JP2007201239A - Etching foil for electrolytic capacitor and method for manufacturing positive electrode foil using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive etching foil for a laminated electrolytic capacitor, and a method for manufacturing it which can connect securely a plurality of positive electrode foil or a positive electrode foil and a lead terminal etc. without damaging the capacitance with such a simple structure that in a part of positive electrode foil a compressed portion is provided for connection whose mechanical strength is resultantly reinforced. <P>SOLUTION: After preparing etching pits in an aluminum foil for an electrolyte capacitor, a compressed portion formed by performing compression processing partially from the upper and lower sides what is like a press machine equipped with a press head is prepared as many as the number of target, then the surface of the foil is processed in its chemical conversion. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an etching foil for electrolytic capacitors and a method for producing an anode foil using the same.

In general, an anode foil for an aluminum electrolytic capacitor is provided with an oxide film by chemical conversion on the surface of an etching foil in which etching pits have been formed by electrochemically or chemically etching in order to increase the capacitance per unit area. (For example, JP-A-3-109711, JP-A-10-256096, etc.). The etching pits include those that penetrate the front and back surfaces of the anode foil (hereinafter referred to as through pits) and those that do not penetrate (hereinafter referred to as non-through pits). In particular, the penetration type anode foil allows penetration of the electrolyte through the penetration pits and ion conduction to the cathode foil, so that two anode foils can be used as a double anode, but on the other hand, In contrast, since there are few metal parts called cores in the center in the thickness direction, mechanical strength is weak, and when performing chemical conversion treatment or stacking and connecting multiple anode foils, foil cracking or cutting Resulting in.
For this reason, conventionally, in order to maintain the mechanical strength, the number of pits is reduced, or a strip-shaped unetched portion that is not etched is provided on the side edge of the foil. Japanese Patent Laid-Open No. 2000-231582 also discloses a method of masking the front and back or either side with an arbitrary shape before etching, partially suppressing the generation of etching pits, and providing an unetched portion as a connection portion. is there.

Japanese Unexamined Patent Publication No. 3-109711 Japanese Patent Laid-Open No. 10-256096 Japanese Unexamined Patent Publication No. 2000-231582

However, if the number of pits is reduced to leave a large number of portions where no through pits are formed, the capacitance obtained per unit area is limited, which is an obstacle to increase the capacity. It was. Even when a strip-like unetched portion is provided on the side edge of the anode foil, the effective surface area is reduced accordingly, which is an obstacle to increasing the capacity.
In addition, the method described in Japanese Patent Application Laid-Open No. 2000-231582 requires masking in advance before etching, and it is necessary to remove the masking application part in the etching process. There has been a problem in that the number of processing steps for the used coating agent generated in the process increases.

The present invention has been made in order to solve the above-described conventional problems, and the object of the present invention is to provide a compression part for connection with enhanced mechanical strength as a result in part of the anode foil. It is an object of the present invention to provide an anode foil for a multilayer electrolytic capacitor having a simple structure and capable of reliably connecting a plurality of anode foils or anode foils to lead terminals and the like without impairing electrostatic capacity.
Further, by adopting this structure, the present invention can be applied not only to the multilayer type but also to the wound type electrolytic capacitor.

An electrolytic capacitor etching foil having an etching pit, which is provided with a compression portion for connection for connecting foils or other necessary members.
An electrolytic capacitor anode comprising a first step of providing an etching pit on the electrolytic capacitor foil, a second step of providing a compressed portion for connection to the foil, and a third step of forming the surface of the foil. A method for producing a foil is provided.

If the anode foil subjected to the partial compression for connection according to the present invention is used, the mechanical strength can be increased by crushing the fine space formed by the roughening by the etching process. .
In addition, since the fine space is compressed, in the chemical conversion process, which is a subsequent manufacturing process, formation of a chemical conversion film inside the fine space is suppressed. The strength can be maintained.
As a result, when a plurality of anode foils are stacked and connected by the cold weld method (crimping method), or when connecting the anode foil and the lead terminals, the foil is cracked or cut at the connecting portion. Can be prevented.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.
FIG. 1 shows a schematic cross-sectional view of an etching foil according to the present invention and a press head.

  In FIG. 1, reference numeral 1 denotes an electrolytic capacitor etching foil using aluminum as a valve metal. This etching foil 1 is obtained by electrochemically or chemically etching aluminum foil 2 having a purity of 99.9% or more and a thickness of about 50 μm to 200 μm in solution to form innumerable etching pits 3 extending from the front surface and the back surface. Thus, the etching pit 3 is formed over substantially the entire surface of the etching foil 1 and communicates with each other in the vicinity of the central portion in the thickness direction of the etching foil 1 to form a through pit.

In addition, after etching, a desired number of compressed portions 4 formed by subjecting the flat portion of the etching foil 1 to the press head 4 and partially compressed from above and below are provided in a desired number. . The diameter of the compressed portion 4 is in a practical range of about 1 mm to 10 mm in terms of a circle.
One side may be a flat plate and one side may be a press head. The compressed portion is compressed up to about half compared to the original thickness.
This compressed portion 5 is formed by forming a film of oxide (Al2O3) as a dielectric on the entire surface of the etching foil 1 by chemical conversion treatment, forming an anode foil, laminating a plurality of sheets, the cold weld method (or caulking method), etc. It is a part used as the connection part at the time of connecting mechanically and electrically.

In the vicinity of the foil surface, the compressed portion 5 forms portions 5a and 5b in which the etching pit 3 is closed, and this portion plays a role of increasing the mechanical strength.
In addition, since the etching pits in the compressed portion 5 reduce the internal voids, formation of a chemical film inside the voids in the compressed portion 5 is suppressed in the chemical conversion process, which is a subsequent manufacturing process.

In order to produce the etching foil and the anode foil of the present invention, the aluminum foil can be produced by performing the following steps.
In general, in the etching step, an aluminum foil is first immersed in an acidic aqueous solution containing an acid such as hydrochloric acid or sulfuric acid or an alkaline aqueous solution containing an alkali such as sodium hydroxide for a predetermined time to perform etching in the first step. After this, a second step of electrochemically forming etching pits in a solution obtained by adding an acid for forming a film such as sulfuric acid, phosphoric acid, nitric acid, or oxalic acid to an aqueous solution containing chlorides such as hydrochloric acid and sodium chloride. I do. Next, chemical or electrochemical etching is performed in an aqueous solution containing acids such as hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, and oxalic acid to dissolve aluminum along the pit inner wall, and the pit diameter is expanded to the desired thickness. The third step of etching is performed. After the aluminum foil after the third step is washed, it is washed with pure water and dried, and the etching process is finished. By these treatments, countless fine etching pits 3 are formed in the aluminum foil.
This etching pit can be adjusted in the thickness direction length in the second step of electrochemically forming the etching pit, and depending on the use of the anode foil, such as when used for a wound electrolytic capacitor, The etching pits 3 are not limited to through pits that are communicated with each other in the vicinity of the central portion in the thickness direction, but may be core remaining states that do not communicate with each other.

Next, the compression part 5 is formed in a part of aluminum foil surface by pressing a part of foil by the compression process using the roll or press which can form arbitrary shapes in a part.
The head shape of the press head for compression treatment can be a columnar body on the bottom surface of each shape such as a circle, an ellipse or a square, or a deformed body with a rounded or oblique chamfer on the bottom edge. In order to prevent the aluminum foil from being broken by the compression treatment, it is preferable that the bottom edge is rounded or obliquely chamfered.

Next, an oxide film as a dielectric is formed on the entire surface of the aluminum foil by chemical conversion treatment. In general, in the chemical conversion treatment, the aluminum foil subjected to the etching treatment is immersed in boiling pure water to form pseudo boehmite on the surface. Next, the aluminum foil is immersed in an aqueous solution containing inorganic acid ions such as boric acid and phosphoric acid, and organic acid ions such as monocarboxylic acid, dicarboxylic acid, and oxycarboxylic acid, and a predetermined voltage is applied, and anodization is performed. I do. Thereafter, heat treatment, depolarization treatment, and anodization are repeated, and then cleaning and drying are performed to complete the chemical conversion step.

  The aluminum foil having a purity of 99.98% and a thickness of 100 μm is used. In the etching process, first, the aluminum foil is immersed in an acidic aqueous solution containing an acid such as hydrochloric acid or sulfuric acid for a predetermined time to perform etching in the first step. Thereafter, a second step of electrochemically forming etching pits is performed in a solution obtained by adding sulfuric acid and phosphoric acid to an aqueous solution containing hydrochloric acid. Next, chemical or electrochemical etching is performed in an aqueous solution containing hydrochloric acid and sulfuric acid to dissolve aluminum along the inner wall of the pit, and etching in the third step is performed to expand the pit diameter to a desired thickness. After the aluminum foil after the third step is washed, it is washed with pure water and dried, and the etching process is finished. By these treatments, countless fine etching pits are formed in the aluminum foil.

  Next, a compressed portion is formed on a part of the surface of the aluminum foil by pressing a part of the foil by a compression process using an ellipsoidal press having an elliptical bottom. As the head shape of the press head for compression treatment, an elliptical columnar body having a major axis of 4 mm and a minor axis of 3 mm is used with a 1 mm round chamfered edge.

Next, an oxide film as a dielectric is formed on the entire surface of the aluminum foil by chemical conversion treatment. The aluminum foil subjected to the etching treatment is immersed in boiling pure water to form pseudo boehmite on the surface. Next, an aluminum foil is immersed in an aqueous solution containing boric acid and carboxylic acid, and a voltage of 300 V is applied to perform anodization. Thereafter, heat treatment, depolarization treatment, and anodization are repeated, and then cleaning and drying are performed to complete the chemical conversion step.
Fig. 2 shows a photograph of the anode foil subjected to partial compression for connection. FIG. 2 shows the state of the etching foil after partial compression for connection. In Example 1, the shape is an oval, but it can be processed into an arbitrary shape. The rolled part has a smooth and flat shape and has a metallic luster, and it can be seen that the roughened part is filled by compression.

The schematic sectional drawing of the etching foil which concerns on this invention, and a press head are shown. The external appearance photograph of the anode foil manufactured by this invention is shown.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Etching foil, 2 ... Aluminum foil, 3 ... Etching pit, 4 ... Press head, 5 ... Compression part, 5a, 5b ... The part where the etching pit closed.

Claims (2)

An electrolytic capacitor etching foil having an etching pit, wherein a compression portion for connection for connecting the foils or other necessary members is provided.
  An electrolytic capacitor comprising: a first step of providing etching pits on the electrolytic capacitor foil; a second step of providing a compressed portion of an arbitrary shape for connection on the foil; and a third step of forming the surface of the foil. Method for manufacturing anode foil.

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