Solid aluminum electrolytic capacitors with etched aluminum foil

Abstract

Ever since the introduction of solid tantalum electrolytic capacitors, attempts have been made to replace the relatively expensive tantalum with other materials. Several patent applications indicate that aluminum, in the form of wire or sintered slugs, has been investigated in this connection. Attempts with aluminum foil are scarcely known, but a British patent, No. 845 698 (patent holder: U. S. Secretary of the Army), indicates that some preliminary work has been done in this line. In the meantime etched aluminum foils of high purity and surface gain have become commercially available, and forming methods resulting in highly stable aluminum oxide layers are now known, so that the successful construction of solid aluminum electrolytic capacitors seemed feasible. A series of experiments were therefore carried on in the laboratories of the Aluminium-Walzwerke Singen, to determine the usefulness of etched aluminum foils in solid aluminum capacitors. Preliminary results indicate that such capacitors can definitely be made with etched aluminum foils.