Composite liquid metal sheet, preparation method thereof and electronic equipment

Abstract

The invention provides a composite liquid metal sheet, a preparation method thereof and electronic equipment, and relates to the field of heat-conducting fins. Comprising an upper composite layer and a lower composite layer, the edges of the upper composite layer and the lower composite layer are directly connected to form an internal cavity, and a flowing layer is arranged in the cavity; the upper composite layer comprises a first base material layer and a first low-temperature alloy layer arranged on the surface of the first base material layer, the lower composite layer comprises a second base material layer and a second low-temperature alloy layer arranged on the surface of the second base material layer, raw materials of the first base material layer and the second base material layer comprise high-melting-point metal materials, and the melting point of the high-melting-point metal materials is larger than 500 DEG C. The flowing layer can automatically deform by different thicknesses according to the warping condition to fill gaps; the first base material layer and the second base material layer have good heat conduction performance and rebound compression performance and can be suitable for equipment with high flatness, and the problem that a traditional liquid metal sheet is poor in heat conduction effect on equipment with low flatness is effectively solved.

Description

Technical Field

[0001] This application relates to the field of thermal conductive sheets, and more particularly to a composite liquid metal sheet, its preparation method, and an electronic device thereof. Background Technology

[0002] With the rapid development of microelectronics technology, the total power density and heat flux density of electronic chips are constantly increasing, and the impact of heat dissipation performance on system stability and hardware lifespan is becoming increasingly serious. Traditional thermal interface materials, such as thermal grease and thermal silicone, have problems such as low thermal conductivity and high thermal resistance, making it difficult to meet the requirements of high-performance heat dissipation. Although liquid metal thermal conductive materials have attracted widespread attention due to their high thermal conductivity and low thermal resistance, some problems still exist in practical applications, such as poor wettability of molten liquid metal and susceptibility to short circuits.

[0003] To address these issues, researchers have begun exploring novel thermal interface materials. Among these, metal-based thermal interface materials have become a research hotspot due to their high thermal conductivity. However, traditional metal heat sinks, due to their high hardness, are prone to creating cavities on uneven surfaces, reducing heat transfer efficiency.

[0004] To improve thermal conductivity, some studies have attempted to eliminate interfacial thermal resistance by coating metal sheets with composite thermal paste. However, this method suffers from poor stability and easy coating peeling. Currently, liquid metal-based composite materials, due to their high thermal conductivity and low thermal resistance, have become an important direction for solving the heat dissipation problem of electronic chips. However, liquid metals tend to become fluid at high temperatures, posing risks of side leakage and short circuits. Therefore, improving the stability of liquid metals while reducing their conductivity is a key focus and challenge in current research. Furthermore, with the surge in AI computing power leading to larger chip sizes and severe warping, traditional liquid metal sheets, due to insufficient springback compression, are only suitable for devices with high flatness. In cases of high warping heat sources, their thermal conductivity is poor, and their performance cannot be fully realized.

[0005] Regarding the problem of poor thermal conductivity due to chip warpage, several invention patents have addressed this issue. For example, patent document CN114919252A discloses a composite high thermal conductivity sandwich pad, which, from top to bottom, comprises a first indium sheet layer, a sandwich layer, and a second indium sheet layer. The raw materials used in its preparation include 1.5-3 parts by weight of indium ingot and 0.5-1 part of liquid metal ingot. This document utilizes an area ratio of indium sheet to liquid metal sheet of 1:(0.3-0.5) to give the sandwich pad good flexibility, improve the tightness of the sandwich pad's contact with the solid surface, enhance heat transfer efficiency, and reduce contact thermal resistance. However, this document still has the issue that the composition and proportion of the liquid metal sheet need further optimization to improve thermal conductivity and heat dissipation speed. Patent document CN114874758A proposes a novel indium-based high-efficiency thermal pad, using indium metal and indium bismuth tin alloy as the materials. The indium metal and indium bismuth tin alloy are rolled into square metal sheets, which are then cut, stacked, and pressed to form a "dam-shaped" thermal pad with indium bismuth tin alloy on both the upper and lower surfaces. By reducing the gaps between the thermal pad itself and the chip and heat sink, the contact thermal resistance is reduced, meeting the requirements for higher power heat dissipation. However, this document still has the problem that the composition and ratio of liquid metal need to be further optimized to enhance its thermal conductivity and oxidation resistance.

[0006] In summary, existing technologies still have the following drawbacks: 1. Traditional liquid metal sheets are only suitable for devices with high flatness due to insufficient springback compression. When the heat source is highly warped, the heat conduction effect is poor and the performance cannot be fully utilized. 2. Liquid metals easily turn into a fluid liquid phase at high temperatures, posing risks of side leakage and short circuits, and are difficult to maintain a stable state; 3. Existing thermal interface materials, such as thermal grease and thermal silicone, have problems such as low thermal conductivity and high thermal resistance, making it difficult to meet the requirements of high-performance heat dissipation; 4. Due to their high hardness, metal heat-conducting sheets are prone to cavities on uneven surfaces, which reduces heat transfer efficiency. Furthermore, they suffer from poor stability and easy peeling of the coating when applying composite thermal paste. 5. The thermal conductivity and stability of existing liquid metal-based composite materials in high-temperature environments still need further improvement, making it difficult to meet the requirements for use under extreme conditions.

[0007] Therefore, a novel liquid metal sheet capable of covering chip warping and reducing contact thermal resistance is needed to solve the above problems. Summary of the Invention

[0008] The purpose of this application is to provide a composite liquid metal sheet, its preparation method, and an electronic device to solve the above-mentioned problems.

[0009] To achieve the above objectives, the first aspect of this application provides a composite liquid metal sheet, comprising an upper composite layer and a lower composite layer, wherein the edges of the upper composite layer and the lower composite layer are directly connected to form an internal cavity, and a flow layer is disposed within the cavity; The upper composite layer includes a first substrate layer and a first low-temperature alloy layer disposed on the surface of the first substrate layer. The lower composite layer includes a second substrate layer and a second low-temperature alloy layer disposed on the surface of the second substrate layer. The raw materials of the first substrate layer and the second substrate layer include high-melting-point metal materials with a melting point > 500°C.

[0010] It should be noted that the composite liquid metal sheet provided in this application forms a material with a structure similar to a hot water bottle, which can effectively improve resilience and compression, so that the liquid metal (flow layer) inside the metal sheet can automatically deform to different thicknesses to fill the gaps according to the warping; it is a truly flexible structural metal material with extremely high thermal conductivity and extremely low thermal resistance.

[0011] Optionally, the raw materials of the first low-temperature alloy layer and the second low-temperature alloy layer, by weight, each independently include: 0.1-0.3 parts indium, 0.1-0.3 parts bismuth, and 0.1-0.3 parts tin; And / or, the raw materials of the flow layer, by mass, include: 0.5-0.8 parts gallium, 0.1-0.3 parts indium and 0.1-0.3 parts tin.

[0012] Optionally, the raw materials of the first and second cryogenic alloy layers, by mass, also independently include: 0.1-0.3 parts zinc, 0.1-0.3 parts silver, and 0.002-0.01 parts gallium.

[0013] Optionally, the raw materials of the flow layer, by weight, further include: 0.1-0.3 parts bismuth, 0.01-0.1 parts zinc, 0.01-0.1 parts copper, 0.01-0.1 parts silver, 0.01-0.1 parts gold, and 0.01-0.1 parts platinum.

[0014] Optionally, the high-melting-point metal material includes copper and / or silver; And / or, the thickness of the first cryogenic alloy layer and the second cryogenic alloy layer are each independently 1-20 μm; And / or, the melting points of the first cryogenic alloy layer and the second cryogenic alloy layer are each independently 50-160°C; And / or, a first transition layer is further provided between the first substrate layer and the first low-temperature alloy layer, and a second transition layer is further provided between the second substrate layer and the second low-temperature alloy layer; The raw materials for the first transition layer and the second transition layer each independently include indium and / or nickel; The surface roughness of the first transition layer and the second transition layer are each independently 0.2-0.5 μm; The thicknesses of the first transition layer and the second transition layer are each 1-20 μm.

[0015] Optionally, the thickness ratio of the upper composite layer to the lower composite layer is 1-2:1; And / or, the thickness of the upper composite layer and the lower composite layer are each independently 50-200 μm; And / or, the volume of the flow layer accounts for 50-80% of the total volume of the cavity.

[0016] And / or, the surface roughness of the first cryogenic alloy layer and the second cryogenic alloy layer are each independently 0.2-0.5 μm.

[0017] A second aspect of this application provides a method for preparing the composite liquid metal sheet, comprising: A first low-temperature alloy layer is deposited on the surface of the first substrate layer to obtain an upper composite layer; a second low-temperature alloy layer is deposited on the surface of the second substrate layer to obtain a lower composite layer. The upper and lower composite layers are bonded together on opposite sides to form a cavity; the raw material of the flow layer is injected into the cavity and sealed to obtain a composite liquid metal sheet.

[0018] Optionally, a first transition layer may be provided between the first substrate layer and the first low-temperature alloy layer; And / or, a second transition layer is further provided between the second substrate layer and the second cryogenic alloy layer; And / or, the methods for setting the first cryogenic alloy layer and the second cryogenic alloy layer each independently include at least one of vacuum sputtering, spraying, pad printing, and roller brushing; And / or, the adhesion is made using an adhesive, the adhesive including high-temperature resistant double-sided adhesive; And / or, the injection is performed under an inert atmosphere; And / or, the sealing is performed in a vacuum environment.

[0019] Optionally, after the first transition layer, the second transition layer, the first cryogenic alloy layer and the second cryogenic alloy layer are prepared, the first transition layer, the second transition layer, the first cryogenic alloy layer and the second cryogenic alloy layer are each subjected to plasma cleaning treatment independently. And / or, methods for setting the first transition layer and the second transition layer include electroplating and / or magnetron sputtering.

[0020] A third aspect of this application provides an electronic device including the aforementioned composite liquid metal sheet.

[0021] Compared with the prior art, the beneficial effects of this application include: The composite liquid metal sheet provided in this application allows the liquid metal in the flow layer to automatically deform to different thicknesses to fill gaps according to the warping situation during use. The first substrate layer and the second substrate layer have good thermal conductivity and spring compression properties, making them suitable for devices with high flatness and effectively solving the problem of poor thermal conductivity of traditional liquid metal sheets on devices with low flatness. The first low-temperature alloy layer and the second low-temperature layer fill the microscopic gaps on the surface of the chip and the composite liquid metal sheet, achieving full coverage of chip warping and elimination of interface thermal resistance.

[0022] The method for preparing the composite liquid metal sheet provided in this application has a simple and reliable product structure design, is easy to manufacture, has good practicality and promotion value, and can meet the requirements of high-performance heat dissipation.

[0023] The electronic device provided in this application has excellent heat dissipation performance, is not prone to short circuits, and has a long service life. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0025] Figure 1 This is a schematic diagram of the structure of the composite liquid metal sheet provided in this application; Figure 2 A physical image of the composite liquid metal sheet provided in Example 1; Figure 3 This is an injection diagram of Example 1 during the preparation of the composite liquid metal sheet; Figure 4 Comparison charts of TTV simulated thermal tests of the composite liquid metal sheets provided in Examples 1-4 and Comparative Examples 1-3.

[0026] Explanation of key component symbols: 110 - First substrate layer; 120 - First transition layer; 130 - First low-temperature alloy layer; 210 - Lower first substrate layer; 220 - Second transition layer; 230 - Second low-temperature alloy layer; 300 - Flow layer. Detailed Implementation

[0027] First, the solution provided in this application will be explained in more detail as follows: The first aspect of this application provides a composite liquid metal sheet, including an upper composite layer and a lower composite layer, wherein the edges of the upper composite layer and the lower composite layer are directly connected to form an internal cavity, and a flow layer is disposed within the cavity; The upper composite layer The composite layer includes a first substrate layer and a first low-temperature alloy layer disposed on the surface of the first substrate layer. The lower composite layer includes a second substrate layer and a second low-temperature alloy layer disposed on the surface of the second substrate layer. The raw materials of the first substrate layer and the second substrate layer include high-melting-point metal materials with a melting point > 500°C.

[0028] Optionally, the melting point of the high melting point metal material can be any point or range value within the published range, such as 501℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃ or >500℃.

[0029] In some embodiments, the raw materials of the first cryogenic alloy layer and the second cryogenic alloy layer, by weight, each independently include: 0.1-0.3 parts indium, 0.1-0.3 parts bismuth, and 0.1-0.3 parts tin; Optionally, the raw materials of the first or second cryogenic alloy layer, by weight, may be any point or range of 0.1, 0.15, 0.2, 0.25, 0.3, or 0.1-0.3 parts of indium, 0.15, 0.2, 0.25, 0.3, or 0.1-0.3 parts of bismuth, 0.15, 0.2, 0.25, 0.3, or 0.1-0.3 parts of tin, or 0.15, 0.2, 0.25, 0.3, or 0.1-0.3 parts of tin. And / or, the raw materials of the flow layer, by mass, include: 0.5-0.8 parts gallium, 0.1-0.3 parts indium and 0.1-0.3 parts tin.

[0030] Optionally, the raw materials of the flow layer, by weight, may be gallium at any point or range within the published range of 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, or 0.5-0.8 parts; indium at any point or range within the published range of 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, or 0.1-0.3 parts; and tin at any point or range within the published range of 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, or 0.1-0.3 parts.

[0031] In some embodiments, the raw materials of the first cryogenic alloy layer and the second cryogenic alloy layer, by mass, also independently include: 0.1-0.3 parts of zinc, 0.1-0.3 parts of silver, and 0.002-0.01 parts of gallium.

[0032] Optionally, the raw materials of the first or second cryogenic alloy layer, by weight, may be: zinc, 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, or 0.1-0.3 parts, etc., any point or range of value within the published range; silver, 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, or 0.1-0.3 parts, etc., any point or range of value within the published range; and gallium, 0.002 parts, 0.003 parts, 0.004 parts, 0.005 parts, 0.006 parts, 0.007 parts, 0.008 parts, 0.009 parts, 0.01 parts, or 0.002-0.01 parts, etc., any point or range of value within the published range.

[0033] It should be noted that zinc and silver, as fillers with high thermal conductivity metals, can improve the thermal conductivity of low-temperature alloys, while gallium, as a liquid metal, can adjust the melting point of the overall low-temperature alloy and at the same time increase the bonding effect between layers.

[0034] In some embodiments, the raw materials of the flow layer, by weight, further include: 0.1-0.3 parts bismuth, 0.01-0.1 parts zinc, 0.01-0.1 parts copper, 0.01-0.1 parts silver, 0.01-0.1 parts gold, and 0.01-0.1 parts platinum.

[0035] Optionally, the raw materials for the flow layer, by weight, may be: bismuth (0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, or 0.1-0.3 parts, etc., any point or range within the published range); zinc (0.01 parts, 0.02 parts, 0.03 parts, 0.04 parts, 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts, 0.1 parts, or 0.01-0.1 parts, etc.); copper (0.01 parts, 0.02 parts, 0.03 parts, 0.04 parts, 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts, 0.1 parts, or 0.01-0.1 parts, etc.); and silver (0.01...). The values ​​can be any point or range within the published range, such as 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or 0.01-0.1. For gold, the values ​​can be any point or range within the published range, such as 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or 0.01-0.1. For platinum, the values ​​can be any point or range within the published range, such as 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or 0.01-0.1.

[0036] It should be noted that adding small amounts of bismuth, zinc, copper, silver, gold, and platinum to the formula will not significantly affect the melting point, but it can adjust the viscosity of the liquid metal to reduce the risks associated with fluidity, increase wettability, and enhance thermal conductivity as a high thermal conductivity metal addition.

[0037] In some embodiments, the high-melting-point metallic material includes copper and / or silver; It should be noted that copper and silver have high thermal conductivity and good ductility; And / or, the thickness of the first cryogenic alloy layer and the second cryogenic alloy layer are each independently 1-20 μm; Optionally, the thickness of the first cryogenic alloy layer and the second cryogenic alloy layer can each be independently set to any point value or range value within the published range, such as 1μm, 5μm, 10μm, 15μm, 20μm or 1-20μm. And / or, the melting points of the first cryogenic alloy layer and the second cryogenic alloy layer are 50-160°C; Optionally, the melting points of the first cryogenic alloy layer and the second cryogenic alloy layer can each be independently any point or range value within the published range, such as 50℃, 60℃, 80℃, 100℃, 120℃, 140℃, 160℃ or 50-160℃. And / or, a first transition layer is further provided between the first substrate layer and the first low-temperature alloy layer, and a second transition layer is further provided between the second substrate layer and the second low-temperature alloy layer; The raw materials for the first transition layer and the second transition layer each independently include indium and / or nickel; It should be noted that the first and second transition layers can increase the wettability of the low-temperature alloy on the substrate and also increase its adhesion. The surface roughness of the first transition layer and the second transition layer are each independently 0.2-0.5 μm.

[0038] Optionally, the surface roughness of the first transition layer and the second transition layer can each be independently any point value or range value within the published range, such as 0.2μm, 0.3μm, 0.4μm, 0.5μm or 0.2-0.5μm; The thickness of the first transition layer and the second transition layer are each 1-20 μm.

[0039] Optionally, the thickness of the first transition layer and the second transition layer can each be an independent point value or range value within the published range, such as 1μm, 5μm, 10μm, 15μm, 20μm or 1-20μm.

[0040] In some embodiments, the thickness ratio of the upper composite layer to the lower composite layer is 1-2:1; Optionally, the thickness ratio of the upper composite layer to the lower composite layer can be any point value or range value within the published range, such as 1:1, 1.5:1, 2:1 or 1-2:1; Preferably, the thickness ratio of the upper composite layer to the lower composite layer is 1:1; And / or, the thickness of the upper composite layer and the lower composite layer are each independently 50-200 μm; Optionally, the thickness of the upper composite layer and the lower composite layer can be any point value or range value within the published range, such as 50μm, 100μm, 150μm, 200μm or 50-200μm. Preferably, the thickness of the upper composite layer and the lower composite layer are each 100 μm. And / or, the volume of the flow layer accounts for 50-80% of the total volume of the cavity.

[0041] Optionally, the volume of the flow layer can be any point or range within the published range, such as 50%, 55%, 60%, 65%, 70%, 75%, 80%, or 50-80% of the total cavity volume.

[0042] And / or, the surface roughness of the first cryogenic alloy layer and the second cryogenic alloy layer are each independently 0.2-0.5 μm.

[0043] Optionally, the surface roughness of the first cryogenic alloy layer and the second cryogenic alloy layer can each be independently any point value or range value within the published range, such as 0.2μm, 0.3μm, 0.4μm, 0.5μm, or 0.2-0.5μm.

[0044] It should be noted that the composite liquid metal sheet provided in this application meets the following conditions: (1) Thermal resistance value is less than 0.05℃·cm 2 / W; (2) The composite liquid metal sheet was tested at 150℃ and maintained its shape stably without any leakage of liquid metal. (3) Conduct a warpage coverage test and perform a temperature simulation test under a warpage heat source of 400-500μm to ensure that the test temperature is kept below 90℃.

[0045] A second aspect of this application provides a method for preparing the composite liquid metal sheet, comprising: A first low-temperature alloy layer is deposited on the surface of the first substrate layer to obtain an upper composite layer; a second low-temperature alloy layer is deposited on the surface of the second substrate layer to obtain a lower composite layer. The upper and lower composite layers are bonded together on their opposite sides to form a cavity; the raw material of the flow layer is injected into the cavity and sealed to obtain a composite liquid metal sheet.

[0046] In some embodiments, a first transition layer is further provided between the first substrate layer and the first low-temperature alloy layer; And / or, a second transition layer is further provided between the second substrate layer and the second cryogenic alloy layer; And / or, the methods for setting the first cryogenic alloy layer and the second cryogenic alloy layer each independently include at least one of vacuum sputtering, spraying, pad printing, and roller brushing; And / or, the adhesion is made using an adhesive, the adhesive including high-temperature resistant double-sided adhesive; And / or, the injection is performed under an inert atmosphere; And / or, the sealing is performed in a vacuum environment.

[0047] In some embodiments, after the first transition layer, the second transition layer, the first low-temperature alloy layer and the second low-temperature alloy layer are prepared, the first transition layer, the second transition layer, the first low-temperature alloy layer and the second low-temperature alloy layer are each subjected to plasma cleaning treatment independently. It should be noted that the surfaces of the transition layer and the low-temperature alloy layer are surface treated, with the surface roughness Ra controlled at 0.2-0.5 micrometers to improve the adhesion with the substrate layer; And / or, methods for setting the first transition layer and the second transition layer include electroplating and / or magnetron sputtering.

[0048] A third aspect of this application provides an electronic device including the aforementioned composite liquid metal sheet.

[0049] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. It can be understood by way of example that in this application, the raw materials of the first transition layer and the second transition layer each independently include indium and / or nickel. This application is only exemplified by indium and does not mean that this application can only use indium. In this application, indium can also be replaced by nickel or an alloy or mixture of the two. Other structures and raw materials of this application can also be understood in this way.

[0050] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0051] Example 1 The first aspect of this embodiment provides a composite liquid metal sheet, including an upper composite layer and a lower composite layer, the edges of the upper composite layer and the lower composite layer are directly connected to form an internal cavity, and a flow layer is disposed in the cavity; The upper and lower composite layers have the same structure and raw materials (thickness ratio of 1:1, thickness of 100μm), both including a substrate layer and a transition layer and a low-temperature alloy layer sequentially disposed on the surface of the substrate layer. The raw material of the substrate layer includes copper foil, the raw material of the transition layer is indium, and the raw material of the low-temperature alloy layer includes 0.5 parts of indium, 0.3 parts of bismuth, 0.2 parts of tin, and 0.01 parts of gallium. The raw materials for the flow layer include 0.7 parts gallium, 0.2 parts indium, and 0.1 parts tin.

[0052] The thickness of both the transition layer and the low-temperature alloy layer is 20 μm, and the melting point of the low-temperature alloy layer is 55-60℃.

[0053] The surface roughness of the transition layer and the low-temperature alloy layer are 0.5 μm and 0.3 μm, respectively.

[0054] The volume of the flow layer accounts for 80% of the total volume of the cavity.

[0055] The structure of this composite liquid metal sheet is as follows: Figure 1 As shown, it includes 110-first substrate layer, 120-first transition layer; 130-first low-temperature alloy layer, 210-second substrate layer, 220-second transition layer; 230-second low-temperature alloy layer, 300-flow layer; in some embodiments, the composite liquid metal sheet has a hot water bag structure.

[0056] The actual product of this composite liquid metal sheet is shown below. Figure 2 As shown.

[0057] The second aspect of this embodiment provides a method for preparing a composite liquid metal sheet, the specific steps of which are as follows: S1: Copper foil is rolled into a metal foil sheet with a thickness of 0.05 mm; S2: The above-mentioned metal foil is used as the cathode and the indium sheet is used as the anode. The foil is placed in the electroplating solution to perform indium electrodeposition. After energizing for 2 hours, the foil is dried to form a transition layer on the opposite two sides of the metal foil. The electroplating solution includes dilute sulfuric acid, indium sulfate, dilute sulfuric acid, sodium dodecyl sulfate, alkoxyethylene hydroxyethanol and sodium hydroxide. Sodium hydroxide is used to adjust the pH. S3: Using 4N pure indium granules, bismuth granules, tin granules and gallium granules as raw materials for the low-temperature alloy layer, the raw materials weighed in proportion are placed in a vacuum medium-frequency melting furnace, vacuumed and heated to 400℃ and kept for 2 hours. The furnace is then removed and placed in a vacuum heating stirrer, and the temperature is kept at 80℃ and stirred at a speed of 400 rad / min for 30 minutes to make the liquid metal mix evenly and obtain a quaternary alloy. S4: Pour the uniformly mixed liquid metal into the mechanical pump to be heated. The mechanical pump is connected to a heating pipe, which is connected to a heated spray head. Maintain the overall temperature at 120℃. Turn on the mechanical pump to pump the liquid metal into the spray pipe for spraying. By setting the movement direction of the nozzle, spray the liquid metal onto the desired area. Adjust the servo motor to control the spraying speed to 200 mm / cm. Place the heat dissipation module to be sprayed below the nozzle, with the nozzle 30cm away from the spraying surface. Spray the liquid metal mist evenly onto the surface of the transition layer to form a low-temperature alloy layer. Cool and solidify to obtain the outer composite layer of the heat-conducting sheet. S5: Using 4N pure indium granules, tin granules, and gallium granules as raw materials, the raw materials weighed in proportion are placed in a vacuum medium-frequency melting furnace, vacuumed and heated to 300℃ and held for 2 hours. The furnace is then removed and placed in a vacuum heating stirrer. The temperature is maintained at 80℃ and stirred at a speed of 400 rad / min for 30 minutes to make the liquid metal mix evenly and obtain a ternary alloy with a melting point of 20℃, thus obtaining room temperature liquid metal. S6: Cut the outer composite layer of the two heat-conducting sheets prepared in S4 into 50×50mm rectangles, attach 1mm wide high-temperature resistant double-sided adhesive to all four sides, and then bond three of the sides together. In an inert atmosphere, inject the above-mentioned room-temperature liquid metal into the two heat-conducting sheets. The injection process is shown in the following photograph. Figure 3 As shown, the injection amount is calculated to be about 14g based on the size of the heat-conducting sheet (assuming an average injection thickness of 1mm to cover the maximum warping, the required mass can be obtained through volume and density). After sealing the fourth edge, a composite liquid metal sheet is formed.

[0058] Example 2 The difference from Example 1 is that the injection volume of room temperature liquid metal (raw material of the flow layer) is 7g, and the volume of the flow layer accounts for 65% of the total volume of the cavity.

[0059] Example 3 The difference from Example 1 is that in step S2, the electroplating time is shortened from 2 hours to 1 hour, and the thickness of the transition layer is 12 μm.

[0060] Example 4 The difference from Example 1 is that gallium is not added to the raw materials of the low-temperature alloy layer, the total mass remains unchanged, and the mass ratio of indium, bismuth and tin is 59:31:10.

[0061] The melting point of the low-temperature alloy layer is 60℃.

[0062] Example 5 The difference from Example 1 is that the raw materials for the low-temperature alloy layer are 0.6 parts indium, 0.4 parts bismuth, 0.5 parts zinc, and 0.05 parts gallium; The melting point of the low-temperature alloy layer is 70℃; The raw materials for the flow layer are 0.8 parts gallium, 0.1 parts indium, 0.1 parts tin, and 0.01 parts silver.

[0063] Example 6 The difference from Example 1 is that no transition layer is set.

[0064] Comparative Example 1 The difference from Example 1 is that no room temperature liquid metal is injected, that is, no flow layer is set, while other conditions remain the same.

[0065] Comparative Example 2 The difference from Example 1 is that no low-temperature alloy layer is provided.

[0066] Comparative Example 3 The difference from Example 1 is that the positions of the transition layer and the low-temperature alloy layer are replaced.

[0067] Comparative Example 4 The difference from Example 1 is that no transition layer and low-temperature alloy layer are provided.

[0068] Comparative Example 5 The difference from Example 1 is that indium is not included in the raw materials of the low-temperature alloy layer.

[0069] Comparative Example 6 The difference from Example 1 is that bismuth is not included in the raw materials of the low-temperature alloy layer.

[0070] Comparative Example 7 The difference from Example 1 is that tin is not included in the raw materials of the low-temperature alloy layer.

[0071] Comparative Example 8 The difference from Example 1 is that gallium is not included in the raw material of the flow layer.

[0072] Comparative Example 9 The difference from Example 1 is that indium is not included in the raw material of the flow layer.

[0073] Comparative Example 10 The difference from Example 1 is that tin is not included in the raw material of the flow layer.

[0074] Comparative Example 11 The difference from Example 1 is that the volume of the flow layer accounts for 85% of the total cavity volume.

[0075] Comparative Example 12 The difference from Example 1 is that the volume of the flow layer accounts for 45% of the total cavity volume.

[0076] The composite liquid metal sheets prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to TTV simulated thermal testing. The specific testing method was as follows: the sample was mounted on the cold plate of the TTV simulated thermal testing equipment and pressed onto the simulated chip. The pressure was controlled at 30-35 psi, and the warpage of the simulated chip was 300-500 μm. The heating power was 1500 W, and the cooling water temperature was set to 35℃. The total testing time was 2 hours, with 30 cycles of 1 hour operation followed by 1 hour intervals. The average steady-state temperature after 10 minutes was taken as the result of a single test. A test temperature of 80-95℃ was considered normal operation, while a temperature exceeding 95℃ indicated failure. Specific test results are as follows: Figure 4 As shown.

[0077] The composite liquid metal sheets prepared in the above embodiments and comparative examples were subjected to performance tests. The specific test results are shown in Table 1. The test methods for each performance are as follows: Thermal conductivity / thermal resistance: Thermal conductivity was tested according to ASTM D 5470 standard; Compression / Rebound Rate: The compression / rebound rate was tested according to ASTM D575-91 (2024).

[0078] Table 1 Performance Tests

[0079] analyze: The above tests show that the flow layer plays a key role: in Comparative Example 1 (without flow layer), the thermal conductivity decreased by 24%, the thermal resistance increased by 67%, and the compression / rebound rate decreased significantly (12% / 8%). This indicates that the flow layer fills the interfacial gaps through the fluidity of liquid metal, thereby improving the contact area and heat transfer efficiency.

[0080] Synergistic effect of low-temperature alloy layer / transition layer: Comparative Example 2 (without the low-temperature alloy layer) had the worst performance (thermal conductivity 8.9 W / m·K), indicating that the low-temperature alloy layer is the core for achieving low-melting-point interface filling.

[0081] Comparative Example 3 (layer sequence reversed) could not be formed, verifying that the transition layer needs to be in direct contact with the substrate to ensure adhesion.

[0082] The necessity of indium, bismuth, and tin in low-temperature alloy layers: Comparative Examples 5-7 (lacking indium, bismuth, and tin respectively) all had thermal conductivity below 12 W / m·K, indicating that the three components together form a eutectic alloy (melting point 50-160℃), and none of them can be omitted.

[0083] The dominant role of gallium in the flow layer: Comparative Example 8 (without gallium) also failed to form due to its fluid dynamics, as gallium's high fluidity (melting point 29.8°C) is crucial for the liquid metal to fill the warp gaps. The absence of indium and tin (Comparative Examples 10-11) also led to a performance degradation, but the impact was minor.

[0084] Structural parameter optimization: thickness ratio and roughness: Example 1 (thickness ratio 1:1, roughness 0.2-0.5 μm) performed best, indicating that symmetrical structure and moderately rough surface are beneficial to interfacial bonding and heat transfer.

[0085] Comparative Examples 11-12 show that too much or too little liquid metal filling the cavity reduces the thermal and mechanical properties of the entire composite product; too much affects the compressibility of the product, while too little affects the resilience, both of which ultimately lead to poor thermal conductivity and increased thermal resistance.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0087] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A composite liquid metal sheet, characterized in that, It includes an upper composite layer and a lower composite layer, the edges of which are directly connected to form an internal cavity, and a flow layer is disposed inside the cavity; The upper composite layer includes a first substrate layer and a first low-temperature alloy layer disposed on the surface of the first substrate layer. The lower composite layer includes a second substrate layer and a second low-temperature alloy layer disposed on the surface of the second substrate layer. The raw materials of the first substrate layer and the second substrate layer include high-melting-point metal materials with a melting point > 500°C.

2. The composite liquid metal sheet according to claim 1, characterized in that, The raw materials of the first and second low-temperature alloy layers, by mass, each independently include: 0.1-0.3 parts indium, 0.1-0.3 parts bismuth, and 0.1-0.3 parts tin; And / or, the raw materials of the flow layer, by weight, include: 0.5-0.8 parts gallium, 0.1-0.3 parts indium and 0.1-0.3 parts tin.

3. The composite liquid metal sheet according to claim 2, characterized in that, The raw materials for the first and second cryogenic alloy layers, by mass fraction, also independently include: Zinc 0.1-0.3 parts, silver 0.1-0.3 parts, gallium 0.002-0.01 parts.

4. The composite liquid metal sheet according to claim 2, characterized in that, The raw materials of the flow layer, by mass, also include: 0.1-0.3 parts bismuth, 0.01-0.1 parts zinc, 0.01-0.1 parts copper, 0.01-0.1 parts silver, 0.01-0.1 parts gold, and 0.01-0.1 parts platinum.

5. The composite liquid metal sheet according to claim 1, characterized in that, The high-melting-point metallic material includes copper and / or silver; And / or, the thickness of the first cryogenic alloy layer and the second cryogenic alloy layer are each independently 1-20 μm; And / or, the melting points of the first cryogenic alloy layer and the second cryogenic alloy layer are each independently 50-160°C; And / or, a first transition layer is further provided between the first substrate layer and the first low-temperature alloy layer, and a second transition layer is further provided between the second substrate layer and the second low-temperature alloy layer; The raw materials for the first transition layer and the second transition layer each independently include indium and / or nickel; The surface roughness of the first transition layer and the second transition layer are each independently 0.2-0.5 μm; The thickness of the first transition layer and the second transition layer are each 1-20 μm.

6. The composite liquid metal sheet according to any one of claims 1-5, characterized in that, The thickness ratio of the upper composite layer to the lower composite layer is 1-2:1; And / or, the thickness of the upper composite layer and the lower composite layer are each independently 50-200 μm; And / or, the volume of the flow layer accounts for 50-80% of the total volume of the cavity; And / or, the surface roughness of the first cryogenic alloy layer and the second cryogenic alloy layer are each independently 0.2-0.5 μm.

7. A method for preparing the composite liquid metal sheet according to any one of claims 1-6, characterized in that, include: A first low-temperature alloy layer is deposited on the surface of the first substrate layer to obtain the upper composite layer; A second low-temperature alloy layer is deposited on the surface of the second substrate layer to obtain the lower composite layer; The upper and lower composite layers are bonded together on opposite sides to form a cavity; the raw material of the flow layer is injected into the cavity and sealed to obtain a composite liquid metal sheet.

8. The method for preparing the composite liquid metal sheet according to claim 7, characterized in that, A first transition layer is further provided between the first substrate layer and the first low-temperature alloy layer; And / or, a second transition layer is further provided between the second substrate layer and the second cryogenic alloy layer; And / or, the methods for setting the first cryogenic alloy layer and the second cryogenic alloy layer each independently include at least one of vacuum sputtering, spraying, pad printing, and roller brushing; And / or, the adhesion is made using an adhesive, the adhesive including high-temperature resistant double-sided adhesive; And / or, the injection is performed under an inert atmosphere; And / or, the sealing is performed in a vacuum environment.

9. The method for preparing the composite liquid metal sheet according to claim 8, characterized in that, After the first transition layer, the second transition layer, the first low-temperature alloy layer and the second low-temperature alloy layer are prepared, each of the first transition layer, the second transition layer, the first low-temperature alloy layer and the second low-temperature alloy layer is separately subjected to plasma cleaning treatment. And / or, methods for setting the first transition layer and the second transition layer include electroplating and / or magnetron sputtering.

10. An electronic device, characterized in that, Includes the composite liquid metal sheet as described in any one of claims 1-6.

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