On Sep 12, 2010, at 1:49 PM, Rick Collins wrote: > At 03:42 PM 9/10/2010, you wrote: > >> On Sep 10, 2010, at 1:01 PM, DJ Delorie wrote: >> >> > I figure we need each layer to specify: >> > >> > * type (copper, silk, mask, anti-copper, keepout, etc) >> >> There are no types, there are only properties. >> >> The conductors may not be copper. I've even worked with a board that had two >> different conductive materials on the same physical layer. > > Wouldn't that by definition then be two different physical layers, just like > the solder mask and silk screen are two physical layers.
Perhaps. > The fact that they connect without vias doesn't mean to me they are the same > physical layer. Well, in this case they didn't "connect without vias". The low current traces used a metal with low thermal conductivity, while the high current traces were copper. > I've worked with boards that had buried resistors. The resistors were a > layer of conductive material that had a controlled resistivity in contact > with a copper layer. The resistors were considered a separate layer. > > >> The support layers are also not always FR4. The board I noted above had >> different numbers of layers in different places, and the support layers >> weren't all the same material and thickness. > > Sounds suspicious. Are you sure you aren't talking about an assembly with > boards and a case? Bolts aren't normally considered vias. ;^) No, I'm talking about a narrow board with two rigid parts at the ends and a flexible part in the middle. The rigid parts had more layers: that's how they got to be rigid. It lived inside a cryostat, with circuitry that ran cold at one end, and circuitry that ran warm at the other. The point here is that the insulating planes are layers also: they need representation in the board description. They have their own shapes and material properties. And I think the only way to do blind/buried vias, buried components, and odd boards like this in a non-kludgy way is to treat the insulating planes as layers, each with its own geometry. > > Rick > > > _______________________________________________ > geda-user mailing list > [email protected] > http://www.seul.org/cgi-bin/mailman/listinfo/geda-user > John Doty Noqsi Aerospace, Ltd. http://www.noqsi.com/ [email protected] _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
