The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 12, 2004
Filed:
Jul. 18, 2002
Ralph Jason Hemphill, Liberty, SC (US);
Thomas V. Graham, Greenville, SC (US);
Thomas F. Strange, Easley, SC (US);
Pacesetter, Inc., Sunnyvale, CA (US);
Abstract
The present invention is directed to a method of creating porous anode foil for use in multiple anode stack configuration electrolytic capacitors, producing a pore structure that is microscopic in pore diameter and spacing, allowing for increased energy density with a minimal increase in ESR. Initially, an anode metal foil is etched, according to a conventional etch process, to produce an enlargement of surface area. The etched foil is then placed into the electrochemical drilling solution of the present invention. Alternatively, the etched foil may be masked, so that only small areas of the etched foil are exposed, prior to being placed in the electrochemical drilling solution. A DC power supply is used to electrochemically etch the masked or unmasked foil in the electrochemical drilling solution of the present invention such that pores on the order of a few microns diameter are produced through the foil. The electrochemical drilling solution of the present invention consists of 1 to 15% by weight sodium chloride, preferably 5% by weight, and 10 to 5000 PPM of a surface passivator, such as sodium nitrate or phosphoric acid, preferably 500 PPM. Finally, the foil pores are widened and the foil is formed to the intended use voltage according to conventional widening and forming processes. When used in conjunction with an electrochemical etch preceding it and an electrochemical widening step following it, the electrochemical drilling step of the present invention results in an electrically porous foil which maintains the high capacitance gain produced by the etching and widening steps alone, but, when used in a multiple anode stack configuration, exhibits a reduced equivalent series resistance.