GB1336592A - Electrical coils and methods of making same - Google Patents

Abstract

1336592 Making electrical coils J DENTON Ltd 21 June 1971 [4 July 1970] 32519/70 Heading B3A [Also in Division H1] A method of making an electrical coil comprises forming in a support surface, which includes at least a surface layer of electrically insulating material, at least two crests bounding at least one groove applying by electroless deposition a coating of conductive material to the surface and selectively removing the apices of the crests to leave at least one conductive strip forming at least part of a coil. A plastics or ceramic blank 1 is turned with a two-start thread 2, cleaned, etched and rinsed in water and is then plated in an electroless nickel solution. The blank is electro-plated with copper 3 and finally machined to remove the crests of the turned threads. The electro-plating of copper may be followed by a similar deposition of silver or gold. The coils are used in RF stages of VHF tuners or in oscillators in the HF, VHF and UHF ranges. A coupling transformer, Fig. 6 (not shown) comprises two coils of different diameters. The larger coil is annular and internally threaded so that it can be screwed on to the smaller coil. A flat disc coil is made similarly to the helical coils Figs. 7, 8 (not shown), its face being machined to remove all the copper except for that in a spiral groove. The supports may be of metal with an insulating layer and of any cross-section, e.g. the helical coils may be tapered or located internally of the support. Alternatively concentric coils may be provided, internally and externally of an annular support. Prior to electroplating, tin and palladium and/or nickel or copper may be deposited. Leads may be soldered directly to the helical strips to provide coils having a desired number of turns or a terminal may be provided in threaded engagement with the or each groove to provide an adjustable or turnable coil.