JP6638407B2 - Heat conductive sheet, method for manufacturing heat conductive sheet, and heat radiating device - Google Patents

Description

  The present invention relates to a heat conductive sheet, a method for manufacturing the heat conductive sheet, and a heat radiating device.

  In recent years, the amount of heat generated by the increase in the mounting density of wiring and electronic components in a semiconductor package using a multilayer wiring board has increased, and the amount of heat generated per unit area has increased due to the higher integration of semiconductor elements. It is desired to enhance the heat dissipation from the air.

  2. Description of the Related Art A heat dissipating device that dissipates heat by interposing a heat conductive grease or a heat conductive sheet between a heat generating element such as a semiconductor package and a heat dissipating element such as aluminum and copper is generally simply used. Usually, the heat conductive sheet is more excellent in workability when assembling the heat radiating device than the heat conductive grease.

  In recent years, chips of a central processing unit (CPU) tend to have a large area due to multi-core and multi-chip. In addition, there is a tendency to reduce the pressure of the pressure applied between the CPU, which is a heating element, and the radiator. Therefore, the heat conductive sheet is required to have flexibility at the time of pressure bonding. Further, the heat conductive sheet is required to have excellent thermal conductivity so that the heat conductive sheet has a low thermal resistance even if the heat conductive sheet becomes thick due to a chip step.

  As a method of bringing the heat generating element and the heat radiating body into close contact with each other via a heat conductive material, there are a method of pressing at a normal temperature with a jig such as a spring, and a method of thermocompression bonding. In any method, it is important that the heat conductive sheet is sufficiently flexible at the temperature at the time of adhesion in order to obtain high adhesion.

  As a method of thermocompression bonding, a method of melting and pressure bonding a heating element and a heat radiator using a low-melting metal such as metal indium as a heat conductive material can be used. According to this method, the obtained heat radiating device has extremely high thermal conductivity, but it may be difficult to separate the heat radiating body from the heat generating body for repair or the like. Further, since the melt of the metal has a low viscosity, the metal may flow out when reheated to a temperature exceeding the melting point. In this respect, a resin-based heat conductive sheet that can maintain viscosity even when heated is advantageous, but generally, a resin-based heat conductive sheet is inferior in heat conductivity to metal indium or the like.

  On the other hand, in the method of pressing with a jig such as a spring at room temperature, a semiconductor element or the like is melted by heat generated by operation and changes from a solid sheet to a liquid fluid body to obtain high adhesion, so-called phase change. Sheets are also commonly used. However, in general, the phase change sheet has a low thermal conductivity and has a low thermal resistance due to liquefaction and a reduction in thickness, so that it is difficult to cope with a multi-chip configuration in which a chip step occurs.

As a heat conductive sheet, a resin sheet filled with a heat conductive filler is also known. Various types of resin sheets have been proposed in which an inorganic powder having high thermal conductivity is selected as a heat conductive filler as a resin sheet having excellent heat conductivity filled with a heat conductive filler, and furthermore, the inorganic powder is oriented perpendicular to the sheet surface. I have.
For example, a heat conductive sheet in which the heat conductive filler (boron nitride) is oriented in a direction substantially perpendicular to the sheet surface (for example, see Patent Document 1), and carbon fibers dispersed in a gel-like material are perpendicular to the sheet surface. A thermally conductive sheet having an oriented structure (for example, see Patent Document 2) has been proposed.

JP-A-2002-26202 JP 2001-250894 A

However, in general, resin-based heat conductive sheets are oxidized or hydrolyzed when exposed to heat or humidity by use, and in some cases, a plasticizer is volatilized, and the resin becomes hard due to progress of cross-linking and the like. Or tend to. When the resin is hardened, the resin cannot be deformed following the thermal expansion of the member due to the temperature fluctuation, so that the adhesiveness of the heat conductive sheet tends to decrease.
As described above, while improving the handling strength and tackiness at room temperature (25 ° C.), while having heat resistance and humidity resistance, high compressibility leading to high thermal conductivity and step absorption is useful. It is difficult to achieve both.

  An object of the present invention is to provide a heat conductive sheet that can make a heat generating body and a heat radiating body adhere to each other with low heat resistance, and that is excellent in compressibility, heat resistance, humidity resistance, and handleability of bonding. .

Specific means for solving the above problems include the following aspects.
<1> an elastomer (A) containing an isobutylene structure;
At least one type of graphite particles (B) selected from the group consisting of flaky particles, oval spherical particles and rod-like particles;
An alicyclic hydrocarbon resin (C),
A heat conductive sheet in which the plane direction is oriented in the case of the flake-shaped particles, the long axis direction in the case of the elliptical particles, or the long axis direction in the case of the rod-shaped particles, in the thickness direction.

<2> The elastomer (A) according to <1>, wherein the elastomer (A) is at least one selected from the group consisting of a copolymer of isobutene and styrene, a copolymer of isobutene and ethylene, and a homopolymer of isobutene. Heat conduction sheet.

<3> The heat conductive sheet according to <1> or <2>, wherein the graphite particles (B) include expanded graphite powder.

<4> The heat conductive sheet according to any one of <1> to <3>, having a tensile strength at 25 ° C of 0.1 MPa or more.

<5> The heat conductive sheet according to any one of <1> to <4>, wherein a tack force at 25 ° C is 3.0 kPa or more and less than 70 kPa.

<6> The heat conductive sheet according to any one of <1> to <5>, wherein the alicyclic hydrocarbon resin (C) is solid at 25 ° C.

<7> The heat conductive sheet according to any one of <1> to <6>, wherein the alicyclic hydrocarbon resin (C) has a softening temperature of 40C to 150C.

<8> The content according to any one of <1> to <7>, wherein the content of the alicyclic hydrocarbon resin (C) is 10% by mass to 200% by mass with respect to the elastomer (A). Heat conduction sheet.

<9> The heat conductive sheet according to any one of <1> to <8>, wherein the content of the graphite particles (B) is 15% by volume to 50% by volume.

<10> An elastomer having an isobutylene structure (A), at least one kind of graphite particles (B) selected from the group consisting of flaky particles, oval spherical particles and rod-like particles, and an alicyclic hydrocarbon resin (C) And preparing a composition containing:
Step of obtaining a sheet by sheeting the composition,
Stacking a plurality of the sheets, or folding one of the sheets, or forming a laminate by winding one of the sheets,
Slicing a side end face of the laminate,
The method for producing a heat conductive sheet according to any one of <1> to <9>, comprising:

<11> The method for producing a heat conductive sheet according to <10>, wherein in the slicing step, the graphite particles (B) are sliced at a thickness of twice or less the mass average particle diameter.

<12> A heat dissipation device in which the heat conductive sheet according to any one of <1> to <9> is interposed between a heating element and a heat dissipation element.

  ADVANTAGE OF THE INVENTION According to this invention, a heat generating body and a heat radiating body can be adhere | attached with low heat resistance, and the heat conductive sheet excellent in compressibility, heat resistance, humidity resistance, and the handling property of attachment can be provided. .

Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, the components (including the element steps and the like) are not essential unless otherwise specified. The same applies to numerical values and their ranges, and does not limit the present invention.
In this specification, the term "step" includes, in addition to a step independent of other steps, even if the purpose of the step is achieved even if it cannot be clearly distinguished from the other steps, the step is also included. It is.
In the present specification, the numerical value range indicated by using “to” includes the numerical value described before and after “to” as the minimum value and the maximum value, respectively.
In the numerical ranges described in stages in this specification, the upper limit or lower limit described in one numerical range may be replaced with the upper limit or lower limit of the numerical range described in other stages. Good. Further, in the numerical ranges described in this specification, the upper limit or the lower limit of the numerical ranges may be replaced with the values shown in the embodiments.
In the present specification, the content of each component in the composition, if there are a plurality of substances corresponding to each component in the composition, unless otherwise specified, the total of the plurality of substances present in the composition Means the content of
In the present specification, the particle diameter of each component in the composition, when there are a plurality of particles corresponding to each component in the composition, unless otherwise specified, a mixture of the plurality of particles present in the composition Means the value of
In this specification, the term "layer" refers to a case where a layer is formed only on a part of the region in addition to a case where the layer is formed on the entire region when the region where the layer is present is observed. Is also included.
As used herein, the term “lamination” refers to stacking layers, where two or more layers may be combined, or two or more layers may be removable.

[Heat conductive sheet]
The heat conductive sheet of the present embodiment is composed of an elastomer (A) having an isobutylene structure (hereinafter also referred to as “component (A)” or “elastomer (A)”), scale-like particles, elliptical particles, and rod-like particles. At least one type of graphite particles (B) selected from the group (hereinafter also referred to as “component (B)”) and an alicyclic hydrocarbon resin (C) (hereinafter also referred to as “component (C)”). In the case of the scaly particles, the plane direction, the long axis direction in the case of the oval spherical particles or the long axis direction in the case of the rod-shaped particles, oriented in the thickness direction of the heat conductive sheet. I have.

  With such a configuration, the heat conductive sheet can make the heat generating body and the heat radiating body adhere to each other with low heat resistance, and are excellent in compressibility, heat resistance, humidity resistance, and handling property of bonding.

<Elastomer containing isobutylene structure (A)>
The heat conductive sheet contains at least one elastomer (A) having an isobutylene structure. Here, the “isobutylene structure” refers to “—CH ₂ —C (CH ₃ ) ₂ —”.
It is considered that the elastomer (A) having an isobutylene structure mainly functions, for example, both as a stress relaxation agent excellent in heat resistance and humidity resistance and as a tackifier. That is, it can be considered that the alicyclic hydrocarbon resin (C) alone plays a role in compensating for the flexibility and adhesiveness, which tend to be insufficient. In other words, it can be said that the alicyclic hydrocarbon resin (C) plays a role of supplementing the cohesive force and the fluidity during heating, which tend to be insufficient with only the elastomer (A) having an isobutylene structure. It is considered that the component and the component (C) have a complementary relationship.

  Elastomer (A) containing an isobutylene structure is not particularly limited as long as it contains an isobutylene structure. Examples of the elastomer (A) having an isobutylene structure include a homopolymer of isobutene (alias: isobutylene, abbreviation: butene), a copolymer of isobutene and styrene, and a copolymer of isobutene and ethylene. . From the viewpoint of achieving both toughness, flexibility and tackiness, it is at least one selected from the group consisting of a copolymer of isobutene and styrene, a copolymer of isobutene and ethylene, and a homopolymer of isobutene. Is preferred.

  The copolymer may be any of a random copolymer, a block copolymer and a graft copolymer, and is preferably a block copolymer (that is, a copolymer having a polyisobutylene structure).

  The content of the isobutylene structure in the copolymer is not particularly limited. For example, the content of the isobutylene structure in the copolymer is 40% by mass to 99% by mass, may be 50% by mass to 95% by mass, or may be 60% by mass to 95% by mass. .

The elastomer (A) having an isobutylene structure may be in a solid state or a liquid state. As used herein, the term “liquid” refers to a substance that exhibits fluidity and viscosity at 25 ° C., and has a viscosity of 0.0001 Pa · s to 1000 Pa · s at 25 ° C. In the present specification, the “viscosity” is defined as a value measured at 25 ° C. using a rheometer at a shear rate of 5.0 s ⁻¹ . Specifically, the “viscosity” is measured as a shear viscosity at a temperature of 25 ° C. using a rotary shear viscometer equipped with a cone plate (diameter 40 mm, cone angle 0 °). On the other hand, in the present specification, "solid state" means one that does not fall under the definition of "liquid".

  The elastomer (A) containing an isobutylene structure may be used alone or in combination of two or more. For example, a homopolymer of isobutene may be used in combination of a solid polymer and a liquid polymer.

The molecular weight of the elastomer (A) having an isobutylene structure is not particularly limited.
The solid isobutene homopolymer preferably has a weight average molecular weight (Mw) or viscosity average molecular weight (Mv) of 40,000 or more, more preferably 40,000 to 100,000, and more preferably 50,000 to 80,000. preferable.
When the weight-average molecular weight (Mw) or viscosity-average molecular weight (Mv) of the homopolymer of solid isobutene is 40,000 or more, sufficient adhesive strength required for temporary fixing can be obtained, and heat resistance is excellent. There is a tendency that the strength of the heat conductive sheet is also excellent. When the viscosity average molecular weight is 100,000 or less, the compatibility with the alicyclic hydrocarbon resin (C) tends to be excellent.

In the present specification, the weight average molecular weight (Mw) is measured by a GPC (Gel Permeation Chromatography) method. The viscosity average molecular weight (Mv) is measured by the FCC method.
In the GPC method, the weight average molecular weight is determined by converting the molecular weight distribution using a calibration curve of standard polystyrene. The calibration curve is approximated by a cubic equation using a 5-sample set of standard polystyrene (Tosoh Corporation, PStQuick MP-H, PStQuick B). The measurement conditions of GPC in this specification are shown below.

Equipment: (Pump: Model L-2130 [Hitachi High-Technologies Corporation])
(Detector: RI: L-2490 type [Hitachi High-Technologies Corporation])
(Column oven: L-2350 [Hitachi High-Technologies Corporation])
Column: Gelpack GL-R440 + Gelpack GL-R450 + Gelpack GL-R400M (three in total) (Hitachi Chemical Co., Ltd., trade name)
Column size: 10.7mm (inner diameter) x 300mm
Eluent: Tetrahydrofuran Sample concentration: 10mg / 2mL
Injection volume: 200 μL
Flow rate: 2.05 mL / min Measurement temperature: 25 ° C

In the FCC method, the viscosity average molecular weight (Mv) is calculated from the following Mark-Houwink equation.
[Η] = K Mv ^α
α and K are known constants determined by the measurement temperature, the type of solvent, and the type of polymer, respectively, and can be referred to Chemical Handbook and the like. The intrinsic viscosity [η] is measured in accordance with JIS K7367-1: 2002 (Plastic-Determination of viscosity of elastomer diluted solution using capillary viscometer-).

  The liquid isobutene homopolymer preferably has a number average molecular weight (Mn) of 1,000 to 3,000, more preferably 1,300 to 3,000, and still more preferably 2,000 to 3,000. If the number average molecular weight is 3,000 or less, the softening effect tends to be sufficient, and if it is 1,000 or more, the heat resistance tends to be sufficient. The number average molecular weight (Mn) is measured by a VPO method (vapor pressure molecular weight measurement method, Vapor Pressure Osomometry).

  In the VPO method, the elastomer is completely dissolved in a solvent, three or more types of sample solutions having different concentrations are prepared, and a temperature difference caused by a change in enthalpy at the time of condensation of the sample solution and a pure solvent as a reference is determined by using a thermistor. The molecular weight is determined by measuring with a probe or the like.

In the heat conductive sheet, the content of the elastomer (A) having an isobutylene structure is preferably, for example, 3% by mass to 50% by mass from the viewpoints of adhesive strength, adhesion, sheet strength, and hydrolysis resistance. , More preferably from 4% by mass to 45% by mass, and still more preferably from 5% by mass to 40% by mass.
When the content of the elastomer (A) containing an isobutylene structure is 3% by mass or more, the adhesiveness and the adhesiveness tend to be further improved. When the content of the elastomer (A) having an isobutylene structure is 50% by mass or less, a decrease in sheet strength and thermal conductivity tends to be more effectively suppressed.

  The heat conductive sheet may contain another elastomer in addition to the elastomer (A) having an isobutylene structure. Other elastomers include, for example, polybutene. The molecular weight of polybutene is not particularly limited.

  The content of polybutene may be 30% by mass or less, or 25% by mass or less.

<Graphite particles (B)>
The heat conductive sheet contains at least one kind of graphite particles (B).
It is considered that the graphite particles (B) mainly function as high thermal conductive fillers. The graphite particles (B) are at least one selected from the group consisting of flaky particles, oval spherical particles and rod-like particles. When the graphite particles (B) are flaky particles, the six-membered ring surface is oriented in the plane direction, in the case of elliptical particles, in the long axis direction, and in the case of rod-shaped particles, in the long axis direction. Is preferred.

  The shape of the graphite particles (B) is more preferably scaly. By selecting flake-like graphite particles, the thermal conductivity tends to be further improved. This may be because, for example, the flaky graphite particles are more easily oriented in a predetermined direction in the heat conductive sheet. The six-membered ring surface is a surface on which a six-membered ring is formed in a hexagonal system, and means a (0001) crystal plane.

  It is confirmed by X-ray diffraction measurement whether or not the six-membered ring surface in the crystal of the graphite particles (B) is oriented in the plane direction of the flaky particles, the major axis of the oval particles or the major axis of the rod-like particles. can do. The orientation direction of the six-membered ring plane in the crystal of the graphite particles (B) is specifically confirmed by the following method.

  First, a measurement sample sheet is prepared in which the surface direction of the flake-like particles of the graphite particles (B), the major axis direction of the oval spherical particles or the major axis direction of the rod-like particles is oriented along the surface direction of the sheet. As a specific production method of the sample sheet for measurement, for example, the following method can be mentioned.

  A mixture of the resin and graphite particles (B) in an amount of 10% by volume or more is formed into a sheet. The “resin” used here is not particularly limited as long as it is a material that does not show a peak that hinders X-ray diffraction and is a material that can form a sheet. Specifically, an amorphous resin having a cohesive force as a binder such as acrylic rubber, NBR (acrylonitrile butadiene rubber), SIBS (styrene-isobutylene-styrene copolymer) can be used.

  A sheet of this mixture is pressed so as to have a thickness of 1/10 or less of the original thickness, and a plurality of pressed sheets are laminated to form a laminate. The operation of crushing the laminate to 1/10 or less is repeated three times or more to obtain a sample sheet for measurement. By this operation, in the measurement sample sheet, the graphite particles (B) are in the plane direction when the flake-like particles are, the long-axis direction when the spheroidal particles are, and the long-axis direction when the graphite particles (B) are the rod-like particles, The measurement sample sheet is oriented along the surface direction.

X-ray diffraction measurement is performed on the surface of the measurement sample sheet prepared as described above. 2 [Theta] = a 77 ° height _{H 1} of the peak corresponding to the (110) plane of graphite appears near, to measure the height _{H 2} of the peak corresponding to the (002) plane of graphite appearing near 2 [Theta] = 27 ° . In such measurement sample sheet prepared, the value obtained by dividing the _{H 1} with _{H 2} is 0 to 0.02.

  From this, "the six-membered ring surface in the crystal of the graphite particles (B) is in the plane direction in the case of flaky particles, in the long axis direction in the case of elliptical particles, and in the case of rod-shaped particles. "Oriented in the direction" means that the surface of the sheet containing the graphite particles (B) is subjected to X-ray diffraction measurement and corresponds to the (110) plane of the graphite particles (B) appearing at around 2θ = 77 °. The value obtained by dividing the height of the peak by the peak height corresponding to the (002) plane of the graphite particles (B) appearing near 2θ = 27 ° is 0 to 0.02.

In this specification, the X-ray diffraction measurement is performed under the following conditions.
Equipment: "D8DISCOVER" manufactured by Bruker AX Co., Ltd.
X-ray source: CuKα having a wavelength of 1.5406 nm, 40 kV, 40 mA
Step (measurement step width): 0.01 °
Step time: 720 sec

  Here, `` the plane direction when the graphite particles are flake-like particles, the long axis direction when the oval spherical particles, and the long axis direction when the rod-like particles are oriented in the thickness direction of the heat conductive sheet. "Is defined as an angle between the plane direction in the case of flake-shaped particles, the long axis direction in the case of oval spherical particles, and the long axis direction in the case of rod-shaped particles, and the surface of the heat conductive sheet (hereinafter," Orientation angle) is 60 ° or more. The orientation angle is preferably 80 ° or more, more preferably 85 ° or more, and even more preferably 88 ° or more.

  The orientation angle is obtained by observing a cross section of the heat conductive sheet with a SEM, and for any 50 graphite particles (B), the plane direction in the case of flake-like particles, the long axis direction in the case of elliptical spherical particles, In the case of rod-shaped particles, the average value is obtained by measuring the angle (orientation angle) between the major axis direction and the surface (main surface) of the heat conductive sheet.

  The particle size of the graphite particles (B) is not particularly limited. The average particle size of the graphite particles (B) is preferably 1/2 to the average thickness of the heat conductive sheet. When the average particle diameter of the graphite particles (B) is at least の of the average thickness of the heat conductive sheet, an efficient heat conductive path is formed in the heat conductive sheet, and the heat conductivity tends to be improved. When the average particle size of the graphite particles (B) is equal to or less than the average thickness of the heat conductive sheet, the protrusion of the graphite particles (B) from the surface of the heat conductive sheet is suppressed, and the adhesion of the surface of the heat conductive sheet tends to be excellent. There is.

  When using the lamination slice method as described in JP-A-2008-280496, the particle size of the graphite particles (B) used as a raw material is 1% of the average thickness of the heat conductive sheet as the mass average particle size. / 2 times or more, and may exceed the average thickness. The reason why the particle diameter of the graphite particles (B) used as a raw material may exceed the average thickness of the heat conductive sheet is, for example, that the graphite particles (B) having a particle diameter exceeding the average thickness of the heat conductive sheet are included. This is because the graphite particles (B) are sliced together to form a heat conductive sheet, and as a result, the graphite particles (B) do not protrude from the surface of the heat conductive sheet. In addition, when the graphite particles (B) are sliced together in this way, a large number of graphite particles (B) penetrating in the thickness direction of the heat conductive sheet are generated, an extremely efficient heat conductive path is formed, and the thermal conductivity tends to be further improved. It is in.

  When the lamination slice method is used, the particle diameter of the graphite particles (B) used as a raw material is more preferably 1 to 5 times the average thickness of the heat conductive sheet as a mass average particle diameter. When the mass average particle diameter of the graphite particles (B) is at least one time the average thickness of the heat conductive sheet, a more efficient heat conductive path is formed, and the heat conductivity is further improved. When the average thickness of the heat conductive sheet is 5 times or less, the area occupied by the graphite particles (B) in the surface portion is prevented from becoming too large, and a decrease in adhesion can be suppressed.

  The mass average particle diameter (D50) of the graphite particles (B) is measured using a laser diffraction type particle size distribution apparatus (for example, “Microtrack Series MT3300” manufactured by Nikkiso Co., Ltd.) to which the laser diffraction / scattering method is applied, and the weight is measured. When the cumulative particle size distribution curve is drawn from the small particle size side, it corresponds to the particle size at which the weight accumulation becomes 50%.

  Examples of the graphite particles (B) include spherical graphite powder, scale graphite powder, artificial graphite powder, exfoliated graphite powder, acid-treated graphite powder, expanded graphite powder, and carbon fiber flake. Above all, as the graphite particles (B), expanded graphite powder obtained by pulverizing sheeted expanded graphite is preferable from the viewpoint of easily obtaining scale having a high crystallinity and a large particle size.

The particle size distribution of the graphite particles (B) is not particularly limited. Even if the particle size distribution in which the horizontal axis represents the particle diameter and the vertical axis represents the frequency is a monodispersed system having a single peak, the particle diameter distribution is not limited. May be a polydisperse system having a plurality of peaks. Further, the particle size distribution may be narrow or the particle size distribution may be wide.
As described above, large particles can form a more efficient heat conduction path and are preferable from the viewpoint of thermal conductivity.However, if the large particles and the particle size distribution are narrow, the voids formed between the large particles also increase. Due to this tendency, the thermal conductivity in the plane of the thermal conductive sheet tends to vary greatly. For this reason, the particle size distribution should be somewhat wide, or be a polydisperse particle size distribution in which a plurality of peaks exist, so that small particles can be appropriately present and voids formed by the large particles can be filled with the small particles. Is preferred. Since the shape of the particle size distribution is greatly different depending on the particle shape and the like, it is not quantitatively limited.However, for the above reasons, the particles are formed by large particles having an average particle size close to the average thickness of the heat conductive sheet, and large particles. And a small particle having an average particle size smaller than the size of the void to be formed, and the particle size distribution is particularly preferably such that the small particle is contained in an amount that fits in the void.

The content of the graphite particles (B) in the heat conductive sheet is, for example, preferably from 15% by volume to 50% by volume, and from 20% by volume to 45% by volume from the viewpoint of the balance between thermal conductivity and adhesion. Is more preferable, and it is further preferable that it is 25 to 40 volume%.
When the content of the graphite particles (B) is 15% by mass or more, the thermal conductivity tends to be further improved. When the content of the graphite particles (B) is 50% by mass or less, a decrease in tackiness and adhesion tends to be more effectively suppressed.

The content (% by volume) of the graphite particles (B) is a value obtained by the following equation.
Content (volume%) of graphite particles (B) = (Bw / Bd) / ((Aw / Ad) + (Bw / Bd) + (Cw / Cd) + (Dw / Dd)) × 100
Aw: mass composition of elastomer (A) (% by mass)
Bw: mass composition (% by mass) of graphite particles (B)
Cw: mass composition (mass%) of alicyclic hydrocarbon resin (C)
Dw: mass composition of other optional components (% by mass)
Ad: Density of the elastomer (A) Bd: Density of the graphite particles (B) (Bd is calculated as 2.1 in this specification).
Cd: Density of alicyclic hydrocarbon resin (C) Dd: Density of other optional components

<Alicyclic hydrocarbon resin (C)>
The heat conductive sheet contains at least one alicyclic hydrocarbon resin (C). The alicyclic hydrocarbon resin (C) has, for example, the effect of improving the cohesive force with excellent heat resistance and humidity resistance and improving the fluidity during heating as complementarily to the component (A), as described above. it is conceivable that.

  Examples of the alicyclic hydrocarbon resin (C) include a hydrogenated aromatic petroleum resin (hereinafter, also referred to as “hydrogen petroleum resin”), a hydrogenated terpene phenol resin, and a cyclopentadiene petroleum resin. . These alicyclic hydrocarbon resins (C) can be appropriately selected from commercially available alicyclic hydrocarbon resins and used.

  Among them, the alicyclic hydrocarbon resin (C) is preferably at least one selected from a hydrogenated aromatic petroleum resin and a hydrogenated terpene phenol resin. These alicyclic hydrocarbon resins (C) are highly stable and have excellent compatibility with the elastomer (A) having an isobutylene structure. Therefore, when a heat conductive sheet is formed, more excellent thermal conductivity is obtained. , Flexibility, and handleability tend to be achieved.

Examples of the hydrogenated aromatic petroleum resin include "Alcon" manufactured by Arakawa Chemical Industries, Ltd. and "Imarb" manufactured by Idemitsu Kosan Co., Ltd.
Further, as the hydrogenated terpene phenol resin, for example, "Clearon" manufactured by Yasuhara Chemical Co., Ltd. can be mentioned.
Examples of the cyclopentadiene-based petroleum resin include “Quinton” manufactured by Zeon Corporation and “Marquarez” manufactured by Maruzen Petrochemical Co., Ltd.

The alicyclic hydrocarbon resin (C) is preferably solid at 25 ° C.
The alicyclic hydrocarbon resin (C) is preferably thermoplastic, and preferably has a softening temperature of 40C to 150C. When a thermoplastic resin is used, the softening fluidity at the time of thermocompression bonding is improved, so that the adhesiveness tends to be improved. On the other hand, if the softening temperature is 40 ° C. or higher, the cohesive force at around room temperature can be maintained, so that the required sheet strength is easily obtained and the handling property tends to be excellent. When the softening temperature is 150 ° C. or lower, the softening fluidity at the time of thermocompression bonding is increased, so that the adhesiveness tends to be improved. The softening temperature is more preferably from 80C to 130C. The softening temperature is measured by the ring and ball method (JIS-K2207: 1996).

  The weight average molecular weight of the alicyclic hydrocarbon resin (C) is not particularly limited. In light of the strength and flexibility of the heat conductive sheet, the weight average molecular weight of the alicyclic hydrocarbon resin (C) is preferably from 200 to 10,000, and more preferably from 500 to 2,000.

The content of the alicyclic hydrocarbon resin (C) in the heat conductive sheet is, for example, from 10% by mass to 200% by mass with respect to the elastomer (A) from the viewpoints of adhesive strength, adhesion, and sheet strength. Is preferably 25% by mass to 100% by mass, and more preferably 40% by mass to 60% by mass.
When the content of the alicyclic hydrocarbon resin (C) is 10% by mass or more with respect to the component (A), the adhesive strength, heat fluidity, and sheet strength tend to be sufficient, and 200% by mass or less. In such a case, flexibility tends to be sufficient, and handling properties and thermal cycle resistance tend to be excellent.

<Other ingredients>
The heat conductive sheet may contain other components other than the component (A), the component (B) and the component (C) according to the purpose. For example, a flame retardant may be contained for the purpose of imparting flame retardancy.

  The flame retardant is not particularly limited, and can be appropriately selected from commonly used flame retardants. For example, a red phosphorus flame retardant and a phosphate ester flame retardant can be mentioned. Among them, phosphate ester-based flame retardants are preferred from the viewpoint of excellent safety and improved adhesion due to the plasticity effect.

  As the red phosphorus-based flame retardant, besides pure red phosphorus powder, those coated with various coatings for the purpose of enhancing safety or stability, those prepared in a master batch, and the like may be used. Specific examples include Nova Red, Nova Excel, Nova Quell, and Nova pellets (all trade names) manufactured by Rin Kagaku Kogyo Co., Ltd.

Phosphate-based flame retardants include aliphatic phosphate esters such as trimethyl phosphate, triethyl phosphate, and tributyl phosphate; triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, trixylenyl phosphate, cresyl di 2,6-xy Aromatic phosphates such as renyl phosphate, tris (t-butylated phenyl) phosphate, tris (isopropylated phenyl) phosphate, and triarylisopropylated phosphate; resorcinol bisdiphenyl phosphate, bisphenol A bis (diphenyl phosphate), resorcinol Aromatic condensed phosphoric acid esters such as bisdixylenyl phosphate are exemplified.
Among these, bisphenol A bis (diphenyl phosphate) is preferred from the viewpoint of excellent hydrolysis resistance and an excellent effect of improving adhesion due to a plasticizing effect.

  The content of the flame retardant in the heat conductive sheet is not limited, and the flame retardant can be used in an amount capable of exhibiting flame retardancy, and is preferably about 30% by mass or less.

  The heat conductive sheet may contain additives such as an antioxidant, a radical trapping agent, and a pH adjuster as needed. The content of these additives is preferably 5% by mass or less in the heat conductive sheet.

[Physical properties and structure of heat conductive sheet]
The heat conductive sheet preferably has a tensile strength at 25 ° C. of 0.1 MPa or more, and more preferably 0.2 MPa or more, from the viewpoint of sticking properties and handling strength.
In addition, the heat conductive sheet has a tack force at 25 ° C. of preferably 3.0 kPa or more and less than 70 kPa, and more preferably 4.0 kPa or more and less than 50 kPa, from the viewpoints of sticking properties and handling strength.

  As for the tensile strength and the tacking force, the types and the contents of the elastomer (A) containing the isobutylene structure, the graphite particles (B), and the alicyclic hydrocarbon resin (C) are appropriately selected from the above-described preferred ranges. By doing so, it is possible to adjust.

The average thickness of the heat conductive sheet is not particularly limited, and can be appropriately selected depending on the purpose. Specifically, the average thickness of the heat conductive sheet can be 50 μm to 3000 μm, and preferably 100 μm to 1000 μm from the viewpoint of heat conductivity and adhesion.
The average thickness of the heat conductive sheet is given as an arithmetic average value by measuring the thickness at three places using a micrometer.

  The heat conductive sheet may have a protective film on at least one surface, and preferably has a protective film on both surfaces. Thereby, the adhesive surface of the heat conductive sheet can be protected.

  As the protective film, for example, resin films such as polyethylene, polyester, polypropylene, polyethylene terephthalate, polyimide, polyetherimide, polyethernaphthalate, and methylpentene, coated paper, coated cloth, and metal foil such as aluminum can be used. These protective films may be used alone or in combination of two or more to form a multilayer film. The protective film is preferably surface-treated with a silicone-based or silica-based release agent or the like.

(Production method of heat conductive sheet)
The method for manufacturing the heat conductive sheet is not particularly limited as long as a sheet having the above configuration is obtained. Examples of the method for manufacturing the heat conductive sheet include the following methods.

  The production method includes an elastomer having an isobutylene structure (A), at least one kind of graphite particles (B) selected from the group consisting of flaky particles, oval spherical particles and rod-like particles, and an alicyclic hydrocarbon resin ( C), a step of preparing a composition containing the composition (also referred to as a “preparation step”), a step of forming the composition into a sheet to obtain a sheet (also referred to as a “sheet production step”), and a plurality of sheets of the sheet. And stacking one of the sheets or winding one of the sheets to form a laminated body (also referred to as a “laminated body manufacturing step”), and slicing the side end surface of the laminated body (Slicing step).

  By manufacturing a heat conductive sheet by such a method, an efficient heat conductive path is easily formed, and therefore, a heat conductive sheet having high heat conductivity and excellent adhesion tends to be obtained.

<Preparation process>
The composition of the heat conductive sheet can be prepared by any method as long as the component (A), the component (B), the component (C), and other components can be mixed as required. And it is not particularly limited. The composition may be prepared by obtaining a commercial product. For details of preparation of the composition, refer to paragraph [0033] of JP-A-2008-280496.

<Sheet preparation process>
The sheet preparation step may be any method as long as the composition obtained in the previous step can be formed into a sheet, and is not particularly limited. For example, it is preferable to use at least one molding method selected from the group consisting of rolling, pressing, extrusion, and coating. For details of the sheet manufacturing step, refer to paragraph [0034] of JP-A-2008-280496.

<Laminated body manufacturing process>
In the laminate production step, a laminate of the sheets obtained in the previous step is formed. The laminated body is not limited to, for example, a form in which a plurality of independent sheets are sequentially stacked, and may be a form in which one sheet is folded without cutting, or a form in which one sheet is wound. It may be. For details of the laminate manufacturing process, refer to paragraphs [0035] to [0037] of JP-A-2008-280496.

<Slicing process>
The slicing step may be any method as long as the side end surface of the laminate obtained in the previous step can be sliced, and is not particularly limited. The graphite particles (B) penetrating in the thickness direction of the heat conductive sheet form an extremely efficient heat conduction path, and from the viewpoint of further improving the heat conductivity, the mass average particle diameter of the graphite particles (B) is twice or less. It is preferable that the slices be sliced at a thickness of not less than 1. For details of the slicing step, refer to paragraph [0038] of JP-A-2008-280496.

<Heat dissipation device>
The heat radiating device has the above-described heat conductive sheet interposed between the heat generating body and the heat radiating body. Since the heat generating element and the heat radiating element are laminated via the heat conductive sheet, heat from the heat generating element can be efficiently transmitted to the heat radiating element. Further, when the heat radiator is removed from the heat generator, the heat conductive sheet can be easily removed.

  Since the temperature range in which the heat conductive sheet can be particularly preferably used is, for example, −10 ° C. to 120 ° C., as the heating element, for example, a semiconductor package, a display, an LED, and an electric lamp are examples of suitable heating elements. Can be mentioned.

  As the radiator, for example, aluminum or copper fins, a heat sink using a plate or the like, an aluminum or copper block connected to a heat pipe, an aluminum or copper block in which a cooling liquid is circulated by a pump, And a Peltier element and an aluminum or copper block provided with the Peltier element.

  The heat radiating device is configured by bringing each surface of the heat conductive sheet into contact with the heat generating body and the heat radiating body. The method of contacting the heat generating element with one surface of the heat conductive sheet, and the method of contacting the heat radiating element with the other surface of the heat conductive sheet are not particularly limited as long as they can be fixed in a state where they are sufficiently adhered to each other. Not restricted.

  Specifically, a heat conductive sheet is arranged between the heat generating element and the heat radiating element, and the heat conductive sheet is fixed with a jig such as a clip that can be pressed to about 0.1 MPa to 2 MPa. Or a method of heating to about 80 ° C. to 180 ° C. by an oven or the like. In this method, a preferable pressure range is 0.15 MPa to 1 MPa, and a preferable temperature range is 100 ° C. to 170 ° C. When the pressure is 0.1 MPa or more or the heating temperature is 80 ° C. or more, excellent adhesiveness tends to be obtained. When the pressure is 2 MPa or less or the heating temperature is 180 ° C. or less, the reliability of adhesion tends to be further improved. It is considered that this is because the heat conductive sheet can be suppressed from being excessively compressed and becoming thinner, and the distortion or residual stress of the peripheral members can be suppressed from becoming too large.

  The thermal conductive sheet may have a thickness (compression ratio) of 5% to 35% of the thickness reduced after the compression relative to the initial thickness before the compression and the arrangement between the heating element and the heat radiator.

  In fixing, a jig such as a screw or a spring may be used in addition to the clip, and it is preferable that the jig is further fixed by a commonly used means such as an adhesive in order to maintain close contact.

  Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples. Unless otherwise specified, “%” is based on mass.

(Example 1)
The following materials were put into a 4 L pressure kneader, and kneaded under the condition of an ultimate temperature of 170 ° C. to prepare a composition.

<Elastomer (A)>
Styrene-isobutene (alias: isobutylene) -styrene triblock copolymer (SIBS) (“SIBSTER102T” manufactured by Kaneka Corporation, styrene content: 15%, density: 0.942 g / cm ³ ): 240 g
· Polybutene 200N (NOF Co., Ltd., number average molecular weight: 2650, Density: 0.91g ^/ cm 3): 360g
<Graphite particles (B)>
Scale-like expanded graphite powder (“HGF-L” manufactured by Hitachi Chemical Co., Ltd., mass average particle diameter: 270 μm, and the six-membered ring surface in the crystal is scale-like particles by the method using the X-ray diffraction measurement described above. Was confirmed to be oriented in the direction of the surface.): 2156 g
<Alicyclic hydrocarbon resin (C)>
- hydrogenated petroleum resin (Arakawa Chemical Industries, Ltd. "Alcon P90", density: 0.991g ^/ cm 3): 400g
<Flame retardant>
Bisphenol A bis (diphenyl phosphate) (phosphate flame retardant, “CR-741” manufactured by Daihachi Chemical Co., Ltd., density: 1.26 g / cm ³ ): 844 g

  The content of each of the component (A), the component (B), the component (C), and the flame retardant with respect to the entire composition is 15.0% by mass, 53.9% by mass, 10.0% by mass, And 21.1% by mass. The content of graphite particles (B) calculated from the density of each material was 37% by volume.

  The composition was placed in an extruder and extruded into a flat plate having a width of 20 cm and a thickness of 1.5 mm to 1.6 mm to obtain a primary sheet. The obtained primary sheet is press-punched using a mold blade of 40 mm × 150 mm, and 61 sheets of the punched sheet are laminated, and a stacking direction of 120 ° C. is sandwiched by an 80 mm-high spacer so that the height becomes 80 mm. For 2 minutes to obtain a laminate. Next, a side end surface of the 80 mm × 150 mm laminate was sliced with a woodworking slicer to obtain a heat conductive sheet (I) having a length of 80 mm × 150 mm × 0.13 mm.

  The cross section of the heat conductive sheet (I) is observed with an SEM, and an angle (hereinafter, also referred to as an “orientation angle”) between the plane direction of the flaky particles and the surface of the heat conductive sheet is obtained for arbitrary 50 graphite particles (B). ) Was measured, the average value of the orientation angle was 90 degrees, and it was confirmed that the plane direction of the flaky particles of the graphite particles (B) was oriented in the thickness direction of the heat conductive sheet.

The following evaluation was performed about the heat conductive sheet obtained above. Table 1 shows the evaluation results.
The change in thermal resistance before and after the heat resistance test was used as an index of heat resistance. The change in thermal resistance before and after the HAST (Highly-Accelerated Temperature and Humidity Stress Test) resistance test was used as an index of heat resistance and humidity resistance. Tack force was used as an index of temporary fixability, and tensile strength was used as an index of handleability.

(Measurement of thermal conductivity)
The heat conductive sheet was punched into a circular shape having a diameter of 14 mm, and two 27 mm square copper plates having a thickness of 1 mm were prepared, and the punched heat conductive sheet was sandwiched in the center between the two copper plates. This was fixed with two clips having a strength of 23N to 24N. The applied pressures each correspond to 0.3 MPa. The sample was heated in a 165 ° C. oven for 1 hour. After cooling to room temperature (25 ° C.), the edge of the copper plate was fixed with an epoxy adhesive so as not to shift, and the clip was removed to obtain a crimped sample.

  Subsequently, the thermal conductivity of the pressure-bonded sample at 25 ° C. was measured using a thermal diffusivity measuring device (“LFA447” manufactured by NETZCH). The thermal conductivity of the copper plate was measured in advance, and the thermal conductivity λ (W / mK) of the heat conductive sheet portion was determined by a three-layer method using a thermal diffusivity measuring device.

(Measurement of thermal resistance)
The thermal resistance Rth (K · cm ² / W) was determined from the above thermal conductivity λ and the thickness t (mm) of the thermal conductive sheet by the following equation. The thickness t (mm) of the heat conductive sheet is a value obtained by subtracting the thickness of the two copper plates measured in advance from the thickness of the pressure-bonded sample. The thickness of each of the pressure-bonded sample and the copper plate was measured with a micrometer. Three pressure-bonded samples were prepared, three shots were measured for each, and the average value was adopted.
Rth = 10 × t / λ

(Measurement of compression ratio)
In the preparation of the above crimping sample, the thermally conductive sheet in advance by measuring the initial thickness t ₁ of the thermally conductive sheet before sandwiching the two copper plates, and it was measured the thickness t ₂ of the crimping samples after the thermocompression bonding. The thickness t ₂ of the initial thickness t ₁ and crimping samples were measured with a micrometer, respectively.
The compression ratio was determined as a ratio (%) of the thickness (t ₁ -t ₂ ) reduced by thermocompression bonding to the initial thickness t ₁ of the heat conductive sheet.
Compression ratio (%) = (t ₁ −t ₂ ) / t ₁ × 100

(Measurement of thermal resistance after heat resistance test)
To prevent the copper plate from peeling even if the epoxy adhesive deteriorates, re-fix the pressure-bonded sample with a clip, place it on a stainless steel bat, and put it in a “safety oven SPHH101 type” manufactured by Espec Corporation set at 150 ° C. Heat treated for 200 hours. The epoxy adhesive was reapplied to the edge of the copper plate when the clip was removed for thermal resistance measurement. Then, the above-described thermal resistance was measured.

(Measurement of thermal resistance after HAST resistance test)
"HASTTEST PC-R8D" manufactured by Hirayama Manufacturing Co., Ltd., which was re-fixed with a clip and placed on a stainless steel bat and set at 110 ° C and 85% RH so that the copper plate did not come off even if the epoxy adhesive deteriorated. For 125 hours. The epoxy adhesive was reapplied to the edge of the copper plate when the clip was removed for thermal resistance measurement. Then, the above-described thermal resistance was measured.

(Measurement of tack force)
The tack force was measured with the following device and conditions.
Equipment used: Rescue Co., Ltd. tacking test machine "TAC2"
Temperature: 25 ° C
Pushing speed: 120 mm / min Pulling speed: 600 mm / min Load: 490 mN (50 gf)
Time: 10 seconds

(Measurement of tensile strength)
The tensile strength was measured using a sample sheet punched out from a heat conductive sheet to 1 cm × 5 cm using the following apparatus and conditions.
Equipment used: “STROGRAPH ES” manufactured by Toyo Seiki Co., Ltd.
Temperature: 25 ° C
Tensile speed: 5 mm / min

The thermal conductive sheet (I) had good initial thermal conductivity of 14.8 (W / mK) and good initial thermal resistance of 0.09 (K · cm ² / W).
Further, the thermal resistance after the heat resistance test maintained a favorable value of 0.08 (K · cm ² / W). Furthermore, the thermal resistance after the HAST resistance test maintained a favorable value of 0.08 (K · cm ² / W).
The compression ratio was as good as 10%.
The tack force was 13.9 (kPa), which was a value capable of exhibiting good temporary fixability.
The tensile strength was 0.39 (MPa), which was a strength at which good handling properties were obtained.

(Example 2)
Instead of styrene-isobutene-styrene triblock copolymer and polybutene, as an elastomer (A) having an isobutylene structure, a homopolymer of isobutene (“Tetrax 6T” manufactured by Nippon Oil Co., Ltd., viscosity average molecular weight: 60000, 25 ° C.) , A composition was prepared in the same manner as in Example 1 except that 600 g of a solid, density: 0.92 g / cm ³ ) was used, and the same as Example 1 except that this composition was used. A heat conductive sheet (II) having a length of 80 mm, a width of 150 mm and a thickness of 0.14 mm was obtained by the method.

  The content rates of the component (A), the component (B), the component (C), and the flame retardant with respect to the entire composition are 15.0% by mass, 53.9% by mass, 10.0% by mass, and 21%, respectively. 0.1% by mass. The content of the graphite particles (B) calculated from the density of each material was 37% by volume.

  In the heat conductive sheet (II), the average value of the orientation angle of the graphite particles (B) is 89 degrees, and the plane direction of the flake-like particles of the graphite particles (B) is oriented in the thickness direction of the heat conductive sheet. Was observed.

  The obtained heat conductive sheet (II) was evaluated in the same manner as in Example 1. Table 1 shows the evaluation results.

The obtained thermal conductive sheet (II) had good initial thermal conductivity of 15.6 (W / (mK)) and good initial thermal resistance of 0.09 (K · cm ² / W).
Further, the thermal resistance after the heat resistance test maintained a favorable value of 0.08 (K · cm ² / W). Furthermore, the thermal resistance after the HAST resistance test maintained a favorable value of 0.08 (K · cm ² / W).
The compression ratio was as good as 10%.
The tack force was 13.0 (kPa), which was a numerical value capable of exhibiting good temporary fixability.
The tensile strength was 0.21 (MPa), which was a strength at which good handling properties were obtained.

(Example 3)
A composition was prepared in the same manner as in Example 1, except that the following materials were used in the following amounts.

<Elastomer (A)>
・ Styrene-isobutene-styrene triblock copolymer (SIBS) (“SIBSTER102T” manufactured by Kaneka Corporation): 210 g
・ Polybutene ("200N" manufactured by NOF Corporation): 390 g
<Graphite particles (B)>
-Scale-like expanded graphite powder ("HGF-L" manufactured by Hitachi Chemical Co., Ltd.): 2156 g
<Alicyclic hydrocarbon resin (C)>
・ Hydrogenated petroleum resin ("Alcon P90" manufactured by Arakawa Chemical Industries, Ltd.): 100 g
<Flame retardant>
・ Bisphenol A bis (diphenyl phosphate) (“CR-741” manufactured by Daihachi Chemical Industry Co., Ltd.): 844 g
<Other resins>
・ Terpene phenol (“YS Polystar T80” manufactured by Yashara Chemical Co., Ltd.): 300 g

The content rates of the component (A), the component (B), the component (C), and the flame retardant with respect to the entire composition are 15.1% by mass, 53.9% by mass, 2.5% by mass, and 21. It was 1% by mass. The content of the graphite particles (B) calculated from the density of each material was 37% by volume.
Using the obtained composition, a heat conductive sheet (III) having a length of 80 mm, a width of 150 mm, and a thickness of 0.14 mm was obtained.

  In the heat conductive sheet (III), the average value of the orientation angle of the graphite particles (B) is 89 degrees, and the plane direction of the flake-like particles of the graphite particles (B) is oriented in the thickness direction of the heat conductive sheet. It was recognized that.

  The following evaluation was performed on the obtained heat conductive sheet (III) in the same manner as in Example 1. Table 1 shows the evaluation results.

The obtained thermal conductive sheet (III) had good initial thermal conductivity of 15.9 (W / mK) and good initial thermal resistance of 0.09 (K · cm ² / W).
Further, the thermal resistance after the heat resistance test maintained a favorable value of 0.08 (K · cm ² / W). Furthermore, the thermal resistance after the HAST resistance test maintained a favorable value of 0.08 (K · cm ² / W).
The compression ratio was as good as 10%.
The tack force was 4.2 (kPa), which was a value capable of exhibiting good temporary fixability.
The tensile strength was 0.21 (MPa), which was a strength at which good handling properties were obtained.

(Example 4)
As the alicyclic hydrocarbon resin (C), instead of hydrogenated petroleum resin ("Arcon P90" manufactured by Arakawa Chemical Industries, Ltd.), hydrogenated terpene resin ("Clearon P85" manufactured by Yashara Chemical Co., Ltd.), softening temperature: 85C , Density: 0.98 g / cm ³ ) except that the composition was prepared in the same manner as in Example 2, and the same method as in Example 1 except that this composition was used, the length was 80 mm × A heat conductive sheet (IV) having a width of 150 mm and a thickness of 0.15 mm was obtained.

  The content rates of the component (A), the component (B), the component (C), and the flame retardant with respect to the entire composition are 15.0% by mass, 53.9% by mass, 10.0% by mass, and 21%, respectively. 0.1% by mass. The content of the graphite particles (B) calculated from the density of each material was 37% by volume.

  The average value of the orientation angle of the graphite particles (B) of the heat conductive sheet (IV) is 90 degrees, and the plane direction of the flake-like particles of the graphite particles (B) is oriented in the thickness direction of the heat conductive sheet. Admitted.

  About the obtained heat conductive sheet (IV), the following evaluations were performed in the same manner as in Example 1 except that the thermocompression bonding temperature was 125 ° C. and the number of clips was 1 (corresponding to a pressure of 0.15 MPa). Table 1 shows the evaluation results.

The obtained thermal conductive sheet (IV) had good initial thermal conductivity of 15.5 (W / mK) and good initial thermal resistance of 0.09 (K · cm ² / W).
Further, the thermal resistance after the heat resistance test maintained a favorable value of 0.08 (K · cm ² / W). Furthermore, the thermal resistance after the HAST resistance test maintained a favorable value of 0.08 (K · cm ² / W).
The compression ratio was as good as 10%.
The tack force was 3.2 (kPa), which was a value capable of exhibiting good temporary fixability.
The tensile strength was 0.17 (MPa), which was a strength at which good handling properties were obtained.

(Example 5)
A composition was prepared in the same manner as in Example 1 except that no flame retardant was used and the following materials were used in the following composition.

<Elastomer (A)>
・ Styrene-isobutene diblock copolymer (SIB) (“SIBSTER062M” manufactured by Kaneka Corporation, styrene content: 23%, density: 0.947 g / cm ³ ): 668 g
・ Polybutene (“200N” manufactured by NOF Corporation): 817 g
<Graphite particles (B)>
Scale-like expanded graphite powder (“HGF-L” manufactured by Hitachi Chemical Co., Ltd.), mass average particle diameter: 270 μm): 1675 g
<Alicyclic hydrocarbon resin (C)>
・ Hydrogenated petroleum resin (Alcon “P90” manufactured by Arakawa Chemical Industries, Ltd.): 817 g

The content rates of the component (A), the component (B), and the component (C) with respect to the entire composition were 37.3% by mass, 42.2% by mass, and 20.5% by mass, respectively. The content of the graphite particles (B) calculated from the density of each material was 25% by volume.
Using the obtained composition, a heat conductive sheet (V) having a length of 80 mm, a width of 150 mm, and a thickness of 0.51 mm was obtained.

  In the heat conductive sheet (V), the average value of the orientation angle of the graphite particles (B) is 90 degrees, and the plane direction of the flake-like particles of the graphite particles (B) is oriented in the thickness direction of the heat conductive sheet. Was observed.

  About the obtained heat conductive sheet (V), the following evaluations were performed in the same manner as in Example 1 except that the thermocompression bonding temperature was 125 ° C. and the number of clips was 1 (corresponding to a pressure of 0.15 MPa). Table 1 shows the evaluation results.

The obtained thermal conductive sheet (V) has a good initial thermal conductivity of 14.7 (W / mK), and an initial thermal resistance of 0.27 (K · cm ² / W), which is a fraction of the thickness. Showed a good value.
Further, the thermal resistance after the heat resistance test maintained a favorable value of 0.24 (K · cm ² / W). Further, the thermal resistance after the HAST resistance test maintained a favorable value of 0.24 (K · cm ² / W).
The compression ratio was as good as 27%.
The tack force was 5.4 (kPa), which was a value capable of exhibiting good temporary fixability.
The tensile strength was 0.40 (MPa), which was a strength at which good handling properties were obtained.

(Comparative Example 1)
A composition was prepared in the same manner as in Example 3 except that 400 g of terpene phenol (“YS Polystar T80” manufactured by Yashara Chemical Co., Ltd.) was used as the other resin instead of using the alicyclic hydrocarbon resin (C). Was prepared, and a heat conductive sheet (VI) having a length of 80 mm, a width of 150 mm and a thickness of 0.14 mm was obtained in the same manner as in Example 1 except that this composition was used.
The content of the component (A), the component (B), the component (C), the other resin, and the flame retardant with respect to the entire composition are 15.1% by mass, 53.9% by mass, 0% by mass, and 10% by mass, respectively. % And 21.1% by mass. The content of the graphite particles (B) calculated from the density of each material was 37% by volume.

  In the heat conductive sheet (VI), the average value of the orientation angle of the graphite particles (B) is 90 degrees, and the plane direction of the flake-like particles of the graphite particles (B) is oriented in the thickness direction of the heat conductive sheet. Was observed.

  The following evaluation was performed on the obtained heat conductive sheet (VI) in the same manner as in Example 1. Table 2 shows the evaluation results.

The obtained thermal conductive sheet (VI) has a good initial thermal conductivity of 15.6 (W / mK) and a good initial thermal resistance of 0.09 (K · cm ² / W). Indicated.
Further, the thermal resistance after the heat resistance test maintained a favorable value of 0.08 (K · cm ² / W). Furthermore, the thermal resistance after the HAST resistance test maintained a favorable value of 0.08 (K · cm ² / W).
The compression ratio was as good as 11%.
The tack force was weak at 2.0 (kPa), and the temporary fixing force was insufficient.
Since the tensile strength was weak at 0.09 (MPa) and the film was easily broken, the handleability was poor.

(Comparative Example 2)
A composition was prepared in the same manner as in Example 1, except that the elastomer (A) having an isobutylene structure and the alicyclic hydrocarbon resin (C) were not used and the following materials were used in the following composition.

<Graphite particles (B)>
-Scale-like expanded graphite powder ("HGF-L" manufactured by Hitachi Chemical Co., Ltd.): 2156 g,
<Other resins>
Butyl acrylate / ethyl acrylate / acrylonitrile / acrylic acid copolymer (“HTR-280 Kai 2DR” manufactured by Nagase ChemteX Corporation, copolymerization mass ratio: 82/10/3/5, Tg: −39 ° C., Weight average molecular weight: 530,000, density: 1.056 g / cm ³ ): 333 g
・ Terpene phenol (“YS Polystar T80” manufactured by Yashara Chemical Co., Ltd., softening temperature: 80 ° C., density: 0.994 g / cm ³ ): 333 g
<Flame retardant>
1067 g of bisphenol A bis (diphenyl phosphate) (phosphate ester flame retardant, “CR-741” manufactured by Daihachi Chemical Industry Co., Ltd., density 1.26 g / cm ³ )

The content of the component (A), the component (B), the component (C), the other resin, and the flame retardant with respect to the entire composition are 0 mass%, 55.4 mass%, 0 mass%, and 17. 2% by mass and 27.4% by mass. The content of the graphite particles (B) calculated from the density of each material was 39% by volume.
Using this composition, a heat conductive sheet (VII) having a length of 80 mm, a width of 150 mm and a thickness of 0.15 mm was obtained in the same manner as in Example 1.

  In the heat conductive sheet (VII), the average value of the orientation angle of the graphite particles (B) is 89 degrees, and the plane direction of the flake-like particles of the graphite particles (B) is oriented in the thickness direction of the heat conductive sheet. Was observed.

The obtained thermal conductive sheet (VII) has a good initial thermal conductivity of 15.5 (W / mK) and a good initial thermal resistance of 0.09 (K · cm ² / W). Indicated.
Further, the thermal resistance after the heat resistance test maintained a favorable value of 0.08 (K · cm ² / W). However, the thermal resistance after the HAST resistance test was deteriorated to 0.15 (K · cm ² / W).
The compression ratio was as good as 10%.
The tack force was 3.4 (kPa), which was a numerical value capable of exhibiting good temporary fixability.
The tensile strength was as low as 0.07 (MPa), and the film was easily broken, so that the handleability was poor.

(Comparative Example 3)
A composition was prepared in the same manner as in Example 1 except that the alicyclic hydrocarbon resin (C) was not used and the following materials were used in the following composition.

<Elastomer (A)>
-Styrene-isobutene-styrene triblock copolymer (SIBS) ("SIBSTER102T" manufactured by Kaneka Corporation): 350 g
・ Polybutene (“200N” manufactured by NOF Corporation): 650 g
<Graphite particles (B)>
-Scale-like expanded graphite powder ("HGF-L" manufactured by Hitachi Chemical Co., Ltd.): 2156 g
<Flame retardant>
・ Bisphenol A bis (diphenyl phosphate) (“CR-741” manufactured by Daihachi Chemical Industry Co., Ltd.): 844 g

The content rates of the component (A), the component (B), the component (C), and the flame retardant with respect to the whole composition are 25.0% by mass, 53.9% by mass, 0% by mass, and 21.1% by mass, respectively. % By mass. The content of the graphite particles (B) calculated from the density of each material was 37% by volume.
Using this composition, a heat conductive sheet (VIII) having a length of 80 mm, a width of 150 mm, and a thickness of 0.15 mm was obtained in the same manner as in Example 1.

  In the heat conductive sheet (VIII), the average value of the orientation angle of the graphite particles (B) is 90 degrees, and the plane direction of the flaky particles of the graphite particles (B) is oriented in the thickness direction of the heat conductive sheet. Was observed.

The initial thermal conductivity of the obtained thermal conductive sheet (VIII) was slightly low at 13.6 (W / mK), and the initial thermal resistance was slightly inferior to 0.12 (K · cm ² / W).
Further, the thermal resistance after the heat resistance test maintained a good value of 0.10 (K · cm ² / W). Further, the thermal resistance after the HAST resistance test maintained a good value of 0.11 (K · cm ² / W).
The compression ratio was as bad as 7%.
The tack force was weak at 1.3 (kPa), and the temporary fixing force was insufficient.
The tensile strength was 0.33 (MPa), which was a strength at which good handling properties were obtained.

(Comparative Example 4)
A composition was prepared in the same manner as in Example 1, except that the alicyclic hydrocarbon resin (C) and the flame retardant were not used and the following materials were used in the following composition.

<Elastomer (A)>
・ Homopolymer of isobutene (“Tetrax 6T” manufactured by Nippon Oil Co., Ltd., viscosity average molecular weight: 60000, density: 0.92 g / cm ³ ): 660 g
・ Polybutene ("200N" manufactured by NOF Corporation): 929 g
<Graphite particles (B)>
-Scale-like expanded graphite powder ("HGF-L" manufactured by Hitachi Chemical Co., Ltd.): 1970 g,
<Other resins>
・ Terpene phenol (“YS Polystar T80” manufactured by Yashara Chemical Co., Ltd.): 440 g

The content rates of the component (A), the component (B), the component (C), and other resins with respect to the entire composition are 39.7% by mass, 49.3% by mass, 0% by mass, and 11. It was 0% by mass. The content of the graphite particles (B) calculated from the density of each material was 30% by volume.
Using this composition, a heat conductive sheet (IX) having a length of 80 mm, a width of 150 mm, and a thickness of 0.59 mm was obtained in the same manner as in Example 1.

  In the heat conductive sheet (IX), the average value of the orientation angle of the graphite particles (B) is 89 degrees, and the plane direction of the flake-like particles of the graphite particles (B) is oriented in the thickness direction of the heat conductive sheet. Was observed.

The obtained thermal conductive sheet (IX) has a good initial thermal conductivity of 22.5 (W / mK), and the initial thermal resistance is 0.23 (K · cm ² / W), which is a good value for the thickness. Showed a good value.
Further, the thermal resistance after the heat resistance test maintained a favorable value of 0.22 (K · cm ² / W). Further, the thermal resistance after the HAST resistance test maintained a favorable value of 0.23 (K · cm ² / W).
The compression ratio was as good as 10%.
The tack force was 3.6 (kPa), which was a numerical value capable of exhibiting good temporary fixability.
The tensile strength was as low as 0.06 (MPa), and the film was easily burned.

(Comparative Example 5)
A composition was prepared in the same manner as in Example 5 except that 817 g of terpene phenol (“YS Polystar T80” manufactured by Yashara Chemical Co., Ltd.) was used as the other resin instead of using the alicyclic hydrocarbon resin (C). Was prepared, and a heat conductive sheet (X) having a length of 80 mm × a width of 150 mm × a thickness of 0.55 mm was obtained.
The content rates of the component (A), the component (B), the component (C), and the other resin with respect to the entire composition are 37.2% by mass, 42.4% by mass, 0% by mass, and 20% by mass, respectively. It was 5% by mass. The content of the graphite particles (B) calculated from the density of each material was 25% by volume.

  In the heat conductive sheet (X), the average value of the orientation angle of the graphite particles (B) is 89 degrees, and the plane direction of the flake-like particles of the graphite particles (B) is oriented in the thickness direction of the heat conductive sheet. Was observed.

The initial thermal conductivity of the obtained thermal conductive sheet (X) is slightly low at 13.3 (W / mK), but the initial thermal resistance is 0.27 (K · cm ² / W), which is good for the thickness. Value.
Further, the thermal resistance after the heat resistance test maintained a favorable value of 0.24 (K · cm ² / W). Further, the thermal resistance after the HAST resistance test maintained a favorable value of 0.24 (K · cm ² / W).
The compression ratio was as good as 28%.
The tack force was 0.1 (kPa), a level that could not be temporarily fixed.
The tensile strength was 0.17 (MPa), which was a strength at which good handling properties were obtained.

  From the above, the heat conductive sheet of the example has excellent heat conductivity, can make the heat generating body and the heat radiating body adhere to each other with low heat resistance, and has compressibility, heat resistance, humidity resistance, and adhesion. It can be seen that the handleability is excellent.

Claims (10)

An elastomer (A) containing an isobutylene structure;
At least one type of graphite particles (B) selected from the group consisting of flaky particles, oval spherical particles and rod-like particles;
An alicyclic hydrocarbon resin (C),
In the case of the scaly particles, the plane direction, in the case of the elliptical particles, the major axis direction or in the case of the rod-like particles, the major axis direction is oriented in the thickness direction ,
A tensile strength at 25 ° C. of 0.1 MPa or more;
A heat conductive sheet having a tack force at 25 ° C of not less than 3.0 kPa and less than 70 kPa .   The heat conduction according to claim 1, wherein the elastomer (A) is at least one selected from the group consisting of a copolymer of isobutene and styrene, a copolymer of isobutene and ethylene, and a homopolymer of isobutene. Sheet.   The heat conductive sheet according to claim 1 or 2, wherein the graphite particles (B) include expanded graphite powder. The heat conductive sheet according to any one of claims 1 to 3 , wherein the alicyclic hydrocarbon resin (C) is solid at 25 ° C. The heat conductive sheet according to any one of claims 1 to 4 , wherein a softening temperature of the alicyclic hydrocarbon resin (C) is 40C to 150C. The heat conduction according to any one of claims 1 to 5 , wherein the content of the alicyclic hydrocarbon resin (C) is 10% by mass to 200% by mass with respect to the elastomer (A). Sheet. The heat conductive sheet according to any one of claims 1 to 6 , wherein the content of the graphite particles (B) is 15% by volume to 50% by volume. An elastomer containing an isobutylene structure (A), at least one kind of graphite particles (B) selected from the group consisting of flaky particles, oval spherical particles and rod-like particles, and an alicyclic hydrocarbon resin (C). Preparing a composition to contain,
Step of obtaining a sheet by sheeting the composition,
Stacking a plurality of the sheets, or folding one of the sheets, or forming a laminate by winding one of the sheets,
Slicing a side end face of the laminate,
The method for producing a heat conductive sheet according to any one of claims 1 to 7 , comprising: The method for producing a heat conductive sheet according to claim 8 , wherein in the slicing step, slicing is performed at a thickness of twice or less the mass average particle diameter of the graphite particles (B). A heat dissipation device comprising the heat conductive sheet according to any one of claims 1 to 7 interposed between a heating element and a heat dissipation element.