JP2000299257A - Aluminum electrolytic capacitor cathode foil and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cathode foil which is capable of lessening an electrostatic capacity change in an aluminum electrolytic capacitor. SOLUTION: An aluminum foil, where metal such as Ti, Zr, Hf, or Nb or its oxide or nitride is evaporated is dipped into a solution which contains phosphoric acid, phosphorous acid, or hypophosphorous acid or its salt and thermally treated for the formation of a cathode foil. An etched foil, whose surface is roughened through an electrochemical or a chemical method, is used as the aluminum foil. Furthermore, this thermal treatment is carried out in the temperature range of 100 to 500 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode foil for an aluminum electrolytic capacitor and a method for producing the same.

[0002]

2. Description of the Related Art With the recent miniaturization and weight reduction of electric and electronic equipment, the demand for miniaturization of aluminum electrolytic capacitors has become stronger. In order to reduce the size of the aluminum electrolytic capacitor, it is necessary to increase the capacitance per unit area of the electrode foil to be used.Therefore, various etching methods have been studied. However, there is a limit to improving the electrostatic capacity per unit area because of melting of the etched portion.
Therefore, there has been a demand for an electrode foil having a high capacitance per unit area and a small change in capacitance when commercialized.

[0003]

In order to solve the above-mentioned problems, a cathode foil having an increased capacitance per unit area is adopted by coating the surface with an element having a higher dielectric constant than Al by a dry process. However, there is a drawback that the capacitance is greatly reduced when commercialized, and there has been a demand for the development of a cathode foil having a small change in capacitance.

[0004]

Means for Solving the Problems The present invention has been found as a result of various studies to solve the above-mentioned problems, and has a high capacitance per unit area and a low static electricity in a product. The present invention relates to a cathode foil for an aluminum electrolytic capacitor, which has a small decrease in electric capacity. That is, Ti, Zr, H
f, an aluminum foil obtained by depositing an Nb metal or an oxide or nitride thereof is immersed in a solution containing phosphoric acid, phosphorous acid, hypophosphorous acid or a salt thereof, and heat-treated. This is a cathode foil for a capacitor. Further, the cathode foil for an aluminum electrolytic capacitor is characterized in that the aluminum foil is an aluminum etching foil whose surface is roughened by an electrochemical or chemical method. And the said heat treatment temperature is 100-
A method for producing a cathode foil for an aluminum electrolytic capacitor, wherein the temperature is 500 ° C.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One of the causes of a decrease in capacitance when a product is manufactured is an increase in pH at the cathode foil interface. Therefore, if phosphoric acid, phosphorous acid, hypophosphorous acid, or a salt thereof is adhered to the cathode foil in advance, these acids gradually dissolve in the electrolytic solution, and the pH at the cathode foil interface increases. It is buffered and the decrease in capacitance is suppressed.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments will be described in detail in comparison with a conventional example. [Example 1] Ti was vapor-deposited on an electrochemically etched aluminum foil, immersed in an aqueous solution of 75 wt% phosphoric acid 1 cc / L, and heat-treated at 250 ° C to form a cathode foil. A 10 V-330 μF electrolytic capacitor was produced. [Example 2] After vacuum-depositing Ti on an electrochemically etched aluminum foil, the foil was immersed in an aqueous solution of 3 g / L ammonium dihydrogen phosphate and heat-treated at 150 ° C to form a cathode foil. An electrolytic capacitor having the same rating as in Example 1 was produced. Example 3 Ti was deposited on an electrochemically etched aluminum foil by a vacuum deposition method, and then 1 g of phosphorous acid
/ L aqueous solution, and heat-treated at 350 ° C. to form a cathode foil. Example 4 Ti was vapor-deposited on an electrochemically etched aluminum foil by a vacuum vapor deposition method.
The electrolytic capacitor was immersed in an aqueous solution of g / L and heat-treated at 450 ° C. to form a cathode foil. [Conventional example] Electrolytic capacitor of the same rating as in Examples 1 to 4 using Ti-deposited aluminum etching foil as a cathode foil which is not immersed in phosphoric acid, phosphorous acid or hypophosphorous acid-based aqueous solution, and not subjected to heat treatment Was prepared. These electrolytic capacitor samples were subjected to a voltage of 10 V at 105 ° C. for 50 hours.
Table 1 shows changes in capacitance after continuous application for 00 hours.

[0007]

[Table 1]

In Examples 1 to 4, the change in capacitance in the high-temperature life test is small and the reliability is remarkably improved as compared with the conventional example.

If the heat treatment temperature is lower than 100 ° C., the attached phosphoric acid, phosphorous acid or hypophosphorous acid is eluted in a short time, and if it exceeds 500 ° C., it is difficult to elute. Therefore, the range of 100 to 500 ° C. is preferable.

[0010]

The cathode foil for an aluminum electrolytic capacitor according to the present invention can greatly reduce the change in capacitance in a product life test and can significantly improve the reliability.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C25F 3/04 C25F 3/04 A H01M 4/04 H01M 4/04 Z F term (Reference) 4K026 AA09 AA22 BA00 BA03 BA08 BA12 BB10 CA16 CA18 CA23 CA26 DA03 EA00 EA02 EA06 EB11 5H014 AA04 BB01 BB03 BB08 BB12 CC04 EE05 HH08

Claims (3)

[Claims] An aluminum foil obtained by depositing a metal of Ti, Zr, Hf, Nb or an oxide or nitride thereof is immersed in a solution containing phosphoric acid, phosphorous acid, hypophosphorous acid or a salt thereof, A cathode foil for an aluminum electrolytic capacitor, which has been heat-treated. 2. The cathode foil for an aluminum electrolytic capacitor according to claim 1, wherein said aluminum foil is an aluminum etching foil whose surface is roughened by an electrochemical or chemical method. 3. The method for producing a cathode foil for an aluminum electrolytic capacitor according to claim 1, wherein the heat treatment temperature is 100 to 500 ° C.