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January 2009

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From:
Vladimir Igoshev <[log in to unmask]>
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Date:
Tue, 27 Jan 2009 17:40:00 +0000
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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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