JPH11240706A - Preparation of graphite sheet and graphite sheet laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a graphite sheet having electroconductivity and high heat conductivity of characteristics of the graphite sheet as a base, and capable of allowing a plural number of sheets thereof to be laminated, and further to produce the graphite sheet laminate. SOLUTION: This method for producing a graphite sheet comprises subjecting a plural number of sheets of graphite film sandwiching a soft metal 2 such as indium to a rolling treatment so that the metal 2 may enter fine concavoconvexs on the surfaces of the graphite sheets at both sides to make the graphite sheets 1 stick to each other. The graphite sheets are stuck and integrated by the production method to form the graphite laminate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a graphite sheet and a graphite sheet laminate, and more particularly to a method for manufacturing a graphite sheet which is a flexible graphite sheet and provides a conductive material having good heat conduction and heat radiation characteristics. The present invention relates to a method and a graphite sheet laminate, which can be applied to heat dissipation of a high-power electronic device that generates a lot of heat.

[0002]

2. Description of the Related Art Conventionally, graphite sheets occupy an important position as industrial materials because of their heat resistance, chemical resistance, and high electrical conductivity, and are widely used as heat conductive materials, heat-resistant seals, electrodes, and the like. ing.

[0003] This sheet is artificially produced, and is described in, for example, page 118 of Shin Carbon Industry (issued in October, 1980, Toshiki Ishikawa, Modern Editing Co., Ltd.). Are known.

Specifically, in the so-called expanding method, flake natural graphite is treated with a mixed solution of sulfuric acid and nitric acid, and then rapidly heated to a high temperature of about 1000 ° C. to cause an interlayer (C-axis direction). Along the way, the graphite sheet is expanded by tens to hundreds of times the apparent thickness of the starting sample graphite, and then compression molded with a binder to form a graphite sheet.

[0005] The sheet produced in this way has the characteristics of having compression restorability, being excellent in stress relaxation, and being excellent in flexibility and thermal conductivity.

However, since the powder is formed into a film shape by molding, the characteristics are limited, and improvement in each characteristic has been desired.

Further, in this method of manufacturing a graphite sheet, since sulfuric acid or nitric acid is used to spread the layers, the cleaning is performed with water or the like, but it cannot be completely removed.

[0008] Therefore, when the acids remaining after forming into a film or the like are used for a long time as a gasket material or the like, phenomena such as leaching out gradually and corroding metals occur.

Further, since the film is processed by using a binder or the like, the contact property between the flaky graphite is deteriorated, and the heat conduction and electric conduction characteristics peculiar to graphite are sufficiently exhibited as a film. It is difficult to be peeled off, and the degree of bonding is weak, so that it tends to peel off like a scale.

[0010] Furthermore, it is weak in bending in terms of flexibility, and it is impossible to use it by bending. In many cases, thermal conductivity is usually several times lower than that of copper.

On the other hand, a method has been proposed in which a flexible sheet-like graphite is directly obtained by heat-treating, rolling and ironing a polyimide film.

The graphite sheet has physical properties similar to those of single-crystal graphite, and is free from problems such as scale-like exfoliation and residual acid, and is a high-quality, highly bendable and highly flexible material. Becomes

Further, since a large-area product can be easily manufactured, and has extremely high thermal conductivity and high flexibility, it is necessary to dissipate heat or uniform heat as a material for heat transfer. It has been used in many places.

As described above, a flexible graphite sheet obtained by heat-treating, rolling, and ironing a polyimide film has excellent conductivity and heat conductivity. 1 mm or less due to the thickness and the ease of the thermal decomposition reaction in the carbonization process.
Or less.

In order to cool a portion that generates a large amount of heat or to transfer a large amount of heat, it may not be enough to use this graphite sheet. Need to use it.

[0016]

However, graphite sheets themselves generally have very low surface reactivity, so they are very slippery to each other, and the workability is not improved at all when graphite sheets are used in layers.

Further, when the graphite sheets are merely stacked, the heat conduction in the direction perpendicular to the surface of the sheets, that is, between the graphite sheets remains extremely poor, and a large amount of heat cannot be transmitted.

[0018] On the other hand, although graphite has conductivity, it does not always have a sufficiently high conductivity as compared with metal. In this regard, it is necessary to transfer electricity with metal and heat with graphite. This is very convenient if it can be performed, but the surface of graphite itself is very stable, so that it cannot be bonded with commonly used solder or the like.

That is, in order to widely apply the graphite sheet as a heat conductor, a method of bonding and integrating the graphite sheets with each other or the graphite sheet and the metal is indispensable.

For example, a thin film of a metal or nickel which is familiar with graphite is formed on the surface of a graphite sheet by a vapor deposition method or the like, and may be adhered by soldering. Not only is the property poor, but the work of stacking many sheets is not easy.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a graphite sheet capable of stacking a plurality of sheets without impairing them while maintaining the electrical conductivity and the high thermal conductivity which are characteristics of the graphite sheet. An object of the present invention is to provide a manufacturing method and a graphite laminate.

[0022]

In order to solve the above problems, the present invention is to roll a plurality of graphite films sandwiching a soft metal such as indium, and the metal is applied to the surface of the graphite sheet on both sides. A graphite sheet manufacturing method in which graphite sheets are bonded to each other by penetrating into fine irregularities, and a graphite laminate by such a manufacturing method.

With such a configuration, a graphite sheet manufacturing method and a graphite laminate, which can be stacked on a plurality of sheets without damaging them based on the electrical conductivity and high thermal conductivity which are the characteristics of the graphite sheet I will provide a.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention according to claim 1 has a thickness of 3 mm.
A pretreatment step of heating a film capable of being graphitized to a size of not more than 00 μm in an inert gas from room temperature to a temperature range of 1000 ° C. to 1600 ° C .; This processing step of sintering to a temperature of not less than ℃ to obtain a graphite sheet, and a rolling processing step of rolling the graphite sheet obtained in the main processing step, wherein in the rolling processing step, the graphite sheet This is a method of producing a graphite sheet in which a plurality of metal materials are arranged between graphite sheets and stacked and rolled.

According to such a configuration, after forming a foamable graphite sheet comprising only carbon atoms, when a more uniform and flexible graphite sheet is formed, a metal material is introduced into the irregularities on the surface of the graphite sheet.
The graphite sheets are bonded together like a so-called anchor effect, and based on the electrical conductivity and high thermal conductivity that are the characteristics of graphite sheets, they are bonded and integrated without damaging them. A laminate is provided.

Incidentally, such a graphite sheet is
The raw material polymer film is selected from polyphenylene oxadiazole, polybenzothiazole, polybenzobisthiazole, polybenzoxazole, polybenzobisoxazole, polythiazole, aromatic polyamide, aromatic polyimide, as it is or cylindrical graphite carbon. The graphite sheet is heated and carbonized in an inert gas or in a vacuum at a temperature of 1800 ° C. or more, particularly a temperature process as described in claim 1.

[0027] After being graphitized, a sheet which is given flexibility by rolling with a press or a roller is, in principle, referred to herein as a graphite sheet.

Here, it is preferable that the metal material is any one of indium, tin, lead and zinc, or an alloy containing the metal material as a main component.

With such a soft metal material, it is possible to surely enter the irregularities on the surface of the graphite sheet.

According to a third aspect of the present invention, the metal material is a foil having a thickness of 10 μm to 200 μm, or as described in a fourth aspect, the metal material has a thickness of 10 μm.
6. The metal material according to claim 5, wherein the metal material has a thickness of 10 μm to 300 μm.
It is preferable that the metal material is in the form of a thin wire having a diameter of m or a mesh having a thickness of 10 μm to 300 μm, or the metal material is in the form of a powder having a diameter of 10 μm to 500 μm.

The reason for this is that if the metal material is smaller than this, the unevenness of the graphite surface will enter and the bonding effect will be lost, and if the metal material is larger than this, the graphite sheet itself will be broken during rolling. is there.

Further, particularly when the material is strongly rolled, it is preferable that the material is in the form of a fine wire or a mesh of fine wires, or a powder.

In the above, as described in claim 7, the temperature at the time of rolling in the rolling process is preferably in the range of −50 ° C. or higher and + 30 ° C. or lower than the melting point of the metal material. .

That is, when the carbonized film is rolled by a press or a roller, the temperature of the roller is not lower than the melting point of the metal material provided between the carbonized films by 50 ° C. or more and does not exceed a temperature higher by 30 ° C. By setting it to be within the range, the metal material enters the concave of minute irregularities on the graphite sheet surface in a softened state,
It can be solidified as it is.

If the temperature is lower than this, the metal material is hard and breaks the graphite, and if the temperature is higher than this, the metal material is completely melted and extruded from between the graphite sheets during rolling. Even if it is not extruded, or if it is not extruded, it is in a molten state for a while after passing through the roller, so that it comes out of a small dent due to its own surface tension and has no anchoring effect.

Further, as described in claim 8, in the rolling step, a configuration may be adopted in which a thin metal plate is also arranged between a plurality of graphite sheets, and the rolling process is performed using a metal material.

With such a configuration, a graphite sheet laminate in which a graphite sheet and a metal thin plate are sequentially laminated and bonded and integrated with a metal material is provided.

In this case, in the rolling step, the graphite sheet is rolled before disposing the metal thin plate, and a claim is provided between the rolled graphite sheet and the metal thin plate. It is preferable to arrange the metal material described in any one of 2 to 6 and perform the rolling treatment from the viewpoint of more surely bonding and integrating the thin metal plate.

Further, even when the metal thin plate contains a metal material harder than the metal material, the bonding and integration can be performed.

More specifically, the metal material of the thin metal plate may be any one of aluminum, copper and zinc, or an alloy containing the metal material as a main component.

In particular, in the case of a copper thin plate, it is preferable to use a solder (an alloy containing lead and tin as a main component) as a metal material to be sandwiched between the copper thin plates because they are securely bonded.

Alternatively, the metal material of the thin metal plate may be stainless steel.

In particular, when stainless steel is used, the surface of the sheet can be made glossy.

In the case where such a hard metal sheet is also laminated, the temperature at the time of rolling in the rolling process is -30 degrees or more higher than the melting point of the metal material. The temperature must be within the range of + 70 ° C. or lower, and it is necessary to set the temperature to a higher temperature side as compared with a case where a thin metal plate is not used.

In the above, as described in claim 14,
In the rolling process, the graphite film is given a rolling action and an ironing action by a press, and the pressure of the press is 5 k.
It is more preferably in the range of not less than g / cm 2 and not more than 70 kg / cm 2, from the viewpoint of the reliability of adhesive integration.

Alternatively, in the rolling step, the rolling action and the ironing action are applied to the graphite film by the roller, and the force of the rolling portion of the roller is reduced to 1%.
Similarly, it is more preferable to be within the range of not less than kg / cm and not more than 7 kg / cm, from the viewpoint of the certainty of bonding and integration.

In the above, as described in claim 16,
After obtaining a laminated graphite sheet in a rolling process step, a plurality of sets of the laminated graphite sheets are further laminated, and the metal material according to any one of claims 2 to 6 is arranged between the plurality of sets of the graphite sheets and rolled. It is also possible to perform the treatment, and the graphite sheet can be rolled more efficiently than when laminating and rolling one by one.

On the other hand, according to the present invention, a plurality of flexible graphite sheets having a film thickness of 1 mm or less use the metal material according to any one of claims 2 to 6. This is a graphite sheet laminate that has been bonded and integrated, and a metal material has penetrated into the unevenness of the surface of the graphite sheet and has been bonded and integrated.

Alternatively, as described in claim 18, the film thickness 1
A graphite sheet having flexibility of not more than 2 mm and a metal thin plate are a graphite metal laminate bonded and integrated using the metal material according to any one of claims 2 to 6, wherein the metal material is a graphite sheet. Into the irregularities on the surface of the substrate, and also bond with the metal thin plate, and are integrated by bonding.

Hereinafter, a more specific description will be given in accordance with each embodiment of the present invention. (Embodiment 1) In the present embodiment, first, as a starting polymer film, a polyimide film (trade name: Kapton) manufactured by Toray DuPont having a thickness of 50 μm was used.

Next, in order to obtain foamability by heat treatment,
The pre-baking was performed in nitrogen at a heating rate of 5 ° C./min at a maximum processing temperature of 1200 ° C.

Then, the main firing is performed in an Ar gas atmosphere at a heating rate of 20 ° C./min.
And

The film in this state was in a foamed state, but had no flexibility and was hard and brittle.

Next, two carbonized and graphitized films were prepared, and a thickness of 50
A μm metal indium foil was placed, and another carbonized graphite sheet was placed thereon.

Then, the temperature of the roller is raised to 150 ° C.
1 in the roller axis direction
Rolled at 1 kg per cm.

FIG. 1 is a schematic cross-sectional view of the structure obtained by integrating the two graphite sheets thus obtained.

In FIG. 1, 1 is a graphite sheet,
2 is metal indium. The bonding surface between the carbon atoms constituting the graphite sheet thus obtained is
On average, it is almost parallel to the plane of the sheet.

However, when viewed in detail, the smaller one has irregularities ranging from a minute one at the level of an electron microscope to a maximum of about 10 μm.

The metal indium enters the irregularities and is solidified, and the upper and lower graphite sheets are joined and integrated by the metal indium.

The graphite sheet thus bonded is harder in terms of flexibility than that obtained by merely stacking two graphite sheets, but can be repeatedly bent, and peeling and cracking occur. I never did.

Furthermore, in particular, the thermal conductivity in the stacking direction shows an excellent result of 1.5 to 5 times as compared with the case where a graphite sheet is simply stuck with a polymer heat-resistant adhesive. This is a very important property when a graphite sheet is used as a heat transfer material.

As a result of various experiments, it was found that the thickness of the indium foil to be used is preferably about 10 μm to 200 μm, since if it is too thin, it will not be possible to adhere, and if it is too thick, it will tend to break graphite.

When the temperature of the roller during rolling is too low, indium does not soften, and it tries to form a lump between graphite sheets, and rather breaks the sheets.
On the other hand, if the temperature of the roller is too high, the indium will melt sufficiently and the viscosity will decrease, and it will be extruded from between the graphite sheets during rolling and will not adhere, so in order to adhere well, in the case of indium foil 13
0 ° C to 160 ° C was a suitable range for the roller temperature.

However, this temperature depends on the size and rotation speed of the roller, the number of graphite sheets to be stacked, and the like.
Although it has a width of about 10 ° C., generally speaking, it can be said that an appropriate temperature range is within a range of −50 ° C. or higher and + 30 ° C. or lower than the melting point of indium.

As the starting polymer film, 30
Similar results were obtained when various of the above-mentioned various materials having a thickness of 0 μm or less were used.

Similar results were obtained not by rolling with rollers but by pressing. Here, in the case of rolling by a roller, the force of the rolling portion of the roller is 1 kg / c.
m or more and within a range of 7 kg / cm or less.

On the other hand, in the case of rolling by a press, the pressure of the press is 5 kg / cm 2 or more and 70 kg / cm 2
It is appropriate to be within the range of 2 or less.

It is needless to say that the present invention is not limited to the above-described foil shape, but may be a ribbon shape obtained by appropriately dividing the foil.

Of course, the number of layers is not limited to two, but may be a multilayer. (Embodiment 2) In this embodiment, except that the indium to be placed between the graphitized films is not a foil but a fine wire having a diameter of 50 μm,
When a graphite sheet laminate was prepared in the same manner as
The graphite sheet was locally adhered at the portion where the fine wire was installed.

The temperature of the roller to which this bonding is performed can be set in a wider range of about 20 ° C. than in the case of the foil.

Various kinds of indium fine wires were prepared and tested to find that the diameter was 400 μm and 5 μm.
Was not successful, so the limit for the thicker was about 300 μm in diameter, and the limit for the thinner was
It is considered that the diameter is about 10 μm when estimated from the case of foil.

(Embodiment 3) In the present embodiment, indium to be placed between the graphitized films is not foil but indium fine particles, specifically powder having a typical average diameter of 45 μm. Except for the fact that a graphite sheet laminate was produced in the same manner as in Embodiment 1, the graphite sheet was adhered with indium powder.

The temperature of the roller to which this bonding was performed was possible within the same range as that of the case of the foil.

When various kinds of indium particles were prepared and tested, the average diameter was 600 μm and the average diameter was 5 μm.
It was considered that the larger limit was about 500 μm in diameter, and the smaller limit was about 10 μm in diameter because the μm did not work.

(Embodiment 4) In this embodiment, various types of metal sandwiched between graphite sheets have been tried, but those that can be bonded are limited to soft metals such as tin and lead in addition to indium. Was.

On the other hand, although zinc and the like are soft, it is necessary to raise the temperature considerably in order to enter the fine irregularities of the graphite, and it is not practical. The flexibility was almost lost, and it was not practical for the purpose of obtaining a soft heat conductor which was the purpose.

(Embodiment 5) In this embodiment, an indium foil having a thickness of 50 μm is sandwiched between a graphite sheet and an aluminum foil, and a roller set at 150 ° C. is used.
When rolling was performed with a linear pressure of kg / cm, the graphite sheet and the aluminum foil were bonded.

However, as compared with the first embodiment, the temperature at the time of the rolling treatment by the roller is lower than the melting point of the metal material by-
It was necessary that the temperature was 30 ° C. or higher and + 70 ° C. or lower.

Further, a lead-tin alloy was used as a metal to be interposed therebetween, and 3 kg / cm
When rolled at a linear pressure of, the graphite sheet could be bonded to a copper plate.

(Embodiment 6) In this embodiment, the first embodiment is carried out except that the pre-baking is performed in nitrogen at a heating rate of 5 ° C./min and the maximum processing temperature is set to 1600 ° C.
In the same manner as described above, a graphite sheet was produced.

The sheet in the state after the main firing was in a foamed state, but had no flexibility and was hard and brittle.

A graphite sheet laminate was produced from the graphite sheet thus produced in the same manner as in Embodiments 1 to 3, and the graphite sheet was adhered.

In the same manner as in the fourth embodiment, various types of metals were tried as the metal sandwiched between the graphite sheets, but the materials that can be adhered were limited to soft metals such as tin and lead in addition to indium.

In the same manner as in the fifth embodiment, an indium foil having a thickness of 50 μm is sandwiched between a graphite sheet and an aluminum foil, and 1 kg / c is applied using a roller set at 150 ° C.
When the sheet was rolled with a linear pressure of m, the graphite sheet and the aluminum foil were bonded.

Further, a lead-tin alloy was used as a metal to be interposed therebetween, and 3 kg / cm
When rolled at a linear pressure of, the graphite sheet could be bonded to a copper plate.

The maximum processing temperature of the pre-firing is set to 1400
When the same experiment as above was performed at a temperature of ° C., the same result as above was obtained.

[0087]

As described above, according to the present invention, a plurality of graphite sheets obtained by heat-treating a polymer are laminated, rolled with a soft metal interposed therebetween, and adhered and integrated to obtain a flexible sheet. A multilayer graphite sheet capable of transferring a large amount of heat without substantially impairing the properties is obtained.

In addition, a thin metal plate such as an aluminum foil is bonded to a graphite sheet to produce a material having both high electrical conductivity and high thermal conductivity, and a structure having high thermal conductivity can be widely applied. The effect is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a graphite sheet laminate according to a first embodiment of the present invention.

[Explanation of symbols]

 1 Graphite sheet 2 Indium foil

Claims (18)

[Claims] 1. A graphitizable film having a thickness of 300 μm or less is heated from room temperature to 100
A pre-treatment step of firing at a temperature in the range of 0 ° C. to 1600 ° C .;
This processing step of sintering to a temperature of 00 ° C. or more to obtain a graphite sheet, and a rolling processing step of rolling the graphite sheet obtained in the main processing step, wherein in the rolling processing step, the graphite sheet is A method for producing a graphite sheet in which a plurality of metal materials are arranged between graphite sheets and stacked and rolled. 2. The method for producing a graphite sheet according to claim 1, wherein the metal material is any one of indium, tin, lead, and zinc, or an alloy containing the metal material as a main component. 3. The method according to claim 1, wherein the metal material has a thickness of 10 μm to 200 μm.
The method for producing a graphite sheet according to claim 1, wherein the graphite sheet has a thickness of μm. 4. The method according to claim 1, wherein the metal material has a thickness of 10 μm to 200 μm.
The method for producing a graphite sheet according to claim 1, wherein the graphite sheet has a ribbon shape of μm. 5. A metal material having a thickness of 10 μm to 300 μm.
Fine line or thickness of 10 μm to 300 μm
3. A mesh comprising a thin wire which is
A method for producing the described graphite sheet. 6. A metal material having a diameter of 10 μm to 500 μm.
The method for producing a graphite sheet according to claim 1 or 2, which is in the form of a powder having a size of μm. 7. The temperature at the time of the rolling process in the rolling process step is higher than the melting point of the metal material by -50 degrees or more and +30 degrees.
The method for producing a graphite sheet according to any one of claims 1 to 6, wherein the temperature is in the range of not higher than 0C. 8. The method for producing a graphite sheet according to claim 1, wherein in the rolling treatment step, a thin metal plate is also arranged between the plurality of graphite sheets, and the rolling treatment is performed using a metal material. . 9. The rolling treatment process according to claim 2, wherein the graphite sheet is rolled before disposing the metal sheet, and between the rolled graphite sheet and the metal sheet. 9. The method for producing a graphite sheet according to claim 8, wherein a rolling process is performed by disposing a metal material. 10. The method for producing a graphite sheet according to claim 8, wherein the metal sheet contains a metal material harder than the metal material. 11. The method for producing a graphite sheet according to claim 10, wherein the metal material of the thin metal plate is any one of aluminum, copper, and zinc, or an alloy containing the metal material as a main component. 12. The method for producing a graphite sheet according to claim 10, wherein the metal material of the thin metal plate is stainless steel. 13. The temperature at the time of the rolling process in the rolling process step is higher than the melting point of the metal material by -30 degrees or more and +7.
The method for producing a graphite sheet according to claim 8, wherein the temperature is within a range of 0 ° C. or lower. 14. In a rolling step, the graphite film is rolled and ironed by a press, and the pressure of the press is 5 kg / cm 2 or more and 70 kg / c.
The method for producing a graphite sheet according to any one of claims 1 to 13, which is within a range of m2 or less. 15. In the rolling step, a rolling action and an ironing action are applied to the graphite film by a roller, and the force of the rolled portion of the roller is 1 kg / cm or more and 7 kg.
The method for producing a graphite sheet according to any one of claims 1 to 13, which is within the range of / cm or less. 16. After obtaining a laminated graphite sheet in a rolling process step, a plurality of sets of the laminated graphite sheets are further laminated, and the metal material according to claim 2 is interposed between the plurality of sets of the graphite sheets. The method for producing a graphite sheet according to any one of claims 1 to 15, wherein the graphite sheet is rolled. 17. A graphite sheet laminate in which a plurality of flexible graphite sheets having a thickness of 1 mm or less are bonded and integrated using the metal material according to claim 2. Description: 18. A graphite metal laminate in which a flexible graphite sheet having a thickness of 1 mm or less and a metal thin plate are bonded and integrated using the metal material according to claim 2. Description: