquid metal thermal interface material based on dynamic wetting control according to claim 1, characterized in that: In step S4, when the heating substrate and the heat dissipation substrate of the attached liquid metal layer are used, the oxide layer of the high-purity liquid metal is first removed, and then the heating substrate and the attached liquid metal layer are coupled and continued to be used by immersion and fusion of the high-purity liquid metal body. The method for removing the oxide layer of the high-purity liquid metal is to react chemically with the oxide layer of the high-purity liquid metal using acidic, alkaline, or reducing reagents. The acidic, alkaline, or reducing reagent 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-based antioxidants.

9. The method for preparing an ultrathin liquid metal thermal interface material based on dynamic wetting control according to claim 1, characterized in that: Ultrathin liquid metal thermal interface materials are suitable for enhancing heat conduction in microelectronic applications, including any of the following: 5G base stations, AI chips, PCs, data center servers, smart charging piles, power batteries, LED lighting, and IGBT equipment. The heat-generating substrate (3) is any one of the following: 5G base station chip or chip shell plating or packaging, AI chip or chip shell plating or packaging, PC chip or chip shell plating or packaging, data center server chip or chip shell plating or packaging, smart charging pile chip or chip shell plating or packaging, power battery or battery shell plating or packaging, LED lighting chip or chip shell plating or packaging, IGBT equipment chip or chip shell plating or packaging; The heat dissipation substrate (4) is any one of the following: 5G base station heat sink or plating or encapsulation, AI chip heat sink or plating or encapsulation, PC heat sink or plating or encapsulation, data center server heat sink or plating or encapsulation, smart charging pile heat sink or plating or encapsulation, power battery heat sink or plating or encapsulation, LED lighting heat sink or plating or encapsulation, IGBT equipment heat sink or plating or encapsulation.

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