GB1346657A - Method of fabricating an apertured photo-mask - Google Patents

Abstract

1346657 Making masks for colour television tubes RCA CORPORATION 14 July 1971 [30 Sept 1970] 32970/71 Heading B3A A mask for printing phosphor deposits on a colour television tube screen and for subsequent use in the tube comprises an apertured metal sheet 56 covered on one surface with a removable metal layer 72 having apertures 73 aligned with and smaller than the apertures 78 in the metal sheet 56. The layer 72 of the mask is used for printing the tube screen by a photoresist process after which the layer 72 is removed and the metal sheet 56 used as a mask in the tube. In one embodiment, the mask is made by first coating opposite surfaces of a steel sheet 56 with etch resistant films 62, 64 of fish glue and forming apertures 66, 68 in the films 62, 64 by a photoresist process, the apertures 66 being aligned with and smaller than the apertures 68. After forming apertures 78 in the steel sheet 56 by etching with ferric chloride, the film 62 is coated by electroless deposition, electrolytic deposition, electrophoresis, evaporation, painting or sputtering with a copper or nickel layer 72 having apertures 73 identical with those in the film 62. Subsequently, the areas 69 of the film 62 overlying the apertures 78 are removed by sodium hydroxide or heating in air above 350‹ C., after which the workpiece is annealed at 900‹ C. in a reducing atmosphere to remove stresses and the films 62, 64, and shaped by a punch and die. In an alternative embodiment (Fig. 9, not shown), the apertures 66 are formed in the film 62 after forming the apertures 78 in the metal sheet 56.