Hi Ioan,
The fact that the jig-saw puzzle doesn't go back together correctly leads me in the direction that the majority of this fracture may have occurred during soldering cool down. Otherwise it is hard to explain all of the (what would be) local plastic deformation after the stress has been (locally) relieved by the fracture. Look at the top of the heal side especially.
This is also consistent with the apparent lack of fatigue banding.
The defect may well become (electrically) obvious as a result of fatigue to the small areas that are soldered. Sequential grinding through the section might help.
Also, fuzzily I'd say that the fracture is too smooth, and has too much z-dimension to have occurred at "low" temp.
Take it for what it's worth; you know the part's history.
Chris
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Tuesday, April 27, 2010 11:33 AM
To: [log in to unmask]
Subject: Re: [TN] Failure fatigue photos
Hi Ioan,
I am with Vladimi—most likely started as overload continued as fatigue.
Werner
-----Original Message-----
From: Ioan Tempea <[log in to unmask]>
To: [log in to unmask]
Sent: Tue, Apr 27, 2010 9:23 am
Subject: Re: [TN] Failure fatigue photos
Victor,
Zero rework, part is socket http://www.tycoelectronics.com/catalog/pn/en/5-316365-0?RQPN=5-316365-0
, the IMC thickness has not been measured
And thank you Guenter, the lack of compliancy of this component has been
mentioned during design review. I'm so proud of myself...
Best regards,
Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer
T | 450.967.7100 ext.244
E | [log in to unmask]
W | www.digico.cc
N'imprimer que si nécessaire - Print only if you must
-----Message d'origine-----
De : Victor Hernandez [mailto:[log in to unmask]]
Envoyé : April-27-10 9:12 AM
À : [log in to unmask]
Objet : Re: [TN] Failure fatigue photos
What type of component is this and what is the thickness of the IMC layer, any
associated rework on the device.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ioan Tempea
Sent: Tuesday, April 27, 2010 8:00 AM
To: [log in to unmask]
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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