A composite vapor chamber and a manufacturing method thereof

Abstract

The present application relates to the technical field of heat plate phase change heat dissipation, and specifically discloses a composite heat plate and a preparation method thereof. The upper cover plate is prepared by a high-thermal-conductivity aluminum-based silicon carbide composite material powder metallurgy method, the bottom plate is processed by an aluminum alloy material, the upper cover plate and the bottom plate are vacuum hetero-diffusion welded to form a sealed heat dissipation and temperature uniformity cavity, the inner surface of the first recessed cavity of the upper cover plate has a hydrophilic capillary characteristic structure, the composite wick of the inner surface of the second recessed cavity of the bottom plate has a two-phase capillary characteristic structure, and the cavity is filled with a liquid cooling working medium. The present application adopts a micro-groove-sintered powder composite wick and other characteristic structure designs, and combines a high-energy laser etching method to realize the effects of promoting bubble separation at the evaporation end and accelerating condensation and dropping at the condensation end, form a stable working medium two-phase rapid circulation mode, reduce the thermal resistance at the evaporation end and the backflow resistance at the condensation end, effectively improve the heat transfer rate and the heat conduction efficiency, and have good impact vibration and fatigue mechanical properties, and meet the heat dissipation application of railway communication signal equipment devices.

Description

Technical Field

[0001] This invention relates to the field of vapor chamber phase change heat dissipation technology, specifically a composite vapor chamber and its preparation method. Background Technology

[0002] The future development trend of railway communication and signaling equipment is towards comprehensive modularization and integration. This leads to a continuous increase in heat dissipation and internal heat flux density, posing a significant challenge to the heat dissipation of high-power modules. Excessive temperatures can affect the performance of electronic components, and in severe cases, concentrated hotspots can even cause component overheating and failure, resulting in equipment shutdown. Data from the electronics industry association shows that failures of industrial electronic equipment due to exceeding operating temperatures account for approximately 55% of all failures. A typical 10°C rule of thumb indicates that within a certain range, the reliability of electronic devices decreases by approximately 50% for every 10°C increase in temperature. The failure rate of typical electronic components such as memory and microprocessors at 120°C is four times that at 90°C and nine times that at 60°C. Therefore, excellent heat dissipation is crucial for electronic equipment.

[0003] Based on differences in heat conduction, heat convection, and energy input methods, current electronic equipment cooling methods mainly fall into two categories: active and passive. Commonly used cooling technologies include natural cooling, forced air cooling, liquid cooling, and thermoelectric cooling. To meet the high safety and reliability requirements of the railway industry, indoor railway signaling equipment primarily employs active cooling, while outdoor equipment uses passive cooling. Indoor equipment can utilize active cooling methods such as air conditioning and forced air cooling to maintain a stable ambient temperature, thus posing minimal heat dissipation challenges. Outdoor equipment primarily relies on passive cooling (natural cooling), which, while offering advantages such as simple structure and reliable operation, is only suitable for low heat flux density conditions. Its application in harsh environments, high heat flux density, or sealed environments is significantly limited.

[0004] Compared to materials like steel and copper alloys, aluminum alloys possess excellent characteristics such as light weight, high specific strength, good machinability, and moderate price. Therefore, outdoor equipment casings often adopt a die-cast aluminum alloy + heat dissipation fin structure to achieve natural heat dissipation. However, it is undeniable that traditional die-cast aluminum alloys suffer from low actual thermal conductivity and low heat dissipation efficiency, which can easily cause a surge in local heat flux density, affecting the equipment's service performance and lifespan. Adding active cooling technologies such as air cooling and liquid cooling is limited by factors such as high energy consumption, complex structure, and increased potential failure points, resulting in limited application. Thermoelectric cooling is small in size and provides rapid cooling, but it suffers from high cost and low efficiency, and is easily limited by key factors in heat dissipation at the hot end, making it only suitable for environments with lower cooling requirements.

[0005] Phase change heat dissipation devices, such as heat pipes and vapor chambers, rapidly transfer heat through the evaporation and condensation of the internal working medium, achieving a thermal conductivity far exceeding that of natural heat dissipation. However, they suffer from susceptibility to environmental conditions and a sharp decrease in heat dissipation efficiency after thermal saturation. Furthermore, both are currently primarily made of copper, resulting in high costs. Traditional aluminum alloy vapor chambers are often designed separately from the radiator, relying on the addition of thermally conductive interface materials to conduct heat. This increases the thermal resistance at the contact interface, negatively impacting thermal conductivity. The aluminum alloy radiator portion is mostly manufactured using die-casting, resulting in low thermal conductivity and limited heat dissipation capacity. Additionally, traditional aluminum alloy vapor chambers often employ grooved wicks, which have high permeability but weak capillary force and poor resistance to gravity, making them unsuitable for the high-efficiency heat dissipation requirements of high-power railway signaling equipment. Summary of the Invention

[0006] The purpose of this invention is to provide a composite heat spreader that improves capillary force at the evaporation end while also having permeability, enhances heat uniformity at the evaporation end and accelerates medium evaporation, accelerates condensation and dripping during medium condensation, and improves the medium's heat transfer rate and thermal conductivity.

[0007] The objective of this invention can be achieved through the following technical solutions: A composite heat exchanger includes a sealed heat dissipation and temperature equalization cavity disposed within the composite heat exchanger. A liquid-absorbing core structure is disposed on the inner bottom surface of the sealed heat dissipation and temperature equalization cavity. The liquid-absorbing core structure includes a first capillary structure and a second capillary structure. The first capillary structure has microgrooves, and a second capillary structure is formed on the bottom of the microgrooves. The second capillary structure is used to balance the capillary force and permeability of the liquid cooling medium during evaporation. The surfaces of the second capillary structure and the first capillary structure connected near the top of the microgrooves are hydrophobic. A third capillary structure is disposed below the upper inner surface of the sealed heat dissipation and temperature equalization cavity. The surface of the third capillary structure is hydrophilic, with the hydrophilic surface facing the hydrophobic surface. A preset liquid cooling medium is stored within the sealed heat dissipation and temperature equalization cavity.

[0008] Furthermore, the thickness of the first capillary structure ranges from 0.2 to 1.5 mm, and the width of the microgroove ranges from 0.1 to 2 mm; the thickness of the third capillary structure ranges from 0.2 to 1.0 mm.

[0009] Further hydrophobic surfaces are those mimicking the papillary structure of lotus leaves.

[0010] Furthermore, the thickness of the second capillary structure ranges from 0.2 to 1.5 mm, and the thickness of the second capillary structure is less than or equal to the thickness of the first capillary structure.

[0011] Furthermore, the composite heat exchange plate includes an upper cover plate and a bottom plate. The bottom inner surface of the upper cover plate is provided with a first cavity, and the upper inner surface of the bottom plate is provided with a second cavity. When the upper cover plate and the lower cover plate are sealed together, the first cavity and the second cavity form the sealed heat dissipation and heat exchange cavity. The first capillary structure is integrally disposed on the inner wall of the second cavity; the third capillary structure is integrally disposed on the inner wall of the first cavity.

[0012] Furthermore, the upper cover plate and the bottom plate are metallurgically welded to form a sealed heat dissipation and temperature equalization cavity, and the liquid suction core is prepared on the inner surface of the second concave cavity by the SLS method (selective laser sintering); Furthermore, a support column is provided between the upper cover plate and the bottom plate. The support column is embedded in the grooves reserved in the upper cover plate and the bottom plate to play a fixed support role.

[0013] Furthermore, the third capillary structure has microgroove capillary features, and the surface of the microgroove capillary features has a flat hydrophilic structure, which makes the surface of the third capillary structure a hydrophilic surface.

[0014] Furthermore, the second capillary structure is a porous structure with a porosity of 40-80% and a pore size of 50-100 μm.

[0015] Furthermore, the contact angle of hydrophilic surfaces is ≤10°, and the contact angle of hydrophobic surfaces is ≥150°.

[0016] Furthermore, the preset liquid cooling medium is acetone, and the liquid filling rate of the sealed heat dissipation and temperature equalization cavity is 25%.

[0017] Another objective of this invention is to provide a method for preparing a composite heat exchanger plate, used to manufacture any of the aforementioned composite heat exchanger plates, comprising the following steps: The sealed heat dissipation and temperature equalization cavity is divided into a first concave cavity and a second concave cavity along its central part. Prepare an upper cover plate and a bottom plate, prepare a first cavity on the upper cover plate, and prepare a second cavity on the bottom plate; A third capillary structure is prepared on the inner surface of the first cavity; A first capillary structure is fabricated on the inner surface of the second cavity, directly opposite the third capillary structure, and a second capillary structure is fabricated on the bottom of the microgroove formed by the first capillary structure. The first and second concave cavities are combined to form a sealed heat dissipation and temperature equalization cavity, and the upper cover plate and the bottom plate outside the sealed heat dissipation and temperature equalization cavity are sealed and connected. A filling port is made for the connected and sealed heat dissipation and heat homogenization cavity. The cavity is then evacuated through the filling port and filled with a preset liquid cooling medium. The filling port is then sealed to complete the preparation of the composite heat homogenization plate.

[0018] Further, the steps of preparing an upper cover plate and a bottom plate, preparing a first cavity on the upper cover plate, and preparing a second cavity on the bottom plate include: A top cover plate and a first cavity of predetermined thickness were prepared using a powder metallurgy method with high thermal conductivity aluminum-based silicon carbide composite materials. A base plate and a second concave cavity of a predetermined thickness are prepared using a precision machining method for aluminum alloy materials.

[0019] Furthermore, a method for preparing a top cover plate of a predetermined thickness using a powder metallurgy method with high thermal conductivity aluminum-based silicon carbide composite materials includes: thoroughly mixing matrix material and reinforcing material powders in an inert atmosphere via high-energy ball milling; transferring the mixture into a mold for cold isostatic pressing to obtain a green blank; and then performing vacuum hot pressing sintering to obtain a sintered blank. The resulting sintered blank is then precision machined to obtain accurate dimensions and shape characteristics.

[0020] The matrix material consists of spherical powder particles of pure aluminum, 2xxx series-AlCuMg, 6xxx series-AlMgSi, and 7xxx series-AlZnMgCu prepared by atomization, with an average particle size ranging from 15 to 45 μm. The reinforcing material is SiC spherical powder particles prepared by carbothermal reduction or chemical vapor deposition, with an average particle size ranging from 5 to 25 μm, added at a ratio of 0.1 to 75 wt% of the matrix material mass. Paraffin oil is added at 0.5 to 1 wt% of the matrix material mass as a binder. During high-energy ball milling, the rotation speed is 300 to 500 rpm, and the milling time is 1 to 2 hours, conducted under high vacuum or argon protection throughout to avoid oxidation. During cold isostatic pressing, the pressure is 200 to 300 MPa, and the holding time is 10 to 15 minutes; the green body must reach at least 75% of the theoretical density. The hot pressing sintering process includes two steps: pre-sintering and effective sintering. The pre-sintering temperature is 350~400℃, and the time is 1~3h, to remove low-boiling-point impurities and binders. The vacuum degree is <10. -2 Pa; the effective sintering temperature range is 400~580℃, the time is 2~8h, the pressure is 30~70MPa, and the vacuum degree is <10 - The sintering temperature is 3Pa to improve the density and overall mechanical properties of the sintered blank, and the final density needs to reach more than 99% of the theoretical density. The maximum effective sintering temperature is generally no higher than 580℃ to avoid significant interfacial reactions between aluminum and silicon carbide particles, which would generate a brittle Al4C3 phase; if the temperature is too low, the sintering density will be insufficient and the mechanical properties will be reduced.

[0021] Furthermore, the step of preparing the third capillary structure on the inner surface of the first cavity includes: The inner surface of the first cavity after cleaning and activation is etched with high-energy laser. During the etching process, the high-energy laser power is 0.5~1.9J / cm², the frequency is 1~10kHz, the scanning speed is 100~300mm / s, and the scanning spacing is 10~50μm. The etching is repeated until the third capillary structure is formed.

[0022] Furthermore, the fabrication of the first capillary structure includes: The inner surface of the second concave cavity after cleaning and activation is etched with a high-energy laser. The high-energy laser power is 0.5~2J / cm², the frequency is 1~10kHz, the scanning speed is 100~300mm / s, and the scanning spacing is 10~50μm. The etching is repeated until the first capillary structure is formed.

[0023] Furthermore, the method for creating the second capillary structure includes: Select coated aluminum alloy particles with an average particle size range of 25~50μm and spread them evenly on the microgrooves of the first capillary structure. The layer thickness is 50~100μm. Preheat the layer to 100~150℃ and use selective laser sintering. After multiple powder spreading and laser sintering processes, a second capillary structure with a thickness range of 0.2~1.5mm and a thickness smaller than that of the first capillary structure is formed.

[0024] Furthermore, the method of combining the first and second concave cavities into a sealed heat dissipation and temperature equalization cavity, and sealing the upper cover plate and bottom plate outside the sealed heat dissipation and temperature equalization cavity, includes: The sealing joint between the top cover plate and the bottom plate is cleaned and activated, and then vacuum diffusion welding is performed. During the vacuum welding process, the surface roughness Ra ≤ 3.2 μm, the effective heating temperature range of the weld is 400~580℃, the pressure is 5~20MPa, the heating time is 0.5~2h, and the vacuum degree is <10. - ³Pa, while simultaneously solidifying and sintering the liquid-absorbing core structure on the base plate to improve strength.

[0025] Furthermore, a filling port is made for the sealed heat dissipation and heat equalization cavity. The cavity is then evacuated and filled with a preset liquid cooling medium through the filling port. The filling port is then sealed to complete the preparation of the composite heat equalization plate. Generally, the filling port is machined when the base plate is machined, which facilitates cleaning in subsequent steps after machining. Alternatively, the filling port is machined after the top cover plate and the base plate are sealed and connected. After machining, the cavity is cleaned, and then a liquid cooling medium, such as acetone, is injected into the cavity after evacuation, accounting for 20-40% of the volume of the sealed heat dissipation and heat equalization cavity.

[0026] The beneficial effects of this invention are: The composite heat spreader of this invention employs a first capillary structure and a second capillary structure at the evaporation end of a sealed heat dissipation and heat equalization cavity. Capillary force facilitates diffusion, evaporation, and heat equalization at the evaporation end. The hydrophobic surface of the first capillary structure promotes bubble detachment and accelerates evaporation. After evaporation, the bubbles encounter the hydrophilic surface of the third capillary structure, which accelerates medium expansion. The third capillary structure accelerates conduction, accelerating bubble condensation and reflux. This achieves a hydrophobic mechanism at the evaporation end (promoting bubble detachment) and a hydrophilic mechanism at the condensation end (accelerating condensation), forming a stable rapid circulation mode of the liquid cooling medium. This reduces the thermal resistance at the evaporation end and the reflux resistance at the condensation end, facilitating reflux and thereby improving the medium's heat transfer rate and thermal conductivity.

[0027] This composite heat spreader is made by heterogeneous vacuum diffusion welding of a high thermal conductivity aluminum-based silicon carbide composite material top cover plate and an aluminum alloy bottom plate. The metallurgical bonding interface has high strength and can effectively reduce the interface thermal resistance, realizing the integrated design of heat dissipation and heat equalization structure, and improving the heat dissipation and heat equalization efficiency.

[0028] In the preparation process of the composite heat spreader plate of this application, compared with the fixing methods such as welding or sintering, the capillary core is directly additively manufactured on the inner surface of the second cavity using the SLS method (selective laser sintering), which realizes the integrated manufacturing of capillary structure and shell, and takes into account the advantages of lightweight, high thermal conductivity and complex structure adaptability.

[0029] The preparation method of this application facilitates the preparation of the liquid-absorbing core and the third capillary structure.

[0030] The composite heat spreader prepared by the method of this application has good overall temperature uniformity, can rapidly diffuse the heat from the heat source at the accumulation point over a large area, has high heat dissipation efficiency, compact structure and high strength, and is suitable for the heat conduction / heat dissipation needs of local heat sources in railway signaling equipment under complex working conditions. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a microscopic schematic diagram of the interior of the composite heat exchanger. Figure 2 This is a schematic diagram of the exterior of the composite heat spreader. Figure 3 This describes the preparation process of a composite heat spreader. In the diagram: 1. First capillary structure; 2. Second capillary structure; 3. Third capillary structure; 4. Sealed heat dissipation and temperature equalization cavity; 5. Top cover plate; 6. Bottom plate; 7. Fins; 8. Support column. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] like Figure 1 As shown, a composite heat exchanger includes a sealed heat dissipation and temperature equalization cavity 4 disposed within the composite heat exchanger. A liquid-absorbing core structure is disposed on the bottom inner surface of the sealed heat dissipation and temperature equalization cavity 4. The liquid-absorbing core structure includes a first capillary structure 1 and a second capillary structure 2. The first capillary structure 1 has microgrooves, and a second capillary structure 2 is formed on the bottom of the microgrooves. The second capillary structure 2 is used to balance the capillary force and permeability of the liquid cooling medium during evaporation. The surfaces of the second capillary structure 2 and the first capillary structure 1 connected near the top of the microgrooves are hydrophobic. A third capillary structure 3 is disposed below the upper inner surface of the sealed heat dissipation and temperature equalization cavity 4. The surface of the third capillary structure 3 is a hydrophilic surface, with the hydrophilic surface facing the hydrophobic surface. The sealed heat dissipation and temperature equalization cavity 4 stores the preset liquid cooling medium.

[0035] See Figure 1 As shown, for ease of illustration of the internal structure of the composite heat exchanger, the sealed heat dissipation and heat equalization cavity 4 in the figure is not drawn in a closed state. When the composite heat exchanger is filled with liquid cooling medium, and the bottom surface of the liquid absorbing core structure is placed on the hot surface for heat equalization, the hydrophobic surface is used to improve the rapid detachment of medium bubbles in the liquid cooling medium during evaporation. Under the hydrophobic effect of the first capillary structure 1, the medium bubbles can be promoted to detach. The upper inner surface of the sealed heat dissipation and heat equalization cavity 4 forms a third capillary structure 3 and a hydrophilic surface to accelerate bubble condensation, making the third capillary structure hydrophilic, which is convenient for falling back after heat dissipation. The second capillary structure 2 balances the capillary force and permeability of the liquid cooling medium during evaporation, making heat absorption more complete and further accelerating evaporation. The circulating arrow indicates that the condensing medium accelerates condensation and reflux, and the medium bubbles quickly detach from the siphon.

[0036] In some embodiments, the thickness of the first capillary structure ranges from 0.2 to 1.5 mm, and the width of the microgrooves ranges from 0.1 to 2 mm. The width of the hydrophobic microgrooves is affected by the shape; the protruding structures are not all rectangular, but can also be conical, trapezoidal, triangular, etc., which can take into account good capillary force and is smaller than the diameter of a typical water droplet in liquid cooling media, facilitating the formation of hydrophobic structures. The thickness of the third capillary structure ranges from 0.2 to 1.0 mm. This size facilitates the formation of the third capillary structure, resulting in good hydrophilicity and facilitating the condensation and fallback of the medium.

[0037] Furthermore, the thickness of the second capillary structure ranges from 0.2 to 1.5 mm, and the thickness of the second capillary structure is less than or equal to the thickness of the first capillary structure. In this way, the second capillary structure 2 does not affect the hydrophobicity of the first capillary structure 1, and enables it to have good permeability and capillary action.

[0038] In some embodiments, the first capillary structure 1 is integrally disposed on the inner wall of the sealed heat dissipation and temperature equalization cavity 4; the third capillary structure 3 is integrally disposed on the inner wall of the sealed heat dissipation and temperature equalization cavity 4. This integral disposal can reduce thermal resistance and improve heat equalization.

[0039] In some embodiments, the second capillary structure 2 is a porous structure with a porosity of 40-80% and a pore size of 50-100 μm. This second capillary structure 2 has good permeability and good capillary action, which can improve heat uniformity.

[0040] In some embodiments, the contact angle of the hydrophilic surface is ≤10°, and the contact angle of the hydrophobic surface is ≥150°. This can accelerate the convection of the medium within the cavity.

[0041] In some application embodiments involving heat dissipation of railway communication signaling equipment components, such as Figure 1 As shown, a composite heat exchanger consists of an upper cover plate 5, a bottom plate 6, a liquid wick, a liquid cooling medium, and support columns 8. The upper cover plate 5 is prepared using powder metallurgy with a high thermal conductivity aluminum-based silicon carbide composite material. The bottom plate 6 is made of aluminum alloy. The upper cover plate 5 and the bottom plate 6 are vacuum heterogeneous diffusion welded to form a sealed heat dissipation and heat exchange cavity 4. The inner surface of the concave cavity of the upper cover plate 5 has a hydrophilic capillary structure, and the composite liquid wick on the inner surface of the concave cavity of the bottom plate 6 has a two-phase capillary structure. The cavity is filled with a liquid cooling medium. The support columns 8 are embedded in the grooves reserved in the upper cover plate 5 and the bottom plate 6, serving a fixed support function. By employing a microgroove-sintered powder composite liquid-absorbing core and other characteristic structural designs, combined with high-energy laser etching, the superhydrophobic effect at the evaporation end (promoting bubble detachment) and the superhydrophilic effect at the condensation end (accelerating condensation and dripping) are achieved, forming a stable two-phase rapid circulation mode of the working fluid. This reduces the thermal resistance at the evaporation end and the reflux resistance at the condensation end, effectively improving the heat transfer rate and thermal conductivity. Furthermore, it exhibits good resistance to impact vibration and fatigue mechanical properties, meeting the heat dissipation requirements of railway communication and signaling equipment devices.

[0042] This invention also provides an embodiment of a method for preparing a composite heat spreader, comprising the following steps: S1. Divide the sealed heat dissipation and temperature equalization cavity 4 into a first concave cavity and a second concave cavity along its middle section. S2. Prepare the upper cover plate 5 and the bottom plate 6. Prepare the first cavity on the upper cover plate 5 and the second cavity on the bottom plate 6. S3. The third capillary structure 3 is prepared on the inner surface of the first concave cavity; S4. The first capillary structure 1 is made on the inner surface of the second cavity, directly opposite the third capillary structure 3, and the second capillary structure 2 is made on the bottom of the microgroove formed by the first capillary structure 1. S5. Combine the first cavity and the second cavity into the sealed heat dissipation and temperature equalization cavity 4, and seal the upper cover plate 5 and the bottom plate 6 outside the sealed heat dissipation and temperature equalization cavity 4.

[0043] Under the current conditions, the composite heat exchanger can be manufactured at a relatively low cost. It is conceivable that a more expensive process could be used to manufacture the composite heat exchanger without disassembling it, such as a combination of 3D printing and high-energy laser.

[0044] In some embodiments, step S2 includes: The upper cover plate 5 and the first cavity of a predetermined thickness were prepared by powder metallurgy of high thermal conductivity aluminum-based silicon carbide composite materials; The base plate 6 and the second cavity, with a preset thickness, are prepared using a precision machining method for aluminum alloy materials. The preset thickness can be appropriately selected based on the processing dimensional requirements. This improves its thermal conductivity and increases its cooling temperature difference.

[0045] Step S3 includes: High-energy laser etching is used on the inner surface of the first cavity after cleaning and activation. During the etching process, the high-energy laser power is 0.5~1.9 J / cm², the frequency is 1~10 kHz, the scanning speed is 100~300 mm / s, and the scanning spacing is 10~50 μm, until a third capillary structure with a thickness ranging from 0.2~1.0 mm is formed. This allows for the rapid fabrication of a third capillary structure with a composite contact angle of less than or equal to 10°.

[0046] The fabrication of the first capillary structure 1 in step S4 includes: The inner surface of the second cavity after cleaning and activation is etched using a high-energy laser. During etching, the high-energy laser power is 0.5~2 J / cm², the frequency is 1~10 kHz, the scanning speed is 100~300 mm / s, and the scanning spacing is 10~50 μm, until a first capillary structure 1 with a thickness ranging from 0.2~1.5 mm is formed. This allows for the rapid fabrication of superhydrophobic surfaces with a contact angle greater than or equal to 150°.

[0047] The method for fabricating the second capillary structure 2 includes: Coated aluminum alloy particles with an average particle size range of 25-50 μm are selected and spread evenly on the microgrooves of the first capillary structure 1, with a layer thickness of 50-100 μm. The layers are preheated to 100-150℃ and selectively laser-sintered. After multiple powder spreading and laser sintering processes, a second capillary structure 2 with a thickness range of 0.2-1.5 mm, smaller than the thickness of the first capillary structure, is formed. This allows for the further fabrication of a second capillary structure 2 with good thermal conductivity, balancing the effects of infiltration and capillary action.

[0048] Step S5 includes: The sealing joint between the upper cover plate 5 and the bottom plate 6 is cleaned and activated, and then vacuum diffusion welding is performed. During the vacuum welding process, the surface roughness Ra ≤ 3.2 μm, the effective heating temperature range of the weld is 400~580℃, the pressure is 5~20MPa, the heating time is 0.5~2h, and the vacuum degree is <10. - ³Pa.

[0049] The aforementioned composite heat spreader can be manufactured not only based on aluminum-based materials, but also based on other similar aluminum-based materials as described below.

[0050] In some embodiments, such as Figure 3 The diagram shows a specific flow chart for the preparation of a composite heat exchanger. Following this flow chart, composite heat exchangers of common volumes are prepared, including an upper cover plate 5, a bottom plate 6, a liquid wick, a liquid cooling medium, and support columns 8. The upper cover plate 5 and the bottom plate 6 are metallurgically welded to form a sealed heat dissipation and heat exchanger cavity 4. The liquid wick is prepared on the inner surface of the second concave cavity using the SLS (Selective Laser Sintering) method. The cavity is filled with liquid cooling medium. The support columns 8 are embedded in the grooves reserved in the upper cover plate 5 and the bottom plate 6, providing a fixed support function.

[0051] The top cover plate 5 is prepared using a powder metallurgy method with high thermal conductivity aluminum-based silicon carbide composite material. The matrix material and reinforcing material powders are thoroughly mixed by high-energy ball milling under an inert atmosphere, then transferred to a mold for cold isostatic pressing to obtain a green blank, followed by vacuum hot pressing sintering to obtain a sintered blank. The resulting sintered blank is precision machined to obtain accurate dimensions and shape characteristics.

[0052] The matrix material consists of spherical powder particles of pure aluminum, 2xxx series-AlCuMg, 6xxx series-AlMgSi, and 7xxx series-AlZnMgCu prepared by atomization, with an average particle size ranging from 15 to 45 μm. The reinforcing material is SiC spherical powder particles prepared by carbothermal reduction or chemical vapor deposition, with an average particle size ranging from 5 to 25 μm, added at a ratio of 0.1 to 75 wt% of the matrix material mass. Paraffin oil is added at 0.5 to 1 wt% of the matrix material mass as a binder. During high-energy ball milling, the rotation speed is 300 to 500 rpm, and the milling time is 1 to 2 hours, conducted under high vacuum or argon protection throughout to avoid oxidation. During cold isostatic pressing, the pressure is 200 to 300 MPa, and the holding time is 10 to 15 minutes; the green body must reach at least 75% of the theoretical density. The hot pressing sintering process includes two steps: pre-sintering and effective sintering. The pre-sintering temperature is 350~400℃, and the time is 1~3h, to remove low-boiling-point impurities and binders. The vacuum degree is <10. -2 Pa; the effective sintering temperature range is 400~580℃, the time is 2~8h, the pressure is 30~70MPa, and the vacuum degree is <10 - The sintering temperature is 3Pa to improve the density and overall mechanical properties of the sintered blank, and the final density needs to reach more than 99% of the theoretical density. The maximum effective sintering temperature is generally no higher than 580℃ to avoid significant interfacial reactions between aluminum and silicon carbide particles, which would generate a brittle Al4C3 phase; if the temperature is too low, the sintering density will be insufficient and the mechanical properties will be reduced.

[0053] like Figure 2 As shown, heat dissipation fins 7 are machined on the outside of the upper cover plate 5 to increase the heat dissipation area and further promote rapid heat dissipation (depending on the actual situation, heat dissipation fins 7 can also be omitted, and the upper cover plate 5 can be attached to the equipment shell for heat dissipation). The surface of the internal cavity of the cleaned and activated condenser end is prepared with a microgroove capillary feature structure using a high-energy laser, with a groove depth ranging from 0.2 to 1.0 mm. During the etching process, the high-energy laser power is 0.5 to 1.9 J / cm², the frequency is 1 to 10 kHz, the scanning speed is 100 to 300 mm / s, and the scanning spacing is 10 to 50 μm. This composite structure is hydrophilic (contact angle ≤ 10°), which can accelerate the cooling and condensation of the high-temperature vaporized working medium; the microgroove structure has low liquid reflux resistance, fast working medium circulation, and a high capillary pumping coefficient, effectively improving its reflux speed. After the above-mentioned strengthening treatment, the thermal conductivity of the top cover plate 5 can reach 180~240 W / (m·K), the thermal diffusion rate can reach 85 mm² / s, and the impact vibration resistance and fatigue performance are improved, which is significantly better than ordinary die-cast aluminum alloy materials.

[0054] The base plate 6 is made of ordinary aluminum alloy using stamping / machining methods, and conventional materials such as 6061 and 6063 can be selected. The inner surface of the evaporation end cavity of the base plate 6 has a microgroove-sintered powder composite wicking structure. After cleaning and activating the surface of the aluminum alloy cavity, a microgroove structure (i.e., the first capillary structure 1) is first prepared using a high-energy laser. This surface has a lotus leaf-like surface papilla hydrophobic composite structure (contact angle ≥150°), with high permeability, which can effectively promote the rapid detachment of medium bubbles. Furthermore, a porous metal structure (second capillary structure 2) is directly prepared on the inner surface of the second cavity using the SLS method (selective laser sintering), which effectively improves capillary force and promotes evaporation. Through the above-mentioned microgroove-sintered powder composite wicking structure, capillary force and permeability can be balanced, and the two work together to significantly improve evaporation efficiency.

[0055] In the preparation of the first capillary structure 1, the high-energy laser power is 0.5~2 J / cm², the frequency is 1~10 kHz, the scanning speed is 100~300 mm / s, the scanning spacing is 10~50 μm, and the microgroove depth ranges from 0.2~1.5 mm. In the preparation of the second capillary structure 2, coated aluminum alloy particles are selected, with the core being eutectic Al-Si or Al-Si-Mg alloy powder (such as Al12Si and AlSi10Mg), and the outer coating being PMMA or conventional pore-forming agents such as NaCl and NH4HCO3, with an average particle size range of 25~50 μm. During additive manufacturing, the outer coating melts or volatilizes to form pores, and the Si element increases the alloy's absorption rate of the laser. In the SLS additive manufacturing process, the preheating temperature of the substrate 6 is 100~150℃, the laser power is 50~200 W, the scanning spacing is 50~100 μm, and the layer thickness is 50~100 μm. After multiple powder spreading and SLS laser sintering processes, a layered structure (second capillary structure 2) is formed on the inner surface of the second cavity using a metallurgical bonding method, with a thickness ranging from 0.2 to 1.5 mm. The above manufacturing process is completed under inert gas protection, followed by removal of residual powder and removal of the base plate 6.

[0056] The liquid cooling medium is selected from low-melting-point, volatile substances such as acetone and ethanol, which will not cause chemical corrosion to the aluminum alloy material. The liquid cooling medium is heated and vaporized at the evaporation end of the bottom plate 6, and rises to the condensation end of the upper cover plate 5, where it condenses into liquid at a lower temperature, releasing the heat absorbed earlier. The condensed liquid returns to the hot end through capillary structure (against gravity) or gravity, and participates in the evaporation and heat absorption cycle again, thereby achieving rapid and uniform heat dissipation from the local heat source. The support column 8 is made of ordinary aluminum alloy and is embedded in the grooves reserved in the upper cover plate 5 and the bottom plate 6. After being pressed, it resists the internal and external pressure difference, prevents the cavity from collapsing, and maintains the unobstructed steam flow channel, assisting in the return flow of the working liquid.

[0057] The upper cover plate 5 (aluminum-based silicon carbide composite material) and the base plate 6 (aluminum alloy) are connected as dissimilar materials using a vacuum diffusion welding method. After the welding surfaces are cleaned and activated using conventional methods, a metallurgical bond is formed by the inter-atomic diffusion of the dissimilar materials under high temperature and pressure (bonding strength reaches over 120 MPa), resulting in good weld strength and surface condition. During the vacuum diffusion welding process, the contact surface roughness Ra ≤ 3.2 μm, the effective heating temperature range is 400~580℃, the pressure is 5~20 MPa, the heating time is 0.5~2 h, and the vacuum degree is <10. - ³Pa. Simultaneously, the sintered core of the base plate 6 undergoes a curing and sintering process, followed by vacuum sintering to remove residual pore-forming agent, forming a high-strength, controllable porous structure. Due to the pressureless molding characteristics of loose-pack sintering, pores are formed by the overlapping of the powder itself, achieving a porosity of 40-80% and a pore size of 50-100μm. The aforementioned cleaning and activation steps involve using conventional methods such as mechanical grinding, sandblasting / shot peening + plasma cleaning, ultrasonic cleaning, laser cleaning + acid and alkali etching, solvent treatment, and coating activation to thoroughly remove surface oil, oxides, dust, and organic matter, and achieve interfacial chemical activation. After welding the upper cover plate 5 to the base plate 6, vacuuming and liquid filling operations are performed, with an optimal filling rate range of 20-40%. The injection port is then sealed, finally completing the preparation of the composite heat exchanger plate. Furthermore, depending on actual requirements, conventional methods can be used for surface anodizing or spraying a heat dissipation and protective coating to improve the wear and corrosion resistance of the heat exchanger plate.

[0058] Test: The prepared composite heat spreader was placed on the surface of the heat source device for a cooling temperature difference test. The surface of the heat source device was 60℃ to 90℃. The thermocouple test method was used to test the surface of the heat source device. It was found that the cooling temperature difference of the composite heat spreader was 30-60℃, which is much greater than the cooling temperature difference of 12℃ of the ADC12 material die-cast aluminum alloy heat sink with the same external dimensions.

[0059] Compared with the prior art, the present invention also has the following significant effects: 1. Compared with the traditional die-cast aluminum alloy heat dissipation structure (around 90 W / (m·K)), this invention adds a certain amount of silicon carbide particles by using powder metallurgy, increasing the thermal conductivity of the aluminum-based silicon carbide composite material of the upper cover plate to 180~240 W / (m·K), resulting in better heat dissipation and improved resistance to impact vibration and fatigue mechanical properties. 2. Compared to traditional powder metallurgy or wire mesh / grooved wicks, this invention employs a microgrooved-sintered powder composite wick design, combined with high-energy laser etching, to achieve hydrophobicity at the evaporation end (promoting bubble detachment) and hydrophilicity at the condensation end (accelerating condensation). This forms a stable rapid circulation mode for the liquid cooling medium, reducing the thermal resistance at the evaporation end and the reflux resistance at the condensation end. The heat transfer limit is increased to over 200 W / cm², which is about 40% higher than that of traditional aluminum-based sintered wicks. 3. This invention utilizes the SLS method (selective laser sintering) to directly additively manufacture a porous metal structure (second capillary structure 2) on the inner surface of the concave cavity of the base plate 6. Compared with fixing methods such as welding or sintering, the metallurgical bonding interface has high strength and can effectively reduce the interface thermal resistance, realizing the integrated manufacturing of capillary structure-shell, and taking into account the advantages of lightweight, high thermal conductivity and compatibility with complex structures, and high forming efficiency. 4. This invention adopts an integrated design of heat dissipation and heat-spreading structure. By using a heterogeneous vacuum diffusion welding method, the heat dissipation structure (aluminum alloy) and the heat-spreading structure (high thermal conductivity aluminum-based silicon carbide material) are metallurgically combined. This makes the composite heat dissipation plate have the advantages of high thermal conductivity and good heat dissipation performance of aluminum-based silicon carbide material, as well as the advantages of good machinability and moderate cost of aluminum alloy. The overall heat dissipation and temperature uniformity efficiency is high, and the bonding interface strength is high, which can realize long-life application in harsh environments.

[0060] In one specific embodiment, the first step is: preparation and processing of the upper cover plate 5. First, pure aluminum spherical powder with an average particle size of 20 μm and SiC powder with an average particle size of 10 μm were mixed uniformly by high-energy ball milling. The SiC particle material addition ratio was 30 wt%, and the paraffin oil addition ratio was 0.5 wt%. The ball milling speed was 300 rpm, the ball milling time was 1 h, and the protective gas was argon. The powder was then cold isostatically pressed into a green body at a pressure of 200 MPa for 15 min, and the green body density was 75% of the theoretical density. Then, hot pressing sintering was performed at a pre-sintering temperature range of 350~400℃ for 1 h to remove low-boiling-point impurities and binders. The vacuum degree was <10. - 2Pa; effective sintering temperature range is 400~580℃, time is 4h, pressure is 70MPa, vacuum degree is <10 - ³Pa was used to improve the density and overall mechanical properties of the sintered blank. Heat dissipation fins 7 and internal cavities were conventionally machined on the exterior of the upper cover plate 5 sintered blank. The surface of the internal cavity was thoroughly cleaned using conventional methods such as organic solvents, acid pickling, and plasma surface treatment to remove surface oil, oxides, water stains, dust, and organic impurities, achieving interfacial chemical activation. A superhydrophilic microgroove capillary feature structure was fabricated using a high-energy laser, with a contact angle of 8° and a groove depth range of 0.2 mm. During etching, the high-energy laser power was 8 J / cm², the scanning speed was 100 mm / s, and the scanning interval was 20 μm.

[0061] Step 2: Preparation and processing of base plate 6 The base plate 6 is made of 6061 aluminum alloy using a stamping method. The inner surface of the evaporation end cavity of the base plate 6 has a microgroove-sintered powder composite wicking structure. After cleaning and activating the inner cavity, a high-energy laser is first used to fabricate the microgroove structure (i.e., the first capillary structure 1). This surface has a superhydrophobic composite structure mimicking the papillae of a lotus leaf, with a contact angle of 153°. During the process, the high-energy laser power is 0.8 J / cm², the frequency is 2 kHz, the scanning speed is 100 mm / s, and the microgroove depth range is 0.3 mm. Further, a porous metal structure (the second capillary structure 2) is directly fabricated on the inner surface of the second cavity using the SLS method (selective laser sintering). During this process, an outer coating layer of PMMA and a core layer of Al are used. 12 The Si spherical powder particles have an average particle size of 25 μm. The preheating temperature of the substrate 6 is 100℃, the laser power is 80W, the scanning spacing is 50 μm, and the layer thickness is 60 μm, resulting in a total thickness of 0.2 mm for the second capillary structure 2. The above manufacturing process is completed under inert gas protection, followed by removal of residual powder and removal of the substrate 6.

[0062] Step 3: Vacuum diffusion welding of the upper cover plate 5 and the bottom plate 6 First, the contact surface between the upper cover plate 5 and the base plate 6 is ground to a roughness of Ra 1.6 μm. Conventional methods such as organic solvents, pickling, and plasma surface treatment are used to thoroughly remove surface oil, oxides, water stains, dust, and organic impurities, achieving interface chemical activation. During vacuum diffusion welding, the effective heating temperature range is 400~580℃, the pressure is 7MPa, the heating time is 2h, and the vacuum degree is <10. - ³Pa. After vacuum diffusion welding, the interface between the upper cover plate 5 and the bottom plate 6 achieves heterogeneous metallurgical bonding with a bonding strength of 120MPa. The sintered core of the bottom plate 6 is simultaneously cured and sintered, achieving a porosity of 40% and an average pore size of 55μm.

[0063] Step 4: Filling, sealing and grouting Vacuuming and liquid filling operations were performed, with acetone as the liquid cooling medium and a filling rate of 25%. The injection port was then sealed to complete the preparation of the composite heat exchanger.

[0064] Using the same test method as above, the temperature difference of the composite heat exchanger is 43℃.

[0065] In another specific embodiment, the first step is: the preparation and processing of the upper cover plate 5.

[0066] First, spherical 6063 aluminum alloy powder with an average particle size of 35 μm and SiC powder with an average particle size of 20 μm were mixed uniformly by high-energy ball milling. The proportion of SiC particles added was 60 wt%, and the proportion of paraffin oil added was 1.0 wt%. The ball milling speed was 400 rpm, the ball milling time was 1.5 h, and the protective gas was argon. The powder was then cold isostatically pressed into a green compact at a pressure of 250 MPa for 10 min, and the green compact density was 75% of the theoretical density. Then, hot pressing sintering was performed at a pre-sintering temperature range of 350~400℃ for 2 h to remove low-boiling-point impurities and binders. The vacuum degree was <10. - 2Pa; effective sintering temperature range is 400~580℃, time is 6h, pressure is 50MPa, vacuum degree is <10 - ³Pa was used to improve the density and overall mechanical properties of the sintered blank. The outer shell plane and internal cavity of the upper cover plate 5 sintered blank were conventionally machined. The surface of the internal cavity was thoroughly cleaned using conventional methods such as organic solvents, acid pickling, and plasma surface treatment to remove surface oil, oxides, water stains, dust, and organic impurities, and to achieve interfacial chemical activation. A superhydrophilic microgroove capillary feature structure was fabricated using a high-energy laser, with a contact angle of 5° and a groove depth range of 0.4 mm. During the etching process, the high-energy laser power was 1.5 J / cm², the scanning speed was 200 mm / s, and the scanning interval was 30 μm.

[0067] Step 2: Preparation and processing of base plate 6 The base plate 6 is made of 6063 aluminum alloy using a stamping method. The inner surface of the evaporation end cavity of the base plate 6 has a microgroove-sintered powder composite wicking structure. After cleaning and activating the inner cavity, a high-energy laser is first used to prepare the microgroove structure (i.e., the first capillary structure 1). This surface has a superhydrophobic composite structure mimicking the papillae of a lotus leaf, with a contact angle of 159°. During the process, the high-energy laser power is 2 J / cm², the frequency is 5 kHz, the scanning speed is 200 mm / s, and the microgroove depth range is 0.5 mm. Further, a porous metal structure (the second capillary structure 2) is directly prepared on the inner surface of the second cavity using the SLS method (selective laser sintering). During this process, an outer coating layer of NH₄HCO₃ + a core of AlSi is selected. 10 Mg spherical powder particles with an average particle size of 45 μm were used. The preheating temperature of the base plate 6 was 130℃, the laser power was 150W, the scanning spacing was 80 μm, and the layer thickness was 100 μm, resulting in a total thickness of 0.5 mm for the second capillary structure 2. The above manufacturing process was completed under inert gas protection, followed by removal of residual powder and removal of the base plate 6.

[0068] Step 3: Vacuum diffusion welding of the upper cover plate 5 and the bottom plate 6 First, the contact surface between the upper cover plate 5 and the base plate 6 is ground to a roughness of Ra 1.6 μm. Conventional methods such as organic solvents, pickling, and plasma surface treatment are used to thoroughly remove surface oil, oxides, water stains, dust, and organic impurities, achieving interface chemical activation. During vacuum diffusion welding, the effective heating temperature range is 400~580℃, the pressure is 15MPa, the heating time is 1h, and the vacuum degree is <10. - ³Pa. After vacuum diffusion welding, the interface between the upper cover plate 5 and the bottom plate 6 achieves heterogeneous metallurgical bonding, with a bonding strength of 132MPa. The sintered core of the bottom plate 6 is simultaneously cured and sintered, achieving a porosity of 60% and an average pore size of 90μm.

[0069] Step 4: Filling, sealing and grouting Vacuuming and liquid filling operations were performed, with acetone as the liquid cooling medium and a filling rate of 40%. The injection port was then sealed to complete the preparation of the composite heat exchanger.

[0070] Using the same test method as above, the temperature difference of the composite heat exchanger is 47℃.

[0071] It should be noted that the terms "first," "second," etc., used in this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein.

[0072] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0073] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A composite heat spreader, characterized in that, The system includes a sealed heat dissipation and temperature equalization cavity (4) disposed within a composite heat equalization plate. A liquid-absorbing core structure is provided on the bottom inner surface of the sealed heat dissipation and temperature equalization cavity (4). The liquid-absorbing core structure includes a first capillary structure (1) and a second capillary structure (2). The first capillary structure (1) has microgrooves. A second capillary structure (2) is formed on the bottom of the microgrooves. The second capillary structure (2) is used to balance the capillary force and permeability of the liquid cooling medium during evaporation. The surfaces of the second capillary structure (2) and the first capillary structure (1) connected near the top of the microgrooves are hydrophobic. A third capillary structure (3) is disposed below the upper inner surface of the sealed heat dissipation and temperature equalization cavity (4). The surface of the third capillary structure (3) is hydrophilic. The hydrophilic surface is positioned opposite the hydrophobic surface. The sealed heat dissipation and temperature equalization cavity (4) stores the preset liquid cooling medium.

2. The composite heat spreader according to claim 1, characterized in that, The composite heat exchange plate includes an upper cover plate (5) and a bottom plate (6). The bottom inner surface of the upper cover plate (5) is provided with a first cavity, and the upper inner surface of the bottom plate (6) is provided with a second cavity. When the upper cover plate (5) and the lower cover plate are sealed together, the first cavity and the second cavity form the sealed heat dissipation and heat exchange cavity (4). The first capillary structure (1) is integrally disposed on the inner wall of the second cavity; the third capillary structure (3) is integrally disposed on the inner wall of the first cavity.

3. A composite heat spreader according to claim 1, characterized in that, The second capillary structure (2) is a porous structure with a porosity of 40-80% and a pore size of 50-100μm.

4. A composite heat spreader according to claim 1, characterized in that, The contact angle of the hydrophilic surface is ≤10°, and the contact angle of the hydrophobic surface is ≥150°.

5. A method for preparing a composite heat spreader, characterized in that, The method for manufacturing a composite heat exchange plate according to any one of claims 1-4 includes the following steps: The sealed heat dissipation and temperature equalization cavity (4) is divided into a first concave cavity and a second concave cavity along the middle part; Prepare an upper cover plate (5) and a bottom plate (6), prepare the first cavity on the upper cover plate (5), and prepare the second cavity on the bottom plate (6); The third capillary structure (3) is prepared on the inner surface of the first cavity. The first capillary structure (1) is made on the inner surface of the second cavity, directly opposite the third capillary structure (3), and the second capillary structure (2) is made on the bottom of the microgroove formed by the first capillary structure (1). The first cavity and the second cavity are combined to form the sealed heat dissipation and temperature equalization cavity (4), and the upper cover plate (5) and the bottom plate (6) outside the sealed heat dissipation and temperature equalization cavity (4) are sealed and connected. Make a filling port for the connected sealed heat dissipation and heat equalization cavity (4), evacuate the sealed heat dissipation and heat equalization cavity (4) through the filling port and fill it with a preset liquid cooling medium, seal the filling port and complete the preparation of the composite heat equalization plate.

6. The method for preparing a composite heat spreader according to claim 5, characterized in that, The steps of preparing the upper cover plate (5) and the bottom plate (6), preparing the first cavity on the upper cover plate (5), and preparing the second cavity on the bottom plate (6) include: A top cover plate (5) and a first cavity of a predetermined thickness were prepared by powder metallurgy of high thermal conductivity aluminum-based silicon carbide composite materials; A base plate (6) and a second cavity of a predetermined thickness are prepared by precision machining of aluminum alloy materials.

7. The method for preparing a composite heat spreader according to claim 6, characterized in that, The step of preparing the third capillary structure (3) on the inner surface of the first cavity includes: High-energy laser etching is used on the inner surface of the first cavity after cleaning and activation. During the etching process, the high-energy laser power is 0.5~1.9J / cm², the frequency is 1~10kHz, the scanning speed is 100~300mm / s, and the scanning spacing is 10~50μm, until a third capillary structure with a thickness range of 0.2~1.0mm is formed.

8. The method for preparing a composite heat spreader according to claim 7, characterized in that, The fabrication of the first capillary structure (1) includes: The inner surface of the second cavity after cleaning and activation is etched with high-energy laser. The high-energy laser power is 0.5~2J / cm², the frequency is 1~10kHz, the scanning speed is 100~300mm / s, and the scanning spacing is 10~50μm, until a first capillary structure with a thickness range of 0.2~1.5mm is formed.

9. The method for preparing a composite heat spreader according to claim 8, characterized in that, The method for fabricating the second capillary structure (2) includes: Select coated aluminum alloy particles with an average particle size range of 25~50μm and spread them evenly on the microgrooves of the first capillary structure (1). The layer thickness is 50~100μm. Preheat the layer to 100~150℃ and use selective laser sintering. After multiple powder spreading and laser sintering, a second capillary structure with a thickness range of 0.2~1.5mm and a thickness smaller than that of the first capillary structure (1) is formed.

10. The method for preparing a composite heat spreader according to claim 9, characterized in that, The method of combining the first cavity and the second cavity into the sealed heat dissipation and temperature equalization cavity (4), and sealing the upper cover plate (5) and the bottom plate (6) outside the sealed heat dissipation and temperature equalization cavity (4) includes: The sealing joint between the upper cover plate (5) and the bottom plate (6) is cleaned and activated, and vacuum diffusion welding is performed. During the vacuum welding process, the surface roughness Ra ≤ 3.2 μm, the effective heating temperature range of the welding joint is 400~580℃, the pressure is 5~20MPa, the heating time is 0.5~2h, and the vacuum degree is <10. - ³Pa, while simultaneously achieving solidification and sintering of the liquid-absorbing core structure on the base plate (6).

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