Vapor chamber manufacturing method and vapor chamber structure

Abstract

The invention relates to a vapor chamber manufacturing method and a vapor chamber structure, and the manufacturing method comprises the steps: forming a main flow channel layer on a middle core layer through an etching technology, forming a tree-shaped fractal microtube network and a microcolumn array on the upper surface and the lower surface of the main flow channel layer, manufacturing a thin film temperature sensor array on the inner surface of an upper cover plate, embedding a miniature piezoelectric valve into a lower cover plate, and manufacturing a temperature sensor array on the inner surface of a lower cover plate; the three layers of structures are combined in a sealed mode through low-temperature plasma activation bonding; a phase change working medium containing nano-particles is poured in a vacuum environment, and a control chip is integrated to form the vapor chamber with real-time sensing and dynamic adjusting capabilities. The three-dimensional graded micro-channel network is arranged in the temperature equalizing plate structure, an intelligent closed-loop control system and the composite nano working medium are combined, full-dimensional efficient heat transfer and dynamic heat management are achieved, integration is completed under the low-temperature process, and the temperature control precision, the response speed and the adaptability to the complex thermal environment are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of thermal management technology, and in particular to a method for manufacturing a heat exchanger and a heat exchanger structure. Background Technology

[0002] As a highly efficient passive heat dissipation and temperature equalization element, the vapor chamber is suitable for scenarios with extremely high requirements for temperature uniformity and dynamic response, such as high-power electronic heat dissipation, precision instrument constant temperature, high-efficiency cooking equipment and medical thermotherapy devices.

[0003] In traditional and existing technologies, the vapor chamber is internally structured with a network of channels filled with a suitable proportion of a gas-liquid phase change medium. Because of the medium's gas-liquid phase change properties, when a heat source contacts the bottom of the vapor chamber, heat is conducted to the internal working medium, causing it to evaporate into steam. This process absorbs a large amount of latent heat, achieving efficient heat absorption. The steam then rapidly diffuses throughout the cavity due to the pressure difference. Since the vapor chamber is a two-dimensional planar structure, the steam can be rapidly distributed across the entire plane. During the absorption and release of latent heat, heat is transferred through the shell, making the temperature more uniform. Furthermore, existing bonding processes typically require relatively high temperatures (generally above 250°C), necessitating more precise process control.

[0004] However, the existing medium flow path is still mainly two-dimensional in the plane, and there is a lack of effective active heat transfer mechanism in the thickness direction of the plate (third dimension), which leads to a decrease in performance when dealing with vertical thermal gradients. Secondly, the existing heat exchange plates are all passive responses and cannot dynamically adjust the heat transfer path or intensity according to the real-time temperature distribution on the plate, resulting in poor adaptability to complex thermal environments. Summary of the Invention

[0005] In view of this, the present invention provides a heat spreader and a manufacturing method thereof, which mainly achieves more precise temperature control by means of three-dimensional graded heat transfer and dynamic adjustment of heat transfer path.

[0006] The following technical solution is adopted in this application:

[0007] A method for manufacturing a heat spreader includes the following steps: S1: A metal intermediate core layer is provided as the intermediate core layer. In the planar area of ​​the intermediate core layer, a main flow channel layer consisting of multiple longitudinal main veins and at least one transverse manifold is formed by ion etching. In the upper and lower surface areas of the intermediate core layer, a tree-like fractal microtube network communicating with the sidewalls of the longitudinal main veins is etched out respectively. At the terminal end of the tree-like fractal microtube network, a micropillar array is formed to form a secondary distribution layer and a capillary structure layer. S2: Provide a transparent upper cover and a lower cover with an integrated functional area. A distributed thin-film temperature sensor array and interconnecting microwires are fabricated on the inner surface of the upper cover using a magnetron sputtering process. A miniature piezoelectric valve is embedded at a predetermined position on the lower cover. S3: In a clean environment, the intermediate core layer is placed between the upper cover plate and the lower cover plate and three-dimensional precision alignment is performed. Low-temperature plasma activation is used for direct bonding. Under the conditions of temperature below 180°C and pressure, the upper cover plate, the intermediate core layer and the lower cover plate are permanently bonded into a sealed, temperature-equalizing main board. S4: Through the injection hole reserved on the edge of the heat spreader, a working fluid is injected into the microchannel network inside the heat spreader under vacuum. The working fluid includes a basic phase change fluid and thermally conductive nanoparticles dispersed therein. Then the injection hole is sealed, and a micro control chip is attached to the sealed area on the edge of the heat spreader. It is electrically connected to the internal thin-film temperature sensor array and micro piezoelectric valve through micro wires to form a heat spreader with real-time sensing and dynamic adjustment.

[0008] Preferably, in step S1, the ion etching process for forming the main flow channel layer is deep reactive ion etching, and the formation of the tree-like fractal microtube network is achieved by femtosecond laser processing. The two processes are performed in separate steps, and the tree-like fractal microtube network is also connected through multiple distributed micropores pre-installed on the sidewall of the longitudinal main vein.

[0009] Preferably, the low-temperature plasma activation direct bonding in step S3 has the following process parameters: bonding temperature range of 150-180℃, applied pressure of 5-10MPa, and bonding time of 30-60min under an inert gas atmosphere.

[0010] Preferably, the working fluid injected in step S4 contains thermally conductive nanoparticles such as graphene or boron nitride nanosheets.

[0011] Preferably, in step S2, a flow guide protrusion matching the shape of the transverse manifold is simultaneously machined at the position where the micro piezoelectric valve is embedded in the lower cover plate, and after bonding, the flow guide protrusion extends into the transverse manifold.

[0012] Preferably, after the bonding is completed in step S3 and before the infusion in step S4, the process further includes a step of performing an airtightness test on the homogeneous motherboard.

[0013] Preferably, the present invention also provides a heat spreader structure, the heat spreader structure comprising a heat spreader main board formed by low-temperature bonding and sealing, wherein a three-dimensional hierarchical microfluidic network is formed inside the heat spreader main board and filled with working fluid, the three-dimensional hierarchical microfluidic network comprising a main channel layer located in the middle layer, which is composed of multiple longitudinal main channels and at least one transverse confluence channel; a secondary distribution layer symmetrically distributed in the upper and lower layers of the main channel layer, which is composed of a tree-like fractal microtube network connected to the longitudinal main channels; and a capillary structure layer formed at the end of the secondary distribution layer, which is composed of a densely arranged array of micropillars; a thin-film temperature sensor array is integrated on the inner surface of the transparent upper cover plate of the heat spreader main board, and a micro piezoelectric valve corresponding to the position of the transverse confluence channel is embedded in the lower cover plate, wherein the thin-film temperature sensor array and the micro piezoelectric valve are electrically connected to a micro control chip disposed at the edge of the heat spreader main board.

[0014] Preferably, the valve body of the miniature piezoelectric valve is embedded in the lower cover plate, and the adjusting end of its valve core is aligned with and partially located in the flow channel of the transverse manifold.

[0015] Preferably, the tree-like fractal microtube network adopts a fractal structure, with the diameter of its primary branches decreasing progressively from the final branch.

[0016] Preferably, the individual micropillars in the micropillar array have a regular columnar structure, and slit gaps are formed between adjacent micropillars to generate capillary forces.

[0017] The beneficial effects of this invention are that the heat spreader produced by the manufacturing method has an internal three-dimensional hierarchical microfluidic network that achieves efficient heat transfer in all dimensions from the in-plane to the thickness direction; the integrated temperature sensing and flow regulation unit constitutes an intelligent closed-loop control system that can dynamically optimize the heat transfer path and cope with uneven or changing heat loads; the composite nano-working fluid further enhances the heat transfer performance; the overall manufacturing process is completed at a relatively low temperature, protecting the internal microelectronic devices, and achieving a high degree of integration of structure, function and reliability, significantly improving the temperature control accuracy, response speed and adaptability of the heat spreader. Attached Figure Description

[0018] Figure 1 This is a flowchart of the manufacturing method of the present invention; Figure 2 This is a side view of the heat exchanger structure of the present invention. Figure 3 This is a partial cross-sectional schematic diagram of the heat exchanger structure of the present invention; Figure 4 for Figure 3 Enlarged structural diagram of section A in the middle; Figure 5 A schematic diagram of the main flow channel layer of the intermediate core layer; Figure 6This is a schematic diagram of the capillary structure layer of the intermediate core layer. Figure 7 This is a schematic diagram of the internal structure of the upper cover plate; in the figure: temperature equalization main board 1, upper cover plate 10, intermediate core layer 11, lower cover plate 12, main flow channel layer 20, secondary distribution layer 21, capillary structure layer 22, longitudinal main vein 201, transverse confluence channel 202, tree-like fractal microtube network 203, micropillar array 204, reinforcing coating 205, thin film temperature sensor array 301, micro wire 302, micro piezoelectric valve 303, injection hole 304, micro control chip 305, micropore 306, flow guiding protrusion 307, and working fluid 40. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0020] In the description of this invention, it should be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this 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 this invention. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0021] Example 1: See Figures 1-7 A method for manufacturing a heat exchanger includes the following steps: S1: A metal intermediate core layer is provided as the intermediate core layer 11. The intermediate core layer 11 is usually made of a metal with good thermal conductivity, such as copper, aluminum or their alloys. In the planar area of ​​the intermediate core layer 11, a main flow channel layer 20 is formed by ion etching, which consists of multiple longitudinal main veins 201 and at least one transverse manifold 202 interconnected. In this embodiment 1, three transverse manifolds 202 are provided. The specific number can be set according to the actual situation, but generally it should not exceed three, as too many will lead to a decrease in conduction efficiency. In the upper and lower surface areas of the intermediate core layer 11, the longitudinal main veins 201 and the transverse main veins 202 are etched respectively. A tree-like fractal microtube network 203 with interconnected sidewalls is formed, and a micropillar array 204 is formed at the terminal end of the tree-like fractal microtube network 203, forming a secondary distribution layer 21 and a capillary structure layer 22. The tree-like fractal microtube network 203 can avoid microstructure deformation or material performance degradation caused by thermal damage, ensuring the integrity and functionality of the capillary structure layer 22. Finally, a hydrophilic alumina capillary reinforcement coating 205 is deposited on the inner wall of all microstructures (including longitudinal main veins 201, transverse confluence channels 202, and tree-like fractal microtube network 203) through atomic layer deposition to enhance capillary force. S2: A transparent upper cover plate 10 and a lower cover plate 12 with an integrated functional area are provided. A distributed thin-film temperature sensor array 301 and interconnecting microwires 302 are fabricated on the inner surface of the upper cover plate 10 by magnetron sputtering. The thin-film temperature sensor inside the upper cover plate 10 is generally composed of multiple Ni thin-film sensors. The thin-film sensor array can be arranged in a grid pattern to realize temperature monitoring of the entire upper cover plate surface. A miniature piezoelectric valve 303 is embedded at a predetermined position on the lower cover plate 12. The valve body size of the miniature piezoelectric valve 303 is generally 2×2×1mm. The valve core can extend into the flow channel to adjust the flow rate. At the position where the miniature piezoelectric valve 303 is embedded, a flow guiding protrusion 307 is simultaneously processed. After bonding, it extends into the transverse manifold 202, mainly to guide the flow of the working fluid 40. During operation, it can smoothly guide the steam flow, reduce turbulence and flow dead zones, and ensure that the steam can be distributed more quickly and evenly to the transverse manifold 202 and other connected longitudinal main veins 201. S3: In a clean environment, the intermediate core layer 11 is placed between the upper cover plate 10 and the lower cover plate 12, and three-dimensional precision alignment is performed. Low-temperature plasma activation is used for direct bonding. Under the conditions of temperature below 180°C and pressure, the upper cover plate 10, the intermediate core layer 11 and the lower cover plate 12 are permanently bonded into a sealed uniform temperature main board 1. S4: Through the injection hole 304 reserved on the edge of the heat spreader 1, a working fluid 40 is injected into the microchannel network inside the heat spreader 1 in a vacuum environment. The working fluid 40 contains a basic phase change fluid and thermally conductive nanoparticles dispersed therein. Then, the injection hole 304 is sealed, and the micro control chip 305 is attached to the sealed area on the edge of the heat spreader 1. It is electrically connected to the thin film temperature sensor array 301 and the micro piezoelectric valve 303 inside through the micro wire 302, thus forming a heat spreader 1 with real-time sensing and dynamic adjustment.

[0022] In some embodiments, in step S1, the ion etching process for forming the main flow channel layer 20 is deep reactive ion etching, and the formation of the tree-like fractal microtube network 203 is achieved using femtosecond laser processing. The two processes are performed in separate steps. The tree-like fractal microtube network 203 is also connected through multiple distributed micropores 306 pre-installed on the sidewall of the longitudinal main flow channel 201. The connection with the fractal network is achieved through the distributed micropores 306 on the sidewall of the longitudinal main flow channel 201. This multi-inlet design shortens the path of the working fluid 40 from the longitudinal main flow channel 201 to each level of fractal branch, reduces flow resistance, and accelerates the distribution and circulation speed of the working fluid 40 in three-dimensional space, thereby improving the overall thermal response speed.

[0023] In some embodiments, the low-temperature plasma activation direct bonding in step S3 has the following process parameters: bonding temperature range of 150-180℃, applied pressure of 5-10MPa, and bonding time of 30-60min under an inert gas atmosphere.

[0024] See Table 1:

[0025] By strictly controlling the bonding temperature within a low-temperature range (150-180℃) below 200℃ through the above process, a crucial protective measure is taken. This effectively prevents the pre-fabricated thin-film temperature sensor array 301 and microwires 302 inside the top cover plate 10 from failing due to high temperatures (such as thin-film oxidation, grain coarsening, and wire melting). It also avoids performance degradation of components such as the micro piezoelectric valve 303 due to high-temperature annealing. Secondly, the plasma activation energy cleans and activates the bonding surface, achieving high-strength bonding at a relatively low temperature. The inert gas atmosphere (such as Ar) prevents oxidation of the bonding interface at high temperatures, ensuring interface purity and bonding strength. The combination of pressure parameters of 5-10 MPa and time parameters of 30-60 minutes provides sufficient energy and time for atomic diffusion and bonding, ensuring the hermeticity and mechanical strength of the package, which is the foundation for the long-term reliable operation of the heat spreader.

[0026] In some embodiments, the working fluid 40 injected in step S4 contains thermally conductive nanoparticles that are graphene or boron nitride nanosheets. Furthermore, the size of the thermally conductive nanoparticles is much smaller than the gaps in the micropillar array 204 and the diameter of the dendritic fractal microtube network 203, and they undergo surface modification treatment to ensure that they are stably dispersed in the basic phase change fluid and will not deposit or block the microstructure.

[0027] Through the above technical solution, since both graphene and boron nitride nanosheets are nanomaterials with extremely high intrinsic thermal conductivity, dispersing them in a basic phase change fluid (such as water or alcohols) to form a nanofluid working fluid 40 can significantly improve the equivalent thermal conductivity and specific heat capacity of the working fluid 40. In addition, these nanoparticles can act as additional vaporization nuclei, promoting boiling and reducing superheating; simultaneously, they can enhance condensation heat transfer at the condensation surface. Furthermore, they may further enhance heat transfer through microconvection and Brownian motion.

[0028] In some embodiments, in step S2, at the position where the micro piezoelectric valve 303 is embedded in the lower cover plate 12, a flow guiding protrusion 307 matching the shape of the transverse manifold 202 is simultaneously machined, and after bonding, the flow guiding protrusion 307 extends into the transverse manifold 202.

[0029] Through the above technical solution, the flow guide protrusion 307 has a channel in the same direction as the working fluid 40, which extends into the transverse confluence groove 202, directly changing the local flow channel geometry near the micro piezoelectric valve 303. When the micro piezoelectric valve 303 is activated, the protrusion can more effectively and directly guide or restrict the passage of the working fluid 40 (especially the steam flow), making the flow regulation more sensitive and precise. The designed flow guide protrusion 307 can improve the streamline shape, reduce the flow stagnation area behind or to the side of the micro piezoelectric valve 303, ensure that the working fluid circulates more smoothly in the entire flow channel network, and avoid local overheating.

[0030] In some embodiments, after bonding in step S3 and before potting in step S4, a step of airtightness testing of the vapor chamber 1 is included. Airtightness is the lifeline for the normal operation of the vapor chamber. Even a small leak can lead to loss of internal vacuum, gradual drying of the working fluid 40, or air accumulation, ultimately causing the phase change heat transfer mechanism to fail. This solution is a key quality checkpoint set before potting the working fluid 40 and integrating the microcontroller chip 305 to improve yield and quality: through strict leak detection (such as helium mass spectrometry leak detection), defective products with poor bonding can be detected and eliminated in time, avoiding waste of subsequent processes and materials, while ensuring the long-term operational reliability of the products.

[0031] Example 2: The present invention also provides a heat spreader structure, the heat spreader structure including a heat spreader main board 1 formed by low temperature bonding and sealing, the heat spreader main board 1 having a three-dimensional hierarchical microchannel network formed inside and filled with working fluid 40, the three-dimensional hierarchical microchannel network including a main channel layer 20 located in the middle layer, which is composed of multiple longitudinal main channels 201 and at least one transverse confluence channel 202 connected together. The secondary distribution layer 21, symmetrically distributed in the upper and lower layers of the main flow channel layer 20, is composed of a tree-like fractal microtube network 203 connected to the longitudinal main vascular tube 201. The capillary structure layer 22 formed at the end of the secondary distribution layer 21 is composed of a densely arranged array of micropillars 204; The transparent upper cover plate 10 of the temperature equalization main board 1 has a thin film temperature sensor array 301 integrated on its inner surface, and a miniature piezoelectric valve 303 corresponding to the position of the transverse manifold 202 is embedded in the lower cover plate 12. The thin film temperature sensor array 301 and the miniature piezoelectric valve 303 are electrically connected to a miniature control chip 305 located on the edge of the temperature equalization main board 1.

[0032] Specifically, the micro control chip 305 is pre-programmed with a control program that continuously collects temperature data from various points on the thin-film temperature sensor array 301. When the temperature difference of the upper cover plate 10 exceeds a preset threshold, the control program calculates and outputs an adjustment signal according to a preset algorithm (such as PID control or fuzzy control) to control the opening of the micro piezoelectric valve 303 in the corresponding area and adjust the flow rate of the working fluid flowing through the transverse manifold 202 in that area, thereby realizing the dynamic redistribution of local heat and temperature uniformity control.

[0033] Working principle of the invention: When an uneven heat source comes into contact with the lower cover plate 12 of the temperature equalization mainboard 1, heat is drawn into the interior. This heat causes the working fluid 40 in the corresponding area to evaporate. The vapor, carrying latent heat, diffuses throughout the cavity via a three-dimensional microfluidic network, condensing and releasing heat in cooler areas to achieve initial temperature equalization. During this process, the thin-film temperature sensor array 301 on the inner surface of the upper cover plate 10 continuously collects temperature data at various points on the upper cover plate 10 and transmits it to the micro control chip 305. The preset algorithm (such as PID or fuzzy control) within the control chip 305 analyzes the temperature field. If a local temperature difference is detected to exceed a set threshold (e.g., the temperature at a certain point is too high), it is determined that the heat flow distribution in that area is uneven. The control chip 305 calculates and sends an adjustment signal to the micro piezoelectric valve 303 in the corresponding high-temperature area. The micro piezoelectric valve 303 changes its opening, thereby adjusting the flow rate of the vapor / liquid working fluid flowing through the transverse manifold 202 in that area. When the flow rate of the cooling working fluid to the high-temperature area is increased, heat dissipation is enhanced; when the opening is decreased, the flow rate of the working fluid to the already sufficiently cooled area is restricted, guiding more working fluid to support the high-temperature area. After adjustment, the new temperature distribution is collected again by the thin-film temperature sensor array 301 and fed back to the control chip 305, forming a closed loop. The system continuously adjusts dynamically until the plate surface temperature reaches the target state of uniformity and stability.

[0034] In some embodiments, the valve body of the miniature piezoelectric valve 303 is embedded in the lower cover plate 12, and the adjusting end of its valve core is aligned with and partially located in the flow channel of the transverse manifold 202.

[0035] With the above technical solution, the valve core of the miniature piezoelectric valve 303 is located in the transverse manifold 202 flow channel. This means that the regulating mechanism acts directly on the main channel of the working fluid 40 circulation, rather than the bypass. This design makes the flow regulation effect the most direct and the response the fastest. It can achieve effective control of the global or regional flow with minimal action. It can more effectively change the pressure balance and flow distribution between different areas, thereby dynamically "guiding" or "restricting" the heat transmission path and achieving precise temperature control.

[0036] In some embodiments, the tree-like fractal microtube network 203 adopts a fractal structure, with the diameter of its primary branches decreasing progressively towards the end branches. This progressively decreasing diameter tree-like network, from a hydrodynamic perspective, allows for the uniform and efficient distribution of the working fluid 40 from the main channel to the entire intermediate core layer 11 with minimal flow resistance. Furthermore, the finer diameter of the end branches generates stronger capillary forces. This capillary force gradient from the main channel to the tip facilitates the driving of the condensate to overcome flow resistance and efficiently return to the evaporation region, ensuring the stability of the circulation. Moreover, this fractal structure significantly increases the internal surface area of ​​the flow channels, providing more phase change heat exchange interfaces for the evaporation and condensation of the working fluid 40, thereby improving heat transfer efficiency.

[0037] In some embodiments, the individual micropillars in the micropillar array 204 have a regular columnar structure, with slit gaps formed between adjacent micropillars to generate capillary forces. The regular columnar structure exhibits good mechanical stability and is less prone to collapse during processing or use. Furthermore, this periodic structure is well-suited for large-scale, high-consistency manufacturing using standard microfabrication techniques (such as photolithography and etching), which helps reduce costs and ensure uniform performance.

[0038] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for manufacturing a heat spreader, characterized in that, Includes the following steps: S1: A metal intermediate core layer is provided as the intermediate core layer. In the planar area of ​​the intermediate core layer, a main flow channel layer consisting of multiple longitudinal main veins and at least one transverse manifold is formed by ion etching. A tree-like fractal microtube network communicating with the sidewalls of the longitudinal main veins is etched in the upper and lower surface areas of the intermediate core layer, and a micropillar array is formed at the end of the tree-like fractal microtube network to form a secondary distribution layer and a capillary structure layer. S2: Provide a transparent upper cover and a lower cover with an integrated functional area. A distributed thin-film temperature sensor array and interconnecting microwires are fabricated on the inner surface of the upper cover using a magnetron sputtering process. A miniature piezoelectric valve is embedded at a predetermined position on the lower cover. S3: In a clean environment, the intermediate core layer is placed between the upper cover plate and the lower cover plate and three-dimensional precision alignment is performed. Low-temperature plasma activation is used for direct bonding. Under the conditions of temperature below 180°C and pressure, the upper cover plate, the intermediate core layer and the lower cover plate are permanently bonded into a sealed, temperature-equalizing main board. S4: Through the injection hole reserved on the edge of the heat spreader, a working fluid is injected into the microchannel network inside the heat spreader under vacuum. The working fluid includes a basic phase change fluid and thermally conductive nanoparticles dispersed therein. Then the injection hole is sealed, and a micro control chip is attached to the sealed area on the edge of the heat spreader. It is electrically connected to the internal thin-film temperature sensor array and micro piezoelectric valve through micro wires to form a heat spreader with real-time sensing and dynamic adjustment.

2. The method for manufacturing a heat spreader according to claim 1, characterized in that, In step S1, the ion etching process for forming the main flow channel layer adopts deep reactive ion etching, and the formation of the tree-like fractal microtube network adopts femtosecond laser processing technology. The two processes are carried out in separate steps. The tree-like fractal microtube network is also connected through multiple distributed micropores preset on the sidewall of the longitudinal main vein.

3. The method for manufacturing a heat spreader according to claim 1, characterized in that, The low-temperature plasma activation direct bonding in step S3 has the following process parameters: bonding temperature range of 150-180℃, applied pressure of 5-10MPa, and bonding time of 30-60min under an inert gas atmosphere.

4. The method for manufacturing a heat spreader according to claim 1, characterized in that, The working fluid injected in step S4 contains thermally conductive nanoparticles, which are graphene or boron nitride nanosheets.

5. The method for manufacturing a heat spreader according to claim 1, characterized in that, In step S2, at the location where the micro piezoelectric valve is embedded in the lower cover plate, a flow guide protrusion matching the shape of the transverse manifold is simultaneously machined. After bonding, the flow guide protrusion extends into the transverse manifold.

6. The method for manufacturing a heat spreader according to claim 1, characterized in that, After the bonding is completed in step S3 and before the injection in step S4, the process also includes a step of testing the airtightness of the homogeneous motherboard.

7. A heat spreader structure, characterized in that, The heat spreader structure includes a heat spreader main board formed by low-temperature bonding and sealing. The heat spreader main board has a three-dimensional hierarchical microchannel network inside and is filled with working fluid. The three-dimensional hierarchical microchannel network includes a main channel layer located in the middle layer, which is composed of multiple longitudinal main channels and at least one transverse confluence channel. The secondary distribution layers, symmetrically distributed in the upper and lower layers of the main flow channel layer, are composed of a tree-like fractal microtube network connected to the longitudinal main vascular bundle. The capillary structure layer formed at the end of the secondary distribution layer is composed of a densely arranged array of micropillars; The transparent upper cover of the temperature equalization motherboard has a thin-film temperature sensor array integrated on its inner surface, and a miniature piezoelectric valve corresponding to the position of the transverse manifold is embedded in the lower cover. The thin-film temperature sensor array and the miniature piezoelectric valve are electrically connected to a miniature control chip located at the edge of the temperature equalization motherboard.

8. The heat spreader structure according to claim 7, characterized in that, The valve body of the miniature piezoelectric valve is embedded in the lower cover plate, and the adjusting end of its valve core is aligned with and partially located in the flow channel of the transverse manifold.

9. A heat spreader structure according to claim 7, characterized in that, The tree-like fractal microtube network adopts a fractal structure, with the diameter of its primary branches and final branches decreasing progressively.

10. A temperature distribution plate structure according to claim 7, characterized in that, The individual micropillars in the micropillar array have a regular columnar structure, and slit gaps are formed between adjacent micropillars to generate capillary forces.

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