Homebrew PCBs

Stefan Trethan wrote:
> i am not too convinced that the "darkness" is most important to be 
> measured...
> 
> do you really have problems with the whole printout being not dark enough?

Not really.
I've mainly used epson stuff which is very dark, so I've never 
had problems with overexposure. I've also made a couple of boards 
using the HP stuff, which isn't as dark (sorry I can't give you 
relative absorption numbers :)) and also didn't have problems 
with overexposure.

I agree that line edge jaggedness and pin holes are more 
important than overall darkness since many of the inkjets I've 
tested seem to look dark enough so that exposure times can be 
resonably flexable (+-30%). However the most importantly defect 
is banding due to blocked or partly blocked jets. This can easily 
create a discontinuity in a track. Other problems are ink 
splattering which I have seen with some refillable inks on my 
Epson. If the splattering is severe enough it can actually create 
a short between closly spaces tracks.