JP2001177024A - Heat diffusing composite plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermodiffusion heat transfer plate which is capable of efficiently and uniformly diffusing and transferring a large amount of heat supplied from a heating element onto the heat receiving plane of a heat dissipat ing means. SOLUTION: A heat diffusing composite plate is composed of a center layer 1 and metal thin films 1 each smaller than 10 μm in thickness and deposited on the center layer 1 sandwiching it between them. The center layer 1 is formed of very pure graphite which is very high in thermal conductivity along its surface but comparatively low in thermal conductivity in its thickness direction. The metal thin film 2 is deposited on the surface of the center layer 1 through a prescribed method such as a plasma ion chemical deposition method, a plasma ion physical deposition method or the like which keeps a deposit very high in bonding strength to the center layer 1. The heat diffusing composite plate is capable of effectively taking advantage of the high thermal conductivity of graphite and enhanced in mechanical strength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the structure of a heat diffusion plate. In particular, the present invention relates to a structure of a heat diffusion heat transfer plate that uniformly and efficiently diffuses and transfers a large amount of heat supplied from a heating element to a heat receiving surface of a heat radiating unit.

[0002]

2. Description of the Related Art In recent years, semiconductor devices have been remarkably developed, and electronic devices formed by using them have been significantly reduced in size and performance. As a result, a small and light semiconductor device having an outer dimension of 11 mm × 11 mm or less and a powerful semiconductor device with a loss heat generation of as much as 80 W is being put to practical use. As a heat dissipating means for cooling such a small heat generating element, a heat diffusing heat transfer plate for heat conductively connecting a heat dissipating surface of the heat generating element and a heat receiving surface of a heat dissipating means such as a heat sink is used. . With the miniaturization of electronic devices, the heat transfer plate for heat diffusion is also required to be lightweight and thin. The present inventor has proposed and put to practical use an inter-plane heat transfer plate disclosed in Japanese Patent Application No. 9-88600 as such a heat diffusion heat transfer plate.

The inter-plane heat transfer plate disclosed in Japanese Patent Application No. 9-88600 has a high-purity graphite sheet as a central layer, and has an adhesive material having a thickness on both sides of the central layer that can ignore the thermal resistance in the vertical direction. A thin film layer (second layer) is formed. Further, a metal layer having good thermal conductivity (third layer) is disposed on both outer surfaces of the adhesive thin film layers on both surfaces. The three-layer structure was pressure-bonded to each other at a high temperature to produce an inter-surface heat transfer plate composed of a laminated structure. In this inter-surface heat transfer plate, the third layer is a pure copper thin plate having a thickness of 200 μm, and the second layer is a silver brazing thin film sheet having a thickness of 50 μm.
The temperature condition during the high-pressure bonding was 800 ° C. The thermal conductivity in the plane direction of the inter-plane heat transfer plate thus configured is 600 W / m · K, which is about 1.7 times that of a conventionally used pure copper thin plate of the same thickness, and excellent heat conductivity. Demonstrated diffusion performance.

[0004] This inter-surface heat transfer plate uses high-purity graphite as a heat transfer means. This high-purity graphite has a high thermal conductivity in the plane direction and has a very low density of 1.0 g / cm ³ . However,
Considering the practicality as an inter-surface heat transfer plate, it is inferior in adhesiveness, mechanical strength and the like. That is, although the single-material structure composed of only the graphite sheet is excellent in the heat diffusion function, as a defect peculiar to carbon, the bonding property to the surface of another substance is extremely poor. Therefore, in practical use, mechanical pressure bonding means is required. Therefore, the heat connecting means is complicated and heavy.

[0005] Furthermore, a single-material structure composed of only a graphite sheet has insufficient mechanical strength, and is fragile to be applied as an equipment part. In particular, the abrasion resistance is extremely poor, and there is a risk of abrasion or breakage even with a slight external force, and it is difficult to bond the reinforcing metal plate. This has the disadvantage of reducing the reliability of the device.

The inter-surface heat transfer plate disclosed in Japanese Patent Application No. 9-88600 is a good heat diffusion plate, but has the following problems to be solved. (1) In order to join the second layer to the center layer of the graphite sheet, as described above, mechanical forced bonding means interposed with a molten metal thin film by high temperature and high pressure was required as a property of carbon. When the high-temperature and high-pressure bonding is performed, a distortion is generated due to a difference in thermal expansion coefficient between the third metal layer and the graphite central layer. For this reason, a smooth inter-surface heat transfer plate surface (third layer surface) was not obtained, and heat transfer performance was reduced.

(2) Since the third metal layer is a layer formed by forcibly bonding a metal thin film plate under high temperature and high pressure, it must first be manufactured in a separate process. Further, it is extremely difficult to form a thin film having a thickness of 0.05 mm or less due to manufacturing technology.
Further, in order to absorb the strain stress of the composite plate due to the difference in the coefficient of thermal expansion, it is necessary to reinforce the plate with the thickness of the third layer being at least 0.1 mm or more.
Since the thermal conductivity in the plane direction of the inter-plane heat transfer plate is determined by the thermal conductivity of the third layer and the central layer, in order to fully utilize the characteristics of high-purity graphite with high thermal conductivity,
It is necessary to make the thickness of the third layer as thin as possible and make it difficult for heat to flow in the plane direction. However, the performance of the inter-surface heat transfer plate is degraded due to such a large thickness of the metal layer.

(3) The center layer and the third layer are joined by the interposition of a second layer which is an adhesive layer. However, this is forced bonding by high temperature and high pressure using the second layer as the bonding medium,
Unlike the case of complete joining, the joining strength is weak. Therefore, when an external force such as partial bending is applied, peeling may occur at that portion. The thermal conductivity in the direction perpendicular to the surface may be reduced due to the contact thermal resistance of the separated portion.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been made in view of the above circumstances. An object is to provide a heat transfer plate.

[0010]

Means for Solving the Problems and Embodiments of the Invention In order to solve the above problems, a heat transfer plate for heat diffusion according to a first aspect of the present invention is a heat transfer plate for conducting and diffusing heat input to a heat receiving portion to the surroundings. A diffusion composite plate; a central layer made of a high-purity graphite sheet; a metal thin film having a thickness not exceeding 10 μm deposited on both surfaces or one surface of the central layer;
It is characterized by having. Effective thermal conductivity of high-purity graphite by using high-purity graphite with extremely high thermal conductivity in the plane direction and relatively low thermal conductivity in the vertical direction, and forming a metal thin film on both sides or one side Utilizing this, it is possible to further impart mechanical strength.

A heat diffusion heat transfer plate according to a second aspect of the present invention is a heat diffusion composite plate for conducting and diffusing heat input to a heat receiving portion to the surroundings; a central layer made of a high-purity graphite sheet; A metal thin film having a thickness not exceeding 10 μm deposited on both or one side of the central layer; and a metal layer having a good thermal conductivity and having a thickness not exceeding 100 μm formed on the outer surface of the metal thin film. It is characterized by having. The mechanical strength can be further increased, and mounting work such as soldering of the heating element and the plate itself can be easily performed.

In these embodiments, the metal thin film can be formed by a plasma ion chemical vapor deposition method or a plasma ion physical vapor deposition method. In order to effectively demonstrate the high thermal conductivity of high-purity graphite,
A thin metal film of 0 μm or less can be formed.

Further, a metal thin film can be reliably formed on the metal layer by plating or vacuum evaporation.

A heat transfer plate for heat diffusion according to a third aspect of the present invention is a heat diffusion composite plate for conducting and diffusing a large amount of heat input into a heat receiving portion to the periphery; a central layer made of a high-purity graphite sheet; A plurality of two-layer plates having a thickness of not more than 10 μm and deposited on both surfaces or one surface of the center layer; and a plurality of the two-layer plates having a thickness negligible in contact thermal resistance. It is characterized in that it is laminated and joined by means of an adhesive means. This makes it possible to cope with a large-capacity heating element.

It is also preferable that the metal layer be a plating layer and be subjected to a softening treatment under a predetermined heat treatment condition or a low melting point soft alloy layer be provided on the outer surface of the metal layer. Thereby, predetermined flexibility can be given to the whole plate, and mounting of the heating element and the plate itself becomes easy.

Hereinafter, description will be made with reference to the drawings. FIG.
FIG. 1 is a perspective view showing a basic structure of a heat diffusion composite plate according to a first embodiment of the present invention. The center layer 1 is made of high-purity graphite having a very high thermal conductivity in the plane direction and a relatively low thermal conductivity in the vertical direction. The high-purity graphite (Panasonic graphite sheet, manufactured by Matsushita Electric Industrial Co., Ltd.) of this example has a thermal conductivity in the plane direction of 800 to 10.
00W / m · K, vertical thermal conductivity 5W / m · K, heat resistance 3000 ° C, tensile strength 19.6MPa, coefficient of linear expansion 0.93 × 10 ^-6 , density 1.0g / cm ³ Have. The metal thin film 2 is made of a material such as pure copper or pure nickel, and has a bonding strength on both sides of the central layer 1 with respect to the central layer such as plating, vacuum deposition, plasma ion chemical vapor deposition, or plasma ion physical vapor deposition. It is deposited in a strong predetermined manner.
At this time, it is preferable to select a metal which does not need to have a very high temperature at the time of deposition in consideration of a difference in expansion coefficient from the central layer 1.

Since the metal thin film 2 is a metal film deposited and formed directly on the surface of the center layer 1 by vapor deposition or the like, not by adhesion or bonding, an extremely thin thin film can be formed. The metal thin film 2 has a thickness of 10 so as not to lower the thermal conductivity of the central layer 1.
μm or less, preferably 1 to 5 μm or less. Further, since the center layer 1 is made of high-purity carbon, the physical strength is insufficient as described above, and it is basically difficult to join or bond the heating element and the plate itself. By providing this metal thin film 2, the surface properties can be improved so as to obtain bonding and adhesion. When a plasma ion deposition method is applied as a method for forming the metal thin film 2, special functions such as heat resistance, chemical resistance, abrasion resistance, and corrosion resistance can be provided by selecting the type of metal.

Since the metal thin film 2 is formed by the above-described method, it is a hard thin film, has poor spreadability, and is difficult to bend. Therefore, in the case of a heat diffusion plate that requires bending, the metal thin film 2 is formed only on the inner surface side of the bending process so as not to receive a compressive buckling effect during the bending operation. Further, since the heat resistance temperature of the center layer 1 is as high as 3000 ° C., the metal thin film 2 can be subjected to softening heat treatment such as annealing. After the softening heat treatment, the bending process can be performed.

FIG. 2 is a perspective view showing a basic structure of a composite plate for heat diffusion according to a second embodiment of the present invention.
This heat diffusion plate has a metal thin film 2 deposited on both surfaces of a high-purity graphite sheet central layer 1. Further, a metal layer 3 (third layer) is formed on both surfaces of the metal thin film 2 (second layer). The thickness of the metal thin film 2 is about 5 μm, and the effect of improving the mechanical strength is small. For this reason, in order to improve the mechanical strength and the bonding or adhesion, the third
A metal layer is formed on the outer surface of the metal thin film 2 as a layer. The metal layer 3 is a thin film of a metal having good thermal conductivity, such as copper or nickel, and is formed by plating, plasma ion deposition, or the like. The metal layer 3 may be softened by a predetermined heat treatment to impart appropriate flexibility.

The thickness of the third layer 3 is made thick (100 μm or less) when high mechanical strength is required, and is made as thin as possible when it is merely sandwiched or pasted and applied. . When the bonding strength between the metal thin film 2 and the metal layer 3 is required to be strong, it is preferable to form the metal layer by plasma ion chemical vapor deposition, and when the bonding strength is to be enhanced and a dense smooth surface is required. Is applied by a plasma ion enamel deposition method or a plasma ion sputtering method. This increases the number of metal ions penetrating between the base carbon molecules, and increases the bonding strength by forming a dense thin film.

The metal layer 3 fills and repairs microcracks that are likely to occur in the hard metal thin film of the second layer 2 to reinforce the metal thin film 2 and increase the mechanical strength of the entire heat diffusion plate. For this reason, it is preferable that the third layer 3 is soft and rich in malleability, and it is desirable to select a metal thin film such as pure copper electroplate that can greatly increase malleability by heat treatment.

The thickness of the thin film is 1 to 5 μm for the second layer 2 and 1 to 5 μm except for the case where the third layer 3 is intended to reinforce mechanical strength.
μm, and the total of the second and third layers is usually 8 μm
It is as follows. Therefore, a thin film of such a thickness has a negligible thermal resistance in the direction perpendicular to the plane, and acts as a thermal resistor rather than plane heat conduction (heat diffusion).
It does not contribute to thermal diffusion. Therefore, most of the thermal diffusion performance of the composite plate for thermal diffusion depends on the high in-plane thermal conductivity of the high-purity graphite of the central layer 1. As described above, the third layer 3 is made as thin as the mechanical or physical conditions permit, thereby increasing the heat conduction share of the high-purity graphite. Plasma ion deposition is effective as a third layer forming means because a thin film of about 1 μm can be firmly formed.

When the thickness of the central layer 1 is 500 μm and the total thickness of the second and third layers is 8 μm, the thickness of the second and third layers is as follows. The ratio of the height is 62.5 times smaller than that of the central layer. Since the second and third layers are thus much thinner than the center layer, the heat spreading function is negligibly low and the heat spreading function depends almost exclusively on the center layer.

The heat receiving effect of the composite plate for heat diffusion largely depends on the state of adhesion between the plate and the heat radiating surface of the heat generating element and the heat receiving surface of the heat radiating element such as a heat sink. Therefore, when the heat receiving effect is poor due to poor surface condition of the heat radiating surface of the heating element or the heat receiving surface of the heat radiating element, the function of the heat diffusion plate cannot be effectively utilized. For this reason,
A fourth layer may be formed outside the third layer to improve the state of adhesion of the heating element to the heat dissipation surface. The material of the fourth layer is preferably a low-temperature solder metal (for example, Sn-In solder) that can be easily soldered at a low temperature, or softens at a low temperature to complement the roughness of the bonding surface and reduce the contact thermal resistance. It is a special metal (for example, In, an indium alloy).

FIG. 3 is a perspective view showing a basic structure of a composite plate for heat diffusion according to a third embodiment of the present invention.
In this composite plate for thermal diffusion, a plurality of (two in this example) two-layer composite plates for thermal diffusion shown in FIG. The joining is performed by a low-temperature silver solder BAg-1 having a low contact thermal resistance. With such a laminated structure, the heat receiving capacity is increased, and the present invention can be applied to a large-capacity heating element.

The composite plate for heat diffusion having the above-described structure exhibits the following effects. (1) Since the heat diffusion function of the composite plate for heat diffusion of the present invention is determined almost exclusively by the heat diffusion function of high-purity graphite by the above-described configuration, a good heat diffusion function is exhibited. That is, the basic heat transfer performance of high-purity graphite is such that the in-plane thermal conductivity is 800 to 1000 W.
/ M · K, which has an excellent heat diffusion ability. This is more than twice as large as the heat diffusion capacity of the pure copper plate, and is superior to that of the heat pipe plate as the heat diffusion capacity of the area within about 80 mm × 80 mm.

(2) By forming the metal thin film of the second layer by a deposition method such as a plasma ion vapor deposition method, a dense and thin thin film can be formed. By reducing the film thickness, the heat conduction in the vertical direction is greatly improved. That is,
The thickness of the second layer is usually 1 to 5 .mu.m, and the total thickness of the second layer and the third layer can be as thin as 2 to 8 .mu.m. Therefore, even when the vertical thermal conductivity of the metal material of the second layer and the third layer is small, the increase in the vertical thermal resistance is small, and the vertical thermal conductivity of the heat diffusion plate is only high-purity graphite. May be considered to be almost equal to the vertical thermal conductivity. In one example, the vertical direction thermal conductivity of the heat diffusion plate is 5 W / m · K, and this value is 0.7 to 1. 1 for the thermal conductivity of the currently used thermal conductive adhesive, thermal conductive grease, and the like. The thermal conductivity is 3 to 7 times higher than 5 W / m · K.

(3) Despite being a heat diffusion plate mainly composed of high-purity graphite, the provision of the second and third layers made of metal allows the heating element and the plate itself to be soldered or bonded. The heat transfer connection can be easily and efficiently performed by the various means described above.

(4) Despite being a heat diffusion plate mainly composed of high-purity graphite, heat resistance, corrosion resistance and abrasion resistance can be attained by selecting the material of the second and third layers. And various other surface functions. Therefore, various surface functions corresponding to the mounting design can be freely added.

(5) The heat-resistant temperature of high-purity graphite is 3
2,000 ° C., and the second layer and the third layer
A heat-resistant temperature of 000 ° C. can be obtained. Therefore, high-temperature thermal diffusion of several hundred degrees Celsius can be continuously maintained for a long time. In the case of a small-sized and large-capacity heating element, the heat receiving surface temperature may exceed 200 ° C. due to a large heat flux, and such a high-temperature heat diffusion can be endured for a long time.

(6) By selecting the thickness and the material of the third layer, the contact thermal resistance with the heat receiving surface of the heat radiator can be adjusted, and the temperature of the bonding boundary can be equalized. That is,
By suppressing the heat transfer in the vertical direction of the heat diffusion plate to some extent, active heat diffusion in the central layer of the heat diffusion plate temporarily stores the amount of heat in the plate and then transmits the amount of heat to the radiating means. . This equalizes the temperature. Such an application is effective when it is necessary to equalize the temperature of each element when the number of heating elements is small and plural.

[0032]

EXAMPLE 1 First Example A high-purity graphite sheet having a thickness of 200 μm was used as a central layer, and a pure copper thin film having a thickness of 5 μm was formed as a second layer on both sides of the central layer by plasma ion deposition. A composite plate was constructed. Plasma ion deposition is performed by employing a physical vapor deposition method.
It could be performed under operating conditions of 0 ° C. or less. A heat-dissipating plane (10 mm × 10 mm) of the small heating element was joined to one surface of the composite plate thus configured by soldering.
Further, the other surface of the plate was soldered to a heat receiving plane (100 mm × 100 mm) with a heat radiating means (aluminum fins or the like). When a heat amount of 80 W was radiated from the heating element, the temperature of the heating element was maintained at 40 ° C. or less, and heat was radiated effectively. Further, this heat diffusion plate could be easily applied not only to solder bonding but also to other bonding means (for example, a heat conductive adhesive).

"Second Embodiment" A 100 .mu.m thick pure copper coating was applied to both surfaces of the composite plate for heat diffusion of the first embodiment by electroplating. Then, it was softened by heat treatment (400 ° C., 10 minutes). Although the thermal conductivity was lower than that of the first embodiment, it showed a superior heat diffusion ability as compared with the pure copper plate. Furthermore, it is highly flexible and has adaptability to the shape of the heat radiating surface of the heating element and the heat receiving surface of the heat radiating means. Also, the bondability was good for both ordinary adhesive bonding and solder bonding.

"Third embodiment" Two heat diffusion composite plates of the first embodiment were laminated and joined with a low-temperature silver solder BAg-1 to form a heat diffusion composite plate having a thickness of 430 µm. When the heat input was set to 150 W using the same combination of the heat generating element and the heat radiating means as in the first embodiment, the temperature rise of the heat generating element was 50 ° C. The heat diffusion performance of the composite plate for heat diffusion having a thickness of 0.43 mm was comparable to that of a pure copper plate having a thickness of 1 mm, and the specific gravity was extremely light at 1.1.

[Fourth Embodiment] As a third layer, an outer thin film of TiN was formed on both sides of the composite plate for heat diffusion of the first embodiment by a plasma ion vapor deposition method. With such a configuration, excellent heat resistance and wear resistance can be obtained in combination with the heat resistance of high-purity graphite. For this reason, it becomes possible to continuously operate the rotary heating element for a long period of time by making it contact with the rotary heating element and absorbing, diffusing, and radiating the heat.

Fifth Embodiment FIG. 4 shows an application example of the heat diffusion composite plate of the present invention. The small heating element 5 is joined to one surface of the heat diffusion composite plate 6 with a heat conductive adhesive. Further, a thin heat receiving plate 7 of a heat sink is joined to the other surface of the heat diffusion composite plate 6 by soldering. The heat receiving plate 7 is provided with a heat radiating fin group 8 of heat radiating heat sinks. The heat diffusion composite plate 6 has the same area as the heat receiving plate 7.

The amount of heat generated from the small heating element 5 is uniformly and efficiently diffused to the heat diffusion composite plate 6. The amount of the diffused heat uniformly raises the temperature of the entire heat receiving surface of the heat receiving plate 7. This equalizes the heat radiation action of all the fins of the fin group 8, and enhances the heat radiation efficiency of the heat sink. Further, this temperature uniforming action is the same even if the heat receiving plate 7 of the heat sink is thin and lightweight,
The thickness of the heat receiving plate 7 can be significantly reduced as compared with the related art. Accordingly, the heat sink device 6 can be reduced in size and weight, in combination with the heat diffusion composite plate 6 being lightweight and thin. Further, when a composite plate for heat diffusion provided with a third layer is used, the bonding with the heat receiving plate 7 and the small heating element 5 becomes more reliable.

"Sixth Embodiment" FIG. 5 is a view showing another embodiment to which the composite plate for heat diffusion of the present invention is applied.
(A) is a plan view and (B) is a side view. Small heating element 5
Is joined to one surface of the heat diffusion composite plate 6 by a heat conductive adhesive. A plate heat pipe 9 is joined to the other surface of the heat diffusion composite plate 6 by soldering. The plate heat pipe 9 has a meandering small diameter tunnel 10 built therein. At this time, the length of the heat diffusion composite plate 6 is a length extending over the end of the entire meandering small diameter tunnel 10 of the plate heat pipe 6.

The plate heat pipe 6 efficiently transfers heat along the small diameter tunnel 10. However, when the small heating element 5 is too small (narrow), there is a problem that the number of tunnels that operate effectively decreases, and the total heat transport capacity decreases. This is because the plate heat pipe has not so high heat conductivity in the direction perpendicular to the small diameter tunnel 10. However, with such a configuration, the amount of heat supplied from the small heating element 5 is first diffused in the width direction of the plate heat pipe 10 and supplied. For this reason, all the tunnels in the group of meandering small diameter tunnels participate in the heat transport, and all the heat transport capabilities of the plate heat pipe 10 can be effectively exhibited. The plate heat pipe is disclosed in Japanese Patent No. 2544701 and Japanese Patent Application No. 11-34455.
No. 3 etc. can be referred to.

[0040]

As is apparent from the above description, it is possible to improve the adhesiveness, bonding property and mechanical problems of the heating element and the plate itself without substantially impairing the excellent surface thermal conductivity of the high-purity graphite. Further, it is possible to provide a composite plate for heat diffusion to which various surface functions corresponding to application fields are added. Also, the weight can be considerably reduced as compared with an aluminum heat diffusion plate having the same thickness. As described above, an excellent heat diffusion function can be provided, and the thickness and weight can be reduced, which can greatly contribute to a reduction in the size and weight of the applied device.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a basic structure of a heat diffusion composite plate according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a basic structure of a heat diffusion composite plate according to a second embodiment of the present invention.

FIG. 3 is a perspective view showing a basic structure of a heat diffusion composite plate according to a third embodiment of the present invention.

FIG. 4 shows an application example of the composite plate for heat diffusion of the present invention.

FIG. 5 is a view showing another embodiment to which the composite plate for heat diffusion of the present invention is applied, (A) is a plan view, and (B) is a side view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Center layer 2 Second layer 3 Third layer 4 Adhesive layer 5 Small heating element 6 Composite plate for heat diffusion 7 Thin plate heat receiving plate 8 Fin group 9 Plate heat pipe 10 Meandering small diameter tunnel 11 Center layer 12 Second layer (adhesive material) Layer) 13 Third layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05K 7/20 H01L 23/36 M

Claims (9)

[Claims] 1. A heat diffusion composite plate for conducting and diffusing heat input to a heat receiving portion to the surroundings; a central layer made of a high-purity graphite sheet, and a central layer of more than 10 μm deposited on both or one side of the central layer. And a metal thin film having no thickness. 2. A composite plate for heat diffusion for conducting and diffusing heat input to a heat receiving portion to the surroundings; a central layer made of a high-purity graphite sheet, and having a thickness of more than 10 μm deposited on both or one side of the central layer. Metal thin film having a small thickness, and a metal film having good thermal conductivity formed on the outer surface of the metal thin film.
A metal plate having a thickness not exceeding 00 μm. 3. The composite plate for heat diffusion according to claim 2, wherein the metal thin film is formed by a plasma ion chemical vapor deposition method or a plasma ion physical vapor deposition method. 4. The heat diffusion composite plate according to claim 2, wherein the metal layer is formed by plating or vacuum evaporation. 5. A heat diffusion composite plate for conducting and diffusing heat input to a heat receiving portion to the surroundings; a central layer made of a high-purity graphite sheet, and having a thickness of more than 10 μm deposited on both or one side of the central layer. A plurality of two-layer plates having a metal thin film having no thickness, and a plurality of the two-layer plates having a thickness negligible in contact thermal resistance. Composite plate for heat diffusion. 6. The plate according to claim 2, wherein said metal layer is a plating layer, has been subjected to a softening treatment under a predetermined heat treatment condition, and has a predetermined flexibility as a whole plate. Composite plate for heat diffusion. 7. The composite plate for heat diffusion according to claim 2, wherein a soft alloy layer having a low melting point is provided on an outer surface of said metal layer. 8. A composite plate for heat diffusion for conducting and diffusing heat input to a heat receiving portion to the surroundings; a central layer made of a high-purity graphite sheet, and having a thickness of more than 10 μm deposited on both or one side of the central layer. A metal thin film having a thickness of not more than 1 mm; wherein a small heating element is joined to one surface of the composite plate for heat diffusion, and the heat spread heat sink is joined to the other surface. plate. 9. A composite plate for heat diffusion for conducting and diffusing heat input to a heat receiving portion to the surroundings; a central layer made of a high-purity graphite sheet, and a central layer of more than 10 μm deposited on both or one side of the central layer. And a metal thin film having no thickness, wherein a small heating element is joined to one surface of the composite plate for heat diffusion, and a plate heat pipe having a built-in meandering small diameter tunnel is joined to the other surface. Composite plate for heat diffusion.