Re: gEDA-user: Preliminary report on gerbers with buried, hidden and micro vias

[DJ Delorie <dj@xxxxxxxxxxx>]

> You can't mix layers. If you have buried via connecting layers 2, 3, and
> 4 you then can not have buried vias connecting layers 3, 4 and 5.
> This is because they will build up the layers 2, 3, and 4 as if it was
> its own board. Drill and plate the holes for them. Next they add the
> other layers to make the complete board. Then they drill and plate all
> the normal vias.

That sounds like what I'd expect based on how boards are made.  You
always drill, plate, etch.  So you can drill buried vias, plate them,
and etch the outer layers of the sandwich.  Then you glue more stuff
on the outsides of that to make a thicker sandwich, which you drill,
plate, etch.

Hmmm... should we assume that any given FR4 layer has a maximum of one
set of buried vias?  I.e. any given layer would be drilled at most
twice, once for its buried vias and once for the through holes?  If
so, we can probably add "via groups" into pcb easier than if we
allowed arbitrary heirarchies of drill/plate/etch (like drill 3-4,
drill 5-6, combine, drill 3-6, combine, drill 1-8)