[SI-LIST] Re: PCB Corners - Need help finding research paper

Dear Chris,

Regarding right-angle bends in traces, this paper might help:  
"Who's Afraid of the Big, Bad Bend"

www.sigcon.com/Pubs/edn/bigbadbend.htm


From the article:  "Layout professionals often point out that modern layout
systems already round off all the outside corners, assuming that this
rounding eliminates the square-corner effect. It doesn't. Rounding the
corners removes 21% of the copper in the corner. Edwards shows that you must
remove 70 to 90% of the copper from a right-angle bend to neutralize (to
first order) the excess capacitance. Rounding removes only a small fraction
of the required amount of copper. Rounded-corner right-angle bends work well
in digital designs not because they are rounded, but because the corners are
too tiny to cause significant problems in the first place."

Best regards,
Dr. Howard Johnson, Signal Consulting Inc.,
tel +1 509-997-0505,  howie03@xxxxxxxxxx
www.sigcon.com -- High-Speed Digital Design seminars, publications and films
 



-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of DAVID CUTHBERT
Sent: Friday, August 08, 2008 11:49 AM
To: Chris.McGrath@xxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: PCB Corners - Need help finding research paper

Chris,
I can run a quick SONNET sim for you to show what happens with sharp 90
degree corners and with chamfered corners. The sharp corners add some
capacitance and lower the Z0. For anything that I have done this effect was
almost negligible.

Howard Johnson's book has a section on this, I think.


    Dave Cuthbert

On Fri, Aug 8, 2008 at 12:11 PM, <Chris.McGrath@xxxxxxxx> wrote:

> I used to have a copy of a public paper that debunked the myth that 
> stated the evils of using 90 degree corners when routing PCB traces.  
> I can't seem to find it on the web, so I'm hoping that one of you may 
> either have a copy of it or can point me to the link.  Feel free to 
> email me directly with the attachment since the SI List server will block
it.
> Thanks!
> Chris
>
>
> -------------------------------------------------------
> Chris McGrath
> Applications Engineer
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