Carbon fiber soft felt reinforced low-melting-point metal heat-conducting sheet

Abstract

The invention relates to the technical field of low-melting-point metal heat-conducting fins, in particular to a carbon fiber soft felt reinforced low-melting-point metal heat-conducting fin which is prepared by conducting surface treatment on a carbon fiber soft felt and then pouring low-melting-point metal into the carbon fiber soft felt. The carbon fiber soft felt reinforced low-melting-point metal heat-conducting sheet has the characteristics of low surface roughness, high tensile strength, slag and chip falling prevention, low thermal resistance and the like, the yield of semiconductor chip packaging can be improved, and the packaging process and automation are facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of low-melting-point metal heat-conducting sheets, and in particular to a low-melting-point metal heat-conducting sheet reinforced with carbon fiber soft felt. Background Art

[0002] With the rapid development of modern electronic technology, the heat dissipation problem of high-power integrated circuits has become increasingly prominent, and there is an urgent need for efficient thermal management materials. Traditional thermal interface materials can no longer meet the growing demand for heat dissipation, especially in the fields of servers, communication equipment, military industry, and aerospace, which have extremely high requirements for the thermal conductivity, mechanical properties, and long-term stability of materials.

[0003] Phase change materials (PCM) are considered as potential thermal management materials due to their high energy storage density and isothermal energy storage characteristics. However, the low thermal conductivity, poor thermal stability, and easy leakage of PCMs generally limit their widespread promotion in practical applications. In addition, carbon-based thermal pads are often conductive, which may affect internal components or even cause short circuits in practical applications. Therefore, carbon-based thermal pads need to be non-slag and anti-vibration. Summary of the invention

[0004] In view of the above shortcomings of the prior art, the present invention provides a carbon fiber soft felt reinforced low melting point metal thermal conductive sheet, which aims to solve the heat dissipation problem of high power integrated circuits in the prior art and provide a thermal interface material with high thermal conductivity, excellent mechanical properties and long-term stability. The thermal conductive sheet of the present invention not only has low surface roughness and high tensile strength, but also can effectively prevent slag and chip falling, and is suitable for high-end chip packaging and high power chip heat dissipation, servers, communications, military industry, aerospace and other fields.

[0005] Technical Solution

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0007] The present invention provides a carbon fiber soft felt reinforced low melting point metal thermal conductive sheet, which is prepared by surface treating the carbon fiber soft felt and then infusing the low melting point metal inside. The carbon fiber soft felt is preferably a carbon fiber soft felt VU-SF-HP produced by Hangzhou Weiken New Material Technology Co., Ltd.

[0008] Furthermore, the low melting point metal includes at least one or more of bismuth (Bi), tin (Sn), indium (In) and silver (Ag).

[0009] Furthermore, the low melting point metal includes bismuth (Bi), tin (Sn), indium (In) and silver (Ag).

[0010] Furthermore, in terms of mass percentage, the low melting point metal includes 40-50% bismuth, 25-35% tin, 10-20% indium and 5-15% silver, and the sum of the components is 100%.

[0011] Furthermore, in terms of mass percentage, the low melting point metal includes 40-45% bismuth, 30-35% tin, 15-20% indium and 5-10% silver, and the sum of the components is 100%.

[0012] Preferably, in terms of mass percentage, the mass fractions of bismuth, tin, indium and silver in the low melting point metal are 40%, 33%, 17% and 10% respectively.

[0013] Preferably, in terms of mass percentage, the mass fractions of bismuth, tin, indium and silver in the low melting point metal are 42%, 35%, 16% and 7% respectively.

[0014] Furthermore, the melting point of the low melting point metal is 40-120°C, preferably 60°C.

[0015] Furthermore, the surface treatment includes one or more of surface oxidation, surface coating, and plasma treatment.

[0016] Furthermore, the internal perfusion includes one or more of natural immersion, vacuum-assisted perfusion and high-pressure-assisted perfusion.

[0017] Furthermore, the carbon fiber soft felt is a high thermal conductivity carbon fiber soft felt with a density of 0.1 to 1 g / cm 3 , thickness is 0.5~5mm, carbon fiber diameter is 0.5~500um, and carbon fibers are arranged randomly within the surface.

[0018] Low melting point metals have a significant impact on products. Specifically, in the field of electronics and electrical, low melting point metals have been partially applied. Similar to phase change materials. The melting point is generally required to be higher than room temperature and lower than the temperature of the heat source of the electronic device. It is solid in daily transportation and at room temperature. During use, as the temperature of the heat source rises, when it is higher than the melting point of the metal, the metal phase changes and melts into a liquid state, increasing the contact with the upper and lower surfaces to improve the heat transfer effect. However, common low melting point metal thermal conductive sheets have metal leakage, pumping out, poor mechanical properties, no tear resistance, reliability problems, and are not resistant to compression. The addition of carbon fiber soft felt will significantly improve this.

[0019] The product form and internal structure of the present invention are as follows Figure 1, carbon fiber and metal material blend with each other to form a continuous structure as a whole. Carbon fibers are arranged randomly in a plane like a non-woven fabric structure, and the whole is oriented in the plane. The metal is a continuous integral structure. The metal material itself can also be used as a thermal interface material. The addition of carbon fiber enhances heat dissipation, enhances the mechanical properties of the material, and prevents metal pumps and metal leakage problems. The present invention is a thermal interface material, which mainly transfers heat longitudinally and transversely, and is in sheet form, and is placed between the heat source and the radiator.

[0020] The present invention provides a carbon fiber soft felt reinforced low-melting-point metal thermal conductive sheet and a preparation method thereof. The composite material significantly improves thermal conductivity by introducing high thermal conductivity carbon fiber soft felt and low melting point metal. Low melting point metals include bismuth (Bi), tin (Sn), indium (In) and silver (Ag) with a melting point of 40 to 120 degrees. These metals have high electrical conductivity and high thermal conductivity and have a wide range of applications in various heat dissipation, heat conduction, sealing and other fields. At the same time, the addition of carbon fiber soft felt enhances the mechanical properties and shape stability of the composite material, while the application of surface treatment and internal infusion technology effectively enhances the thermal oxidation stability of the material, making it less prone to aging and performance degradation during long-term use.

[0021] The carbon fiber soft felt reinforced low-melting-point metal thermal conductive sheet of the present invention has not only high thermal conductivity and good mechanical properties due to its unique formula and preparation method, but also no obvious pumping out and creep problems after long-term use. It is suitable for high-power integrated circuit heat dissipation, servers, communications, military industry, aerospace and other fields.

[0022] Beneficial Effects

[0023] Compared with the known public technology, the technical solution provided by the present invention has the following beneficial effects:

[0024] (1) Compared with the unreinforced low-melting-point metal thermal conductive sheet, the carbon fiber soft felt reinforced low-melting-point metal thermal conductive sheet of the present invention has better mechanical properties, tear resistance, better reliability, anti-pumping effect, and prevents metal leakage, and is more resistant to compression. The thermal conductivity of the thermal conductive sheet prepared by the present invention is greater than 120W / mK, and the thermal resistance is less than 0.1Kcm 2 / W.

[0025] (2) The carbon fiber soft felt reinforced low-melting-point metal thermal conductive sheet of the present invention has the characteristics of low surface roughness, high thermal conductivity, high tensile stress, good compressibility, anti-slag and chipping, low thermal resistance, etc., and has no obvious pumping and creep problems after long-term use, meeting the heat dissipation needs of high-power integrated circuits; it can improve the yield of semiconductor chip packaging, and is beneficial to packaging process and automation; it effectively solves the pumping and creep problems of traditional PCM, meeting the heat dissipation needs of high-power integrated circuits.

[0026] (3) The carbon fiber soft felt reinforced low-melting-point metal thermal conductive sheet of the present invention can be industrially mass-produced, has the advantage of low cost, and is suitable for the heat dissipation needs of high-end chip packaging and high-power servers, military industry, aerospace and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 Schematic diagram of the preparation of a low-melting-point metal thermal conductive sheet reinforced with carbon fiber soft felt. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. 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.

[0030] The present invention will be further described below in conjunction with the embodiments.

[0031] The raw materials in the embodiments and comparative examples were purchased from the following manufacturers:

[0032] Carbon fiber soft felt: Hangzhou Weiken New Material Technology Co., Ltd., carbon fiber soft felt VU-SF-HP.

[0033] (I) Embodiment

[0034] Example 1

[0035] In this embodiment, carbon fiber soft felt is selected as the reinforcing material, and its thermal conductivity is 600W / (mK); its thickness is 1mm, and its density is 0.5g / cm 3 , the diameter of the carbon fiber is about 1um. The mass fractions of bismuth, tin, indium and silver in the low melting point metal are 40 parts, 33 parts, 17 parts and 10 parts respectively. After the carbon fiber soft felt is treated with plasma, it is immersed in a low melting point metal mixture at 100°C and a vacuum degree of -0.1mPa. After being taken out and molded and cooled, a low melting point metal thermal conductive sheet with a thickness of 0.4mm is obtained.

[0036] Example 2

[0037] In this embodiment, carbon fiber soft felt is selected as the reinforcing material, and its thermal conductivity is 600W / (mK); its thickness is 2mm, and its density is 0.2g / cm 3 , the diameter of the carbon fiber is about 2um. The mass fractions of bismuth, tin, indium and silver in the low melting point metal are 42 parts, 35 parts, 16 parts and 7 parts respectively. After the carbon fiber soft felt is soaked in acrylic solution, it is poured into the low melting point metal mixture at 80℃ and high pressure 5mPa. After the molding is cooled, a low melting point metal thermal conductive sheet with a thickness of 0.5mm is obtained.

[0038] Comparative Example 1

[0039] In this comparative example, carbon fiber soft felt is not used as a reinforcing material, and only low melting point metal is used, and the mass fractions of bismuth, tin, indium and silver are 42 parts, 35 parts, 16 parts and 7 parts respectively. After compression molding at 120 degrees Celsius and cooling, a low melting point metal thermal conductive sheet with a thickness of 0.3 mm is obtained.

[0040] Comparative Example 2

[0041] In this comparative example, carbon fiber soft felt is not used as a reinforcing material, and only a low melting point metal is used, and the ratio is 40 parts of bismuth (Bi), 30 parts of tin (Sn), 20 parts of indium (In), and 10 parts of silver (Ag). After molding at 140 degrees Celsius and cooling, a low melting point metal thermal conductive sheet with a thickness of 0.3 mm is prepared.

[0042] Comparative Example 3

[0043] Compared with Example 1, the only difference is that the low-melting-point metal is different, the low-melting-point metal does not contain silver, and the mass fractions of bismuth, tin and indium in the low-melting-point metal are 40 parts, 33 parts and 17 parts respectively.

[0044] Comparative Example 4

[0045] Compared with Example 1, the only difference is that the low-melting-point metal is different, the low-melting-point metal does not contain bismuth, and the mass fractions of tin, indium and silver in the low-melting-point metal are 33 parts, 17 parts and 10 parts respectively.

[0046] Comparative Example 5

[0047] Compared with Example 1, the only difference is that the low melting point metal is different, the low melting point metal does not contain tin, and the mass fractions of bismuth, indium and silver in the low melting point metal are 40 parts, 17 parts and 10 parts respectively.

[0048] Comparative Example 6

[0049] Compared with Example 1, the only difference is that the low-melting-point metal is different, the low-melting-point metal does not contain indium, and the mass fractions of bismuth, tin and silver in the low-melting-point metal are 40 parts, 33 parts and 10 parts respectively.

[0050] (II) Performance test

[0051] Thermal conductivity and application thermal resistance are tested according to ASTM D 5470 standard;

[0052] Tensile stress was tested according to ASTM D 412.

[0053]

[0054]

[0055] The metal thermal conductive sheet prepared by the embodiment has good thermal conductivity and thermal resistance, good tensile stress and good plane surface roughness; in addition, it has good anti-oxidation and anti-leakage capabilities, is resistant to compression, and has good reliability.

[0056] Comparative Examples 1-2 show that, without using carbon fiber soft felt, the thermal conductivity, thermal resistance and tensile stress of the thermal conductive sheet prepared therefrom are all poor; in addition, due to the lack of fiber reinforcement, it is easy to leak and pump out, easy to oxidize and not resistant to compression, and does not have good reliability. It is difficult to be applied on a large scale.

[0057] As can be seen from Comparative Examples 3-6, when the low melting point metal of the present invention uses bismuth, tin, indium and silver at the same time, the various properties of the thermal conductive sheet prepared are better. In addition, silver (Ag) has high electrical conductivity and thermal conductivity, and the absence of silver will reduce the overall thermal conductivity of the thermal conductive sheet. Silver also helps to improve the corrosion resistance and oxidation resistance of the material. The lack of silver significantly reduces the corrosion resistance and oxidation resistance of the thermal conductive sheet. The material is easily oxidized when exposed to air, and it is easy to corrode the surface of the device. It cannot be used. Bismuth (Bi) usually plays a role in lowering the melting point in the alloy. The lack of bismuth will cause the melting point of the thermal conductive sheet to rise to more than 150 degrees Celsius, and it cannot melt between the operating temperature of 50-150 degrees, and it cannot play a good interface contact to further reduce the thermal resistance. Bismuth can also improve the plasticity of the alloy. The lack of bismuth will reduce the flexibility of the thermal conductive sheet and make it harder. The thermal resistance is high, the thermal conductivity is poor, it is not resistant to compression, and the reliability is low. It is difficult to meet the heat dissipation requirements of applications such as high-end chip packaging and high-power servers. Tin (Sn) can increase fluidity and plasticity in alloys. Lack of tin will make the thermal conductive sheet more brittle and hard, affecting its use in applications with complex shapes or requiring a certain degree of flexibility. Tin also helps to lower the melting point of the alloy, and lack of tin will cause the melting point to increase. It cannot meet the material's fluidity, low melting point, and plasticity requirements in a flowing state. It is difficult to meet the heat dissipation requirements of applications such as high-end chip packaging and high-power servers. Indium (In) plays a role in lowering the melting point and improving thermal conductivity in the alloy. Lack of indium will cause the melting point of the thermal conductive sheet to increase and reduce its thermal conductivity. Indium can also improve the ductility of the alloy, and lack of indium will reduce the processing performance of the thermal conductive sheet. In general, each metal has its specific function and role in low-melting-point metal thermal conductive sheets. The lack of any metal may have a negative impact on the physical and chemical properties of the thermal conductive sheet, thereby affecting its performance in practical applications.

[0058] In the present invention, after the carbon fiber soft felt is treated, the surface has more chemical functional groups, which can be better compatible with metal materials. The carbon fiber enhances the tensile stress of the low-melting-point metal, and the material stability is better after enhancement. The carbon fiber network wraps the low-melting-point metal to make it less likely to leak and oxidize, thereby meeting the heat dissipation needs of my country's high-end chips, high-power servers, communications, automobiles, aerospace and other fields.

[0059] 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 will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the embodiments of the present invention.

Claims

1. A carbon fiber soft felt reinforced low melting point metal thermal conductive sheet, characterized in that: The carbon fiber soft felt is surface treated and then filled with low melting point metal to obtain a carbon fiber soft felt reinforced low melting point metal thermal conductive sheet.

2. The carbon fiber soft felt reinforced low melting point metal thermal conductive sheet according to claim 1, characterized in that: The low melting point metal includes at least one or more of bismuth (Bi), tin (Sn), indium (In) and silver (Ag).

3. The carbon fiber soft felt reinforced low melting point metal thermal conductive sheet according to claim 1, characterized in that: The low melting point metal includes bismuth (Bi), tin (Sn), indium (In), and silver (Ag).

4. The carbon fiber soft felt reinforced low melting point metal thermal conductive sheet according to claim 3, characterized in that: In terms of mass percentage, the low melting point metal includes 40-50% bismuth, 25-35% tin, 10-20% indium and 5-15% silver, and the sum of the components is 100%.

5. The carbon fiber soft felt reinforced low melting point metal thermal conductive sheet according to claim 3, characterized in that: In terms of mass percentage, the low melting point metal includes 40-45% bismuth, 30-35% tin, 15-20% indium and 5-10% silver, and the sum of the components is 100%.

6. The carbon fiber soft felt reinforced low melting point metal thermal conductive sheet according to claim 3, characterized in that: The melting point of the low melting point metal is 40-120°C.

7. The carbon fiber soft felt reinforced low melting point metal thermal conductive sheet according to claim 1, characterized in that: The surface treatment includes one or more of surface oxidation, surface coating, and plasma treatment.

8. The carbon fiber soft felt reinforced low melting point metal thermal conductive sheet according to claim 1, characterized in that: The internal perfusion includes one or more of natural immersion, vacuum-assisted perfusion and high-pressure-assisted perfusion.

9. The carbon fiber soft felt reinforced low melting point metal thermal conductive sheet according to claim 1, characterized in that: The carbon fiber soft felt is a high thermal conductivity carbon fiber soft felt with a density of 0.1-1g / cm³, a thickness of 0.5-5mm, a carbon fiber diameter of 0.5-500um, and the carbon fibers are arranged randomly within the surface.

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