Process for the production of solder masks for printed circuits

A process for producing solder masks on printed circuits having at least one aperture therethrough by applying a thin layer of a liquid substance curable by irradiation to a printed circuit, irradiating the layer except in the those areas of the circuit to be soldered, and developing the layer with an agent which disolves the unirradiated zones:

• wherein the improvement comprises, applying said layer to said circuit by conveying the circuit beneath a free falling curtain of said liquid substance whose viscosity is selected from the range 500 to 1200 mPa's at impingement on said circuit, adjusting the height of said curtain above said circuit to produce a rate of flow at impingement selected from the range 60 to 100 m/min, and adjusting the rate at which said circuit is conveyed beneath said curtain to be greater than a rate slightly less than the rate at which said curtain falls on said circuit.