Thanks Yuriy I have only to add some practical observations which may be obvious to many. Your very useful figures show that right through the frequency range of 1KHz to 1 GHz (and beyond actually), the resistive part outweighs the inductive part by a factor of several thousand or more. Also, the larger permeability of nickel makes the resistive (real) part much larger due to the reduced skin depth compared to copper, much larger than the effect of the increased resistivity alone. [Skin depth is 1/(sqrt(pi*conductivity*frequency*mu*muzero)) from which we see skin depth goes in proportion to the square root of resistivity and inversely as the square root of magnetic permeability.] This means that nickel on its own will show some significant signal loss in the region of roughly 100 MHz into the GHz range. However this is not the practical case. In microstrip, the nickel plating may sit on top of relatively thick copper, with gold (often 1 to 5 micron) on top. In microstrip, due to the skin effect, most of the high frequency current flows on the lower surface of the signal conductor in the copper where the electromagnetic field in the dielectric is strongest. What little current flows in the nickel is further attenuated (but not a great amount) by the skin effect in the gold on top. Therefore the loss is not great and many RF and high-speed digital (or analogue) circuits can be built this way unless the application is highly critical. I am wondering, may I ask, are you the same Mr Shlepnev well-known to many RF engineers for your good work on the method of lines used in Eagleware EMPower? For some people this could be an alternative to the relatively high cost solutions from Ansoft (HFSS) and CST (Microwave Studio), and still provide improved accuracy over quasi-static analysis. Thanks again Geoff Stokes Systems Engineer Zetex Semiconductors plc Zetex Technology Park Chadderton Oldham OL9 9LL UK =20 +44-161-622-4857 www.zetex.com www.zetex.cn =20 =20 -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Yuriy Shlepnev Sent: 10 May 2006 19:41 To: ryan.satrom@xxxxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Microstrip Trace under Nickel Ryan, The internal impedance of a trace or slab is obviously going to be higher for nickel. But, it might have little effect on the total inductance p.u.l. and on the characteristic impedance of a transmission line overall. Though, the resistive losses in such line are going to increase considerably. Also, take a closer look at the imaginary part of the characteristic impedance. Here are internal resistance and inductance p.u.l. for a single rectangular conductor 5 mil by 1.4 mil made of nickel:=20 f=3D1 KHz; R=3D15.16 Ohm/m; L=3D1.6 nHn/m (trace thickness is about 0.2 skin depths - almost DC solution); f=3D1 MHz; R=3D44.31 Ohm/m; L=3D0.627 nHn/m (trace thickness is about 6 skin depths); f=3D1 GHz; R=3D1244 Ohm/m; L=3D0.019 nHn/m (trace thickness is about 209 sk= in depths). Copper conductor resistance and inductance p.u.l. for comparison: f=3D1 KHz; R=3D3.82 Ohm/m; L=3D2.72 fHn/m (DC solution); f=3D1 MHz; R=3D3.82 Ohm/m; L=3D2.71 fHn/m (trace thickness is about 0.5 skin depths); f=3D1 GHz; R=3D26.66 Ohm/m; L=3D0.4 fHn/m (trace thickness is about 17 skin depths); Bulk resistivity of nickel is assumed to be 6.85e-8 Ohm-m, and relative permeability is 600, resistivity of copper 5.8e-8 Ohm-m. It is easy to do the same estimations for a gold-plated nickel trace for instance. Yuriy Shlepnev Simberian Inc.=20 shlepnev@xxxxxxxxxxxxx=20 -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of ryansatrom Sent: Wednesday, May 10, 2006 7:08 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Microstrip Trace under Nickel Hello All- I have been concerned with a microstrip trace traveling under a slab of nickel. There is only a .020" gap between the trace and the nickel. I have done simulations in HFSS to confirm that the Nickel has minimal effect on the impedance. However, it brought up an interesting discussion point that i don't really understand: How does the magnetic properties of a material effect Signal Integrity? I understand that some traces are made out of nickel. But they are typically plated with enough gold that any signal in the MHz and higher will only travel in the gold due to skin effect. Nickel has a relative PERMEABILITY of about 600. Does this effect anything? Thanks for any help on this. Regards Ryan Satrom Everett Charles Technologies ------------------------------------------------------------------ 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 FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at:=20=20=20=20=20 //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 =20=20 ------------------------------------------------------------------ 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 FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at:=20=20=20=20=20 //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 =20=20 _________________________________________________________ Zetex Semiconductors - Solutions for an analog world. http://www.zetex.com http://www.zetex.cn E-MAILS are susceptible to interference. 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