RE: [SI-LIST] : What's your favorite Screwy SI Concept?

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From: Alderete, Michael (MICHAEL.ALDERETE@Aerojet.com)
Date: Fri Jan 14 2000 - 07:01:10 PST


John-

This is an eye-opener!

Variations in board trace cross section may produce noticeable [and surely
measurable] changes in signal behavior! It does make perfect sense, though,
simply because so many e-m and SI phenomena are geometry driven; of course,
the magnitude of geometry variation, at a given signal frequency, determines
the degree of signal degradation.

Dave [Groovy]: you're one SI'er who is intimately familiar with real world
PWB fab variances. Have you ever seen application problems that were due to
unevenness of finished trace geometry?

Michael Alderete
Aerojet

-----Original Message-----
From: John Howard [mailto:jhoward@emcguru.com]
Sent: Thursday, January 13, 2000 11:25 AM
To: si-list@silab.eng.sun.com
Subject: Re: [SI-LIST] : What's your favorite Screwy SI Concept?

Hi Doug,
     While I don't feel huge argument with any of the foregoing I do think
one important point is missing (at least I missed it). I believe it is much
more important to maintain a uniform conductor cross section than to
exert great effort in avoiding a right angle turn. As someone mentioned,
a right angle turn isn't noticably detrimental until the dimensions of the
turn are comparable to a wavelength (at the highest frequency of interest).
However a change in the cross section dimensions will affect the
incremental inductance and capacitance at the point where the cross
section changes. It is a minor challange to fabricate a right angle trace
turn without changing the trace width - but worth the effort if you intend
to propagate high frequency energy.
     I've just joined this group........greetings to all!
John

Doug McKean wrote:

> Interesting comments. Anyone have any data on right
> angles in traces causing an increase in crosstalk?
>
> Regards, Doug McKean
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