Patent GB-692614-A (GB)
Title: Improvements in or relating to the metallisation of the surfaces of dielectric material
Inventor: BOOTH FRANK OLIVER
IPC: H01G13/06
Filed: 1949-09-08
Abstract: 692,614. Printing processes; stencilling;' etching. HUNT, Ltd., A. H. Sept. 8, 1950 [Sept. 8, 1949], No. 23324/49. Class 100(ii) [Also in Groups II and VIII) A process for the metallization of the surfaces of dielectric material, for example in the manufacture of electrical condensers, consists in applying metalbearing ink to the dielectric surfaces through a printing screen in the form of a thin lamina, for example of metal foil, having a finely perforated printing area, so that the ink forms a continuous coating on the part of the surface corresponding to the printing area, removing the screen and treating the ink so applied to cause the printed area to become a continuous conductive surface. The screen may be a copper lamina 0.01 inch thick, or may be of a hard copper alloy such as berylliumcopper. The ink may be that known under the Registered Trade Marks " Melton Silver Solution S450", "Elargol W.8" or " Elargol W.12 ". For coating a series of mica plates, the latter axe placed on a printing table and held thereon by suction, the screen being placed on the plates, being stretched over a frame having low upstanding walls to form a container for the ink. The screen is provided with a series of printing areas, each corresponding to and located above the part of a plate to be metallized, and each formed by means of fine perforations. the printing areas being located in recesses so as to leave a space between the screen and the parts of the plates to be metallized. The ink is forced through the screen by a squeegee, and spreads in the printing areas to form a continuous surface, this being facilitated by the recesses. After drying, the reverse sides of the plates can then be treated, and the plates are then fired in an oven to make the metallized layer, in this case silver, conductive and firmly adherent. Opposite marginal portions of the two sides of each plate are left unmetallized, the plates are stacked, and metal sprayed or painted across the stack to connect like portions of the two electrodes, to form stack-condensers. For metallizing a web 45 of dielectric material in strips 46, the screen 30 is mounted on end-formers 32, 33 and joined at its ends to constitute a cylinder 38. The formers are mounted on hollow bearings 36, 37, within which are stationary shafts 40, 44 secured to brackets 51. A conduit 50 from an ink pressure-supply passes through the shaft 40 and runs along above a rubber squeegee 43 carried by the brackets 51, the ink impinging on the screen through a series of ports in the conduit. A second screen cylinder 39 is provided if both sides of the web are to be treated, otherwise a plain rubber cylinder. The web is pulled down by a power-driven spool and rotates the cylinders. Alternatively, the cylinders may be power-driven. A heat treatment compartment may be provided, through which the web passes before being wound on the spool, and after heating the web may be slit into separate metallized strips and the condensers wound immediately. In another form, the screens constitute endless belts, power-driven and each stretched round two rollers, the web being drawn between the belts. Etching.-The printing screen may be produced by photographically reproducing a desired pattern on a metal sheet and etching perforations therein, or a negative master may be provided, with a pattern of conical projections, a layer of metal electroplated thereon, the layer removed, and the hollow conical projections etched away to leave the required pattern of perforations.