Ultra-thin heat sink and preparation method thereof

Abstract

The present invention relates to the technical field of electronic heat dissipation, and more specifically, to an ultra-thin heat spreader and a preparation method thereof, comprising a first plate and a second plate, the first plate and the second plate are packaged and a closed cavity is formed between the first plate and the second plate; an array groove structure is provided in the closed cavity, the array groove structure comprises a steam cavity, a boss and a liquid wick, the liquid wick and the steam cavity are both provided between the bosses and the steam cavity is located above the liquid wick, and the upper and lower ends of the boss are respectively abutted against the inner side surfaces of the first plate and the second plate. The present invention adopts the electrospark forming technology to process the array groove structure, and the support column and the reflux column, the liquid wick and the steam cavity are naturally formed during the processing, and no additional processing is required, thereby simplifying the internal structure design of the heat spreader, reasonably allocating the internal space of the heat spreader, and helping to reduce the thickness of the heat spreader; and the array groove structure of the present invention forms fins and micro-pits at the bottom, which can effectively increase the capillary pressure of the liquid wick and improve the heat transfer performance of the ultra-thin heat spreader.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic heat dissipation, and more specifically, to an ultra-thin heat spreader and a preparation method thereof. Background Art

[0002] With the rapid development of microelectronics technology and the information industry, the high performance, miniaturization and integration of electronic devices have become the mainstream trend of the development of modern electronic equipment. The high integration, high power consumption and small size of electronic chips have led to a significant increase in the heat flux density of the chips, and the heat transfer and heat dissipation problems have become more severe. The ultra-thin heat spreader is a closed cavity formed by welding and encapsulating a thin flat plate with a wick structure. It has a large heat dissipation area and good flexibility, and is widely used in the heat dissipation of electronic devices with high heat flux density. With the further reduction of the thickness of the ultra-thin heat spreader, the micro-groove wick has become a better choice. At present, the micro-groove wick is mainly processed by special manufacturing processes such as plowing-extrusion forming, laser etching, and chemical corrosion. Due to the limitations of the processing technology, the micro-groove structure after processing is single and the precision is poor, resulting in low capillary pressure and relatively large size of the wick, which in turn affects the heat transfer performance of the ultra-thin heat spreader and limits the reduction of the thickness of the ultra-thin heat spreader. At present, the thickness of the ultra-thin heat spreader is mostly above 1mm. In addition, the key components of the ultra-thin heat sink, such as the liquid wick structure, steam chamber, reflux column and support column, cannot be processed in one go, and the manufacturing process is cumbersome and complex with low efficiency.

[0003] Chinese patent CN107008981A discloses a micro-groove EDM tool electrode and its preparation method. The resistivity of the machining surface of the micro-groove EDM tool electrode is different. The part with high resistivity of the machining surface of the electrode end face has large loss, while the part with low resistivity has small loss. Multiple micro-grooves are gradually formed on the machining surface, and the micro-groove structure of the machining surface is also copied to the machining surface of the stainless steel workpiece at the same time. Although the above scheme is suitable for EDM of micro-grooves with large aspect ratio, the machining process requires a rotating disc tool to drive the EDM tool electrode to reciprocate the stainless steel workpiece. The manufacturing process is cumbersome and complicated, and the micro-grooves obtained by machining have no micro-pits and fin structures, and the capillary pressure is low. In the later stage, the reflux column and steam chamber need to be processed additionally, which increases the design difficulty and manufacturing difficulty. Therefore, the above scheme is difficult to be applied to the manufacture of high-performance ultra-thin heat spreaders. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an ultra-thin heat spreader and a preparation method thereof. The liquid wick, steam chamber and reflux column are formed simultaneously without the need for additional processing of the reflux column and support column. The design and manufacturing difficulties are low, which is conducive to reducing the thickness of the heat spreader.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] Provided is an ultra-thin heat spreader, comprising a first plate and a second plate, wherein the first plate and the second plate are packaged and a closed cavity is formed between the first plate and the second plate; an array groove structure is arranged in the closed cavity in a vertically staggered manner, wherein the array groove structure comprises a steam cavity, a boss and a plurality of groups of parallelly distributed liquid wicks, wherein the liquid wick and the steam cavity are arranged between the bosses and the steam cavity is located above the liquid wick, and the upper and lower ends of the boss are respectively in contact with the inner side surfaces of the first plate and the second plate.

[0007] The ultra-thin heat spreader of the present invention is used to evacuate the closed cavity and inject the working medium. The boss can serve as a reflux column for the liquid working medium and also as a support column to prevent the ultra-thin heat spreader from sinking / expanding. The liquid wick, steam chamber and reflux column are processed and formed at the same time, and there is no need to add additional reflux columns and support columns. The steam chamber and the liquid wick are arranged up and down and are located in the array groove structure, which can simplify the internal structure design of the heat spreader and reasonably allocate the internal space of the heat spreader. The design difficulty and manufacturing difficulty are low, which helps to reduce the thickness of the heat spreader.

[0008] Furthermore, the liquid wick includes micro-pits and fins, a plurality of micro-pits are neatly arranged in multiple rows and columns, and the fins surround the micro-pits.

[0009] Furthermore, the top of the fin is concave to form a first arc surface structure; and the bottom surface of the micro-pit is concave to form a second arc surface structure.

[0010] Furthermore, the fin includes a first fin and a second fin, wherein the first fin is adjacent to the micro-pit and the second fin is located between adjacent bosses.

[0011] Furthermore, the second fin is a groove structure, and the top surface height of the second fin is equal to the top surface height of the first fin.

[0012] The present invention also provides a method for preparing an ultra-thin vapor chamber, comprising the following steps:

[0013] S10. Preparation of an EDM tool electrode: The EDM tool electrode comprises a low-resistivity conductive layer and a high-resistivity conductive layer which are stacked and bonded, and the thickness end surface after bonding is a machining surface; the low-resistivity conductive layer and the high-resistivity conductive layer are arranged at intervals, and the low-resistivity conductive layer and the high-resistivity conductive layer have different degrees of loss, forming a concave-convex structure on the machining surface;

[0014] S20. Processing a micro groove: uniformly and continuously engraving the concave-convex structure in step S10 on the surface of the first plate in a direction parallel to one side surface to form a micro groove;

[0015] S30. Processing secondary micro grooves: uniformly and continuously engraving the concave-convex structure in step S10 on the surface of the first plate in a direction perpendicular to the primary micro grooves to form secondary micro grooves, wherein the secondary micro grooves and the primary micro grooves are vertically and horizontally staggered to form an array groove structure;

[0016] S40. Packaging to obtain an ultra-thin vapor chamber: Packaging the first flat plate and the second flat plate, forming a closed cavity between the first flat plate and the second flat plate, evacuating the closed cavity, injecting a working medium and sealing the closed cavity to obtain the ultra-thin vapor chamber.

[0017] The preparation method of the ultra-thin heat spreader of the present invention adopts the electric spark forming technology to process the array groove structure. Compared with the traditional groove processing method, the processing accuracy is higher, and a micro groove structure with smaller size and larger aspect ratio can be processed; the liquid absorption core, steam chamber and reflux column are obtained at the same time, and the design difficulty and manufacturing difficulty are low.

[0018] Preferably, in step S10, the low-resistivity conductive layer is tinned copper foil, and the high-resistivity conductive layer is copper foil; the multiple layers of the low-resistivity conductive layer and the high-resistivity conductive layer are clamped and fixed on both sides by a clamp.

[0019] Preferably, the distance between adjacent primary micro grooves is equal to the distance between adjacent secondary micro grooves; the length of the primary micro grooves and the secondary micro grooves is equal to the length of the processed surface.

[0020] Preferably, a boss is formed at the intersection of the primary micro-groove and the secondary micro-groove, and the boss is used as a support column and a reflux column of the ultra-thin heat spreader; the boss is a columnar boss.

[0021] Preferably, in step S40, the first plate and the second plate are packaged by welding.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The ultra-thin heat spreader of the present invention has its own reflux column and support column, does not require additional processing, and has low application difficulty; the steam chamber and the liquid wick are arranged up and down and are located in the same array groove, which simplifies the internal structure design of the heat spreader, reasonably allocates the internal space of the heat spreader, and helps to reduce the thickness of the heat spreader; and the ultra-thin heat spreader of the present invention can effectively increase the capillary pressure of the liquid wick due to the structural setting of the micro-pits and fins, thereby improving the heat transfer performance of the ultra-thin heat spreader.

[0024] The preparation method of the ultra-thin heat spreader of the present invention adopts the electric spark forming technology to process the array groove structure. Compared with the traditional groove processing method, the processing accuracy is higher, and a micro-groove structure with smaller size and larger aspect ratio can be processed; the liquid absorption core, the steam chamber, and the reflux column are processed and formed at the same time, and there is no need to additionally process the reflux column and the support column. The design difficulty and the manufacturing difficulty are low, which is conducive to reducing the thickness of the heat spreader and improving the processing accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the structure of the ultra-thin vapor chamber in Example 1;

[0026] Figure 2 This is a schematic structural diagram of an array groove structure of Embodiment 1;

[0027] Figure 3 This is a schematic diagram of processing the array groove structure in the second embodiment;

[0028] Figure 4 This is a scanning electron microscope image of a vapor chamber prepared according to the preparation method of Example 2;

[0029] In the accompanying drawings: 1-first plate; 2-second plate; 3-steam chamber; 4-liquid wick; 41-micro pits; 42-fins; 421-first fins; 422-second fins; 5-boss; 7-primary micro grooves; 8-secondary micro grooves; 10-array groove structure; 11-low resistivity conductive layer; 12-high resistivity conductive layer; 13-clamp; 14-processed workpiece. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with specific implementation methods. The accompanying drawings are only used for exemplary descriptions and are only schematic diagrams, not actual drawings, and cannot be understood as limiting this patent; in order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the accompanying drawings may be omitted.

[0031] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, it is 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 direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limitations on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0032] Embodiment 1

[0033] like Figure 1 to Figure 2The figure shows an embodiment of the ultra-thin heat spreader of the present invention, including a first plate 1 and a second plate 2, which are packaged and a closed cavity is formed between the first plate 1 and the second plate 2; an array groove structure 10 is provided in the closed cavity, and the array groove structure 10 includes a steam cavity 3, a boss and a plurality of groups of parallel distributed liquid absorbent cores 4, the liquid absorbent core 4 and the steam cavity 3 are both provided between the boss 5 and the steam cavity 3 is located above the liquid absorbent core 4, and the upper and lower ends of the boss 5 are respectively abutted against the inner side surfaces of the first plate 1 and the second plate 2.

[0034] When this embodiment is implemented, the closed cavity is evacuated and the working medium is poured in. The boss can be used as a reflux column for the liquid working medium and a support column to prevent the ultra-thin heat spreader from sinking / expanding. The liquid wick 4, the steam chamber 3 and the reflux column are processed and formed at the same time, and there is no need to add additional reflux columns and support columns. The steam chamber and the liquid wick are arranged up and down and are located in the array groove structure. The internal structure design of the heat spreader can be simplified and the internal space of the heat spreader can be reasonably allocated. The design difficulty and manufacturing difficulty are low, which helps to reduce the thickness of the heat spreader. It can be known that a liquid filling port and a vacuum port are provided in communication with the closed cavity. Of course, the liquid filling port and the vacuum port can also be combined into one.

[0035] In one embodiment, the closed cavity is provided on the first plate 1, the second plate 2 is a plate-like structure with a flat surface, and the height of the boss is equal to the depth of the closed cavity. In this arrangement, the array groove structure 10 is processed on the first plate 1, the closed cavity is also processed on the first plate 1, and the second plate 2 adopts a plate-like structure with a flat surface, which can simplify the processing process and reduce the processing cost. In addition, the boss in this embodiment is a structure formed during the processing of the liquid absorbent core 4, rather than a structure obtained by additional processing, and has strong practicality and applicability.

[0036] In one embodiment, the liquid absorbent core 4 includes micro-pits 41 and fins 42, and a plurality of micro-pits 41 are neatly arranged in multiple rows and columns, and the fins 42 surround the micro-pits 41. When the closed cavity is evacuated and the working medium is poured, each micro-pit 41 is equivalent to a miniature liquid reservoir, which can store the working medium, effectively increase the capillary pressure of the liquid absorbent core 4, and improve the heat transfer performance of the ultra-thin heat spreader; the fins arranged around the micro-pits 41 can also help improve the heat transfer performance of the heat spreader. Among them, the tops of a plurality of fins are concave to form a first curved surface structure, and the bottom surfaces of the micro-pits 41 are concave to form a second curved surface structure. The arrangement of the first curved surface structure and the second curved surface structure helps the flow of the working medium, avoiding the formation of eddies during the flow process that affect the heat transfer effect. In one embodiment, the fins 42 include a first fin 421 and a second fin 422, the first fin 421 is adjacent to the micro-pit 41, and the second fin 422 is located between adjacent bosses 5. In this embodiment, the structures of the first fin 421 and the second fin 422 are different, with rich structures and small sizes, which can increase the capillary pressure of the wick, help to evenly distribute the working medium, and improve the uniform effect of the heat spreader, but the first fin 421 and the second fin 422 are not intended to be restrictive provisions of the present invention.

[0037] In one embodiment, the second fin 422 is a groove structure, and the top surface height of the second fin 422 is equal to the top surface height of the first fin 421. The second fin 422 is formed naturally when processing the primary micro groove 7, and the first fin 421 is formed naturally when processing the secondary micro groove 8. The boss 5, the first fin 421 and the second fin 422, and the steam chamber 3 are all formed naturally when processing the primary micro groove 7 and the secondary micro groove 8, without additional processing. When the present embodiment is implemented, the primary micro groove 7 is formed between the adjacent bosses 5 in the same row or column, and the secondary micro groove 8 is the reprocessing of the primary micro groove 7. The first fin 421 is located at the staggered overlap of the primary micro groove 7 and the secondary micro groove 8, and the second fin 422 is located in the primary micro groove 7 and the secondary micro groove 8. The first fin 421 is located at the center of the four groups of second fins 422.

[0038] In one embodiment, the primary micro grooves 7 are continuously and evenly distributed, the secondary micro grooves 8 are continuously and evenly distributed, and the distance between adjacent primary micro grooves 7 is equal to the distance between adjacent secondary micro grooves 8. It should be noted that this is a preference made to obtain a better heat transfer effect and is not a limiting provision of the present invention.

[0039] In one embodiment, the primary micro groove 7 and the secondary micro groove 8 are processed in the same processing method, the processing directions of the primary micro groove 7 and the secondary micro groove 8 are perpendicular, and the secondary micro groove 8 is processed on the primary micro groove 7. The array groove structure 10 composed of such a structure has low processing requirements and is easy to implement.

[0040] In one of the embodiments, the steam chamber 3 is formed between the top of the fin and the top of the boss, and the micro-pits 41 and the fins 42 constitute a liquid wick, which is located at the lower part of the steam chamber. In this arrangement, the liquid wick and the steam chamber are both in the array groove, which simplifies the internal structure design of the heat spreader, and the internal space of the heat spreader is reasonably allocated, which can effectively reduce the thickness of the heat spreader. The thickness of the heat spreader in this embodiment can be less than 0.5 mm.

[0041] In the specific contents of the above-mentioned specific implementation methods, the various technical features can be combined in any non-contradictory manner. In order to make the description concise, not all possible combinations of the above-mentioned technical features are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0042] Embodiment 2

[0043] like Figure 3 The embodiment of the method for preparing the ultra-thin vapor chamber of the present invention is shown, comprising the following steps:

[0044] S10. Preparation of an EDM tool electrode: The EDM tool electrode comprises a low resistivity conductive layer 11 and a high resistivity conductive layer 12 which are stacked and bonded, and the end face of the thickness after bonding is a machining surface; the low resistivity conductive layer 11 and the high resistivity conductive layer 12 are spaced apart, and the low resistivity conductive layer 11 and the high resistivity conductive layer 12 are lost to different degrees, forming a concave-convex structure on the machining surface;

[0045] S20. Processing a micro groove 7: uniformly and continuously reproducing the concave-convex structure in step S10 on the surface of the first plate 1 in a direction parallel to one side surface to form a micro groove 7;

[0046] S30. Processing secondary micro grooves 8: uniformly and continuously replicating the concave-convex structure in step S10 on the surface of the first plate 1 in a direction perpendicular to the primary micro grooves 7 to form secondary micro grooves 8, wherein the secondary micro grooves 8 and the primary micro grooves 7 are vertically and horizontally staggered to form an array groove structure 10;

[0047] S40. Packaging to obtain an ultra-thin vapor chamber: Cover the second flat plate 2 on the first flat plate 1 and package the first flat plate 1 and the second flat plate 2 to form a closed cavity between the first flat plate 1 and the second flat plate 2, evacuate the closed cavity, inject working medium and seal it to obtain an ultra-thin vapor chamber.

[0048] In step S10, the low resistivity conductive layer 11 is tinned copper foil, and the high resistivity conductive layer 12 is copper foil; the two sides of the multi-layer low resistivity conductive layer 11 and the high resistivity conductive layer 12 are clamped and fixed by a clamp 13. In this embodiment, the tinned copper foil is selected as the low resistivity conductive layer 11 and the copper foil is selected as the high resistivity conductive layer 12. This is a preferred choice based on the easy availability of raw materials and the reduction of processing costs. It is not a restrictive provision of the present invention. Other electrode materials with one large and one small resistivity and electrodes that will produce losses during electrospark forming processing can also be applied to the present invention. During electrospark forming processing, since the loss of tin electrode during processing is greater than that of copper electrode, a concave-convex structure will be generated at the bottom of the electrode during the processing process. During the electrospark processing, the concave-convex structure of the processing surface is replicated on the surface of the workpiece 14, and the surface of the workpiece 14 is processed into a primary micro-groove 7 and a secondary micro-groove 8. The structure and number of the primary micro-groove 7 and the secondary micro-groove 8 can be controlled by adjusting the number of superpositions of the low resistivity conductive layer 11 and the high resistivity conductive layer 12. However, no matter how many low-resistivity conductive layers 11 and high-resistivity conductive layers 12 are stacked, in order to ensure the accuracy and precision of the processing, high-resistivity conductive layers 12 must be used on both sides of the stacked electrodes. In addition, the processing height of the primary micro-grooves 7 and the secondary micro-grooves 8 can be controlled by the processing time, and the height of the fins 42 can be controlled by the thickness of the tinned layer of the tinned copper foil.

[0049] The distance between adjacent primary micro grooves 7 is equal to the distance between adjacent secondary micro grooves 8; the lengths of the primary micro grooves 7 and the secondary micro grooves 8 are equal to the length of the processing surface. The distance between adjacent primary micro grooves 7 and the distance between adjacent secondary micro grooves 8 can be controlled by the distance that the electrode moves each time during processing, and the processing of the primary micro grooves 7 and the secondary micro grooves 8 can be processed by the same electrode.

[0050] The primary micro groove 7 and the secondary micro groove 8 form a boss at their intersections, which is used as a support column and a reflux column of the ultra-thin heat spreader; the boss is a columnar boss. The boss can be used as a reflux column for the liquid working medium and as a support column to prevent the ultra-thin heat spreader from sinking / expanding. There is no need to add additional reflux columns and support columns, which simplifies the processing procedures and gives the present invention better practicality and applicability.

[0051] In step S40, the first plate 1 and the second plate 2 are packaged by welding. It should be noted that the welding packaging is not a limiting provision of the present invention, and other packaging methods that can form a closed cavity between the first plate 1 and the second plate 2 are also applicable to the present invention.

[0052] After the above steps, the scanning electron microscope image of the array groove structure 10 obtained by processing is as follows: Figure 4The primary micro groove 7 and the secondary micro groove 8 are obtained by electrospark forming technology, which is easy to operate and has higher processing accuracy. It can process a micro groove structure with a smaller size and a larger aspect ratio, and can process a heat spreader with a thickness of less than 0.5 mm; and the intersection of the primary micro groove 7 and the secondary micro groove 8 forms a boss that plays a supporting and reflux role, without the need for additional processing of reflux columns and support columns, simplifying the processing process and improving processing efficiency.

[0053] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. An ultra-thin heat spreader, characterized in that: The invention comprises a first plate (1) and a second plate (2), wherein the first plate (1) and the second plate (2) are packaged and a closed cavity is formed between the first plate (1) and the second plate (2); an array groove structure (10) is provided in the closed cavity and is vertically staggered; the array groove structure (10) comprises a steam cavity (3), a boss (5) and a liquid wick (4); the liquid wick (4) and the steam cavity (3) are both provided between the boss (5) and the steam cavity (3) is located above the liquid wick (4); the boss (5) has a plurality of upper and lower ends. The wick (4) is respectively in contact with the inner side surfaces of the first plate (1) and the second plate (2); the wick (4) comprises a micro-dimple (41) and a fin (42); the fin (42) comprises a first fin (421) and a second fin (422); the first fin (421) is adjacent to the micro-dimple (41) and the second fin (422) is located between adjacent bosses (5); the second fin (422) is a groove structure, and the top surface height of the second fin (422) is equal to the top surface height of the first fin (421).

2. The ultra-thin vapor chamber according to claim 1, characterized in that: The plurality of micro-pits (41) are neatly arranged in multiple rows and columns.

3. The ultra-thin vapor chamber according to claim 2, characterized in that: The top of the fin (42) is concave to form a first arc surface structure, and the bottom of the micro-pit (41) is concave to form a second arc surface structure.

4. A method for preparing an ultra-thin vapor chamber according to any one of claims 1 to 3, characterized in that: The following steps are involved: S10. Preparing an electrospark machining tool electrode: The electrospark machining tool electrode comprises a low-resistivity conductive layer (11) and a high-resistivity conductive layer (12) which are stacked and bonded, and the thickness end surface after bonding is a machining surface; the low-resistivity conductive layer (11) and the high-resistivity conductive layer (12) are arranged at intervals, and the low-resistivity conductive layer (11) and the high-resistivity conductive layer (12) have different degrees of loss, forming a concave-convex structure on the machining surface; S20. Processing a micro groove (7): uniformly and continuously replicating the concave-convex structure in step S10 on the surface of the first plate (1) in a direction parallel to one side surface to form a micro groove (7); S30. Processing secondary micro grooves (8): uniformly and continuously replicating the concave-convex structure in step S10 on the surface of the first plate (1) in a direction perpendicular to the primary micro grooves (7) to form secondary micro grooves (8), wherein the secondary micro grooves (8) and the primary micro grooves (7) are vertically and horizontally staggered to form an array groove structure (10); S40. Encapsulating to obtain an ultra-thin vapor chamber: encapsulating a first plate (1) and a second plate (2), wherein a closed cavity is formed between the first plate (1) and the second plate (2), and the closed cavity is evacuated, filled with a working medium, and sealed to obtain an ultra-thin vapor chamber; The primary micro groove (7) and the secondary micro groove (8) form a boss (5) at the intersection, and the boss (5) is used as a support column and a reflux column of the ultra-thin heat spreader; the boss is a columnar boss; The bottoms of the primary micro groove (7) and the secondary micro groove (8) form a second fin (422) in a groove structure, and the intersection of the primary micro groove (7) and the secondary micro groove (8) forms a micro pit (41) and a first fin (421) adjacent to the micro pit (41).

5. The method for preparing an ultra-thin vapor chamber according to claim 4, characterized in that: In step S10, the low-resistivity conductive layer (11) is a tinned copper foil, and the high-resistivity conductive layer (12) is a copper foil; the two sides of the multiple layers of the low-resistivity conductive layer (11) and the high-resistivity conductive layer (12) are clamped and fixed by a clamp (13).

6. The method for preparing an ultra-thin vapor chamber according to claim 4, characterized in that: The distance between adjacent primary micro grooves (7) is equal to the distance between adjacent secondary micro grooves (8); the length of the primary micro grooves (7) and the secondary micro grooves (8) is equal to the length of the processed surface.

7. The method for preparing an ultra-thin vapor chamber according to any one of claims 4 to 6, characterized in that: In step S40, the first plate (1) and the second plate (2) are packaged using a welding process.

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