Low-melting-point alloy heat-conducting sheet as well as preparation method and application thereof

Abstract

The invention relates to the field of heat management, in particular to a low-melting-point alloy heat-conducting fin and a preparation method and application thereof. The preparation method of the low-melting-point alloy heat-conducting fin comprises the steps that (1) low-melting-point alloy raw materials are smelted, and low-melting-point alloy liquid is obtained; (2) the low-melting-point alloy liquid is subjected to micronization treatment, and low-melting-point alloy powder is obtained; 3, the precursor material containing the low-melting-point alloy powder is subjected to pressure casting and pressed into sheets.The preparation method of the low-melting-point alloy heat-conducting fin enables alloy components to be more uniform, the problems that the low-melting-point alloy heat-conducting fin is not uniform and the like are solved, meanwhile, the temperature uniformity condition after the heat-conducting fin is heated can be effectively improved, and the performance of the heat-conducting fin is improved.

Description

Technical Field

[0001] The present invention relates to the field of thermal management, and in particular to a low melting point alloy thermal conductive sheet and a preparation method and application thereof. Background Art

[0002] With the miniaturization and high integration of electronic components, the power density of chips continues to rise, and heat dissipation has become a key factor restricting the development of electronic components. As a key link in the heat dissipation process, the selection of thermal interface materials is crucial. The thermal conductivity of traditional thermal interface materials such as thermal grease, thermal gel and polymer thermal pads is difficult to meet the current heat dissipation needs. In recent years, the thermal conductivity of liquid metal has been widely recognized and has been applied on a large scale. However, due to the characteristics of gallium-based liquid metal such as easy flow and conductivity and easy corrosion, it needs to be packaged and anti-corrosion treated when used, and the supporting process is complicated. The low-melting-point alloy with a melting point of 60℃-300℃ is solid at room temperature and has a high thermal conductivity. After the chip heats up, the alloy melts and wets the interface, thereby achieving a good thermal conductivity. This material has attracted much attention in recent years due to its convenient use performance and good thermal conductivity.

[0003] However, there are still many problems in the actual application of low melting point alloys. In order to prevent the alloy from melting completely and causing metal leakage during use, non-eutectic alloys with a longer melting range are used. The alloy melting process is uneven, which makes the prepared thermal conductive sheet uneven, resulting in a large difference in the wetting effect on the interface, affecting the effect of the thermal conductive sheet. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a low melting point alloy thermal conductive sheet and its preparation method and application. Most of the melting point alloy thermal conductive sheets currently used are non-eutectic alloys, which are basically prepared into thermal conductive sheets of specified thickness by casting and then pressing. There is a situation of uneven composition, and in actual application, some thermal conductive sheets fail to perform. Preparing it into powder first and then die-casting can improve the situation of uneven composition (uneven temperature of the thermal conductive sheet), and by compounding it with materials with good in-plane thermal conductivity such as graphene powder, the temperature uniformity of the thermal conductive sheet after heating can be greatly improved, thereby improving the performance of the thermal conductive sheet.

[0005] In a first aspect, the present invention provides a method for preparing a low melting point alloy thermally conductive sheet, comprising: 1) Smelting the low melting point alloy raw materials to obtain low melting point alloy liquid.

[0006] 2) The low melting point alloy liquid is subjected to micronization treatment to obtain low melting point alloy powder.

[0007] 3) die-casting the precursor material containing the low melting point alloy powder and pressing it into tablets.

[0008] The present invention provides a method for preparing a low melting point alloy thermally conductive sheet. The present invention changes the traditional preparation process of a low melting point alloy thermally conductive sheet. The low melting point alloy raw material is smelted, and after the alloy is smelted, the alloy is prepared into small particles of a certain particle size, and then die-cast into blocks, and finally pressed into a thermally conductive sheet of a specified thickness. Through this process, on the one hand, the alloy composition is more uniform, which improves the problem of uneven low melting point alloy thermally conductive sheets, and can also be simply and quickly compounded with other materials to improve the comprehensive performance of the thermally conductive sheet.

[0009] Preferably, in step 1), the melting point of the low melting point alloy raw material is not higher than 320°C; preferably, the composition of the low melting point alloy raw material includes one or more of Bi, In, and Sn; more preferably, in terms of weight percentage, Bi: 20%~60%, Sn: 20%~40%, and the balance is In. In the present invention, the melting point of the low melting point alloy raw material is not higher than 300°C, preferably Bi: 20%~60%, Sn: 20%~40%, and the balance is In, and the melting point is 60-300°C, for example, 65°C, 75°C, 100°C, 120°C, 150°C, 200°C, 220°C, 280°C, etc. and the numerical range therebetween. The alloy raw material of the preferred formula used in the present invention is more suitable for the preparation process of the present invention, and can make the performance of the thermal conductive sheet better. The smelting temperature of the present invention is not lower than the melting point of the low melting point alloy; for example, the smelting temperature is 0-15°C higher than the melting point of the low melting point alloy raw material, and the smelting temperature in the embodiment of the present invention is 5-10°C higher than the melting point of the low melting point alloy.

[0010] It is further preferred that in step 2), the particle size of the low melting point alloy powder is less than 20 μm; preferably, the particle size of the low melting point alloy powder is less than 10 μm. In the present invention, the low melting point alloy is prepared into powder, preferably 20 μm, and the uniformity and overall performance of the thermal conductive sheet prepared under the alloy powder in the preferred particle size range are further improved, especially less than 10 μm, but the larger particle size powder size is also within the protection range, for example, the particle size of the low melting point alloy powder of the present invention can be 25 μm, 12 μm, 13 μm, 14 μm, 15 μm, 18 μm, 20 μm, 1 μm, 2 μm, 5 μm, 7 μm, 9 μm, 10 μm, etc. and the numerical range therebetween.

[0011] More preferably, in step 2), the micronization treatment comprises one or more of ultrasonic dispersion, high-speed shearing and atomization.

[0012] In the present invention, the micronization treatment method can adopt the conventional treatment method in the art, but preferably ultrasonic dispersion, high-speed shearing, atomization, etc. are adopted. More preferably, the micronization treatment of the present invention adopts atomization, and the particle size is controlled between 1 and 20 microns, preferably less than 10 microns. The present invention can effectively prepare the alloy into uniform and fine powder particles, thereby improving the uneven composition of the low-melting-point alloy thermal conductive sheet, and improving its thermal conductivity and molding quality. This treatment method can significantly improve the uniformity of the alloy powder and the comprehensive performance of the thermal conductive sheet.

[0013] Further preferably, step 3) further comprises mixing the low melting point alloy powder with a high thermal conductivity material to obtain the precursor material. The present invention improves the uniformity and overall performance of the thermal conductive sheet by preparing the alloy into powder and mixing it with a high thermal conductivity material, and then die-casting and pressing the low melting point alloy thermal conductive sheet through process optimization.

[0014] Preferably, the high thermal conductivity material includes one or more of carbon fiber, graphene powder, nano copper powder, and nano aluminum powder. In the present invention, graphene powder is preferably used, and the graphene powder used is preferably graphene oxide powder, which has better bonding performance with low melting point alloys. Further preferably, in step 3), the mass ratio of the low melting point alloy powder to the high thermal conductivity material is 100:0.1~5.

[0015] The preparation process of the low melting point alloy composite thermally conductive sheet provided by the present invention is preferably prepared by preparing the alloy into powder, mixing it with a specific high thermal conductivity material, and then die-casting, especially preparing the low melting point alloy into powder, mixing it with graphene powder, and then die-casting it into blocks to prepare the preparation process of the low melting point alloy thermally conductive sheet and optimizing the preparation parameters, which not only improves the uniformity of the alloy composition, but also solves the problem of adding modified materials to the alloy, so that the composite material is highly viscous after melting, is not easy to flow and cause metal precipitation. This process is simple and the alloy is not easy to oxidize, which greatly expands the application range of low melting point alloys and significantly improves the thermal resistance and copying effect of the thermally conductive sheet. At the same time, there is no metal overflow during the test process, which can significantly improve the thermal conductivity and comprehensive performance of the thermally conductive sheet, and meet the needs of high-performance thermally conductive sheets.

[0016] Preferably, in step 3), the pressing thickness of the thermal conductive sheet is 50-160 μm.

[0017] Further preferably, in step 3), the die-casting pressure is 5-30 MPa and the time is 5-30 min; and / or, the heat conductive sheet is pressed into a specified thickness by roller pressing.

[0018] The present invention improves the problem of uneven low-melting-point alloy thermal conductive sheet by optimizing the preparation process. By preparing into powder and then pressing, each component is weighed according to the low-melting-point alloy formula (main components are Bi, In, Sn) and then smelted in a smelting furnace. After smelting, the alloy is prepared into small particles below 20 μm. The preparation method is preferably ultrasonic dispersion, high-speed shearing, and atomization. After preparation, it is pressed into blocks and finally pressed into a thermal conductive sheet of a specified thickness, which can improve the uneven situation. At the same time, by mixing with high thermal conductivity materials (high thermal conductivity carbon fiber, graphene powder, nano copper powder, nano aluminum powder) after preparation, pressing into blocks, and finally pressing into a thermal conductive sheet of a specified thickness, the problem of uneven alloy composition can be further improved.

[0019] In a second aspect, the present invention provides a low melting point alloy thermally conductive sheet, which is obtained by the preparation method of the low melting point alloy thermally conductive sheet.

[0020] In a third aspect, the present invention provides a low melting point alloy thermally conductive sheet obtained by the preparation method of the low melting point alloy thermally conductive sheet or the use of the low melting point alloy thermally conductive sheet in thermal interface materials of electronic components.

[0021] The beneficial effects of the present invention are at least that: the present invention provides a new method for preparing a low-melting-point alloy thermal conductive sheet, which improves the traditional process by first smelting the alloy into small particles, then die-casting into blocks, and finally pressing into a thermal conductive sheet of a specified thickness. This process not only solves the problem of uneven alloy composition, but also can directly die-cast the alloy powder by mixing it with the added material, thus solving the problem of adding modified materials to the alloy, and greatly expanding the application range of low-melting-point alloys. In addition, the process is simple, the alloy is not easy to oxidize, and after adding materials such as graphene, copper powder, and aluminum powder, the composite material is highly viscous after melting, and is not easy to flow and cause metal precipitation. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods. If no specific techniques or conditions are specified in the examples, they are all conventional methods or the techniques or conditions described in the literature in this field, or according to the product instructions. If the manufacturers of the reagents and instruments are not specified, they are all conventional products that can be purchased through regular channels.

[0024] In the embodiment of the present invention, the graphene powder used is graphene oxide powder with a thickness of less than 3 layers and a particle size of 10-20 μm; the hydraulic press used is a double-column gantry hydraulic press.

[0025] Example 1

[0026] A eutectic alloy with a melting point of 60°C was selected, namely In: 51%, Bi: 32.5%, Sn: 16.5%, and 100g of alloy was prepared according to the ratio. The above alloy was smelted at 70°C for 30 minutes to obtain a low-melting-point alloy liquid, and the low-melting-point alloy liquid was atomized to prepare the alloy into a powder with a particle size of less than 20 microns. The powder was die-cast into blocks using a hydraulic press, and die-cast for 10 minutes at a pressure of 20MPa. The block alloy was pressed into a thermal conductive sheet of specified thickness by a roller press. In the experiment, the thickness of the pressed thermal conductive sheet was 150 microns.

[0027] Example 2

[0028] The alloy selected is the same as that in Example 1, and graphene powder is used as an additive to prepare a composite thermally conductive sheet. A eutectic alloy with a melting point of 60°C is selected, namely In: 51%, Bi: 32.5%, and Sn: 16.5%, and 100g of alloy is prepared according to the ratio. The above alloy is smelted at 70°C for 30 minutes to obtain a low-melting point alloy liquid, and the low-melting point alloy liquid is atomized to prepare the alloy into a powder with a particle size of less than 20 microns. 0.1%-5% of graphene powder is added to the above powder, and the mixture is stirred and mixed evenly. The powder is die-cast into blocks using a hydraulic press, and die-cast at a pressure of 20MPa for 10 minutes. The block alloy is passed through a roller press to be pressed into a thermally conductive sheet of specified thickness. In the experiment, the thickness of the pressed thermally conductive sheet is 150 microns.

[0029] Example 3

[0030] A eutectic alloy with a melting point of 60°C-145°C is selected, wherein the components are Bi: 20-60%, Sn: 20-40%, and the remaining components are In, and 100g of alloy is prepared according to the ratio. The above alloy is smelted at 150°C for 10 minutes to obtain a low-melting-point alloy liquid, and the low-melting-point alloy liquid is atomized to prepare the alloy into a powder with a particle size of less than 20 microns. The powder is die-cast into blocks using a hydraulic press, and the block alloy is pressed into a specified thickness thermal conductive sheet by a roller press. In the experiment, the thickness of the pressed thermal conductive sheet is 150 microns.

[0031] Example 4

[0032] The alloy selected is the same as that in Example 3, and graphene powder is used as an additive to prepare a composite thermally conductive sheet. A eutectic alloy with a melting point of 60°C-145°C is selected, and the components Bi: 20-60%, Sn: 20-40%, and the remaining components are In, and 100g of alloy is prepared according to the ratio. The above alloy is smelted at 150°C for 10 minutes to obtain a low-melting point alloy liquid, and the low-melting point alloy liquid is atomized to prepare the alloy into a powder with a particle size of less than 20 microns. 0.1%-5% of graphene powder is added to the above powder, and the mixture is stirred and mixed evenly. The powder is die-cast into blocks using a hydraulic press, and the block alloy is pressed into a thermally conductive sheet of specified thickness using a roller press. In the experiment, the thickness of the pressed thermally conductive sheet is 150 microns.

[0033] Comparative Example 1

[0034] The same method as in Example 1 is used, except that a eutectic alloy with a melting point of 60°C is selected, i.e., In: 51%, Bi: 32.5%, Sn: 16.5%, and 100g of alloy is prepared according to the ratio. The alloy is melted at 70°C for 30min and directly cast into a block. Then, a 150-micron thick thermal conductive sheet is pressed by a roller press.

[0035] Comparative Example 2

[0036] The same method as in Example 1 is used, except that a eutectic alloy with a melting point of 60°C-145°C is selected, and the components Bi: 20-60%, Sn: 20-40%, and the remaining components are In. 100g of alloy is prepared according to the proportion. The alloy is melted at 150°C for 30 minutes and directly cast into a block. Then, a 150-micron thick thermal conductive sheet is pressed by a roller press.

[0037] The above-mentioned thermal conductive sheet was subjected to a thermal resistance test, and a system stress test was performed on a desktop computer. The CPU package temperature was recorded. The chip model was i9-11900K, and the power consumption was 180W.

[0038] Table 1

[0039] From the above test results, it can be seen that the thermal resistance and copying effect of the heat sink prepared by the powder pressing process are better, which means that the heat sink is more uniform. However, since the liquid phase component of the heat sink is relatively large after melting during the test, metal overflow is prone to occur.

[0040] The thermal conductive sheet is prepared by mixing the prepared powder with graphene and pressing it, which not only significantly improves the thermal resistance and copy machine effect performance, but also has no metal overflow during the test process. The composite thermal conductive sheet preparation method and process provided by the present invention can well meet the requirements.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a low melting point alloy thermal conductive sheet, characterized in that: include: 1) Smelting the low melting point alloy raw material to obtain a low melting point alloy liquid; 2) micronizing the low melting point alloy liquid to obtain low melting point alloy powder; 3) die-casting the precursor material containing the low melting point alloy powder and pressing it into tablets.

2. The method for preparing the low melting point alloy thermal conductive sheet according to claim 1, characterized in that: In step 1), the melting point of the low melting point alloy raw material is not higher than 320°C; preferably, the composition of the low melting point alloy raw material includes one or more of Bi, In, and Sn; more preferably, in terms of weight percentage, Bi: 20%~60%, Sn: 20%~40%, and the balance is In.

3. The method for preparing a low melting point alloy thermally conductive sheet according to claim 1 or 2, characterized in that: In step 2), the particle size of the low melting point alloy powder is less than 20 μm; preferably, the particle size of the low melting point alloy powder is less than 10 μm.

4. The method for preparing the low melting point alloy thermal conductive sheet according to claim 3, characterized in that: In step 2), the micronization treatment includes one or more of ultrasonic dispersion, high-speed shearing and atomization.

5. The method for preparing a low melting point alloy thermally conductive sheet according to any one of claims 1 to 4, characterized in that: Step 3) further includes mixing the low melting point alloy powder with a high thermal conductivity material to obtain the precursor material; preferably, the high thermal conductivity material includes one or more of carbon fiber, graphene powder, nano copper powder, and nano aluminum powder.

6. The method for preparing the low melting point alloy thermal conductive sheet according to claim 5, characterized in that: In step 3), the mass ratio of the low melting point alloy powder to the high thermal conductivity material is 100:0.1-5.

7. The method for preparing a low melting point alloy thermally conductive sheet according to any one of claims 1 to 6, characterized in that: In step 3), the pressing thickness of the thermal conductive sheet is 50-160 μm.

8. The method for preparing a low melting point alloy thermally conductive sheet according to any one of claims 1 to 7, characterized in that: In step 3), the die-casting pressure is 5-30 MPa and the time is 5-30 min.

9. A low melting point alloy thermal conductive sheet, characterized in that: The low melting point alloy thermal conductive sheet is obtained by the preparation method of any one of claims 1 to 8.

10. Use of the low melting point alloy thermally conductive sheet obtained by the preparation method of the low melting point alloy thermally conductive sheet according to any one of claims 1 to 8 or the low melting point alloy thermally conductive sheet according to claim 9 in thermal interface materials of electronic components.

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