JP2013095991A - Metal foil with high emissivity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metallic foil for heat dissipation which is excellent in heat dissipation property, thermal conductivity, and flexibility, and applicable for electric, electronic components, and the like.SOLUTION: A base metal of the metallic foil is copper, aluminum, nickel, iron, and stainless steel and at least one side surface thereof is roughened by attaching nickel with sticking property or nickel alloy particles and their aggregate. On the roughened surface, a layer comprising nickel and sulphur or/and phosphorus is coated to obtain a surface-roughened metallic foil having an emissivity of 0.35 or more.

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, the emissivity is not so changed, and is 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 discloses that a metal substrate made of copper foil, an insulating layer, and a metal plate is provided with an oxide film having an absorptivity (emissivity) of 0.5 or more on the surface of the metal substrate, that is, 5 to 100 μm aluminum oxide. Proposals have been made to make membranes.
In Patent Document 3, although heat conduction is good and heat diffusion is good in the transverse direction (sheet surface) of the carbon graphite sheet in the heat dissipation sheet, heat conduction is extremely low in the longitudinal direction (thickness direction), Because of the problems, it has been proposed to stack a ceramic filler sheet on top of 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.

  It is not sufficient to simply bond a copper or aluminum metal foil or plate through an insulating material to a conventional technology, that is, 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 aluminum, copper, and iron as in the prior art, but a thin foil and a light weight are achieved by a form of a foil. The thermal conductivity improves the heat radiation characteristics while maintaining the value inherent to the metal.

  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, it is not preferable as a work environment, and it is difficult to treat the foil without wrinkles because of the high temperature.

  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 adding improvements to the surface of the metal foil without using another material other than metal, and can be provided as a heat dissipation substrate is proposed. To do.

  The present invention solves such a conventional problem, that is, at least one surface has an emissivity of 0.35 roughened with adhesive nickel or nickel alloy fine particles having a particle diameter of 0.1 to 2 μm and aggregates thereof. A metal foil containing no organic matter or ceramic as described above, and having a roughened metal coated with an alloy layer of nickel and phosphorus or / and sulfur on nickel or nickel alloy fine particles and aggregates thereof It is a foil. The base metal foil is copper, aluminum, nickel, iron, or stainless steel. Further, the metal foil is characterized in that the roughening is obtained by aqueous electrolysis.

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

Sectional views and plan views of tests used for temperature measurement regarding heat dissipation in Examples and Comparative Examples are shown. The SEM observation photograph of the roughening process surface obtained in Example 2 is shown. The SEM observation photograph of the roughening process surface obtained in Example 3 is shown.

  In order to obtain a metal foil with high emissivity, first, a foil of copper, aluminum, iron, stainless steel, nickel or the like is used, and the thickness is preferably 10 to 100 μm. It is ideal that continuous production from raw foil production to surface roughening is required, and electrolytic copper foil, electrolytic nickel foil, electrolytic iron foil, etc. produced by electrolysis do not require degreasing and have some surface roughening precipitation surface Is effective because it is formed. However, there is no problem with the rolled foil, and it is not limited.

Nickel or nickel alloy fine particles and aggregates thereof are applied and roughened on the surface of these metal foils, and the formation is performed by 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 500 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. In the case of nickel alloy fine particles, a small amount of Ni as a main component and one or more of elements such as Co, Fe, Cu, Sn, Mo, W, Zn, P, and S may be included. Further, in order to further prevent powder falling, the roughened particles may be coated and plated as necessary. The coating plating is nickel or nickel alloy plating. Note that coating with nickel after nickel roughening is effective in increasing the adhesion, but if the coating amount is increased too much, the emissivity decreases and the heat dissipation decreases. The amount of electricity is preferably ²⁰ to 200 coulomb / dm ² . The amount of nickel is 0.6-6 g / m ² .

  A higher emissivity can be obtained by applying an alloy plating layer of nickel and phosphorus and / or sulfur instead of the nickel coating. In this case, after nickel roughening, a nickel and phosphorus or / and sulfur plating layer may be continuously performed. 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. . In the case of nickel plating containing sulfur, a nickel water-soluble salt and a sulfur-containing additive such as sodium thiosulfate, thiourea, and aromatic sulfonic acid are added to the nickel water-soluble salt to co-precipitate with nickel.

Amount of nickel is 0.5 to 5 g / m ^2, in phosphorus content is 50 to 500 mg / m ^2, the sulfur content is 30 to 200 mg / m ^2. Phosphorus and sulfur may be mixed and added. The phosphorus or / and sulfur content in this nickel-coated plating layer is 2 to 20%.

  The resulting nickel 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. In this case, 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. Copper may be plated and the nickel or nickel alloy fine particles of the present invention may be further formed thereon. 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, it is difficult to form coarse particles of nickel or nickel alloy as it is, so a general zinc replacement treatment is performed twice as a pretreatment, and then a thin plating layer of about 0.5 to 1.5 μm of nickel. And nickel or nickel alloy roughening is performed thereon, and then an alloy plating layer of nickel and phosphorus or / and sulfur is applied.

  In the case of electrolytic foil such as electrolytic copper foil, there are usually rough surface and glossy surface. In such a case, a known roughening treatment with high adhesion to the resin is added to the rough surface side, while the glossy surface side is the main surface. By carrying out the nickel roughening treatment and the coating plating of the invention, a metal foil having both heat radiation resin adhesion can be obtained.

  As for the surface to improve the emissivity, for example, the rough surface side of the copper foil is also described above, but a roughening treatment with a known copper particle is performed, and an alloy plating coating of nickel and phosphorus or / and sulfur is further formed thereon. However, it does not improve the emissivity much.

  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 immersed in a pickling bath (A) (5% sulfuric acid aqueous solution) for 10 seconds, then washed with water, and its glossy surface is 19 A / dm ² in a nickel roughening treatment bath (B) for 15 seconds. Electrolytically treated. Next, after washing with water, the surface was coated and plated at 4 A / dm ² for 20 seconds in a nickel plating bath (C), washed with water and dried.

(B) Nickel sulfate (hexahydrate) 90 g / l
Ammonia 18 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 surface roughness of this nickel-roughened copper foil was Rzjis 3.3 μm, and the emissivity was 0.48. 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 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 amount of Ni deposited was 7.92 g / m ² . 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, a constant current of 2.5 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 57 ° C. When the sample was not attached, the same current was applied, and after 15 minutes, the stable temperature was 69 ° 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)
An electrolytic copper foil having a thickness of 35 μm was pickled in a pickling bath (A), washed with water, and the glossy surface was subjected to cathodic electrolysis at 19 A / dm ² in a nickel roughening bath (B) for 15 seconds. Next, after washing with water, the surface was coated with 2.5 A / dm ² for 20 seconds in a nickel phosphorus plating bath (D), washed with water, and dried.

(D) Nickel sulfate (hexahydrate) 60 g / l
Sodium hypophosphite (monohydrate) 55 g / l
pH 4.0
Temperature 30 ℃

The surface roughness of this nickel-roughened copper foil was Rzjis 2.3 μm, and the emissivity was 0.66. Moreover, SEM observation of the surface was performed, and the photograph is shown in FIG.
This nickel roughening-treated copper foil had an adhesion amount of Ni of 6.56 g / m ² and an adhesion amount of P of 0.18 g / m ² . Here, since the Ni amount was 5.50 g / m ² for the foil which was just nickel roughened under the same conditions in the same (B) bath, the Ni amount in the nickel phosphorus-coated plating layer in this example was 1.06. a g / m ^2, the phosphorus content was about 15%. Next, 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. The temperature stabilized by energization for 15 minutes was 54 ° C.

(Example 3)
An electrolytic copper foil having a thickness of 35 μm was pickled in a pickling bath (A), washed with water, and the glossy surface was subjected to cathodic electrolysis at 19 A / dm ² in a nickel roughening bath (B) for 15 seconds. Then, the surface was coated and plated at 2.5 A / dm ² for 20 seconds in a nickel sulfur plating bath (E).

(E) Nickel sulfate (hexahydrate) 150g / l
Sodium thiosulfate (pentahydrate) 40g / l
pH 4.5
Temperature 30 ℃

The surface roughness of this nickel-roughened copper foil was Rzjis 2.1 μm, and the emissivity was 0.65. Moreover, SEM observation of the surface was performed, and the photograph is shown in FIG. The adhesion amount of Ni was 6.51 g / m ² and the adhesion amount of S was 0.08 g / m ² . The amount of sulfur in the nickel sulfur coating layer was about 7%. Next, 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. The temperature stabilized by energization for 15 minutes was 56 ° C.

Example 4
Prepare 30μm-thick 1N30 aluminum foil, dip both sides in a degreasing bath (F) (NaOH 10 g / l aqueous solution) for 30 seconds, wash with water, and soak in a pickling bath (G) (20% nitric acid aqueous solution) for 15 seconds. Next, after washing with water, immerse in a zinc replacement bath (H) (ZnO 9 g / l, NaOH 80 g / l, Rossell salt 25 g / l, ferric chloride tetrahydrate 2 g / l) for 30 seconds, then in the pickling bath (G) After dipping for 20 seconds, it was washed with water, and then dipped again in the zinc replacement bath (H) for 30 seconds.

Next, after washing with water, one side of the nickel plating bath (C) is 7 A / dm ² for 60 seconds by cathodic electrolysis and nickel plating, then after washing with water, 19 A / dm ^{2 for} 15 seconds in the nickel roughening treatment bath (B) Cathodic electrolysis was performed. Subsequently, after washing with water, coating plating was carried out in a nickel plating bath (C) at 2.5 A / dm ² for 20 seconds. The surface roughness of the nickel-roughened aluminum foil was Rzjis 3.2 μm, and the emissivity was 0.39. This aluminum 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. The temperature stabilized by energization for 15 minutes was 62 ° C.

(Example 5)
Prepare 1N30 aluminum foil with a thickness of 30 μm, and use the same method except that the glossy surface was nickel phosphate bath (D) 2.5 A / dm ² for 20 seconds as the last nickel coating bath (C) in Example 4. Processed and plated. The surface roughness of the nickel-roughened aluminum foil was Rzjis 2.9 μm, and the emissivity was 0.64. This aluminum 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. The temperature stabilized by energization for 15 minutes was 57 ° C.

(Example 6)
Prepare stainless steel foil SUS304 with a thickness of 20μm, degrease bath (I) (NaOH 50g / l) at 3A / dm ² , cathode degrease for 30 seconds, water wash and 5A / dm ^{2 in} acid bath (A) for 60 seconds. Then, one side was subjected to cathodic electrolysis in a nickel roughening bath (A) at 23 A / dm ^{2 for} 15 seconds. Then, the surface was coated and plated at 2.5 A / dm ² for 20 seconds in a nickel phosphorus plating bath (D).

  The surface roughness of this nickel-roughened copper foil was Rzjis 1.6 μm, and the emissivity was 0.46. This stainless steel 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. The temperature stabilized by energization for 15 minutes was 62 ° C.

(Example 7)
The electrolytic copper foil having a thickness of 35 μm was treated on the glossy surface in the same manner except that the nickel-phosphorous plating bath (D) was bath (J) 2.5 A / dm ² for 20 seconds in Example 2.

(J) Nickel sulfate (hexahydrate) 60g / l
Sodium hypophosphite (monohydrate) 15g / l
pH 4.0
Temperature 30 ℃

The surface roughness of this nickel-roughened copper foil was Rzjis 2.4 μm, and the emissivity was 0.60. The adhesion amount of Ni was 6.63 g / m ² and the adhesion amount of P was 0.13 g / m ² . Phosphorus in the nickel-phosphorus coating layer was about 10%. 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. The temperature stabilized by energization for 15 minutes was 57 ° C.

(Example 8)
The electrolytic copper foil having a thickness of 35 μm was treated on the glossy surface in the same manner except that the nickel-sulfur plating bath (E) was used as the bath (K) in Example 3.

(K) Nickel sulfate (hexahydrate) 150g / l
Sodium thiosulfate (pentahydrate) 20g / l
pH 4.5
Temperature 30 ℃

The surface roughness of this nickel roughened copper foil was Rzjis 2.5 μm, and the emissivity was 0.68. The adhesion amount of Ni was 6.70 g / m ² , and the adhesion amount of S was 0.04 g / m ² . The sulfur in the nickel sulfur coating layer was about 3%. 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. The temperature stabilized by energization for 15 minutes was 56 ° C.

Example 9
An electrolytic copper foil having a thickness of 35 μm was prepared, and all the treatments were performed in the same manner except that the surface treatment was changed to the rough side in Example 2. The surface roughness of this nickel roughening-treated copper foil was Rzjis 8.1 μm, and the emissivity was 0.58. The adhesion amount of Ni was 6.65 g / m ² , and the adhesion amount of P was 0.13 g / m ² . Phosphorus in the nickel-phosphorus coating layer was about 10%. 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. The temperature stabilized by energization for 15 minutes was 58 ° C.

(Example 10)
Prepare an electrolytic copper foil with a thickness of 35μm. In Example 2, the nickel roughening treatment bath was set to (L) instead of (B), the electrolysis time was set to 20 seconds, and the Ni-P coating of the (D) bath was applied. All were processed in the same way except 2.5A / dm ² , 40 seconds.

(L) Nickel sulfate hexahydrate 110 g / l
Ammonia 25 g / l
pH 5.7
40 ℃

The surface roughness of the nickel-roughened copper foil was Rzjis 2.7 μm, and the emissivity was 0.61. The adhesion amount of Ni was 9.90 g / m ² and the adhesion amount of P was 0.27 g / m ² . Here, since the amount of Ni was 7.30 g / m ² for the foil that was just nickel roughened under the same conditions in the same (L) bath, the phosphorus in the nickel-phosphorous-coated plating layer in this example was About 9%.
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. The temperature stabilized by energization for 15 minutes was 57 ° C.

(Example 11)
An electrolytic copper foil having a thickness of 35 μm was prepared, and all the treatments were performed in the same manner except that the nickel phosphorus-coated plating was changed to a nickel-sulfur-phosphorus-coated (M) bath in Example 2.

(M) Nickel sulfate (hexahydrate) 80g / l
Sodium hypophosphite (monohydrate) 25g / l
Sodium thiosulfate (pentahydrate) 5g / l
pH 4.0
Temperature 30 ℃

The surface roughness of this nickel-roughened copper foil was Rzjis 2.4 μm, and the emissivity was 0.57. The adhesion amount of Ni was 6.25 g / m ² , and the adhesion amount of P was 0.01 g / m ² S. The adhesion amount of S was 0.03 g / m ² . The sulfur in the nickel sulfur-phosphorus coating layer was about 4% and phosphorus was about 1%. 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. The temperature stabilized by energization for 15 minutes was 58 ° C.

(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. The surface roughness was Rzjis 1.9 μm and the emissivity was 0.02. 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. The temperature stabilized by energization for 15 minutes was 68 ° C.

(Comparative Example 2)
An electrolytic copper foil having a thickness of 35 μm was prepared, and the glossy surface thereof was plated with nickel phosphorous in a plating bath (D) at 2.5 A / dm ² for 20 seconds, washed with water and dried. The surface roughness was Rzjis 1.8 μm and the emissivity was 0.16. The adhesion amount of Ni was 1.07 mg / m ² and the adhesion amount of P was 0.24 mg / m ² . The amount of phosphorus in the nickel phosphorus plating was about 18%. 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. The temperature stabilized by energization for 15 minutes was 66 ° C.

(Comparative Example 3)
A 30 μm thick 1N30 aluminum foil was prepared, and the surface roughness and emissivity were examined. The surface roughness was Rzjis 0.2 μm and the emissivity was 0.03. 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. The temperature stabilized by energization for 15 minutes was 68 ° C.

(Comparative Example 4)
Prepare electrolytic copper foil with a thickness of 35μm and blacken the glossy surface (N)
(N) NaOH 15g / l NaClO ₂ 40g / l Trisodium phosphate (12 hydrate) 5g / l 90 ° C
Was immersed in an aqueous solution and surface oxidation was performed for 150 seconds. The surface roughness and emissivity of this surface were examined. The surface roughness was Rzjis 2.0 μm and the emissivity was 0.07. 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. The temperature stabilized by energization for 15 minutes was 64 ° C.

(Comparative Example 5)
Prepare electrolytic copper foil with a thickness of 35μm, and treat this rough side with a treatment bath (O).
(O) Sulfuric acid 100 g / L, Copper sulfate (pentahydrate) 50 g / L
At 10 A / dm ² for 8 seconds. Then treatment bath (P)
(P) Sulfuric acid 100 g / L, Copper sulfate (pentahydrate) 220 g / L
Was subjected to cathodic electrolysis at 5 A / dm ² for 70 seconds. Next, after washing with water, nickel phosphorous plating was carried out in a plating bath (D) at 2.5 A / dm ² for 20 seconds, washed with water and dried. The treated surface roughness of this copper foil was Rzjis 9.8 μm. The emissivity was 0.16. 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. The temperature stabilized by energization for 15 minutes was 65 ° C.

  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, is lightweight because it is in the form of a foil, and has flexibility, so that heat dissipation substrates such as LED substrates, automotive electronics substrates, power module substrates, organic EL substrates, etc. It can be applied to a wide range of fields that can exhibit its shape and characteristics, such as for heat sinks and printed wiring boards, as well as other heat sinks and electrically conductive materials.

1 Sample foil 2 Polyimide film 3 Stainless steel foil 4 Heat insulation material 5 Measurement point

Claims (4)

  A roughened metal foil characterized in that at least one surface of a base metal foil has an emissivity of 0.35 or more to which adherent nickel or nickel alloy fine particles having a particle diameter of 0.1 to 2 μm and an aggregate thereof are adhered.   2. The roughened metal foil according to claim 1, wherein an alloy layer comprising nickel and phosphorus or / and sulfur is coated on the sticking nickel or nickel alloy fine particles and aggregates thereof.   The roughened metal foil according to claim 1 or 2, wherein the base metal foil is copper, aluminum, nickel, iron, or stainless steel.   The roughened metal foil according to any one of claims 1 to 3, wherein the roughening is obtained by aqueous electrolysis.