JP2001315244A - Heat conductive sheet, method for manufacturing same and radiation structure using heat conductive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat conductive sheet having high anisotropic heat conductivity in its thickness direction, ensuring insulating properties, effective for a radiation structure requiring insulating properties between a heating unit such as a semiconductor element or package and a radiation member, excellent in heat resistance, durability and mechanical strength and also excellent in the adhesion with a heating unit. SOLUTION: The heat conductive sheet consists of a heat conductive layer wherein carbon fibers are oriented in a binder in a thickness direction and the electric insulating layer provided on a part or the whole of the surface of the heat conductive layer. This heat conductive sheet is manufactured by curing or semi-curing a sheetlike composition for the heat conductive sheet consisting of the binder, carbon fibers and a magnetic material while allowing a magnetic field to act on the composition in the thickness direction thereof to orient the magnetic material and the carbon fibers in the thickness direction of the composition. The radiation structure is constituted by bonding the heating unit and the radiation member or a circuit board through the heat conductive sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat conductive sheet, a method for manufacturing the same, and a heat dissipation structure using the heat conductive sheet.

[0002]

2. Description of the Related Art The number of electrodes of a semiconductor device is increasing with the further improvement of the performance of electric devices or electronic devices, and the semiconductor device tends to consume higher power. It is important to dissipate heat well. Conventionally, in order to efficiently dissipate heat from a semiconductor package or a semiconductor, an attempt has been made to dissipate heat by providing a heat dissipation mechanism in a semiconductor package or the like, or to dissipate heat from a wiring board on which a semiconductor element is mounted. For example, heat dissipation of a semiconductor package is generally performed by natural convection from the body surface of the heating element or forced convection by a fan provided in the unit. However, in this method, the amount of heat generated is increased as the function of the semiconductor package is improved. When the number increases, the heat radiation effect becomes insufficient, and there is a problem that the performance degradation of the semiconductor package cannot be reliably prevented. There is also provided a method in which a heat radiator is pressed against the surface of the semiconductor package to improve heat dissipation by convection. However, in this method, the contact area of the pressure contact surface between the semiconductor package and the heat radiator is reduced due to the generation of a gap. ,
There was a problem in exhibiting the heat radiation effect as designed. For this reason, for example, when a heat radiator is joined to a semiconductor package, heat dissipation is effectively performed while a heat conductive resin sheet or the like is interposed between the semiconductor package and the heat radiator so that the semiconductor package and the heat radiator are in close contact with each other. What is done is done. In addition, for example, in bonding a semiconductor element and a heat spreader that comes into contact with the semiconductor element, heat is radiated from the semiconductor element while maintaining the adhesion between the semiconductor element and the heat spreader with an adhesive having high thermal conductivity interposed therebetween. Has been done.

[0003] As such a resin composition or the like for increasing thermal conductivity interposed between a semiconductor element or a semiconductor package and a radiator, for example, Japanese Patent Application Laid-Open No. 5-32691 is disclosed.
In Japanese Patent Application Laid-Open No. 6-26, a clay-like thermosetting adhesive type silicone rubber sheet is used. However, this silicone rubber sheet is not sufficient in terms of thermal conductivity to cope with high power consumption of a semiconductor element. There was a point. In order to increase the thermal conductivity, metal particles having a high thermal conductivity are randomly dispersed in a resin sheet such as silicone rubber.In order to further improve the thermal conductivity, the metal particles are dispersed in the resin sheet. Attempts have been made to achieve high dispersion and high filling. However, even if the metal particles are highly dispersed and filled, the heat is diffused in a random direction, so that the thermal conductivity between the semiconductor element and the heat radiator is not sufficiently improved. However, there is a problem that the tensile strength and elasticity of the resin sheet are reduced due to the high filling of the resin sheet, and the moldability is also reduced.

[0004] From such a viewpoint, the present inventors have found that carbon fibers having a magnetic substance adhered to the surface, or magnetic substance particles and carbon fibers, are oriented in the thickness direction of the resin sheet in the binder. It has been found that the use of a high thermal conductive sheet greatly improves the anisotropic thermal conductivity in the thickness direction of the sheet (Japanese Patent Application Nos. 11-325757 and 2000-027738).

[0005] These thermal conductive sheets provide high thermal conductivity but do not have sufficient electrical insulation. However, depending on the type of the heating element, for example, in a case where heat is radiated from a circuit board whose surface is not sufficiently insulated, the heat conductive sheet is required to be insulative in order to prevent an electrical short. . The present inventors have intensively studied the above problems, and by covering a part or the entire surface of a heat conductive sheet in which carbon fibers are oriented in the thickness direction of the sheet with a binder, a heat insulating sheet is formed. While finding that sufficient insulation can be ensured without significantly impairing the conductivity, the heat conductive sheet is excellent in heat resistance, durability and mechanical strength, and also excellent in adhesion to the heating element. This led to the completion of the present invention.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to solve the problems associated with the prior art as described above, and has a high thermal conductivity in the thickness direction of a heat conductive sheet and a heat transfer sheet. An object of the present invention is to provide a heat conductive sheet excellent in heat resistance, durability, mechanical strength, and adhesion to a heating element while ensuring insulation, and a method for manufacturing the same. Another object of the present invention is to provide a heat dissipation structure using such a heat conductive sheet.

[0007]

SUMMARY OF THE INVENTION A heat conductive sheet according to the present invention comprises a heat conductive layer in which carbon fibers are oriented in a thickness direction in a binder, and an electric insulating layer provided on a part or all of the surface of the heat conductive layer. And a layer. The electric insulating layer preferably contains a heat conductive filler, and the heat conductive filler is preferably an oxide, nitride, or carbide ceramic. Preferably, the binder is photocurable and / or thermosetting. The heat conductive layer of the heat conductive sheet contains a magnetic material,
The magnetic substance is preferably oriented in the thickness direction of the heat conductive sheet in the binder, and the magnetic substance is preferably attached to the surface of the carbon fiber or is a magnetic particle. The method for producing a heat conductive sheet according to the present invention is characterized in that a magnetic field acts in the thickness direction of a heat conductive layer sheet-like composition comprising a binder, carbon fiber, and a magnetic material to cause the magnetic material and the carbon fiber to form a heat conductive layer. The present invention is characterized in that the heat-conductive layer sheet composition is cured or semi-cured while being oriented in the thickness direction of the sheet composition.

[0008] A heat dissipation structure according to the present invention is characterized in that a heat generating element and a heat dissipation member or a circuit board are joined via the heat conductive sheet. The heating element is
It is preferably a semiconductor element or a semiconductor package.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The heat conductive sheet according to the present invention comprises:
It comprises a heat conductive layer in which carbon fibers contained in the binder are oriented in the thickness direction of the sheet, and an electric insulating layer provided on part or all of the surface of the heat conductive layer. Further, the heat conductive sheet according to the present invention may have both surfaces of the heat conductive layer covered with the electric insulating layer, or may have only one surface covered with the electric insulating layer, depending on its use. Good.

Further, the heat conductive layer of such a heat conductive sheet may contain a magnetic material oriented in the thickness direction of the sheet. In the present specification, "orientation" means that the rod-like carbon fiber or the like is oriented in a substantially constant direction,
Alternatively, it means that the particles are arranged in a substantially constant direction. <Composition for heat conductive layer> First, the composition for a heat conductive layer capable of forming the heat conductive layer of the heat conductive sheet according to the present invention will be described. The composition for a heat conductive layer according to the present invention,
It comprises a binder, carbon fibers, and, if necessary, a magnetic substance, a photoinitiator, a thermosetting agent, and other additives.

Carbon Fiber The carbon fiber used in the present invention preferably has a thermal conductivity (W m ^-1 K ^-1 ) in the fiber direction of 100 or more,
More preferably 500 or more, particularly preferably 1200
It is desirable that this is the case. Such carbon fibers include, for example, cellulose-based, P
It can be selected from AN-based and pitch-based carbon fibers, but in the present invention, it is preferable to use pitch-based carbon fibers from the viewpoint of good thermal conductivity. Among pitch-based carbon fibers, any of anisotropic carbon fibers and isotropic carbon fibers can be used as long as they exhibit high thermal conductivity.

The carbon fiber according to the present invention can be prepared by a generally known method, and a commercially available carbon fiber can be used. The diameter of such carbon fibers is preferably 5 to 500 μm, more preferably 1 to 500 μm.
0 to 200 μm. The aspect ratio of carbon fiber is 2
To 100, more preferably 5 to 100.
100, particularly preferably 10 to 50.

[0013] Such a carbon fiber has a volume fraction of 2 to 70%, preferably 10 to 60%, based on the composition for a heat conductive layer.
% Is preferably used. If this ratio is less than 2%, the thermal conductivity of the cured heat conductive sheet may not be sufficiently increased, while if this ratio exceeds 70%, the resulting heat conductive sheet may be It tends to be brittle, and the elasticity required for a heat conductive sheet may not be obtained.

Binder In the composition for the heat conductive layer forming the heat conductive sheet of the present invention, either a rubbery polymer or a resinous polymer can be used as the binder, and the binder before curing or semi-curing can be used. And a liquid binder can be preferably used. Further, a photo-curable component and / or a thermo-curable component can be added to the binder, and the rubber-like polymer or the resin-like polymer as the binder component can be added to the photo-curable component and / or the thermo-curable component. It can also serve as a component.

The rubbery polymer, resinous polymer, photocurable component and thermosetting component used in the present invention will be described below. (Rubber-like polymer) Specific examples of the rubber-like polymer used in the present invention include conjugated diene-based rubbers such as polybutadiene, natural rubber, polyisoprene, SBR and NBR, hydrogenated products thereof, and styrene-butadiene block. Copolymers, block copolymers such as styrene isoprene block copolymers and their hydrogenated products, chloroprene, urethane rubber, polyester rubber, epichlorohydrin rubber, silicone rubber, ethylene propylene copolymer, ethylene propylene diene copolymer And the like. Among these, silicone rubber is particularly preferred from the viewpoint of moldability, weather resistance, heat resistance and the like. Here, the silicone rubber will be described in more detail. It is preferable to use liquid silicone rubber as the silicone rubber. The liquid silicone rubber may be any of condensation type, addition type and the like. Specifically, dimethylsilicone raw rubber, methylphenylvinylsilicone raw rubber or a vinyl group, a hydroxyl group, a hydrosilyl group,
Examples thereof include those containing a functional group such as a phenyl group and a fluoro group. (Resinous polymer) As the resinous polymer according to the present invention,
Specifically, an epoxy resin, a phenol resin, a melamine resin, an unsaturated polyester resin, or the like can be used.
Of these, it is preferable to use an epoxy resin.

As the epoxy resin, those having two or more epoxy groups in one molecule are preferable. For example, phenol novolak type epoxy resin, cresol novolak type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, Bisphenol AD type epoxy resin, alicyclic epoxy resin, or polyglycidyl (meth) acrylate, a copolymer of glycidyl (meth) acrylate and another copolymer monomer, and the like can be given. (Photo-curable component) As the photo-curable component contained in the binder according to the present invention, there are photo-radical polymerizable, photo-cationic polymerizable, coordinating photo-polymerizable, which is cured by ultraviolet light, electron beam,
Examples include monomers, oligomers, prepolymers or polymers that are photopolyaddition reactive. Such photocurable monomers, oligomers, prepolymers or polymers include (meth) acrylic compounds, vinyl ether-
Photo-radical polymerizable polymer such as maleic acid copolymer, thiol-
Preferred are photopolyaddition-reactive compounds such as ene-based compounds, and among them, (meth) acrylic-based compounds are particularly preferred. As the photocurable component according to the present invention, a monomer of a (meth) acrylic compound, which requires a short time for photocuring, is preferably used.

Examples of such photopolymerizable monomers, oligomers, prepolymers or monomers of (meth) acrylic compounds include, specifically, cyano group-containing vinyl compounds such as acrylonitrile and methacrylonitrile. , (Meth) acrylamide compounds and (meth) acrylic esters. Examples of the (meth) acrylamide compound include acrylamide, methacrylamide, N, N-dimethylacrylamide and the like, and these may be used alone or as a mixture.

The (meth) acrylates include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, hydroxyethyl (meth) acrylate, and phenyl (meth) acrylate. ) Monofunctional (meth) acrylates such as acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, and tricyclodecanyl (meth) acrylate; Used alone or as a mixture.

Examples of the polyfunctional (meth) acrylate include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, and tetraethylene glycol. Di (meth) acrylate, polyethylene glycol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, neopentyl glycol di (meth)
Acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, glycerol di (meth) acrylate, ethylene oxide of bisphenol A Bifunctional (meth) acrylates such as diacrylate of propylene oxide adduct, bisphenol A-diepoxy-acrylic acid adduct, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate,
Examples include trifunctional (meth) acrylates such as glycerin tri (meth) acrylate.

These may be used alone or as a mixture. (Thermosetting component) Examples of the thermosetting component that can be preferably used as the binder according to the present invention include monomers, oligomers, prepolymers and polymers having a functional group that is cured by heat.

As such functional groups, epoxy groups, hydroxyl groups, carboxyl groups, amino groups, isocyanate groups,
Examples thereof include a vinyl group and a hydrosilyl group, and an epoxy group, a vinyl group, and a hydrosilyl group are preferable from the viewpoint of reactivity. Monomers, oligomers having such functional groups,
Examples of the prepolymer or polymer include an epoxy compound, a urethane compound, and a silicone compound. Among these, it is preferable to use an epoxy compound and a silicone compound from the viewpoint of shortening the heat curing time. Further, the epoxy compound or the silicone compound has two or more epoxy groups, vinyl groups or hydrosilyl groups in the molecule. It is desirable to have.

The molecular weight of such an epoxy compound is not particularly limited, but is usually from 70 to 20,000.
Preferably, it is 300 to 5000, and specifically, various epoxy resins having a certain molecular weight or more, such as oligomers, prepolymers, or polymers of the epoxy compound, are preferably used. Specific examples of such an epoxy compound include, for example, the above-mentioned phenol novolak type epoxy resin, cresol novolak type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, alicyclic ring Examples include a formula epoxy resin, a polyglycidyl (meth) acrylate, and a copolymer of glycidyl (meth) acrylate with another copolymerized monomer.

When these phenol novolak type epoxy resins and the like are used as thermosetting components, they can also serve as resinous polymer components at the same time. Examples of the silicone-based compound include the above-described vinyl-containing silicone rubber, and a vinyl-containing silicone type is preferred as a silicone-based compound because of its reactivity with a hydrosilyl-containing compound used as a curing agent. When these silicone compounds are used as thermosetting components, they can also serve as rubbery polymer components at the same time.

A commercially available silicone compound which can also serve as a rubber-like polymer component is a room-temperature-curable two-part addition-type thermosetting liquid silicone rubber containing a hydrosilyl compound as a curing agent. Can be mentioned. These resins are used alone or as a mixture. (Combined Use of Photocurable Component and Thermosetting Component) As the binder according to the present invention, the photocurable component and the thermosetting component can be used in combination. In such a combined system, it is preferable that the thermosetting component does not cure under light curing conditions. As described above, when the photo-curable component and the thermo-curable component are used in combination as the binder according to the present invention, the mixing ratio (photo-curable component / thermo-curable component) is preferably from 80/20 to 20/20. /
80% by weight, more preferably 70/30 to 30/70
% By weight, particularly preferably 40/60 to 40/60% by weight
It is desirable that When the photo-curable component and the thermo-curable component are in such a range, the orientation of the carbon fibers in the semi-cured heat conductive sheet in the thickness direction of the sheet is sufficiently performed, When the sheet is cured, a heat conductive sheet having excellent adhesiveness can be obtained.

As such a photo-curable component and a thermo-curable component according to the present invention, the combination of the (meth) acrylic compound and the epoxy-based compound can be used for the molding time of the semi-cured heat conductive sheet. It is preferable from the viewpoint of shortening and excellent adhesiveness. The method of mixing the photocurable component and the thermosetting component is not particularly limited.For example, when the acrylic compound monomer is used as the photocurable component and the epoxy resin is used as the thermosetting component, acrylic The epoxy resin can be dissolved and mixed with the system compound monomer.

As a component of the binder according to the present invention, a compound containing, in one molecule, a photocurable functional group and a thermosetting functional group that is not cured under photocuring conditions is used. You can also double. Examples of the compound containing such a photocurable functional group include the (meth) acrylic compound, and the thermosetting functional group include the epoxy group. Specific examples of the compound that can serve as both components include: Epoxy (meth) acrylamide such as glycidyl (meth) acrylamide, epoxy (meth) acrylate such as glycidyl (meth) acrylate, and 3,4-epoxycyclohexyl (meth) acrylate are exemplified.

Also, a reactive monomer having an unsaturated double bond can be contained as a binder component. Examples of such a reactive monomer include hydroxystyrene, isopropenylphenol, styrene, α-
Aromatic vinyl compounds such as methylstyrene, p-methylstyrene, chlorostyrene, p-methoxystyrene,
Hetero atom-containing alicyclic vinyl compounds such as vinylpyrrolidone and vinylcaprolactam. (Photoinitiator) The composition for a heat conductive layer according to the present invention may be mixed with a photoinitiator according to the type of radiation used for curing the photocurable component, for example, in the case of ultraviolet curing. it can.

Such a photoinitiator may be any as long as it can cure the photocurable component contained in the composition for a heat conducting layer under the photocuring conditions according to the present invention. When the component and the thermosetting component are used in combination, the photocurable component is cured, and the thermosetting component may not be cured,
Known photoinitiators can be used. Such photoinitiators include, for example, α- such as benzyl and diacetyl.
Diketones; acyloins such as benzoin; acyloin ethers such as benzoin methyl ether, benzoin ethyl ether and benzoin isopropyl ether; thioxanthone, 2,4-diethylthioxanthone, thioxanthone-4-sulfonic acid, benzophenone, 4,4
(-Bis (dimethylamino) benzophenone, 4,4 '
Benzophenones such as -bis (diethylamino) benzophenone; acetophenone, p-dimethylaminoacetophenone, α, α′-dimethoxyacetoxybenzophenone, 2,2′-dimethoxy-2-phenylacetophenone, p-methoxyacetophenone, 2-methyl [4 −
(Methylthio) phenyl] -2-morpholino-1-propanone, 2-benzyl-2-dimethylamino-1-
Acetophenones such as (4-morpholinophenyl) -butan-1-one; quinones such as anthraquinone and 1,4-naphthoquinone; phenacyl chloride, tribromomethylphenylsulfone, and tris (trichloromethyl)
Halogen compounds such as -s-triazine; peroxides such as di-t-butyl peroxide; acylphosphine oxides such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide. Also,
Commercial products include Irgacure 184, 651, 50
0,907, CG1369, CG24-61, Darocur 1116, 1173 (manufactured by Ciba Specialty Chemicals Co., Ltd.), Lucirin LR8728, TPO (BA
SF) and Ubecryl P36 (UCB).

When the photocurable component and the thermosetting component are used together as a binder, the photocurable component contained in the composition for a heat conductive layer is a (meth) acrylic compound, and the thermosetting component is Is an epoxy compound, a photoinitiator such as Irgacure 651 or Lucirin TPO, which has a high curing rate, can be preferably used. The amount of the photoinitiator used is preferably an appropriate amount in consideration of the actual curing speed, the balance with the pot life, and the like. Specifically, based on 100 parts by weight of the photocurable component, , 1-5
It is preferably contained in the binder in a proportion of 0 parts by weight, and particularly preferably in a proportion of 5 to 30 parts by weight. When the amount is less than 1 part by weight, the sensitivity is easily reduced by oxygen, and when the amount is more than 50 parts by weight, the compatibility becomes poor,
The storage stability may decrease.

A photoinitiator may be used in combination with such a photoinitiator. When a photoinitiator is used in combination, the initiation reaction is promoted as compared with the use of the photoinitiator alone,
The curing reaction can be performed efficiently. As such a photo-initiating aid, a commonly used photo-initiating aid can be used. Such photoinitiating aids include, for example, triethanolamine, methyldiethanolamine, triisopropanolamine, n-butylamine, N-
Aliphatic amines such as methyldiethanolamine and diethylaminoethyl (meth) acrylate, Michler's ketone, 4,4′-diethylaminophenone, ethyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate,
Isoamyl dimethylaminobenzoate and the like. (Thermosetting agent) The composition for a heat conductive layer according to the present invention may be mixed with a thermosetting agent for accelerating the thermosetting of the thermosetting component. As such a thermosetting agent according to the present invention, a known thermosetting agent can be used. Examples of such a thermosetting agent include amines, dicyandiamide, dibasic dihydrazide, imidazoles, hydrosilyl compounds, vinylsilyl compounds, and the like.

Specifically, polymethylenediamine, diethylenetriamine, dimethylaminopropylamine, bishexamethylenetriamine, diethylaminopropylamine, polyetherdiamine, 1,3-diaminocyclohexane, diaminodiphenylmethane, diaminodiphenylsulfone, 4,4 ′ -Bis (o-toluidine), m-phenylenediamine, 2-phenyl-4-methyl-5-hydroxymethylimidazole, block imidazole, polydimethylsiloxane containing both ends hydrosilyl group, polydimethylsiloxane containing both ends vinyl group, etc. Can be

The amount of the thermosetting agent used is preferably an appropriate amount in consideration of the balance between the actual curing speed and the pot life, etc. Specifically, the thermosetting agent is preferably a thermosetting agent. The binder is preferably contained in a proportion of 1 to 50 parts by weight, particularly preferably 1 to 30 parts by weight, based on 100 parts by weight of the active ingredient. The method of adding the photoinitiator and the thermosetting agent is not particularly limited, but it is preferable that the photoinitiator and the thermosetting agent are preliminarily mixed with a binder from the viewpoint of storage stability, prevention of uneven distribution of the catalyst when mixing the components, and the like. .

Magnetic Material The composition for a heat conductive layer capable of forming the heat conductive sheet according to the present invention may contain a magnetic material. As such a magnetic material, a magnetic material particle or a material in which a magnetic material is attached to the surface of carbon fiber is preferable. Examples of the material used for the magnetic material according to the present invention include ferromagnetic metals such as iron, cobalt and nickel or alloys made of such metals, and further exhibit ferromagnetism such as iron, cobalt and nickel. Metal compounds such as an intermetallic compound containing a metal or a metal oxide of the metal are exemplified. (Magnetic Particles) The magnetic particles used as a preferred form of the magnetic material according to the present invention are not particularly limited as long as they exhibit a degree of magnetism that can be oriented in the direction of the magnetic field when a magnetic field is applied by a method described below.

The magnetic particles are metal particles obtained by converting the magnetic material into particles. Such magnetic particles,
Particles of metal such as iron, nickel, cobalt, etc. are used as core particles, and the surface of the core particles is plated with another metal, for example, a metal having high thermal conductivity, or an inorganic substance such as non-magnetic metal particles or glass beads. Particles or polymer particles as core particles, the surface of the core particles, iron, nickel,
Examples include particles that have been plated with at least a ferromagnetic metal such as cobalt. The method of coating the surface of the core particles with a metal is not particularly limited, but may be, for example, chemical plating, electroless plating, or the like. The coating amount of the magnetic substance on the surface of the core particles is preferably 0.5 to 50% by weight, more preferably 1 to 50% by weight based on the core particles.
-30% by weight, more preferably 2-25% by weight, particularly preferably 4-20% by weight.

The particle diameter of such magnetic particles is 1 to 1
000 μm, more preferably 2 to
It is 500 μm, more preferably 5 to 300 μm, particularly preferably 10 to 200 μm. The shape of the magnetic particles is not particularly limited, but may be spherical, star-shaped, agglomerated secondary particles formed by aggregation of these particles, or elongated rod-shaped particles.

The water content of the magnetic particles is preferably 5% or less, more preferably 3% or less, further preferably 2% or less, particularly preferably 1% or less.
By using the magnetic particles satisfying such conditions, in the production method described below, when obtaining a semi-cured heat conductive sheet by semi-curing the composition for a heat conductive layer,
The generation of bubbles in the heat conductive sheet is prevented or suppressed.

In the case where such magnetic particles are used, a volume fraction of 10 to 50% by volume with respect to the composition for a heat conductive layer,
It is preferably used in a ratio of 15 to 40% by volume. If this ratio is less than 10%, it may be difficult to orient the carbon fibers in the semi-cured heat conductive sheet in the magnetic field direction together with the magnetic particles. On the other hand, when this proportion exceeds 50%, the obtained semi-cured heat conductive sheet and the heat conductive sheet obtained by curing the same tend to be brittle, and the elasticity required as a high heat conductive sheet cannot be obtained. Sometimes.

[0038] Such magnetic particles and carbon fibers are preferably contained in a total amount of 20 to 80% by volume, more preferably 30 to 6% by volume, in the total volume of the composition for a heat conductive layer.
Desirably, it is contained in an amount of 0% by volume. Further, magnetic particles whose surfaces are treated with a coupling agent such as a silane coupling agent can also be used as appropriate. When the surface of the magnetic particles is treated with the coupling agent, the adhesiveness between the magnetic particles and the binder is increased, and as a result, the resulting heat conductive sheet has high durability. (Magnetic Body Attached to Carbon Fiber Surface) The “magnetic body attached to a carbon fiber surface” according to the present invention is a carbon fiber having the above-described magnetic body attached to a carbon fiber surface.

The magnetic substance attached to the surface of the carbon fiber according to the present invention has a degree of magnetism that can be oriented in the direction of the magnetic field when a magnetic field is applied by the method described later. It may be attached in a layered manner or may be attached to a part of the carbon fiber surface without forming a layer, and the material and thickness of the magnetic material are not particularly limited. The method of attaching the magnetic substance to the carbon fiber surface can be performed by, for example, electroless plating such as chemical plating.

The total amount of such “carbon fibers having a magnetic material adhered to the surface” in the total volume of the composition for a heat conductive layer is equal to the total amount in the total volume of the composition for a heat conductive layer. 2-7
The amount is preferably 0% by volume, more preferably 10 to 60% by volume. If this ratio is less than 2% by volume, the thermal conductivity of the cured heat conductive sheet may not be sufficiently increased, while if this ratio exceeds 70% by volume, the obtained thermal conductivity may be insufficient. The sheet tends to be brittle, and the elasticity required as a heat conductive sheet may not be obtained.

In addition, a carbon fiber having a magnetic material adhered to the surface, the surface of which has been further treated with a coupling agent such as a silane coupling agent, may be used as appropriate. When the surface of the carbon fiber having the magnetic substance adhered to the surface thereof is further treated with a coupling agent, the adhesiveness between the carbon fiber having the magnetic substance adhered to the surface and the binder is increased, and as a result, the resultant is obtained. The high thermal conductive sheet has high durability.

Other Additives In the present invention, the composition for a heat conductive layer may contain, if necessary, an inorganic filler such as ordinary silica powder, colloidal silica, airgel silica, and alumina. By including such an inorganic filler,
The thixotropic property at the time of uncuring is secured, the viscosity is increased, and the dispersion stability in the composition of the carbon fiber having the magnetic substance adhered to the surface is improved, and the heat conductive sheet after curing or semi-curing Can be improved in strength. The amount of the inorganic filler used is not particularly limited, but if used in an excessively large amount, the magnetic particles and carbon fibers, or the carbon fibers having a magnetic substance adhered to the surface can be sufficiently oriented by the magnetic field. It is not preferable because it disappears. Composition for Thermal Conductive Layer The composition for thermal conductive layer according to the present invention comprises the above-mentioned binder, carbon fiber, and, if necessary, a magnetic substance, a photocuring agent, a thermal curing agent, the above-mentioned other additives, and the like.

The composition for a heat conductive layer may contain a silane coupling agent and a titanium coupling agent. If necessary, an ultraviolet absorber, a thermal polymerization stabilizer, an antioxidant, It may contain additives such as an agent, a heat stabilizer, an antistatic agent, a flame retardant, an adhesion improver, and a fungicide. For the preparation of the composition for a heat conductive layer according to the present invention, any of the conventionally known methods can be adopted. Examples of the preparation method include a binder, carbon fiber, and, if necessary, a magnetic substance, And a method of mixing and kneading an agent, a thermosetting agent or an inorganic filler.

The viscosity of the composition for a heat conductive layer of the present invention is preferably in the range of 10,000 to 1,000,000 cp at a temperature of 25 ° C. It is preferably in the form. In order to form the composition for a heat conductive layer according to the present invention into a sheet, a conventionally known method can be employed, but a roll rolling method, a casting method, a coating method, or the like can be employed.

The thickness of such a sheet-like composition varies depending on the use of the heat conductive sheet and is not particularly limited, but is usually about 50 μm to 1000 μm. <Electrical Insulating Layer> In the heat conductive sheet according to the present invention, part or all of the surface of the heat conductive layer is covered with the electrical insulating layer. Such an electrical insulating layer may contain a thermally conductive filler.

Composition for Electric Insulating Layer The composition for electric insulating layer according to the present invention includes the same rubber-like polymer, resin-like polymer, photo-curable component, and thermo-curable component as the binders described above. Those which are in a liquid state before curing or semi-curing can be preferably used. Further, similarly to the binder, a rubber-like polymer or a resin-like polymer can also serve as a photo-curable component and / or a thermo-curable component.

The composition for an electric insulating layer may contain a silane coupling agent and a titanium coupling agent. If necessary, an ultraviolet absorber, a thermal polymerization stabilizer, an antioxidant, It may contain additives such as an agent, a heat stabilizer, an antistatic agent, a flame retardant, an adhesion improver, and a fungicide. Such a composition for an electrical insulating layer may be the same as the binder component used for the heat conductive layer, or may be a different component. It is preferable to use the same component from the viewpoint of enhancing the bondability with the same.

Such a composition for an electric insulating layer may contain a heat conductive filler from the viewpoint of improving the heat conductivity. As the heat conductive filler contained in the electric insulating layer, a material having high heat conductivity that does not significantly impair the heat conductivity of the binder portion is preferable. As such a thermally conductive filler, oxide ceramics, nitride ceramics or carbide ceramics can be preferably used.

As the oxide ceramics, alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), magnesia (MgO),
Examples include simple oxide ceramics such as beryllium oxide (BeO), and composite oxide ceramics such as mullite (3Al ₂ O ₃ .2SiO ₂ ) and zircon (ZrSiO ₄ ).

As the nitride ceramics, silicon nitride (Si ₂ N ₄ ), aluminum nitride (AlN), boron nitride (BN), titanium nitride (TiN), zirconium nitride (Zr
N), tantalum nitride (TaN) and the like. Silicon carbide (SiC), titanium carbide (TiC), boron carbide (B ₄ C), tungsten carbide (W
C) and the like.

As the heat conductive filler according to the present invention,
Among the above-mentioned oxide-based ceramics, nitride-based ceramics or carbide-based ceramics, nitride-based ceramics or oxide-based ceramics are preferable, and among them, boron nitride, aluminum nitride, alumina, and magnesia are particularly preferable. These thermally conductive fillers are:
Species or a mixture of two or more can be used.

The form of the oxide-based ceramic, nitride-based ceramic or carbide-based ceramic is not particularly limited, but is usually preferably in the form of powder. The average particle size of such a powder is 0.1 to 100 μm
Is more preferable, and more preferably 1 to 30 μm. When such a thermally conductive filler is included in the composition for an electrical insulating layer, its content is preferably 2 to 60% by volume, more preferably 5 to 45% by volume, based on the capacity of the electrical insulating layer. Desirably, it is volume%.

Such a composition for an electric insulating layer can be prepared by a known method, and comprises a rubber-like polymer, a resin-like polymer or a photocurable component, What is necessary is just to mix and prepare the said heat conductive filler etc. uniformly as needed to an active ingredient. The viscosity of the composition for a heat conductive layer of the present invention is preferably in the range of 10,000 to 1,000,000 cp at a temperature of 25 ° C, and such a composition for a heat conductive layer is in the form of a paste. Is preferred.

Electric Insulating Layer In order to form the composition for an electric insulating layer according to the present invention into a sheet, a conventionally known method can be employed.
A casting method or a coating method may be employed. The thickness of the composition for such an electrical insulating layer is not particularly limited, and varies depending on the use of the heat conductive sheet, required heat conductive performance and insulating performance, but is usually 1 to 100 μm, preferably about 5 to 50 μm. Is preferable. <Thermal Conductive Sheet> Method of Forming Thermal Conductive Layer and Electrical Insulating Layer The thermal conductive sheet 1 according to the present invention has a thermal conductive layer 2 in which carbon fibers are oriented in a thickness direction in a binder as shown in FIG. And an electrical insulating layer 3 covering part or all of the surface of the heat conductive layer. Further, the heat conductive layer may contain a magnetic material as needed, and the electric insulating layer may contain a heat conductive filler as needed.

Hereinafter, the molding method will be described in more detail by taking, as an example, a heat conductive sheet in which a binder contains carbon fibers and a magnetic material. FIG. 2 and FIG. 3 are specific examples of the obtained heat conductive sheet. As shown in FIG. 2, the heat conductive sheet 1 has a heat conductive layer in which carbon fibers 5 and, if necessary, magnetic particles 6 are oriented in the binder 4 in the direction of the thickness of the heat conductive sheet. 2 and an electrical insulating layer 3 made of a binder 8 containing a heat-containing conductive filler 7 as required.

As shown in FIG. 3, in the heat conductive sheet 1 according to the present invention, carbon fibers 9 having a magnetic material adhered to the surface of the binder 4 if necessary are contained in the binder 4. It comprises a heat conductive layer 2 oriented in the thickness direction, and an electric insulating layer 3 made of a binder 8 containing a heat conductive filler 7 as required. Such a heat conductive sheet may be such that a part or all of the surface of the heat conductive layer according to the present invention is finally covered with the electric insulating layer, and the order of forming these layers is not particularly limited. .

For example, a cured sheet of the electric insulating layer is formed first, and the surface of the electric insulating layer sheet is coated with the composition for the heat conductive layer by coating or the like, and then the carbon fibers in the composition for the heat conductive layer are coated. The heat conductive layer is cured or semi-cured while orienting the heat conductive layer in the thickness direction of the sheet, whereby the heat conductive sheet according to the present invention can be formed. Also, the heat conductive layer is formed first, and the surface of the heat conductive layer is coated with a composition for an electrical insulating layer by coating or the like, and then the electrical insulating layer is cured or semi-cured by heat or light, An electric insulating layer can be formed on the surface of the heat conductive layer.

Further, it is also possible to form a heat conductive layer and an electric insulating layer, and adhere these to form a heat conductive sheet according to the present invention. In this case, when one of the heat conductive layer and the electric insulating layer is in a semi-cured state, a heat conductive sheet is thermocompressed to form a heat conductive sheet having high adhesion between the heat conductive layer and the electric insulating layer. Can be done.
Further, at least when the electrical insulating layer is in a semi-cured state,
The heat conductive sheet is sandwiched between a heating element and a heat dissipating member and thermocompression bonded to form a heat dissipating structure having excellent adhesion between the heat generating element and the heat dissipating member. (Method of Manufacturing Heat Conductive Layer) The method for orienting carbon fibers in the thickness direction of the heat conductive layer constituting the heat conductive sheet according to the present invention may be such that the carbon fibers are substantially oriented in the thickness direction of the heat conductive layer. Although not particularly limited, for example, the composition for a heat conductive layer containing a magnetic substance and carbon fibers in a binder is formed into a sheet, and a magnetic field is applied in a thickness direction of the sheet composition for the heat conductive layer. In addition to orienting the magnetic material and the carbon fibers, the heat conductive layer sheet composition can be cured or semi-cured by light irradiation or heating to form the heat conductive layer according to the present invention.

When the carbon fibers are oriented by containing the magnetic material as described above, the orientation of the magnetic material and the carbon fibers and the curing or semi-curing of the sheet composition for the heat conductive layer may be performed simultaneously. After orientation, curing or semi-curing may be performed. More specifically, the strength of the magnetic field applied to orient the magnetic material and the carbon fiber in the heat conductive layer sheet composition in the thickness direction of the heat conductive layer sheet composition is as follows. , Preferably about 500 to 50,000 Gauss, more preferably about 2000 to 20,000 Gauss, the magnetic field application time is preferably about 1 to 120 minutes,
More preferably, it is about 5 to 30 minutes. The application of the magnetic field may be performed at room temperature, or may be performed by heating and curing as needed.

The method for curing or semi-curing the composition for a heat conductive layer according to the present invention differs depending on the kind of the binder used and the required sheet performance and is not limited.
For example, using the epoxy resin as a binder component,
Preferably 80 to 180 ° C, more preferably 100 to 180 ° C
By heating in the range of 160 ° C., the sheet composition for a heat conductive layer can be cured. The heating method is not particularly limited, and a known method can be used. The sheet composition for a heat conductive layer may be cured using a usual heater or the like. The heating time is not particularly limited, but is usually preferably in the range of about 5 to 120 minutes.

For example, when the (meth) acrylic resin is used as a binder component, light such as visible light, ultraviolet light, infrared light, far ultraviolet light, electron beam, X-ray, etc. is emitted in the presence of a photoinitiator. It is also possible to obtain a heat conductive layer by selectively irradiating. The method of light irradiation is not particularly limited, and a known method can be used.For example, using a normal photopolymerization apparatus, the sheet composition for a heat conductive layer is irradiated with ultraviolet light having a specific wavelength or the like. Just do it. In the case of an ultraviolet fluorescent lamp, the irradiation time is usually about 2 to 3 minutes, and the irradiation distance is 5 minutes.
In the case of a high-pressure mercury lamp, the irradiation time is preferably about 10 to 20 seconds, and the irradiation distance is preferably about 7 to 20 cm. (Method of Forming Thermally Conductive Sheet Using Photocurable Component and Thermosetting Component Together) As a binder constituting a thermal conductive layer or an electrical insulating layer, (meth) as the photocurable component
When an acrylic compound and an epoxy compound are used as the thermosetting component, for example, a composition for an electric insulating layer of a combination of the photocurable component and the thermosetting component is applied to the surface of a cured heat conductive layer. Coating to form a sheet composition for an electrical insulating layer, and further selectively irradiating light such as visible light, ultraviolet light, infrared light, far ultraviolet light, electron beam, X-ray, etc. By curing the photocurable component contained therein, a heat conductive sheet in which the heat conductive layer or the electric insulating layer is in a semi-cured state can be obtained.

When the photocurable component and the thermosetting component are used in combination, the method of curing the photocurable component by irradiation with light to produce a semi-cured heat conductive sheet is not particularly limited, and a known method can be used. A method can be used. For example, the composition for an electrical insulating layer may be applied to the surface of the heat conductive layer by using a usual photopolymerization apparatus, and may be irradiated with ultraviolet rays having a specific wavelength. In the case of an ultraviolet fluorescent lamp, the irradiation time is about 2 to 3 minutes, the irradiation distance is about 5 to 10 cm, and in the case of a high pressure mercury lamp, the irradiation time is about 10 to 20 seconds, and the irradiation distance is about 7 to 20 cm. Preferably, there is.

When the photo-curable component and the thermo-curable component are used together in the heat conductive layer, a magnetic field is applied to the heat conductive layer sheet composition so that the magnetic material and the carbon fibers are oriented in the thickness direction of the heat conductive sheet. The process procedure for obtaining a semi-cured heat conductive sheet by performing light irradiation while orienting to is not particularly limited, and the light irradiation may be performed simultaneously with the application of a magnetic field, or the magnetic material and the carbon fibers may be applied by applying a magnetic field. After orientation in the thickness direction of the sheet, the sheet composition may be semi-cured by light irradiation. From the viewpoint of sufficiently orienting the magnetic material and the carbon fibers, it is preferable that after applying a magnetic field to orient them, the sheet composition is semi-cured by light irradiation.
The temperature at which such a semi-cured heat conductive sheet is obtained is not particularly limited as long as the thermosetting component contained in the sheet-like composition is not cured, but may be usually performed at about room temperature, and is preferably performed. 20-100 ° C, more preferably 2
Desirably, the temperature is 0 to 60 ° C.

According to such photo-curing, a semi-cured heat conductive sheet can be formed simply and in a short time. The composition ratio of the binder, carbon fiber, and magnetic material in the heat conductive layer thus obtained is the same as that of the above-described composition for a heat conductive layer. The composition ratio of the heat conductive filler in the electric insulating layer is the same as the composition for the electric insulating layer. (Thermal Conductive Sheet with Protective Film) The thermal conductive sheet according to the present invention may be covered on both sides or one side of the surface with a protective film. In the process of forming the heat conductive layer or the electric insulating layer, one or both surfaces of each layer may be covered with a protective film.

The material of such a protective film is not particularly limited as long as the material of the protective film is not deteriorated by application of a magnetic field and irradiation of light such as ultraviolet rays without impairing the application of a magnetic field and light irradiation. It has elasticity and light resistance, and has such a strength that the semi-cured heat conductive sheet can be easily peeled off without being broken when the protective film is peeled off to be subjected to thermocompression bonding or the like. For example, polyethylene terephthalate (PET), polyimide (PI), polyethylene (PE) and the like can be preferably used.

The thickness of such a protective film is not particularly limited, but is preferably about 5 to 150 μm from the viewpoint of easy peeling of the heat conductive sheet. Also,
When the heat conductive sheet according to the present invention has two protective films, it may have a spacer for separating these protective films by a certain distance. The material of such a spacer is not particularly limited.
Alternatively, polyethylene terephthalate or the like can be preferably used. The length of the spacer in the thickness direction of the sheet (thickness) and the length in the outer peripheral direction can be changed depending on the thickness and size of the heat conductive sheet, and the composition for the heat conductive layer or the composition for the electric insulating layer can be changed. There is no particular limitation as long as the object can be held.

The method of covering such a composition for a heat conductive layer or the composition for an electrical insulating layer with a protective film is not particularly limited. For example, when the composition for a heat conductive layer is formed into a sheet by a roll rolling method, The composition can be obtained by rolling while sandwiching the composition with a protective film. Further, for example, the protective film can be formed by holding two protective films in parallel at a predetermined distance by a spacer or the like and filling the composition between the protective films. At this time, the process may be performed with a magnetic field applied. <Heat Dissipating Structure Using Thermal Conductive Sheet> As shown in FIG. 4, in the heat dissipating structure 10 according to the present invention, the heat generating element 11 and the heat dissipating member 12 are interposed via the heat conductive sheet 1 according to the present invention. The heat conductive sheet contains a binder, carbon fiber, and a magnetic material as needed, and the heat conductive layer is arranged such that the carbon fiber and the magnetic material are oriented in the thickness direction of the heat conductive sheet. And an electrical insulating layer containing a thermally conductive filler as required. Examples of such a heating element include a semiconductor element and a semiconductor package.

The bonding between the heating element and the heat radiating member or the circuit board through the heat conductive sheet according to the present invention is performed by bonding the cured or semi-cured heat conductive sheet.
Heating element, sandwiched between the heat dissipation member or circuit board,
Then, the heat conductive sheet can be pressed by pressing. In this case, as the heat conductive sheet, a heat conductive sheet containing the photo-curable component and the thermo-curable component, and a semi-cured electric insulating layer covering the surface of the heat conductive sheet can be preferably used. .

When such a semi-cured heat conductive sheet is thermocompression-bonded, a heating element according to the heat dissipation structure,
It is desirable that the heat radiation member or circuit board, wiring, bumps and other components in the heat radiation structure be deformed, damaged or melted by the temperature and pressure associated with thermocompression bonding, at room temperature or to the extent that the curing reaction does not proceed sufficiently Temporary bonding in a state where pressure is applied in a heated state, and then heating to complete the curing reaction, or a method in which bonding and curing are simultaneously performed by heating sufficiently at the time of pressure bonding, etc., should be appropriately selected as necessary Can be. For example, the thermocompression bonding temperature is preferably 80 to 180 ° C, more preferably 100 to 16 ° C.
It is desirable to carry out at 0 ° C., particularly preferably at 120 to 150 ° C. When the temperature is lower than 80 ° C., the heat curing is not performed smoothly, and a long reaction time may be required. When the temperature is higher than 180 ° C., the solder or the like attached to the heating element or the like may be dissolved. . The pressure for thermocompression bonding is preferably 0.1 to 5 kg / cm ² , particularly preferably 0.5 to ² kg / cm ² .
It is desirable to carry out in the range of kg / cm ² . Pressure is 0.1kg / c
When the pressure is less than m ² , adhesion between the heating element and the heat radiating member may be insufficient, and when the pressure is more than 5 kg / cm ² , the semiconductor element as the heating element may be damaged.

The time for such thermocompression bonding is usually preferably about 1 minute to 120 minutes, and more preferably about 20 minutes to 60 minutes. As described above, when the heat generating element and the heat radiating member are thermocompression-bonded via the semi-cured heat conductive sheet according to the present invention, the heat generating element and the heat radiating member or the circuit board can be sufficiently bonded to each other. It is possible to prevent the heating element, heat radiating member, and the like from peeling off from the heat conductive sheet due to expansion, contraction, or external vibration, impact, etc. of the member due to heat generation from the body,
It is possible to improve the heat radiation or the reliability of the function of the semiconductor package. In addition, the thermocompression bonding of the heat-generating element and the heat radiating member using the semi-cured heat conductive sheet is performed by cutting the semi-cured heat conductive sheet into a predetermined shape and sandwiching the heat-generating element and the heat radiating member. Just do it.

Since the heat conductive sheet according to the present invention is excellent in elasticity, it can withstand expansion and contraction of the members in the heat dissipation structure. Then, in the heat conductive sheet according to the present invention, since the carbon fibers are oriented in the thickness direction of the heat conductive sheet, and part or all of the surface of the heat conductive layer is covered with the electrical insulating layer, It is possible to obtain a heat radiating structure having excellent electric insulation between the heat generating element and the heat radiating member and having high heat radiating efficiency.

[0072]

The heat conductive sheet according to the present invention comprises a heat conductive layer in which carbon fibers are oriented in the direction of the thickness of the heat conductive sheet in a binder in a cured or semi-cured state; Therefore, the anisotropic thermal conductivity in the thickness direction is high, and the insulating property is ensured. Therefore, it is effective for a heat radiating structure that requires insulation between a heat generating element such as a semiconductor element or a semiconductor package and a heat radiating member. Moreover, the heat conductive sheet according to the present invention is excellent in heat resistance, durability, mechanical strength, and also excellent in adhesion to a heating element.

[0073]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by these Examples.

[0074]

Example 1 [Production of a heat conductive sheet] A nickel metal was electrolessly plated on a surface of a two-part addition type thermosetting liquid silicone rubber (viscosity: 100 P) so as to have an average film thickness of 1 μm. Average diameter 10μm, average length 200
μm pitch-based carbon fiber (thermal conductivity 140 in the fiber axis direction)
0 W / mK) in 15 volume fractions (%), and 3
After mixing for 0 minutes, a composition (A) for a heat conductive layer was obtained. For the same silicone rubber as above, BN having an average particle size of 3 μm
After adding 25 volume fraction (%) of (boron nitride) powder and mixing in a vacuum for 30 minutes, a PET film (50 μm thick) was formed so that the thickness of the silicone rubber composition was about 20 μm.
m) was applied on top. Thereafter, the sheet was heated at 100 ° C. for 30 minutes to obtain an electric insulating sheet protected on one side by PET. On the electromagnet through which the magnetic field lines pass in the thickness direction of the sheet, a PET film is placed between two previously prepared sheets for electrical insulation with a PET film, which are placed in parallel via a spacer having a thickness of 0.2 mm. To the outside,
The composition for a heat conductive layer was filled to obtain a sheet for a molded product. Next, the sheet for a molded article is treated with an electromagnet at room temperature at a magnetic field strength of about 4000 gauss for 20 minutes so that the lines of magnetic force pass in the thickness direction of the molded article sheet.
C. to obtain a cured sheet. By removing the PET film from both sides of the cured sheet, a heat conductive sheet having a thickness of 0.24 mm, both sides of which were covered with an electrical insulating layer, was obtained.

The obtained heat conductive sheet was evaluated for heat conductivity and electrical insulation by the following methods. Table 1 shows the obtained results. <Thermal conductivity test> The thermal diffusivity of the obtained thermal conductive sheet was measured by a thermal alternating current method, and the thermal conductivity was evaluated from the values of the heat capacity and the density separately obtained by an ordinary method.

More specifically, FIG. 7 shows a method for evaluating the thermal diffusivity of a heat conductive sheet by a thermal alternating current method, in which the phase difference (△ θ) of a temperature change is measured by the thermal alternating current method. The thermal diffusivity (α) is calculated based on the relationship shown in the following formula 2, and the thermal conductivity in the thickness direction of the heat conductive sheet is calculated from the values of the heat capacity and density separately obtained by a conventional method based on the following formula 1. (Λ) can be obtained.

As shown in FIG. 5, the system for measuring the phase difference (△ θ) of the temperature change by the thermal AC method comprises a function generator 16, a lock-in amplifier 17, a personal computer 18, a sample 13, electrodes 14 and 15. .
By sandwiching both surfaces of sample 13 between electrodes 14 and 15 (a metal thin film provided on a glass plate by sputtering) and applying an AC voltage to one electrode 14, sample 1
3 was heated, the temperature change was detected from the resistance change of the other electrode 15, and the phase difference (Δθ) of the temperature change (ΔT) was measured from the response delay as shown in FIG. The thermal diffusivity (α) was determined based on Equation 2, and the conductivity (λ) was determined based on Equation 1.

[0078]

(Equation 1)

[0079]

(Equation 2)

<Electrical Insulation Test> The obtained heat conductive sheet was sandwiched between two copper plates whose surfaces were plated with gold, and the insulation was examined by evaluating the resistance between the copper plates.

[0081]

Example 2 A photoinitiator was added to a mixture of 60 parts of polyethylene glycol dimethacrylate (PDE400, manufactured by Kyoeisha Co., Ltd.) and 40 parts of a bisphenol A type epoxy resin (EP1001, manufactured by Yuka Shell Epoxy Co., Ltd.). 3% by weight of Irgacure 651, Ciba-Geigy Co., Ltd. based on methacrylate, imidazole-based curing agent (2P4M
HZ-PW, manufactured by Shikoku Kasei Co., Ltd.)
Pitch-based carbon fibers having an average diameter of 10 μm and an average length of 200 μm were electrolessly plated with nickel metal on the surface of the binder (I) obtained by adding 0% by weight so as to have an average film thickness of 1 μm. Thermal conductivity 1400W / m · K)
Was added in 15 volume fractions (%) and mixed in vacuum for 30 minutes,
A composition (B) for a heat conductive layer was obtained.

Binder (I) comprising the same components as described above
Then, 25 volume fraction (%) of BN (boron nitride) powder having an average particle diameter of 3 μm is added, and the mixture is mixed in a vacuum for 30 minutes, so that the thickness of the composition comprising the binder (A) is about 20 μm. P
Coated on ET film (50 μm). Then 1
By heating at 00 ° C. for 30 minutes, an electric insulating sheet having one surface protected by PET was obtained.

On the electromagnet through which the lines of magnetic force pass in the thickness direction of the sheet, between the two PET films placed in parallel via a spacer having a thickness of 0.2 mm, the composition for a heat conductive layer (B) To obtain a sheet-like composition comprising the composition for thermal conductivity. Next, the sheet-shaped composition is treated with an electromagnet at room temperature at a magnetic field strength of about 4000 gauss for 20 minutes so that magnetic lines of force pass in the thickness direction of the sheet-shaped composition. The apparatus was irradiated with ultraviolet rays for 1 minute to obtain a sheet constituting a heat conductive layer having a thickness of 0.2 mm in a semi-cured state. The heat conductive sheet from which PET on both sides was removed was sandwiched between the two electrically insulating sheets, one side of which was protected by a PET film, with the PET film facing outside, and pressure was applied under a hot press. After heating in the state, the PET film was peeled off and the thickness was 0.2
A 4 mm cured heat conductive sheet was obtained.

The obtained heat conductive sheet was subjected to a heat conductivity test and an electrical insulation test in the same manner as in Example 1.

[0085]

[Comparative Example 1] In Example 1, instead of using an electric insulating sheet, two PET films (50 μm each) having no electric insulating layer disposed in parallel via a spacer having a thickness of 0.24 mm were used. A sheet was obtained in the same manner as in Example 1, except that the composition for a heat conductive layer (A) was filled in between, and the composition was heated and cured at 100 ° C. without applying a magnetic field.

In the same manner as in Example 1, the obtained sheet was subjected to a thermal conductivity test and an electrical insulation test.

[0087]

Comparative Example 2 In Example 1, instead of using an electric insulating sheet, two PET films (50 μm each) having no electric insulating layer provided in parallel via a spacer having a thickness of 0.24 mm were used. In between the resin composition for the heat conductive layer (A)
A sheet was obtained in the same manner as in Example 1 except that 充填 was filled.

In the same manner as in Example 1, the obtained sheet was subjected to a thermal conductivity test and an electrical insulation test.

[0089]

Comparative Example 3 The composition for a heat conductive layer (B) was cured under application of a magnetic field in the same manner as in Example 2 except that the sheet for electrical insulation was not used. I got a sheet. In the same manner as in Example 1, the obtained sheet was subjected to a thermal conductivity test and an electrical insulation test.

The thermal conductivity of the sheets obtained in Examples 1 and 2 and Comparative Examples 1 to 3 was less than 5 times the thermal conductivity of the sheet obtained in Comparative Example 1; A sample of 5 times or more and less than 20 times was evaluated as Δ, and a sample of 20 times or more was evaluated as ○.
Regarding the electrical insulation test, a resistance of 10 MΩ or more was evaluated as Ω, and a resistance of less than 10 MΩ was evaluated as ×. Table 1 shows the results.

[0091]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a cross section of a heat conductive sheet including a heat conductive layer and an electric insulating layer.

FIG. 2 is a schematic diagram of a cross section of a heat conductive sheet including a heat conductive layer containing magnetic particles and carbon fibers, and an electric insulating layer containing a heat conductive filler.

FIG. 3 is a schematic diagram of a cross section of a heat conductive sheet including a heat conductive layer containing a carbon fiber having a magnetic substance adhered to the surface and an electric insulating layer containing a heat conductive filler.

FIG. 4 is a schematic view of a cross section of a heat dissipation structure.

FIG. 5 is a diagram showing a method of measuring thermal conductivity by a thermal alternating current method.

FIG. 6 is a diagram showing a phase difference of a temperature change in a method of measuring thermal conductivity by a thermal alternating current method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 heat conductive sheet 2 heat conductive layer 3 electric insulating layer 4 binder 5 carbon fiber 6 magnetic particles 7 heat conductive filler 8 binder 9 carbon fiber with magnetic material adhered to surface 10 heat dissipation structure 11 heat generator 12 heat dissipation member 13 Sample 14 electrode 15 electrode 16 function generator 17 lock-in amplifier 18 personal computer

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C09K 5/08 C09K 5/00 E (72) Inventor: Hozumi Sato 2--11-24 Tsukiji, Chuo-ku, Tokyo Jay F Co., Ltd. F-term (reference) 4F100 AB16 AD03B AD04B AD07B AD11A AN02 AR00C AR00D AS00E BA04 BA06 CA20A EJ421 EJ521 EJ611 GB41 JB13A JB14A JG04B JG06A JJ01A JJ03 JJ06C JJ10DJK0 JL01 DA054

Claims (10)

[Claims] 1. A thermoelectric device comprising: a heat conductive layer in which carbon fibers are oriented in a thickness direction in a binder; and an electric insulating layer provided on a part or all of the surface of the heat conductive layer. Conductive sheet. 2. The heat conductive sheet according to claim 1, wherein the electric insulating layer contains a heat conductive filler. 3. The heat conductive sheet according to claim 1, wherein the heat conductive filler is an oxide-based, nitride-based, or carbide-based ceramic. 4. The heat conductive sheet according to claim 1, wherein the binder is photo-curable and / or thermo-curable. 5. The heat conductive layer of the heat conductive sheet contains a magnetic material, and the magnetic material is oriented in a binder in a thickness direction of the heat conductive sheet.
5. The heat conductive sheet according to any one of items 1 to 4. 6. The heat conductive sheet according to claim 5, wherein the magnetic material is attached to a surface of a carbon fiber. 7. The heat conductive sheet according to claim 5, wherein the magnetic material is magnetic particles. 8. A magnetic field is applied in the thickness direction of the heat conductive layer sheet composition comprising a binder, carbon fibers and a magnetic material to cause the magnetic material and carbon fibers to move in the thickness direction of the heat conductive layer sheet composition. The method for producing a heat conductive sheet according to any one of claims 5 to 7, wherein the heat conductive layer sheet composition is cured or semi-cured while being oriented. 9. A heat conductive sheet, wherein a heat generating element and a heat radiating member or a circuit board are joined via the heat conductive sheet according to claim 1. Heat dissipation structure. 10. The heat radiating structure using a heat conductive sheet according to claim 9, wherein the heating element is a semiconductor element or a semiconductor package.