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Abstract
In the use of liquid photoresists for photoetching, measurement of coating thickness is important for process control. Relative average thickness can be determined from weight/unit areas, but values for specific gravity are required to convert the data to absolute thickness. Manufacturers were unable to supply information about the specific gravity of dry layers of their resists, and methods for determining this quantity are described.
Although it is usually customary to pre-bake photoresist layers before exposure, one resist used on stainless steel suffered heat fogging. The developed stencil showed retention of filaments of resist which could not be removed by prolonged development. They did not appear when the pre-bake was omitted.
Whilst using a spray etching system to study the etched edge profile of stainless steel sheet, it was found that catastrophic failure could occur if the spray impact caused unsupported Haps of resist, left by undercutting, to fracture at the edge of the etched pit.
Notes
Paper presented at a symposium on “Unconventional Photographic Systems” organized by the Science Committee of The Royal Photographic Society, 12-16 September, 1977, in Oxford.