JP2013222918A - Thermoconductive sheet and method for manufacturing the same - Google Patents

Abstract

An object of the present invention is to obtain a heat conductive sheet having high peel strength and excellent heat conductivity and heat dissipation.
A heat conductive sheet 18 using a graphite sheet 11 obtained by thermally decomposing an organic film, wherein a region other than an end face of the graphite sheet 11 has each surface direction of each graphene layer constituting the graphite sheet 11 The 14 layers are configured to be substantially perpendicular to the c-axis, and the end surface of the graphite sheet 11 is configured such that a surface perpendicular to the c-axis of the graphene layer 14 is exposed.
[Selection] Figure 1

Description

  The present invention relates to a heat conductive sheet used for various electronic devices and a method for producing the same.

  In recent years, various functions and processing capabilities of electronic devices have rapidly improved, and accordingly, the amount of heat generated from electronic components such as semiconductor elements tends to increase. For this reason, in order to maintain the operating characteristics and reliability of a semiconductor element or the like, heat is transmitted from a heating element to a heat sink or the like using a heat conductive sheet. The graphite sheet is used as a heat conductive sheet because of its excellent thermal conductivity in the surface direction, but has a weakness that it is brittle in the thickness direction although it has structural strength in the surface direction. Therefore, as shown in FIG. 4, the insulating tape 2 having a larger area than the graphite sheet is bonded to both surfaces of the graphite sheet 1, and the end surface of the graphite sheet is covered with the insulating tape 2.

  As prior art document information related to the invention of this application, for example, Patent Document 1 is known.

JP 2011-105531 A

  However, if the end face of the graphite sheet is covered with an insulating tape, the area of the graphite sheet is reduced correspondingly, and the overall thermal conductivity and heat dissipation are impaired.

  An object of the present invention is to provide a heat conductive sheet having high peel strength and excellent heat conductivity and heat dissipation by increasing the area of the graphite sheet.

  In order to solve the above problems, the present invention is a heat conductive sheet using a graphite sheet obtained by thermally decomposing an organic film, and the surface direction of the region other than the end face of the graphite sheet constitutes the graphite sheet. Each graphene layer is configured to be substantially perpendicular to the c-axis, and the end surface of the graphite sheet is configured to expose a surface substantially perpendicular to the c-axis of the graphene layer.

  With the above configuration, it is possible to improve the peel strength of the end face of the graphite sheet, and it is not necessary to cover the end face with an insulating tape, the area of the graphite sheet can be increased, and heat with excellent thermal conductivity and heat dissipation is achieved. A conductive sheet can be provided.

The cross-sectional schematic diagram of the heat conductive sheet in one embodiment of this invention The end surface perspective view of the heat conductive sheet in one embodiment of this invention The figure explaining the cutting process of the heat conductive sheet in one embodiment of this invention Sectional view of a conventional heat conductive sheet

  Hereinafter, the heat conductive sheet in one embodiment of the present invention is explained, referring to drawings.

  FIG. 1 is a schematic cross-sectional view of a heat conductive sheet according to an embodiment of the present invention. This heat conductive sheet is a graphite sheet 11 graphitized by thermally decomposing polyimide, and is thus formed. Thus, the graphene layer 14 having a planar crystal structure is expanded in the plane direction, and has a large thermal conductivity in the plane direction (a-b axis direction in which carbon 6-membered rings are connected), and has a thickness. The thermal conductivity in the c-axis direction, which is the direction, is relatively small. In FIG. 1, the graphene layer 14 is schematically represented by respective lines. An insulating sheet 12 is bonded to the upper surface side of the graphite sheet 11, and an adhesive sheet 13 is bonded to the lower surface side. By doing in this way, handling as the heat conductive sheet 18 becomes easy.

  Usually, the pyrolytic graphite sheet has a predetermined shape by punching with a mold or the like, so that its end surface has a cross-sectional shape obtained by cutting a graphene layer expanded in a plane shape, and the end surface has a shape in which the ab axis direction is exposed. It has become. Since the strength between the graphene layers is not so high, the peel strength at the end face is weak.

  On the other hand, the heat conductive sheet of the present invention is such that a surface perpendicular to the c-axis of the graphene layer is exposed at the end face of the sheet. Here, the fact that the surface perpendicular to the c-axis of the graphene layer is exposed means that 60% or more of the end surface is composed of a surface perpendicular to the c-axis. By doing in this way, while improving the peeling strength of the interlayer in an end surface, and the heat conductivity of the thickness direction of a heat conductive sheet can be improved, the heat conductive sheet excellent in heat conductivity and heat dissipation is obtained. Can be obtained.

  The end face of the graphite sheet is preferably configured such that the graphene layer 14 facing the plane perpendicular to the c-axis overlaps like a scale, as shown in FIG. Can be further improved.

  Next, the manufacturing method of the heat conductive sheet in one embodiment of this invention is demonstrated.

  First, a polyimide sheet having a thickness of about 100 μm is carbonized and then graphitized by heat treatment at about 2700 ° C., and this is licked with a roller to obtain a pyrolytic graphite sheet 11 having a thickness of about 70 μm.

  Next, an insulating sheet 12 made of polyethylene terephthalate having a thickness of about 30 μm is bonded to the upper surface side of the pyrolytic graphite sheet 11. Further, an adhesive sheet 13 having a thickness of about 10 μm is bonded to the lower surface side of the pyrolytic graphite sheet. The insulating sheet 12 is colored black. The adhesive sheet 13 is made of a polyethylene terephthalate sheet coated with an acrylic adhesive material on both sides.

  Next, the heat conductive sheet 18 in which the insulating sheet 12 is bonded to the pyrolytic graphite sheet 11 is cut into a predetermined shape using a laser.

  FIG. 3 is a diagram for explaining this cutting process. The laser beam emitted from the laser 15 is reflected by the galvanometer mirror 16 and irradiated to the heat conductive sheet 18 through the lens 17. A YAG laser is used as the laser 15, and the irradiation position of the laser light is moved by moving the galvanometer mirror 16 and the lens 17. The laser light is condensed near the upper surface of the pyrolytic graphite sheet 11 by the lens 17.

  The heat conductive sheet 18 has a surface irradiated with laser light as a surface to which the insulating sheet 12 is bonded, and this cutting step is performed in air or in an oxygen atmosphere. The heat conductive sheet 18 can be cut even in an oxygen-free atmosphere, but can be cut with lower power by being in the air or in an oxygen atmosphere. If an attempt is made to perform laser processing in the air or in an oxygen atmosphere with the graphite sheet exposed, the graphite sheet is excellent in thermal conductivity in the surface direction, and the vicinity of the laser irradiation position becomes high. Since the graphite sheet is made of carbon, it becomes gasified by combining with oxygen at high temperatures. Therefore, the cut surface becomes tapered.

  On the other hand, since the insulating sheet 12 is bonded to the surface of the graphite sheet 11 as in the present embodiment, since it is not in contact with oxygen except at the position irradiated with the laser beam, it can be a substantially vertical surface. .

  By cutting the graphite sheet by the method as described above, the cut surface of the graphite sheet can be exposed so that the surface perpendicular to the c-axis of each graphene layer constituting the graphite sheet is exposed.

  Further, the graphite sheet 11 is cut by irradiating the laser beam at such a power that the graphite sheet 11 is not cut by a single scan and repeatedly scanning the same position three times. Even if it is cut in multiple steps, the surrounding temperature rises due to the heat at the time of cutting, making it difficult to cut well, but the graphite sheet has excellent thermal conductivity in the surface direction, so it has little effect Can be cut without receiving.

  In this way, by dividing the cutting into a plurality of times and gradually cutting, the graphene layer facing the plane perpendicular to the c-axis can be overlapped like a scale. By doing as described above, it is possible to improve the peel strength between the layers at the end face, and to improve the thermal conductivity in the thickness direction of the thermal conductive sheet, so that the thermal conductive sheet excellent in thermal conductivity and heat dissipation Can be obtained.

  The insulating sheet 12 is preferably one that easily absorbs laser light, and it is desirable to use one that is colored black as in the present embodiment.

  The heat conductive sheet and the method for producing the same according to the present invention have a strong peel strength, and by increasing the area of the graphite sheet, it is possible to obtain a heat conductive sheet having excellent heat conductivity and heat dissipation, and a more complicated shape. Can be formed freely and is industrially useful.

11 Graphite Sheet 12 Insulating Sheet 13 Adhesive Sheet 14 Graphene Layer 15 Laser 16 Galvano Mirror 17 Lens 18 Thermal Conductive Sheet

Claims (6)

A heat conductive sheet using a graphite sheet obtained by thermally decomposing an organic film, wherein the area other than the end face of the graphite sheet is substantially perpendicular to the c-axis of each graphene layer constituting the graphite sheet The heat conductive sheet is characterized in that a surface perpendicular to the c-axis of the graphene layer is exposed at the end face of the graphite sheet. 2. The heat conductive sheet according to claim 1, wherein the end face of the graphite sheet is formed by overlapping a graphene layer facing a plane perpendicular to the c-axis in a scale shape. The heat conductive sheet according to claim 1 or 2, wherein an insulating sheet or an adhesive sheet is bonded to each of the upper and lower surfaces of the graphite sheet, and end faces of the graphite sheet are exposed. Thermal conduction comprising a step of thermally decomposing an organic film to obtain a graphite sheet, a step of bonding an insulating sheet to at least one surface of the graphite sheet, and a cutting step of cutting the insulating sheet and the graphite sheet by laser light In the sheet manufacturing method, the cutting step is performed by irradiating a laser beam from a surface side to which the insulating sheet is bonded, so that the cut surface of the graphite sheet is c-axis of each graphene layer constituting the graphite sheet. A method for manufacturing a heat conductive sheet in which a surface perpendicular to the surface is exposed. The said cutting process is performed in the air or oxygen atmosphere, The manufacturing method of the heat conductive sheet of Claim 4 characterized by the above-mentioned. The said cutting process irradiates, moving the position which irradiates a laser beam, The said graphite sheet is cut | disconnected by repeating this movement in multiple times, The manufacturing method of the heat conductive sheet of Claim 4 characterized by the above-mentioned. .

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