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December 2013

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From:
Vladimir <[log in to unmask]>
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Date:
Tue, 17 Dec 2013 22:21:27 +0000
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Hi Chris,

First of all have you established what kind of metal you see? There is no free Ag in a Pb-free solder?



Best regards,

Vladimir  Igoshev, Ph.D.                       

SENTEC Testing Laboratory Inc.
11 Canadian Road, Unit 7.
Scarborough, ON M1R 5G1
Tel: (647) 495-8727
Cell: (416) 899-1882
E-mail: [log in to unmask]
www.sentec.ca

-----Original Message-----
From: Chris Mahanna <[log in to unmask]>
Sender: TechNet <[log in to unmask]>
Date: Tue, 17 Dec 2013 22:14:46 
To: <[log in to unmask]>
Reply-To: TechNet E-Mail Forum <[log in to unmask]>, Chris Mahanna
	<[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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