JP2006165482A - Thermal diffusion sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To well prevent a graphite from overbrimming, in a thermal diffusion sheet which diffuses the heat to the periphery by utilizing the graphite. <P>SOLUTION: The thermal diffusion sheet 1 is constituted by coating an almost square flat graphite sheet 2 with a pair of aluminum foils 3 and 3. The aluminum foils 3 and 3 protrude from four corners of the graphite sheet 2, and are bonded together at the protruded parts. Consequently, the graphite is prevented from overbrimming. The graphite sheet 2 is extended by applying pressure, and extremely superior in thermal conductivity along a surface. Further, the part where the aluminum foils 3 and 3 are bonded together also acts as a radiation fin. For example, if a heating element such as a CPU, etc. is brought into contact with the center of the thermal diffusion sheet 1, the heat generated by the heating element is rapidly diffused to the periphery to radiate the heat, and overheat of the heating element is prevented well. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thermal diffusion sheet that is disposed and used so as to be in contact with a heating element such as an electronic component and diffuses heat generated by the heating element to the surroundings.

  Conventionally, a heat conductive material obtained by filling a silicone rubber with a heat conductive filler, kneading and molding has been considered. This type of heat conducting material is disposed in an electric / electronic device so as to be in contact with, for example, an electronic component serving as a heating element, and is used for the purpose of releasing heat generated by the electronic component. For this reason, this type of heat conducting material is attracting attention as an indispensable material for increasing the speed of CPUs, for example.

Moreover, it is known that graphite is extremely excellent in thermal conductivity. In particular, a so-called graphite sheet formed in a sheet shape has a high thermal diffusivity obtained by dividing the thermal conductivity by the density and specific heat, and quickly diffuses the heat of the heating element contacting a part of the sheet to the entire sheet. Can do. Thus, it has been considered that the heat generated by the electronic component or the like is released by the heat conducting material provided with the sheet-like graphite layer (see, for example, Patent Document 1).
JP 2003-92384 A

  However, graphite has relatively fragile mechanical properties, and there is a possibility that graphite powder (so-called cut residue) spills out from the cut portion of the edge. Since graphite is electrically conductive, such spilled graphite powder can cause damage to the surrounding circuitry. Then, this invention was made | formed for the purpose of preventing well that a graphite spills down in the thermal diffusion sheet which diffuses a heat | fever to surroundings using a graphite.

  The heat diffusion sheet of the present invention made to achieve the above object is formed by laminating a graphite sheet and a metal, a resin, or a metal layer and a resin layer, which are pressed in the thickness direction and rolled to form a flat plate. And a pair of covering sheets that cover the graphite sheet from the front and back surfaces, protrude from the entire circumference of the graphite sheet, and are bonded to each other at the protruding portions. It is a feature.

  In the present invention configured as described above, the graphite sheet is pressed and rolled in the thickness direction, so that the thermal conductivity along the surface is extremely excellent. For this reason, for example, when a heating element such as a CPU is brought into contact with the center of the heat diffusion sheet of the present invention, the heat generated by the heating element can be quickly diffused to the surroundings, and overheating of the heating element Can be prevented satisfactorily.

  The graphite sheet is covered with a pair of covering sheets on the front and back surfaces, and the covering sheets protrude from the entire circumference of the graphite sheet and are bonded to each other at the protruding portions. For this reason, it is possible to satisfactorily prevent the graphite powder constituting the graphite sheet from spilling.

  In addition, as the said covering sheet, various metals or resin can be used, Furthermore, the composite material formed by laminating | stacking a metal layer and a resin layer can also be used. Further, in the pair of covering sheets, at least one of the covering sheets is configured by a base material having excellent thermal conductivity, and the pair of covering sheets are bonded in the middle of the thickness direction of the graphite sheet. In this case, the following effects are further produced.

  In this case, a configuration in which the covering sheet having excellent thermal conductivity projects in the circumferential direction from the middle in the thickness direction of the graphite sheet is obtained. If the thin member (the covering sheet) having excellent thermal conductivity protrudes in the circumferential direction as described above, the member acts as a heat radiating fin. Therefore, in this case, not only can the heat generated by the heat generating element be diffused to the surroundings, but also the heat can be dissipated well, and overheating of the heat generating element can be further prevented.

  Further, the same effect can be obtained when the pair of covering sheets are bonded together in the middle of the graphite sheet in the thickness direction, and the graphite powder is dispersed in the bonded portion. That is, in this case, a structure is obtained in which graphite powder having excellent thermal conductivity protrudes in the circumferential direction from the middle in the thickness direction of the graphite sheet, and the member acts as a heat radiating fin. Therefore, in this case as well, the heat generated by the heating element can be diffused not only to the surroundings, but also the heat can be radiated well, and overheating of the heating element can be prevented even better. Furthermore, in this case, since the graphite powder is dispersed in the bonded portion of the pair of covering sheets, the temperature difference between the pair of covering sheets can also be reduced. Therefore, overheating of the heating element can be prevented even better.

  In addition, when the bonded portion of the covering sheet acts as a radiating fin as described above, if the edge of the graphite sheet is in contact with the bonded portion of the covering sheet, the following effects are further obtained. Arise. In this case, heat transfer from the graphite sheet for diffusing heat to the portion acting as the heat radiating fin can be performed more satisfactorily, and overheating of the heating element can be further prevented.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view illustrating a configuration of a thermal diffusion sheet 1 to which the present invention is applied. As shown in FIG. 1, the thermal diffusion sheet 1 is formed by coating a graphite sheet 2 configured in a substantially square (see FIG. 2B) flat plate with a pair of aluminum foils 3 and 3 as covering sheets. It is configured.

  The aluminum foils 3 and 3 protrude from the four corners of the graphite sheet 2 and are bonded together at the protruding portions. In the thermal diffusion sheet 1, the graphite sheet 2 is sealed with the pair of aluminum foils 3 and 3 as described above, so that the graphite powder constituting the graphite sheet 2 can be prevented from spilling down.

  Next, FIG. 2 is a perspective view showing a method for manufacturing the thermal diffusion sheet 1. First, the graphite sheet 2 is formed into a sheet having a thickness of 0.05 mm to 2 mm and a specific gravity of 1.5 to 2.2 by pressing and rolling expanded graphite in a thickness direction with a roller. The graphite sheet 2 manufactured in this manner is overlapped with a single aluminum foil 3 as shown in FIG. 2 (A) and rolled while pressing in the thickness direction, whereby the aluminum foil 3 and the graphite sheet 2 are rolled. Can be crimped.

  Subsequently, as shown in FIG. 2B, the graphite sheet 2 is cut into a large number of squares, and another aluminum foil 3 is further stacked on the surface and rolled while pressing in the thickness direction. Accordingly, the large number of square graphite sheets 2 can be individually sealed with the two aluminum foils 3.

  And many above-mentioned thermal diffusion sheets 1 can be manufactured simultaneously by cut | disconnecting the aluminum foils 3 and 3 around each graphite sheet 2 so that the part by which aluminum foils 3 and 3 were crimped | compressed remains. . The thicknesses of the aluminum foils 3 and 3 were both 0.05 to 0.5 mm. In each of the rolling steps, rolling was performed with a commercially available acrylic adhesive sandwiched between the graphite sheet 2 and the aluminum foil 3.

  Since the graphite sheet 2 is rolled as described above, the thermal diffusion sheet 1 configured as described above has extremely excellent thermal conductivity along the surface. For this reason, for example, when a heating element such as a CPU is brought into contact with the center of the thermal diffusion sheet 1, the heat generated by the heating element can be quickly diffused to the surroundings, so that the heating element is excellently overheated. Can be prevented.

  In addition, since this thermal diffusion sheet 1 can be compressed to some extent in the thickness direction, it can be used well as a so-called interface material. For example, as shown in FIG. 3, the heat diffusion sheet 1 can be used by being sandwiched between a sheet metal 11 as a heat radiating plate and a CPU 13 as a heating element fixed on a substrate 12.

  Further, the graphite sheet 2 is sealed with the aluminum foil 3, and it is possible to prevent the graphite powder from spilling out as described above, so that the conductive graphite powder spills out and causes a failure in the surrounding circuit. Can be prevented well.

  Furthermore, since the aluminum foils 3 and 3 are also excellent in thermal conductivity, the heat generated by the heating element can be diffused better. Further, as shown in FIG. 1, the aluminum foils 3 and 3 are bonded so as to protrude in the circumferential direction from the center in the thickness direction of the graphite sheet 2, so that these portions function as heat radiation fins. Therefore, in this case, not only can the heat generated by the heat generating element be diffused to the surroundings, but also the heat can be dissipated well, and overheating of the heat generating element can be further prevented.

  In addition, as shown in FIG. 1, the edge of the graphite sheet 2 is crushed by the rolling process after being cut into a square as described above, and the edge is a bonded portion of the aluminum foils 3 and 3 (that is, the radiating fin). A portion acting as a). For this reason, heat transfer from the graphite sheet 2 for diffusing the heat generated by the heating element to the portion acting as the heat radiating fin is performed more satisfactorily, and the heating element can be further prevented from overheating.

  Furthermore, since the heat diffusion sheet 1 is thinly formed as described above, it has flexibility. For this reason, the thermal diffusion sheet 1 can be bent and used, and if the bent portion is disposed, for example, at a location where the wind from the fan passes, the heat dissipation can be further improved. The graphite sheet 2 contains sulfur and is corrosive to metals such as copper. However, in the thermal diffusion sheet 1, the graphite sheet 2 is sealed with the aluminum foil 3 as described above. There is no worry of corrosion.

  In addition, this invention is not limited to the said embodiment at all, It can implement with a various form in the range which does not deviate from the summary of this invention. For example, a resin film (for example, PET or heat conductive polyimide) can be used instead of the aluminum foils 3 and 3. In this case, the surface of the thermal diffusion sheet 1 can be made insulating. A composite material in which a metal layer and a resin layer are laminated instead of the aluminum foils 3 and 3 can also be used. In the case of a composite material formed by laminating a metal layer and a resin layer, the surface of the heat diffusion sheet 1 can be made conductive or insulating depending on the order of lamination of the layers. Moreover, mechanical strength can also be improved with a resin layer, utilizing the electroconductivity and thermal conductivity by a metal layer. When using a composite material formed by laminating such a metal layer and a resin layer, it is possible to arbitrarily design how many layers each layer is provided, and what order each layer is laminated. . In addition, such a laminate of a metal and a resin is formed by laminating a metal film and a resin film, applying a resin coating to the metal film, or a known thin film forming method (for example, a sputtering method) on the resin film. Or a metal layer formed by an ion plating method or the like).

  Further, when the graphite sheet 2 is cut into a square as shown in FIG. 2 (B), the graphite powder 2a (see FIG. 4) is scattered on the surrounding aluminum foil 3 at that time. You may perform the process of. In this case, as shown in FIG. 4, the graphite powder 2a is dispersed in the pressure-sensitive adhesive 4 interposed between the bonded portions of the aluminum foils 3 and 3, so that the heat radiation action as the heat radiation fin is further improved. In addition, the presence of the graphite powder 2a between the pair of aluminum foils 3 and 3 can also reduce the temperature difference between the aluminum foils 3 and 3, and better prevent the heating element from overheating. Can do.

  In addition, when the graphite powder 2a is dispersed in this way, even when a resin sheet is used instead of the aluminum foil 3, the bonded portion functions as a heat radiating fin. Therefore, in this case as well, the heat generated by the heating element can be diffused not only to the surroundings, but also the heat can be radiated well, and overheating of the heating element can be prevented even better.

  Further, since the graphite sheet 2 can be formed into a three-dimensional shape by press working, if the surface is provided with irregularities to function as fins, the heating element such as the CPU 13 can be used without using the sheet metal 11 or the like. Overheating can be prevented satisfactorily. Moreover, the thermal diffusion sheet of the present invention may be manufactured by a method other than the above-described manufacturing method, and the graphite sheet can be appropriately configured in a shape other than a square, such as a rectangle or a circle, as necessary. Furthermore, in the said embodiment, although aluminum foil 3 and 3 is crimped | bonded using an adhesive, aluminum foil 3 and 3 is coated with a thermoplastic resin, or thermoplasticity is used instead of aluminum foil 3 and 3. When the resin is used, the graphite sheet can be sealed by welding.

It is sectional drawing showing the structure of the thermal diffusion sheet to which this invention was applied. It is a perspective view showing the manufacturing method of the thermal diffusion sheet. It is sectional drawing showing the usage example of the thermal diffusion sheet. It is a fragmentary sectional view showing the composition of the modification of the thermal diffusion sheet.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Thermal diffusion sheet 2 ... Graphite sheet 3 ... Aluminum foil 4 ... Adhesive

Claims (4)

A graphite sheet that is pressed and rolled in the thickness direction and configured in a flat plate shape;
It is composed of metal, resin, or a composite material made by laminating a metal layer and a resin layer as a base material, covering the graphite sheet from the front and back surfaces, protruding from the entire circumference of the graphite sheet, and pasting each other at the protruding portion A pair of combined covering sheets;
A heat diffusion sheet comprising: 2. The cover sheet according to claim 1, wherein at least one of the cover sheets is composed of a base material having excellent thermal conductivity, and the pair of cover sheets are bonded in the middle of the thickness direction of the graphite sheet. The thermal diffusion sheet described. The heat diffusion sheet according to claim 1 or 2, wherein the pair of covering sheets are bonded together in the middle of the thickness direction of the graphite sheet, and graphite powder is dispersed in the bonded portion. The thermal diffusion sheet according to claim 2 or 3, wherein an edge of the graphite sheet is in contact with a bonded portion of the covering sheet.

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