Yep, that could be an advantage of the "one side" method.
As far as the aligning is concerned, I'm mostly doing 4-layers here,
hence aligning layers is something I have to have under control anyways.
I do this using diagonally placed shafts, printing on clear films and
using a home made puncher to punch out the shaft holes in the film using
magnifier googles. The printed black rings I use to position the hole
are just about 1mil bigger than the physical hole in the puncher. I thus
simply align the hole so as a very tiny ring of the punchers metal can
be seen through the magnifier googles. This gives a very high precision
in alignement.
I have no personal experience with the toner transfer method but since
it relies on lasers I'm not sure if one can achive a reproduceable match
on multiple printouts as it would be requiered for the purpose. Don't
get this wrong, it very well might be that todays lasers can do that. I
just decided on the traditional way long time ago and never had a reason
to switch.
I'm looking foreward on trying this out anyways and if you are
interested will report my results back here.
Markus
DJ Delorie schrieb:
>
>
> Markus Zingg <homebrew-pcb@...
> <mailto:homebrew-pcb%40shdesign.info>> writes:
> > I intend to use dryfilm laminate on both sides. The idea is to etch
> > from both sides which I think might help keeping the undercuts at
> > about half your rate. Just guessing though, and again, I definately
> > will try this soon.
>
> I thought of that. In my case, I couldn't align the toner sheets
> accurately enough for that to work with the hole sizes I needed (0.5mm
> pitch TQFP). I'm guessing with photoresist that's not a problem.
>
> Working from one side also gives you a nice trapezoidal hole shape,
> which helps release the paste. Big side down, of course ;-)
>
>