Re: [SI-LIST] : effect of trace width on the performance

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From: Bill Owsley (owsley@cisco.com)
Date: Tue Oct 31 2000 - 18:21:18 PST


not enough info, to reduce the wide range of possibles. One wild guess
might be not enough copper...
such as; what is the bad behaviour? Jus spank'm and send them to the
corner...

At 05:34 PM 10/31/2000 -0800, Muhammad S. Sagarwala wrote:
>Hi SI Gurus,
>
>I am in a big problem. I designed two boards which are pretty much the same.
>The changes between them are:
>
>(1) One has traces that are 7.5 mils wide and the other has 9 mils wide
>traces (both have a characteristic impedence of 50 ohms)
>(2) The one that has 9 mil wide traces has 1 oz copper for the pwr planes
>and the one with 7.5 mil wide traces has 0.5 oz. copper
> on pwr planes.
>
>The stackup is pretty much the same.
>The Frequency of signals on the boards is 400 Mhz.
>The decoupling scheme on both boards is pretty much the same.
>
>
>The problems is the board with 9 mil wide traces and 1oz. copper is
>performing very good and the other board with 7.5 mil wide
>traces and 0.5 oz. copper is behaving very very bad.
>
>My question is "do you think these changes make a big difference or is
>there another variable(s) that I am missing?????"
>
>Comments suggestions are most welcome....(I need to be sure before I make
>a decision to respin the board )
>
>Muhammad
>
>
>
>
>
>
>
>
>Muhammad S. Sagarwala
>Schlumberger SABER
>Ph. (408) 586 7065
>Fax (408) 586 4668

----------------------------
Bill Owsley, owsley@cisco.com
919) 392-8341

TMBU Compliance
Cisco Systems
7025 Kit Creek Road
POB 14987
RTP. NC. 27709

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