Homebrew PCBs

derekhawkins wrote:
> 
> 
>  >I've transferred finer lines with TT that looked ok, but they
>  >disappeared completely during etching.
> 
> No surprises there, transferred toner is actually a poor resist in
> comparison to resist that was developed properly. And when you
> say "looked ok", what magnification are you referring to?
> 
> I did that 6/6 rules torture test to debunk a collimation myth. The
> only reason why it wasn't 5/5 was because the artwork didn't make the
> grade. I can do less tortuous 5/5 or 4/4 rules (to the limit of the
> printer) to debunk the etching myth as well. How about .003" or .002"
> lines with .005" or .004" spacing? What will it take to convince you
> that etching should be the least of your worries provided you know what
> you're doing? Do I have to walk on water?

What is your etching technique ?
What is your foil thickness ?

Ok, you got me curious. Now you've made me waste the past 3 hours of my 
time  determining if etching undercut does indeed limiting line widths.
My test showed for 18um foil  PCB the limited factor is the printer, and 
not the etch process. I have compile a quick web page showing the 
results of this mornings experiment, enjoy.

http://members.optusnet.com.au/~eseychell/pcbtest1/line_width_tests.html

Even thought my results demonstrated a printer limitation, I still think 
etch undercut can be an issue, especially for bubble etchers or 70um 
("2oz") foils.

Adam