An overwhelming counterpoint to this rumor concerning immersion silver
is the very favorable experience at Lucent. A complete report was
presented in a Circuitree article by Bob Furrow, George Wenger and
others. A great deal of reliability data was included; all of it was
positive.
Lee
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Reuven ROKAH
Sent: Sunday, November 16, 2003 6:13 AM
To: [log in to unmask]
Subject: [LF] Silver finish out Immersion Tin in???
Hi All,
During my visit in Europe PCB shop and in prudoctronica, I was informed
that Silver finish was rejected as an alternative by one of the big
international telecom companies and also there is a whiskers free
process
in Immersion Tin process.
Does anyone have backup to the above information?
Best Regards
ROKAH Reuven
MA/NY DDave
<[log in to unmask] To: [log in to unmask]
M> cc:
Sent by: Subject: Re: [LF]
Potential Problems with Mold Compound
Leadfree
<[log in to unmask]
G>
21/09/2003 17:16
Please respond
to "(Leadfree
Electronics
Assembly
Forum)"; Please
respond to MA/NY
DDave
Hi Brian, Werner, TI-Doug, and IPC LF Listservers,
Well I was hoping that by today someone would give a link so that I
would
know for the Maxim article first listed in this series if I had a leg to
stand on, or if Brian was correct that the Ag migration problem was
inside
the package.
When I read the article I looked at some of the names involved with the
package in question and I initially felt it couldn't be an internal
package
problem.
So anyway two articles and I am gone till later.
http://www.ul.com/pwb/
- A UL article kind of supporting me that my position may have value.
After I sent my other scenario I realized I forgot to add higher Ag
concentration in the solder, high voltage etc.
http://www.circuitree.com/ct/cda/articleinformation/coverstory/bnpcovers
tory
item/0,2135,86472,00.html
- a Circuitree "Tin Man" article on Surface finishes that tends
to agree with Brian
<=== copied from the above Circuitree article
"One more high-profile issue with respect to electrical reliability:
electrochemical migration. Questions of electrochemical migration were
raised with the recent revival of silver as a PCB surface finish. By
now,
many are familiar with the stories decades ago of dendrite formation on
thick, electrolytic silver used in high voltage switching apparatus.
Acutely aware of this experience, the industry has exhaustively tested
the
new immersion silver finishes. Hundreds of studies conducted by the
chemical suppliers, fabricators, assemblers, OEMs, and independent labs
have tested the heck out of the new finishes. Telcordia's GR-78-CORE and
IPC's TM-6502.6.14.1 detail the procedures. Even with such a reference
list
of migration studies, some engineers remain reluctant to specify silver.
The added burden of a UL test specific to high-voltage devices may have
slowed silver's penetration of the surface finish market. UL recently
provided some relief with documentation changes."
<=== copied from the above Circuitree article
YiEngr, MA/NY DDave
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