JP2008159995A - Heat sink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat sink which reduces the resistance to heat. <P>SOLUTION: The heat sink 40 includes a vertical anisotropic heat conductive sheet 41, and a horizontal anisotropic heat conductive sheet 42, formed on the vertical anisotropic heat conductive sheet 41. The outer peripheral edge of the horizontal anisotropic heat conductive sheet 42 is disposed inside the outer peripheral edge of the vertical anisotropic heat conductive sheet 41, when the heat sink 40 is seen from above. The vertical anisotropic heat conductive sheet 41 has a recess, and the horizontal anisotropic heat conductive sheet 42 is arranged so as to fill the recess. The heat sink 40 also includes a metal film 44, which is formed on the surface of the horizontal anisotropic heat conductive sheet 42 and carries a heat source 45. The heat sink 40 further includes a radiation fin 46, which is connected to at least either of the vertical anisotropic heat conductive sheet 41 and the horizontal anisotropic heat conductive sheet 42. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat sink, and more particularly, to a heat sink having a composite structure of longitudinal and transverse anisotropic thermal conductive sheets.

  In recent years, electronic devices have been improved in performance and miniaturized, and accordingly, electronic components such as semiconductors have been increased in density and functionality. Due to the increase in density and functionality of electronic components, the electronic components themselves generate a large amount of heat. If this heat is left as it is, the quality of the electronic component is deteriorated or the electronic component is damaged. Therefore, an apparatus or mechanism for efficiently removing the heat generated by the electronic component is desired. .

  As a method for removing the heat generated by the heat source in such an electronic device, Japanese Patent Application Laid-Open No. 2002-76217 (Patent Document 1) discloses carbon that forms anisotropic thermally conductive fibers having anisotropy in the lateral direction. A heat dissipation unit having fibers is disclosed. The heat dissipating unit disclosed in Patent Document 1 is intended to effectively release heat to a housing or the like.

  Here, in order to efficiently remove the heat generated by the heat source, it is effective to reduce the thermal resistance of the member that removes the heat. Thermal resistance is proportional to the thickness of the member, and inversely proportional to thermal conductivity and heat dissipation area.

  In the method disclosed in Patent Document 1, anisotropic heat conductive fibers having anisotropy in the lateral direction are used. In such a transversely anisotropic thermal conductive sheet, fibers with high thermal conductivity in the transverse direction are oriented in the polymer sheet, so that the polymer is filled in the meantime, and the heat is little in the longitudinal direction. I don't get it. Therefore, although the heat radiation area of the heat source is enlarged, the thermal conductivity in the vertical direction is low. As a result, there is a problem that the thermal resistance is not sufficiently reduced.

  In addition, when using a longitudinal anisotropic heat conductive sheet in which fibers with high thermal conductivity are oriented in the polymer sheet in the longitudinal direction, the polymer is filled between the fibers in the longitudinal direction. Hardly receives heat. Therefore, since the bottom area of the heat generation source is projected as it is, the area cannot be expanded. As a result, there is a problem that the thermal resistance is not sufficiently reduced.

Furthermore, when an isotropic thermal conductive sheet having the same thermal conductivity in the vertical direction and the horizontal direction is used, heat is transmitted downward from the heat source 225 at an angle of approximately 45 ° as shown in FIG. . That is, the heat radiation area is expanded at an angle of about 45 ° from the area of the heat source. Although the heat radiation area is enlarged, the thickness D3 of the member (heat sink 200) for removing heat is also enlarged. As a result, there is a problem that the thermal resistance is not sufficiently reduced. FIG. 10 is a schematic cross-sectional view showing a conventional heat sink using an isotropic heat conductive sheet.
JP 2002-76217 A

  An object of the present invention is to solve the above-described problems, and is to provide a heat sink that can reduce thermal resistance.

  The heat sink of the present invention includes a longitudinally anisotropic heat conductive sheet and a transversely anisotropic heat conductive sheet formed on the vertically anisotropic heat conductive sheet. The outer peripheral edge of the transversely anisotropic heat conductive sheet when viewed from above is arranged on the inner side of the outer peripheral edge of the longitudinally anisotropic heat conductive sheet.

  According to the heat sink of the present invention, heat is transferred in the lateral direction by the laterally anisotropic heat conductive sheet, so that the heat radiation area is increased. And heat can be transmitted to the vertical direction with the expanded heat dissipation area by the longitudinal anisotropic heat conductive sheet. Therefore, the thermal resistance can be reduced as a whole.

  In the present specification, the “longitudinal anisotropic heat conductive sheet” means a polymer sheet in which a medium for conducting heat is oriented in a resin only in the vertical direction. In addition, the “transversely anisotropic thermal conductive sheet” means a polymer sheet in which a heat conducting medium is oriented in a resin only in the lateral direction. Further, “viewed from above” means that the laterally anisotropic heat conductive sheet is viewed from the surface opposite to the surface facing the longitudinal anisotropic heat conductive sheet. Further, in the present invention, a relatively large amount of heat is transmitted from the transversely anisotropic heat conductive sheet on the surface intersecting with a direction in which a relatively large amount of heat is transmitted from the longitudinally anisotropic heat conductive sheet. It arrange | positions so that the surface extended along a direction may contact.

  In the heat sink, preferably, the longitudinally anisotropic heat conductive sheet has a recess, and the transversely anisotropic heat conductive sheet is disposed so as to fill the recess.

  Thereby, since the thickness of a longitudinal direction anisotropic heat conductive sheet can be made thinner, thermal resistance can be reduced more.

  Preferably, the heat sink further includes a metal film formed on the surface of the transversely anisotropic heat conductive sheet and for mounting a heat source.

  Thereby, the heat from the heat source mounted on the metal film can be spread uniformly by the transversely anisotropic heat conductive sheet.

  The “surface of the transversely anisotropic heat conductive sheet” means a surface opposite to the surface formed on the longitudinally anisotropic heat conductive sheet in the transversely anisotropic heat conductive sheet. .

  Preferably, the heat sink further includes a radiating fin connected to at least one of the longitudinally anisotropic heat conductive sheet and the transversely anisotropic heat conductive sheet.

  Since heat can also be transmitted to the heat radiating fins, the effect of radiating heat from the heat generation source is further increased.

  According to the heat sink of the present invention, since the longitudinally anisotropic thermal conductive sheet and the laterally anisotropic thermal conductive sheet are provided, the thermal resistance can be reduced as a whole.

  Hereinafter, embodiments and examples of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a schematic perspective view showing a heat sink according to Embodiment 1 of the present invention. 2 is a schematic cross-sectional view taken along line II-II in FIG. With reference to FIG. 1 and FIG. 2, the heat sink in Embodiment 1 of this invention is demonstrated. As shown in FIGS. 1 and 2, the heat sink 10 in the first embodiment includes a longitudinally anisotropic heat conductive sheet 11 and a laterally anisotropic heat conductive sheet 12. The heat sink 10 is a member that is attached to a heat source and diffuses heat.

  The longitudinally anisotropic heat conductive sheet 11 is a polymer sheet in which a heat conducting medium is oriented in a resin only in the longitudinal direction. As a material having such properties, for example, a carbon fiber and a nickel fiber oriented in a polymer can be cited. Specifically, LM-2, TF-1, IOB-3, TP-1, and the like manufactured by Btech can be used as the longitudinal anisotropic heat conductive sheet 11.

  The shape of the longitudinally anisotropic thermal conductive sheet 11 is the lateral direction when the outer peripheral edge 11a of the longitudinally anisotropic thermal conductive sheet 11 is viewed from above (upper side in FIGS. 1 and 2). Although it will not specifically limit if it is arrange | positioned outside the outer periphery 12a of the anisotropic heat conductive sheet 12, The lateral area of the horizontal direction anisotropic heat conductive sheet 12 is so preferable that it is large. As shown in FIG. 1, the shape of the longitudinal anisotropic heat conductive sheet 11 is not limited to a quadrangular column, and may be, for example, a cylinder.

  Moreover, the thickness of the longitudinally anisotropic heat conductive sheet 11 is preferably 1.0 mm or greater and 3.0 mm or less. By setting it to 1.0 mm or more, handling of the longitudinal direction anisotropic heat conductive sheet 11 becomes easy. Manufacturing cost can be reduced by setting it as 3.0 mm or less.

  The thermal conductivity in the vertical direction of the longitudinal anisotropic heat conductive sheet 11 (the direction in which the lateral anisotropic heat conductive sheets 12 are laminated) is preferably 400 W / mK or more. By setting it to 400 W / mK or more, the amount of heat generated by the heating element can be moved quickly and the thermal resistance can be lowered.

  The transversely anisotropic heat conductive sheet 12 is a polymer sheet in which a heat conducting medium is oriented in a resin only in the transverse direction. Specifically, as the laterally anisotropic heat conductive sheet 12, a PGS graphite sheet manufactured by Matsushita Electric Industrial Co., Ltd. can be used.

  The transversely anisotropic heat conductive sheet 12 is formed on the longitudinally anisotropic heat conductive sheet 11. Further, a relatively large amount of heat is transmitted from the transversely anisotropic heat conductive sheet 12 on the surface intersecting the direction (arrow 13b) in which a relatively large amount of heat is transmitted from the longitudinally anisotropic heat conductive sheet 11. It arrange | positions so that the surface extended along the direction (arrow 13a) may be contacted. That is, the direction in which the longitudinal anisotropic heat conductive sheet 11 is relatively easy to transmit heat and the direction in which the transverse anisotropic heat conductive sheet is relatively easy to transmit heat intersect (orthogonal).

  Further, the outer peripheral edge 12a of the transversely anisotropic heat conductive sheet 12 when viewed from above (the upper side in FIGS. 1 and 2) is disposed on the inner side of the outer peripheral edge 11a of the longitudinally anisotropic heat conductive sheet 11. ing.

  The area of the upper surface of the transversely anisotropic heat conductive sheet 12 is preferably 2.0 mm or more and 15 mm or less. By setting the thickness to 2.0 mm or more, it can be mounted on a small package. By setting it to 15 mm or less, it can be mounted on a package corresponding to the power device chip.

  Further, the thermal conductivity of the lateral anisotropic heat conductive sheet 12 in the horizontal direction (the direction parallel to the upper surface of the lateral anisotropic heat conductive sheet 12) is preferably 400 W / mK or more. By setting it to 400 W / mK or more, it becomes possible to diffuse a large amount of heat over a wide area.

  Further, the shape of the transversely anisotropic heat conductive sheet 12 is not limited to a quadrangular column as shown in FIG. 1 and may be, for example, a cylinder.

  When heat sink 10 in the present embodiment receives heat from a heat source, first, as shown by arrow 13a in FIG. Heat is transferred to a region corresponding to the area in the direction. At this time, the temperature of the transversely anisotropic heat conductive sheet 12 is substantially the same as the temperature of the heat generation source.

  And, as indicated by an arrow 13b, the longitudinally anisotropic heat conductive sheet 11 causes a surface opposite to the surface on which the laterally anisotropic heat conductive sheet 12 is formed in the longitudinally anisotropic heat conductive sheet 11 as shown by an arrow 13b. Heat is transferred quickly (downward in FIG. 1). At this time, since heat is transferred from the transversely anisotropic heat conductive sheet 12, heat is transferred in the vertical direction from a region corresponding to the area of the transversely anisotropic heat conductive sheet 12. Therefore, the area of the laterally anisotropic heat conductive sheet 12 becomes the heat radiation area S of the heat sink 10.

As described above, according to the heat sink 10 in the first embodiment of the present invention, the longitudinal anisotropic heat conductive sheet 11 and the lateral anisotropy formed on the vertical anisotropic heat conductive sheet 11 are used. The outer peripheral edge 12a of the laterally anisotropic heat conductive sheet 12 is disposed inside the outer peripheral edge 11a of the longitudinally anisotropic heat conductive sheet 11 when viewed from above. . The thermal resistance is expressed by the following formula (1). Therefore, since heat is transmitted in the lateral direction by the laterally anisotropic heat conductive sheet 12, the heat radiation area S can be increased. Then, the longitudinal anisotropic heat conductive sheet 11 can transfer heat downward as indicated by the arrow 13b while having the expanded heat radiation area S. Therefore, the thermal resistance can be reduced as a whole.
Thermal resistance R _th = heat sink thickness / (thermal conductivity × heat radiation area S) (1)
Moreover, since the heat radiation area S can be increased, it can be made thinner than the thickness of the longitudinal anisotropic heat conductive sheet 11 as compared with a heat sink including a single longitudinal anisotropic heat conductive sheet. As a result, the thermal resistance _Rth can be reduced.

(Embodiment 2)
With reference to FIG. 3 and FIG. 4, the heat sink in Embodiment 2 of this invention is demonstrated. FIG. 3 is a schematic perspective view showing a heat sink according to Embodiment 2 of the present invention. 4 is a schematic cross-sectional view taken along line IV-IV in FIG.

  As shown in FIGS. 3 and 4, the heat sink 20 in the second embodiment is basically the same as the heat sink 10 in the first embodiment. In the second embodiment, only in the point that the longitudinally anisotropic heat conductive sheet 21 has a recess 21b and in the point that the laterally anisotropic heat conductive sheet 22 is arranged to fill the recess 21b. 1 and FIG. 2 are different from the heat sink 10 in the first embodiment.

  Specifically, the longitudinally anisotropic heat conductive sheet 21 and the transversely anisotropic heat conductive sheet 22 are respectively the longitudinally anisotropic heat conductive sheet 11 and the laterally anisotropic heat conductive sheet of the first embodiment. Since it is the same as 12, the description thereof will not be repeated.

  Further, in the heat sink 20, the upper surface of the laterally anisotropic heat conductive sheet 22 is flush with the surface of the longitudinal anisotropic heat conductive sheet 11 that is not covered by the lateral anisotropic heat conductive sheet 22. It is preferable to constitute.

  The planar shape of the recess 21b is not particularly limited to a quadrangle as shown in FIG. 4, and may be a circle or another rectangle, and is preferably matched to the shape of the heat source to be mounted to be described later. Also, the depth of the recess 21b can be locally increased or decreased.

  Next, referring to FIG. 5 and FIG. 10, the thermal resistance of the heat sink 20 in the second embodiment and the thermal resistance of the conventional heat sink 200 will be described. FIG. 5 is a schematic cross-sectional view when a chip is mounted on the heat sink in Embodiment 2 of the present invention.

  In the heat sink 20 in the second embodiment, the upper surface of the transversely anisotropic heat conductive sheet 22 shown in FIG. 5 is covered with the transversely anisotropic heat conductive sheet 22 in the longitudinally anisotropic heat conductive sheet 11. Chips 25 and 225 in the shape of square pillars having a length of 1 mm, a width of 1 mm, and a thickness of 0.3 mm are provided on the heat sinks 20 and 200 shown in FIGS. Is assumed to be installed.

  The longitudinal direction anisotropic heat conductive sheet 21 of the heat sink 20 in the second embodiment has a rectangular column shape of 5 mm in length, 5 mm in width, and 0.75 mm in thickness (D1), and has a heat conductivity of 780 W / mK in the vertical direction. The directional thermal conductivity is 0 W / mK. The transversely anisotropic heat conductive sheet 22 has a rectangular column shape with a length of 4 mm, a width of 4 mm, and a thickness of 0.25 mm. To do.

In the second embodiment, the heat radiation area _Se is 1.6 × 10 ⁻⁵ m ² (4 mm × 4 mm) because heat is transferred as described in the first embodiment. The thickness of the heat sink 20 is the thickness (D1-D2) below the recess 21b of the longitudinal anisotropic heat conductive sheet 11, and the transverse anisotropic heat conductive sheet 12 is formed in the recess 21b of the longitudinal anisotropic heat conductive sheet 11. Since it is embedded, it becomes 0.5 mm. As a result, the thermal resistance R _th is 0.0401 (= 0.0005 / {780 × 1.6 × 10 ⁻⁵ }) ° C./W.

  On the other hand, it is assumed that the conventional heat sink 200 uses an isotropic thermal conductive sheet 222 having the same thermal conductivity in the vertical direction and the horizontal direction. The isotropic heat conductive sheet 222 has a length of 5 mm, a width of 5 mm, a thickness of 0.075 mm, is made of copper, and has a heat conductivity of 393 W / mK.

In this case, the heat radiating area S _h will ^{6.25 × 10 -6 m 2 (=} 2.5mm × 2.5mm). The thickness of the heat sink 200 is 0.75 mm. As a result, the thermal resistance R _th is 0.305 (= 0.00075 / {393 × 6.25 × 10 ⁻⁶ }) ° C./W.

Thus, when the heat sink 20 in the second embodiment having the same size is compared with the conventional heat sink 200, it can be seen that the thermal resistance _Rth of the heat sink 20 in the second embodiment can be reduced as compared with the conventional heat sink.

As described above, according to the heat sink 20 in the second embodiment of the present invention, the longitudinal anisotropic heat conductive sheet 21 has the recesses 21b, and the transverse anisotropic heat conductive sheet 22 has the recesses. It arrange | positions so that 21b may be filled. Thereby, since the thickness of the longitudinal direction anisotropic heat conductive sheet 21 can be made thinner, thermal resistance _Rth can be reduced more.

(Embodiment 3)
With reference to FIG. 6 and FIG. 7, the heat sink in Embodiment 3 of this invention is demonstrated. FIG. 6 is a schematic perspective view showing a heat sink according to Embodiment 3 of the present invention. FIG. 7 is a schematic cross-sectional view taken along line VII-VII in FIG.

  As shown in FIGS. 6 and 7, the heat sink 30 in the third embodiment is basically the same as the heat sink 20 in the second embodiment shown in FIGS. In the third embodiment, the second embodiment shown in FIGS. 3 and 4 is only provided on the surface of the transversely anisotropic heat conduction sheet 32 and further provided with a metal film 34 for mounting the heat source 35. Different from the heat sink 20 in FIG.

  Specifically, the longitudinally anisotropic heat conductive sheet 31 and the transversely anisotropic heat conductive sheet 32 are respectively the longitudinally anisotropic heat conductive sheet 11 and the transversely anisotropic heat conductive sheet of the first embodiment. Since it is the same as 12, the description thereof will not be repeated.

  The metal film 34 is not particularly limited as long as the heat source 35 can be mounted. For example, the metal film 34 can use die bond metallization or the like. The metal film 34 can be formed by evaporating a thin metal solder, for example. The metal film 34 is preferably made of a laminated film of chromium, nickel and gold from the upper surface of the laterally anisotropic heat conductive sheet 32.

  The heat source 35 is not particularly limited, and a generally known one such as a semiconductor element can be mounted on the metal film 34.

  As described above, according to the heat sink 30 in the third embodiment of the present invention, the heat sink 30 is further provided with the metal film 34 that is formed on the surface of the transversely anisotropic heat conductive sheet 32 and on which the heat source 35 is mounted. ing. Thereby, the heat from the heat generation source 35 mounted on the metal film 34 can be spread uniformly by the laterally anisotropic heat conductive sheet 32.

  Further, since the heat sink 30 has a low thermal resistance and a high heat dissipation effect, a heat source 35 such as an element that generates a large amount of heat or an element that consumes a large amount of power can be suitably mounted.

(Embodiment 4)
With reference to FIG. 8 and FIG. 9, the heat sink in Embodiment 4 of this invention is demonstrated. FIG. 8 is a schematic perspective view showing a heat sink according to Embodiment 3 of the present invention. FIG. 9 is a schematic cross-sectional view taken along line IX-IX in FIG.

  As shown in FIGS. 8 and 9, the heat sink 40 in the fourth embodiment is basically the same as the heat sink 30 in the third embodiment shown in FIGS. 6 and 7. In the fourth embodiment, only in that the heat dissipating fins 46 connected to at least one of the longitudinal anisotropic heat conductive sheet 41 and the lateral anisotropic heat conductive sheet 42 are further provided in FIGS. 6 and 7. Different from the heat sink 30 in the third embodiment shown.

  Specifically, the longitudinally anisotropic heat conductive sheet 41 and the transversely anisotropic heat conductive sheet 42 are respectively the longitudinally anisotropic heat conductive sheet 11 and the transversely anisotropic heat conductive sheet of the first embodiment. Since it is the same as 12, the description thereof will not be repeated.

  The heat radiating fins 46 are members for diffusing heat. The radiating fin 46 is not particularly limited as long as it is connected to at least one of the longitudinally anisotropic heat conductive sheet 41 and the laterally anisotropic heat conductive sheet 42, but is connected to the longitudinally anisotropic heat conductive sheet 41. It is preferable. Further, as shown in FIGS. 8 and 9, the heat radiating fins 46 are connected to the surface opposite to the surface on which the transversely anisotropic heat conductive sheet 42 is formed in the vertically anisotropic heat conductive sheet 41. More preferably, the larger the surface area is, the higher the effect of diffusing heat is. Therefore, the laterally anisotropic heat conductive sheet 42 is formed on the outer peripheral edge of the radiating fin 46 in the longitudinal anisotropic heat conductive sheet 41. It is even more preferable that it is arranged outside the outer peripheral edge of the surface opposite to the surface on which it is located.

  The radiating fins 46 may be connected to the side surfaces of the longitudinally anisotropic heat conductive sheet 41 (the surface on which the laterally anisotropic heat conductive sheet 42 is formed and other surfaces). In addition, the case where the radiating fins 46 are connected to the laterally anisotropic heat conductive sheet 42 includes, for example, the case where the radiating fins 46 extend upward or the case where the radiating fins 46 extend substantially vertically.

  The number of heat radiation fins 46 is not particularly limited as long as it is one or more, but it is preferable to have a plurality of heat radiation fins from the viewpoint of increasing the surface area. When the heat dissipating fin 46 has a plurality of fins, the shape of each fin may be the same, or the shape may be different for each fin. Moreover, the shape of the radiation fin 46 is not specifically limited, As shown to FIG. 8 and FIG. 9, a planar shape may be a rectangle, may be bent, and a planar shape may be circular. Further, the heat radiating fins 46 may have a structure with many pores and irregularities.

  Moreover, the material of the radiation fin 46 is not particularly limited, but, for example, aluminum or copper can be used.

  Further, the pitch P between the fins of the radiating fin 46 may be locally changed. For example, the pitch P of the fins disposed below the laterally anisotropic heat conductive sheet 42 may be reduced. In this case, heat dissipation efficiency can be improved in a region where heat is transmitted.

  As described above, according to the heat sink 40 in the fourth embodiment of the present invention, the radiating fins 46 connected to at least one of the longitudinal anisotropic heat conductive sheet 41 and the lateral anisotropic heat conductive sheet 42 are provided. It has more. Thereby, since heat can be transmitted also to the radiation fin 46, the effect of radiating the heat from the heat generation source 45 is further increased.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above-described embodiment but by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

  Since the heat sink of the present invention can reduce thermal resistance, the effect of diffusing heat is high. Therefore, it is suitably used for elements that generate a large amount of heat and heat sources that consume a large amount of power.

It is a schematic perspective view which shows the heat sink in Embodiment 1 of this invention. It is a schematic sectional drawing in line segment II-II in FIG. It is a schematic perspective view which shows the heat sink in Embodiment 2 of this invention. It is a schematic sectional drawing in line segment IV-IV in FIG. It is a schematic sectional drawing when a chip | tip is mounted in the heat sink in Embodiment 2 of this invention. It is a schematic perspective view which shows the heat sink in Embodiment 3 of this invention. It is a schematic sectional drawing in line segment VII-VII in FIG. It is a schematic perspective view which shows the heat sink in Embodiment 3 of this invention. It is a schematic sectional drawing in line segment IX-IX in FIG. It is a schematic sectional drawing which shows the heat sink using an isotropic heat conductive sheet.

Explanation of symbols

  10, 20, 30, 40 Heat sink, 11, 21, 31, 41 Longitudinal anisotropic thermal conductive sheet, 11a, 12a Outer peripheral edge, 12, 22, 32, 42 Lateral anisotropic thermal conductive sheet, 13a, 13b Arrow, 21b Recess, 25 Chip, 34, 44 Metal film, 35, 45 Heat source, 46 Radiation fin.

Claims (4)

A longitudinally anisotropic thermal conductive sheet;
A transversely anisotropic anisotropic heat conductive sheet formed on the longitudinally anisotropic heat conductive sheet,
A heat sink, wherein an outer peripheral edge of the transversely anisotropic heat conductive sheet as viewed from above is disposed on an inner side than an outer peripheral edge of the longitudinally anisotropic heat conductive sheet. The longitudinally anisotropic anisotropic heat conductive sheet has a recess,
The heat sink according to claim 1, wherein the transversely anisotropic heat conductive sheet is disposed so as to fill the concave portion.   The heat sink according to claim 1, further comprising a metal film formed on a surface of the laterally anisotropic conductive sheet and for mounting a heat source.   The heat sink according to any one of claims 1 to 3, further comprising a radiation fin connected to at least one of the longitudinally anisotropic conductive sheet and the laterally anisotropic conductive sheet.

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