Heat transfer member and electronic device

Abstract

A heat transfer member according to the present disclosure includes a first heat transfer body and a second heat transfer body. The first heat transfer body includes: a graphite block having a structure in which a plurality of graphene layers are stacked; and a hole portion that opens in a first surface of the graphite block that is positioned at one end in the graphene stacking direction. The second heat transfer body is positioned in the hole and is thermally connected to the graphite block inside the hole. In the stacking direction, the thermal conductivity of the second heat transfer body is higher than the thermal conductivity of the first heat transfer body. In a direction orthogonal to the stacking direction, the thermal conductivity of the second heat transfer body is lower than the thermal conductivity of the first heat transfer body.

Description

Heat transfer member and electronic device

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

[0002] 2. Description of the Related Art Conventionally, heat transfer members that transfer heat generated in a heat source such as an electronic element from the heat source have been known. Patent Document 1 discloses a structure in which an electronic element is mounted on a metal heat transfer member.

[0003] International Publication No. 2020 / 045480

[0004] The heat transfer member of the present disclosure includes a first heat transfer body and a second heat transfer body. The first heat transfer body includes a graphite block having a structure in which a plurality of graphenes are stacked, and a hole opening in a first surface of the graphite block located at one end in the stacking direction of the graphenes. The second heat transfer body is located in the hole and is thermally connected to the graphite block within the hole. In the stacking direction, the thermal conductivity of the second heat transfer body is higher than that of the first heat transfer body. In a direction perpendicular to the stacking direction, the thermal conductivity of the second heat transfer body is lower than that of the first heat transfer body.

[0005] FIG. 1 is a schematic side view showing an example of the configuration of a heat transfer member according to an embodiment. FIG. 2 is a schematic perspective view of a heat transfer member according to an embodiment. FIG. 3 is a schematic cross-sectional view of a heat transfer member according to an embodiment. FIG. 4 is a diagram showing a state in which heat generated at a heat source moves through a first heat transfer body and a second heat transfer body according to an embodiment. FIG. 5 is a schematic cross-sectional view showing another example of the configuration of a heat transfer member according to an embodiment. FIG. 6 is a schematic cross-sectional view showing another example of the configuration of a heat transfer member according to an embodiment. FIG. 7 is a schematic side view showing the configuration of an electronic device according to an embodiment. FIG. 8 is a schematic plan view showing the configuration of an electronic device according to an embodiment. FIG. 9 is a schematic side view showing the configuration of an electronic device according to another embodiment. FIG. 10 is a schematic plan view showing the configuration of an electronic device 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] Furthermore, in the following embodiments, expressions such as "constant," "orthogonal," "perpendicular," or "parallel" may be used, but these expressions do not necessarily mean "constant," "orthogonal," "perpendicular," or "parallel" in the strict sense. In other words, the above expressions allow for deviations due to, for example, manufacturing precision or installation precision.

[0008] In addition, in the drawings referred to below, for ease of understanding, an orthogonal coordinate system may be shown in which the X-axis direction, Y-axis direction, and Z-axis direction, which are perpendicular to each other, are defined, and the positive Z-axis direction is the vertically upward direction.

[0009] Metallic heat transfer members have room for improvement in terms of thermal diffusivity. Thermal diffusivity here refers to the ability of a heat transfer member to diffuse heat within or across the heat transfer member. In other words, thermal diffusivity refers to the ability to diffuse heat transferred from a heat source throughout the heat transfer member. A heat transfer member with low thermal diffusivity has a higher temperature in areas closer to the heat source and a lower temperature in areas farther from the heat source. On the other hand, a heat transfer member with high thermal diffusivity is less likely to have the above-mentioned temperature distribution imbalance.

[0010] The present disclosure provides a heat transfer member with high thermal diffusivity.

[0011] (Embodiment) <Heat Transfer Member> Fig. 1 is a schematic side view showing an example of the configuration of a heat transfer member according to an embodiment. Fig. 2 is a schematic perspective view of the heat transfer member according to an embodiment. Fig. 3 is a schematic cross-sectional view of the heat transfer member according to an embodiment. Fig. 3 is a cross-sectional view taken along the line III-III in Fig. 2. Fig. 4 is a schematic view showing how heat generated in a heat source moves through a first heat transfer body and a second heat transfer body according to an embodiment.

[0012] 1 to 3 , the heat transfer member 1 may include a first heat transfer body 10, a second heat transfer body 20, and a protective structure 30. The first heat transfer body 10 may include a graphite block 11 and a hole portion 12.

[0013] The graphite block 11 may have a structure in which a plurality of graphenes 13 are stacked in one direction. The graphenes 13 may be a sheet-like substance in which a honeycomb structure formed by bonding carbon atoms spreads in a two-dimensional direction. The graphenes 13 may be bonded to each other by intermolecular forces, which are van der Waals forces.

[0014] In the embodiment, the plurality of graphenes 13 are stacked in the Z-axis direction. The honeycomb structure of the graphenes 13 may extend along the XY plane.

[0015] Graphite block 11 may have, for example, a thin plate shape that is rectangular in a plan view. Specifically, graphite block 11 may have first surface 111 and second surface 112 located opposite first surface 111. Graphite block 11 may also have a plurality of third surfaces 113 extending in a direction intersecting first surface 111 and second surface 112 and connecting first surface 111 and second surface 112. First surface 111 may be a surface extending along the XY plane and located at one end in the stacking direction of the plurality of graphenes 13. Second surface 112 may be a surface extending along the XY plane and located at the other end in the stacking direction of the graphenes 13.

[0016] The graphite block 11 has anisotropic thermal conductivity. Specifically, the graphite block 11 may have very high thermal conductivity in directions along the crystal plane, in this case, in the X-axis direction and the Y-axis direction.

[0017] The thermal conductivity of graphite block 11 in the direction along the crystal plane may be, for example, 200 W / m·K or more. On the other hand, the thermal conductivity of graphite block 11 in the stacking direction of graphene 13 may be, for example, 7 W / m·K.

[0018] The thermal conductivity of graphite block 11 in the direction along the crystal plane may preferably be 370 W / m·K or more. More preferably, the thermal conductivity of graphite block 11 in the direction along the crystal plane may be 450 W / m·K or more. Even more preferably, the thermal conductivity of graphite block 11 in the direction along the crystal plane may be 800 W / m·K or more. In an embodiment, the thermal conductivity of graphite block 11 in the direction along the crystal plane may be 1200 W / m·K or more, more specifically, approximately 1700 W / m·K.

[0019] As a specific material, the graphite block 11 may be mainly composed of pyrolytic graphite. In the present disclosure, the term "main component" means that the volume ratio is 50% or more.

[0020] Pyrolytic graphite may be produced, for example, as follows: Pyrolytic graphite is produced by, for example, evaporating and laminating hydrocarbons, followed by pressure annealing.

[0021] First surface 111 and second surface 112 of graphite block 11 may be wider surfaces of graphite block 11. Specifically, the area of ​​first surface 111 and second surface 112 may be larger than the area of ​​third surface 113.

[0022] In other words, the dimension of the heat transfer member 1 in the stacking direction of the graphenes 13 may be smaller than the dimension of the heat transfer member 1 in the direction perpendicular to the stacking direction of the graphenes 13 .

[0023] In this way, by reducing the dimension of the first heat transfer body 10 in the stacking direction in which the thermal conductivity is relatively low, heat can be efficiently diffused throughout the heat transfer member 1 .

[0024] Hole 12 opens to first surface 111 of graphite block 11. Hole 12 may extend along the stacking direction of multiple graphenes 13 and penetrate graphite block 11. That is, hole 12 may open to first surface 111 and second surface 112 of graphite block 11.

[0025] In the embodiment, the hole 12 extends along the Z-axis direction, which is the stacking direction of the graphene 13. However, the hole 12 may extend obliquely with respect to the stacking direction of the graphene 13, for example.

[0026] The second heat transfer body 20 is located in the hole 12 of the graphite block 11 and is thermally connected to the graphite block 11 inside the hole 12 .

[0027] In the stacking direction of graphene 13, the thermal conductivity of second heat transfer body 20 is higher than the thermal conductivity of graphite block 11. In addition, in a direction perpendicular to the stacking direction of graphene 13, the thermal conductivity of second heat transfer body 20 is lower than the thermal conductivity of first heat transfer body 10. As such second heat transfer body 20, for example, a metal material such as copper, silver, an aluminum-based metal, or stainless steel can be used.

[0028] Second heat transfer body 20 is not limited to the above-mentioned metal material, and may be made of, for example, a carbon material, more specifically, a material in which a plurality of graphenes are stacked, similar to graphite block 11. In this case, the graphite block constituting second heat transfer body 20 preferably has a plurality of graphenes stacked in a direction perpendicular to the stacking direction of the plurality of graphenes 13 constituting graphite block 11. Second heat transfer body 20 may also be made of, for example, a ceramic material such as AlN (aluminum nitride).

[0029] As described above, graphite block 11 having a structure in which a plurality of graphenes 13 are stacked has anisotropic thermal conductivity, i.e., has very high thermal conductivity in the direction along the crystal plane, but relatively low thermal conductivity in the stacking direction. In contrast, heat transfer member 1 according to the embodiment has second heat transfer body 20 whose thermal conductivity in the stacking direction is higher than that of graphite block 11. Second heat transfer body 20 is located in hole 12 of first heat transfer body 10 and is thermally connected to graphite block 11.

[0030] The second heat transfer body 20 functions as a heat conduction path in the stacking direction. That is, as shown by the open arrows in Fig. 4 , heat generated in the heat source 200 moves through the second heat transfer body 20, which has a relatively high thermal conductivity, along the stacking direction, and then is transferred from the second heat transfer body 20 to the first heat transfer body 10, and then moves through the first heat transfer body 10 in a direction perpendicular to the stacking direction. In this way, the heat generated in the heat source 200 is efficiently diffused throughout the heat transfer member 1. Therefore, the heat transfer member 1 according to the embodiment has high thermal diffusivity.

[0031] In the present disclosure, thermal diffusivity refers to the ability of the heat transfer member 1 to diffuse heat within the surface or inside the heat transfer member 1. In other words, thermal diffusivity refers to the ability to diffuse heat transferred from a heat source throughout the heat transfer member 1. The heat source may be, for example, an electronic element 2.

[0032] One end of second heat transfer body 20 may be located on first surface 111 of graphite block 11, and the other end of second heat transfer body 20 may be located on second surface 112 of graphite block 11. One end of second heat transfer body 20 may be flush with first surface 111, and the other end of second heat transfer body 20 may be flush with second surface 112. However, this is not limiting, and one end of second heat transfer body 20 may protrude from first surface 111 or may be located inside hole 12. Similarly, the other end of second heat transfer body 20 may protrude from second surface 112 or may be located inside hole 12.

[0033] In this way, the hole 12 penetrates the graphite block 11, and the hole 12 is filled with the second heat transfer material 20, so that the heat generated by the heat source can be diffused more efficiently throughout the heat transfer member 1.

[0034] It is sufficient that second heat transfer body 20 is located in the inner region of hole 12 including at least the central portion of graphite block 11 in the stacking direction of graphene 13 .

[0035] In the stacking direction of the graphene 13 , the thermal expansion coefficient of the first heat transfer body 10 may be higher than the thermal expansion coefficient of the second heat transfer body 20 .

[0036] In this configuration, the second heat transfer body 20 restrains the thermal expansion of the first heat transfer body 10 in the stacking direction of the graphene 13, thereby reducing dimensional changes when the temperature of the heat transfer member 1 changes.

[0037] The thermal expansion coefficient of the first heat transfer body 10 may be lower than the thermal expansion coefficient of the second heat transfer body 20 in a direction perpendicular to the stacking direction of the graphene 13 , i.e., in a direction along the crystal plane.

[0038] In this configuration, when the temperature of the heat transfer member 1 rises, the second heat transfer body 20 expands more than the first heat transfer body 10, improving the adhesion between the second heat transfer body 20 and the first heat transfer body 10. This makes it easier for heat to be transferred from the second heat transfer body 20 to the first heat transfer body 10, further improving the thermal diffusivity of the heat transfer member 1.

[0039] In the stacking direction of the graphene 13 , the toughness of the first heat transfer body 10 may be lower than the toughness of the second heat transfer body 20 .

[0040] In this configuration, the second heat transfer body 20 restrains the first heat transfer body 10, thereby reducing the stress applied to the heat transfer member 1 due to repeated thermal expansion and contraction.

[0041] The thermal expansion coefficient of the graphite block 11 in the stacking direction of the graphene 13 is, 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.

[0042] The thermal expansion coefficient of the graphite block 11 in the stacking direction of the graphene 13 is 24×10 －６ / K. The thermal expansion coefficient of the graphite block 11 in the stacking direction of the graphene 13 may be about 27×10 －６ / K or less.

[0043] On the other hand, the thermal expansion coefficient of the graphite block 11 in the direction along the crystal plane is, for example, 0.050×10 －６ / K.

[0044] The thermal expansion coefficient of the graphite block 11 in the direction along the crystal plane may be a negative value, specifically, −0.001×10 －６ / K or less. The thermal expansion coefficient of the graphite block 11 in the direction along the crystal plane may be −0.01×10 －６ / K or more.

[0045] The second heat transfer body 20 may be bonded to the plurality of graphenes 13 inside the hole 12 .

[0046] The plurality of graphenes 13 are bonded by intermolecular forces. For this reason, if the second heat transfer body 20 were bonded to a single graphene 13, for example, when an external force is applied to the second heat transfer body 20, the graphene 13 bonded to the second heat transfer body 20 would easily peel off from the graphite block 11. In contrast, the second heat transfer body 20 according to the embodiment is bonded across the plurality of graphenes 13, and therefore peeling of the graphene 13 is less likely to occur. As such, the heat transfer member 1 according to the embodiment has high adhesion between the second heat transfer body 20 and the first heat transfer body 10.

[0047] The heat transfer member 1 according to the embodiment may have a first bonding material 40 between the hole portion 12 and the second heat transfer body 20. As the first bonding material 40, for example, a brazing filler metal may be used. As the brazing filler metal, for example, titanium brazing filler metal may be used. Furthermore, as the brazing filler metal, for example, a brazing filler metal other than titanium brazing filler metal, such as silver brazing filler metal, copper brazing filler metal, or aluminum brazing filler metal may be used.

[0048] In this way, by positioning first bonding material 40 between graphite block 11 and second heat transfer body 20, it is possible to increase the bonding strength between first heat transfer body 10 and second heat transfer body 20. For example, when titanium brazing filler metal is used as first bonding material 40, a titanium carbide layer is formed at the interface between graphite block 11 and first bonding material 40, thereby increasing the bonding strength between graphite block 11 and second heat transfer body 20.

[0049] The surface roughness of the inner circumferential surface of the hole 12 may be greater than the surface roughness of the first surface 111 and the second surface 112. The roughness of the inner circumferential surface of the hole 12 increases the contact area between the hole 12 and the first bonding material 40. This increases the adhesive strength between the hole 12 and the first bonding material 40, thereby improving the bonding strength between the first heat transfer body 10 and the second heat transfer body 20.

[0050] The surface roughness of the inner peripheral surface of hole 12 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 111 and second surface 112. The surface roughness of the inner peripheral surface of hole 12 may be smaller than the surface roughness of first surface 111 and second surface 112.

[0051] In the present disclosure, the term "surface roughness" refers to the arithmetic mean roughness Ra defined in JIS_B_0601:2001.

[0052] Ends of the plurality of graphenes 13 are exposed on the inner circumferential surface of the hole 12. The positions of the ends of the plurality of graphenes 13 exposed on the inner circumferential surface of the hole 12 are not aligned. In other words, when the inner circumferential surface of the hole 12 is viewed at the molecular level, the inner circumferential surface of the hole 12 has irregularities due to the misalignment of the ends of the plurality of graphenes 13. In this way, the presence of minute irregularities at the molecular level on the inner circumferential surface of the hole 12 increases the contact area between the hole 12 and the first bonding material 40. This increases the adhesion between the hole 12 and the first bonding material 40, thereby improving the bonding strength between the first heat transfer body 10 and the second heat transfer body 20.

[0053] In the embodiment, the heat transfer member 1 has been described as having one hole 12 and one second heat transfer body 20. However, the heat transfer member 1 may have a plurality of holes 12 and a plurality of second heat transfer bodies 20.

[0054] The protective structure 30 protects the plurality of graphite blocks 11 and the second heat transfer body 20. The protective structure 30 may be made of at least one of a metal material, a ceramic material, and an organic material. The protective structure 30 may be provided on the heat transfer member 1 using various processing methods such as plating, vapor deposition, or thermal spraying. The protective structure 30 may also be a plate-shaped member. As shown in FIG. 3 , the protective structure 30 may have a first portion 31, a second portion 32, and a third portion 33.

[0055] The first portion 31 is bonded to the first surface 111 of the graphite block 11. The first portion 31 is also bonded to the second heat transfer body 20. The second portion 32 is bonded to the second surface 112 of the graphite block 11. The second portion 32 is also bonded to the second heat transfer body 20. The third portion 33 is bonded to each of the plurality of third surfaces 113 of the graphite block 11. In this way, the protective structure 30 may entirely cover the first heat transfer body 10 and the second heat transfer body 20.

[0056] The hardness of the protective structure 30 may be higher than the hardness of the first heat transfer body 10 at the third surface 113. With this configuration, even if an external force is applied to the protective structure 30 at the third surface 113, the external force acts on the graphite block 11 in a dispersed state, making it less likely that chipping or the like will occur in the graphite block 11. Note that the relationship between the hardness of the protective structure 30 and the hardness of the first heat transfer body 10 is not limited to this. For example, the hardness of the protective structure 30 may be lower or higher than the hardness of the third surface 113 of the first heat transfer body 10. Furthermore, for example, the hardness of the protective structure 30 may be lower or higher than the hardness of the first surface 111 or the second surface 112 of the first heat transfer body 10.

[0057] The hardness may be measured using the Shore hardness. In the present disclosure, the Shore hardness may be measured using the measurement method described in JIS Z 2246:2022.

[0058] The first portion 31, the second portion 32, and the third portion 33 may be made of various metal materials such as copper, aluminum, or stainless steel, or ceramic materials such as aluminum nitride, alumina, or zirconia.

[0059] The thermal conductivity of the protective structure 30 may be higher than the thermal conductivity of the first heat transfer body 10 in the stacking direction of the graphene 13. For example, the thermal conductivity of the third portion 33 may be higher than the thermal conductivity of the first heat transfer body 10 in the stacking direction of the graphene 13.

[0060] According to this configuration, the protective structure 30 functions as a heat conduction path in the stacking direction, and thus heat can be diffused more efficiently throughout the heat transfer member 1 than in the case where the protective structure 30 is not provided.

[0061] The first portion 31, the second portion 32, and the third portion 33 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] The thermal expansion coefficient of graphite block 11 in the stacking direction of graphene 13 is denoted by C1, the thermal expansion coefficient of second heat transfer body 20 in the stacking direction of graphene 13 is denoted by C2, and the thermal expansion coefficient of protective structure 30 in the stacking direction of graphene 13 is denoted by C3. In this case, C1 > C3 and C1 - C3 > |C2 - C3| may be satisfied. C3 may be the thermal expansion coefficient of first portion 31 or second portion 32.

[0063] In the heat transfer member 1 according to the embodiment, the graphite block 11 is constrained by the second heat transfer body 20, and therefore is less susceptible to thermal expansion than when it is not constrained by the second heat transfer body 20. Therefore, if the thermal expansion coefficient of the protective structure 30 were to approach the thermal expansion coefficient of the graphite block 11, specifically, the thermal expansion coefficient of the graphite block 11 when it is not constrained by the second heat transfer body 20, the protective structure 30 would thermally expand more than the graphite block 11 constrained by the second heat transfer body 20, which could result in stress being applied to the protective structure 30. If the protective structure 30 is susceptible to stress, it is likely that measures such as increasing the thickness of the protective structure 30 will be required.

[0064] In contrast to this, as described above, by making the relationships of the thermal expansion coefficients in the stacking direction of graphene 13 C1>C3 and C1-C3>|C2-C3|, that is, by making the thermal expansion coefficient of protective structure 30 relatively close to that of second heat transfer body 20, it is possible to reduce the stress applied to protective structure 30 when graphite block 11 is thermally deformed. Reducing the stress applied to protective structure 30 makes it easier to reduce the thickness of protective structure 30. In other words, it is easier to reduce the thickness of heat transfer member 1.

[0065] The bonding strength between first heat transfer body 10 and protective structure 30 at first surface 111 and second surface 112 may be lower than the bonding strength between second heat transfer body 20 and protective structure 30. For example, the bonding strength between graphite block 11 and first portion 31 may be lower than the bonding strength between second heat transfer body 20 and first portion 31. Furthermore, the bonding strength between graphite block 11 and second portion 32 may be lower than the bonding strength between second heat transfer body 20 and second portion 32.

[0066] If the first heat transfer body 10 and the protective structure 30 were firmly bonded at the first surface 111 and the second surface 112, force would be easily transmitted from the protective structure 30 to the first heat transfer body 10. In this embodiment, the graphite block 11 has a structure in which graphene 13 is stacked in the Z-axis direction. In this case, stress is applied to the graphene 13 bonded to the protective structure 30 in response to deformation of the protective structure 30, which may result in cleavage, in which intermolecular bonds between the graphene 13 are broken. The deformation of the protective structure 30 may be warping due to, for example, thermal expansion or thermal contraction. In the heat transfer member 1 according to the embodiment, the bonding strength between the first heat transfer body 10 and the protective structure 30 is relatively weak, thereby reducing the possibility of cleavage occurring in the graphite block 11 as described above, compared to when the bonding strength between the first heat transfer body 10 and the protective structure 30 is strong. Note that cleavage is a phenomenon specific to the graphite block 11 in which graphene 13 is stacked.

[0067] The thermal expansion coefficients of the first portion 31, the second portion 32, and the third portion 33 are, 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.

[0068] The first portion 31 and the second portion 32 have a thermal expansion coefficient of 4.0×10 －６ / K or more and 20 x 10 －６ For example, the first portion 31 and the second portion 32 may be made of a metal material such as copper or stainless steel, or a ceramic material such as aluminum nitride, alumina, or zirconia.

[0069] The first portion 31, the second portion 32, and the third portion 33 may be mainly composed of a copper-based metal or alloy such as oxygen-free copper. This configuration allows high thermal conductivity to be obtained in the first portion 31, the second portion 32, and the third portion 33, thereby achieving higher heat transfer performance of the heat transfer member 1.

[0070] The first portion 31, the second portion 32, and the third portion 33 may be mainly composed of a metal with high thermal conductivity, such as aluminum. This configuration also allows high thermal conductivity to be obtained in the first portion 31, the second portion 32, and the third portion 33, thereby achieving higher heat transfer performance of the heat transfer member 1.

[0071] The main component of the first portion 31 and the second portion 32 may be a ceramic such as alumina, silicon nitride, or aluminum nitride. Even with this configuration, by forming the first portion 31, the second portion 32, and the third portion 33 from ceramics, when the heat transfer member 1 is required to have insulating properties, this requirement can be met.

[0072] The main components of the first portion 31, the second portion 32, and the third portion 33 may be alumina or silicon nitride, which provides high rigidity against residual stress in the graphite block 11.

[0073] Furthermore, the main component of the first portion 31, the second portion 32, and the third portion 33 may be silicon nitride. By using this material, it is possible to impart high thermal conductivity characteristics in addition to rigidity to the first portion 31, the second portion 32, and the third portion 33, thereby achieving higher thermal performance of the heat transfer member 1.

[0074] Furthermore, for example, the thermal expansion coefficient of the graphite block 11 is 24×10 in the stacking direction of the graphene 13. －６ / K or more, the first portion 31, the second portion 32, and the third portion 33 may be made of a metal material, such as aluminum, that has a higher thermal expansion coefficient than copper.

[0075] In the present disclosure, the comparison of the thermal expansion coefficients of the first portion 31, the second portion 32, and the third portion 33 with the thermal expansion coefficient of the graphite block 11 may be performed using the thermal expansion coefficients measured by changing the temperature from 20°C to 100°C.

[0076] 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 first portion 31, the second portion 32, and the third portion 33 are made of a metal material, the measurement method specified in JIS Z 2285:2003 may be used. If the first portion 31, the second portion 32, and the third portion 33 are made of a ceramic material, the measurement method specified in JIS R 1618:2002 may be used.

[0077] The thickness of the first portion 31, the second portion 32, and the third portion 33 may be 0.1 mm or more.

[0078] In the embodiment, an example has been described in which the protective structure 30 includes the first portion 31, the second portion 32, and the third portion 33. However, the present invention is not limited to this, and the protective structure 30 may, for example, be configured to include only the first portion 31 and the second portion 32. In other words, the protective structure 30 may not include multiple third portions 33. Furthermore, the protective structure 30 may, for example, be configured to include only the first portion 31 on which the electronic element 2 described below is mounted.

[0079] Furthermore, the protective structure 30 may further include a protective layer in addition to the first portion 31, the second portion 32, and the third portion 33. Such a protective layer may be a plating layer or a resin layer. By using a plating layer as the protective layer of the protective structure 30, a protective layer with high thermal conductivity can be realized, which contributes to the high heat transfer performance of the heat transfer member 1. Furthermore, when electrical conductivity is required for the heat transfer member 1, this requirement can be met.

[0080] <Other Configuration Examples of Heat Transfer Member 1> FIGS. 5 and 6 are schematic cross-sectional views showing other configuration examples of the heat transfer member according to the embodiment.

[0081] 5, the holes 12 of the first heat transfer body 10 do not necessarily need to penetrate the graphite block 11. Although Fig. 5 shows an example in which the holes 12 of the first heat transfer body 10 are open only to the first surface 111, the holes 12 of the first heat transfer body 10 may be open only to the second surface 112 of the graphite block 11.

[0082] Furthermore, the width of the second heat transfer body 20 in a cross-sectional view does not necessarily need to be constant in the stacking direction of the graphene 13. For example, in the above-described embodiment, an example in which the second heat transfer body 20 has a cylindrical shape has been described. However, this is not limited to this, and the second heat transfer body 20 may have a truncated cone shape, for example, as shown in FIG. 6 . In this case, the width of the second heat transfer body 20 in a cross-sectional view may be narrower at the end on the first surface 111 side on which the electronic element 2 described later is mounted than at the end on the second surface 112 side. Conversely, the width of the second heat transfer body 20 in a cross-sectional view may be narrower at the end on the second surface 112 side than at the end on the first surface 111 side.

[0083] The shape of the second heat transfer body 20, in which the width of the second heat transfer body 20 in cross section changes along the stacking direction of the graphene 13, is not limited to the above-described truncated cone shape and may be, for example, a truncated pyramid shape. Furthermore, the width of the second heat transfer body 20 in cross section may change stepwise. That is, the shape of the second heat transfer body 20, in which the width of the second heat transfer body 20 in cross section changes along the stacking direction of the graphene 13, may be a shape having steps on the side surface, such as a so-called pyramid shape.

[0084] The width of the second heat transfer body 20 in a cross-sectional view may be narrower at the end on the first surface 111 side on which the electronic element 2 described below is mounted than at the end on the second surface 112 side.

[0085] <Electronic Device> Next, the configuration of the electronic device according to the embodiment will be described with reference to Fig. 7 and Fig. 8. Fig. 7 is a schematic side view showing the configuration of the electronic device according to the embodiment. Fig. 8 is a schematic plan view showing the configuration of the electronic device according to the embodiment.

[0086] 7, the electronic device 100 includes a heat transfer member 1, an electronic element 2, and a heat dissipation member 3. The electronic element 2 is an example of a heat source.

[0087] As described above, the heat transfer member 1 may have a thin plate shape that is rectangular in a plan view. The heat transfer member 1 has a fourth surface 101 and a fifth surface 102 located opposite the fourth surface 101. Specifically, the fourth surface 101 may be the surface of the first portion 31 of the protective structure 30, and the fifth surface 102 may be the surface of the second portion 32 of the protective structure 30. The fourth surface 101 and the fifth surface 102 correspond to the wider surfaces of the heat transfer member 1, in other words, the main surfaces. The fourth surface 101 is a mounting surface on which the electronic element 2 is mounted.

[0088] The electronic element 2 is mounted on the fourth surface 101 of the heat transfer member 1 via a third bonding material 103 such as solder. That is, the electronic element 2 is thermally connected to the heat transfer member 1 via the third bonding material 103. With this configuration, the heat of the electronic element 2 can be quickly conducted from the fourth surface 101 on one side to the fifth surface 102 on the other side of the heat transfer member 1.

[0089] Specifically, as shown in FIG. 8, the electronic element 2 is disposed at a position where it overlaps with the second heat transfer body 20 of the heat transfer member 1 in a planar perspective view.

[0090] With this configuration, the heat generated in the electronic element 2, which is a heat source, is efficiently transferred to the second heat transfer body 20, and the heat generated in the electronic element 2 can be efficiently dissipated.

[0091] Although FIG. 8 shows an example in which the entire second heat transfer body 20 overlaps with the electronic element 2 in plan view, it is sufficient that the electronic element 2 and the second heat transfer body 20 overlap at least partially.

[0092] The fifth surface 102 of the heat transfer member 1 may be thermally connected to the heat dissipation member 3 via a fourth bonding material 104 such as solder. The heat dissipation member 3 is, for example, a heat sink.

[0093] With this configuration, the heat from the electronic element 2 can be quickly conducted to the heat dissipation member 3 via the heat transfer member 1 and dissipated from the heat dissipation member 3 .

[0094] The thermal expansion coefficient of the graphite block 11 may be smaller than the thermal expansion coefficient of the heat dissipation member 3 in a direction intersecting the stacking direction of the graphene 13 , for example, in a direction along the XY plane.

[0095] The heat source thermally connected to the heat transfer member 1 is not limited to the electronic element 2. For example, various objects such as a heat pipe for exhausting heat or a heater for heating can be used as the heat source.

[0096] The electronic device 100 may have a heat transfer member thermally connected to the side surface of the heat transfer member 1, i.e., the third portion 33. As described above, the heat transfer member 1 has extremely high thermal conductivity in the direction perpendicular to the stacking direction of the graphene 13. Therefore, by thermally connecting the heat transfer member to the third portion 33, the heat generated in the electronic element 2 can be dissipated more efficiently.

[0097] 9 and 10 are schematic side and plan views showing the configuration of an electronic device according to another embodiment.

[0098] In the above-described embodiment, an example has been shown in which the dimension of the second heat transfer body 20 in the direction orthogonal to the stacking direction of the graphene 13 is smaller than the dimension of the electronic element 2 in the direction orthogonal to the stacking direction of the graphene 13 (see FIG. 7 ). In addition, in the above-described embodiment, an example has been shown in which the second heat transfer body 20 is located inside the outer shape of the electronic element 2 when the electronic device 100 is seen through a plan view (see FIG. 8 ).

[0099] However, the dimensional relationship and positional relationship between the electronic element 2 and the second heat transfer body 20 are not limited to the above example. For example, as shown in Fig. 9 , the dimension of the second heat transfer body 20 in the direction perpendicular to the stacking direction of the graphene 13 may be larger than the dimension of the electronic element 2 in the direction perpendicular to the stacking direction of the graphene 13. Furthermore, as shown in Fig. 10 , when the electronic device 100 is seen through a plan view, the electronic element 2 may be located inside the outer shape of the second heat transfer body 20.

[0100] In the example shown in Figure 10, the entire electronic element 2 is located inside the outer shape of the second heat transfer body 20, but the electronic element 2 may also partially extend outside the outer shape of the second heat transfer body 20.

[0101] In the above-described embodiment, the protective structure 30 is directly bonded to the first heat transfer body 10 and the second heat transfer body 20, but this is not limiting. For example, the protective structure 30 may be bonded to the first heat transfer body 10 and the second heat transfer body 20 via a bonding material such as a brazing material.

[0102] Although the present disclosure has been described in detail above, the present disclosure is not limited to the above-described embodiments, and various modifications and improvements can be made without departing from the spirit and scope of the present disclosure.

[0103] 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.

[0104] Note that the present technology may also have the following configurations: (1) A heat transfer member including a first heat transfer body and a second heat transfer body, wherein the first heat transfer body includes a graphite block having a structure in which a plurality of graphenes are stacked, and a hole portion opening in a first surface of the graphite block located at one end in a stacking direction of the graphenes, the second heat transfer body is located in the hole portion and thermally connected to the graphite block inside the hole portion, wherein the thermal conductivity of the second heat transfer body is higher than that of the first heat transfer body in the stacking direction, and the thermal conductivity of the second heat transfer body is lower than that of the first heat transfer body in a direction perpendicular to the stacking direction. (2) The heat transfer member according to (1), wherein the hole portion penetrates the graphite block, and the second heat transfer body is located in an internal region of the hole portion including a central portion of the graphite block in the stacking direction. (3) The heat transfer member according to (1) or (2), wherein the thermal expansion coefficient of the first heat transfer body is higher than the thermal expansion coefficient of the second heat transfer body in the stacking direction. (4) The heat transfer member according to any one of (1) to (3), wherein the thermal expansion coefficient of the first heat transfer body is lower than the thermal expansion coefficient of the second heat transfer body in a direction perpendicular to the stacking direction. (5) The heat transfer member according to any one of (1) to (4), wherein the toughness of the first heat transfer body is lower than the toughness of the second heat transfer body in the stacking direction. (6) The heat transfer member according to any one of (1) to (5), wherein the second heat transfer body is bonded to the plurality of graphenes inside the hole. (7) The heat transfer member according to (6), wherein a bonding material is provided between the hole and the second heat transfer body. (8) The heat transfer member according to any one of (1) to (6), which has a protective structure that protects the first heat transfer body and the second heat transfer body, and where the thermal expansion coefficient of the first heat transfer body in the stacking direction is C1, the thermal expansion coefficient of the second heat transfer body in the stacking direction is C2, and the thermal expansion coefficient of the protective structure in the stacking direction is C3, C1 > C3 and C1 - C3 > |C2 - C3|.(9) The heat transfer member according to any one of (1) to (6), further comprising a protective structure that protects the first heat transfer body and the second heat transfer body, wherein the thermal conductivity of the first heat transfer body in the stacking direction is lower than the thermal conductivity of the protective structure. (10) The heat transfer member according to any one of (1) to (6), further comprising a protective structure that protects the first heat transfer body and the second heat transfer body, wherein the bonding strength between the first heat transfer body and the protective structure is lower than the bonding strength between the second heat transfer body and the protective structure. (11) The heat transfer member according to any one of (1) to (10), wherein the dimension in the stacking direction is smaller than the dimension in a direction perpendicular to the stacking direction. (12) An electronic device comprising the heat transfer member according to any one of (1) to (11), and a heat source thermally connected to the heat transfer member. (13) The electronic device according to (12), wherein the heat source and the second heat transfer body at least partially overlap in a planar perspective view.

[0105] REFERENCE SIGNS LIST 1 heat transfer member 2 electronic element 3 heat dissipation member 10 first heat transfer body 11 graphite block 12 hole 13 graphene 20 second heat transfer body 30 protective structure 40 first bonding material 100 electronic device

Claims

1. A heat transfer member comprising: a first heat transfer body and a second heat transfer body; the first heat transfer body comprises a graphite block having a structure in which a plurality of graphenes are stacked; and a hole portion that opens into a first surface of the graphite block and is located at one end in a stacking direction of the graphenes; the second heat transfer body is located in the hole portion and is thermally connected to the graphite block within the hole portion; and the thermal conductivity of the second heat transfer body is higher than that of the first heat transfer body in the stacking direction, and the thermal conductivity of the second heat transfer body is lower than that of the first heat transfer body in a direction perpendicular to the stacking direction.

2. The heat transfer member according to claim 1, wherein the hole penetrates the graphite block, and the second heat transfer body is located in an internal region of the hole that includes a central portion of the graphite block in the stacking direction.

3. The heat transfer member according to claim 1 or 2, wherein the thermal expansion coefficient of the first heat transfer body is higher than the thermal expansion coefficient of the second heat transfer body in the stacking direction.

4. A heat transfer member according to any one of claims 1 to 3, wherein the thermal expansion coefficient of the first heat transfer body is lower than the thermal expansion coefficient of the second heat transfer body in a direction perpendicular to the stacking direction.

5. The heat transfer member according to any one of claims 1 to 4, wherein the toughness of the first heat transfer body is lower than the toughness of the second heat transfer body in the stacking direction.

6. The heat transfer member according to any one of claims 1 to 5, wherein the second heat transfer body is bonded to a plurality of the graphenes inside the holes.

7. The heat transfer member according to claim 6, further comprising a bonding material between the hole and the second heat transfer body.

8. A heat transfer member according to any one of claims 1 to 6, which has a protective structure that protects the first heat transfer body and the second heat transfer body, wherein, when the thermal expansion coefficient of the first heat transfer body in the stacking direction is C1, the thermal expansion coefficient of the second heat transfer body in the stacking direction is C2, and the thermal expansion coefficient of the protective structure in the stacking direction is C3, C1 > C3 and C1 - C3 > |C2 - C3|.

9. A heat transfer member according to any one of claims 1 to 6, further comprising a protective structure that protects the first heat transfer body and the second heat transfer body, and the thermal conductivity of the protective structure in the stacking direction is greater than the thermal conductivity of the first heat transfer body.

10. A heat transfer member according to any one of claims 1 to 6, further comprising a protective structure that protects the first heat transfer body and the second heat transfer body, and wherein the bonding strength between the first heat transfer body and the protective structure is lower than the bonding strength between the second heat transfer body and the protective structure.

11. A heat transfer member according to any one of claims 1 to 10, wherein the dimension in the stacking direction is smaller than the dimension in a direction perpendicular to the stacking direction.

12. An electronic device comprising: a heat transfer member according to any one of claims 1 to 11; and a heat source thermally connected to the heat transfer member.

13. The electronic device according to claim 12, wherein the heat source and the second heat transfer body at least partially overlap each other in a planar perspective view.

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