Composite vapor chamber with vertical gradient capillary channels and preparation process and application thereof

Abstract

The invention relates to a composite vapor chamber with vertical gradient capillary channels as well as a preparation method and application of the composite vapor chamber. The composite vapor chamber comprises an upper shell, a lower shell, a liquid absorption core and a heat transfer working medium, the upper shell and the lower shell are both composite boards formed by combining outer side base layers and inner side copper layers, the lower shell is provided with supporting columns protruding towards the inner side, and the supporting columns are located in the cavity and connected with the upper shell; the wick comprises a first wick, a second wick and a third wick, and the first wick is located at one end of the upper shell and combined with the copper layer of the upper shell; the second wick is positioned at one end of the lower shell and is combined with the copper layer of the lower shell; the third wick is an annular sleeve and sleeves the periphery of the supporting column, one end of the third wick is connected with the first wick, the other end of the third wick is connected with the second wick, and a heat transfer working medium backflow channel penetrating through the upper shell and the lower shell is formed; the heat transfer working medium is located in the cavity.

Description

Technical Field

[0001] This invention relates to the field of phase change heat transfer and electronic heat dissipation technology, and particularly to a composite heat exchanger with vertical gradient capillary channels, its preparation process, and its application. Background Technology

[0002] As modern electronic devices evolve towards miniaturization and high power density, thermal management systems face significant challenges. Heat sinks, utilizing the latent heat of the working fluid's phase change for efficient heat dissipation, have become the mainstream solution. Among these solutions, to balance casing strength, lightweight design, and cost reduction, the use of stainless steel-copper composite materials instead of pure copper in heat sink manufacturing is gradually becoming an industry trend. However, existing stainless steel-copper composite heat sink technology still has significant defects in manufacturing process and thermal performance: On the one hand, the inner copper layer in the composite material is usually thin and soft. During the stamping process of the high aspect ratio support column, due to the difference in elongation between the copper and stainless steel substrate, micro-cracks or even ruptures are easily generated at the stretching point, causing the stainless steel substrate to be directly exposed to the water medium, triggering an irreversible hydrogen evolution corrosion reaction and severely shortening the device life; On the other hand, the support column formed by traditional stamping usually only serves as a mechanical support component. Its surface is smooth and lacks capillary structure, which cannot guide the condensate to flow back quickly and vertically. This results in the liquid phase circulation path between the upper and lower shells being interrupted, and the evaporation end is prone to "dry burning" due to insufficient liquid supply under high heat load; In addition, existing packaging processes mostly use brazing or ordinary diffusion welding, and there are often pores or non-dense bonding at the interface, resulting in high contact thermal resistance and easy delamination failure under long-term thermal cycling shock. Therefore, there is an urgent need for a composite heat exchanger and its preparation method that can ensure the integrity of the copper layer during the molding process, construct an efficient vertical reflux channel, and achieve high-strength interfacial fusion. Summary of the Invention

[0003] Based on this, the purpose of this invention is to provide a composite heat exchanger with vertical gradient capillary channels, its preparation process and application, which achieves efficient vertical heat transfer and high-reliability sealing through microstructure design and process control.

[0004] First aspect:

[0005] A composite heat exchanger with vertical gradient capillary channels includes an upper shell, a lower shell, a liquid wick, and a heat transfer medium. Both the upper and lower shells are composite plates formed by combining an outer base layer and an inner copper layer. The upper and lower shells form a cavity when they are closed together. The lower shell is provided with an inwardly protruding support column, which is located in the cavity and connected to the upper shell. The outer base layer is made of at least one of stainless steel, nickel, molybdenum and titanium. The liquid-absorbing core includes a first liquid-absorbing core, a second liquid-absorbing core, and a third liquid-absorbing core. The first liquid-absorbing core is located at one end of the upper shell and is bonded to the copper layer of the upper shell. The second liquid-absorbing core is located at one end of the lower shell and is bonded to the copper layer of the lower shell. The third liquid-absorbing core is an annular sleeve fitted around the outer periphery of the support column. One end is connected to the first liquid-absorbing core, and the other end is connected to the second liquid-absorbing core, forming a heat transfer medium return channel that connects the upper shell and the lower shell. The heat transfer medium is located inside the cavity.

[0006] This invention, through the inclusion of a third wicking core—a unique "ring-shaped sleeve supporting the column" design—transforms the support column from a simple structural component into a three-in-one assembly integrating structure, heat transfer, and heat transfer medium channel. Furthermore, the third wicking core creates a continuous heat transfer medium return channel: "first wicking core → third wicking core around the support column → second wicking core," a three-dimensional heat transfer medium return channel that solves the problem of delayed heat transfer medium return from the first wicking core under high power conditions. When the heat transfer medium evaporates in the lower shell, the vapor rises to the upper shell and condenses into droplets at the first wicking core. These droplets can flow horizontally, and when they reach the vicinity of the third wicking core, they are rapidly captured by the strong capillary force generated by the third wicking core and vertically "drawn" back to the second wicking core. The heat transfer medium then flows horizontally through the second wicking core and is evenly distributed on the lower shell, continuing to evaporate upon heating, forming a high-speed circulation. Traditional single-support columns lack a third wicking structure, allowing the heat transfer medium to only undergo "two-dimensional horizontal reflux" within the plane of the upper and lower wicking cores. The "three-dimensional" channel constructed in this invention improves reflux efficiency by more than three times compared to the traditional "two-dimensional horizontal reflux" method.

[0007] As a preferred embodiment, the second suction core is provided with a clearance hole through which the support column passes, and the third suction core is located in the gap between the outer periphery of the support column and the inner side of the clearance hole.

[0008] As a preferred embodiment, the first suction core also has a clearance hole for the support column to pass through. By providing clearance holes in the first and second suction cores, the support column can be directly connected to the upper and lower housings, resulting in a more secure connection.

[0009] As a preferred embodiment, the method for preparing the support column includes the following steps: preheating the deformation area of ​​the lower shell to 200-300℃; using at least three progressive dies to gradually stretch the support column, and controlling the deformation amount of each stretching stage to be within 60% of the material's ultimate tensile strength; providing a rounded corner transition structure at the connection between the root of the support column and the lower shell, wherein the radius of the rounded corner transition structure is greater than twice the thickness of the composite plate.

[0010] By employing a temperature-controlled step-by-step stamping method, the sheet metal is first preheated to 200-300℃, a temperature below the recrystallization temperature and above the softening point of copper, to increase the ductility of the copper layer. Simultaneously, multi-stage punches (such as a 3-stage progressive die) are used to gradually increase the drawing depth, with each stage of deformation controlled within 60% of the ultimate tensile strength. This effectively solves the industry problem of easy cracking during deep drawing of thin copper-layer composite materials, ensuring the integrity of the anti-corrosion layer and guaranteeing the long lifespan of the heat spreader (no hydrogen evolution). Furthermore, rounded corners are used to reduce stress concentration, ensuring that the inner copper layer extends synchronously with the stainless steel layer without cracking, maintaining continuous copper coverage.

[0011] As a preferred embodiment, the first, second, and third absorbent cores are at least one of copper wire mesh, copper foam, and copper braided tape, respectively. The absorbent cores are made of copper, consistent with the inner copper layers of the upper and lower shells. This not only reduces interfacial thermal resistance but also allows for the formation of a seamless, integrated structure through copper atom diffusion and fusion, achieving zero thermal resistance.

[0012] As a preferred embodiment, the third liquid-absorbing core is a sintered copper powder ring structure, and the porosity of the sintered copper powder ring is 40-60%.

[0013] By controlling the porosity within this range, the capillary suction force generated by the microporous structure of the sintered ring is sufficient to overcome the evaporation pressure under high heat flux density, ensuring that the heat transfer medium can quickly flow back to the heat source center (lower shell). Simultaneously, this porosity guarantees low hydraulic flow resistance (permeability), effectively reducing circulation pressure drop and preventing dry burning. Furthermore, a porosity of 40-60% allows the copper powder ring to possess excellent radial thermal conductivity while also ensuring sufficient mechanical support strength, effectively resisting deformation caused by the vacuum negative pressure inside the heat spreader, thereby improving the overall thermal performance stability and structural reliability of the heat spreader.

[0014] The second aspect: A method for preparing the composite heat exchange plate described in the first aspect includes the following steps: S1, Shell Forming: A composite plate formed by combining an outer base layer and an inner copper layer is used to perform multi-stage stamping on the lower shell to form the support column; S2, Liquid absorbent core assembly: The first liquid absorbent core is provided on the inner copper layer surface of the upper housing, the second liquid absorbent core is provided on the inner copper layer surface of the lower housing, and the third liquid absorbent core is fitted or formed around the outer periphery of the support column, the third liquid absorbent core being located between the first liquid absorbent core and the second liquid absorbent core. S3, diffusion fusion: The upper shell and the lower shell are fastened together and placed in a vacuum furnace. While applying vertical pressure, they are heated to cause atomic diffusion fusion between the copper layer at the top of the support column and the inner copper layer of the upper shell. S4, Liquid injection and sealing: Inject the heat transfer medium, degas it, and then seal it.

[0015] As a preferred embodiment, in step S3, the heating temperature range is 850-950℃, the applied vertical pressure range is 0.5-2.0 MPa, and the heat and pressure holding time is 30-120 min.

[0016] Under these temperature and pressure conditions, the copper layer at the top of the support column and the inner copper layer of the upper shell undergo intense atomic diffusion, with grain boundaries interpenetrating and the original interface completely eliminated at the microscopic level. They fuse into a single crystalline phase structure, forming an integrated, seamless connection. Simultaneously, the surrounding outer matrix material does not melt, maintaining structural rigidity. This high-temperature, high-pressure diffusion process achieves copper layer "fusion," avoiding the introduction of low thermal conductivity solder (such as solder paste), significantly reducing contact thermal resistance, and eliminating the risk of cold solder joints after long-term use, thus combining high thermal conductivity with long-term reliability.

[0017] As a preferred embodiment, in step S2, the third liquid-absorbing core is formed by first pre-pressing copper powder into a ring-shaped green blank, which is then fitted onto the support column. Subsequently, during the heating process in step S3, the sintering and forming of the third liquid-absorbing core and its diffusion fusion with the upper and lower shells are completed simultaneously through a single heating process.

[0018] Third aspect: A heat dissipation device includes the composite heat exchange plate described in the first aspect. Attached Figure Description

[0019] Figure 1 This is a top view of the composite heat exchanger.

[0020] Figure 2 This is an exploded view of the composite heat exchanger.

[0021] Figure 3 This is a cross-sectional view of the composite heat exchanger.

[0022] Figure 4 This is a schematic diagram of a finned heat exchanger.

[0023] Figure 5 This is a partial structural diagram of the heat dissipation device.

[0024] Among them, 1-upper shell, 2-lower shell, 21-support column, 22-screw hole, 3-cavity, 41-first liquid suction core, 411-first clearance hole, 42-second liquid suction core, 421-second clearance hole, 43-third liquid suction core, 5-liquid injection port, 6-liquid injection pipe, 7-weld, 8-finned heat exchanger, 9-fan. Detailed Implementation

[0025] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0026] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. In the description of this invention, it should be noted that terms such as "vertical direction," "up," "down," and "horizontal," indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0027] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0028] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0029] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0030] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0031] A composite heat exchanger with vertical gradient capillary channels includes an upper shell, a lower shell, a liquid wick, a heat transfer medium, a liquid injection port, and a liquid injection pipe.

[0032] Both the upper and lower shells are composite panels formed by an outer base layer and an inner copper layer. When the upper and lower shells are joined, they form a cavity. The lower shell has an inwardly protruding support column located within the cavity and connected to the upper shell. The outer base layer is made of at least one of stainless steel, nickel, molybdenum, and titanium. The base of the support column connects to the lower shell with a rounded corner transition structure, the radius of which is greater than twice the thickness of the composite panel.

[0033] The wicking core is made of at least one of copper wire mesh, copper foam, and copper braided tape, or a composite material of these three. The wicking core includes a first wicking core, a second wicking core, and a third wicking core. The first wicking core is located at one end of the upper shell and has a clearance hole for the support column to pass through, and is bonded to the copper layer of the upper shell. The second wicking core is located at one end of the lower shell and has a clearance hole for the support column to pass through, and is bonded to the copper layer of the lower shell. The third wicking core is a circular sleeve fitted around the gap between the outer circumference of the support column and the inner side of the clearance hole. One end is connected to the first wicking core, and the other end is connected to the second wicking core, forming a heat transfer fluid return channel connecting the upper and lower shells. The third wicking core can also be a sintered copper powder ring structure, with a porosity of 40-60%.

[0034] The heat transfer medium is located inside the wick, and the injection port is located between the upper and lower shells, communicating with the wick. The injection pipe can communicate with the wick through the injection port, facilitating the injection of the heat transfer medium. In this embodiment of the invention, pure water is selected as the heat transfer medium.

[0035] A method for preparing a composite heat exchanger with vertical gradient capillary channels includes the following steps: S1, Shell Forming: A composite plate formed by combining an outer base layer and an inner copper layer is used to perform multi-stage stamping on the lower shell to form support columns.

[0036] S2, Liquid absorbent core assembly: A first liquid absorbent core is provided on the inner copper layer surface of the upper housing, a second liquid absorbent core is provided on the inner copper layer surface of the lower housing, and a third liquid absorbent core is fitted or formed around the outer periphery of the support column, with the third liquid absorbent core located between the first and second liquid absorbent cores.

[0037] S3, Diffusion Fusion: The upper and lower shells are fastened together and placed in a vacuum furnace. While applying vertical pressure, the furnace is heated to cause atomic diffusion fusion between the copper layer at the top of the support column and the inner copper layer of the upper shell.

[0038] S4, Liquid Injection and Sealing: The edges of the upper and lower shells are sealed by welding. A liquid injection pipe is inserted into the liquid injection port, and the heat transfer medium is injected. After degassing, the shell is sealed.

[0039] In step S1, the multi-stage stamping adopts a temperature-controlled step-by-step stretching process, which specifically includes: preheating the deformation area of ​​the composite plate to 200-300℃; using at least three progressive dies to gradually stretch the support column, and controlling the deformation of each stretching stage to within 60% of the material's ultimate tensile strength.

[0040] In step S2, the third liquid-absorbing core is formed as follows: copper powder is first pre-pressed into a ring-shaped green blank and placed on the support column. Then, during the heating process in step S3, the sintering and forming of the third liquid-absorbing core and the diffusion fusion with the upper and lower shells are completed simultaneously through one heating.

[0041] In step S3, the heating temperature range is 850-950℃, the applied vertical pressure range is 0.5-2.0 MPa, and the heat and pressure holding time is 30-120 min.

[0042] A heat dissipation device includes a composite heat exchange plate.

[0043] Example 1 like Figures 1-3 As shown, a composite heat exchanger with vertical gradient capillary channels includes an upper shell 1, a lower shell 2, a liquid wick, a heat transfer medium, a liquid injection port 5, and a liquid injection pipe 6.

[0044] The upper shell 1 and the lower shell 2 both have a total thickness of 0.4 mm and each includes a stainless steel layer and a copper layer arranged sequentially, with the stainless steel layer being 0.35 mm thick and the copper layer being 0.05 mm thick. The copper layers of the upper shell 1 and the lower shell 2 are arranged facing inwards towards each other, forming a cavity 3 between the upper shell 1 and the lower shell 2. The cavity 3 has a height of 2 mm and is equipped with a liquid wick structure and a heat transfer medium.

[0045] The lower housing 2 is equipped with a support column 21, which is 2mm high and 3mm in diameter. Located within the cavity 3, it is fused with the upper housing 1. The upper housing 1 and lower housing 2 are sealed around their perimeter by laser welding to form a weld seam 7. A rounded corner transition structure is provided at the connection between the base of the support column 21 and the lower housing 1. The radius of the rounded corner transition structure is greater than twice the thickness of the lower housing 2, i.e., greater than 0.8mm. An injection port 5 is located at the connection between the upper housing 1 and the lower housing 2, and an injection pipe 6 is provided at the injection port 5. Screw holes 22 are present on the outer surface of the lower housing 2 for the assembly and installation of the composite heat exchange plate.

[0046] The liquid-absorbing core includes a first liquid-absorbing core 41, a second liquid-absorbing core 42, and a third liquid-absorbing core 43. The first liquid-absorbing core 41 is sintered on the copper layer of the upper shell 1 and is a single layer of 100-mesh copper wire mesh. In this embodiment, the first liquid-absorbing core 41 is also provided with a first clearance hole 411, through which the support column 21 passes, allowing it to be directly fused with the upper shell 1, resulting in a stronger bond. The second liquid-absorbing core 42 is sintered on the copper layer of the lower shell 2 and is provided with a second clearance hole 421, through which the support column 21 passes. In this embodiment, to improve the capillary effect, the second liquid-absorbing core 42 is a three-layer copper wire mesh, consisting of 200 mesh, 250 mesh, and 300 mesh layers from top to bottom. The third liquid-absorbing core 43 is fitted into the gap between the outer periphery of the support column 21 and the inner side of the second clearance hole 421, and is a ring made of sintered spherical copper powder with a porosity controlled at 40-50%.

[0047] A method for preparing a composite heat exchanger with vertical gradient capillary channels includes the following steps: S1, Shell Forming: A local induction heating mold is used to heat the deformation zone of the lower shell 2 to 250°C. The first stage of stretching is 0.8 mm, the second stage is 1.5 mm, and the third stage is stretching and shaping to 2.0 mm, forming the support column 21. In this embodiment, the stretching amount at each stage is controlled at 40-55% of the material's ultimate tensile strength, effectively avoiding shear failure at the composite interface and work hardening cracks in the stainless steel layer, ensuring the continuity of the thinned copper layer. The copper layer of the support column 21 is thinned to approximately 15-20 μm, and the structure is continuous and dense, without penetrating cracks, still effectively isolating the stainless steel from the heat transfer medium.

[0048] S2, Liquid Absorbing Core Assembly: Set the sintering temperature to 650℃. A first liquid absorbing core 41 is installed and fused to the inner copper layer surface of the upper shell 1, and a second liquid absorbing core 42 is installed and fused to the inner copper layer surface of the lower shell 2. Spherical copper powder is pre-pressed into a ring-shaped green blank and fitted onto the support column 21. S3, diffusion fusion: The upper shell 1 and the lower shell 2 are fastened together and placed in a vacuum furnace, heated to 900°C, and a vertical pressure of 1MPa is applied. The temperature and pressure are maintained for 60 minutes, so that the copper layer at the top of the support column 21 and the inner copper layer of the upper shell 1 undergo atomic diffusion fusion. At the same time, the annular green blank in step S2 is sintered and formed to form the third liquid-absorbing core 43.

[0049] After encapsulation, dissection revealed a seamless transition at the connection area between the top of the support column 21 and the upper shell 1. No obvious seams or delamination lines were observed with the naked eye or under a low-power microscope. The microhardness and conductivity of this area were essentially consistent with the original copper material, indicating that the upper and lower copper layers had achieved metallurgical bonding, forming a homogeneous metallic entity. This connection method exhibits almost zero thermal resistance and tensile strength far exceeding that of traditional brazing or adhesive bonding.

[0050] S4, Liquid Injection and Sealing: The edges of the upper shell 1 and lower shell 2 are sealed together using laser welding to form weld 7. The injection pipe 6 is fixed to the injection port 5 using AB adhesive, and a leak test is performed. Then, a certain amount of heat transfer medium is injected into the cavity 3 through the injection pipe 6. After freezing for more than 30 minutes, a vacuum is drawn to reduce the internal pressure of the cavity 3 to below 3 Pa, and the injection pipe 6 is sealed. Next, the bottom of the composite heat spreader is heated to push residual impurities into the injection pipe 6, which is then pressed together at the injection port 5. The injection port is sealed using laser welding. Finally, the excess part is cut off, completing the fabrication of the heat spreader.

[0051] In this embodiment, the specific working principle of the composite heat exchanger is as follows: During operation, the stainless steel layer of the lower shell 2 of the stainless steel heat exchanger is close to the heat source and absorbs the heat generated by the heat source, causing the temperature of the lower shell 2 to rise. Part of the heat is conducted to the upper shell 1 through the copper layer, multiple layers of copper wire mesh, and support column 21, and the heat is dissipated by the upper shell 1. As the water working medium absorbs some heat and vaporizes and moves upward, it liquefies upon contact with the lower-temperature upper shell 1. The small-mesh copper wire mesh on the inner surface of the upper shell 1 promotes the return of the liquefied droplets to the evaporation zone of the lower shell 2. The gas-liquid phase change cycle repeats in this way, and the high temperature generated by the heat source is carried away through the phase change of the liquid water working medium.

[0052] Example 2 like Figures 4-5 As shown, a heat dissipation device includes a composite heat exchange plate, a finned heat exchanger 8, and a fan 9 as described in Embodiment 1.

[0053] The composite heat exchanger is equipped with a finned heat exchanger 8 at the end away from the heat source. The finned heat exchanger is either a pure fin or a fin with a heat sink. The fin material can be copper and copper alloys, aluminum and aluminum alloys, or other high thermal conductivity materials. The fin surface has a corrugated structure to increase the heat exchange area.

[0054] The composite heat exchanger plate and the finned heat exchanger 8 are fixedly connected by solder paste welding, and connected to the heating element by means of clips, threads, etc. A thermal interface material is applied between the heating element and the lower shell 1 of the composite heat exchanger plate.

[0055] The finned heat exchanger at the end furthest from the heat source is equipped with a fan 9, which further enhances the heat exchange effect of the finned heat exchanger 8 and ensures that the heat from the heat source is dissipated in a timely manner.

[0056] In this embodiment, the working principle of the heat dissipation device is as follows: the heat generated by the heat source is conducted to the composite heat exchange plate through the heat interface material, and then the heat undergoes a gas-liquid phase change cycle inside the composite heat exchange plate, which diffuses the heat to the end away from the heat source. The heat dissipation effect of the composite heat exchange plate can be enhanced by the external heat dissipation of the finned heat exchanger 8 and the fan 9.

[0057] The above embodiments are merely illustrative of several implementations of the present invention, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the invention patent. For those skilled in the art, any changes, modifications, substitutions, integrations, and parameter alterations to these embodiments without departing from the concept of the present invention are all within the protection scope of the present invention.

Claims

1. A composite heat exchanger with vertical gradient capillary channels, characterized in that, It includes an upper shell, a lower shell, a liquid wick, and a heat transfer medium; Both the upper and lower shells are composite plates formed by combining an outer base layer and an inner copper layer. The upper and lower shells form a cavity when they are closed together. The lower shell is provided with an inwardly protruding support column, which is located in the cavity and connected to the upper shell. The outer base layer is made of at least one of stainless steel, nickel, molybdenum and titanium. The liquid-absorbing core includes a first liquid-absorbing core, a second liquid-absorbing core, and a third liquid-absorbing core. The first liquid-absorbing core is located at one end of the upper shell and is bonded to the copper layer of the upper shell. The second liquid-absorbing core is located at one end of the lower shell and is bonded to the copper layer of the lower shell. The third liquid-absorbing core is an annular sleeve that is fitted around the outer periphery of the support column. One end is connected to the first liquid-absorbing core, and the other end is connected to the second liquid-absorbing core, forming a heat transfer fluid return channel that runs through the upper shell and the lower shell. The heat transfer medium is located inside the cavity.

2. The composite heat spreader with vertical gradient capillary channels according to claim 1, characterized in that, The second suction core is provided with a clearance hole for the support column to pass through, and the third suction core is located in the gap between the outer periphery of the support column and the inner side of the clearance hole.

3. The composite heat spreader with vertical gradient capillary channels according to claim 2, characterized in that, The first liquid-absorbing core is also provided with a clearance hole for the support column to pass through.

4. The composite heat spreader with vertical gradient capillary channels according to claim 1, characterized in that, The method for preparing the support column includes the following steps: preheating the deformation area of ​​the lower shell to 200-300℃; using at least three progressive dies to gradually stretch the support column, and controlling the deformation of each stretching stage to within 60% of the material's ultimate tensile strength; providing a rounded corner transition structure at the connection between the root of the support column and the lower shell, wherein the radius of the rounded corner transition structure is greater than twice the thickness of the composite plate.

5. The composite heat exchanger with vertical gradient capillary channels according to claim 1, characterized in that, The first absorbent core, the second absorbent core, and the third absorbent core are at least one of copper wire mesh, copper foam, and copper braided tape, respectively.

6. The composite heat exchanger with vertical gradient capillary channels according to claim 1, characterized in that, The third liquid-absorbing core is a sintered copper powder ring structure, and the porosity of the sintered copper powder ring is 40-60%.

7. A method for preparing a composite heat spreader as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1, Shell forming: A composite plate formed by combining an outer base layer and an inner copper layer is selected, and the deformation area of ​​the lower shell is preheated to 200-300℃; the support column is gradually stretched using at least three progressive dies, and the deformation of each stretching stage is controlled within 60% of the material's ultimate tensile strength. S2, Liquid absorbent core assembly: The first liquid absorbent core is provided on the inner copper layer surface of the upper housing, the second liquid absorbent core is provided on the inner copper layer surface of the lower housing, and the third liquid absorbent core is fitted or formed around the outer periphery of the support column, the third liquid absorbent core being located between the first liquid absorbent core and the second liquid absorbent core. S3, diffusion fusion: The upper shell and the lower shell are fastened together and placed in a vacuum furnace. While applying vertical pressure, they are heated to cause atomic diffusion fusion between the copper layer at the top of the support column and the inner copper layer of the upper shell. S4, Liquid injection and sealing: Inject the heat transfer medium, degas it, and then seal it.

8. The method for preparing the composite heat spreader according to claim 7, characterized in that, In step S3, the heating temperature range is 850-950℃, the applied vertical pressure range is 0.5-2.0 MPa, and the heat and pressure holding time is 30-120 min.

9. The method for preparing the composite heat spreader according to claim 7, characterized in that, The third liquid-absorbing core is formed as follows: copper powder is first pre-pressed into a ring-shaped green blank, which is then fitted onto the support column. Subsequently, during the heating process in step S3, the sintering and forming of the third liquid-absorbing core and its diffusion fusion with the upper and lower shells are completed simultaneously through a single heating process.

10. A heat dissipation device, characterized in that, Includes the composite heat spreader as described in any one of claims 1 to 6.

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