Chemical conversion film of tantalum or niobium, method for forming the same and electrolytic capacitor using the same

摘要

The present invention provides an electrolytic capacitor that operates stably even when used for a long period of time under severe conditions, and forms an intermediate composition portion of metal and oxide within a chemical conversion film to a thickness of 40 nm or more so as to suppress the migration of oxygen atoms within a chemical conversion film of a valve metal. This intermediate composition portion is obtained by subjecting a base metal comprised by containing nitrogen in a valve action metal to anodic oxidation treatment.