Hi Ken - I suggest taking apart one of the capacitors in the "as received" 
condition and in the "as wave soldered" condition - if there is 
metallization missing then you would have proof that the cleaning process 
is not the root cause.

Dave Hillman
Rockwell Collins
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"Bloomquist, Ken" <[log in to unmask]> 
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04/27/2007 10:28 AM
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Re: [TN] Metalized Poly Caps






Thanks Steve for putting up the pictures, now here's the situation.

We are having a higher than expected failure rate on these capacitors.
They are supposed to be .22 mfd and are testing at around .12 mfd after
assembly.

The manufacturer is saying that it is because we are getting water
inside of them during the cleaning process. A possible cause is that we
are breaking the "seal" on the end or possibly putting them into the
cleaning process while they are still hot from the wave solder.

We've built assemblies using these types of parts for decades and
haven't seen this sort of problem in the past.

We pulled a couple of these caps apart and that is what the photos are
showing. It appears that the metallization is missing on part of the
film. They say that this is due to the wash process. The wash is an
inline wash system using DI water, no saponifier. The contractor got a
new wash system a few months ago but it's a typical inline wash using
the same temps and speeds that they used on the old system.

Have any of you been seeing problems with these caps lately or have any
insight into this problem? See the photos below.

http://stevezeva.homestead.com/files/cap1.jpg 

http://stevezeva.homestead.com/files/cap2.jpg 

Thanks,

KennyB

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