--- 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.
I don't think that's super critical for signal traces--as long as the
trace exists & survives etching without breaking; we don't care if
it's a little wavy.
> ∗ Getting that print onto the board as etch resist.
That's what limits my toner transfer's resolution presently. Fine
lines don't survive the transfer process intact.
A second, lesser problem is smearing of the toner during
transfer--lines that are too close together will be joined, producing
a short-circuit.
> ∗ Consistent etching with little side-etch.
Floating the board face-down on FeCl works really well -- see post 14965.
> ∗ Thinner copper?
Maybe, but why? (for high currents?) Could electroless plate it up
afterwards--that's not hard.
> Does anyone get 5/5 or better, reliably, with home etch? If so, how?
8/8 has been my limit, with baked Sharpie markups needed to fix gaps
in traces that didn't transfer well.
I've just done my first experiments with magazine paper at 0.010"
traces and spaces. I found it transfers and releases ∗much∗ better /
more completely than the inkjet paper I had been using.
(Preliminary reason seems to be, in part, the magazine paper is
thinner, allowing better heating of the coppper foil underneath it
when passing through my laminator. A hot air gun also helps keep
everything at temperature.)
Best,
James Arthur