It has been found that metal stampers, and more particularly nickel stampers, can be simultaneously hardened and passivated by cathodically treating the stampers in an aqueous bath of a passivation agent.

Fixedly arranging an array of electroformed letters or patterns on a product which includes the steps of forming a layer of resist on a metallic plate, electroforming letters, removing the electroformed letters from the plate with adhesive tape, coating each of the exposed surfaces of the electroformed letters with an adhesive, placing the electroformed letters and tape on the product and peeling the tape from the electroformed letters. The adhesive has an adhering power stronger than that of the adhesive tape so that the tape can be removed readily from the electroformed letters. The resist is applied to an area on the metallic plate except for the area occupied by the letters to be electroformed. The adhesive coated surface of the electroformed letters may be covered with protective paper. To inhibit excessive electroforming along the periphery of the letters and minimize excessive application of the adhesive on the tape there are electroformed "sacrifice portions" adjacent the electroformed letters with a narrow layer of resist deposited therebetween. The sacrifice portions are removed from the tape after the adhesive agent is coated on each of the exposed surfaces of the letters and the sacrifice portions.

A novel laminate adapted for use in the manufacture of capacitors comprising layers of microthin pin-hole free electroformed copper bonded together by a thin layer of hardened dielectric material, said bonded surfaces of said microthin copper having first been treated to form thereon a superficial coating of cupric oxide, bonded to the outer surfaces of said microthin copper, layers of self-sustaining copper foil, the bonded surfaces of said copper foil having been passivated under reducing or cathodic conditions in an aqueous solution of chromic oxide to passivate the surface thereof and to render said copper foil peelably removable from said microthin copper. A method of forming capacitor networks which comprises establishing a laminate having layers of microthin pin-hole free electroformed copper bonded together by a thin layer of hardened dielectric material, said bonded surfaces of said microthin copper having first been treated to form thereon a superficial coating of cupric oxide, bonded to the outer surfaces of said microthin copper, layers of self-sustaining copper foil, the bonded surfaces of said copper foil having been passivated under reducing or cathodic conditions in an aqueous solution of chromic oxide to passivate the surface thereof and to render said copper foil peelably removable from said microthin copper, peeling away one of said copper foils, photoprocessing the exposed microthin copper to a desired pattern, bonding a reinforced plastic material to said pattern to form an adherent substrate in abutment thereto, removing the other copper foil, and photoprocessing the second exposed microthin copper to a desired pattern.

An image development method is disclosed. In the method, a photoresist layer on a metal surface is exposed for development. The developer then used is a solution which will both develop the photoresist image and cause any exposed metal surface to change to a predetermined color. The development process then proceeds until the predetermined color is exposed whereupon the process ceases. The preferred metal is copper and the preferred developer is an aqueous solution of sodium sulphide and ammonium polysulfide.

An improved copper electroplating method typically for use on a carrier material such as aluminum is provided by pretreating of the carrier surface and electrodepositing copper foil utilizing a single-step copper plating process comprising an acidic plating bath containing copper, nitrate, and fluoride ions which can be operated at a single-current density.