Ernie,
1.try AVX, they are very generous giving adequate information, know they have something about deltaT cases.
http://www.avxcorp.com/techinfo_doclisting.asp?Category=Ceramic+Capacitors
2. In fact we are just now examining cercaps with internal microcracks . Don't think any cracks will 'enlarge' after temp change exposure, because the BaT/Al2O3/MgO etc is sintered at a very high temperature, and has nill ductility. A possibility is maybe that a crack can continue until the whole cap falls apart, but I've never seen it.
You can decide cracks indirectly by means of sophisticated RF measurement setups. A guy in France, professor Ousten at l'Institute Polytechnique in Paris, spent months together with cap manufacturers, to arrange such measurements. Maybe someone at TN has the adress to him, he ought to have a lot to learn you.
But, before doing so, read John Maxwell's article from his work at AVX. John is a guru on caps, if you didn't know that. He'll probably see these lines. If not, I may have some Maxwell reports to send you offline. No promise, too much in my puter.
http://www.avxcorp.com/docs/techinfo/cracks.pdf
Good Luck
Ingemar Hernefjord
Ericsson Microwave Systems
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Ernie Fung
Sent: den 8 september 2004 10:01
To: [log in to unmask]
Subject: [TN] Thermal shock of Multi layer ceramics capacitor
All,
Some questions about multi layer ceramics capacitor (MLCC):
1. Any specification for temperature ramp rate, that is the rate of temp
raise or reduce, of MLCC?
2. When mechanical stress is applied to the MLCC, fine crack may induce.
However, this may not be checked thru visual inspection or capacitance
change. So, is it a good idea to use thermal shock to enlarge this kind of
fine crack so that the failure is detectable?
Thanks for any suggestion.
Rgds,
Ernie
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