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

Abstract

The present application relates to the technical field of low-melting-point metal heat-conducting sheet, and particularly relates to a carbon-fiber soft felt reinforced low-melting-point metal heat-conducting sheet, which is prepared by filling low-melting-point metal into carbon-fiber soft felt after surface treatment. The carbon-fiber soft felt reinforced low-melting-point metal heat-conducting sheet has the characteristics of low surface roughness, high tensile strength, anti-dropping of slag and scraps, low thermal resistance, etc., and can improve the yield of semiconductor chip packaging and be beneficial to packaging process and automation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of low-melting-point metal heat-conducting sheets, in particular to a low-melting-point metal heat-conducting sheet reinforced by carbon fiber soft felt. BACKGROUND

[0002] Under the background of the rapid development of modern electronic technology, the heat dissipation problem of high-power integrated circuits is increasingly prominent, and there is an urgent need for high-efficiency thermal management materials. Traditional thermal interface materials have been unable to meet the growing demand for heat dissipation, especially in the fields of servers, communication equipment, military and aerospace, which have extremely high requirements for the thermal conductivity, mechanical properties and long-term stability of materials.

[0003] Phase change materials (PCMs) 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 limit their widespread application in practical applications. In addition, carbon-based heat-conducting pads are often electrically conductive, which affects internal components and even causes short circuits in practical applications, so it is necessary for carbon-based heat-conducting pads to be free of debris and resistant to vibration. SUMMARY

[0004] In view of the above-mentioned shortcomings of the prior art, the present application provides a low-melting-point metal heat-conducting sheet reinforced by carbon fiber soft felt, aiming 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 heat-conducting sheet of the present application not only has low surface roughness and high tensile strength, but also effectively prevents debris from falling off, and is suitable for high-end chip packaging and high-power chip heat dissipation, servers, communication, military, aerospace and other fields.

[0005] TECHNICAL SCHEME

[0006] To achieve the above-mentioned purposes, the present application is realized by the following technical scheme:

[0007] The present application provides a low-melting-point metal heat-conducting sheet reinforced by carbon fiber soft felt, which is prepared by filling low-melting-point metal into carbon fiber soft felt after surface treatment. The carbon fiber soft felt is preferably a carbon fiber soft felt VU-SF-HP produced by Hangzhou Wukeng New Material Technology Co., Ltd.

[0008] Further, the low-melting-point metal comprises at least one of bismuth (Bi), tin (Sn), indium (In) and silver (Ag).

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

[0010] Further, the low melting point metal comprises Bi 40-50%, Sn 25-35%, In 10-20%, and Ag 5-15% by mass percentage, and the sum of each component is 100%.

[0011] Further, the low melting point metal comprises Bi 40-45%, Sn 30-35%, In 15-20%, and Ag 5-10% by mass percentage, and the sum of each component is 100%.

[0012] Preferably, the low melting point metal comprises Bi 40%, Sn 33%, In 17%, and Ag 10% by mass percentage.

[0013] Preferably, the low melting point metal comprises Bi 42%, Sn 35%, In 16%, and Ag 7% by mass percentage.

[0014] Further, the low melting point metal has a melting point of 40-120℃, preferably 60℃.

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

[0016] Further, the internal infusion comprises one or more of natural soaking, vacuum-assisted infusion, and high-pressure assisted infusion.

[0017] Further, the carbon fiber soft felt is a high-thermal-conductivity carbon fiber soft felt, having a density of 0.1-1 g / cm 3 , a thickness of 0.5-5 mm, a carbon fiber diameter of 0.5-500 um, and the carbon fibers being arranged randomly in the plane.

[0018] The low melting point metal has a significant impact on the product, and specifically, in the field of electronics and electrical appliances, the low melting point metal has 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 electronic devices. It is solid at room temperature in daily transportation and at room temperature. During use, as the temperature of the heat source rises, when the metal melting point is higher than the metal melting point, 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, the common low melting point metal heat conduction sheet has the problems of metal leakage, pumping out, poor mechanical properties, tearing resistance, reliability, and compression resistance. The addition of the carbon fiber soft felt can significantly improve the above problems.

[0019] The product form and internal structure of the present application are as shown in Figure 1, carbon fiber and metal material interpenetration, co-continuous structure as a whole. Carbon fiber such as similar non-woven fabric structure in-plane arbitrary arrangement, the whole is in-plane orientation. Metal is a continuous whole structure. Metal material itself can also be used as thermal interface material, the addition of carbon fiber enhances heat dissipation, enhances the mechanical properties of the material, prevents metal pump and metal leakage problem. The present application is a thermal interface material, mainly longitudinal and transverse heat transfer, and is sheet-shaped, pad between the heat source and the heat sink.

[0020] The present application provides a kind of carbon fiber soft felt reinforced low melting point metal heat-conducting sheet and preparation method thereof.The composite material is significantly improved by introducing high thermal conductivity carbon fiber soft felt and low melting point metal.The low melting point metal includes bismuth (Bi), tin (Sn), indium (In) and silver (Ag), with a melting point of 40-120 degrees, and these metals have high electrical conductivity and high thermal conductivity, which have a wide range of applications in various heat dissipation, sealing and other fields.The addition of carbon fiber soft felt enhances the mechanical properties and shape stability of the composite material, and the use of surface treatment and internal infusion technology effectively improves the thermal oxidation stability of the material, so that it is not prone to aging and performance degradation during long-term use.

[0021] The carbon fiber soft felt reinforced low melting point metal heat-conducting sheet of the present application has high thermal conductivity and good mechanical properties due to its unique formula and preparation method, and has no obvious pumping out and creep problem after long-term use, which is suitable for high-power integrated circuit heat dissipation, server, communication, military, aerospace and other fields.

[0022] Advantages

[0023] The technical solution provided by the present application has the following advantages compared with known public technology:

[0024] (1) The carbon fiber soft felt reinforced low melting point metal heat-conducting sheet of the present application has better mechanical properties, tear resistance, better reliability, anti-pumping effect, prevents metal leakage, and is more resistant to compression than the original low melting point metal heat-conducting sheet without reinforcement.The thermal conductivity of the heat-conducting sheet prepared by the present application is greater than 120 W / mK, and the thermal resistance is less than 0.1 Kcm 2 / W.

[0025] (2) The carbon fiber soft felt reinforced low melting point metal heat-conducting sheet has low surface roughness, high thermal conductivity, high tensile stress, good compressibility, prevents slag and debris, low thermal resistance, and has no obvious pumping out and creep problem after long-term use, which meets the demand of high-power integrated circuit heat dissipation;It can improve the yield of semiconductor chip packaging, is beneficial to packaging process and automation, effectively solves the pumping out and creep problem of traditional PCM, and meets the demand of high-power integrated circuit heat dissipation.

[0026] (3) The carbon fiber soft felt reinforced low melting point metal heat conduction sheet can be produced on a large scale in industry, has a low cost advantage, and is suitable for heat dissipation requirements in high-end chip packaging, high-power servers, military, aerospace and other fields. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, below the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0028] Figure 1 It is a preparation schematic diagram of a carbon fiber soft felt reinforced low melting point metal heat conduction sheet. DETAILED DESCRIPTION

[0029] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, below the technical solutions in the embodiments of the present application will be clearly and completely described with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0030] The present application will be further described below with reference to the embodiments.

[0031] The raw material suppliers in the examples and comparative examples are as follows:

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

[0033] (I) Examples

[0034] Example 1

[0035] In this embodiment, carbon fiber soft felt is selected as the reinforcing material, the thermal conductivity of which is 600 W / (mK); the thickness is 1 mm, the density is 0.5 g / cm 3 , and the carbon fiber diameter is about 1 um. 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 plasma treatment of the carbon fiber soft felt, it is soaked in the low melting point metal mixed solution at 100℃ under a vacuum degree of-0.1 mPa. After taking out and molding, a low melting point metal heat conduction sheet with a thickness of 0.4 mm is obtained.

[0036] Example 2

[0037] In this embodiment, carbon fiber soft felt is selected as the reinforcing material, which has a thermal conductivity of 600 W / (mK), a thickness of 2 mm, and a density of 0.2 g / cm 3 The carbon fiber soft felt is soaked in an acrylic solution, and then a mixed solution of low-melting-point metals is injected into the carbon fiber soft felt at a high pressure of 5 mPa at 80°C. After molding and cooling, a low-melting-point metal heat-conducting sheet with a thickness of 0.5 mm is obtained.

[0038] Comparative Example 1

[0039] In this comparative example, no carbon fiber soft felt is used as the reinforcing material, and only low-melting-point metals are used. The low-melting-point metals include bismuth (Bi) 42 parts by mass, tin (Sn) 35 parts by mass, indium (In) 16 parts by mass, and silver (Ag) 7 parts by mass. After molding and cooling at 120°C, a low-melting-point metal heat-conducting sheet with a thickness of 0.3 mm is obtained.

[0040] Comparative Example 2

[0041] In this comparative example, no carbon fiber soft felt is used as the reinforcing material, and only low-melting-point metals are used. The low-melting-point metals include bismuth (Bi) 40 parts by mass, tin (Sn) 30 parts by mass, indium (In) 20 parts by mass, and silver (Ag) 10 parts by mass. After molding and cooling at 140°C, a low-melting-point metal heat-conducting sheet with a thickness of 0.3 mm is obtained.

[0042] Comparative Example 3

[0043] The difference between this comparative example and Example 1 is only that the low-melting-point metals are different. The low-melting-point metals do not contain silver, and the low-melting-point metals include bismuth (Bi) 40 parts by mass, tin (Sn) 33 parts by mass, and indium (In) 17 parts by mass.

[0044] Comparative Example 4

[0045] The difference between this comparative example and Example 1 is only that the low-melting-point metals are different. The low-melting-point metals do not contain bismuth, and the low-melting-point metals include tin (Sn) 33 parts by mass, indium (In) 17 parts by mass, and silver (Ag) 10 parts by mass.

[0046] Comparative Example 5

[0047] The difference between this comparative example and Example 1 is only that the low-melting-point metals are different. The low-melting-point metals do not contain tin, and the low-melting-point metals include bismuth (Bi) 40 parts by mass, indium (In) 17 parts by mass, and silver (Ag) 10 parts by mass.

[0048] Comparative Example 6

[0049] The difference between this comparative example and Example 1 is only that the low-melting-point metals are different. The low-melting-point metals do not contain indium, and the low-melting-point metals include bismuth (Bi) 40 parts by mass, tin (Sn) 33 parts by mass, and silver (Ag) 10 parts by mass.

[0050] (ii) Performance test

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

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

[0053]

[0054]

[0055] The metal heat-conducting sheet prepared by the example has good thermal conductivity and thermal resistance performance, and good tensile stress, and good plane surface roughness; in addition, it has good oxidation resistance and leakage prevention ability, compression resistance, and good reliability.

[0056] And from the comparative example 1-2, it can be seen that without using carbon fiber soft felt, the thermal conductivity, thermal resistance and tensile stress of the heat-conducting sheet prepared therefrom are all poor; in addition, without fiber reinforcing material, 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 obtain large-scale application.

[0057] It can be seen from Comparative Examples 3-6 that when the low-melting-point metal in the application is bismuth, tin, indium and silver, the prepared heat-conducting sheet has good performance. In addition, silver (Ag) has high electrical conductivity and thermal conductivity, and the absence of silver will reduce the overall thermal conductivity of the heat-conducting sheet. Silver also helps to improve the corrosion resistance and oxidation resistance of the material, and the absence of silver will significantly reduce the corrosion resistance and oxidation resistance of the heat-conducting sheet, which is easily oxidized in the air and easily corrodes the surface of the device. It cannot be used. Bismuth (Bi) in the alloy usually plays a role in reducing the melting point, and the absence of bismuth will cause the melting point of the heat-conducting sheet to rise above 150 degrees Celsius, which cannot be melted at a working temperature of 50-150 degrees Celsius, and cannot play a good interface contact to further reduce the thermal resistance. Bismuth also improves the plasticity of the alloy, and the absence of bismuth will reduce the flexibility of the heat-conducting sheet, making it harder. High thermal resistance, poor thermal conductivity, not resistant to compression, low reliability, difficult to meet the heat dissipation requirements of high-end chip packaging and high-power servers and other applications. Tin (Sn) in the alloy can increase the fluidity and plasticity, and the absence of tin will make the heat-conducting sheet become more brittle and hard, affecting its use in complex shapes or applications that require a certain degree of flexibility. Tin also helps to reduce the melting point of the alloy, and the absence of tin will cause the melting point to rise. It cannot meet the material fluidity, low melting point and plasticity requirements in the flow state. Difficult to meet the heat dissipation requirements of high-end chip packaging and high-power servers and other applications. Indium (In) in the alloy plays a role in reducing the melting point and improving the thermal conductivity, and the absence of indium will cause the melting point of the heat-conducting sheet to rise, while reducing its thermal conductivity. Indium also improves the ductility of the alloy, and the absence of indium will reduce the processing performance of the heat-conducting sheet. In general, each metal in the low-melting-point metal heat-conducting sheet has its specific function and role. The absence of any metal may have a negative impact on the physical and chemical properties of the heat-conducting sheet, thereby affecting its performance in actual applications.

[0058] In the application, the carbon fiber soft felt after treatment has more chemical functional groups on the surface, can better adhere to the metal material, the carbon fiber enhances the tensile stress of the low-melting-point metal, the stability of the enhanced material is better, the carbon fiber network wraps the low-melting-point metal, which is not easy to leak and oxidize, and meets the heat dissipation requirements of high-end chips, high-power servers, communications, automobiles, aerospace and other fields in China.

[0059] The above examples are only used to illustrate the technical solutions of the application, but not to limit it; although the application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements will not make the essence of the corresponding technical solutions deviate from the protection scope of the technical solutions of the embodiments of the application.

Claims

1. A carbon fiber soft mat reinforced low melting point metal heat conducting sheet, characterized by, The carbon fiber soft felt reinforced low-melting metal heat-conducting sheet is prepared by filling low-melting metal into carbon fiber soft felt after surface treatment; the low-melting metal comprises bismuth 40-50%, tin 25-35%, indium 10-20% and silver 5-15% by mass percentage, the sum of each component is 100%, the carbon fiber soft felt is high-heat-conducting carbon fiber soft felt, the density is 0.1-1 g / cm 3 , the thickness is 0.5-5 mm, the carbon fiber diameter is 0.5-500 um, and the carbon fiber is arranged randomly in the plane; the heat conductivity of the low-melting metal heat-conducting sheet is greater than 120 W / mK, and the thermal resistance is less than 0.1 Kcm 2 / W.

2. A low melting point metal heat conducting sheet reinforced with carbon fiber soft felt according to claim 1, characterized in that, The low-melting metal comprises, by mass percentage, 40-45% bismuth, 30-35% tin, 15-20% indium, and 5-10% silver, the sum of the components being 100%.

3. The carbon fiber soft felt reinforced low melting point metal heat conducting sheet according to claim 1, characterized in that, The low-melting metal has a melting point of 40-120°C.

4. The carbon fiber soft felt reinforced low melting point metal heat conducting sheet according to claim 1, wherein, The surface treatment comprises one or more of surface oxidation, surface coating, and plasma treatment.

5. The carbon fiber soft felt reinforced low melting point metal heat conducting sheet according to claim 1, wherein, The internal infusion comprises one or more of natural soaking, vacuum-assisted infusion, and high-pressure assisted infusion.

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