Heat transfer member and electronic device

Abstract

This heat transfer member comprises: a plurality of graphite blocks having a structure in which a plurality of graphenes are laminated in a first direction; and a protective structure for protecting the plurality of graphite blocks. The protective structure is physically and thermally connected to the plurality of graphite blocks. The graphite blocks have anisotropy of thermal conductivity and the thermal expansion coefficient. In the first direction, the thermal conductivity of the protective structure is greater than the thermal conductivity of the graphite blocks, and 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 conductivity of the graphite blocks is greater than the thermal conductivity of the protective structure, and the thermal expansion coefficient of the protective structure is greater than the thermal expansion coefficient of the graphite blocks. The graphite blocks adjacent to each other are joined by a bonding material. The protective structure has a protective layer that collectively covers the plurality of graphite blocks.

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. Adjacent graphite blocks are bonded together with a bonding material, and the protective structure has a protective layer that collectively covers the plurality of graphite blocks.

[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 the 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 the arrows A-A in FIG. 5. FIG. 7 is a diagram illustrating a configuration near the interface between a graphite block, a protective layer, and a bonding material according to an embodiment. FIG. 8 is a diagram illustrating a configuration near the interface between a graphite block and a protective layer according to an embodiment. FIG. 9 is a diagram illustrating a configuration near the interface between a graphite block and a bonding material according to an embodiment. FIG. 10 is a side view showing an example of the configuration of an electronic device according to an embodiment. FIG. 11 is a side view showing another example of the configuration of an electronic device according to an embodiment. FIG. 12 is a cross-sectional view showing an example of the configuration of a heat transfer member according to another embodiment.

[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] Technologies using graphite as a heat transfer material have been proposed. Graphite blocks are known as a material with high heat transfer performance. However, graphite blocks alone have the problem of being more brittle than metals such as copper.

[0008] Therefore, it is desired to solve the above problems and realize a heat transfer member and an electronic device having 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. 9. 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 is easily broken 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: First, a resin material such as polyimide is carbonized and decomposed into gaseous hydrocarbons. Next, the decomposed hydrocarbons are vapor-deposited and laminated. After that, a pressure annealing treatment is performed to produce pyrolytic graphite.

[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. This allows for greater freedom in designing the heat transfer member 1.

[0037] 4, the plurality of graphite blocks 10 included in the heat transfer member 1 may be arranged in a line with their first surfaces 10a (see FIG. 1) facing each other. That is, in the heat transfer member 1 according to the embodiment, the plurality of graphite blocks 10 may be positioned in a line along the first direction A1.

[0038] In the present disclosure, the plurality of graphite blocks 10 may be manufactured by cutting a larger-sized graphite block along the stacking direction of the graphene 11 using a processing machine such as a wire saw.

[0039] 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.

[0040] 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.

[0041] Adjacent graphite blocks 10 may be joined together by a joining material 30. The joining material 30 may be a brazing material or a solder.

[0042] The bonding material 30 may be configured to cover the bonding surface of at least one of the graphite blocks 10, i.e., clad, at the stage of bonding adjacent graphite blocks 10. 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.

[0043] Joining material 30 may be configured to be formed in a sheet shape at the stage of joining adjacent graphite blocks 10. In this configuration, sheet-shaped joining material 30 may be sandwiched between adjacent graphite blocks 10, and then subjected to a heating process and a cooling process to exert a brazing effect.

[0044] According to this configuration, the adhesiveness between adjacent graphite blocks 10 via bonding material 30 can be improved.

[0045] The bonding material 30 may be located only in a partial area of ​​the first surface 10a, which is the bonding surface. Gaps may be formed in areas other than the area where the bonding material 30 is located.

[0046] In the embodiment, the bonding material 30 may contain a metal element capable of forming a carbide, thereby improving the adhesiveness between the adjacent graphite blocks 10.

[0047] 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).

[0048] 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 ３C (cementite), but when it becomes alloy steel, carbides other than cementite are produced.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] The protective structure 20 protects the plurality of graphite blocks 10. The protective structure 20 may have a protective layer 21. The protective layer 21 may cover the plurality of graphite blocks 10 collectively.

[0053] This reduces the occurrence of peeling or breakage of graphene 11 from first surface 10 a (see FIG. 1 ), second surface 10 b (see FIG. 1 ), and third surface 10 c (see FIG. 1 ) of graphite block 10. Therefore, according to the embodiment, high toughness of heat transfer member 1 can be achieved.

[0054] Furthermore, in the embodiment, the protective layer 21 may be positioned so as to cover the first surface 10a of the graphene 11. In this way, the presence of the edge portion E1 (see FIG. 2 ) can reduce peeling or breakage of the graphene 11 on the first surface 10a, where peeling or breakage of the graphene 11 is more likely to occur than on the second surface 10b and the third surface 10c. Therefore, according to the embodiment, high toughness of the heat transfer member 1 can be achieved.

[0055] In addition, in the embodiment, the protective layer 21 may be positioned so as to cover the second surface 10b and the third surface 10c of the graphene 11. The second surface 10b and the third surface 10c of the graphene 11 have a larger surface roughness than the first surface 10a of the graphene 11, and therefore, an anchor effect works, making it easier for the second surface 10b and the third surface 10c to be bonded to the protective layer 21 with high strength.

[0056] Therefore, by positioning the protective layer 21 so as to cover the second surface 10b and the third surface 10c of the graphene 11, peeling of the protective layer 21 can be reduced.

[0057] In the embodiment, protective layer 21 may contain a metal material or a ceramic material as a main component. When protective layer 21 contains a metal material as a main component, heat can be quickly conducted to multiple graphite blocks 10 via protective layer 21 when a heat source such as electronic element 101 (see FIG. 10 ) comes into contact with protective layer 21 of heat transfer member 1.

[0058] Therefore, according to the embodiment, it is possible to achieve high heat transfer performance of the heat transfer member 1. Furthermore, by forming the protective layer 21 from a metal material, when the heat transfer member 1 is required to have electrical conductivity, this requirement can be met.

[0059] When protective layer 21 contains a metal material as a main component, protective layer 21 may contain a metal element capable of forming a carbide, which can improve the adhesion between graphite block 10 and protective layer 21.

[0060] In the present disclosure, the metal element capable of forming carbides may be the same metal element as the metal element contained in the joining material 30 described above, and may be, for example, Cr, V, Mo, Ti, Nb, W, or Zr.

[0061] In the embodiment, protective layer 21 is mainly composed of a ceramic material, which reduces the force that would cleave graphite block 10, thereby achieving high toughness for heat transfer member 1. Furthermore, by forming protective layer 21 from ceramic, when heat transfer member 1 is required to have insulating properties, this requirement can be met.

[0062] When the protective layer 21 contains a ceramic material as a main component, the protective layer 21 may contain aluminum nitride, alumina, zirconia, or the like as a main component.

[0063] In the embodiment, the thickness of the protective layer 21 may be 10 μm or more and 1 mm or less. When the thickness of the protective layer 21 is 10 μm or more, high toughness can be achieved in the heat transfer member 1. When the thickness of the protective layer 21 is 1 mm or less, high heat transfer performance can be achieved in the heat transfer member 1.

[0064] The protective layer 21 may be a sprayed layer. By using a sprayed layer for the protective layer 21, not only the protective layer 21 made of a metal material but also the protective layer 21 made of a ceramic material can be easily formed.

[0065] In the embodiment, the thermal conductivity of protective layer 21 may be highly isotropic compared to that of graphite block 10. In addition, the thermal conductivity of protective layer 21 may be greater than the thermal conductivity of graphite block 10 in first direction A1.

[0066] Furthermore, the thermal conductivity of graphite block 10 may be greater than the thermal conductivity of protective layer 21 in directions perpendicular to first direction A1, such as second direction A2 and third direction A3.

[0067] According to this configuration, when heat is applied from a heat source to one second surface 1b of heat transfer member 1, the heat is isotropically dispersed by protective layer 21 located on one second surface 1b 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.

[0068] The heat that is quickly dispersed in the second direction A2 and the third direction A3 is then conducted to the protective layer 21 on the second surface 1b located on the opposite side from the heat source, and is dispersed isotropically in the protective layer 21.

[0069] Furthermore, a wide area of ​​the protective layer 21 located on the opposite side from the heat source is thermally connected to the support that supports the heat transfer member 1, so that heat can be dissipated from this wide area of ​​the protective layer 21. Therefore, according to the embodiment, high heat transfer performance of the heat transfer member 1 can be achieved.

[0070] 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.

[0071] Second surface 1b may be a surface of heat transfer member 1 that extends along first direction A1, or may be a surface corresponding to second surface 10b of graphite block 10. 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.

[0072] The protective layer 21 may be made of a material having a thermal conductivity of 10 W / m·K or more and less than 400 W / m·K.

[0073] In the embodiment, the thermal expansion coefficient of the protective layer 21 may be isotropic and higher than that of the graphite block 10. In addition, the thermal expansion coefficient of the graphite block 10 may be higher than that of the protective layer 21 in the first direction A1.

[0074] Furthermore, the thermal expansion coefficient of the protective layer 21 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.

[0075] This configuration makes it possible to bring the thermal expansion coefficient of the 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 a heat source is mounted on one of the second surfaces 1 b of the heat transfer member 1, the reliability of the mounting can be improved.

[0076] Furthermore, according to the embodiment, when the other second surface 1b of the heat transfer member 1 is mounted on a support body, the reliability of the mounting can be improved.

[0077] The protective layer 21 has a thermal expansion coefficient of 2×10 －６ / K or more and 30 x 10 －６ A material having a .DELTA..times ...

[0078] In the present disclosure, the comparison between the thermal expansion coefficient of protective layer 21 and the thermal expansion coefficient of graphite block 10 may be performed using the thermal expansion coefficient measured by changing the temperature from 20° C. to 100° C. Also, in the present disclosure, the measurement of the thermal expansion coefficient may be performed using a measurement method specified in JIS depending on the material.

[0079] In addition, in an embodiment, as shown in Figures 5 and 6, at least one of the pair of first surfaces 1a and the pair of third surfaces 1c may have an overlapping portion 21a where the protective layer 21 is formed twice.

[0080] This reduces peeling or damage of the protective layer 21 on the first surface 1 a, where peeling or damage of the graphene 11 is likely to occur, as described above. Also, it reduces peeling or damage of the protective layer 21 on the third surface 1 c. Therefore, according to the embodiment, high toughness of the heat transfer member 1 can be achieved.

[0081] 5, the overlapping portions 21a may be located continuously around the entire circumference of the pair of first surfaces 1a and the pair of third surfaces 1c. This reduces the occurrence of peeling or damage to the protective layer 21 on the pair of first surfaces 1a and the pair of third surfaces 1c. Therefore, according to the embodiment, the heat transfer member 1 can have high toughness.

[0082] Furthermore, in the heat transfer member 1 according to the embodiment, adjacent graphite blocks 10 may be bonded to each other by bonding material 30. This can reduce separation of adjacent graphite blocks 10, thereby improving the strength of the heat transfer member 1.

[0083] 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.

[0084] 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.

[0085] 7 is a diagram illustrating the configuration of the vicinity of the interface between graphite block 10, protective layer 21, and bonding material 30 according to the embodiment. As shown in FIG. 7 , protective layer 21 may cover not only the plurality of graphite blocks 10 but also bonding material 30.

[0086] This prevents the bonding material 30 from being directly exposed, thereby reducing the risk of damage to the bonding material 30 due to external factors. Therefore, according to the embodiment, the heat transfer member 1 can have high toughness.

[0087] In addition, in the embodiment, as shown in FIG. 7 , bonding material 30 may have a first bonding material 30 a positioned between adjacent graphite blocks 10 and a second bonding material 30 b positioned between graphite block 10 and protective layer 21.

[0088] In this manner, bonding material 30 is positioned so as to cover at least a part of the corner of graphite block 10, thereby reducing the occurrence of breakage at the corner of graphite block 10. Therefore, according to the embodiment, high toughness of heat transfer member 1 can be achieved.

[0089] 8 is a diagram illustrating the configuration of the vicinity of the interface between graphite block 10 and protective layer 21 according to the embodiment. As shown in FIG. 8 , in the embodiment, diffusion layer 22 may be located at the interface between graphite block 10 and protective layer 21.

[0090] When protective layer 21 contains a metal element capable of forming a carbide, the metal element capable of forming a carbide contained in protective layer 21 may be diffused in diffusion layer 22. This can further improve the adhesion between graphite block 10 and protective layer 21.

[0091] In addition, in an embodiment, diffusion layer 22 may be located only on the graphite block 10 side of the interface between graphite block 10 and protective layer 21. This can further improve the adhesion between graphite block 10 and protective layer 21.

[0092] 9 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. 9 , in the embodiment, diffusion layer 31 may be located at the interface between graphite block 10 and bonding material 30.

[0093] 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.

[0094] 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.

[0095] In the embodiment described above, the protective structure 20 that protects the plurality of graphite blocks 10 is not limited to the protective layer 21. For example, the protective structure 20 may include one or more plate members.

[0096] Such a plate material may be located on at least one of the second surfaces 1b of the heat transfer member 1. This reduces the force that would cleave the graphite block 10, thereby achieving high toughness of the heat transfer member 1.

[0097] The plate may be made of a metal material such as copper or stainless steel, a ceramic material such as aluminum nitride, alumina or zirconia, or a resin material.

[0098] 10 is a side view showing an example of the configuration of an electronic device 100 according to an embodiment. As shown in Fig. 10, 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] In the embodiment, the protective layer 21 is located 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.

[0104] 11 is a side view showing another example of the configuration of the electronic device 100 according to the embodiment. As shown in Fig. 11, 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.

[0105] 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.

[0106] 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.

[0107] 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 .

[0108] 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.

[0109] In the embodiment, the protective layer 21 is positioned between the plurality of graphite blocks 10 and the heat sink 110, so that the protective layer 21 deforms in response to stress caused by a difference in thermal expansion coefficient between the graphite blocks 10 and the heat sink 110. That is, in this configuration, the protective layer 21 serves as a buffer that absorbs the difference in deformation amount between the graphite blocks 10 and the heat sink 110.

[0110] 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.

[0111] 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.

[0112] <Other Embodiments> Next, the configuration of a heat transfer member 1 according to various other embodiments will be described with reference to Fig. 12. Fig. 12 is a cross-sectional view showing an example of the configuration of a heat transfer member 1 according to another embodiment.

[0113] 12 , in another embodiment, the positions of overlapping portions 21 a where the protective layer 21 is formed twice are different from those in the above-described embodiment. Specifically, in another embodiment, the overlapping portions 21 a may be located only partially, rather than extending over the entire circumference, of the pair of first surfaces 1 a and the pair of third surfaces 1 c.

[0114] This also reduces the occurrence of peeling or damage of the protective layer 21 in the part of the pair of first surfaces 1 a and the part of the pair of third surfaces 1 c where the overlapping portions 21 a are located. Therefore, according to the embodiment, high toughness of the heat transfer member 1 can be achieved.

[0115] 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.

[0116] 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.

[0117] The present technology may also be configured as follows: (1) 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, 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 orthogonal to the first direction, the thermal expansion coefficient 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 the direction orthogonal to the first direction, the thermal expansion coefficient of the protective structure is greater than that of the graphite blocks in the direction orthogonal to the first direction, adjacent graphite blocks are bonded together by a bonding material, and the protective structure has a protective layer that collectively covers the plurality of graphite blocks. (2) The heat transfer member according to (1), wherein the plurality of graphite blocks are aligned in a row along the first direction. (3) The heat transfer member according to (1) or (2), wherein the heat transfer member has a pair of first surfaces intersecting the first direction, a pair of second surfaces extending along the first direction, and a pair of third surfaces intersecting the second surfaces and extending along the first direction and having an area smaller than that of the second surfaces, and at least one of the pair of first surfaces and the pair of third surfaces has an overlapping portion where the protective layer is formed twice. (4) The heat transfer member according to (3), wherein the pair of first surfaces and the pair of third surfaces have an overlapping portion continuously positioned over the entire periphery. (5) The heat transfer member according to any one of (1) to (4), wherein the protective layer covers the bonding material. (6) The heat transfer member according to any one of (1) to (5), wherein the bonding material contains a metal element capable of forming carbide.(7) An electronic device comprising: the heat transfer member according to any one of (1) to (6); 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.

[0118] DESCRIPTION OF SYMBOLS 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 21 Protective layer 21a Overlapping portion 22 Diffusion layer 30 Bonding material 31 Diffusion layer 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) 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 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, adjacent graphite blocks are joined by a joining material, and the protective structure has a protective layer that collectively covers the plurality of graphite blocks, a heat transfer member.

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. It has a pair of first surfaces intersecting the first direction, a pair of second surfaces extending along the first direction, and a pair of third surfaces intersecting the second surface and extending along the first direction and having a smaller area than the second surface, and at least one of the pair of first surfaces and the pair of third surfaces has a overlapping portion where the protective layer is formed in duplicate, the heat transfer member according to claim 1 or 2.

4. The heat transfer member according to claim 3, wherein the overlapping portions are continuously located over the entire circumference on the pair of first surfaces and the pair of third surfaces.

5. The heat transfer member according to any one of claims 1 to 4, wherein the protective layer covers the joining material.

6. The heat transfer member according to any one of claims 1 to 5, wherein the joining material contains a metal element capable of forming a carbide.

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 thermal expansion coefficient of the graphite blocks is greater than the thermal expansion coefficient of the support.

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