Ingemar,
We must also remember that nickel is  magnetic as well increasing its 
impedance at high frequencies. That is a reason that many GHz passive 
components do not use a nickel barrier on their terminations.

John maxwell


>That's something else! You did not tell what purpose. It's right, for
>some multiGHZ bands, where low losses are wanted, we don't use nickel
>plating because it's higher resistivity. Some nickel platings can have
>10 times higher losses than Copper and Gold! In these cases, we use just
>copper (no plating at all)if it's possible in environmental point of
>view, or we use tinned copper lines. So, silver over copper is
>theoretically right. And metallurgically spoken, silver on copper has
>been used for centuries. What I don't understand is why add gold. Maybe
>to avoid silver tarnish, if the package is not hermetic. 
>
>Resistivity microOhm x cm :
>
>Electronic solder       17-20
>Pure Tin                9-11
>Electroless nickel      50-100
>Electrolytic nickel      8-10
>Electrolytic Gold        2.5
>Copper lines             1.8
>Electrolytic Silver      1.6
>
>When you look at the above table, you will understand why Silver.
>
>Inge
>  
>

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------