A liquid absorption core and a preparation method thereof

Abstract

The present disclosure provides a wick and a preparation method thereof. The wick comprises raw materials in the following mass percentages: 91% - 99% of metal powder; and 1% - 9% of alloy powder with a liquidus temperature lower than the melting point of the metal. The preparation method of the wick is to uniformly mix the aforementioned metal powder and alloy powder; fill the mixed powder into a sintering mold and vibrate and compact it to obtain a precursor, and sinter the precursor to obtain the wick.

Description

Technical Field

[0001] The present disclosure relates to the field of heat conductors, and particularly to a wick and a preparation method thereof. Background Art

[0002] Currently, heat pipes and heat spreaders widely used in high-power or high-integration electronic products both adopt porous media such as powder sintered wicks, screen sintered wicks, foam material wicks, and micro-grooves. Among them, the wick placed inside the heat spreader plays a crucial role in the heat transfer performance of the heat spreader. The wick can increase the heat transfer surface area, strengthen liquid boiling, and is beneficial to improving the heat dissipation performance of the finished heat spreader. The three-dimensional shape, preparation method, and thickness of the wick will directly affect the heat transfer performance of the heat spreader.

[0003] However, in the process of preparing the wick by the powder sintering process, the existing technology mainly has the following disadvantages: (1) During the sintering process, pressure needs to be applied, which will inevitably make the pores between metal particles smaller, making it difficult to achieve a high porosity and affecting the three-dimensional shape of the wick; (2) The pressure sintering method will also result in the situation that metal particles are not firmly bonded, and there is a risk of particle detachment; (3) The metal powder needs to be sintered in a high-temperature environment, consuming too much electric power resources, not meeting the green and environmental protection production concept, and the corresponding production cost will also be high. Therefore, it is urgent to propose a new wick and its preparation method to solve the above problems. Summary of the Invention

[0004] The present disclosure provides a wick and a preparation method thereof to at least solve the above technical problems existing in the prior art.

[0005] According to the first aspect of the present disclosure, a wick is provided, characterized in that the wick comprises raw materials in the following mass percentages: 91%-99% of metal powder; and 1%-9% of alloy powder with a liquidus temperature lower than the melting point of the metal.

[0006] Wherein, the alloy powder is melted and filled in the gaps between the metal powders.

[0007] Wherein, the particle sizes of the metal powder and the alloy powder are 80-150 mesh.

[0008] According to the second aspect of the present disclosure, a preparation method of a wick is provided, the method comprising: mixing 91%-99% by mass of metal powder with 1%-9% by mass of alloy powder evenly, the liquidus temperature of the alloy being lower than the melting point of the metal; filling the mixed powder into a sintering mold and vibrating and compacting to obtain a precursor, and sintering the precursor to obtain the wick.

[0009] In one possible implementation, the temperature for sintering the precursor is lower than the melting point of the metal and higher than the liquidus temperature of the alloy.

[0010] In one possible implementation, the temperature for sintering the precursor is 20 - 30 °C higher than the liquidus temperature of the alloy.

[0011] In one possible implementation, the particle sizes of the metal powder and the alloy powder are 80 - 150 mesh.

[0012] In one possible implementation, the duration for sintering the precursor is 10 - 60 min.

[0013] In one possible implementation, if the metal is prone to forming an oxide film, correspondingly, the precursor is sintered in a vacuum.

[0014] In one possible implementation, if the metal is not prone to forming an oxide film, correspondingly, the precursor is sintered in a reducing atmosphere or in a vacuum.

[0015] For the wick of the present disclosure and its preparation method, alloy powder with a mass fraction of 1% - 9% and a liquidus temperature lower than the melting point of the metal is uniformly mixed in metal powder with a mass fraction of 91% - 99%, and a precursor is obtained by vibrating and compacting in a sintering mold. The precursor is sintered to obtain the wick. Since the alloy powder will melt prior to the metal powder during the sintering process, there is no need for pressurization. The molten alloy will fill the pores formed between the metal particles. After porosity testing, the porosity of the wick prepared by the traditional pressure sintering process is 40% - 60%, while the porosity of the wick obtained by using the preparation method of the present disclosure is increased to 45% - 65%. At the same time, the particles of the metal powder are firmly bonded through the molten alloy, so there will be no powder shedding.

[0016] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present disclosure, nor is it used to limit the scope of the present disclosure. Other features of the present disclosure will become easily understandable through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] By reading the following detailed description with reference to the accompanying drawings, the above and other objects, features, and advantages of the exemplary embodiments of the present disclosure will become easily understandable. In the drawings, several embodiments of the present disclosure are shown in an exemplary rather than restrictive manner, wherein:

[0018] In the drawings, the same or corresponding reference numerals represent the same or corresponding parts.

[0019] Figure 1 An optical microscope image of a wick prepared by a traditional pressure sintering process is shown;

[0020] Figure 2 Figure 1 shows an optical microscope image of the wick prepared according to the present disclosure;

[0021] Figure 3 Figure 2 shows another optical microscope image of the wick prepared according to the present disclosure;

[0022] Figure 4 Figure 3 shows a schematic flowchart of the implementation of the method for preparing the wick according to the embodiments of the present disclosure. Detailed Embodiments

[0023] To make the objectives, features, and advantages of the present disclosure more obvious and understandable, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present disclosure.

[0024] Figure 1 Figure 4 shows a light microscope image of the wick obtained by the traditional preparation process magnified 100 times. It can be seen that for the wick prepared by the traditional process, since pressure needs to be applied during the sintering process, the surface of the wick is flattened and the pores are also damaged to a certain extent, and the porosity is 40%-60%. To solve the above problems of the traditional process, the present disclosure provides a wick, which includes the following raw materials by mass percentage: 91%-99% of metal powder; and 1%-9% of alloy powder with a liquidus temperature lower than the melting point of the metal.

[0025] The metal powder used can be copper powder or aluminum powder. Correspondingly, the alloy powder can be an alloy powder of this metal, such as copper alloy powder or aluminum alloy powder, or an alloy powder of other metals, such as nickel alloy powder or silver alloy powder, as long as it is ensured that the liquidus temperature of the alloy powder used is lower than the melting point of the metal.

[0026] Among them, the alloy powder is filled in the gaps between the metal powders after melting. In this way, the alloy powder will melt prior to the metal powder and form the pores of the wick by filling between the metal particles after melting.

[0027] Further, the particle size of the metal powder and the alloy powder is 80-150 mesh, which is a common particle size in the powder sintering process and will not be elaborated here.

[0028] Figure 2 Figure 5 shows an optical microscope image of the wick prepared according to the present disclosure magnified 100 times, Figure 3 Figure 6 shows an optical microscope image of the wick prepared according to the present disclosure magnified 300 times. FromFigure 2 and Figure 3 As can be seen, compared with the wick prepared by the traditional process in Figure 1 , the wick prepared in the present disclosure has round and plump particles, which is beneficial to liquid flow. The pores are not significantly damaged. At the same time, the particles of the metal powder are stably and firmly bonded by the alloy after melting, so the situation of powder falling off will not occur.

[0029] The present disclosure also provides a method for preparing the wick in the above example, as Figure 4 shown. The method includes:

[0030] Step 401: Mix uniformly the metal powder with a mass fraction of 91%-99% and the alloy powder with a mass fraction of 1%-9%. The liquidus temperature of the alloy is lower than the melting point of the metal.

[0031] The metal powder used can be copper powder or aluminum powder. Correspondingly, the alloy powder can be the alloy powder of this metal, such as copper alloy powder or aluminum alloy powder, or can also be the alloy powder of other metals, as long as it is ensured that the liquidus temperature of the alloy powder used is lower than the melting point of the metal.

[0032] Step 402: Fill the mixed powder into a sintering mold and vibrate and compact it to obtain a precursor, and sinter the precursor to obtain a wick.

[0033] After obtaining the wick, the porosity of the wick is measured by the weighing method. Specifically, first weigh and measure the volume of the sample wick, then immerse the sample wick in a liquid, weigh the sample wick filled with the liquid, calculate the mass difference before and after the sample wick as the mass of the inhaled liquid, calculate the volume of the inhaled liquid using the density formula, and divide the volume of the liquid by the volume of the sample wick to obtain the porosity of the wick.

[0034] In the method for preparing the wick of the present disclosure, the alloy powder with a mass fraction of 1%-9% and a liquidus temperature lower than the melting point of the metal is uniformly mixed in the metal powder with a mass fraction of 91%-99%, and the precursor is obtained by vibrating and compacting in a sintering mold, and the precursor is sintered to obtain a wick. Since during the sintering process, as the sintering temperature increases, the alloy powder will melt prior to the metal powder, so no pressure is required. The molten alloy will fill the gaps between the metal particles to form pores. After the porosity test, compared with the wick prepared by the traditional pressure sintering process, the porosity of the wick obtained by using the preparation method of the present disclosure is significantly improved; at the same time, the metal powder particles are stably and firmly bonded by the molten alloy, so the situation of powder falling off will not occur.

[0035] In one example, the sintering temperature of the precursor is lower than the melting point of the metal and higher than the liquidus temperature of the alloy.

[0036] The liquidus temperatures of the selected alloy powders are all lower than the melting point temperature of the metal. For example, the melting point of pure Cu powder particles is 1083 °C, and the liquidus temperature of CuP 8 Ag 18 powder particles is 645 °C. Therefore, during sintering, the sintering temperature of the precursor can be selected to be lower than the melting point temperature of the metal and higher than the liquidus temperature of the alloy. The sintering temperature of this example can not only ensure that the alloy melts before the metal, but also is more environmentally friendly compared to the sintering temperature close to or exceeding the melting point of the metal in the traditional process.

[0037] In one example, the sintering temperature of the precursor is 20 - 30 °C higher than the liquidus temperature of the alloy.

[0038] In this example, the sintering temperature of the precursor only needs to be 20 - 30 °C higher than the liquidus temperature of the alloy. With the sintering temperature of this example, it can not only ensure that the alloy powder can be completely melted, but also minimize the sintering temperature, reduce power consumption and achieve environmental protection.

[0039] For example, following the above example, using pure Cu powder particles and CuP 8 Ag 18 powder particles to prepare a copper wick, the sintering temperature of the precursor can be selected to be 665 - 675 °C, preferably 665 °C.

[0040] In one example, the particle sizes of the metal powder and the alloy powder are 80 - 150 mesh. This particle size is a commonly used particle size in the powder sintering process and will not be elaborated here.

[0041] In one example, the sintering duration of the precursor is 10 - 60 min. Depending on the selected raw materials, correspondingly, the sintering duration of the precursor that can be selected is also different. After sufficient sintering duration, the alloy powder is completely melted, and then it can better fill between the metal particles.

[0042] In one example, if the metal is prone to form an oxide film, correspondingly, the precursor is sintered in a vacuum.

[0043] The melting point of metal oxides is usually much higher than that of pure metals. If this metal is prone to form a dense oxide film on the surface of metal particles, for example, the melting point of pure aluminum powder is 660 °C, while the melting point of Al 2 O 3 oxide film attached to the surface of aluminum powder particles is 2054 °C. When preparing a wick using the traditional process, even if the sintering temperature is higher than the melting point of the metal, it is difficult for adjacent metal particles to form a bonding phenomenon through molecular diffusion, so the aluminum powder wick cannot be sintered into shape.

[0044] Therefore, in this example, for metal materials such as aluminum that are prone to form oxide films, their precursors can be sintered in a vacuum environment. For example, the sintering environment can be a high-temperature vacuum brazing furnace.

[0045] In one example, if the metal is not prone to form an oxide film, correspondingly, the precursor is sintered in a reducing atmosphere or in a vacuum.

[0046] For metal materials that are not prone to form oxide films, the sintering environment options for their precursors are more extensive. They can be sintered in a reducing atmosphere or in a vacuum. If sintered in a reducing atmosphere, the sintering environment for the precursor can be a high-temperature reducing atmosphere furnace.

[0047] To further understand the implementation process of the method for preparing the wick, it will be described in detail below in conjunction with embodiments. The protection scope of the present disclosure is not limited by the following embodiments.

[0048] Embodiment 1:

[0049] Mix pure copper powder and CuP 8 Ag 18 powder to prepare a copper wick.

[0050] Specifically, mix 80-150 mesh pure copper powder and CuP 8 Ag 18 powder evenly, and obtain a precursor by vibration pressing. Among them, the melting point of pure Cu powder particles is 1083 °C, and the liquidus temperature of CuP 8 Ag 18 powder particles is 645 °C. Sinter the precursor in a high-temperature reducing atmosphere furnace at 665 °C for 10-60 minutes to obtain a copper wick.

[0051] Embodiment 2:

[0052] Mix pure aluminum powder and AlSi 10 Mg powder to prepare an aluminum wick.

[0053] Specifically, mix 80-150 mesh pure aluminum powder and AlSi 10 Mg powder evenly, and obtain a precursor by vibration pressing. Among them, the melting point of pure aluminum powder is 660 °C, and the liquidus temperature of AlSi 10 Mg powder is 582 °C. Sinter the precursor in a high-temperature vacuum brazing furnace at 602 °C for 10-60 minutes to obtain an aluminum wick.

[0054] The porosity of the wicks obtained in the above two embodiments is measured by the weighing method, and it is all 45%-65%. Compared with the wicks prepared by traditional processes, the porosity has been greatly improved.

[0055] It should be understood that the various forms of processes shown above can be used, with steps reordered, added or deleted. For example, the steps described in this disclosure can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solutions disclosed in this disclosure can be achieved, and no limitations are imposed herein.

[0056] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In the description of this disclosure, "a plurality" means two or more, unless otherwise specifically defined.

[0057] As described above, the above are only specific embodiments of this disclosure, but the protection scope of this disclosure is not limited thereto. Any person skilled in the art within the technical scope disclosed in this disclosure can easily think of changes or substitutions, which should all be covered within the protection scope of this disclosure. Therefore, the protection scope of this disclosure should be subject to the protection scope of the claims.

Claims

1. A method for preparing a wick, characterized in that, the method comprises: mixing metal powder with a mass fraction of 91%-99% and alloy powder with a mass fraction of 1%-9%, wherein the liquidus temperature of the alloy is lower than the melting point of the metal; the metal powder includes copper powder and aluminum powder, the alloy powder is an alloy powder of this metal including copper alloy powder and aluminum alloy powder, or the alloy powder is an alloy powder of other metals including nickel alloy powder and silver alloy powder; the particle sizes of the metal powder and the alloy powder are 80-150 mesh; filling the mixed powder into a sintering mold and vibrating and compacting to obtain a precursor, and sintering the precursor to obtain a wick; the sintering temperature of the precursor is lower than the melting point of the metal and higher than the liquidus temperature of the alloy; the sintering duration of the precursor is 10-60 min; if the metal is prone to forming an oxide film, correspondingly, sinter the precursor in a vacuum; if the metal is not prone to forming an oxide film, correspondingly, sinter the precursor in a reducing atmosphere or in a vacuum.

2. The method according to claim 1, characterized in that, the sintering temperature of the precursor is 20-30 °C higher than the liquidus temperature of the alloy.

3. A wick prepared by the preparation method according to any one of claims 1-2, characterized in that, the wick comprises raw materials with the following mass percentages: 91%-99% of metal powder, the metal powder includes copper powder and aluminum powder; and 1%-9% of alloy powder with a liquidus temperature lower than the melting point of the metal; the alloy powder is an alloy powder of this metal including copper alloy powder and aluminum alloy powder, or the alloy powder is an alloy powder of other metals including nickel alloy powder and silver alloy powder; the alloy powder is melted and filled in the gaps between the metal powders; the particle sizes of the metal powder and the alloy powder are 80-150 mesh.

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