Problem: Not routing GND pins despite GND power plane
Posted by dagr at
Hi,
I'm hoping someone can point me in the right direction to help solve this strange routing failure.
I am trying to route a small board (~5 x 3cm) with SMD components on both sides. The board population is not very dense and, from experience, it should be not overly difficult to route as a Class IV, 4-layer board (1 Gnd powerplane & 3 signal planes).
As expected, there are a few signal nets that could not be autorouted. However, it seems it cannot route most of the "GND" pins/nets to the power plane, even when there is no restriction on the use of vias. The software generates a lot of vias, too much, many of them uneeded. It is not a simple "lost" net issue as it manages to connect a few GND pins/nets to the power plane, but not always the same ones.
It is very frustrating as it looks like a "no-brainer" to connect the GND pins, and indeed feels like a simple configuration problem, but I have tried many options, including going to 6 layers which seems to make routing even worse.
Any ideas?
I'm still on V3.0.
Cheers
Replies
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Auto-routing is difficult even on top of the range CADs like Mentor Graphics and the like, so i would not depend upon them too much.
Have you tried un-routing everything then confining the router to only connect power so that the auto-router only has the power planes to do. If it can't do that then the auto-router might as well be switched off as it will be totally impractical to use anyway. You can manually connect the odd one or two power pins if necessary.
You now have at least that as a starting position; then you can try auto-routing the rest if you want. I think you might stand a better chance this way as you are forcibly assigning a priority. -
Umm... You did do Menu > View > Powerplane > Regenrate, didn't you?
At first I thought a manual copper pour was needed.
R.