JP2014019914A - High emissivity metal foil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide metal foil for heat dissipation including electrical-electronic fields, which has excellent heat dissipation and thermal conductivity and has excellent flexibility.SOLUTION: In the metal foil, substrate metal foil is made of copper, aluminum, nickel, iron or stainless steel, at least one side of the substrate metal foil is stuck with nickel or cobalt fine particles and/or its aggregate, the surface thereof is provided with an alloy covering layer composed of one or more kinds selected from Co, Ni, Fe, Cu, P, Zn and Sn. The metal foil has a fine particle roughened face with a grain size of 0.1 to 2 μm, and has an emissivity of 0.40 or higher.

Description

  The present invention relates to a heat radiating substrate material and a metal foil as a heat radiating conductive material in electrical and electronic equipment.

  Metals usually have a very high thermal conductivity, and are used for all heat dissipation means by taking advantage of their characteristics. On the other hand, the surface has a characteristic of extremely low thermal radiation. For example, copper is the second element in the metal after silver in terms of thermal conductivity, but the emissivity is extremely low, and is about 0.02 to 0.05 on the polished and glossy surfaces. Although it is often used as a heat dissipation board because of its good thermal conductivity, its high thermal conductivity performance is not fully utilized due to its low thermal radiation. The same applies to aluminum, which has a very high thermal conductivity and is commonly used, but its thermal emissivity is still low at 0.02 to 0.06 on the polished and glossy surfaces. The same applies to other metals. Further, even when the surface is slightly roughened to make a semi-glossy surface and a matte surface, this emissivity is not so changed, and both copper and aluminum are about 0.05 to 0.1.

  In terms of heat dissipation, the demand for heat dissipation boards such as LED boards, power module boards, automobile electrical boards, organic EL boards, and large current boards has been increasing. Conventionally, there are metal core substrates and metal base substrates for heat dissipation substrates and large current substrates, and specifically, there are various metal substrates such as copper substrates, aluminum substrates, and iron substrates.

Patent Document 1 proposes a metal substrate in which 5 to 50 μm of a copper-based layer formed on one side of a 10 to 500 μm stainless steel foil is provided and bonded to the copper foil by an insulating layer. Patent Document 2 proposes a copper foil, an insulating layer, and a metal plate provided with an oxide film having an absorptivity (emissivity) of 0.5 or more, that is, an aluminum oxide film having a thickness of 5 to 100 μm.
In Patent Document 3, although heat conduction is good and heat diffusion is good in the lateral direction (sheet surface) of the carbon graphite sheet, there is a problem because heat conduction is extremely low in the longitudinal direction (thickness direction). It has been proposed to further stack a ceramic filler sheet on carbon graphite.

  In addition, LEDs have recently attracted attention as energy-saving products and have been rapidly put into practical use and applied as light sources. It is also rapidly expanding and used as a backlight for liquid crystal display devices. Compared to incandescent bulbs, LEDs use less power and save energy, but their luminous efficiency is not very high, and energy is released as heat. Increasing the brightness and size of the equipment is increasing, and countermeasures against heat generation are increasingly required, such as an increase in the number of LEDs mounted and an increase in input current. When heat is accumulated, the LED itself is also deteriorated by heat, the luminous efficiency is lowered, and the lifetime is shortened. Countermeasures against this heat generation are an important issue. Recently, metal-based circuit boards using copper foil and aluminum foil of 10 to 70 μm have been developed using insulating materials that are filled with heat conductive filler and have good heat dissipation at room temperature. ing.

  Thus, in recent circuit boards, countermeasures against heat are very important from the viewpoint of weight reduction and thickness reduction.

JP 2010-98246 A Japanese Patent No. 2529780 JP 2007-108547 A

  It is an object of the present invention to provide a metal material having high thermal radiation that can be applied to electric and electronic parts.

  In the prior art, that is, it is not sufficient to simply bond a copper or aluminum metal foil or plate through an insulating material to a circuit having a heating element such as a semiconductor or LED. Although the thermal conductivity is excellent, if the metal surface is not processed, the heat dissipation from the surface is extremely low, and there is a problem as a heat dissipation substrate. Therefore, it has been necessary to increase the thickness of the metal, coat the surface with an organic or ceramic material having high emissivity, or provide a heat sink such as a heat radiating fin.

  When the metal heat sink is thick, the heat capacity is large and the heat dissipation is improved. However, when the price of copper is high, the price of the product becomes a problem and the weight increases, which is a problem. When the thickness is increased, the specific gravity is increased, so that not only the weight is remarkably increased, but also the bending cannot be performed, and the flexible characteristics must be abandoned. In the present invention, it is not a thick plate such as copper, aluminum, and iron as in the prior art, but the thickness and weight are reduced by the form of a foil. The thermal conductivity is a value inherent to the metal, but the thermal radiation characteristics are improved.

  In the case of copper, the surface emissivity is increased by oxidizing copper. For example, there is a so-called blackening treatment as an oxidation treatment, but it is necessary to immerse it in an aqueous solution containing a high-temperature oxidizing agent close to the boiling point. In addition, the working environment is not good, and because of the high temperature, it is difficult to process the foil without wrinkling.

  There is a method of anodizing the surface of aluminum, but a thick plate is required, and it is difficult to use a thin foil. In addition, since the treatment process requires a long time such as several tens of minutes, it is practically difficult to apply to a roll-to-roll roll or the like and to obtain mass productivity for the foil.

  Furthermore, there is a method of applying carbon to a metal plate or foil, but the thermal conductivity in the film thickness direction is insufficient, and a carbon material and a separate process of application are required. Stacking a ceramic sheet on the carbon film is excellent in thermal diffusion but requires many steps.

  In the present invention, a metal foil that can be applied to a flexible foil form, improves the thermal emissivity by improving the surface of the metal foil without using another material other than metal, and can be provided as a heat dissipation substrate is proposed. Is.

  The present invention solves such a conventional problem, that is, deposits cobalt or nickel or their alloy fine particles and / or aggregates on at least one surface of the base metal foil, and Co, It has a coarse particle surface with a particle diameter of 0.1-2 μm provided with an alloy coating layer made of one or more of Ni, Fe, Cu, P, Zn, Sn, and has an emissivity of 0.40 or more Metal foil.

The metal foil of the present invention has high heat radiation and thermal conductivity, and is suitable for electrical and electronic board applications that require heat dissipation, particularly flexible, and is advantageous for thermal design of wiring.
And since this invention material takes the form of foil, continuous manufacture of a roll toe roll is possible, it is very easy to respond to mass production, and it is easy to provide this material.

The cross-sectional schematic showing an example of the structure of this invention is shown. The scanning electron microscope (SEM) observation photograph of the roughened surface obtained in Example 2 is shown. Sectional and plan views of tests used for temperature measurement related to heat dissipation in Examples and Comparative Examples are shown.

  In order to obtain a metal foil with high emissivity, first, copper, aluminum, iron, stainless steel, nickel or the like is used, and the thickness is preferably 10 to 100 μm. It is ideal to make continuous production from raw foil production to surface roughening, and electrolytic copper foil, electrolytic nickel foil, electrolytic iron foil, etc. produced by electrolysis do not require degreasing and have some surface roughening precipitation This is effective because the surface is formed. However, it is only necessary to insert a degreasing step in the rolled foil, which is not limited.

As one form of the present invention, cobalt or cobalt alloy fine particles and / or aggregates thereof are first deposited on the surface of these metal foils as a first step, and the formation method is carried out by an aqueous electrolysis method. As the liquid composition, a water-soluble salt of cobalt and ammonia are used. As the water-soluble salt of cobalt, cobalt sulfate, cobalt ammonium sulfate, cobalt chloride, cobalt carbonate and the like are preferable. The cobalt concentration is preferably 15 to 30 g / l in terms of metal concentration. Ammonia is preferably 5 to 30 g / l, and in addition to aqueous ammonia, it may be added as a salt such as ammonium sulfate or ammonium chloride. The pH of the aqueous solution is preferably 4-7. To adjust the pH, sulfuric acid and sodium hydroxide are used. The temperature is preferably 30 to 60 ° C. The current density is preferably 10 to 30 A / dm ² and the amount of electricity is preferably 70 to 250 coulomb / dm ² . The precipitation amount of the cobalt or cobalt alloy particles is approximately 1.5 to 6.0 g / m ² . If it is small, the emissivity is insufficient and the heat dissipation is low. In many cases, the emissivity is high, but even if the amount of electricity is increased, the emissivity does not increase, and the productivity is low.

Next, in order to further prevent the surface from falling off, the roughened particles are coated. The coating is an alloy coating layer made of one or more of Co, Ni, Fe, Cu, P, Zn, and Sn. Note that coating with nickel or cobalt after the formation of the fine particles is effective in increasing the adhesion, but if the coating amount is increased too much, the emissivity decreases and the heat dissipation decreases. Also, copper reduces the emissivity, so if you add it, keep it small. As the coating layer, Co—P, Ni—P, Ni—Co—P and the like are particularly preferable. The amount of electricity is preferably 100 to 500 coulomb / dm ² . The coating amount is 0.6-6 g / m ² . In order to perform this coating plating, in the case of nickel-phosphorus alloy plating, plating is performed with an aqueous solution to which a water-soluble salt of nickel and hypophosphorous acid, sodium hypophosphite, phosphorous acid, sodium phosphite and the like are added. . The phosphorus content in this nickel-coated plating layer is 2 to 20%.

As another embodiment of the present invention, nickel or nickel alloy particles and aggregates are attached on the surface of the metal foil. The formation method is an aqueous electrolysis method. As a liquid composition, nickel water-soluble salt and ammonia are used, and nickel water-soluble salt is preferably nickel sulfate, nickel ammonium sulfate, nickel chloride, nickel carbonate or the like. The nickel concentration is preferably 15 to 30 g / l in terms of metal concentration. Ammonia is preferably 5 to 30 g / l, and in addition to aqueous ammonia, it may be added as a salt such as ammonium sulfate or ammonium chloride. The pH of the aqueous solution is preferably 4-7. To adjust the pH, sulfuric acid and sodium hydroxide are used. The temperature is preferably 30 to 60 ° C. The current density is preferably 10 to 30 A / dm ² and the amount of electricity is preferably 150 to 600 coulomb / dm ² . The amount of the rough nickel or nickel alloy particles deposited is about 3 to 15 g / m ² . If it is small, the emissivity is insufficient and the heat dissipation is low. In many cases, the emissivity is high, but even if the amount of electricity is increased, the emissivity does not increase, and the productivity is low.

Next, in order to further prevent the powder from falling on the surface, the roughened particles are coated. The coating is an alloy coating layer made of one or more of Co, Fe, Cu, P, Zn, and Sn. Although coating with cobalt or the like after the formation of the fine particles is effective in increasing the fixing property, when the coating amount is excessively increased, the emissivity is decreased and the heat dissipation is decreased. Copper improves the thermal conductivity but lowers the emissivity, so if added, keep it small. As the coating layer, Co—P, Co—Ni—P or the like is particularly preferable. The amount of electricity is preferably ²⁰ to 200 coulomb / dm ² . The coating amount is 0.6-6 g / m ² .

  Further, as yet another embodiment of the present invention, nickel and cobalt fine particles are not each element alone, but nickel and cobalt alloy fine particles, and coating plating thereon Co, Ni, Fe, Cu, P, Zn, The same effect can be obtained by providing an alloy coating layer composed of one or more of Sn.

  As described above, the resulting fine particle size is preferably about 0.1 to 2 μm, and may exist as an aggregate in which the particles are fixed to each other. At this time, the aggregate has a size of about 0.5 to 5 μm.

  The roughness of the roughened surface depends on the roughness of the substrate, but it is preferably 1.5 μm to 5 μm in terms of Rzjis for glossy surfaces. For rough surfaces, it is preferable to increase the roughness by 2 to 6 μm as Rzjis. The rough surface of the copper foil is subjected to a roughening treatment with a known copper particle of about 0.2 to 2 μm. As an example, dendritic copper is deposited at a current density higher than or equal to the limit current density in a sulfuric acid-copper sulfate aqueous solution. The fine particles of the present invention may be further formed thereon by coating with copper. However, although the emissivity tends to increase as the surface roughness increases, it is not proportional and varies greatly depending on the amount of roughening, the shape of the roughened particles, the adhering elements, the substrate foil, and the like.

In the case of aluminum or aluminum alloy foil, since it is difficult to form alloy coarse particles such as nickel or cobalt as it is, the zinc substitution treatment is performed twice as a general pretreatment, and then nickel or cobalt or an appropriate one is used. A thin plating layer of about 0.5 to 1.5 μm of metal is provided, and the above-described various metal or alloy roughening and roughening particles are adhered thereon to apply a coating plating layer.
As described above, the rough surface obtained by the above-described method has an emissivity of 0.40 or more, and becomes a metal foil having high thermal radiation.

  In the case of electrolytic foil such as electrolytic copper foil, there is usually a rough surface on the precipitation surface side and a gloss surface on the drum surface side. In such a case, a known roughening treatment with high adhesion to the resin is added to the rough surface side. On the other hand, on the glossy surface side, a metal foil having both heat dissipation and resin adhesion can be obtained by subjecting the fine particle roughening treatment and coating plating of the present invention to coating.

  For the surface to improve the emissivity, for example, the rough surface side of the copper foil is subjected to the roughening treatment with the known copper particles as described above, and further, the alloy plating coating of nickel or cobalt and phosphorus is performed thereon. However, the emissivity does not improve much. Cobalt or nickel or alloy fine particle coarsening is an important factor.

  Examples are shown below. However, the present invention is not limited to these.

Example 1
An electrolytic copper foil with a thickness of 35 μm is dipped in a pickling bath (A) (5% sulfuric acid aqueous solution) for 10 seconds, then washed with water, and its glossy surface is 15 A / dm ² in a cobalt roughening bath (B) for 10 seconds. Electrolytically treated. After washing with water, the surface was plated with nickel plating bath (C) at 3.8 A / dm ² for 80 seconds, washed with water and dried.

(B) Cobalt sulfate (pentahydrate) 90 g / l
Ammonia 14 g / l
pH 6.0
Temperature 45 ℃

(C) Nickel sulfate (hexahydrate) 250 g / l
Nickel chloride (hexahydrate) 50 g / l
Boric acid 20 g / l
pH 4.0
40 ℃

The roughened copper foil had a surface roughness of Rzjis 4.0 μm and an emissivity of 0.71. The surface roughness was measured using Surfcoder SE500 (manufactured by Kosaka Laboratory), and the emissivity was measured using a D & S AERD emissometer (manufactured by Kyoto Electronics Industry). The measurement wavelength region of this emissometer is 3 to 30 μm. The same measurement was performed in the following examples and comparative examples. The amount of adhering elements was examined by fluorescent X-ray analysis (RIX2000, manufactured by Rigaku Denki). The adhesion amounts of Ni and Co were 6.99 g / m ² and 2.47 g / m ² , respectively. The following examples and comparative examples were similarly analyzed.

  On the other hand, SUS304 stainless steel foil with a thickness of 20 μm is cut into a width of 3 mm and a length of 11 cm, an adhesive polyimide film with a thickness of 5.5 × 5.5 cm and a thickness of 50 μm is pasted on both sides, and this roughened copper foil is further processed on one side. The surface side was affixed with a size of 5 × 5 cm, and this was placed on a heat insulating material as shown in FIG. Then, a distance between terminals of 10 cm was taken on the stainless steel foil wire, and a constant current of 2.6 A was continuously applied with a rectifier, and the temperature due to heat generation at 5 points (on the sample surface) was examined. The temperature was stabilized by energization for 15 minutes, and the temperature was 59 ° C. When the sample was not attached, the same current was applied, and after 15 minutes, the stable temperature was 70 ° C. The same measurement was performed in the following examples and comparative examples.

  The results are shown in Table 1 including the following examples and comparative examples.

(Example 2)
Same as Example 1 except that the electrolytic copper foil having a thickness of 35 μm was plated with nickel phosphorous plating bath (D) in the nickel plating bath (C) in Example 1 and plated with 2.5 A / dm ² for 140 seconds. Processed in the way.

(D) Nickel sulfate (hexahydrate) 60 g / l
Sodium hypophosphite (monohydrate) 7 g / l
pH 4.0
Temperature 30 ℃

Each characteristic of this roughened copper foil and the amount of foreign element adhesion were examined. The results are shown in Table 1.
Next, this copper foil was affixed to a polyimide film in the same manner as in Example 1, the temperature due to heat generation of the SUS foil wire was examined, and the results are shown in Table 1.

(Example 3)
The electrolytic copper foil having a thickness of 35 μm was treated on the glossy surface in the same manner except that nickel phosphorus plating in the nickel phosphorus plating bath (D) was performed at 2.5 A / dm ² for 100 seconds in Example 2. Each characteristic of this roughened copper foil and the amount of foreign element adhesion were examined. The results are shown in Table 1.

  Next, this copper foil was affixed to a polyimide film in the same manner as in Example 1, the temperature due to heat generation of the SUS foil wire was examined, and the results are shown in Table 1.

Example 4
An electrolytic copper foil with a thickness of 35 μm is immersed in a pickling bath (A) (5% sulfuric acid aqueous solution) for 10 seconds, then washed with water, and its glossy surface is 21 A / dm ² in a nickel roughening bath (E), cathode for 20 seconds. Electrolytically treated. After washing with water, the surface was plated with a cobalt phosphorus plating bath (F) at 2.5 A / dm ² for 40 seconds, washed with water and dried.

(E) Nickel sulfate (hexahydrate) 110 g / l
Ammonia 25 g / l
pH 5.8
Temperature 43 ℃

(F) Cobalt sulfate (pentahydrate) 80 g / l
Sodium hypophosphite (monohydrate) 15 g / l
pH 4.7
Temperature 30 ℃

Each characteristic of this roughened copper foil and the amount of foreign element adhesion were examined. The results are shown in Table 1.
Next, this copper foil was affixed to a polyimide film in the same manner as in Example 1, the temperature due to heat generation of the SUS foil wire was examined, and the results are shown in Table 1.

(Example 5)
A 35 μm-thick electrolytic copper foil was treated in the same manner except that the glossy surface was catholyzed for 15 seconds at 19 A / dm ² in the (G) bath instead of the nickel roughening bath (E) in Example 4. .

(G) Nickel sulfate (hexahydrate) 90 g / l
Ammonia 16 g / l
pH 5.7
Temperature 45 ℃

Each characteristic of this roughened copper foil and the amount of foreign element adhesion were examined. The results are shown in Table 1.
Next, this copper foil was affixed to a polyimide film in the same manner as in Example 1, the temperature due to heat generation of the SUS foil wire was examined, and the results are shown in Table 1.

(Example 6)
An electrolytic copper foil with a thickness of 35 μm is immersed in a pickling bath (A) (5% sulfuric acid aqueous solution) for 10 seconds, then washed with water, and its glossy surface is 21 A / dm ² in a nickel roughening bath (E), cathode for 20 seconds. Electrolytically treated. After washing with water, the surface was plated with a cobalt plating bath (H) at 2.5 A / dm ² for 40 seconds, washed with water and dried.

(H) Cobalt sulfate (pentahydrate) 200 g / l
pH 4.0
40 ℃

Each characteristic of this roughened copper foil and the amount of foreign element adhesion were examined. The results are shown in Table 1.
Next, this copper foil was affixed to a polyimide film in the same manner as in Example 1, the temperature due to heat generation of the SUS foil wire was examined, and the results are shown in Table 1.

(Example 7)
An electrolytic copper foil having a thickness of 35 μm was immersed in a pickling bath (A) for 10 seconds, then washed with water, and its glossy surface was subjected to cathodic electrolytic treatment for 15 seconds at 15 A / dm ² in a cobalt roughening treatment bath (B). After washing with water, the surface was plated with a cobalt-phosphorous plating bath (F) at 2.5 A / dm ² for 120 seconds, washed with water and dried.
Each characteristic of this roughened copper foil and the amount of foreign element adhesion were examined. The results are shown in Table 1.
Next, this copper foil was affixed to a polyimide film in the same manner as in Example 1, the temperature due to heat generation of the SUS foil wire was examined, and the results are shown in Table 1.

(Example 8)
35μm thick electrolytic copper foil was immersed for 10 seconds in a pickling bath (A) of, and then washed with water, nickel on the glossy surface - was 19 A / dm ^2, 15 sec cathodic electrolysis treatment in the cobalt roughening treatment bath (I) . After washing with water, the surface was plated with nickel / phosphorus plating bath (D) at 2.5 A / dm ² for 100 seconds, washed with water and dried.

(I) Nickel sulfate (hexahydrate) 90 g / l
Cobalt sulfate (pentahydrate) 20 g / l
Ammonia 16 g / l
pH 5.5
Temperature 45 ℃

Each characteristic of this roughened copper foil and the amount of foreign element adhesion were examined. The results are shown in Table 1.
Next, this copper foil was affixed to a polyimide film in the same manner as in Example 1, the temperature due to heat generation of the SUS foil wire was examined, and the results are shown in Table 1.

Example 9
Prepare 30μm thick 1N30 aluminum foil, soak in degreasing bath (J) (NaOH 10 g / l aqueous solution) for 30 seconds, rinse with water, soak in pickling bath (K) (20% nitric acid aqueous solution) for 15 seconds, then After washing with water, immerse in a zinc replacement bath (L) (ZnO 9 g / l, NaOH 80 g / l, Rossell salt 25 g / l, ferric chloride tetrahydrate 2 g / l) for 30 seconds, then pickling bath ( After being immersed in K) for 20 seconds, washed with water, and then again immersed in the zinc replacement bath (L) for 30 seconds. Next, after washing with water, the one-side glossy surface was subjected to cathodic electrolysis in a nickel plating bath (C) at 3.8 A / dm ² for 80 seconds to perform nickel plating (undercoat plating).

Next, the surface was washed with water, and the surface was subjected to cathodic electrolysis in a cobalt roughening bath (B) at 15 A / dm ² for 10 seconds. Further, after washing with water, the surface was plated with nickel / phosphorus plating bath (D) at 2.5 A / dm ² for 140 seconds, washed with water and dried.

Each characteristic of the roughened aluminum foil and the amount of foreign elements attached were examined. The results are shown in Table 1. Here, the amount of Ni includes the amount of base plating Ni.
Next, this copper foil was affixed to a polyimide film in the same manner as in Example 1, the temperature due to heat generation of the SUS foil wire was examined, and the results are shown in Table 1.

(Comparative Example 1)
An electrolytic copper foil having a thickness of 35 μm was prepared, and the surface roughness and emissivity on the glossy side were examined. This copper foil was attached to a polyimide film in the same manner as in Example 1, and the temperature due to heat generation of the SUS foil wire was examined. Table 1 shows the measured values.

(Comparative Example 2)
An electrolytic copper foil having a thickness of 35 μm was prepared, and the glossy surface was subjected to cathodic electrolysis in a plating bath (D) at 2.5 A / dm 2 for 60 seconds, Ni—P plating was performed, washed with water, and dried.
Each characteristic of this roughened copper foil and the amount of foreign element adhesion were examined. The results are shown in Table 1.
Next, this copper foil was affixed to a polyimide film in the same manner as in Example 1, the temperature due to heat generation of the SUS foil wire was examined, and the results are shown in Table 1.

(Comparative Example 3)
An electrolytic copper foil having a thickness of 35 μm was immersed in a pickling bath (A) for 10 seconds, then washed with water, and its glossy surface was subjected to cathodic electrolytic treatment at 8.8 A / dm ² for 20 seconds in a nickel-copper roughening bath (M). . It was then washed with water and dried.

(M) Nickel sulfate (hexahydrate) 120 g / l
Copper sulfate (pentahydrate) 50 g / l
pH 1.8
35 ℃

Each characteristic of this roughened copper foil and the amount of foreign element adhesion were examined. The results are shown in Table 1.
Next, this copper foil was affixed to a polyimide film in the same manner as in Example 1, the temperature due to heat generation of the SUS foil wire was examined, and the results are shown in Table 1.

(Comparative Example 4)
An electrolytic copper foil having a thickness of 35 μm was immersed in a pickling bath (A) for 10 seconds, then washed with water, and its glossy surface was subjected to cathodic electrolytic treatment for 6.3 A / dm ² in a cobalt-copper roughening bath (N) for 20 seconds. . Next, after washing with water, the surface was plated at 3.8 A / dm ² for 20 seconds in a nickel plating bath (C), washed with water and dried.

(N) Cobalt sulfate (pentahydrate) 60 g / l
Copper sulfate (pentahydrate) 10 g / l
pH 1.8
40 ℃

Each characteristic of this roughened copper foil and the amount of foreign element adhesion were examined. The results are shown in Table 1.
Next, this copper foil was affixed to a polyimide film in the same manner as in Example 1, the temperature due to heat generation of the SUS foil wire was examined, and the results are shown in Table 1.

  From the above, in the examples of the present invention, the emissivity was remarkably higher than that of the comparative example, and it was confirmed that the heat dissipation efficiency was good for the heat generation through the polyimide film, and the temperature rise by the heat generation circuit was also low.

  The material of the present invention is excellent in thermal emissivity and thermal conductivity and is lightweight because it is in the form of a foil, and is flexible, for heat dissipation substrates such as LED substrates, automotive electronics substrates, power module substrates, and organic EL substrates. It can be applied to a wide range of fields that can exhibit its shape and characteristics, such as other heat sinks and electrically conductive materials, as well as for printed wiring boards.

DESCRIPTION OF SYMBOLS 10 Base metal foil 11 Primary particle layer 12 Coating layer 20 Sample foil 21 Polyimide film 22 Stainless steel foil 23 Heat insulating material 24 Measurement point

Claims (6)

  An alloy composed of at least one of Co, Ni, Fe, Cu, P, Zn and Sn on which cobalt or cobalt alloy fine particles and / or aggregates thereof are attached to at least one surface of the base metal foil A metal foil having a coarse particle surface with a particle diameter of 0.1 to 2 μm provided with a coating layer and an emissivity of 0.40 or more.   At least one surface of the base metal foil is attached with nickel or nickel alloy fine particles and / or aggregates thereof, and then an alloy coating layer composed of one or more of Co, Fe, Cu, P, Zn, and Sn A metal foil characterized by having a roughened surface of fine particles having a particle diameter of 0.1 to 2 μm and having an emissivity of 0.40 or more.   At least one surface of the base metal foil is attached with alloy fine particles of nickel and cobalt and / or aggregates thereof, and then comprises one or more of Co, Ni, Fe, Cu, P, Zn, Sn on it. A metal foil characterized by having an alloy-coated coarse particle surface with a particle diameter of 0.1 to 2 μm and an emissivity of 0.40 or more.   The metal foil according to any one of claims 1 to 3, wherein the elements of the alloy coating layer are cobalt and phosphorus.   The metal foil according to claim 1 or 3, wherein the elements of the alloy coating layer are nickel and phosphorus.   6. The metal foil according to claim 1, wherein the base metal foil is copper, aluminum, nickel, iron, or stainless steel.