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April 2010

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Tue, 27 Apr 2010 11:31:04 -0400
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TechNet E-Mail Forum <[log in to unmask]>, Werner Engelmaier <[log in to unmask]>
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Werner Engelmaier <[log in to unmask]>
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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]
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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 nĂ©cessaire - Print only if you must

 


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