The science: Nickel has a Ur which is NOT =3D 1. But good luck finding out what the Ur is since MANY things alter that value. Aubrey Sparkman=20 Enterprise Engineering Signal Integrity Team Dell, Inc.=20 Aubrey_Sparkman@xxxxxxxx=20 (512) 723-3592 -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Clayton Wrobel Sent: Tuesday, February 22, 2005 7:21 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: si-list Digest V5 #82 If you are using ENIG (electroless nickel immersion gold), which I beleive is the most common soft gold finish, it isn't the gold layer you have to worry about, but the nickel. The gold is only 0.05 um in thickness, but the nickel is 3 um according to IPC 2221. I read an article about a year ago, I don't have it handy, that explained the science of why it was so bad. Perhaps somone here remembers it and has access to it. Clayton Wrobel From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of richard moffat Sent: Monday, February 21, 2005 2:23 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Skin Effect, Au, and Cu Hi all This discussion developed in another forum, so I thought I'd throw it into this one to get some more comments. For GHz signals, some people leave off the resist covering and have traces gold-plated instead: "At high enough frequencies (we do 18 GHZ on rogers) the soldermask changes the impedance of the line." I have a bit of trouble with this reasoning, as (non-corroded) copper has less resistivity than gold. =3D20 I would have thought that copper at skin effect freqs would be a better conductor than gold. Is the loss due to the soldermask coating greater than the skin effect loss at very high frequencies? Cheers, Richard ------------------------------------------------------------------ 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 //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 ------------------------------------------------------------------ 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: //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