Multi-scale metal powder sintered capillary core, preparation method and heat pipe

Abstract

The invention discloses a multi-scale metal powder sintered capillary core, a preparation method and a heat pipe, and relates to the technical field of heat pipe manufacturing. Double faced adhesive tape is attached to the upper surface of a shell, high-mesh red copper powder is evenly adhered to the upper surface of the shell, the shell and a pre-sintered red copper capillary core are limited and fixed through an outer ring, a graphite pressing block and a stainless steel pressing block are combined, and secondary sintering is conducted after pressurization; the problem that the interface strength of a large-particle-size powder sintering capillary core and a shell is insufficient is solved. The contact area is increased through the high-mesh powder layer, the interface strength is improved, and meanwhile gasification nucleation points are provided to enhance the performance of the heat pipe. The process is simple and reliable, and is suitable for efficient preparation of capillary cores made of red copper and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat pipe manufacturing, and specifically relates to a multi-scale metal powder sintered capillary wick, a preparation method and a heat pipe, which is suitable for the manufacture of heat pipe capillary wicks for heat dissipation of high-power electronic devices. Background Art

[0002] With the exponential growth of electronic device power density, the heat transfer limitations of traditional homogeneous capillary wick heat pipes, caused by insufficient liquid working fluid delivery rates, are becoming increasingly prominent. Metal powder sintering is widely used for capillary wick preparation due to its simplicity and controllable porosity. However, the isotropic pore structure formed by sintering single-particle powders makes it difficult to meet the conflicting demands of high capillary force at the evaporation end and low flow resistance at the condensation end. Furthermore, the interfacial bonding strength between large-particle capillary wicks and the metal shell is limited by the insufficient sintering contact area, making them prone to delamination failure under thermal stress.

[0003] Chinese patent CN110303153B proposes to connect the capillary wick and the shell through adhesive-assisted secondary sintering. However, since the number of contact points between large-particle powder and the shell decreases in inverse square proportion, the interface bonding strength of this method decreases significantly with increasing powder particle size. Summary of the Invention

[0004] To address these issues, the present invention proposes a multi-scale sintered metal powder capillary wick, a preparation method, and a heat pipe. This method utilizes a high-mesh powder layer to increase contact area, enhance interfacial strength, and provide vaporization nucleation sites to enhance heat pipe performance. The present invention's process is simple and reliable, suitable for the efficient preparation of capillary wicks made of materials such as copper. Copper can be sintered at 850°C, requiring only a small amount of copper to melt and bond together, eliminating the need for complete melting of the copper to form a capillary wick of the same material.

[0005] To achieve the above objectives, the technical solutions adopted by the present invention are as follows:

[0006] A multi-scale metal powder sintered capillary wick comprises an outer shell, an outer ring, a double-sided adhesive layer, high-mesh copper powder, a pre-sintered copper capillary wick, a graphite press block, a stainless steel press block and a release agent; the outer shell is made of copper material as a substrate, and a double-sided adhesive layer is attached to its upper surface. High-mesh copper powder is adhered to the surface of the double-sided adhesive layer, and the high-mesh copper powder is evenly distributed on the surface of the double-sided adhesive layer by mechanical vibration to form a transition interface layer; the inner surface of the outer ring is coated with a release agent, and after being blown dry, the outer ring and the outer shell are assembled to form an axial limiting structure; the pre-sintered copper capillary wick is placed on the transition interface layer, and a graphite press block and a stainless steel press block are stacked in sequence to provide pressure in the vertical direction; the assembly consisting of the outer shell, outer ring, double-sided adhesive layer, high-mesh copper powder, pre-sintered copper capillary wick, graphite press block, stainless steel press block and release agent is subjected to secondary sintering, the double-sided adhesive layer is pyrolyzed, and the remaining transition interface layer is sintered and connected to the outer shell and the pre-sintered copper capillary wick.

[0007] Furthermore, the shell, outer ring, high-mesh copper powder, and pre-sintered copper capillary core are all made of copper with a purity of ≥99.9%.

[0008] The present invention also provides a method for preparing a multi-scale metal powder sintered capillary wick, comprising the following steps:

[0009] Step 1: Using a copper shell as a substrate, attaching a double-sided tape layer to its upper surface, adhering high-mesh copper powder to the surface of the double-sided tape layer, and using a mechanical vibration method to evenly distribute the high-mesh copper powder on the surface of the double-sided tape layer to form a transition interface layer;

[0010] Step 2: Apply a release agent on the inner surface of the outer ring, blow dry and solidify it, and then assemble the outer ring and the outer shell to form an axial limit structure;

[0011] Step 3: Place a pre-sintered copper capillary wick on the transition interface layer, and stack a graphite block and a stainless steel block in sequence to provide pressure in the vertical direction;

[0012] Step 4: Place the assembly consisting of the outer shell, outer ring, double-sided adhesive layer, high-mesh copper powder, pre-sintered copper capillary wick, graphite block, stainless steel block, and release agent in a vacuum sintering furnace and heat it to 850°C~900°C for secondary sintering. The double-sided adhesive layer is completely pyrolyzed at 600°C, leaving a transition interface layer that is sintered and connected to the outer shell and pre-sintered copper capillary wick.

[0013] Furthermore, the mesh number of the high-mesh copper powder is ≥1000 mesh.

[0014] Furthermore, in step 1, the vibration frequency of the mechanical vibration method is 50-100 Hz, the amplitude is 0.1-0.5 mm, and the duration is 30-60 s, ensuring that the single layer coverage of the high-mesh copper powder is ≥95%.

[0015] Furthermore, the density of the graphite compact is 1.7-1.9 g / cm 3 , the thermal expansion coefficient is 4.5×10 -6 / ℃, which compensates the thermal stress of the metal parts through plastic deformation during the sintering process.

[0016] Furthermore, the working vacuum degree of the vacuum sintering furnace is ≤0.01Pa.

[0017] Furthermore, the thickness of the transition interface layer is ≤20 μm.

[0018] Furthermore, the release agent is a water-based boron nitride high-temperature resistant release agent, which forms an anti-sintering isolation film after drying.

[0019] The present invention also provides a heat pipe using the multi-scale metal powder sintered capillary wick.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The present invention uses high-mesh copper powder to connect the pre-sintered copper capillary core and the shell, solving the problem of insufficient contact of the capillary core sintered with large particles during the secondary sintering.

[0022] (2) The high-mesh copper powder layer on the shell of the present invention also provides more vaporization nucleation points, further improving the thermal performance of the heat pipe.

[0023] (3) The present invention uses double-sided tape to fix the powder, and the excess powder can be removed by vibration, ultimately obtaining an ultra-thin powder layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of a multi-scale metal powder sintered capillary wick of the present invention;

[0025] Figure 2 is a schematic cross-sectional view of an assembly of the present invention;

[0026] Figure 3 A schematic diagram of the present invention applied to a flat-plate heat pipe;

[0027] Figure 4 A cross-sectional schematic diagram of the present invention applied to a flat-plate heat pipe;

[0028] Among them, the figures are marked as follows: 1-shell, 2-outer ring, 3-double-sided adhesive layer, 4-high-mesh copper powder, 5-pre-sintered copper capillary core, 6-graphite block, 7-stainless steel block, 8-release agent. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. The present invention is described in detail below with reference to the accompanying drawings and specific examples.

[0030] like Figure 1 、 Figure 2 As shown, a multi-scale metal powder sintered capillary core of the present invention includes an outer shell 1, an outer ring 2, a double-sided adhesive layer 3, high-mesh copper powder 4, a pre-sintered copper capillary core 5, a graphite block 6, a stainless steel block 7, and a release agent 8. The outer shell 1 of copper is used as a substrate, and a double-sided adhesive layer 3 is attached to its upper surface. The high-mesh copper powder 4 is bonded to the surface of the double-sided adhesive layer 3 and is evenly distributed on the surface of the adhesive layer by mechanical vibration to form a transition interface layer. The release agent 8 is coated on the inner surface of the outer ring 2. After drying, the outer ring 2 and the outer shell 1 are assembled to form an axial limiting structure. The pre-sintered copper capillary core 5 is placed on the transition interface layer, and the hot-pressed graphite block 6 and the 304 stainless steel block 7 are stacked in sequence to provide pressure in the vertical direction. The assembly consisting of the shell 1, outer ring 2, double-sided adhesive layer 3, high-mesh copper powder 4, pre-sintered copper capillary wick 5, graphite compact 6, stainless steel compact 7, and release agent 8 is placed in a vacuum sintering furnace and heated to 850°C~900°C for secondary sintering. The double-sided adhesive layer 3 is pyrolyzed, and the remaining transition interface layer is sintered and connected to the shell 1 and the pre-sintered copper capillary wick 5.

[0031] In this context, the concept of multi-scale refers to dimensional interactions spanning at least two orders of magnitude. For example, the particle size of a 1000-mesh powder is approximately 13 microns, while the thickness of the outer shell and pre-sintered copper wick is in the millimeter range, a size difference of one order of magnitude. Furthermore, the pores formed between the powder particles range in size from microns to submicrons, further contributing to dimensional interactions spanning at least two orders of magnitude.

[0032] Preferably, the shell 1, outer ring 2, high-mesh copper powder 4, and pre-sintered copper capillary wick 5 are all made of copper with a purity of ≥99.9%. Other metals of the same material may also be used, but the sintering temperature must be considered.

[0033] Preferably, the double-sided adhesive layer 3 is made of polyethylene terephthalate, which is fully pyrolyzed at 600°C.

[0034] Preferably, the high-mesh copper powder 4 is powder with a mesh size of ≥1000. The present invention avoids the adhesion of powder before sintering by sieving and baking. During the sintering process, the powder layer is a single layer of powder with a thickness of only one powder, and the powder layer is uniform, thus avoiding problems such as agglomeration.

[0035] Preferably, the pre-sintered copper capillary wick 5 can be a sintered wire mesh or a powder capillary wick.

[0036] Preferably, the graphite block 6 is made of hot pressed graphite with a density of 1.7-1.9 g / cm 3 , the thermal expansion coefficient is 4.5×10 -6 / ℃.

[0037] Preferably, the stainless steel pressing block 7 is made of 304 stainless steel.

[0038] Preferably, the release agent 8 is a water-based boron nitride high-temperature resistant release agent, which forms an anti-sintering isolation film after drying.

[0039] The present invention also provides a method for preparing a multi-scale metal powder sintered capillary wick, comprising the following steps:

[0040] Step 1: Shell pretreatment: A double-sided adhesive layer 3 is attached to the upper surface of the copper shell 1, with a coverage rate of >95%.

[0041] Step 2, preparation of transition interface layer: high-mesh copper powder 4 is evenly bonded to the surface of the double-sided adhesive layer 3, and a mechanical vibration method is used with a frequency of 50-100 Hz, an amplitude of 0.1-0.5 mm, and a duration of 30-60 s to ensure that the single layer coverage of the high-mesh copper powder 4 is ≥95%, forming a transition interface layer with a thickness of ≤20 μm.

[0042] Step 3: Position limiting assembly: Coat the inner surface of the outer ring 2 with a release agent 8, blow dry it, and then assemble it with the outer shell 1 to form an axial position limiting structure.

[0043] Step 4: Capillary wick positioning: Place the pre-sintered copper capillary wick 5 on the transition layer.

[0044] Step 5: Assembly and Pressure Sintering: Graphite compact 6 and stainless steel compact 7 are stacked in sequence and heated to 850°C–900°C in a vacuum sintering furnace (vacuum < 0.01 Pa) for secondary sintering. The double-sided adhesive layer 3 is fully pyrolyzed at 600°C, leaving a transition interface layer that is sintered and bonded to the housing 1 and the pre-sintered copper wick 5.

[0045] like Figure 3 The schematic diagram of the present invention applied to a flat plate heat pipe is shown in FIG. Figure 4The figure shows a cross-sectional schematic diagram of the present invention applied to a flat-plate heat pipe. The flat-plate heat pipe comprises a housing 1, a pre-sintered copper wick 5, and high-mesh copper powder 4. The high-mesh copper powder 4 is disposed at the bottom of the housing 1, while the pre-sintered copper wick 5 is positioned above the high-mesh copper powder 4 and within the housing 1. The housing 1 is a closed structure.

[0046] Although specific embodiments of the present invention have been described above, those skilled in the art will appreciate that these are merely illustrative and that the scope of the present invention is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, and such changes and modifications are intended to fall within the scope of the present invention.

Claims

1. A multi-scale metal powder sintered capillary wick, characterized in that: The invention comprises an outer shell, an outer ring, a double-sided adhesive layer, high-mesh copper powder, a pre-sintered copper capillary core, a graphite block, a stainless steel block and a release agent; the outer shell is made of copper material as a substrate, a double-sided adhesive layer is attached to the upper surface thereof, high-mesh copper powder is adhered to the surface of the double-sided adhesive layer, and the high-mesh copper powder is evenly distributed on the surface of the double-sided adhesive layer by mechanical vibration to form a transition interface layer; the inner surface of the outer ring is coated with a release agent, and after drying, the outer ring and the outer shell are assembled into a An axial limiting structure is formed; a pre-sintered copper capillary wick is placed on the transition interface layer, and a graphite block and a stainless steel block are stacked in sequence to provide pressure in the vertical direction; the assembly consisting of the outer shell, outer ring, double-sided adhesive layer, high-mesh copper powder, pre-sintered copper capillary wick, graphite block, stainless steel block, and release agent is subjected to secondary sintering, the double-sided adhesive layer is pyrolyzed, and the remaining transition interface layer is sintered and connected with the outer shell and the pre-sintered copper capillary wick; the mesh number of the high-mesh copper powder is ≥1000 mesh.

2. The multi-scale metal powder sintered capillary wick according to claim 1, characterized in that: The shell, outer ring, high-mesh copper powder and pre-sintered copper capillary core are all made of copper material with a purity of ≥99.9%.

3. A method for preparing a multi-scale metal powder sintered capillary wick, characterized in that: The following steps are involved: Step 1: Using a copper shell as a substrate, attaching a double-sided tape layer to its upper surface, adhering high-mesh copper powder to the surface of the double-sided tape layer, and using a mechanical vibration method to evenly distribute the high-mesh copper powder on the surface of the double-sided tape layer to form a transition interface layer; Step 2: Apply a release agent to the inner surface of the outer ring, blow dry and solidify it, and then assemble the outer ring and the outer shell to form an axial limit structure; Step 3: Place a pre-sintered copper capillary wick on the transition interface layer, and stack a graphite block and a stainless steel block in sequence to provide pressure in the vertical direction; Step 4: Place the assembly consisting of the outer shell, outer ring, double-sided adhesive layer, high-mesh copper powder, pre-sintered copper capillary wick, graphite block, stainless steel block, and release agent in a vacuum sintering furnace and heat it to 850°C~900°C for secondary sintering. The double-sided adhesive layer is completely pyrolyzed at 600°C, leaving a transition interface layer that is sintered and connected to the outer shell and pre-sintered copper capillary wick.

4. The preparation method according to claim 3, characterized in that The mesh number of high-mesh copper powder is ≥1000 mesh.

5. The preparation method according to claim 3, characterized in that In the step 1, the vibration frequency of the mechanical vibration method is 50-100 Hz, the amplitude is 0.1-0.5 mm, and the duration is 30-60 s, ensuring that the single layer coverage of the high-mesh copper powder is ≥95%.

6. The preparation method according to claim 3, characterized in that The density of the graphite block is 1.7-1.9 g / cm 3 , the thermal expansion coefficient is 4.5×10 -6 / ℃, which compensates thermal stress through plastic deformation during sintering.

7. The preparation method according to claim 3, characterized in that The working vacuum degree of the vacuum sintering furnace is ≤0.01Pa.

8. The preparation method according to claim 3, characterized in that The thickness of the transition interface layer is ≤20 μm.

9. The preparation method according to claim 3, characterized in that The release agent is a water-based boron nitride high-temperature resistant release agent, which forms an anti-sintering isolation film after drying.

10. A heat pipe, characterized in that: A multi-scale metal powder sintered capillary wick as described in claim 1 or 2 is used.

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