JP2010171030A - Heat radiating structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat radiating structure with which design and fitting work of an electronic apparatus are easy, which efficiently sets heat of a heating element free to an external part and prevents a temperature of the external part from locally becoming high. <P>SOLUTION: The heat radiating structure is provided with the heating element 11, a substrate 12 fixing the heating element 11, a heat diffusion film 13, a supporting body 14 and a thermally conductive material layer 15 which is brought into contact with the heating element 11, the substrate 12 and the heat diffusion film 13. The thermally conductive material layer 15 covers a surface of the heating element 11. Thermal conductivity of the thermally conductive material layer 15 is 0.9 W/mK or above. The heat diffusion film 13 is desirable to include a graphite film whose thermal conductivity in a face direction is 200 W/mK or above, whose thermal conductivity in a thickness direction is 60 W/mK or below and whose thickness is 350 μm or below. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a heat radiating structure for radiating heat from a heat generating body used in electronic equipment, precision equipment, and the like.

  Currently, the heat generation density of electronic devices such as mobile phones and notebook computers is rapidly increasing, and the heat dissipation design of these devices is becoming essential. In particular, in a small mobile device that is required to be small and light, a heat radiating sheet such as a graphite film is used as a heat spreader material (see, for example, Patent Document 1).

  When using a graphite film as a heat radiating member, it is necessary to sufficiently adhere to a heat generation source in order to exhibit the excellent thermal conductivity of graphite. When a graphite film is actually incorporated into an apparatus, a general method is to join the graphite film and a heat source using an adhesive such as an epoxy resin, an acrylic resin or a polyimide resin, an adhesive material, or the like. Further, there is a method of mechanically contacting and fixing the heating element with screws or caulking (see, for example, Patent Document 2).

  In addition, for the purpose of reducing the contact thermal resistance between a heat generating element and a heat spreader material such as a graphite film, a heat dissipation sheet in which a graphite film is coated with a heat conductive silicone rubber has been proposed.

  Also, electronic devices are equipped with heating elements of various sizes, large and small, and there is a difference in the height of each electronic component and tolerance due to assembly processing, making it difficult to bring the electronic component and heat dissipation member into close contact with each other However, a sheet is disclosed in which a thermally conductive material layer is provided on the surface of a graphite film that is reduced in viscosity, softened or dissolved by heat generation during operation of an electronic component (see, for example, Patent Document 3).

  In addition, when there is a gap between the CPU and the heat dissipating member (metal) arranged so as to face the CPU, the CPU and the heat dissipating member are connected using an urging member such as a U-shaped spring-shaped copper foil. A module is disclosed. That is, a heat dissipating structure having improved heat dissipating capability by moving heat generated by the CPU to a large area heat dissipating member via a U-shaped biasing member is disclosed (for example, see Patent Document 4). ).

  In addition, a small mobile device such as a mobile phone may be required to have a design in which the maximum temperature on the outer surface of the housing is 42 ° C. or lower in order to prevent low-temperature burns. In order to simplify the design and installation work of electronic equipment and to provide a heat dissipation structure that does not transmit the heat of the heating element to the outside, the heating element and the heat diffusion film are brought into contact with each other, and the distance is set to 0. 0. A heat dissipation structure characterized by being 3 mm or less is disclosed (see, for example, Patent Document 5).

JP 61-275116 A JP-A-11-317480 JP 2003-158393 A Japanese Patent Laid-Open No. 7-202083 JP 2008-277432 A

  In an electronic device, several heat generating elements are mounted on the same substrate, and there is a difference in height of each electronic component, so that it is difficult to connect the heat radiating member and all the heat generating elements. The following countermeasures have been implemented for this problem. Matching the heights of the heating elements is difficult and costly. The method of bending and connecting the heat radiating member to fill the space makes it difficult to attach the heat radiating member and increases the processing cost of the heat radiating member. In addition, the connection using silicone rubber or the like has a problem of contamination in the electronic equipment due to siloxane, which increases the cost. In a structure in which the heating element and the heat diffusion film are not in contact with each other and the distance is 0.3 mm or less, the heat dissipation effect may be insufficient when the heat generation amount of the heating element increases.

  In addition, since the heat generation of small electronic devices in recent years is becoming increasingly serious, there is an increasing need to further increase the heat dissipation efficiency of the heat dissipation member. If there is an air layer around the heating element, the air layer acts as a heat insulating layer and the heat dissipation efficiency decreases, so it is desirable to design the heat dissipation structure so that the heating element is not in contact with the air layer as much as possible. Therefore, it is not easy to change the structure for heat countermeasures, and a heat dissipation structure that can be widely used for general-purpose electronic boards is desired.

  The present invention has been made to solve the above-described problems. The design of the electronic device is extremely simple and the heat dissipation structure is excellent, while preventing the outside from becoming locally high temperature. An object is to provide a heat dissipation structure capable of diffusing heat and then escaping to the outside.

  That is, the present invention includes a heating element, a substrate that fixes the heating element, a heat diffusion film, a support that supports the heat diffusion film opposite to the heating element, the heating element, the heat diffusion film, and A thermal conductive material layer in contact with the substrate, wherein the thermal diffusion film includes a film having a thermal conductivity in a plane direction of 100 W / mK or more and a thickness of 500 μm or less, and the thermal conductive material layer includes the heat generation The heat dissipation structure is characterized in that the surface of the body is covered and the thermal conductivity of the thermal conductive material layer is 0.9 W / mK or more.

  In the heat dissipation structure according to the present invention, the thermal diffusion film is a graphite film having a thickness of 350 μm or less, having a thermal conductivity in the plane direction of 200 W / mK or more and a thermal conductivity in the thickness direction of 60 W / mK or less. It is preferable to contain.

  In the heat dissipation structure according to the present invention, the thermally conductive material layer is coated with the thermally conductive curable composition so as to contact any of the heating element, the thermal diffusion film, and the substrate, and then cured. Preferably, the material is

  Furthermore, in the heat dissipation structure according to the present invention, the heat conductive material layer is preferably a cured product of a heat conductive curable composition containing at least a curable acrylic resin and a heat conductive filler.

  According to the present invention, the design of an electronic device is very simple and the heat dissipation structure is excellent, but the outside can be prevented from being locally heated, and the heat of the heating element can be diffused and then released to the outside. A heat dissipation structure can be provided.

It is the schematic which shows an example of the thermal radiation structure concerning this invention. Here, (a) is a schematic cross-sectional view of a heat dissipation structure, and (b) is a schematic plan view showing a heating element, a substrate, a heat conductive material layer, and a heat diffusion film as seen from the top surface of the heat dissipation structure. is there. It is the schematic which shows the other example of the thermal radiation structure concerning this invention. Here, (a) is a schematic cross-sectional view of a heat dissipation structure, and (b) is a schematic plan view showing a heating element, a substrate, a heat conductive material layer, and a heat diffusion film as seen from the top surface of the heat dissipation structure. is there. It is the schematic which shows the further another example of the thermal radiation structure concerning this invention. Here, (a) is a schematic cross-sectional view of a heat dissipation structure, and (b) is a schematic plan view showing a heating element, a substrate, a heat conductive material layer, and a heat diffusion film as seen from the top surface of the heat dissipation structure. is there. It is the schematic which shows the further another example of the thermal radiation structure concerning this invention. Here, (a) is a schematic cross-sectional view of the heat dissipation structure, and (b) is a schematic plan view showing a heating element, a substrate, and a thermally conductive material layer as viewed from the upper surface of the heat dissipation structure. It is the schematic which shows an example of a typical heat dissipation structure. Here, (a) is a schematic cross-sectional view of a heat dissipation structure, and (b) is a schematic plan view showing a heating element, a substrate, a heat conductive material layer, and a heat diffusion film as seen from the top surface of the heat dissipation structure. is there.

  Referring to FIG. 1, one embodiment of a heat dissipation structure of the present invention is a heating element 11, a substrate 12 that fixes the heating element 11, a heat diffusion film 13, and a heat diffusion film 13 that faces the heating element 11. The support 14 and the thermally conductive material layer 15 are supported, and the thermal diffusion film 13 includes a film having a thermal conductivity in the plane direction of 100 W / mK or more and a thickness of 500 μm or less. The material layer 15 is in contact with any of the heating element 11, the substrate 12, and the thermal diffusion film 13.

  In the heat dissipation structure of the present embodiment, since the heating element 11 is covered with the heat conductive material layer 15 without coming into contact with air, the heat generated by the heating element is transmitted from the entire surface of the heating element to the thermal diffusion film 13. As compared with the case where the heat conductive material layer 15 is in contact with only the top surface of the heating element, the heat transfer efficiency can be increased, and the temperature of the heating element can be kept lower. On the other hand, since the heat diffusion film 13 has a structure in which the heat generated from the heating element is efficiently spread in the surface direction and then released to the support, the temperature of the support (housing in the electronic device or the like) partially rises too much. Therefore, it is possible to greatly reduce concerns such as burns when using electronic devices.

  The heat dissipation structure of the present embodiment can absorb variations in dimensions due to tolerances of the heating element by using a sufficiently flexible material as the heat conductive material layer, so there is variation in the height of the heating element. In addition, the heat diffusion film can follow the shape of the heating element, and the planar heat diffusion film can be used as it is.

  Further, in the heat dissipation structure of the present embodiment, the thermally conductive material layer is applied after the thermally conductive curable composition is applied so as to contact any of the heating element, the thermal diffusion film, and the substrate, and then cured. By adopting the construction method, the liquid material can absorb the dimensional variation due to the tolerance of the heating element, so that the thermal diffusion film follows the shape of the heating element even if the heating element has a height variation. Therefore, a planar heat diffusion film can be used as it is. Moreover, by using a liquid heat conductive curable composition for the heat conductive material layer, the heat conductive material layer and the heating element can be securely adhered to each other, and the thermal resistance between the two can be greatly reduced. Will be.

  In addition, there is no restriction | limiting in particular in the form of the support body 14 which supports the thermal diffusion film 13 facing the heat generating body 11, and the support body 14 is the heat generating body 11, the board | substrate 12, and the thermal diffusion film 13 as shown in FIG. The support 14 may be connected to the substrate 12 by a support column.

  The thermal diffusion film 13 includes a film having a thermal conductivity in the plane direction of 100 W / mK or more and a thickness of 500 μm or less, and has a high thermal diffusibility in the plane direction even if the thickness is small. For this reason, a thin heat dissipation structure can be formed. As a preferred example of a film having a thermal conductivity in the plane direction of 100 W / mK or more and a thickness of 500 μm or less, a thermal conductivity in the thickness direction of 200 W / mK or more and 60 W / mK or less, and a thickness of 350 μm or less. A graphite film is mentioned. The heat diffusion film 13 may include a protective film 17 and an adhesive layer 18 in addition to the graphite film 16.

  <Temperature of outer surface of support> Since there is a thermal diffusion film between the heat conductive material layer and the support (housing), the heat conductive material layer and the support (housing) are in direct contact with each other. The maximum temperature of the outer surface can be kept lower than if it is present. In addition, when the heating element and the heat diffusion film are in direct contact with each other, heat resistance is generated due to the contact between the heating element and the heat diffusion film, and the heating element is exposed to the air as compared to the case without the heat conductive material layer. Since there is an area in contact, it is difficult to efficiently transfer heat generated by the heating element to the heat diffusion film. In actuality, when designing a mobile phone or the like, there is a case where a design that does not transmit heat to the outside surface is required for the purpose of preventing low-temperature burns (in some cases, it is actually limited to 42 ° C. or lower). By adopting the structure, such a request can be met. The temperature of the outer surface of the support of the present invention is preferably 60 ° C. or lower, more preferably 50 ° C., and further preferably 42 ° C. or lower. If the temperature exceeds 60 ° C., low temperature burns may occur when the support is a housing such as a small electronic device.

  <The temperature of a heat generating body> On the other hand, the temperature of a heat generating body becomes low, so that the distance D of a heat generating body and a thermal diffusion film approaches. The temperature of the heating element is preferably 130 ° C. or less, more preferably 120 ° C., and still more preferably 111 ° C. or less from the viewpoint of setting the temperature to the heat resistant temperature or less. If the temperature is 130 ° C. or higher, the function of the semiconductor element forming the heating element may become dull or malfunction. Depending on the electronic device, the heat-resistant temperature of the heating element may be limited to 120 ° C. or less.

  <Distance between heating element and thermal diffusion film> As described in the previous section, the greater the distance between the heating element and the thermal diffusion film, the lower the temperature of the outer surface of the support (housing), and the higher the temperature of the heating element. Get higher. Therefore, it is important to select the distance between the heating element and the thermal diffusion film so that the temperature of the heating element does not become too high.

  The distance between the heating element of the present invention and the thermal diffusion film is greater than 0 mm and 5.0 mm or less, preferably 0.01 mm or more and 2.5 mm or less, more preferably 0.03 mm or more and 2.0 mm or less. When the distance between the heating element and the heat diffusion film is larger than 3.0 mm, the temperature of the heating element becomes too high because the temperature of the heating element cannot be efficiently transmitted to the heat diffusion film. In addition, when the distance between the heating element and the thermal diffusion film is 0 mm, that is, in direct contact, since there is no installation space for the heat conductive material layer, the variation in dimensions due to the tolerance of the heating element cannot be absorbed, and the thermal resistance is reduced. Reduction effect is small.

  <Wattage of heating element> The output (wattage) of the heating element of the present invention is 10 W or less, preferably 2 W or less, more preferably 1.5 W or less. When the output of the heating element is greater than 10 W, it is difficult to sufficiently release the heat of the heating element, so that the temperature of the heating element may rise to the heat resistant temperature or higher.

  <Number of heating elements> Only one heating element 11 of the present invention may be provided on the substrate 12, or a plurality of heating elements 11 may be mounted on the substrate. When a plurality of heating elements are mounted on the substrate, the heights of the heating elements from the substrate do not need to match. By covering the entire heating element with the heat conductive material layer 15, it is possible to efficiently transfer the heat generated from the heating element to the thermal diffusion film 13 even when the heating elements do not have the same height.

  <Area of heat diffusion film> The area of the heat diffusion film of the present invention is preferably 4 times to 100 times the area of the heating element (referring to the area of the surface facing the heat diffusion film, hereinafter the same). More preferably, they are 5 times or more and 80 times or less, More preferably, they are 6 times or more and 50 times or less. When the area of the heat diffusing film is smaller than four times the area of the heating element, the temperature of the heating element rises due to poor thermal diffusibility. On the other hand, if the area of the heat diffusing film is larger than 100 times the area of the heating element, the heat dissipation characteristic will reach its peak, while increasing the cost and making it difficult to reduce the space. When there are a plurality of heating elements, the total area of the entire heating element is used for calculation.

  <The thermal conductivity of the surface direction of a thermal diffusion film> The thermal diffusion film of this invention needs to contain the film whose thermal conductivity of a surface direction is 100 W / mK or more. The thermal conductivity in the plane direction of the film is preferably 200 W / mK or more, more preferably 500 W / mK or more, still more preferably 700 W / mK or more, and most preferably 1000 W / mK or more. By having high thermal conductivity in the plane direction, it is possible to spread the heat generated from the heating element in the plane direction and release it. Examples of such films having high thermal conductivity in the plane direction include copper foil, aluminum foil, natural graphite film produced by the expanding method, synthetic graphite film produced by high-temperature firing of a polymer film, etc. can do. Among these, by using a material having thermal conductivity anisotropy in the plane direction and the thickness direction as a thermal diffusion film, it is possible to spread the heat of the heating element more efficiently in the plane direction. It can be preferably used. Examples of thermal diffusion films that have thermal conductivity anisotropy in the plane direction and thickness direction include natural graphite films produced by the expanding method, synthetic graphite films produced by high-temperature firing of polymer films, etc. can do.

  <Thickness of thermal diffusion film> The thickness of the film having high thermal conductivity in the surface direction used for the thermal diffusion film used in the present invention is 500 μm or less, preferably 250 μm or less, more preferably 200 μm or less, most preferably 100 μm. It is as follows. In recent years, electronic devices have been reduced in thickness, and a gap in which a heat dissipation member can be mounted has become very small. Therefore, unless the thickness is 500 μm or less, the film cannot be installed in the gap. On the other hand, in order to mount a film thicker than 500 μm, it must be designed in consideration of the space for mounting the heat diffusion film. In such a case, the thickness of the electronic device becomes thick, and thus the thick heat diffusion film is avoided from use of a small electronic device that is required to be thin.

<The thermal conductivity in the surface direction of the graphite film>
The thermal diffusion film of the present invention includes a graphite film having a thermal conductivity in a plane direction of 200 W / mK or more, preferably 500 W / mK or more, more preferably 700 W / mK or more, and most preferably 1000 W / mK or more. preferable. In general, compared to the case where the heating element and the heat diffusion film including the graphite film are in contact with each other without assuming the thermal resistance of the contact surface, the field where the heat conductive material layer exists between the two is more This is disadvantageous. However, when the thermal conductivity of the graphite film is 200 W / mK or more, the heat of the heating element can be effectively dissipated even if the heat conductive material layer is present. On the other hand, when the thermal conductivity of the graphite film is less than 200 W / mK, when the thermal conductive material layer is applied so as to have a large thickness, the heat dissipation of the heating element is not in time and the temperature becomes high. Here, the thermal conductivity of the graphite film is expressed by the following formula (1).
_{λ = α × d × C p} (1)
It can be calculated from In Equation (1), λ represents thermal conductivity, α represents thermal diffusivity, d represents density, and C _p represents specific heat capacity. In addition, the thermal diffusivity, density, and specific heat capacity of a graphite film can be calculated | required by the method shown below.

  <Thermal conductivity in the thickness direction of the graphite film> The thermal conductivity in the thickness direction of the graphite film of the present invention is 60 W / mK or less, preferably 30 W / mK or less, more preferably 20 W / mK or less, most preferably. It is good that it is 10 W / mK or less. If the thermal conductivity in the thickness direction of the graphite film is greater than 60 W / mK, the heat generated from the heating element is directly transmitted to the outer surface of the support before being diffused. On the other hand, if the thermal conductivity in the thickness direction is 60 W / mK or less, it is preferable because the ratio of releasing the heat transmitted from the heating element in the thickness direction without increasing the thickness is increased.

  For measuring the thermal diffusivity and thermal conductivity in the thickness direction of the graphite film by the laser flash method, LFA-502 manufactured by Kyoto Electronics Industry Co., Ltd. in accordance with JIS R1611-1997 was used. The graphite film was cut to a diameter of 10 mm, and both sides of the film were blackened, and then the thermal diffusivity in the thickness direction was measured by a laser flash method at room temperature. Moreover, the heat capacity of the graphite film was calculated from comparison with a reference standard substance Mo having a known heat capacity. The thermal conductivity in the thickness direction was calculated from the measured thermal diffusivity, density, and heat capacity of the graphite film. It means that the larger the thermal diffusivity and thermal conductivity in the thickness direction, the higher the thermal conductivity in the thickness direction.

  <Thermal diffusivity of graphite film> The progress of graphitization was determined by measuring the thermal diffusivity in the surface direction of the film. The higher the thermal diffusivity in the plane direction, the more remarkable the graphitization. The thermal diffusivity was measured at 10 Hz in a 20 ° C. atmosphere by cutting a graphite film into a 4 mm × 40 mm sample shape using a thermal diffusivity measuring apparatus (LaserPit manufactured by ULVAC-RIKO Co., Ltd.) using an optical alternating current method. .

  <Thickness of Graphite Film> The thickness of the graphite film used in the present invention is 350 μm or less, preferably 100 μm or less, more preferably 70 μm or less, and most preferably 50 μm or less. In recent years, electronic devices have been reduced in thickness, and a gap in which a heat dissipation member can be mounted has become very small. Therefore, it cannot be mounted in the gap unless the graphite film has a thickness of 350 μm or less. On the other hand, in order to mount a film thicker than 350 μm, it must be designed in consideration of the space for mounting the heat diffusion film. In such a case, the thickness of the electronic device becomes thick, so that the thick graphite film is not used for a small electronic device that is required to be thin.

  As a method for measuring the thickness of the graphite film, a film of 50 mm × 50 mm was measured using a thickness gauge (manufactured by HEIDENHAIN Co., Ltd.) at a room temperature (25 ° C.) and measured at any 10 points. The average value was taken as the measured value.

<Density of Graphite Film> The density of the graphite film was calculated by dividing the mass (g) of the graphite film by the volume (cm ³ ) calculated by the product of the vertical, horizontal and thickness of the graphite film. In addition, the average value measured by arbitrary 10 points | pieces was used for the thickness of a graphite film. The higher the density, the more remarkable the graphitization.

  <Protective film> As for a graphite film, powder fall may occur depending on the case, and there is a possibility of contaminating the inside of an apparatus. Moreover, since a graphite film, copper foil, etc. show electroconductivity, there exists a possibility of causing the short circuit of an electronic device board | substrate. For these reasons, it is preferable that the heat diffusion film of the present invention is used by being bonded to a protective film. That is, referring to FIG. 1, the heat diffusion film 13 preferably has a protective film 17 bonded to the graphite film 16. The protective film 17 is preferably a film in which an acrylic, silicone, epoxy, or polyimide adhesive or adhesive is formed on one surface of a film such as polyimide, polyethylene terephthalate, polyethylene, polypropylene, or polyester. Further, it may be a hot-melt type (thermoplastic) film such as polyester. In addition, a tape having a high thermal emissivity is preferable because the amount of heat transfer in non-contact increases when bonded. The resin tape has a low thermal conductivity, so it should be thin. In addition, about the surface which is in contact with the heat conductive material layer 15 among the thermal diffusion films 13, since there is little possibility of causing the powder fall of a graphite film or a short circuit, it is not necessary to use a protective film. Although it is preferable not to use a protective film because the thermal conductivity is improved, it is necessary to remove only a part of the protective film at the time of manufacturing the thermal diffusion film 13, which may cause an increase in production cost.

  <Adhesive Layer> Referring to FIG. 1, a thermal diffusion film 13 including a graphite film 16 is provided with an adhesive material and an adhesive on the inner surface of a support 14 (a casing referred to as an electronic device) located on the opposite side of the heating element 11. It is preferable to use the adhesive layer 18 such as affixed. In the present invention, the material of the pressure-sensitive adhesive or adhesive used as the adhesive layer 18 is an acrylic, silicone, epoxy or polyimide resin. Since such adhesives and adhesives have poor thermal conductivity, the adhesive layer 18 should basically be thin.

  <Material of Support Body> With reference to FIG. 1, the support body 14 corresponds to a housing of an electronic device. Usually, an electronic device has a substrate 12 on which several heating elements 11 are mounted, and this substrate 12 is covered with a resin or metal casing (support 14). In the heat dissipation structure of the present invention, the heat diffusion film 13 is disposed in the gap between the heating element 11 and the casing (support 14) of such an electronic device. At that time, the heat diffusion film 13 is bonded to the inner surface of the support 14 using an adhesive layer 18 such as an adhesive or an adhesive. The support of the present invention includes polycarbonate (PC) resin, acrylonitrile butadiene styrene (ABS) resin, polyester resin, polyamide (PA) resin, filler reinforced grades such as glass fiber of these resins, stainless steel plate (SUS), A material containing Mg, Al, Cu, or the like is used.

  <Thermal Conductive Material Layer> Referring to FIG. 1, the thermally conductive material layer 15 is in contact with any of the heating element 11, the substrate 12, and the thermal diffusion film 13, so that the entire heating element is a thermally conductive material layer. It becomes a covered structure. These contact surfaces need to be in close contact so that the thermal resistance is as small as possible. Thereby, the heat generated from the heating element can be efficiently transmitted to the heat diffusion film. By using a thermally conductive curable composition having fluidity as a material of the thermally conductive material layer, and curing after applying a liquid material, a thermally conductive material layer, a heating element, a substrate, a thermal diffusion film, It is possible to make the thermal resistance during

  <Thermal conductivity of the thermally conductive material layer> Since the thermally conductive material layer needs to conduct heat efficiently to the outside, it is necessary to use a highly thermally conductive material. Specifically, the thermal conductivity is 0.9 W / mK or more, preferably 1.0 W / mK or more, and more preferably 1.2 W / mK or more. By using such a high thermal conductivity material, it is possible to efficiently release the heat of the heating element as compared with the case where the heating element is in contact with air. In the case of using a curable composition as the material, the thermal conductivity measurement of the thermally conductive material layer is performed after sufficiently curing the material, and then hot disk method thermal conductivity measuring device TPA-501 manufactured by Kyoto Electronics Industry Co., Ltd. Was measured at 23 ° C. by a method in which a 4φ-size sensor was sandwiched between two disc-shaped samples having a thickness of 3 mm and a diameter of 20 mm.

  <Heat conductive curable composition> As the heat conductive curable composition, a curable composition containing at least a curable liquid resin and a heat conductive filler is used. In addition to these, if necessary, a curing catalyst for curing the curable liquid resin, a heat aging inhibitor for the thermally conductive curable composition, a plasticizer, an extender, a thixotropic agent, an adhesion promoter, A dehydrating agent, a coupling agent, an ultraviolet absorber, a flame retardant, an electromagnetic wave absorber, a filler, a solvent, or the like may be added.

  <Curable liquid resin> The curable liquid resin is preferably a curable liquid resin having a reactive group in the molecule. Specific examples of the curable liquid resin include a curable acrylic resin, a curable polyether resin typified by a curable polypropylene oxide resin, a curable polyolefin resin typified by a curable polyisobutylene resin, and a cured resin. For example, a functional silicone-based resin. Various reactive functional groups such as epoxy groups, hydrolyzable silyl groups, vinyl groups, acryloyl groups, SiH groups, urethane groups, carbodiimide groups, combinations of carboxylic anhydride groups and amino groups are used as reactive groups. be able to. When these are cured by a combination of two types of reactive groups, or by reaction of reactive groups with a curing catalyst, after preparing as a two-component composition, two components are applied when applied to a substrate or heating element. Curability can be obtained by mixing. Alternatively, in the case of a curable resin having a hydrolyzable silyl group, it can be cured by reacting with moisture in the air, so that it can be a one-component room temperature curable composition. In the case of a combination of a vinyl group, a SiH group, and a Pt catalyst, or in the case of a combination of a radical initiator and an acryloyl group, a one-component curable composition or a two-component curable composition is used, and then crosslinked. It can also be cured by heating to a temperature or applying crosslinking energy such as ultraviolet rays or electron beams. In general, when it is easy to heat the entire heat dissipation structure to some extent, it is preferable to use a thermosetting composition, and when it is difficult to heat the heat dissipation structure, two-component curing is used. It is preferable to use a water-soluble composition or a moisture-curable composition, but it is not limited thereto.

  <Curable Acrylic Resin> Among curable liquid resins, it is preferable to use a curable acrylic resin because there are few problems of contamination in electronic equipment due to low molecular weight siloxane. As the curable acrylic resin, various known reactive acrylic resins can be used. Among these, it is preferable to use an acrylic oligomer having a reactive group at the molecular end. As these curable acrylic resins, a combination of a curable acrylic resin produced by living radical polymerization, especially atom transfer radical polymerization, and a curing catalyst can be most preferably used. As an example of such a resin, Kaneka XMAP manufactured by Kaneka Corporation is well known.

  <Thermal conductive filler> As the thermally conductive filler used in the thermally conductive curable composition, a commercially available general heat conductive filler can be used. Among them, carbon compounds such as graphite, diamond, and the like from various viewpoints such as thermal conductivity, availability, electrical insulating properties, electromagnetic shielding properties and electromagnetic wave absorption properties, filling properties, toxicity, etc .; aluminum oxide Metal oxides such as magnesium oxide, beryllium oxide, titanium oxide, zirconium oxide, and zinc oxide; metal nitrides such as boron nitride, aluminum nitride, and silicon nitride; metal carbides such as boron carbide, aluminum carbide, and silicon carbide; Metal hydroxides such as aluminum and magnesium hydroxide; metal carbonates such as magnesium carbonate and calcium carbonate; crystalline silica: calcined acrylonitrile polymer, calcined furan resin, calcined cresol resin, calcined polyvinyl chloride, sugar Baked product of organic polymer such as baked product of charcoal, baked product of charcoal; Zn ferrite Composite ferrite; Fe-Al-Si ternary alloy; metal powders, and the like preferably.

  Further, from the viewpoint of availability and thermal conductivity, graphite, aluminum oxide, magnesium oxide, boron nitride, aluminum nitride, silicon carbide, aluminum hydroxide, magnesium carbonate, and crystallized silica are more preferable, graphite, α-alumina, hexagonal More preferred are crystalline boron nitride, aluminum nitride, aluminum hydroxide, Mn—Zn soft ferrite, Ni—Zn soft ferrite, Fe—Al—Si ternary alloy (Sendust), carbonyl iron, iron nickel alloy (Permalloy) Spheroidized graphite, round or spherical α-alumina, spheroidized hexagonal boron nitride, aluminum nitride, aluminum hydroxide, Mn—Zn soft ferrite, Ni—Zn soft ferrite, spherical Fe—Al—Si three Original alloy (Sendust), Carbo Nyl iron is particularly preferred. When carbonyl iron is used in the present invention, reduced carbonyl iron powder is desirable. The reduced carbonyl iron powder is not a standard grade but a carbonyl iron powder classified into a reduced grade, and is characterized by a lower carbon and nitrogen content than the standard grade.

  In addition, these thermally conductive fillers are improved in dispersibility with respect to the resin, so that silane coupling agents (vinyl silane, epoxy silane, (meth) acryl silane, isocyanate silane, chlorosilane, aminosilane, etc.) and titanate coupling are used. Agents (alkoxy titanate, amino titanate, etc.) or fatty acids (caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, etc., sorbic acid, elaidic acid, oleic acid , Unsaturated fatty acids such as linoleic acid, linolenic acid, erucic acid, etc.) and resin acids (abietic acid, pimaric acid, levopimaric acid, neoapitic acid, parastrinic acid, dehydroabietic acid, isopimaric acid, sandaracopimaric acid, columic acid, Secodehydroabietic acid, The hydroabietic acid) or the like, it is preferable that the surface has been treated.

  The amount of the heat conductive filler used is such that the heat conductivity of the heat conductive material obtained from the composition of the present invention can be increased, so that the volume ratio (%) of the heat conductive filler is high. Is preferably 25% by volume or more of the total composition. If it is less than 25% by volume, the thermal conductivity tends to be insufficient. When a higher thermal conductivity is desired, the amount of the thermally conductive filler used is more preferably 40% by volume or more in the total composition.

Here, the volume fraction (%) of the thermally conductive filler is calculated from the weight fraction and specific gravity of the resin component and the thermally conductive filler, and is obtained by the following equation. In the following formula, the thermally conductive filler is simply referred to as “filler”.
Filler volume ratio (volume%) = (filler weight ratio / filler specific gravity) ÷ [(resin weight ratio / resin weight specific gravity) + (filler weight ratio / filler specific gravity)] × 100
Here, the resin component refers to all components excluding the thermally conductive filler.

  Moreover, it is suitable to use together 2 or more types of thermally conductive fillers from which a particle diameter differs as one technique which raises the filling rate of the thermally conductive filler with respect to resin. In this case, it is preferable that the particle size ratio between the heat conductive filler having a large particle diameter and the heat conductive filler having a small particle diameter is about 10/1.

  These thermally conductive fillers can be used not only in the same type of thermally conductive filler but also in combination of two or more different types. Moreover, you may use various fillers other than a heat conductive filler as needed to such an extent that the effect of this invention is not prevented. Various fillers other than the heat conductive filler are not particularly limited, but wood powder, pulp, cotton chips, asbestos, glass fiber, carbon fiber, mica, walnut shell powder, rice husk powder, diatomaceous earth, white clay, silica ( Fumed silica, precipitated silica, fused silica, dolomite, silicic anhydride, hydrous silicic acid, amorphous spherical silica, etc.), reinforcing filler such as carbon black; diatomaceous earth, calcined clay, clay, talc, oxidation Titanium, bentonite, organic bentonite, ferric oxide, aluminum fine powder, flint powder, activated zinc white, zinc powder, zinc carbonate and shirasu balloon, glass microballoon, organic microballoon of phenol resin and vinylidene chloride resin, PVC powder, Filler such as resin powder such as PMMA powder; asbestos, glass fiber and glass filament Carbon fibers, Kevlar fibers, fibrous fillers such as polyethylene fiber and the like. Of these fillers, precipitated silica, fumed silica, fused silica, dolomite, carbon black, titanium oxide, talc and the like are preferable. Some of these fillers have a slight function as a heat conductive filler, and the composition and synthesis of carbon fibers, various metal powders, various metal oxides, and various organic fibers. Some methods, crystallinity, and crystal structures can be used as excellent thermal conductive fillers.

  The heat dissipating structure of the present invention can be used in an apparatus having a heating element inside, for example, an electronic device, a precision machine, an automobile and the like. In particular, it is suitable for small mobile devices such as mobile phones and laptop computers among electronic devices.

  Embodiments and effects of the present invention will be described below with reference to examples, but the present invention is not limited thereto.

  <Graphite film> [Graphite film A] [Preparation of polyimide film A] Dissolve 1 equivalent of pyromellitic dianhydride in a DMF (dimethylformamide) solution in which 1 equivalent of 4,4'-oxydianiline is dissolved. Thus, a polyamic acid solution (18.5% by mass) was obtained.

  While this solution was cooled, an imidation catalyst containing 1 equivalent of acetic anhydride, 1 equivalent of isoquinoline, and DMF was added to the carboxylic acid group contained in the polyamic acid to degas. Next, this mixed solution was applied onto an aluminum foil so as to have a predetermined thickness after drying. The mixed solution layer on the aluminum foil was dried using a hot air oven and a far infrared heater.

The drying conditions for film production when the finished thickness is 75 μm are shown below. The mixed solution layer on the aluminum foil was dried in a hot air oven at 120 ° C. for 240 seconds to form a self-supporting gel film. The gel film is peeled off from the aluminum foil, fixed to the frame, and heated in a hot air oven at 120 ° C. for 30 seconds, 275 ° C. for 40 seconds, 400 ° C. for 43 seconds, 450 ° C. for 50 seconds, and further with a far infrared heater 460 It was dried by heating stepwise at 23 ° C. for 23 seconds. As described above, a polyimide film A having a thickness of 75 μm (elasticity 3.1 GPa, water absorption 2.5%, birefringence 0.10, linear expansion coefficient 3.0 × 10 ⁻⁵ ° C. ⁻¹ ) was produced. .

  [Preparation of Carbonized Film A] A 75 μm thick polyimide film A was sandwiched between graphite plates, heated to 1000 ° C. in a nitrogen atmosphere using an electric furnace, and then heat treated at 1000 ° C. for 1 hour for carbonization treatment. (Carbonization treatment) was performed to obtain a carbonized film A.

[Production of Graphite Film A] Carbonized film A (length 200 mm × width 200 mm; area 400 cm ² ) is sandwiched from above and below by a plate-like smooth graphite plate of length 270 mm × width 270 mm × thickness 3 mm, 300 mm × width 300 mm. X It was held in a graphite container (container A) having a thickness of 60 mm and heated until the temperature of the container A reached 3000 ° C., and the carbonized film A was graphitized to produce a graphite film. The graphite film after the heat treatment was compressed in the thickness direction with a single plate press to obtain a graphite film A (thickness: 40 μm). The plane direction thermal diffusivity was 9.0 cm ² / s, the plane direction thermal conductivity was 1150 W / mK, the thickness direction thermal conductivity was 5.0 W / mK, and the thickness was 40 μm.

[Graphite Film B] Graphite film B is PGS graphite film “EYGS182310” manufactured by Matsushita Electric Industrial Co., Ltd. The plane direction thermal diffusivity was 7.2 cm ² / s, the plane direction thermal conductivity was 600 W / mK, and the thickness direction thermal conductivity was 5.0 W / mK.

[Graphite film C] The graphite film C is a natural graphite film produced by an expanding method. As a result of the measurement, the surface direction thermal diffusivity was 3.0 cm ² / s, the surface direction thermal conductivity was 200 W / mK, the thickness direction thermal conductivity was 6 W / mK, and the thickness was 50 μm.

[Graphite Film D] Graphite film D is a natural graphite film “λ300 μm product” manufactured by the expanding method, which is commercially available from Geltech Corporation. The plane direction thermal diffusivity was 3.0 cm ² / s, the plane direction thermal conductivity was 210 W / mK, the thickness direction thermal conductivity was 50 W / mK, and the thickness was 300 μm.

<Measurement of Thermal Conductivity of Graphite Film> The thermal conductivity of the graphite film is expressed by the following formula (1).
_{λ = α × d × C p} (1)
Calculated from In Equation (1), λ represents thermal conductivity, α represents thermal diffusivity, d represents density, and C _p represents specific heat capacity. The thermal diffusivity, density, and specific heat capacity of the graphite film were determined by the following method.

  <Measurement of thermal diffusivity in the plane direction of graphite film by optical alternating current method> The progress of graphitization was determined by measuring the thermal diffusivity in the plane direction of the film. The higher the thermal diffusivity, the more remarkable the graphitization. The thermal diffusivity was measured at 10 Hz in a 20 ° C. atmosphere by cutting a graphite film into a 4 mm × 40 mm sample shape using a thermal diffusivity measuring apparatus (LaserPit manufactured by ULVAC-RIKO Co., Ltd.) using an optical alternating current method. .

  <Measurement of thermal diffusivity and thermal conductivity in the thickness direction of the graphite film by the laser flash method> The measurement of thermal diffusivity and thermal conductivity in the thickness direction of the graphite film by the laser flash method was based on JIS R1611-1997. LFA-502 manufactured by Kyoto Electronics Industry Co., Ltd. was used. The graphite film was cut to a diameter of 10 mm, and both surfaces of the film were graphitized (graphitized), and then the thermal diffusivity was measured in the thickness direction by a laser flash method at room temperature. Moreover, the heat capacity of the graphite film was calculated from comparison with a reference standard substance Mo having a known heat capacity. The thermal conductivity in the thickness direction was calculated from the measured thermal diffusivity, density and heat capacity in the thickness direction of the graphite film.

<Density Measurement of Graphite Film> The density of the graphite film was calculated by dividing the mass (g) of the graphite film by the volume (cm ³ ) calculated by the product of the vertical, horizontal and thickness of the graphite film. In addition, the average value measured by arbitrary 10 points | pieces was used for the thickness of a graphite film. The higher the density, the more remarkable the graphitization.

  <Thickness measurement of graphite film> As a method of measuring the thickness of the graphite film, a film of 50 mm x 50 mm was kept at room temperature (25 ° C) using a thickness gauge (HEIDENHAIN-CERTO manufactured by HEIDENHAIN Co., Ltd.). Any 10 points were measured in a room and averaged to obtain a measured value.

  <Specific Heat Measurement of Graphite Film> The specific heat measurement of the graphite film is performed by using a thermal analysis system manufactured by SII Nano Technology, Inc., a differential scanning calorimeter DSC220CU, and a temperature increase condition of 10 ° C./min from 20 ° C. to 260 ° C. The measurement was carried out.

<Thermal Conductive Material Layer> [Synthesis Example 1 of Curable Acrylic Resin] Synthesis example of poly (acrylic acid-n-butyl) polymer A having a crosslinkable silyl group:
Under a nitrogen atmosphere, CuBr (1.09 kg), acetonitrile (11.4 kg), butyl acrylate (26.0 kg) and diethyl 2,5-dibromoadipate (2.28 kg) were added to a 250 L reactor, and 70-80 Stir at about 30 minutes. To this was added pentamethyldiethylenetriamine to initiate the reaction. 30 minutes after the start of the reaction, butyl acrylate (104 kg) was continuously added over 2 hours. During the reaction, pentamethyldiethylenetriamine was appropriately added so that the internal temperature became 70 ° C to 90 ° C. The total amount of pentamethyldiethylenetriamine used so far was 220 g. Four hours after the start of the reaction, volatile components were removed by heating and stirring at 80 ° C. under reduced pressure. Acetonitrile (45.7 kg), 1,7-octadiene (14.0 kg) and pentamethyldiethylenetriamine (439 g) were added thereto, and stirring was continued for 8 hours. The mixture was heated and stirred at 80 ° C. under reduced pressure to remove volatile components.

  Toluene is added to this concentrate to dissolve the polymer, diatomaceous earth is added as a filter aid, aluminum silicate and hydrotalcite are added as adsorbents, and an oxygen-nitrogen mixed gas atmosphere (oxygen concentration 6%) is set to an internal temperature of 100. The mixture was heated and stirred at ° C. The solid content in the mixed solution was removed by filtration, and the filtrate was heated and stirred at an internal temperature of 100 ° C. under reduced pressure to remove volatile components.

  Furthermore, aluminum silicate, hydrotalcite, and a heat deterioration inhibitor were added as adsorbents to this concentrate, and the mixture was heated and stirred under reduced pressure (average temperature of about 175 ° C., reduced pressure of 10 Torr or less).

  Further, aluminum silicate and hydrotalcite were added as adsorbents, an antioxidant was added, and the mixture was heated and stirred at an internal temperature of 150 ° C. in an oxygen-nitrogen mixed gas atmosphere (oxygen concentration 6%).

  Toluene was added to this concentrate to dissolve the polymer, and then the solid content in the mixed solution was removed by filtration. The filtrate was heated and stirred under reduced pressure to remove volatile matter, and the polymer having an alkenyl group was removed. Obtained.

Polymer having this alkenyl group, dimethoxymethylsilane (2.0 molar equivalents relative to alkenyl group), methyl orthoformate (1.0 molar equivalents relative to alkenyl group), platinum catalyst [bis (1,3-divinyl -1,1,3,3-tetramethyldisiloxane) platinum complex catalyst xylene solution: hereinafter referred to as platinum catalyst] (10 mg as platinum relative to 1 kg of polymer) is mixed and heated and stirred at 100 ° C. in a nitrogen atmosphere. did. After confirming disappearance of the alkenyl group, the reaction mixture was concentrated to obtain a poly (acrylic acid-n-butyl) polymer A having a dimethoxysilyl group at the terminal. The number average molecular weight of the obtained polymer was about 26000, and the molecular weight distribution was 1.3. When the average number of silyl groups introduced per molecule of the polymer was determined by ¹ H NMR analysis, it was about 1.8.

<Thermal conductive material layer> [Synthesis example 2 of curable acrylic resin] Synthesis example of poly (acrylic acid-n-butyl) polymer having a crosslinkable silyl group In the same manner as in Synthesis example 2, a monomer and an initiator. The poly (acrylic acid-n-butyl) polymer [P2] having dimethoxysilyl groups at almost both ends was obtained. The number average molecular weight of the obtained polymer was about 14,000, and the molecular weight distribution was 1.1. When the average number of silyl groups introduced per molecule of the polymer was determined by ¹ H NMR analysis, it was about 2.0.

  <Heat conductive material layer> [Production Example 1 of heat conductive curable composition] 100 parts by weight of polymer A obtained in Synthesis Example 1 of curable acrylic resin, plasticizer: UP-1020 (acrylic plasticizer , Manufactured by Toagosei Co., Ltd.) 100 parts by weight, antioxidant: 1 part by weight of Adeka Stub AO-60 (manufactured by Adeka), heat conductive filler: AS-40 (rounded alumina, manufactured by Showa Denko), 1130 parts by weight, dehydrating agent: 1 part by weight of A171 (vinyltrimethoxysilane, Toray Dow Corning Silicone) was thoroughly mixed by hand mixing, and then passed through three paint rolls three times to obtain various curable compositions. These curable compositions are defoamed with a vacuum defoaming apparatus, and then mixed with 2 parts by weight of a curing catalyst: Neostan U-220H (dibutyltin diacetylacetonate, manufactured by Nitto Kasei) to form a thermally conductive curable composition. Product A was obtained. The heat conductivity after curing was 2.1 W / mK.

  <Thermal Conductive Material Layer> [Production Example 2 of Thermally Conductive Curable Composition] 100 parts by weight of the polymer B obtained in Synthesis Example 2 of the curable acrylic resin, plasticizer: DIDP (diisodecyl phthalate, Jay 100 parts by weight of antioxidant, 1 part by weight of antioxidant: Adeka Stub AO-60 (manufactured by Adeka), heat conductive filler: 660 parts by weight of BF083 (aluminum hydroxide, Nippon Light Metal), dehydrating agent: A171 (vinyl tri) 1 part by weight of methoxysilane (Toray Dow Corning Silicone), thixotropic agent: 1 part by weight of Dispalon # 6500 (hydrogenated castor oil, manufactured by Enomoto Kasei), and after thorough mixing by hand, 3 times on 3 paint rolls Various curable compositions were obtained through this. These curable compositions are defoamed with a vacuum defoaming apparatus, and then mixed with 2 parts by weight of a curing catalyst: Neostan U-220H (dibutyltin diacetylacetonate, manufactured by Nitto Kasei) to form a thermally conductive curable composition. Product B was obtained. The thermal conductivity after curing was 1.7 W / mK.

  <Thermal Conductive Material Layer> [Production Example 3 of Thermally Conductive Curable Composition] 100 parts by weight of polymer B obtained in Synthesis Example 2 of curable acrylic resin, plasticizer: DIDP (diisodecyl phthalate, Jay 100 parts by weight of antioxidant, 1 part by weight of antioxidant: Adeka Stub AO-60 (manufactured by Adeka), heat conductive filler: 300 parts by weight of PTX-60 (spheroidized boron nitride, manufactured by Momentive Performance Materials), dehydrating agent : A171 (vinyltrimethoxysilane, manufactured by Toray Dow Corning Silicone) 1 part by weight, thixotropic agent: Disparon # 6500 (hydrogenated castor oil, manufactured by Enomoto Kasei), 3 parts after thoroughly stirring and mixing. Various curable compositions were obtained by passing through a paint roll three times. These curable compositions are defoamed with a vacuum defoaming apparatus, and then mixed with 2 parts by weight of a curing catalyst: Neostan U-220H (dibutyltin diacetylacetonate, manufactured by Nitto Kasei) to form a thermally conductive curable composition. Product C was obtained. The thermal conductivity after curing was 4.5 W / mK.

  <Measurement of Thermal Conductivity of Thermal Conductive Material Layer by Hot Disk Method> Using a hot disk method thermal conductivity measuring device TPA-501 (manufactured by Kyoto Electronics Co., Ltd.), a 4φ size sensor is a disk having a thickness of 3 mm and a diameter of 20 mm. The thermal conductivity of the heat conductive material layer was measured by a method of sandwiching the two samples. When a curable composition is used as the thermally conductive material layer, it is allowed to stand at 50 ° C. for 1 day after curing and at 23 ° C. and 50% humidity for 1 day. It was measured.

(Example 1) The heat dissipation structure of the present example has the following configuration. Referring to FIG. 1, a heating element 11 made of silicon having a width W _H1 5 mm × width W _H2 5 mm × thickness 1 mm and having an output 0.3 W has a width W _S1 50 mm × width W _S2 50 mm × thickness 0.8 mm. It is fixed to the central part of the substrate 12 made of epoxy resin. A protective film 17 made of polyethylene terephthalate (PET) resin having a thickness of 30 μm is formed on one side of a graphite film A (graphite film 16) having a width W _F1 50 mm × width W _F2 50 mm × thickness 40 μm, and the thickness is 30 μm on the other side. The heat diffusion film 13 (thickness: 100 μm) on which the adhesive layer 18 of the acrylic pressure-sensitive adhesive material is formed is supported at a position facing the heating element 11 and having a distance D of 0.16 mm. A thickness of 0.4 mm SUS is bonded to the inner surface of the support 14 having a thickness of 1.4 mm and laminated in such a manner that an ABS resin having a thickness of 1.0 mm comes to the outer surface. The heat conductive material layer 15 was provided by a method in which the heat generating body 11 was completely covered and the heat conductive curable composition A was applied and cured in contact with the substrate 12 and the heat diffusion film 13. The thermally conductive material layer 15 is in contact with the substrate 12 with a size of width W _G1 7 mm × width W _G2 7 mm. Here, the central part of the heating element 11 and the central part of the thermal diffusion film are opposed to each other. Regarding the heat dissipation structure of the example, the temperature T _H (° C.) of the center of the heating element after 600 seconds from the start of heat generation (when it reaches a constant temperature state) and the central part of the outer surface of the support (this part is the central part of the heating element) The heat dissipation characteristics were evaluated by measuring the temperature T _C (° C.) of (located directly above). The heating element center temperature T _H was 55.4 ° C., and the support outer surface center temperature T _C was 36.6 ° C.

(Example 2) Except that the distance D between the heating element 11 and the thermal diffusion film 13 was 0.32 mm, the heat dissipation property of the heat dissipation structure having the same configuration as that of Example 1 was evaluated. The heating element center temperature T _H was 75.3 ° C., and the support outer surface center temperature T _C was 35.2 ° C.

(Example 3) Except that the distance D between the heating element 11 and the thermal diffusion film 13 was 0.08 mm, the heat dissipation property of the heat dissipation structure having the same configuration as in Example 1 was evaluated. The heating element center temperature T _H was 44.5 ° C., and the support outer surface center temperature T _C was 37.2 ° C.

(Example 4) Except having used the graphite film B as the thermal-diffusion film 13, the heat dissipation of the thermal radiation structure which has the structure similar to Example 1 was evaluated. The heating element center temperature T _H was 55.5 ° C., and the support outer surface center temperature T _C was 37.4 ° C.

(Example 5) Except having used the graphite film C, the heat dissipation of the heat dissipation structure which has the same structure as Example 1 was evaluated. The heating element center temperature T _H was 56.3 ° C., and the support outer surface center temperature T _C was 37.0 ° C.

(Example 6) Except having used the graphite film D, the heat dissipation of the heat dissipation structure which has the same structure as Example 1 was evaluated. The heating element center temperature T _H was 58.2 ° C., and the support outer surface center temperature T _C was 38.8 ° C.

(Example 7) The heat dissipation of a heat dissipation structure having the same configuration as that of Example 1 was evaluated except that the heat conductive curable composition B was applied as the heat conductive material layer 15 and then cured. The heating element center temperature T _H was 56.2 ° C., and the support outer surface center temperature T _C was 37.8 ° C.

(Example 8) The heat dissipation of a heat dissipation structure having the same configuration as in Example 1 was evaluated except that the heat conductive curable composition C was applied as the heat conductive material layer 15 and then cured. The heating element center temperature T _H was 51.8 ° C., and the support outer surface center temperature T _C was 35.9 ° C.

Example 9 Referring to FIG. 2, a thermal diffusion film having a width W _{F1 of} 80 mm × width W _{F2 of} 50 mm × thickness of 100 μm was used, and an epoxy of width W _S1 30 mm × width W _S2 30 mm × thickness 0.8 mm A heat dissipating structure having the same configuration as that of Example 1 except that a resin substrate 12 is used and the central portion of the heating element 11 is opposed to a position 15 mm from the end of the short side of the heat diffusion film. The heat dissipation was evaluated. The heating element center temperature T _H was 51.2 ° C., and the support outer surface center temperature T _C was 35.3 ° C.

(Example 10) Referring to FIG. 3, a heating element 11a having an output of 0.3 W made of silicon having a width W _Ha1 5 mm × width W _Ha2 5 mm × thickness 1 mm, and width W _Hb1 5 mm × width W _Hb2 5 mm × thickness A heat generating element 11b made of silicon having a thickness of 1.2 mm and an output of 0.2 W, fixed to the center of an epoxy resin substrate 12 having a width W _S1 60 mm × width W _S2 30 mm × thickness 0.8 mm. A protective film 17 made of polyethylene terephthalate (PET) resin having a thickness of 30 μm is formed on one surface of a graphite film A (graphite film 16) having a width W _{F1 of} 80 mm × width W _{F2 of} 50 mm × thickness of 40 μm, and a thickness of 30 μm on the other surface. The thermal diffusion film 13 (thickness 100 μm) on which the adhesive layer 18 of acrylic adhesive material is formed is opposed to the heating element 11 and has a distance Da of 0.28 mm and a distance Db of 0.08 mm. In order to be supported at the position, 0.4 mm SUS in thickness is bonded to the inner surface of a support 14 having a thickness of 1.4 mm in a two-layer structure in which an ABS resin having a thickness of 1.0 mm is laminated on the outer surface. Yes. The heat conductive material layer 15 was provided by a method in which the heat generating body 11 was completely covered and the heat conductive curable composition A was applied and cured in contact with the substrate 12 and the heat diffusion film 13. The thermally conductive material layer 15 is in contact with the substrate 12 with a size of width W _G1 15 mm × width W _G2 7 mm. Here, the central part of the heating element 11a faces 15 mm from the short side end of the heat diffusion film, and the central part of the heating element 11b faces 45 mm from the short side end of the heat diffusion film. ing. For the heat dissipation structure of the example, the temperature T _H (° C.) of the center of the heating element after 600 seconds from the start of heat generation (when it reaches a constant temperature state) and the center of the outer surface of the support (this part is the center of the heating element) by measuring the temperature T _C of the position directly above) (° C.), to evaluate the heat radiation characteristics. The center temperature T _Ha of the heating element 11a is 57.5 ° C., the center temperature T _Ca of the support outer surface is 37.9 ° C., the center temperature T _Hb of the heating element 11b is 56.8 ° C., and the center temperature of the support outer surface is 56.8 ° C. T _Cb was 36.2 ° C.

(Comparative example 1) Except not having used the heat conductive material layer 15, the heat dissipation of the thermal radiation structure which has the structure similar to Example 1 was evaluated. The heating element center temperature T _H was 69.9 ° C., and the support outer surface center temperature T _C was 40.0 ° C.

(Comparative example 2) With reference to FIG. 4, without using the thermal diffusion film 13, the heat conductive material layer 15 and the support 14 are in direct contact, and the distance D between the heating element 11 and the support 14 is 0. Except for being 26 mm, the heat dissipation performance of the heat dissipation structure was evaluated in the same configuration as in Example 1. The heating element center temperature T _H was 67.8 ° C., and the support outer surface center temperature T _C was 44.2 ° C.

Comparative Example 3 Referring to FIG. 5, thermal conductive material layer 15 is in contact only with the top surface of heating element 11 and thermal diffusion film 13, and is in contact with the side surface of heating element 11 and substrate 12. Except for the absence, the heat dissipation property of the heat dissipation structure having the same configuration as in Example 1 was evaluated. The heating element center temperature T _H was 60.0 ° C., and the support outer surface center temperature T _C was 38.9 ° C.

Comparative Example 4 With reference to FIG. 5, the heat conductive material layer 15 is in contact only with the top surface of the heating element 11 and the thermal diffusion film 13, and is in contact with the side surface of the heating element 11 and the substrate 12. Except for the absence, the heat dissipation property of the heat dissipation structure having the same configuration as in Example 5 was evaluated. The heating element center temperature T _H was 61.9 ° C., and the support outer surface center temperature T _C was 40.4 ° C.

  Since Comparative Example 1 does not use a heat conductive material layer, Comparative Example 2 does not use a heat diffusion film, and in Comparative Examples 3 and 4, the heat conductive material layer does not sufficiently cover the heating element. Also, the heating element temperature and the temperature at the center of the outer surface of the support are high.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

10: heat dissipation structure, 11: heating element, 12: substrate, 13: thermal diffusion film, 14: support, 15: thermally conductive material layer, 16: graphite film, 17: protective film, 18: adhesive layer, S _F: area of the heat diffusion film, S _G: area of the thermally conductive material layer, S _H: area of the heat generating element, S _S: area of the substrate, T _C: supporting the outer surface center portion temperature, T _H: heating element center Temperature, W _F1 , W _F2 : width of the thermal diffusion film, W _G1 , W _G2 : width of the heat conductive material layer, W _H1 , W _H2 : width of the heating element, W _S1 , W _S2 : width of the substrate.

11a: heating element a, S _Ha : area of heating element a, T _Ca : temperature at the center of the outer surface of the support (heating element a side), T _Ha : temperature at the heating element a center, W _Ha1 , W _Ha2 : heating element a Width.

11b: heating element b, S _Hb : area of heating element b, T _Cb : center temperature of outer surface of support (heating element b side), T _Hb : heating element b center temperature, W _Hb1 , W _Hb2 : heating element b Width.

Claims (4)

A heating element, a substrate that fixes the heating element, a heat diffusion film, a support that supports the heat diffusion film so as to face the heating element, and heat that is in contact with the heating element, the heat diffusion film, and the substrate A conductive material layer, and the thermal diffusion film includes a film having a thermal conductivity in a plane direction of 100 W / mK or more and a thickness of 500 μm or less, and the thermal conductive material layer covers a surface of the heating element. The heat conductive material layer has a heat conductivity of 0.9 W / mK or more. The thermal diffusion film includes a graphite film having a thickness of 350 μm or less, wherein a thermal conductivity in a plane direction is 200 W / mK or more and a thermal conductivity in a thickness direction is 60 W / mK or less. Item 2. The heat dissipation structure according to Item 1. The thermally conductive material layer is a material obtained by applying a thermally conductive curable composition so as to be in contact with any of the heating element, the thermal diffusion film, and the substrate, and then curing the material. The heat dissipation structure according to claim 1 or 2. The heat-conductive material layer is a cured product of a heat-conductive curable composition containing at least a curable acrylic resin and a heat-conductive filler. The heat dissipation structure according to item.