[SI-LIST] spice modeling for organic build-up substrates

  • From: "Javier DeLaCruz" <jdelacruz@xxxxxxxxxxxx>
  • To: "Si-List (E-mail)" <si-list@xxxxxxxxxxxxx>
  • Date: Thu, 16 Jan 2003 15:00:44 -0500

All,
        I'm looking for some help in modeling organic build-up package =
substrates in order to output spice models, etc.  The trick here is that =
in order attain a 100 ohm differential pair, the common mode impedance =
must be designed to a 85-88 ohm target.  During manufacture, the traces =
are roughened which reduces the height, and more importantly, the width =
of the traces.  This reduction in capacitance to ground, and the =
increase in both resistance and inductance causes the lines to increase =
in impedance about 15%.  This means using the extraction routines in =
software such as Cadence APD/APE or Ansoft SIwave/Q3D would generate =
incorrect spice models since they were designed (in CAD) to have an =
85-88 ohm impedance. =20
        Does anyone have an idea of how to generate a negative offset in height 
=
and width of traces in any of these programs, or any other popular =
package design/analysis package?  I'd like to avoid having to generate =
two designs for each package substrate.  One would be for the =
fabrication masks, and the other would represent reality.

Thanks,
Javier DeLaCruz

Sr. Principal Packaging Engineer
eSilicon Corporation
890 Mountain Avenue
Murray Hill, NJ 07974
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