JP2017112334A - Heat conduction structure, manufacturing method of the same, cooling device, and semiconductor module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat conduction structure having flexibility capable of efficiently dissipating heat of a heat storage body which is a heat radiation object, and a manufacturing method of the same.SOLUTION: A graphite composite body 10 has plate-like graphite members 11, 12 formed by laminating graphene sheets 15. The graphite members 11, 12 have a structure in which bonding surfaces in a direction orthogonal to the lamination direction are bonded to each other by a predetermined bonding material 19 in a state in which the lamination direction of the graphene sheets 15 is aligned.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a heat conduction structure having a heat conductor in which graphene sheets are laminated, a method for manufacturing the heat conduction structure, a cooling device, and a semiconductor module.

  As a heat conductor that dissipates heat by moving the heat of a heating element that is a heat dissipation object, a heat conductor that uses graphite having a structure in which graphene sheets are stacked is known. For example, Patent Document 1 discloses a heat conductor configured such that a metal is embedded in a part of graphite and a heat receiving portion that receives heat from a heat source is in contact with the metal.

  In general, the graphite has a property that the composition is brittle and breaks down. Therefore, conventionally, a support member is provided so as to cover the periphery of the plate-like heat conductor, and a heat conductor (anisotropic heat conduction) capable of increasing the strength while realizing efficient heat conduction. Element) has been proposed (see Patent Document 2).

  In recent years, in the automotive industry such as electric vehicles and hybrid vehicles, power modules (power semiconductor elements) including power semiconductors with high withstand voltage and high rated current have come to be used as the output of motors increases. It was. Since a large current exceeding several hundred amperes flows in the current path controlled by such a power module, heat of several kW may be generated in the power module, and a heat conducting member that efficiently dissipates the generated heat is provided. It has been demanded.

JP 2008-28283 A JP 2011-23670 A

  By the way, there are various installation environments of devices in which the power module is used. For example, in a power module mounted on an automobile, it is affected by impacts and vibrations caused by traveling of the automobile, vibrations of an engine, and the like. Further, when heated by the heat generated by the power module itself or the influence of external heat, the power module itself may be deformed depending on the expansion coefficient of the material used for the power module.

  In recent years, flexible liquid crystal panels using flexible resin substrates have been distributed in the market. As the screen of such a liquid crystal panel increases, a heat conductive member that efficiently dissipates heat is required even in semiconductors used in the liquid crystal panel.

  However, when a heat conductor using graphite is applied for heat dissipation of a power module that receives vibration or undergoes thermal deformation, there is a problem that the heat conductor is detached from the power module or a crack occurs in the heat conductor. . In addition, when a heat conductor using graphite is applied for heat dissipation of a semiconductor mounted on a substrate that is assumed to be bent, the heat conductor can follow the bending of the substrate. However, there is a problem that the heat conductor is damaged.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to efficiently dissipate the heat of a heat generating body that is a heat dissipating target, and to have a flexible heat conduction structure and this It is providing the manufacturing method of a heat conductive structure. Another object is to provide a cooling device for a heating element using a heat conducting structure and a semiconductor module.

  The heat conduction structure of the present invention has a plate-like first heat conductor and a second heat conductor in which graphene sheets are laminated. This heat conducting structure has a structure in which bonding surfaces in a direction orthogonal to the stacking direction are bonded to each other by a predetermined bonding material in a state where the stacking directions of the graphene sheets are matched.

  The bonding material is a metal having a lower melting point than the first thermal conductor and the second thermal conductor. In this case, in the heat conduction structure, the bonding material is heated and melted in a state where the bonding material is interposed between the bonding surface of the first heat conductor and the bonding surface of the first heat conductor. Thus, the joining surfaces are joined to each other.

  Moreover, this invention is a manufacturing method which manufactures the heat conductive structure which has a plate-shaped 1st heat conductor with which a graphene sheet is laminated | stacked, and a 2nd heat conductor. The manufacturing method of the heat conductive structure of the present invention is characterized in that bonding surfaces in a direction orthogonal to the stacking direction are bonded to each other with a predetermined bonding material in a state where the stacking directions of the graphene sheets are matched.

  The bonding material is a metal having a lower melting point than the first thermal conductor and the second thermal conductor. In this case, in the manufacturing method of the heat conductive structure of the present invention, the bonding material is interposed between the bonding surface of the first heat conductor and the bonding surface of the first heat conductor. The joining surfaces are joined together by heating and melting the joining material.

  In the method for manufacturing a heat conductive structure according to the present invention, the bonding material is interposed between the bonding surface of the first heat conductor and the bonding surface of the first heat conductor, and the first heat is generated by heating. By heating the whole while regulating the expansion amount of the conductor and the second heat conductor in the stacking direction, that is, the length in the stacking direction after expansion to be within a predetermined allowable range, The joining surfaces are joined together by melting the joining material.

  The allowable range is 105% to 125% with respect to the length in the stacking direction of the first thermal conductor and the second thermal conductor before heating.

  The cooling device of the present invention includes the heat conduction structure, a thin adhesion layer made of metal or ceramics bonded to both end faces of the heat conduction structure in a direction orthogonal to the stacking direction, and the heat conduction structure. And a heat radiator joined to at least one end face of the body. The cooling device radiates heat from a heat generating body attached to the other end face of the heat conducting structure through the heat conducting structure and the heat radiating body.

  The semiconductor module of this invention is equipped with the said cooling device and the semiconductor element attached to the other end surface of the said heat conductive structure of the said cooling device.

  According to the present invention, it is possible to efficiently dissipate the heat of the heating element that is the object of heat dissipation, and it is possible to realize a heat conduction structure that is less likely to be damaged due to deformation such as vibration and bending. In addition, it is possible to efficiently dissipate the heat of the heating element and to manufacture a flexible heat conduction structure.

FIG. 1 is a perspective view showing a graphite complex according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view in which the cross-sectional structure taken along the line II-II in FIG. 1 is partially enlarged in the graphite composite. FIG. 3 is an exploded perspective view for explaining a mold apparatus used for manufacturing a graphite composite. 4A and 4B are diagrams for explaining the mold apparatus. FIG. 4A is a plan view of the mold apparatus, and FIG. 4B is a cutting line IVB-IVB in FIG. 4A in the mold apparatus. FIG. FIG. 5 is a cross-sectional view of the mold apparatus, FIG. 5 (A) shows a state in which the graphite member is mounted on the mold, and FIG. 5 (B) shows that the graphite member is thermally expanded in the mold apparatus. FIG. 5C shows a state where the expansion of the graphite member is regulated by the regulating member in the mold apparatus. 6 (A) and 6 (B) are diagrams for explaining that the graphite complex has flexibility. FIG. 7 is a view showing a cooling device and a semiconductor module to which the graphite composite according to the embodiment of the present invention is applied.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.

  Hereinafter, with reference to FIG.1 and FIG.2, the graphite complex 10 which is an example of the heat conductive structure of this invention is demonstrated.

  As shown in FIG. 1, the graphite complex 10 is a rectangular plate having a two-layer structure. The graphite complex 10 has a graphite member 11 formed in a flat plate shape on the upper side, and has a graphite member 12 formed in a flat plate shape on the lower side. In this embodiment, the graphite members 11 and 12 are joined to each other by a joining material 19 (see FIG. 3) described later. The upper graphite member 11 is an example of the first thermal conductor of the present invention, and the lower graphite member 12 is an example of the second thermal conductor of the present invention.

  The graphite members 11 and 12 have a crystal structure in which a plurality of graphene sheets 15 are stacked along one direction. The graphene sheet 15 is a sheet-like graphene, which is formed by covalently bonding six-membered rings in the plane direction, and has a thickness of one carbon atom. Since the layers of the graphene sheets 15 of the graphite members 11 and 12 are bonded by van der Waals force, the graphene sheet 15 has a property of being easily peeled off in layers. The graphite members 11 and 12 of the present embodiment are formed in a plate shape having a small size (thickness) in the thickness direction (Y direction in FIG. 1) perpendicular to the stacking direction (X direction in FIG. 1) in which the graphene sheets 15 are stacked. Has been. Specifically, each of the graphite members 11 and 12 has a thickness of 1.5 [mm] to 2.0 [mm]. Moreover, the graphite members 11 and 12 are formed in a rectangular shape in plan view, and are formed in a square shape with one side of 30 [mm], for example. In addition, although the actual thickness of the graphene sheet 15 is one carbon atom, the graphene sheet 15 represented more than actual thickness is shown in each figure for convenience of explanation.

  As the graphite members 11 and 12, highly oriented pyrolytic graphite (HOPG) having higher thermal conductivity than general graphite is employed. Specifically, US MINTEQ International Inc. The product name “PYROID HT” is used.

  The graphite members 11 and 12 have anisotropy with respect to thermal conductivity. That is, the graphite members 11 and 12 have heat in the direction along the YZ plane rather than the thermal conductivity in the X direction (direction perpendicular to the YZ plane), that is, in the thickness direction of the graphite members 11 and 12 in FIG. Very high conductivity. Thus, the property that the thermal conductivity differs depending on the direction of the material is called anisotropy, and the graphite members 11 and 12 having this anisotropy are generally an anisotropic heat conductor or an anisotropic heat conduction element. It is called. Specifically, the graphite members 11 and 12 have a thermal conductivity in the direction along the YZ plane of about 1500 [W / mK] to 1700 [W / mK], and a thermal conductivity in the X direction of 5 [W / MK] to 10 [W / mK].

  Further, while the linear expansion coefficient of the general graphite in the stacking direction (X direction) is 4.5 [ppm / K] to 5.5 [ppm / K], it is a highly oriented pyrolytic graphite. The linear expansion coefficient of the graphite member 11 or 12 in the stacking direction (X direction) is extremely high, specifically about 25 [ppm / K].

  In the graphite composite 10 according to the present embodiment, the thickness of the graphite member 11 and the joint surface on the lower side in the thickness direction of the graphite member 11 are set in a state where the stacking directions of the graphene sheets 15 in the graphite member 11 and the graphite member 12 are matched. It has a structure in which the bonding surface on the upper side in the direction is bonded to each other by a bonding material 19 (see FIG. 3).

  The bonding material 19 is also referred to as an insert material, and a metal having a melting point lower than that of the graphite members 11 and 12, an alloy made of the metal, or a material composed of a plurality of types of metals is used. Specifically, the bonding material 19 has a thin plate shape (sheet shape) made of silver, copper, and titanium. The bonding material 19 is formed in a sheet shape having a thickness of 0.05 [mm]. The bonding material 19 is not limited to a sheet-like material, and a slurry-like material can also be applied. However, in view of uniforming the thickness of the bonding layer between the graphite members 11 and 12 in the graphite composite 10 and suppressing the generation of bubbles in the bonding layer, the bonding material 19 was formed to have a uniform thickness. A sheet is preferable. Note that a material containing silver, copper, titanium, and tin may be applied as the bonding material 19.

  The graphite complex 10 is obtained by joining the joining surface of the graphite member 11 and the joining surface of the graphite member 12 using a sheet-like joining material 19. When the bonding material 19 is heated and melted with the bonding material 19 interposed between the bonding surfaces, the bonding surfaces are bonded to each other. As a bonding method between the bonding surfaces, brazing (brazing), solid phase diffusion bonding, liquid phase diffusion bonding, or the like can be applied. In this embodiment, as will be described later, liquid phase diffusion bonding is used. The joint surfaces are joined to each other. A specific joining process will be described later.

  The joint surfaces of the graphite members 11 and 12 are in a state in which the edges of the plurality of graphene sheets 15 are overlapped, and are generally referred to as edge surfaces. As described above, since the graphene sheet 15 is formed by covalently bonding six-membered rings, the plane direction in the graphene sheet 15 (direction along the YZ plane) is a strong covalent bond due to the six-membered ring, Are connected. However, since the supply bond in the plane direction by the six-membered ring is cut at the bonding surface, the bonding of carbon atoms on the bonding surface is in an unsaturated state. Therefore, the bonded surface is in an active state in which carbon atoms easily react with other substances.

  In the present embodiment, as described above, the bonding material 19 for bonding the bonding surfaces in the active state contains titanium. Titanium is a so-called active metal, and has extremely high wettability with respect to the bonding surface, that is, bonding reactivity with unsaturated carbon atoms. For this reason, when the bonding material 19 is heated and melted, atomic diffusion of the bonding surface is induced, titanium and carbon react positively, and titanium carbide (TiC) which is a titanium compound between the bonding surfaces. Is generated. Of course, not only the titanium compound but also a metal compound of each metal (copper, silver, etc.) constituting the bonding material 19 and carbon is generated. Thereby, there is no joining interface on the joining surfaces of the graphite members 11 and 12, and the graphite member 11 and the graphite member 12 are firmly joined by the metal compound.

  The thus configured graphite composite 10 can achieve a thermal conductivity of approximately 1500 [W / mK] to 1700 [W / mK] in the Y direction and Z direction of the graphite composite 10. .

  Hereinafter, the manufacturing method of the graphite complex 10 is demonstrated.

  For the manufacture of the graphite composite 10, a mold apparatus 30 shown in FIG. 3 is used. The mold apparatus 30 accommodates graphite members 11 and 12 that are components of the graphite complex 10 and a bonding material 19 for bonding them. As shown in FIG. 3, the mold apparatus 30 has a female mold 31 and a male mold 32.

  The female mold 31 and the male mold 32 are made of general graphite (graphite that does not have non-high orientation), and are obtained by cutting a graphite block (black smoke block). The linear expansion coefficient of the female mold 31 and the male mold 32 is about 4.5 [ppm / K] to 5.5 [ppm / K]. Although graphite is inferior to aluminum in terms of thermal conductivity, its thermal conductivity is 116 [W / mK], which is relatively large, good heat transfer in vacuum, high heat resistance, and few impurities. Therefore, it is suitable for the mold apparatus 30 for manufacturing the graphite composite 10. In addition, even when the bonding material 19 is heated and melted and sticks to the inner wall of the female die 31 as will be described later, if the material of the female die 31 is graphite, the fixing can be easily removed. Can do.

  The female die 31 is a block body having a square cross section in the horizontal direction. The female die 31 is formed with an accommodating portion 34 having a square cross section that is recessed from the upper surface 31A to the lower surface. The accommodating portion 34 is formed in a size that allows the graphite members 11 and 12 to have a gap in the front and rear and right and left. Moreover, the depth of the accommodating part 34 is formed in the size which does not protrude from the upper surface 31A of the female type | mold 31 in the state in which the graphite members 11 and 12 and the joining material 19 were accommodated. The graphite members 11 and 12 are accommodated in the accommodating portion 34.

  A plurality of screw holes 36 for attaching the male die 32 are formed on the upper surface 31A of the female die 31. Eight screw holes 36 are formed so as to surround the accommodating portion 34.

  As with the female die 31, the male die 32 is a block body having a square cross section in the horizontal direction. On the lower surface 32A of the male mold 32, a convex fitting portion 37 protruding downward from the lower surface 32A is formed. 37 A of fitting parts are the parts inserted in the accommodating part 34, and are formed in the cross-sectional square similarly to the accommodating part 34. FIG.

  The male mold 32 is formed with eight through holes 38 penetrating from the upper surface 31A to the lower surface. These through holes 38 are formed at positions corresponding to the screw holes 36.

  When the male die 32 is combined with the upper surface of the female die 31 and the fitting portion 37 is fitted into the accommodating portion 34, the female die 31 and the male die 32 are assembled vertically.

  In manufacturing the graphite composite 10, first, as shown in FIG. 3, the graphite members 11 and 12 and the bonding material 19 are accommodated in the accommodating portion 34. Specifically, the graphite member 12 is disposed on the bottom of the housing portion 34, the joining material 19 is placed thereon, and the graphite member 11 is placed on the joining material 19 so as to sandwich the joining material 19 in the vertical direction. At this time, the graphite members 11 and 12 are accommodated in the accommodating portion 34 so that the lamination direction of the graphite member 11 and the lamination direction of the graphite member 12 coincide. Thereafter, a later-described regulating plate 35 is inserted into the accommodating portion 34.

  As shown in FIG. 4, the restriction plate 35 is inserted into the gap ΔT <b> 1 between the graphite members 11, 12 and the inner walls 34 </ b> A, 34 </ b> B of the housing portion 34. The restriction plate 35 is for restricting the amount of expansion of the graphite members 11 and 12 in the stacking direction by heating to be within a predetermined allowable range. The restriction plate 35 is a plate-like member having a predetermined thickness and made of the same material as the graphite members 11 and 12.

  As described above, the graphite members 11 and 12 have a structure in which the graphene sheets 15 are laminated in one direction. When the graphite members 11 and 12 are heated, each of the graphene sheets 15 expands in the sheet thickness direction (the same direction as the stacking direction) according to the linear expansion coefficient. When each of the graphene sheets 15 expands in the thickness direction and the expansion amount is stacked, the graphite members 11 and 12 expand in the stacking direction. Since highly oriented pyrolytic graphite is used as the graphite members 11 and 12, when the graphite members 11 and 12 are heated without restricting the expansion in the stacking direction, the graphite members 11 and 12 expand greatly compared to a general graphite member. Therefore, in this embodiment, the regulating plate 35 is inserted into the gap ΔT1, and the expansion amount of the graphite members 11 and 12 in the stacking direction, that is, the length after expansion is set to the length L1 in the stacking direction before heating. (Refer to FIG. 5 (A)) is adjusted to be 105% to 125% (corresponding to the allowable range of the present invention), that is, to be 1.05 to 1.25 times the length L1. doing.

  In order to stabilize the graphite members 11 and 12 in the accommodating portion 34, a support plate for supporting the graphite members 11 and 12 in the gap ΔT2 between the graphite members 11 and 12 and the inner walls 34C and 34D of the accommodating portion 34. (Not shown) may be inserted.

  When the graphite members 11 and 12, the bonding material 19, and the regulation plate 35 are accommodated in the accommodation portion 34, the male die 32 is combined with the upper surface of the female die 31, and the female die 31 and the male die 32 are assembled vertically. . At this time, the lower surface of the fitting portion 37 of the male mold 32 comes into contact with the upper surface of the graphite member 11. In this state, the screw 39 is inserted into the through hole 38 and attached to the screw hole 36, and the female die 31 and the male die 32 are fixed (see FIG. 4B).

  In the mold apparatus 30, the tightening depth of the screw 39 can be arbitrarily adjusted. By adjusting the tightening depth of the screw 39, a predetermined load can be applied to the graphite members 11 and 12 in the vertical direction. In this embodiment, a weight of 5.0 to 25 [MPa] can be applied to the graphite members 11 and 12 in the vertical direction.

The mold apparatus 30 is heated in a vacuum furnace in a state where the members such as the graphite members 11 and 12 are accommodated in the accommodating portion 34. Thereby, the joining material 19 is heated and melted in a state where the joining material 19 is interposed between the joining surfaces of the graphite members 11 and 12. Specifically, in the mold apparatus 30, the graphite members 11 and 12 are applied with a load of about 15 [MPa] in the vertical direction, and the vacuum environment is 10 ⁻³ Pa and the temperature environment is 805 degrees Celsius. It is heated for 30 minutes to 1 hour.

  FIG. 5 is a diagram showing a change in the state of the graphite members 11 and 12 when the mold apparatus 30 is heated in the vacuum furnace. FIG. 5A shows a state before heating, FIG. 5B shows a state during heating, and FIG. 5C shows a state after completion of heating. Note that arrows P1 and P2 in FIG. 5 indicate the direction of pressure applied to the graphite members 11 and 12, arrows P3 and P4 indicate the expansion direction of the graphite members 11 and 12, and arrows P5 and P6 indicate the direction from the restriction plate 35. It shows the direction of the reaction force.

  When heating of the mold apparatus 30 is started in the vacuum furnace, the graphite members 11 and 12 begin to gradually expand in the stacking direction (see FIG. 5B). When the expansion further proceeds, both ends of the graphite members 11 and 12 in the stacking direction come into contact with the restriction plate 35, and further expansion is restricted by the reaction force received from the restriction plate 35 (see FIG. 5C). ).

  When the in-furnace temperature of the vacuum furnace exceeds 760 ° C., the bonding material 19 starts to melt and diffuses from the bonding surfaces of the graphite members 11 and 12 into the graphite members 11 and 12. As the bonding material 19 diffuses into the graphite members 11 and 12, the composition of the bonding surface starts to change. Specifically, titanium and carbon react positively on the joint surfaces of the graphite members 11 and 12, and the joint layer 17 made of titanium carbide (TiC) is generated on the joint surfaces. The average thickness of the bonding layer 17 is about 0.02 [mm]. The melting point of titanium carbide is 3170 ° C., which is higher than each element of the bonding material 19. Therefore, the melting point near the joint surface rises and solidifies with the composition change of the joint surface, and the joint surfaces of the graphite members 11 and 12 are joined to each other. At this time, the bonding layer 17 is solidified while maintaining a length of 1.05 to 1.25 times the original length L1. Thereby, the graphite complex 10 in which the minute gap ΔD (see FIG. 2) corresponding to the expansion amount in the stacking direction is formed between the graphene sheets 15 is manufactured. In addition, the above-mentioned joining method is called liquid phase diffusion joining.

  Thereafter, the mold apparatus 30 is slowly cooled in the furnace. Here, the bonding layer 17 is made of titanium carbide, and its linear expansion coefficient is 8.0 [ppm / K], which is smaller than the linear expansion coefficient of the graphite members 11 and 12. Therefore, the bonding layer 17 hardly shrinks in the stacking direction as the mold apparatus 30 is cooled, and maintains a length of 1.05 to 1.25 times the original length L1. That is, the graphite composite 10 having a length 1.05 to 1.25 times as long as the original length L1 in the stacking direction is obtained.

  The graphite composite 10 manufactured in this way has flexibility that can be bent in the thickness direction perpendicular to the stacking direction. That is, as shown in FIG. 2, the joining surfaces of the graphite members 11 and 12 are firmly fixed by the joining layer 17, and the other surface of the graphite members 11 and 12 is the end of each graphene sheet 15. The part is not fixed. Further, the graphite members 11 and 12 are held by the bonding layer 17 in a state where the graphite members 11 and 12 extend 1.05 to 1.25 times in the stacking direction with respect to the original length L1 (see FIG. 5A). ing. Therefore, as shown in FIG. 6A, when a downward force (force in the direction indicated by the arrow) is applied to the upper surface of the graphite composite 10, the bonding layer 17 is shaped like a mortar like a leaf spring. Is bent. At this time, the gap ΔD (see FIG. 2) between the adjacent graphene sheets 15 in the graphite member 11 is narrowed, and the gap ΔD (see FIG. 2) between the adjacent graphene sheets 15 in the graphite member 12 is widened. Thereby, the graphite complex 10 bends in the thickness direction. Similarly, as shown in FIG. 6B, when an upward force (force in the direction indicated by the arrow) is applied to the lower surface of the graphite composite 10, the bonding layer 17 is as if it is a leaf spring. It is bent like an arch. At this time, the gap ΔD (see FIG. 2) between the adjacent graphene sheets 15 in the graphite member 11 is widened, and the gap ΔD (see FIG. 2) between the adjacent graphene sheets 15 in the graphite member 12 is narrowed. Thereby, the graphite complex 10 bends in the thickness direction.

  Since the graphite composite 10 has flexibility as described above, even when a heat generating element such as a power semiconductor or power module that is a heat dissipation object vibrates or deforms, the graphite composite 10 follows the vibration or deformation. It can be deformed. Thereby, heat can be efficiently dissipated in the thickness direction of the graphite composite 10, and damage that affects the vibration and deformation of the heat storage body can be prevented.

  The graphite composite 10 described above is mainly used for radiating a semiconductor element 56 as a heat generating element that generates heat, such as a power semiconductor or a power module (an example of a semiconductor element). Hereinafter, the cooling device 50 having the graphite complex 10 and the semiconductor module 60 including the cooling device 50 and the semiconductor element 56 will be described with reference to FIG. 7.

  As shown in FIG. 7, the cooling device 50 includes a graphite complex 10, two copper plates 51 and 52 (an example of an adhesion layer of the present invention) provided so as to sandwich the graphite complex 10, a heat sink, and the like. The heat radiator 55 is provided.

  The copper plates 51 and 52 are formed in a thin foil shape or plate shape, and are joined to both end surfaces (upper surface and lower surface) in the Y direction of the graphite composite 10 as shown in FIG. The thickness of the copper plates 51 and 52 is 0.3 [mm]. Copper plates 51 and 52 are bonded to the upper and lower surfaces of the graphite composite 10 using the same bonding material as the bonding material 19. As a method of joining the graphite composite 10 and the copper plates 51 and 52, brazing (brazing), solid phase diffusion bonding, liquid phase diffusion bonding, or the like can be applied. In addition, although the copper plates 51 and 52 are illustrated as an adhesion layer of this invention, it may replace with the copper plates 51 and 52 and the ceramic plate formed with ceramics, for example. The adhesion layer of the present invention may be a metal film formed by sputtering on the upper and lower surfaces of the graphite composite 10.

  A semiconductor element 56 as a heating element such as a power semiconductor or a power module is attached to the center of the copper plate 51 on the upper surface side of the graphite composite 10. A semiconductor module 60 including the cooling device 50 and the semiconductor element 56 is configured by attaching the semiconductor element 56 to the copper plate 51 on the upper surface side.

  Further, a heat radiator 57 such as a heat sink is attached to the copper plate 52 on the lower surface side. Thereby, the cooling device 50 can efficiently dissipate heat from the semiconductor element 56 attached to the upper side of the graphite complex 10 through the graphite complex 10 and the heat radiator 57.

  In the above-described embodiment, the graphite composite 10 that has been extended to a length of 1.05 to 1.25 times (105% to 125%) in the stacking direction with respect to the original length L1 is illustrated. Within this range, the size of the graphite complex 10 can be changed as appropriate. When the length of the graphite composite 10 in the stacking direction is less than 105%, the minute gap ΔD (see FIG. 2) between the graphene sheets 15 becomes too dense and sufficient bending cannot be obtained. Further, when it exceeds 125%, the gap ΔD becomes too large and the graphene sheets 15 are not supported stably.

10: Graphite composite 11: Graphite member 12: Graphite member 15: Graphene sheet 17: Joining layer 19: Joining material 30: Mold device 31: Female die 32: Male die 35: Restriction plate 50: Cooling devices 51, 52: Copper plate 56: Semiconductor element 57: Heat radiator

Claims (8)

It has a plate-like first heat conductor and a second heat conductor formed by laminating graphene sheets,
A heat conduction structure in which bonding surfaces in a direction orthogonal to the stacking direction are bonded to each other with a predetermined bonding material in a state where the stacking directions of the graphene sheets are matched. The bonding material is a metal having a lower melting point than the first thermal conductor and the second thermal conductor,
The bonding surfaces are bonded to each other by heating and melting the bonding material with the bonding material interposed between the bonding surface of the first heat conductor and the bonding surface of the first heat conductor. The heat conducting structure according to claim 1. A manufacturing method for manufacturing a heat conductive structure having a plate-like first heat conductor and a second heat conductor formed by stacking graphene sheets,
A method of manufacturing a heat conducting structure, characterized in that bonding surfaces in a direction orthogonal to the stacking direction are bonded to each other with a predetermined bonding material in a state where the stacking directions of the graphene sheets are matched. The bonding material is a metal having a lower melting point than the first thermal conductor and the second thermal conductor,
By heating and melting the bonding material in a state where the bonding material is interposed between the bonding surface of the first heat conductor and the bonding surface of the first heat conductor, the bonding surfaces are mutually bonded. The manufacturing method of the heat conductive structure of Claim 3 joined.   The lamination of the first thermal conductor and the second thermal conductor by heating with the bonding material interposed between the joint surface of the first thermal conductor and the joint surface of the first thermal conductor. The heat conduction according to claim 4, wherein the joining surfaces are joined to each other by melting the joining material by heating the whole while restricting the expansion amount in a direction to be within a predetermined allowable range. Manufacturing method of structure.   The said tolerance | permissible_range is 105%-125% with respect to the length of the said lamination direction of the said 1st heat conductor and the said 2nd heat conductor before a heating, The manufacture of the heat conductive structure of Claim 5 Method. The heat conducting structure according to claim 1 or 2,
A thin adhesion layer made of metal or ceramics bonded to both end faces of the heat conducting structure in a direction orthogonal to the laminating direction;
A heat radiator joined to at least one end face of the heat conducting structure,
A cooling device for a heating element that radiates heat from the heating element attached to the other end face of the thermal conduction structure through the thermal conduction structure and the radiator. A cooling device according to claim 7;
And a semiconductor element attached to the other end face of the heat conducting structure of the cooling device.

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