JP2022026653A - Graphite laminate, graphite plate, and manufacturing method of graphite laminate - Google Patents

Abstract

To newly provide a graphite laminate, graphite plate, and graphite laminate with high thermal conductivity easily by a simple process.SOLUTION: In graphite laminate 1 having anisotropic thermal conductivity, graphite film layers 10 and nano-metal-derived sintered nano-metal layers 20 with an average particle size of 100 nm or less are alternately laminated.SELECTED DRAWING: Figure 1

Description

The present invention relates to a graphite laminate, a graphite plate, and a method for producing a graphite laminate, which are high heat conductive materials using a graphite film.

As the speed, output, and density of electronic devices increase, the importance of heat countermeasures for heat-generating mounted parts is increasing. As a measure against heat, it is effective to use a material having as high a thermal conductivity as possible as a constituent member, and the industry is promoting the adoption or development of a material having excellent thermal conductivity.
Silver, copper, and aluminum, which are metallic materials, are well known as materials having excellent thermal conductivity, and are widely used as heat sink members for heat dissipation. In addition to the above materials, graphite has been attracting attention in recent years. Graphite has the second highest thermal conductivity after diamond in the plane direction in which crystal particles are lined up, and has nearly three times the thermal conductivity of copper. On the contrary, in the vertical direction of the crystal plane, the thermal conductivity is 1/200 or less lower than that of the crystal plane and has the characteristic of so-called anisotropic heat conduction. The study to make the best use of the anisotropic thermal conductivity of is being energetically promoted.
Conventionally, a graphite film is made of natural graphite by expanding the layers of natural graphite particles with sulfuric acid or the like, crushing the layers, and making them into scaly pieces in the same process as paper.
In addition, synthetic graphite graphite film, which is obtained by carbonizing the polyimide film and then graphitizing it by high heat treatment at nearly 3000 ° C, is also manufactured and sold. The thermal conductivity in the plane direction has a thermal conductivity of 1200 W / m · K or more, which is close to the theoretical value of graphite.

Utilizing the high thermal conductivity of graphite, a graphite film is attached to the back of the smartphone as an application of various heat countermeasure materials using graphite film, for example, in smartphones, as a measure to eliminate hot spots due to heat generation of the mounted semiconductor. It is used as a heat spreader by utilizing its high thermal conductivity in the plane direction. Further, after laminating graphite films to form a laminate, the sections cut perpendicular to the plane direction of the film are used as heat sinks for power semiconductors such as IGBTs and high-power LED elements or Pelche elements, which are eagerly awaited in the market. (Patent Document 1).

Various means have been tried as a method for producing the above-mentioned graphite laminate. For example, natural graphite and a metal are melt-mixed and then rolled into a sheet to form a graphite laminate in which graphite particles are oriented in the metal (Patent Document 2). Further, there is also known a means of laminating graphite films and then sintering the graphite films at a high temperature while applying pressure, or pressurizing and injecting molten metallic copper between the layers of the graphite films (Patent Documents 3 to 5). Further, a heat conductive material in which a graphite film is coated with an adhesive resin and then laminated is also known (Patent Document 6).

Japanese Unexamined Patent Publication No. 2013-4733 Japanese Patent No. 5640239 Japanese Patent No. 4711165 Japanese Patent No. 4490723 Japanese Patent No. 3345986 Japanese Unexamined Patent Publication No. 2019-10773

However, the structure and manufacturing means of the graphite laminate have problems. For example, a graphite laminate obtained by laminating and pressurizing only a synthetic graphite film and sintering it at a high temperature has excellent thermal conductivity, but the adhesive strength between the graphite layers is weak, and it is damaged during section processing and thin leaves. It was difficult to convert. In addition, the method of laminating a roll-rolled sheet after melting and kneading a metal such as copper or aluminum with natural graphite particles is as high as expected because the filling amount of the graphite particles is limited and the graphite particles are not continuously connected. No thermal conductivity has been obtained.
The method of press-fitting the molten metal between the graphite films has the disadvantage that the press-fitting device is large and the investment is large, which is disadvantageous in terms of manufacturing cost. Furthermore, when the press-fitting method was used for a synthetic graphite film with high density, it was difficult to manufacture because of poor wetting with molten copper, and it was possible to manufacture only when a natural graphite film was used. Therefore, the thermal conductivity is significantly inferior to that when the synthetic graphite film is used.
As described above, a method for producing a graphite laminate having a balance between performance and cost that sufficiently meets the market demand has not yet been established.

The graphite laminate, which is a graphite laminate, is thinned by cutting it with a dicer, a wire saw, or the like. This section serves as a heat radiating member that contributes to rapid heat transfer from the heat-generating component by utilizing the function of having high thermal conductivity. However, this section requires strength, productivity and price competitiveness necessary for shape retention.
INDUSTRIAL APPLICABILITY The present invention provides a new method for producing a graphite laminate, a graphite plate, and a graphite laminate having high thermal conductivity easily in a simple process, which can meet the above demands.

As a result of repeated studies on a new means for producing a graphite laminate that meets the above requirements, the present inventors have conducted low-temperature firing of metal nanoparticles as a method for forming a metal layer without injecting molten metal between graphite films. We have come up with the idea of applying the knotting reaction, and have found that a graphite laminate with excellent practical characteristics that can achieve both cost and performance can be obtained, and have reached the present invention.
The metal nanoparticles are fine metal particles having an average particle diameter of nanometer units, and in the present invention, metal particles having an average particle diameter of 100 nm or less are referred to as metal nanoparticles. In particular, it is known that silver nanoparticles having an average particle size of 20 nm or less cause a phenomenon of sintering at a low temperature of about 100 ° C., that is, a Gibbs-Thomson effect in which the curvature of the particles is inversely proportional to the sintering temperature.
In addition, silver nanopaste in which silver nanoparticles are dispersed in a solvent has been applied and developed in printed electronics technology used as a conductive circuit material. This feature is that the sintering reaction of nano-silver particles proceeds at low temperature to form a silver conductive circuit.
The graphite film used in the present invention has a strong bond between carbons in the in-plane direction, but is layered in the thickness direction and is a weak bond having only a van der Waals force. Therefore, it is known that the surface energy is extremely weak and the wetting with metal is poor. For example, if a molten metal is placed on a graphite film, it will not spread and will curl into a spherical shape.
The present inventors have studied various measures for improving the adhesiveness of the graphite film, and found that silver nanoparticles are used to have an anchoring effect on the surface of graphite with a carbon six-membered ring, and the affinity of the surface is improved. In anticipation, I tried to apply the nano-silver paste on the graphite film. Then, it was confirmed that a uniform silver nanoconjunctiva was formed on the graphite surface by heat treatment at 250 ° C., and it was found that a special effect could be obtained by the silver nanoparticles. Furthermore, applying this effect, graphite films coated with silver nanopaste are laminated in multiple stages, and by heating at 250 ° C. for 1 hour while applying a load of about 50 KPa, silver nanoparticles are sintered and a new graphite laminate is obtained. Was able to be obtained.

The graphite laminate according to the present invention is characterized in that a graphite film layer and a metal nanoparticle sintered layer derived from a nanometal having an average particle size of 100 nm or less are alternately laminated and have anisotropic thermal conductivity. do.
The graphite laminate can be configured such that the metal nanoparticles sintered layer is derived from a paste material containing silver nanoparticles.
The graphite laminate can be configured such that at least 30% by weight or more of the components of the metal nanoparticles sintered layer are derived from silver nanoparticles.

The graphite plate according to the present invention is a graphite plate obtained by cutting the graphite laminated body in the laminating direction of the graphite film layer and slicing it, and has higher thermal conductivity in the direction perpendicular to the cut surface than in the cut surface direction. It is characterized by having.

The method for producing a graphite laminate according to the present invention is a step of applying a paste material containing metal nanoparticles on the surface of a graphite film, and a paste containing metal nanoparticles by drying a graphite film on which the paste material is applied on the surface. In the process of forming a graphite film coated with a material, the graphite film coated with the paste material is laminated in multiple layers and heat-treated under pressure at 250 ° C. or lower to sinter the paste material and form a graphite film layer. It is characterized by comprising a step of obtaining a graphite laminate in which and metal nanoparticles sintered layers are alternately laminated.
In the method for producing a graphite laminate, the step of applying the paste material may be a step of applying the paste material to one side or both sides of the graphite film.

According to the present invention, it is possible to provide a graphite laminate having high adhesion strength between laminated graphite layers and excellent thermal conductivity, and a method for producing the same. In addition, it does not require heat treatment at a high temperature of 1000 ° C or higher or press-fitting of molten metal, and it is excellent in productivity and can be made in a simple process with a small investment amount. Can be manufactured.

It is sectional drawing which shows the outline of the graphite laminated body which concerns on this embodiment. It is a figure for demonstrating the manufacturing method of the graphite laminate and the graphite plate which concerns on this Embodiment. It is a photograph which magnified and imaged the cut cross section of the graphite plate which concerns on Example 1 with an electron microscope. It is a photograph which magnified and imaged the cut cross section of the graphite plate which concerns on Example 3 with an electron microscope. It is a figure which shows the graphite laminated body which concerns on other embodiment.

An embodiment of the graphite laminate according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an outline of a graphite laminate according to the present embodiment. As shown in FIG. 1, the graphite laminate 1 according to the present embodiment has a structure in which a metal nanoparticle sintered layer 20 and a graphite film layer 10 in which graphite crystals are oriented in the plane are alternately laminated. ..

(Graphite film layer 10)
The graphite film layer 10 uses a graphite film as a starting material. The starting material is, for example, film-like graphite in which graphite crystals are oriented in the plane direction, but the orientation direction of graphite is not limited as long as it is in-plane. Both natural graphite and synthetic graphite can be preferably used as the starting material for the graphite film layer 10. A natural graphite film can be obtained in an arbitrary thickness by expanding the layers of rough graphite with an acid treatment such as sulfuric acid, crushing it into a scaly powder, and then making it in a liquid phase. Further, the synthetic graphite film can be produced by carbonizing the polyimide film in an inert atmosphere and then performing a graphitization treatment at a high temperature of about 3000 ° C. In particular, the synthetic graphite film obtained by carbonizing and graphitizing the polyimide film has a high thermal conductivity, and the thermal conductivity in the in-plane direction can show performance close to the theoretical value.

The thickness of the graphite film, which is the starting material of the graphite film layer 10, can be selected according to the required thermal conductivity, strength, and cost. When a natural graphite film is used, it is a thicker and harder film than synthetic graphite, and a graphite film having a thickness of 50 μm or more can be obtained. By using a thick graphite film, a graphite laminate with even higher rigidity can be obtained by heat sintering of silver nanopaste. When a synthetic graphite film is used, a graphite film having a thickness of 100 μm or less and being thinner and more flexible than a natural graphite film can be obtained because of the thermal decomposition of the polyimide film as a starting material. It should be noted that even after the silver nanopaste is applied and the nanosilver is sintered by heating, the rigidity of the graphite film is weak and the silver sintered layer is easily destroyed by an external force. As a means for improving this problem, the strength is improved by making fine through holes in the graphite film, applying silver nanopaste, and heat-sintering the graphite film. In order to obtain a high-density graphite laminate, it is desirable to laminate the graphite film layer 10 thickly when using a natural graphite film, and when using a synthetic graphite film, the thickness is 100 μm or less, more preferably thick. It is preferably as thin as 50 μm or less.

(Metal Nanoparticle Sintered Layer 20)
The metal nanoparticles sintered layer 20 is a layer formed by applying a paste material containing metal nanoparticles to a microfilm layer 10 and sintering the layers. The type of metal nanoparticles contained in the metal nanoparticles sintered layer 20 is not particularly limited as long as it is a metal having high thermal conductivity such as silver, copper, and aluminum, but it is preferable to use silver nanoparticles. The metal nanoparticles sintered layer 20 according to the present embodiment is formed by heating and sintering a coating film formed by applying a silver nanopaste material to a graphite film as a starting material as a starting material. The silver nanoparticles contained in the metal nanoparticles sintered layer 20 are not particularly limited as long as they are silver nanoparticles having an average particle size of 100 nm or less that are sintered by heating, in order to maintain the characteristics of the silver sintered layer. It is preferable that 30% or more of the solid content after heating contains silver nanoparticles. In the present embodiment, the coating film formed by applying the silver nanopaste material to the graphite film which is the starting material of the graphite film layer 10 is the starting material. The silver nanopaste material is not particularly limited as long as it is sintered at 250 ° C. or lower, preferably 200 ° C. or lower when 100% of silver nanoparticles are contained to form a continuous film. Low temperature sinterability can be exhibited by setting the silver nanoparticles to 20 nm or less. Paste materials containing such silver nanoparticles are being studied in the field of printed electronics technology to form electric circuits by coating or printing, and are available on the market. In particular, silver nanoparticles having an average particle size of 20 nm or less have the advantage that a circuit can be directly drawn on a non-heat resistant plastic film because silver is sintered at a low temperature of about 100 ° C.

In addition to the silver nanoparticles, an organic solvent or an additive for maintaining the function as a paste can be added to the silver nanopaste material. The organic solvent and the additive are not particularly limited as long as they do not inhibit the function of the graphite laminate 1 according to the present embodiment. In addition to low-temperature sintered silver nanoparticles, inorganic substances such as μm-order silver particles, silver oxide particles, ceramic particles such as alumina and silica, and silver are used for the purpose of promoting structural stability after silver sintering. Other metal particles such as copper and titanium and graphite particles can also be added. However, in that case, it is necessary that the silver nanopaste content is 30% by weight or more as a solid content, and a complete sintered layer can be obtained by treating at a slightly higher heating temperature of 200 to 250 ° C. after coating. ..

Further, in the metal nanoparticles sintered layer 20 according to the present embodiment, the silver nanopaste material to be surface-coated on the graphite film should be derived from nanosilver particles at least 30% by weight or more of the solid content remaining during heat sintering. For example, the remaining solid content may be a silver compound such as silver or silver oxide having a particle size of more than 1 μm. It has been confirmed that a paste having such a composition changes into a sintered body of metallic silver by heating at 250 ° C. or lower. Further, the remaining solid content can be used as long as it has a metal composition other than silver such as copper nanomaterials, and even if it is ceramic, it is in a state where graphite films are bonded to each other. When the content of silver nanoparticles is low, sintering does not proceed and a strong silver sintered layer cannot be obtained.

The silver nanoparticles sintered layer 20 is formed by applying a silver nanoparticles paste material on the graphite film layer 10, drying it, and heat-treating it in a state of being laminated in multiple layers so that the nanosilver particles can be formed on the fine uneven surface of the graphite film surface. It is considered to be sintered in a bitten state and exhibits high bonding strength. The thickness of the metal nanoparticles sintered silver layer 20 formed between the graphite film layers 10 is 100 μm or less after sintering in order to prevent cracks from occurring due to volume shrinkage, whereby a uniform graphite laminate can be obtained. Be done. Therefore, the coating thickness of the silver nanopaste varies depending on the solid content concentration, but can be, for example, about 100 μm on the assumption that the solid content concentration is 40%.

(Manufacturing method of graphite laminate 1)
Next, a method for manufacturing the graphite laminate 1 will be described. FIG. 2 is a diagram showing a graphite laminate 1 according to the present embodiment and a graphite plate 2 described later. First, as shown in FIGS. 2 (a) and 2 (b), a metal nanoparticle paste (silver nanoparticle paste in this embodiment) is applied on the surface of the graphite film as a starting material of the graphite film layer 10. The method of applying the metal nanoparticle paste can be applied by a usual coating method, for example, screen printing, roll coating, bar coating, flexographic printing, gravure printing, or the like.

The coating film thickness of silver nanopaste needs to be adjusted appropriately depending on the solid content concentration of the silver nanopaste material, but if there is a problem that the surface cracks after drying after one application, it can be improved by recoating. It is possible. Further, by applying the silver nanopaste material to both surfaces of the starting raw material film of the graphite film layer 10, a high-strength graphite laminate with few voids can be produced after heat sintering described later.

Next, as shown in FIGS. 2 (c) and 2 (d), a graphite film coated with a silver nanopaste material is laminated in multiple layers. Then, the multilayer laminated graphite film is heat-treated at 250 ° C. or lower. The heating temperature may be higher than the temperature at which the silver nanoparticles are sintered. For example, the strong silver nanoparticles are baked by holding the silver nanoparticles at a temperature about 100 ° C. higher than the temperature at which the silver nanoparticles start sintering for 1 hour or longer. A conjunctival is obtained.

The silver nanoparticles undergo a sintering reaction in the atmosphere to form a graphite laminate 1 formed by alternately laminating a graphite film layer 10 in which crystal grains are oriented in the plane and a silver particle sintered layer 20 alternately. Will be done. In order to remove volatile components such as solvents contained in the silver nanopaste material applied to the graphite film, the temperature was gradually raised to around 100 ° C. and then held for a certain period of time in the heat treatment, and then the silver nanoparticles were sintered. It is desirable to use a heating method in which the heating temperature is gradually lowered so that the temperature is raised to a temperature, held for a certain period of time, and then slowly cooled.

Further, in the heat treatment, in order to densely sinter the silver nanoparticles interposed between the graphite films into the graphite film, heating under a pressurized state gives a higher density graphite laminate. As the pressure to pressurize, it is preferable to apply a pressure in the range of 50 to 2000 KPa, particularly 50 to 500 KPa.

(Graphite plate 2)
Further, as shown in FIG. 2 (e), the graphite laminate 1 obtained in the above-described embodiment is cut in the laminating direction of the graphite laminate 1 and sliced to cut the graphite laminate 1. The graphite plate 2 having high thermal conductivity in the direction perpendicular to the surface can be manufactured. The thickness of the graphite plate 2 is not particularly limited, but is preferably as thin as possible from the viewpoint of cost reduction and strength maintenance, and is preferably 0.1 mm to 1.0 mm. Such a graphite plate 2 is expected to be a useful heat-dissipating material by joining it to, for example, an electronic element that generates heat.

(Example 1)
Using a 100 μm thick natural graphite film (manufactured by Toyo Tanso Co., Ltd.), a silver nanopaste (manufactured by Nagase Chemtex Co., Ltd.) with a silver content of 40% and a viscosity of 1800 mPa · S is applied to the surface using a bar coater. It was applied at a thickness of about 50 μm. Further, 19 layers of a graphite film similarly coated with silver nanopaste were laminated on this, and a laminated body in which 20 layers of a graphite sheet / silver paste were laminated was prepared. Then, after drying at room temperature for 8 hours, the mixture was held for 1 hour while being weighted at an equivalent of 0.5 MPs · m ² and raised to 100 ° C. at a heating rate of 5 ° C./min, and then held at 5 ° C./min. It was held for 2 hours while raising the temperature to 250 ° C. at a heating rate of 1 minute, and after performing a sintering reaction, it was gradually cooled.
(Comparative Example 1)
A graphite plate 2 was prepared using a silver paste standard grade (TR-3025 manufactured by Tanaka Kikinzoku Co., Ltd.) having an average particle size of about 1 μm, and using exactly the same materials and means as in Example 1 except for this.

In the laminate having a thickness of about 2 mm obtained in Example 1, the interface between the graphite film layer 10 and the metal nanoparticles sintered layer 20 containing silver nanoparticles is firmly adhered, and when strongly bent, graphite is used. Delamination occurred within the layer of the graphite film layer 10 rather than at the interface between the film layer 10 and the metal nanoparticles sintered layer 20. This is because in the silver nanoparticles sintered layer 20 according to the present embodiment, sintering occurs in a state where the silver nanoparticles are bitten into the fine uneven surface of the graphite film surface, and the graphite film layer 10 and the metal nanoparticles are sintered. It is considered that the strength at the interface with the layer 20 was higher than that in the layer of the graphite film layer 10. FIG. 3 shows a photograph obtained by magnifying a cut cross section of a graphite plate 2 obtained by cutting a graphite laminate of Example 1 into small pieces of about 20 mm × 20 mm with a dicer having a diamond blade and enlarging it with an electron microscope. As shown in FIG. 3, in the graphite plate 2 of Example 1, it can be seen that the silver nanoparticles are sintered in a state of being bitten into the fine uneven surface of the graphite film surface. On the other hand, in the graphite plate obtained in Comparative Example 1, it was confirmed that the silver paste between the layers was not sintered, and when bent, the silver powder was scattered and the adhesion was clearly weak.
As described above, in the graphite laminate 1 according to the first embodiment, the interface between the graphite film layer 10 and the silver nanoparticles sintered layer 20 is formed by applying silver nanopaste between the graphite film layers 10 and sintering the graphite. It was found that the graphite film layer 10 adhered firmly and a high adhesion strength was obtained in the layer of the graphite film layer 10.

Further, as a result of measuring the thermal conductivity of the graphite plate 2 of Example 1 by the laser flash method, the thermal conductivity in the direction of the cut surface is 10 W / K · m, whereas the thermal conductivity in the direction perpendicular to the cut surface is The thermal conductivity was 430 W / K · m. As described above, in the graphite plate 2 of Example 1, the thermal conductivity is higher in the direction perpendicular to the cut surface of the graphite film layer 10 than in the direction of the cut surface of the graphite film layer 10. Was found to have.

(Example 2)
Further, in Example 2, a synthetic graphite film (manufactured by Kaneka Corporation) having a thickness of 40 μm was used, and a silver nanopaste (manufactured by Nagase Chemtex Co., Ltd.) having an average particle size of 50 nm was applied onto this film in the same manner as in Example 1. Then, this was laminated to prepare a laminated body in which 50 layers of graphite sheet / silver nanopaste were laminated. Then, the prepared laminate was heat-treated at 250 ° C. for 2 hours.

Similar to Example 1, the obtained graphite laminate of Example 2 was cut into small pieces of 20 mm × 20 mm × 3 mm with a dicer having a diamond blade, the cut cross section was observed, and the thermal conductivity was measured. did. FIG. 4 shows a photograph of the cut cross section of the graphite plate 2 obtained by cutting the graphite laminate of Example 3 into small pieces, magnified by an electron microscope. As a result, it can be seen that even in the graphite plate 2 of Example 2, the silver nanoparticles are sintered in a state of being bitten into the fine uneven surface of the graphite film surface.
Further, in the graphy plate of Example 2, it was confirmed that the synthetic graphite itself inherited the high thermal conductivity and had a high thermal conductivity of 1100 W / K · m in the direction perpendicular to the cut surface.

As described above, the graphite laminate 1 according to the present embodiment has a structure in which the metal nanoparticles sintered layer 20 is interposed between the graphite film layers 10. Since the metal nanoparticles undergo a sintering reaction at a low temperature of 150 ° C. or lower, a structure having the metal nanoparticles sintered layer 20 between the graphite film layers 10 (a silver nanoparticles paste between the layers of the graphite film layer 10) is used. By stacking the silver nanoparticles sintered layers, the silver nanoparticles bite into the fine uneven surface of the graphite film surface, and the adhesion strength between the graphite film layers 10 can be increased, so that the graphite film layer can be increased. Adhesion strength higher than the adhesion strength inside 10 can be obtained. Further, when the metal nanoparticles sintered 20 is a metal nanoparticles sintered layer 20 containing silver nanoparticles having an average particle size of 50 nm or less, the temperature is 100 ° C. The so-called Gibbs-Thomson effect, in which silver particles sinter at low temperatures before and after, occurs and adheres to the graphite film at a temperature much lower than the melting point of silver.

Although the preferred embodiment of the present invention has been described above, the technical scope of the present invention is not limited to the description of the above embodiment. Various changes and improvements can be added to the above-described embodiments, and those in which such changes or improvements have been made are also included in the technical scope of the present invention.

For example, in the above-described embodiment, a method of manufacturing a graphite laminate 1 by applying a paste material containing metal nanoparticles on one side or both sides of a graphite film has been exemplified, but the method of manufacturing a graphite laminate is described as follows. For example, as shown in FIG. 5, a method may be used in which a graphite film coated with silver nanopaste is wound around a shaft material to form a coil, and then heat-sintered. In this case, a dense silver nanosintered layer may not be obtained because the pressure cannot be applied during heating, but the end face of the graphite film does not easily come out to the outer periphery, so that the shape retention is excellent. Note that FIG. 5 is a diagram showing a graphite laminate 1'according to another embodiment.

Further, in addition to the above-described embodiment, the graphite laminate can be reinforced with electrolytic plating such as copper or nickel to impart mechanical strength and dust resistance.

1,1'... Graphite laminate 10 ... Graphite film layer 20 ... Metal nanoparticles sintered layer 2 ... Graphite plate

Claims (6)

A graphite laminated body in which graphite film layers and sintered layers of metal nanoparticles derived from nanoparticles having an average particle size of 100 nm or less are alternately laminated and have anisotropic thermal conductivity. The graphite laminate according to claim 1, wherein the metal nanoparticles sintered layer is derived from a paste material containing silver nanoparticles. The graphite laminate according to claim 1 or 2, wherein at least 30% by weight or more of the components of the metal nanoparticles sintered layer are derived from silver nanoparticles. A graphite plate obtained by cutting the graphite laminate according to any one of claims 1 to 3 in the layering direction of the graphite film layer to form flakes, which is higher in the direction perpendicular to the cut surface than in the cut surface direction. A graphite plate characterized by having thermal conductivity. The process of applying a paste material containing metal nanoparticles on the surface of a graphite film,
A step of drying a graphite film on which a paste material is applied on a surface to obtain a graphite film coated with a paste material containing metal nanoparticles.
The graphite film coated with the paste material is laminated in multiple layers and heat-treated under pressure at 250 ° C. or lower to sintered the paste material, and the graphite film layer and the metal nanoparticle sintered layer alternate. A method for producing a graphite laminate, which comprises a step of obtaining a graphite laminate laminated in the above. The method for producing a graphite laminate according to claim 5, wherein the step of applying the paste material is a step of applying the paste material to one side or both sides of the graphite film.

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