GB705606A - Improvements in or relating to a manufacturing process of an electric metal resistance - Google Patents

Abstract

705,606. Making electric resistors by electrolysis; magnetic field-variable resistors. VOLTOHM PROCESSES, Ltd. July 9, 1951 [July 13, 1950], No. 16209/51. Classes 37 and 41 A process of producing magnetic fieldvariable metal resistance elements in any desired pattern by electrolytically depositing the metal of the resistance element on a conductor support which is subsequently partly or wholly dissolved away chemically is characterized in that before dissolving away any of the conductor support an insulating base for the resistance element is applied. The invention is particularly concerned with the production by this process of bismuth, antimony and tellurium magnetic field-variable resistors. In Fig. 6 a completed resistor is shown comprising a bismuth ribbon 3 of sinuous pattern, Fig. 1, embedded in hardened varnish 4, 5 and connected to copper terminal strips 6. The steps leading to this product are outlined in Fig. 1 to 3 and Fig. 5. A copper plate 1 Fig. 1 and 2 is masked with varnish 2 and the bismuth ribbon 3, Fig. 3, is electrolytically deposited in the unmasked area. The varnish resist 2 is then removed and the bismuth coated side of the copper plate 1 covered with a hardened or polymerized "Araldite" (Registered Trade Mark) or silicone varnish or other plastics varnish constituting a thin insulating support 4 Fig. 5. The terminal areas of the copper plate 1 are varnish protected and the whole plate 1 is then dipped in a selected chemical solution which dissolves away the unwanted copper and is non-corrosive with respect to the bismuth and varnish. Finally top layers 5 of insulating varnish are applied and the Fig. 6 product is realized. The electrolytic bath may have the following composition : Carbonate of bismuth 40 grams per litre-Perchloric acid at 60 per cent. 100 grams per litre-Glue 0.1 grams per litre ; also the copper dissolving solution utilized may consist of a 10 per cent. solution of trichloreacetate of ammonium. In a modification Fig. 4 the bismuth deposit is applied to the whole of one side of the copper plate 1 and the unwanted bismuth removed by acid treatment or mechanically using, e.g. a tracing machine. A metallized insulating support may be employed instead of the copper plate 1 and may consist of celluloid, cellulose acetate or polystyrene coated with silver or copper so that a varnish resist is not necessary as exemplified Fig. 8 wherein 8 is a metal layer on a non-conducting support 7. If a conducting support plate is used having a dissolution potential higher than that of the electrolytic coating the plate should be coated with a metal having a lower dissolution potential, e.g. in the case of bismuth electrolysis a copper or silver coating may be used. Figs. 9 and 11 are examples of wound ribbon resistors produced by the process with the ribbon 3 in Fig. 11 effectively a bifilar winding so that the resistor is non-inductive.