Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!njin!princeton!siemens!demon!fwb
From: fwb@demon.siemens.com (Frederic W. Brehm)
Newsgroups: sci.electronics
Subject: Re: Batty monitors and cheap video
Message-ID: <16144@siemens.siemens.com>
Date: 3 Oct 89 19:03:18 GMT
References: <1989Sep28.122217.26867@watcsc.waterloo.edu> <57732@psuecl.bitnet> <3863@blake.acs.washington.edu> <57950@psuecl.bitnet> <1989Oct2.011535.23529@utzoo.uucp>
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Reply-To: fwb@demon.UUCP (Frederic W. Brehm)
Organization: Siemens Corporate Research
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henry@utzoo.uucp (Henry Spencer) writes:
>and that exposure to the air was not, in the short run at least, a problem.
>For the RAMs of the time, anyway.

Most of the area of an IC is covered by a thick (in IC terms) glass
passivation layer.  This layer is a silicate glass and today also contains
a few atoms of other elements to increase its effectiveness.  The only part
that is not covered by the passivation layer is the bond pads.  These bond
pads are usually made of thick aluminum to which gold (usually) wire is
welded.  The other end of the wire is welded to a lead frame made of
electroplated copper, I think (my knowledge gives out around this part of
the device).

All this means that the most likely problem area is bond wires coming loose
because of atmospheric corrosion of the bond pad or maybe the lead frame.
This won't happen overnight.  It will probably take longer than the life of
your experimental (it is experimental, isn't it?)  system.

Fred
--
Frederic W. Brehm	Siemens Corporate Research	Princeton, NJ
fwb@demon.siemens.com	-or-	princeton!siemens!demon!fwb