There's good printers and crappy printers. Crappy: lasers, many
inkjets. Good: epson stylus colour. I did various comparisons.
The main thing with the epson ones is that the genuine epson
inkjet transparency has a smooth absorbant layer, and the
printout is also smooth.
To test for exposure, expose segments of a pcb in 30s increments,
then develop. Make your exposure time a couple of minutes longer
than the minimum. Crappy printouts are easily over-exposed. With
an epson printout, i expose for 5mins using a small light-box with
4 tubes, but if i forget and expose it for half an hour, i still
get an excellent result (just some tracks get slightly thinner).
johnman9146 wrote:
That kind of misses the point. I am looking to see if anyone knows
of a suitable etch resist ink, and/or a suitable soldermask ink.
If I do decide to go your way and do the transparancy method with UV
sensitive photoresist, I have a few questions.
How do I know when I have the proper exposure?
Can you over-expose?
How dark black does the transparancy need to be for this method to be
effective?
I have access to some pretty sophisticated hardware if I do decide to
try this method. Items such as a photoplotter, a vacuum backed UV
table (for exposing printing plates) and more, but it is a hassle to
go there for all the neat toys.
I don't think there would be any issues with the image size not being
exactly 100% as it is a professional photoplotter designed to make
printing plates for magazine reproduction.
Potentially, I may just have to experiment with different inks if
nobody has any suggestions.
Does anyone print legends on thier prototype boards?
Some labels on the top copper.
Does anyone use anything to add a soldermask?
Does anyone even use any type of conformal coating?
Sometimes, for water-proofing.
Im my opinion you're much better off using photoresist coated
boards.
Print your layouts using the right transparent medium for your
printer
(laser or inkjet) and use that to expose the board under UV. I made
a
suitable lightbox with tubes sold as spare parts for the ready-made
unit sold by Maplin. I also use ready-prepared developer and etcher
from them and get a great result every time.
Cheers
Derryck
