Increasing utilisation efficiency of ferric chloride etchant in industrial photochemical machining

The environmental effects of photochemical machining (PCM) can be appreciable in view of the nature of the industry whereby various chemicals are used in the preparation and cleaning of metal surfaces, photographic processing of phototooling, coating and selective removal (development) of photoresists, etching through apertures in the resist stencils and stripping of resist after etching. This paper concerns the environmental impact of ferric chloride, the most commonly used etchant in PCM, and is believed to be the first quantitative analysis for the PCM industry. The findings showed that more than half of the PCM companies used regeneration of ferric chloride etchant and 76.3% of companies were prepared to use a more environment-friendly regeneration system at a higher overall cost. Regarding ferric chloride consumption, it was found that the performance of companies varies greatly: companies using regeneration were, on average, nearly seven times (340.8% compared with 51.1%) more efficient than those that do not regenerate, and the most efficient company used 135 times less etchant than the least efficient company. The findings of this study and the analysis carried out can be used by PCM companies as a benchmark in assessing their environmental performance with respect to etchant consumption efficiency.