Copper migration due to Kirkendall Effect--- one of the lovely advantages of Pb-free solder?
Can't wait to hear from the experts-- Paul Read, Laura Turbini, Brian Ellis, Bob Landman.
Did I guess right, guys?



________________________________
 From: "Wenger, George M. [Contractor]" <[log in to unmask]>
To: [log in to unmask] 
Sent: Tuesday, December 17, 2013 2:28 PM
Subject: Re: [TN] High Temperature Solder Migration/Creep
 

Chris,

Send Steve a photo of the migration and you might get some good advice

Regards,
George
George M. Wenger
Failure Signature & Characterization Lab LLC
609 Cokesbury Road, High Bridge, NJ 08829
(908) 638-8771 Home (732) 309-8964 Mobile
E-mail: [log in to unmask]
[log in to unmask]

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Chris Mahanna
Sent: Tuesday, December 17, 2013 5:15 PM
To: [log in to unmask]
Subject: [TN] High Temperature Solder Migration/Creep

We have an FA project that appears to be migration of 10Sn/88Pb/2Ag solder across a 0.024 inch antipad to ground plane on the surface of the polyimide board.
It is not dendritic in appearance.  Looks more like Ag creep corrosion.
Failure occurred under dry heat testing at our lab.
Bias is 48 volts
The test temperatures are 200-250C over 12 weeks Ran at atmosphere, no added moisture The failure coincides with the loss of solder mask adhesion, under which the metal can be seen...sort of, as mask is just about charcoal now.
There is also some evidence of flux residue, which would likely be very corrosive, but don't we need moisture?

Literature searches get swamped by Ag migration/creep.  Anyone got an idea?  Keywords?  Tests for differential diagnosis.

Chris

Chris Mahanna
Robisan Lab





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