Heat transfer member and electronic device

Abstract

This heat transfer member comprises a plurality of graphite blocks that have a structure in which a plurality of graphenes are stacked in a first direction, and a protection structure that protects the plurality of graphite blocks. The protective structure is physically and thermally connected to the plurality of graphite blocks. The graphite blocks have anisotropy in terms of thermal conductivity and thermal expansion coefficient. In the first direction, the thermal conductivity of the protective structure is greater than the thermal conductivity of the graphite blocks. In a direction orthogonal to the first direction, the thermal conductivity of the graphite blocks is greater than the thermal conductivity of the protective structure. In the first direction, the thermal expansion coefficient of the graphite blocks is greater than the thermal expansion coefficient of the protective structure. In a direction orthogonal to the first direction, the thermal expansion coefficient of the protective structure is greater than the thermal expansion coefficient of the graphite blocks. The protective structure has one plate member, and the plurality of graphite blocks are positioned side by side on one principal surface of the plate member.

Description

Heat transfer member and electronic device

[0001] The present disclosure relates to a heat transfer member and an electronic device.

[0002] Conventionally, a technique using graphite as a heat transfer member has been proposed (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2021-150358

[0004] The heat transfer member of the present disclosure includes a plurality of graphite blocks and a protective structure. The graphite blocks have a structure in which a plurality of graphenes are stacked in a first direction. The protective structure protects the plurality of graphite blocks. The protective structure is physically and thermally connected to the plurality of graphite blocks. The graphite blocks have anisotropy in thermal conductivity and thermal expansion coefficient. In the first direction, the thermal conductivity of the protective structure is greater than that of the graphite blocks. In a direction perpendicular to the first direction, the thermal conductivity of the graphite blocks is greater than that of the protective structure. In the first direction, the thermal expansion coefficient of the graphite blocks is greater than that of the protective structure. In a direction perpendicular to the first direction, the thermal expansion coefficient of the protective structure is greater than that of the graphite blocks. The protective structure includes a plate material. The plurality of graphite blocks are positioned side by side on one main surface of the plate material.

[0005] FIG. 1 is a perspective view showing an example of the configuration of a graphite block according to an embodiment. FIG. 2 is an enlarged cross-sectional view showing an example of the configuration of a first surface of a graphite block according to an embodiment. FIG. 3 is an enlarged cross-sectional view showing an example of the configuration of a second surface and a third surface of a graphite block according to an embodiment. FIG. 4 is a perspective view showing an example of an arrangement of a plurality of graphite blocks included in a heat transfer member according to an embodiment. FIG. 5 is a perspective view showing an example of the configuration of a heat transfer member according to an embodiment. FIG. 6 is a cross-sectional view taken along line A-A in FIG. 5. FIG. 7 is a diagram illustrating a configuration near the interface between a graphite block and a bonding material according to an embodiment. FIG. 8 is a side view showing an example of the configuration of an electronic device according to an embodiment. FIG. 9 is a side view showing another example of the configuration of an electronic device according to an embodiment. FIG. 10 is a cross-sectional view showing an example of the configuration of a heat transfer member according to another embodiment. FIG. 11 is a perspective view showing an example of the configuration of a heat transfer member according to another embodiment. FIG. 12 is a cross-sectional view taken along line B-B in FIG. 11. FIG. 13 is a cross-sectional view showing an example of the configuration of a heat transfer member according to another embodiment. FIG. 14 is a perspective view showing an example of the configuration of a graphite base according to another embodiment. Fig. 15 is a perspective view showing an example of the configuration of a heat transfer member according to another embodiment 4. Fig. 16 is a cross-sectional view taken along line CC shown in Fig. 15. Fig. 17 is a perspective view showing an example of the configuration of an electronic device according to another embodiment 4. Fig. 18 is a cross-sectional view taken along line DD shown in Fig. 17. Fig. 19 is a perspective view showing an example of the configuration of a heat transfer member according to another embodiment 5.

[0006] Hereinafter, a heat transfer member and an electronic device according to the present disclosure (hereinafter referred to as "embodiments") will be described in detail with reference to the drawings. Note that the present disclosure is not limited to these embodiments. Furthermore, the embodiments can be appropriately combined within the scope of not causing any contradiction in the processing content. Furthermore, the same components in the following embodiments will be assigned the same reference numerals, and redundant explanations will be omitted.

[0007] Graphite blocks are known as a material with high heat transfer performance, but they are more brittle than metals such as copper.

[0008] Therefore, there is a need to provide a heat transfer member and an electronic device that have high heat transfer performance and toughness.

[0009] <Heat Transfer Member> First, the configuration of a heat transfer member 1 according to the embodiment will be described with reference to Fig. 1 to Fig. 7. The heat transfer member 1 according to the embodiment (see Fig. 5) may include a plurality of graphite blocks 10. Fig. 1 is a perspective view showing an example of the configuration of a graphite block 10 according to the embodiment.

[0010] 1 , the graphite block 10 may have a structure in which a plurality of graphenes 11 are stacked in a first direction A1. The graphenes 11 may be a sheet-like substance in which a honeycomb structure formed by bonding carbon atoms is spread in two dimensions.

[0011] The graphenes 11 may extend in a direction perpendicular to the first direction A1, for example, along the second direction A2 and the third direction A3. In the graphite block 10, adjacent graphenes 11 may be bonded to each other by intermolecular forces, which are van der Waals forces.

[0012] In the drawings referred to below, for ease of understanding, an orthogonal coordinate system consisting of a first direction A1, a second direction A2, and a third direction A3 that are orthogonal to one another may be shown.

[0013] The graphite block 10 may have a rectangular parallelepiped shape and may have a pair of first surfaces 10a, a pair of second surfaces 10b, and a pair of third surfaces 10c.

[0014] The first surface 10a may be a surface intersecting the first direction A1, for example, a surface perpendicular to the first direction A1. The first surface 10a may be a surface in which the graphene 11 spreads in a two-dimensional direction.

[0015] The second surface 10b is a surface extending along the first direction A1 and may be, for example, a surface perpendicular to the third direction A3. The second surface 10b may be a surface on which a plurality of layers of graphene 11 appear.

[0016] The third surface 10c is a surface that intersects with the second surface 10b and extends along the first direction A1, and may be, for example, a surface that is perpendicular to the second direction A2. The third surface 10c may be a surface on which multiple layers of graphene 11 appear, or may be a surface that has an area smaller than that of the second surface 10b.

[0017] Hereinafter, a surface on which graphene 11 spreads in a two-dimensional direction, for example, first surface 10a, will also be referred to as a "crystal surface," and a surface on which a layer of graphene 11 appears, for example, second surface 10b and third surface 10c, will also be referred to as a "crystal layer surface." In addition, in the drawings referred to below, a "crystal surface" will be represented by a honeycomb pattern, and a "crystal layer surface" will be represented by a striped pattern.

[0018] Graphite block 10 may have anisotropy in its brittleness. As the anisotropy in its brittleness, graphite block 10 may have a property of being easily cleaved along a plane in which graphene 11 extends in a two-dimensional direction, i.e., a plane intersecting first direction A1. Cleavage means breaking along a certain plane.

[0019] Furthermore, as an anisotropy of the brittleness property, graphite block 10 may have a property in which graphene 11 located on a crystal plane is easily peeled off when stress is generated along the plane direction of the crystal plane.

[0020] Furthermore, the graphite block 10 may have a property that the edge portion E1 of the graphene 11 shown in Fig. 2 is weak and easily breaks from the edge portion E1. Fig. 2 is an enlarged cross-sectional view showing an example of the configuration of the first surface 10a of the graphite block 10 according to the embodiment.

[0021] As a specific material, the graphite block 10 may be mainly composed of pyrolytic graphite. In the present disclosure, the term "main component" means that the volume ratio is 50% or more.

[0022] Pyrolytic graphite may be produced, for example, as follows: Pyrolytic graphite is produced by, for example, evaporating and laminating hydrocarbons, followed by pressure annealing.

[0023] The graphite block 10 may have anisotropy in thermal conductivity and thermal expansion coefficient. The graphite block 10 may have very high thermal conductivity in directions along the crystal planes, for example, in the second direction A2 and the third direction A3.

[0024] The thermal conductivity of graphite block 10 in second direction A2 and third direction A3 may be, for example, 200 W / m·K or more.

[0025] On the other hand, the thermal conductivity of the graphite block 10 in the first direction A1 may be lower than the thermal conductivity in the second direction A2 or the third direction A3, for example, 7 W / m·K.

[0026] The thermal conductivity of the graphite block 10 in the second direction A2 and the third direction A3 may be preferably 370 W / m·K or more, more preferably 450 W / m·K or more, and even more preferably 800 W / m·K or more.

[0027] In the embodiment, the thermal conductivity of the graphite block 10 in the second direction A2 and the third direction A3 may be 1200 W / m·K or more, more specifically, approximately 1700 W / m·K.

[0028] The graphite block 10 may have a very high thermal expansion coefficient in the first direction A1. The thermal expansion coefficient of the graphite block 10 in the first direction A1 may be, for example, 20×10 －６ / K or more. In the present disclosure, when the term "coefficient of thermal expansion" is simply mentioned, it means the linear expansion coefficient.

[0029] The thermal expansion coefficient of the graphite block 10 in the first direction A1 is preferably 24×10 －６ / K or more. The thermal expansion coefficient of the graphite block 10 in the first direction A1 may be 27×10 －６ / K or less.

[0030] On the other hand, the thermal expansion coefficient in the directions along the crystal planes of the graphite block 10, for example, in the second direction A2 and the third direction A3, is, for example, 0.050×10－６ / K, or may be a value lower than the thermal expansion coefficient in the first direction A1.

[0031] The thermal expansion coefficients of the graphite block 10 in the second direction A2 and the third direction A3 may be negative values, specifically, −0.001×10 －６ / K or less. The thermal expansion coefficient of the graphite block 10 in the second direction A2 and the third direction A3 may be −0.01×10 －６ / K or more.

[0032] In graphite block 10, the surface roughness of first surface 10a, which is a crystal plane, may be smaller than the surface roughness of second surface 10b and third surface 10c, which are crystal layer planes. Specifically, the surface roughness of second surface 10b and third surface 10c may be 20 times or more, 10 times or more but less than 20 times, or 5 times or more but less than 10 times the surface roughness of first surface 10a.

[0033] In the present disclosure, the term "surface roughness" refers to the arithmetic mean roughness Ra defined in JIS_B_0601:2001.

[0034] In this way, by reducing the surface roughness of the first surface 10a, the edge portions E1 (see FIG. 2 ) of the graphene 11 appearing on the first surface 10a are reduced, and therefore, according to the embodiment, the brittleness of the first surface 10a can be reduced.

[0035] 3 is an enlarged cross-sectional view showing an example of the configuration of the second surface 10b and the third surface 10c of the graphite block 10 according to the embodiment. As shown in FIG. 3, the second surface 10b and the third surface 10c of the graphite block 10 may include relatively large irregularities due to the above-described surface roughness, or may have recesses F1. Note that in the present disclosure, the irregularities included in the second surface 10b and the third surface 10c may be fine irregularities.

[0036] Fig. 4 is a perspective view showing an example of the arrangement of a plurality of graphite blocks 10 included in the heat transfer member 1 according to the embodiment. As shown in Fig. 4, in the embodiment, the heat transfer member 1 (see Fig. 5) may have a plurality of graphite blocks 10, three in the figure. This allows for greater freedom in designing the heat transfer member 1.

[0037] In the embodiment, as shown in FIG. 4, the plurality of graphite blocks 10 included in the heat transfer member 1 may be arranged in a row with the first surfaces 10a (see FIG. 1) facing each other.

[0038] That is, in the heat transfer member 1 according to the embodiment, the plurality of graphite blocks 10 may be arranged in a line along the first direction A1. Note that in the heat transfer member 1 according to the embodiment, the adjacent graphite blocks 10 may be in close contact with each other or may have a small gap therebetween.

[0039] In the present disclosure, the plurality of graphite blocks 10 may be produced by cutting a larger-sized graphite block along the stacking direction of the graphene 11 using a processing machine such as a wire saw.

[0040] Although the following drawings show an example in which a plurality of graphite blocks 10 of the same size are arranged side by side along the first direction A1, the present disclosure is not limited to such an example. For example, in the present disclosure, a plurality of graphite blocks 10 may be arranged side by side along the second direction A2 or the third direction A3.

[0041] In the present disclosure, a plurality of graphite blocks 10 of different sizes may be arranged side by side, and the heat transfer member 1 may include two or four or more graphite blocks 10.

[0042] Fig. 5 is a perspective view showing an example of the configuration of the heat transfer member 1 according to the embodiment. Fig. 6 is a cross-sectional view taken along line A-A in Fig. 5. As shown in Figs. 5 and 6, the heat transfer member 1 according to the embodiment may include a plurality of graphite blocks 10, a protective structure 20, and a bonding material 30. Note that the bonding material 30 is not shown in Fig. 5.

[0043] The protective structure 20 protects the plurality of graphite blocks 10. The protective structure 20 may include a plate member 21A and a plate member 21B. The plate member 21B is an example of another plate member.

[0044] 6, main surface 21A1 of plate material 21A may be positioned to face one of a plurality of second surfaces 10b that are substantially flush with each other in a plurality of graphite blocks 10. In other words, in heat transfer member 1 according to this embodiment, a plurality of graphite blocks 10 may be positioned side by side on one main surface 21A1 of plate material 21A.

[0045] This reduces the force that would cleave graphite block 10, thereby achieving high toughness of heat transfer member 1. Plate material 21A may be bonded to one of the second surfaces 10b of the plurality of graphite blocks 10 by bonding material 30, thereby being physically and thermally connected to the plurality of graphite blocks 10.

[0046] In addition, in the embodiment, plate material 21A and plate material 21B may be positioned so as to sandwich a plurality of graphite blocks 10 therebetween.

[0047] That is, main surface 21B1 of plate material 21B may be positioned to face the other second surfaces 10b of the plurality of graphite blocks 10 that are positioned substantially flush with each other. In other words, in heat transfer member 1 according to this embodiment, the plurality of graphite blocks 10 may be positioned side by side on one main surface 21B1 of plate material 21B.

[0048] This reduces the force that would cleave graphite block 10, thereby achieving high toughness of heat transfer member 1. Plate material 21B may be joined to the other second surfaces 10b of the plurality of graphite blocks 10 by joining material 30, thereby being physically and thermally connected to the plurality of graphite blocks 10.

[0049] Furthermore, in heat transfer member 1 according to the embodiment, plate material 21A and plate material 21B may both be joined to the crystal layer surfaces of a plurality of graphite blocks 10. That is, in the embodiment, plate material 21A and plate material 21B may be positioned so that any one of a plurality of surfaces extending along first direction A1 in graphite block 10 faces main surface 21A1 of plate material 21A or main surface 21B1 of plate material 21B.

[0050] This reduces the force that would cleave the graphite block 10 , thereby achieving high toughness for the heat transfer member 1 .

[0051] Furthermore, by joining the plate materials 21A and 21B to the crystal layer surface, which has a surface roughness greater than that of the crystal surface, the joining material 30 is positioned in the recess F1 (see Figure 3) of the crystal layer surface, which produces an anchor effect and improves the adhesion of the plate materials 21A and 21B to the graphite block 10.

[0052] Therefore, according to the embodiment, it is possible to reduce the likelihood that plate material 21A and plate material 21B will peel off from graphite block 10. Furthermore, by positioning bonding material 30 within recess F1 of the unevenness, it is possible to reduce the thermal resistance between plate material 21A and plate material 21B and graphite block 10, compared to a configuration in which a gap is created in recess F1.

[0053] In the embodiment, the thermal conductivity of the plate material 21A may be highly isotropic compared to that of the graphite block 10. In addition, the thermal conductivity of the plate material 21A may be greater than the thermal conductivity of the graphite block 10 in the first direction A1.

[0054] Furthermore, in directions perpendicular to the first direction A1, such as the second direction A2 and the third direction A3, the thermal conductivity of the graphite block 10 may be greater than the thermal conductivity of the plate material 21A.

[0055] According to this configuration, when heat is applied to a part of plate material 21A from outside heat transfer member 1, the heat is isotropically dispersed in plate material 21A and then conducted to graphite block 10. Then, in graphite block 10, the heat is quickly dispersed in second direction A2 and third direction A3, which have high thermal conductivity.

[0056] In this way, in the heat transfer member 1 according to the embodiment, even if heat is applied to a part of the plate material 21A, the heat can be dispersed over a wide area of ​​the graphite block 10. Therefore, according to the embodiment, the heat transfer member 1 can achieve high heat transfer performance.

[0057] In the embodiment, the thermal conductivity of the plate material 21B may be highly isotropic compared to that of the graphite block 10. In addition, the thermal conductivity of the plate material 21B may be higher than that of the graphite block 10 in the first direction A1.

[0058] Furthermore, in directions perpendicular to the first direction A1, such as the second direction A2 and the third direction A3, the thermal conductivity of the graphite block 10 may be greater than the thermal conductivity of the plate material 21B.

[0059] With this configuration, when heat is applied to a part of the plate material 21A from outside the heat transfer member 1, and this heat is quickly dispersed in the second direction A2 and the third direction A3, which have high thermal conductivity, by the graphite block 10, this heat is conducted to the plate material 21B and dispersed isotropically in the plate material 21B.

[0060] Furthermore, since a wide area of ​​the plate material 21B is thermally connected to the support body that supports the heat transfer member 1, heat can be dissipated from a wide area of ​​the plate material 21B. Therefore, according to the embodiment, high heat transfer performance of the heat transfer member 1 can be achieved.

[0061] The plate materials 21A and 21B may be made of a material having a thermal conductivity of 20 W / m·K or more and less than 400 W / m·K.

[0062] In the embodiment, the plate material 21A may have a higher thermal expansion coefficient and be isotropic than the graphite block 10. In addition, the thermal expansion coefficient of the graphite block 10 may be higher than the thermal expansion coefficient of the plate material 21A in the first direction A1.

[0063] Furthermore, the thermal expansion coefficient of the plate material 21A may be greater than the thermal expansion coefficient of the graphite block 10 in directions perpendicular to the first direction A1, such as the second direction A2 and the third direction A3.

[0064] This configuration makes it possible to make the thermal expansion coefficient of the second surface 1 b of the heat transfer member 1 closer to an isotropic value than in the configuration of the graphite block 10 alone. Therefore, according to the embodiment, when a component is mounted on the second surface 1 b of the heat transfer member 1, the reliability of the mounting can be improved.

[0065] Heat transfer member 1 may have a rectangular parallelepiped shape and may have a pair of first surfaces 1 a, a pair of second surfaces 1 b, and a pair of third surfaces 1 c. First surfaces 1 a may be surfaces of heat transfer member 1 that intersect, for example, are perpendicular to, first direction A1, or may be surfaces corresponding to first surfaces 10 a of graphite block 10.

[0066] Second surface 1b may be a surface of heat transfer member 1 that extends along first direction A1 and may be a surface corresponding to plate material 21A or plate material 21B. Third surface 1c may be a surface that intersects with second surface 1b, extends along first direction A1, and has a smaller area than second surface 1b, or may be a surface corresponding to third surface 10c of graphite block 10.

[0067] In the embodiment, the plate material 21B may have a higher thermal expansion coefficient and be isotropic than the graphite block 10. In addition, the thermal expansion coefficient of the graphite block 10 may be higher than the thermal expansion coefficient of the plate material 21B in the first direction A1.

[0068] Furthermore, the thermal expansion coefficient of the plate material 21B may be greater than the thermal expansion coefficient of the graphite block 10 in directions perpendicular to the first direction A1, such as the second direction A2 and the third direction A3.

[0069] This configuration makes it possible to bring the thermal expansion coefficient of the other second surface 1 b of the heat transfer member 1 closer to an isotropic value, compared to a configuration using only the graphite block 10. Therefore, according to the embodiment, when the other second surface 1 b of the heat transfer member 1 is mounted on a support, the reliability of mounting can be improved.

[0070] Furthermore, in the heat transfer member 1 according to the embodiment, the plurality of graphite blocks 10 may be arranged in a row along the first direction A1, thereby reducing the possibility that the bonding material 30 or gaps between the adjacent graphite blocks 10 will hinder the heat conduction of the heat transfer member 1 in a direction intersecting the first direction A1.

[0071] Furthermore, by arranging the plurality of graphite blocks 10 in a row along the first direction A1, when the plurality of graphite blocks 10 thermally expand along the first direction A1, the bonding material 30 or gaps between the adjacent graphite blocks 10 can allow deformation due to this thermal expansion to escape.

[0072] The thermal expansion coefficient of the plate material 21A and the plate material 21B is, for example, 4.0×10 －６ / K or more and 20 x 10 －６ / K, and may be less than 6.0 × 10 －６ / K or more and 18 x 10 －６ / K.

[0073] The plate material 21A and the plate material 21B have a thermal expansion coefficient of 4.0×10 －６ / K or more and 20 x 10 －６ Materials having a Tc below 1 / K, for example metallic materials such as copper or stainless steel, or ceramic materials such as aluminum nitride, alumina or zirconia may also be used.

[0074] The main component of the plate materials 21A and 21B may be a copper-based metal or alloy, such as oxygen-free copper. This configuration reduces the anisotropy of the thermal expansion coefficient of the second surface 1b. Furthermore, since the plate materials 21A and 21B have high thermal conductivity, the heat transfer member 1 can achieve higher heat transfer performance.

[0075] The main component of the plate materials 21A and 21B may be a metal with high thermal conductivity, such as aluminum. This configuration also reduces the anisotropy of the thermal expansion coefficient, as in the case of copper. Furthermore, since the plate materials 21A and 21B have high thermal conductivity, the heat transfer member 1 can achieve higher heat transfer performance.

[0076] The main component of the plates 21A and 21B may be ceramics such as alumina, silicon nitride, or aluminum nitride. This configuration also reduces the anisotropy of the thermal expansion coefficient, as in the case of copper. Furthermore, by forming the plates 21A and 21B from ceramics, when the heat transfer member 1 is required to have insulating properties, this requirement can be met.

[0077] The main component of the plates 21A and 21B may be alumina or silicon nitride, which provides high rigidity against the residual stress of the graphite block 10.

[0078] Furthermore, the main component of the plate members 21A and 21B may be silicon nitride. By using this material, the plate members 21A and 21B can be endowed with high thermal conductivity in addition to rigidity, thereby achieving higher thermal performance of the heat transfer member 1.

[0079] For example, the thermal expansion coefficient of the graphite block 10 in the first direction A1 is 24×10 －６ / K or more, the plate materials 21A and 21B may be made of a metal material, such as aluminum, having a thermal expansion coefficient greater than that of copper.

[0080] In the present disclosure, the thermal expansion coefficients of the plates 21A and 21B may be compared with the thermal expansion coefficient of the graphite block 10 using the thermal expansion coefficients measured by changing the temperature from 20°C to 100°C.

[0081] In the present disclosure, the thermal expansion coefficient may be measured using a measurement method specified in JIS depending on the material. For example, if the plate materials 21A and 21B are made of a metal material, the measurement method specified in JIS Z 2285:2003 may be used. If the plate materials 21A and 21B are made of a ceramic material, the measurement method specified in JIS R 1618:2002 may be used.

[0082] The hardness of plate material 21A and plate material 21B may be higher than the hardness of graphite block 10. With this configuration, even if an external force is applied to plate material 21A and plate material 21B, the external force is dispersed and acts on graphite block 10. Therefore, it is possible to reduce breakage of graphite block 10 inside plate material 21A and plate material 21B.

[0083] In the present disclosure, the hardness may be represented by Vickers hardness. Furthermore, in the present disclosure, the Vickers hardness may be represented by a value obtained by converting the unit HV into pressure.

[0084] The hardness of graphite block 10 may be 10 MPa or more and 40 MPa or less in Vickers hardness. The hardness of plate material 21A and plate material 21B may be preferably 10 times or more, more preferably 20 times or more, that of graphite block 10.

[0085] The hardness of the plate material 21A and the plate material 21B may be preferably 200 MPa or more in Vickers hardness, more preferably 500 MPa or more in Vickers hardness, and even more preferably 900 MPa or more in Vickers hardness.

[0086] The Vickers hardness of plate material 21A and plate material 21B can be measured using the measurement method specified in JIS Z 2244: 2009. The Vickers hardness of graphite block 10 may be a value converted from the measurement results of a nanoindentation test with a load of 20 mN / 10 seconds.

[0087] Materials having a hardness ten times or more that of the graphite block 10 include, for example, various metallic materials such as copper, aluminum, or stainless steel, or ceramic materials such as aluminum nitride, alumina, or zirconia.

[0088] In the present disclosure, the material having a hardness 10 times or more that of the graphite block 10 is not limited to a metal material or a ceramic material, but may be various materials such as a resin material.

[0089] The thickness of the plate material 21A and the plate material 21B may be 0.1 mm or more. When the thickness of the plate material 21A and the plate material 21B is 0.1 mm or more, the plate material 21A and the plate material 21B can withstand deterioration due to the influence of corrosion caused by the reducing action of components contained in the bonding material 30, such as Sn.

[0090] Furthermore, the thickness of the plate material 21A and the thickness of the plate material 21B may be approximately equal. This allows the thermal expansion coefficient of the pair of second surfaces 1b of the heat transfer member 1 to approach an isotropic value, thereby reducing the occurrence of warping due to temperature changes. Therefore, according to the embodiment, the reliability of mounting can be improved.

[0091] The joining material 30 for joining the plate material 21A and the plate material 21B to the plurality of graphite blocks 10 described above may be a brazing material or a solder.

[0092] The bonding material 30 may be configured to cover the bonding surface of the plate material 21A or the plate material 21B, i.e., clad, during the manufacturing stage of the heat transfer member 1. This configuration allows the bonding material 30 to be thin after bonding. Therefore, according to the embodiment, the thermal resistance of the bonding material 30 can be reduced.

[0093] The bonding material 30 may be formed into a sheet shape during the manufacturing process of the heat transfer member 1. In this case, the sheet-shaped bonding material 30 may be sandwiched between the plate material 21A or the plate material 21B and the graphite block 10, and then subjected to a heating process and a cooling process to exert a brazing effect.

[0094] According to this configuration, even if second surface 10b of graphite block 10 has a large area, the adhesion between plate material 21A or plate material 21B and graphite block 10 via bonding material 30 can be improved.

[0095] Furthermore, by improving the adhesion between plate material 21A or plate material 21B and graphite block 10, the thermal resistance between plate material 21A or plate material 21B and graphite block 10 can be reduced compared to a configuration in which a gap is present.

[0096] The bonding material 30 may be located only in a partial region of the second surface 10b of the graphite block 10. A gap may be formed in the range other than the region where the bonding material 30 is located.

[0097] 6, the bonding material 30 may also be located in a partial region of the gap between adjacent graphite blocks 10. This makes it possible to more firmly support the plurality of graphite blocks 10 bonded to the plate material 21A and the plate material 21B.

[0098] In the embodiment, the bonding material 30 may contain a metal element capable of forming a carbide, thereby improving the adhesion between the graphite block 10 and the bonding material 30.

[0099] In the present disclosure, the metal element capable of forming a carbide may be, for example, Cr (chromium), V (vanadium), Mo (molybdenum), Ti (titanium), Nb (niobium), W (tungsten), or Zr (zirconium).

[0100] In this disclosure, the definition of "carbide" refers to a compound of carbon and an element that is more electropositive than carbon. For example, the most typical carbide in steel materials is Fe ３ C (cementite), but when it becomes alloy steel, carbides other than cementite are produced.

[0101] Each of the above metal elements forms its own carbide in steel, and so are called carbide-forming elements in steel. When multiple alloying elements are added at the same time, the various elements form solid solutions in the carbides.

[0102] For example, Fe ３ C dissolves Cr or Mn (manganese), and in high-speed steel, it contains (Fe, W, Cr, V) ６ C is formed. These are sometimes called M3C carbides and M6C carbides. Although Si, Al, and Ni also form carbides, these carbides are not formed in steel, and so they are called non-carbide-forming elements.

[0103] 7 is a diagram illustrating a configuration near the interface between graphite block 10 and bonding material 30 according to the embodiment. As shown in FIG. 7 , in the embodiment, diffusion layer 31 may be located at the interface between graphite block 10 and bonding material 30.

[0104] A metal element capable of forming carbide, which is contained in bonding material 30, may be diffused into diffusion layer 31. This can further improve the adhesion between graphite block 10 and bonding material 30.

[0105] In addition, in the embodiment, diffusion layer 31 may be located only on the graphite block 10 side of the interface between graphite block 10 and bonding material 30. This can further improve the adhesion between graphite block 10 and bonding material 30.

[0106] In the embodiment described so far, protective structure 20 protecting multiple graphite blocks 10 is not limited to plate material 21A and plate material 21B. For example, protective structure 20 may include a protective layer in addition to plate material 21A and plate material 21B. Such a protective layer may be a plating layer or a resin layer.

[0107] By using a plating layer as the protective layer of the protective structure 20, it is possible to realize a protective layer with high thermal conductivity, which contributes to the high heat transfer performance of the heat transfer member 1. Furthermore, when the heat transfer member 1 is required to have electrical conductivity, this requirement can be met.

[0108] The protective layer of the protective structure 20 may be located, for example, on at least a part of the pair of first surfaces 1 a or at least a part of the pair of third surfaces 1 c of the heat transfer member 1. The first surface 10 a of the graphite block 10 is located on the first surface 1 a of the heat transfer member 1.

[0109] 2 , the first surface 10a is a crystal plane that is prone to peeling of the graphene 11, and may have edge portions E1 that are prone to breakage of the graphene 11. Therefore, by positioning the protective layer of the protective structure 20 on the first surface 1a of the heat transfer member 1, it is possible to reduce the occurrence of peeling or breakage of the graphene 11, and achieve high toughness of the heat transfer member 1.

[0110] Furthermore, the protective layer of protective structure 20 may be located on the side surface of plate material 21A or the side surface of plate material 21B in addition to the exposed surfaces of the plurality of graphite blocks 10 exposed from plate material 21A and plate material 21B.

[0111] The side surfaces of plate material 21A and plate material 21B are more likely to adhere to the protective layer with higher strength than the exposed surface of graphite block 10. Therefore, by positioning the protective layer on the side surface of plate material 21A or the side surface of plate material 21B, peeling of the protective layer can be reduced.

[0112] The protective layer of the protective structure 20 may be located on at least a portion of the surface opposite to the main surface 21A1 of the plate material 21A, or on at least a portion of the surface opposite to the main surface 21B1 of the plate material 21B. This configuration also reduces peeling of the protective layer.

[0113] Furthermore, the protective layer of protective structure 20 may be located on all of the exposed surfaces of the plurality of graphite blocks 10, all of the side surfaces of plate material 21A, all of the side surfaces of plate material 21B, all of the surfaces of plate material 21A opposite to main surface 21A1, and all of the surfaces of plate material 21B opposite to main surface 21B1. In other words, the protective layer of protective structure 20 may collectively cover the structure constituted by the plurality of graphite blocks 10, plate material 21A, plate material 21B, and bonding material 30.

[0114] This configuration reduces, for example, eliminates the edge portion of the protective layer, thereby further reducing peeling and damage of the protective layer. Furthermore, this configuration reduces the complexity of the process of forming the protective layer.

[0115] When the protective layer of the protective structure 20 is located on at least a portion of the surface opposite the main surface 21A1 of the plate material 21A or at least a portion of the surface opposite the main surface 21B1 of the plate material 21B, a material with high thermal conductivity such as a metal plating layer may be used for the protective layer.

[0116] With this configuration, when a heat source comes into contact with the protective layer of the heat transfer member 1, the heat can be quickly conducted to the plate material 21A or the plate material 21B via the protective layer.

[0117] The thermal conductivity of the protective layer of the protective structure 20 may be highly isotropic compared to the graphite block 10. The thermal conductivity of the protective layer may be higher than the thermal conductivity of the graphite block 10 in the first direction A1.

[0118] This configuration provides the effect of dispersing heat in the first direction A1 through the protective layer on the third surface 1c. Therefore, by adding this dispersion effect, the heat transfer member 1 can achieve higher heat transfer performance.

[0119] <Electronic Device> Fig. 8 is a side view showing an example of the configuration of an electronic device 100 according to an embodiment. As shown in Fig. 8, the electronic device 100 may include a heat transfer member 1, an electronic element 101, and a module substrate 102. The electronic element 101 is an example of a heat source, and the module substrate 102 is an example of a support.

[0120] The electronic element 101 may be mounted on one second surface 1b of the heat transfer member 1 via a bonding material 103 such as solder. That is, the electronic element 101 may be thermally connected to the heat transfer member 1 via the bonding material 103. With this configuration, the heat of the electronic element 101 can be quickly conducted from one second surface 1b of the heat transfer member 1 to the other second surface 1b.

[0121] The other second surface 1b of the heat transfer member 1 may be supported on the module substrate 102 via a bonding material 104 such as solder. The other second surface 1b of the heat transfer member 1 may be thermally connected to a heat sink (not shown) via the module substrate 102.

[0122] This configuration allows heat from the electronic element 101 to be quickly conducted to the module substrate 102 and the heat sink via the heat transfer member 1, and then dissipated from the heat sink.

[0123] In addition, in the embodiment, the thermal expansion coefficient of the graphite block 10 (see FIG. 6) may be greater than the thermal expansion coefficient of the module substrate 102 in the first direction A1.

[0124] In the embodiment, the plate material 21B is positioned between the plurality of graphite blocks 10 and the module substrate 102, thereby reducing the difference in thermal expansion coefficient between the graphite blocks 10 and the module substrate 102. Therefore, this configuration allows the electronic device 100 to have high toughness.

[0125] 9 is a side view showing another example of the configuration of the electronic device 100 according to the embodiment. As shown in Fig. 9, the electronic device 100 may include a heat transfer member 1, an electronic element 101, and a heat sink 110. The heat sink 110 is another example of a support.

[0126] The electronic element 101 may be mounted on one second surface 1b of the heat transfer member 1 via a bonding material 103 such as solder. That is, the electronic element 101 may be thermally connected to the heat transfer member 1 via the bonding material 103. With this configuration, the heat of the electronic element 101 can be quickly conducted from one second surface 1b of the heat transfer member 1 to the other second surface 1b.

[0127] The other second surface 1b of the heat transfer member 1 may be supported on the heat sink 110 via a bonding material 111 such as solder. That is, the other second surface 1b of the heat transfer member 1 may be thermally connected to the heat sink 110.

[0128] This configuration allows the heat from the electronic element 101 to be quickly conducted to the heat sink 110 via the heat transfer member 1 and dissipated from the heat sink 110 .

[0129] In addition, in the embodiment, the thermal expansion coefficient of the graphite block 10 (see FIG. 6) may be greater than the thermal expansion coefficient of the heat sink 110 in the first direction A1.

[0130] In the embodiment, the plate material 21B is positioned between the plurality of graphite blocks 10 and the heat sink 110, thereby reducing the difference in thermal expansion coefficient between the graphite blocks 10 and the heat sink 110. Therefore, this configuration allows the electronic device 100 to have high toughness.

[0131] In the present disclosure, the heat source thermally connected to the heat transfer member 1 is not limited to the electronic element 101. For example, various objects such as a heat pipe for exhausting heat or a heater for heating can be used as the heat source.

[0132] Furthermore, in the present disclosure, the support that supports the heat transfer member 1 is not limited to the module substrate 102 or the heat sink 110. For example, when a heater is used as the heat source, an object to be heated may be placed as a support on the second surface 1b of the heat transfer member 1 opposite to the second surface 1b on which the heat source is located. With this configuration, it is possible to equalize the thermal variations in each part of the heater and transfer heat to the object to be heated.

[0133] <Other Embodiments> Next, configurations of heat transfer members 1 according to various other embodiments will be described with reference to Fig. 10 to Fig. 13. Fig. 10 is a cross-sectional view showing an example of the configuration of a heat transfer member 1 according to another embodiment 1.

[0134] 10 , in another embodiment 1, the position of the bonding material 30 is different from that of the above-described embodiment. Specifically, in another embodiment 1, the bonding material 30 may be positioned in the entire region of the gap between the adjacent graphite blocks 10.

[0135] This makes it possible to more firmly support the plurality of graphite blocks 10 joined to the plate materials 21A and 21B.

[0136] Fig. 11 is a perspective view showing an example of the configuration of a heat transfer member 1 according to another embodiment 2. Fig. 12 is a cross-sectional view taken along line B-B in Fig. 11. As shown in Figs. 11 and 12, in another embodiment 2, the configuration of the protective structure 20 differs from that of the above-described embodiment. Specifically, in another embodiment 2, the protective structure 20 may include a plate member 21A.

[0137] Main surface 21A1 of plate material 21A may be positioned to face one of a plurality of second surfaces 10b that are positioned approximately flush with each other in a plurality of graphite blocks 10. In other words, in heat transfer member 1 according to another embodiment 2, a plurality of graphite blocks 10 may be positioned side by side on one main surface 21A1 of plate material 21A.

[0138] This reduces the force that would cleave graphite block 10, thereby achieving high toughness of heat transfer member 1. Plate material 21A may be bonded to one of the second surfaces 10b of the plurality of graphite blocks 10 by bonding material 30, thereby being physically and thermally connected to the plurality of graphite blocks 10.

[0139] In addition, in a heat transfer member 1 according to another embodiment 2, plate material 21A may be joined to the crystal layer surfaces of a plurality of graphite blocks 10. That is, in another embodiment 2, plate material 21A may be positioned so that any one of a plurality of surfaces extending along first direction A1 in graphite block 10 faces main surface 21A1.

[0140] This reduces the force that would cleave the graphite block 10 , thereby achieving high toughness for the heat transfer member 1 .

[0141] Furthermore, by joining the plate material 21A to the crystal layer surface, which has a surface roughness greater than that of the crystal surface, the joining material 30 is positioned in the recess F1 (see Figure 3) of the crystal layer surface, which produces an anchor effect and improves the adhesion of the plate material 21A to the crystal layer surface.

[0142] Therefore, according to the second alternative embodiment, it is possible to reduce the likelihood that plate material 21A will peel off from graphite block 10. Furthermore, by positioning bonding material 30 within recess F1 of the unevenness, it is possible to reduce the thermal resistance between plate material 21A and graphite block 10 compared to a configuration in which a gap is created in recess F1.

[0143] In another embodiment 2, the thermal conductivity of the plate material 21A may be highly isotropic compared to that of the graphite block 10. In addition, the thermal conductivity of the plate material 21A may be greater than that of the graphite block 10 in the first direction A1.

[0144] Furthermore, in directions perpendicular to the first direction A1, such as the second direction A2 and the third direction A3, the thermal conductivity of the graphite block 10 may be greater than the thermal conductivity of the plate material 21A.

[0145] According to this configuration, when heat is applied to a part of plate material 21A from outside heat transfer member 1, the heat is isotropically dispersed in plate material 21A and then conducted to graphite block 10. Then, in graphite block 10, the heat is quickly dispersed in second direction A2 and third direction A3, which have high thermal conductivity.

[0146] In this way, in the heat transfer member 1 according to the second embodiment, even if heat is applied to a part of the plate material 21A, the heat can be dispersed over a wide area of ​​the graphite block 10. Therefore, according to the second embodiment, the heat transfer member 1 can achieve high heat transfer performance.

[0147] In another embodiment 2, the plate material 21A may have a higher thermal expansion coefficient and be isotropic than the graphite block 10. In addition, the thermal expansion coefficient of the graphite block 10 may be higher than the thermal expansion coefficient of the plate material 21A in the first direction A1.

[0148] Furthermore, the thermal expansion coefficient of the plate material 21A may be greater than the thermal expansion coefficient of the graphite block 10 in directions perpendicular to the first direction A1, such as the second direction A2 and the third direction A3.

[0149] This allows the coefficient of thermal expansion of the second surface 1 b of the heat transfer member 1 to approach an isotropic value, compared to a configuration of the graphite block 10 alone. Therefore, according to the embodiment, when a component is mounted on the second surface 1 b of the heat transfer member 1, the reliability of the mounting can be improved.

[0150] In another embodiment 2, the bonding material 30 may be located in a partial region of the gap between adjacent graphite blocks 10. This makes it possible to more firmly support the plurality of graphite blocks 10 bonded to the plate material 21A.

[0151] In another embodiment 2, the protective structure 20 that protects the plurality of graphite blocks 10 is not limited to the plate material 21A. For example, the protective structure 20 may include a protective layer in addition to the plate material 21A. Such a protective layer may be a plating layer or a resin layer.

[0152] By using a plating layer as the protective layer of the protective structure 20, it is possible to realize a protective layer with high thermal conductivity, which contributes to the high heat transfer performance of the heat transfer member 1. Furthermore, when the heat transfer member 1 is required to have electrical conductivity, this requirement can be met.

[0153] The protective layer of the protective structure 20 may be located on at least a part of the second surface 1b of the heat transfer member 1 opposite to the second surface 1b on which the plate material 21A is located.

[0154] Furthermore, the protective layer of the protective structure 20 may be located on at least a part of the pair of first surfaces 1 a and the pair of third surfaces 1 c of the heat transfer member 1. By having the protective layer of the protective structure 20 located on the first surface 1 a of the heat transfer member 1, peeling or breakage of the graphene 11 can be reduced, and high toughness of the heat transfer member 1 can be achieved.

[0155] Furthermore, the protective layer of protective structure 20 may be located on the side surface of plate material 21A in addition to the exposed surfaces of multiple graphite blocks 10 exposed from plate material 21A. The side surface of plate material 21A is more likely to bond to the protective layer with higher strength than the exposed surfaces of graphite blocks 10. Therefore, by having the protective layer located on the side surface of plate material 21A, peeling of the protective layer can be reduced.

[0156] Furthermore, the protective layer of the protective structure 20 may be located on at least a part of the surface opposite to the main surface 21A1 of the plate material 21A. This configuration also makes it possible to reduce peeling of the protective layer.

[0157] Furthermore, the protective layer of protective structure 20 may be located on all of the exposed surfaces of the plurality of graphite blocks 10, all of the side surfaces of plate material 21A, and all of the surface opposite to main surface 21A1 of plate material 21A. In other words, the protective layer of protective structure 20 may collectively cover the structure constituted by the plurality of graphite blocks 10, plate material 21A, and bonding material 30.

[0158] This configuration reduces, for example, eliminates the edge portion of the protective layer, thereby further reducing peeling and damage of the protective layer. Furthermore, this configuration reduces the complexity of the process of forming the protective layer.

[0159] When the protective layer of the protective structure 20 is located on at least a part of the surface opposite to the main surface 21A1 of the plate material 21A, the protective layer may be made of a material with high thermal conductivity, such as a metal plating layer. With this configuration, even when a heat source comes into contact with the heat transfer member 1 through the protective layer, heat can be quickly conducted to the plate material 21A through the protective layer.

[0160] Fig. 13 is a cross-sectional view showing an example of the configuration of a heat transfer member 1 according to another embodiment 3. As shown in Fig. 13, another embodiment 3 differs from the above-described another embodiment 2 in the position of the bonding material 30. Specifically, in another embodiment 3, the bonding material 30 may be positioned in the entire region of the gap between adjacent graphite blocks 10.

[0161] This allows the plurality of graphite blocks 10 joined to the plate material 21A to be supported more firmly.

[0162] Next, the configuration of a heat transfer member 1 according to another embodiment 4 will be described with reference to Figs. 14 to 16. In another embodiment 4, the heat transfer member 1 may have a graphite substrate 200 which is a structure including a plurality of graphite blocks 10. Fig. 14 is a perspective view showing an example of the configuration of the graphite substrate 200 according to another embodiment 4.

[0163] 14 , graphite substrate 200 may be a structure including a plurality of graphite blocks 10 aligned along first direction A1. In the example shown in FIG. 14 , graphite substrate 200 has three graphite blocks 10. Adjacent graphite blocks 10 along first direction A1 may be joined together by joining material 210.

[0164] The bonding material 210 may be a brazing material or a solder. The bonding material 210 may contain a metal element capable of forming a carbide. That is, the bonding material 210 may be the same bonding material as the bonding material 30 described above.

[0165] Graphite substrate 200 may have first surface 201 and second surface 202 located opposite first surface 201. In Fig. 14, first surface 201 may be a surface including one second surface 10b of multiple graphite blocks 10 located substantially flush with each other, and second surface 202 may be a surface including the other second surface 10b of multiple graphite blocks 10 located substantially flush with each other.

[0166] In the graphite substrate 200 , the first direction A1 of the plurality of graphite blocks 10 may be parallel to the first surface 201 , and the third direction A3 of the plurality of graphite blocks 10 may be perpendicular to the first surface 201 .

[0167] The thickness of graphite block 10 in a direction perpendicular to first surface 201, i.e., along third direction A3, may be, for example, 0.5 mm or more. Alternatively, it may be, for example, 0.8 mm or more. With this configuration, the toughness of graphite block 10 can be increased.

[0168] The thickness of graphite block 10 along third direction A3 may be, for example, 15 mm or less, or may be, for example, 10 mm or less.

[0169] Fig. 15 is a perspective view showing an example of the configuration of heat transfer member 1 according to another embodiment 4. Fig. 16 is a cross-sectional view taken along line CC shown in Fig. 15. As shown in Figs. 15 and 16, in another embodiment 4, heat transfer member 1 may have protective structure 20 that protects graphite substrate 200. Specifically, heat transfer member 1 may have plate 21A located on first surface 201 and plate 21B located on second surface 202.

[0170] In another embodiment 4, the plate materials 21A and 21B may be made of, for example, ceramics. Specifically, the plate materials 21A and 21B may be made of, for example, silicon nitride. Alternatively, the plate materials 21A and 21B may be made of, for example, aluminum nitride or alumina. Hereinafter, the plate material 21A is also referred to as a first insulating substrate 21A, and the plate material 21B is also referred to as a second insulating substrate 21B.

[0171] The thickness of first insulating substrate 21A and second insulating substrate 21B may be, for example, 0.1 mm or more. More preferably, the thickness may be, for example, 0.2 mm or more. With this configuration, the insulation properties of heat transfer member 1 can be improved.

[0172] The thickness of first insulating substrate 21A and second insulating substrate 21B may be, for example, 0.4 mm or less. With this configuration, the thermal conductivity of heat transfer member 1 can be increased.

[0173] Main surface 21A1 of first insulating substrate 21A may be joined to first surface 201 of graphite base 200 by bonding material 60. Furthermore, main surface 21B1 of second insulating substrate 21B may be joined to second surface 202 of graphite base 200 by bonding material 60. In this way, first insulating substrate 21A and second insulating substrate 21B may be physically and thermally connected to graphite base 200.

[0174] The bonding material 60 may be a brazing material or a solder. The bonding material 60 may contain a metal element capable of forming a carbide. That is, the bonding material 60 may be the same bonding material as the above-described bonding material 30 and the above-described bonding material 210.

[0175] The surface roughness of first insulating substrate 21A and second insulating substrate 21B may be, for example, 0.03 μm or more. More preferably, the surface roughness may be, for example, 0.05 μm or more. With this configuration, when first insulating substrate 21A and second insulating substrate 21B are bonded to graphite base 200 with bonding material 60, the bonding can be more firmly achieved by the anchor effect.

[0176] The surface roughness of the first insulating substrate 21A and the second insulating substrate 21B may be, for example, 1.0 μm or less. More preferably, it may be, for example, 0.8 μm or less. With this configuration, gaps are less likely to occur between the first insulating substrate 21A and the second insulating substrate 21B and the bonding material 60, thereby improving the thermal conductivity of the heat transfer member 1.

[0177] The heat transfer member 1 may have a first metal electrode 40 located on the main surface 21A2 of the first insulating substrate 21A. The number of first metal electrodes 40 may be plural. In another embodiment 4, the heat transfer member 1 may have four first metal electrodes 40. The first metal electrode 40 may be, for example, a thin plate having a rectangular shape in a plan view. The first metal electrode 40 may also be, for example, a copper electrode.

[0178] The first metal electrode 40 has a higher thermal conductivity than the first insulating substrate 21 A. That is, the first metal electrode 40 has a better in-plane thermal uniformity than the first insulating substrate 21 A.

[0179] The first metal electrode 40 may be bonded to the main surface 21A2 by a bonding material such as brazing material or solder (not shown). With this configuration, the first metal electrode 40 may be physically and thermally connected to the first insulating substrate 21A. Such a bonding material may be the same as the bonding material 30, the bonding material 60, and the bonding material 210 described above.

[0180] According to heat transfer member 1 having first metal electrode 40, when heat is applied from the outside to first surface 201 side of heat transfer member 1, the heat is uniformly conducted to the surface of first insulating substrate 21A via first metal electrode 40. This allows heat to be dispersed over a wide range of graphite base 200. Therefore, the heat transfer performance of heat transfer member 1 can be improved.

[0181] As will be described later in detail, a semiconductor element 70 described later may be connected to the first metal electrode 40. The heat transfer member 1 having the first metal electrode 40 allows the semiconductor element 70 to be easily connected to the heat transfer member 1.

[0182] The heat transfer member 1 may have a second metal electrode 50 located on the main surface 21B2 of the second insulating substrate 21B. There may be a plurality of second metal electrodes 50. In another embodiment 4, the heat transfer member 1 may have four second metal electrodes 50. The second metal electrode 50 may be, for example, a thin plate having a rectangular shape in a plan view. The second metal electrode 50 may be, for example, a copper electrode.

[0183] The second metal electrode 50 may be located opposite the first metal electrode 40. The second metal electrode 50 has a higher thermal conductivity than the second insulating substrate 21B. That is, the second metal electrode 50 has better in-plane thermal uniformity than the second insulating substrate 21B.

[0184] The second metal electrode 50 may be bonded to the main surface 21B2 by a bonding material such as brazing material or solder (not shown). With this configuration, the second metal electrode 50 may be physically and thermally connected to the second insulating substrate 21B. Such a bonding material may be the same as the bonding material 30, the bonding material 60, and the bonding material 210 described above.

[0185] According to heat transfer member 1 having second metal electrode 50, for example, heat conducted from the outside to first surface 201 side of heat transfer member 1 via graphite base 200 and second insulating substrate 21B can be uniformly dispersed in the in-plane direction in second metal electrode 50. This allows heat to be effectively dissipated via second metal electrode 50. Therefore, the heat dissipation properties of heat transfer member 1 can be improved.

[0186] As will be described later in detail, a cooling member 80 (described later) may be connected to the second metal electrode 50. According to the heat transfer member 1 having the second metal electrode 50, the cooling member 80 can be easily connected to the heat transfer member 1.

[0187] Although the example in which second metal electrode 50 is located on second insulating substrate 21B has been described so far, the present invention is not limited to this, and second metal electrode 50 may be located directly on second surface 202 of graphite base 200. In other words, heat transfer member 1 may not have second insulating substrate 21B.

[0188] In such a case, the second metal electrode 50 may be joined to the second surface 202 by a joining material such as brazing material or solder (not shown). Such a joining material may contain a metal element capable of forming a carbide.

[0189] In such a case, the portion of graphite substrate 200 where graphite block 10 is exposed may be coated with metal plating or the like. Specifically, second surface 202 and the surface of graphite substrate 200 located between first surface 201 and second surface 202 may be coated with metal plating or the like. This can reduce the diffusion of fragments of graphite block 10.

[0190] In such a case, the positioning of second metal electrode 50 on second surface 202 reduces deformation due to thermal stress of heat transfer member 1. For example, when only first surface 201 is fixed by first insulating substrate 21A, warping is likely to occur in graphite base 200. When second metal electrode 50 is positioned on second surface 202, the concentration of thermal stress in graphite base 200 is alleviated, thereby reducing the occurrence of warping.

[0191] Next, the configuration of an electronic device 300 according to another embodiment 4 will be described with reference to Fig. 17 and Fig. 18. Fig. 17 is a perspective view showing an example of the configuration of the electronic device 300 according to another embodiment 4. Fig. 18 is a cross section taken along line D-D shown in Fig. 17. As shown in Fig. 17 and Fig. 18, the electronic device 300 may include a heat transfer member 1, a semiconductor element 70, and a cooling member 80.

[0192] 17 , in an electronic device 300, a first metal electrode 40 of a heat transfer member 1 may be thermally connected to a semiconductor element 70. The semiconductor element 70 may be, for example, a SiC element or a GaN element. The first metal electrode 40 and the semiconductor element 70 may be joined by a joining material (not shown), such as solder.

[0193] 18 , in an electronic device 300, the second metal electrode 50 of the heat transfer member 1 may be thermally connected to a cooling member 80. The cooling member 80 may be, for example, a metal plate or the like through which a cooling medium such as water can flow. The second metal electrode 50 and the cooling member 80 may be joined by a joining material (not shown) such as solder.

[0194] According to the electronic device 300, the semiconductor element 70 can be quickly cooled using the heat transfer member 1 according to the fourth embodiment. Specifically, the electronic device 300 may be mounted on, for example, a power device module.

[0195] According to electronic device 300, semiconductor element 70 can be cooled, for example, by placing semiconductor element 70 on the surface of first metal electrode 40. Therefore, semiconductor element 70 can be cooled with a simpler configuration than when semiconductor element 70 is directly cooled, for example.

[0196] In recent years, SiC elements, GaN elements, and the like have been put to practical use as semiconductor elements mounted on, for example, power device modules. While these next-generation semiconductor elements can be made smaller than conventional semiconductor elements such as Si elements, they generate a large amount of heat per unit volume. For this reason, next-generation semiconductor elements require improved cooling efficiency.

[0197] The electronic device 300 can effectively cool such next-generation semiconductor elements, that is, semiconductor elements that require higher cooling performance than conventional semiconductor elements.

[0198] Specifically, the electronic device 300 effectively cools the semiconductor elements in a power device module or the like that incorporates the next-generation semiconductor elements, thereby maintaining the operating temperature of the module at, for example, 175°C or less. Here, 175°C is the upper limit standard value for the operating temperature of general electrical elements, including semiconductor elements. Therefore, by using the electronic device 300, it becomes possible to use general electrical elements in a power device module or the like.

[0199] Next, the configuration of a heat transfer member 1 according to another embodiment 5 will be described with reference to Fig. 19. Fig. 19 is a perspective view showing an example of the configuration of a heat transfer member 1 according to another embodiment 5. As shown in Fig. 19, a graphite substrate 200 according to another embodiment 5 may be a laminate in which a plurality of graphite blocks 10 are stacked.

[0200] With this configuration, the thickness of graphite substrate 200 along the direction perpendicular to first surface 201 can be easily adjusted.

[0201] Specifically, as shown in FIG. 19 , graphite substrate 200 according to Alternative Embodiment 5 may be a laminate having first layer 203 including a plurality of graphite blocks 10, for example, three graphite blocks 10, aligned along first direction A1, second layer 204 including a plurality of graphite blocks 10, for example, four graphite blocks 10, aligned along first direction A1, and third layer 205 including a plurality of graphite blocks 10, for example, three graphite blocks 10, aligned along first direction A1.

[0202] 19 , first direction A1 of graphite blocks 10 in first layer 203 and third layer 205 is oriented, for example, in the X-axis direction, and first direction A1 of graphite blocks 10 in second layer 204 is oriented, for example, in the Y-axis direction.

[0203] Graphite substrate 200 may be a laminate in which first layer 203, second layer 204, and third layer 205 are stacked, for example, along the negative direction of the Z axis. Graphite blocks 10 adjacent to each other along the stacking direction (negative direction of the Z axis) may be joined together by bonding material 60. That is, bonding material 60 may be located between first layer 203 and second layer 204, and between second layer 204 and third layer 205.

[0204] In graphite substrate 200 according to another embodiment 5, first surface 201 is a surface including multiple second faces 10 b of first layer 203, and second surface 202 is a surface including multiple second faces 10 b of third layer 205. In graphite substrate 200, the orientation of first direction A1 of multiple graphite blocks 10 is parallel to first surface 201.

[0205] 19 , the orientations of first directions A1 of graphite blocks 10 adjacent to each other along the stacking direction of graphite substrate 200 may be shifted by 90°. That is, first layer 203 and second layer 204 may be stacked with the orientations of first directions A1 rotated by 90° from each other. Similarly, second layer 204 and third layer 205 may be stacked with the orientations of first directions A1 rotated by 90° from each other.

[0206] With this configuration, when graphite substrate 200 is a stack of a plurality of graphite blocks 10, it is possible to reduce the anisotropy of heat conduction in a direction parallel to the stacking direction, i.e., in the XY plane direction in FIG. 19.

[0207] Specifically, graphite substrate 200 can conduct heat favorably along the Y-axis direction in first layer 203 and third layer 205, and can conduct heat favorably along the X-axis direction in second layer 204. This allows graphite substrate 200 to disperse heat isotropically as a whole.

[0208] The present disclosure has been described in detail above, but the present disclosure is not limited to the above-described embodiments, and various modifications, improvements, etc. are possible within the scope that does not deviate from the gist of the present disclosure.

[0209] The disclosed embodiments should be considered in all respects as illustrative and not restrictive. Indeed, the above-described embodiments may be embodied in various forms. Furthermore, the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

[0210] The present technology can also be configured as follows: (A1) A heat transfer member comprising: a plurality of graphite blocks, each having a structure in which a plurality of graphenes are stacked in a first direction; and a protective structure that protects the plurality of graphite blocks, wherein the protective structure is physically and thermally connected to the plurality of graphite blocks, the graphite blocks have anisotropy in thermal conductivity and thermal expansion coefficient, wherein the thermal conductivity of the protective structure is greater than that of the graphite blocks in the first direction, the thermal conductivity of the graphite blocks is greater than that of the protective structure in a direction perpendicular to the first direction, the thermal expansion coefficient of the graphite blocks is greater than that of the protective structure in the first direction, and the thermal expansion coefficient of the protective structure is greater than that of the graphite blocks in a direction perpendicular to the first direction, the protective structure has a single plate material, and the plurality of graphite blocks are positioned side by side on one main surface of the plate material. (A2) The heat transfer member according to (A1), wherein the plurality of graphite blocks are aligned in a row along the first direction. (A3) The heat transfer member according to (A1) or (A2), wherein the graphite block has a rectangular parallelepiped shape and is positioned so that one of a plurality of faces extending along the first direction faces one main surface of the plate. (A4) The heat transfer member according to any one of (A1) to (A3), wherein the protective structure has another plate, and the plate and the another plate are positioned so as to sandwich the plurality of graphite blocks. (A5) The heat transfer member according to any one of (A1) to (A4), wherein the plate is joined to the graphite block by a joining material containing a metal element capable of forming carbide. (A6) The heat transfer member according to (A5), wherein the joining material is positioned between adjacent graphite blocks. (A7) An electronic device comprising: the heat transfer member according to any one of (A1) to (A6); a heat source thermally connected to the heat transfer member; and a support supporting the heat transfer member, wherein the thermal expansion coefficient of the graphite block is greater than the thermal expansion coefficient of the support in the first direction.

[0211] The present technology can also be configured as follows. (B1) A heat transfer member comprising: a graphite substrate having a first surface, a first insulating substrate protecting the graphite substrate at the first surface and physically and thermally connected to the graphite substrate; and a first metal electrode located on the first insulating substrate and physically and thermally connected to the first insulating substrate, wherein the first direction of the graphite blocks is parallel to the first surface. (B2) The heat transfer member according to (B1), wherein the graphite substrate has a second surface located opposite the first surface, and further comprising a second metal electrode located on the second surface and physically and thermally connected to the graphite substrate. (B3) The heat transfer member according to (B1), wherein the graphite substrate has a second surface located opposite the first surface, and further comprises: a second insulating substrate physically and thermally connected to the graphite substrate at the second surface; and a second metal electrode located on the second insulating substrate and physically and thermally connected to the second insulating substrate. (B4) The heat transfer member according to any one of (B1) to (B3), wherein the graphite substrate is a laminate formed by stacking a plurality of the graphite blocks along a direction perpendicular to the first surface. (B5) The heat transfer member according to (B4), wherein the graphite blocks adjacent to each other along the stacking direction of the laminate are shifted by 90° in the first direction. (B6) The heat transfer member according to any one of (B1) to (B5), wherein the graphite substrate and the first insulating substrate, and the first insulating substrate and the first metal electrode are joined by a joining material containing a metal element. (B7) The heat transfer member according to (B4) or (B5), wherein the graphite blocks adjacent to each other in the stacking direction of the stack are joined together by a joining material containing a metal element.(B8) The heat transfer member according to any one of (B1) to (B7), wherein the graphite block has anisotropy in thermal conductivity and thermal expansion coefficient, wherein the thermal conductivity of the first insulating substrate is greater than that of the graphite block in the first direction, wherein the thermal conductivity of the graphite block is greater than that of the first insulating substrate in a direction perpendicular to the first direction, wherein the thermal expansion coefficient of the graphite block is greater than that of the first insulating substrate in the first direction, and wherein the thermal expansion coefficient of the first insulating substrate is greater than that of the graphite block in the direction perpendicular to the first direction. (B9) The heat transfer member according to any one of (B1) to (B8), wherein the first metal electrode is thermally connected to a semiconductor element. (B10) The heat transfer member according to any one of (B1) to (B9), wherein the second metal electrode is thermally connected to a cooling member. (B11) The heat transfer member according to any one of (B1) to (B10), wherein the thickness of the graphite block along a direction perpendicular to the first surface is 0.5 mm to 15 mm. (B12) The heat transfer member according to any one of (B1) to (B11), wherein the thickness of the first insulating substrate is 0.1 mm to 0.4 mm. (B13) The heat transfer member according to any one of (B1) to (B12), wherein the surface roughness of the first insulating substrate is 0.03 μm to 1.0 μm.

[0212] 1 Heat transfer member 1a First surface 1b Second surface 1c Third surface 10 Graphite block 10a First surface 10b Second surface 10c Third surface 20 Protective structure 21A Plate material, first insulating substrate 21A1 Main surface 21A2 Main surface 21B Plate material (an example of another plate material), second insulating substrate 21B1 Main surface 21B2 Main surface 30 Bonding material 31 Diffusion layer 40 First metal electrode 50 Second metal electrode 60 Bonding material 70 Semiconductor element 80 Cooling member 100 Electronic device 101 Electronic element (an example of a heat source) 102 Module substrate (an example of a support) 110 Heat sink (an example of a support) 200 Graphite base 201 First surface 202 Second surface 210 Bonding material 300 Electronic device A1 First direction A2 Second direction A3 Third direction

Claims

1. A plurality of graphite blocks having a structure in which a plurality of graphenes are stacked in a first direction, and a protective structure for protecting the plurality of graphite blocks, wherein the protective structure is physically and thermally connected to the plurality of graphite blocks, the graphite blocks have anisotropy in thermal conductivity and coefficient of thermal expansion, in the first direction, the thermal conductivity of the protective structure is greater than the thermal conductivity of the graphite blocks, in a direction orthogonal to the first direction, the thermal conductivity of the graphite blocks is greater than the thermal conductivity of the protective structure, in the first direction, the coefficient of thermal expansion of the graphite blocks is greater than the coefficient of thermal expansion of the protective structure, in a direction orthogonal to the first direction, the coefficient of thermal expansion of the protective structure is greater than the coefficient of thermal expansion of the graphite blocks, the protective structure has one plate material, and the plurality of graphite blocks are heat transfer members located side by side on one main surface of the plate material.

2. The heat transfer member according to claim 1, wherein the plurality of graphite blocks are arranged in a row along the first direction.

3. The heat transfer member according to claim 1 or 2, wherein the graphite block has a rectangular parallelepiped shape and is positioned such that any one of a plurality of surfaces extending along the first direction faces one main surface of the plate material.

4. The heat transfer member according to any one of claims 1 to 3, wherein the protective structure has another plate material, and the plate material and the another plate material are positioned so as to sandwich the plurality of graphite blocks.

5. The heat transfer member according to any one of claims 1 to 4, wherein the plate material is joined to the graphite block by a joining material containing a metal element capable of forming a carbide.

6. The heat transfer member according to claim 5, wherein the joining material is located between adjacent graphite blocks.

7. An electronic device comprising the heat transfer member according to any one of claims 1 to 6, a heat source thermally connected to the heat transfer member, and a support for supporting the heat transfer member, wherein in the first direction, the coefficient of thermal expansion of the graphite blocks is greater than the coefficient of thermal expansion of the support.

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