Via stitching to bottomside ground plane

jorlando wrote on Wed, 18 November 2009 13:35

Hi All,

I'm in the process of designing a 2-layer RF board, with RF signals

routed on the top side and a nearly full ground plane on the bottom side.

I'd like to be able to stitch vias to ground on either side of the RF

signals on the top-side.  My first method of doing this was to simply run

my RF tracks, create my ground plane polygon on the bottomside (with

thermals off), place the vias where I want them, and re-name the net

associated with the via so that it is now the ground net. 

 

This method seemed to work, until I did a rip-up of the ground to

modify a few items.  Of course, all my via stitching went away too.  I

tried several other ideas, but the only one that I could come up with

that worked was to actually create a "ground stitch" device in a library,

followed by placing one of these devices in the schematic for every

ground stitch I wanted (and there are a lot).  Then, when I go to layout,

the stitching is all there (and stays there) even when I do a rip-up of

ground.

 

I'm guessing there is a better way that doesn't force the schematic to

have tens (if not hundreds) of these stitching devices represented, but I

haven't found it.  Any ideas?

Hello John,

When I need via stitching I do just want you did.  You can ripup just one

trace of a signal (including ground) without ripping up everything to do

with the signal.  If you ripup an airwire it will ripup everything on the

current trace (with some heuristics applied I think to figure out what is

ripped up).

See "help ripup" to get more info about how the command works and the

various ways to filter how it behaves.

You library device idea will work except it's a lot of work if you have a

lot of stitching.  You could create one device that has the all the vias

you want but then you'll get all kinds of DRC errors because (currently)

there is no way to associate copper other than SMD or PAD in a package with

a signal name.  So the DRC sees those as an error.

Hope that helps...

Cheers,

James.

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Thanks for the quick response James.  I was just playing around a bit more,

and realized that the ripup command only operates on visible layers.  So,

it works just fine to simply de-select the via layer before ripping up

ground.  This will preserve the via placement (even though their net is

still ground).  Much better solution compared to adding a boatload of

"ground stitch" devices on the schematic.

Of course, if you forget to de-select the via layer prior to running a

ripup command on ground, a simple undo will take you back.

Thanks again,

John

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