Heat dissipation device

Abstract

To provide a heat dissipation device for which high heat dissipation can be achieved.SOLUTION: The heat dissipation device includes a heat generating body, a heat dissipating body, and a heat conductive sheet sandwiched between the heat generating body and the heat dissipating body. The heat conductive sheet has a thermal conductivity of 15 W / m K or more in the direction of the thicknesses. The area of the surface of the heat conductive sheet sandwiched is smaller than the area of the surface to which the heat generating body and the heat dissipating body are adhered. The ratio of the area of the sandwiched surface of the heat conductive sheet to the area of the adherend surface of the heat generating body and heat dissipating body is 10% or more and 40% or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a heat dissipation device, and more particularly to a heat dissipation device including a heat generating body, a heat radiating body, and a heat conduction sheet.

Background Art

[0002] In recent years, the heat generation amount of electronic elements included in semiconductor packages, power modules, integrated circuits (ICs, LSIs), plasma display panels (PDPs), etc. that make up electronic devices has been increasing with the improvement of performance. Examples of such electronic elements include semiconductor elements such as transistors such as insulated gate bipolar transistors (IGBTs) and field effect transistors (FETs), and diodes such as light emitting diodes (LEDs).

[0003] Therefore, in order to prevent malfunctions of electronic devices caused by the temperature rise of these electronic elements, for example, it is necessary to enhance the heat dissipation performance from the electronic elements and efficiently release the heat generated from the electronic elements to the outside.

[0004] Here, as a method for enhancing the heat dissipation performance from electronic elements, generally, a method of promoting heat dissipation by attaching a heat radiating body such as a metal heat sink to the heat generating body of the electronic element or a power module including the electronic element is adopted. When using a heat radiating body, in order to efficiently transfer heat from the heat generating body to the heat radiating body, a sheet-like member having heat conductivity (heat conduction sheet) is used, and a heat dissipation device in which the heat generating body and the heat radiating body are brought into close contact via the heat conduction sheet is used to promote heat dissipation.

[0005] In order to efficiently dissipate heat from the heat dissipation device, usually, it is necessary that the heat conduction sheet sandwiched between the heat generating body and the heat radiating body has high heat conductivity and that the thermal resistance between the heat generating body and the heat radiating body is low, and it is required to efficiently transfer heat from the heat generating body to the heat radiating body.

[0006] Therefore, for example, in Patent Document 1, attention is paid to the fine irregularities on the surface of the heat dissipation member, and a heat conduction sheet including a thermally conductive fine filler having a particle diameter of 1 / 10 or less with respect to the fine irregularities, an inorganic filler having a predetermined particle diameter, and a thermosetting resin is used. And in Patent Document 1, high thermal conductivity is achieved by filling the fine irregularities on the surface of the heat dissipation member with the thermally conductive fine filler in the heat conduction sheet.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, in a conventional heat dissipation device in which a heat conduction sheet is interposed between a heat generating body and a heat dissipating body, it has been required to further reduce the thermal resistance between the heat generating body and the heat dissipating body and dissipate heat more favorably.

[0009] Therefore, an object of the present invention is to provide a heat dissipation device capable of achieving high heat dissipation performance.

Means for Solving the Problems

[0010] The inventors of the present invention have conducted intensive studies to achieve the above object. Then, the inventors of the present invention tried to reduce the thermal resistance between the heat generating body and the heat radiating body by increasing the thermal conductivity in the thickness direction of the heat conductive sheet. However, as a result of the studies conducted by the inventors of the present invention, there were cases where the thermal resistance between the heat generating body and the heat radiating body could not be sufficiently reduced even when the thermal conductivity in the thickness direction of the heat conductive sheet was increased. Therefore, the inventors of the present invention further repeated the studies, and surprisingly, in a heat dissipation device provided with a heat conductive sheet having a thermal conductivity of a predetermined value or more between the heat generating body and the heat radiating body, when the heat conductive sheet having a high thermal conductivity is sandwiched between the heat generating body and the heat radiating body over the entire surface of the region where they face each other, compared to the case where the heat conductive sheet having a high thermal conductivity is sandwiched only in a part of the region where the heat generating body and the heat radiating body face each other, it was found that the thermal resistance between the heat generating body and the heat radiating body is reduced, and the present invention was completed.

[0011] That is, the object of the present invention is to advantageously solve the above problems, and the heat dissipation device of the present invention is a heat dissipation device including a heat generating body, a heat radiating body, and a heat conductive sheet sandwiched between the heat generating body and the heat radiating body, wherein the thermal conductivity in the thickness direction of the heat conductive sheet is 15 W / m·K or more, and the area of the sandwiching surface of the heat conductive sheet is smaller than the area of the adhering surfaces of the heat generating body and the heat radiating body. In this way, by using a heat conductive sheet having a predetermined thermal conductivity and making the area of the sandwiching surface of the heat conductive sheet narrower than the area of the adhering surfaces of the heat generating body and the heat radiating body, the thermal resistance between the heat generating body and the heat radiating body can be sufficiently reduced, and high heat dissipation performance can be realized in the heat dissipation device. In the present invention, the "thermal conductivity" can be measured by the method described in the examples of this specification. In the present invention, the "clamping surface of the heat conduction sheet" refers to the surface (the contacting portion) of the heat conduction sheet provided in the heat dissipation device that contacts the heat generating body or the heat dissipating body. In the present invention, when the area of the surface of the heat conduction sheet that contacts the heat generating body is different from the area of the surface that contacts the heat dissipating body, the "area of the clamping surface" shall refer to the smaller of the above two areas. Further, when a plurality of heat conduction sheets are arranged in the plane between the heat generating body and the heat dissipating body, the "area of the clamping surface" shall refer to the total area of the clamping surfaces of all the heat conduction sheets. Furthermore, in the present invention, the "adhering surfaces of the heat generating body and the heat dissipating body" refer to the opposing surfaces of the heat generating body and the heat dissipating body within the entire opposing surface (the entire opposing area) on the side where the heat generating body and the heat dissipating body face each other, within the range where they oppose each other (regardless of whether a heat conduction sheet is actually interposed, the maximum range where the heat generating body and the heat dissipating body can be in close contact via the heat conduction sheet). In the present invention, the "area" of each surface shall be calculated from the outer dimensions (such as the outer diameter) of each surface without considering the surface unevenness described later.

[0012] Also, in the heat dissipation device of the present invention, it is preferable that the Asker C hardness of the heat conduction sheet at 25°C is 30 or more. If the hardness of the heat conduction sheet is at or above the above lower limit, sufficient physical strength can be imparted to the heat conduction sheet, the thermal resistance between the heat generating body and the heat dissipating body can be further reduced, and the heat dissipation performance of the heat dissipation device can be further enhanced. In the present invention, the "Asker C hardness" (hereinafter, may be simply abbreviated as "hardness") can be measured at a temperature of 25°C using a hardness tester in accordance with the Asker C method of the Japan Rubber Association Standard (SRIS0101).

[0013] Also, in the heat dissipation device of the present invention, it is preferable that the thickness of the heat conduction sheet is 2.0 mm or less. If the thickness of the heat conduction sheet is at or below the above upper limit, the thermal resistance between the heat generating body and the heat dissipating body can be further reduced, and the heat dissipation performance of the heat dissipation device can be further enhanced.

[0014] Further, in the heat dissipation device of the present invention, it is preferable that the ratio of the area of the clamping surface of the heat conduction sheet to the area of the adhesion surface of the heating element and the heat dissipation element is 10% or more and 70% or less. If the ratio of the area of the clamping surface of the heat conduction sheet is equal to or greater than the above lower limit, a sufficient size of the heat conduction sheet in contact with the heating element and the heat dissipation element can be ensured, and high heat dissipation performance can be imparted to the heat dissipation device. Also, if the ratio of the area of the clamping surface of the heat conduction sheet is equal to or less than the above upper limit, the thermal resistance between the heating element and the heat dissipation element can be further reduced, and the heat dissipation performance of the heat dissipation device can be further enhanced.

[0015] Further, in the heat dissipation device of the present invention, it is preferable that the surface unevenness of at least one of the surfaces of the adhesion surface of the heating element and the heat dissipation element is more than 5 μm. When the surface unevenness of the adhesion surface of the heating element and / or the heat dissipation element is more than the above lower limit, the effect of reducing the thermal resistance when the area of the clamping surface of the heat conduction sheet having the above predetermined thermal conductivity is made smaller than the area of the adhesion surface is great. In the present invention, "surface unevenness" can be measured by the method shown below. That is, first, a reference plane is set based on the horizontal spread centered on the center point located substantially at the center of the surface to be measured. Here, the above center point can be set visually. For example, when the surface to be measured is polygonal, it can be a point equidistant from each vertex or the intersection of the diagonals; when the surface to be measured is circular, it can be the center of the circle or the intersection of the major axis and the minor axis. Next, using a laser microscope such as a three-dimensional shape measuring machine, a graph representing the surface unevenness state in the thickness direction on a predetermined line on the surface to be measured is obtained. Here, the above predetermined line is a straight line passing through the highest point and the lowest point in the thickness direction within the plane of the surface to be measured. Then, the larger of the absolute values of the height difference between the height of the reference plane and the maximum height (highest value) and the height difference between the height of the reference plane and the minimum height (lowest value) in the thickness direction of the obtained graph is defined as "surface unevenness". Here, in this specification, a surface with surface unevenness of 5 μm or less is defined as "smooth".

[0016] Further, in the heat dissipation device of the present invention, it is preferable that the heat conductive sheet contains a resin and a carbon material. This is because if the heat conductive sheet contains the above components, the heat conductive sheet included in the heat dissipation device can easily exhibit high thermal conductivity. As a result, the heat dissipation performance of the heat dissipation device can be further enhanced.

[0017] And, in the heat dissipation device of the present invention, it is preferable that the resin is a thermoplastic resin. If the heat conductive sheet contains a thermoplastic resin, the flexibility for sandwiching between the heat generating body and the heat dissipating body can be made better while maintaining the high thermal conductivity of the heat conductive sheet included in the heat dissipation device. As a result, the heat dissipation performance of the heat dissipation device can be more efficiently enhanced.

Advantages of the Invention

[0018] According to the present invention, a heat dissipation device capable of achieving high heat dissipation performance can be provided.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described in detail. The heat dissipation device of the present invention can be used as an electronic member including the electronic element, for example, in an electronic device having the electronic element inside. Here, the heat dissipation device of the present invention may be completely incorporated inside various devices such as the above electronic device, or may be partially or entirely provided outside the device. And, the heat dissipation device of the present invention can be manufactured by assembling a heat generating body, a heat dissipating body, and a predetermined heat conductive sheet, which will be described later, under predetermined conditions by an arbitrary method.

[0020] Here, various devices for which the heat dissipation device of the present invention can be suitably used are not particularly limited, and include electronic devices such as servers, personal computers for servers, and desktop personal computers; portable electronic devices such as notebook personal computers, electronic dictionaries, PDAs, mobile phones, and portable music players; display devices such as liquid crystal displays (including backlights), plasma displays, liquid crystal projectors, and clocks; image forming devices such as inkjet printers (ink heads); electrophotographic devices (developing devices, fixing devices, heat rollers, heat belts); manufacturing devices such as vacuum processing devices; semiconductor manufacturing devices; display device manufacturing devices; heat insulation devices provided with heat insulation materials, vacuum heat insulation materials, radiant heat insulation materials, etc.; data recording devices such as DVDs (optical pickups, laser generating devices, laser receiving devices), hard disk drives; image recording devices such as cameras, video cameras, digital cameras, digital video cameras, microscopes, CCDs; battery devices such as charging devices, lithium ion batteries, fuel cells; and the like.

[0021] (Heat dissipation device) The heat dissipation device of the present invention includes a heat generating body, a heat radiating body, and a heat conduction sheet having a predetermined thermal conductivity. The heat conduction sheet is sandwiched between the heat generating body and the heat radiating body under the condition that the area of the sandwiched surface of the heat conduction sheet is smaller than the area of the adhered surfaces of the heat generating body and the heat radiating body. Note that the heat dissipation device of the present invention may further include any other members such as fixing parts for fixing between the respective constituent members, in addition to the heat generating body, the heat radiating body, and the heat conduction sheet. And in the heat dissipation device of the present invention, since the heat conduction sheet having a predetermined thermal conductivity is sandwiched between the heat generating body and the heat radiating body under the above-mentioned predetermined area condition, the thermal resistance between the heat generating body and the heat radiating body is low, and the heat dissipation performance as a heat dissipation device is high. That is, the heat dissipation device of the present invention can efficiently dissipate heat generated from a heat generating body such as an electronic element itself or a power module including the electronic element to the outside. As a result, for example, it is possible to prevent the occurrence of functional failures due to heat from the heat generating body in various devices such as electronic devices provided with the heat dissipation device of the present invention.

[0022] <Heat generating body> The heating element is a component that constitutes the heat dissipation device of the present invention. In the heat dissipation device of the present invention, together with the heat sink described later, it sandwiches a heat conduction sheet. In other words, the heating element is a type of adherend that adheres to the heat conduction sheet in the heat dissipation device of the present invention.

[0023] [Type] Here, the heating element is not particularly limited as long as it generates heat in various devices such as electronic devices. Examples of the types of heating elements include semiconductor elements such as transistors, diodes, thyristors, organic ELs, and inorganic ELs; and integrated circuits (ICs, LSIs) such as memories and central processing units (CPUs) equipped with such semiconductor elements, as well as IC chips, semiconductor packages, semiconductor encapsulation cases, semiconductor die bonding, power modules, power transistors, power transistor cases, and other semiconductor-related components; wiring boards such as rigid wiring boards, flexible wiring boards, ceramic wiring boards, build-up wiring boards, and multilayer substrates (printed wiring boards are also included in the wiring boards); and the like. In addition, examples of the above-mentioned transistors include field effect transistors (FETs), metal oxide semiconductor field effect transistors (MOSFETs), insulated gate bipolar transistors (IGBTs), and the like. Furthermore, examples of the above-mentioned diodes include light-emitting diodes (LEDs), photo-diodes, and the like.

[0024] Among those described above, from the perspective of handleability, the heating element that adheres to the heat conduction sheet in the heat dissipation device of the present invention is preferably an IC chip equipped with a semiconductor element, a power module, or the like.

[0025] [Adhering surface] Here, the heating element has an adhering surface that faces the heat sink described later. Generally, most of the heat generated from the heating element is transferred to the heat sink through the adhering surface and dissipated.

[0026] [[Surface irregularities]] Further, it is preferable that the surface unevenness of the heat generating body on the adherend surface is more than 5 μm, more preferably 15 μm or more, still more preferably 25 μm or more, preferably 50 μm or less, and more preferably 35 μm or less. If the surface unevenness of the adherend surface of the heat generating body exceeds the above lower limit, the effect of reducing the thermal resistance between the heat generating body and the heat radiating body can be further enhanced, and the heat radiating performance of the heat radiating device can be more efficiently enhanced. Further, if the surface unevenness of the adherend surface of the heat generating body is below the above upper limit, it is possible to prevent the strain of the surface portion of the heat generating body in contact with the heat conductive sheet from becoming excessively large, maintain good adhesion between the heat generating body and the heat conductive sheet, and further reduce the thermal resistance between the heat generating body and the heat radiating body, thereby enabling more efficient enhancement of the heat radiating performance of the heat radiating device.

[0027] <Heat radiator> The heat radiator is a component constituting the heat radiating device of the present invention. In the heat radiating device of the present invention, the heat radiator sandwiches the heat conductive sheet together with the above-described heat generating body. In other words, the heat radiator is a kind of adherend that adheres to the heat conductive sheet in the heat radiating device of the present invention.

[0028] [Type] Here, examples of the type of the heat radiator include a heat sink having a shaped portion such as a plate or fins; a block connected to a heat pipe; a block having a structure in which a cooling liquid is circulated by a pump inside; a Peltier element; a heat sink provided with a Peltier element; and a block provided with a Peltier element; and the like. Here, from the viewpoint of good heat dissipation, the above heat sink and block are usually made of a metal such as aluminum or copper. Among the above, in the heat radiating device of the present invention, the heat radiator that contacts the heat conductive sheet is preferably a metal heat sink such as aluminum or copper from the viewpoints of handleability and heat radiating performance.

[0029] [Adherend surface] Further, the heat radiator has an adherend surface facing the above-described heat generating body. Generally, most of the heat generated from the heat generating body is transferred to the heat radiator through the adherend surface and dissipated.

[0030] [[Surface unevenness]] Further, the surface unevenness of the adhering surface of the heat sink is not particularly limited, and is preferably 50 μm or less, more preferably 35 μm or less, and still more preferably 10 μm or less. If the surface unevenness of the adhering surface of the heat sink is below the above upper limit, it is possible to prevent the distortion of the surface portion of the heat sink in contact with the heat conduction sheet from becoming excessively large, and to maintain good adhesion between the heat sink and the heat conduction sheet. Therefore, the thermal resistance between the heating element and the heat sink can be further reduced, and the heat dissipation performance of the heat dissipation device can be more efficiently enhanced.

[0031] Among the above, it is more preferable that at least the adhering surface of the heating element has the above-described surface unevenness, and it is even more preferable that the adhering surfaces of both the heating element and the heat sink have the surface unevenness within the above range. If the surface unevenness of at least the adhering surface of the heating element exceeds the above lower limit, when the heat conduction sheet is sandwiched between the heating element and the heat sink under a predetermined area condition described later, the effect of reducing the thermal resistance between the heating element and the heat sink can be further enhanced, and the heat dissipation performance of the heat dissipation device can be more efficiently enhanced. Further, if the surface unevenness of at least the adhering surface of the heating element is below the above upper limit, it is possible to prevent the distortion of the surface portions of the heating element and the heat sink in contact with the heat conduction sheet from becoming excessively large, and to maintain better adhesion between the heating element and the heat sink and the heat conduction sheet, so that the thermal resistance between the heating element and the heat sink can be further reduced, and the heat dissipation performance of the heat dissipation device can be more efficiently enhanced.

[0032] [[Heat conduction sheet]] The heat conduction sheet has a predetermined thermal conductivity, and in the heat dissipation device of the present invention, the heat conduction sheet is sandwiched between the heating element and the heat sink under the condition that the area of the sandwiched surface of the heat conduction sheet is smaller than the areas of the adhering surfaces of the heating element and the heat sink. Note that if the heat conduction sheet does not have the above-described predetermined thermal conductivity, or if it is not sandwiched between the heating element and the heat sink under the above-described area condition, the heat dissipation device cannot exhibit high heat dissipation performance.

[0033] Here, generally, since the heat conduction sheet has a higher thermal conductivity than air, heat transfer between the heat generating body and the heat radiating body through the heat conduction sheet is improved, and heat dissipation from the heat generating body to the heat radiating body is promoted. Therefore, usually, the better the heat conduction sheet adheres well to a larger area of the adherend surfaces of the heat generating body and the heat radiating body, in other words, the smaller the area where the heat conduction sheet does not exist between the adherend surfaces of the heat generating body and the heat radiating body, the more the thermal resistance between the heat generating body and the heat radiating body can be reduced. However, although there may generally be unevenness on the surfaces of the heat generating body and the heat radiating body that is difficult to visually distinguish, when the heat conduction sheet has a thermal conductivity of a predetermined value or more as in the present invention, rather than sandwiching the heat conduction sheet over the entire area where the heat generating body and the heat radiating body face each other, sandwiching the heat conduction sheet only in a part of the area where the heat generating body and the heat radiating body face each other is presumed to increase the degree of adhesion between the heat conduction sheet and the heat generating body and / or the heat radiating body, and heat transfer is more efficient.

[0034] [Properties] [[Thermal Conductivity]] Here, the heat conduction sheet is required to have a thermal conductivity in the thickness direction of 15 W / m·K or more at 50°C. Further, the thermal conductivity of the heat conduction sheet in the thickness direction is preferably 20 W / m·K or more at 50°C, and more preferably 25 W / m·K or more. If the thermal conductivity is at least the above lower limit, surprisingly, when the heat conduction sheet is sandwiched between the heat generating body and the heat radiating body with the area of the sandwiching surface of the heat conduction sheet being narrower than the area of the adherend surfaces of the heat generating body and the heat radiating body, the thermal resistance between the heat generating body and the heat radiating body can be efficiently reduced. As a result, high heat dissipation performance can be exhibited in the heat dissipation device.

[0035] [[Hardness]] Also, the thermal conductive sheet preferably has an Asker C hardness of 30 or more, more preferably 40 or more, still more preferably 50 or more, even more preferably 60 or more, preferably 90 or less, and more preferably 80 or less at 25°C. If the hardness of the thermal conductive sheet is at least the above lower limit, sufficient physical strength can be imparted to the thermal conductive sheet, the thermal resistance between the heating element and the heat sink can be further efficiently reduced, and the heat dissipation performance of the heat dissipation device can be further enhanced. Further, if the hardness of the thermal conductive sheet is at most the above upper limit, the thermal conductive sheet does not become excessively hard, good adhesion between the heating element and the heat sink via the thermal conductive sheet can be ensured, and a heat dissipation device with high heat dissipation performance can be obtained.

[0036] [[Thickness]] Also, the thermal conductive sheet preferably has a thickness of 2.0 mm or less, more preferably 1.5 mm or less, still more preferably 0.6 mm or less, even more preferably 0.4 mm or less, and preferably 0.25 mm or more. If the thickness of the thermal conductive sheet is at most the above upper limit, the thermal resistance of the thermal conductive sheet itself (hereinafter sometimes referred to as "bulk thermal resistance") can be reduced, and the heat dissipation performance of the heat dissipation device can be further enhanced. In addition, the flexibility of the thermal conductive sheet can be increased, and the shape followability of the thermal conductive sheet to the adherend surfaces of the heating element and the heat sink can be improved, thereby further enhancing the heat dissipation performance of the heat dissipation device. Further, if the thickness of the thermal conductive sheet is at least the above lower limit, the high thermal conductivity of the thermal conductive sheet can be maintained without excessively reducing the thickness of the thermal conductive sheet, thereby ensuring good heat dissipation performance of the heat dissipation device. In addition, the handleability during attachment of the thermal conductive sheet and the like can be improved.

[0037] [Composition] Here, the thermal conductive sheet preferably contains a resin and a carbon material. If the thermal conductive sheet contains a resin and a carbon material, a thermal conductive sheet having high thermal conductivity can be easily obtained, and a heat dissipation device capable of exhibiting high heat dissipation performance can be easily manufactured.

[0038] [[Resin]] Here, the resin is not particularly limited, and known resins that can be used for forming the heat conduction sheet can be used. Specifically, as the resin, a thermoplastic resin or a thermosetting resin can be used. Further, the thermoplastic resin and the thermosetting resin may be used in combination. In the present invention, rubber and elastomer are included in the "resin".

[0039] -Thermoplastic resin- Among those described above, as the resin, it is preferable to use a thermoplastic resin, and more preferably a thermoplastic fluororesin. By using a thermoplastic resin, for example, in a high-temperature environment during the use (heat dissipation) of the heat dissipation device, the flexibility of the heat conduction sheet can be made better, and the heating element and the heat dissipation body can be well adhered to each other through the heat conduction sheet. As a result, the thermal resistance between the heating element and the heat dissipation body can be further reduced, and the heat dissipation performance of the heat dissipation device can be further improved. Further, by using a thermoplastic fluororesin, in addition to the above effects, the heat resistance, oil resistance, and chemical resistance of the heat conduction sheet can be improved.

[0040] Furthermore, the thermoplastic resin can include a thermoplastic resin that is solid at 23°C and 1 atm, and a thermoplastic resin that is liquid at 23°C and 1 atm. When a thermoplastic resin that is solid at normal temperature and pressure and a thermoplastic resin that is liquid at normal temperature and pressure are used in combination, in a normal temperature and pressure environment such as during installation and replacement, the solid thermoplastic resin component and the liquid thermoplastic resin component coexist in the heat conduction sheet. Therefore, the balance between the hardness and flexibility of the heat conduction sheet can be made good, and the handleability can be further improved. Also, in a high-temperature environment during the use (heat dissipation) of the heat dissipation device, the solid thermoplastic resin at normal temperature and pressure is plasticized, so that the heating element, the heat dissipation body, and the heat conduction sheet adhere better to each other. As a result, the thermal resistance between the heating element and the heat dissipation body can be more efficiently reduced, and the heat dissipation performance of the heat dissipation device can be more efficiently improved. In this specification, "normal temperature" refers to 23°C, and "normal pressure" refers to 1 atm (absolute pressure).

[0041] =Thermoplastic resin that is solid at normal temperature and pressure= Here, examples of thermoplastic resins that are solid at 23°C and 1 atm include acrylic resins such as poly(2-ethylhexyl acrylate), copolymers of acrylic acid and 2-ethylhexyl acrylate, polymethacrylic acid or its esters, polyacrylic acid or its esters; silicone resins; fluororesins; polyethylene; polypropylene; ethylene-propylene copolymers; polymethylpentene; polyvinyl chloride; polyvinylidene chloride; polyvinyl acetate; ethylene-vinyl acetate copolymers; polyvinyl alcohol; polyacetal; polyethylene terephthalate; polybutylene terephthalate; polyethylene naphthalate; polystyrene; polyacrylonitrile; styrene-acrylonitrile copolymers; acrylonitrile-butadiene-styrene copolymers (ABS resins); styrene-butadiene block copolymers or their hydrogenated products; styrene-isoprene block copolymers or their hydrogenated products; polyphenylene ether; modified polyphenylene ether; aliphatic polyamides; aromatic polyamides; polyamide-imide; polycarbonate; polyphenylene sulfide; polysulfone; polyethersulfone; polyether nitrile; polyether ketone; polyketone; polyurethane; liquid crystal polymers; ionomers; and the like. These may be used alone or in combination of two or more.

[0042] Among those described above, the thermoplastic resin that is solid at normal temperature and pressure is preferably a thermoplastic fluororesin that is solid at normal temperature and pressure. As thermoplastic fluororesins that are solid under normal temperature and pressure, examples include elastomers obtained by polymerizing fluorine-containing monomers such as vinylidene fluoride-based fluororesins, tetrafluoroethylene-propylene-based fluororesins, and tetrafluoroethylene-perfluorovinyl ether-based fluororesins. More specifically, polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene, ethylene-chlorofluoroethylene copolymer, tetrafluoroethylene-perfluorodioxole copolymer, polyvinyl fluoride, tetrafluoroethylene-propylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, acrylic-modified polytetrafluoroethylene, ester-modified polytetrafluoroethylene, epoxy-modified polytetrafluoroethylene, and silane-modified polytetrafluoroethylene can be mentioned. Among these, from the perspective of processability, polytetrafluoroethylene, acrylic-modified polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer are preferred.

[0043] In addition, commercially available thermoplastic fluororesins that are solid under normal temperature and pressure include, for example, Daiel (registered trademark) G-700 series (polyol vulcanization · binary polymer, vinylidene fluoride-based fluororesin) manufactured by Daikin Industries, Ltd., Daiel G-550 series / G-600 series (polyol vulcanization · ternary polymer, vinylidene fluoride-based fluororesin); KYNAR (registered trademark) series (vinylidene fluoride-based fluororesin), KYNAR FLEX (registered trademark) series (ternary fluororesin of copolymer of vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene) manufactured by ALKEMA; and the like.

[0044] =Thermoplastic Resin That Is Liquid under Normal Temperature and Pressure= In addition, examples of the thermoplastic resin that is liquid under normal temperature and pressure include acrylic resin, epoxy resin, silicone resin, fluororesin, and the like. These may be used alone or in combination of two or more.

[0045] Among the above, the thermoplastic resin that is liquid under normal temperature and pressure is preferably a thermoplastic fluororesin that is liquid under normal temperature and pressure. The thermoplastic fluororesin that is liquid under normal temperature and pressure is not particularly limited as long as it is a thermoplastic fluororesin that is liquid under normal temperature and pressure. Examples of the thermoplastic fluororesin that is liquid under normal temperature and pressure include vinylidene fluoride / hexafluoropropylene copolymer, vinylidene fluoride - hexafluoropentene - tetrafluoroethylene terpolymer, perfluoropropene oxide polymer, tetrafluoroethylene - propylene - vinylidene fluoride copolymer, and the like.

[0046] In addition, examples of the commercially available thermoplastic fluororesin that is liquid under normal temperature and pressure include Viton (registered trademark) LM (manufactured by DuPont), Daiel (registered trademark) G101 (manufactured by Daikin Industries, Ltd.), Dynion FC2210 (manufactured by 3M Company), Sifel series (manufactured by Shin-Etsu Chemical Co., Ltd.), and the like.

[0047] Note that the viscosity of the thermoplastic fluororesin that is liquid under normal temperature and pressure is not particularly limited. However, from the viewpoints of good kneadability, fluidity, crosslinking reactivity, and excellent moldability, the viscosity at a temperature of 105°C is preferably 500 cps or more and 30,000 cps or less, and more preferably 550 cps or more and 25,000 cps or less.

[0048] =Mixing ratio in the thermoplastic resin= When used in combination as a thermoplastic resin, the mixing ratio of the thermoplastic resin that is solid at normal temperature and pressure and the thermoplastic resin that is liquid at normal temperature and pressure is not particularly limited. Among 100% by mass of the thermoplastic resin, it is preferable that the thermoplastic resin that is solid at normal temperature and pressure is 80% by mass or less and 30% by mass or more, and the thermoplastic resin that is liquid at normal temperature and pressure is 20% by mass or more and 70% by mass or less. In addition, when used in combination as a thermoplastic resin, among 100% by mass of the thermoplastic resin, the mixing ratio of the thermoplastic fluororesin that is solid at normal temperature and pressure and the thermoplastic fluororesin that is liquid at normal temperature is preferably such that the thermoplastic fluororesin that is solid at normal temperature and pressure is 80% by mass or less and 30% by mass or more, and the thermoplastic fluororesin that is liquid at normal temperature is 20% by mass or more and 70% by mass or less. Further, among 100% by mass of the thermoplastic resin, it is more preferable that the thermoplastic fluororesin that is solid at normal temperature and pressure is 65% by mass or less and 40% by mass or more, and the thermoplastic fluororesin that is liquid at normal temperature and pressure is 35% by mass or more and 60% by mass or less. If the mixing ratio of the thermoplastic resin that is solid at normal temperature and pressure and the thermoplastic resin that is liquid at normal temperature and pressure is within the above range, the balance between the hardness and flexibility of the heat conduction sheet can be made better, and the handleability can be further improved in an environment of normal temperature and pressure such as during installation and replacement. Also, in a high-temperature environment during the use (heat dissipation) of the heat dissipation device, the adhesion between the heat generating body and the heat dissipation body and the heat conduction sheet can be enhanced, the thermal resistance between the heat generating body and the heat dissipation body can be further efficiently reduced, and the heat dissipation performance of the heat dissipation device can be more efficiently improved.

[0049] -Thermosetting resin- Examples of the thermosetting resin 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; polyisobutylene rubber; epoxy resin; polyimide resin; bismaleimide resin; benzocyclobutene resin; phenol resin; unsaturated polyester; diallyl phthalate resin; polyimide silicone resin; polyurethane; thermosetting polyphenylene ether; thermosetting modified polyphenylene ether; and the like. These may be used alone or in combination of two or more.

[0050] [[Carbon material]] The carbon material is not particularly limited, and known carbon materials can be used. Specifically, as the carbon material, particulate carbon materials, fibrous carbon materials, and the like can be used. Note that either the particulate carbon material or the fibrous carbon material may be used alone, or both may be used in combination. However, from the viewpoint of easily enhancing the thermal conductivity of the thermal conductive sheet, it is preferable to use at least the particulate carbon material. Further, from the viewpoint of further enhancing the thermal conductivity of the thermal conductive sheet, it is more preferable to use the particulate carbon material and the fibrous carbon material in combination.

[0051] -Particulate carbon material- The particulate carbon material is not particularly limited, and for example, graphite such as artificial graphite, flaky graphite, exfoliated graphite, natural graphite, acid-treated graphite, expandable graphite, expanded graphite; carbon black; and the like can be used. These may be used alone or in combination of two or more. Among them, it is preferable to use expanded graphite as the particulate carbon material. This is because the use of expanded graphite can further improve the thermal conductivity of the thermal conductive sheet.

[0052] =Expanded graphite= Here, the expanded graphite that can be suitably used as the particulate carbon material can be obtained, for example, by chemically treating graphite such as flake graphite with sulfuric acid or the like to obtain expandable graphite, expanding it by heat treatment, and then refining it. Examples of the expanded graphite include EC1500, EC1000, EC500, EC300, EC100, and EC50 (all are trade names) manufactured by Ito Graphite Industry Co., Ltd.

[0053] =Properties of the Particulate Carbon Material= Here, the average particle diameter of the particulate carbon material contained in the heat conductive sheet is preferably 0.1 μm or more, more preferably 1 μm or more, still more preferably 200 μm or more, and preferably 250 μm or less. This is because if the average particle diameter of the particulate carbon material is at least the above lower limit, the thermal conductivity of the heat conductive sheet will be further enhanced. And if the average particle diameter of the particulate carbon material is within the above range, a heat conductive sheet having high thermal conductivity can be easily obtained. Note that the average particle diameter of the particulate carbon material may be adjusted by changing the average particle diameter of the particulate carbon material itself used as the raw material, or by changing the production conditions of the heat conductive sheet (such as the crushing conditions of the composition used for forming the sheet and the pressure conditions during sheet forming). Also, the aspect ratio (major axis / minor axis) of the particulate carbon material contained in the heat conductive sheet is preferably 1 or more and 10 or less, and more preferably 1 or more and 5 or less.

[0054] In the present invention, the "average particle diameter" can be obtained by observing a cross section in the thickness direction of the heat conductive sheet with an SEM (scanning electron microscope), measuring the maximum diameter (major axis) for any 50 particulate carbon materials, and calculating the arithmetic mean value of the measured major axis diameters. Also, in the present invention, the "aspect ratio" can be obtained by observing a cross section in the thickness direction of the heat conductive sheet with an SEM (scanning electron microscope), measuring the maximum diameter (major axis) and the particle diameter (minor axis) in the direction perpendicular to the maximum diameter for any 50 particulate carbon materials, and calculating the average value of the ratio of the major axis to the minor axis (major axis / minor axis).

[0055] = Content ratio of particulate carbon material = And, the content ratio of the particulate carbon material contained in the heat conductive sheet is preferably 30% by mass or more, more preferably 40% by mass or more, preferably 90% by mass or less, more preferably 70% by mass or less, and still more preferably 60% by mass or less with respect to 100% by mass of the total composition of the heat conductive sheet. If the content ratio of the particulate carbon material in the heat conductive sheet is at least the above lower limit, a heat conductive sheet having high thermal conductivity can be more easily obtained. Further, if the content ratio of the particulate carbon material in the heat conductive sheet is at most the above upper limit, an appropriate flexibility that can be well adhered to the heating element and the heat radiator is imparted to the heat conductive sheet, and powder falling of the particulate carbon material can be sufficiently prevented.

[0056] - Fibrous carbon material - The fibrous carbon material is not particularly limited, and for example, carbon nanotubes, vapor grown carbon fibers, carbon fibers obtained by carbonizing organic fibers, and cuttings thereof can be used. These may be used alone or in combination of two or more. And, if the heat conductive sheet contains a fibrous carbon material, the thermal conductivity of the heat conductive sheet can be further improved and powder falling of the particulate carbon material can be prevented. The reason why powder falling of the particulate carbon material can be prevented by blending the fibrous carbon material is not clear, but it is presumed that the fibrous carbon material forms a three-dimensional network structure, thereby enhancing the thermal conductivity and strength of the heat conductive sheet while preventing the particulate carbon material from detaching.

[0057] Among those described above, as the fibrous carbon material, it is preferable to use a fibrous carbon nanostructure such as carbon nanotubes, and more preferably to use a fibrous carbon nanostructure containing carbon nanotubes. By using a fibrous carbon nanostructure such as carbon nanotubes, the thermal conductivity of the heat conductive sheet can be further improved and the strength can be made good.

[0058] =Fibrous carbon nanostructure containing carbon nanotubes= Here, the fibrous carbon nanostructure containing carbon nanotubes, which can be suitably used as the fibrous carbon material, may consist only of carbon nanotubes (hereinafter sometimes referred to as "CNT"), or may be a mixture of CNT and a fibrous carbon nanostructure other than CNT. In addition, as the CNT in the fibrous carbon nanostructure, single-walled carbon nanotubes and / or multi-walled carbon nanotubes can be used without particular limitation, but the CNT is preferably a carbon nanotube having 1 to 5 layers, and more preferably a single-walled carbon nanotube. This is because when single-walled carbon nanotubes are used, the thermal conductivity and strength of the thermal conductive sheet can be further improved as compared with the case where multi-walled carbon nanotubes are used.

[0059] Further, as the fibrous carbon nanostructure containing CNT, it is preferable to use a carbon nanostructure in which the ratio (3σ / Av) of the value (3σ) obtained by multiplying the standard deviation (σ) of the diameter by 3 to the average diameter (Av) is more than 0.20 and less than 0.60, more preferably a carbon nanostructure in which 3σ / Av is more than 0.25, and still more preferably a carbon nanostructure in which 3σ / Av is more than 0.50. By using a fibrous carbon nanostructure containing CNT with 3σ / Av more than 0.20 and less than 0.60, even if the blending amount of the carbon nanostructure is small, the thermal conductivity and strength of the thermal conductive sheet can be sufficiently increased. Therefore, it is possible to suppress a large decrease in the flexibility of the thermal conductive sheet due to the blending of the fibrous carbon nanostructure containing CNT, and to make the thermal conductivity and flexibility of the thermal conductive sheet coexist at a sufficiently high level. The "average diameter (Av) of the fibrous carbon nanostructure" and the "standard deviation of the diameter of the fibrous carbon nanostructure (σ: sample standard deviation)" can be obtained by measuring the diameters (outer diameters) of 100 randomly selected fibrous carbon nanostructures using a transmission electron microscope, respectively. The average diameter (Av) and standard deviation (σ) of the fibrous carbon nanostructure containing CNT may be adjusted by changing the manufacturing method and manufacturing conditions of the fibrous carbon nanostructure containing CNT, or may be adjusted by combining multiple types of fibrous carbon nanostructures containing CNT obtained by different manufacturing methods.

[0060] As the fibrous carbon nanostructure containing CNT, when plotting with the diameter measured as described above on the horizontal axis and the frequency on the vertical axis and approximating with a Gaussian, those having a normal distribution are usually used.

[0061] Furthermore, when the fibrous carbon nanostructure containing CNT is evaluated using Raman spectroscopy, it preferably has a peak of Radial Breathing Mode (RBM). Note that there is no RBM in the Raman spectrum of a fibrous carbon nanostructure composed only of multi-walled carbon nanotubes with three or more layers.

[0062] Also, for the fibrous carbon nanostructure containing CNT, the ratio of the G-band peak intensity to the D-band peak intensity (G / D ratio) in the Raman spectrum is preferably 1.0 or more and 20 or less. If the G / D ratio is 1.0 or more and 20 or less, even if the blending amount of the fibrous carbon nanostructure is small, the thermal conductivity and strength of the thermal conductive sheet can be sufficiently increased. Therefore, it is possible to suppress a large decrease in the flexibility of the thermal conductive sheet due to the blending of the fibrous carbon nanostructure, and to make the thermal conductivity and flexibility of the thermal conductive sheet coexist at a sufficiently high level.

[0063] Furthermore, the average diameter (Av) of the fibrous carbon nanostructure containing CNT is preferably 0.5 nm or more, more preferably 1 nm or more, preferably 15 nm or less, and more preferably 10 nm or less. If the average diameter (Av) of the fibrous carbon nanostructure is 0.5 nm or more, aggregation of the fibrous carbon nanostructure can be suppressed and the dispersibility of the carbon nanostructure can be enhanced. Also, if the average diameter (Av) of the fibrous carbon nanostructure is 15 nm or less, the thermal conductivity and strength of the thermal conductive sheet can be sufficiently increased.

[0064] In addition, the fibrous carbon nanostructure containing CNT preferably has an average length of the structure during synthesis of 100 μm or more and 5000 μm or less. Note that the longer the length of the structure during synthesis, the more likely it is that damage such as breakage or cutting occurs in the CNT during dispersion. Therefore, the average length of the structure during synthesis is preferably 5000 μm or less.

[0065] Furthermore, the BET specific surface area of the fibrous carbon nanostructure containing CNT is preferably 600 m 2 / g or more, more preferably 800 m 2 / g or more, preferably 2500 m 2 / g or less, and more preferably 1200 m 2 / g or less. If the BET specific surface area of the fibrous carbon nanostructure containing CNT is 600 m 2 / g or more, the thermal conductivity and strength of the thermal conductive sheet can be sufficiently increased. Also, if the BET specific surface area of the fibrous carbon nanostructure containing CNT is 2500 m 2 / g or less, aggregation of the fibrous carbon nanostructure can be suppressed and the dispersibility of the CNT in the thermal conductive sheet can be enhanced. Note that in the present invention, the "BET specific surface area" refers to the nitrogen adsorption specific surface area measured using the BET method.

[0066] Furthermore, according to the super-growth method described below, the fibrous carbon nanostructure containing CNT can be obtained as an aggregate (oriented aggregate) oriented in a direction substantially perpendicular to the substrate on a substrate having a catalyst layer for carbon nanotube growth on its surface. The mass density of the fibrous carbon nanostructure as the aggregate is 0.002 g / cm 3 or more and 0.2 g / cm 3 or less. If the mass density is 0.2 g / cm 3 or less, the connection between the fibrous carbon nanostructures becomes weak, so that the fibrous carbon nanostructures can be uniformly dispersed in the thermal conductive sheet. Also, if the mass density is 0.002 g / cm 3 or more, the integrity of the fibrous carbon nanostructures is improved and the dispersion can be suppressed, making handling easier.

[0067] And the fibrous carbon nanostructure containing CNT having the above-described properties can be efficiently produced, for example, by supplying a raw material compound and a carrier gas onto a substrate having a catalyst layer for carbon nanotube production on its surface and synthesizing CNT by chemical vapor deposition (CVD method), by making a trace amount of an oxidizing agent (catalyst activating substance) present in the system to dramatically improve the catalytic activity of the catalyst layer (super-growth method; see International Publication No. 2006 / 011655). Hereinafter, the carbon nanotubes obtained by the super-growth method may be referred to as "SGCNT".

[0068] Here, the fibrous carbon nanostructure containing CNT produced by the super-growth method may be composed only of SGCNT, or may contain other carbon nanostructures such as non-cylindrical carbon nanostructures in addition to SGCNT.

[0069] =Properties of fibrous carbon material= And the average fiber diameter of the fibrous carbon material that can be included in the heat conduction sheet is preferably 1 nm or more, more preferably 3 nm or more, preferably 2 μm or less, and more preferably 1 μm or less. If the average fiber diameter of the fibrous carbon material is within the above range, the thermal conductivity, flexibility, and strength of the heat conduction sheet can be made to coexist at a sufficiently high level. Here, the aspect ratio of the fibrous carbon material is preferably more than 10.

[0070] In the present invention, the "average fiber diameter" can be obtained by observing a cross section in the thickness direction of the heat conduction sheet with an SEM (scanning electron microscope) or a TEM (transmission electron microscope), measuring the fiber diameters of any 50 fibrous carbon materials, and calculating the number average value of the measured fiber diameters. In particular, when the fiber diameter is small, it is preferable to observe a similar cross section with a TEM (transmission electron microscope).

[0071] = Content ratio of fibrous carbon material = And the content ratio of the fibrous carbon material in the heat conduction sheet is preferably 0.03% by mass or more, more preferably 0.04% by mass or more, preferably 5% by mass or less, more preferably 1% by mass or less, and even more preferably 0.06% by mass or less with respect to 100% by mass of the total composition of the heat conduction sheet. If the content ratio of the fibrous carbon material in the heat conduction sheet is at least the above lower limit, the thermal conductivity and strength of the heat conduction sheet can be sufficiently improved, and the powder fall of the particulate carbon material can be sufficiently prevented. Furthermore, if the content ratio of the fibrous carbon material in the heat conduction sheet is at most the above upper limit, it is possible to suppress a large decrease in the flexibility of the heat conduction sheet due to the blending of the fibrous carbon material, and to make the thermal conductivity and flexibility of the heat conduction sheet coexist at a sufficiently high level.

[0072] [[Additive]] Furthermore, if necessary, known additives that can be used in the formation of the heat conductive sheet can be incorporated into the heat conductive sheet. The additives that can be incorporated into the heat conductive sheet are not particularly limited, and examples thereof include plasticizers such as fatty acid esters such as sebacic acid ester; flame retardants such as red phosphorus-based flame retardants and phosphate ester-based flame retardants; additives that serve as both a plasticizer and a flame retardant such as fluorine oil (Demnum series manufactured by Daikin Industries, Ltd.); toughness improvers such as urethane acrylate; moisture absorbents such as calcium oxide and magnesium oxide; adhesion improvers such as silane coupling agents, titanium coupling agents, and acid anhydrides; wetting improvers such as nonionic surfactants and fluorine-based surfactants; ion trap agents such as inorganic ion exchangers; and the like.

[0073] [Method for producing heat conductive sheet] And the heat conductive sheet can be produced, without particular limitation, for example, by pressing a composition containing components such as the above-described resin and carbon material into a sheet shape. Here, the heat conductive sheet may be, for example, (A) composed of a single sheet-shaped molded body obtained by the above pressing, or (B) a sheet-shaped molded body obtained by the above pressing is used as a pre-heat conductive sheet, and the heat conductive sheet may be composed of slice pieces obtained by slicing a laminate in which a plurality of the pre-heat conductive sheets are stacked in a substantially stacking direction. Among the above, from the viewpoint of exhibiting high thermal conductivity in the thickness direction, the heat conductive sheet of (B) is preferable. Hereinafter, an example of a method for producing the heat conductive sheet of (B) will be described, but the present invention is not limited thereto.

[0074] First, for example, components such as the above-described thermoplastic resin that is solid at normal temperature and normal pressure, thermoplastic resin that is liquid at normal temperature and normal pressure, particulate carbon material, and fibrous carbon material are mixed under arbitrary conditions using a known mixing device such as a kneader, a roll, a Henschel mixer, or a Hobart mixer to prepare a composition for a heat conductive sheet.

[0075] Next, the obtained composition for a heat conduction sheet is formed into a sheet shape using a known forming method such as press forming, rolling forming, or extrusion forming to form a pre-heat conduction sheet. Here, in the formed pre-heat conduction sheet, it is presumed that the carbon material is mainly arranged in the in-plane direction, and particularly the in-plane thermal conductivity of the pre-heat conduction sheet is improved.

[0076] Subsequently, the obtained pre-heat conduction sheets are laminated in a plurality of layers in the thickness direction by an arbitrary method, or the pre-heat conduction sheets are folded or wound to obtain a laminate. Here, in the obtained laminate, it is presumed that the carbon material is mainly arranged in a direction substantially orthogonal to the lamination direction.

[0077] Then, the obtained laminate is sliced, for example, using a known method such as a multi-blade method, a laser processing method, a water jet method, a knife processing method, etc., at an angle of 45° or less with respect to the substantially lamination direction, that is, the lamination direction, to obtain a heat conduction sheet composed of sliced pieces of the laminate. Here, from the viewpoint of enhancing the thermal conductivity of the heat conduction sheet, the angle at which the laminate is sliced is preferably 30° or less with respect to the lamination direction, more preferably 15° or less with respect to the lamination direction, and preferably substantially 0° with respect to the lamination direction (that is, the direction along the lamination direction). And in the heat conduction sheet thus obtained, it is presumed that the carbon material is arranged in the thickness direction. Therefore, it is presumed that the heat conduction sheet obtained by the above-described method has high thermal conductivity in the thickness direction and is also excellent in conductivity in the thickness direction.

[0078] <Configuration of the heat dissipation device> The heat dissipation device of the present invention is not particularly limited as long as it has a configuration in which the heat conduction sheet having the above-described predetermined thermal conductivity is sandwiched between the above-described heating element and the heat sink under the following-described predetermined area conditions. Also, as a method of sandwiching the heat conduction sheet between the heating element and the heat sink, any method can be used as long as it is a method capable of sandwiching the heat conduction sheet by arranging the heating element on one side in the thickness direction and the heat sink on the other side in the thickness direction.

[0079] [The surface in contact with the heat-generating element and the heat-dissipating element] Here, the surface in contact with the heat-generating element and the heat-dissipating element of the heat-conducting sheet is the surface that comes into contact with the heat-generating element and the heat-dissipating element, and is usually a surface orthogonal to the thickness direction of the heat-conducting sheet. In the heat-dissipating device of the present invention, it is necessary that the area of the surface in contact with the heat-generating element and the heat-dissipating element of the heat-conducting sheet is smaller than the area of the adherent surfaces of the heat-generating element and the heat-dissipating element. As described above, generally, since the thermal conductivity of air is significantly lower than that of the heat-conducting sheet, usually, the thermal resistance between the heat-generating element and the heat-dissipating element can be reduced to the extent that air is not interposed between the opposing heat-generating element and heat-dissipating element. That is, generally, it is considered that the thermal resistance between the heat-generating element and the heat-dissipating element can be reduced by sandwiching the heat-conducting sheet across the entire adherent surfaces of the heat-generating element and the heat-dissipating element. However, in the heat-dissipating device of the present invention, surprisingly, by sandwiching the heat-conducting sheet with a smaller area of the surface in contact with the heat-generating element and the heat-dissipating element than the area of the adherent surfaces of the heat-generating element and the heat-dissipating element, the thermal resistance between the heat-generating element and the heat-dissipating element can be reduced. That is, in the heat-dissipating device of the present invention, unexpectedly, the heat dissipation performance of the heat-dissipating device can be efficiently enhanced by using a heat-conducting sheet with a smaller size compared to the size of the conventional heat-conducting sheet.

[0080] Also, the ratio of the area of the surface in contact with the heat-generating element and the heat-dissipating element of the heat-conducting sheet to the area of the adherent surfaces of the heat-generating element and the heat-dissipating element is preferably 10% or more, more preferably 20% or more, preferably 70% or less, more preferably 60% or less, still more preferably 50% or less, and even more preferably 40% or less. If the ratio of the area of the adherent surfaces of the heat-generating element and the heat-dissipating element to the area of the surface in contact with the heat-conducting sheet is below the above upper limit, the thermal resistance between the heat-generating element and the heat-dissipating element can be more efficiently reduced, and the heat dissipation performance of the heat-dissipating device can be more efficiently enhanced. Also, if the ratio of the area of the adherent surfaces of the heat-generating element and the heat-dissipating element to the area of the surface in contact with the heat-conducting sheet is above the above lower limit, the high heat dissipation performance of the heat-dissipating device can be maintained without excessively reducing the area of the heat-conducting sheet in contact with the heat-generating element and the heat-dissipating element.

[0081] Also, when sandwiching the heat conduction sheet, although not particularly limited, from the viewpoint of more efficiently utilizing the heat conductivity of the heat conduction sheet, it is preferable to directly attach the heat conduction sheet to the portion where the temperature is highest in the heat generating body. For example, when using a power module equipped with an insulated gate bipolar transistor (IGBT) as the heat generating body, generally, since the IGBT, which is the heat source, is located at approximately the center of the power module, it is preferable to attach the heat conduction sheet to approximately the center of the surface of the heat generating body facing the radiator. Also, the region for sandwiching the heat conduction sheet is usually preferably a region including the center point of the adherend surface of the heat generating body. Note that the center point of the adherend surface of the heat generating body can be set according to the method for setting the center point on the surface to be measured in the measurement of the above-mentioned "surface unevenness".

[0082] [Sandwiching method] The method of sandwiching the heat conduction sheet between the heat generating body and the radiator is not particularly limited except that a heat conduction sheet having the above-mentioned predetermined thermal conductivity is sandwiched and interposed between the heat generating body and the radiator, and each surface is adhered in the above-mentioned predetermined area relationship. Also, as a method of sandwiching the heat conduction sheet, for example, even when there is distortion on the surfaces of the heat generating body and the radiator, a method of fixing the heat generating body and the radiator and the heat conduction sheet interposed therebetween in a state of being sufficiently adhered is preferable. From the viewpoint of maintaining such good adhesion and the simplicity of the operation, as a method of sandwiching the heat conduction sheet, a sandwiching method in which the pressing force continues, such as a method of screwing through a spring or a method of clamping with a clip; and a sandwiching method in which pressure is applied with an arbitrary force; can be cited as suitable methods. Note that the pressure during pressurization is usually 0.05 MPa to 1.5 MPa, preferably 0.1 MPa to 1.0 MPa.

Examples

[0083] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" representing amounts are based on mass unless otherwise specified. Then, in the examples and comparative examples, the surface unevenness and surface unevenness shape of the heating element; the thermal conductivity and Asker C hardness of the thermal conductive sheet; and the thermal resistance value of the heat dissipation device; were measured using the following methods, respectively.

[0084] <Surface unevenness and surface unevenness shape> The surface unevenness of the heating element and the heat dissipation element was measured using a three-dimensional shape measuring machine (manufactured by Keyence, product name "VR-3100 one-shot 3D shape measuring machine"). Here, the surface to be measured was the entire opposing surface on the side facing the heat dissipation element of the heating element (that is, the entire surface on the side where the thermal conductive sheet adheres), and the entire opposing surface on the side facing the heating element of the heat dissipation element, respectively. At this time, the surface to be measured had a substantially rectangular shape. Also, the short side direction of the surface to be measured was set as the X-axis, the long side direction was set as the Y-axis, the direction orthogonal to the X-axis and Y-axis (thickness direction) was set as the Z-axis, the point where the diagonals intersect was set as the center point, and a range of 10 mm × 10 mm parallel to the X-axis and Y-axis with the center point as the center was set as the reference plane (measurement range). Next, the entire surface to be measured was measured using the above three-dimensional shape measuring machine. Subsequently, among the measured surfaces to be measured, a graph representing the surface unevenness shape state in the Z-axis direction was obtained on a line parallel to the Y-axis (parallel Y line) passing through the point moved 0.6 mm in the X-axis direction from the center point (center X point). Note that on the parallel Y line, the highest point and the lowest point in the thickness direction within the plane of the surface to be measured passed through. That is, a graph representing the cross-sectional state of the surface to be measured with the horizontal axis as the parallel Y line and the vertical axis as the Z-axis was obtained. Then, in the obtained graph, the absolute value of the height difference between the height of the reference plane and the maximum height (highest value) in the Z-axis direction (thickness direction), and the absolute value of the height difference between the height of the reference plane and the minimum height (lowest value) were calculated, and the larger of the absolute values was obtained as "surface unevenness" (μm).

[0085] Also, the surface uneven shape of the heating element was determined as follows. That is, the surface uneven shape was determined based on the relationship of the height in the Z-axis direction between the center X point and both ends of the parallel Y line (both ends of the measurement range) in the graph obtained above. Specifically, when the height of the center X point in the Z-axis direction is higher than either of the heights of both ends of the parallel Y line in the Z-axis direction, it was defined as a convex shape. Also, when the height of the center X point in the Z-axis direction is lower than either of the heights of both ends of the parallel Y line in the Z-axis direction, it was defined as a concave shape. Further, when the height of the center X point in the Z-axis direction is between the height of one end of the parallel Y line in the Z-axis direction and the height of the other end of the parallel Y line in the Z-axis direction, it was defined as having no unevenness.

[0086] <Thermal conductivity> The measurement of the thermal conductivity of the thermal conductive sheet was carried out using a resin material thermal resistance tester (manufactured by Hitachi Technology and Services Co., Ltd., product name "C47108"). Specifically, a sample obtained by cutting the thermal conductive sheet into 1 cm × 1 cm was used, and the value of the thermal resistance was measured with the sample temperature set at 50°C under a pressure of 0.5 MPa. Then, the thermal conductivity λ (W / m·K) automatically converted from the measured value of the thermal resistance was obtained. The higher the thermal conductivity, the more excellent the thermal conductivity of the thermal conductive sheet, indicating that it has excellent heat dissipation performance when interposed between the heating element and the heat sink to form a heat dissipation device.

[0087] <Asker C hardness> The Asker C hardness of the thermal conductive sheet was measured in an environment at a temperature of 25°C using a hardness tester in accordance with the Asker C method of the Japan Rubber Association Standard (SRIS0101). Specifically, the original sheets of the obtained thermal conductive sheets were cut into sizes of 25 mm in length × 50 mm in width × 0.3 mm in thickness in Examples 1 to 4, Example 6, Comparative Examples 1 to 4, and Comparative Example 6, into sizes of 25 mm in length × 50 mm in width × 1.3 mm in thickness in Example 5 and Comparative Example 5, and into sizes of 25 mm in length × 50 mm in width × 0.5 mm in thickness in Comparative Examples 7 to 12. Then, 50 sheets were stacked on top of each other to obtain test pieces. And the obtained test pieces were left standing in a constant temperature chamber maintained at a temperature of 25°C for 48 hours or more to obtain test specimens. Next, the damper height was adjusted so that the pointer would be between 95 and 98, and the test specimen and the damper were made to collide. Then, the Asker C hardness of the test specimen 60 seconds after the collision was measured twice using a hardness meter (manufactured by Polymer Instruments Co., Ltd., product name "ASKER CL-150LJ"), and the average value of the measurement results was adopted. Generally, the smaller the Asker C hardness, the higher the flexibility.

[0088] <Thermal resistance> The value of the thermal resistance of the heat dissipation device was measured as follows for the manufactured heat dissipation device using an overheat measurement device (manufactured by Mentor Graphics, product name "T3Ster") and a pressure jig (manufactured by Key Design). Note that an IGBT-mounted power module was used as the heating element. Also, a heat sink (manufactured by Key Design) cooled by a Peltier element was used as the heat dissipation body. First, for the obtained heat dissipation device, the initial temperature of the heat dissipation body was set to 25°C. Next, a current was passed through the heating element of the heat dissipation device under the conditions of a heating current of 10 A and a heating time of 150 seconds to heat the heating element. Note that when heating the heating element, a pressure of 0.50 MPa was applied to the thermal conductive sheet sandwiched between the heating element and the heat dissipation body. Subsequently, a current was passed between the heated heating element and the heat dissipation body under the conditions of a measurement current of 20 mA and a measurement time of 150 seconds, and the temperature T1 (°C) of the heated heating element and the temperature T2 (°C) of the heat dissipation body were measured. Then, using the obtained T1, T2, and the power W (W) applied to the heating element, the following formula (I): X = (T1 - T2) / W ···(I) The value X (°C / W) of the thermal resistance between the heat-generating body and the heat sink through the thermal conductive sheet in the heat sink was determined. The smaller the value of the thermal resistance, the easier it is for heat to be transferred from the heat-generating body to the heat sink and dissipated. In addition, in this specification, the value of the thermal resistance (the amount of decrease in thermal resistance) decreased by making the area of the sandwiched surface of the thermal conductive sheet smaller than the area of the adhered surface can be obtained using the value X1 of the thermal resistance when the area of the sandwiched surface of the thermal conductive sheet is smaller than the area of the adhered surface and the value X2 of the thermal resistance when the area of the sandwiched surface of the thermal conductive sheet is the same as the area of the adhered surface in the following formula (II): Amount of decrease in thermal resistance = (X2 - X1) ···(II) And in this specification, when the amount of decrease in thermal resistance (°C / W) is positive, it indicates that the value of the thermal resistance has decreased, and when it is negative, it indicates that the value of the thermal resistance has increased. Also, in this specification, the ratio of the decrease in thermal resistance (the rate of decrease in thermal resistance) decreased by making the area of the sandwiched surface of the thermal conductive sheet smaller than the area of the adhered surface can be obtained using the above X1 and X2 in the following formula (III): Rate of decrease in thermal resistance = (X1 / X2)×100 ···(III) And when the rate of decrease in thermal resistance (%) is less than 100%, it indicates that the value of the thermal resistance has decreased, and when it is more than 100%, it indicates that the value of the thermal resistance has increased.

[0089] (Example 1) (Preparation of a fibrous carbon nanostructure containing CNT) According to the description in International Publication No. 2006 / 011655, a fibrous carbon nanostructure containing SGCNT was obtained by the super-growth method. In addition, the obtained fibrous carbon nanostructure had a G / D ratio of 3.0, a BET specific surface area of 800 m 2 / g, and a mass density of 0.03 g / cm 3This was the case. Further, using a transmission electron microscope, the diameters of 100 randomly selected fibrous carbon nanostructures were measured. As a result, the average diameter (Av) was 3.3 nm, the value obtained by multiplying the specimen standard deviation (σ) of the diameter by 3 (3σ) was 1.9 nm, the ratio thereof (3σ / Av) was 0.58, and the average length was 100 μm. Further, the obtained fibrous carbon nanostructures were mainly composed of single-walled CNTs (hereinafter sometimes referred to as "SWCNT").

[0090] <Preparation of easily dispersible aggregate of fibrous carbon nanostructure> [Preparation of dispersion] 400 mg of the obtained fibrous carbon nanostructures as a fibrous carbon material was weighed and mixed into 2 L of methyl ethyl ketone as a solvent, and stirred with a homogenizer for 2 minutes to obtain a crude dispersion. Next, using a wet jet mill (manufactured by Tsunehikari Co., Ltd., product name "JN-20"), the obtained crude dispersion was passed through a 0.5 mm flow path of the wet jet mill at a pressure of 100 MPa for 2 cycles to disperse the fibrous carbon nanostructures in methyl ethyl ketone. Then, a dispersion having a solid content concentration of 0.20 mass% was obtained. [Removal of solvent] Thereafter, the dispersion obtained above was filtered under reduced pressure using Kiriyama filter paper (No. 5A) to obtain a sheet-like easily dispersible aggregate.

[0091] <Preparation of composition for heat conductive sheet> 0.1 part by mass of an easily dispersible aggregate of the fibrous carbon nanostructure obtained above as a fibrous carbon material, 85 parts by mass of expanded graphite (manufactured by Ito Graphite Industry Co., Ltd., trade name "EC-50", average particle diameter: 250 μm) as a particulate carbon material, 40 parts by mass of a thermoplastic fluororesin that is solid at room temperature (manufactured by Daikin Industries, Ltd., trade name "Daiel G-704BP") and 45 parts by mass of a thermoplastic fluororesin that is liquid at room temperature (manufactured by Daikin Industries, Ltd., trade name "Daiel G-101") as resins, and 5 parts by mass of sebacic acid ester (manufactured by Daihachi Chemical Industry Co., Ltd., trade name "DOS") as a plasticizer were stirred and mixed for 5 minutes using a Hobart mixer (manufactured by Kohei Seisakusho Co., Ltd., product name "ACM-5LVT type") in the presence of 100 parts of ethyl acetate as a solvent. Next, the obtained stirred mixture was vacuum degassed for 30 minutes, and at the same time, ethyl acetate was removed to obtain a composition for a heat conduction sheet containing a thermoplastic fluororesin that is solid at room temperature, a thermoplastic fluororesin that is liquid at room temperature, expanded graphite, and a fibrous carbon nanostructure (SGCNT). Then, the obtained composition was put into a crusher and crushed for 10 seconds.

[0092] <Formation of pre-heat conduction sheet> Next, 5 g of the crushed composition was sandwiched between sandblasted PET films (protective films) with a thickness of 50 μm, and roll-formed under the conditions of a roll gap of 550 μm, a roll temperature of 50 °C, a roll linear pressure of 50 kg / cm, and a roll speed of 1 m / min to obtain a pre-heat conduction sheet with a thickness of 0.5 mm.

[0093] <Formation of laminate> Subsequently, the obtained pre-heat conduction sheet was cut into a size of 60 mm in length × 60 mm in width × 0.5 mm in thickness, and 120 sheets were laminated with double-sided tape in the thickness direction of the pre-heat conduction sheet to obtain a laminate with a thickness of about 60 mm.

[0094] <Fabrication of heat conduction sheet> Thereafter, while pressing the laminated cross-section of the obtained pre-thermal conduction sheet stack at a pressure of 0.3 MPa, using a woodworking slicer (manufactured by Marunaka Iron Works Co., Ltd., trade name "Super Finishing Plane Super Meka S"), it was sliced at an angle of 0 degrees with respect to the lamination direction (in other words, sliced in the normal direction of the main surface of the laminated pre-thermal conduction sheet), and a raw piece of a thermal conduction sheet with a length of 60 mm × width of 60 mm × thickness of 0.3 mm was obtained. Furthermore, by adjusting the size of the obtained raw piece to a length of 15 mm × width of 15 mm × thickness of 0.3 mm, a thermal conduction sheet was obtained. In addition, the clamping surface of the thermal conduction sheet thus obtained is a square with an outer diameter of 15 mm × 15 mm in length, and the area is 225 mm 2 becomes. In addition, for the knife of the woodworking slicer, two single-edged blades are in contact with each other on the side opposite to the cutting edge, and the tip of the front edge of the front blade is arranged 0.5 mm higher than the tip of the back edge and has a protruding length of 0.11 mm from the slit part, and a double-edged blade with a front blade angle of 21° was used. Then, for the obtained thermal conduction sheet, the thermal conductivity and Asker C hardness were measured according to the above measurement method. The results are shown in Table 1.

[0095] <Manufacture of Heat Dissipation Device> As a heating element, an IGBT-mounted power module (manufactured by STMicroelectronics, model number "STGE200NB60S", surface unevenness: 30 μm, surface unevenness shape: concave type) was prepared. Here, the surface unevenness and surface unevenness shape of the heating element were measured and determined according to the above measurement method. The results are also shown in Table 1. In addition, as a heat sink, an aluminum heat sink (manufactured by Keenath Design, product name "PDS-100", Peltier element cooling, surface unevenness: 5 μm or less) was prepared. In addition, the entire opposing surface of the prepared heating element is a square with an outer diameter of 38 mm × 25 mm in length and an area of 950 mm 2 and the entire opposing surface of the prepared heat sink is a square with an outer diameter of 50 mm × 50 mm in length and an area of 2500 mm 2 respectively. Also, the area of the adhering surface of the heating element and the heat sink was 950 mm 2 respectively.

[0096] Then, the heat conduction sheet obtained above was bonded onto the heating element such that the substantially central portion of the surface of the heating element facing the heat radiator and the substantially central portion of the heat conduction sheet overlapped. Also, the surface of the bonded heat conduction sheet that was not in contact with the heating element and the heat radiator were brought into contact such that their respective substantially central portions overlapped. Further, the heating element and the heat radiator facing each other with the heat conduction sheet therebetween were pressed using a pressing device (manufactured by Kinas Design, product name "PDPT-50-250N") such that a force of 0.5 MPa was applied to the heat conduction sheet. Then, for the manufactured heat dissipation device, the value of the thermal resistance was measured according to the above-described measurement method. The results are shown in Table 1.

[0097] (Example 2) In the manufacture of the heat dissipation device, the heat conduction sheet composition, the pre-heat conduction sheet, the heat conduction sheet, and the heat dissipation device were manufactured in the same manner as in Example 1, except that the type of the heating element was changed to a different type of IGBT-mounted power module (manufactured by Vishay, model number "VS-GA200SA60UP", surface unevenness: 10 μm, surface unevenness shape: concave). The entire opposing surface of the prepared heating element was a rectangle with an outer diameter of 38 mm in length × 25 mm in width and an area of 950 mm 2 and the entire opposing surface of the prepared heat radiator was a rectangle with an outer diameter of 50 mm in length × 50 mm in width and an area of 2500 mm 2 Also, the area of the adherend surfaces of the heating element and the heat radiator was 950 mm 2 . Then, the measurement was performed in the same manner as in Example 1. The results are shown in Table 1.

[0098] (Example 3) In the manufacture of the heat dissipation device, the heat conduction sheet composition, the pre-heat conduction sheet, the heat conduction sheet, and the heat dissipation device were manufactured in the same manner as in Example 1, except that the type of the heating element was changed to a different type of IGBT-mounted power module (manufactured by IXYS, model number "IXYN80N90C3H1", surface unevenness: 40 μm, surface unevenness shape: convex). The entire opposing surface of the prepared heating element was a rectangle with an outer diameter of 38 mm in length × 25 mm in width and an area of 950 mm2 and the entire opposing surface of the prepared heat sink was a square with an outer diameter of 50 mm in length and 50 mm in width, and the area was 2500 mm 2 The area of the adhering surfaces of the heating element and the heat sink was 950 mm 2 was. Then, the measurement was carried out in the same manner as in Example 1. The results are shown in Table 1.

[0099] (Example 4) In the preparation of the composition for the heat conduction sheet, the composition was prepared as follows. In addition, in the manufacture of the heat dissipation device, except that the type of the heating element was changed to a different type of IGBT-mounted power module (manufactured by Vishay, model name "VS-GA200SA60UP", surface unevenness: 10 μm, surface unevenness shape: concave type) from that in Example 1, the composition for the heat conduction sheet, the pre-heat conduction sheet, the heat conduction sheet, and the heat dissipation device were manufactured in the same manner as in Example 1. The entire opposing surface of the prepared heating element was a square with an outer diameter of 38 mm in length and 25 mm in width, and the area was 950 mm 2 and the entire opposing surface of the prepared heat sink was a square with an outer diameter of 50 mm in length and 50 mm in width, and the area was 2500 mm 2 The area of the adhering surfaces of the heating element and the heat sink was 950 mm 2 was. Then, the measurement was carried out in the same manner as in Example 1. The results are shown in Table 1. <Preparation of Composition for Heat Conduction Sheet> 0.1 part by mass of an easily dispersible aggregate of fibrous carbon nanostructures as a fibrous carbon material, 50 parts by mass of expanded graphite (manufactured by Ito Graphite Industry Co., Ltd., trade name "EC-100", average particle diameter: 190 μm) as a particulate carbon material, and 100 parts by mass of a thermoplastic fluororesin (manufactured by Daikin Industries, Ltd., trade name "Dai-el G-101") that is liquid at room temperature as a resin were put into a Hobart mixer (manufactured by Kobayashi Seisakusho Co., Ltd., trade name "ACM-5LVT type"), heated to 80 °C and maintained, and stirred and mixed for 30 minutes. By this mixing, a composition for a heat conduction sheet containing a thermoplastic fluororesin that is liquid at room temperature, expanded graphite, and fibrous carbon nanostructures (SGCNT) was obtained. Then, the obtained composition was put into a Wonder Crash Mill (manufactured by Osaka Chemical Co., Ltd., product name "D3V-10") and crushed for 1 minute.

[0100] (Example 5) In the production of the heat conduction sheet, the laminate was sliced into a size of 60 mm in length × 60 mm in width × 1.3 mm in thickness to obtain a raw piece of the heat conduction sheet. In the same manner as in Example 4, except that the size of the obtained raw piece was adjusted to 15 mm in length × 15 mm in width × 1.3 mm in thickness to obtain a heat conduction sheet, a composition for a heat conduction sheet, a pre-heat conduction sheet, a heat conduction sheet, and a heat dissipation device were manufactured. The clamping surface of the heat conduction sheet thus obtained was a square with an outer diameter of 15 mm in length × 15 mm in width, and the area was 225 mm 2 and became. Then, it was measured in the same manner as in Example 1. The results are shown in Table 1.

[0101] (Example 6) In the production of the heat conduction sheet, in the same manner as in Example 1, except that the size of the obtained raw piece was adjusted to 25 mm in length × 25 mm in width × 0.3 mm in thickness to obtain a heat conduction sheet, a composition for a heat conduction sheet, a pre-heat conduction sheet, a heat conduction sheet, and a heat dissipation device were manufactured. The clamping surface of the heat conduction sheet thus obtained was a square with an outer diameter of 25 mm in length × 25 mm in width, and the area was 625 mm 2 and became. Then, it was measured in the same manner as in Example 1. The results are shown in Table 1.

[0102] (Comparative Examples 1 - 4) Comparative Examples 1 - 4 are mainly examples for comparing the thermal resistance of the heat dissipation device with Examples 1 - 4 above respectively. In the production of the thermal conductive sheet, the size of the original sheet was adjusted to 38 mm in length × 25 mm in width × 0.3 mm in thickness to obtain a thermal conductive sheet. Note that the clamping surface of the thermal conductive sheet thus obtained is a rectangle with an outer diameter of 38 mm in length × 25 mm in width, and the area is 950 mm 2 becomes. Also, in the production of the heat dissipation device, except that the thermal conductive sheet was bonded onto the heat generating element so as to cover the entire surface on the side facing the heat radiator of the heat generating element, the thermal conductive sheet composition, pre - thermal conductive sheet, thermal conductive sheet, and heat dissipation device were produced in the same manner as in Examples 1 - 4 respectively. And it was measured in the same manner as in Example 1. The results are shown in Table 1.

[0103] (Comparative Example 5) Comparative Example 5 is mainly an example for comparing the thermal resistance of the heat dissipation device with Example 5 above. In the production of the thermal conductive sheet, the size of the obtained original sheet was adjusted to 38 mm in length × 25 mm in width × 1.3 mm in thickness to obtain a thermal conductive sheet. Note that the clamping surface of the thermal conductive sheet thus obtained is a rectangle with an outer diameter of 38 mm in length × 25 mm in width, and the area is 950 mm 2 becomes. Furthermore, in the production of the heat dissipation device, except that the thermal conductive sheet was bonded onto the heat generating element so as to cover the entire surface on the side facing the heat radiator of the heat generating element, the thermal conductive sheet composition, pre - thermal conductive sheet, thermal conductive sheet, and heat dissipation device were produced in the same manner as in Example 5. And it was measured in the same manner as in Example 1. The results are shown in Table 1.

[0104] (Comparative Example 6) Comparative Example 6 is mainly an example for comparing the thermal resistance of the heat dissipation device with Example 6 above. In the production of the heat conduction sheet, the size of the original sheet was adjusted to 38 mm in length × 25 mm in width × 0.3 mm in thickness to obtain the heat conduction sheet. Note that the clamping surface of the heat conduction sheet thus obtained is a rectangle with an outer diameter of 38 mm in length × 25 mm in width, and the area is 950 mm 2 becomes Also, in the production of the heat dissipation device, the heat conduction sheet composition, pre-heat conduction sheet, heat conduction sheet, and heat dissipation device were produced in the same manner as in Example 6, except that the heat conduction sheet was bonded onto the heating element so as to cover the entire surface on the side facing the heat dissipation body of the heating element. Then, the measurement was carried out in the same manner as in Example 1. The results are shown in Table 1.

[0105] (Comparative Example 7) Without producing the heat conduction sheet, a commercially available heat conduction sheet (manufactured by Denka Co., Ltd., model number "FSL-050B", adjusted to an outer diameter of 15 mm in length × 15 mm in width × 0.5 mm in thickness) was used instead of the heat conduction sheet produced by the method described in Example 1, and a heat dissipation device was produced in the same manner as in Example 1. Note that the clamping surface of the heat conduction sheet thus obtained is a rectangle with an outer diameter of 15 mm in length × 15 mm in width, and the area is 225 mm 2 becomes Then, the measurement was carried out in the same manner as in Example 1. The results are shown in Table 1.

[0106] (Comparative Example 8) Without producing the heat conduction sheet, a commercially available heat conduction sheet (manufactured by Denka Co., Ltd., model number "FSL-050B", adjusted to an outer diameter of 15 mm in length × 15 mm in width × 0.5 mm in thickness) was used instead of the heat conduction sheet produced by the method described in Example 1. Note that the clamping surface of the heat conduction sheet thus obtained is a rectangle with an outer diameter of 15 mm in length × 15 mm in width, and the area is 225 mm 2 becomes In addition, in the manufacture of the heat dissipation device, a heat dissipation device was manufactured in the same manner as in Example 1, except that the type of the heating element was changed to an IGBT-mounted power module of a type different from that in Example 1 (manufactured by Vishay, model number "VS-GA200SA60UP", surface unevenness: 10 μm, surface unevenness shape: concave type). The entire opposing surface of the prepared heating element was a rectangle with an outer diameter of 38 mm in length and 25 mm in width, and the area was 950 mm 2 The entire opposing surface of the prepared heat sink was a rectangle with an outer diameter of 50 mm in length and 50 mm in width, and the area was 2500 mm 2 The area of the adhering surfaces of the heating element and the heat sink was 950 mm 2 The measurement was carried out in the same manner as in Example 1. The results are shown in Table 1. And it was measured in the same manner as in Example 1. The results are shown in Table 1.

[0107] (Comparative Example 9) Without manufacturing a heat conduction sheet, a commercially available heat conduction sheet (manufactured by Denka Co., Ltd., model number "FSL-050B", adjusted to an outer diameter of 15 mm in length × 15 mm in width × 0.5 mm in thickness) was used instead of the heat conduction sheet manufactured by the method described in Example 1. The clamping surface of the heat conduction sheet thus obtained was a rectangle with an outer diameter of 15 mm in length and 15 mm in width, and the area was 225 mm 2 And it became so. In addition, in the manufacture of the heat dissipation device, a heat dissipation device was manufactured in the same manner as in Example 1, except that the type of the heating element was changed to an IGBT-mounted power module of a type different from that in Example 1 (manufactured by IXYS, model name "IXYN80N90C3H1", surface unevenness: 40 μm, surface unevenness shape: convex type). The entire opposing surface of the prepared heating element was a rectangle with an outer diameter of 38 mm in length and 25 mm in width, and the area was 950 mm 2 The entire opposing surface of the prepared heat sink was a rectangle with an outer diameter of 50 mm in length and 50 mm in width, and the area was 2500 mm 2 The area of the adhering surfaces of the heating element and the heat sink was 950 mm 2 The measurement was carried out in the same manner as in Example 1. The results are shown in Table 1. And it was measured in the same manner as in Example 1. The results are shown in Table 1.

[0108] (Comparative Examples 10 to 12) Comparative Examples 10 to 12 are mainly examples for comparing the heat resistance of the heat dissipation device with the above Comparative Examples 7 to 9 respectively. Without producing a heat conduction sheet, the size of a commercially available heat conduction sheet was adjusted to 38 mm in length × 25 mm in width × 0.5 mm in thickness and used as the heat conduction sheet. The clamping surface of the heat conduction sheet thus obtained was a rectangle with an outer diameter of 38 mm in length × 25 mm in width, and the area was 950 mm 2 becomes. Also, in the manufacture of the heat dissipation device, the heat dissipation device was manufactured in the same manner as in Comparative Examples 7 to 9, except that the heat conduction sheet was bonded onto the heating element so as to cover the entire surface on the side facing the heat dissipation body of the heating element. Then, the measurement was performed in the same manner as in Example 1. The results are shown in Table 1.

[0109]

Table 1

[0110] From Table 1, in Examples 1 to 6 in which a heat conduction sheet having a thermal conductivity higher than a predetermined value was used and the area of the clamping surface of the heat conduction sheet was made smaller than the area of the adhering surfaces of the heating element and the heat dissipation body, it can be seen that the value of the thermal resistance is lower and the heat dissipation performance of the heat dissipation device is higher than that of Comparative Examples 7 to 12 in which the thermal conductivity of the heat conduction sheet is less than the predetermined value. Also, in Examples 1 to 6 in which a heat conduction sheet having a thermal conductivity higher than a predetermined value was used and the area of the clamping surface of the heat conduction sheet was made smaller than the area of the adhering surfaces of the heating element and the heat dissipation body, compared with Comparative Examples 1 to 6 in which the same heat conduction sheet was used and the area of the clamping surface of the heat conduction sheet was made the same as the area of the adhering surface, in all comparison patterns (for example, each pattern of Example 1 and Comparative Examples 1 to Example 6 and Comparative Examples 6), it can be seen that the value of the thermal resistance has decreased and the heat dissipation performance of the heat dissipation device has improved. On the other hand, in the case of Comparative Examples 7 to 12 where the thermal conductivity of the heat conductive sheet is less than a predetermined value, in Comparative Examples 7 to 9 where the area of the sandwiched surface of the heat conductive sheet is made smaller than the area of the adhered surface, the value of the thermal resistance increases as compared with Comparative Examples 10 to 12 where the area of the sandwiched surface of the heat conductive sheet is made the same as the area of the adhered surface, and it can be seen that the heat dissipation performance of the heat dissipation device deteriorates.

Industrial Applicability

[0111] According to the present invention, it is possible to provide a heat dissipation device capable of achieving high heat dissipation performance.

Claims

1. A heat dissipation device comprising a heating element, a heat radiator, and a heat conduction sheet sandwiched between the heating element and the heat radiator, wherein the thermal conductivity of the heat conduction sheet in the thickness direction is 15 W / m·K or more, the area of the sandwiched surface of the heat conduction sheet is smaller than the area of the adhered surfaces of the heating element and the heat radiator, the adhered surfaces of the heating element and the heat radiator are the opposing surfaces of the heating element and the heat radiator within the range where they oppose each other among the entire surfaces on the side where the heating element and the heat radiator face each other, and a ratio of the area of the sandwiched surface of the heat conduction sheet to the area of the adhered surfaces of the heating element and the heat radiator is 10% or more and 40% or less. The heat dissipation device is characterized by this.

2. The heat dissipation device according to Claim 1, wherein the Asker C hardness of the heat conduction sheet at 25°C is 30 or more.

3. The heat dissipation device according to Claim 1 or 2, wherein the thickness of the heat conduction sheet is 2.0 mm or less.

4. The heat dissipation device according to any one of Claims 1 to 3, wherein a ratio of the area of the sandwiched surface of the heat conduction sheet to the area of the adhered surfaces of the heating element and the heat radiator is 20% or more and 40% or less.

5. The heat dissipation device according to any one of Claims 1 to 4, wherein the heat conduction sheet contains a resin and a carbon material.

6. The heat dissipation device according to any one of Claims 1 to 5, wherein the surface unevenness of at least one of the adhered surfaces of the heating element and the heat radiator is more than 5 μm.

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