It's the other way round.
Kovar, Fernico  and other interestingly named alloys were developed to have as good a TEC match as possible  for/by the mil aerospace people.
Alloy 42 is a later more commercial alternative without the expensive cobalt for a nearly as good result.
 

Regards

Mike

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Rudy Sedlak
Sent: Thursday, August 08, 2002 3:36 AM
To: [log in to unmask]
Subject: Re: [TN] Leadframe material

Phil:

Probably Copper is the most popular/common, for plastic packages.

When you use ceramic packages, the coefficient of expansion of Copper causes problems, so, I think most folks use Alloy 42, so called because it is 42% Nickle, and the rest Iron.  Kovar is quite similar to Alloy 42, with some added Cobalt.

What advantages the Cobalt brings, I am uncertain.

Rudy Sedlak
RD Chemical Company --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------
--------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------