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

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From: Muhammad S. Sagarwala ([email protected])
Date: Wed Nov 01 2000 - 08:26:53 PST

Thanks a lot for your input Mike...

The stackup is the same but the dielectric thickness is different...I mean the arrangement of the planes is the same but the thickness of the
dielectric (and hence the boards is different)..

The lengths of the traces on these boards is between 7-10 inches.

One more question...I am suspecting ground you think that copper weight and trace widths could play a major role...

    -----Original Message-----
    From: Michael Nudelman <[email protected]>
    To: Muhammad S. Sagarwala <[email protected]>
    Cc: [email protected] <[email protected]>
    Date: Wednesday, November 01, 2000 6:18 AM
    Subject: Re: [SI-LIST] : effect of trace width on the performance
    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 :-)))


    "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
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