US2199445A

US2199445A - Electrolytic condenser and method of preparing etched electrodes therefor

Info

Publication number: US2199445A
Application number: US88533A
Authority: US
Inventors: Ruben Samuel
Original assignee: Individual
Current assignee: Individual
Priority date: 1936-07-02
Filing date: 1936-07-02
Publication date: 1940-05-07
Anticipated expiration: 1957-05-07

Description

UNITED STATES PATENT OFFICE ELECTROLYTIC CONDENSER AND METHOD OF PREPARING ETCHED ELECTRODES THEREFOR Samuel Ruben, New Rochelle, N. Y.

No Drawing. Application July 2, 1936, Serial No. 88,533

7 Claims. (Cl. 175-315) This invention relates to the method of pretion tends to dissolve the foil and if the maxiparing etched surfaces and particularly etched mum benefit arising from the increased area obelectrodes for electrolytic devices. tained by a deep etching is desired, it is neces- The present application is a continuation-insary to use a much thicker foil than would otherpart of my co-pending application, Serial Numwise be required. Furthermore, care must be exher 734,134, filed July 7, 1934 now Patent No. ercised to prevent the etching from being too 2,066,912. deeply applied. These limitations are avoided by An object of the invention is to improve the the method of etching and the type of electrodes methods of preparing etched metal surfaces. used.

Another object is to provide an etched electrode My invention comprises, in its preferred form for electrolytic devices, such as electrolytic cona novel method of preparing etched electrodes for densers. electrolytic condensers, said electrodes being Other objects of the invention will be apparent formed of a metalsuch as aluminum or tantalum from the following description taken in connecupon which it is possible electrolytically to form v tion with the appended claims. a current-blocking film after etching. These 16 The present invention comprises. the combinametals may be in any suitable form for use, for tion of elements, methods of manufacture, and example, as foil W By the use 0! W e the product thereof brought out and'exemplified stead of foil electrodes, the limitation'on deep in the disclosure hereinafter set forth, the scope etching is removed and an exceptionally large of th i ention being indicated in the appended effective current blocking area is made available 2 claims. While a preferred embodiment of the without substantially weakening the electrode invention is described herein, it is contemplated structure. It will be seen that by using an aluthat considerable variation may be made in the minum wire having a diameter in the order of method of procedure and the combination of .040" or a narrow aluminum tape of the same elements without departing from the spirit of thickness and prefe y not Wide,

the invention. that it is possible to obtain a very deep etching Dry electrolytic condensers have heretofore utiwith consequent increased film blocking area. lized sheet foil electrodes usuallyv of. aluminum The impurities in commercial aluminum are ranging in thickness from .002" 110 .004" and in chiefly iro a Silicon. although inor amounts width from one inch to three or four inches. of copper ar sometimes found- In t A rad These foils have been spaced by a reticular cloth the aluminum content will normally average spacer such as disclosed in my United States Letabout 99.2 per ce t, w Silicon Varying m 5 ters Patent 1,710,073 and 1,714,191, or by paper' o 0- 0 per ent nd ir n v ryin from 0.25 to spacer as shown in my United States Letters pe c te iron content is usually ate Patent 1,891,206, or by a regenerated sheet eelluthan the silicon content. Copp Will Vary from lose spacer, for instance, Cellophane as illusa trace only tODVeI D cent- SOdiU-m i in trated in my United States Letters Patent recent years found only in traces if present at 1,918,716. In -the construction of these cona With rad A t p s t metal is enerde sers a spacer of approximately the same dially reserved for manufacture of electrical conmensions as the foils, is placed on each side of ductors on account of its lower electrical resistiv- 0 one of the electrodes and the two foils and spacy- Electrolytic d o is of y high ers are then rolled, usually in cylindrical form; Pu ty, uc as 9 to pu alum um- Prior to rolling the spacer is impregnated or per- According t0 On feature of y invention t meated with a viscous electrolyte so as to afford et g s Co e 50 as t avoid tOO great a a conductive path between the electrode foils, dllct m in mass Of t e elect ode metal during although in some cases the condenser roll is asetching by providing, instead of substantially pure sembled and the electrolyte thereafter introduced metals, an alloy of suc Composition as t Obtain by impregnation. a selective etching action. For example, I pro- It has been long known in the art that if the pose to substitute for the pure aluminum foil elecaluminum plates are etched or otherwise roughtrodes of the prior art, an aluminum alloy having ened, an increased capacitance is obtained due a content of a material readily soluble in an etchto increased surface and lower average oxide film ing agent which does not substantially dissolve thickness formed on such etched plateh aluminum, suchas nitric acid. For example, add- However, the employment of an etching process ing 10% magnesium to the pure aluminum and is limited, due to the fact that the etching'soluetching the electrode in nitric acid, the magneu slum is rapidly etched out and the aluminum, other than becoming slightly oxidized on its surface, is unaffected. For the usewith a nitric acid etching agent, an alloy of aluminum with one or more of the metals, calcium, lithium or beryllium may be substituted for the aluminum-magneslumv alloy electrode. Neither magnesium, calcium, lithium nor beryllium is present as impuri ties in electrolytic condenser foil or other grades of commercially pure aluminum.

Generally, it may be stated, with the film forming metal used, wheth er aluminum or tantalum, that the material alloyed therewith, should be one which is readily capable of being etched out or dissolved by the etching compound and that the etching compound itself should be such as not to adversely attack or affect the film forming metal base. For instance, in place of the nitric acid I may use sulphuric acid, chromic acid or an acid salt such as aluminum ammonium sulphate.

The foil or wire may be prepared as follows for use as electrodes for electrolytic condensers: The foil or wire of aluminum-magnesium alloy is passed through hot nitric acid and the etching accomplished by the dissolving of the magnesium. The etched foil or wire is then filmformed by the customary continuous formation "dry" and "we electrolytic condensers.

While the present invention, as to its objects and advantages, has been described herein as carried out in specific embodiments thereof, it is not desired to be limited thereby but it is intended to cover the invention broadly within the spirit and scope of the appended claims.

What is claimed is:

1. An'electrode for electrolytic condensers and the like composed of aluminum of a purity of at least 99.2% having magnesium intentionally alloyed therewith, said magnesium being present in a relatively small but appreciable amoimt, said electrode having an etched roughened surface resulting from the removal of the magnesium from said surface whereby the effective film forming surface of said electrode is greatly increased.

2. An electrode for electrolytic condensers and the like comprising pure aluminum having intentionally alloyed therewith a relatively smaller but appreciable amount of magnesium, said electrode having an etched roughened surface resulting from the removal of the magnesium from said surface.

3. In the process of providing film forming electrodes for electrolytic condensers and the like, the steps of combining with a pure film forming metal such as aluminum, a relatively smaller but appreciable quantity of magnesium, thereafter exposing said metal composition to the action of an etching solution to remove said magnesium from the surface thereof.

4. In the process of providing film forming electrodes for electrolytic condensers and the like, the steps of combining with pure aluminum, a relatively smaller but appreciable quantity of magnesium, thereafter exposing said metal composition to the action of nitric acid to remove the magnesium from the surface thereof.

5. In the process of providing film forming electrodes for electrolytic condensers and the like, the steps of combining with pure aluminum, a relatively smaller but appreciable quantity of magnesium, thereafter exposing said metal composition to the action of sulfuric acid to remove the magnesium from the surface thereof.

6. An electrode for electrolytic condensers comprising aluminum and a relatively muchsmaller amount of magnesium, said electrode having an etched surface of high effective electrical capacity resulting from the removal of the magnesium therefrom, and a dielectric oxide film on said surface.

7. An electrolytic condenser comprising two electrodes and an electrolyte, one of said electrodes comprising aluminum, and a relatively much smaller amount of magnesium. said dectrode having an etched surface of high effective electrical capacity resulting from the removal of the magnesium therefrom, and a dielectrlc'oxide film on said surface.

SAMUEL RUBEN.