how to create and connect to a ground plane

[zenworksengineer]

I seem to be missing something. All the guides are for really clever stuff. I need chapter one, page one.

Do I just draw a rectangle? How do I connect vias to it? I get overlap errors, or they refuse to join, or something else is wrong.

My board is all surface mount so the whole underside can be the ground plane. But I can't seem to label it at all with the right buss, or node, or anything.

It is very frustrating the "ground plane" doesn't appear at all in the help files.

The circuit was created in Eagle and has been in production on a two layer board for a couple of years now, but we now have to meet incident EMC standards.

[one-of-the-robs · Accepted solution]

I'm sure this is all the the tutorial somewhere but...

1. You draw a polygon - it can be a simple rectangular one but it MUST be drawn with the POLYGON tool and must be continuous, closed, and non-overlapping - on one of the copper layers
2. You name that polygon 'GND' (or whatever your ground net is called)
3. You set the "orphans" property to OFF, so that you can see where it doesn't get to
4. You run RATSNEST

That's it. Eagle will fill any part of that copper layer within the polygon for which there is a pad, trace or via on the GND net accessible using the trace width defined for that polygon and obeying your DRC limits for clearance etc.

[zenworksengineer]

I have now watched the tutorials and it is exactly as you say, but it isn't working. I draw with Polygon and I get a solid line. I finish the polygon and the line becomes dotted. I name the polygon. I click Ratsnest and...nothing. If I right click on the dotted line I get Properties. Oddly if I tick the Orphans box, my polygon becomes solid.

And when I then run the Autorouter, it ignores the Keepout areas, which it didn't used to do.

Do I just need to buy a much more powerful PC?

[zenworksengineer]

Oooh, is it getting confused because I have a board covered in airwires? Do I need to route everything first?

In which case, how do I make the bottom layer one continous plane with no tracks, only ground vias?

This board has to cope with field strengths of 30V/m across 2Mhz to 2GHz, plus what gets conducted down the 50 wires that connect it to the rest of the mchine.

[one-of-the-robs]

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@zenworksengineer wrote:

Oooh, is it getting confused because I have a board covered in airwires?

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If that's all the board is covered with, then you've not satisfied the "accessible trace, pad or via of the GND signal" requirement. If you're starting with a single-sided design and want a ground plane on the other side, you need to explicitly place a few GND vias.

[zenworksengineer]

Now I understand.

I have now made a board with ground planes. They are of course full of gaps where the traces run.

I would like to try a single sided design and then add a continuous ground plane on the bottom. Is there a way to exclude ground buss from the auto router?