Heat transport structure

Abstract

Heat transport structure includes a plurality of layers, the heat transport structure including a plurality of graphite plates provided side by side in a plane direction of the plurality of graphite plates with ends facing each other, the plurality of graphite plates being included in each of the plurality of layers, and a plurality of metal rivets penetrating, in a lamination direction of the plurality of layers, two or more graphite plates arranged side by side in the lamination direction to couple the two or more graphite plates, the two or more graphite plates each being included in the plurality of graphite plates in a corresponding one of the plurality of layers, in which all graphite plates including the plurality of graphite plates in each of the plurality of layers are integrally coupled by the plurality of rivets.

Description

BACKGROUND1. Technical Field

[0001] The present disclosure relates to a heat transport structure.2. Description of the Related Art

[0002] PTL 1 discloses a heat dissipation plate in which a plate-like metal laminated material made from metal and a plate-like graphite laminated material made from graphite are alternately laminated (Paragraph 0012 of the description). The graphite laminated material has a substantially square shape of 50 mm×50 mm in plan view, and has a thickness dimension of 0.025 mm (Paragraph 0017 of the description).CITATION LISTPatent LiteraturePTL 1: Unexamined Japanese Patent Publication No. 2011-129634SUMMARY

[0004] The present disclosure relates to a heat transport structure including a plurality of layers, the heat transport structure including a plurality of graphite plates provided side by side in a plane direction of the plurality of graphite plates with ends facing each other, the plurality of graphite plates being included in each of the plurality of layers, and a plurality of metal rivets penetrating, in a lamination direction of the plurality of layers, two or more graphite plates arranged in the lamination direction, and coupling the two or more graphite plates, the two or more graphite plates each being included in the plurality of graphite plates in a corresponding one of the plurality of layers, in which all graphite plates including the plurality of graphite plates in each of the plurality of layers are integrally coupled by the plurality of rivets.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1 is a plan view illustrating a first layer of a heat transport structure according to a first exemplary embodiment;

[0006] FIG. 2 is a plan view illustrating a second layer of the heat transport structure;

[0007] FIG. 3 is an exploded perspective view schematically illustrating the heat transport structure;

[0008] FIG. 4 is a cross-sectional view of the heat transport structure taken along line IV-IV in FIGS. 1 to 2;

[0009] FIG. 5 is a top view illustrating a lamination state in the heat transport structure;

[0010] FIG. 6 is a perspective view illustrating a precursor of a three-dimensional structure prepared by combining the heat transport structures;

[0011] FIG. 7 is a perspective view illustrating the three-dimensional structure;

[0012] FIG. 8 is a perspective view illustrating an inner mold and an outer mold for pouring molten metal onto an outer surface and an inner surface of the three-dimensional structure;

[0013] FIG. 9 is a plan view illustrating each layer of the heat transport structure in a second exemplary embodiment;

[0014] FIG. 10 is a diagram corresponding to FIG. 5 and according to the second exemplary embodiment;

[0015] FIG. 11 is a diagram illustrating an X-ray image of a sample of the heat transport structure obtained in Examples 1 to 3;

[0016] FIG. 12 is a diagram illustrating a photograph and an X-ray image of a sample of the heat transport structure obtained in Example 4; and

[0017] FIG. 13 is a diagram illustrating a photograph and an X-ray image of a sample of the heat transport structure obtained in Example 5.DETAILED DESCRIPTIONS

[0018] The graphite laminated material (hereinafter referred to as “heat transport structure”) disclosed in PTL 1 has a relatively small size of 50 mm×50 mm in plan view, but it is required to increase an area (dimension in a plane direction) from the viewpoint of versatility. However, there is a limit to increasing an area of each graphite sheet, and it is difficult to increase size of the heat transport structure while allowing high thermal conductivity of graphite to effectively utilized in the conventional technique.

[0019] An object of the present disclosure is to increase size of a heat transport structure while maintaining high thermal conductivity.First Exemplary Embodiment—Heat Transport Structure—

[0020] Hereinafter, a first exemplary embodiment of the present disclosure will be described. Heat transport structure 1 according to the present exemplary embodiment can be used with electronic equipment including a semiconductor device, an in-vehicle device, and the like, and equipment used in the space field such as a rocket and an artificial satellite. Heat transport structure 1 can efficiently transport heat from these devices and suppress occurrence of a problem due to heat stagnation and the like.

[0021] Heat transport structure 1 includes a plurality of layers 2 illustrated in FIGS. 1 to 2. The number of layers 2 is not particularly limited as long as the number is two or more, but is preferably 10 or more, more preferably 20 or more, and still more preferably from 30 to 100 inclusive (for example, 60 layers). Note that, hereinafter, “plan view” means that heat transport structure 1 is viewed from the upper side (the near side in FIGS. 1 and 2) or the lower side (the far side in FIGS. 1 and 2). Indication of directions such as “upper” and “lower” is an expression used to describe a configuration of the present disclosure, and does not limit the use of the present disclosure.

[0022] Heat transport structure 1 is configured by alternately laminating first layer 2a illustrated in FIG. 1 and second layer 2b illustrated in FIG. 2 as illustrated in FIG. 3. FIG. 4 illustrates a cross section of heat transport structure 1 along the direction of line IV-IV in FIGS. 1 to 2. In FIG. 4, for the sake of explanation, only first layer 2a and second layer 2b immediately above first layer 2a are illustrated.

[0023] Heat transport structure 1 includes a plurality of plates 3, . . . , 3 made from graphite in each of layers 2a and 2b. By providing the plurality of plates 3, . . . , 3 in each of layers 2a, 2b, it is possible to increase size of heat transport structure 1. The thickness of plate 3 is not limited, but is preferably from 0.01 mm to 0.5 mm inclusive. The specific gravity of plate 3 is not limited, but is preferably from 1.0 to 2.2 inclusive. The thermal conductivity of plate 3 in the plane direction is preferably from 1000 W / m·K to 1500 W / m·K inclusive. Further, the thermal conductivity in the lamination direction is preferably 400 W / m·K or more.

[0024] Plate 3 has a structure in which planes formed by fused benzene rings are stacked in layers, and a fused-benzene-ring plane functions as a basal plane. Note that, hereinafter, a basal plane direction is simply referred to as a “plane direction”. Each plate 3 is obtained by firing one or more polymer films (for example, at least one type selected from a group including polyoxadiazole, polybenzothiazole, polybenzobisthiazole, polybenzoxazole, polybenzobisoxazole, polypyromellitimide, aromatic polyamide, poly(p-phenylene benzimidazole), poly(p-phenylene benzobisimidazole), polythiazole, and poly(p-phenylene vinylene)) while controlling applied pressure, and is highly oriented and graphitized.

[0025] In each of layers 2a and 2b, plates 3 are provided side by side in the plane direction with ends 3a facing each other. In each of first layer 2a and second layer 2b, four plates 3, . . . , 3 are provided, and, among them, two plates 3, 3 (plates 3, 3 illustrated in the upper left and the upper right of each of FIGS. 1 and 2) have the same shape. Further, when entire first layer 2a is turned over (in other words, FIG. 1 is entirely horizontally inverted), first layer 2a has the same shape as second layer 2b. In this way, required variations of the shape of plate 3 are reduced, and manufacturing is facilitated. In each of first layer 2a and second layer 2b, plates 3, 3 adjacent in the plane direction are arranged with gaps 3b, 3c between ends 3a and 3a.

[0026] Plate 3 illustrated in the upper left of FIG. 1 overlaps two plates 3, 3 illustrated in the upper left and the lower left of FIG. 2 in plan view. Plate 3 illustrated in the upper right of FIG. 1 overlaps two plates 3, 3 illustrated in the upper left and upper right of FIG. 2 in plan view. Plate 3 illustrated in the lower right of FIG. 1 overlaps three plates 3, 3, 3 illustrated in the upper right, lower right, and lower left of FIG. 2 in plan view. Therefore, as illustrated in FIG. 5, heat transport structure 1 has first region R1 in which gaps 3b and 3c are located and second region R2 (dot hatching in FIG. 5) in which gaps 3b and 3c are not located and which is sandwiched between first regions R1 in plan view.

[0027] In FIG. 5, a region excluding first region R1 in a region where plate 3 is disposed forms facing region R0 where an upper surface of plate 3 of first layer 2a and a lower surface of plate 3 of second layer 2b immediately above first layer 2a face each other. Facing surfaces (an upper surface of first layer 2a and a lower surface of second layer 2b) between plates 3, 3 adjacent in the lamination direction are in contact with each other over at least half of an area of facing region R0. Therefore, since plates 3, 3 adjacent to each other in the lamination direction are in contact with each other in a wide area, high thermal conductivity can be obtained in the lamination direction.

[0028] Heat transport structure 1 includes a plurality of metal rivets 4, 4, . . . that penetrate, in the lamination direction, two or more plates 3, 3, . . . arranged in the lamination direction and couple two or more plates 3, 3, . . . . A material of rivets 4, 4, . . . is not limited as long as it is metal, but is preferably brass from the viewpoint of high thermal conductivity and strength. A plurality of holes h, . . . , h through which rivets 4 are inserted are formed to penetrate each plate 3 in a vertical direction. Although plates 3, 3 adjacent in the plane direction are not directly coupled to each other, plates 3, 3, . . . arranged in the lamination direction are coupled to each other by a plurality of rivets 4, 4, . . . , so that plates 3, 3, . . . in a plurality of layers 2, 2, . . . are integrally coupled. That “plates 3, 3, . . . are integrally coupled” means that plates 3, . . . , 3 constituting heat transport structure 1 do not come apart even if plates 3 are not adhered to each other.

[0029] For example, plate 3 illustrated in the upper left of FIG. 1 is coupled to two plates 3, 3 illustrated in the upper left and the lower left of FIG. 2, respectively, by a plurality of rivets 4, . . . , 4. Similarly, plates 3, 3 illustrated in the upper right and lower right of FIG. 1 are respectively coupled to two plates 3, 3 and three plates 3, 3, 3 of FIG. 2 by a plurality of rivets 4, . . . , 4.

[0030] In a case where heat transport structure 1 is increased in size by increasing the number of plates 3 without increasing size of each plate 3, the number of gaps 3b, 3c is increased. In gaps 3b and 3c, heat conduction in the plane direction through graphite is cut off in each layer 2. Further, even if plates 3, 3 are arranged so as to be in contact with each other in the plane direction so as to eliminate gaps 3b and 3c, thermal conductivity in the plane direction decreases at end 3a of plate 3. For this reason, in a case where size of heat transport structure 1 is increased, how to ensure thermal conductivity in the plane direction becomes a problem.

[0031] Here, in the present disclosure, since plates 3, . . . , 3 are integrally coupled by a plurality of metal rivets 4, . . . , 4, heat transport structure 1 is increased in size, and thermal conductivity is secured through rivets 4. For example, referring to FIG. 4, in plates 3, 3 adjacent to each other in the plane direction in first layer 2a, direct heat conduction in the plane direction through graphite is cut off in gap 3b, but heat conduction can be performed through rivet 4 illustrated in a central portion of FIG. 4 and the periphery of rivet 4, so that heat conductivity between the layers is increased. That is, a path of heat in the lamination direction is more reliably secured by rivet 4. As a result, heat conduction in the plane direction is also possible beyond gaps 3b and 3c. Therefore, according to the present disclosure, high thermal conductivity can be maintained even when the number of plates 3 increases.

[0032] Further, since second region R2 is sandwiched between first regions R1 in plan view, thermal conduction in the plane direction in each layer 2 is likely to be cut off by gaps 3b and 3c near second region R2. In the present exemplary embodiment, since at least one rivet 4 is provided in second region R2, high thermal conductivity can be more reliably maintained. In the present exemplary embodiment, as illustrated in FIG. 5, in plan view, second regions R2 are provided at four places with first region R1 interposed among them, and a plurality of rivets 4, . . . , 4 are provided in each of second regions R2. Note that, as in the present exemplary embodiment, when plates 3 arranged in the lamination direction have different shapes and sizes between first layer 2a and second layer 2b, it is easy to obtain heat transport structure 1 having second region R2.—Three-Dimensional Structure—

[0033] Although heat transport structure 1 described above spreads in a planar shape, as illustrated in FIGS. 6 to 7, for example, a box-shaped heat transport structure 1 (hereinafter referred to as “three-dimensional structure 5”) having a three-dimensional spread can be manufactured by providing bent portion C (curved portion C) bent (curved) in a direction deviated from the plane direction. Note that, hereinafter, bent portion C means a relatively sharply bent portion (a portion with a large curvature) in three-dimensional structure 5, and curved portion C means a relatively gently bent portion (a portion with a small curvature) in three-dimensional structure 5.

[0034] In each plate 3 of three-dimensional structure 5, a cutout portion may be formed on a surface (upper surface in FIG. 6) on the opposite side to a bending (curving) direction in bent portion C (curved portion C). When the cutout portion is formed in each plate 3, bent portion C (curved portion C) is easily formed. Note that depth of the cutout portion is preferably 10% to 50% of the thickness of plate 3.

[0035] Note that three-dimensional structure 5 may be manufactured by combining a plurality of planar heat transport structures 1 provided with bent portion C.—Metal Body—

[0036] Heat transport structure 1 and three-dimensional structure 5 may include metal body M in which a plurality of layers 2, . . . , 2 (hereinafter referred to as “graphite laminate”) are embedded as specifically described in Examples described later. By being embedded in metal body M, the graphite laminate is less likely to be damaged. Metal body M covers both surfaces and ends of the graphite laminate. A specific material of metal body M is not limited, but metal body M is preferably made from, for example, an aluminum alloy. A dimension of metal body M is not limited, but it is preferable that the thickness is from 0.1 mm to 50 mm inclusive on each of both surfaces of the graphite laminate. In a case where metal body M is provided, hole H penetrating in the lamination direction is preferably formed in the graphite laminate so that a material of metal body M spreads over both surfaces.

[0037] FIG. 8 illustrates inner mold 6 and outer mold 7 which are sand molds for forming metal body M. Inner mold 6 is formed in a substantially cubic shape, and outer mold 7 is formed in a square frame shape in top view surrounding a side surface of inner mold 6. A fixing plate 8 to which a lower portion of the graphite laminate is fixed is provided below inner mold 6 and outer mold 7, and heater plate 9 is provided below fixing plate 8. Heater (electric heating wire) 10 is connected to heater plate 9.

[0038] Metal body M can be produced, for example, as follows by using above inner mold 6, outer mold 7, and the like. First, as illustrated in FIG. 8, the graphite laminate is installed so as to cover an upper surface and a side surface of inner mold 6 and have a lower portion fixed to fixing plate 8. Next, in this state, molten metal at a high temperature (for example, 700° C. or more) is poured into outer mold 7 while heating heater plate 9 and the graphite laminate with electric heating wire 10. When hole H is provided in the graphite laminate, the molten metal easily spreads over both surfaces through hole H. Heating with electric heating wire 10 is continued until the molten metal is completely solidified. After the molten metal is completely solidified, heating with electric heating wire 10 is stopped. As described above, metal body M in which the graphite laminate is embedded is obtained.

[0039] Heat transport structure 1 (or three-dimensional structure 5) including metal body M preferably has a specific gravity less than or equal to 2.7, a thermal conductivity in the lamination direction is preferably more than or equal to 400 W / m·K, and a thermal conductivity in the plane direction of plate 3 is preferably from 1000 W / m·K to 1500 W / m·K inclusive.Second Exemplary Embodiment

[0040] Hereinafter, a second exemplary embodiment of the present disclosure will be described below, focusing on differences from the first exemplary embodiment. Heat transport structure 1 according to the present exemplary embodiment is different from the first exemplary embodiment in the shape of each plate 3. In the present exemplary embodiment, as illustrated in FIG. 9, when entirely rotated by 90° in the plane, four plates 3, . . . , 3 constituting each layer 2 become four plates 3, . . . , 3 constituting other layers 2. When one of two plates 3, 3 among four plates 3, . . . , 3 of each layer 2 is reversed (an upper surface and a lower surface are reversed), the plate has the same shape as the other. In heat transport structure 1 according to the present exemplary embodiment, four layers 2, . . . , 2 illustrated in order from the left side to the right side in FIG. 9 are laminated in order from the bottom to the top or from the top to the bottom. Note that, in FIG. 9, holes h are not illustrated, and positions of holes h are illustrated in FIG. 10.

[0041] In each layer 2, gaps 3b to 3e are provided between plates 3, 3 adjacent in the plane direction. As illustrated in FIG. 10, heat transport structure 1 has, in plan view, first region R1 where gaps 3b to 3e are located and second region R2 where gaps 3b to 3e are not located, second region R2 being sandwiched between first regions R1. FIG. 10 illustrates five second regions R2 divided by first regions R1, and one rivet 4 is inserted through each of four second regions R2 excluding a central portion. Further, in facing regions R0 between plates 3, four rivets 4 are also inserted into portions other than second region R2.

[0042] As in the present exemplary embodiment, when one layer 2 that is rotated has the same shape as other layers 2, variations in the shape of plate 3 required are reduced, and manufacturing is facilitated.Other Exemplary Embodiments

[0043] In the present disclosure, plates 3, . . . , 3 in a plurality of layers 2, . . . , 2 only need to be integrally coupled by coupling plates 3, . . . , 3 arranged in the lamination direction by a plurality of rivets 4, . . . , 4, and thus, for example, a specific configuration such as the number and shape of plates 3 is not limited to the above embodiment. However, at least one of plates 3, . . . , 3 arranged in the lamination direction overlaps two or more plates 3, . . . , 3 adjacent in the plane direction in another layer in plan view, and is coupled to the two or more plates 3, . . . , 3 by rivets 4.

[0044] In each of the above embodiments, gaps 3b to 3e are provided between ends 3a and 3a of adjacent plates 3, 3 in each layer 2, but ends 3a and 3a of adjacent plates 3, 3 may be in contact with each other without gaps 3b to 3e. EXAMPLESExample 1

[0045] A graphite laminate was prepared by laminating 60 graphite plates having a dimension of 6 mm×110 mm in plan view and a thickness of 0.1 mm. A liquid aluminum alloy A5052 was poured around the graphite laminate at a molten metal temperature (heater temperature) of 700° C., curing time was set to 5 minutes to prepare a metal body, and a sample of a heat transport structure was obtained. The metal body covered the graphite laminate with a substantially constant thickness of about 2 mm on each side of the graphite laminate. The thickness of the entire sample including the graphite laminate and the metal body was about 10 mm. The sample was not provided with a curved portion or a bent portion. Note that FIG. 11 illustrates an X-ray image of the sample obtained in Examples 1 to 3.

[0046] Specific gravity and thermal conductivity in the plane direction of the obtained sample were measured. The specific gravity was calculated by first measuring the weight by using an electronic balance (AUX220 manufactured by Shimadzu Corporation), and then dividing the weight by volume. In order to measure the thermal conductivity, a hot plate was brought into contact with one of both ends in the plane direction of the sample, a cooling plate was brought into contact with the other end to generate a temperature difference, and the other outer peripheral surfaces of the sample were covered with a heat insulating material. In this state, the temperature difference of the sample was measured, and the thermal conductivity was calculated based on the one-dimensional steady-heat conduction equation. Further, flexural strength of the sample was also measured.Example 2

[0047] A sample of a heat transport structure was obtained in the same manner as in Example 1 except that cutout portions having a depth of about 0.05 mm and a length of about 6 mm were formed at two places in each of 60 plates, and specific gravity, thermal conductivity, and flexural strength were measured. Note that positions of the cutout portions are the same between each plate.Example 3

[0048] A sample of a heat transport structure was obtained in the same manner as in Example 1 except that a fractured portion was formed at one place in each of 60 plates, and specific gravity, thermal conductivity, and flexural strength were measured. Note that the fractured portion was provided at different positions in each plate so that the graphite laminate would not come apart by the fractured portions (and a path of heat conduction would be secured).Example 4

[0049] As in Example 2, two cutout portions were formed in each plate to prepare a graphite laminate. Two bent portions were formed by bending the portions of the cutout portions of the graphite laminate by about 90° in a direction of a surface on the opposite side to a surface where the cutout portions were formed. A metal body was prepared around the graphite laminate under the same condition as in Example 1 to obtain a sample of the heat transport structure, and specific gravity and thermal conductivity were measured. Note that a photograph of the sample obtained in Example 4 is shown on the left side of FIG. 12, and an X-ray image of this sample is shown on the right side of FIG. 12.Example 5

[0050] As in Example 1, a graphite laminate without a cutout portion was prepared. Two curved portions were formed by bending two portions of the graphite laminate at about 90°. A metal body was prepared around the graphite laminate under the same condition as in Example 1 to obtain a sample of the heat transport structure, and specific gravity and thermal conductivity were measured. Note that a photograph of the sample obtained in Example 5 is shown on the left side of FIG. 13, and an X-ray image of this sample is shown on the right side of FIG. 13.Result

[0051] Table 1 shows specific gravity and thermal conductivity measured in Examples 1 to 5.TABLE 1Example 1Example 2Example 3Example 4Example 5Sample shapeFlatFlatFlatCutout portionCurved portionand featurecutout portionfracturedis formedis formedis formedportionbent portionis formedis formedThermal406399366382390conductivity(W / mK)Specific gravity2.392.402.372.382.37(g / cm3)Flexural strength132132136(N / mm2)

[0052] As shown in Table 1, in all of Examples 1 to 5, a heat transport structure having high thermal conductivity and low specific gravity was obtained.

[0053] Since the heat transport structure of the present disclosure includes a plurality of plates made from graphite provided side by side in the plane direction in each layer, the heat transport structure can be increased in size. Further, a plurality of metal rivets penetrate, in the lamination direction, and couple a plurality of plates arranged in the lamination direction, by which the plates are integrally coupled. As a result, the heat transport structure is increased in size, and thermal conductivity is secured through the rivets. Therefore, according to the present disclosure, it is possible to increase the size of the heat transport structure while maintaining high thermal conductivity.

[0054] The present disclosure is useful as a heat transport structure.

Claims

1. A heat transport structure including a plurality of layers, the heat transport structure comprising:a plurality of graphite plates provided side by side in a plane direction of the plurality of graphite plates with ends facing each other, the plurality of graphite plates being included in each of the plurality of layers; anda plurality of metal rivets penetrating, in a lamination direction of the plurality of layers, two or more graphite plates arranged in the lamination direction, and coupling the two or more graphite plates, the two or more graphite plates each being included in the plurality of graphite plates in a corresponding one of the plurality of layers,wherein all graphite plates including the plurality of graphite plates in each of the plurality of layers are integrally coupled by the plurality of rivets.

2. The heat transport structure according to claim 1,wherein the plurality of layers includes at least a first layer and a second layer laminated on the first layer,wherein in each of the first layer and the second layer, adjacent plates which are adjacent to each other among the two or more graphite plates arranged side by side in the plane direction are disposed with a gap between ends of the adjacent plates, andin plan view, the each of the first layer and the second layer includes a first region in which the gap is located and a second region in which the gap is not located, the second region being sandwiched between a plurality of first regions, and at least one of the plurality of rivets is provided in the second region.

3. The heat transport structure according to claim 1, wherein facing surfaces between the two or more graphite plates adjacent in the lamination direction are in contact with each other over at least half of an area of the two or more graphite plates.

4. The heat transport structure according to claim 1, further comprising a curved portion or a bent portion curved or bent in a direction deviated from the plane direction.

5. The heat transport structure according to claim 4, whereina thickness of each of the plurality of graphite plates is from 0.01 mm to 0.5 mm inclusive, andthe plurality of graphite plates include a cutout portion having a depth of 10% to 50% of the thickness, the cutout portion being formed in the plate on a surface of the curved portion or the bent portion on an opposite side to the direction in which the curved portion or the bent portion is curved or bent.

6. The heat transport structure according to claim 1, further comprising a metal body in which the plurality of layers are embedded, whereinthermal conductivity of each of the plurality of graphite plates in the plane direction is from 1000 W / m·K to 1500 W / m·K inclusive,thermal conductivity of each of the plurality of graphite plates in the lamination direction is more than or equal to 400 W / m·K, andspecific gravity of each of the plurality of graphite plates is less than or equal to 2.7

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