Patent GB-1098182-A (GB)
Title: Electrolyte or electroless plating process
Inventor: LENOBLE JEAN PAUL
IPC: C25F3/14
Filed: 1963-12-27
Abstract: Metal is deposited locally on a workpiece by electrolytic or electroless action by using an insulating mask having one or more openings in <PICT:1098182/C6-C7/1> contact with the workpiece and a porous backing member engaging the surface of the mask remote from the workpiece, a solution for effecting the deposition being present in the backing member and one or more of the openings in the mask. The mask may be formed by a photographic technique using a photo-sensitive resist or sensitized polyvinyl alcohol or nylon and may be adhered to a porous metallic backing.  Alternatively a plastics sheet may be coated on to the backing and the masking openings formed in the sheet by mechanical scribing or by an electron or laser beam, or a punched plastic sheet may be secured to the metal backing.  The workpiece and mask may be pressed together by flexible pressure bags.  In one arrangement, a workpiece sandwiched between two masks is placed inside a bag 46 of rubber or plastic secured to a frame 45 and supported within a pressure applying vessel 40 which also contains a heater 50 and ultrasonic generators 48, 49. If desired the surface of the support member adjacent the mask may be channelled and connected to a supply pipe to allow for forced circulation of an electro-plating electrolyte to which additions may be made externally of the plating chamber. By passing successively different plating and intermediate washing solutions, successive different metal deposits may be provided, e.g. copper followed by gold.  In another arrangement the workpiece and mask are held by a pressure bag against a rigid grid on the far side of which is disposed a soluble metal anode.  The anode may be bagged or surrounded by a wad of glass fibre in a plastics net.  For electro-depositing copper on a copper coated insulator an acid sulphate solution containing potash alum may be used.  The copper coating in the unplated area may be removed by treating with acidified dichromate or ferric chloride solution.  If the electrodeposited metal is tin-lead alloy from a fluoborate bath or gold the unplated copper coating may be removed with ammonium persulphate or ferric chloride solution respectively.  Electroless plating with copper may be effected directly on to an insulating workpiece which has been sensitized by dipping successively in stannous chloride and palladium chloride solutions followed by washing.  For printed circuit production conductors of different cross-sections may be deposited by employing a mask having openings of complementary profile.  The spaces between the deposited metal may be filled with epoxy resin, cured, ground and polished to provide conducting pins flush with the resin surface and a uniform metal coating may be applied thereover.  By so treating both faces of a workpiece a coil or multiple plate capacitor may be formed or connections extending through an insulator produced.  In an arrangement for forming an electro-plated printed circuit, a copper coated insulating strip is fed around a porous cylinder bearing an insulating mask and partially immersed in an electrolytic bath, an endless moving belt conveyer holding the copper surface of the strip, to which cathodic connection is made by a roller, against the mask.