There may be one way to reveal microcracks in ceramic caps. I have not
practised that myself. We had severe problems many years ago, and had
some help from Yves Ousten, french scientist. He developed a method to
indicate and follow the development of microcracks in ceramic
capacitors. Rather complex method, I don't think you will pay for the
instruments that are necessary, like HP spectrum analyser, frequency
generators, calibrated RF cables and fixtures. Maybe you can by these
instruments on the BID market.
The principle is based on ceramic material's ferromagnetic/piezoelectric
properties. By means of a selected RF signal, you create a resonance
circuit which one is extremly sensitive to dielectric changes. You
create a reference capacitor model, and from this one, you can indicate
any deviations caused by microcracks. I have lost the telephone number
and adress to Yves Ousten, maybe you can find him yourself. Anyway, his
work was named as follows:
Yves Ousten: Nondestructive detection and localization of defects in
multilayer cer chip caps using electromechanical resonances.
If you are interested, I can dig in my stack of reports and see if
Yves's paper is still there....
Good Luck
Inge
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall
Sent: den 6 mars 2007 01:22
To: [log in to unmask]
Subject: [TN] Chip Capacitor Reliability Question
Everyone,
I'm trying to find out a couple of things...
First of all, has anyone conducted any studies on the probability of a
fractured chip capacitor moving from an open to a shorted condition?
Secondly, if an open condition cannot be detected during electrical
testing, and the unit has been sealed with adhesive around the enclosure
(unable to open without having to scrap), is there a method available to
check if the component has seen any damage? We have a Feinfocus X-ray
unit, and the results we've been able to obtain have not been
encouraging. The board is in an aluminum and zinc frame and has been
conformally coated with acrylic material.
Thanks in advance for your help!
Leland Woodall
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