Composite ultrathin heat pipe and production process thereof

Abstract

The application discloses a composite ultrathin heat pipe and a production process thereof. The composite ultrathin heat pipe comprises a pipe shell, a combined wick and an operating liquid. The pipe shell has a closed heat conduction cavity. The combined wick is arranged in the heat conduction cavity. The combined wick comprises a wire mesh, a flat woven belt and metal powder. The flat woven belt is wrapped by the wire mesh, and a gas channel is formed by the gap between the wire mesh and the flat woven belt. The wire mesh, the flat woven belt and the metal powder are adhered to the inner circumferential wall of the pipe shell by sintering, and a porous capillary structure is formed. The porous capillary structure and the pores on the flat woven belt jointly form a liquid channel. The operating liquid is filled in the heat conduction cavity, can be vaporized at the heated end of the heat pipe, and flows to the condensing end of the heat pipe along the gas channel. The condensed operating liquid flows back to the heated end along the liquid channel by capillary force. The application can consider the advantages of high capillary force and rapid backflow of the condensed operating liquid, improve the heat conduction performance of the heat pipe, and realize ultrathin.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat pipe, in particular to a composite ultra-thin heat pipe and a production process thereof. BACKGROUND

[0002] At present, the common practice of the existing heat pipe is to obtain sufficient water storage capacity by increasing the capillary force of the heat pipe, so that the liquid can quickly carry heat to other parts after being heated. However, the increase of the capillary force will increase the resistance to the return flow of the condensed liquid, resulting in a slow return flow speed of the cooling liquid. If the return flow speed of the liquid is to be increased, the capillary force must be reduced, and the water storage capacity will also be reduced accordingly. Therefore, high capillary force and fast return flow of the liquid are usually contradictory, and the existing heat pipe cannot take both into account, resulting in the performance of the heat pipe being limited.

[0003] In addition, with the increasing number of mobile terminal users year by year, and in order to cater to the aesthetic view of modern people, mobile phones, PADs, high-end business notebooks and other terminal devices are pursuing ultra-thin products. However, the performance of CPU processors is constantly improving, and even the CPU of some products reaches the same level as a PC. Due to the increase in CPU power and the speed of operation, the contradiction between the heat dissipation demand of mobile devices is increasingly prominent. The groove pipe, sintered pipe and ordinary thin sintered pipe commonly used in the current market cannot be used in ultra-thin mobile devices. SUMMARY

[0004] In order to solve the above technical problems, the present application provides a composite ultra-thin heat pipe and a production process thereof, which can quickly move and diffuse heat under the condition of meeting ultra-thin, effectively solving the problem of overheating of mobile devices such as mobile phones during use; at the same time, the advantages of high capillary force and fast return flow of the condensed liquid can be taken into account, and the heat dissipation performance of the heat pipe is improved.

[0005] The technical scheme adopted by the present application to solve the technical problems is as follows: a composite ultra-thin heat pipe, comprising:

[0006] a pipe shell having a closed heat conduction cavity inside, and the heat conduction cavity is in a negative pressure state after being vacuumized;

[0007] a combined wick built in the heat conduction cavity; the combined wick comprises a wire mesh, a flat woven tape and metal powder, the flat woven tape is wrapped by the wire mesh, and a gas passage is formed by the gap therebetween; the wire mesh, the flat woven tape and the metal powder are sintered and adhered to the inner circumferential wall of the pipe shell, and a porous capillary structure is formed, and the porous capillary structure and the pores on the flat woven tape together constitute a liquid passage;

[0008] An operating liquid is filled in the heat conducting cavity, which can be vaporized at the heated end of the heat pipe and flow to the condensing end of the heat pipe along the gas channel, and the condensed operating liquid flows back to the heated end along the liquid channel by capillary force.

[0009] As a further improvement of the present application, the flat braided belt is tubular and is made of a plurality of metal wires which are interlaced and flattened into a double-layer flat structure.

[0010] As a further improvement of the present application, the flat braided belt is tubular and is made of a plurality of metal wires which are interlaced and flattened into a double-layer flat structure.

[0011] As a further improvement of the present application, the flat braided belt is tubular and is made of a plurality of metal wires which are interlaced and flattened into a double-layer flat structure.

[0012] As a further improvement of the present application, the flat braided belt is tubular and is made of a plurality of metal wires which are interlaced and flattened into a double-layer flat structure.

[0013] The present application also provides a production process of the composite ultra-thin heat pipe.

[0014] S1, a circular hollow tube shell is prepared, one end of which is open and the other end is closed;

[0015] S2, a wire mesh and a flat braided belt are inserted into the tube shell by means of a mandrel;

[0016] S3, metal powder is filled into the tube shell;

[0017] S4, a plurality of tube shells filled with metal powder are placed on a jig and placed in a sintering furnace for sintering, and after sintering, the wire mesh, the flat braided belt and the metal powder adhere to the inner circumferential wall of the tube shell and form a porous capillary structure;

[0018] S5, the mandrel is pulled out of the tube shell;

[0019] S6, operating liquid is added to the tube shell;

[0020] S7, vacuumizing the pipe shell after the working fluid is added in S6;

[0021] S8, clamping and sealing the open end of the pipe shell after vacuumizing to the required level, so that the heat conducting cavity of the pipe shell is in a negative pressure state;

[0022] S9, flattening the sealed pipe shell to the required size to form an ultra-thin heat pipe; after flattening, the wire mesh, the flat woven belt and the metal powder in the heat pipe form a combined wick, and the air gap between the flat woven belt and the wire mesh forms a gas passage for the working fluid vaporized at the heated end of the heat pipe to flow to the condensing end; meanwhile, the porous capillary structure and the pores on the flat woven belt jointly form a liquid passage for the condensed working fluid to quickly flow back to the heated end.

[0023] As a further improvement of the present application, in S1, the prepared pipe shell needs to be cleaned and annealed in a reducing furnace; the heating temperature of the reducing furnace is 600-700℃, and the heating time is 2.5-3.5h.

[0024] As a further improvement of the present application, S2 specifically includes the following steps:

[0025] S21, preparing the core rod, cutting a cutting plane on one side of the core rod along the axial direction, and setting a clamping groove at the lower end of the core rod;

[0026] S22, arranging the flat woven belt on the cutting plane;

[0027] S23, clamping one edge portion of the sheet-shaped wire mesh into the clamping groove, bending the remaining portion to be parallel to the core rod, and then rolling it around the core rod, and wrapping the flat woven belt;

[0028] S24, manually inserting the core rod with the wire mesh and the flat woven belt into the pipe shell, and the wire mesh will expand outward and adhere to the inner circumferential wall of the pipe shell due to its own elastic force.

[0029] As a further improvement of the present application, in S4, sintering is carried out in a hydrogen-nitrogen mixed gas atmosphere, the sintering temperature is 850-1050℃, and the sintering time is 2.5-3.5h, and at the same time, the metal surface oxide is reduced by hydrogen, so as to improve the metal purity.

[0030] As a further improvement of the present application, S9 specifically includes the following steps:

[0031] S91, the pipe shell after sealing is placed on the baking tray for heating, the heating temperature is 200-250 DEG C, and the heating time is 3-5 min;

[0032] S92, the pipe shell after the S91 heating is placed in a pressure mold and is flattened to form an ultra-thin heat pipe, wherein the temperature of the pressure mold is 100-150 DEG C, and the flattening is kept for 1-3 s.

[0033] The beneficial effects of the present application are:

[0034] 1) The present application provides a composite ultra-thin heat pipe and a production process thereof, which is composed of a combination of three materials: a wire mesh, a flat braided belt and metal powder. The capillary force is improved by the wire mesh and the porous capillary structure formed by sintering the metal powder, and sufficient water storage capacity is achieved, so that the working fluid can quickly carry heat to other parts after being heated. At the same time, the flat braided belt can quickly diffuse the condensed working fluid to the heated end, realizing the rapid circulation of the working fluid, and taking into account the advantages of high capillary force and rapid return of the condensed working fluid, improving the heat conduction performance of the heat pipe, and the heat conduction efficiency is higher.

[0035] 2) The thickness of the combined wick after compounding is within 0.5 mm, and the overall thickness of the heat pipe can be made to be within 1 mm, which can be installed in electronic devices such as mobile phones and PADs that require heat dissipation. In the case of meeting the ultra-thin condition, the heat can be quickly moved and diffused, effectively solving the problem of overheating of electronic devices during use.

[0036] 3) The composite ultra-thin heat pipe manufactured by the production process of the present application has a smooth surface and high product quality. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a schematic view of the transverse cross-sectional structure of the composite ultra-thin heat pipe of the present application;

[0038] Figure 2 is a schematic view of the longitudinal cross-sectional structure of the composite ultra-thin heat pipe of the present application;

[0039] Figure 3 is a step block diagram of the production process of the composite ultra-thin heat pipe of the present application;

[0040] Figure 4 is a perspective view of the mandrel used in the production process of the composite ultra-thin heat pipe of the present application.

[0041] The following description is made in conjunction with the drawings:

[0042] 1, pipe shell; 101, gas channel; 2, wire mesh; 3, flat braided belt; 4, mandrel; 401, cutting plane; 402, clamping groove. DETAILED DESCRIPTION

[0043] A preferred embodiment of the present application will be described in detail below with reference to the accompanying drawings.

[0044] Embodiment 1

[0045] Referring to Figure 1 and Figure 2 , the present application provides a composite ultra-thin heat pipe, comprising: a pipe shell 1, a combined wick and an operating liquid. The pipe shell 1 is flat, has a closed heat-conducting cavity inside, and the heat-conducting cavity is in a negative pressure state after being vacuumized, with a vacuum degree less than 1.3·10 -4 Pa.

[0046] Further, the combined wick is built in the heat-conducting cavity, and the combined wick comprises a wire mesh 2, a flat braided belt 3 and metal powder. The wire mesh 2 is sheet-shaped, wraps around the flat braided belt 3 after being coiled, and covers the inner circumferential wall of the pipe shell 1. The wire mesh 2, the flat braided belt 3 and the metal powder are adhered to the inner circumferential wall of the pipe shell 1 after being sintered at high temperature.

[0047] Figure 1 is a schematic view of a transverse section along the axis of the heat pipe, the outer top surface of the flat braided belt 3 is adhered to the inner top wall of the wire mesh 2 after sintering, and the outer bottom surface of the flat braided belt 3 is adhered to the inner bottom wall of the wire mesh 2 after the pipe shell 1 is flattened; at the same time, the metal powder forms a porous capillary structure on the wire mesh 2 and the flat braided belt 3 after sintering, and the porous capillary structure and the pores of the flat braided belt 3 itself jointly constitute a liquid channel.

[0048] Figure 2 is a schematic view of a longitudinal section perpendicular to the axis of the heat pipe, the gaps between the left and right sides of the flat braided belt 3 and the wire mesh 2 form gas channels 101 parallel to the axis of the heat pipe, and the gas channels 101 are separate from the liquid channel and are used in cooperation, so that the heat conduction performance of the product is more excellent.

[0049] In this embodiment, the operating liquid is pure water but is not limited thereto, which is filled in the heat-conducting cavity. The heat pipe has a heated end directly or indirectly in contact with a heat source, and a condensing end away from the heated end. The operating liquid is heated at the heated end of the heat pipe, and is rapidly boiled and vaporized into water vapor under the condition of negative pressure and low temperature. The water vapor flows along the gas channels to the condensing end of the heat pipe, and is condensed into liquid operating liquid after releasing heat at the condensing end, and is quickly returned to the heated end along the liquid channel by capillary force, so as to realize rapid heat dissipation.

[0050] The flat braided belt 3 is a tubular structure interlaced by dozens or even hundreds of metal wires, and is flattened into a double-layer flat structure. In this embodiment, the metal wires are specifically copper wires.

[0051] The present application improves the capillary force through the silk screen 2 and the porous capillary structure formed by sintering metal powder, realizes sufficient water storage capacity, so that the operating liquid can quickly carry heat and diffuse to other parts after being heated; at the same time, the condensed operating liquid can quickly return to flow by relying on the straight line rapid diffusion capacity of the flat woven belt 3. The water absorption test results show that the flow speed of the operating liquid on the metal powder is one fourth of the flow speed of the operating liquid on the flat woven belt 3, because the porous capillary structure formed by sintering metal powder is uneven and has many bends under the microscope, which increases the return flow path of the operating liquid and has large resistance to the return flow of the operating liquid; the flat woven belt 3 has small resistance to the return flow of the operating liquid and has a straight line guiding return flow effect, the operating liquid flows fast in the flat woven belt 3, which can make the condensed water quickly return to the heated end, realize rapid circulation, take into account the advantages of high capillary force and fast return flow of the condensed operating liquid, improve the heat conduction performance of the heat pipe, and have higher efficiency.

[0052] As an important feature of the present application, the tube shell 1, the silk screen 2, the flat woven belt 3 and the metal powder are all made of oxygen-free electrolytic copper with a purity of more than 99.99%; in the present embodiment, the purity of the oxygen-free electrolytic copper is more than 99.999%; in principle, the higher the purity of copper, the better the heat conduction performance, which avoids the significant decrease of the heat conduction and electrical conductivity caused by impure copper. The materials used need to be tested by an elemental analyzer.

[0053] Further, the wall thickness of the tube shell 1 is 0.1-0.3mm, the thickness of the silk screen 2 is 0.1-0.2mm, the silk screen 2 has a mesh number of 150-250 meshes, the flat woven belt 3 is woven by copper wires with a diameter of 0.03-0.04mm and has a thickness of 0.1-0.3mm, and the particle diameter of the metal powder is 45-120μm, so that the overall thickness of the heat pipe is less than 1mm, which meets the condition of ultra-thin heat pipe to quickly move and diffuse heat, effectively solving the problem of overheating of mobile devices such as mobile phones during use.

[0054] Specifically, in the present embodiment, the silk screen 2 has a mesh number of 200 meshes and a thickness of 0.1mm, the flat woven belt 3 is woven by copper wires with a diameter of 0.03mm and has a thickness of 0.2mm, the particle diameter of the metal powder is 60μm, the combined liquid absorption core after compounding can be within 0.5mm, and the wall thickness of the tube shell 1 is 0.2mm, so that the overall thickness of the heat pipe can be made to be within 1mm of the ultra-thin type.

[0055] It should be noted that the thickness of the combined wick should not exceed the thickness of the heat conduction cavity; for example, if the overall thickness of the heat pipe is required to be 1 mm and the wall thickness of the pipe shell 1 is 0.2 mm, then the thickness of the combined wick is not greater than 0.6 mm (usually, the overall thickness of the combined wick is also made to be 0.6 mm, and of course, a 0.1 mm gap can be reserved between the upper and lower layers of the flat woven belt 3), so as to avoid the combined wick being compacted during the flattening process, causing the liquid flow to be unsmooth and affecting the return of the actuating liquid after condensation.

[0056] Embodiment two

[0057] The present application also provides a production process of a composite ultrathin heat pipe, which is used to manufacture the composite ultrathin heat pipe described in embodiment one, and includes steps S1-S9.

[0058] S1, preparing a circular hollow pipe shell 1, wherein one end of the pipe shell 1 is open and the other end is closed.

[0059] In addition, the prepared pipe shell 1 needs to be cleaned to remove surface impurities and foreign matters. Then, the pipe shell 1 is placed in a reduction furnace for annealing treatment, the heating temperature of the reduction furnace is 600-700℃, and the heating time is 2.5-3.5h, so as to ensure the cleanliness inside the pipe shell 1 and the overall pure copper characteristics.

[0060] Preferably, the heating temperature of the reduction furnace is 650℃, and the heating time is 3h.

[0061] S2, inserting the wire mesh 2 and the flat woven belt 3 into the pipe shell 1 after reduction processing by means of the mandrel 4.

[0062] Specifically, S2 includes the following steps S21-S24.

[0063] S21, preparing a special mandrel 4; a cylindrical rod is cut along the axial direction on one side to form the special mandrel 4, and the cut surface is a cut plane 401, and the cut plane 401 extends to both ends of the mandrel 4. The lower end of the mandrel 4 is tapered to be inserted into the pipe shell 1, and the mandrel 4 is provided with a clamping groove 402 at the lower end, and the clamping groove 402 is distributed perpendicularly to the cut plane 401.

[0064] The size of the mandrel 4 is smaller than the inner diameter of the pipe shell 1.

[0065] S22, arranging the flat woven belt 3 on the cut plane 401.

[0066] S23, clamping the lower edge part of the sheet-shaped wire mesh 2 into the clamping groove 402, bending the remaining part to be parallel to the mandrel 4, and then rolling the mandrel 4, and wrapping the flat woven belt 3.

[0067] S24, the mandrel 4 is inserted into the pipe shell 1 with the wire mesh 2 and the flat braid 3, and the wire mesh 2 is expanded outwardly and adheres to the inner wall of the pipe shell 1 by the elastic force of the wire mesh 2.

[0068] S3, the pipe shell 1 is filled with metal powder by using a copper powder filling machine, and the pipe shell 1 is vibrated while the metal powder is filled, so that the metal powder is uniformly distributed in the pipe shell 1, and the copper powder is distributed on the wire mesh 2 and the flat braid 3.

[0069] S4, a plurality of pipe shells 1 filled with metal powder are placed on a jig and sintered in a sintering furnace in a hydrogen-nitrogen mixed gas atmosphere, and the sintering temperature is 850-1050℃, and the sintering time is 2.5-3.5h. During sintering, the hydrogen can reduce the metal surface oxide (i.e. copper oxide), thereby improving the metal purity, and the appearance of the sintered pipe shell 1 has high gloss. After sintering, the wire mesh 2, the flat braid 3 and the metal powder adhere to the inner wall of the pipe shell 1 and form a porous capillary structure.

[0070] Specifically, the hydrogen accounts for about 5% of the hydrogen-nitrogen mixed gas, the sintering temperature is 950℃, and the sintering time is 3h.

[0071] S5, the mandrel 4 is pulled out of the pipe shell 1 by a pulling rod machine, and since the wire mesh 2, the flat braid 3 and the metal powder adhere to the inner wall of the pipe shell 1 after sintering, the mandrel 4 is separated from them during the pulling process.

[0072] S6, the pipe shell 1 after the mandrel 4 is pulled out is filled with working fluid by a water injection machine.

[0073] S7, the pipe shell 1 after the working fluid is added in S6 is vacuumized by a vacuum degassing machine to remove the air in the pipe shell 1.

[0074] S8, after the vacuum degree in the pipe shell 1 reaches the required set target value or the set vacuumization time is reached, the open end of the pipe shell 1 is clamped and sealed, so that the heat conduction cavity of the pipe shell 1 is in a negative pressure state.

[0075] S9, the sealed pipe shell 1 is flattened to form an ultra-thin heat pipe. After flattening, the wire mesh 2, the flat braid 3 and the metal powder in the heat pipe are combined into a combined wick, and the air gap between the flat braid 3 and the wire mesh 2 forms a gas channel 101 for the working fluid to flow to the condensing end after vaporization at the heating end of the heat pipe; at the same time, the porous capillary structure and the pores on the flat braid 3 together form a liquid channel for the condensed working fluid to quickly flow back to the heating end.

[0076] Specifically, S9 includes the following steps:

[0077] S91, the sealed pipe shell 1 is placed on a baking tray for heating, the heating temperature is 200-250 DEG C, and the heating time is 3-5 min; preferably, the baking tray heating temperature is 230 DEG C, and the heating time is 4 min.

[0078] S92, the pipe shell 1 heated in S91 is placed in a press mold to be flattened and formed into an ultra-thin heat pipe; wherein the temperature of the press mold is 100-150 DEG C, and the flattening time is 1-3 s; preferably, the temperature of the press mold is 120 DEG C, and the flattening time is 1 s, to ensure high-efficiency production operation.

[0079] The pipe shell 1 is heated first in the application, so that the internal actuating liquid is vaporized, and the internal pressure of the pipe shell 1 is increased, so that the surface of the ultra-thin heat pipe formed in the process of using the press mold to flatten is very smooth, preventing the pipe shell 1 surface from being not smooth due to the concave and strip-shaped groove conditions; at the same time, the heat on the heat pipe is absorbed by the press mold, and the flattening time is 1 s, to reduce the internal pressure of the heat pipe and avoid causing the bulging and other adverse defects, improving the product quality.

[0080] It can be understood that the reduction furnace, copper powder filling machine, rod drawing machine, vacuum degassing machine, water injection machine, and press mold used in the production of the composite ultra-thin heat pipe in the embodiment are all existing technologies, and are not the focus of the application, and will not be described in detail here.

[0081] In the above description, many specific details are set forth in order to provide a thorough understanding of the present application. However, the above description is only a preferred embodiment of the present application, and the present application can be implemented in many other ways different from the description. Therefore, the present application is not limited by the specific implementation disclosed above. Meanwhile, any person skilled in the art can make many possible changes and modifications to the above disclosed methods and technical contents without departing from the scope of the present application, or modify the above embodiments into equivalent embodiments. Any simple modification, equivalent change and modification made to the above embodiments without departing from the technical solution of the present application, all belong to the scope of protection of the present application.

Claims

1. A composite ultrathin heat pipe, characterized in that, include: The shell (1) is flat and has a sealed heat-conducting cavity inside, and the heat-conducting cavity is under negative pressure after being evacuated. A combined liquid-absorbing core is built into the heat-conducting cavity; the combined liquid-absorbing core includes a wire mesh (2), a flat braided tape (3) and metal powder. The wire mesh (2), the flat braided tape (3) and the metal powder are sintered and adhered to the inner peripheral wall of the tube shell (1) to form a porous capillary structure. The porous capillary structure and the pores on the flat braided tape (3) together constitute a liquid channel. The wire mesh (2) covers the inner peripheral wall of the tube shell (1). The outer top surface of the flat braided tape (3) is sintered and adhered to the inner top wall of the wire mesh (2). The outer bottom surface of the flat braided tape (3) is flattened on the tube shell (1) and abuts against the inner bottom wall of the wire mesh (2), so that the flat braided tape (3) is wrapped by the wire mesh (2). At the same time, gas channels (101) are formed in the gaps between the flat braided tape (3) and the wire mesh (2). The actuating fluid, which fills the heat-conducting cavity, can be heated and vaporized at the heated end of the heat pipe and flow along the gas channel to the condensing end of the heat pipe. After condensation, the actuating fluid flows back to the heated end along the liquid channel by capillary force.

2. The composite ultrathin heat pipe according to claim 1, characterized in that: The flat braided strip (3) is a tubular structure made of multiple metal wires interwoven together and flattened into a double-layer flat structure.

3. The composite ultrathin heat pipe according to claim 1, characterized in that: The wire mesh (2) is sheet-like and is rolled into a circle to cover the inner circumferential wall of the tube shell (1).

4. The composite ultrathin heat pipe according to claim 1, characterized in that: The tube shell (1), the wire mesh (2), the flat braided belt (3) and the metal powder are all made of oxygen-free electrolytic copper with a purity greater than 99.99%.

5. The composite ultrathin heat pipe according to claim 1, characterized in that: The wall thickness of the tube shell (1) is 0.1~0.3mm, the thickness of the wire mesh (2) is 0.1~0.2mm, and the mesh number of the wire mesh (2) is 150~250 mesh. The flat braided tape (3) is woven from copper wire with a diameter of 0.03~0.04mm and a thickness of 0.1~0.3mm. The particle diameter of the metal powder is 45~120μm, thereby making the overall thickness of the heat pipe less than 1mm.

6. A manufacturing process for a composite ultrathin heat pipe, used to manufacture the composite ultrathin heat pipe as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1, prepare a circular hollow tube shell (1), with one end of the tube shell (1) open and the other end closed; S2, insert the wire mesh (2) and the flat braided tape (3) together into the tube shell (1) by means of the mandrel (4); S3, fill the tube shell (1) with metal powder; S4, several tube shells (1) filled with metal powder are placed on a fixture and placed in a sintering furnace for sintering. After sintering, the wire mesh (2), the flat braided belt (3) and the metal powder will adhere to the inner peripheral wall of the tube shell (1) and form a porous capillary structure. S5, the mandrel (4) is pulled out from the tube shell (1); S6, add actuating fluid into the shell (1); S7, vacuum treatment is performed on the shell (1) after the actuating fluid is added in S6; S8. After the vacuum reaches the required level, clamp and seal the open end of the shell (1) so that the heat-conducting cavity of the shell (1) is under negative pressure. S9, the sealed shell (1) is flattened to the required size to form an ultra-thin heat pipe; the wire mesh (2), the flat braided tape (3) inside the heat pipe and the metal powder are combined to form a liquid absorbent core, and the gap between the flat braided tape (3) and the wire mesh (2) forms a gas channel (101) for the actuating liquid to vaporize at the heated end of the heat pipe and flow to the condensing end; at the same time, the porous capillary structure and the pores on the flat braided tape (3) together form a liquid channel for the condensed actuating liquid to quickly flow back to the heated end.

7. The manufacturing process of the composite ultrathin heat pipe according to claim 6, characterized in that: In step S1, the prepared tube shell (1) needs to be cleaned and placed in a reduction furnace for annealing; wherein the heating temperature of the reduction furnace is 600~700℃ and the heating time is 2.5~3.5h.

8. The manufacturing process of the composite ultrathin heat pipe according to claim 6, characterized in that, S2 specifically includes the following steps: S21, the mandrel (4) is prepared by cutting along the axial direction on one side of the mandrel (4) to form a cutting plane (401), and a slot (402) is provided at the lower end of the mandrel (4). S22, the flat braided strip (3) is arranged on the cutting plane (401); S23, insert one edge of the sheet-like wire mesh (2) into the slot (402), bend the remaining part to be parallel to the core rod (4), then roll it into a circle on the core rod (4) and wrap the flat braided strip (3); S24, the manipulator (4) carrying the wire mesh (2) and the flat braided tape (3) is inserted into the tube shell (1) by hand. The wire mesh (2) will expand outward and stick to the inner circumferential wall of the tube shell (1) by its own elastic force.

9. The manufacturing process of the composite ultrathin heat pipe according to claim 6, characterized in that: In step S4, sintering is carried out in a hydrogen-nitrogen mixed gas atmosphere at a temperature of 850-1050°C for 2.5-3.5 hours. Simultaneously, hydrogen is used to reduce the oxides on the metal surface, thereby improving the metal purity.

10. The manufacturing process of the composite ultrathin heat pipe according to claim 6, characterized in that, S9 specifically includes the following steps: S91, place the sealed tube shell (1) on a baking tray and heat it at a temperature of 200~250℃ for 3~5 minutes; S92, the tube shell (1) heated by S91 is placed in the mold and flattened to form an ultra-thin heat pipe; wherein, the temperature of the mold is 100~150℃, and the flattening is held for 1~3s.

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