JPH06267800A - Manufacture of electrolytic capacitor - Google Patents

Abstract

PURPOSE:To form a titanium oxide coating film on the surface of aluminum at a low price, which excels in spreadability and relative permittirrty by melting a titanium oxide powder by heating by use of the plasma flame of induction plasma for thermal spraying to form a titanium oxide coating film on the surface of aluminum foil. CONSTITUTION:Alumminn foil 14 is arranged. A plasma gas such as argon gas is supplied from a plasma gas supplying pipe 5 between a carrier gas introducing pipe 4 and an intermediate pipe 3, and a sheath gas such as argon gas is supplied from a sheath gas supplying pipe 6 between the intermediate pipe 3 and an outside pipe 2, and a titanium oxide fine powder is supplied from the carrier gas introducing pipe 4. When high-frequency electric power is applied to a high-frequency induction coil 11, normal plasma flame 12 which is balanced on both left and right sides is generated, and the titanium oxide fine powder supplied together with the carrier gas is melted by heating, so that a thermal spray coating film 15 of a titanium oxide layer may be obtained on the aluminum foil 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an electrolytic capacitor, which produces a titanium oxide film having an excellent relative permittivity on the surface of an aluminum foil forming the anode of the electrolytic capacitor, thereby providing an inexpensive and high-performance electrolytic capacitor. This is a method of manufacturing a capacitor.

[0002]

2. Description of the Related Art In electrolytic capacitors, metals such as aluminum and tantalum that form a dense oxide film with a dense surface and are highly insulating are selected, and aluminum is used because of its price. Conventionally, electrolytic capacitors using aluminum foil are subjected to anodic oxidation by using an aqueous solution of boric acid or ammonium borate as an electrolytic solution after etching the surface with hydrochloric acid or the like to form an aluminum oxide film as a dielectric film. I am letting you. An electrolyte is put between the anodized anode foil and the anodized cathode foil to seal it.

[0003]

As a method of increasing the capacitance of the electrolytic capacitor, there are a method of increasing the surface area and a method of increasing the relative dielectric constant. By the way, conventionally, the surface area of aluminum foil has been increased by etching to increase the surface area by a factor of 20 to 50. However, since the surface is almost uniformly roughened, the surface area cannot be increased any further. Further, when the aluminum foil is positively oxidized, only an aluminum oxide film can be formed on the surface of the aluminum foil, so there is a limit to increase the relative dielectric constant by anodic oxidation.

On the other hand, it is known that there is a titanium oxide film as a film having a relative dielectric constant superior to that of an aluminum oxide film, but titanium oxide must use a titanium foil as a positive material. Further, there are problems that the titanium foil is hard and inferior in winding property, and it is more difficult to positively oxidize the titanium foil than the aluminum foil and is expensive.

In view of the above, the present invention has been accomplished as a result of studies to realize the production of a titanium oxide film having an excellent relative dielectric constant on an aluminum foil by improving the production method.

[0006]

Means for Solving the Problems That is, according to the present invention, a titanium oxide fine particle powder is heated and melted in an induction plasma torch, and the heat-melted titanium oxide fine particle powder is formed on the surface of an aluminum foil arranged below the induction plasma torch. By spraying, a titanium oxide film is formed on the aluminum foil to form an electrolytic capacitor.

[0007]

In the present invention, fine particles of titanium oxide are heated and melted by the plasma in the induction plasma torch. The induction plasma has a low flow rate, and the titanium oxide that has been heated and melted is slowly sprayed onto the etched aluminum foil surface, and a titanium oxide film is formed on the aluminum foil surface.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments. Prior to that, the induction plasma spraying apparatus shown in FIG. 1 used for carrying out the method of the present invention will be described. In the figure, 1 is a cylindrical support obtained by processing a boron nitride sintered body, and inside this support 1, multi-stage insertion holes 1a to 1e are formed. It is provided concentrically by repeating machining and threading, and the carrier gas introducing pipe 4, the intermediate pipe 3, and the outer pipe 2 are fixed to the insertion holes by fitting screws.

The shape of the insertion hole for the concentric support body 1 is such that the insertion hole 1a for inserting the carrier gas introduction pipe 4 through is first formed through the support body 1, and then the intermediate pipe 3 is formed. The insertion hole 1b is formed at a position approximately in the middle of the support 1 so as to be concentric with the insertion hole 1a, and then the insertion hole 1c of the outer tube 2 is inserted. Next, an insertion hole 1b having the same diameter as or slightly smaller than the inner diameter of the intermediate tube 3 is provided above the intermediate tube 3 supporting insertion hole 1b, and an inner diameter of the outer tube 2 is provided above the outer tube 2 supporting insertion hole 1c. An insertion hole 1e having the same diameter as or a slightly smaller diameter is formed.

In this way, concentric circles 1a to 1 are formed inside.
An outer tube 2, an intermediate tube 3, and a carrier gas introduction tube, which are each formed in a cylindrical shape by using a boron nitride sintered body, on a cylindrical support body 1 made of a boron nitride sintered body in which an insertion hole of e is formed. 4 and plasma gas supply pipe 5, sheath gas supply pipe 6
In order to attach, the carrier gas introduction pipe 4 is first passed through the insertion hole 1a from below, and the screw 9 is screwed and fixed by the fixing bolt 7. After that, similarly, the intermediate pipe 3 is inserted into the insertion hole 1b.
The outer tube 2 is sequentially screwed into the insertion hole 1c, and then the plasma gas supply pipe 5 and the sheath gas supply pipe 6 are respectively inserted into the insertion hole 1c.
The threaded portions 1f and 1g provided tangentially to d and 1e are inserted and screwed. A small gap of about 1 mm is provided between the inner peripheral surface of the outer tube 2 and the outer peripheral surface of the intermediate tube 3 in order to increase the speed of the supplied gas and enhance the cooling efficiency. 11 is the outer tube 2
Is a high frequency induction coil provided on the lower outer periphery of, and is connected to a high frequency power supply (not shown). 12 is a plasma flame.

In the above thermal spraying apparatus, the electrolytic capacitor of the present invention is produced as follows. First, the holder base material 13 is arranged below the apparatus and below the plasma flame 12 generated in the apparatus, and the holder base material 13 is etched on the holder base material 13.
An aluminum foil 14 having a thickness of 0 to 200 μm is arranged. Then, a plasma gas such as argon gas is supplied from the plasma gas supply pipe 5 between the carrier gas introduction pipe 4 and the intermediate pipe 3 at 5 liters / minute, and the sheath gas supply pipe 6 supplies the intermediate pipe 3 with the plasma gas.
A sheath gas such as argon gas is placed between the outer tube 2 and the outer tube 2.
Supply at 0 liters / minute, from carrier gas inlet pipe 4 to 2
Particle size is 1-2μ with carrier gas / liter
m of the titanium oxide fine particles is supplied to the high frequency induction coil 11 at a rate of 3 kW. 13.56MHz
When a high-frequency power is applied, a well-balanced normal plasma flame 12 is generated, the fine particles of titanium oxide supplied together with the carrier gas are heated and melted, and the aluminum foil 14 is oxidized to a thickness of 1 to 2 μm. A sprayed coating 15 of titanium layer was obtained.

In this way, the aluminum foil on which the titanium oxide film is formed is anodized by using an aqueous solution of boric acid or ammonium borate as an electrolytic solution. Then, an electrolyte is provided between the positively-oxidized anode foil and the non-anodized cathode foil, and the electrolyte is sealed.

In the electrolytic capacitor thus formed, the titanium oxide film 15 is formed on the surface of the positively oxidized aluminum foil 14 as shown in the enlarged sectional view of FIG. Will be increased by the amount. Further, since the film is made of titanium oxide having a high relative dielectric constant, the capacity of the electrolytic capacitor can be increased. Further, since the plasma velocity of the induction plasma spraying is slower than that of the DC plasma spraying and the spraying is performed in a short time, no damage due to overheating of the aluminum foil was observed due to the spraying.

In the above embodiment, after etching the aluminum foil, titanium oxide was sprayed by induction plasma and then anodized. However, after etching the aluminum foil, the anodized aluminum was anodized. Titanium oxide may be sprayed onto the surface of the foil by induction plasma to form a titanium oxide film. Further, although the above-mentioned induction plasma spraying is performed in the atmosphere, the induction plasma spraying may be performed under reduced pressure.

[0015]

As described above, according to the present invention, the titanium oxide powder is heated and melted by the plasma flame of the induction plasma and sprayed to form the titanium oxide film on the aluminum foil surface. In addition, a titanium oxide film having an excellent relative dielectric constant can be formed on the aluminum surface at low cost, and the surface area can be increased, so that an inexpensive and high-performance electrolytic capacitor can be obtained. Also, the same capacitance can be miniaturized as compared to conventional electrolytic capacitors produced.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an example of an induction plasma spraying apparatus used in the present invention.

FIG. 2 is an enlarged cross-sectional view of an aluminum foil having a titanium oxide film produced by the present invention.

[Explanation of symbols]

 1 Support 2 Outer Tube 3 Intermediate Tube 4 Carrier Gas Introducing Tube 5 Plasma Gas Supply Tube 6 Sheath Gas Supply Tube 11 High Frequency Induction Coil 12 Plasma Flame 13 Holder Base Material 14 Aluminum Foil 15 Titanium Oxide Film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hidehisa Tachibana, 2-14-3 Awaji, Higashiyodogawa-ku, Osaka, Osaka Prefecture Sansha Electric Manufacturing Co., Ltd. (72) Hiroyasu Murata 2-chome, Awaji, Higashiyodogawa, Osaka-shi, Osaka No.14-3 Sansha Electric Manufacturing Co., Ltd.

Claims (1)

[Claims] 1. The titanium oxide fine particles are heated and melted in an induction plasma torch, and the heat-melted titanium oxide fine particles are sprayed onto the surface of an aluminum foil arranged below the induction plasma torch. Method for producing electrolytic capacitor.