Flat plate heat pipe and manufacturing method

Abstract

The application discloses a flat plate heat pipe, comprising an evaporation plate and a condensation plate, wherein the evaporation plate comprises a groove, a microarray structure is arranged in the groove, the microarray structure comprises a plurality of micro columns, and the micro columns are super-hydrophilic; the condensation plate comprises a flange and a confluence area; during operation, the evaporation plate absorbs heat, liquid working medium is vaporized, steam diffuses through steam channels between the micro columns, the steam condenses into liquid after contacting the condensation plate, and the liquid returns to the evaporation plate to continue heat exchange. The condensation plate has discrete hydrophobic gradient flanges, the flanges are provided with super-hydrophilic confluence areas, the confluence areas are provided with confluence grooves of micro-groove structures, and the flanges and the confluence areas cooperate to enable the confluence areas to have excellent capillary wicking capacity, so that the flat plate heat pipe can realize rapid pump-free return of condensation working medium. The application further provides a preparation method of the flat plate heat pipe, the prepared evaporation plate and condensation plate are connected, circulating working medium is injected into a circulating cavity, and then vacuumization is performed, so that the working reliability of the flat plate heat pipe is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to heat exchange equipment and its peripheral supporting facilities technical field, in particular to a kind of flat heat pipe and preparation method. BACKGROUND

[0002] With the rapid development of microelectronics technology, core components are constantly developing towards high frequency, high power consumption, high integration and miniaturization, and the power and cooling demand will increase significantly, how to efficiently dissipate heat in limited space is the key to ensure the normal operation of electronic equipment. Flat heat pipe can be directly matched with chip and other electronic devices, has strong temperature control ability for centralized heat source, smooth and flat outer surface and good geometric adaptability. Under the premise of endless pursuit of small size and high cooling efficiency in future thermal management system, it is particularly important to develop compact flat heat pipe with superior heat transfer performance.

[0003] Traditional flat heat pipe is composed of evaporation end, condensation end and wick, heat is transferred from the evaporation end, the working medium is rapidly vaporized and contacts the condensation end, the gaseous working medium is supercooled to liquid and returns to the evaporation section through the wick to complete the cycle, the whole process relies on latent heat of phase change of working medium to transfer heat, and the working temperature remains stable. As the bridge of working medium circulation, wick is the main factor limiting the size of ultra-thin flat heat pipe. Reducing the volume of traditional sintered wick structure will cause a series of problems such as decrease of liquid storage capacity and reduction of vapor diffusion space, which seriously affects the heat transfer performance. The groove type wick structure with small volume occupancy rate often has problems such as insufficient capillary force, small flow and difficult working medium return. SUMMARY

[0004] The purpose of the present application is to provide a kind of flat heat pipe and preparation method, to solve the problems existing in the prior art, improve the heat transfer performance of flat heat pipe.

[0005] To achieve the above purpose, the present application provides the following scheme: the present application provides a kind of flat heat pipe, comprising:

[0006] Evaporation plate, the evaporation plate includes first plate body, the first plate body is provided with groove, the groove is provided with microarray structure, the microarray structure includes a plurality of microcolumns, the microcolumns are arrayed, the adjacent microcolumns have gap, the microcolumns are superhydrophilic;

[0007] The condensing plate comprises a second plate body and a flange matched with the groove, the second plate body is connected with the flange, the flange is hydrophobic, and the hydrophobicity of the flange changes in a discrete gradient; a flow convergence area is arranged on the flange, the flow convergence area is super-hydrophilic, the flow convergence area comprises a plurality of serial flow convergence units, along the connection direction of the plurality of flow convergence units, the flow convergence units have a narrow end opening and a wide end opening; the flow convergence unit comprises a plurality of flow convergence grooves, the flow convergence grooves are micro-grooves, the length direction of the flow convergence grooves is parallel to the connection direction of the plurality of flow convergence units; along the direction from the wide end opening to the narrow end opening, the bottom surface of the flow convergence grooves is arranged in an inclined manner towards the second plate body.

[0008] The condensing plate is located on the top of the evaporating plate, the flange extends into the groove, the edge of the first plate body is connected with the edge of the second plate body, and the evaporating plate and the condensing plate form a circulation cavity capable of accommodating working medium circulation.

[0009] Preferably, the adjacent micro columns have a U-shaped recess therebetween.

[0010] Preferably, the micro columns are prismatic structures, and the micro columns are arranged in a rectangular array.

[0011] Preferably, the narrow end opening is one end opening of the flow convergence unit, the other end opening of the flow convergence unit is an end opening, the wide end opening is located between the narrow end opening and the end opening, the width of the flow convergence unit decreases from the wide end opening to the end opening, the spacing between the wide end opening and the end opening is greater than the spacing between the wide end opening and the narrow end opening, and the sidewall at the wide end opening is an arc surface.

[0012] Preferably, the gradient change of the hydrophobicity of the flange follows the following rule:

[0013] Δθ s =θ a -θ r

[0014] Wherein, θ a is the advancing angle of the working medium droplet at the connection of adjacent flow convergence units, θ r is the receding angle of the working medium droplet at the connection of adjacent flow convergence units, and θ s is the rolling angle of the flange.

[0015] Preferably, the slope of the bottom surface of the flow convergence groove is less than 2°.

[0016] Preferably, the number of the flow convergence areas is multiple groups, and the flow convergence areas are arranged in parallel on the flange.

[0017] Preferably, the evaporation plate and the condensation plate are provided with liquid injection ports, which are connected to the circulation cavity and can be connected to liquid injection pipes.

[0018] The application also provides a preparation method of the flat-plate heat pipe, comprising the following steps:

[0019] Step 1: processing the evaporation plate and the condensation plate, and sealingly connecting the edges of the first plate body and the second plate body;

[0020] Step 2: injecting a working medium into the circulation cavity and performing vacuumizing treatment on the circulation cavity.

[0021] Preferably, the edges of the first plate body and the second plate body are connected by welding, liquid working medium is injected into the confluence area, and the cavity surrounded by the condensation plate and the groove is vacuumized.

[0022] The flat-plate heat pipe of the application comprises an evaporation plate and a condensation plate, wherein the evaporation plate comprises a first plate body, the first plate body is provided with a groove, the groove is provided with a microarray structure, the microarray structure comprises a plurality of microcolumns, the microcolumns are arranged in an array, there are gaps between adjacent microcolumns, and the microcolumns are super-hydrophilic; the condensation plate comprises a second plate body and a flange matched with the groove, the second plate body is connected with the flange, the flange is hydrophobic, and the hydrophobicity of the flange changes in a discrete gradient manner; the flange is provided with a confluence area, the confluence area is super-hydrophilic, the confluence area comprises a plurality of series-connected confluence units, the confluence units have narrow-end openings and wide-end openings along the connecting direction of the plurality of confluence units; the confluence unit comprises a plurality of confluence grooves, the confluence grooves are micro-groove structures, the length direction of the confluence grooves is parallel to the connecting direction of the plurality of confluence units; along the direction from the wide-end opening to the narrow-end opening, the bottom surface of the confluence groove is obliquely arranged towards the second plate body; the condensation plate is located at the top of the evaporation plate, the flange extends into the groove, the edge of the first plate body is connected with the edge of the second plate body, and the evaporation plate and the condensation plate form a circulation cavity capable of accommodating the circulation of a working medium.

[0023] The flat plate heat pipe of the present application works, the evaporation plate absorbs heat, the liquid working medium vaporizes, the steam diffuses through the steam channel between the micro columns, the steam condenses into liquid after contacting the condensing plate, and returns to the evaporation plate to continue the cycle heat exchange. The condensing plate has discrete hydrophobic gradient flanges, the flanges are provided with super-hydrophilic flow collection areas, and the flow collection areas are provided with flow collection grooves with micro groove structures. The flanges cooperate with the flow collection areas to enable the flow collection areas to have excellent capillary wicking capacity, so that the rapid pump-free return of the condensed working medium can be realized, and good anti-gravity characteristics are also provided. The micro columns on the evaporation plate are hydrophilic and can be used as an auxiliary wicking structure to quickly spread the liquid working medium. In addition, the flow collection grooves are inclined structures, which can provide a height difference for the return of the working medium on the one hand, and expand the steam flow channel on the other hand, further improving the heat transfer performance of the ultra-thin flat plate heat pipe. The flat plate heat pipe of the present application sets the micro array structure in the groove and sets the flow collection area on the flange. When the first plate body and the second plate body are connected, the flange extends into the groove, which is conducive to reducing the thickness of the flat plate heat pipe. The micro array structure can also support the flat plate heat pipe and prevent the ultra-thin flat plate heat pipe from collapsing, thereby improving the stability of the flat plate heat pipe.

[0024] At the same time, the present application also provides a preparation method of the above-mentioned flat plate heat pipe. The prepared evaporation plate and condensing plate are connected, the circulating working medium is injected into the circulating cavity, and the circulating cavity is vacuumized to ensure the working reliability of the flat plate heat pipe. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings described below only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0026] Figure 1 It is a structure diagram of the evaporation plate of the flat plate heat pipe of the present application.

[0027] Figure 2 It is a structure diagram of the condensing plate of the flat plate heat pipe of the present application.

[0028] Figure 3 It is a structure diagram of the condensing plate of the flat plate heat pipe of the present application.

[0029] Among them, 100 is the evaporation plate, 200 is the condensing plate;

[0030] 1 is the first plate body, 2 is the groove, 3 is the micro column, 4 is the recess, 5 is the second plate body, 6 is the flange, 7 is the flow collection area, 8 is the flow collection groove, 9 is the flow collection unit, 10 is the narrow end opening, 11 is the wide end opening, and 12 is the end opening. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work belong to the scope of protection of the present application.

[0032] The present application aims to provide a flat heat pipe and a preparation method to solve the problems in the prior art and improve the heat transfer performance of the flat heat pipe.

[0033] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0034] The present application provides a flat heat pipe, comprising an evaporation plate 100 and a condensation plate 200, wherein the evaporation plate 100 comprises a first plate body 1, the first plate body 1 is provided with a groove 2, the groove 2 is provided with a microarray structure, the microarray structure comprises a plurality of microcolumns 3, the microcolumns 3 are arranged in an array, there is a gap between adjacent microcolumns 3, and the microcolumns 3 are super-hydrophilic; the condensation plate 200 comprises a second plate body 5 and a flange 6 matched with the groove 2, the second plate body 5 is connected with the flange 6, the flange 6 is hydrophobic, and the hydrophobicity of the flange 6 changes in a discrete gradient; the flange 6 is provided with a confluence area 7, the confluence area 7 is super-hydrophilic, the confluence area 7 comprises a plurality of series-connected confluence units 9, along the connection direction of the plurality of confluence units 9, the confluence units 9 have a narrow end opening 10 and a wide end opening 11; the confluence unit 9 comprises a plurality of confluence grooves 8, the confluence grooves 8 are micro-groove structures, the length direction of the confluence grooves 8 is parallel to the connection direction of the plurality of confluence units 9; along the direction from the wide end opening 11 to the narrow end opening 10, the bottom surface of the confluence grooves 8 is obliquely arranged towards the direction of the second plate body 5; the condensation plate 200 is located at the top of the evaporation plate 100, the flange 6 extends into the groove 2, the edge of the first plate body 1 is connected with the edge of the second plate body 5, and the evaporation plate 100 and the condensation plate 200 form a circulation cavity capable of accommodating working fluid circulation.

[0035] The flat plate heat pipe of the present application works, the evaporation plate 100 absorbs heat, the liquid working medium vaporizes, the steam diffuses through the steam channel between the micro columns 3, the steam condenses into liquid after contacting the condensation plate 200, and returns to the evaporation plate 100 to continue the heat exchange cycle. The condensation plate 200 has discrete hydrophobic gradient flanges 6, the flanges 6 are provided with super-hydrophilic flow collection areas 7, and the flow collection areas 7 are provided with micro-groove structure flow collection channels 8, the flanges 6 cooperate with the flow collection areas 7 to make the flow collection areas 7 have excellent capillary wicking capacity, so that the rapid pump-free return of the condensed working medium can be realized, and the good anti-gravity characteristics are also provided; the micro columns 3 on the evaporation plate 100 are hydrophilic, which can be used as an auxiliary liquid wicking structure to quickly spread the liquid working medium; in addition, the flow collection channels 8 are inclined structures, which can provide a height difference for the working medium return on the one hand, and expand the steam flow channel on the other hand, further improving the heat transfer performance of the ultra-thin flat plate heat pipe. The flat plate heat pipe of the present application sets the micro-array structure in the groove 2 and sets the flow collection area 7 on the flange 6, when the first plate body 1 and the second plate body 5 are connected, the flange 6 extends into the groove 2, which is beneficial to reduce the thickness of the flat plate heat pipe, the micro-array structure can also play a supporting role for the flat plate heat pipe, preventing the collapse of the ultra-thin flat plate heat pipe, and improving the stability of the flat plate heat pipe.

[0036] It is also necessary to emphasize that please refer to Figure 1 The adjacent micro columns 3 have recesses 4, the recesses 4 are U-shaped, and the micro structure array constructed by the micro columns 3 and the recesses 4 is processed in the groove 2, which can provide certain mechanical properties to support the ultra-thin flat plate heat pipe and prevent collapse after vacuumizing; on the other hand, the U-shaped recess 4 can provide space for steam diffusion to accelerate the evaporation rate of the working medium. After the micro structure array is treated by super-hydrophilic treatment, the critical heat flux of the working medium can be improved, and the nucleation site is more easily wetted by the working medium liquid and undergoes repeated phase change. When bubbles are generated on the superheated wall surface, there is a micro-liquid layer between the bubbles and the wall surface, and the evaporation of the micro-liquid layer takes away most of the heat. Only when the micro-liquid layer is continuously replenished from the surrounding medium, the position of the broken bubble can be re-wetted, and the bubble can continue to grow and break, and the whole boiling process can continue. The better the wettability means that the micro-liquid layer contacts the surface more fully, which can cover every active hole on the surface. In the case of high heat flux, the active hole is completely activated, and the phase change is faster.

[0037] The micro column 3 is a prism structure, and the micro column 3 is arranged in a rectangular array. In the embodiment, the micro column 3 is a cuboid structure. The depth of the groove 2 is 0.05mm-0.5mm. The length of the micro column 3 is 0.3mm-0.5mm. The height of the micro column 3 is 0.04mm-0.4mm. The distance between adjacent micro columns 3 is 1mm. The depth of the U-shaped recess 4 is 0.02mm-0.2mm. The groove 2 can be machined on the first plate body 1 by micro milling, and then the micro array structure is machined by a micro milling cutter. In other embodiments of the present application, the micro column 3 can also adopt other structures to improve the flexible adaptability of the evaporation plate 100.

[0038] Specifically, the flow converging unit 9 is in the shape of a water drop, or in other words, the shape of the flow converging unit 9 is a shape after chamfering of a spindle shape. Please refer to Figure 2 and Figure 3, the narrow end opening 10 is located at one end of the confluence unit 9, the other end opening of the confluence unit 9 is an end opening 12, and the wide end opening 11 is located between the narrow end opening 10 and the end opening 12. The width of the confluence unit 9 decreases from the wide end opening 11 to the end opening 12. Similarly, the width of the confluence unit 9 decreases from the wide end opening 11 to the narrow end opening 10. The spacing between the wide end opening 11 and the end opening 12 is greater than the spacing between the wide end opening 11 and the narrow end opening 10. The side wall of the wide end opening 11 is arc-shaped. In practical applications, the long edge wedge angle of the spindle-shaped confluence unit 9 is 2°-4°, the short edge is linearly optimized to an arc, the length of a single confluence unit 9 is 20mm-40mm, the end opening 12 of the confluence unit 9 is connected to the narrow end opening 10 of the adjacent confluence unit 9, and the interface width is 1mm-5mm. In this specific embodiment, the second plate body 5 and the flange 6 are of an integrated structure. The flange 6 is machined on the plate material. The surface of the flange 6 is first subjected to discrete hydrophobic treatment, and then the confluence area 7 formed by the series connection of the confluence units 9 is machined on the surface of the flange 6. The spindle-shaped confluence area 7 can provide a Laplace force for the working fluid, realizing self-transport from the narrow end opening 10 to the wide end opening 11. The series connection of the confluence units 9 can reduce the length between the wide end opening 11 and the end opening 12, prevent the working fluid droplets from spreading to form a liquid film in the area between the wide end opening 11 and the end opening 12, and participate in the phase change cycle in the form of droplets. The series connection of the confluence units 9 can artificially construct an energy barrier at the connection. The circular arc connection can avoid the occurrence of energy singular point phenomenon. The energy barrier at the transition is overcome by discrete hydrophobic gradient. When the droplets pass through this part, the difference between the front and rear contact angles is significant due to the change of the hydrophobic substrate, giving the liquid a wetting gradient force to break through the energy barrier. The confluence area 7 is composed of the confluence channels 8 of the micro-groove structure. After nucleation, the condensation droplets are first transported in the confluence channels 8. At this time, due to the capillary phenomenon, the droplets quickly spread to the top. The later nucleated condensation droplets are self-transported in the pre-wetted confluence area 7. Since the liquid-liquid contact is changed to partial liquid-liquid contact, the movement resistance is greatly reduced, and the working fluid transport speed can be greatly improved. The confluence channel 8 has a relatively small slope, which can not only further expand the steam diffusion area, but also can improve the working fluid return speed by using the gravitational potential energy.

[0039] It should be further pointed out that the discrete hydrophobic gradient change of the flange 6 starts from the narrow end opening 10 of the confluence unit 9. The range of the hydrophobic gradient change depends on the size and overall length of the confluence unit 9. The hydrophobic gradient change follows the following rules:

[0040] Δθ s = θ a - θ r

[0041] Where, θ ais the advancing angle of the working fluid droplet at the junction of the adjacent confluence units 9, θ r is the retreating angle of the working fluid droplet at the junction of the adjacent confluence units 9, θ s is the rolling angle of the flange 6, the difference of the rolling angles of the flange 6 regions corresponding to the adjacent two confluence units 9 is equal to the difference between the advancing angle and the retreating angle of the working fluid droplet at the corresponding interface.

[0042] In the specific embodiment, the slope of the bottom surface of the confluence channel 8 is less than 2°, so that the narrow end opening 10 of the confluence unit 9 has the maximum gravitational potential energy.

[0043] In practical applications, the number of the confluence regions 7 is multiple groups, and the confluence regions 7 are arranged in parallel on the flange 6, further enhancing the reflux capacity of the liquid working medium.

[0044] More specifically, the evaporation plate 100 and the condensation plate 200 are both provided with a liquid injection port, which is connected to the circulating cavity and can be connected to a liquid injection pipe, facilitating the injection of circulating working medium into the circulating cavity and the vacuumizing operation.

[0045] Further, the application also provides a preparation method of the flat plate heat pipe, comprising the following steps:

[0046] Step one: a copper alloy plate with a thickness of 0.2 mm is used to process the evaporation plate 100 as the first plate body 1, micro-milling is used to process a groove 2 with a depth of 0.12 mm on the first plate body 1, and a microarray structure is processed on the bottom surface of the groove 2 using a micro-milling cutter, the spacing between adjacent micro columns 3 is 1 mm, the length of the micro column 3 is 0.5 mm, and the height is 0.05 mm.

[0047] Step two: a ball head micro-milling cutter is used to process a U-shaped recess 4 at the gap between adjacent micro columns 3, the bottom diameter of the recess 4 is 1 mm, and the depth is 0.1 mm, and the microarray structure is subjected to super-hydrophilic treatment.

[0048] Step three: a copper alloy plate with a thickness of 0.2 mm is used to process the condensation plate 200, micro-milling is used to process a flange 6 with a height of 0.12 mm on the plate material corresponding to the groove 2, a discrete hydrophilic gradient surface is processed on the surface of the flange 6 by adjusting the laser power, the entire surface is subjected to super-lyophobic fluorination treatment, then the profile of the confluence region 7 is scanned longitudinally on the surface of the flange 6 using laser, the confluence channel 8 structure with a slope of 1° is processed by adjusting the laser power and repeating the scanning times, the confluence region 7 is super-hydrophilic, the long side wedge angle of the spindle-shaped confluence unit 9 is 2°, the short side is connected in series by selecting a circular arc transition connection mode, and the length of a single confluence unit 9 is 25 mm.

[0049] Step four: cover the evaporating plate 100 on the condensing plate 200, the flange 6 of the condensing plate 200 extends into the groove 2 of the evaporating plate 100, the edges of the first plate body 1 and the second plate body 5 are sealed by brazing, the first plate body 1 and the second plate body 5 have a backflow gap, a sealed shell with a liquid injection port is formed, and a liquid injection pipe is installed at the liquid injection port.

[0050] Step five: fill the liquid working medium into the flow channel 8 through the liquid injection pipe, and vacuumize the cavity surrounded by the groove 2 and the condensing plate 200.

[0051] Step six: first, weld the liquid injection pipe, and then perform secondary degassing, then weld the liquid injection port position, remove the liquid injection pipe, and complete the packaging of the flat plate heat pipe.

[0052] The flat plate heat pipe of the present application comprises an evaporating plate 100 and a condensing plate 200, the evaporating plate 100 and the condensing plate 200 are processed with a mortise-tenon structure to form a groove 2 and a flange 6 respectively, and the condensing plate 200 is connected by sealing after being mortised on the evaporating plate 100. The groove 2 of the evaporating plate 100 is provided with a microarray structure, the microcolumn 3 separates the groove 2 to build multiple superheated steam flow channels; the flange 6 of the condensing plate 200 has a discrete hydrophobic gradient, and a plurality of flow convergence units 9 are arranged in series in the flow convergence area 7, and the flow convergence area 7 is composed of the flow convergence channel 8 with a microgroove structure. The groove type wick of the flow convergence channel 8, combined with the discrete gradient hydrophobic interface, can realize the rapid pump-free delivery of the condensing working medium, and the flow convergence channel 8 has a small slope, which can further accelerate the working medium backflow speed and expand the steam flow channel. The mortise-tenon structure and the groove type wick make the wettability gradient structure flat plate heat pipe thinner, while meeting the mechanical properties of the components, and improving the heat exchange performance of the flat plate heat pipe.

[0053] The specific examples are applied in the present application to illustrate the principles and implementation modes of the present application, and the above examples are only used to help understand the method and core idea of the present application; meanwhile, for those skilled in the art, according to the idea of the present application, the specific implementation mode and application range can be changed. In conclusion, the content of the present application should not be understood as a limitation of the present application.

Claims

1. A flat heat pipe, characterized in that: include: An evaporation plate, the evaporation plate comprising a first plate body, the first plate body being provided with a groove, the groove being provided with a microarray structure, the microarray structure comprising a plurality of micropillars arranged in an array, with gaps between adjacent micropillars, and the micropillars being superhydrophilic; A condensation plate, the condensation plate includes a second plate body and a flange adapted to the groove, the second plate body is connected to the flange, the flange is hydrophobic, and the hydrophobicity of the flange changes in a discrete gradient; a confluence area is provided on the flange, the confluence area is super-hydrophilic, the confluence area includes a plurality of confluence units connected in series, and along the connection direction of the plurality of confluence units, the confluence unit has a narrow end opening and a wide end opening; the confluence unit includes a plurality of confluence channels, the confluence channels are micro-grooves, and the length direction of the confluence channels is parallel to the connection direction of the plurality of confluence units; along the direction from the wide end opening to the narrow end opening, the bottom surface of the confluence channel is inclined toward the direction of the second plate body; The condensing plate is located on the top of the evaporating plate, the flange extends into the groove, the edge of the first plate body is connected to the edge of the second plate body, and a circulation cavity capable of accommodating the circulation of the working medium is formed between the evaporating plate and the condensing plate.

2. The flat plate heat pipe according to claim 1, characterized in that: There is a depression between adjacent microcolumns, and the depression is U-shaped.

3. The flat plate heat pipe according to claim 1, wherein: The microcolumns are prism structures and are arranged in a rectangular array.

4. The flat plate heat pipe according to claim 1, wherein: The narrow end opening is one end opening of the confluence unit, the other end opening of the confluence unit is the end opening, the wide end opening is located between the narrow end opening and the end opening, the width of the confluence unit decreases from the wide end opening toward the end opening, and the spacing between the wide end opening and the end opening is greater than the spacing between the wide end opening and the narrow end opening, and the side wall at the wide end opening is a curved surface.

5. The flat plate heat pipe according to claim 4, characterized in that: The hydrophobicity gradient of the flange follows the following rules: Dth s =θ a -θ r Among them, θ a is the advancing angle of the working fluid droplet at the connection of the adjacent confluence units, θ r is the receding angle of the working fluid droplet at the connection of the adjacent confluence units, θ s is the roll angle of the flange.

6. The flat plate heat pipe according to claim 1, characterized in that: The slope of the bottom surface of the confluence channel is less than 2°.

7. The flat plate heat pipe according to claim 1, characterized in that: The number of the confluence areas is multiple, and the confluence areas are arranged in parallel on the flange.

8. The flat plate heat pipe according to claim 1, characterized in that: The evaporation plate and the condensation plate are both provided with a liquid injection port, the liquid injection port is communicated with the circulation cavity, and the liquid injection port can be connected to a liquid injection pipe.

9. A method for preparing a flat plate heat pipe according to any one of claims 1 to 8, characterized in that: The steps include: Step 1: Processing the evaporation plate and the condensation plate, and sealing the edges of the first plate body and the second plate body; Step 2: injecting a working medium into the circulation cavity and performing a vacuum treatment on the circulation cavity.

10. The method for preparing a flat plate heat pipe according to claim 9, wherein: The edges of the first plate and the second plate are connected by welding, a liquid working medium is injected into the confluence area, and a vacuum treatment is performed on the cavity surrounded by the condensation plate and the groove.

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