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 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu