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

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From: Michael Nudelman (mnudelman@tellium.com)
Date: Wed Nov 01 2000 - 06:13:25 PST


Muhammad:

1. If your stackup is the same (dielectr. thicknesses etc) - then how
does the impedance stays the same with traces' widths changed? (if it is
different, than it is possible.)
2. How long are the traces? In case of 7.5 mils your skin effect losses
increase and at certain lengths they may impaire your signal quality.
3. The pwr plane copper oz are not that important. Or at least I think
so :-)))

Mike.

"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 widetraces 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

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