Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!apple!vsi1!daver!mips!vaso
From: vaso@mips.COM (Vaso Bovan)
Newsgroups: sci.electronics
Subject: Re: Which is a better conductor: gold or silver?
Message-ID: <23818@quacky.mips.COM>
Date: 22 Jul 89 08:55:01 GMT
References: <14172@swan.ulowell.edu> <19729@louie.udel.EDU> <20483@cup.portal.com> <1378@nosc.NOSC.MIL>
Reply-To: vaso@mips.COM (Vaso Bovan)
Organization: MIPS Computer Systems, Sunnyvale, CA
Lines: 17

In article <1378@nosc.NOSC.MIL> koziarz@halibut.nosc.mil.UUCP (Walter A. Koziarz) writes:
>Gee, I thought the problem with plastic packages from military standpoint
>was hermeticity.  But, I only share office space with those who write the
>specs.  Agreed on the gold-wire vs aluminum wire portion.
>
>Walt K.

Does the military still consider that ceramic/cerdip packages also have better
thermal characteristics, in general. Even with copper lead frames, a problem
with plastic packages is that the plastic is (relatively) a heat insulator,
so that little heat gets out the top of the package. Most heat must flow 
through the leads. Thus, fan cooling is less effective with plastic packages.

With this in mind, many companies have a rule of thumb which says that junction
temperatures determine whether plastic or ceramic/cerdip is used. My rule of
thumb is 125C worst case junction temperature, well below the glass transition
temperature. Is this a reasonable rule of thumb in ROME's opinion ?