JP5873244B2 - Heat dissipation board - Google Patents

Description

  The present invention relates to a heat dissipation board that dissipates heat from an element applied thereon, and more particularly, to a heat dissipation board made of a composite material including thermally conductive fibers disposed along a main surface of the substrate.

  When an element that generates a large amount of heat is mounted on an electronic circuit board, the temperature of the element rises during use, causing problems such as unstable operation of the element or early deterioration of the element life. Sometimes. In order to avoid such problems due to heat generation of the element, it is considered to dissipate the heat of the element through an electronic circuit board in addition to attaching a radiator to the element. In particular, for the latter method, many methods such as a method using an electronic circuit board provided with holes for heat dissipation and a method using an electronic circuit board made of a material such as a metal having good thermal conductivity are proposed. ing.

  For example, Patent Literature 1 discloses a composite material substrate in which a glass fiber mixed with a metal filler is impregnated with a resin. A metal filler having a high thermal conductivity is embedded in the substrate so as to extend in a random direction with respect to the main surface of the substrate, and the thermal anisotropy of the thermal conductivity of the substrate is reduced. The thermal conductivity is increased. Thereby, the heat of the element can be dissipated to the electronic circuit board.

  Further, for example, Patent Document 2 discloses a resin substrate made of an epoxy resin or the like in which organic polymer fibers such as polybenzazole fibers having high thermal conductivity are controlled and arranged in the thickness direction and the surface direction of an electronic circuit board. Yes. In a substrate in which such organic polymer fibers are embedded, the thermal conductivity in the fiber length direction is good. Therefore, in accordance with the desired direction of thermal conductivity of the electronic circuit board, the organic polymer fibers are oriented and arranged at a predetermined distribution ratio in the thickness direction and the surface direction to give thermal anisotropy to the board. Heat can be dissipated to the electronic circuit board.

  By the way, even if the thermal conductivity of the electronic circuit board itself is increased or the heat from the element that generates a large amount of heat is conducted to a predetermined part of the electronic circuit board, the heat dissipation from the electronic circuit board to the surrounding area is not sufficient. The temperature of the electronic circuit board gradually increases. In other words, the temperature of elements on other electronic circuit boards may rise and operation may become unstable.

  For example, in Patent Document 3, heat generated in an element is not accumulated in an electronic circuit board, but a composite material made of a composite material that can conduct heat to a relatively low temperature portion such as the outer periphery of the electronic circuit board to radiate the element. A material substrate is disclosed. In such an electronic circuit board, a plurality of connecting portions for fixing to a chassis or the like that accommodates the electronic circuit board are provided on the outer peripheral portion of the board, and the connecting portion is connected while covering the portion where the element having a large amount of heat generation is attached. A plurality of thermally conductive long fibers are oriented and arranged in a matrix. Almost no heat generated in the element is given to the matrix, but is dissipated from the thermally conductive long fibers to the chassis via the connecting portion on the outer periphery of the electronic circuit board. As a result, an increase in the temperature of the electronic circuit board can be prevented, and an increase in the temperature of the element thereon can also be prevented.

JP 2008-243976 A JP 2000-273196 A Japanese Patent Laid-Open No. 2004-22828

  If the heat capacity of the electronic circuit board is sufficiently large with respect to the amount of heat generated by the element, the heat of the element can be radiated to the electronic circuit board and the temperature rise of the element can be suppressed. However, when the substrate is downsized, the heat capacity is generally reduced. Even in such a case, when the heat radiation from the substrate to the periphery thereof is sufficiently possible as in the electronic circuit substrate disclosed in Patent Document 3, the temperature rise of the element and the substrate can be suppressed. However, it greatly depends on the design conditions for accommodating the substrate. In particular, in order to reduce the size, weight, and cost of the device, the electronic circuit board is downsized, and a general-purpose resin having relatively poor thermal conductivity is used for the chassis and the like. Countermeasures against heat generation of elements are required.

  The present invention has been made in view of such circumstances, and an object of the present invention is a composite material including thermally conductive fibers arranged in a direction along the main surface of the substrate, and is provided thereon. Another object of the present invention is to provide a heat dissipating substrate that excels in heat dissipation of the obtained element.

  The present invention is a heat radiating substrate made of a fiber reinforced composite material and dissipating the heat of an element applied thereon, and a plurality of thermally conductive fibers are placed on a plane while being in contact with each other in a direction perpendicular to the main surface. A plurality of arranged sheet bodies are laminated so as to be in contact with each other and embedded in a cured resin.

  According to this invention, the heat capacity of the heat dissipation substrate is increased by laminating a plurality of sheet bodies obtained by bringing a plurality of thermally conductive fibers into contact with each other in the thickness direction so as to contact each other. Heat can be dissipated to the electronic circuit board, and this heat can be dissipated in the direction of the surface of the sheet. That is, it is excellent in heat dissipation of the element given on such a heat dissipation board.

  In the above-described invention, an intermediate sheet member in which the heat conductive fibers are integrated like a felt may be inserted between the sheet members. According to this invention, the plurality of heat conductive long fibers of the sheet can be brought into contact with each other in the thickness direction, and the heat dissipation of the element applied on the heat dissipation substrate is excellent.

  In the above-described invention, the thermally conductive fiber may have a branch portion that extends in a direction substantially perpendicular to a main surface of the sheet body or the intermediate sheet body and connects the thermally conductive fibers to each other. . According to this invention, since the heat conductivity can be increased by bringing the plurality of heat conductive long fibers of the sheet body into contact with each other in the thickness direction, the heat dissipation of the element applied on the heat dissipation substrate is excellent.

  In the above-described invention, the heat conductive fibers may be characterized in that short fibers made of heat conductive fibers are dispersed between the sheet body or the intermediate sheet body. According to this invention, since the heat conductivity can be increased by bringing the plurality of heat conductive long fibers of the sheet body into contact with each other in the thickness direction, the heat dissipation of the element applied on the heat dissipation substrate is excellent.

  In the above-described invention, the thermally conductive fibers of the sheet body may be arranged by stitching long fibers together in a stitch-like manner. According to this invention, the plurality of heat conductive long fibers of the sheet can be brought into contact with each other in the thickness direction, and the heat dissipation of the element applied on the heat dissipation substrate is excellent.

  In the above-described invention, the thermally conductive fibers of the sheet body may be characterized in that long fibers are interwoven with each other. According to this invention, the plurality of heat conductive long fibers of the sheet can be brought into contact with each other in the thickness direction, and the heat dissipation of the element applied on the heat dissipation substrate is excellent.

  In the above-described invention, the thermally conductive fibers may have warp portions that are spaced apart from each other and arranged substantially in parallel. According to this invention, since the heat radiation efficiency in the surface direction in which the sheet body expands is increased, the heat radiation of the element applied on the heat radiation substrate is excellent.

  In the above-described invention, the thermally conductive fibers of the sheet body may be arranged so as to be accumulated in a felt-like manner. According to this invention, since the heat radiation efficiency in the surface direction in which the sheet body expands is increased, the heat radiation of the element applied on the heat radiation substrate is excellent.

It is the (a) perspective view of the thermal radiation board by this invention, and (b) the expanded sectional view of the principal part. It is the (a) top view of the principal part of the thermal radiation board by this invention, and (b) expanded sectional view. It is the (a) perspective view of the thermal radiation board by this invention, and (b) the expanded sectional view of the principal part. It is the (a) top view of the principal part of the thermal radiation board | substrate by this invention, and (b) sectional drawing. It is sectional drawing of the principal part of the thermal radiation board | substrate by this invention. It is the (a) perspective view of the thermal radiation board by this invention, and (b) the expanded sectional view of the principal part. It is the (a) top view of the principal part of the thermal radiation board | substrate by this invention, and (b) sectional drawing. It is a figure which shows the conditions and result of a verification test using the thermal radiation board | substrate by this invention.

<Example 1>
Details of the heat dissipation substrate 10 according to one embodiment of the present invention will be described with reference to FIGS. 1 and 2.

  As shown in FIG. 1, the heat dissipation substrate 10 is a substrate made of a fiber-reinforced composite material in which a plurality of laminated sheet bodies 1 are embedded in a resin 7 and fixed in a plate shape. In the resin 7, the plurality of sheet bodies 1 are laminated so as to contact each other in a direction perpendicular to the main surface. Here, as the resin 7, a thermosetting resin such as an epoxy resin or a thermoplastic resin such as an acrylic resin having a high insulating property can be used.

  As shown in FIG. 2, the sheet body 1 is a felt-like non-woven sheet in which fibers 3 to be described later are entangled in a random direction and accumulated on a plane so as to form a sheet. The laminated sheet bodies 1 have a large number of contacts that are in contact with each other in the direction perpendicular to the main surface by the fibers 3 protruding from the surface of the nonwoven fabric. Further, the fibers 3 of the sheet body 1 have branched nappings on the surface, and connect the fibers 3 to each other, particularly, the fibers 3 of the stacked sheet bodies 1. Here, a heat conductive fiber such as a carbon fiber having higher tensile strength than the resin 7 and excellent in heat conductivity can be used for the fiber 3. Further, the fiber 3 may be a PBO (polyparaphenylene benzobisoxazole) fiber having a high insulating property, an ultrahigh molecular weight polyethylene fiber, or the like.

  In addition, the short fiber (chopped strand) excellent in heat conductivity is inserted and distributed between the laminated sheet bodies 1. As such a short fiber, it is preferable to use a fiber having high tensile strength, excellent thermal conductivity, and high insulation properties as in the case of the fiber 3.

  Next, a method for manufacturing the heat dissipation substrate 10 will be described.

  First, the sheet body 1 is laminated to obtain a laminated body. At this time, short fibers are dispersed and arranged between the layers of the sheet body 1. Next, a so-called needle punch is applied to the laminated body of the sheet body 1 to raise the fibers 3 and the short fibers of the sheet body 1. In such a needle punch, it is carried out by repeatedly applying an operation of reciprocating a needle (needle) having fine protrusions in the laminated body of the sheet body 1 to pierce and extract in the thickness direction. The fibers 3 and a part of the short fibers are branched by the fine protrusions of the needles, and become brushed extending in the thickness direction that is the direction of the reciprocating movement of the needles. Next, the laminated body of the sheet body 1 is impregnated with the resin 7 in a liquid state before being cured, and the entire laminated body is spread so that the sheet body 1 is embedded. Thereafter, the resin 7 is cured into a plate shape to obtain the heat dissipation substrate 10.

  According to Example 1 described above, since the sheet body 1 is a felt-like non-woven sheet in which the fibers 3 are tangled in a random direction and accumulated on a plane, the fibers 3 are mutually connected to the main surface of the sheet body 1. It touches vertically. Further, the plurality of sheet bodies 1 are laminated so as to contact each other. In particular, the laminated sheet bodies 1 have a large number of contacts that are in contact with each other in the direction perpendicular to the main surface by the fibers 3 protruding from the surface of the nonwoven fabric. For this reason, the heat capacity of the heat dissipation substrate 10 is increased, and the thermal conductivity in the thickness direction is also increased. Thereby, the heat of the element given on this can be radiated to the heat radiating substrate 10, and this heat can be radiated in the surface direction in which the sheet body 1 spreads, that is, the direction along the main surface. That is, the heat dissipation substrate 10 is excellent in heat dissipation of the element applied thereon, and can suppress the temperature rise of the element. In addition, since the heat dissipation substrate 10 is made of a fiber-reinforced composite material, it can be made thinner and thinner than a substrate made of ceramics such as silicon nitride or aluminum nitride.

  Further, since the sheet body 1 is a felt-like nonwoven fabric sheet in which the fibers 3 are tangled in a random direction and accumulated on a plane, the heat dissipation efficiency in the surface direction in which the sheet body 1 spreads can be increased. That is, the heat dissipation efficiency in the surface direction in which the sheet body 1 of the heat dissipation substrate 10 expands can be increased. Therefore, the heat dissipation substrate 10 is more excellent in the heat dissipation of the element applied thereon.

  Further, the fibers 3 and the sheet bodies 1 are connected to each other by the raised portions extending in a direction substantially perpendicular to the main surface of the sheet body 1. Furthermore, since the short fibers are dispersedly arranged between the layers of the sheet body 1, the sheet bodies 1 are also connected to each other. By these, since the fibers 3 and the sheet bodies 1 can be connected to each other in the thickness direction to increase the thermal conductivity, the heat dissipation substrate 10 is further excellent in the heat dissipation of the element applied thereon.

<Example 2>
Details of a heat dissipation substrate 10a according to another embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 3, the heat dissipation substrate 10a is a substrate made of a fiber-reinforced composite material in which a plurality of laminated sheet bodies 1a and intermediate sheet bodies 2 are embedded in a resin 7 and fixed in a plate shape. In the resin 7, the plurality of sheet bodies 1 a and the intermediate sheet bodies 2 are alternately stacked so as to contact each other in a direction perpendicular to the main surface.

  As shown in FIG. 4, the sheet body 1 a is a stitch-like sheet in which a plurality of long fibers 3 ′ made of heat conductive fibers made of the same material as in the first embodiment are knitted together. The long fibers 3 ′ are pre-opened and arranged in the warp portion 4 so as to be spaced apart from each other in substantially parallel to each other. They are knitted to sew. As a result, the long fibers 3 ′ arranged in the warp yarn portion 4 and the weft yarn portion 5 come into contact with each other in the thickness direction of the sheet body 1 a.

  The intermediate sheet 2 inserted between the sheets 1a is a felt-like non-woven sheet in which fibers 3 similar to those in Example 1 are entangled in a random direction and accumulated on a flat surface so as to form a sheet. It is. The intermediate sheet body 2 has a large number of contacts that are in contact with each other in the direction perpendicular to the main surface between the sheet body 1a and the fibers 3 protruding from the surface of the nonwoven fabric.

  Furthermore, as shown in FIG. 5, the sheet body 1 a has raised hairs 6 that branch from the long fibers 3 ′ so as to extend in a direction substantially perpendicular to the main surface and connect the long fibers 3 ′. Similar raising is given to the intermediate sheet 2. In addition, short fibers excellent in heat conduction similar to those in Example 1 are inserted and distributed between the sheet body 1a and the intermediate sheet body 2.

  Next, a method for manufacturing the heat dissipation substrate 10a will be described.

  First, the sheet body 1a and the intermediate sheet body 2 are alternately stacked to obtain a stacked body. At this time, short fibers are dispersedly arranged between the sheet body 1 a and the intermediate sheet body 2. Next, needle punching is applied to the laminate of the sheet body 1a and the intermediate sheet body 2 to raise the long fibers 3 'of the sheet body 1a and the fibers 3 and short fibers of the intermediate sheet body 2. The impregnation and curing of the resin 7 are the same as in Example 1.

  According to the second embodiment described above, the plurality of long fibers 3 'knitted on the sheet body 1a are in contact with each other in the thickness direction, so that the heat capacity of the heat dissipation substrate 10a can be increased as in the first embodiment. In addition, the long fibers 3 ′ spaced apart from each other in the warp portion 4 can improve the heat dissipation efficiency in the surface direction in which the sheet body expands. That is, the heat dissipation substrate 10a is excellent in heat dissipation of the element applied thereon and can suppress the temperature rise of the element.

  Further, the fibers 3 oriented in a random direction of the intermediate sheet 2 which is a non-woven sheet has a large number of contacts with the sheet 1a, and the thermal conductivity in the thickness direction can be increased. Further, the raised fibers 6 extending in a direction substantially perpendicular to the main surfaces of the sheet body 1 a and the intermediate sheet body 2 connect the long fibers 3 ′ and the fibers 3, and the sheet body 1 a and the intermediate sheet body 2 are connected to each other. . Moreover, since the short fibers are dispersed and arranged between the sheet body 1a and the intermediate sheet body 2, the layers of the sheet body 1a and the intermediate sheet body 2 are connected to each other. Also by these, the heat conductivity in the thickness direction can be increased, so that the heat dissipation substrate 10a is more excellent in heat dissipation of the element applied thereon.

  Although FIG. 4 shows an embodiment in which the long fibers 3 ′ arranged in the weft portion 5 are knitted into the long fibers 3 ′ arranged in the warp portion 4 like wave stitches, other known sewing methods are shown. May be knitted together. Further, the material and thickness of the long fibers 3 ′ used for the warp yarn portion 4 and the weft yarn portion 5, the presence / absence of opening, etc. may be different.

<Example 3>
Details of a heat dissipation board 10b according to another embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 6, the heat dissipation substrate 10b is a substrate made of a fiber-reinforced composite material in which a plurality of laminated sheet bodies 1b and intermediate sheet bodies 2 are embedded in a resin 7 and fixed in a plate shape. In the resin 7, the plurality of sheet bodies 1 b and the intermediate sheet bodies 2 are alternately stacked so as to contact each other in a direction perpendicular to the main surface.

  As shown in FIG. 7, the sheet body 1 b is a cloth-like sheet in which a plurality of long fibers 3 ′ made of heat conductive fibers similar to those in the first and second embodiments are woven together. The long fibers 3 ′ are pre-opened and arranged in the warp portion 4 so as to be spaced apart from each other in parallel, and the plurality of long fibers 3 ′ arranged in the weft yarn portion 5 so as to be substantially parallel to each other are floated alternately and plain weave. Is interwoven. Thereby, the long fibers 3 ′ arranged in the warp yarn portion 4 and the weft yarn portion 5 come into contact with each other in the thickness direction of the sheet body 1 b. Moreover, the continuous fiber 3 'opened in the weft portion 5 can be arranged. By opening the long fibers 3 ′ of the warp portion 4 and / or the weft portion 5, the long fibers 3 ′ can be arranged uniformly, the sheet body 1 b can be homogenized, and the thickness of the sheet body 1 b is reduced. Can do. Thereby, the thickness of the heat dissipation substrate 10b can be reduced.

  The intermediate sheet body 2 inserted between the sheet bodies 1b is a nonwoven fabric sheet similar to that of the second embodiment. The intermediate sheet 2 has a large number of contacts that are in contact with each other in the direction perpendicular to the main surface between the sheet 1b and the fibers 3 protruding from the surface of the nonwoven fabric.

  Further, the sheet body 1b and the intermediate sheet body 2 have raised fibers branched from the long fibers 3 'and the fibers 3 similar to those in the second embodiment. Further, short fibers excellent in heat conduction similar to those in Example 1 and Example 2 are inserted and distributed between the sheet body 1b and the intermediate sheet body 2.

  Since the manufacturing method of the heat dissipation board 10b is the same as that of the heat dissipation board 10a of the second embodiment, the description thereof is omitted.

  According to Example 3 described above, since the plurality of long fibers 3 ′ interwoven with the sheet body 1 b are in contact with each other in the thickness direction, the heat capacity of the heat dissipation substrate 10 b is increased as in Examples 1 and 2. it can. In addition, the long fibers 3 ′ arranged in the warp portion 4 so as to be spaced apart from and parallel to each other increase the heat radiation efficiency in the surface direction in which the sheet body expands. That is, the heat dissipation substrate 10b is excellent in heat dissipation of the element applied thereon and can suppress the temperature rise of the element.

  In addition, the fibers 3 facing the random direction of the intermediate sheet 2 that is a non-woven sheet has many contacts with the sheet 1b, and the thermal conductivity in the thickness direction can be increased. Further, the raised fibers 6 extending in a direction substantially perpendicular to the main surfaces of the sheet body 1b and the intermediate sheet body 2 connect the long fibers 3 'and the fibers 3 to each other, and the sheet body 1b and the intermediate sheet body 2 are connected to each other. . Moreover, since the short fibers are dispersed and arranged between the sheet body 1b and the intermediate sheet body 2, the layers of the sheet body 1b and the intermediate sheet body 2 are connected to each other. Also by these, since the thermal conductivity in the thickness direction can be increased, the heat dissipation substrate 10b is excellent in the heat dissipation of the element applied thereon.

  The weaving method of the sheet body 1 may be twill weaving, satin weaving, etc., but the weaving method capable of increasing the contact in the thickness direction between the long fibers 3 ′ of the sheet body 1b is preferable, It is preferable because the thermal conductivity in the thickness direction can be improved. In addition, the material and thickness of the long fibers 3 ′ arranged in the warp portion 4 and the weft portion 5 may be appropriately changed according to the required opportunity strength.

<Verification test>
In the heat dissipation substrate constituting the sheet body by the cloth-like sheet of Example 3 described above, when raising the sheet body, when providing short fibers between the layers, when inserting an intermediate sheet body made of nonwoven fabric between the layers The change of the thermal conductivity about each of was verified.

  Under each condition shown in FIG. 8, sheet bodies obtained by plain weaving long fibers of PBO fibers were laminated, and a heat dissipation board in which these laminated bodies were embedded in an epoxy resin was produced, and each was used as a test piece. In addition, the test pieces 1-5 have laminated | stacked the sheet | seat body of 2 layers, and the test pieces 6-10 laminated | stacked 6 layers. In addition to the test pieces 1 and 6, a predetermined needle punch is applied to raise the brush. Further, short fibers made of PBO fibers having a length of 1 mm for test pieces 3 and 8 and 3 mm for test pieces 4 and 9 were dispersed and arranged between the layers of the sheet body. Further, in the test pieces 5 and 10, an intermediate sheet body made of a nonwoven fabric in which PBO fibers were accumulated in a felt-like manner between the sheet bodies was inserted.

  The thickness of each test piece was measured with a micrometer and used for calculation of thermal conductivity. That is, for the calculation of thermal conductivity, the thermal diffusivity measured by a thermal diffusivity measuring device using a xenon lamp in accordance with JIS H7801, and the density measured by an underwater substitution method in accordance with A method of JIS K7112. And the specific heat capacity measured by differential scanning calorimetry based on JIS K7123 were used. FIG. 8 shows the thickness of the obtained test piece, the thermal conductivity in the thickness direction, and the thermal conductivity in the direction parallel to the main surface (plane direction).

  As shown in FIG. 8, when each of the test piece 1 and the test piece 2 and the test piece 5 and the test piece 6 are compared, the thickness of the test piece is changed without changing the thermal conductivity in the plane direction by applying the needle punch. The lateral thermal conductivity can be significantly increased. That is, it is considered that the raising was obtained by the needle punch, and the long fibers and the sheet bodies were thereby connected.

  Next, when the test pieces 2, 3 and 4 are compared, the thermal conductivity in the thickness direction increases in order. Moreover, when the test pieces 7, 8, and 9 were compared, the thermal conductivity in the thickness direction was almost the same. Combined with these results, the thermal conductivity in the thickness direction can be increased by inserting the short fibers and making the inserted short fibers longer. That is, since the sheet bodies are connected to each other by the short fibers, it is considered that the number of connected portions can be increased by lengthening the short fibers.

  Moreover, when each of the test pieces 2 and 5 and the test pieces 7 and 10 are compared, the thermal conductivity in the thickness direction can be increased when an intermediate sheet is inserted between the layers. That is, it is considered that the intermediate sheet body made of non-woven fabric can increase the number of contacts that are in contact with the main surface in the direction perpendicular to the main surface between the sheet body.

  As described above, it is possible to improve the thermal conductivity in the thickness direction by imparting raising, dispersing and arranging short fibers, and inserting an intermediate sheet made of nonwoven fabric. That is, these can provide a heat dissipation substrate that is more excellent in heat dissipation of the element.

  So far, representative embodiments and modifications based thereon have been described. However, the present invention is not necessarily limited thereto, and those skilled in the art will understand the gist of the present invention or the scope of the appended claims. Various alternative embodiments and modifications may be found without departing from the invention. The heat dissipation substrate according to the present invention can be employed not only as an electronic circuit substrate, but also as an insulating substrate used in a power device package such as an insulated gate bipolar transistor.

1, 1a, 1b Sheet body 2 Intermediate sheet body 3 Fiber 3 'Long fiber 6 Raised 7 Resin 10, 10a, 10b Heat dissipation board

Claims (6)

A heat dissipating board made of a fiber reinforced composite material and dissipating the heat of the element applied thereon,
A plurality of sheet bodies composed of warp and weft yarns provided with a plurality of thermally conductive fibers spaced apart and substantially parallel to each other are laminated in a cured resin so as to contact each other and dissipate heat in the surface direction in which the sheet body expands. In the cured resin, a branch portion branched from the surface of the thermally conductive fiber extends in a direction substantially perpendicular to the main surface of the sheet body and connects the thermally conductive fibers of the plurality of sheet bodies. A heat dissipating board characterized in that it has a large heat capacity by being embedded in the heat sink.   The heat dissipation board according to claim 1, wherein an intermediate sheet body in which the heat conductive fibers are integrated in a felt-like manner is inserted between the sheet bodies.   The heat dissipation substrate according to claim 2, wherein the heat conductive fiber has a branch portion that extends in a direction substantially perpendicular to a main surface of the intermediate sheet body and connects the heat conductive fibers to each other.   The heat dissipation substrate according to claim 1, wherein short fibers made of thermally conductive fibers are dispersed between the sheet body or the intermediate sheet body.   The heat radiating substrate according to claim 1, wherein the sheet body is formed by weaving the warp yarn and the weft yarn in a stitch-like manner. The heat radiating substrate according to claim 1, wherein the sheet body is formed by weaving the warp and the weft.