CN100379706C - High thermal conductivity component, manufacturing method thereof, and heat dissipation system using the same - Google Patents

Abstract

An object of the present invention is to provide a high thermal conductivity member that maintains the high thermal conductivity in the plane direction of graphite and improves the thermal conductivity in the layer direction. The present invention relates to a high thermal conductivity component formed by dispersing carbon particles in a highly oriented graphite structure composed of a graphite matrix, characterized in that: (1) the c axes of each graphite layer constituting the graphite are parallel ; (2) The thermal conductivity κ‖ in the direction perpendicular to the above-mentioned c-axis is in the range of 400W/m·K to 1000W/m·K; (3) The thermal conductivity κ⊥ in the direction parallel to the above-mentioned c-axis is 10W/m·K The range above m·K and below 100W/m·K.

Description

High thermal conductivity component, manufacturing method thereof, and heat dissipation system using the component

technical field

The present invention relates to a highly thermally conductive member whose main component is carbon (C) and a manufacturing method thereof.

The present invention also relates to a heat dissipation system (radiation device) having the high thermal conductivity component.

More specifically, the present invention relates to an improved thermally conductive member composed of an anisotropic graphite structure that maintains high thermal conductivity in a direction perpendicular to the c-axis direction while maintaining high thermal conductivity in the c-axis direction. High thermal conductivity parts that have high thermal conductivity also in the axial direction.

Background technique

In recent years, with increasing performance, miniaturization, and high density of electronic equipment, how to efficiently dissipate heat generated by the equipment and electronic components constituting the equipment has become a problem. In particular, it can be said that it is urgent to deal with the heat generated by the CPU and semiconductor lasers, which are the heart of the computer.

In order to cool effectively, it is important to combine convection, radiation, conduction, etc. skillfully. When the above-mentioned electronic components and the like are cooled, the heat is transferred to the low-temperature region mainly by heat conduction, thereby effectively cooling.

Currently, as heat sinks for electronic devices, electronic components, etc., heat sinks made of metals with high thermal conductivity such as copper (Cu), aluminum (Al), and the like are preferably used.

However, with the refinement of components or the increase of heat generation, the existing heat sink becomes unable to achieve the purpose. Therefore, it is necessary to develop high thermal conductivity components with higher thermal conductivity. In addition, there is a desire to develop a highly thermally conductive member with a high degree of freedom in geometric shape.

In this context, graphite composed of carbon (C) is expected to be used as a material to replace the above heat sink due to its outstanding heat resistance, chemical resistance, high electrical conductivity, etc., and high thermal conductivity. .

Graphite has a crystal structure as shown in FIG. 4 . More specifically, it has a stacked structure of six-membered ring planar structures (graphite layers) composed of six carbon (C) atoms. Due to this crystal structure, the characteristic of graphite is that it exhibits its properties in two directions, that is, the direction perpendicular to the graphite layer (c-axis direction) and the direction parallel to the graphite layer (a-b axis direction, that is, the direction perpendicular to the c-axis). feature.

For example, in an ideal graphite crystal, the thermal conductivity κ⊥ in the direction perpendicular to the graphite layer 7 (c-axis direction, hereinafter also referred to as "layer direction" (thickness direction)) is not so high as 10 W/m·K or less . On the contrary, the thermal conductivity κ∥ in the direction parallel to the graphite layer 7 (a-b axis direction, hereinafter also referred to as “plane direction”) is greater than 1000 W/m·K. The thermal conductivity is more than 2 times that of copper (κ(Cu)~350-400W/m·K), and more than 4 times that of aluminum (κ(Al)~200-250W/m·K). In fact, it has been reported that single crystal graphite κ‖=about 200-900W/m·K, and other graphite-based materials κ‖=about 50-400W/m·K. Therefore, various graphite heat conductors that effectively utilize the high thermal conductivity in the plane direction have been proposed so far.

For example, it has been reported that graphite powder is dispersed in a silicone resin or a polymer matrix to improve thermal conductivity (Japanese Patent Application No. 61-145266, Japanese Publication No. Publications, JP-A-09-102562, JP-09-283955, JP-2002-299534, JP-2002-363421, JP-2003-105108, etc.). FIG. 10 shows a schematic diagram of a thermally conductive member (conventional example 1) disclosed in these documents. In Conventional Example 1, it has been reported that thermal conductivity can be improved (κ to several 10 W/m K) by dispersing and orienting graphite powder 12 with high thermal conductivity in the plane direction in a matrix 11 such as a polymer.

In addition, parts in which flaky graphite particles are compression-molded together with a polymer binder have been proposed (JP-A-01-009869 and JP-A-11-001621). In addition, it has been reported that a product obtained by combining metal powder and crystalline carbon material is hot-pressed and manufactured (JP-A-10-168502). FIG. 11 is a schematic diagram showing a thermally conductive member (conventional example 2) disclosed in these documents. In Conventional Example 2, it is shown that the thermally conductive member 13 (κ=400～ 970W/m·K) method.

In addition, there are known sheet-shaped heat transfer members composed of a single graphite with high in-plane orientation (JP-A-58-147087, JP-A-60-012747, and JP-A-07-109171). FIG. 12 is a schematic diagram showing a heat conductive member (conventional example 3) disclosed in these documents. In Conventional Example 3, it is shown that a thermally conductive member (κ=600 to 1000W/m·K) composed of a graphite structure with very high in-plane orientation is provided by firing an organic polymer sheet .

As described above, a thermally conductive member using graphite as a thermally conductive substance is characterized by superior thermal conductivity and shape freedom compared to conventional members made of copper (Cu) or aluminum (Al).

However, conventional thermally conductive components using graphite have the following problems.

In the structure of Conventional Example 1, since graphite powder 12 having high thermal conductivity is dispersed in matrix 11, thermal conductivity can be improved. However, since the thermal conductivity of the matrix 11 itself made of resin or polymer is low, it is difficult to obtain high thermal conductivity as a whole. That is, according to conventional reports, the limit of thermal conductivity is about several 10 W/m·K, which is not sufficient for performance required in the future.

Furthermore, in Conventional Example 1, since graphite is dispersed in the low thermal conductivity matrix 11 to improve thermal characteristics, it is necessary to use a relatively large amount of graphite powder 12 relative to the whole, resulting in poor formability.

In the structure of Conventional Example 2, the component 13 is composed of the graphite powder 14 having high thermal conductivity as the main component, thereby improving the thermal conductivity in the plane direction, but due to the influence of the contact thermal resistance between the particles and the orientation Insufficient, so the high thermal conductivity of graphite has not been fully utilized.

In addition, in Conventional Example 2, since the in-plane orientation of the graphite particles 14 was made uniform by compression molding, it was difficult to improve the thermal conductivity in the layer direction.

Furthermore, in Conventional Example 2, since the powder must usually be compression-molded, there were problems in terms of shape freedom and ease of manufacture.

In the structure of Conventional Example 3, since it is composed of single-crystal graphite with very high in-plane orientation, it has very high thermal conductivity in the plane direction. However, as mentioned above, since the crystal structure of graphite has significant anisotropy, the thermal conductivity in the layer direction is only about a few tenths of that in the plane direction. Therefore, as long as it is only used for the purpose of transferring heat in the surface direction of the component, the performance of the thermally conductive component is very high. However, in order to adapt to the development trend of higher performance/high density of equipment/components in the future, it is necessary to improve thermal conductivity properties.

Contents of the invention

Therefore, an object of the present invention is to provide a high thermal conductivity member which can effectively utilize the high thermal conductivity in the plane direction of graphite and exhibit higher thermal conductivity also in the layer direction.

As a result of intensive research to solve the above-mentioned conventional problems, the present inventors found that a carbon material having a specific structure can achieve the above-mentioned object, and thus completed the present invention.

That is, the present invention relates to the following highly thermally conductive member, its manufacturing method, and a heat dissipation system using the same.

1. A high thermal conductivity component is formed by dispersing carbon particles in a highly oriented graphite structure composed of a graphite matrix, characterized in that:

(1) The c axes of each graphite layer constituting the above-mentioned graphite are parallel;

(2) The thermal conductivity κ‖ in the direction perpendicular to the c-axis is in the range of 400W/m·K to 1000W/m·K;

(3) The thermal conductivity κ⊥ in the direction parallel to the c-axis is in the range of not less than 10 W/m·K and not more than 100 W/m·K.

2. The high thermal conductivity component as described in item 1 above, characterized in that:

The shape of the high thermal conductivity member is a film, and the c-axis is parallel to the thickness direction of the film.

3. The high thermal conductivity component as described in item 2 above, characterized in that:

The thickness of the film is not less than 10 μm and not more than 300 μm.

4. The high thermal conductivity component as described in item 2 above, characterized in that:

The above-mentioned high thermal conductivity member has flexibility.

5. The high thermal conductivity component as described in item 1 above, characterized in that:

In the X-ray diffraction pattern of the above-mentioned graphite-based substrate, there are peaks on the (002 ⁿ ) plane (where n represents a natural number).

6. The high thermal conductivity component as described in item 1 above, characterized in that:

In the X-ray diffraction pattern of the above-mentioned graphite-based substrate, there are peaks of the (002) plane and the (004) plane.

7. The high thermal conductivity component as described in item 1 above, characterized in that:

The interior of the above-mentioned graphite-based substrate contains pores.

8. The high thermal conductivity component as described in item 1 above, characterized in that:

The density of the high thermal conductivity member is in the range of 0.3 g/cm ³ to 2 g/cm ³ .

9. The high thermal conductivity component as described in item 1 above, characterized in that:

The content of the carbon particles is in the range of 10 wt. ppm to 10 wt. %.

10. The high thermal conductivity component as described in item 1 above, characterized in that:

The carbon particles are at least one of 1) graphite particles and 2) carbon structures other than graphite particles.

11. The high thermal conductivity component as described in item 10 above, characterized in that:

The carbon structure is at least one of carbon nanotubes, fullerenes, diamonds, and diamond-like carbon.

12. The high thermal conductivity component according to item 1 above, characterized in that:

Some or all of the above carbon particles are graphite particles.

13. The high thermal conductivity component according to item 1 above, characterized in that:

The average particle diameter of the carbon particles is in the range of 0.05 μm to 20 μm.

14. The high thermal conductivity component according to item 1 above, characterized in that:

The shape of the above-mentioned carbon particles is flaky.

15. A manufacturing method for manufacturing a high thermal conductivity component formed by dispersing carbon particles in a highly oriented graphite structure composed of a graphite matrix, characterized in that it comprises:

(1) A preparation process of preparing a mixed solution containing polyamic acid and at least one dispersed particle selected from carbon particles and its precursor particles;

(2) A coating film forming step of forming a coating film in which the above-mentioned particles are dispersed in the above-mentioned polyamic acid using the above-mentioned mixed solution;

(3) an imidization process of imidizing the above-mentioned polyamic acid; and

(4) A heat treatment step of obtaining the above-mentioned highly thermally conductive member by heat-treating the above-mentioned coating film.

16. The manufacturing method according to item 15 above, characterized in that:

Some or all of the dispersed particles are carbon structure particles of at least one of carbon nanotubes, fullerenes, diamonds, and diamond-like carbon.

17. The manufacturing method according to item 15 above, characterized in that:

Part or all of the above dispersed particles are graphite particles.

18. The manufacturing method according to item 15 above, characterized in that:

The aforementioned precursor particles are polyimide particles.

19. The manufacturing method according to item 15 above, characterized in that:

The heat treatment includes 1) a preliminary firing step of firing in a temperature range of 1000°C to 1500°C, and 2) a main firing step of firing in a temperature range of 2000°C to 3000°C.

20. A heat dissipation system having a heat source, a heat dissipation component and a high thermal conductivity component, characterized in that:

(1) The above-mentioned heat source and heat dissipation component are thermally connected through a high thermal conductivity component;

(2) The high thermal conductivity member is the high thermal conductivity member described in item 1 above.

21. The cooling system as described in item 20 above, characterized in that:

The shape of the above-mentioned highly thermally conductive member is a film.

22. The cooling system as described in item 21 above, characterized in that:

At least one of the heat source and the heat dissipation member is provided in surface contact with the film.

23. The cooling system as described in item 20 above, characterized in that:

The above-mentioned high thermal conductivity member has flexibility.

24. The cooling system as described in item 20 above, characterized in that:

The above-mentioned high thermal conductivity member has one or two or more bent portions.

25. The cooling system as described in item 20 above, characterized in that:

The above-mentioned heat-dissipating components are heat-dissipating fins.

Description of drawings

Fig. 1 is a schematic diagram of a high thermal conductivity member of the present invention.

Fig. 2 is a schematic diagram of a high thermal conductivity member of the present invention.

Fig. 3 is a schematic diagram of a high thermal conductivity member of the present invention.

Figure 4 is a crystal structure diagram of graphite.

Fig. 5 is a representative X-ray diffraction pattern of an oriented graphite structure.

Fig. 6 is a schematic diagram showing the process of transition from an organic polymer film to an aligned graphite structure.

Fig. 7 is a diagram showing the manufacturing process of the high thermal conductivity member in Example 1-1.

Fig. 8 is a diagram showing an example of a temperature program in a firing step in Example 1-1.

Fig. 9 is a schematic diagram of a heat dissipation system using the high thermal conductivity member of the present invention.

Fig. 10 is a schematic diagram of a conventional heat conductive member (conventional example 1).

Fig. 11 is a schematic diagram of a conventional heat conductive member (conventional example 2).

Fig. 12 is a schematic diagram of a conventional heat conductive member (conventional example 3).

Symbol Description

1 Graphite structure 2 Graphite layer

3 Graphite particles 4 Pores

5 Highly oriented graphite flakes 6 Carbon atoms

7 Graphite layer 8 Heating element

9 High thermal conductivity components 10 Heat dissipation components

11 Matrix 12 Graphite particles

13 Graphite compression molded body 14 Graphite particles

15 Highly oriented graphite film 16 Graphite layer

Detailed ways

1. High thermal conductivity parts

The high thermal conductivity component of the present invention is a high thermal conductivity component formed by dispersing carbon particles in a graphite matrix, and is characterized in that:

(1) The c axes of each graphite layer constituting the above-mentioned graphite are substantially parallel;

(2) The thermal conductivity κ‖ in the direction perpendicular to the c-axis is in the range of 400W/m·K to 1000W/m·K;

(3) The thermal conductivity κ⊥ in the direction parallel to the c-axis is in the range of not less than 10 W/m·K and not more than 100 W/m·K.

The graphite matrix of the present invention uses graphite as the basic structure. That is, the basic structure is a laminate of graphite layers composed of a plurality of carbon six-membered rings. Therefore, the c-axes of the graphite layers in the graphite-based matrix are substantially parallel. However, the graphitic matrix may not have a complete graphitic structure. At least in the X-ray diffraction pattern of the above-mentioned graphite-based substrate, it is sufficient that a peak of the (002 ⁿ ) plane (where n represents a natural number) exists. In particular, in the X-ray diffraction pattern of the graphite thin film, it is preferable that at least peaks of the (002) plane and the (004) plane exist.

In addition, when the graphite-based matrix has a completely approximate graphite structure, it is preferable that in its X-ray diffraction pattern, there is a peak of the (002 ⁿ ) plane (where n represents a natural number), and no other peaks are found. .

Furthermore, when the graphite-based matrix is evaluated by the X-ray diffraction method, the distance (d) between the crystal planes is preferably in the range of 0.335 nm to 0.340 nm. Also, the reported value for single crystal graphite is 0.335 nm.

In addition, it is preferable that the interior of the graphite-based substrate contains pores. Due to the presence of voids, the density of the high thermal conductivity component of the present invention can be lower than the original graphite density value (~2.26 g/cm ³ ). That is, the density of the highly thermally conductive member of the present invention is generally preferably in the range of 0.3 g/cm ³ to 2 g/cm ³ , and particularly more preferably in the range of 0.6 g/cm ³ to 1.5 g/cm ³ .

In the present invention, carbon particles are dispersed materials dispersed in the above-mentioned matrix. The carbon particles have the function of thermally connecting graphite layers so that the heat conducted in the graphite-based matrix is conducted not only in the plane direction but also in the layer direction (thickness direction).

Therefore, the type of carbon particles is not particularly limited as long as it has the above functions. In the present invention, at least one of 1) graphite particles and 2) carbon structures other than graphite (carbon structure particles) is particularly preferred.

As the graphite particles as the dispersion material, graphite with high thermal conductivity (especially graphite with high crystallinity) is preferably used. For example, a) natural graphite, b) synthetic graphite obtained by pyrolyzing carbon-containing gases such as hydrocarbons, c) highly oriented pyrolytic graphite (so-called "HOPG") obtained by annealing synthetic graphite can be used wait. These can be used 1 type or 2 or more types.

Any graphite particles (graphite powder) can be used as the dispersion material as long as they have high thermal conductivity as described above. Whether or not graphite particles can be used can be judged directly from the magnitude of thermal conductivity, or indirectly from crystallinity evaluated by X-ray diffraction method or the like. For example, as a criterion for judgment by the X-ray diffraction method, graphite particles having a crystal plane spacing in the range of 0.335 to 0.340 nm can be used, similarly to the above-mentioned graphite-based substrate.

Graphite particles can be obtained by appropriately pulverizing graphite or the like. The method of pulverization treatment is not limited, and it can be carried out using a known device such as a ball mill, a jet mill, a high-speed drum mill, and the like. In particular, it is relatively easy to pulverize with a jet mill. The uniformity of particle size can be improved by using a particle size meter or the like during pulverization. In addition, after pulverization, a classification treatment can be performed according to a known method if necessary.

As the carbon structure (particles) of the dispersion material, it is preferable to use a carbon structure with high thermal conductivity (especially a carbon structure with high crystallinity) similarly to graphite particles. For example, carbon nanotubes such as single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs), carbon nanocoils (CNC), fullerenes, natural diamonds, and high-pressure synthetic diamonds can be used. , explosive synthetic diamond (implosion synthetic diamond), vapor phase synthetic diamond, etc. These can be used suitably by selecting 1 type or 2 or more types. Among them, from the viewpoint of uniformity in shape and particle diameter to some extent, it is preferable to use carbon particles of at least one of carbon nanotubes, fullerenes, diamonds, and diamond-like carbon. In addition, the above-mentioned carbon nanotubes also include carbon nanohorns and the like.

In addition, when the size of the carbon structure is large, it can be pulverized into smaller particles as needed. This facilitates its dispersion in the graphite matrix. The method of pulverizing the large-sized carbon structure can be carried out in the same way as the above-mentioned pulverization treatment of graphite.

In the present invention, among these carbon particles, it is particularly preferable that a part or all of the above-mentioned carbon particles are graphite.

The content of carbon particles can be appropriately determined according to desired thermal conductivity, the type of carbon particles, and the like. Usually, it is the range of 10 weight ppm or more and 10 weight% or less, Especially preferably, it is the range of 1000 weight ppm or more and 7 weight% or less.

The particle size of the carbon particles can be set according to desired thermal conductivity and the like. Usually, the average particle diameter is in the range of 0.05 μm or more, preferably in the range of 0.05 μm or more and 20 μm or less, particularly preferably in the range of 0.1 μm or more and 4 μm or less.

The shape of the carbon particles is not limited, and may be any of spherical, amorphous, flake, and fibrous. In the present invention, it is particularly preferable that the shape of the above-mentioned carbon particles is flaky. By using flaky carbon particles, the thermal conductivity of the dispersed carbon particles can be more effectively utilized, so the thermal conductivity in the layer direction can be significantly improved as a whole.

In the high thermal conductivity member of the present invention, the thermal conductivity κ∥ in the direction perpendicular to the c-axis is in the range of 400 W/m·K to 1000 W/m·K, particularly preferably 700 W/m·K to 1000 W/m·K range.

In addition, the thermal conductivity κ⊥ in the direction parallel to the c-axis is in the range of 10 W/m·K to 100 W/m·K, particularly preferably 50 W/m·K to 100 W/m·K.

The shape of the highly thermally conductive member of the present invention is not particularly limited, but is preferably film-like (sheet-like). When the highly thermally conductive member is in the form of a film, its thickness can be appropriately determined depending on the application, use method, etc., but usually it is preferably in the range of 10 μm or more and 300 μm or less.

When the high thermal conductivity member is in the form of a film, it is preferable that the c-axis direction of the graphite-based substrate is substantially parallel to the thickness direction of the film. In other words, it is preferable that the graphite layers of the graphite-based substrate are arranged such that the c-axis is substantially perpendicular to the film surface (main surface).

Thereby, the above-mentioned thermal conductivity κ⊥ which is the thermal conductivity in the thickness direction can be ensured in the range of 10 W/m·K or more and 100 W/m·K or less. That is, it is possible to provide a high thermal conductivity member having excellent thermal conductivity also in the thickness direction. In this case, the thermal conductivity κ∥ in the film surface (main surface) direction is in the range of 400 W/m·K to 1000 W/m·K.

The highly thermally conductive member of the present invention (particularly a film-like highly thermally conductive member) preferably has flexibility. That is, it is preferably bendable. In this way, the degree of freedom of design can be increased, and it can be applied to a wide range of applications.

In addition, flexibility in this specification means bending resistance against bending treatment. Flexibility can be freely controlled by the formation of voids, the thickness of the highly thermally conductive member, the type of carbon particles, and the like. In particular, due to the voids contained in the component of the present invention, the number of times of bending resistance can be significantly increased.

2. Manufacturing method of high thermal conductivity parts

The manufacturing method of the highly thermally conductive member of the present invention is not limited, but the following manufacturing methods are particularly preferable.

That is, a suitable manufacturing method is a method of manufacturing a high thermal conductivity component formed by dispersing carbon particles in a graphite-based matrix, comprising:

(1) The first step of preparing a mixed solution containing a raw material capable of forming an organic polymer and at least one dispersed particle selected from carbon particles and their precursor particles;

(2) a second step of forming a coating film in which the above-mentioned particles are dispersed in the above-mentioned organic polymer using the above-mentioned mixed solution; and

(3) The third step of obtaining the above-mentioned highly thermally conductive member by heat-treating the above-mentioned coating film.

first process

In the first step, a liquid mixture containing a raw material capable of forming an organic polymer and at least one particle selected from carbon particles and precursor particles thereof is prepared.

The raw material capable of forming an organic polymer may be a raw material capable of forming a highly oriented graphite structure by the heat treatment in the third step. Examples include polyimide (PI), polyamide (PA), polyparaphenylene terephthalamide (PPTA), polyphenylene oxadiazole (POD), polybenzothiazole (PBT) , polybenzobisthiazole (PBBO), polyphenylene benzimidazole (PBI), polyphenylene benzobisimidazole (PPBI), polythiazole (PT), polyparaphenylene vinylene (PPV), poly Amide-imide, polyacrylonitrile, etc. Among them, polyimide is preferable.

In addition, in the present invention, in addition to using these organic polymers as they are as raw materials, their precursors can also be used as the above-mentioned raw materials. For example, when the purpose is to form a polyimide coating film in the second step, its precursor polyamic acid can be used as the raw material.

In the present invention, in addition to the organic polymer solution obtained by dissolving the various organic polymers described above in a solvent, a reaction product obtained by reacting monomers capable of constituting the organic polymer can also be used as the raw material.

As the dispersed particles, at least one of carbon particles and precursor particles thereof is used.

As the carbon particles, the same particles as the above-mentioned carbon particles can be used. In particular, at least one of 1) graphite particles and 2) carbon structures other than graphite can be suitably used.

As the precursor of the carbon particles, those capable of becoming carbon particles (preferably graphite particles) by heat treatment may be used. Examples include polyimide (PI), polyamide (PA), polyamide-imide, polyparaphenylene terephthalamide (PPTA), polyphenylene oxadiazole (POD), Polybenzothiazole (PBT), polybenzobithiazole (PBBO), polyphenylenebenzimidazole (PBI), polyphenylenebenzobisimidazole (PPBI), polythiazole (PT), polyparaphenylene Vinyl (PPV) and polyacrylonitrile (PAN), etc. Among them, polyimide is preferable. These can use known or commercially available products. For example, when polyimide is used, "Kapton" manufactured by Toray-DuPont Co., Ltd. processed into a powder form, etc. can be used suitably. In addition, a polymer fiber having a diameter of several μm or the like having a cut length of approximately several to several tens of μm may also be used.

When preparing the liquid mixture in the first step, an appropriate solvent can be used. In particular, in the present invention, as a raw material capable of forming an organic polymer, a solution obtained by dissolving the above-mentioned various organic polymers or precursors thereof in a solvent can be suitably used. Such a solution also includes a solution of a reaction product obtained by reacting a monomer capable of forming an organic polymer, and the like.

As the above-mentioned solvent, a solvent capable of dissolving these organic polymers and the like is preferable. For example, it can be appropriately selected from common organic solvents such as dimethylacetamide and N-methylpyrrolidone according to the type of the target organic polymer. These solvents can be used individually by 1 type or in mixture of 2 or more types.

In addition, appropriate known additives may be added to the above-mentioned liquid mixture as needed. For example, in addition to a viscosity modifier such as ethylene glycol, a filler such as calcium hydrogen phosphate may be appropriately mixed in order to reduce the chargeability of the formed organic polymer.

The concentration of each component in the mixed solution can be appropriately set so as to obtain the high thermal conductivity member described in item 1 above. In addition, as long as each component can be mixed uniformly, the solid phase concentration of the mixed liquid is not particularly limited, and it can usually be set in the range of 5 wt. ppm to 5 wt. %.

second process

In the second step, the above-mentioned mixed solution is used to form a coating film (thin film) in which the above-mentioned particles are dispersed in the above-mentioned organic polymer.

The method of forming the coating film is not limited, and for example, the coating film can be formed by applying the above-mentioned mixed solution on a suitable substrate. As the coating method, for example, brush coating, spray coating, blade coating, roll coating, or a known printing method may be used. The type of base material is not limited, and base materials of various materials such as metals, alloys, resins, and ceramics can be used. Therefore, the coating film can be formed directly using a heat dissipation member etc. as a base material.

There is no limit to the thickness of the coating film, and it can be appropriately adjusted to achieve the thickness of the film when manufacturing film-like high thermal conductivity parts. For example, the thickness of the obtained thin film can be adjusted so that it is in the range of 10 μm or more and 300 μm or less. At this time, the coating film can be laminated|stacked suitably in 2 layers, 3 layers, etc. as needed.

In addition, when using a precursor of an organic polymer as a raw material in the first step, it can be converted into the target organic polymer by subjecting it to a predetermined treatment. For example, when polyamic acid, a precursor of polyimide, is used as a raw material, a polyamic acid coating film is formed from a mixed solution containing polyamic acid, and then converted into a polyimide film by imidizing the polyamic acid. As the imidization method, known methods can be used. For example, imidization can be performed by heating a coating film of polyamic acid at a predetermined temperature.

third process

In the third step, the above-mentioned highly thermally conductive member is obtained by heat-treating the above-mentioned coating film.

The conditions of the heat treatment can be appropriately set such that the matrix of the above-mentioned coating film becomes graphite. For example, it can preferably implement in an inert gas atmosphere in the range of 1000°C to 3000°C. As the inert gas, for example, at least one inert gas selected from argon, helium, nitrogen and the like can be used. The heat treatment time can be appropriately determined according to the heat treatment temperature and the like.

In the present invention, it is particularly preferable to carry out heat treatment including the following two steps: 1) a pre-firing step of firing in a temperature range of 1000°C to 1500°C and 2) a temperature of 2000°C to 3000°C The main firing process of firing within the range.

In the pre-firing process, by firing the organic polymer at the above temperature, components other than carbon (C) contained in the organic polymer (oxygen (O), nitrogen (N), hydrogen (H), etc. ).

The heat treatment time at this time also varies depending on the shape and size of the sample to be fired, but usually can be in the range of 0.5 hours to 5 hours.

In addition, there is no limit to the temperature increase rate for entering the pre-firing step, and heating is usually in the range of 1°C/min to 15°C/min, particularly preferably in the range of 3°C/min to 10°C/min. In addition, the cooling rate after the pre-firing treatment is not limited, but it is usually cooled in the range of 5°C/min to 20°C/min, particularly preferably in the range of 5°C/min to 10°C/min.

By carrying out the preliminary firing step under the above conditions, the thermal conductivity and the degree of orientation in the plane direction of the graphite structure obtained after the subsequent main firing treatment can be improved.

In the main firing process, in order to obtain graphite with higher orientation, it implements at the predetermined temperature selected from the temperature range of 2000-3000 degreeC. At this time, the degree of orientation of the obtained graphite-based substrate can be further improved by performing an intermediate treatment at a predetermined heating temperature (a temperature range of approximately 2000°C to 2400°C).

The heat treatment time at this time also varies depending on the shape and size of the sample to be fired, but usually can be in the range of 0.5 hours to 10 hours.

In addition, there is no limit to the temperature increase rate for entering the main firing process or intermediate treatment, and it is usually heated in the range of 5°C/min to 15°C/min, particularly preferably in the range of 5°C/min to 10°C/min. . Furthermore, the cooling rate after the main firing treatment is not limited, but it is usually cooled in the range of 5°C/min to 20°C/min, particularly preferably in the range of 5°C/min to 10°C/min.

3. Cooling system

The present invention relates to a heat dissipation system (heat dissipation device). The heat dissipation system includes a heat source, a heat dissipation component and a high thermal conductivity component, wherein: (1) the above heat source and heat dissipation component are thermally connected by a high thermal conductivity component, (2) the above high heat conductivity The thermally conductive member is the high thermal conductivity member described in claim 1.

The heat dissipation system of the present invention can be used in various existing electronic equipment or components that need heat dissipation. That is, the system of the present invention can be used in place of the cooling system of existing devices. For example, as shown in FIGS. 9( a ) to ( c ), when a heat sink is used as the heat dissipation member, effective heat dissipation (cooling) can be performed by interposing a high thermal conductivity member between the heat sink and the heat source.

In the present invention, the high thermal conductivity component may be thermally connected to the heat source and the heat dissipation component. That is, it may be configured such that heat is efficiently transferred from the heat source to the high thermal conductivity component, and then from the high thermal conductivity component to the heat dissipation component. Generally, it is preferable that the high thermal conductivity member be in direct contact with the heat generating source and the heat dissipation member.

In addition, there are no restrictions on the size, shape, arrangement method, etc. of the heat source, high thermal conductivity member, and heat dissipation member, and may be appropriately designed so as to effectively dissipate heat.

In the heat dissipation system of the present invention, when a film-shaped high thermal conductivity member is used, it can usually be arranged so that the film surface (principal surface) is in contact with the heat generating part or the heat dissipation member. For example, as shown in FIGS. 9( a ) to ( c ), it is possible to provide a heat generating part or a heat dissipation member in contact with the film surface.

In the present invention, when a flexible and highly thermally conductive member is used, it is possible to design a heat dissipation system that adapts to the shape, installation position, etc. of the heat source. For example, as shown in FIG. 9( c ), it is possible to design a heat dissipation system having one or two or more bent portions. Thus, it is possible to construct a heat dissipation system with a high degree of freedom in design.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)

FIG. 1 shows a schematic diagram of a high thermal conductivity member in Embodiment 1 of the present invention.

The basic structural elements of this highly thermally conductive member include: a graphite structure 1 whose c-axis is oriented substantially parallel to the thickness direction; and graphite particles 3 substantially uniformly dispersed in the graphite structure 1 .

This graphite structure 1 has a stacked structure in which graphite layers 2 composed of carbon six-membered ring structures depend on each other as described above. That is, in terms of graphite itself, graphite layers are not only stacked, but also have a definite position when stacked (see FIG. 4 ), and are stacked while maintaining their positional relationship.

When evaluating the graphite structure (graphite-based matrix) 1 by X-ray diffraction, it is preferable to use the distance d of the crystal planes in the range of d=0.335 to 0.340 nm, and to observe the (002) plane and its higher-order peaks, and to observe simultaneously A graphite structure that does not have diffraction peaks other than these.

FIG. 5 shows a representative X-ray diffraction pattern of the graphite structure 1 . Regarding the crystallinity (orientation) of graphite, it is preferable to use graphite having a half band width (half band width) of 1° or less with respect to the main peak near 26.5° as shown in FIG. 5 . That is, there is a correlation between half bandwidth and crystallinity, and in the present invention, the narrower the half bandwidth is, the more preferable it is. The thermal conductivity κ∥ of the graphite structure 1 itself having such crystallinity (orientation) in the plane direction varies depending on the manufacturing method and the like, but is about 400 W/m·K or more. In the present invention, the thermal conductivity κ∥ in the plane direction is preferably 400 W/m·K or more.

Thus, the graphite structure 1 used as a base in the present invention can use any graphite as long as it has a high thermal conductivity in the plane direction. Graphite obtained by firing and pyrolyzing an organic polymer (for example, polyimide) which is a precursor of carbon is particularly preferable because it has a structure close to a single crystal (high orientation) and thus has high thermal conductivity in the plane direction. In the following examples, the graphite structure obtained by firing the organic polymer is taken as an example for illustration.

The carbon particles 3 used in the present invention, in addition to the function of conducting the heat transferred in the graphite structure 1 in the plane direction, also have the function of connecting the graphite layers 2 (that is, between the stacked graphite layers) Thermal connection, the function of conducting heat in the layer direction (thickness direction). Therefore, as the carbon particles 3 , it is preferable to use graphite powder with high thermal conductivity, that is, graphite powder with high crystallinity.

In the present invention, oriented graphite powder having very high thermal conductivity in the plane direction is preferable as the carbon particles. Among them, highly oriented graphite flakes produced by firing organic polymers and pulverized are particularly preferable in terms of crystallinity (thermal conductivity) and uniformity.

In addition, a carbon structure can also be used as the carbon particles 3 . This carbon structure also has the function of thermally connecting the graphite layers 2 to each other so that the heat transmitted in the graphite structure 1 is conducted not only in the plane direction but also in the layer direction (thickness direction). Therefore, it is preferable to use a carbon structure with high thermal conductivity, and it is particularly preferable to use a carbon structure with high crystallinity.

In addition, the particle size of the carbon particles 3 is not particularly affected as long as it is a size that can be uniformly dispersed in the graphite structure. In particular, when using a method of forming a graphite structure by firing an organic polymer, it is preferable to use carbon particles in the range of 0.1 μm to 5 μm in order not to hinder its graphitization.

As the carbon particles, in addition to the above-mentioned prepared graphite particles, organic polymers that can become predetermined carbon particles (graphite particles, etc.) during the firing process of graphitizing the organic polymer as a matrix material as a raw material for carbon particles. For example, the organic polymer (matrix) can be graphitized by heat-treating the organic polymer of powdery polyimide dispersed in a particle size range of 0.1 μm to 10 μm, and the powdery polyimide can also be made Amine graphitization. As a result, a highly thermally conductive member in which graphite particles are dispersed in the graphite structure can be obtained.

(Embodiment 2)

There are several methods for producing the above-mentioned graphite structure 1, but from the viewpoint of easiness of production and the properties of the obtained high thermal conductivity member, etc., the method of forming the graphite structure 1 by heat-treating an organic polymer is preferably used.

The method of obtaining a high thermal conductivity member composed of a graphite structure using an organic polymer as a starting material can be roughly divided into the following steps: step (I) obtaining an organic polymer in which graphite particles are dispersed; Molecules undergo heat treatment to graphitize organic polymers.

In the present invention, for example, polyimide can be preferably used as the organic polymer. The purpose is that when polyimide is used as an organic polymer, its precursor polyamic acid can be used as a raw material. Therefore, in Embodiment 2, this method will be described as an example.

First, the step of forming an organic polymer containing graphite powder in the step (I) will be described.

For the organic macromolecules containing graphite particles, a specified amount of graphite particles 3 is mixed and dispersed in the polyamic acid solution as the first organic macromolecule, and after forming a predetermined shape, the target organic polymer can be obtained by implementing heating dehydration reaction, etc. molecular. At this time, a catalyst may also be used as needed.

In this case, the molecular arrangement of the organic polymer can be controlled depending on the type of the organic polymer used and the like. Specifically, the type of organic polymer as a solid content, the type of solvent, and the like are determined so as to obtain a material in which properly mixed graphite particles 3 have a predetermined orientation and are dispersed. A catalyst, a viscosity modifier, etc. are added to the solution prepared with this composition as needed, and it is made into the desired shape for use by stirring, casting, coating, etc. By volatilizing the solvent in this state, the first organic polymer solution solidifies. The temperature conditions during production may be around room temperature, which is a normal operating temperature, or may be heated in a temperature range lower than the boiling point of the solvent if necessary.

When the first organic polymer is converted into the second organic polymer (polyimide) as a carbon precursor through a reaction process such as heating and dehydration, heat treatment can usually be carried out in a nitrogen atmosphere or a vacuum atmosphere, or chemical The reaction was dehydrated. The optimum method can be appropriately selected according to the type of organic polymer to be formed and the like. From the viewpoint of easiness of production, a method of performing heat treatment in a temperature range of 100° C. to 400° C. is particularly preferable. In addition, if necessary, stretching treatment may be performed at the same time to control the orientation of the graphite structure.

Next, in the step (II), oriented graphite is obtained from the organic polymer containing graphite particles. This step itself can be basically the same as the method of firing the polymer sheet (product name "Kapton", manufactured by Toray-DuPont) described in the above document (JP-A-07-109171).

First, the second organic polymer as a carbon precursor is calcined to remove components (oxygen (O), nitrogen (N), hydrogen (H), etc.) other than carbon (C) contained in the organic polymer. The treatment temperature and treatment time vary with the shape and size of the sample to be fired. In the atmosphere of argon (Ar) or nitrogen (N ₂ ) or their mixed gas, the temperature can be generally above 1000°C and 1500°C. The following treatment is not less than 0.5 hours and not more than 5 hours. In addition, the temperature increase rate is preferably in the range of 1°C/min to 15°C/min, and particularly preferably in the range of 3°C/min to 10°C/min. In addition, the cooling rate after the pre-firing treatment is preferably in the range of 5°C/min to 20°C/min, and particularly preferably cooling in the range of 5°C/min to 10°C/min.

According to the above conditions, the in-plane thermal conductivity and the degree of orientation of the graphite structure obtained after the main firing treatment can be improved.

In order to obtain truly oriented graphite, the pre-fired organic polymer can be main-fired at a temperature selected from a temperature range of 2000°C to 3000°C. At this time, the degree of orientation of the obtained graphite structure 1 can be improved by temporarily maintaining a predetermined heating temperature and performing an intermediate treatment (about 2000° C. to 2400° C.). Specifically, heating is performed from room temperature to an intermediate temperature at a rate of temperature increase ranging from 5° C./min to 10° C./min, and after holding for about 1 hour, the temperature is raised again to perform main firing. The main firing conditions are heating at a temperature range of approximately 2000°C to 3000°C for 0.5 hours to 10 hours. For cooling after the main firing treatment, the cooling rate is preferably in the range of 5°C/min to 20°C/min, particularly preferably in the range of 5°C/min to 10°C/min.

Through the above steps, the graphite structure 1 having high thermal conductivity in the plane direction of the present invention can be formed, and the thermal conductivity in the layer direction is also improved by the action of the graphite particles 3 dispersed in the structure. The reaction schematic diagram of the above process is shown in Figure 6.

Moreover, in the graphite structure 1 obtained by this method, by adjusting the firing conditions (mainly the heating rate) or mixing an appropriate amount of the above-mentioned fillers for firing treatment, the two-dimensional orientation of the graphite layer can be produced, and the structure contains many structure of fine pores. When predetermined pores are formed, the density of the obtained graphite structure 1 can be made smaller (0.3 to 2 g/cm ³ ) than the original graphite density (~2.26 g/cm ³ ). The state of the graphite structure with pores formed is shown in FIG. 2 . In FIG. 2 , many pores 4 exist in the graphite structure 1 .

By forming such a structure, the obtained graphite structure 1 has flexibility, is hard to break even when bent, and can be moderately deformed against compression. Such characteristics can improve the degree of freedom in design when used as a thermally conductive member, and also have the effect of reducing thermal contact resistance with a heat source.

(Embodiment 3)

As described in Embodiment 2 above, the highly thermally conductive member of the present invention can be produced by using a graphitized material as carbon particles. On the contrary, in Embodiment 3, the precursor of carbon is mixed in advance as the raw material of carbon particles, and then, in the process of graphitizing the substrate in the above-mentioned step (II), the above-mentioned precursor is simultaneously graphitized, and by dispersing the graphite particles The highly thermally conductive member of the present invention can also be produced in a graphite structure. Here, an example thereof will be described in Embodiment 3. FIG.

The basic manufacturing process can be the same as that of the second embodiment.

As a step (I), the organic polymer that is a precursor of carbon is mixed and dispersed in the first organic polymer solution dissolved in a solvent, and after being formed into a predetermined shape, the solvent is volatilized to solidify, and dehydration is performed by heating. reaction etc. to synthesize the second organic polymer (polyimide) which is easily graphitized.

The subsequent step (II) may also be the same as in Embodiment 2. Through this step, the second organic polymer becomes a graphite structure having high thermal conductivity in the plane direction, and the organic polymer dispersed inside is also carbonized and further graphitized. As a result, a highly thermally conductive member in which graphite particles are dispersed within a graphite structure can be obtained. Thereby, the thermal conductivity in the layer direction can also be improved.

The high thermal conductivity part of the present invention has a structure in which carbon particles supplementing the thermal conductivity in the layer direction are dispersed in a graphite structure with high thermal conductivity in the plane direction, so it is possible to provide a high thermal conductivity part with high thermal conductivity as a whole. With this structure, heat can be efficiently conducted through the carbon particles also in the layer direction (thickness direction). As a result, the layer-direction thermal conductivity κ⊥ can be improved compared to the case of only the graphite structure.

In the structure of the present invention, when the shape of the high thermal conductivity member is a film, space saving and shape diversity are improved, so the possibility (degree of freedom) of use as a thermal conductivity member can be expanded.

In addition, in the structure of the present invention, when the interior of the graphite structure contains pores, it is easy to contain carbon particles that promote heat conduction in the layer direction in an appropriate form, and the obtained high thermal conductivity member can have flexibility and compressibility.

In addition, the softness mentioned in this specification means the bending resistance with respect to a bending process. In the component of the present invention, the number of times of bending resistance can be significantly increased due to the inclusion of voids. In addition, the term "compressibility" refers to deformability to compression treatment. In the highly thermally conductive member of the present invention, since voids are included, the degree of adhesion to heat sources and the like is improved, and thermal resistance can be suppressed.

In the production method of the present invention, a highly oriented graphite structure can be produced relatively easily, and carbon particles can be relatively easily dispersed in the graphite structure in a desired state.

In addition, in the production method of the present invention, when using a polyamic acid solution as a solution for forming the first organic polymer, because the second organic polymer is polyimide (PI), it is easy to handle and can form an orientation It is a graphite structure with high properties, so it is preferable.

Since the above-mentioned high thermal conductivity member is used in the heat dissipation system of the present invention, it is possible to exhibit excellent thermal conductivity not only in the plane direction but also in the layer direction. Accordingly, it is possible to construct a heat dissipation system having excellent heat dissipation characteristics. In addition, especially when a sheet-shaped high thermal conductivity member is used, due to its flexibility, the degree of freedom in the shape of the heat dissipation system increases, and it is possible to design a heat dissipation system suitable for various purposes.

Example

In the following, Examples and Comparative Examples are given to illustrate the features of the present invention in more detail. However, the scope of the present invention is not limited to the examples.

(Example 1-1)

An example of producing a graphite structure by using polyimide as an organic polymer material for mixing/dispersing graphite powder and firing it will be described. Fig. 7 shows its main process diagram.

First, a polyamic acid solution is prepared as a precursor organic polymer solution of polyimide. In a dry box filled with nitrogen (N ₂ ), add 5.00 g of bis(4-aminophenyl) ether and 120 ml of dimethylacetamide into a round-bottomed flask, and stir to dissolve them.

5.45 g of pyromellitic anhydride was mixed with this solution, and stirred for about 3 hours to synthesize a polyamic acid solution as the first organic polymer material.

With a weight ratio of 5%, graphite powder (thermal conductivity: ~200W/m K) pulverized by a jet mill with an average particle size of 4 μm was mixed into the synthesized polyamic acid solution, and it was ground by a ball mill for 12 hours to make it Disperse evenly. In addition, the particle size of the graphite powder is not limited to 4 μm, and slightly larger particles (>20 μm) or slightly smaller particles can be substantially uniformly dispersed.

The graphite powder-containing polyamic acid solution prepared in this way was applied on a slide glass to form a graphite powder-containing polyamic acid film (thickness: ~500 μm). The coating film was dried in a nitrogen atmosphere for about 1 hour, dried in a vacuum oven under reduced pressure for 2 hours (at room temperature), and then heated to 100° C. for 1 hour of heat treatment. As a result, the solvent component of the solution was removed by evaporation, and a polyamic acid film in which graphite powder was dispersed was formed.

The above-mentioned polyamic acid film was placed in a glass tube oven, and after the pressure was reduced to vacuum, heat treatment was performed at 300° C. for 1 hour to imidize the polyamic acid film.

The obtained polyimide film was peeled off from the slide, and its thickness was measured with a micrometer, and it was about 50 μm.

The organic polymer (polyimide) obtained by the above process is put into an electric furnace for firing treatment. Fig. 8(a) shows a temperature profile of pre-firing used in this example.

First, as pre-firing, the temperature was raised from room temperature to 1200° C. at a rate of temperature increase of 3° C./min in an Ar gas atmosphere, and kept at a pre-firing temperature of 1,200° C. for 3 hours. The rate of temperature increase can be determined in consideration of the type and shape of the organic polymer film to be fired, but it is usually in the range of 15° C./min or less, and 3° C./min is adopted in this embodiment. After the firing treatment, cool down to room temperature at a cooling rate of 5°C/min. Usually, the temperature drop rate during cooling does not need to be controlled as strictly as the temperature rise rate, but it is preferably 10°C/min or less, and 5°C/min is used in this embodiment.

In the pre-firing process, the organic polymer is heated and decomposed to release nitrogen, oxygen, and hydrogen, and the weight ratio becomes 50-60% of the initial raw material, and it is transformed into a carbonized film dispersed with graphite powder. Therefore, there is no effect on the dispersed graphite powder.

After pre-firing under the above conditions, the sample was transferred to an ultra-high temperature furnace for main firing. Its temperature curve is shown in Fig. 8(b). In this embodiment, the temperature is raised to 1000° C. at a rate of 10° C./min, then lowered to 5° C./min, and kept at an intermediate treatment temperature of 2200° C. for 1 hour. Then the temperature is raised to the main firing temperature of 2700° C. at a heating rate of 5° C./min, and the holding time at 2700° C. is 3 hours. After the main firing temperature is maintained, the temperature is lowered to 2200°C at a cooling rate of 5°C/min, then to 1300°C at a cooling rate of 10°C/min, and to room temperature at a cooling rate of 20°C/min.

The film thickness of the thus-obtained graphite structure (hereinafter sometimes simply referred to as "structure") was about 100 μm. When the cross-section of the obtained structure was observed with a scanning electron microscope (SEM), it was confirmed that it had a graphite structure in which graphite layers were stacked. It was also confirmed that many minute voids existed inside the structure (reference symbol 4 in FIG. 2 ). The formation mechanism of the voids is not clear, but it is considered to be attributable to the main firing process. The presence of pre-mixed, dispersed graphite powder was also observed across the graphite layers oriented in the planar direction.

In addition, the crystal structure of the formed graphite structure was evaluated by X-ray diffraction analysis. As a result, graphite (002) and its higher order peaks equivalent to those in Fig. 5 were observed, as well as several faint graphite diffraction pattern. Since the former is attributable to the crystal planes of the graphite structure, it can be seen that even when powdery graphite is contained, a graphite structure with sufficiently high plane orientation can be obtained. In addition, the latter is considered to be due to several diffraction patterns observed except for the (00a) plane of the graphite powder dispersed in the graphite structure.

The thermal conductivity of the graphite structure containing graphite powder obtained in the above steps was evaluated. As a result, the thermal conductivity κ‖ in the plane direction was 600 W/m·K, which was the same value as when the graphite powder was not contained. On the other hand, the thermal conductivity κ⊥ in the layer direction (thickness direction) is 25W/m·K, which is several times higher than before.

Therefore, it was confirmed that by mixing and dispersing graphite powder in a graphite structure with high orientation, a graphite structure with high thermal conductivity also in the layer direction can be obtained.

In addition, since the graphite structure produced in this example has many fine pores inside it, as a result, a highly thermally conductive member having excellent bendability, compressibility, and the like can be obtained.

(Example 1-2)

Through the same process as in the above-mentioned Example 1, the size of the graphite particles was changed to produce a high thermal conductivity member.

In Example 1-2, the graphite particles used in Example 1-1 were further pulverized so that the particle diameter was about 0.1 to 0.3 μm. A highly thermally conductive member composed of a graphite structure was formed by the same procedure except that 3% by weight of the graphite particles were mixed/dispersed in the first organic polymer solution polyamic acid.

As a result of evaluating the thermal conductivity of the obtained sample, it was found that the in-plane thermal conductivity κ⊥ was 600 W/m·K, which was the same as in Example 1 above. On the other hand, the layer-wise thermal conductivity κ⊥ was increased to 50W/m·K. This is considered to be due to the increased dispersibility of the mixed graphite particles and the increase in thermal junctions between the graphite layers due to the particle size reduction.

In addition, the size of the above-mentioned graphite powder was varied in the range of 0.05 to 20 μm to produce a graphite structure. As a result, it was confirmed that the thermal conductivity in the layer direction was improved in any case.

(Example 1-3)

By the same procedure as in Example 1-1 above, when producing a high thermal conductivity member composed of a graphite structure, the results were recorded when the concentration of graphite particles mixed/dispersed was changed.

In Example 1-3, the graphite particles used in Example 1-1 were further pulverized so that the particle size was about 0.1 to 0.3 μm. The content of the graphite particles added to the polyamic acid of the first organic polymer solution was varied in the range of 1.0 ppm to 10% by weight to form a highly thermally conductive member composed of a graphite structure.

As a result of evaluating the thermal conductivity of the obtained sample, it was found that the in-plane thermal conductivity κ∥ was 600 W/m·K, which was the same as in Example 1 above. On the other hand, the layer direction thermal conductivity κ⊥ is 10 to 50 W/m·K.

(Example 1-4)

By the same process as in the above-mentioned Example 1-2, when preparing polyimide containing graphite powder as a carbon precursor, adjust the concentration of the polyamic acid solution so that the thickness of the polyimide film is about 15 μm, and the first Two organic polymer polyimide.

This sample was fired under the same temperature profile as in Example 1-1 above. As a result, it was confirmed that pores were hardly formed inside the obtained graphite structure. The reason for this is unclear, but it was found that reducing the film thickness of polyimide as a carbon precursor leads to a denser graphite structure with fewer void regions.

Compared with the sample of Example 1-1 mentioned above, the obtained sample was somewhat lacking in flexibility and slightly inferior in bending resistance test characteristics, etc., but it was not to such an extent that it would cause problems in practical use. The thermal conductivity of this sample was evaluated, and the results showed that the thermal conductivity κ‖ in the plane direction was 980W/m·K. On the other hand, the thermal conductivity κ⊥ in the layer direction was maintained at 50 W/m·K. This is considered to be because the reduction in the amount of voids improves the degree of orientation in the plane direction.

(Example 1-5)

In the above-mentioned embodiments, graphite powder with a thermal conductivity κ∥ of about 200 W/m·K produced by pyrolysis was used to produce high thermal conductivity components. In this embodiment, oriented graphite with high in-plane thermal conductivity (κ∥=600W/m·K) was pulverized and added to the graphite structure.

In Examples 1-5, "PGS graphite (thickness: 125 μm, graphite flakes)" manufactured by Matsushita Electric Industrial Co., Ltd. pulverized by the jet milling method was used. When the graphite particles obtained by the pulverization treatment were observed, the particle diameter was about 1 μm. However, since the original PGS graphite flakes were graphite strongly oriented in the plane direction, the graphite layer parts were significantly peeled off during pulverization, which was different from that of the above-mentioned Example 1. -1 compared to get flake (scale structure) graphite powder technique.

The graphite powder was mixed into polyamic acid in the same manner as in Example 1-1 above, imidized, and then fired to produce a graphite structure.

Fig. 3 shows a schematic diagram of a high thermal conductivity member composed of the graphite structure obtained in this example.

As a result of evaluating the thermal conductivity of the obtained sample, it was found that the thermal conductivity κ‖ in the plane direction was approximately the same as 600 W/m·K. In addition, the thermal conductivity κ⊥ in the layer direction was 80 W/m·K. This is considered to be because the thermal conductivity of the graphite powder dispersed in the graphite structure is higher than that of the conventional graphite material, so the thermal connection in the layer direction is improved.

Next, graphite powder composed of PGS graphite flakes was pulverized more finely (particle size: 0.2 to 0.4 μm) to produce the same graphite structure. As a result, its layer-wise thermal conductivity κ⊥ increased to 98W/m·K.

(Example 1-6)

The carbon precursor organic polymer material used in the above-mentioned Example 1-1 is polyimide, but it is confirmed that even if other organic polymer materials are used, the same production method as above can be used to produce graphite powder. graphite structure.

Graphite powder is added to various precursor solutions, and after solidification, organic polymers obtained by thermal dehydration reaction etc. are fired under a predetermined temperature profile to produce highly thermally conductive parts. Specifically, in addition to polyimide, polyamide (PA), polyparaphenylene terephthalamide (PPTA), polyphenylene oxadiazole (POD), polybenzothiazole (PBT) can be used ), polybenzobisthiazole (PBBO), polyphenylene benzimidazole (PBI), polyphenylene benzobisimidazole (PPBI), polythiazole (PT), polyparaphenylene vinylene (PPV), etc. An organic polymer material is obtained to obtain a graphite structure containing graphite powder.

(Example 1-7)

Using the same procedure as in Example 1-1 above, a highly thermally conductive member was produced by dispersing graphite powder mixed with a powder of an organic polymer material capable of graphitization during firing.

In Examples 1-7, the polyimide powder with an average particle diameter of about 5 to 10 μm was mixed into the polyamic acid solution to form a polyamic acid film in which the powder composed of a polymer material was dispersed, and then the polyimide acid polyimidization.

The polyimide obtained by the above process is put into an electric furnace for firing treatment. The temperature curve adopted in this embodiment is the same as that of the above-mentioned embodiment 1-1.

As a result, first, in the pre-firing process, the second organic polymer part is thermally decomposed and converted into a carbon film, and at the same time, the organic polymer powder contained inside is also carbonized.

It was confirmed that during the main firing process, the second organic polymer part was converted into a graphite structure in which graphite layers were laminated, and at the same time, the carbonized part of the organic polymer powder was also carbonized and converted into graphite having a layered structure.

The thermal conductivity of the graphite structure containing graphite powder obtained as above was evaluated. The results show that the thermal conductivity κ‖ in the plane direction is the same as that of Example 1, which is about 600W/m·K. In addition, the thermal conductivity κ⊥ in the layer direction (thickness direction) is 20 to 40 W/m·K.

Therefore, it can be seen that graphite powder with high thermal conductivity in the plane direction and improved thermal conductivity in the layer direction can also be obtained by dispersing graphite powder starting from a polymer powder material in a graphite structure with high orientation. structure.

(Example 1-8)

A heat dissipation system was tested using a high thermal conductivity member composed of the graphite structure obtained in Example 1-1 above, and its thermal resistance was measured. FIG. 9( a ) is a structure in which the high thermal conductivity member 9 of the present invention is placed in close contact between the heat source 8 and the heat dissipation member 10 to dissipate heat. For comparison, evaluation was also performed on the case where a copper plate and highly oriented graphite (PGS graphite flake produced by Panasonic) were applied. The measurement was performed under a constant pressure (10 N/cm ² ).

As a result, when a copper plate was used, the thermal resistance was 1.0°C/W, and when a highly oriented graphite sheet was used, the thermal resistance was about 0.4°C/W. On the contrary, when the high thermal conductivity member of the present invention was used, the thermal resistance was 0.3°C/W, and it was confirmed that the thermal resistance characteristics were improved.

In addition, in the structure of FIG. 9( b ) or FIG. 9( c ), it was also confirmed that the heat dissipation characteristics were improved.

(Example 2-1)

An example will be described in which a carbon nanotube (CNT) is used as a carbon structure material, polyimide is used as an organic polymer for mixing and dispersing the CNT, and a graphite structure is produced by firing the CNT.

First, a polyamic acid solution is prepared as a precursor organic polymer solution of polyimide. The process is: in a dry box filled with nitrogen (N ₂ ), add 5.00 g of bis(4-aminophenyl) ether and 250 ml of dimethylacetamide into a round-bottomed flask, stir to dissolve them.

5.45 g of pyromellitic anhydride was added to the above solution, and stirred for about 3 hours to synthesize a polyamic acid solution as the first organic polymer.

CNTs (length: ~1 μm) pulverized by a jet mill or the like were mixed into the obtained polyamic acid solution at a weight ratio of 0.5%, and ground by a ball mill for 12 hours to uniformly disperse them in the solution.

The thus prepared CNT-containing polyamic acid solution was coated on a slide to form a CNT-containing polyamic acid film (thickness: ~150 μm). This coating film was dried in a nitrogen atmosphere for more than 1 hour, and dried under reduced pressure in a vacuum oven at room temperature for 2 hours, and then heated to 100° C. for 1 hour of heat treatment. As a result, a dark gray film was obtained.

The obtained film was placed in carbon nanotubes, and after decompression to vacuum, heat treatment was performed at 300° C. for 1 hour to form a CNT-containing polyimide film.

The obtained polyimide film was peeled off from the slide, and its thickness was measured with a micrometer, and it was about 15 μm.

The carbon precursor organic polymer film obtained by the above steps is put into an electric furnace for firing treatment. Fig. 8(a) shows the temperature profile of the pre-firing used in this example.

First, as pre-firing, the temperature was raised from room temperature to 1200° C. at a rate of temperature increase of 3° C./min in an Ar gas atmosphere, and kept at a pre-firing temperature of 1,200° C. for 3 hours. The rate of temperature rise can be determined in consideration of the type and shape of the organic polymer film to be fired. Usually, it can be in the range of 1° C./min to 15° C./min. In this embodiment, 3° C./min is used. After the firing treatment, cool down to room temperature at a cooling rate of 5°C/min. Usually, the temperature drop rate during cooling does not need to be controlled as strictly as the temperature rise rate, but it is preferably 1°C/min to 10°C/min, and 5°C/min is used in this embodiment.

In this pre-firing step, it is observed that the organic polymer film is heated and decomposed to release nitrogen, oxygen, and hydrogen. As a result, it is converted into a carbonized film in which CNTs are dispersed in a weight ratio of 50 to 60% of the starting material. Therefore, there is no effect on the dispersed CNTs.

After pre-firing under the above conditions, the sample was transferred to an ultra-high temperature furnace for main firing. Its temperature curve is shown in Fig. 8(b). In this embodiment, the temperature is raised to 1000° C. at a rate of 10° C./min, then lowered to 5° C./min, and kept at an intermediate treatment temperature of 2200° C. for 1 hour. Then the temperature is raised to the main firing temperature of 2700° C. at a heating rate of 5° C./min, and the holding time at 2700° C. is 3 hours. After the main firing, keep the temperature and cool down to 2200°C at a cooling rate of 5°C/min, then to 1300°C at a cooling rate of 10°C/min, and to room temperature at a cooling rate of 20°C/min.

The film thickness of the graphite structure thus obtained was about 30 μm. When the cross-section of the obtained structure was observed with a scanning electron microscope (SEM), it was confirmed that it had a graphite structure in which graphite layers were stacked in layers. It was also observed that pre-mixed and dispersed CNTs were arranged across the graphite layers oriented in the plane direction.

As a result of evaluating the crystal structure of the formed graphite structure by X-ray diffraction, graphite (002) and its higher sub-peaks were observed, which were equivalent to those in FIG. 5 . From this, it can be seen that even when CNT is contained, a graphite structure with high in-plane orientation can be sufficiently obtained.

The thermal conductivity of the CNT-containing graphite structure obtained in the above steps was evaluated. As a result, the thermal conductivity κ∥ in the plane direction was ~980 W/m·K, which was approximately the same value as that of the graphite structure produced without CNT. On the other hand, the thermal conductivity κ⊥ in the layer direction (thickness direction) is 50 to 60 W/m·K, approximately 10 times higher than before.

Therefore, it was confirmed that by mixing and dispersing CNTs in a graphite structure with high orientation, a graphite structure with high thermal conductivity in the layer direction can be obtained.

(Example 2-2)

By the same procedure as in Example 2-1, when producing a high thermal conductivity member composed of a graphite structure, the concentration of CNTs to be mixed/dispersed was changed.

The CNT in the polyamic acid of the first organic polymer solution was varied in the range of 10 ppm to 10% by weight to form a highly thermally conductive member composed of a graphite structure.

As a result of evaluating the thermal conductivity of the obtained sample, it was found that the in-plane thermal conductivity κ∥ was 900 to 980 W/m·K, which was the same as that in Example 2-1 above. On the other hand, the thermal conductivity κ⊥ in the layer direction is 10 to 70 W/m·K.

(Example 2-3)

Through the same process as in Example 2-1, the concentration of the polyamic acid solution was adjusted so that the thickness of the polyimide film was about 50 μm, and a second organic polymer polyimide film was produced.

When this sample was fired under the same temperature profile as in Example 2-1, it was confirmed that many fine pores ("voids 4" in Fig. 2 ) existed inside the obtained graphite structure. The reason for this is not clear, but it was found that when the thickness of the polyimide film as a carbon precursor was increased in the main firing step, a porous graphite structure with many void regions was formed.

The thermal conductivity of the sample was evaluated, and the results showed that the thermal conductivity κ‖ in the plane direction decreased to 600-750W/m·K, but the thermal conductivity κ⊥ in the layer direction remained at 50W/m·K. This is considered to be because the degree of orientation in the plane direction was slightly lowered due to the inclusion of voids. On the contrary, since the graphite structure produced in this example has many minute void regions inside, as a result, a highly thermally conductive member having excellent bendability and compressibility can be obtained.

(Example 2-4)

In Example 2-1, CNTs were used to produce a high thermal conductivity member, and diamond particles were added to the graphite structure in this example.

In this example, diamond particles with an average particle diameter of 1 μm were mixed into polyamic acid by the same method as in the above example, polyimidized, and then fired to produce a graphite structure.

The thermal conductivity of the obtained samples was evaluated, and the results showed that the thermal conductivity in the plane direction κ‖ (700-900W/m·K) and the thermal conductivity in the layer direction κ⊥ (∼50W/m·K) both obtained approximately the same value.

Also, when the average particle diameter of the diamond particles to be mixed is changed within the range of 0.1 to 10 μm, the same high thermal conductivity member can be obtained.

(Example 2-5)

The carbon precursor organic polymer material used in Example 2-1 is polyimide, but it was confirmed that graphite containing a carbon structure can be produced by the same production method as above even if other organic polymer materials are used structure. After adding a carbon structure to various precursor solutions to form a film, the film obtained by thermal dehydration polymerization or the like is fired under a predetermined temperature profile to produce a high thermal conductivity member. Specifically, in addition to polyimide, polyparaphenylene terephthalamide (PPTA), polyphenylene oxadiazole (POD), polybenzothiazole (PBT), polybenzobithiazole (PBBO), polyphenylenebenzimidazole (PBI), polyphenylenebenzimidazole (PPBI), polythiazole (PT), polyparaphenylenevinyl (PPV) and other organic polymer materials, also A graphite structure containing a carbon structure can be obtained.

(Example 2-6)

The carbon structures used in Examples 2-1 and 2-4 were CNT and diamond, but it was confirmed that even if other carbon structural materials were used, a graphite structure containing a carbon structure could be produced by the same production method as above. body. Specifically, a highly thermally conductive member (a graphite structure containing a carbon structure) can be obtained by using a carbon structure such as fullerene or diamond-like carbon particles.

(Example 2-7)

A heat dissipation system was assembled using a high thermal conductivity member composed of the graphite structures obtained in Examples 2-1 to 2-6, and its thermal resistance was measured.

FIG. 9( a ) shows a system in which the high thermal conductivity member 9 of the present invention is brought into close contact between the heat source 8 and the heat dissipation member 10 to dissipate heat. In addition, as a comparison, the case of using a copper plate and a highly oriented graphite sheet was also evaluated in the same manner. The measurement was performed under a constant pressure (10 N/cm ² ).

As a result, the thermal resistance when using a copper plate was 1.0°C/W, and the thermal resistance when using a highly oriented graphite sheet was about 0.4°C/W. On the contrary, when the high thermal conductivity member of the present invention was used, the thermal resistance was 0.3°C/W, and it was confirmed that the thermal resistance characteristics were improved.

In addition, in the structure of FIG. 9( b ) or FIG. 9( c ), it was also confirmed that the heat dissipation characteristics were improved.

Industrial availability

The high thermal conductivity component of the present invention is not only useful as a heat dissipation system material for various electronic devices/components such as CPUs and lasers that require heat dissipation, but also can be processed into various forms and can be applied to Wide range of applications such as substrate stages, mask stages, etc. that require uniform heat dissipation.

Claims (25)

1. high thermal conductivity parts are dispersed in carbon granule in the high directionality graphite-structure body that is made of the graphite-like matrix and form, and it is characterized in that:

(1) the c axle of each graphite linings of the described graphite of formation is parallel;

(2) with the scope of thermal conductivity κ ‖ below the above 1000W/mK of 400W/mK of the vertical direction of described c axle;

(3) scope of thermal conductivity κ ⊥ below the above 100W/mK of 10W/mK of the direction parallel with described c axle.

2. high thermal conductivity parts as claimed in claim 1 is characterized in that:

The shape of described high thermal conductivity parts is film like, and described c axle is parallel with the thickness direction of described film.

3. high thermal conductivity parts as claimed in claim 2 is characterized in that:

The thickness of film is below the above 300 μ m of 10 μ m.

4. high thermal conductivity parts as claimed in claim 2 is characterized in that:

Described high thermal conductivity parts have snappiness.

5. high thermal conductivity parts as claimed in claim 1 is characterized in that:

In the X-ray diffractogram of described graphite-like matrix, have (002 ⁿ) peak of face, wherein, n represents natural number.

6. high thermal conductivity parts as claimed in claim 1 is characterized in that:

In the X-ray diffractogram of described graphite-like matrix, there is the peak of (002) face and (004) face.

7. high thermal conductivity parts as claimed in claim 1 is characterized in that:

Emptying aperture is contained in the inside of described graphite-like matrix.

8. high thermal conductivity parts as claimed in claim 1 is characterized in that:

The density of described high thermal conductivity parts is at 0.3g/cm ³Above 2g/cm ³Following scope.

9. high thermal conductivity parts as claimed in claim 1 are characterised in that altogether:

The scope of the content of described carbon granule below 10 weight % more than 10 ppm by weight.

10. high thermal conductivity parts as claimed in claim 1 is characterized in that:

Described carbon granule is 1) graphite granule and 2) in the carbon structure beyond the graphite granule at least a kind.

11. high thermal conductivity parts as claimed in claim 10 is characterized in that:

Described carbon structure is at least a kind in carbon nanotube, soccerballene, diamond and the diamond-like-carbon.

12. high thermal conductivity parts as claimed in claim 1 is characterized in that:

Part or all of described carbon granule is graphite granule.

13. high thermal conductivity parts as claimed in claim 1 is characterized in that:

The scope of the median size of described carbon granule below 20 μ m more than the 0.05 μ m.

14. high thermal conductivity parts as claimed in claim 1 is characterized in that:

The shape of described carbon granule is laminar.

15. a manufacture method is used for making the method that carbon granule is dispersed in the high thermal conductivity parts that the high directionality graphite-structure body that is made of the graphite-like matrix forms, and it is characterized in that, comprising:

(1) modulation contains polyamic acid and the modulating process of mixed solution that is selected from carbon granule and its precursor granules at least a kind discrete particles;

(2) use described mixed solution, form and make the film formation operation of filming of described particles dispersed in described polyamic acid; (3) make the imidization operation of described polyamic acid imidization; (4) by described filming heat-treated, obtain the heat treatment step of described high thermal conductivity parts.

16. manufacture method as claimed in claim 15 is characterized in that:

Part or all of described discrete particles is at least a kind carbon structure particle in carbon nanotube, soccerballene, diamond and the diamond-like-carbon.

17. manufacture method as claimed in claim 15 is characterized in that:

Part or all of described discrete particles is graphite granule.

18. manufacture method as claimed in claim 15 is characterized in that:

Described precursor granules is a polyimide particles.

19. manufacture method as claimed in claim 15 is characterized in that:

Thermal treatment has: the pre-burned operation of 1) firing in the temperature range below 1500 ℃ more than 1000 ℃; With 2) the main ablating work procedure in the temperature range below 3000 ℃ more than 2000 ℃, fired.

20. a heat-removal system has pyrotoxin, thermal component and high thermal conductivity parts, it is characterized in that:

(1) described pyrotoxin and thermal component are by the hot tie-in of high thermal conductivity parts;

(2) described high thermal conductivity parts are the described high thermal conductivity parts of claim 1.

21. heat-removal system as claimed in claim 20 is characterized in that:

The shape of described high thermal conductivity parts is film like.

22. heat-removal system as claimed in claim 21 is characterized in that:

Pyrotoxin is set to contact with pellicular front with at least one side of thermal component.

23. heat-removal system as claimed in claim 20 is characterized in that:

Described high thermal conductivity parts have snappiness.

24. heat-removal system as claimed in claim 20 is characterized in that:

Described high thermal conductivity parts have the bend more than 1 or 2.

25. heat-removal system as claimed in claim 20 is characterized in that: described thermal component is a radiator element.

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