[SI-LIST] Re: "checkered" copper plane question
- From: "Ingraham, Andrew" <a.ingraham@xxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Tue, 13 May 2003 13:54:49 -0400
> I've been hitting a couple embedded design shows lately
> and have been seeing a couple prototype boards that have
> the top and bottom copper planes 'checkered'
>
> That is instead of a large continuous plane, the plane has
> been cut into a grid of 1-2mm squares.
If it's copper squares where you didn't ask for any, I think it's called
"auto-thieving" and it's intended to balance the amount of copper etching
across the board. Otherwise they can get uneven etching.
If it was supposed to be a solid plane but was cut up into lots of little
unconnected copper squares, then it sounds like a mistake.
If it's a grid of square holes, leaving a mesh of continuous lines, a few
things come to mind. One is (again) to balance the amount of etching.
Another might be to provide a surface for something else to adhere to. I've
heard of this done on layers of IC packages (to get the dielectric layers to
adhere to one another, they don't adhere to metal very well). I suppose the
same might happen on a circuit board? Although usually they roughen up the
copper surface to help with that, I think.
Or maybe the layout person didn't know how to do a solid fill so he built it
using a mesh of traces.
If it's supposed to be a solid plane (reference for an adjacent stripline
layer), making it a grid does noticeably change the impedance.
Regards,
Andy
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
