Eagle and autorouting and ground planes w/ SMD devices

Ok, so I’ll admit it, I’m the type of person who likes to let Eagle’s autorouter do a bunch of the grunt work for me. If I don’t like what it does, I’ll hit “rip up: all”, juggle some things around, maybe move components or set some restrict blocks, and let it do it over again. I like it this way because I like to be able to add new components to the schematic and possibly move things around without having to redo a bunch of manual routing.

However, as I shift more toward SMD work, I’m noting a real annoyance out of the autorouter. I put a nice big ground plane on the back of the board. The autorouter decides that it will snake an annoying long winding trace all over the top of the board and connect it to a via to my ground plane in one spot. This is not what I wanted. I want it to put vias in and connect the SMD devices to the ground plane as necessary.

So, I figure I can add some vias myself, put them in the right spots, name them “GND”, and like magic the autorouter will use those vias and avoid snaking a ground trace all over the top of my board.

However, the first time I do a “rip up: all”, it removes my vias. Well, duh. That’s what it’s supposed to do.

So, I’d like to find a way to either:

  1. Convince the autorouter to do what I want on it’s own, using vias to the ground plane in a reasonably intelligent manner. I’ve tried tweaking the via cost in the optimize settings, but usually this ends in signal traces getting excessive vias. It’s possible I just haven’t played with it enough. I wish I could set the via cost just for “GND” to a lower value, and leave everything else alone.

-or-

  1. Find a way to convince it to rip-up everything but the vias (or manually routed traces) that I’ve manually placed. If I could just rip-up the autorouted traces when I want to, that’d be great, then I could experiment with more and more manual routing and still be able to have a quick and easy rip-up/autoroute cycle.

I don’t know if this will help your situation, but I am also a fan of the autorouter for doing the tough runs and I typically work in stages. I like to save my basic layout, with the parts in place. Then save a new file of the same board with somthing in the filename like “-manual-route”. I then hand route anything that is crucial on this board file. Once I am done with that, I save it again under a new file with “-autoroute” in the filename, in place of the “-manual-route” designation. I then run the autorouter and once I am happy with that, I save that file as-is.

My whole point is, I left myself back-up points that I can go back to, without losing all of my manual work. If need be, I can delete the “-autoroute” file, go back to the “-manual-route” file and start over with my autorouter…after I have made the component placement changes, orientation, ect.

Hope that helps!

Well, I did manage to find a poor mans way of solving the VIA issue at least. I took one of the solder pads (lsp10, maybe?) and modified it to look and act like a via. I can drop half a dozen of them into the schematic and connect them to ground, and then put them where I want on the board.

I wish eagle had a way to lock traces and vias to prevent deletion. I think it would help out considerably.