Hi Inge! Apparently, the lack of material science knowledge can go a long 
way. Just because a metal oxidizes, doesn't necessarily mean it can't play 
a role in electrochemical migration. And silver oxide is as conductive as 
silver metal (silver is one of those metals with some pretty wild 
properties). Sorry, I don't buy the "plasma oxidation" process validity.

Dave Hillman
Rockwell Collins
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Hernefjord Ingemar <[log in to unmask]> 
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08/31/2007 03:52 AM
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[TN] Plasma "oxidation"






 
Yup. Strange title. I've been asked about a strange process, which one
was introduced without my knowledge, and I'm going to throw it out. But
I thought of consulting TN before. This is the case:

LTCC substrates are silver epoxy dispensed for chip mounting. In order
to avoid risk for silver migration, a guy invented plasma "oxidation",
i.e. he use a plasma cleaner, runs Argon with 6% Oxygen for a couple of
minutes on mounted substrates. The silver epoxy dots become blackish
because of oxidation, and oxidized epoxy is meant to minimize risk for
silver migration. The oxide is of course just nanometer thick. The guy
worked at a wafer manufacturing plant and had experience of cleaning
procedures.

I mean that this process is nonsense. If humidity gets in and condense
on the substrate, and if the electric field is high enough, and if there
are salts or contaminations, there is still enough silver to start
migration. Oxidation of the silver dot's surface is meaningless. Anyone
heard of such a strange process? Plasma operation on mounted LTCC
substrates is foreign to me, I want it out.

TrikeMan?

Inge

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