Homebrew PCBs

Markus Zingg <homebrew-pcb@...> writes:
> As far as the aligning is concerned, I'm mostly doing 4-layers here, 

Woot!  Another one!  http://www.delorie.com/electronics/usb-gpio/

How are you managing vias and stackup details?

> The printed black rings I use to position the hole are just about
> 1mil bigger than the physical hole in the puncher.

What I've been doing is adding a registration target, and using an awl
to mark a dimple for a 13 mil drill in the PCB stock.  I use that to
line up the two sides.  For four layer boards, the outer layers are
see-through anyway, so I just line them up visually when I tape them
on.  Or, I drill all the 13 mil registration points and use spare
drill bits or wire to line them up.

> 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.

The size is not 100% scale, but it is very predictable.  I've added a
correction factor in my output specs, and can usually get the two
layers lined up within a few mil of each other.

I'm guessing that photomask alignment would be easier; just draw
registration marks outside the pcb area and line them up visually.  At
least, if you're exposing both sides at once.