Werner, pic 1 and 2, what I call good joints, are several times stronger 
than ther "rotten" ones. These later crack , and the leads separate from the 
pad clearly. Lifted is too strong a word, but they are disconnected by as 
much as one third the lead thickness. My customer has spent months to find 
out why.
Inge


----- Original Message ----- 
From: "Werner Engelmaier" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, May 04, 2007 12:34 PM
Subject: Re: [TN] Metalurgists, need assistance


Hi Ingemar,
Looking at pic1, I would not call what I am seeing a "good joint"—it is an
interfacial separation, and thus the interface [whatever it is] is the weak. 
and
unpredictable, link.
Pic3 looks more like a ductile separation—see the directionality of the
cup-like 'voids', in the solder [easy to confirm if the composition is the 
same on
both fracture surfaces.] Pic4 looks like the Ni layer is showing 
through—>the
solder properly wetted in some areas, but not all.
Sn spheres—beats me.



Werner



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