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

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From: Muhammad S. Sagarwala (msagarwa@san-jose.tt.slb.com)
Date: Tue Oct 31 2000 - 19:04:16 PST


Patrick,

The lines are single ended but the spacing betweent them is 2x, 3x or
4x.(2x or greater) so
I do not think cross talk is an issue.

The edge rates on the boards are exactly the same.

The problem I feel is because of "ground bounce"...I was wondering if the
trace width and copper on power planes play a major
part ?????

Muhammad
-----Original Message-----
From: Zabinski, Patrick J. <zabinski.patrick@mayo.edu>
To: msagarwa@san-jose.tt.slb.com <msagarwa@san-jose.tt.slb.com>;
si-list@silab.eng.sun.com <si-list@silab.eng.sun.com>
Date: Tuesday, October 31, 2000 6:54 PM
Subject: RE: [SI-LIST] : effect of trace width on the performance

>Muhammad,
>
>This alone would make me think the 7.5 mil wide trace board would
>work better than the 9 mil wide trace board due to the lower crosstalk.
>This assumes single-ended lines, but the opposite would be true
>for differential lines. Are the lines differential or single ended?
>
>If this isn't it, my next best guess is the attenuation of the lines.
>With cyanate ester, the loss tangent is quite low (around 0.001 if I
>recall??), so I don't think you'll be running into much dielectric
>loss at 400 MHz. However, the wider/thicker traces will have much
>less loss at both DC and higher freqs than the narrower/thinner
>traces (at least a factor of two better).
>
>Have you looked at the signal degradation differences between the
>two boards? Are the edge rates on the two board different?
>
>If this isn't it, then I'm clueless.
>
>Pat
>
>>
>> Exactly the same...
>>
>>
>> >How about center-to-center pitch on routing tracks?
>> >
>> >>
>> >>
>> >> I am sorry Patrick,
>> >>
>> >> I forgot to mention ... the thickness of the boards is
>> >> different. The one
>> >> with 9 mil wide traces is thicker than the one
>> >> with 7.5 mil wide traces.
>> >>
>> >> As regards other possibilities, the boards use the same
>> >> dielectric material
>> >> (Cynate Ester), the power planes on them
>> >> are exactly the same, and the stackup is the same too and the
>> >> placement of
>> >> the decoupling caps is pretty much the same too
>> >> (both the physical location and quantity)..
>> >>
>> >> Muhammad
>>
>

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