ETCHING METHOD FOR ELECTRODE FOIL OF ALUMINUM ELECTROLYTIC CAPACITOR

PURPOSE:To manufacture an electrode foil for an aluminum electrolytic capacitor having an area increasing magnification by 20% or more higher than a conventional one and to reduce in size and cost a product by etching the surface of the foil with a positive symmetrical waveform with 5ms or less of rising time of maximum current value of each cycle of an AC current. CONSTITUTION:When the surface of an aluminum foil is etched with an AC current in hydrochloric acid solution containing 3-25% of aluminum chloride at 10-70 deg.C of liquid temperature, it is etched in solution containing acidic acid or ions of one or more types of nitric acid, sulfuric acid, phosphoric acid, oxalic acid as an additive with symmetrical positive and negative waveform having 5ms or less of rising time up to maximum current value of each cycle of an AC current. An etching current at the anode is abruptly raised at 5ms or less to generate an etching pitch uniformly from a defect of a strong film to obtain the foil having an area increasing magnification by approx. 20% higher than that of a conventional one.