Optimizing the Dry Film Process

June 2008

Optimizing the Dry Film Process

In a fast paced, ever changing world, some things never change. Getting a dry film photopolymer process optimized to consistently adhere to a metal surface for photochemical machining (PCM) is always a challenge. But, the principles of how to obtain optimal process yields never change. Poor performance and variations in yield typically result in variations in the process itself, rather than in the basic metals, chemicals and dry films.

Optimizing the process depends greatly on available equipment. Obtaining complex imaging is much easier on a collimated light source as compared to a non-collimated light source. Conveyorized cleaning equipment usually gives better results than a hand-dip cleaning line. Unfortunately, due to metal type variation, the PCM job shop, as compared to a printed circuit board (PCB) job shop, has a distinct disadvantage. PCB job shops work with copper surfaces which are much softer, easier to clean and more consistent than PCM metals. Also, since the PCB industry is much larger than the PCM industry, most, if not all, dry films are made to adhere to copper surfaces. Therefore, getting a dry film to adhere to and perform on a PCM metal, such as a high chrome content stainless steel, has always been a challenge.

Ken Bridges, Past President, PCMI