I was battling to make PCBs using the photo etching technique with an inkjet printer and transparencies until I ran across this little gem of info. http://astro.umsystem.edu/atm/ARCHIVES/JAN02/msg00287.html
The common problem when trying to make positive plates with inkjet printers and transparencies is that the black is never dark enough to block all the UV (I've been trying for 2 days without success). Also stacking the positive plates gives fuzzy edges because of the thickness of the transparencies. The trick is to use GREEN as the mask and not black because most inkjet photo cartridges are dye-based and contain Photo Yellow which is a natural UV filter plus Photo Cyan which contains a UV inhibitor! Pure green is half yellow and half cyan when printing in photo mode and it creates a good UV mask even though it is easier to see through than black. Just make sure you have a decent photo cartridge and use photographic mode when printing so that the photo colors get used. The author of the article above used a Canon inkjet printer but today I tried it out on my HP Deskjet 5550 with a HP 57 tri-color cartridge and I made perfect 5 mil tracks! Just want to share this info because I know a lot of people throw the inkjet and transparency technique out of the window because they don't know this trick. Regards Paul Surgeon
