CN110002427B

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

Info

Publication number: CN110002427B
Application number: CN201910366457.7A
Authority: CN
Inventors: 张卫红; 刘旭; 叶怀宇; 张国旗
Original assignee: Shenzhen Third Generation Semiconductor Research Institute
Current assignee: Southwest University of Science and Technology
Priority date: 2019-05-05
Filing date: 2019-05-05
Publication date: 2020-11-17
Anticipated expiration: 2039-05-05
Also published as: WO2020224258A1; CN110002427A

Abstract

The invention relates to the field of heat conduction materials, in particular to a preparation method of a high-heat-conductivity carbon film and the high-heat-conductivity carbon film prepared by the method, and the method comprises the following steps: firstly, mixing a graphene suspension with a short-chain polymer which has strong hydrophilicity and contains a benzene ring in a physical stirring manner; step two, spreading the mixture obtained in the step one on a wafer in a spin coating mode to form a thin film; and step three, drying the film obtained in the step two, and then obtaining the high-thermal-conductivity carbon film containing the graphene arranged in the direction perpendicular to the wafer direction in a vacuum environment in a high-temperature cracking mode. The preparation method is simple and low in cost, and the high-thermal-conductivity carbon film prepared by the method can be made into a supported high-thermal-conductivity film, an independent high-thermal-conductivity carbon film can be obtained, and a composite film of carbon and plastic can be derived; the patterned and cracked lithium battery active positive electrode with high reversible capacity can be prepared, and the carbon-based biosensor and other applications can meet special performance.

Description

High-thermal-conductivity carbon film and preparation method thereof

Technical Field

The invention relates to the field of heat conduction materials, in particular to a composite carbon film with high heat conduction performance.

Background

Heat dissipation is a hot topic today and is a key factor in determining whether modern electronic devices can meet the requirements for reliability and high performance. The interface material with high thermal conductivity is an important factor, and the high thermal conductivity composite material is an important element for advanced packaging and cooling of LEDs, power electronics and the like, as described in prior art 1. The composite material of the high polymer matrix is the most common composite material, such as the use of a plurality of conductive silver adhesives, heat conductive silica gel pads and the like, wherein the fillers are mostly high heat conductive metal and ceramic particles. In the last 10 years, graphene has attracted attention for its ultra-high in-plane thermal conductivity, as well as its very high in-plane electrical conductivity and excellent mechanical properties due to its ballistic transport properties. Graphene (graphene) is a hexagonal honeycomb structure consisting of carbon atoms according to SP2 hybrid orbitals, and the thickness of the graphene is only the diameter of a single-layer carbon atom. Due to the unique two-dimensional structure and excellent crystal quality, graphene has great specific surface area (2630m2g-1), electrical conductivity (electron mobility 20000cm2V-1S-1), thermal conductivity (the coefficient of thermal conductivity can reach nearly 5300W/Km), mechanical strength (42N/m) and other aspects, and shows very excellent unidirectional performance. However, the ultrahigh unidirectional property of the graphene cannot be effectively exerted because the graphene monomers cannot be aligned in the same direction when the composite material is synthesized, and particularly, the technology for improving the thermal conductivity perpendicular to the plane is a difficult point, and people put a lot of efforts to find an effective solution. Some devices can only be directly manufactured after the production of the special vertically-grown graphene, such as the prior art 2, and other devices and methods for rapidly manufacturing the large-range vertically-oriented graphene discharge reduction device, such as the prior art 3 and the prior art 4, are rapid and cost-saving compared with other vertical production methods. How to effectively utilize these vertically grown graphene is a difficult task. Then, it is a direction of research and development in recent years to be able to efficiently vertically align the produced graphene nanoplatelets to resynthesize a composite material (prior art 1). A more effective method is to synthesize a graphene polymer composite material through a series of surface modifications, and then transversely slice the graphene polymer composite material to form thin sheets containing vertical graphene (prior art 5); a vertical magnetic field is applied to obtain a composite heat-conducting adhesive containing a vertical graphene heat-conducting filler when a casting colloid is prepared (prior art 6). However, these synthetic methods are still relatively complex and costly and are high polymer based composites. The patent is directed to the manufacture of a composite carbon film, and some people use a designed hole template and combine a multi-layer growth nano carbon-based material method to form a heat-conducting carbon composite film of a plurality of layers of nano carbon materials which are mutually interpenetrated, but the carbon film at least does not have a uniform heat-conducting direction, and the heat conduction is concentrated in two directions or a plurality of directions which are approximately vertical and parallel to heat flow, and is comparatively dispersed (prior art 7); the graphene in the composite carbon film manufactured by the method can obtain a uniform direction perpendicular to the film, and the perpendicular heat conductivity of the graphene can be very high (> 500-2000W/mK). At present, a plurality of methods and manufacturers for producing graphene are available, and if graphene nanosheets produced in a simple and cheap manner, such as a manner of ball milling graphite production (prior art 8) and the like, can be used as a filler, the high-thermal-conductivity composite carbon film material containing the vertically-arranged graphene nanosheets is synthesized by the simple method in the invention, so that the method has a great popularization prospect value.

Prior art 1: "microscopic engineering of graphene devices high throughput composite Composites" Haoming Fang, Shu-lin Bai, Ching Ping Wong, Composites Part A112 (2018) 216-;

prior art 2: WO2012/163130a 1;

prior art 3: CN 102560437A;

prior art 4: CN101966987B

Prior art 5: CN108504016A

Prior art 6: CN106928886B

Prior art 7: CN105803242B

Prior art 8: CN 103570004A.

Disclosure of Invention

In order to solve the problems and fully exert the ultrahigh thermal conductivity of graphene, the invention provides a preparation method of a high thermal conductivity carbon film and the carbon film prepared by the method. The method has simple production process, and because the interface bonding property of the base material and the filler is good, the low thermal conductivity of the high polymer base material is avoided, the thermal conductivity of the prepared composite carbon film can reach more than 2000W/km, which is higher than that of most graphene high polymer composite materials and carbon films. The carbon film prepared by the method has adjustable mechanical property and density, low cost and capability of matching with a semiconductor manufacturing process.

In order to achieve the above object, the method for preparing a high thermal conductive carbon film provided by the invention 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.

Preferably, before the first step, a surface treatment step is further 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 phenol novolac resin.

Preferably, the mixing in the first step is performed by physical stirring.

Preferably, the wafer in the second step is a substrate which is resistant to high temperature and has a smooth surface.

Preferably, in the second step, the mixture a is spread on the wafer by spin coating, and the wafer is rotated to throw the excess mixture off the surface of the wafer, so that the thicknesses of the mixtures at different positions on the surface of the wafer are as uniform as possible.

Preferably, the pyrolysis mode in the fourth step is a vacuum conduction heating pyrolysis mode; other special pyrolysis methods can be used, but the heating atmosphere needs to ensure vacuum or no oxygen.

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

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

The invention uses simple material production method, adopts simple low-cost preparation method, realizes large-scale production, can match with semiconductor process, can manufacture battery electrodes with high reversible capacity (the reversible capacity is estimated to be much higher than 700mAh/g according to the prior art 9 and the prior art 10), can also provide wafers for manufacturing carbon-based biosensors and the like, can manufacture supported high-heat-conducting films by cutting thin back wafers, can also obtain independent high-heat-conducting carbon films, can be superposed into thicker carbon films by a hot-pressing method if needed, can also derive high-polymer-based composite films containing the heat-conducting carbon films, and can also obtain the heat-conducting carbon films with protective performance on substrates to replace protective films of other noble materials. The invention utilizes 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 has adjustable mechanical properties, compactness and other characteristics, and parameters such as hardness, elastic modulus, rigidity and the like can be adjusted according to the parameters of the pyrolysis process. And the interface bonding property of the base material which is also carbon element and the filler is good, the mechanical and heat-conducting properties of the composite film are improved, and meanwhile, the base material with relatively low heat conductivity in the high polymer composite material is separated.

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

Drawings

FIG. 1 is a flow chart of the preparation method of the present invention.

FIG. 2(a) is a schematic diagram of step one of the preparation method of the present invention.

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

FIG. 2(c) is a schematic diagram of steps three and four of the preparation method of the present invention.

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

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

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

Detailed Description

In order that the objects, features and advantages of the invention will be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings, in which numerous specific details are set forth in order to provide a thorough understanding of the invention, but the invention can be practiced in many ways other than as described. Accordingly, the invention is not limited by the specific implementations disclosed below.

In a preferred embodiment, as shown in fig. 1, the method for preparing a high thermal conductive carbon film according to the present invention comprises the steps of:

s101, mixing the graphene suspension with a short-chain polymer (such as linear phenolic resin like AZ positive photoresist) with strong hydrophilicity and containing a benzene ring in a physical stirring mode to obtain a mixture A. The mixing pattern is shown in FIG. 2 (a). The graphene suspension may also be subjected to a surface treatment in combination with the carbon nanotubes, or not, prior to this mixing step.

S102, spreading the mixture a obtained in step S101 on a wafer by spin coating, similar to the coating form of semiconductor photoresist, and throwing the excess mixture a out of the surface of the wafer by rotating the wafer, so that the thicknesses of the mixtures at different positions on the surface of the wafer are as consistent as possible, thereby forming a thin film B, such as a thin film with a thickness less than 10um, where the spin coating is as shown in fig. 2 (B). In the method, silicon (Si) can be replaced by other high-temperature-resistant and smooth-surface substrates, such as ceramic substrates, but ordinary glass substrates are not suitable for use because they cannot resist high temperature of 800 ℃.

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

And S104, drying, and obtaining the graphene high-thermal-conductivity carbon film C directly growing on the surface of the wafer in a vacuum high-temperature cracking mode in a vacuum environment, wherein the graphene high-thermal-conductivity carbon film C is in a vertical direction, as shown in fig. 2 (C).

Wherein the cracking temperature of the vacuum high-temperature cracking is generally controlled to be about 1000 ℃, the time is one hour, and the vacuum degree is about 10^-5the torr, the temperature and the time can be adjusted up and down according to the requirement of the performance of the carbon film material; during cracking, the vacuum atmosphere ensures the cracking quality and reduces the impurity mixing, and a compact carbon film can be obtained at the same time; inert gases (e.g., Ar, N2, N2/H2 synthesis gas, etc.) may also be used depending on low density requirements, etc. Pyrolysis is not limited to conventional conductive heating techniques. Before the high temperature, low temperature dehydration treatment for one hour can be added according to the requirement, and the temperature is about 250 ℃.

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

as shown in fig. 3(a), the carbon film has a cross section with a vertical morphology as shown in a scanning electron microscope SEM, wherein most of the benzene ring molecular chains are vertical or nearly vertical to the surface, as shown in fig. 3(b), the graphene surface grows along the gap slits of the benzene ring molecular chains, as shown in fig. 4(a), which is a completely new growth method. The carbon film finally grown is shown in FIG. 4 (b).

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

1) the thin film can be stripped out through special treatment of a substrate to form a thin-layer carbon film, such as a carbon film with the thickness of less than 5 um;

2) according to the thickness requirement, a plurality of thin carbon films can be pressed at high temperature to form a thicker carbon film;

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

4) or the base material can be directly thinned, so that a composite film supported by the base material is formed;

5) can also be used as a high heat-conducting carbon film which grows on a certain base material and is used as a protective base material;

6) patterns can be formed by a photoetching process before carbonization, and a carbon-based sensor can be manufactured after carbonization;

7) it is also possible to use this to prepare active electrodes for lithium batteries having a high reversible capacity.

By the preparation method, the thermal conductivity of the carbon film is greatly improved, so that the thermal management problem of the chip during working is solved.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

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

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

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.