I've got a tiny little 100-pin 0.5mm pitch TQFP chip that needs a whole lotta I/O connected to it. I'm doing a 4-layer board (internal VCC and GND planes), but I'm still getting all tied up in knots, with vias all over the place. The connections tend to go off in different directions -- these aren't pretty 16-channel busses. Anybody have any general tips for dealing with this? I have seen that some layout programs do automatic fan-out on chips like this. I could certainly do that manually, but I'm not sure it will really help a whole lot. I still have a lot of signals to connect, and plus several of these pins are power pins that require their own decoupling capacitor and specify that it needs to be as close to the pin as possible. I find I might have to redefine "as close as possible" as I try to cram more connections in there. (Needless to say, the autorouter shrieks and flees in terror at the sight of this ratsnest, so I am stuck doing it all manually.)
One thing that would help would be if I could use the internal VCC/GND planes for routing the odd trace or two, but I have heard that it is a bad idea to run traces through the planes. Anybody have any thoughts on this? I don't suppose anybody has written any fan-out scripts or plugins? Would it help? (I've never done it myself.) TIA, -- Randall _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
