A method for manufacturing a three-dimensional capillary wick structure heat sink

Abstract

The application relates to a preparation method of a three-dimensional capillary core structure heat dissipation sheet, which comprises the following steps: S1, printing a single-layer metal capillary structure or a multi-layer metal capillary structure through a 3D printing technology; S2, sintering to obtain a sintered blank; S3, performing surface passivation treatment after electroplating a pure copper plating layer on the sintered blank; S4, obtaining a single or multiple metal capillary structures through wire cutting; S5, respectively welding the metal capillary structures with upper and lower copper substrates through diffusion welding or burn welding processes to form upper and lower covers; and S6, finally welding the upper and lower covers to form the heat dissipation sheet. Compared with a traditional copper mesh or copper powder two-dimensional heat dissipation structure, the three-dimensional structure is formed through 3D printing, the cooling liquid can be transmitted in XYZ directions, and the heat dissipation effect is greatly improved; meanwhile, the application replaces the traditional mesh structure with a multi-layer metal capillary structure of aluminum alloy or stainless steel to achieve the purpose of greatly reducing the cost.

Description

Technical Field

[0001] This invention relates to the field of heat sink fabrication for electronic devices, and particularly to a method for fabricating a three-dimensional capillary core structure heat sink. Background Technology

[0002] In recent years, electronic components have increasingly shown a trend towards miniaturization and high power consumption. How to solve the problem of performance degradation caused by high heat generation in electronic components has attracted attention. Among these solutions, heat sinks are used in some high-performance electronic devices due to their good heat dissipation effect. A heat sink consists of upper and lower substrates, a capillary layer, and a coolant. To ensure efficient heat dissipation, the outer shell is usually made of copper or aluminum alloy with high thermal conductivity, and capillary wicks are attached to the inner walls. To meet pressure resistance requirements, some heat sinks are designed with solid or sintered pillars inside as connections and supports between the upper and lower substrates. When heat is applied to the bottom of the heat sink, the liquid evaporates as the heat increases. The vapor rises to the top of the container and condenses, then flows back to the evaporation surface through the wick to form a circulation.

[0003] Common wick structures mainly include three types: microchannel, copper mesh, and powder sintering. Microchannel wicks are created by machining grooves into the heat sink wall to serve as return channels, reducing flow resistance; however, the process is complex and costly. Copper mesh wicks are made by sintering wire mesh onto the substrate surface. The mesh pores can be controlled according to the weaving process, offering advantages such as simple structure, easy manufacturing, and low cost; however, they have high thermal resistance and poor heat dissipation performance. Powder sintering wicks involve directly sintering metal powder onto the inner wall of the board, providing significant capillary action. This type has the widest application range and the most mature technology, but its disadvantage is poor permeability.

[0004] Therefore, the development of a capillary layer with high permeability, high water absorption, low cost, and good adhesion to the substrate has become the focus of current research. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a three-dimensional capillary core structure heat sink.

[0006] The technical solution to achieve the objective of this invention is: the preparation method of the three-dimensional capillary core structure heat sink in this invention includes the following steps:

[0007] S1. A single-layer or multi-layer metal capillary structure is printed using 3D printing technology; the metal capillary structure is a three-period minimal surface unit layer; the multi-layer metal capillary structure is composed of multiple layers of three-period minimal surface unit layers stacked in one direction; the three-period minimal surface unit layer is composed of multiple minimal surface cells arrayed on the same plane and connected as a whole; the voids on the minimal surface cells are 0.1-0.3 mm;

[0008] S2. Sintering a single-layer or multi-layer metal capillary structure to form a sintered blank.

[0009] S3. After electroplating the sintered billet with a pure copper coating, the surface is passivated.

[0010] S4. When using a multi-layered metal capillary structure, the multi-layered metal capillary structure is cut into three-period minimal curved surface unit layers of 0.2-2mm by wire cutting; if it is a single-layered metal capillary structure, proceed directly to the next step.

[0011] S5. The upper copper substrate and the lower copper substrate are respectively welded to a three-period minimal curved surface unit layer to form the upper cover and the lower cover by diffusion soldering or welding process.

[0012] S6. Finally, weld the top cover and bottom cover together to form a heat sink.

[0013] Furthermore, the aforementioned 3D printing technologies include one of selective laser melting, binder jetting 3D printing, or feed extrusion 3D printing.

[0014] Furthermore, the aforementioned multi-layered metal capillary structure comprises no more than 10 stacked tri-period minimal curved surface unit layers. If there are too many layers, it can easily lead to incomplete removal of powder from the gaps, resulting in unremoved powder clogging the gaps and ultimately affecting heat dissipation performance. Therefore, the number of stacked layers is controlled to 10 or less.

[0015] During the dust removal process, first use a nozzle vacuum cleaner to remove loose powder from the mesh, and then use an air gun to blow away surface powder, thus ensuring thorough dust removal.

[0016] Furthermore, the material of the aforementioned multi-layered metal capillary structure is stainless steel, aluminum alloy, or copper alloy; when copper alloy is used, step S3 is not required.

[0017] Furthermore, the thickness of the aforementioned electroplated layer is 2 to 20 micrometers.

[0018] Furthermore, the above-mentioned surface passivation treatment involves introducing a small amount of oxygen partial pressure into the sintering furnace, holding it at 400℃~600℃ for 1 hour, and then removing it. This surface passivation treatment can avoid oxidation aging of the metal capillary structure during use.

[0019] When using the welding process, the technical parameters are: temperature 1000℃, hydrogen atmosphere, 3 hours.

[0020] Furthermore, in step S4 above, fast wire EDM or slow wire EDM is used, and the cutting wire diameter is 0.1 to 0.2 mm.

[0021] Furthermore, in step S1, both single-layer and multi-layer metal capillary structures are printed on the positioning base; in step S4, during wire cutting, the positioning base is fixed by the workpiece table of the wire cutting equipment; when a single-layer metal capillary structure is used, wire cutting cuts the single-layer metal capillary structure off the positioning base; when a multi-layer metal capillary structure is used, wire cutting cuts the metal capillary structure layer by layer from top to bottom, and finally separates the last layer of metal capillary structure from the positioning base.

[0022] The present invention has positive effects: (1) Compared with the traditional two-dimensional heat dissipation structure of copper mesh or copper powder, the present invention forms a three-dimensional structure through 3D printing, and the coolant can be transported along the XYZ direction, which greatly improves the heat dissipation effect.

[0023] (2) The present invention achieves significant cost reduction by replacing the traditional mesh structure with a multi-layer metal capillary structure of aluminum alloy or stainless steel. Attached Figure Description

[0024] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...

[0025] Figure 1 This is a schematic diagram of the multilayer metal capillary structure of the present invention;

[0026] Figure 2 This is a schematic diagram of the structure of the minimal curved cell in this invention;

[0027] Figure 3 This is a schematic diagram of the welding between the upper copper substrate and the three-period minimal curved surface unit layer in this invention. Detailed Implementation

[0028] (Example 1)

[0029] The method for preparing the three-dimensional capillary core structure heat sink of the present invention includes the following steps:

[0030] S1. Printing multi-layered metal capillary structures using 3D printing technology (see...) Figure 1 The metal capillary structure is a three-period minimal surface unit layer 1; the metal capillary structure is made of 316L stainless steel; the multi-layered metal capillary structure is composed of multiple layers of three-period minimal surface unit layers 1 stacked in one direction; the three-period minimal surface unit layer 1 is composed of multiple minimal surface cells 11 arrayed on the same layer and connected as a whole; the voids on the minimal surface cells 11 are 0.1mm; the height of the multi-layered metal capillary structure in the stacking direction is 30mm;

[0031] S2. Sinter the multi-layered metal capillary structure to form a sintered blank; wherein the sintering temperature is 1370℃, hydrogen atmosphere, and the holding time is 2 hours.

[0032] S3. After electroplating a 20-micron pure copper layer onto the sintered billet, a surface passivation treatment is performed. The surface passivation treatment involves introducing a small amount of oxygen partial pressure into the sintering furnace, holding it at 600°C for 3 hours, and then removing it.

[0033] S4. Cut the three-cycle minimal curved surface unit layer 1 of 0.8mm layer by layer using slow wire EDM;

[0034] S5. The upper copper substrate 2 and the lower copper substrate are welded to a three-period minimal curved surface unit layer 1 by a welding process to form the upper cover and the lower cover.

[0035] S6. Finally, weld the top cover and bottom cover together to form a heat sink.

[0036] The multi-layered metal capillary structure has no more than 10 stacked three-period minimal curved surface unit layers 1. If there are too many layers, it is easy for the powder in the gaps to not be completely removed, which will cause the unremoved powder to clog the gaps and ultimately affect the heat dissipation performance. Therefore, the number of stacked layers is controlled to be 10 or less.

[0037] During the dust removal process, first use a nozzle vacuum cleaner to remove loose powder from the mesh, and then use an air gun to blow away surface powder, thus ensuring thorough dust removal.

[0038] Of course, the multi-layered metal capillary structure in step S1 can also be printed on the positioning base; in step S4, when wire cutting is performed, the positioning base is fixed by the workpiece table of the wire cutting equipment; the wire cutting cuts the metal capillary structure layer by layer from top to bottom, and finally cuts and separates the last layer of metal capillary structure from the positioning base.

[0039] (Example 2)

[0040] The method for preparing the three-dimensional capillary core structure heat sink of the present invention includes the following steps:

[0041] S1. A multi-layered metal capillary structure is printed using 3D printing technology; the metal capillary structure is a three-period minimal surface unit layer 1; the metal capillary structure is made of 5-series aluminum alloy; the multi-layered metal capillary structure consists of multiple layers of three-period minimal surface unit layers 1 stacked in one direction; the three-period minimal surface unit layer 1 is composed of multiple minimal surface cells 11 arrayed on the same layer and connected as a whole; the voids on the minimal surface cells 11 are 0.3 mm; the height of the multi-layered metal capillary structure in the stacking direction is 30 mm;

[0042] S2. Sinter the multi-layered metal capillary structure to form a sintered blank;

[0043] S3. After electroplating a 2-micron pure copper layer onto the sintered billet, a surface passivation treatment is performed. The surface passivation treatment involves introducing a small amount of oxygen partial pressure into the sintering furnace, holding it at 400°C for 3 hours, and then removing it.

[0044] S4. Cut the three-cycle minimal curved surface unit layer 1 of 0.8mm layer by layer using slow wire EDM;

[0045] S5. The upper copper substrate 2 and the lower copper substrate are welded to a three-period minimal curved surface unit layer 1 by a welding process to form the upper cover and the lower cover.

[0046] S6. Finally, weld the top cover and bottom cover together to form a heat sink.

[0047] Thermal resistance performance tests were conducted on the traditional VC (copper mesh) and Examples 1 and 2. The test results are shown in the table below.

[0048] Example 1 Example 2 Traditional VC (copper mesh) 300W heat source 0.66℃ / W 0.54℃ / W 0.78℃ / W 400W heat source 0.61℃ / W 0.5℃ / W 0.75℃ / W 500W heat source 0.59℃ / W 0.47℃ / W 0.73℃ / W

[0049] The above tests show that the effects of Examples 1 and 2 are significantly better than those of traditional VC (copper mesh), with Example 2 showing the best results. This is mainly because aluminum alloy copper mesh not only has a better three-dimensional microstructure, but also has better heat transfer and dissipation effects.

[0050] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a three-dimensional capillary core structure heat sink, characterized in that... Includes the following steps: S1. A multi-layered metal capillary structure is printed using 3D printing technology; the metal capillary structure is a three-period minimal surface unit layer; the multi-layered metal capillary structure is a three-period minimal surface unit layer with no more than 10 layers stacked in one direction; the three-period minimal surface unit layer is composed of multiple minimal surface cells arrayed on the same plane and connected into one unit; the voids on the minimal surface cells are 0.1~0.3mm; S2. Sinter the multi-layered metal capillary structure to form a sintered blank; S3. After electroplating the sintered billet with a pure copper coating, the surface is passivated. S4. The multi-layered metal capillary structure is cut into three-period minimal curved surface unit layers of 0.2~2mm by wire cutting; S5. The upper copper substrate and the lower copper substrate are respectively welded to a three-period minimal curved surface unit layer to form the upper cover and the lower cover by diffusion soldering or welding process. S6. Finally, weld the top cover and bottom cover together to form a heat sink.

2. The method for preparing a three-dimensional capillary core structure heat sink according to claim 1, characterized in that: The 3D printing technology includes one of selective laser melting, binder jetting 3D printing, or feed extrusion 3D printing.

3. The method for preparing a three-dimensional capillary core structure heat sink according to claim 1, characterized in that: The multi-layered metal capillary structure is made of stainless steel, aluminum alloy, or copper alloy; when copper alloy is used, step S3 is not required.

4. The method for preparing a three-dimensional capillary core structure heat sink according to claim 1, characterized in that: The coating thickness is 2 to 20 micrometers.

5. The method for preparing a three-dimensional capillary core structure heat sink according to claim 1, characterized in that: The surface passivation treatment involves introducing a trace amount of oxygen at a partial pressure into a sintering furnace, holding it at 400℃~600℃ for 1 hour, and then removing it.

6. The method for preparing a three-dimensional capillary core structure heat sink according to claim 1, characterized in that: When using the welding process, the technical parameters are: temperature 1000℃, hydrogen atmosphere, 3 hours.

7. The method for preparing a three-dimensional capillary core structure heat sink according to claim 1, characterized in that: In step S4, fast wire EDM or slow wire EDM is used, and the cutting wire diameter is 0.1~0.2mm.

8. The method for preparing a three-dimensional capillary core structure heat sink according to claim 1, characterized in that: In step S1, the multi-layered metal capillary structure is printed on the positioning base; in step S4, during wire cutting, the positioning base is fixed by the workpiece table of the wire cutting equipment; when using a multi-layered metal capillary structure, the wire cutting cuts the metal capillary structure layer by layer from top to bottom, and finally cuts and separates the last layer of metal capillary structure from the positioning base.

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