JP2007019285A - Flexible heat-sink plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-sink plate having a raised thermal conductivity in a direction perpendicular to the surface of graphite paper, a flexibility and a fragility improved to raise the strength. <P>SOLUTION: The heat-sink plate has a perforated graphite paper and a metal layer composed of a metal foil or a metal-aluminum or inorganic-aluminum composite. The layer continues from the perforations to both sides of the graphite paper. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heat sink plate that is lightweight and has excellent flexibility in heat conduction.

  A paper-like material made of graphite is mass-produced as a material having excellent thermal conductivity in the plane direction, and is inexpensive. However, although this has flexibility, it is fragile and is difficult to handle due to its low strength.

  In recent years, various methods have been proposed to overcome the harmful effects, but those that are widely used as heat sinks for plasma display panels and liquid crystal panels are made of aluminum foil on both sides of graphite paper. There is something pasted. However, this also has an excellent thermal conductivity in the plane direction, but the direction perpendicular to the plane has a very small thermal conductivity, so that the heat radiation effect on the heat flow coming from the perpendicular direction is small.

  Examples of the heat sink plate excellent in the right-angle direction include a graphite-aluminum composite material disclosed in Japanese Patent Application Laid-Open No. 2000-203973 and a silicon carbide aluminum composite material such as Japanese Patent Application No. 2002-323749, but these have no flexibility. Accordingly, the place where heat dissipation such as a plasma display or liquid crystal is required has various curved shapes, and therefore, the heat dissipation effect cannot be exhibited unless it has flexibility.

  An object of the present invention is to increase the thermal conductivity in the perpendicular direction of the graphite paper, and to improve the brittleness and increase the strength while having flexibility.

  In order to achieve the above object, the present invention solves the problem by placing aluminum on both sides of graphite paper so that the graphite paper is sandwiched between thin aluminum plates.

  In the present invention, the graphite paper is punched into a perforated paper, and then the aluminum is continuous through the perforated portion cast on the both sides by a high-pressure casting method using a molten aluminum and punched out, so that the plate has flexibility. As a result, the aluminum portions on both sides of the graphite paper are firmly integrated with the graphite paper, improving the thermal conductivity in the direction perpendicular to the paper surface and improving the strength of the paper.

  Furthermore, the present invention has a flexibility in which copper or aluminum foil is placed on both sides of the graphite paper punched at the time of high pressure casting, and then cast with molten aluminum by a high pressure casting method so that aluminum or part of copper is continuous. It shall be plate-shaped. Thereby, since the thickness of the metal layer on both sides of the graphite paper can be controlled, the shape of the plate can be easily determined. The thickness of the copper or aluminum foil is desirably 2 mm or less.

  Also, a flexible plate-like material in which an inorganic paper made of ceramic, carbon, alumina or the like is placed instead of the copper or aluminum foil, and then cast with molten aluminum by a high-pressure casting method and aluminum is continuous. And Thereby, since the thickness of the aluminum layer on both sides of the graphite paper can be controlled, the plate shape can be easily determined.

  Inorganic paper such as ceramic, carbon, and alumina may be continuous fibers or may be made of bulk short fiber material. The thickness of the inorganic paper is desirably 2 mm or less. The volume ratio of the inorganic paper placed on both sides of the punched graphite paper is about 1 to 10%. If it is 10% or more, flexibility is lost, which is not preferable. If it is 1% or less, it cannot serve as a spacer for determining the thickness of the aluminum layer, which is not preferable.

  Placed on both sides of graphite paper punched using a fibrous or granular material made of metallic material instead of the inorganic fiber, and then cast with molten aluminum by a high pressure casting method. It is assumed that the plate has a continuous flexibility. Thereby, since the thickness of the aluminum layer on both sides of the graphite paper can be controlled, the shape of the plate can be easily determined.

  Sintered metal fibers and metal powder are desirable. The material is preferably copper, nickel, silicon, titanium, or the like having an aluminum melting point or higher. Further, the volume ratio of a sintered metal body or the like disposed on both sides of the punched graphite paper is set to about 1% to 10%. If it is 10% or more, flexibility may be lost. If it is 1% or less, it cannot be used as a spacer for controlling the thickness of the aluminum layer, which is not preferable.

  As the graphite paper used in the present invention, graphite paper or powder made by a method such as roll rolling is used. Since such graphite paper has crystals arranged in a plane, the thermal conductivity parallel to the surface is as large as 200 to 500 W / mK, but the thermal conductivity in the direction perpendicular to the surface is as small as 5 to 10 W / mK.

Therefore, according to the present invention, if graphite paper is made to have an opening of about 10 to 40% and the opening is filled with aluminum, the thermal conductivity of aluminum increases in proportion to the opening area in the direction perpendicular to the surface. However, since aluminum penetrates into the voids of the graphite paper, the thermal conductivity can be further improved.

In order to open the graphite paper, a method of opening a paper or the like is desirable, and a method of opening a metal is not preferable because a burr is large. The shape of the opening is round, elliptical, square, cross-shaped, etc., and there is no special designation. Further, the arrangement may be any arrangement as long as the distribution is uniform.

  Next, the thickness of the graphite paper is not particularly specified, but 0.2 mm to 2 mm is commercially available and is preferable because it is easily available. Further, for example, five sheets of 0.5.mm thickness may be used in piles to obtain 2.5 mm thick graphite paper.

  The thickness of the heat sink plate is preferably about 0.5 mm to 5 mm because of ease of weight and cutting. Among them, the proportion of graphite paper is preferably about 20 to 90% because flexibility is not lost and the thermal conductivity in the direction parallel to the surface is increased.

As aluminum used in the present invention, JIS-A1000 series alloy, 3000 series alloy, and 6000 series alloy are more flexible, but can be used with casting alloys such as JIS-AC3A and AC4C alloys. . Although not particularly limited, JIS-A1000 is preferable because an alloy having a higher thermal conductivity and exhibiting more flexibility matches the purpose of the present invention.

The manufacturing method of the present invention is based on a high pressure casting method. The method will be described with reference to FIG. 1 in FIG. 1 is a mold, and 2 is a press punch, each preheated to about 150 to 300 ° C. Reference numeral 3 in FIG. 1 is a metal plate, mainly an iron plate. 5 is graphite paper with holes (17) provided for the present invention, 6 is made of either metal foil, inorganic paper or metallic paper, and 3 iron plates and 4 It is fixed with bolts. 3 to 6 are assembled together and preheated to 700 to 800 ° C. in a non-oxidizing atmosphere such as argon. Thereafter, as shown in FIG. 1, the aluminum melt 7 is poured into the mold and pressurized with the punch 2. Although it takes about 1 to 20 minutes to complete the coagulation, pressurization is continued during that time.

After completion of solidification in FIG. 1, the casting is cut as shown in FIG. 2, and the object of the present invention is obtained. In the structure, 16 is an inorganic paper or metallic paper impregnated with a metal foil or aluminum, and 27 is aluminum impregnated in an opening portion of graphite paper. 15 is graphite paper partially impregnated with aluminum.

  Table 1 shows the characteristic values of the flexible heat sink plate in which aluminum is continuous through a hole formed by providing a metal layer on both sides of the graphite paper having the holes according to the present invention. At this time, the present invention has a total thickness of 2 mm, graphite paper having 1.5 mm aluminum foil bonded to both sides of 1.5 mm, and graphite paper having a diameter of 3 mm and a pitch of 5 mm. The graphite paper for comparison has a thickness of 2 mm.

  As is apparent from Table 1, it can be said that the device according to the present invention is sufficiently flexible because the minimum bending radius is small. Also, the brittleness is overcome because the tensile strength is much higher than that of graphite paper. Further, it is understood that the thermal conductivity is excellent in the horizontal direction with respect to the paper or board, and is excellent in the perpendicular direction.

Hereinafter, the details of the invention will be described with reference to examples.

  Holes were formed in an orthogonal arrangement with a diameter of 2.5 mm and a pitch of 4 mm on graphite paper having a vertical and horizontal size of 1000 mm and a thickness of 1 mm. On the both sides of this graphite paper, an inorganic paper made of alumina short fibers having a thickness of 0.5 mm and having a volume ratio of 3% was stacked in the vertical and horizontal sizes. This was fixed with bolts in the form as shown in FIG. 1 with two steel plates (SS400) having a thickness of 9 mm. This was heated to 800 ° C. in argon, and placed in a high-pressure casting mold preheated to 250 ° C., and a molten aluminum of JIS 1050 melted at 800 ° C. was poured, and immediately after that, it was added. A pressure of 100 MPa was applied with a pressure punch. Pressurization was held for 10 minutes. Thereafter, the solidified casting was taken out to obtain a heat sink plate as shown in FIG. Table 1 shows physical property data of the heat conductivity, tensile strength, and flexibility of the heat sink plate thus obtained.

  In Example 1, instead of inorganic paper, bulk fibers in 0.1 mm of JIS-SUS304, which is one of the metallic papers, were arranged on both sides of the graphite paper, and a heat sink plate was obtained in the same manner. The physical property data of the heat sink plate thus obtained are also shown in Table 1.

    The heat sink plate according to the present invention can efficiently dissipate heat from the backlight portion of the liquid crystal, heat from the back of the screen of the plasma display, and heat from the back of the laptop personal computer. Therefore, since the obstacle from the heat | fever of the semiconductor element used for them is reduced significantly, it contributes greatly to the lifetime improvement of each equipment.

Manufacturing form of the heat sink plate of the present invention and Schematic cross-sectional explanatory drawing which shows the structure of a heat sink.

Explanation of symbols

1 Mold
2 punch
3 Iron jig
4 Screws, bolts
5 Graphite paper
6 Any of inorganic paper, metal foil or metal paper
7 Aluminum hot water
17 Opening of graphite paper
15 Composite of graphite paper and aluminum
16 Any of metal foil or inorganic paper or a composite of metal and aluminum
27 Aluminum

Claims (6)

A heat sink plate having flexibility, sandwiched between both surfaces of graphite paper by aluminum or an alloy thereof (hereinafter, aluminum). A heat sink plate having flexibility in which aluminum or an alloy thereof is continuously cast through a perforated porous portion after being punched into graphite paper and made into perforated paper and then cast on both sides with a molten aluminum or an alloy thereof by a high pressure casting method. A flexible heat sink plate in which copper or aluminum foil is placed on both surfaces of graphite paper in advance during casting, and then cast with molten aluminum by a high-pressure casting method, and aluminum or partial copper is continuous. A flexible heat sink plate in which an inorganic paper made of ceramic, carbon, alumina, or the like is disposed in place of the aluminum foil at the time of casting, and then cast with molten aluminum by a high pressure casting method, and aluminum is continuous. A flexible heat sink in which aluminum is continuous by placing a fibrous or granular material made of metallic material into a paper shape instead of the inorganic paper of the preceding paragraph, and then casting it with molten aluminum by a high pressure casting method Board. The volume ratio of the inorganic or metallic paper of Item 4 or Item 5 is 1 to 10%.

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