RE: [SI-LIST] : skin effect

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From: Jian X. Zheng ([email protected])
Date: Thu Aug 31 2000 - 10:33:35 PDT

Hi, Muhammad:

I think you need to clarify what you mean "skin effect".

For many microwave people, skin effect normally refers to the effect of the
trace thickness to the surface impedance of the trace, which determines the
ohmic loss in the trace. In such a sense, skin effect is more for the
thickness. In some sense, the surface impedance of the trace is normally
dependent upon the trace thickness only. When the strip thickness is not
much thickner than the penetration depth, the surface impedance will be
affected by the thickness much. However, when the strip thickness 3 times or
more as big as the penetration depth, the surface impedance will not change
much with the strip thickness. Surface impedance is one determining factor
for trace loss. Trace width is the other one.

Your boss may consider the skin effect as the metallic loss vs. strip
thickness and strip width. In such a situation, skin effect certainly is
related to both strip thickness and strip width. In fact, the metallic loss
should always decrease with increased strip width. However, the metallic
loss will not decrease significantly with increased strip thickness after
the strip thickness is much thickner than the penetration depth. In this
sense, skin effect (metallic loss) is more dependent upon the trace width.


Jian-X. Zheng, Ph.D
Zeland Software, Inc., 48890 Milmont Drive, 105D, Fremont, CA 94538, U.S.A.
Tel: 510-623-7162, Fax: 510-623-7135, Web:
Special Announcements: (1) The FIDELITY 3.0 is formally released. It has
many good features to enhance 3D modeling in wireless communications; (2)
IE3D 7.0 is released. It is a big step from IE3D 6.0 according to its
optimization capability. It has the implementation of symbolic optimization
goals. It als features integrated IE3D+CURVIEW+PATTERNVIEW for auomated
pattern calculation and optimization.

  -----Original Message-----
  From: [email protected]
[mailto:[email protected]]On Behalf Of Muhammad S. Sagarwala
  Sent: Thursday, August 31, 2000 9:45 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 traces". 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 particular...

Muhammad S. Sagarwala Design Engineer Schlumberger SABER Ph. (408) 586 7065 Fax (408) 586 4668

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