Patent GB-1298228-A (GB)
Title: Thin film capacitors on flexible dielectric substrate
Inventor: WATTERS CLARENCE JAY
IPC: H01L49/02
Filed: 1969-12-12
Abstract: 1298228 Capacitors; circuit assemblies GENERAL ELECTRIC CO 12 Dec 1969 [16 Dec 1968] 60869/69 Headings H1M and H1R A capacitor comprises a flexible tape substrate, a film electrode deposited thereon, a dielectric layer deposited on the film electrode by ultraviolet surface photopolymerization of a monomer gas and a second film electrode deposited on the dielectric layer, the layers constituting the capacitor being flexible with the substrate, and means for making electrical connection to the electrodes. The substrate may be paper, polyethylene terephthalate, fluorinated ethylene propylene copolymer, P.T.F.E., polyimide or polyolefin. The dielectric layer may be polymerized ethylene, 2,4- hexadiene, 1,5-hexadiene, methyl methacrylate, hexachlorobutadiene, tetrafluoroethylene, tri-  fluoromonochloroethylene, monofluorotrichloroethylene, hexafluorobutadiene or acrylonitrile. Fig. 1 illustrates a capacitor 18 comprising electrodes 19, 20 separated by dielectric layer 21 the capacitor forming part of a flexible circuit on tape substrate 11. The circuit includes resistors 12, 13, conductors 15, 16, 17 and terminals 14, 14<SP>1</SP>. The circuit is manufactured using deposition, etching and masking techniques, e.g. the tape may be coated with a layer of chromium and copper, the copper being retained where conductors are required or removed to leave chromium resistors. The capacitor electrodes may be continuous with the conductors or separately deposited zinc or aluminium layers. Metal deposition may be by plating, sputtering, printing or preferably vapour deposition. Exposed copper layers may be tin-plated. Resistors may alternatively be nickel, and the circuit may also include inductors. In a semi-continuous process metallized tape bearing undeveloped etch resist passes round a large wheel (23), (Fig. 3, not shown), forming part of a photolithographic process assembly, and the ultraviolet photopolymerization may also be carried out continuously (Fig. 4, not shown). Fig. 5 illustrates a multiple capacitor assembly comprising a first deposited electrode 44, a dielectric layer 21, then two side-by-side electrodes 45, 46 having interdigitated projecting portions which overlap electrode 44. Terminals are constituted by portions 47, 48, 49 and a second covering dielectric layer 21 also increases the capacitance between adjacent edges of electrodes 45, 46. In an alternative multiple assembly (Fig. 6, not shown) pairs of electrodes are deposited on the tape substrate with terminals at opposite edges of the substrate, then a dielectric layer then a single common electrode layer overlapping all the first ones. A sliding connector may vary the number of lower electrodes brought into play. The tape supporting the capacitors or circuits may be rolled up preferably round a metal spindle to dissipate heat, and placed in a can (Fig. 7, not shown). To incorporate active components such as semi-conductor chip circuits, a flexible tape bearing deposited conductors radiating from the area of attachment of a chip may be used (Fig. 8, not shown). The end portion conductors are arranged to register with the terminals on a tape such as illustrated in Fig. 1 and the tapes are brought together face to face and heat is applied to form a solder joint. Alternatively the tape bearing the chip and connecting conductors may be an integral part of the Fig. 1 tape.