Re: [SI-LIST] : Broadside v edge coupled striplines

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From: Scott McMorrow (scott@vasthorizons.com)
Date: Fri Jan 19 2001 - 09:59:44 PST


Aubrey,

The manufacturing issues can be reduced by constructing the
broadside pair on core material and keeping the spacing between
the pairs small compared to the spacing to the planes. Then the
separation between the pair is well controlled and the fields are
well contained between the pairs.

Another solution which works quite well is to use CPW or
grounded CPW construction for diff pairs on outer layers.

regards,

scott

--
Scott McMorrow
Principal Engineer
SiQual, Signal Quality Engineering
18735 SW Boones Ferry Road
Tualatin, OR  97062-3090
(503) 885-1231
http://www.siqual.com

Aubrey_Sparkman@Dell.com wrote:

> Thanks for that correction. Isn't the difference is really in > manufacturing, not physics? An EDGE-coupled diff pair is more uniform > because the pattern is etched in the same process. The BROADSICE-coupled > diff pair is etched at two different times and additionally has to be > mechanically aligned for lamination. This adds two additional error terms > to the accuracy of your BROADSICE-coupled diff pair that the EDGE-coupled > diff pair does not have. So IMHO, you should really have a packing density > problem before you consider using BROADSICE-coupled traces. > > But if you are doing work for Compaq or Sun, you should use > BROADSICE-coupled diff pairs whenever possible. :-) > > Aubrey Sparkman > Signal Integrity > Aubrey_Sparkman@Dell.com > (512) 723-3592 > > >

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