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
