That's the post I've been waiting for :-)
Vladimir
SENTEC
11 Canadian Road, Unit 7.
Scarborough, ON M1R 5G1
Tel: (416) 899-1882
Fax: (905) 882-8812
www.sentec.ca
-----Original Message-----
From: "David D. Hillman" <[log in to unmask]>
Date: Tue, 27 Jan 2009 10:45:30
To: <[log in to unmask]>
Subject: Re: [TN] SnPbAg solder and Immersion Silver PCBs
Hi Werner! I don't believe that there is an silver embrittlement issue
with the use of ImAg PCBs. Rockwell Collins has been using ImAg PCBs for
over 10 years with no issues of silver embrittlement. We have also
conducted several lead-free assembly studies using the SAC305 solder alloy
and have found no issue with silver embrittlement. And, the IPC 4-14
Plating committee did not find any silver embrittlement issues with a test
assembly that was excessively silver loaded - ImAg PCB finish and silver
in the solder paste - and we did not find any evidence of silver
embrittlement. The 4-14 committee will be publishing that study as an IPC
Technical Report in the near future after completing the necessary
committee reviews. As a general rule of thumb, I think silver
embrittlement is on a much lower risk register than gold embrittlement.
However, I have seen the PLCC study data and it indeed was a case of
silver embrittlement so I think that each situation needs to be understood
to avoid having an embrittlement issue.
Dave Hillman
Rockwell Collins
[log in to unmask]
Werner engelmaier <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
01/27/2009 10:30 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Werner engelmaier <[log in to unmask]>
To
[log in to unmask]
cc
Subject
Re: [TN] SnPbAg solder and Immersion Silver PCBs
Hi Kevin,
That "thin (?) silver finishes...prevent the dissolution of the component
lead into the solder joint" is a Red Herring.
All you may be getting is AG-embrittlement which is just as bad as
Au-embrittlement. It was just such 'silver finishes' on TI PLCCs that
caused those PLCCs to fall off PCBs during bed-of-nail testing in 1982 at
IBM-Austin and resulted in the formationof the IEEE Compliant Lead Task
Force.
Also, how would an Ag-finish prevent the formation of IMCs with the lead
metal?
Werner
-----Original Message-----
From: Kevin Glidden <[log in to unmask]>
To: [log in to unmask]
Sent: Tue, 27 Jan 2009 8:35 am
Subject: [TN] SnPbAg solder and Immersion Silver PCBs
Morning all,
Question today about SnPbAg solder. We have always used Sn63Pb37 solder
alloy for all products, with exception of some high temp solders for
special
cases. The lion's share of our PCBs are ImAg finish, 5 to 12
micro-inches,
per IPC-4553. In reading about SnPbAg solder, it appears to be
recommended
for use on SMT components with thin (?) silver finishes. This is to
prevent
the dissolution of the component lead into the solder joint. Drawbacks
appear to be only that the joint is not as shiny and reduced mobility of
the
solder. Is it also considered good practive to use an SnPbAg alloy for
immersion silver PCBs for the same reasons? Any tech articles available
on
this?
Thanks (again!)
Kevin Glidden
Manufacturing Engineer
Luminescent Systems Inc.
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