JP2003026827A - Heat-conductive sheet, method for producing heat- conductive sheet and heat-radiating structure using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-conductive sheet, improved in anisotropic heat conductivity in the thickness direction, excellent in heat resistance, endurance and mechanical strength and adhesiveness to heating elements. SOLUTION: In this heat-conductive sheet, are orientated graphite powders attaching a magnetic material on the surface in the thickness direction in a binder. A composition for heat-conductive sheet composed of an uncured binder and graphite powders attaching the magnetic material on the surface of a sheet, applying a magnetic field to the thickness direction of the sheet and curing the sheet to orientate the graphite powders in the thickness direction of the sheet.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As electric equipment or electronic equipment is further improved in performance, the number of electrodes of semiconductor elements is increasing, and the semiconductor elements tend to have higher power consumption, so that heat generated from electronic parts can be radiated more efficiently. It is important to do. In order to efficiently dissipate heat from a semiconductor package or a semiconductor, attempts have been made to dissipate heat by providing a heat dissipating mechanism in the semiconductor package or the like, or to dissipate heat from a wiring board on which a semiconductor element is mounted. For example, the heat radiation of a semiconductor package is generally performed by natural convection from the main body surface of the heating element or forced convection by a fan provided in the unit. With this method, however, the heat generation amount increases as the function of the semiconductor package improves. However, there is a problem in that the heat dissipation effect becomes insufficient and the deterioration of the performance of the semiconductor package cannot be reliably prevented. Also, a heat sink is pressed against the surface of the semiconductor package,
A method to improve heat dissipation by convection is also provided, but this method reduces the contact area at the pressure contact surface between the semiconductor package and the heat sink due to the formation of a gap, and there is a problem in achieving the heat dissipation effect as designed. there were. Therefore, for example, when joining a heat radiator to a semiconductor package, a resin sheet or the like having thermal conductivity is sandwiched between the semiconductor package and the heat radiator, and the heat radiation is effective while the semiconductor package and the heat radiator are brought into close contact with each other. Is being done to. Further, for example, in joining a semiconductor element and a heat spreader in contact with the semiconductor element, an adhesive having a high thermal conductivity is interposed between the semiconductor element and the heat spreader to maintain heat dissipation from the semiconductor element. Is being done.

As such a resin composition or the like for providing high heat conductivity, which is interposed between the semiconductor element or the semiconductor package and the heat radiator, for example, JP-A-5-32691 is known.
In the publication No. 6, a clay-like thermosetting adhesive type silicone rubber sheet is used, but this silicone rubber sheet is not sufficient in terms of thermal conductivity to cope with high power consumption of semiconductor elements. There was a point. Further, 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, and in order to further improve the high thermal conductivity, the metal particles are dispersed in the resin sheet. Attempts have also been made to achieve high dispersion and high packing. However, even if the metal particles are highly dispersed and highly filled, heat diffuses in random directions, so that there is a problem that the thermal conductivity between the semiconductor element and the radiator is not sufficiently improved. However, there is a problem in that the tensile strength and elasticity of the resin sheet may be deteriorated and the molding processability may be deteriorated because the resin is highly filled.

Therefore, the inventors of the present invention have conducted extensive studies to solve the above problems, and the graphite-based carbon powder having a magnetic substance attached to the surface of the binder is oriented in the thickness direction of the high thermal conductive sheet. It is found that the use of the high thermal conductivity sheet significantly improves the anisotropic thermal conductivity in the thickness direction of the high thermal conductivity sheet, and the high thermal conductivity sheet has excellent heat resistance, durability and mechanical strength. They have found that they are excellent and also have excellent adhesion to a heating element, and have completed the present invention.

Further, the present inventors have found a composition for a high thermal conductivity sheet which gives high thermal conductivity in the thickness direction as described above, and have found a simple method for producing a high thermal conductivity sheet. Further, the present inventors have found a heat dissipation structure using a high thermal conductivity sheet, and have completed the present invention.

[0006]

SUMMARY OF THE INVENTION The present invention is intended to solve the problems associated with the prior art as described above, in which the high thermal conductive sheet has high anisotropic thermal conductivity in the thickness direction, heat resistance and durability. It is an object of the present invention to provide a high thermal conductive sheet excellent in mechanical strength and adhesiveness with a heating element, and a method for producing the same. Moreover, this invention aims at providing the composition for high thermal conductivity sheets which can manufacture such a high thermal conductivity sheet. Another object of the present invention is to provide a heat dissipation structure using such a high thermal conductivity sheet.

[0007]

SUMMARY OF THE INVENTION The high thermal conductive sheet according to the present invention is characterized in that a graphite-based carbon powder having a magnetic material attached to the surface of a binder is oriented in the thickness direction of the high thermal conductive sheet. . This graphite-based carbon powder has a thermal conductivity of 5
It is preferably 0 W · m −1 · K −1 or more. further,
It is preferable that the graphite-based carbon powder having a magnetic substance attached to the surface is contained in a total amount of 2 to 70% by volume in the total volume of the high thermal conductivity sheet.

A method for producing a high thermal conductivity sheet in which graphite-based carbon powder having a magnetic substance adhered to the surface in such a binder is oriented in the thickness direction of the high thermal conductivity sheet,
A composition for high thermal conductivity sheet containing an uncured binder and a graphite-based carbon powder having a magnetic substance attached to the surface is formed into a sheet, and a magnetic field is applied to the sheet-shaped composition in the thickness direction thereof. The sheet-shaped composition is cured or semi-cured while orienting the graphite-based carbon powder having a magnetic substance attached to the surface in the thickness direction of the sheet-shaped composition.

The heat dissipation structure using the high heat conductivity sheet according to the present invention is characterized in that the heat generating element and the heat dissipation member or the circuit board are bonded via the high heat conductivity sheet. The heating element is preferably a semiconductor device or a semiconductor package.

[0010]

DETAILED DESCRIPTION OF THE INVENTION The high thermal conductive sheet, the method for producing the high thermal conductive sheet, and the heat dissipation structure using the high thermal conductive sheet according to the present invention will be described in more detail below. [Composition for High Thermal Conductivity Sheet] The composition for high thermal conductivity sheet according to the present invention is characterized by containing an uncured binder and a graphite-based carbon powder having a magnetic substance attached to the surface thereof. Furthermore, the composition for a high thermal conductive sheet according to the present invention may contain other additives, if desired. Below, the composition for high thermal conductivity sheets will be described first. <Binder> In the sheet composition for forming the high thermal conductive sheet of the present invention, either a rubber-like polymer or a resin-like polymer can be used as a binder, and the binder is liquid before curing or semi-curing. It is possible to preferably use a binder that is Further, a photocurable component and / or a thermosetting component may be added to the binder, and the rubber-like polymer or resinous polymer as the binder component may be added to the photocurable component and / or the thermosetting component. It can also serve as an ingredient.

The rubber-like polymer, resin-like 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 rubbers such as polybutadiene, natural rubber, polyisoprene, SBR and NBR, and hydrogenated products thereof, and styrene-butadiene block. Block copolymers such as copolymers and styrene isoprene block copolymers and hydrogenated products thereof, chloroprene, urethane rubber, polyester rubber, epichlorohydrin rubber, silicone rubber, ethylene propylene copolymer, ethylene propylene diene copolymer And so on. Of these, silicone rubber is particularly preferable from the viewpoints of molding processability, weather resistance, heat resistance and the like.

Here, the silicone rubber will be described in more detail. Liquid silicone rubber is preferably used as the silicone rubber. Liquid silicone rubber is
It may be either a condensation type or an addition type. Specific examples thereof include dimethyl silicone raw rubber, methylphenyl vinyl silicone raw rubber, and those containing functional groups such as vinyl group, hydroxyl group, hydrosilyl group, phenyl group and fluoroalkyl group. (Resin-like polymer) As the resin-like polymer used in 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, and examples thereof include phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, Examples thereof include a bisphenol AD type epoxy resin, an alicyclic epoxy resin, polyglycidyl (meth) acrylate, and a copolymer of glycidyl (meth) acrylate and another copolymerization monomer. (Photocurable component) The photocurable component contained in the binder used in the present invention includes photoradical-polymerizable, photocationic-polymerizable, coordinated-photopolymerizable, and photopolyaddition reactions that are cured by ultraviolet rays and electron beams. Included are monomers, oligomers, prepolymers or polymers that are organic. Such photocurable monomers, oligomers, prepolymers or polymers include (meth) acrylic compounds, photoradical polymerizable compounds such as vinyl ether-maleic acid copolymers, and photopolyaddition reactions such as thiol-ene compounds. Of these, a (meth) acrylic compound is particularly preferable. Of these, as the photocurable component according to the present invention, a monomer of a (meth) acrylic compound, which takes a short time for photocuring, is preferably used.

The photopolymerizable monomer, oligomer, prepolymer or monomer capable of inducing a polymer of such a (meth) acrylic compound is specifically a cyano group-containing vinyl compound such as acrylonitrile or methacrylonitrile. , (Meth) acrylamide compounds and (meth) acrylic acid esters. Examples of the (meth) acrylamide compound include acrylamide, methacrylamide, and N, N-dimethylacrylamide, which may be used alone or in combination.

Examples of the (meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, hydroxyethyl (meth) acrylate and phenyl (meth). ) Monofunctional (meth) acrylates such as acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, tricyclodecanyl (meth) acrylate, and the like. Used alone or as a mixture. Further, as the polyfunctional (meth) acrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate ) 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 , Diacrylate of propylene oxide adduct, bifunctional (meth) acrylate such as 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.

Among these, particularly preferable are di (meth) acrylates such as diethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate and glycerol di (meth) acrylate. . These may be used alone or as a mixture. (Thermosetting Component) The thermosetting component that can be preferably used as the binder used in the present invention includes a monomer, an oligomer, a prepolymer or a polymer having a functional group that is cured by heat.

As such a functional group, an epoxy group, a hydroxyl group, a carboxyl group, an amino group, an isocyanate group,
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 epoxy compounds, urethane compounds, and silicone compounds. Among these, it is preferable to use an epoxy compound and a silicone compound from the viewpoint of shortening the heat curing time. Furthermore, the epoxy compound or the silicone compound has two or more epoxy groups, vinyl groups or hydrosilyl groups in the molecule. Is desirable.

The molecular weight of such an epoxy compound is not particularly limited, but is usually 70 to 20,000,
It is preferably 300 to 5000, and specifically, various epoxy resins having a certain molecular weight or more, such as oligomers, prepolymers or polymers of the epoxy compounds are preferably used. Specific examples of such an epoxy compound include the above-mentioned phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, and alicyclic ring. Examples thereof include formula epoxy resins, polyglycidyl (meth) acrylate, and copolymers of glycidyl (meth) acrylate and other copolymerization monomers.

When these phenol novolac type epoxy resins and the like are used as the thermosetting component, they can simultaneously serve as the resinous polymer component. Examples of the silicone-based compound include the above-mentioned vinyl rubber containing a silicone group, and a vinyl group-containing silicone type is a preferable silicone-based compound in view of reactivity with a hydrosilyl group-containing compound used as a curing agent. When these silicone compounds are used as the thermosetting component, they can simultaneously serve as the rubber-like polymer component.

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

As the photo-curable component and the thermo-curable component used in the present invention, a combination of the (meth) acrylic compound and the epoxy compound is used to form a semi-cured heat conductive composite sheet. It is preferable from the viewpoint of shortening the time and excellent adhesiveness. A method for mixing such a photocurable component and a thermosetting component is not particularly limited, but for example, when the acrylic compound monomer is used as the photocurable component and the epoxy resin is used as the thermosetting component, an acrylic resin is used. The epoxy resin can be dissolved and mixed in 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 does not cure under photocuring conditions is used. You can also combine. Examples of the compound containing such a photocurable functional group include the (meth) acrylic compound, and examples of the thermosetting functional group include the epoxy group, and specific compounds that can serve as both components include: Examples thereof include epoxy (meth) acrylamide such as glycidyl (meth) acrylamide, glycidyl (meth) acrylate, and epoxy (meth) acrylate such as 3,4-epoxycyclohexyl (meth) acrylate.

A reactive monomer having an unsaturated double bond can also be contained as a binder component, and examples of such a reactive monomer include hydroxystyrene, isopropenylphenol, styrene and α-.
Aromatic vinyl compounds such as methylstyrene, p-methylstyrene, chlorostyrene, p-methoxystyrene,
Examples thereof include heteroatom-containing alicyclic vinyl compounds such as vinylpyrrolidone and vinylcaprolactam. (Photoinitiator) The composite sheet composition according to the present invention, depending on the type of radiation used in curing the photocurable component,
For example, in the case of ultraviolet curing, a photoinitiator or the like can be mixed.

Such a photoinitiator may be one that cures the photocurable component contained in the sheet composition under the photocurable conditions according to the present invention, and the photocurable component and heat When used together with the curable component, it is sufficient that the photocurable component is cured and the thermosetting component is not cured, and a known photoinitiator can be used. Examples of such a photoinitiator include α-diketones such as benzyl and diacetyl; 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, tribromomethylphenyl sulfone, tris (trichloromethyl)
Examples thereof include halogen compounds such as -s-triazine; peroxides such as di-t-butyl peroxide; and acylphosphine oxides such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide. Also,
As commercial products, Irgacure 184, 651, 50
0, 907, CG1369, CG24-61, Darocur 1116, 1173 (manufactured by Ciba Specialty Chemicals), Lucillin LR8728, TPO (BA
SF manufactured), Yubecryl P36 (UCB manufactured), and the like.

Of these, when a photocurable component and a thermosetting component are used together as a binder, the photocurable component contained in the sheet composition is a (meth) acrylic compound,
When the thermosetting component is an epoxy compound, a photoinitiator such as Irgacure 651 or Lucillin TPO, which has a high curing rate, can be preferably used. The amount of such a photoinitiator to be used is preferably an appropriate amount in consideration of the actual curing speed, the balance with the pot life, and the like. Specifically, with respect to 100 parts by weight of the photocurable component. , Preferably 1 to 50 parts by weight in the binder.
It is particularly preferable that the content is ˜30 parts by weight. 1
If it is less than 50 parts by weight, the sensitivity tends to be lowered by oxygen, and if it exceeds 50 parts by weight, the compatibility may be poor or the storage stability may be deteriorated.

Further, a photoinitiator aid can be used in combination with such a photoinitiator. When the photoinitiator aid 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-initiation aid, a photo-initiation aid that is usually used can be used. Examples of such photoinitiator aids include triethanolamine, methyldiethanolamine, triisopropanolamine, n-butylamine, N-
Aliphatic amines such as methyldiethanolamine, diethylaminoethyl (meth) acrylate, Michler's ketone, 4,4'-diethylaminophenone, ethyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, 4-
Examples include dimethylaminobenzoate isoamyl and the like. (Thermosetting Agent) The composition for a sheet according to the present invention may be mixed with a thermosetting agent in order to accelerate 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 acid dihydrazide, imidazoles, hydrosilyl compounds, and vinylsilyl compounds.

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

The amount of such a thermosetting agent used is preferably an appropriate amount in consideration of the actual curing rate and the balance with the pot life, but specifically, the thermosetting agent is a thermosetting agent. The binder is preferably contained in the binder in an amount of 1 to 50 parts by weight, and particularly preferably in an amount of 1 to 30 parts by weight, based on 100 parts by weight of the sex component. The method of adding the photoinitiator and the thermosetting agent is not particularly limited, but from the viewpoint of storage stability, prevention of uneven distribution of the catalyst during mixing of the components, etc., it is preferable to premix with the binder. .

Other Additives In the present invention, the sheet composition may optionally contain an inorganic filler such as ordinary silica powder, colloidal silica, airgel silica or alumina. By containing such an inorganic filler,
The thixotropy at the time of uncured is secured, the viscosity becomes high, and the dispersion stability in the composition of the fibrous filler (A) having magnetism is improved, and the strength of the sheet after curing or semi-curing is improved. Can be made. <Graphite-based carbon powder having magnetic substance attached to surface > The "graphite-based carbon powder having magnetic substance attached to the surface" according to the present invention is
It is a graphite-based carbon powder in which a magnetic material is attached to the surface of the graphite-based carbon powder.

Such graphite-based carbon powder is obtained naturally, such as scale-like graphite and earth-like graphite, or is obtained by heating (graphitizing) amorphous carbon to 2500 to 3000 ° C. An example is artificial graphite. Further, in artificial graphite, the shape and the physical property values are greatly different due to the difference in the degree of graphitization depending on the raw material and the treatment method, but as long as it has good thermal conductivity, it is appropriately selected and used according to the application. be able to. In addition, of the graphite-based carbon powders, either anisotropic graphite-based carbon powder or isotropic graphite-based carbon powder can be used as long as it exhibits high thermal conductivity, but it has an orientation effect on the thermal conductivity. In order to exert the effect more remarkably, it is preferable to use flake-shaped anisotropic graphite.

The graphite-based carbon powder according to the present invention can be prepared by a generally known method, and a commercially available graphite-based carbon powder can be used. The size of the graphite-based carbon powder obtained by passing through a sieve is preferably 5 to 500 μm, more preferably 10
Although it is about 200 μm, the shape thereof does not need to be spherical, and scale-like or rod-like is more preferable. In order for the graphite-based carbon powder used in the present invention to be oriented in the thickness direction in the sheet and sufficiently improve the thermal conductivity, the particle size is 1/2 to 1/100 with respect to the sheet thickness. It is preferably 1/5 to 1/20, and more preferably 1/20. If the particle size is 1/2 or more of the sheet thickness, the orientation tends to be insufficient, and if it is 1/100 or less, a large number of contact points are generated between the particles. May impair conductivity.

The magnetic substance adhered to the surface of the graphite-based carbon powder according to the present invention is the entire surface of the graphite-based carbon powder as long as it exhibits magnetism that can be oriented in the magnetic field direction when a magnetic field is applied by the method described later. May be adhered to the surface of the graphite-based carbon powder without forming a layer.
The material and thickness of the magnetic material are not particularly limited. Examples of the material used for such a magnetic material include a metal exhibiting ferromagnetism such as iron, cobalt, and nickel, or an alloy of the metals, and further, a metal exhibiting ferromagnetism such as iron, cobalt, and nickel. Examples thereof include metal compounds such as intermetallic compounds contained and metal oxides of the metals.

The magnetic substance can be attached to the surface of the graphite-based carbon powder by electroless plating such as chemical plating. Further, a graphite-based carbon powder having a magnetic substance attached to the surface thereof, the surface of which is further treated with a coupling agent such as a silane coupling agent, can be appropriately used. If the surface of the graphite-based carbon powder with the magnetic substance attached to the surface is further treated with a coupling agent, the adhesiveness between the graphite-based carbon powder with the magnetic substance attached to the surface and the binder increases, and As a result, the obtained high thermal conductive sheet has high durability.

The amount of the coupling agent used is appropriately selected within a range that does not affect the thermal conductivity and orientation of the graphite-based carbon powder having the magnetic substance attached to the surface, but the magnetic substance is attached to the surface. It is preferably 0.1 to 10% by weight, more preferably 0.5 to 10%, based on the graphite-based carbon powder.
It is desirable that the amount is, by weight, particularly preferably 1 to 10% by weight. The total amount of the "graphite-based carbon powder having a magnetic substance attached to the surface" according to the present invention contained in the total volume of the composition for high thermal conductivity sheet is the whole of the high thermal conductivity sheet composition. It is preferable that the product is contained in an amount of 2 to 70% by volume in total, more preferably 10 to 60% by volume.

If this proportion is less than 2% by volume, the thermal conductivity of the high thermal conductivity sheet may not be sufficiently enhanced, while if this proportion exceeds 70% by volume,
The resulting high thermal conductive sheet tends to be fragile,
The elasticity required for the high thermal conductivity sheet may not be obtained. <Other Additives> In the present invention, the composition for a high thermal conductivity sheet may contain an inorganic filler such as ordinary silica powder, colloidal silica, airgel silica, or alumina, if necessary. By containing such an inorganic filler, thixotropy at the time of uncured is secured, the viscosity becomes high, and further, the dispersion stability in the composition of the graphite-based carbon powder having the magnetic substance attached to the surface is stable. In addition to the improvement, the strength of the high thermal conductive sheet after curing or semi-curing can be improved. The amount of the inorganic filler used is not particularly limited, but if it is used in an excessively large amount, the orientation of the graphite-based carbon powder having the magnetic substance adhered to the surface due to the magnetic field cannot be sufficiently achieved, which is not preferable.

The composition for high thermal conductivity sheet of the present invention preferably uses a curing catalyst for curing the uncured binder. Examples of such curing catalysts include organic peroxides, fatty acid azo compounds, and hydroxylation catalysts. As the organic peroxide, benzoyl peroxide, bisdicyclobenzoyl peroxide, dicumyl peroxide,
Examples include ditertiary butyl peroxide and the like. Also,
Examples of the fatty acid azo compound include azobisisobutyronitrile. Specific examples of the catalyst that can be used in the hydrosilylation reaction include chloroplatinic acid and its salts, platinum-unsaturated group-containing siloxane complexes, vinylsiloxane-platinum complexes, platinum-1,3-divinyltetrachloride. Known compounds such as a complex with methyldisiloxane, a complex with triorganophosphine or phosphite and platinum, a platinum chelate of acetylacetonate, and a complex with cyclic diene and platinum can be mentioned.

The high thermal conductivity sheet may be cured by irradiation with radiation. The method of adding the curing catalyst is not particularly limited, but it is preferably mixed in the binder in advance from the viewpoints of storage stability, prevention of uneven distribution of the catalyst when the components are mixed, and the like. The amount of the curing catalyst used is preferably an appropriate amount in consideration of the actual curing speed and the balance with the pot life. Further, a hydrosilylation reaction control agent such as an amino group-containing siloxane or a hydroxy group-containing siloxane, which is usually used for controlling the curing speed and the pot life, can be used in combination.

The composition for high thermal conductivity sheet of the present invention may contain a silane coupling agent and a titanium coupling agent. <Preparation of Composition for High Thermal Conductivity Sheet> As a method for preparing the composition for high thermal conductivity sheet according to the present invention, any conventionally known method can be adopted. For example, the binder and the magnetic substance on the surface are used. There is a method in which the adhered graphite-based carbon powder is further mixed with an inorganic filler or a curing catalyst, and the mixture is heated, melted and kneaded. The viscosity of the composition for a high thermal conductivity sheet of the present invention is 10,000 to 1, at a temperature of 25 ° C.
It is preferably in the range of, 000,000 cp. The composition for high thermal conductivity sheet of the present invention is a highly thermally conductive sheet having a large elasticity formed by cross-linking or condensation reaction, and contains a specific graphite-based carbon powder having a magnetic substance attached to the surface. By doing so, it has a function as a high thermal conductive sheet.

[High Thermal Conductivity Sheet] The high thermal conductivity sheet according to the present invention will be described with reference to FIG. In this high thermal conductivity sheet 1, graphite-based carbon powder 2 having a magnetic substance adhered to the surface of the binder 3 in a hardened or semi-cured state is oriented in the thickness direction of the high thermal conductivity sheet. 1 is a schematic drawing of the high thermal conductivity sheet of the present invention.

The composition for a high thermal conductivity sheet of the present invention is preferably in the form of a paste, which is formed into a sheet and a magnetic field is applied in the thickness direction of the sheet composition as shown in FIG. Then, the high thermal conductivity sheet can be formed by orienting the graphite-based carbon powder having the magnetic substance adhered to the surface and curing or semi-curing the binder. In particular, in the present invention, a magnetic field is applied to the uncured sheet-shaped composition to orient the graphite-based carbon powder having a magnetic substance attached to the surface in the thickness direction of the sheet,
It is preferable to heat to cure the sheet-shaped composition.

Specifically, protective films are provided on the front and back surfaces of the sheet-shaped composition 5, a pressure 8 is applied and a magnetic field 7 is applied, and the magnetic graphite-based carbon powder 2 in the composition is applied to the sheet. Orient in the thickness direction. Incidentally, in order to form the composition for a high thermal conductivity sheet into a sheet shape, a conventionally known method can be adopted, but a roll rolling method, a casting method, a coating method or the like can be adopted.

The amount of the binder and the graphite-based carbon powder having the magnetic substance adhered to the surface thereof in the high thermal conductive sheet is the same as in the above-mentioned high thermal conductive sheet composition. The strength of the magnetic field applied to orient the graphite-based carbon powder having a magnetic substance attached to the surface of such a high thermal conductivity sheet is about 500 to 50,000 gauss, preferably about 2,000 to 20,000 gauss, The magnetic field application time is about 1 to 120 minutes, preferably about 5 to 30 minutes. The magnetic field may be applied at room temperature or may be heated if necessary.

Curing or semi-curing of the composition for a high thermal conductive sheet may be carried out at room temperature or may be carried out by heating if necessary. In the present invention, while applying a magnetic field in the thickness direction of the high thermal conductivity sheet containing a graphite-based carbon powder having a magnetic material attached to the surface, by curing or semi-curing, the graphite-based carbon powder under the influence of the magnetic layer Is presumably oriented in the thickness direction. (See FIG. 1) As described above, in the high thermal conductivity sheet of the present invention, since the graphite-based carbon powder having the magnetic substance adhered to the surface is oriented in the thickness direction of the high thermal conductivity sheet, Excellent anisotropic thermal conductivity.

[ Heat Dissipating Structure Using High Thermal Conductivity Sheet] In the heat radiating structure according to the present invention, the heat generating element and the heat radiating member or the circuit board are joined via the high thermal conductive sheet. Examples of such a heating element include a semiconductor element or a semiconductor package. Such a heat dissipation structure can be formed, for example, by bonding a semiconductor element or a semiconductor package and a heat dissipation member or a circuit board through the cured high thermal conductive sheet, and a semiconductor element or a semiconductor package, It can also be formed by sandwiching a semi-cured high heat conductive sheet between the heat dissipation member or the circuit board and further curing by heat generated from the semiconductor element or the semiconductor package.

Further, the composition for high thermal conductivity sheet of the present invention is directly applied to the surface of any of the regions where the semiconductor element or the semiconductor package is joined to the heat dissipation member or the circuit board to form the high thermal conductivity sheet. It is also possible to form a heat dissipation structure by forming and applying a magnetic field in the thickness direction and curing the composition for a high thermal conductivity sheet.

[0046]

EFFECT OF THE INVENTION In the high thermal conductive sheet according to the present invention, graphite-based carbon powder having a magnetic substance adhered to the surface of a binder in a hardened or semi-cured state is oriented in the thickness direction of the high thermal conductive sheet. Therefore, it has high anisotropic thermal conductivity in the thickness direction and can efficiently remove heat from a heating element such as a semiconductor element or a semiconductor package. Moreover, it has excellent heat resistance, durability, and mechanical strength. It also has excellent adhesion to the body.

Further, the heat dissipation structure in which the semiconductor element or the semiconductor package and the heat dissipation member or the circuit board are joined via the high heat conductive sheet according to the present invention has excellent heat conductivity.

[0048]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited by these examples.

[0049]

[Example 1] [Production of high thermal conductivity sheet] Two-component type addition type thermosetting liquid silicone rubber (viscosity 2500P)
On the other hand, 20 volume fraction (%) of graphite-based carbon powder with nickel metal being electroless plated on the surface so that the average film thickness is 1 μm and having a particle size of 50 μm obtained by sieving is added for 30 minutes in vacuum. By mixing, a composition for high thermal conductivity sheet was obtained.

A frame-shaped spacer (thickness: 0.3 mm) is placed on an iron plate, the required amount of the above composition is poured into the frame, and after sufficiently defoaming under vacuum, another iron plate is put on the lid. Then, after applying pressure so that the composition becomes a sheet having a predetermined thickness,
By the electromagnet so that the magnetic field lines pass in the thickness direction of the molded product,
It was treated at room temperature with a magnetic field strength of about 4000 gauss for 20 minutes. Next, raise the temperature to about 100 ° C and perform crosslinking for 1 hour,
A high thermal conductive sheet having a thickness of 0.3 mm was obtained. <Thermal conductivity test> FIG. 3 shows a method for evaluating the thermal diffusivity of the high thermal conductivity sheet by the thermal alternating current method. The phase difference (Δθ) of the temperature change was measured by the thermal alternating current method, and the following mathematical formula was used. Calculate the thermal diffusivity (α) based on the relationship shown in 2.
Further, the thermal conductivity (λ) in the thickness direction of the heat conductive composite sheet can be obtained from the values of the heat capacity and the density separately obtained by the ordinary method based on the following mathematical formula 1. As shown in FIG.
The system for measuring the phase difference (Δθ) of temperature change by the heat exchange method is the function generator 12, the lock-in amplifier 13, the personal computer 14, the sample 9, the electrode 1.
It consists of 0 and 11. Both sides of the sample 9 are sandwiched by electrodes 10 and 11 (metal thin film provided on a glass plate by sputtering), and one side of the sample 9 is heated by applying an AC voltage to one side of the electrode 9, The temperature change was detected from the resistance change, and as shown in FIG. 4, the phase difference (Δθ) of the temperature change (ΔT) was measured from the response delay. The thermal diffusivity (α) was calculated based on the formula 2, and the conductivity (λ) was calculated based on the formula 1. Under normal conditions, the measurement was performed under the condition that the sample was not compressed as much as possible.

[0051]

[Equation 1]

[0052]

[Equation 2]

[0053]

Example 2 Graphite having a magnetic substance attached to the surface prepared in the same manner as in Example 1 with respect to the solid content of a 60% by weight solution of butyl cellosolve acetate in epoxy resin (EP154, manufactured by Yuka Shell Epoxy Co., Ltd.) -Based carbon powder (heat conductivity 100
W / mK) 20 volume fraction (%), imidazole curing agent (2P4MHZ, manufactured by Shikoku Kasei Co., Ltd.) in a predetermined amount, and uniformly dispersed using 3 rolls to obtain a high thermal conductive sheet. A composition for use was obtained.

This composition was placed on a steel plate with a frame-shaped spacer (thickness: 0.5 mm), and the required amount of the composition was poured into the frame. After covering with a sheet of iron plate and applying pressure so that the composition becomes a sheet with a predetermined thickness, a magnetic field of about 4000 Gauss at room temperature is applied by an electromagnet so that magnetic lines of force pass through in the thickness direction of the molded product. Intense treatment for 20 minutes. Then the temperature is about 100
The temperature was raised to 0 ° C. and crosslinking was performed for 1 hour to obtain a high thermal conductive sheet having a thickness of 0.5 mm. The thermal conductivity of the obtained high thermal conductive sheet was measured by the same method as in Example 1.

[0055]

Comparative Example 1 A heat conductive sheet was obtained in the same manner as in Example 1 except that the graphite-based carbon powder having a magnetic substance adhered to the surface was not blended. The thermal conductivity was measured by the same method as in Example 1.

[0056]

Comparative Example 2 A heat conductive sheet was obtained in the same manner as in Example 2 except that the magnetic field was not applied to the sheet-shaped composition. The thermal conductivity was measured by the same method as in Example 1. Examples 1, 2 and Comparative Examples 1, 2
The thermal conductivity of the sheet of No. 5 was less than 5 times the thermal conductivity of the sheet obtained in Comparative Example 1, and the thermal conductivity was x10.
A value of more than twice was evaluated as ◯. The results are shown in Table 1.

[0057]

[Table 1]

[Brief description of drawings]

FIG. 1 is a schematic view of a cross section of a high thermal conductive sheet.

FIG. 2 is a schematic view showing an example of a method for producing a high thermal conductivity sheet.

FIG. 3 is a diagram showing a method of measuring thermal conductivity by a heat exchange method.

FIG. 4 is a diagram showing a phase difference of a temperature change in a method of measuring thermal conductivity by a heat exchange method.

[Explanation of symbols]

1 composite sheet 2 Graphite-based carbon powder with magnetism 3 Heat and / or light curable binder 4 protective film 5 Sheet-like composition 6 protective film 7 magnetic field 8 pressure 9 samples 10 electrodes 11 electrodes 12 Function generator 13 Lock-in amplifier 14 PC

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 23/36 H01L 23/36 DF term (reference) 4F071 AA01 AB03 AE14 AF14 AF44Y AF45 AF57 AH12 BC01 4J002 AC011 AC031 AC071 AC081 AC091 AC111 BB151 BP011 CC031 CC181 CD021 CD051 CD061 CD191 CF001 CF211 CH041 CK021 CP031 CP081 CP141 DA026 FA016 FB076 FB096 FD010 FD140 FD150 FD206 GF00 GQ00 4J037 AA01 AEE36 5F

Claims (6)

[Claims] 1. A high thermal conductivity sheet characterized in that a graphite-based carbon powder having a magnetic substance attached to the surface of a binder is oriented in the thickness direction of the high thermal conductivity sheet. 2. The thermal conductivity of the graphite-based carbon powder is 50 W.
The high thermal conductivity sheet according to claim 1, wherein the high thermal conductivity sheet is m ^-1 · K ^-1 or more. 3. The graphite-based carbon powder having a magnetic substance attached to the surface thereof is contained in an amount of 2 to 70% by volume in the total volume of the high thermal conductivity sheet.
The high thermal conductive sheet described in. 4. A high thermal conductivity sheet composition comprising an uncured binder and a graphite-based carbon powder having a magnetic substance adhered to the surface thereof is formed into a sheet, and the sheet composition is provided with a thickness direction thereof. A magnetic material is applied to the surface of the sheet-shaped composition while the graphite-based carbon powder having the surface-attached magnetic material is oriented in the thickness direction of the sheet-shaped composition, and the sheet-shaped composition is cured. A method for producing a high thermal conductive sheet, in which the graphite-based carbon powder to which is attached is oriented in the thickness direction of the high thermal conductive sheet. 5. The heating element and the heat radiating member or the circuit board,
A heat dissipation structure using a high thermal conductivity sheet, which is joined via the high thermal conductivity sheet according to claim 1. 6. The heat dissipation structure using a high thermal conductivity sheet according to claim 5, wherein the heating element is a semiconductor element or a semiconductor package.