DJ,
My limiting factor on a small board is etching.
I can make a phototool with 4/4 on a 1200dpi
laser that has very little "Fuzz".
The photomask on the copper looks perfect.
Then after etching some traces magicaly
vanish or are so thin they may as well have.
If I am doing a tiny PCB I can put down 20
or so in a panel and I will get a few that
are usable at 4/4
I found I used to get less undercut whith
FeCl3 than I do with CuCl - but not enough
less for me to bother keeping FeCl3 on hand.
One of the posters here advocates "float
etching" with FeCl3 to get better line
def. I have yet to try it myself though.
1 Oz copper should be OK for 4/4 (I see
comercial shops offering this) but for less
than 4/4 they drop down the copper thickness.
Maybe Adam Seychell will be able to say if
spray etching is the answer to this part of
the problem.
--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:
>
>
> I seem to be seeing a trend here, that regardless of the techniques
> used, with care one can get to 6/6 rules. How do we get past that?
> It must be possible in theory, as the big fabs do it.
>
> My laser printer does 1.3 mil "lines" (600dpi) but the quality isn't
> good enough to do so reliably (fuzzy edges); I need at least 3-4
> pixels across to get good definition with TT.
>
> I think the various elements are:
>
> ∗ Getting a print with crisp edges at fine resolutions.
>
> ∗ Getting that print onto the board as etch resist.
>
> ∗ Consistent etching with little side-etch.
>
> ∗ Thinner copper?
>
> Does anyone get 5/5 or better, reliably, with home etch? If so,
how?
>
> Random thoughts:
>
> Would a 1200 dpi laser printer give better edges, or just smoother
> curves? Is there a paper trick to keeping the toner were it's
> supposed to be?
>
> I read one home fabber printed their TT at a 45 degree angle to get
> more consistent results.
>
> Photo: Inkjets can do 1440 and sometimes 2880 dpi, what limits those
> to 6/6? Would having the UV source further away from the board
result
> in better edges? What about the thickness of the photomask?
>
> What about 1/4 oz copper? I usually use 1/2 oz, and I haven't seen
> 1/4 oz in my usual places.
>
> Injets: Anyone try writing a custom print driver that forces all the
> colors to be used, overlapping, making a nice thick print? I've
tried
> doing that with my color laser, but I haven't found the command to
> turn off the "smarter than the user" mode.
>