Re: [SI-LIST] : Q: HSPICE w-elements' RLCGs - conversion coefficients from XFX

Pat Zabinski (
Wed, 7 Apr 1999 14:04:11 -0500


Back in 1942, Harold Wheeler went through the analytics to derive
the equivalent to "lambda" for various forms of surface roughness
(e.g., rectangular, triangular, etc). In his paper referenced
below, lambda varies depending up several factors, primarily
the RMS surface roughness and skin depth (i.e., frequency and
material properties). He was able to show how lambda could
reach 2.

TI Formulas for the Skin Effect
AU Harold A. Wheeler
SOURCE Proceedings of the IRE
DATE September, 1942
PP 412-424

Obtaining a copy of this paper would be an excellent start in understanding
the skin effect on effective resistance.

Pat Zabinski

> Another issue... XFX provides an optional fudge factor "lambda" that
> effectively accounts for copper plane/trace surface roughness. This fudge
> factor effectively scales the default copper resistivity in the skin layer.
> The default value of "lambda" is 1.
> Has anyone of you done any study as to what this Lambda should be? How does
> this value vary (if at all) from one board vendor to another ? Is there any
> particular value for Lambda if one is going to use XFX' data with Hspice
> W-elements?

  Pat Zabinski                                     ph: 507-284-5936
  Mayo Foundation                                  fx: 507-284-9171
  200 First Street SW           
  Rochester, MN 55905

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