Ultra-thin graphene vapor chamber and preparation method thereof

Abstract

The invention discloses an ultra-thin graphene vapor chamber and a preparation method thereof. The ultra-thin graphene vapor chamber comprises a packaging body, a columnar heat conductor, heat-conducting particles and a working solution, the packaging body is a plate-shaped body with a cavity, and the plurality of columnar heat conductors are distributed in the cavity in an array manner; the columnar heat conductor comprises a plurality of graphene heat conduction layers which are arranged at intervals, and heat conduction particles are combined in gaps between the graphene heat conduction layers and on the peripheral side wall of the columnar heat conductor; and the working solution is packaged in the cavity. According to the ultra-thin graphene vapor chamber provided by the invention, the multi-layer graphene structure of the columnar heat conductor is utilized, the composite particles are arranged between the layers and around the columnar heat conductor to form a working solution adsorption structure, and two different heat transfer mechanisms of intrinsic heat transfer mechanisms of graphene and metal and phase change of a working solution can be combined through a series of structural designs; therefore, the upper limit of the existing phase change heat transfer value is improved, and the problems of large product mass and insufficient light weight are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of heat-conducting and heat-dissipating materials, and particularly relates to an ultra-thin graphene heat pipe and a preparation method thereof. Background Art

[0002] With the rapid development of the electronics industry and 5G technology, the computing power of computers and servers has been greatly improved, the heat generation of devices has increased rapidly, and the upper limit of the heat dissipation demand for electronic thermal management products has also been increasing day by day. Among them, the heat pipe is an efficient thermal management technology and is widely used in various devices and systems that require high-performance heat dissipation. As an efficient thermal management technology, the heat pipe has been widely used in many fields and has broad prospects in future development.

[0003] The mainstream ultra-thin heat pipe is usually made of copper, stainless steel or aluminum into a sealed cavity with a thickness of 0.4 mm - 1 mm. The internal cavity forms a capillary liquid absorption and diversion structure by sintering metal powder or metal mesh. Then, working liquids such as water or ethanol are injected. Its main working principle is to achieve efficient heat transfer and distribution through the evaporation and condensation processes of the working liquid.

[0004] Traditional heat pipes have the following three disadvantages: a. Large thickness. To ensure good gas-liquid phase circulation of the working liquid, the cavity thickness often needs to be ensured to be above 0.4 mm and cannot be applied to thinner scenarios; b. Large mass. The density of copper is about 8.96 g / cm3, which cannot meet the lightweight requirements of industries such as aerospace; c. Single heat transfer mechanism. The heat transfer mechanism of the ultra-thin copper heat pipe is single-phase change heat transfer. Limited by space and shape, the heat transfer value has an upper limit, and the equivalent thermal conductivity is about 300 W / (m·K) - 1000 W / (m·K). Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide an ultra-thin graphene heat pipe and a preparation method thereof.

[0006] To achieve the foregoing invention purpose, the technical solutions adopted by the present invention include: In the first aspect, the present invention provides an ultra-thin graphene heat pipe, which includes a package body, columnar heat conductors, heat-conducting particles and a working liquid; The package body is a plate-like body with a cavity, including a first surface and a second surface facing away from each other; a plurality of the columnar heat conductors are distributed in the cavity in an array, the axial direction of the columnar heat conductor is from the first surface to the second surface, and each columnar heat conductor is at least combined with the first surface; The columnar heat conductor includes multiple graphene heat conduction layers arranged at intervals, the normal direction of the graphene heat conduction layer is arranged at an angle with the axial direction of the columnar heat conductor, and the heat conduction particles are combined in the gaps between the graphene heat conduction layers and on the outer peripheral side wall of the columnar heat conductor; The working fluid is encapsulated in the cavity and can be in direct contact with the graphene heat conduction layer and the heat conduction particles.

[0007] In a second aspect, the present invention also provides a preparation method for an ultra-thin graphene heat pipe, which includes: Providing a longitudinal heat conduction sheet, the longitudinal heat conduction sheet includes alternately stacked graphene heat conduction layers and metal composite layers, the metal composite layer contains heat conduction particles and an adhesive, and the normal directions of the graphene heat conduction layer and the metal composite layer are arranged at an angle with the normal direction of the longitudinal heat conduction sheet; Covering a metal base layer on one side of the longitudinal heat conduction sheet; Performing a first cutting on the side facing away from the metal base layer to remove part of the material of the longitudinal heat conduction sheet and retain a plurality of columnar precursors; Removing the adhesive in the columnar precursors and retaining the heat conduction particles between adjacent graphene heat conduction layers to form a columnar heat conductor; Packing heat conduction particles in the spaced spaces between adjacent columnar heat conductors and sintering them into shape to form a filling layer; Performing a second cutting on the filling layer to retain part of the heat conduction particles on the outer periphery of the columnar heat conductor to form a particle layer and obtain a pre-structure; Encapsulating and filling the working fluid in the pre-structure to obtain an ultra-thin graphene heat pipe.

[0008] Based on the above technical solutions, compared with the prior art, the beneficial effects of the present invention at least include: The ultra-thin graphene heat pipe provided by the present invention utilizes the multi-layer graphene structure of the columnar heat conductor, sets composite particles between layers and around the columnar heat conductor to form a working fluid adsorption structure, and through a series of structural designs, it can combine the two different heat transfer mechanisms of the intrinsic properties of graphene and metal and the phase change of the working fluid, thereby improving the upper limit of the existing phase change heat transfer value and solving the problems of large product quality and insufficient light weight.

[0009] The above description is only an overview of the technical solutions of the present invention. In order to enable those skilled in the art to understand the technical means of the present application more clearly and implement it in accordance with the content of the specification, the following is a detailed description with reference to the preferred embodiments of the present invention and accompanying drawings. Description of the Drawings

[0010] Figure 1It is a schematic three-dimensional view of the product state after the first cutting in the preparation method provided by a typical embodiment of the present invention; Figure 2 It is a schematic front view of the product state after the first cutting in the preparation method provided by a typical embodiment of the present invention; Figure 3 It is a schematic sectional view of the product state after the first cutting in the preparation method provided by a typical embodiment of the present invention; Figure 4 It is a schematic structural state diagram of the columnar heat conductor in the preparation method provided by a typical embodiment of the present invention; Figure 5 It is a schematic interlayer state diagram of the columnar heat conductor in the preparation method provided by a typical embodiment of the present invention. Detailed implementation manners

[0011] In view of the deficiencies in the prior art, the inventors of this case have proposed the technical solution of the present invention through long-term research and a large number of practices. The following will further explain the technical solution, its implementation process, principles, etc.

[0012] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0013] Moreover, relative terms such as "first" and "second" are only used to distinguish one component or method step with the same name from another, and do not necessarily require or imply any such actual relationship or order between these components or method steps.

[0014] An embodiment of the present invention provides an ultra-thin graphene heat pipe, which includes a package body, columnar heat conductors, heat-conducting particles, and a working fluid; the package body is a plate-shaped body with a cavity, including a first surface and a second surface facing each other; a plurality of the columnar heat conductors are distributed in an array in the cavity, the axial direction of the columnar heat conductor is from the first surface to the second surface, and each columnar heat conductor is at least combined with the first surface; the columnar heat conductor includes multiple graphene heat-conducting layers arranged at intervals, the normal direction of the graphene heat-conducting layer is arranged at an angle with the axial direction of the columnar heat conductor, and the heat-conducting particles are combined in the gaps between the graphene heat-conducting layers and on the outer peripheral side walls of the columnar heat conductors; the working fluid is encapsulated in the cavity and can be in direct contact with the graphene heat-conducting layer and the heat-conducting particles.

[0015] As a typical example, in the above technical solution, the first surface and the second surface are parallel, the axial direction of the columnar heat conductor is perpendicular to both the first surface and the second surface, and the normal direction of the graphene heat conduction layer is perpendicular to this axial direction; however, the above situation is generally a relatively conventional approximation. In actual situations, due to manufacturing precision or the deformability of the material itself, the axial direction and the two surfaces may not be completely perpendicular, or the direction of the graphene heat conduction layer may not be completely orthogonal. Even in some applications, the axial direction may be actively tilted, or the normal direction of the graphene heat conduction layer may be tilted to meet certain structural and functional requirements. These equivalent transformation methods are all within the feasible scope of the present invention.

[0016] For the columnar heat conductor, in some embodiments, the ultra-thin graphene heat pipe further includes a heat conduction base layer. A plurality of the columnar heat conductors and the heat conduction base layer are integrated, and the heat conduction base layer is directly bonded to the first surface.

[0017] Or in some embodiments, the columnar heat conductor is directly bonded to the first surface.

[0018] Two forms are provided in the above specific embodiments, corresponding to the depth of a single cut in the following manufacturing method. One way is to control the depth to only cut a part of the thickness of the longitudinal heat conduction sheet, and retain the remaining thickness as the heat conduction base layer. The structure of this embodiment is more stable, but the space for the working fluid will be affected accordingly; the other way is to cut directly to the metal base layer, so that the columnar heat conductor directly contacts the first surface. In this way, the space for the working fluid can be maximized, and at the same time, the heat exchange area is also the largest.

[0019] Further, in some embodiments, the height of the columnar heat conductor is 50%-90% of the total thickness of the ultra-thin graphene heat pipe, preferably 60%-80%. As described above, the depth of the cylinder is 50%-90% of the thickness of the longitudinal heat conductor. The smaller the depth, the stronger the finished product, but at the same time, the available space for the working fluid is also reduced. In multiple practices, the depth is preferably in the range of 60%-80% as the best ratio.

[0020] In addition, regarding other dimensional characteristics, in some embodiments, the width of the gap between adjacent graphene heat conduction layers is 20-40 μm.

[0021] In some embodiments, the diameter of the columnar heat conductor is 0.5-2 mm, and the spacing between adjacent columnar heat conductors is 2-3 mm. In actual applications, the larger the spacing between the columnar heat conductors, the larger the heat exchange space for the working liquid. However, at the same time, the available volume of the interlayer diversion space in the columnar heat conductor will also be reduced, and the heat exchange surface area will also be reduced, resulting in a decrease in the heat exchange efficiency of the finished heat pipe. Therefore, the preferred cylinder spacing is 2 mm - 3 mm.

[0022] In some embodiments, part of the heat-conducting particulate matter wraps around the outer periphery of the columnar heat-conducting body to form a particulate layer, and the thickness of the particulate layer is 40-60 μm.

[0023] In some embodiments, the first surface is a first metal coating, and the second surface is a solid metal foil.

[0024] In some embodiments, the side of the encapsulation body is a second metal coating.

[0025] In addition, the present invention also proposes a more preferred technical solution. That is, in some embodiments, the edge of the graphene heat-conducting layer is further covered with a third metal coating. Preferably, the thickness of the third metal coating is 0.1-0.2 mm.

[0026] In the above preferred solution, thin copper can be electroplated on the columnar heat-conducting body. Due to the influence of current distribution and electrolyte diffusion, when electroplating the columnar heat-conducting body, the coating usually only covers the edge of the graphene heat-conducting layer and will not extend into the interlayer. Therefore, this coating actually only exists on the outer periphery of the columnar heat-conducting body. The function of this coating is, on the one hand, to provide hydrophilicity and avoid the decline in the ability of the working fluid to enter the interlayer for heat exchange and phase change due to the certain water-repellent property of the edge of the graphene heat-conducting layer. On the other hand, it can provide firm support, improve the structural firmness, avoid deformation and collapse during subsequent processes such as stuffing and sintering, maintain the multi-layer structure, and avoid loss of heat exchange area.

[0027] Generally, the thickness of this coating is generally 0.1 mm - 0.2 mm. The thinner the coating, the lower the density of the finished product. The thinner the thickness, the more the application advantages are improved, but at the same time, it will also reduce the function of copper as a sintering substrate and reduce the effective copper surface distribution rate of the subsequent copper flow guide groove, further leading to a reduction in the heat flow exchange efficiency. Therefore, in practice, the thickness of this coating is preferably 0.15 mm.

[0028] In addition, regarding the heat-conducting particulate matter, in some embodiments, the heat-conducting particulate matter is a metal particulate matter, and / or a particulate matter formed by metal-wrapped graphene, such as copper powder or copper-coated graphene powder. The density of copper powder is relatively high, which is usually not conducive to lightweighting. Using copper-coated graphene powder can not only achieve better heat-conducting performance but also take into account the lightweighting requirements. Of course, it is not limited to this. The heat-conducting particulate matter used in the present invention can also be particles formed by other forms of graphene-metal composites. Usually, the preferred metal is copper (elemental copper, alloys based on copper, etc. all belong to copper materials), which is a commonly used material for making heat pipes, but it is not limited to this. Other metals with strong heat-conducting performance should also be used as alternative choices, which also means that for the selection of metal materials, the feasible implementation scope is not limited to the copper metal specifically exemplified in the present invention.

[0029] In some embodiments, the particle size of some of the heat-conducting particulate matters between the graphene heat-conducting layers is 20-40 μm.

[0030] In some embodiments, the particle size of some of the heat-conducting particulate matters that form a particle layer on the outer periphery of the columnar heat conductor is 40-60 μm.

[0031] The second aspect of the embodiments of the present invention also provides a method for preparing an ultra-thin graphene heat pipe, which includes the following steps: Provide a longitudinal heat-conducting sheet, the longitudinal heat-conducting sheet includes alternately stacked graphene heat-conducting layers and metal composite layers, the metal composite layer contains heat-conducting particulate matters and an adhesive, and the normal directions of the graphene heat-conducting layer and the metal composite layer are arranged at an angle to the normal direction of the longitudinal heat-conducting sheet; Cover a metal base layer on one side of the longitudinal heat-conducting sheet; Perform a first cutting on the side facing away from the metal base layer to remove part of the material of the longitudinal heat-conducting sheet and retain a plurality of columnar precursors; Remove the adhesive in the columnar precursors and retain the heat-conducting particulate matters between adjacent graphene heat-conducting layers to form a columnar heat conductor; Fill the spaced space between adjacent columnar heat conductors with heat-conducting particulate matters and sinter them into shape to form a filling layer; Perform a second cutting on the filling layer to retain part of the heat-conducting particulate matters on the outer periphery of the columnar heat conductor to form a particle layer, and obtain a pre-structure; Package and fill the working fluid in the pre-structure to obtain an ultra-thin graphene heat pipe.

[0032] Regarding specific preparation conditions, in some embodiments, the mass fraction of the heat-conducting particulate matters in the metal composite layer is 50-90%, and according to density conversion, the volume ratio of the heat-conducting particulate matters to the adhesive is usually 1:2-1:1.

[0033] In some embodiments, the thickness of the longitudinal heat-conducting sheet is 0.1-0.2 mm.

[0034] In some embodiments, the metal base layer is formed by electroplating and has a thickness of 0.1-0.2 mm.

[0035] In some embodiments, the volume fraction of the metal composite layer in the longitudinal heat-conducting sheet is 30-50%.

[0036] In some embodiments, the first cutting and / or the second cutting is performed by any one of laser etching cutting, water jet cutting, electric discharge machining cutting, and numerical control precision carving cutting.

[0037] In some embodiments, the removal method of the adhesive includes ultraviolet laser vaporization.

[0038] In some embodiments, the stuffing pressure of the heat-conducting particulate matter is 0.2 - 0.8 MPa, the temperature of sintering and forming is 800 - 1100 °C, the heating rate is 800 - 1100 °C / min, and the atmosphere is a protective atmosphere.

[0039] In some embodiments, the preparation method specifically includes the following steps: Form a first metal coating as the metal base layer by electroplating; Bond a metal foil to the surface of the pre-structure facing away from the metal base layer to form a full-surface coverage; Plating the side surface of the pre-structure by electroplating to form a second metal coating; Open holes at the corners of the second metal coating, and pour the working fluid through the holes; Freeze the working fluid to make the holes contact the electroplating solution, and block the holes by electroplating; In some embodiments, the preparation method may further include the following steps: After removing the adhesive, electroplate the edge of the graphene heat-conducting layer to form a third metal coating.

[0040] Based on the above technical solutions, the present invention mainly provides a novel ultra-thin graphene heat pipe, which includes a graphene heat-conducting film, an adhesive (most of which has been sintered or cleaned and removed), copper-coated graphene particles, and a copper encapsulation body. Among them, the adhesive is used to bond the graphene heat-conducting film to make the graphene heat-conducting film uniformly and densely stacked to form a longitudinal heat conductor, which is further cut into longitudinal heat-conducting sheets. The copper-coated graphene particles are used for surface modification of the longitudinal heat conductor, and the copper encapsulation body is used to encapsulate the longitudinal heat conductor.

[0041] According to multiple embodiments of the present invention, a preparation method of a novel ultra-thin graphene heat pipe is provided. Referring to the graphene composite longitudinal heat conductor used in the prior art (for example, the Chinese invention patent with the application number 202311617399), the main change is to replace the resin layer therein with a blend mixture of copper-coated graphene particulate matter and an adhesive described below. The specific process flow includes the following steps: 1. Take copper-coated graphene particulate matter with a particle size of 30 μm and a coating thickness of 5 μm, and a hot-pressing adhesive of polyester or epoxy resin with a melting point of 100 °C. Use a planetary mixer with a main shaft rotation speed of 50 RPM and a mixing time of 30 minutes to mix the two evenly.

[0042] 2. Take a graphene oxide film with a thickness of 2 mm. Using a vacuum doctor blade coater, under the conditions of a vacuum degree of -0.08 MPa, a doctor blade speed of 2 m / min, and a coating thickness of 50 μm, uniformly coat the above-mentioned mixed slurry on the rough surface of the graphene thermal conductive film.

[0043] 3. Use an automatic composite laminator to laminate the above-mentioned graphene film to a thickness of 9 cm. Take a vacuum hot press, apply a pressure of 20 t, and conduct hot pressing treatment at 150 °C until the finished product thickness reaches 6 cm, which is the longitudinal heat conductor matrix. 4. Use a multi-wire cutting machine to perform wire cutting on the above-mentioned finished longitudinal heat conductor matrix. Cut it into thin slices with a thickness of 50 mm * 60 mm * 1 mm, which are graphene / copper-coated graphene particulate / adhesive composite longitudinal heat conducting sheets.

[0044] 5. Take 0.1 mm of the above-mentioned graphene / copper-coated graphene particulate / adhesive composite longitudinal heat conductor sheet. Adopt the electroplating method, use a copper plate as the anode, select an electrolyte with a molar content ratio of copper sulfate pentahydrate to sulfuric acid of 3:1, and a current density of 3 A / dm -2 , in an environment of 25 °C and 65 ± 20% rh, electroplate on one side for 5 ± 1 hours to obtain a copper layer with a thickness of about 0.1 mm.

[0045] 6. As shown in Figures 1 - 3 , use methods such as laser etching, water jet cutting, and wire electrical discharge machining, preferably a numerically controlled precision engraving machine, to cut the reverse side of the copper-plated surface of the longitudinal heat conductor matrix. Perpendicular to the graphene thermal conductive film, cut the longitudinal heat conductor matrix into multiple cylinders with a fixed diameter, height, and spacing.

[0046] 7. Use an ultraviolet laser cleaning machine, set the conditions: output power 100 W, pulse frequency 30 kHz, pulse width 10 ns, scanning speed 10 mm / s, and scan 5 times to laser vaporize the adhesive in the longitudinal heat conductor. Leave the copper-coated graphene particles remaining and evenly distribute them in the middle of the graphene thermal conductive film. Its overall single-column state is as shown in Figure 4 , and the microscopic morphology of the surface of the graphene thermal conductive layer is as shown in Figure 5 .

[0047] 8. Use the same or similar electroplating process as above to electroplate a thin copper layer on the surface of the cylinder. This thin layer only covers the edge of the graphene heat-conducting layer and intermittently surrounds the columnar body for one week, forming a certain degree of support and hydrophilically modifying the edge of the graphene heat-conducting layer to improve the wetting performance. After electroplating, take the copper-coated graphene powder with a nominal diameter of 20 microns, use a circular vibrating screen, screen at a mesh size of 300 - 500 meshes, a vibration frequency of 30 Hz, and an amplitude of 5 mm for half an hour to screen the particle size of the copper-coated graphene particles, and obtain the preferred powder with a particle size basically at 20 microns. Use a compression filling machine, set the compression pressure to 0.5 MPa, and uniformly and densely fill the cavity formed by the above first cutting with the copper graphene powder after removing impurities. Use a high-frequency induction sintering furnace, introduce an inert gas atmosphere, with a working temperature of 1000 °C, a heating rate of 1000 °C / min, and a power frequency of 100 kHz, to instantaneously high-temperature sinter the copper-coated graphene particles to form a copper conduction and phase change structure.

[0048] 9. Use the ultrasonic cleaning method to place the longitudinal heat-conducting body substrate after sintering the copper powder in ethanol or deionized water to clean the combustion products generated by the adhesive at the sintering temperature until there is no black residue visible to the naked eye.

[0049] 10. Use precise cutting methods such as laser etching to perform secondary cutting on the longitudinal heat-conducting body substrate after sintering the copper powder. The cut cylinder retained is basically concentric with the columnar body shown above and has a slightly larger diameter. In this way, a particle layer sintered with copper-coated graphene particles is formed on the surface of the heat-conducting columnar body formed after the first cutting and cleaning the adhesive.

[0050] 11. Take a dense copper foil with an area of 50 mm * 60 mm and a thickness of 0.1 mm as the encapsulation cover plate. Use an adhesive to encapsulate the copper foil on the upper surface layer of the above heat pipe (the side that has not undergone the first electroplating).

[0051] 12. Use the same electroplating method to electroplate the remaining surfaces with copper. Use mechanical grinding to remove 1 mm * 1 mm * 0.1 mm of the coating to form a liquid injection port, and inject ethanol or deionized water with an inner cavity volume fraction of 5 Vol% - 20 Vol% as the working liquid along the liquid injection port. Then place the liquid injection port upward and place the specimen in a low-temperature vacuum precision environmental test chamber with an environmental temperature of -40 °C and a vacuum degree of 100 Pa for 2 - 3 hours to freeze and crystallize the working liquid. Place the liquid injection port downward. After ensuring that the working liquid does not flow out, under the same electroplating conditions as above, take a vertical limiter with an adjustable accuracy of micron level, immerse the plane of the liquid injection port 0.1 mm into the electroplating solution, and extend the electroplating time to 48 hours to form a dense copper layer with a thickness of 0.1 mm to complete the encapsulation of the liquid injection port, which is the integrated ultra-thin heat pipe of the graphene longitudinal heat conductor.

[0052] In the above specific preparation case, the mass fraction ratio of the mixed slurry is copper-coated graphene powder: epoxy resin = 4:1; among them, the blend is composed of an adhesive and copper-coated graphene powder, and due to the different densities of the two, the volume fraction ratio is usually 1:2 - 1:1 (powder: adhesive), and the volume ratio accounts for 30Vol% - 50Vol% of the longitudinal heat conductor. To ensure the uniform distribution of copper graphene powder between the graphene heat-conducting films to achieve a good subsequent flow guiding effect, it is preferably 40Vol% - 50Vol%.

[0053] The graphene oxide film is a DMC aqueous multi-layer graphene oxide film, but of course it is not limited to this; the hot pressing treatment time is based on reaching the sheet thickness, about 60 min; the parameters of the multi-wire cutting machine are set as the tangent spacing of 1 mm, the cutting speed of 5 mm / s, and the cutting round-trip times of 3 times. The specific cutting spacing should be determined according to the designed thickness of the heat sink, and the cutting condition parameters can be adjusted by oneself to be appropriate for a smooth and flat cut surface; the adhesive is selected from at least one of epoxy resin, acrylic resin, and silicone rubber. Among them, the epoxy resin is preferably one or more of bisphenol A epoxy resin, phenolic glycidyl ether epoxy resin, and aliphatic polyol glycidyl ether epoxy resin; the acrylic resin is an aqueous emulsion acrylic resin; the silicone rubber is one or more of polydimethylsiloxane, polyphenylsiloxane, and polymethylvinylsiloxane. Of course, the specific selection of the adhesive is not limited to this, and any material that can play a multi-layer bonding role and can be removed by sintering or laser cleaning can be used.

[0054] The thickness of the single-sided electroplated copper layer is 0.1 mm - 0.2 mm. The thinner the coating, the lower the density of the finished product, and the thinner the thickness, the more the application advantages are improved. But at the same time, it will also reduce the function of copper as a packaging material and increase the probability of damage to the heat sink during use. The specific thickness is preferably 0.15 mm.

[0055] The fixed diameter of the column formed by one-time cutting is 0.5 mm - 2 mm. The larger the cylinder diameter, the better the flow guiding effect. But at the same time, the space occupancy rate will also increase, which will instead lead to a reduction in the heat exchange efficiency of the finished heat sink. Therefore, through experiments, it can be determined that the usually preferred diameter is 1 mm - 1.5 mm.

[0056] And the depth of the cylinder is 50% - 90% of the thickness of the longitudinal heat conductor. The smaller the depth, the stronger the finished product, but at the same time, the available space for the working fluid is also reduced. Therefore, through experiments, the depth is preferably 60% - 80%; The larger the cylinder spacing, the larger the heat exchange space of the working liquid. But at the same time, the number of columns and the available volume of the particulate flow guiding groove will also decrease, resulting in a reduction in the heat exchange efficiency of the finished heat sink. Therefore, the cylinder spacing is preferably 2 mm - 3 mm.

[0057] The thickness of the electroplated thin copper on the cylinder is 20μm - 60μm. The thinner the coating, the lower the density of the finished product. The thinner the thickness, the more prominent the application advantages. However, it will also reduce the function of copper as a sintering substrate, decrease the effective copper surface distribution rate of the subsequent copper flow guide groove, and in addition, it will lead to insufficient hydrophilicity, further reducing the heat flow exchange efficiency. Through experiments, the preferred coating thickness of the columnar body is 40μm.

[0058] For the secondary cutting, the same center of the circle as the first cutting is selected, and the cutting diameter is 1mm - 2mm, preferably 1.25mm - 1.75mm. The depth is basically the same as that of the first cutting, which is 50% - 90% of the thickness of the longitudinal heat conductor, preferably 60% - 80%. The purpose of this step is to sinter and retain a thin copper hydrophilic structure with a uniform thickness on the surface of the cylinder as the flow guide support column in the heat pipe structure. However, since the product prepared by the present invention is an ultra-thin heat pipe, the copper powder used has a small particle size, and the general filling and sintering process cannot ensure that the copper powder is laid on the surface of the cylinder with the required thickness, and the actual thickness may be greater than the target thickness. Therefore, the above sintering-secondary cutting steps are adopted to ensure that the thickness of the thin copper structure is uniform and controllable. Among them, the difference in radius between the two cuts is the thickness of the required thin copper structure.

[0059] The particle size of the copper-coated graphene powder used is 10μm - 50μm, preferably 20μm. The number of coated layers is 1 layer - 3 layers, preferably 2 layers.

[0060] Finally, the preferred adhesive for encapsulation is a sealing and waterproof adhesive such as epoxy resin and silicone glue. Of course, it is not limited to this, and any material with bonding or welding properties that can bond the copper foil to the columnar body can theoretically be used.

[0061] Based on the above technical solutions, the present invention utilizes the high thermal conductivity and low density characteristics of the graphene thermal conductive film, combined with the phase change heat conduction mechanism of the traditional heat pipe, and proposes a new design and preparation method for the ultra-thin graphene heat pipe structure. The present invention not only improves the upper limit of the heat conduction of the heat pipe, but also reduces the mass and volume of the finished heat pipe.

[0062] The following further details the technical solutions of the present invention through several embodiments in conjunction with the drawings. However, the selected embodiments are only used to illustrate the present invention and do not limit the scope of the present invention. In addition, for some condition parameters not clearly defined in the following embodiments, which do not involve relatively core process steps, reference can be made to the above technical solution overview or many existing technologies. For example, for the electroplating conditions, as long as a qualified coating with the corresponding thickness can be obtained, these process conditions do not have to be limited to the specific formulations and parameters of the specific examples of the present invention.

[0063] Example 1 This example illustrates the preparation process of an ultra-thin graphene heat pipe, which is specifically as follows: 1. The graphene / copper-coated graphene particulate / adhesive composite longitudinal heat conductor sheet with a thickness of 0.11 mm is obtained by the method described above. Using the electroplating method, a copper plate is used as the anode, and an electrolyte with a molar ratio of copper sulfate pentahydrate to sulfuric acid of 3:1 is selected. The current density is 3 A / dm -2 , and in an environment of 25°C and 65 ± 20% rh, electroplate on one side for 5 hours to obtain a copper layer with a thickness of about 0.1 mm.

[0064] 2. Use a numerically controlled precision engraving machine to cut the reverse side of the copper-plated surface of the longitudinal heat conductor substrate. Perpendicular to the graphene heat conduction film, cut the longitudinal heat conductor substrate into a plurality of cylinders with a diameter of 1 mm, a depth of 0.09 mm, and a spacing of 0.2 mm.

[0065] 3. Use an ultraviolet laser cleaning machine, set the conditions: output power 100 W, pulse frequency 30 kHz, pulse width 10 ns, scanning speed 10 mm / s, and scan 5 times to laser vaporize the adhesive in the longitudinal heat conductor. Leave the copper-coated graphene particles remaining and evenly distribute them in the middle of the graphene heat conduction film.

[0066] 4. Use the electroplating process to electroplate a thin copper layer with a thickness of 0.01 mm on the surface of the cylinder. After electroplating, take 50-micron copper-coated graphene powder that has passed through particle size screening, and use a compression filling machine with a compression pressure set to 0.5 MPa to evenly and densely fill the cavity formed by the first cutting with the copper-coated graphene powder. Use a high-frequency induction sintering furnace, introduce an inert gas atmosphere of Ar, with a working temperature of 1000°C, a heating rate of 1000°C / min, and a power frequency of 100 kHz to perform instantaneous high-temperature sintering on the copper-coated graphene particulate matter to form a copper conduction and phase change structure.

[0067] 5. Use the ultrasonic cleaning method to place the longitudinal heat conductor substrate after sintering the copper powder in ethanol or deionized water to clean the combustion products generated by the adhesive at the sintering temperature until there is no black residue visible to the naked eye.

[0068] 6. Use precise cutting methods such as laser etching to perform secondary cutting on the longitudinal heat conductor substrate after sintering the copper powder. The diameter of the retained cylinder after cutting is 1 mm, forming a particle layer of sintered copper-coated graphene particulate matter.

[0069] 7. Take a dense copper foil with an area of 50 mm * 60 mm and a thickness of 0.1 mm as the encapsulation cover plate. Use an adhesive to encapsulate the copper foil on the upper surface of the above-mentioned heat pipe.

[0070] 8. Using the same electroplating method, electroplate the remaining surfaces with copper. Use mechanical grinding to remove 1 mm * 1 mm * 0.1 mm of the coating to form a liquid injection port. Inject deionized water with a volume fraction of 20 Vol% into the inner cavity as the working liquid. Then place the liquid injection port upwards and place the specimen in a low-temperature vacuum precision environmental test chamber at an environmental temperature of -40 °C and a vacuum degree of 100 Pa for 2 - 3 hours to freeze and crystallize the working liquid. Place the liquid injection port downwards. After ensuring that the working liquid will not flow out, under the same electroplating conditions as above, take a vertical limiter with an adjustable precision of micron level and immerse the plane of the liquid injection port 0.1 mm into the electroplating solution. Extend the electroplating time to 48 hours to form a dense copper layer with a thickness of 0.1 mm, completing the encapsulation of the liquid injection port, which is the integrated ultra-thin vapor chamber of graphene longitudinal heat conductor.

[0071] Example 2 The preparation process of the ultra-thin graphene vapor chamber in Example 1 of this example is as follows: 1. Use the method above to obtain a 0.1 mm thick graphene / copper-coated graphene particulate / adhesive composite longitudinal heat conductor sheet. Use the electroplating method, use a copper plate as the anode, select a mol content ratio of 3:1 of copper sulfate pentahydrate to sulfuric acid as the electrolyte, and the current density is 3 A / dm -2 , in an environment of 25 °C and 65 ± 20% rh, electroplate on one side for 5 hours to obtain a copper layer with a thickness of about 0.1 mm.

[0072] 2. Use a numerical control engraving machine to cut the reverse side of the copper-plated surface of the longitudinal heat conductor matrix. Perpendicular to the graphene heat conduction film, cut the longitudinal heat conductor matrix into a plurality of cylinders with a diameter of 1.5 mm, a depth of 0.05 mm, and a spacing of 0.25 mm.

[0073] 3. Use an ultraviolet laser cleaning machine to vaporize the adhesive in the longitudinal heat conductor by laser. Leave the copper-coated graphene particles remaining and evenly distribute them in the middle of the graphene heat conduction film.

[0074] 4. Use the electroplating process to electroplate a thin copper layer with a thickness of 0.02 mm on the surface of the cylinder. After electroplating, take 60-micron copper-coated graphene powder after particle size screening, and use a compression filling machine to evenly and densely fill the copper-coated graphene powder into the cavity formed by the first cutting. Use a high-frequency induction sintering furnace to pass an inert gas atmosphere to perform instantaneous high-temperature sintering on the copper-coated graphene particulate matter to form a copper conduction and phase change structure.

[0075] 5. Use the ultrasonic cleaning method to place the longitudinal heat conductor matrix after sintering copper powder in ethanol or deionized water to clean the combustion products generated by the adhesive at the sintering temperature until there is no black residue visible to the naked eye.

[0076] 6. Using precise cutting methods such as laser etching, the longitudinal heat conductor substrate after sintering copper powder is cut for the second time, and the retained cylinder has a diameter of 1.5 mm, forming a particle layer sintered with copper-coated graphene particles.

[0077] 7. Take a dense copper foil with an area of 50 mm * 60 mm and a thickness of 0.1 mm as the encapsulation cover plate. Use an adhesive to encapsulate the copper foil on the upper surface of the above heat pipe.

[0078] 8. Using the same electroplating method, the remaining surfaces are electroplated with copper. Use mechanical grinding to remove 1 mm * 1 mm * 0.1 mm of the coating to form a liquid injection port, and inject ethanol with an inner cavity volume fraction of 5 Vol% along the liquid injection port as the working liquid. Then place the liquid injection port upward to freeze and crystallize the working liquid. After placing the liquid injection port downward and ensuring that the working liquid does not flow out, under the same electroplating conditions as above, take a vertical limiter with an adjustable accuracy of micron level, immerse the liquid injection port plane 0.1 mm into the electroplating solution, and electroplate to form a dense copper layer with a thickness of 0.1 mm to complete the encapsulation of the liquid injection port, which is the integrated ultra-thin heat pipe of graphene longitudinal heat conductor.

[0079] In this embodiment, by changing some structural parameters, it is still possible to obtain a graphene heat pipe with high-performance thermal conductivity, thinness, and light weight.

[0080] Example 3 This example illustrates the preparation process of an ultra-thin graphene heat pipe, which is specifically as follows: 1. Using the above method, a 0.2-mm-thick graphene / copper-coated graphene particle / adhesive composite longitudinal heat conductor thin sheet is obtained. Using the electroplating method, a copper plate is used as the anode, and an electrolyte with a molar content ratio of 3:1 of copper sulfate pentahydrate to sulfuric acid is selected, and the current density is 3 A / dm -2 , and it is electroplated on one side for 5 hours at 25 °C and 65 ± 20% rh to obtain a copper layer with a thickness of about 0.2 mm.

[0081] 2. Use a numerical control engraving machine to cut the reverse side of the copper-plated surface of the longitudinal heat conductor substrate. Perpendicular to the graphene heat conduction film, the longitudinal heat conductor substrate is cut into a plurality of cylinders with a diameter of 1 mm, a depth of 0.09 mm, and a spacing of 0.2 mm.

[0082] 3. Use an ultraviolet laser cleaning machine to vaporize the adhesive in the longitudinal heat conductor by laser. Leave the copper-coated graphene particles remaining and evenly distribute them in the middle of the graphene heat conduction film.

[0083] 4. Use the electroplating process to electroplate a thin copper layer on the surface of the cylinder with a thickness of 0.01 mm. After electroplating, take the copper-coated graphene powder with a particle size of 60 microns that has passed through particle size screening, and use a compression filling machine to uniformly and densely fill the copper-coated graphene powder into the cavity formed by the first cutting. Use a high-frequency induction sintering furnace to introduce an inert gas atmosphere to instantaneously sinter the copper-coated graphene particles at high temperature to form a copper conduction and phase change structure.

[0084] 5. Use the ultrasonic cleaning method to place the longitudinal heat-conducting body substrate after sintering the copper powder in ethanol or deionized water to clean the combustion products generated by the adhesive at the sintering temperature until there is no black residue visible to the naked eye.

[0085] 6. Use precise cutting methods such as laser etching to perform secondary cutting on the longitudinal heat-conducting body substrate after sintering the copper powder. The retained cylinder after cutting has a diameter of 1 mm, forming a particle layer of sintered copper-coated graphene particles.

[0086] 7. Take a dense copper foil with an area of 50 mm * 60 mm and a thickness of 0.1 mm as the encapsulation cover plate. Use an adhesive to encapsulate the copper foil on the upper surface of the above-mentioned heat pipe.

[0087] 8. Use the same electroplating method to electroplate the remaining surfaces with copper. Use the mechanical grinding method to remove 1 mm * 1 mm * 0.1 mm of the coating to form a liquid injection port, and inject ethanol with a volume fraction of 5 Vol% in the inner cavity as the working liquid along the liquid injection port. Then place the liquid injection port upward to freeze and crystallize the working liquid. Place it with the liquid injection port downward. After ensuring that the working liquid will not flow out, under the same electroplating conditions as above, take a vertical limiter with an adjustable precision of micron level, immerse the plane of the liquid injection port 0.1 mm into the electroplating solution, and electroplate to form a dense copper layer with a thickness of 0.1 mm to complete the encapsulation of the liquid injection port, which is the integrated ultra-thin heat pipe of graphene longitudinal heat conductor.

[0088] Example 4 This example demonstrates the preparation process of an ultra-thin graphene heat pipe, which is specifically as follows: 1. Use the method described above to obtain a graphene / copper-coated graphene particle / adhesive composite longitudinal heat-conducting body thin sheet with a thickness of 0.11 mm. Use the electroplating method, use a copper plate as the anode, select an electrolyte with a molar content ratio of copper sulfate pentahydrate to sulfuric acid of 3:1, and the current density is 3 A / dm -2 , in an environment of 25 °C and 65 ± 20% rh, electroplate on one side for 5 hours to obtain a copper layer with a thickness of about 0.1 mm.

[0089] 2. Use a numerical control precision engraving machine to cut the reverse side of the copper-plated surface of the longitudinal heat-conducting body substrate. Perpendicular to the graphene heat-conducting film, cut the longitudinal heat-conducting body substrate into multiple cylinders with a diameter of 0.5 mm, a depth of 0.09 mm, and a spacing of 0.2 mm.

[0090] 3. Use an ultraviolet laser cleaning machine to laser vaporize the adhesive in the longitudinal heat conductor, leaving the copper-coated graphene particles remaining and evenly distributed in the middle of the graphene heat-conducting film.

[0091] 4. Use the electroplating process to electroplate a thin copper layer on the surface of the cylinder with a thickness of 0.01 mm. After electroplating, take 60-micron copper-coated graphene powder that has been screened by particle size, and use a compression filling machine to evenly and densely fill the cavity formed by the first cutting with the copper-coated graphene powder. Use a high-frequency induction sintering furnace to instantaneously sinter the copper-coated graphene particles in an inert gas atmosphere to form a copper conduction and phase change structure.

[0092] 5. Use the ultrasonic cleaning method to place the longitudinal heat conductor matrix after sintering the copper powder in ethanol or deionized water to clean the combustion products generated by the adhesive at the sintering temperature until there is no black residue visible to the naked eye.

[0093] 6. Use precision cutting methods such as laser etching to perform secondary cutting on the longitudinal heat conductor matrix after sintering the copper powder. The retained cylinder after cutting has a diameter of 0.5 mm, forming a particle layer of sintered copper-coated graphene particles.

[0094] 7. Take a dense copper foil with an area of 50 mm * 60 mm and a thickness of 0.1 mm as the encapsulation cover plate. Use an adhesive to encapsulate the copper foil on the upper surface layer of the above-mentioned heat pipe.

[0095] 8. Use the same electroplating method to electroplate the remaining surfaces with copper. Use the mechanical grinding method to remove 1 mm * 1 mm * 0.1 mm of the coating to form a liquid injection port, and inject ethanol with an inner cavity volume fraction of 5 Vol% along the liquid injection port as the working liquid. Then place the liquid injection port upward to freeze and crystallize the working liquid. Place it with the liquid injection port downward, and after ensuring that the working liquid does not flow out, under the same electroplating conditions as above, take a vertical limiter with an adjustable precision of the micron level and immerse the plane of the liquid injection port 0.1 mm into the electroplating solution to electroplate a dense copper layer with a thickness of 0.1 mm to complete the encapsulation of the liquid injection port, which is the integrated ultra-thin heat pipe of graphene longitudinal heat conductor.

[0096] Example 5 This example demonstrates the preparation process of an ultra-thin graphene heat pipe, which is specifically as follows: 1. Use the method above to obtain a graphene / copper-coated graphene particle / adhesive composite longitudinal heat conductor thin sheet with a thickness of 0.11 mm. Use the electroplating method, use a copper plate as the anode, select an electrolyte with a molar ratio of copper sulfate pentahydrate to sulfuric acid of 3:1, and a current density of 3 A / dm -2 , in an environment of 25 °C and 65 ± 20% rh, electroplate on one side for 5 hours to obtain a copper layer with a thickness of approximately 0.1 mm.

[0097] 2. Use a numerically controlled engraving machine to cut the reverse side of the copper-plated surface of the longitudinal heat conductor substrate. Perpendicular to the graphene heat-conducting film, cut the longitudinal heat conductor substrate into a plurality of cylinders with a diameter of 2 mm, a depth of 0.09 mm, and a spacing of 0.2 mm.

[0098] 3. Use an ultraviolet laser cleaning machine to vaporize the adhesive in the longitudinal heat conductor by laser. Leave the copper-coated graphene particles remaining and evenly distribute them in the middle of the graphene heat-conducting film.

[0099] 4. Use the electroplating process to electroplate a thin copper layer with a thickness of 0.01 mm on the surface of the cylinder. After electroplating, take 60-micron copper-coated graphene powder that has been screened by particle size, and use a compression filling machine to evenly and densely fill the cavity formed by the first cutting with the copper-coated graphene powder. Use a high-frequency induction sintering furnace to introduce an inert gas atmosphere to instantaneously sinter the copper-coated graphene particles at high temperature to form a copper flow-guiding and phase-change structure.

[0100] 5. Use the ultrasonic cleaning method to place the longitudinal heat conductor substrate after sintering the copper powder in ethanol or deionized water to clean the combustion products generated by the adhesive at the sintering temperature until there is no black residue visible to the naked eye.

[0101] 6. Use precise cutting methods such as laser etching to perform secondary cutting on the longitudinal heat conductor substrate after sintering the copper powder. The cylinders retained after cutting have a diameter of 2 mm, forming a particle layer of sintered copper-coated graphene particles.

[0102] 7. Take a dense copper foil with an area of 50 mm * 60 mm and a thickness of 0.1 mm as the encapsulation cover plate. Use an adhesive to encapsulate the copper foil on the upper surface layer of the above heat pipe.

[0103] 8. Use the same electroplating method to electroplate the remaining surfaces with copper. Use the mechanical grinding method to remove 1 mm * 1 mm * 0.1 mm of the coating to form a liquid injection port, and inject ethanol with a volume fraction of 5 Vol% in the inner cavity as the working liquid along the liquid injection port. Then place the liquid injection port upward to freeze and crystallize the working liquid. Place it with the liquid injection port downward. After determining that the working liquid will not flow out, under the same electroplating conditions as above, take a vertically limiting device with an adjustable precision of the micron level, immerse the plane of the liquid injection port 0.1 mm into the electroplating solution, and electroplate to form a dense copper layer with a thickness of 0.1 mm to complete the encapsulation of the liquid injection port, which is the integrated ultra-thin heat pipe of the graphene longitudinal heat conductor.

[0104] Example 6 This example demonstrates the preparation process of an ultra-thin graphene heat pipe, which is specifically as follows: 1. A graphene / copper-coated graphene particulate / adhesive composite longitudinal heat conductor sheet with a thickness of 0.11 mm is obtained by the method described above. Using the electroplating method, a copper plate is used as the anode, and an electrolyte with a molar ratio of copper sulfate pentahydrate to sulfuric acid of 3:1 is selected. The current density is 3 A / dm -2 , and in an environment of 25°C and 65 ± 20% rh, a copper layer with a thickness of about 0.1 mm is obtained by single-sided electroplating for 5 hours.

[0105] 2. Use a numerically controlled precision engraving machine to cut the reverse side of the copper-plated surface of the longitudinal heat conductor substrate. Perpendicular to the graphene heat-conducting film, the longitudinal heat conductor substrate is cut into a plurality of cylinders with a diameter of 1 mm, a depth of 0.06 mm, and a spacing of 0.2 mm.

[0106] 3. Use an ultraviolet laser cleaning machine to laser vaporize the adhesive in the longitudinal heat conductor. Leave the copper-coated graphene particles remaining and evenly distribute them in the middle of the graphene heat-conducting film.

[0107] 4. Use the electroplating process to electroplate a thin copper layer with a thickness of 0.01 mm on the surface of the cylinder. After electroplating, take 60-micron copper-coated graphene powder that has passed through particle size screening, and use a compression filling machine to evenly and densely fill the cavity formed by the first cutting with the copper-coated graphene powder. Use a high-frequency induction sintering furnace to pass an inert gas atmosphere to perform instantaneous high-temperature sintering on the copper-coated graphene particulate matter to form a copper conduction and phase change structure.

[0108] 5. Use the ultrasonic cleaning method to place the longitudinal heat conductor substrate after sintering the copper powder in ethanol or deionized water to clean the combustion products generated by the adhesive at the sintering temperature until there is no black residue visible to the naked eye.

[0109] 6. Use a precise cutting method such as laser etching to perform secondary cutting on the longitudinal heat conductor substrate after sintering the copper powder. The cut and retained cylinders have a diameter of 1 mm, forming a particle layer of sintered copper-coated graphene particulate matter.

[0110] 7. Take a dense copper foil with an area of 50 mm * 60 mm and a thickness of 0.1 mm as the encapsulation cover plate. Use an adhesive to encapsulate the copper foil on the upper surface of the above heat pipe.

[0111] 8. Using the same electroplating method, electroplate the remaining surfaces with copper. Use mechanical grinding to remove 1 mm × 1 mm × 0.1 mm of the coating to form a liquid injection port, and inject ethanol with a volume fraction of 5 Vol% into the inner cavity as the working liquid. Then place the liquid injection port upward and freeze the working liquid into crystals. Place it with the liquid injection port downward. After ensuring that the working liquid does not flow out, under the same electroplating conditions as above, take a vertical limiter with an adjustable accuracy of micron level, immerse the plane of the liquid injection port 0.1 mm into the electroplating solution, and electroplate a dense copper layer with a thickness of 0.1 mm to complete the encapsulation of the liquid injection port, which is the integrated ultra-thin heat pipe of graphene longitudinal heat conductor.

[0112] Comparative Example 1 This comparative example is generally the same as Example 1, and the main difference is that: The process of electroplating a thin copper layer on the surface of the cylinder in Step 4 is omitted, and no thin copper coating is formed on the outer periphery of the cylinder.

[0113] Comparative Example 2 This comparative example is generally the same as Example 1, and the main difference is that: in Step 1, a composite longitudinal heat conductor thin sheet with a thickness of 0.11 mm prepared with the publication number CN117507504A is used.

[0114] Test the ultra-thin heat pipes obtained in the above examples and comparative examples. The test items include: a) Thermal conductivity: Measure the thermal conductivity of the material using the industry-conventional laser flash method. Considering the high thermal conductivity of the material and the anisotropy of graphene, use a Netzsch 467 laser thermal conductivity meter and a 2 mm × 2 mm mold to measure the thermal conductivity in the thickness direction of the sample; b) Density: Determine the density using the method specified in GB / T 4472-2011.

[0115] The specific test results are shown in the following table: Table 1 Test Results of Sample Properties of Examples and Comparative Examples

[0116] In the above example, the present invention proposes a novel ultra-thin graphene heat pipe and its preparation method. The density of the graphene heat conduction film is about 2.10 g / cm 3 , and the density of the adhesive used in the present invention is about 0.9 - 1.3 g / cm 3 . Using the longitudinal heat conductor composed of graphene heat conduction film and adhesive as the matrix can effectively solve the problem of high product quality; the thermal conductivity of the commercial graphene heat conduction film is about 1200 W / (m·K) - 1500 W / (m·K). Through a series of structural designs in the present invention and then injecting the working liquid, the two different heat transfer mechanisms of intrinsic and phase change can be combined, thereby raising the upper limit of the existing phase change heat transfer value and solving the problem of large product quality.

[0117] It should be understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and should not be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. An ultra-thin graphene heat pipe, characterized in that, It includes a package body, columnar heat conductors, heat-conducting particulate matters, and a working fluid; The package body is a plate-shaped body with a cavity, including a first surface and a second surface facing away from each other; a plurality of the columnar heat conductors are distributed in the cavity in an array, the axial direction of the columnar heat conductor is from the first surface to the second surface, and each columnar heat conductor is at least combined with the first surface; The columnar heat conductor includes multiple graphene heat-conducting layers arranged at intervals, the normal direction of the graphene heat-conducting layer is arranged at an angle with the axial direction of the columnar heat conductor, and the heat-conducting particulate matters are combined in the gaps between the graphene heat-conducting layers and on the outer peripheral side walls of the columnar heat conductors; The working fluid is encapsulated in the cavity and can be in direct contact with the graphene heat-conducting layer and the heat-conducting particulate matters.

2. The ultra-thin graphene heat spreader according to claim 1, wherein, It further includes a heat-conducting base layer, and a plurality of the columnar heat conductors are integrated with the heat-conducting base layer, and the heat-conducting base layer is directly combined with the first surface; Or, the columnar heat conductor is directly combined with the first surface.

3. The ultra-thin graphene heat spreader according to claim 1 or 2, characterized in that, The height of the columnar heat conductor is 50-90% of the total thickness of the ultra-thin graphene heat pipe, preferably 60-80%; And / or, the width of the gap between adjacent graphene heat-conducting layers is 20-40 μm; And / or, the diameter of the columnar heat conductor is 0.5-2 mm, and the spacing distance between adjacent columnar heat conductors is 2-3 mm; And / or, part of the heat-conducting particulate matters wrap the outer periphery of the columnar heat conductor to form a particle layer, and the thickness of the particle layer is 40-60 μm.

4. The ultra-thin graphene vapor chamber according to claim 1, wherein The first surface is a first metal coating, and the second surface is a solid metal foil; And / or, the side of the package body is a second metal coating.

5. The ultra-thin graphene heat spreader according to claim 1, characterized in that, The edge of the graphene heat-conducting layer is further covered with a third metal coating. Preferably, the thickness of the third metal coating is 0.1-0.2 mm.

6. The ultra-thin graphene heat spreader according to claim 1, wherein, The heat-conducting particulate matters are metal particulate matters and / or particulate matters formed by metal-wrapped graphene; And / or, the particle size of part of the heat-conducting particulate matters between the graphene heat-conducting layers is 20-40 μm; And / or, the particle size of part of the heat-conducting particulate matters that wrap the outer periphery of the columnar heat conductor to form a particle layer is 40-60 μm.

7. A preparation method of an ultra-thin graphene heat pipe, characterized in that, It includes: Providing a longitudinal heat-conducting sheet, the longitudinal heat-conducting sheet includes alternately stacked graphene heat-conducting layers and metal composite layers, the metal composite layer contains heat-conducting particulate matters and an adhesive, and the normal directions of the graphene heat-conducting layer and the metal composite layer are arranged at an angle with the normal direction of the longitudinal heat-conducting sheet; Covering a metal base layer on one surface of the longitudinal heat-conducting sheet; Performing a first cutting on the surface facing away from the metal base layer to remove part of the material of the longitudinal heat-conducting sheet and retain a plurality of columnar precursors; Removing the adhesive in the columnar precursors and retaining the heat-conducting particulate matters between adjacent graphene heat-conducting layers to form columnar heat conductors; Filling the heat-conducting particulate matters in the interval space between adjacent columnar heat conductors and sintering and forming to form a filling layer; Performing a second cutting on the filling layer to retain part of the heat-conducting particulate matters on the outer periphery of the columnar heat conductor to form a particle layer, and obtaining a pre-structure; Encapsulate the pre - structure and fill it with working fluid to obtain an ultra - thin graphene heat pipe.

8. The preparation method according to claim 7, wherein The mass fraction of the heat - conducting particulate matter in the metal composite layer is 50 - 90%; and / or, the thickness of the longitudinal heat - conducting sheet is 0.1 - 0.2 mm; and / or, the metal base layer is formed by electroplating, and the thickness is 0.1 - 0.2 mm; and / or, the volume fraction of the metal composite layer in the longitudinal heat - conducting sheet is 30 - 50%.

9. The preparation method according to claim 7, characterized in that, The first cutting and / or the second cutting is carried out by any one of laser etching cutting, water jet cutting, electrical discharge cutting, and numerical control precision carving cutting; and / or, the removal method of the adhesive includes ultraviolet laser gasification; and / or, the stuffing pressure of the heat - conducting particulate matter is 0.2 - 0.8 MPa, the temperature of sintering and forming is 800 - 1100 °C, the heating rate is 800 - 1100 °C / min, and the atmosphere is a protective atmosphere.

10. The preparation method according to claim 7, wherein, Specifically, it includes: Form the first metal coating as the metal base layer by electroplating; Bond a metal foil on the surface of the pre - structure facing away from the metal base layer to form a whole - surface coverage; Plating the side surface of the pre - structure by electroplating to form a second metal coating; Open holes at the corners of the second metal coating, and pour the working fluid through the holes; Freeze the working fluid to make the holes contact with the electroplating solution, and seal the holes by electroplating; and / or, it further includes: After removing the adhesive, electroplate the edge of the graphene heat - conducting layer to form a third metal coating.

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