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I tried to add photos showing this better, but the photos did not go on the gallery.
Werner
-----Original Message-----
From: David D. Hillman <[log in to unmask]>
To: [log in to unmask]
Sent: Tue, Apr 27, 2010 9:33 am
Subject: Re: [TN] Failure fatigue photos
Hi Ioan - Do you have any optical photos of the fracture? Thermal cycle
fatigue failures typically develop "banding (aka microstructure
coarsening)" in the solder joint shear zone. The solder joint
microstructure evolves into distinct grains of tin and lead which shows up
better in optical photos. The fracture in your photos appears to be
fatigue but its hard to see the microstructure in your photos. I added a
photo of what typical thermal cycle induced SnPb coarsening looks like on
the IPC Photo Gallery.
http://ipc-technet.groupsite.com/gallery/13118
Dave Hillman
Rockwell Collins
[log in to unmask]
Ioan Tempea <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
04/27/2010 07:59 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Ioan Tempea <[log in to unmask]>
To
[log in to unmask]
cc
Subject
[TN] Failure fatigue photos
Dear Technos,
It looks like, for the first time, I have the occasion to look at fatigue
failed joints. The lab analysis we've got states this, but does not
abounds in details.
One of the conclusions is "the crack propagates around harder Sn shearing
the softer Pb, but the Sn and Pb zones seem fairly large for regular
solder structure". Citing from Klein Wassink "During cyclic plastic
deformation the microstructure inside the material changes in the zones
where the deformation is concentrated. This leads to local grain
growth..."
I have deposited the micro-sections on the IPCs website
http://ipc-technet.groupsite.com/gallery/13116
I would need your expert opinion regarding the failure. Is this fatigue?
The big pure Sn and pure Pb areas, are they normal size for fatigued
joints?
Thanks,
Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer
T | 450.967.7100 ext.244
E | [log in to unmask] <mailto:[log in to unmask]>
W | www.digico.cc <http://www.digico.cc/>
N'imprimer que si nécessaire - Print only if you must
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