An extremely thin capillary structure, a preparation method thereof and an extremely thin vapor chamber

Abstract

The present application relates to the technical field of heat uniform devices, and specifically discloses an extremely thin capillary structure, a preparation method thereof and an extremely thin heat uniform plate. The extremely thin capillary structure comprises a plate with a thickness T of 5-60 microns, and the front and back surfaces of the plate both contain parallel capillary grooves with a depth of 10-90%T, a width of 50-100%T and a spacing of 50-300%T. The included angle of the capillary grooves on the two surfaces is 0-90 degrees. A through hole is further provided, with a hole diameter of 40-100%T and a hole spacing of 80-300%T. The extremely thin heat uniform plate comprises the above extremely thin heat uniform plate, an upper cover plate, a lower cover plate and a water injection port, and the upper cover plate is provided with a support column. The present application solves the problems of the prior art, such as thick capillary structure, large steam flow resistance, low liquid return efficiency, poor capillary structure adaptability and unreasonable structure design, and realizes the preparation of a high-performance extremely thin heat uniform plate with a thickness of less than 0.3 mm.

Description

Technical Field

[0001] This invention relates to the field of heat dissipation device technology, and in particular to an ultra-thin capillary structure and its preparation method, as well as an ultra-thin heat dissipation plate. Background Technology

[0002] With the rapid development of electronic devices towards miniaturization and high integration, especially driven by applications such as 5G / 6G communication, AI terminals, and foldable screen devices, the heat flux density of chips has significantly increased, placing more stringent demands on the thinner, lighter, and more efficient thermal management systems. Vapor chambers (VCs), as a mainstream two-phase high-efficiency heat transfer device, achieve rapid temperature homogenization through working fluid evaporation—vapor transport—condensation—capillary reflux. Their core performance depends on the design and fabrication of their internal capillary structure. The thickness and form of the capillary structure directly determine the overall thickness and heat dissipation efficiency of the vapor chamber. The key lies in balancing capillary force, flow resistance, and thickness compatibility to meet the heat dissipation requirements of ultra-thin, high-power, and high-density integrated electronic devices.

[0003] Existing heat spreader capillary structures mainly include wire mesh type, powder sintering type, single groove type, and composite structure type: 1. The thickness of wire mesh / sintered capillary core is usually ≥60μm, which occupies a large cavity space, making it difficult to reduce the total thickness of the heat spreader to below 300μm, and also resulting in high flow resistance and limited reflux efficiency; 2. The single-sided groove structure can only provide capillary force on one side. After being bonded to the upper and lower cover plates, the liquid phase channel is singular, and the capillary driving force is significantly reduced after ultra-thinning. 3. Conventional ultrathin VC has overlapping gas-liquid channels inside, and the steam resistance and water resistance restrict each other, making it difficult to achieve both low temperature difference and high heat transfer limit. 4. Existing ultrathin capillary structures mostly use a single material and a single arrangement, which has poor adaptability and lacks a gas-liquid synergistic transport mechanism assisted by through holes. After extreme thinning, they are prone to drying out and a surge in thermal resistance.

[0004] In existing technologies, the capillary structure of heat spreaders often employs a multi-layer design or a single-surface groove structure. For example, Chinese invention patent CN 112802810 B discloses a heat spreader that uses a multi-layer design connecting a first capillary structure, a second capillary structure, and a central capillary structure. The central capillary structure reduces the resistance to backflow of the working fluid. However, this structural design is complex, and the stacking of multiple capillaries makes it difficult to reduce the overall thickness, failing to meet the requirements for ultra-thinness. In the research of ultra-thin heat spreaders, relevant literature (such as "Manufacturing and Performance Research of Ultra-thin Heat Spreaders Based on Vapor-Liquid Composite Channels") proposes using copper braided wire mesh and bundled braided fibers stacked and sintered to form a liquid-absorbing core structure. Combined with alkaline corrosion process to optimize liquid transport performance, a heat spreader with a thickness of 0.55 mm is prepared. However, this liquid-absorbing core structure has a large thickness, and the sintering process is complex, making it difficult to further break through the thickness limit. In terms of capillary structure fabrication processes, existing technologies mostly employ laser processing of groove structures to enhance capillary performance. For example, in the study "Ultrafast Laser-Induced Periodic Structure on Groove Surface to Enhance Capillary Diffusion Performance", a picosecond laser was used to prepare V-shaped microgrooves on a copper surface, and the capillary diffusion performance was enhanced by inducing periodic surface structures. However, this technology only targets single-surface grooves and does not involve the composite design of double-sided cross grooves and through holes. There is still room for improvement in capillary force and vapor flow efficiency.

[0005] Existing solutions have the following problems: Existing capillary structures are mostly single-layer or multi-layer stacked designs, with thicknesses generally exceeding 60μm, making it difficult to meet the fabrication requirements of ultra-thin vapor chambers (100μm~300μm). Furthermore, thinning can easily lead to insufficient capillary force and poor liquid reflux. Existing grooved capillary structures are mostly single-surface designs with limited capillary force and lack effective through-hole structures, resulting in high vapor flow resistance and low liquid reflux efficiency, affecting the heat dissipation performance of the vapor chamber. Existing capillary structures are mostly adapted to single materials, and the fabrication process is complex, making it difficult to flexibly adjust different materials and different groove parameters (spacing, cross-section, angle), resulting in insufficient adaptability and practicality. The connection between the upper and lower cover plates and the capillary structures of existing vapor chambers is unstable, with uneven thickness distribution and poor sealing performance, preventing further reduction in the overall thickness of the vapor chamber and affecting heat dissipation efficiency.

[0006] In summary, existing capillary structures are mostly single-spacing and single-section forms, and have a limited range of applicable materials. They are difficult to meet the comprehensive requirements of ultra-thinness, high capillary force, and low resistance, which means that heat spreaders cannot achieve both ultra-thin thickness and excellent heat dissipation performance at the same time, thus limiting their application in miniaturized electronic devices. Summary of the Invention

[0007] In view of this, the present invention provides an ultra-thin capillary structure and its preparation method, as well as an ultra-thin heat spreader, to solve the problems of existing capillary structures being difficult to further thin, having high steam flow resistance, low liquid reflux efficiency, poor capillary structure adaptability, and unreasonable structural design.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: An ultrathin capillary structure comprising a plate having a thickness T = 5~60 μm; The plate has parallel capillary grooves on both the front and back sides, and the groove angle between the capillary grooves on the front and the capillary grooves on the back is 0~90°. The depth of the capillary grooves on the front and the capillary grooves on the back are independently 10~90%T, the width is independently 50~100%T, and the spacing between adjacent capillary grooves is independently 50~300%T. The capillary groove is provided with several through holes, the diameter of which is 40~100%T and the spacing between which is 80~300T.

[0009] Preferably, the cross-sectional shapes of the capillary grooves on the front and the capillary grooves on the back are independent, including rectangular, trapezoidal, semi-circular, U-shaped and triangular.

[0010] Preferably, the inner surfaces of the capillary grooves on the front and back sides independently contain submicron and / or nanostructures, wherein the submicron and nanostructures independently include one or more of the following: nodular structure, corrugated structure, granular structure and villous structure.

[0011] Preferably, the capillary grooves on the front and the capillary grooves on the back are arranged independently with equal spacing or with variable spacing. The variable spacing arrangement is a gradient change.

[0012] Preferably, the material of the plate includes copper, oxygen-free copper, copper alloy, stainless steel, aluminum alloy, titanium alloy, copper-steel composite material, PI, PE, PET or PC.

[0013] Another object of the present invention is to provide a method for preparing an extremely thin capillary structure, comprising the following steps: Grooves and through-holes are fabricated on a plate using laser, stamping, or etching methods to obtain an extremely thin capillary structure; The laser method includes pulsed lasers, which include femtosecond pulsed lasers, picosecond pulsed lasers, and nanosecond pulsed lasers.

[0014] Another object of the present invention is to provide an ultrathin heat spreader, the ultrathin heat spreader comprising an ultrathin capillary structure, an upper cover plate, a lower cover plate and a water inlet; The upper cover plate is provided with support columns; The extremely thin capillary structure is the aforementioned extremely thin capillary structure.

[0015] Preferably, the lower cover plate is provided with a pressing structure, the depth of which is equal to or less than the thickness of the ultra-thin capillary structure; the upper cover plate and the lower cover plate form a sealed cavity, the ultra-thin capillary structure is located within the pressing structure of the lower cover plate, and the ultra-thin capillary structure is in contact with the lower cover plate.

[0016] Preferably, the thickness of the ultrathin heat spreader plate is H=100~300μm, the thickness of the upper cover plate is hs=10~15%H, the thickness of the lower cover plate is hx=10~15%H, the thickness of the ultrathin capillary structure is hm=T=5~20%H, and the thickness of the hollow cavity in the sealed cavity is hk=50~75%H.

[0017] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects: 1. Extremely thin capillary structure with excellent performance: The thickness of the capillary structure is reduced to 5~200μm, breaking through the thickness limit of existing technologies. At the same time, the double-sided cross-groove design maintains dual capillary forces. Combined with the bottom through-hole structure, the steam resistance and water resistance are significantly reduced, achieving comprehensive performance of extremely thin thickness, low temperature difference and high Qmax, thus solving the contradiction between capillary structure thinning and performance improvement.

[0018] 2. Wide adaptability and flexible process: The capillary structure can be adapted to a variety of materials such as metals and polymers. The groove parameters (spacing, cross-section, angle) can be flexibly adjusted. The manufacturing process can use a variety of methods such as stamping, etching, and laser, which can be adapted to different application scenarios and production cost requirements, making it highly practical.

[0019] 3. Thin and lightweight heat spreader with a stable structure: The thickness of the ultra-thin heat spreader is controlled at 100~300μm with a reasonable thickness distribution. The connection between the upper and lower cover plates and the capillary structure is stable and the sealing performance is excellent. It not only ensures the overall structural strength, but also leaves enough space for steam circulation. The heat dissipation efficiency is outstanding and can meet the heat dissipation requirements of miniaturized electronic devices.

[0020] 4. Simple manufacturing process and controllable cost: Whether it is a capillary structure or a heat spreader, the manufacturing process is simple and does not require complex multi-layer stacking or sintering processes. Laser, stamping, etching and other processes are mature and can achieve large-scale production and reduce production costs. Attached Figure Description

[0021] 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 only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0022] Figure 1: A schematic diagram of the cross-sectional structure of the ultrathin capillary structure of this invention; Figure 2 : A three-dimensional structural diagram of the ultra-thin capillary structure of this invention; Figure 3 : A schematic diagram of the cross-sectional structure of the ultra-thin heat spreader of the present invention; Figure 4 : A three-dimensional structural diagram of the ultra-thin heat spreader of the present invention; Figure 5 : A schematic diagram of the overall structure of the ultra-thin heat spreader of this invention; Figure 6 : A side view of the ultra-thin heat spreader of the present invention; Among them: 1-extremely thin capillary structure, 2-capillary groove on the front, 3-capillary groove on the back, 4-through hole, 5-upper cover plate, 6-support column, 7-lower cover plate, 8-downward pressure structure, 9-water inlet, 10-sealed cavity, 11-cavity. Detailed Implementation

[0023] This invention provides an ultrathin capillary structure, the cross-sectional structure of which is shown in the figure below. Figure 1 As shown in the diagram, the three-dimensional structure is as follows: Figure 2 As shown in the figure, 1 is an ultra-thin capillary structure, 2 is the capillary groove on the front, 3 is the capillary groove on the back, and 4 is a through hole.

[0024] In this invention, the ultrathin capillary structure includes a plate with a thickness T of 5~60μm, specifically 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, or 55μm.

[0025] In this invention, the front and back sides of the plate are provided with parallel capillary grooves, and the groove angle between the capillary grooves on the front side and the capillary grooves on the back side is 0~90°, specifically 15°, 30°, 45°, 60°, and 75°.

[0026] In this invention, the depth of the capillary grooves on the front and the back are independently 10-90%T, specifically 20%T, 30%T, 40%T, 50%T, 60%T, 70%T, and 80%T; the width is independently 50-100%T, specifically 60%T, 70%T, 80%T, and 90%T; and the spacing between adjacent capillary grooves is independently 50-300%T, specifically 80%T, 100%T, 120%T, 150%T, 180%T, 200%T, 220%T, 250%T, and 280%T.

[0027] In this invention, the capillary groove is provided with a plurality of through holes, the diameter of which is independently 40~100%T, specifically 50%T, 60%T, 70%T, 80%T, or 90%T; the hole spacing is 80~300T%, specifically 100%T, 120%T, 150%T, 180%T, 200%T, 220%T, 250%T, or 280%T.

[0028] In this invention, the shape of the through hole includes circular and / or elliptical.

[0029] In this invention, the cross-sectional shapes of the capillary grooves on the front and the capillary grooves on the back are independently rectangular, trapezoidal, semi-circular, U-shaped, and triangular.

[0030] In this invention, the inner surfaces of the capillary grooves on the front and back sides independently contain submicron and / or nanostructures, and the submicron and nanostructures independently include one or more of the following: nodular structure, corrugated structure, granular structure and villous structure.

[0031] In this invention, the capillary grooves on the front and the capillary grooves on the back are independently arranged with equal spacing or with varying spacing; the varying spacing arrangement is a gradient change.

[0032] In this invention, the material of the plate includes copper, oxygen-free copper, copper alloy, stainless steel, aluminum alloy, titanium alloy, copper-steel composite material, PI, PE, PET or PC.

[0033] This invention also provides a method for preparing an extremely thin capillary structure, comprising the following steps: Grooves and through holes are fabricated on a plate using laser, stamping, or etching methods to obtain an extremely thin capillary structure.

[0034] In this invention, the laser method includes pulsed laser, which includes femtosecond pulsed laser, picosecond pulsed laser and nanosecond pulsed laser.

[0035] The present invention also provides an ultra-thin heat spreader, the cross-sectional structure of which is shown in the figure below. Figure 3 As shown in the diagram, the three-dimensional structure is as follows: Figure 4 As shown in the diagram, the overall structure is as follows: Figure 5 As shown, the side view diagram is as follows Figure 6 As shown in the figure, 1 is an ultra-thin capillary structure, 2 is the capillary groove on the front, 3 is the capillary groove on the back, 4 is a through hole, 5 is an upper cover plate, 6 is a support column, 7 is a lower cover plate, 8 is a pressing structure, 9 is a water inlet, 10 is a sealed cavity, and 11 is a cavity; the ultra-thin heat spreader includes an ultra-thin capillary structure, an upper cover plate, a lower cover plate, and a water inlet; the ultra-thin capillary structure is the aforementioned ultra-thin capillary structure.

[0036] In this invention, the upper cover plate is provided with support columns; In this invention, the lower cover plate is provided with a pressing structure, the depth of which is equal to or less than the thickness of the ultra-thin capillary structure; the upper cover plate and the lower cover plate form a sealed cavity, the ultra-thin capillary structure is located inside the pressing structure of the lower cover plate, and the ultra-thin capillary structure is in contact with the lower cover plate.

[0037] In this invention, the ultrathin capillary structure forms a cavity with the upper cover plate.

[0038] In this invention, the thickness H of the ultra-thin heat spreader is 100~300μm, specifically 120μm, 150μm, 180μm, 200μm, 220μm, 250μm, or 280μm; the thickness hs of the upper cover plate is 10~15%H, specifically 11%H, 12%H, 13%H, or 14%H; and the thickness hx of the lower cover plate is 10~15%H, specifically 11%H. H, 12%H, 13%H, 14%H; ultra-thin capillary structure hm=5~20%H, specifically 8%H, 10%H, 12%H, 14%H, 15%H, 16%H, 18%H; thickness of the cavity in the sealed cavity hk=50~75%H, specifically 55%H, 58%H, 60%H, 62%H, 64%H, 65%H, 66%H, 68%H, 70%H.

[0039] In this invention, the upper and lower cover plates of the ultra-thin heat spreader are preferably made of the same material as the ultra-thin capillary structure; wherein, the heat spreader made of metal material is preferably sealed by laser welding process, and the heat spreader made of polymer material is preferably sealed by thermal connection method.

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0041] Example 1

[0042] The fabrication of an ultra-thin capillary structure (rectangular grooves with equal spacing) in stainless steel is as follows: 1. Material selection: Stainless steel foil with a thickness of T=50μm is selected as the plate. Stainless steel has excellent strength and processing performance, which is suitable for the heat dissipation requirements of metal heat sinks.

[0043] 2. Groove preparation: Using picosecond pulsed laser processing, horizontally parallel rectangular grooves are processed on the front side of the stainless steel foil. The groove depth is 40%T (i.e., 20μm), the width is 80%T (i.e., 40μm), and the groove spacing is 200%T (i.e., 100μm). On the back side of the stainless steel foil, parallel rectangular grooves perpendicular to the capillary grooves on the front side are processed. The intersection angle between the front and back grooves is 90°. The depth, width, and spacing of the back grooves are consistent with those on the front side, forming a double-sided intersecting groove structure.

[0044] 3. Through-hole preparation: Picosecond pulsed laser is used to process regularly arranged circular through-holes at the bottom of the front groove. The diameter of the through-hole is 100%T (i.e., 50μm) and the spacing between the holes is 300%T (i.e., 150μm). The through-holes penetrate the entire capillary structure to ensure that steam and liquid can flow freely.

[0045] 4. Surface treatment: Laser micromachining is performed on the surface around the groove through hole to form a nano-wave structure, which enhances the capillary adsorption capacity; then the entire capillary structure is cleaned and dried to remove processing residues and obtain the finished ultra-thin capillary structure.

[0046] The capillary structure prepared in this embodiment has a thickness of only 50μm. The double-sided intersecting rectangular grooves provide dual capillary forces, and the through-hole structure reduces steam resistance and water resistance. Its capillary force is improved, and the steam resistance is reduced compared with the traditional single-groove capillary structure. This achieves a temperature difference reduction of 2℃ and a Qmax of 20W, which significantly improves the overall performance of the heat spreader.

[0047] The preparation of an ultra-thin vapor chamber made of stainless steel is as follows: 1. Cover plate preparation: Stainless steel is selected as the base material for the upper and lower cover plates. The overall thickness of the heat spreader is H=280μm, of which the thickness of the upper cover plate is hs=15%H (42μm), the thickness of the lower cover plate is hs=15%H (42μm), the thickness of the capillary structure is hm=18%H (50μm), and the thickness of the cavity is hk=52%H (146μm). An array of support columns is processed on the inner side of the upper cover plate. The height of the support columns is the same as the thickness of the cavity (146μm) to enhance the compressive strength of the heat spreader. A pressing structure is processed on the inner side of the lower cover plate. The recess depth is 50μm (the same as the thickness of the capillary structure) to place the capillary structure.

[0048] 2. Capillary structure fixation: The stainless steel capillary structure prepared above is fixed in the lower pressing structure of the lower cover plate by using fiber laser welding encapsulation method, ensuring that the capillary structure and the lower cover plate are tightly fitted without gaps, thereby improving heat conduction efficiency.

[0049] 3. Cavity sealing: Fiber laser welding is used to align the upper and lower cover plates and weld them together to form a sealed cavity. During the welding process, the weld formation and quality are controlled to prevent air leakage from the sealed cavity and ensure the sealing performance of the heat spreader.

[0050] 4. Water Injection and Vacuuming: Weld a water injection pipe to the reserved interface (water injection port) of the sealed cavity, and inject deionized water into the cavity as the working medium through the water injection pipe, with the injection volume being 35% of the cavity volume; then perform a first evacuation process to initially evacuate to 10 Pa to remove air and impurities from the cavity; then perform a second evacuation process to deeply evacuate to below 1 Pa to ensure that there is no residual gas in the cavity; finally, seal the water injection pipe to complete the preparation of the ultra-thin heat spreader.

[0051] The heat spreader prepared in this embodiment has a thickness of only 280μm. After testing, the temperature difference is controlled within 2℃, and the Qmax can reach 20W, which meets the heat dissipation requirements of high-performance small electronic devices.

[0052] Example 2

[0053] The preparation of the oxygen-free copper ultrathin capillary structure (semi-circular grooves + equally spaced arrangement) in the copper-steel composite heat exchanger is as follows: 1. Material selection: Oxygen-free copper with a thickness of T=10μm is selected as the plate. Oxygen-free copper has excellent strength and processing performance, which is suitable for the heat dissipation requirements of metal heat sinks.

[0054] 2. Trench preparation: Using an etching process, horizontally parallel semi-circular trenches are machined on the front side of the oxygen-free copper material. The trench depth is 20%T (i.e., 2μm), the width is 100%T (i.e., 10μm), and the trench spacing is 100%T (i.e., 10μm). Parallel semi-circular trenches are machined on the back side of the copper-steel composite material. The intersection angle between the front and back trenches is 0°. The depth, width, and spacing of the back trenches are consistent with those of the front side.

[0055] 3. Through-hole preparation: Using etching, regularly arranged circular through-holes are machined at the bottom of the front trench. The diameter of the through-hole is 50%T (i.e., 5μm) and the spacing between the holes is 100%T (i.e., 10μm). The through-holes penetrate the entire capillary structure to ensure that steam and liquid can flow freely.

[0056] 4. Surface treatment: The surface around the groove is kept flat, and no additional microstructure processing is required; the capillary structure is cleaned and dried to remove etching and stamping residues, resulting in an ultra-thin capillary structure.

[0057] The capillary structure prepared in this embodiment has a thickness of only 10 μm. The double-sided semi-circular grooves provide dual capillary forces, and the through-hole structure reduces steam resistance and water resistance, achieving a temperature difference of 3℃ and a maximum QW ​​of 10W, thus improving the overall performance of the heat spreader.

[0058] The preparation of the ultra-thin copper-steel composite heat exchanger is as follows: 1. Cover plate preparation: Copper-steel composite material is selected as the substrate for the upper and lower cover plates. The overall thickness of the heat spreader is H=100μm, of which the thickness of the upper cover plate is hs=10%H (10μm), the thickness of the lower cover plate is hx=10%H (10μm), the thickness of the capillary structure is hm=10%H (10μm), and the thickness of the cavity is hk=70%H (70μm). An array of support columns is processed on the inner side of the upper cover plate. The height of the support columns is consistent with the thickness of the cavity, which is used to enhance the compressive strength of the heat spreader. A pressure structure is processed on the inner side of the lower cover plate. The depth of the depression is 10μm (consistent with the thickness of the capillary structure), which is used to place the capillary structure.

[0059] 2. Capillary structure fixation: The oxygen-free copper ultrathin capillary structure prepared above is fixed in the lower pressing structure of the lower cover plate by laser welding, ensuring that the capillary structure is tightly attached to the lower cover plate without gaps, thereby improving the heat conduction efficiency.

[0060] 3. Cavity sealing: The upper and lower cover plates are aligned and welded together using a diffusion welding process to form a sealed cavity. Temperature and pressure are controlled during the welding process to prevent air leakage from the sealed cavity and ensure the sealing performance of the heat spreader.

[0061] 4. Water Injection and Vacuuming: Weld a water injection pipe to the reserved interface (water injection port) of the sealed cavity, and inject deionized water into the cavity as the working medium through the water injection pipe, with the injection volume being 35% of the cavity volume; then perform a first evacuation process to initially evacuate to 10 Pa to remove air and impurities from the cavity; then perform a second evacuation process to deeply evacuate to below 1 Pa to ensure that there is no residual gas in the cavity; finally, seal the water injection pipe to complete the preparation of the ultra-thin heat spreader.

[0062] The heat spreader prepared in this embodiment has a thickness of only 100μm. After testing, the temperature difference is controlled within 5℃, and the Qmax can reach 10 W, which meets the heat dissipation requirements of high-performance small electronic devices.

[0063] Example 3

[0064] The fabrication of an ultrathin capillary structure (trapezoidal grooves + variable spacing arrangement) made of PI material is as follows: 1. Material selection: PI film with a thickness of T=60μm is selected as the capillary structure substrate. PI material is lightweight and corrosion resistant, and is suitable for lightweight polymer heat exchange plates.

[0065] 2. Trench Preparation: Using femtosecond laser processing, inclined parallel trapezoidal trenches are processed on the front side of the PI film. The trench depth is 60%T (36μm), the center width is 80%T (48μm), the trench width on the substrate surface is 90%T, and the trench width at the bottom is 70%T. The trench spacing is gradient-increased from 50%T (30μm) to 200%T (120μm). Inclined parallel trapezoidal trenches are also processed on the back side of the PI film. The intersection angle between the front and back trenches is 45°. The depth and width of the back trenches are the same as those on the front, and the spacing is also gradient-increased.

[0066] 3. Through-hole preparation: Using laser drilling technology, regularly arranged elliptical through-holes are processed at the bottom of the back groove. The diameter (major axis) of the through-hole is 50%T (i.e., 30μm), and the hole spacing is 200%T (i.e., 120μm). The through-holes penetrate the entire capillary structure, which is adapted to the processing characteristics of polymer materials.

[0067] 4. Surface treatment: The surface around the groove is kept flat, and no additional microstructure processing is required. The surface characteristics of the PI substrate itself can meet the basic capillary requirements. The capillary structure is cleaned and dried to remove etching and stamping residues, resulting in an ultra-thin capillary structure.

[0068] The capillary structure prepared in this embodiment has a thickness of 60 μm. The variable-spacing trapezoidal grooves can be adapted to the liquid transport requirements of different areas. The stamping through-hole process is simple and low-cost. According to the test, its water resistance is reduced by 28% compared with the traditional capillary structure. It is suitable for lightweight and low-cost polymer heat exchange plates.

[0069] The preparation of an ultra-thin vapor chamber made of PI material is as follows: 1. Cover plate preparation: PI material is selected as the substrate for the upper and lower cover plates. The overall thickness of the heat spreader is H=300μm, of which the thickness of the upper cover plate is hs=15%H (45μm), the thickness of the lower cover plate is hx=15%H (45μm), the thickness of the capillary structure is hm=20%H (60μm), and the thickness of the cavity is hk=50%H (150μm). A grid-like support column is processed on the inner side of the upper cover plate, and the height of the support column is consistent with the thickness of the cavity (150μm). A pressing structure is processed on the inner side of the lower cover plate, with a recess depth of 58μm (slightly less than the thickness of the capillary structure 60μm) to ensure that the capillary structure fits tightly and is not damaged by compression.

[0070] 2. Capillary structure fixation: The PI capillary structure prepared above is fixed in the lower pressing structure of the lower cover plate by using a hot-melt bonding method. The hot-pressing temperature is controlled at 120℃ and the pressure is controlled at 0.5MPa to ensure that the capillary structure is firmly connected to the lower cover plate.

[0071] 3. Cavity sealing: The upper and lower cover plates are aligned and heat-pressed together to form a sealed cavity using a hot-melt welding process. The heat-pressing parameters are consistent with the capillary structure to ensure sealing performance and prevent leakage of the working medium.

[0072] 4. Water injection and vacuuming: After welding the water injection pipe, inject ethanol into the cavity as the working medium (to adapt to the compatibility of PI material), and the injection volume is 35% of the cavity volume; the first vacuuming process is carried out to 15Pa to remove air and impurities; the second vacuuming process is carried out to below 2Pa to complete deep degassing; finally, the water injection pipe is sealed to obtain the finished ultra-thin heat spreader plate.

[0073] The heat spreader prepared in this embodiment has a thickness of 300μm, is lightweight and corrosion-resistant, and has a temperature difference of 3℃ and a Qmax of 15W, making it suitable for portable electronic devices and lightweight heat dissipation scenarios.

[0074] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0075] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An ultrathin capillary structure, characterized in that, The ultrathin capillary structure includes plates with a thickness T = 5~60 μm; The plate has parallel capillary grooves on both the front and back sides, and the groove angle between the capillary grooves on the front and the capillary grooves on the back is 0~90°. The depth of the capillary grooves on the front and the capillary grooves on the back are independently 10~90%T, the width is independently 50~100%T, and the spacing between adjacent capillary grooves is independently 50~300%T. The plate is also provided with several through holes, the diameter of which is 40~100%T and the spacing between which is 80~300T.

2. The ultrathin capillary structure according to claim 1, characterized in that, The cross-sectional shapes of the capillary grooves on the front and back sides are independent, including rectangular, trapezoidal, semi-circular, U-shaped, and triangular.

3. The ultrathin capillary structure according to claim 2, characterized in that, The inner surfaces of the capillary grooves on the front and back sides independently contain submicron and / or nanostructures, and the submicron and nanostructures independently include one or more of the following: nodular structure, corrugated structure, granular structure and villous structure.

4. The ultrathin capillary structure according to claim 3, characterized in that, The capillary grooves on the front and the capillary grooves on the back are independently arranged with equal spacing or with variable spacing. The variable spacing arrangement is a gradient change.

5. The ultrathin capillary structure according to claim 4, characterized in that, The materials of the plates include copper, oxygen-free copper, copper alloy, stainless steel, aluminum alloy, titanium alloy, copper-steel composite material, PI, PE, PET or PC.

6. A method for preparing an ultrathin capillary structure according to any one of claims 1 to 5, characterized in that, Includes the following steps: Grooves and through-holes are fabricated on a plate using laser, stamping, or etching methods to obtain an extremely thin capillary structure; The laser method includes pulsed lasers, which include femtosecond pulsed lasers, picosecond pulsed lasers, and nanosecond pulsed lasers.

7. An ultra-thin heat spreader, characterized in that, The ultra-thin heat spreader includes an ultra-thin capillary structure, an upper cover plate, a lower cover plate, and a water inlet. The upper cover plate is provided with support columns; The ultrathin capillary structure is the ultrathin capillary structure described in any one of claims 1 to 5.

8. The ultra-thin heat spreader according to claim 7, characterized in that, The lower cover plate is provided with a pressing structure, the depth of which is equal to or less than the thickness of the ultra-thin capillary structure; the upper cover plate and the lower cover plate form a sealed cavity, the ultra-thin capillary structure is located inside the pressing structure of the lower cover plate, and the ultra-thin capillary structure is in contact with the lower cover plate.

9. The ultra-thin heat spreader according to claim 8, characterized in that, The thickness of the ultrathin heat spreader plate is H=100~300μm, the thickness of the upper cover plate is hs=10~15%H, the thickness of the lower cover plate is hx=10~15%H, the thickness of the ultrathin capillary structure is hm=T=5~20%H, and the thickness of the hollow cavity in the sealed cavity is hk=50~75%H.

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