Nicole,
IMHO - since the electrode layers are printed upon the dielectric layers,
some degree of warpage (as long as the dielectric is intact) should be
permissible. Ditto for electrode alignment - as long as the electrode
makes electrical contact with the end terminal, for a general purpose, low
frequency cap - why should it matter (as long as the electrodes are not
hanging out the side of the body, that is)? As far as varying electrode
lengths - isn't that how they create differing values?
With the extremely thin tape layers the cap guys are using, it would seem
that it would be difficult to X-ray a profile view of the cap being able to
distinguish the individual plates - yet have enough energy to go all the way
though the component. Send some sample to the x-ray manufacturers. They
should be willing to do a few parts for free, if they think they may be able
to sell you a system.
Check out CR Technology at www.crtechnology.com as an example. (there are
many other good suppliers out there, I just do not have them at my
fingertips, at the moment).
Acoustically, you could easily detect delaminations (air gaps) within the
body of the capacitor, but imaging the individual plates can be really
tricky. Under some conditions it is do-able, but I have found that when
more than a couple plates deep I got shadowing (or fringing) of the
underlying plates caused by the sound being distorted by plates above. I
used Sonix equipment. Sonoscan also makes good acoustic microimaging
equipment. Again, hit them up for a freebee.
Hope this helps somewhat.
Steve Creswick - Gentex Corp
-----Original Message-----
From: Nicole Landreville [mailto:[log in to unmask]]
Sent: Tuesday, June 26, 2001 11:37 AM
To: [log in to unmask]
Subject: [TN] Multilayer Ceramic Chip Capacitors Quality
Bonjour a tous!
We have found some internal manufacturing defects in some Multilayers
Ceramic Chip Capacitors. After discovering reliability problems with these
types of capacitors (extreme leakage increasing with time) we have decided
to perform a construction analysis. The type of issues found relates to
misalignment of electrodes, electrode layers varying in length, warping of
dielectric plates. Unfortunately, to be able to find these manufacturing
defect we had to do a caps microsection. Now that we know that these
capacitor are prone to manufacturing defects, I would like to know if there
is any way (processes, low cost equipment or service house) to detect these
defects without scraping or damaging the caps? Originally I was thinking
that these could be X-rayed but I am not sure that the resolution would be
sharp enough. I would really appreciate if anyone could help me with this
important problem.
Thank you and good day!
Nicole Landreville, Eng.
Electrical & Supplier QC Engineer
World Heart Corporation
Ottawa, Ontario
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