Any one looking at printing on copper boards (or any material for that
matter) using non-standard fluids might want to check out the print
heads and inks being offered at this site:
http://www.dimatix.com/. They offer piezoelectric print heads capable of 450 dpi to 900 dpi,
printing fluids ranging from UV cured inks to hot wax. The printer is a
bit expensive at $35K, but the print heads seem to be mostly self
contained and are refillable, they range from $59 to $99 and may be
adaptable to a cnc machine.
Dave