Rca Inc.

Richard B Maynard

John J Moscony

Margaret H Saunders

A method for etching an array of apertures through a carbon-steel sheet wherein, for each of the majority of said apertures, the ratio of the desired smallest cross-sectional dimension thereof to the thickness of said sheet is less than about 0.9, said sheet having etch-resistant stencils on opposite major surfaces thereof, said method comprising contacting said stencilled major surfaces with ferric chloride etchant having a specific gravity in a range at which a smooth finish is realized.

Method for etching small-ratio apertures into a strip of carbon steel

A method for etching a strip of iron-nickel alloy, such as invar steel, having etch-resistant stencils on opposite major surfaces thereof includes contacting the stencilled surfaces with a ferric-chloride etchant. The etchant is controlled (a) to contain not more than 5 molar percent nickel ion with respect to the total content of nickel and iron ions, (b) to have a specific gravity greater than about 1.495 (48.degree. Baume) (c) and to have a temperature greater than 70.degree. C.

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Colerain Township, Lancaster County, PA, United States of America

Richard B Maynard