A multi-scale metal powder sintered capillary core, its preparation method, and a heat pipe

Abstract

This invention discloses a multi-scale metal powder sintered capillary core, its preparation method, and a heat pipe, relating to the field of heat pipe manufacturing technology. By attaching double-sided adhesive to the upper surface of the outer shell and uniformly adhering high-mesh copper powder, and using an outer ring to fix the outer shell and pre-sintered copper capillary core, a secondary sintering is performed under pressure using graphite and stainless steel blocks. This solves the problem of insufficient interface strength between the large-particle-size powder sintered capillary core and the outer shell. This invention increases the contact area and improves the interface strength through the high-mesh powder layer, while also providing vaporization nucleation sites to enhance heat pipe performance. The process is simple and reliable, suitable for the efficient preparation of capillary cores made of copper or similar materials.

Description

Technical Field

[0001] This invention belongs to the field of heat pipe manufacturing technology, specifically relating to a multi-scale metal powder sintered capillary core, its preparation method, and a heat pipe, which is applicable to the manufacture of heat pipe capillary cores for heat dissipation of high-power electronic devices. Background Technology

[0002] With the exponential growth of power density in electronic devices, the heat transfer limit problem caused by insufficient liquid working fluid transport rate in traditional homogeneous capillary heat pipes is becoming increasingly prominent. In existing technologies, metal powder sintering is widely used for capillary wick preparation due to its simple process and controllable porosity. However, the isotropic porous structure formed by sintering single-size powders cannot meet the contradictory requirements of high capillary force at the evaporation end and low flow resistance at the condensation end. Furthermore, the interfacial bonding strength between large-size capillary wicks and the metal shell is limited by insufficient sintering contact area, making them prone to delamination failure under thermal stress.

[0003] Chinese patent CN110303153B proposes to achieve the connection between the capillary core and the shell through adhesive-assisted secondary sintering. However, since the number of contact points between large-diameter powder and the shell decreases in an inverse square relationship, the interfacial bonding strength of this method decreases significantly with the increase of powder particle size. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a multi-scale metal powder sintered capillary core, its preparation method, and a heat pipe. The high-mesh powder layer increases the contact area and improves interfacial strength, while simultaneously providing vaporization nucleation sites to enhance heat pipe performance. This invention features a simple and reliable process, suitable for the efficient preparation of capillary cores made of copper or similar materials. Copper can be sintered at 850℃; sintering only requires a small amount of copper to melt and bond together, without the need for completely melting the copper capillary core of the same material.

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

[0006] A multi-scale metal powder sintered capillary core includes a 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 shell is made of copper as a substrate, with a double-sided adhesive layer attached to its upper surface. High-mesh copper powder is bonded 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 shell are assembled to form an axial limiting structure. The pre-sintered copper capillary core is placed on the transition interface layer, and the graphite block and stainless steel block are stacked in sequence to provide pressure in the vertical direction. The assembly consisting of the shell, outer ring, double-sided adhesive layer, high-mesh copper powder, pre-sintered copper capillary core, 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 to the shell and the pre-sintered copper capillary core.

[0007] Furthermore, the outer 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%.

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

[0009] Step 1: Use a copper shell as the base, attach a double-sided adhesive layer to its upper surface, adhere high-mesh copper powder to the surface of the double-sided adhesive layer, and use mechanical vibration to make the high-mesh copper powder evenly distributed on the surface of the double-sided adhesive layer to form a transition interface layer.

[0010] Step 2: Apply a release agent to the inner surface of the outer ring, and after it is dried and cured, assemble the outer ring and the outer shell to form an axial limiting structure;

[0011] Step 3: Place the pre-sintered copper capillary core on the transition interface layer, and then stack graphite blocks and stainless steel blocks 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 core, graphite block, stainless steel block, and release agent into a vacuum sintering furnace and heat it to 850℃~900℃ for secondary sintering. The double-sided adhesive layer is completely pyrolyzed at 600℃, and the remaining transition interface layer is sintered and connected to the outer shell and pre-sintered copper capillary core.

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

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

[0015] Furthermore, the density of the graphite briquettes is 1.7-1.9 g / cm³. 3 The coefficient of thermal expansion is 4.5 × 10⁻⁶. -6 / ℃, which compensates for the thermal stress of 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 ≤20μm.

[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 a multi-scale metal powder sintered capillary core as described above.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

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

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

[0023] (3) The present invention uses double-sided adhesive to fix the powder, and the excess powder can be removed by vibration to finally obtain an ultra-thin powder layer. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a multi-scale metal powder sintered capillary core according to the present invention;

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

[0026] Figure 3 This is a schematic diagram of the application of the present invention on a flat heat pipe;

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

[0028] The attached figures are labeled 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 Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other. The invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0030] like Figure 1 , Figure 2 As shown, a multi-scale metal powder sintered capillary core of the present invention includes a 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 copper shell 1 serves as the substrate, with the double-sided adhesive layer 3 attached to its upper surface. High-mesh copper powder 4 is then bonded to the surface of the double-sided adhesive layer 3 and evenly distributed on the adhesive layer surface using mechanical vibration to form a transition interface layer. The release agent 8 is coated on the inner surface of the outer ring 2, and after drying, the outer ring 2 and the 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 sequentially stacked to provide pressure in the vertical direction. The assembly consisting of outer shell 1, outer ring 2, double-sided adhesive layer 3, high-mesh copper powder 4, pre-sintered copper capillary core 5, graphite block 6, stainless steel block 7, and release agent 8 is placed in a vacuum sintering furnace and heated to 850℃~900℃ for secondary sintering. The double-sided adhesive layer 3 is pyrolyzed, and the remaining transition interface layer is sintered and connected to the outer shell 1 and the pre-sintered copper capillary core 5.

[0031] In this invention, the concept of multi-scale refers to the existence of dimensional interactions spanning at least two orders of magnitude. For example, the particle size of 1000-mesh powder is approximately 13 micrometers, while the thickness of the outer shell and the pre-sintered copper capillary core is on the millimeter scale, representing a dimensional difference of one order of magnitude. Simultaneously, the pores formed between the powder particles fall within the micrometer to submicrometer scale range, further constituting a dimensional interaction spanning at least two orders of magnitude.

[0032] Preferably, the outer shell 1, outer ring 2, high-mesh copper powder 4, and pre-sintered copper capillary core 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 a powder with a mesh size ≥ 1000. This invention avoids powder agglomeration before sintering by combining sieving with baking. During sintering, because the powder layer is a single layer with only one powder thickness and is uniform, problems such as agglomeration are avoided.

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

[0036] Preferably, the graphite block 6 is made of hot-pressed graphite with a density of 1.7-1.9 g / cm³. 3 The coefficient of thermal expansion is 4.5 × 10⁻⁶. -6 / ℃.

[0037] Preferably, the stainless steel pressure 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] This invention also provides a method for preparing multi-scale metal powder sintered capillary cores, comprising the following steps:

[0040] Step 1, pretreatment of the outer shell: Apply double-sided adhesive layer 3 to the upper surface of the outer shell 1 made of copper material, with a coverage rate of >95%.

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

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

[0043] Step 4, Capillary Core Positioning: Place the pre-sintered copper capillary core 5 on the transition layer.

[0044] Step 5, Assembly and Pressure Sintering: Graphite blocks 6 and stainless steel blocks 7 are stacked sequentially, and secondary sintering is performed in a vacuum sintering furnace (vacuum degree < 0.01 Pa) at 850℃~900℃. The double-sided adhesive layer 3 is fully pyrolyzed at 600℃, and the remaining transition interface layer is sintered and connected to the outer shell 1 and the pre-sintered copper capillary core 5.

[0045] like Figure 3 The diagram shown illustrates the application of this invention to a flat heat pipe. Figure 4The diagram shown is a cross-sectional view of the present invention applied to a flat plate heat pipe. The flat plate heat pipe includes a shell 1, a pre-sintered copper capillary wick 5, and high-mesh copper powder 4. The high-mesh copper powder 4 is disposed at the bottom of the shell 1, and the pre-sintered copper capillary wick 5 is disposed above the high-mesh copper powder 4 and inside the shell 1. The shell 1 is a closed structure.

[0046] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A multi-scale metal powder sintered capillary core, characterized in that, The components include 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 as a substrate, with a double-sided adhesive layer attached to its upper surface. High-mesh copper powder is then bonded to the surface of the adhesive layer, and mechanical vibration is used to evenly distribute the high-mesh copper powder on the surface of the adhesive layer, forming a transition interface layer. The inner surface of the outer ring is coated with the release agent, and after drying, the outer ring is assembled with the outer shell. An axial limiting structure is formed; a pre-sintered copper capillary core is placed on the transition interface layer, and graphite blocks and stainless steel blocks 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 core, graphite blocks, stainless steel blocks, and release agent is sintered twice, the double-sided adhesive layer is pyrolyzed, and the remaining transition interface layer is sintered and connected to the outer shell and pre-sintered copper capillary core; the high-mesh copper powder has a mesh size ≥1000 mesh.

2. The multi-scale metal powder sintered capillary core according to claim 1, characterized in that, The outer 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 multi-scale metal powder sintered capillary cores, characterized in that, Includes the following steps: Step 1: Use a copper shell as the base, attach a double-sided adhesive layer to its upper surface, adhere high-mesh copper powder to the surface of the double-sided adhesive layer, and use mechanical vibration to make the high-mesh copper powder evenly distributed on the surface of the double-sided adhesive layer to form a transition interface layer. Step 2: Apply a release agent to the inner surface of the outer ring, and after it is dried and cured, assemble the outer ring and the outer shell to form an axial limiting structure; Step 3: Place the pre-sintered copper capillary core on the transition interface layer, and then stack graphite blocks and stainless steel blocks 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 core, graphite block, stainless steel block, and release agent into a vacuum sintering furnace and heat it to 850℃~900℃ for secondary sintering. The double-sided adhesive layer is completely pyrolyzed at 600℃, and the remaining transition interface layer is sintered and connected to the outer shell and pre-sintered copper capillary core.

4. The preparation method according to claim 3, characterized in that, High-mesh copper powder has a mesh size ≥ 1000 mesh.

5. The preparation method according to claim 3, characterized in that, In step 1, the vibration frequency of the mechanical vibration method is 50-100Hz, the amplitude is 0.1-0.5mm, and the duration is 30-60s, 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 briquettes is 1.7-1.9 g / cm³. 3 The coefficient of thermal expansion is 4.5 × 10⁻⁶. -6 / ℃, which compensates for 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 ≤20μm.

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, The application of a multi-scale metal powder sintered capillary core as described in claim 1 or 2.

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