Ultrathin flat heat pipe based on punch forming and manufacturing process

Abstract

The invention relates to the technical field of flat heat pipes, in particular to an ultrathin flat heat pipe based on punch forming and a manufacturing process. The ultrathin flat heat pipe comprises an upper shell and a lower shell which are formed by stamping a metal sheet, the upper shell and / or the lower shell is provided with a micro-column array, the upper shell, the lower shell and the micro-column array are synchronously formed by stamping, and the micro-column end face of the micro-column array is attached to the inner wall of the upper shell or the lower shell; gaps among the micro-column arrays form capillary core cavities, the top surface and the bottom surface in each capillary core cavity are respectively provided with a liquid absorption core layer, and a gap is formed between the two liquid absorption core layers; the capillary core cavity is used for containing a heat exchange working medium. According to the flat heat pipe, the upper shell, the lower shell and the micro-column array structure can be obtained only by stamping once, the manufacturing process is greatly simplified, and meanwhile the production cost is reduced. The micro-column array forms a pressure-resistant support and a capillary structure between the upper shell and the lower shell, so that the pressure-bearing capacity and the stability of the flat heat pipe can be greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of flat plate heat pipes, and in particular to an ultra-thin flat plate heat pipe based on stamping and a manufacturing process thereof. Background Art

[0002] With the rapid development of the information industry, electronic products are constantly developing in the direction of high performance and lightness. As a good heat transfer device, heat pipes have the advantages of compact structure, reliable operation, no other energy consumption, and high effective thermal conductivity. Therefore, they are widely used in various fields. Heat pipes are generally divided into three sections, namely the evaporation section, the insulation section, and the condensation section; there are wicks and working fluids inside, and the internal environment is generally a vacuum or negative pressure state. Heat pipe heat transfer uses the principle of phase change: the working fluid in the evaporation section is heated and vaporized, and a pressure difference is generated under the action of the temperature difference between the evaporation section and the condensation section, causing the steam to flow toward the condensation section. After liquefaction in the condensation section, the working fluid is sent to the evaporation section through the capillary force of the wick, thereby realizing cyclic heat transfer.

[0003] Ultra-thin heat pipes are a new type of heat pipe manufactured to adapt to the narrow heat dissipation space of thin and light electronic devices. They have the characteristics of high thermal conductivity and excellent temperature uniformity. However, for the ultra-thin heat pipes currently manufactured, due to their reduced thickness, they are prone to problems of insufficient strength and insufficient pressure resistance. For example, the manufacturing process of existing ultra-thin heat pipes is extremely complicated and the manufacturing cost is high. For example, the aluminum-based ultra-thin heat pipe with a super-hydrophilic structure and the preparation method disclosed in patent application CN109631637A obtains a capillary structure by laser processing. For example, an ultra-thin heat spreader and its preparation method disclosed in patent application CN112129151A use electric sparks to process a liquid absorbent core on a plate. For example, an ultra-thin heat spreader and its manufacturing method disclosed in patent application CN111465293A obtains a liquid absorbent core by powder sintering, electroplating, foam metal compression, or metal powder filling foam metal and sintering. The process of setting the capillary structure is complicated. Another example is a manufacturing process for ultra-thin refrigerant phase change heat transfer plates based on stamping disclosed in patent application CN116727515A. The wire mesh is sintered twice, and a duct cover is used as support between the upper shell and the base, which increases the resistance to refrigerant movement, makes the manufacturing process complex, and increases the thickness of the heat transfer plate.

[0004] Therefore, in order to meet the heat dissipation needs of electronic equipment, designing and manufacturing an ultra-thin flat heat pipe that takes into account ultra-thin size, high pressure bearing capacity and low cost is an urgent problem to be solved in the field of heat pipes. Summary of the invention

[0005] The purpose of the present invention is to provide an ultra-thin flat heat pipe based on stamping, which has the characteristics of high heat exchange efficiency, strong pressure bearing capacity and simple manufacturing process;

[0006] Another object of the present invention is to provide a manufacturing process of an ultra-thin flat heat pipe based on stamping, which has the characteristics of simplifying the process and reducing the manufacturing cost.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] An ultra-thin flat heat pipe based on stamping, comprising an upper shell and a lower shell stamped from a metal sheet, the upper shell and / or the lower shell having a micro-column array, the upper shell, the lower shell and the micro-column array being stamped synchronously, and the micro-column end faces of the micro-column array being attached to the inner wall of the upper shell or the lower shell;

[0009] The gaps between the microcolumn arrays form a capillary wick cavity, the top surface and the bottom surface of the capillary wick cavity are respectively provided with a liquid wick layer, and there is a gap between the two liquid wick layers;

[0010] The capillary core cavity is used to accommodate a heat exchange medium.

[0011] Furthermore, the upper shell and the lower shell are covered with a tin layer, and the liquid absorbing core layer is fixed to the tin layer.

[0012] Furthermore, the upper shell and the lower shell are respectively provided with micro-column arrays, and the micro-column end faces of the micro-column array of the upper shell and the micro-column end faces of the micro-column array of the lower shell are positioned opposite and in contact with each other.

[0013] Furthermore, the liquid-absorbing core layer is a multi-layer sintered wire mesh, and the liquid-absorbing core layer includes a plurality of large-pore wire meshes and a plurality of small-pore wire meshes, and the large-pore wire meshes and the small-pore wire meshes are alternately stacked.

[0014] Furthermore, the height of the micro-pillars in the micro-pillar array is 0.2-1.0 mm, the interval between the bottom ends of two adjacent micro-pillars is 0.5-2 mm, and the diameter of the micro-pillars is 1-3 mm.

[0015] Furthermore, the thickness of the large-aperture screen in the absorbent core layer is 0.08-0.12 mm, and the aperture is 50-100 mesh; the thickness of the small-aperture screen in the absorbent core layer is 0.04-0.06 mm, and the aperture is 300-500 mesh.

[0016] Furthermore, the thickness of the upper shell and the lower shell are both 0.1-0.3 mm.

[0017] A manufacturing process of an ultra-thin flat plate heat pipe based on stamping, the manufacturing process is used to manufacture the above-mentioned ultra-thin flat plate heat pipe based on stamping, and the manufacturing process comprises the following steps:

[0018] S1: forming a micro-pillar array and an edge sealing surface on a metal sheet by stamping;

[0019] S2: After stamping is completed, a tin layer is deposited on the side of the metal sheet having the micro-pillar array;

[0020] S3: laying a liquid wick layer on one side of the metal sheet having the micro-column array and sintering and fixing it, wherein the liquid wick layer is located between two adjacent micro-columns of the micro-column array;

[0021] S4: folding the metal sheet on which the liquid absorbent core layer is laid in half to form an upper shell and a lower shell, and then sealing and welding the edges of the upper shell and the lower shell;

[0022] S5: Filling the space between the upper shell and the lower shell with a heat exchange medium and performing vacuum treatment.

[0023] Furthermore, in S3, sintering and fixing are performed once after each layer of wire mesh is laid on the side of the metal sheet having the micro-pillar array.

[0024] Furthermore, in S2, a tin layer is deposited on the surface of the metal sheet by using an electroplating process.

[0025] The technical solution provided by the present invention may include the following beneficial effects:

[0026] 1. The present invention adopts a stamping process to prepare the sealing welding surface of the micro-column array and the shell on the surface of the metal sheet, and forms the outer shell of the flat heat pipe by stacking. Therefore, only one stamping is required to obtain the upper shell, the lower shell and the micro-column array structure, and the upper shell and the lower shell are folded in half to complete the splicing, so that the outer shell of the flat heat pipe reduces one weld, which greatly simplifies the manufacturing process and reduces the production cost.

[0027] 2. The micro-column array constitutes the compressive support between the upper shell and the lower shell, which can greatly improve the pressure bearing capacity and stability of the flat heat pipe. The distribution of the micro-column array on the upper shell and the lower shell is uniform distribution, gradient distribution or tree distribution.

[0028] 3. In the present invention, the top and bottom surfaces of the capillary wick cavity are respectively provided with liquid absorbing core layers, which can improve the reflux capacity of the condensed liquid in the condensation section and enhance the boiling heat transfer in the evaporation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic structural diagram of an ultra-thin flat heat pipe according to an embodiment of the present invention;

[0030] Figure 2 is a cross-sectional schematic diagram of an ultra-thin flat plate heat pipe;

[0031] Figure 3 It is a thin metal plate with a liquid-absorbing core layer fixed;

[0032] Figure 4 It is a thin metal plate with a uniformly distributed array of micropillars;

[0033] Figure 5 It is a metal sheet with micro-pillar arrays distributed in a tree shape;

[0034] Figure 6 It is a metal sheet with gradient distribution of micro-pillar array;

[0035] Reference numerals: metal sheet 01 , upper shell 1 , lower shell 2 , capillary core cavity 3 , microcolumn array 4 , liquid wick layer 5 , large-aperture wire mesh 51 , small-aperture wire mesh 52 , vacuum tube 6 . DETAILED DESCRIPTION

[0036] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0037] Combine the following Figures 1 to 6 , describing an ultra-thin flat heat pipe based on stamping forming in an embodiment of the present invention.

[0038] An ultra-thin flat heat pipe based on stamping, comprising an upper shell 1 and a lower shell 2 stamped from a metal sheet 01, the upper shell 1 and / or the lower shell 2 having a micro-column array 4, the upper shell 1, the lower shell 2 and the micro-column array 4 are stamped synchronously, and the micro-column end faces of the micro-column array 4 are attached to the inner wall of the upper shell 1 or the lower shell 2;

[0039] The gaps between the micro-pillar arrays 4 form a capillary core cavity 3, and the top and bottom surfaces of the capillary core cavity 3 are respectively provided with a liquid absorbent core layer 5, and there is a gap between the two liquid absorbent core layers 5;

[0040] The capillary core cavity 3 is used to accommodate a heat exchange medium.

[0041] The present invention forms an upper shell 1, a lower shell 2 and a micro-column array 4 on a metal sheet 01 by a stamping process, thereby simplifying the forming process of the heat pipe shell and the auxiliary supporting structure. Then, the liquid absorbing core layer 5 and the edge of the sealed shell can be fixed in the gap between the micro-column arrays 4, thereby greatly simplifying the manufacturing process of the flat heat pipe.

[0042] The micro-column array 4 constitutes a compressive support between the upper shell 1 and the lower shell 2, which can greatly improve the pressure bearing capacity and stability of the flat heat pipe. The distribution of the micro-column array 4 in the upper shell 1 and the lower shell 2 is uniform distribution, gradient distribution or tree distribution. The cavity formed between the micro-column arrays 4 in the outer shell constitutes a capillary structure. When the micro-column array 4 is distributed in a gradient, the capillary pore size of the capillary structure is changed by changing the distribution density of the micro-column array 4 along the flow direction of the working medium. A smaller pore size will produce a greater capillary force. By gradually reducing the pore size, the best balance between the capillary force and the permeability is achieved, thereby achieving the fastest capillary transmission performance. The tree-shaped distribution of the micro-column array 4 forms a main and secondary channel with a smaller flow resistance by processing multiple branch paths in the micro-column array 4, thereby improving the efficiency of liquid transmission. Specifically, the axial cross-section of the micro-columns in the micro-column array 4 is trapezoidal.

[0043] In the present invention, the top and bottom surfaces of the capillary wick cavity 3 are respectively provided with a liquid wick layer 5, which can improve the reflux capacity of the condensed liquid in the condensation section and enhance the boiling heat transfer in the evaporation section.

[0044] Preferably, the material of the metal sheet 01 is selected from, but not limited to, high-strength metal materials such as copper alloy, aluminum alloy, and iron-carbon alloy, so that the prepared flat heat pipe has an ultra-thin size while ensuring its high pressure bearing capacity. Further preferably, the thickness of the upper shell 1 and the lower shell 2 are both 0.1-0.3 mm.

[0045] Specifically, a vacuum tube 6 is inserted into one end of the shell composed of the upper shell 1 and the lower shell 2. The vacuum tube 6 is connected to the shell by hot pressing, and a sealant is provided between the vacuum tube 6 and the shell to seal and fix. The vacuum tube 6 can be used to inject working fluid and evacuate. The inside of the shell is evacuated to reduce the vacuum inside the shell, thereby reducing the boiling point of the working fluid solution in the shell, making the working fluid solution easier to evaporate, so that the flat heat pipe can meet the normal operation of the electronic equipment at the required temperature.

[0046] In order to improve solderability, the upper shell 1 and the lower shell 2 are further covered with a tin layer, and the liquid wick layer 5 is fixed to the tin layer. The tin layer is used to improve the solderability of the upper shell 1 and the lower shell 2, and is also conducive to the fixation of the liquid wick layer 5 on the upper shell 1 and the lower shell 2. Specifically, the electroplating process is used to form a deposited tin layer on the surface of the metal sheet 01 after stamping. Compared with the tin layer obtained by other methods, the electroplated tin layer has better bonding force with the metal sheet 01.

[0047] Preferably, the upper shell 1 and the lower shell 2 are respectively provided with a micro-column array 4, and the micro-column end faces of the micro-column array 4 of the upper shell 1 and the micro-column end faces of the micro-column array 4 of the lower shell 2 are positioned opposite and in contact. The micro-columns of the upper shell 1 and the lower shell 2 are opposite to form a shell support, and the small-sized micro-columns can realize the support of the shell, effectively improving the stability and pressure bearing capacity of the heat pipe, and the small-sized micro-columns can make the micro-column array 4 form a smaller capillary structure, thereby improving the flow capacity of the working medium.

[0048] In one embodiment of the present invention, the absorbent core layer 5 is a multi-layer sintered wire mesh, and the absorbent core layer 5 includes a plurality of large-aperture wire meshes 51 and a plurality of small-aperture wire meshes 52, and the large-aperture wire meshes 51 and the small-aperture wire meshes 52 are alternately stacked. The large-aperture wire meshes 51 provide a greater permeability for the working fluid, and the small-aperture wire meshes 52 provide a greater capillary force for liquid circulation. Through this multi-layer capillary core coupling method, the contradiction between capillary force and permeability is effectively resolved. Compared with the unidirectional arrangement of large and small wire mesh apertures, the alternating multi-layer porous structure produces multiple layers of channels with large apertures but small flow resistance inside the absorbent core. This type of channel bears the main capillary transmission flow, which can greatly increase the rate of capillary transmission. In the present invention, a multi-layer porous capillary core with alternating large and small apertures is prepared on the surface of the capillary core by a multi-layer wire mesh sintering process. Preferably, the bottom layer and the top layer of the liquid-absorbing core layer 5 in the present invention are both small-pore mesh 52, which have strong capillary driving force, are conducive to the flow of steam and liquid, improve the reflux capacity of the condensed liquid of the ultra-thin heat pipe, and enhance the boiling heat transfer of the evaporation section, thereby greatly improving the heat transfer performance inside the ultra-thin heat pipe.

[0049] In one embodiment of the present invention, the microcolumn height in the microcolumn array is 0.2-1.0 mm, the interval between the bottom ends of two adjacent microcolumns is 0.5-2 mm, and the microcolumn diameter is 1-3 mm. Therefore, based on the thickness of the upper shell 1 and the lower shell 2 being 0.1-0.3 mm, the thickness of the flat heat pipe of the present invention is 0.5-2.3 mm. It can be understood that the size of the microcolumn is designed by comprehensively considering the space of the application object, the anti-expansion mechanical strength, and the capillary transmission performance formed by the gap between the microcolumns.

[0050] In one embodiment of the present invention, the large-aperture screen 51 in the absorbent core layer 5 has a thickness of 0.08-0.12 mm and a pore size of 50-100 meshes; the small-aperture screen 52 in the absorbent core layer 5 has a thickness of 0.04-0.06 mm and a pore size of 300-500 meshes.

[0051] Correspondingly, the present invention also provides a manufacturing process of an ultra-thin flat heat pipe based on stamping, the manufacturing process is used to manufacture the above-mentioned ultra-thin flat heat pipe based on stamping, and the manufacturing process comprises the following steps:

[0052] S1: forming a micro-pillar array 4 and an edge sealing surface on a metal sheet 01 by stamping;

[0053] S2: After stamping is completed, a tin layer is deposited on the side of the metal sheet 01 having the micro-pillar array 4;

[0054] S3: Laying a liquid wick layer 5 on one side of the metal sheet 01 having the micro-pillar array 4 and sintering and fixing it, wherein the liquid wick layer 5 is located between two adjacent micro-pillars of the micro-pillar array 4;

[0055] S4: Folding the metal sheet 01 on which the liquid absorbent core layer 5 is laid in half to form an upper shell 1 and a lower shell 2, and then sealing and welding the edges of the upper shell 1 and the lower shell 2;

[0056] S5: Filling the space between the upper shell 1 and the lower shell 2 with a heat exchange medium and performing vacuum treatment.

[0057] The present invention adopts a stamping process to prepare the sealing welding surface of the micro-column array 4 and the shell on the surface of the metal sheet 01, and forms the outer shell of the flat heat pipe by stacking. Therefore, only one stamping is required to obtain the upper shell 1, the lower shell 2 and the micro-column array 4 structure, and the upper shell 1 and the lower shell 2 are folded in half to complete the splicing, so that the outer shell of the flat heat pipe reduces one weld, which greatly simplifies the manufacturing process and reduces the production cost.

[0058] Exemplarily, in S4, a hot pressing diffusion welding process is used to seal the edges of the upper shell 1 and the lower shell 2. After welding, the overall deformation of the heat pipe is small and the quality of the welded joint is good. Preferably, in S2, the electroplating process is used to deposit a tin layer on the surface of the metal sheet 01, thereby improving the weldability of the sealing weld and improving the bonding strength between the upper shell 1 and the lower shell 2. It should be noted that the tin layer prepared by the electroplating process has better bonding strength with the metal sheet 01 than other processes. SnCl2·2H2O solution can be used as an electroplating solution, and the density of the tin-plated layer can be changed by adjusting the current density to adjust its weldability.

[0059] For example, in S4, after the upper shell 1 and the lower shell 2 are sealed and connected, a filling hole is reserved at the corner, and a vacuum tube 6 is inserted into the filling hole for filling the working medium and vacuuming. After the filling of the working medium and vacuuming are completed, the vacuum tube 6 is sealed and packaged by a cold welding process. The cold welding process is to place a tool at one end of the vacuum tube 6, squeeze the end of the vacuum tube 6 with the blade of the tool to deform it, and seal and cut it.

[0060] In one embodiment of the present invention, in S3, after each layer of wire mesh is laid on the side of the metal sheet 01 having the micro-pillar array 4, sintering and fixing is performed to ensure the sintering state and to ensure that each layer of wire mesh is firmly connected.

[0061] An ultra-thin flat heat pipe based on stamping and other components and operations of the manufacturing process according to the embodiment of the present invention are well known to those skilled in the art and will not be described in detail here.

[0062] In the description of the present invention, it is necessary to understand that the terms "longitudinal", "transverse", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, features defined as "first" or "second" may explicitly or implicitly include one or more of the features, and are used to distinguish and describe features, without distinction of order or importance.

[0063] In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0064] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0065] In the description of this specification, the description with reference to the terms "embodiment", "example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0066] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. An ultra-thin flat heat pipe based on stamping, characterized in that: It comprises an upper shell and a lower shell formed by stamping a metal sheet, the upper shell and / or the lower shell has a micro-column array, the upper shell, the lower shell and the micro-column array are stamped synchronously, and the end surface of the micro-columns of the micro-column array is attached to the inner wall of the upper shell or the lower shell; The gaps between the microcolumn arrays form a capillary wick cavity, the top surface and the bottom surface of the capillary wick cavity are respectively provided with a liquid wick layer, and there is a gap between the two liquid wick layers; The capillary core cavity is used to accommodate a heat exchange medium.

2. The ultra-thin flat heat pipe based on stamping according to claim 1, characterized in that: The upper shell and the lower shell are covered with tin layers, and the liquid absorbing core layer is fixed to the tin layers.

3. The ultra-thin flat heat pipe based on stamping according to claim 1, characterized in that: The upper shell and the lower shell are respectively provided with micro-column arrays, and the micro-column end faces of the micro-column array of the upper shell and the micro-column end faces of the micro-column array of the lower shell are directly opposite and in contact with each other.

4. The ultra-thin flat heat pipe based on stamping according to claim 1, 2 or 3, characterized in that: The liquid-absorbing core layer is a multi-layer sintered wire mesh, and the liquid-absorbing core layer includes a plurality of large-aperture wire meshes and a plurality of small-aperture wire meshes, and the large-aperture wire meshes and the small-aperture wire meshes are alternately stacked.

5. The ultra-thin flat heat pipe based on stamping according to claim 4, characterized in that: The micro-columns in the micro-column array have a height of 0.2-1.0 mm, a spacing between the bottom ends of two adjacent micro-columns of 0.5-2 mm, and a diameter of the micro-columns of 1-3 mm.

6. The ultra-thin flat heat pipe based on stamping according to claim 5, characterized in that: The thickness of the large-aperture screen in the liquid-absorbing core layer is 0.08-0.12 mm, and the aperture is 50-100 meshes; the thickness of the small-aperture screen in the liquid-absorbing core layer is 0.04-0.06 mm, and the aperture is 300-500 meshes.

7. The ultra-thin flat heat pipe based on stamping according to claim 1, characterized in that: The thickness of the upper shell and the lower shell are both 0.1-0.3 mm.

8. A manufacturing process of an ultra-thin flat heat pipe based on stamping, characterized in that: The manufacturing process is used to manufacture the ultra-thin flat heat pipe based on stamping as described in any one of claims 1 to 7, and the manufacturing process comprises the following steps: S1: forming a micro-pillar array and an edge sealing surface on a metal sheet by stamping; S2: After stamping is completed, a tin layer is deposited on the side of the metal sheet having the micro-pillar array; S3: laying a liquid wick layer on one side of the metal sheet having the micro-column array and sintering and fixing it, wherein the liquid wick layer is located between two adjacent micro-columns of the micro-column array; S4: folding the metal sheet on which the liquid absorbent core layer is laid in half to form an upper shell and a lower shell, and then sealing and welding the edges of the upper shell and the lower shell; S5: Filling the space between the upper shell and the lower shell with a heat exchange medium and performing vacuum treatment.

9. The manufacturing process according to claim 8, characterized in that: In S3, sintering and fixing are performed once after each layer of wire mesh is laid on the side of the metal sheet having the micro-pillar array.

10. The manufacturing process according to claim 8, characterized in that: In S2, a tin layer is deposited on the surface of the metal sheet by using an electroplating process.

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