CN110002427B - High-thermal-conductivity carbon film and preparation method thereof - Google Patents

Abstract

The invention relates to the field of thermally conductive materials, in particular to a method for preparing a high thermal conductivity carbon film and the prepared high thermal conductivity carbon film. The method comprises the following steps: step 1, mixing a graphene suspension with a strongly hydrophilic benzene-containing The cyclic short-chain polymers are mixed by physical stirring; in step 2, the mixture obtained in step 1 is spread on a wafer by spin coating to form a film; in step 3, the film obtained in step 2 is dried in a vacuum environment A high thermal conductivity carbon film containing graphene aligned perpendicular to the wafer direction is obtained by high-temperature pyrolysis. The preparation method of the invention is simple and low in cost, the high thermal conductivity carbon film prepared by the method of the invention can be made into a supported high thermal conductivity film, an independent high thermal conductivity carbon film can also be obtained, and a composite of carbon and plastic can also be derived Membrane; through patterning and then cracking, it can be made into a lithium battery active positive electrode with high reversible capacity, which can be used to make carbon-based biosensors and other applications that meet special properties.

Description

A kind of high thermal conductivity carbon film and preparation method thereof

technical field

The invention relates to the field of thermally conductive materials, in particular to a composite carbon film with high thermal conductivity.

Background technique

Thermal dissipation is a hot topic these days and is a key factor in determining whether modern electronic devices can meet the reliability and high performance requirements. The interface material with high thermal conductivity is a very important factor, and the high thermal conductivity composite material is an important element for advanced packaging and packaging cooling of LED and power electronics, etc., as described in the prior art 1. The composite material of the polymer matrix is the most common kind of composite material, such as the use of many conductive silver glue, thermal conductive silicone pad, etc., and the fillers are mostly high thermal conductivity metal and ceramic particles. In the past 10 years, graphene has attracted attention for its ultra-high in-plane thermal conductivity, high in-plane electrical conductivity due to ballistic transport properties, and excellent mechanical properties. Graphene is a hexagonal honeycomb structure composed of carbon atoms according to SP2 hybrid orbits, and the thickness is only the diameter of a single layer of carbon atoms. Due to its unique two-dimensional structure and excellent crystal quality, graphene has a huge specific surface area (2630m2g-1), electrical conductivity (electron mobility 20000cm2V-1S-1), thermal conductivity (thermal conductivity can reach a coefficient of nearly 5300W/ Km), mechanical strength (42N/m) and other aspects show very superior unidirectional performance. However, its ultra-high unidirectional characteristic has been unable to be effectively exerted because it is difficult to unify the direction of each graphene monomer when synthesizing composite materials, especially in the technology of improving the thermal conductivity perpendicular to the plane. This put a lot of effort into finding an efficient solution. Some are that after the production of particularly vertically grown graphene, only some individual devices can be directly manufactured, such as prior art 2, and there are also devices and methods for rapidly producing large-scale vertically oriented graphene discharge reduction devices, such as prior art 3 and current technology. There is technology 4, which is fast and economical compared to other vertical production methods. But how to effectively use these vertically grown graphene is a very difficult task. Then, the ability to effectively vertically align the produced graphene nanosheets to synthesize composite materials is the direction of research and development in recent years (existing technology 1). A more effective method is to synthesize a graphene high polymer composite material through a series of surface modifications, and then transversely slice to form a thin sheet containing vertical graphene (existing technology 5); A vertical magnetic field is used to obtain a composite thermally conductive adhesive containing vertical graphene thermally conductive fillers (prior art 6). However, these synthetic methods are still relatively complex and expensive, and are polymer-based composites. This patent is purely aimed at the manufacture of composite carbon films. Some people use the design of hole templates and the method of multi-layer growth of nano-carbon-based materials to form a thermally conductive carbon composite film of interpenetrating multilayer nano-carbon materials, but this carbon film at least does not have a uniform The direction of heat conduction, the heat conduction is concentrated in two or more directions that are roughly vertical and parallel to the heat flow, and is relatively dispersed (prior art 7); the graphene in the composite carbon film manufactured by this patent will obtain a uniform direction perpendicular to the film, which The vertical thermal conductivity will be very high (>500～2000W/mK). At present, there are many methods and manufacturers for producing graphene. If the graphene nanosheets made in a simple and low-cost way, such as the method of ball-milling graphite (Prior Art 8), etc., can be used as fillers, in the present invention The simple method to synthesize high thermal conductivity composite carbon film materials containing vertically aligned graphene nanosheets is of great value for promotion.

Prior art 1: "Microstructure engineering of graphene towards highly thermal conductive composites" Haoming Fang, Shu-lin Bai, Ching Ping Wong, Composites Part A 112 (2018) 216-238;

Prior art 2: WO2012/163130A1;

Prior art 3: CN102560437A;

Prior art 4: CN101966987B

Prior art 5: CN108504016A

Prior art 6: CN106928886B

Prior art 7: CN105803242B

Prior art 8: CN103570004A.

SUMMARY OF THE INVENTION

In order to solve the above problems and give full play to the ultra-high thermal conductivity of graphene, the present invention provides a preparation method of a high thermal conductivity carbon film and the prepared carbon film. The thermally conductive carbon material composite film forms a composite film of a single carbon element. The production process of this method is simple, and due to the good interface between the substrate and the filler, and at the same time avoiding the low thermal conductivity of the polymer substrate, the thermal conductivity of the prepared composite carbon film can be as high as 2000W/km or more, which is higher than that of most graphites. Thermal conductivity of olefin polymer composites and carbon films. And the carbon film prepared by the method has adjustable mechanical properties and density, low cost, and can match the semiconductor manufacturing process.

In order to achieve the above purpose, the preparation method of the high thermal conductivity carbon film provided by the present invention comprises the following steps:

Step 1, the graphene suspension is mixed with the short-chain polymer containing benzene ring to obtain mixture A;

In step 2, the obtained mixture A is spread on the wafer, so that the thickness of the mixture A at different positions on the wafer surface is as consistent as possible, thereby forming the film B;

Step 3, drying the wafer covered with the film B;

In step 4, a high thermal conductivity carbon film C composed of graphene with a vertical morphology directly grown on the surface of the wafer is obtained by high-temperature pyrolysis.

Preferably, before the first step, a surface treatment step is also included, and the graphene suspension is subjected to surface treatment combined with carbon nanotubes.

Preferably, the short-chain polymer in the first step has strong hydrophilicity.

Preferably, the short-chain polymer in the first step is a novolac resin.

Preferably, the mixing in the step 1 adopts a physical stirring method.

Preferably, the wafer in the second step is a substrate with high temperature resistance and smooth surface.

Preferably, in the second step, the mixture A is spread on the wafer by spin coating, and the excess mixture is thrown off the surface of the wafer by rotating the wafer, so that the surface of the wafer is in different positions The thickness of the mixture is as consistent as possible.

Preferably, the high-temperature pyrolysis method in the fourth step is a vacuum conduction heating pyrolysis method; other special high-temperature pyrolysis methods can also be used, but the heating atmosphere needs to ensure vacuum or oxygen-free.

Preferably, the thickness of the thin film B formed in the second step is less than 10um.

On the other hand, the present invention also provides a high thermal conductivity carbon film prepared by the above preparation method.

The present invention uses a simple material production method, adopts a simple and low-cost preparation method, realizes large-scale production, can match the semiconductor manufacturing process, and can manufacture battery electrodes with high reversible capacity (estimated reversible according to the prior art 9 and prior art 10). The capacity is much higher than 700mAh/g), and it can also provide wafers for the production of carbon-based biosensors. The back wafer can be cut into a supported high thermal conductivity film, and an independent high thermal conductivity carbon film can also be obtained, such as If there is a need, it can be superimposed into a thicker carbon film by hot pressing, and a polymer-based composite film containing a thermally conductive carbon film can also be derived. protective film. The invention utilizes the vacuum oxygen-free high temperature cracking technology to form a carbon film on the back of the wafer. The carbon film prepared by the method of the present invention has adjustable properties such as mechanical properties and density. For example, parameters such as hardness, elastic modulus and stiffness can be adjusted according to high temperature pyrolysis process parameters. In addition, the base material, which is also a carbon element, has good interface bonding with the filler, which improves the mechanical and thermal conductivity of the composite film, and at the same time removes the relatively low thermal conductivity base material in the polymer composite material.

Prior art 9: T Zheng, Q. Zhang, and J. R. Dahn, J. Electrochem. Soc. 142 (1995), L211

Prior art 10: J.S.Xue and J.R.Dahn, J. Electrochem. Soc. 142 (1995) 3668

Description of drawings

Fig. 1 is the flow chart of the preparation method of the present invention.

Figure 2(a) is a schematic diagram of step 1 of the preparation method of the present invention.

Figure 2(b) is a schematic diagram of step 2 of the preparation method of the present invention.

Figure 2(c) is a schematic diagram of steps 3 and 4 of the preparation method of the present invention.

3(a) and 3(b) are schematic diagrams of carbon films prepared by the method of the present invention.

FIG. 4( a ) is a schematic diagram of a carbon film growth method.

Figure 4(b) is a schematic diagram of the grown carbon film.

Detailed ways

In order to make the objectives, features and advantages of the present invention clearer, the specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. In the following description, many specific details are set forth to facilitate full understanding. The invention, but the invention can be carried out in many other ways than described. Accordingly, the present invention is not limited by the specific implementations disclosed below.

In a preferred embodiment, as shown in FIG. 1 , the preparation method of the high thermal conductivity carbon film of the present invention comprises the following steps:

S101, the graphene suspension is mixed with a strong hydrophilic short-chain polymer containing a benzene ring (such as a novolac resin such as AZ positive photoresist) through physical stirring to obtain a mixture A. The mixing method is shown in Figure 2(a). Prior to this mixing step, the graphene suspension can also be surface-treated in conjunction with carbon nanotubes, or not.

S102, the mixture A obtained in step S101 is spread on the wafer by spin coating, which is similar to the coating form of semiconductor photoresist, and the excess mixture A is thrown off the surface of the wafer by rotating the wafer, and makes The thickness of the mixture at different positions on the wafer surface should be as consistent as possible to form a thin film B, such as a thin film with a thickness of less than 10um. The spin coating method is shown in Figure 2(b). Among them, the wafer can also replace silicon (Si) with other high temperature resistant and smooth surface substrates, such as ceramic substrates, but ordinary glass substrates are not suitable for use because they are not resistant to high temperature of 800°C.

S103, drying the wafer coated with the thin film B obtained in step S102.

S104 , after drying, a highly thermally conductive carbon film C with graphene having a vertical direction directly grown on the surface of the wafer is obtained by vacuum pyrolysis in a vacuum environment, as shown in FIG. 2( c ).

Among them, the pyrolysis temperature of vacuum pyrolysis is generally controlled at about 1000℃, the time is one hour, and the vacuum degree is about 10 ^-5 torr. The temperature and time can also be adjusted up and down according to the performance requirements of the carbon film material; during pyrolysis, the vacuum atmosphere ensures The quality of cracking and the mixing of impurities are reduced, and dense carbon films can be obtained at the same time; inert gases (such as Ar, N2, N2/H2 synthesis gas, etc.) can also be used according to the requirements of low density. Pyrolysis is not limited to traditional conduction heating techniques. Before the high temperature, one hour of low temperature dehydration treatment can be added as needed, and the temperature is about 250 ℃.

The structure of the carbon film formed by the above steps is as follows:

As shown in Fig. 3(a), the carbon film has a vertical cross-section shown by SEM, in which most of the benzene ring molecular chains are perpendicular or nearly perpendicular to the surface, as shown in Fig. 3(b), the graphite The olefinic surface will grow along the gap slit of the benzene ring molecular chain, as shown in Fig. 4(a), which is a brand new growth method. The finally grown carbon film is shown in Fig. 4(b).

After the carbon film is formed through the above steps, the carbon film can be used in various forms:

1) The thin film can be peeled off to form a thin carbon film through special treatment of the substrate, such as a carbon film with a carbon film thickness less than 5um;

2) According to the thickness requirements, multiple thin carbon films can be crimped at high temperature to form thicker carbon films;

3) The carbon film can also form a preform or cured film containing a single-layer or multi-layer carbon film together with the polymer;

4) The substrate can also be directly thinned to form a composite film supported by the substrate;

5) It can also be used as a high thermal conductivity carbon film grown on a certain substrate as a protective substrate;

6) Patterns can also be formed by photolithography before carbonization, and carbon-based sensors can be made after carbonization;

7) This can also be used to prepare active electrodes of lithium batteries with high reversible capacity.

Through the above preparation method, the thermal conductivity of the carbon film is greatly improved, thereby solving the problem of thermal management during chip operation.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications can be made. It should be regarded as the protection scope of the present invention.

Claims (10)

1. A preparation method of a high-thermal-conductivity carbon film comprises the following steps:

mixing a graphene suspension with a short-chain polymer containing a benzene ring to obtain a mixture A;

secondly, paving the obtained mixture A on a wafer to enable the thickness of the mixture A at different positions on the surface of the wafer to be as consistent as possible, so as to form a film B;

step three, drying the wafer covered with the film B;

and step four, obtaining the high-thermal-conductivity carbon film C which is directly grown on the surface of the wafer and is composed of the graphene with the vertical morphology in a high-temperature cracking mode.

2. The method of claim 1, further comprising a surface treatment step of subjecting the graphene suspension to a surface treatment in combination with carbon nanotubes, prior to the first step.

3. The method according to claim 2, wherein the short-chain polymer in the first step has a strong hydrophilic property.

4. The method of claim 2, wherein the short-chain polymer in step one is a novolac resin.

5. The method of claim 2, wherein the mixing in step one is by physical agitation.

6. The method according to claim 2, wherein the wafer in the second step is a substrate with high temperature resistance and smooth surface.

7. The method according to claim 1, wherein in the second step, the mixture A is spread on a wafer by spin coating, and excess mixture is thrown off the surface of the wafer by rotating the wafer, so that the thickness of the mixture at different positions on the surface of the wafer is as uniform as possible.

8. The method according to claim 1, wherein the pyrolysis in the fourth step is a conduction heating pyrolysis.

9. The method according to any one of claims 1 to 8, wherein the thickness of the thin film B formed in the second step is less than 10 μm.

10. A highly thermally conductive carbon film produced by the production method according to any one of claims 2 to 6.

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