Dave,

 

I'm taking notes, being just a rookie in the field!  A lab analysis is good, but a lab analysis where you know what to ask for is way better. Big optical zoom, checked.

You have no idea how much I would appreciate a check list for things to do and ask for when doing failure analysis; I would even jump to save you from the sharks in that Graham Collins picture. 

 

I have found something in the report, see addition to http://ipc-technet.groupsite.com/gallery/13116 but I believe it is not comprehensive enough.

 

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

 

De : [log in to unmask] [mailto:[log in to unmask]] 
Envoyé : April-27-10 9:33 AM
À : TechNet E-Mail Forum; Ioan Tempea
Cc : [log in to unmask]
Objet : 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 
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Ioan Tempea <[log in to unmask]> 
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04/27/2010 07:59 AM 

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[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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