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August 2007

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Subject:
From:
"Whittaker, Dewey (EHCOE)" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Whittaker, Dewey (EHCOE)
Date:
Fri, 31 Aug 2007 08:16:09 -0700
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It was an oxidant, so hopefully not tarnishable.

Dewey

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Eric CHRISTISON
Sent: Friday, August 31, 2007 7:55 AM
To: [log in to unmask]
Subject: Re: [TN] Plasma "oxidation"

Dave,

Can I just pick you up on your assertion that Silver oxide is as 
conductive as Silver. As I'm very bored this afternoon I did a quick web

search and came across the following:

"First let's begin with some resistivities for the materials being 
discussed. Resistivity is the opposite of conductivity so the smaller 
the number, the less intrinsic resistance (greater conductivity) it 
possesses.

Copper: 1.7 X 10^-8 ohm-m
Silver: 1.6 X 10^-8 ohms-m
Gold: 2.4 X 10^-8 ohms-m
Silver Sulfide: 1.5 to 2.0 X 10^-3 ohm-m
Silver Oxide: 1 x 10^+9 ohms-m    "

So this guy thinks silver oxide is 17 orders of magnitude less 
conductive than silver. Did he just mix up a plus sign with a minus
sign?

Regards,




Hernefjord Ingemar wrote:
> Furthermore, it seems as oxidation MUST occur before silver migrates,
> i.e. silver ions have to be created. And as such
> humidity>corrosion>oxidation is a perfect way. So, instead of
> inhibitation of silver migration, we have enhanced migration. Please,
> don't laugh, someone can begin to ask what kind of processing
engineers
> we have..he-he
> /Inge 
>
> -----Original Message-----
> From: Hernefjord Ingemar 
> Sent: den 31 augusti 2007 14:55
> To: 'TechNet E-Mail Forum'; [log in to unmask]
> Subject: RE: [TN] Plasma "oxidation"
>
> Hi Dave!
> In fact, that is what I wanted to hear! Ditto Bev.
> If my decision is anchored in the rockwell&rim cliffs, that's enough.
> Thanks both. Alea acta est...
> /Inge
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
> Sent: den 31 augusti 2007 14:08
> To: [log in to unmask]
> Subject: Re: [TN] Plasma "oxidation"
>
> 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
> [log in to unmask]
>
>
>
>
> Hernefjord Ingemar <[log in to unmask]>
> Sent by: TechNet <[log in to unmask]>
> 08/31/2007 03:52 AM
> Please respond to
> TechNet E-Mail Forum <[log in to unmask]>; Please respond to Hernefjord
> Ingemar <[log in to unmask]>
>
>
> To
> [log in to unmask]
> cc
>
> Subject
> [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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>   

-- 
Eric Christison Msc
Mechanical Engineer
Home Personal, Communication Sector
Imaging Division

STMicroelectronics (R&D) Ltd
33 Pinkhill
Edinburgh EH12 7BF
United Kingdom

Tel:	+44 (0)131 336 6165
Fax:	+ 44 (0)131 336 6001

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