Method for producing foil electrodes for electrolytic capacitor

Abstract

Optimum conditions, employed in an etching process of an aluminum foil for use in an electrolytic capacitor, are selected and combined together for realizing an extension of the effective surface area of the foil. This extension also gives an enlargement of the electrostatic capacitance of the foil electrode as well as an enhancement of the mechanical strength of the foil itself, the latter had been considered to be hardly compatible with the former.

What is claimed is: .[.1. In the method for producing electrodes for use in aluminum electrolytic capacitor whose effective surface area is enlarged by electrochemically etching aluminum foil in an aqueous solution including hydrogen chloride and at least one additive capable of anodizing said aluminum foil with electric powder supplied in alternating current, an improvement characterized in that; 
     
        boric acid and sulfamilic acid, and any salt thereof..]. .Iadd.4.  In the method for producing electrodes for use in aluminum electrolytic capacitor whose effective surface area is enlarged by electrochemically etching aluminum foil in an aqueous solution including hydrogen chloride and at least one additive capable of anodizing said aluminum foil with electric power supplied in alternating current, an improvement characterised in that; the concentration of the hydrogen chloride in said solution is set at a range between 0.5 N and 3.5 N, the concentration of said additive is set at a range between 0.001 mole/liter and 0.4 mole/liter, the frequency of said alternating current power supply is ranging from 5 Hz to 120 Hz and its current density is ranging from 0.1 A/cm 2  to 0.6 A/cm 2 , while the temperature of said solution is being maintained at 25° C.-60° C.,   
     
     
       said additive being acetic acid or a salt thereof. .Iaddend. .Iadd.5.  In the method for producing electrodes for use in aluminum electrolytic capacitor whose effective surface area is enlarged by electrochemically etching aluminum foil in an aqueous solution including hydrogen chloride and at least one additive capable of anodizing said aluminum foil with electric power supplied in alternating current, an improvement characterized in that; the concentration of the hydrogen chloride in said solution is set at a range between 0.5 N and 3.5 N, the concentration of said additive is set at a range between 0.001 mole/liter and 0.4 mole/liter, the frequency of said alternating current power supply is ranging from 5 Hz to 120 Hz and its current density is ranging from 0.1 A/cm 2  to 0.6 A/cm 2 , while the temperature of said solution is being maintained at 25° C.-60° C.,   said additive being glycolic acid or a salt thereof. .Iaddend. .Iadd.6. In the method for producing electrodes for use in aluminum electrolytic capacitor whose effective surface area is enlarged by electrochemically etching aluminum foil in an aqueous solution including hydrogen chloride and at least one additive capable of anodizing said aluminum foil with electric power supplied in alternating current, an improvement characterized in that;   the concentration of the hydrogen chloride in said solution is set at a range between 0.5 N and 3.5 N, the concentration of said additive is set at a range between 0.001 mole/liter and 0.4 mole/liter, the frequency of said alternating current power supply is ranging from 5 Hz to 120 Hz and its current density is ranging from 0.1 A/cm 2  to 0.6 A/cm 2 , while the temperature of said solution is being maintained at 25° C.-60° C.,   
     
     
       said additive being boric acid or a salt thereof. .Iaddend. .Iadd.7.  In the method for producing electrodes for use in aluminum electrolytic capacitor whose effective surface area is enlarged by electrochemically etching aluminum foil in an aqueous solution including hydrogen chloride and at least one additive capable of anodizing said aluminum foil with electric power supplied in alternating current, an improvement characterized in that; the concentration of the hydrogen chloride in said solution is set at a range between 0.5 N and 3.5 N, the concentration of said additive is set at a range between 0.001 mole/liter and 0.4 mole/liter, the frequency of said alternating current power supply is ranging from 5 Hz to 120 Hz and its current density is ranging from 0.1 A/cm 2  to 0.6 A/cm 2 , while the temperature of said solution is being maintained at 25° C.-60° C.,   said additive being sulfamidic acid or a salt thereof. .Iaddend.