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.

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to 
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to 
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 
for 
additional information, or contact Keach Sasamori at [log in to unmask] or 
847-615-7100 ext.2815
-----------------------------------------------------



 


---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to 
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to 
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 
for additional information, or contact Keach Sasamori at [log in to unmask] or 
847-615-7100 ext.2815
-----------------------------------------------------


---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------