US2203253A

US2203253A - Electroplating process

Info

Publication number: US2203253A
Application number: US102696A
Authority: US
Inventors: Brown Morris
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1936-09-26
Filing date: 1936-09-26
Publication date: 1940-06-04
Anticipated expiration: 1957-06-04

Description

June 4', 1940. BROWN 2,203,253

ELECTROFLATING PROCESS Filed Sept. 26, 1936 Mmvm? M BROWN I 50 a conductor Patented June 4, 1940 PATENT OFFICE 2,203,253 ELECTROPL ATING PROCESS Morris Brown, La Grange, em Electric Company, Incorporated,

111., assi'gnor to'west- New York,

N. Y., a corporation of New York AppIieation SeptemberZG, 1936, Serial No. 102,696

1 Claim.

This invention relates to electroplating processes, and-more particularly to the manufacture of sheet metal by electrodeposition. The manufacture of certain metal articles, such as tubes or foil, by electrodeposition processes, has been restricted by the tendency of the metal to adhere to the mandrel or mould on which it is deposited. In the production of foil by this method, the tension required to remove'the foil 10 from the mandrel has limited the minimum thickness and also the composition of the product. Coatings of grease, tin, zinc or mercury amalgam have been applied to the mandrel to overcome this'difliculty but some of these expedients do not 15 give entirely satisfactory results and all of them are further objectionable in that they require periodic replacement.

Objects of this invention are to provide improved methods and apparatus for the efficient 20 electrodeposition of metal..

In accordance with one embodiment of the invention, apparatus is provided for the continuous manufacture of metal foil by electrodepositing the metal on a chromium'coated rotating mandrel, and stripping the deposited metal from the mandrel in the form of a continuous sheet.

A complete understanding of the invention may be had from the following detailed description taken in conjunction with the appended drawing, in which Fig. 1 is a' se'chematic view, partly insection, of an electroplating apparatus, embodying the invention;

Fig. 2 is a section of the apparatus shown in 35 Fig. 1, taken on the line 2-4, and

Fig 3 is a sectional view taken. on line 3-3 of Fig. 2. l

Referring now to the drawing, a conventional continuous electroplating installation comprises a cylindrical drum or mandrel it) which is rotatably mounted on a shaft ll over a tank or container l2. The tank .is lined with lead I3 and contains an electrolyte ll of suitable metal salt in which the mandrel is partially immersed. In accordance with well known practises, plating "current of suitable characteristics is supplied from a battery l5 or other source with its negative terminal l6 connected to the mandrel or cathode through a sliding contactor I'l engaging i8 which is imbedded in insulation in the mandrel shaft and connected to the mandrel through a wire 19. The positive terminal 20 of the battery is connected directly to the lead sheet lining of the tank which serves as an inu soluble anode.

'Ihe'electrolyte is circulated through, the'tank against the rotating mandrel by a pump or other suitable. means (not shown). The tank has a rounded bottom approximately conforming with the mandrel contour. Depleted electrolyte is 5 withdrawn from one end of the tank, replenished with metal salt in an external apparatus, (not shown) and recirculated. The metal deposited on the rotating mandrel is stripped from the mandrel surface in the form of a continuous sheet or foil 2| by a revolving takeup spool 22 supported in bearings 23 over the mandrel and driven through a belt 24 by suitable and conventional mechanism (not shown) for applying a constant tension to thefoil.

The general features of the apparatus and process so far described are old and well known and this invention is directed primarily to the construction of the mandrel on which the metal is deposited. The preferred construction is particularly suitable for the production of copper foil ,under .0093" thick which is useful in the manufacture of condensers and other products. Foil used for this purpose must be uniform in thick? ness and preferably has a smooth, continuous sur- 25 face.

It is possible to control 'the thickness of the deposited sheet in general by regulation and coordination of the plating current, electrolyte composition, mandrel size and operating speed. However, copper in this dimension possesseslittle' tensile strength and even very slight tendency of the foil to adhere to the mandrel results in breakage. It is undesirable to use temporary coatings of foreign substances on the mandrel surface to reduce sticking of the foil because the deposited metal conforms rigidly to the contour of the mandrel and reproduces any surface irregularities. It is difficult to apply these coatings I smoothly and their repeated use may destroy the 40 surface on the mandrel.

To overcome these objections, the mandrel is provided with a permanently smooth, uniform surface from which the deposited metal can be readily removed. The mandrel comprises a steel cylinder 25 (Figs. 2 and 3) which is formed to v shape and ground on the outside surface to re-. move all irregularities and imperfections. Other materials can be used for this member, but steel is preferred because of its stability in retaining the surface and shape produced in the grinding operation. A layer of nickel 26 is plated unlformly on the ground surface of the cylinder and subsequently buffed to a high polish. A nickel coating .0005" thick is satisfactory for most inpolish. This coating may alsovary inthickness,

but coatings around .00005" thick give good results.

The composite mandrel cylinder is supported at each end by a disk shaped member '28 made of wood, fiber, or other insulating material and secured to the mandrel shaft. At each end of the mandrel cylinder, a-ring 30 made of rubber or other insulating material is imbedded in the periphery of the disk. The ring projects above the surface of the mandrel to form the deposited foil with uniform, unbroken edges. g

The side of the foil next to the mandrel-has a smooth surface, determined by the finish on the mandrel, but the other side may be spongy or rough. To smooth this outer surface, a roller 3| is rotatably mounted parallel to the mandrel in' bearings 32 in contact .with the foil on themandrel surface. The roller is driven from the man drel shaft through a twisted belt 33 engaging pulleys on the mandrel and roller shafts. pulleys are selected to rotate the rollerat a surface speed approximately 15% higher than the surface speed of the mandrel which produces a burnishing action and imparts a smooth polished surface to the foil. The relative surface speeds of the roller and mandrel may be varied for different foil thicknesses and compositions arid under various conditions the roller mayoperate at speeds from 10% to higher than the 'mandrel. The position of the burnishing roll is made adjustable relative to the mandrel by any suitable means (not shown) and the roll is located to control the final thickness dimension of the foil.

In the operation of the process, the chromium, being passive, prevents adherence between the foil and mandrel. As a result the foil is readily removed with a slight takeup tension which preited metal.

The

vents damage to the product ariddacilitatesthe manufacture of thinner foil. It is also possible with this'apparatus'to produce-foil from materials having relatively. low tensile strengths, such as gold or nickel. 1

A mandrel constructed in accordance with the above description is also suitable for. the manufacture of tubes or'shapes. In this process-,the metal is plated on the mandrel, which may be stationery or rotating, after which 'the mandrel is readily withdrawn from the completed article.- If desired, the chromium can be plated directly on'the steel cylinder to provide a mandrel with a passivesurface that will not adhere to the depos- However, the intermediate layer of nickel is beneficialas it facilitates the application of the. chromium and the development'of a smooth uniform surface. A mandrel formed entirely of chromium will operate satisfactorily, butv the composite mandrel is more serviceable and less costly.

Other adaptations and modifications of the specific embodiment above described are feasible and it is to be understood that the invention islimited only by the scopeof the appended claim.

I Whatis claimed is: -A method of producing thin comprises electrodepositing" a copper layer less than .0003" in thickness on a chromium surface while said surface is moving at a predetermined speed, compressing 'the deposited copper against the chromium surface by means of a cylinder having a metallic surface maintained a fixed distance from the chromium surface to size the copper into foil of -a'predetermined thickness, withdrawing the foil from the chromium surface with a predetermined tension around an arc of said cylinder, and rotating the cylinder at a surface speed from 10% to- 25% higher than the copper foil .which speed of the chromium surface to polish the foil in the arc of contactwith said cylinder.

MORRIS BROWN. I v