JP7613652B2 - Thermally conductive member, its manufacturing method, and heat dissipation structure - Google Patents

Description

The present invention relates to a heat-conducting member, a manufacturing method thereof, and a heat dissipation structure.

In semiconductor elements mounted on electrical equipment such as personal computers and other equipment, accumulation of heat generated by operation can adversely affect the operation of the semiconductor elements and peripheral equipment. In particular, in electronic components such as CPUs in personal computers, the amount of heat dissipated tends to increase year by year as speed and performance improves, but the chip size of processors and the like is becoming the same as that of conventional components or is becoming smaller due to advances in microsilicon circuit technology, and the amount of heat generated per unit area is increasing.
For this reason, various cooling methods are used for the semiconductor elements. Known cooling methods include attaching a fan to the device to cool the air inside the device housing, and attaching a heat sink such as a heat dissipation fin or heat sink to the semiconductor element to dissipate heat.
In a method of attaching a heat sink to a semiconductor element to dissipate heat, a thermally conductive member is provided between the semiconductor element and the heat sink in order to efficiently dissipate heat from the semiconductor element. A conventional thermally conductive member has been proposed in which a filler such as a thermally conductive filler, e.g., carbon fiber, is dispersed in silicone resin (see, for example, Patent Document 1).
Known examples of the thermally conductive filler include carbon fiber, boron nitride, and the like, which have anisotropic thermal conductivity. When carbon fiber is used as the thermally conductive filler, it has a thermal conductivity of about 600 W/m·K to 1,200 W/m·K in the fiber direction, and when boron nitride is used, it has a thermal conductivity of about 110 W/m·K in the planar direction and about 2 W/m·K in the direction perpendicular to the planar direction.

JP 2012-23335 A

In order to improve the thermal conductivity of the heat conductive member, it is necessary to highly fill the heat conductive filler, but highly filling the heat conductive member with the heat conductive filler makes the heat conductive member hard and reduces its flexibility, and there is a problem in that the use of such a heat conductive member imposes a physical load on the semiconductor element.
The present invention aims to solve the above-mentioned problems in the prior art and to achieve the following objectives: That is, the present invention aims to provide a heat conductive member having high thermal conductivity and excellent flexibility, a manufacturing method thereof, and a heat dissipation structure using the heat conductive member.

The means for solving the above problems are as follows.
<1> A thermally conductive member including at least a binder resin, a thermally anisotropic material, and a non-thermally anisotropic material,
The cylindrical heat conducting member is sandwiched between two rectangular plate-like objects so as to be in contact with the circular surface of the heat conducting member, and compressed. The compressive stress (A) is
The thermal conduction member is characterized in that the rectangular thermal conduction member having a rectangular surface with approximately the same area as the circular surface is sandwiched between two rectangular plate-like objects so as to be in contact with the rectangular surfaces of the thermal conduction member, and the compressive stress (B) when compressed satisfies A < B.
<2> The heat conduction member according to <1>, wherein the thermally anisotropic material is a fibrous material, and the longitudinal direction of the fibers is oriented in a thickness direction of the heat conduction member.
<3> The heat conductive member according to <2>, wherein the fibrous material is carbon fiber.
<4> The heat conductive member according to <3>, wherein an outer periphery of the carbon fiber is coated.
<5> The heat conductive member according to any one of <1> to <4>, wherein the non-thermally anisotropic material is at least one of alumina, aluminum, zinc oxide, boron nitride, and aluminum nitride.
<6> A heat dissipation structure including, in this order, a heat generating body, the heat conductive member according to any one of <1> to <5> that is processed into a substantially circular shape, and a heat dissipation member.
<7> A method for producing a thermal conductive member according to any one of <1> to <5>,
A resin composition preparation step of kneading at least a binder resin, a thermally anisotropic material, and a non-thermally anisotropic material to obtain a resin composition;
a molded body preparation step of orienting the thermally anisotropic material in one direction to obtain a molded body of the resin composition;
a molded body sheet preparation step of cutting the molded body in a direction substantially perpendicular to the orientation direction of the thermally anisotropic material to obtain a molded body sheet;
The method for producing a thermal conductive member includes the steps of:

The present invention can solve the above-mentioned problems of the conventional art and achieve the above-mentioned objective, and can provide a heat-conducting member having high thermal conductivity and excellent flexibility, a manufacturing method thereof, and a heat dissipation structure using the heat-conducting member.

FIG. 1 is a schematic cross-sectional view showing an example of a heat dissipation structure of the present invention. FIG. 2 is a perspective view of a schematic cross-sectional view showing an example of a heat dissipation structure of the present invention.

(Heat conductive material)
The thermally conductive member of the present invention contains at least a binder resin, a thermally anisotropic material, and a non-thermally anisotropic material, and preferably contains additives, and may further contain other components as necessary.

The thermally conductive member of the present invention satisfies the following requirement (1), which makes it possible to realize a thermally conductive member having high thermal conductivity and excellent flexibility.
(1) The compressive stress (A) when the cylindrical heat conducting member is sandwiched between two rectangular plate-like objects so as to be in contact with the circular surface of the heat conducting member and compressed;
The rectangular heat conduction member having a rectangular surface with approximately the same area as the circular surface is sandwiched between two rectangular plate-like objects so that the rectangular surfaces of the heat conduction member are in contact with each other, and when compressed, the compressive stress (B) is A<B.

The compressive stress is, for example, the stress when the heat conductive member is sandwiched between two rectangular plate-like objects and compressed by 50% at a speed of 10 mm/min at 25°C (room temperature) using a bench-top precision universal testing machine Autograph (AGS-50NX, manufactured by Shimadzu Corporation). There are no particular restrictions on the rectangular plate-like objects and they can be selected appropriately depending on the purpose, and examples include SUS304.

It is preferable that the area of the circular surface and the area of the rectangular surface of the heat conductive member are approximately the same, and the difference between the area of the circular surface and the area of the rectangular surface is 0.5% or less.

<Binder Resin>
The binder resin is not particularly limited and can be appropriately selected depending on the purpose. Examples of the binder resin include thermoplastic resins, thermoplastic elastomers, and thermosetting polymers.

Examples of the thermoplastic resin include ethylene-α-olefin copolymers such as polyethylene, polypropylene, and ethylene-propylene copolymers; fluorine-based polymers such as polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, ethylene-vinyl acetate copolymers, polyvinyl alcohol, polyvinyl acetal, polyvinylidene fluoride, and polytetrafluoroethylene; polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polystyrene, polyacrylonitrile, styrene-acrylonitrile copolymers, acrylonitrile-butadiene-styrene copolymer (ABS) resins, polyphenylene-ether copolymers (PPE) resins, modified PPE resins, aliphatic polyamides, aromatic polyamides, polyimides, polyamideimides, polymethacrylic acid, polymethacrylic acid esters such as polymethacrylic acid methyl ester, polyacrylic acids, polycarbonates, polyphenylene sulfide, polysulfones, polyethersulfones, polyethernitriles, polyetherketones, polyketones, liquid crystal polymers, silicone resins, and ionomers. These may be used alone or in combination of two or more.

Examples of the thermoplastic elastomer include styrene-butadiene block copolymers or hydrogenated products thereof, styrene-isoprene block copolymers or hydrogenated products thereof, styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, etc. These may be used alone or in combination of two or more types.

Examples of the thermosetting polymer include crosslinked rubber, epoxy resin, polyimide resin, bismaleimide resin, benzocyclobutene resin, phenol resin, unsaturated polyester, diallyl phthalate resin, silicone resin, polyurethane, polyimide silicone, thermosetting polyphenylene ether, and thermosetting modified polyphenylene ether. These may be used alone or in combination of two or more.

Examples of the crosslinked rubber include natural rubber, butadiene rubber, isoprene rubber, nitrile rubber, hydrogenated nitrile rubber, chloroprene rubber, ethylene propylene rubber, chlorinated polyethylene, chlorosulfonated polyethylene, butyl rubber, halogenated butyl rubber, fluororubber, urethane rubber, acrylic rubber, polyisobutylene rubber, and silicone rubber. These may be used alone or in combination of two or more.

Among these, silicone resin is particularly preferred as the thermosetting polymer, because of its excellent moldability and weather resistance, as well as its adhesion and conformability to electronic components.

The silicone resin is not particularly limited and can be selected appropriately depending on the purpose, but it is preferable that it contains a liquid silicone gel base and a curing agent. Examples of such silicone resins include addition reaction type silicone resins and heat vulcanization type millable silicone resins that use peroxide for vulcanization. Among these, addition reaction type silicone resins are particularly preferable because they require adhesion between the heat generating surface and the heat sink surface of electronic components.

The addition reaction type silicone resin is preferably a two-liquid addition reaction type silicone resin that uses a polyorganosiloxane having a vinyl group as the base agent and a polyorganosiloxane having a Si-H group as the curing agent.

In the combination of the base agent of the liquid silicone gel and the curing agent, the mixing ratio of the base agent and the curing agent is not particularly limited and can be selected appropriately depending on the purpose.

The content of the binder resin is not particularly limited and can be selected appropriately depending on the purpose, but is preferably 5% by volume or more and 60% by volume or less, and more preferably 10% by volume or more and 50% by volume or less.

<Thermal anisotropic materials>
Examples of the thermally anisotropic material include boron nitride (BN) powder, graphite, fibrous materials, etc. Among these, fibrous materials are preferred from the viewpoint of thermal anisotropic conductivity.
The fibrous material is not particularly limited as long as the longitudinal direction of the fibrous material is oriented in the thickness direction of the heat conductive member, and examples thereof include carbon fibers.

The carbon fiber is not particularly limited and can be appropriately selected depending on the purpose. Examples of the carbon fiber include pitch-based carbon fiber, PAN-based carbon fiber, carbon fiber obtained by graphitizing PBO fiber, and carbon fibers synthesized by arc discharge, laser evaporation, CVD (chemical vapor deposition), CCVD (catalytic chemical vapor deposition), etc. These may be used alone or in combination of two or more. Among these, from the viewpoint of thermal conductivity, carbon fiber obtained by graphitizing PBO fiber, PAN-based carbon fiber, and pitch-based carbon fiber are preferred, with pitch-based carbon fiber being particularly preferred.

The average fiber diameter (average short axis length) of the carbon fibers is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 4 μm to 20 μm, and more preferably 5 μm to 14 μm.

The thermal conductivity of the carbon fiber itself is appropriately selected depending on the desired thermal conductivity when made into a thermally conductive sheet, but is preferably 150 W/m·K to 1,200 W/m·K.

The carbon fiber content in the thermal conductive sheet is preferably 16% to 40% by volume, since too little carbon fiber will result in low thermal conductivity, and too much carbon fiber will tend to increase viscosity.

- Non-thermally anisotropic materials -
Examples of the non-thermally anisotropic material include aluminum, aluminum nitride, silica, alumina, boron nitride, titania, glass, zinc oxide, silicon carbide, silicon (silicon), silicon oxide, aluminum oxide, and metal particles. Among these, alumina, aluminum, zinc oxide, boron nitride, and aluminum nitride are preferred, and alumina and aluminum nitride are more preferred from the viewpoint of thermal conductivity. These may be used alone or in combination of two or more. The non-thermally anisotropic material may be referred to as an inorganic filler other than carbon fiber, or a thermally conductive filler.
The volume average particle size of the non-thermally anisotropic material is preferably 0.01 μm to 100 μm, more preferably 0.02 μm to 80 μm. When the volume average particle size is 0.01 μm or more, mixing during production is easy, and when the volume average particle size is 100 μm or less, compression during sheet compression is easy.
The volume average particle size can be measured, for example, by a particle size distribution measuring device using a laser diffraction/scattering method.

The non-thermally anisotropic material may be surface-treated. There are no particular limitations on the surface treatment and it can be selected appropriately depending on the purpose, but it is preferable to treat the non-thermally anisotropic material with an alkoxysilane compound, for example.

An alkoxysilane compound is a compound in which one to three of the four bonds that a silicon atom (Si) has are bonded to an alkoxy group, and the remaining bonds are bonded to an organic substituent. Examples of alkoxy groups that an alkoxysilane compound has include methoxy, ethoxy, propoxy, butoxy, pentoxy, and hexoxy groups. The alkoxysilane compound may be contained in the thermal conductive sheet as a dimer.

Among the alkoxysilane compounds, from the viewpoint of easy availability, an alkoxysilane compound having a methoxy group or an ethoxy group is preferred. The number of alkoxy groups in the alkoxysilane compound is preferably 3 from the viewpoint of increasing affinity with the thermally conductive filler as an inorganic substance.
Examples of the alkoxysilane compound include a trimethoxysilane compound, a triethoxysilane compound, etc. These may be used alone or in combination of two or more kinds.

Examples of functional groups contained in the organic substituents of the alkoxysilane compound include acryloyl groups, alkyl groups, carboxyl groups, vinyl groups, methacryl groups, aromatic groups, amino groups, isocyanate groups, isocyanurate groups, epoxy groups, hydroxyl groups, and mercapto groups. Here, when an addition reaction type organopolysiloxane containing a platinum catalyst is used as the precursor of the matrix, it is preferable to select and use an alkoxysilane compound that is less likely to affect the curing reaction of the organopolysiloxane. Specifically, when an addition reaction type organopolysiloxane containing a platinum catalyst is used, it is preferable that the organic substituents of the alkoxysilane compound do not contain amino groups, isocyanate groups, isocyanurate groups, hydroxyl groups, or mercapto groups.

The alkoxysilane compound preferably contains an alkylalkoxysilane compound having an alkyl group bonded to a silicon atom, that is, an alkoxysilane compound having an alkyl group as an organic substituent, because the alkoxysilane compound enhances the dispersibility of inorganic fillers other than carbon fibers, making it easier to highly fill inorganic fillers other than carbon fibers. The number of carbon atoms in the alkyl group bonded to the silicon atom is preferably 4 or more. In addition, the number of carbon atoms in the alkyl group bonded to the silicon atom is preferably 16 or less, from the viewpoint that the viscosity of the alkoxysilane compound itself is relatively low and the viscosity of the resin composition is kept low.

Examples of the alkoxysilane compound include an alkyl group-containing alkoxysilane compound, a vinyl group-containing alkoxysilane compound, an acryloyl group-containing alkoxysilane compound, a methacryl group-containing alkoxysilane compound, an aromatic group-containing alkoxysilane compound, an amino group-containing alkoxysilane compound, an isocyanate group-containing alkoxysilane compound, an isocyanurate group-containing alkoxysilane compound, an epoxy group-containing alkoxysilane compound, and a mercapto group-containing alkoxysilane compound. These may be used alone or in combination of two or more.

Examples of the alkyl group-containing alkoxysilane compound include methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, cyclohexylmethyldimethoxysilane, n-octyltriethoxysilane, and n-decyltrimethoxysilane. Among these, isobutyltrimethoxysilane, isobutyltriethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, cyclohexylmethyldimethoxysilane, n-octyltriethoxysilane, and n-decyltrimethoxysilane are preferred. These may be used alone or in combination of two or more.

Examples of the vinyl group-containing alkoxysilane compound include vinyltrimethoxysilane and vinyltriethoxysilane. These may be used alone or in combination of two or more.

The acryloyl group-containing alkoxysilane compound may, for example, be 3-acryloxypropyltrimethoxysilane. These may be used alone or in combination of two or more.

Examples of the methacryl group-containing alkoxysilane compounds include 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, and 3-methacryloxypropyltriethoxysilane. These may be used alone or in combination of two or more.

Examples of the aromatic group-containing alkoxysilane compound include phenyltrimethoxysilane and phenyltriethoxysilane. These may be used alone or in combination of two or more.

Examples of the amino group-containing alkoxysilane compound include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane. These may be used alone or in combination of two or more.

The isocyanate group-containing alkoxysilane compound may, for example, be 3-isocyanatepropyltriethoxysilane. These may be used alone or in combination of two or more types.

The isocyanurate group-containing alkoxysilane compound may, for example, be tris-(trimethoxysilylpropyl) isocyanurate. These may be used alone or in combination of two or more.

Examples of the epoxy group-containing alkoxysilane compound include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropyltriethoxysilane. These may be used alone or in combination of two or more.

Examples of the mercapto group-containing alkoxysilane compound include 3-mercaptopropyltrimethoxysilane.

The content of the non-thermally anisotropic material is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 15% by volume or more and 90% by volume or less, and more preferably 20% by volume or more and 80% by volume or less. If the content is less than 15% by volume, the thermal resistance of the thermal conductive sheet may increase, and if it exceeds 90% by volume, the flexibility of the thermal conductive sheet may decrease.

-Additives-
The heat conductive member of the present invention may contain, in addition to the binder resin, the thermally anisotropic material, and the non-thermally anisotropic material, the above-mentioned additives within the range that does not impair the effects of the present invention.
The additives are not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include antioxidants, silicon compounds, etc. By including the antioxidant, it is possible to suppress the change over time in the physical properties of the heat conductive member and to improve the filling rate.

Examples of the antioxidant include phenol-based antioxidants, thiol-based antioxidants, and phosphorus-based antioxidants. Among these, hindered phenol-based antioxidants are preferred.

The content of the antioxidant in the thermal conductive member is not particularly limited and can be selected appropriately depending on the purpose, and is preferably 0.01% by weight or more and 20% by weight or less relative to 100% by weight of the binder resin.

Examples of the silicon compound include alkoxysilane compounds and alkoxysiloxane compounds.

The content of the silicon compound is not particularly limited and can be appropriately selected depending on the purpose, and is preferably 0.1% by weight or more and 5% by weight or less based on the total weight of the inorganic filler.

-Other ingredients-
The other components are not particularly limited and can be appropriately selected depending on the purpose. Examples of the other components include solvents, thixotropy imparting agents, dispersants, curing agents, curing accelerators, retarders, slight tackifiers, plasticizers, flame retardants, stabilizers, colorants, and the like.

(Method of manufacturing heat conductive member)
The method for producing the thermal conductive member of the present invention is a method for producing the thermal conductive member of the present invention, and includes a resin composition preparation step, a molded body preparation step, and a molded body sheet preparation step, and may further include other steps as necessary.
The method for producing a heat conductive member is a method for producing a heat conductive member of the present invention.

<Resin composition preparation process>
The resin composition preparation step is a step of kneading at least a binder resin, a thermally anisotropic material, and a non-thermally anisotropic material to obtain a resin composition.
Examples of the binder resin include the binder resins exemplified in the description of the heat conductive member above.
Examples of the thermally anisotropic material include the thermally anisotropic materials exemplified in the description of the heat conductive member above.
Examples of the non-thermally anisotropic material include the non-thermally anisotropic materials exemplified in the description of the heat conductive member above.
The kneading method is not particularly limited and can be appropriately selected depending on the purpose.

<Molded body production process>
This is a process in which the resin composition is molded into a predetermined shape, cured, and the thermally anisotropic material is oriented in one direction to obtain a molded article of the resin composition.

In the molded body production process, the method for molding the resin composition into a predetermined shape is not particularly limited and can be appropriately selected depending on the purpose. Examples of the method include extrusion molding and die molding.

The extrusion molding method and the die molding method are not particularly limited, and can be appropriately selected from various known extrusion molding methods and die molding methods depending on the viscosity of the resin composition and the properties required for the resulting thermal conductive sheet.

The method for orienting the thermally anisotropic material in one direction is not particularly limited and can be selected appropriately depending on the purpose, but examples include extrusion molding and applying a magnetic field.

The size and shape of the molded body (block-shaped molded body) can be determined according to the size of the desired thermal conductive sheet. For example, it can be a rectangular prism with a cross-sectional vertical dimension of 0.5 cm to 15 cm and a horizontal dimension of 0.5 cm to 15 cm. The length of the rectangular prism can be determined as needed.

The resin composition is preferably cured by heat in the molded body production process. The curing temperature in the heat curing is not particularly limited and can be appropriately selected depending on the purpose. For example, when the binder resin contains a liquid silicone gel base agent and a curing agent, a temperature of 60°C to 150°C is preferred. The curing time in the heat curing is not particularly limited and can be appropriately selected depending on the purpose. For example, 0.5 hours to 10 hours is given as the curing time.

<Molded body sheet production process>
The molded body sheet preparation step is a step of cutting the molded body in a direction approximately perpendicular to the direction in which the thermally anisotropic material is oriented to obtain a molded body sheet, and can be performed using, for example, a slicing device.

The slicing device is not particularly limited and can be appropriately selected depending on the purpose. Examples of the slicing device include an ultrasonic cutter and a plane.
The substantially perpendicular direction is preferably 60 degrees to 120 degrees, more preferably 70 degrees to 100 degrees, and particularly preferably 90 degrees (perpendicular) to the direction in which the thermally anisotropic material is oriented.

The average thickness of the molded sheet is not particularly limited and can be selected appropriately depending on the purpose, but is preferably 0.06 mm to 5.01 mm, more preferably 0.08 mm to 4.01 mm, and particularly preferably 0.11 mm to 3.01 mm.

<Other processes>
The other steps are not particularly limited and may be appropriately selected depending on the purpose. Examples of the other steps include a pressing step and a polishing step.
The pressing step is a step of pressing the molded body sheet.
The pressing can be carried out, for example, by using a pair of pressing devices each consisting of a flat plate and a press head having a flat surface, or by using a pinch roll.

There are no particular limitations on the pressure used during the pressing and it can be selected appropriately depending on the purpose, but if it is too low, the thermal resistance tends to remain the same as when no pressing is performed, and if it is too high, the sheet tends to stretch, so 0.1 MPa to 100 MPa is preferable, and 0.5 MPa to 95 MPa is more preferable.

There are no particular limitations on the pressing time, and it can be selected appropriately depending on the binder resin components, pressing pressure, sheet area, amount of exuded components, etc.

The pressing process may be performed while heating using a press head with a built-in heater to further promote the exudation of the exuded components and the effect of coating the surface of the molded sheet. To enhance such effects, it is preferable to heat the molded sheet at a temperature equal to or higher than the glass transition temperature of the binder resin. This allows the pressing time to be shortened.

In the press treatment, the molded sheet is pressed to cause the exuded components to exude from the molded sheet, and the surface is coated with the exuded components. Therefore, the resulting thermally conductive sheet has improved conformability and adhesion to the surfaces of electronic components and heat spreaders, and can reduce thermal resistance. Furthermore, if the coating with the exuded components is thick enough to reflect the shape of the insulating coated carbon fibers on the surface of the thermally conductive member, an increase in thermal resistance can be avoided.

In addition, the molded sheet is compressed in the thickness direction by pressing, which increases the frequency of contact between the insulating coated carbon fiber and the thermally conductive filler. This makes it possible to reduce the thermal resistance of the thermally conductive member.

The pressing process is preferably performed using a spacer to compress the molded body sheet to a predetermined thickness. That is, the heat conductive member can be formed to a predetermined sheet thickness according to the height of the spacer, for example, by placing a spacer on the mounting surface facing the press head and pressing the molded body sheet.

(Heat dissipation structure)
The heat dissipation structure of the present invention is a heat dissipation structure that includes a heat generating body, the heat conductive member of the present invention that is processed into a substantially circular shape, and a heat dissipation member.

The heat dissipation structure may, for example, consist of a heat generating body such as an electronic component, a heat dissipation member such as a heat sink, heat pipe, or heat spreader, and a heat conducting member sandwiched between the heat generating body and the heat dissipation member.

There are no particular limitations on the electronic components, and they can be selected appropriately depending on the purpose. Examples include a CPU (Central Processing Unit), an MPU (Micro Processing Unit), and a GPU (Graphics Processing Unit).

The heat dissipation structure is not particularly limited as long as it is a structure that dissipates heat generated by an electronic component (heat generating element), and can be appropriately selected depending on the purpose. Examples of the heat dissipation structure include a heat spreader, a heat sink, a vapor chamber, and a heat pipe.
The heat spreader is a member for efficiently transferring heat from the electronic component to other components. The material of the heat spreader is not particularly limited and can be appropriately selected depending on the purpose, and examples of the material include copper and aluminum. The heat spreader is usually in a flat plate shape.
The heat sink is a member for releasing heat from the electronic component into the air. The material of the heat sink is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include copper and aluminum. The heat sink has, for example, a plurality of fins. The heat sink has, for example, a base portion and a plurality of fins provided so as to extend in a non-parallel direction (for example, a direction perpendicular to) one surface of the base portion.
The heat spreader and the heat sink are generally solid structures with no internal voids.
The vapor chamber is a hollow structure. A volatile liquid is sealed in the internal space of the hollow structure. Examples of the vapor chamber include a hollow structure of the heat spreader, a hollow plate-shaped structure of the heat sink, and the like.
The heat pipe is a hollow structure having a cylindrical, approximately cylindrical, or flattened tubular shape, and a volatile liquid is sealed in the internal space of the hollow structure.

Here, FIG. 1 is a schematic diagram of a semiconductor device as an example of the heat dissipation structure of the present invention. This FIG. 1 is a schematic cross-sectional view of an example of a semiconductor device. The thermally conductive sheet 1 of the present invention dissipates heat generated by an electronic component 3 such as a semiconductor element, and as shown in FIG. 1, is fixed to the main surface 2a of the heat spreader 2 facing the electronic component 3, and is sandwiched between the electronic component 3 and the heat spreader 2. The thermally conductive sheet 1 is also sandwiched between the heat spreader 2 and a heat sink 5. The thermally conductive sheet 1, together with the heat spreader 2, constitutes a heat dissipation member that dissipates heat from the electronic component 3.

The heat spreader 2 is formed, for example, in the shape of a rectangular plate, and has a main surface 2a facing the electronic components 3, and side walls 2b erected along the outer periphery of the main surface 2a. The heat spreader 2 has a thermally conductive sheet 1 provided on the main surface 2a surrounded by the side walls 2b, and a heat sink 5 provided on the other surface 2c opposite the main surface 2a via the thermally conductive sheet 1. The higher the thermal conductivity of the heat spreader 2, the lower the thermal resistance and the more efficiently it absorbs heat from the electronic components 3 such as semiconductor elements, so it can be formed, for example, from copper or aluminum, which have good thermal conductivity.

The electronic component 3 is, for example, a semiconductor element such as a BGA, and is mounted on the wiring board 6. The tip surface of the side wall 2b of the heat spreader 2 is also mounted on the wiring board 6, so that the side wall 2b surrounds the electronic component 3 at a predetermined distance.

The heat spreader 2 is bonded to the main surface 2a of the heat spreader 2 with the thermally conductive sheet 1, forming a heat dissipation member that absorbs heat generated by the electronic components 3 and dissipates the heat through the heat sink 5. The heat spreader 2 and the thermally conductive sheet 1 are bonded together by the adhesive force of the thermally conductive sheet 1 itself.

Examples of the present invention will be described below, but the present invention is not limited to these examples.
In the following examples and comparative examples, the volume average particle size of the non-thermally anisotropic material is a value measured by a particle size distribution meter, and the average major axis length and the average minor axis length of the thermally anisotropic material are values measured by a microscope (VHX-5000, manufactured by KEYENCE).

Example 1
A two-component addition reaction type liquid silicone resin was mixed as a binder resin, 37 vol% of alumina particles (alumina DAW05, spherical, manufactured by Denka Co., Ltd., volume average particle size: 5 μm, coupling treatment with a silane coupling agent) and 5 vol% of aluminum powder (#350F, manufactured by Minalco Co., Ltd., volume average particle size: 15 μm) as non-thermally anisotropic materials, and 23 vol% of pitch-based carbon fiber (average major axis length 150 μm, average minor axis length 9 μm, XN-100-15M, manufactured by Nippon Graphite Fiber Co., Ltd.) as a non-thermally anisotropic material, to prepare a silicone composition.
The two-component addition reaction type liquid silicone resin was added in an amount of 34 vol % together with additives to a material mainly composed of organopolysiloxane.
The obtained silicone composition was extrusion molded into a hollow rectangular prism mold (50 mm × 50 mm) to obtain a silicone molded body, which was then heated in an oven at 100°C for 6 hours to obtain a silicone cured product. The obtained silicone cured product was cut with a slicer to a thickness of 2.0 mm to obtain a sheet-like silicone cured product.
The obtained sheet-like silicone cured product was sandwiched between release-treated PET films and pressed at 87° C., 0.5 MPa, and for 3 minutes to obtain a thermally conductive member (50 mm×50 mm).

Example 2
A two-component addition reaction type liquid silicone resin was mixed as a binder resin with 20 vol% alumina particles (alumina DAW05, spherical, manufactured by Denka Co., Ltd., volume average particle size: 5 μm, coupling treatment with a silane coupling agent) as non-thermally anisotropic materials, 21 vol% aluminum nitride (volume average particle size: 2 μm), and 0.1 vol% zinc oxide (volume average particle size: 0.5 μm), and 21 vol% pitch-based carbon fiber (average major axis length 150 μm, average minor axis length 9 μm, XN-100-15M, manufactured by Nippon Graphite Fiber Co., Ltd.) as a non-thermally anisotropic material to prepare a silicone composition.
The two-component addition reaction type liquid silicone resin was added in an amount of 36 vol % together with additives to a material mainly composed of organopolysiloxane.
The obtained silicone composition was extrusion molded into a hollow rectangular prism mold (50 mm × 50 mm) to obtain a silicone molded body, which was then heated in an oven at 100°C for 6 hours to obtain a silicone cured product. The obtained silicone cured product was cut with a slicer to a thickness of 2.0 mm to obtain a sheet-like silicone cured product.
The obtained sheet-like silicone cured product was sandwiched between release-treated PET films and pressed at 87° C., 0.5 MPa, and for 3 minutes to obtain a thermally conductive member (50 mm×50 mm).

Example 3
In a glass container, 100 g of pitch-based carbon fiber (trade name XN-100-10M: manufactured by Nippon Graphite Fiber Co., Ltd.) with an average fiber diameter of 9 μm and an average fiber length of 100 μm and 450 g of ethanol were added and mixed with a stirring blade to obtain a slurry liquid. While nitrogen was added to the slurry liquid at a flow rate of 160 mL/min to perform inertization, 25 g of divinylbenzene (93% divinylbenzene, manufactured by Wako Pure Chemical Industries, Ltd.) was added to the slurry. 10 minutes after the addition of divinylbenzene, 0.500 g of polymerization initiator (trade name V-65, oil-soluble azo polymerization initiator, manufactured by Wako Pure Chemical Industries, Ltd.) that had been dissolved in 50 g of ethanol in advance was added to the slurry liquid. After the addition, the mixture was stirred for 5 minutes, and then the inertization by nitrogen was stopped. Thereafter, the temperature was raised while stirring, the temperature was maintained at 70 ° C., and the temperature was lowered to 40 ° C. The reaction time was determined as the time from the start of the temperature rise to the start of the temperature drop. After the temperature was lowered, the mixture was left to stand for 15 minutes to allow the solids dispersed in the slurry to settle. After settling, the supernatant was removed by decantation, and 750 g of the solvent was added again and stirred for 15 minutes to wash the solids. After washing, the solids were collected by suction filtration, and the collected solids were dried at 100° C. for 6 hours to obtain DVB insulation-coated carbon fibers.
Next, a two-component addition reaction type liquid silicone resin was used as a binder resin, and 25 vol% of alumina particles (alumina DAW10, spherical, manufactured by Denka Co., Ltd., volume average particle diameter: 10 μm, coupling treatment with a silane coupling agent) and 13 vol% of aluminum nitride (volume average particle diameter: 2 μm) were used as a non-thermally anisotropic material, and 15 vol% of the DVB insulation-coated carbon fiber was used as a non-thermally anisotropic material was mixed to prepare a silicone composition.
The two-component addition reaction type liquid silicone resin was made by adding 46 vol % of an organopolysiloxane as the main component together with additives.
The obtained silicone composition was extrusion molded into a hollow rectangular prism-shaped mold (50 mm x 50 mm) to obtain a silicone molded body, which was then heated in an oven at 100°C for 6 hours to obtain a silicone cured product. The obtained silicone cured product was cut with a slicer to a thickness of 2.0 mm to obtain a sheet-like silicone cured product.
The obtained sheet-like silicone cured product was sandwiched between release-treated PET films and pressed at 87° C., 0.5 MPa, and for 3 minutes to obtain a thermally conductive member (50 mm×50 mm).

Example 4
In a polyethylene container, 100 g of pitch-based carbon fiber (trade name XN-100-10M: manufactured by Nippon Graphite Fiber Co., Ltd.) with an average fiber diameter of 9 μm and an average fiber length of 100 μm, 200 g of tetraethoxysilane (TEOS), and 900 g of ethanol were added and mixed with a stirring blade. Then, while heating to 50 ° C, 176 g of a reaction initiator (10% ammonia water) was added over 5 minutes. The time when the solvent was added was set to 0 minutes, and stirring was performed for 3 hours. After stirring, the temperature was lowered, and the solid content was collected by suction filtration, washed with water and ethanol, and suction filtration was performed again to collect the solid content. The collected solid content was dried at 100 ° C for 2 hours, and then baked at 200 ° C for 8 hours to obtain SiO ₂ insulation-coated carbon fiber.
Next, a two-component addition reaction type liquid silicone resin was used as a binder resin, and 25 vol% of alumina particles (alumina DAW10, spherical, manufactured by Denka Co., Ltd., volume average particle size: 10 μm, coupling treatment with a silane coupling agent) and 13 vol% of aluminum nitride (volume average particle size: 2 μm) were used as a non-thermally anisotropic material, and 15 vol% of the _SiO2 insulation-coated carbon fiber was used as a non-thermally anisotropic material, to prepare a silicone composition.
The two-component addition reaction type liquid silicone resin was made by adding 46 vol % of an organopolysiloxane as the main component together with additives.
The obtained silicone composition was extrusion molded into a hollow rectangular prism mold (50 mm × 50 mm) to obtain a silicone molded body, which was then heated in an oven at 100°C for 6 hours to obtain a silicone cured product. The obtained silicone cured product was cut with a slicer to a thickness of 2.0 mm to obtain a sheet-like silicone cured product.
The obtained sheet-like silicone cured product was sandwiched between release-treated PET films and pressed at 87° C., 0.5 MPa, and for 3 minutes to obtain a thermally conductive member (50 mm×50 mm).

Example 5
A thermally conductive member (50 mm x 50 mm) was obtained in the same manner as in Example 1, except that the obtained silicone cured product was cut with a slicer to a thickness of 0.5 mm to obtain a sheet-like silicone cured product.

(Comparative Example 1)
A two-component addition reaction type liquid silicone resin was used as a binder resin, and as a non-thermally anisotropic material, 42 vol% alumina particles (Alumina DAW05, spherical, manufactured by Denka Company, Ltd., volume average particle diameter: 5 μm, coupling treatment with a silane coupling agent), 6 vol% alumina particles (Alumina DAW45, spherical, manufactured by Denka Company, Ltd., volume average particle diameter: 50 μm), and 27 vol% aluminum nitride (volume average particle diameter: 2 μm) were mixed to prepare a silicone composition.
The two-component addition reaction type liquid silicone resin was added in an amount of 24 vol % together with additives to a material mainly composed of organopolysiloxane.
The obtained silicone composition was applied onto a release film and then cured at 80° C. for 6 hours to obtain a 2 mm thermally conductive sheet.

The thermal conductive members obtained in Examples 1 to 5 and Comparative Example 1 were measured for compressive stress and compressive stress improvement rate, and were also evaluated for thermal conductivity and flexibility, as described below. The results are shown in Table 1.

<Compressive stress>
The obtained heat conduction members were processed to obtain cylindrical heat conduction members (diameter: 13 mm, thickness: 0.5 mm or 2 mm, area clamped by compression jig: 132 ^mm2 ) and rectangular heat conduction members (11.5 mm x 11.5 mm, thickness: 0.5 mm or 2 mm, area clamped by compression jig: 132 ^mm2 ). The obtained cylindrical heat conduction members and rectangular heat conduction members were clamped between 15 mm square and 25 mm square compression jigs, respectively, and the maximum compressive stress was measured when the heat conduction members were compressed by 50% at a compression speed of 10 mm/min.

<Improvement rate of compressive stress>
The reduction rate (improvement rate) of the compressive stress (A) of the cylindrical heat conductive member relative to the compressive stress (B) of the rectangular heat conductive member was calculated by the following formula.
Improvement rate (%) = (B-A)/B x 100

<Thermal conductivity>
The bulk thermal conductivity was calculated from the thermal conductivity of the obtained heat conductive member. The bulk thermal conductivity was calculated from the thermal resistance of the heat conductive member having a thickness of 0.5 mm, 1.0 mm, and 2.0 mm, and the thermal conductivity was calculated from the slope when the horizontal axis represents the thickness at the time of measurement and the vertical axis represents the thermal resistance.
The thermal resistance was measured by the following procedure: A thermally conductive sheet having the above thickness was processed into a circle having a diameter of 20 mm to obtain a test piece.
The thermal resistance [° C.·cm ² /W] of the obtained test piece was measured under a load of 1 kgf/cm ² by a method in accordance with ASTM-D5470.

<Flexibility>
The resulting heat conductive member was evaluated for flexibility by measuring the Shore hardness in accordance with ASTM-D2240 Type 00. An ASTM-D2240 Type 00 value of 50 or less was evaluated as having high flexibility.

1 Thermally conductive sheet 2 Heat dissipation member (heat spreader)
2a: main surface; 2b: side wall; 2c: other surface on the opposite side; 3: heating element (electronic component)
3a Upper surface 5 Heat dissipation member (heat sink)
6 Wiring board 7 Electrode

Claims (6)

A thermally conductive member including at least a binder resin, a thermally anisotropic material, and a non-thermally anisotropic material,
the thermally anisotropic material is a fibrous material, the longitudinal direction of the fibers is oriented in the thickness direction of the heat conductive member,
The cylindrical heat conducting member is sandwiched between two rectangular plate-like objects so as to be in contact with the circular surface of the heat conducting member, and compressed. The compressive stress (A) is
A thermal conduction member characterized in that a rectangular thermal conduction member having a rectangular surface with approximately the same area as the circular surface is sandwiched between two rectangular plate-like objects so as to be in contact with the rectangular surfaces of the thermal conduction member, and the compressive stress (B) when compressed satisfies A < B. The thermal conduction member of claim 1 , wherein the fibrous material is carbon fiber. The heat conducting member according to claim 2 , wherein the carbon fibers are coated on their outer periphery. 4. The heat conductive member according to claim 1, wherein the non-thermally anisotropic material is at least one of alumina, aluminum, zinc oxide, boron nitride, and aluminum nitride. A heat dissipation structure comprising: a heat generating body; the heat conductive member according to claim 1 which is processed into a substantially circular shape; and a heat dissipation member, in that order. A method for producing the heat conductive member according to any one of claims 1 to 4 , comprising the steps of:
A resin composition preparation step of kneading at least a binder resin, a fibrous material , and a non-thermally anisotropic material to obtain a resin composition;
a molded body preparation step of orienting the fibrous material in one direction to obtain a molded body of the resin composition;
a molded body sheet preparation step of cutting the molded body in a direction substantially perpendicular to the orientation direction of the thermally anisotropic material to obtain a molded body sheet;
A method for producing a heat conductive member, comprising:

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