On Mon, Oct 19, 2009 at 10:07:00AM -0500, John Griessen wrote: > Andy Fierman wrote: > > So your consultant thinks it's a bad idea to have a Vcc plane because > > it takes up space > . > . > . > > > Hopefully you can gently persuade your boss that this is not quite > > what the very expensive consultant meant to say. > > So, are there no conditions where leaving out a VCC plane makes sense? > He might not have meant to compare to 3GHz motherboards. > > If he meant to deal with RF transceivers as special case zones, > and the rest of the circuits operate below some clock speed like 600MHz, > I can imagine a stack up like: > > for a four layer board... > > signal + VCC > ============= > GND1 > ============= > signal2 > ============= > GND2 > ============= > signal3 + VCC2 >
Congratulations, you've fitted 3 signal planes and 2 ground planes on a 4 layer board! I must admit that making an additional plane come out of nowhere would sometimes simplify my boards... > > or for a six layer board > > signal1 > ============= > signal2 > ============= > GND1 > ============= > signal3 > ============= > GND2 > ============= > signal4 > ============= > signal5 Again, 5 signal planes plus 2 ground planes out of 6. Lack of caffeine? > Now if we could just specify blind vias easily with pcb... Holy grail. But first thing (even for 3 D viewing) would be to be able to specify a Z coordinate for each layer, layers with the same Z corrdinate being merged. Gabriel _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user