RE: [SI-LIST] : skin effect

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From: Daniel, Erik S. ([email protected])
Date: Thu Aug 31 2000 - 10:23:07 PDT

Your boss is right. The short explanation is that skin effect resistance is
approximately inversely proportional to conductor perimiter, which is
dominated by conductor width rather than thickness for typical geometries
(thickness of 0.7-1.4 mils for 0.5-1 oz copper compared with trace widths of
5-10 mils, say). Therefore, increasing the thickness by a factor of two
makes a small percentage increase in the total perimeter, and hence a small
percentage decrease in resistance. One could also argue that since the
electric fields are largely vertical (i.e., perpendicular to the width of
the conductor) that there is less fractional current carried along the
sidewalls than along the top/bottom surfaces in a stripline, although this
is a second-order effect.
                    - Erik

Erik Daniel, Ph.D. Mayo Foundation
Voice: (507) 284-1634 Guggenheim 1011B
Fax: (507) 284-9171 200 First Street SW
E-mail: [email protected] Rochester, MN 55905

-----Original Message-----
From: Muhammad S. Sagarwala [mailto:[email protected]]
Sent: Thursday, August 31, 2000 11:45 AM
To: [email protected]
Subject: [SI-LIST] : skin effect

Hello Si Gurus,
I just had an interesting discussion with my boss on "skin effect on pcb
I was of the opinion that increasing the trace thickness from 1/2 oz. to
1oz. would help reduce the
skin effect but according to him skin effect does not reduce significantly
with the increase in trace thickness.
He was of the opinion ( and also had some data to back him up) that skin
effect is more dependent on the
width of the trace.
I always thought that if one increases the overall perimeter of the pcb
trace - regardless of whether it is done by
increasing the width or increasing the thickness - the skin effect would
reduce. I would appreciate if somebody
could come up with a better explanation...
p.s.: when we talked about pcb traces we were talking about striplines in
Muhammad S. Sagarwala
Design Engineer
Schlumberger SABER
Ph. (408) 586 7065
Fax (408) 586 4668

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