Low-melting-point alloy composite heat-conducting fin 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 composite heat-conducting fin and a preparation method and application thereof. The preparation method of the low-melting-point alloy composite heat-conducting fin comprises the following steps: 1) heating and stirring a low-melting-point alloy and graphene to obtain a pasty mixture; (2) cooling the pasty mixture, and then solidifying and forming; 3, the block-shaped mixture obtained through solidification forming is pressed into sheets, and the low-melting-point alloy composite heat-conducting fin is obtained.According to the preparation method, the viscosity of molten alloy is effectively improved, metal precipitation is inhibited, meanwhile, the temperature uniformity of the heat-conducting fin is improved after the heat-conducting fin is heated through the super-strong heat-conducting property of graphene, and therefore the performance of the heat-conducting fin is better exerted.

Description

Technical Field

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

[0002] With the miniaturization and high integration of electronic components, power density continues to rise. Traditional thermal interface materials such as thermal grease, thermal gel, thermal pads, etc., due to the limitations of their own product performance, such as low thermal conductivity, not resistant to high temperatures, easy to volatilize and deteriorate, are increasingly difficult to meet the needs of high-density heat flow occasions. Liquid metal has been considered the first choice for many thermal barrier problems in recent years due to its high thermal conductivity, wide liquid phase temperature range, and no volatility at high temperatures. Its market share in the field of chip thermal interface materials is increasing. Among them, low-melting-point alloys with a melting point of 50℃-300℃ are made into thermal conductive sheets. Compared with liquid metals that are liquid at room temperature, they are solid at room temperature and easy to use. When used as thermal interface materials, when the chip temperature rises, the thermal conductive sheet is fully or partially melted to fill the gap and play a good thermal conductive role. In actual applications, if the thermal conductive sheet is completely melted and becomes liquid, there is a risk of metal extrusion leakage.

[0003] To avoid leakage during use, the researchers used partially melted alloys as heat conductors and multi-layer structure designs to improve the system. However, due to uneven composition or alloying during use, the thermal conductivity varied during use and fluctuated, and the performance did not meet the requirements. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a low melting point alloy composite thermal conductive sheet and its preparation method and application. At present, the thermal conductive sheet uses non-eutectic alloy, which has uneven composition. In practical applications, the thermal conductive sheet is unevenly heated, resulting in uneven temperature of the thermal conductive sheet, metal overflow and local excessive temperature leading to performance failure. By adding high thermal conductivity graphene powder to the alloy, on the one hand, the viscosity of the alloy after melting is improved and metal precipitation is inhibited. On the other hand, the super thermal conductivity of graphene improves the temperature uniformity of the thermal conductive sheet after heating, thereby giving full play to 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 composite thermally conductive sheet, comprising: 1) The low melting point alloy and graphene are heated and stirred to obtain a paste-like mixture.

[0006] 2) The paste-like mixture is cooled and then solidified into a shape.

[0007] 3) Pressing the blocky mixed material obtained by solidification molding into sheets to obtain a low melting point alloy composite thermal conductive sheet.

[0008] The preparation method of the present invention obtains a low-melting-point alloy composite thermal conductive sheet by mixing and treating a low-melting-point alloy with graphene under certain conditions, which effectively suppresses metal overflow leakage and improves uniformity. It is not easy to leak during use, and the thermal conductivity is significantly improved.

[0009] Preferably, in step 1), the low melting point alloy includes a eutectic or non-eutectic alloy having a melting point of 50-300°C; preferably, the melting point is 60-145°C, preferably 60-120°C. For example, the melting point is 70°C, 90°C, 100°C, 150°C, 200°C, 250°C, 60-118°C, 60-115°C, etc. and the numerical range therebetween.

[0010] 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.

[0011] Further preferably, in step 1), the mass ratio of the low melting point alloy to the graphene is 30:0.03-0.6.

[0012] In the present invention, the graphene used can be graphene powder obtained by different preparation methods, such as mechanical graphene and graphene prepared by chemical method; the present invention does not limit the morphology and size of graphene. For example, the graphene powder used in the embodiment of the present invention is graphene oxide powder with a thickness of less than 3 layers and a particle size of 10-20 microns.

[0013] Preferably, in step 1), a method of adding a certain amount of graphene to a low melting point alloy under specific conditions and heating and stirring the alloy helps to improve the state of a high viscosity paste, further inhibit metal overflow, and improve thermal conductivity.

[0014] Preferably, the heating temperature is not higher than the melting point of the low melting point alloy, for example, the smelting temperature is 0-10° C. lower than the melting point of the low melting point alloy, preferably 0-5° C.

[0015] Further preferably, in step 1), the stirring speed is 50-500 r / min, preferably 100-300 r / min. A stirring speed of 200 r / min is preferably used for better effect.

[0016] Further preferably, in step 2), the paste mixture is cooled to below 50°C.

[0017] Further preferably, in step 2), after the cooling treatment, the method further comprises: repeating step 1) and the cooling treatment, and the number of repetitions is preferably 3 to 5 times; obtaining a paste-like low-melting-point alloy and graphene composite, and then introducing the paste into a mold for solidification to obtain a block-like mixture. The above preferred method is helpful to further improve the performance of the composite thermal conductive sheet.

[0018] More preferably, in step 3), the block mixture is pressed into sheets by roller pressing, and the pressing thickness is 140-160 μm.

[0019] In the present invention, under specific temperature and processing conditions, a certain amount of high thermal conductivity graphene is added to a low melting point alloy to form a paste material, which is then solidified to obtain a block material, and then die-cast into a specific thickness to obtain a low melting point alloy composite thermal conductive sheet. After graphene is added to the low melting point alloy by a specific method, on the one hand, it is melted to form a paste product, which is not easy to leak during use, and on the other hand, due to the super thermal conductivity of graphene, the thermal conductivity uniformity of the composite material is further improved.

[0020] In a second aspect, the present invention provides a low melting point alloy composite thermally conductive sheet, which is obtained by the preparation method of the low melting point alloy composite thermally conductive sheet.

[0021] In a third aspect, the present invention provides a low melting point alloy composite thermally conductive sheet obtained by the preparation method of the low melting point alloy composite thermally conductive sheet or the use of the low melting point alloy composite thermally conductive sheet in thermal interface materials of electronic components.

[0022] The beneficial effects of the present invention are at least that: the present invention has a significant improvement effect in suppressing metal overflow and leakage and improving uniformity by adding graphene to the low-melting-point alloy. After the graphene of the present invention is added to the low-melting-point alloy by a specific method, on the one hand, it forms a paste product after melting, which is not easy to leak during use, and on the other hand, due to the super thermal conductivity of graphene, the thermal conductivity uniformity of the composite material is further improved. The thermal resistance of the composite thermal conductive sheet prepared by the present invention is significantly reduced, and the thermal conductivity is significantly improved after the addition of graphene. At the same time, there is no metal overflow after the addition of graphene, and the composite material is a paste with high viscosity after melting, which suppresses the overflow of metal. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1It is a schematic diagram of the thermal conductive sheet provided in Comparative Example 2 and Example 2 of the present invention. DETAILED DESCRIPTION

[0025] 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.

[0026] 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.

[0027] Example 1

[0028] A eutectic alloy with a melting point of 60° C. was prepared. The main components were Bi: 51%, In: 32.5%, Sn: 16.5%, and 30 g of the alloy was prepared.

[0029] Add graphene powder to the alloy. Add 0.03g of graphene powder to the above alloy. Heat the alloy to 55°C, add graphene and stir (200r / min), lower the temperature to 50°C to solidify the alloy. Heat it to 55°C and stir, lower the temperature to solidify the alloy. Repeat 3 times to get a graphene and low-melting-point alloy composite. Finally, mix the composite material thoroughly at 60°C to obtain a paste-like low-melting-point alloy and graphene composite. Introduce it into a specific mold to solidify and form it into a block. Press molding. The above-formed block composite material is pressed into a set thickness by a roller press. In the experiment, the composite thermal conductive sheet was pressed to 150 microns.

[0030] Example 2

[0031] The specific preparation method is the same as that of Example 1, and an alloy with a melting point of 60°C-120°C is selected, and the main components are Bi: 15-20%, In: 40-50%, and the rest is Sn, and 30g of alloy is prepared.

[0032] Add graphene powder to the alloy. Add 0.02g of graphene powder to the above alloy. Heat the alloy to 115°C, add graphene and stir (200r / min), and lower the temperature to 50°C to solidify the alloy. Raise the temperature to 115°C and stir, and lower the temperature to solidify the alloy. Repeat 3 times to obtain a composite of graphene and low-melting-point alloy. Finally, mix the composite material thoroughly at 120°C to obtain a paste-like low-melting-point alloy and graphene composite. Introduce it into a specific mold to solidify and form it into a block. Press molding. The above-formed block composite material is pressed into a set thickness by a roller press. In the experiment, the composite thermally conductive sheet was pressed to 150 microns. The composite thermally conductive sheet obtained in this embodiment (after testing) is as follows Figure 1 Shown on the right.

[0033] Example 3

[0034] The specific preparation method is the same as that of Example 1, and an alloy with a melting point of 60°C-145°C is selected, and the main components are Sn: 40-60%, In: 20-40%, and the rest is Bi, and 30g of alloy is prepared.

[0035] Add graphene powder to the alloy. Add 0.02g of graphene powder to the above alloy. Heat the alloy to 140°C, add graphene and stir slowly (200r / min), lower the temperature to 50°C to solidify the alloy. Heat it to 140°C again and stir, lower the temperature to solidify the alloy. Repeat 3 times to obtain a graphene and low-melting-point alloy composite. Finally, mix the composite material thoroughly at 145°C to obtain a paste-like low-melting-point alloy and graphene composite. Introduce it into a specific mold to solidify and form it into a block. Press molding. The above-formed block composite material is pressed into a set thickness by a roller press. In the experiment, the composite thermal conductive sheet was pressed to 150 microns.

[0036] Comparative Example 1

[0037] The low melting point alloy with a melting point of 60°C is directly pressed into a 150μm thermal conductive sheet.

[0038] Comparative Example 2

[0039] The low melting point alloy with a melting point of 60℃-120℃ is directly pressed into a 150μm thermal conductive sheet. The thermal conductive sheet obtained in this comparative example (after testing) is as follows Figure 1 Shown on the left.

[0040] Comparative Example 3

[0041] The low melting point alloy with a melting point of 60℃-145℃ is directly pressed into a 150μm thermal conductive sheet.

[0042] Table 1 shows the thermal resistance of different samples at 30psi and a hot surface temperature of 70°C and the metal overflow under heating and pressure.

[0043] Table 1

[0044] From the thermal resistance, it can be seen that the thermal resistance of the composite thermal conductive sheet prepared by adding graphene is significantly lower than that of the alloy. This shows that the thermal conductivity is significantly improved after the addition of graphene. At the same time, from the overflow of the material under heating, there is no metal overflow after adding graphene, which means that after adding graphene, the composite material becomes a paste with high viscosity after melting, which inhibits the overflow of metal.

[0045] 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 composite thermal conductive sheet, characterized in that: include: 1) heating and stirring the low melting point alloy and graphene to obtain a paste-like mixture; 2) cooling the paste mixture and then solidifying it into a shape; 3) Pressing the blocky mixed material obtained by solidification molding into sheets to obtain a low melting point alloy composite thermal conductive sheet.

2. The method for preparing the low melting point alloy composite thermal conductive sheet according to claim 1, characterized in that: In step 1), the low melting point alloy includes a eutectic or non-eutectic alloy having a melting point of 50-300°C; preferably, the melting point is 60-145°C; And / or, the low melting point alloy raw material comprises one or more of Bi, In and Sn.

3. The method for preparing the low melting point alloy composite thermal conductive sheet according to claim 1 or 2, characterized in that: In step 1), the mass ratio of the low melting point alloy to the graphene is 30:0.03-0.

6.

4. The method for preparing the low melting point alloy composite thermal conductive sheet according to any one of claims 1 to 3, characterized in that: In step 1), the heating temperature is not higher than the melting point of the low-melting-point alloy raw material.

5. The method for preparing the low melting point alloy composite thermal conductive sheet according to any one of claims 1 to 4, characterized in that: In step 1), the stirring speed is 50-500 r / min.

6. The method for preparing the low melting point alloy composite thermal conductive sheet according to any one of claims 1 to 5, characterized in that: In step 2), the paste mixture is cooled to below 50°C.

7. The method for preparing the low melting point alloy composite thermal conductive sheet according to any one of claims 1 to 6, characterized in that: In step 2), after the cooling treatment, the method further comprises: repeating step 1) and the cooling treatment, and the number of repetitions is preferably 3 to 5 times; obtaining a paste-like composite of low-melting-point alloy and graphene, and then introducing the paste into a mold for solidification to obtain a block-like mixture.

8. The method for preparing the low melting point alloy composite thermal conductive sheet according to any one of claims 1 to 7, characterized in that: In step 3), the block mixture is pressed into sheets by roller pressing, and the pressing thickness is 140-160 μm.

9. A low melting point alloy composite thermal conductive sheet, characterized in that: The low melting point alloy composite 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 composite thermally conductive sheet obtained by the preparation method of the low melting point alloy composite thermally conductive sheet according to any one of claims 1 to 8 or the low melting point alloy composite thermally conductive sheet according to claim 9 in thermal interface materials of electronic components.

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