JP2000299258A - Aluminum electrolytic capacitor cathode foil and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cathode foil which is capable of decreasing an electrostat ic capacity changes 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 silicate 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 in order to solve the above-mentioned problems, and has a high capacitance per unit area and a high product quality. The present invention relates to a cathode foil for an aluminum electrolytic capacitor having a small decrease in capacitance. That is, Ti, Zr,
A cathode foil for an aluminum electrolytic capacitor, wherein an aluminum foil formed by depositing a metal of Hf or Nb or an oxide or nitride thereof is immersed in a solution containing silicate and heat-treated. 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 processing temperature is 100-500 degreeC, It is the manufacturing method of the cathode foil for aluminum electrolytic capacitors characterized by the above-mentioned.

[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 interface of the cathode foil.
Therefore, by forming a film containing silicic acid on the cathode foil in advance, it is possible to suppress the reaction at the cathode foil interface even when the pH increases. By this effect, a decrease in capacitance can be suppressed.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments will be described in detail in comparison with a conventional example. [Example] After vacuum-depositing Ti on an electrochemically etched aluminum foil, sodium silicate 3 was deposited.
Using a foil immersed in a g / L aqueous solution (100 ° C.) and heat-treated at 250 ° C. as a cathode foil, a capacitor having a rating of 10 V-330 μF was produced. [Conventional example] Ti not subjected to immersion treatment in a solution containing silicate
An electrolytic capacitor having the same rating as that of the example was manufactured using the deposited aluminum etching foil as a cathode foil. Table 1 shows the change in capacitance after continuously applying a voltage of 10 V to these electrolytic capacitor samples at 105 ° C. for 5000 hours.
Shown in

[0007]

[Table 1]

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

The heat treatment temperature is preferably in the range of 100 to 500 ° C. if the temperature is lower than 100 ° C., since the effect is small, and if it exceeds 500 ° C., the foil is likely to be distorted.

[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.

Claims (3)

[Claims] 1. A cathode for an aluminum electrolytic capacitor, wherein an aluminum foil formed by depositing a metal of Ti, Zr, Hf, Nb or an oxide or nitride thereof is immersed in a solution containing silicate and heat-treated. Foil. 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.