Vapor chamber with composite wick and design method thereof

Abstract

The invention relates to a vapor chamber with a composite wick and a design method thereof, and the design method comprises the following steps: sintering at least two evaporation end wick on an evaporation end cover plate, and enabling the at least two evaporation end wick to be tightly sleeved with each other; a condensation end wick is sintered on the condensation end cover plate; wetting gradients are formed between the at least two evaporation end wick as well as between the condensation end wick and the evaporation end wick; supporting columns are welded between the condensation end cover plate and the evaporation end cover plate, at least part of the supporting columns are sleeved with powder rings, and the two ends of the powder rings are connected to the evaporation end wick and the condensation end wick correspondingly; and the condensation end cover plate and the evaporation end cover plate are welded, so that the sum of the thickness of the evaporation end wick and the thickness of the condensation end wick is smaller than 40% of the distance between the condensation end cover plate and the evaporation end cover plate. Through the method, the vapor chamber with the composite wick structure can be conveniently designed, the problem that the design of the composite wick structure of the current vapor chamber excessively depends on the production experience of engineers is solved, the production cost is saved, and the production efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of phase change heat transfer, in particular to a vapor chamber with a composite liquid wick and a design method thereof. Background Art

[0002] The traditional preparation process of the heat spreader includes making the condensing end cover plate and the evaporating end cover plate, sintering the liquid absorption core on the condensing end cover plate and the evaporating end cover plate and welding the support column, welding the liquid injection pipe, injecting the working fluid, vacuum degassing, sealing and leveling, etc. to obtain the required heat spreader.

[0003] As an important component to solve high heat flux density, the internal wick structure of the vapor chamber occupies a dominant position in the vapor chamber design. With the increase of the heat flux density of the chip, the vapor chamber wick design has become more and more complex. The traditional single wick structure has been gradually replaced by a multi-component composite wick to achieve the purpose of increasing the maximum power of the vapor chamber and reducing thermal resistance. The parameters of the single wick of the vapor chamber are complex, and the composite wick structure formed is of various types and has different performances, which greatly affects the design and heat transfer performance of the vapor chamber.

[0004] At present, the design of the vapor chamber wick structure mainly relies on the production experience of engineers. When a single wick structure cannot meet the performance requirements, it is usually necessary to select different single wick structure combinations, manufacture samples, conduct a large number of experimental tests, and repeatedly optimize the wick structure, which not only takes a lot of time, but also increases production costs and causes waste of resources. Summary of the invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide a heat spreader with a composite liquid absorbent core and a design method thereof, by which a heat spreader with a composite liquid absorbent core structure can be easily prepared without relying too much on the production experience of engineering personnel, thereby improving production efficiency and avoiding waste of resources.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: A method for designing a vapor chamber with a composite liquid wick comprises the following steps: At least two evaporation end liquid wicks are sintered on the evaporation end cover plate, and at least two evaporation end liquid wicks are closely sleeved with each other; A condensation end liquid wick is sintered on the condensation end cover plate; There is a wetting gradient between at least two evaporation end wicks and between the condensation end wick and the evaporation end wick; A support column is welded between the condensation end cover plate and the evaporation end cover plate, and a powder ring is arranged on the outer surface of at least part of the support column, so that the two ends of the powder ring are respectively connected to the evaporation end liquid absorption core and the condensation end liquid absorption core; The condensing end cover plate and the evaporating end cover plate are welded so that the sum of the thickness of the evaporating end liquid absorption core and the condensing end liquid absorption core is less than 40% of the distance between the condensing end cover plate and the evaporating end cover plate.

[0007] Furthermore, the capillary force of at least two evaporation end liquid wicks gradually decreases from the inside to the outside, and the porosity and permeability gradually increase.

[0008] Furthermore, the capillary force gradually decreases from the evaporation end wick to the condensation end wick, and the porosity and permeability gradually increase.

[0009] Furthermore, the sum of the thicknesses of the evaporation end wick and the condensation end wick is 15% to 40% of the distance between the condensation end cover plate and the evaporation end cover plate.

[0010] Furthermore, among the mutually nested evaporation end liquid absorption cores, the innermost evaporation end liquid absorption core is located in the middle of the evaporation end cover plate and is sintered with copper powder, and the particle size of the copper powder is 0.075mm to 0.03mm.

[0011] Furthermore, among the mutually sleeved evaporation end liquid wicks, the evaporation end liquid wick sleeved outside the copper powder is sintered with a copper flat wire mesh, the wire mesh number is 200-300 meshes, and the wire diameter is 0.03mm-0.05mm.

[0012] Furthermore, in the evaporation end liquid absorption core, the copper powder and the copper plane wire mesh are sintered simultaneously.

[0013] Furthermore, before sintering the evaporation end liquid absorption core, a dripping method is used to make the copper plane screen close to the evaporation end cover plate.

[0014] Furthermore, the condensation end liquid absorption core is sintered with a copper flat screen, the screen mesh number is 100-150 meshes, and the wire diameter is 0.05mm-0.1mm. The powder ring provided on the outer shell of the support column uses copper powder with a particle size of 0.15mm-0.1mm.

[0015] A heat spreader is prepared by using the above-mentioned design method.

[0016] In general, the present invention has the following advantages: The present invention focuses on providing a specific implementation method for the design of a composite wick for a vapor chamber, and through experimental tests on a variety of composite wick structures, three criteria for the design of a composite wick are constructed, including an axial wick structure design criterion, a radial wick structure design criterion, and a vapor-liquid channel ratio design criterion, that is, there is a wetting gradient between adjacent evaporation-end wicks and between the condensation-end wicks and the evaporation-end wicks, and the ratio of the sum of the thickness of the evaporation-end wick and the condensation-end wick to the distance between the condensation-end cover plate and the evaporation-end cover plate is controlled, so that a vapor chamber with a composite wick structure can be easily prepared by this method. The design criterion for the composite wick for a vapor chamber has a wide range of applications and can meet most vapor chamber design and use requirements, solving the problem that the current design of the composite wick structure for a vapor chamber relies too much on the production experience of engineers, saving production costs, improving production efficiency, and avoiding waste of resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a Cartesian coordinate system established according to the design method of the heat spreader composite liquid wick structure of the present invention.

[0018] Figure 2 It is a schematic diagram of the heat sink shell structure and the support column structure.

[0019] Figure 3 Schematic diagram of the liquid absorption core structure at the evaporation end.

[0020] Figure 4 Schematic diagram of the liquid absorption core structure at the condensation end.

[0021] Figure 5 It is a cross-sectional schematic diagram of a heat spreader with a composite liquid wick structure.

[0022] In the figure: 1-heating copper block, 2-copper powder, 3-200 mesh copper flat wire mesh, 4-100 mesh copper flat wire mesh, 5-steam, 6-evaporation end cover plate, 7-steam chamber, 8-copper support column, 9-condensation end cover plate, 10-powder ring. DETAILED DESCRIPTION

[0023] The present invention will be described in further detail below.

[0024] A vapor chamber with a composite liquid wick and a design method thereof, the design method comprising the following steps: At least two evaporation end liquid wicks are sintered on the evaporation end cover plate 6, and at least two evaporation end liquid wicks are sleeved with each other; wherein the evaporation end liquid wick corresponding to the heat source has a large capillary force, a small porosity, and a low permeability; The condensation end liquid wicks are sintered evenly distributed on the condensation end cover plate 9; A support column is welded between the condensation end cover plate 9 and the evaporation end cover plate 6, and a powder ring 10 is disposed on at least part of the support column, so that the two ends of the powder ring 10 are respectively connected to the evaporation end liquid absorption core and the condensation end liquid absorption core; There is a wetting gradient between at least two evaporation end wicks and between the condensation end wick, the powder ring 10 and the evaporation end wick; The condensation end cover plate 9 and the evaporation end cover plate 6 are welded so that the sum of the thickness of the evaporation end liquid absorption core and the condensation end liquid absorption core is less than 40% of the distance between the condensation end cover plate 9 and the evaporation end cover plate 6.

[0025] The present invention establishes a Cartesian coordinate system according to the flow direction of the steam 5 inside the vapor chamber, and summarizes the design criteria of the vapor chamber wick structure through experiments.

[0026] like Figure 1 As shown, assuming that the middle of the evaporation end cover plate 6 is in contact with the heating copper block 1 (heat source), according to the heat transfer path, the evaporation end wick located in the middle of the evaporation end cover plate 6 will first boil and generate steam 5, and the steam 5 rises from the evaporation end to the condensation end. Therefore, the Z-axis direction is defined as the radial direction; after the steam 5 leaves the evaporation end wick, the diffusion resistance decreases sharply, and the steam 5 expands and diffuses rapidly from the center to the surroundings. Therefore, the XY plane is defined as the axial direction; the sum of the thickness of the evaporation end wick and the thickness of the condensation end wick, and the ratio of the inner cavity height of the heat spreader (that is, the distance between the condensation end cover plate 9 and the evaporation end cover plate 6) is defined as the vapor-liquid channel ratio.

[0027] Based on this, three principles for the design of composite wicks are constructed. The composite wick structure is composed of two or more single wick structures. The single wick structure includes grooves, copper powder 2, copper flat wire mesh, copper fiber, etc.

[0028] The three principles for composite wick design include: Design criteria for radial wick structure: From the evaporation end to the condensation end, a wetting gradient is established through different single wick structures. The wick pores increase from 0.001mm to 0.1mm along the radial direction, and the capillary force gradually decreases. The wick pores are layered along the radial direction according to the influencing factors such as the wick pores to reduce the thermal resistance of the vapor chamber. Design criteria for axial wick structure: From the center to the periphery, a wetting gradient is established through different single wick structures. The wick pores increase from 0.001mm to 0.075mm along the axial direction, and the capillary force decreases gradually. The axial direction is layered according to the wick pores and other influencing factors to enhance the ultimate power of the vapor chamber. Design criteria for the ratio of vapor-liquid channels: By improving the ratio of vapor-liquid channels in the vapor chamber, the contradiction between the thermal resistance and the maximum power of the vapor chamber can be coordinated. The thickness of the wick is the main factor affecting the maximum power and thermal resistance of the vapor chamber. When the height of the cavity inside the vapor chamber remains unchanged, the thickness of the wick increases and the thermal resistance increases; the thickness of the wick decreases and the maximum power decreases. Depending on the type of wick, the ratio ranges from 15% to 40%.

[0029] Based on the composite wick structure design criteria, the manufacturing process of the vapor chamber provided in this embodiment is as follows: (1) Preparation of copper substrate for heat spreader like Figure 2 As shown, two copper substrates of 80mm*60mm*0.6mm are taken, and a groove is processed on one of the copper substrates by a stamping process as a steam chamber 7. The overall size of the steam chamber 7 is 76mm*56mm*1.8mm, which is used as the evaporation end cover plate 6, and the other copper substrate is used as the condensation end cover plate 9. At the same time, a copper support column 8 with a diameter of 2mm and a height of 2mm is used as a supporting structure to ensure the mechanical strength and reliability of the heat spreader. The surface of the substrate and the copper support column 8 are cleaned by professional equipment and dried for use.

[0030] (2) Sintered wick structure like Figure 3 As shown, the evaporation end cover plate 6 adopts a composite liquid wick structure. First, take a 200-mesh copper flat screen 3 with a size of 76mm*56mm*0.24mm and a wire diameter of 0.03mm, and cut a square hole with a size of 30mm*30mm in the center area. The 200-mesh copper flat screen 3 is made close to the evaporation end cover plate 6 by the dripping method. The dripping method uses the surface tension of water to adsorb the cut 200-mesh copper flat screen 3 to the heat spreader evaporation end cover plate 6; then, through a powder filling machine, copper powder 2 with a particle size of 0.075mm to 0.03mm is filled into the square holes of the 200-mesh copper flat screen 3, and the size of the copper powder 2 is 30mm*30mm*0.24mm. Finally, the liquid wicks with different pores are sintered at high temperature in a sintering furnace.

[0031] like Figure 4 As shown, the condensation end cover plate 9 adopts a 100-mesh copper flat wire mesh 4 with a size of 76mm*56mm*0.2mm and a wire diameter of 0.05mm. The 100-mesh copper flat wire mesh 4 is sintered onto the condensation end cover plate 9 through a sintering furnace.

[0032] The evaporation end liquid absorption core and the condensation end liquid absorption core are both fixed by sintering in an oxygen-free high-temperature sintering furnace, the sintering temperature is 880° C. to 930° C., and the sintering time is 5 to 8 hours.

[0033] Among them, the composite liquid-absorbing cores with different pores at the evaporation end are sintered simultaneously.

[0034] (3) Heat sink packaging like Figure 5 As shown, a copper support column 8 with a height of 2 mm and a diameter of 2 mm is placed in the inner cavity of the evaporation end cover plate 6, and a powder ring 10 of 100 mesh copper powder sintered with an outer diameter of 4.6 mm and an inner diameter of 2 mm is placed on part of the copper support column 8, wherein the copper support column 8 serves as a supporting structure, and the powder ring 10 serves as a liquid connection channel between the evaporation end wick and the condensation end wick. After that, the riveted evaporation end cover plates 6 are welded together by pressure diffusion welding, and then the liquid injection pipe is welded by resistance welding, annealing reduction, injection of working fluid, vacuum degassing, sealing and leveling are carried out to prepare a heat spreader that meets the design criteria of the composite wick structure.

[0035] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for designing a vapor chamber with a composite liquid wick, characterized in that: The following steps are included: At least two evaporation end liquid wicks are sintered on the evaporation end cover plate, and at least two evaporation end liquid wicks are closely sleeved with each other; A condensation end liquid wick is sintered on the condensation end cover plate; There is a wetting gradient between at least two evaporation end wicks and between the condensation end wick and the evaporation end wick; A support column is welded between the condensation end cover plate and the evaporation end cover plate, and a powder ring is arranged on the outer surface of at least part of the support column, so that the two ends of the powder ring are respectively connected to the evaporation end liquid absorption core and the condensation end liquid absorption core; The condensing end cover plate and the evaporating end cover plate are welded so that the sum of the thickness of the evaporating end liquid absorption core and the condensing end liquid absorption core is less than 40% of the distance between the condensing end cover plate and the evaporating end cover plate.

2. The design method according to claim 1, characterized in that: The capillary force of at least two evaporation end liquid wicks gradually decreases from the inside to the outside, and the porosity and permeability gradually increase.

3. The design method according to claim 1, characterized in that: The capillary force gradually decreases along the evaporation end wick toward the powder ring and the condensation end wick, and the porosity and permeability gradually increase.

4. The design method according to claim 1, characterized in that: The sum of the thickness of the evaporation end liquid wick and the condensation end liquid wick is 15% to 40% of the distance between the condensation end cover plate and the evaporation end cover plate.

5. The design method according to claim 1, characterized in that: Among the evaporation end liquid absorption cores which are closely sleeved with each other, the innermost evaporation end liquid absorption core is located in the middle of the evaporation end cover plate and is sintered with copper powder, and the particle size of the copper powder is 0.075mm-0.03mm.

6. The design method according to claim 5, characterized in that: In the mutually sleeved evaporation end liquid absorbing cores, the evaporation end liquid absorbing core sleeved outside the copper powder is sintered with a copper flat wire mesh, the wire mesh number is 200-300 meshes, and the wire diameter is 0.03mm-0.05mm.

7. The design method according to claim 6, characterized in that: In the evaporation end liquid absorption core, copper powder and copper flat wire mesh are sintered simultaneously.

8. The design method according to claim 6, characterized in that: Before sintering the evaporation end liquid absorption core, the copper plane screen is made to stick to the evaporation end cover plate by using the dripping method.

9. The design method according to claim 1, characterized in that: The condensation end liquid absorption core is made of sintered copper flat wire mesh, the wire mesh number is 100 mesh to 150 mesh, the wire diameter is 0.05mm to 0.1mm, The powder ring arranged outside the supporting column adopts copper powder with a particle size of 0.15mm to 0.1mm.

10. A heat spreader, characterized in that: The invention is prepared by the design method described in any one of claims 1 to 9.

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