Extreme ultrathin vapor chamber and preparation method thereof

Abstract

The invention belongs to the related technical field of phase-change heat exchange, and discloses an extreme ultrathin vapor chamber and a preparation method thereof. The vapor chamber comprises an upper shell plate and a lower shell plate, a closed cavity is formed between the upper shell plate and the lower shell plate, the lower shell plate is provided with micro-column array areas and supporting structure areas which are arranged at intervals, the micro-column array areas serve as circulation channels of liquid media, and the supporting structure areas serve as circulation channels of gas media; a nano grass structure is etched on the surface of the micro-column array area, and micro-columns arranged in an array and three-dimensional spiral woven metal wires covering the micro-column array are arranged in the micro-column array area. According to the vapor chamber, the problems that the vapor chamber liquid working medium is prone to liquid accumulation and the vapor-liquid phase change process is limited are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field related to phase change heat transfer, and more specifically, relates to an extremely ultra-thin heat spreader and a preparation method thereof. Background Art

[0002] In recent years, the heat flux density generated by electronic devices in the fields of personal electrical equipment, civil infrastructure, military weapons, and aerospace has continued to increase. Among them, portable electronic devices tend to develop in the direction of high performance, miniaturization, and integration, resulting in an exponential increase in the heat generated by chips per unit scale. Among the causes of failure of electronic devices, high temperature is the main factor leading to failure, and as the operating temperature gradually increases, the service life of the device will be significantly shortened, and its failure probability will also increase significantly. Among the cooling methods of electronic devices, phase change heat transfer is a new type of heat dissipation method that uses the phase change latent heat of the heat transfer medium to absorb or release heat and transfer heat through the flow of the medium. Because of its advantages of high heat transfer efficiency, high stability, and long life, it has gradually become a feasible way to solve the problem of heat dissipation of high heat flux density electronic devices. Heat spreader, referred to as VC, realizes heat diffusion through the process of evaporation phase change, steam flow, and condensation phase change of the medium in a closed space. It overcomes the limitations of traditional heat pipes and realizes efficient in-plane heat conduction.

[0003] Generally speaking, a vapor chamber with an overall thickness of less than 0.3mm can be called an extremely ultra-thin vapor chamber. Currently, extremely ultra-thin vapor chambers face severe challenges of performance degradation. During the operation of the vapor chamber, part of the liquid medium usually overflows into the gas channel to cause vapor-liquid mixing. In extremely ultra-thin vapor chambers, due to the extremely small thickness of the inner cavity, vapor-liquid mixing will lead to a more serious problem of increased vapor flow resistance. Traditional wick structures, such as multi-layer wire mesh or sintered powder wicks, cannot effectively alleviate the problem of liquid medium overflow, so the thickness needs to be increased to reduce vapor flow resistance. This makes it difficult to reduce the thickness of the vapor chamber to below 0.3mm, which cannot meet the thickness requirements of today's portable electronic devices.

[0004] Therefore, it is of great significance to design an extremely ultra-thin high-performance heat sink. Summary of the invention

[0005] In view of the above defects or improvement needs of the prior art, the present invention provides an extremely ultra-thin vapor chamber and a preparation method thereof, which solves the problem of large flow resistance of the gas medium generated by the gas-liquid mixture in the vapor chamber.

[0006] To achieve the above-mentioned purpose, according to one aspect of the present invention, an extremely ultra-thin heat spreader is provided, which includes an upper shell plate and a lower shell plate, and a closed chamber is formed between the upper shell plate and the lower shell plate, wherein the lower shell plate is provided with a micro-column array area and a support structure area arranged at intervals, the micro-column array area serves as a circulation channel for a liquid medium, and the support structure area serves as a circulation channel for a gas medium; a nano-grass structure is etched on the surface of the micro-column array area, and the micro-column array area is provided with array-arranged micro-columns and a three-dimensional spirally braided metal wire covering the micro-column array, and the surfaces of the micro-columns and the three-dimensional spirally braided metal wire are both etched with nano-grass structures.

[0007] Further preferably, the micro-columns and the three-dimensional spirally braided metal wires are both made of copper.

[0008] Further preferably, a cylindrical support structure and a strip support structure are provided in the support area, the cylindrical support structure is provided at both ends of the support area, the strip support structure is provided in the middle of the support area, the strip support structures are arranged in parallel, and a support structure area corresponding to the lower shell plate and having the same structure is provided on the upper shell plate.

[0009] More preferably, the thickness of the heat spreader is 0.22 mm to 0.32 mm.

[0010] Further preferably, the diameter of the three-dimensional spiral braided metal wire is 0.15 mm to 0.25 mm, the diameter of the microcolumn is 0.08 mm to 0.12 mm, the spacing is 0.2 mm to 0.25 mm, and the height is 0.03 mm to 0.17 mm.

[0011] Further preferably, the material of the upper shell plate and the lower shell plate is one of copper, copper alloy, stainless steel and aluminum alloy.

[0012] Further preferably, a liquid injection port is provided on one side of the heat spreader.

[0013] According to another aspect of the present invention, a method for preparing the extremely thin vapor chamber described above is provided, the method comprising the following steps:

[0014] Processing a micro-pillar array on the lower shell plate, and processing a support structure in a support structure region on the upper shell plate and the lower shell plate;

[0015] Covering the micro-pillar array with a three-dimensional spiral braided metal wire and sintering the three-dimensional spiral braided metal wire to connect the two;

[0016] Etching the micro-pillar array and the three-dimensional spiral braided metal wire so that nano-grass structures are formed on the surfaces of the two;

[0017] The upper shell plate and the lower shell plate are welded to form a closed chamber with a liquid injection port at one end.

[0018] More preferably, the sintering temperature is 600° C. to 800° C., and the sintering time is 4 hours to 6 hours.

[0019] Further preferably, the etching uses a strongly oxidizing alkaline liquid, the etching temperature is 90° C. to 98° C., and the time is 20 minutes to 30 minutes.

[0020] In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art:

[0021] 1. The surface of the micro-pillar array region of the present invention is etched with a nano-grass structure, and the micro-pillar array region is provided with arrayed micro-pillars and three-dimensional spiral woven metal wires covering the micro-pillar array. The surface of the micro-pillar array covered with the nano-grass structure is a rough surface with super hydrophilicity. The nano-grass structure has a layered morphology similar to grass, a characteristic size of less than 2 microns, and a composition of metal oxides. The nano-grass has ultra-high specific surface area characteristics, and has higher hydrophilicity and faster wetting ability than metals that have not been etched. The micro-nano pore structure formed by the nano-grass has the effects of suction, collection, and directional transportation on the liquid medium. The liquid medium overflowing to the support structure region during the operation of the vapor chamber can be timely collected to the micro-pillar array region by suction, and the liquid medium can be transported to one end of the vapor chamber along the length direction of the micro-pillar array region through directional transportation to participate in evaporation heat exchange, which is beneficial to reduce the flow resistance of the gas medium caused by gas-liquid mixing in the support structure region of the vapor chamber, and improve the medium circulation efficiency when the vapor chamber is working, thereby achieving a better heat exchange effect;

[0022] 2. The lower shell plate of the present invention is provided with a micro-pillar array area and a support structure area arranged at intervals. The micro-pillar array area serves as a circulation channel for the liquid medium, and the support structure area serves as a circulation channel for the gas medium, so that the circulation channels for the liquid medium and the gas medium are arranged at intervals, thereby reducing the obstruction of gas flow caused by gas-liquid mixing during the operation of the vapor chamber, and significantly improving the effective thermal conductivity of the vapor chamber; when the gas medium flows, the thickness space of the vapor chamber cavity can be fully utilized, and the thickness of the vapor chamber can be reduced to less than 0.3 mm while ensuring the performance;

[0023] 3. The thickness of the heat spreader of the present invention is 0.22mm~0.32mm, and it has a high effective thermal conductivity at an extremely thin thickness, which can meet the heat dissipation requirements of portable electronic devices. The disclosed method for preparing an extremely ultra-thin heat spreader has simple steps, reasonable design, easy implementation, strong operability, and is convenient for large-scale preparation and production, and has important practical value and promotion significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 An extremely thin vapor chamber constructed according to a preferred embodiment of the present invention;

[0025] Figure 2 is a schematic structural diagram of a lower shell plate constructed according to a preferred embodiment of the present invention;

[0026] Figure 3 is a schematic structural diagram of an upper shell plate constructed according to a preferred embodiment of the present invention;

[0027] Figure 4 is a schematic diagram of a three-dimensional spiral braided metal wire structure constructed according to a preferred embodiment of the present invention;

[0028] Figure 5 This is a SEM image of the copper oxide nanograss structure on the surface of the liquid wick constructed according to the preferred embodiment of the present invention.

[0029] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0030] 1-upper shell plate, 2-three-dimensional spiral braided metal wire, 3-lower shell plate, 31-micro-column array, 32-cylindrical support structure, 33-strip support structure, 4-liquid injection port. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] like Figure 1 As shown, an extremely ultra-thin heat spreader includes an upper shell plate 1 and a lower shell plate 3, which are welded to form a chamber, and the chamber includes a three-dimensional spirally woven metal 2 and a liquid phase change medium.

[0033] like Figure 2 As shown, a three-dimensional spiral braided metal wire 2 is sintered at a corresponding position above the micro-column array 31 structure on the lower shell plate 3, and each braided metal wire and the micro-column array 31 together constitute a group of liquid wick structures; in one embodiment of the present invention, the three-dimensional spiral braided metal wire 2 is a three-dimensional spiral braided copper wire.

[0034] A copper oxide nanograss structure is etched on the surface of a lower shell plate sintered with three-dimensional spirally woven metal wires, and the surface of the nanograss is plasma cleaned to obtain a copper oxide nanograss surface with super hydrophilicity.

[0035] The upper shell plate 1 and the lower shell plate 3 are sealed by laser welding, so that a chamber with a certain thickness is formed between the upper shell plate 1 and the lower shell plate 3, and a liquid phase change medium is injected into the chamber.

[0036] In the heat sink, the surface support structure and micro-column array structure of the upper shell plate and the lower shell plate can be manufactured by wet etching, 3D printing, powder sintering and other processes.

[0037] like Figure 3 As shown, the upper shell plate and the lower shell plate are provided with cylindrical support structures 32 and strip support structures 33 on their surfaces, and the lower shell plate is provided with a micro-column array area 31 on its surface. The support structure and the micro-column array can be obtained by a wet etching process, and the shell plate retains a thickness of 0.03 to 0.06 mm during the etching process, and the retained thickness is the minimum thickness that should be ensured at the thinnest part of the shell plate to ensure that the shell plate has the structural strength for normal operation. The support structure and the micro-column array can also be obtained by 3D printing or powder sintering process, and the shell plate thickness selected for processing is 0.03 to 0.06 mm to ensure that the shell plate has the structural strength for normal operation.

[0038] In one embodiment of the present invention, the upper shell plate is made of C19400 copper alloy plate with a main body length of 100 mm, a width of 30 mm, and a thickness of 0.1 mm. A support structure with a height of 0.05 mm is obtained by wet etching, wherein the radius of the cylindrical support column is 0.03 mm, and the width of the strip support column is 0.06 mm. At the same time, an internal chamber with a length of 93 mm, a width of 26 mm, and a thickness of 0.05 mm is obtained.

[0039] In one embodiment of the present invention, the lower shell plate is made of C19400 copper alloy plate with a main body length of 100 mm, a width of 30 mm, and a thickness of 0.15 mm. A support structure and a micro-column array structure with a height of 0.1 mm are obtained by wet etching, wherein the radius of the cylindrical support column of the support structure is 0.03 mm, the width of the strip support column is 0.06 mm, the diameter of the cylinder of the micro-column array structure is 0.1 mm, and the spacing between adjacent cylinders is 0.225 mm. At the same time, an internal chamber with a length of 93 mm, a width of 26 mm, and a thickness of 0.1 mm is obtained.

[0040] like Figure 4 As shown, in one embodiment of the present invention, the diameter of a single metal wire of the three-dimensional spiral braided metal wire is 0.02mm~0.03mm, so as to ensure the strength of the metal wire structure while achieving a scale that can generate capillary pressure. Every 9 strands of metal wire are arranged in parallel to form an ingot to form a strip gap structure. This strip gap structure is beneficial to the directional transport of the liquid medium in the gap along the length direction of the metal wire. Then, 24 ingots of metal wire are woven in a three-dimensional spiral manner to form a pore structure with suction capability. The number of braided layers is one layer, the mesh number is 10, and the material is copper. The length of a single metal wire is 92mm through cutting to match the length of the inner cavity of the heat spreader.

[0041] The diameter of the three-dimensional spiral woven metal wire is 0.15mm~0.25mm. After sintering, it can cover most areas of the microcolumn array and adapt to the inner cavity of the heat spreader in terms of thickness. The diameter of the microcolumn is 0.08mm~0.12mm, and the spacing is 0.2mm~0.25mm. The microcolumn array at this scale has a certain suction capacity and a height of 0.03mm~0.17mm, so that the microcolumn has a higher liquid storage capacity. It can be combined with the advantage of the strong suction force of the three-dimensional spiral woven metal wire to form a high-performance composite liquid absorbent core, which plays a role in increasing the liquid carrying capacity in the directional transport process of the liquid medium, so as to improve the ultimate heat transfer power of the heat spreader.

[0042] In one embodiment of the present invention, in the above-mentioned extremely ultra-thin heat spreader, the diameter of a single metal wire of the three-dimensional spirally woven metal wire is 0.02mm~0.03mm, so as to ensure the structural strength of the metal wire while reaching a scale that can generate capillary pressure. Every 9 strands of metal wire are arranged in parallel to form an ingot to form a strip gap structure. This strip gap structure is beneficial to the directional transport of the liquid medium in the gap along the length direction of the metal wire. Then, 24 ingots of metal wire are woven in a three-dimensional spiral manner to form a pore structure with suction capability. The number of woven layers is one layer, the mesh number is 10, and the material is copper.

[0043] In one embodiment of the present invention, the diameter of the cylinders in the micro-column array structure of the lower shell plate is 0.1 mm, the distance between adjacent cylinders is 0.225 mm, and the arrangement is a rectangular straight array.

[0044] In one embodiment of the present invention, the upper shell plate and the lower shell plate are both made of C19400 copper alloy, or copper, other copper alloys, stainless steel, or aluminum alloy.

[0045] The lower shell plate is provided with a microcolumn array area and a support structure area arranged at intervals, the microcolumn array area serves as a circulation channel for the liquid medium, and the support structure area serves as a circulation channel for the gas medium; in one embodiment of the present invention, a wick structure composed of a microcolumn array and a three-dimensional spiral woven metal wire is arranged in parallel in the chamber, the wick and the shell plate are surrounded to form a plurality of steam flow channels, a strip support structure is arranged in the channel, and a cylindrical support structure is arranged near the edge of the shell plate.

[0046] The present invention also provides a method for preparing an extremely ultra-thin vapor chamber, by which the ultra-thin vapor chamber can be prepared efficiently and controllably. Specifically, the method comprises the following steps:

[0047] According to the pre-designed graphics, wet etching or 3D printing or powder sintering is performed on the surface of the upper and lower shell plates, so that the upper and lower shell plates have a support array structure, and the lower shell plate has a micro-column array structure. When using the wet etching process, the shell plate needs to retain 0.03 to 0.06 mm to ensure the structural strength of the shell plate. When using the 3D printing or powder sintering process, a shell plate with a thickness of 0.03 to 0.06 mm should be selected to ensure the structural strength of the shell plate; the sintering temperature is 600℃ to 800℃, which is lower than the melting point of copper. At this temperature, surface diffusion and plastic flow occur between metals, so that a rigid connection is formed between the metals while avoiding excessive temperature causing large deformation of the shell plate. The sintering time is 4 hours to 6 hours. Within this time range, the metal is fully reacted and sintered to avoid excessive sintering time causing large deformation of the shell plate.

[0048] A three-dimensional spiral braided metal wire is sintered at a corresponding position above the micro-pillar array structure on the lower shell plate, and each three-dimensional spiral braided metal wire and the micro-pillar array together form a group of liquid wick structures;

[0049] A copper oxide nanograss structure is etched on the surface of a micro-pillar array region of a lower shell plate sintered with three-dimensional spirally woven metal wires, and the nanograss surface is plasma cleaned to obtain a copper oxide nanograss surface with super hydrophilicity;

[0050] The upper shell plate and the lower shell plate treated as above are sealed by laser welding, so that a chamber with a certain thickness is formed between the upper and lower shell plates, and a liquid phase change medium is injected into the chamber;

[0051] Before sintering, the metal wire and the lower shell plate are ultrasonically cleaned in ethyl acetate and ethanol environments for 5 minutes or more to remove organic impurities attached to the surface of the material. Then, they are kept in a dilute sulfuric acid environment at 70°C to 80°C for more than 15 minutes to remove the oxide layer on the surface of the material. After completion, they are taken out and rinsed with deionized water and blown dry for use.

[0052] In one embodiment of the present invention, the method for sintering the three-dimensional spiral braided metal wire on the surface of the lower shell plate is to place the three-dimensional spiral braided metal wire at the corresponding position of the micro-column array on the surface of the lower shell plate, the metal wire is in a straight state and covers the micro-column array, fix the metal wire and the shell plate by a graphite clamp, place them in a vacuum environment at 600°C for high temperature sintering for 1 to 2 hours, and then cool them naturally to obtain a lower shell plate with a three-dimensional spiral braided metal wire-micro-column array composite liquid absorbent core.

[0053] The upper and lower shell plates are provided with injection ports by stamping.

[0054] The sintered lower shell plate is ultrasonically cleaned again in an ethyl acetate and ethanol environment for 5 minutes or more, and then maintained at 70°C to 80°C in a dilute sulfuric acid environment for more than 15 minutes. After completion, it is taken out and rinsed with deionized water and blown dry for use.

[0055] In one embodiment of the present invention, the method for etching the nanograss structure on the surface of the lower shell plate is to fix the shell plate by an acrylic mold, expose the area to be etched, place it in an alkaline etching liquid environment with strong oxidizing properties, set the etching temperature to 90°C to 98°C, at this temperature, the surface to be etched and the etching liquid can react efficiently, the etching time is 20 minutes to 30 minutes, and after the etching is completed within this time range, the surface to be etched is covered with nanograss structures, so as to avoid the messy morphology of the nanograss structure due to the long etching time, which in turn leads to a decrease in the suction performance. Then quickly rinse with deionized water and blow dry. In one embodiment of the present invention, the etching solution is sodium phosphate, sodium hydroxide, sodium chlorite, and deionized water in a ratio of 40:15:20:100, maintained at 96°C for 20 minutes, then quickly rinsed with deionized water and blown dry, placed in a plasma cleaning machine, and cleaned for 300 seconds at 80W power. After completing this step, the surface structure of the sample is copper oxide nanograss, and the structure is as follows Figure 5 shown.

[0056] The upper shell plate and the processed lower shell plate are placed in the laser welding machine accordingly, the welding speed is set to 4000 mm / s, the power is selected to 75%, the frequency is 100 kHz, the pulse width is 10 us, and then the welding machine automatically completes the welding.

[0057] The phase change working fluid is injected into the cavity formed by the shell plate through the injection port using a micro-precision syringe, and then the shell plate is immersed in liquid nitrogen as a whole, and the injection port is connected to a vacuum pump to draw a vacuum.

[0058] When the chamber pressure is 1×10 -3 When the pressure is below hPa, a resistance welder is used to complete the heat spreader packaging.

[0059] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An extremely thin vapor chamber, characterized in that: The heat spreader comprises an upper shell plate (1) and a lower shell plate (3), wherein a closed chamber is formed between the upper shell plate (1) and the lower shell plate (3), wherein the lower shell plate (3) is provided with a micro-column array region and a support structure region arranged at intervals, the micro-column array region serves as a flow channel for a liquid medium inside the closed chamber, and the support structure region serves as a flow channel for a gas medium inside the closed chamber; a nano-grass structure is etched on the surface of the micro-column array region, and the micro-column array region is provided with arrayed micro-columns and a three-dimensional spiral braided metal wire (2) covering the micro-column array, and the surfaces of the micro-columns and the three-dimensional spiral braided metal wire (2) are both etched with nano-grass structures.

2. The ultra-thin vapor chamber according to claim 1, characterized in that: The micro-columns and the three-dimensional spiral braided metal wires (2) are both made of copper.

3. An extremely thin vapor chamber as claimed in claim 1 or 2, characterized in that: A cylindrical support structure (32) and a strip support structure (33) are provided in the support area, the cylindrical support structure is provided at both ends of the support area, the strip support structure is provided in the middle of the support area, the strip support structures are arranged in parallel, and a support structure area corresponding to the lower shell plate and having the same structure as the lower shell plate is provided on the upper shell plate (1).

4. An extremely thin vapor chamber as claimed in claim 1 or 2, characterized in that: The thickness of the heat spreader is 0.22 mm to 0.32 mm.

5. The ultra-thin vapor chamber according to claim 4, characterized in that: The diameter of the three-dimensional spiral braided metal wire is 0.15 mm to 0.25 mm, the diameter of the microcolumn is 0.08 mm to 0.12 mm, the spacing is 0.2 mm to 0.25 mm, and the height is 0.03 mm to 0.17 mm.

6. An extremely thin vapor chamber as claimed in claim 4 or 5, characterized in that: The material of the upper shell plate (1) and the lower shell plate (3) is one of copper, copper alloy, stainless steel and aluminum alloy.

7. The ultra-thin vapor chamber according to claim 1, characterized in that: A liquid injection port (4) is provided on one side of the heat diffusion plate.

8. A method for preparing the ultra-thin vapor chamber according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: Processing a micro-pillar array on the lower shell plate, and processing a support structure in a support structure region on the upper shell plate and the lower shell plate; Covering the micro-pillar array with a three-dimensional spiral braided metal wire and sintering the three-dimensional spiral braided metal wire to connect the two; Etching the micro-pillar array and the three-dimensional spiral braided metal wire so that nano-grass structures are formed on the surfaces of the two; The upper shell plate and the lower shell plate are welded to form a closed chamber with a liquid injection port at one end.

9. The preparation method according to claim 1, characterized in that: The sintering temperature is 600° C. to 800° C., and the sintering time is 4 hours to 6 hours.

10. The preparation method according to claim 1, characterized in that: The etching uses a strong oxidizing alkaline liquid, the etching temperature is 90° C. to 98° C., and the time is 20 minutes to 30 minutes.

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