JP2005290491A - Aluminum anode foil for electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide aluminum anode foil for an electrolytic capacitor having high acid resistance and alkali resistance. <P>SOLUTION: The aluminum anode foil for an electrolytic capacitor is obtained by forming a chemical film having a voltage resistance of ≥800 V on etching foil having a mean pit diameter of ≥1.2 μm, preferably, 1.3 μm, and, more preferably 1.4 μm, thus has a voltage resistance of ≥700 V, and satisfactory electrostatic capacitance properties as well. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an aluminum anode foil for electrolytic capacitors, and more particularly to an aluminum anode foil for electrolytic capacitors having high withstand voltage characteristics.

An aluminum electrolytic capacitor generally has the following configuration. In other words, the high-purity aluminum foil formed in a strip shape is chemically or electrochemically etched to expand the surface, and the expanded aluminum foil is formed in a chemical conversion solution such as an aqueous ammonium borate solution. The capacitor element is formed by winding the anode foil having a dielectric film formed on the surface of the aluminum foil by the treatment and the cathode foil having the same high-purity aluminum foil subjected to surface enlargement through a separator. The capacitor element is impregnated with a driving electrolyte solution and stored in a metal bottomed cylindrical outer case. Further, a sealing body made of elastic rubber is accommodated in the opening end portion of the outer case, and the opening end portion of the outer case is sealed by drawing to constitute an aluminum electrolytic capacitor.

In such an aluminum electrolytic capacitor, there is a high demand for high pressure, and various high-voltage electrolytic capacitor electrode foils have been proposed.
(See Patent Documents 1 and 2).
JP-A-11-307399 JP 2003-318069 A

  By the way, the power supply voltage of a general industrial machine is 400V. However, if an electrolytic capacitor is to be used at this voltage, a rated voltage of 700V or more is required in consideration of an effective value and a safety factor. However, the above electrode foil for electrolytic capacitors cannot withstand such a high voltage, and the actual situation is that two electrolytic capacitors having a rated voltage of 400V are used.

  Therefore, the present invention has been proposed in order to solve such problems of the prior art, and an object of the present invention is to provide an aluminum anode foil for electrolytic capacitors having a high withstand voltage characteristic of 700 V or higher. is there.

  The aluminum anode foil for electrolytic capacitors of the present invention is characterized in that a chemical conversion film of 800 V or more is formed on an etching foil having pits having an average pit diameter of 1.2 μm or more.

    The aluminum anode foil for electrolytic capacitors of the present invention will be described. Pits having an average pit diameter of 1.2 μm or more are formed on the aluminum foil by direct current etching. If the average pit diameter is 1.2 μm or more, the effect of the present invention is exhibited, but the pit diameter is preferably 1.3 μm or more, more preferably 1.4 μm or more. If it is less than this pit diameter, the pits are filled with a chemical conversion film by the subsequent high pressure chemical conversion, and the capacitance decreases.

    Then, the etching foil is subjected to a chemical conversion treatment by applying a voltage of 800 V or higher in a chemical conversion solution such as boric acid, and then subjected to a depolarization treatment and a re-chemical conversion to form the aluminum anode foil for an electrolytic capacitor of the present invention. .

  Such an aluminum anode foil for electrolytic capacitors has a withstand voltage of 800 V or more, and has a sufficient dielectric film area, so that the capacitance characteristics are also good.

  In the above aluminum anode foil for electrolytic capacitors of the present invention, since the chemical conversion film of 800 V or more is formed on the etching foil having pits having an average pit diameter of 1.2 μm or more, the electrolytic capacitor having a withstand voltage characteristic of 700 V or more It can be used as an aluminum anode foil.

  Next, examples of the aluminum anode foil for electrolytic capacitors of the present invention will be shown.

    Etching with a pit diameter of 1.5 μm was performed on a 100 μm aluminum foil, and a chemical conversion treatment was performed with a chemical conversion voltage of 1100 V in the boriding, followed by a depolarization treatment and a re-chemical conversion treatment to form an aluminum anode foil for an electrolytic capacitor. . As a comparative example, an aluminum foil having a pit diameter of 1.1 μm was etched on an aluminum foil having a thickness of 1.1 μm, and a chemical conversion treatment was performed by a chemical conversion voltage of 550 V during boriding, and thereafter an aluminum anode foil for an electrolytic capacitor was formed in the same manner.

    A voltage was applied to these anode foils, the correlation between the application time and the voltage was measured, and the voltage at equilibrium was measured. The results were 1050 V for the example and 530 V for the comparative example.

    Subsequently, in an Example and a comparative example, it formed with the conversion voltage of 900V, and measured the electrostatic capacitance per unit area. The results were 0.28 μF / cm 2 for the example and 0.24 μF / cm 2 for the comparative example.

As described above, it can be seen that the example has a withstand voltage of 1050 V and can form an electrolytic capacitor of 700 V or higher. Moreover, when formed with the conversion voltage of 900V, it turns out that it has a 15% or more electrostatic capacity from a comparative example, and an electrostatic capacitance characteristic is also favorable.

Claims (2)

An aluminum anode foil for an electrolytic capacitor having a dielectric film, wherein a chemical conversion film of 800 V or more is formed on an etching foil having pits having an average pit diameter of 1.2 μm or more.  2. The aluminum anode foil for an electrolytic capacitor according to claim 1, wherein the etching foil is subjected to a boil treatment in pure water and then subjected to a chemical conversion treatment in a chemical conversion solution containing boric acid to form a chemical conversion film.