Steve,

When you say "massive failures", are you talking electrical or just the
delamination problem?

Some of our military products use PPS caps, and we see delamination after
going through water wash.  There are many layers of the plastic film to
protect the dielectric layers underneath.  We had similar concerns about
the delam so we have run 2000 temperature cycles, from -54C to +125C on 200
of  various package sizes of these parts with 50% of the rated voltage
applied, postcoated and unpostcoated, without any failures or increase in
leakage current.  We have since allowed for delamination of these parts in
our component specification.

These are great capacitors electrically, that can have higher capacitance
values without the leakage issues of ceramic caps.

Jim Carlson
Rockwell Collins Reliability Engineer




[log in to unmask]@ipc.org> on 05/23/2002 08:51:58 PM

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Subject:    [TN] Film Capacitors...geeze!


Hi all!

Just started building an assembly that calls out film capacitors to be used
in 64-locations on the board. Processed the assemblies in a typical manner
as
one would for most SMT assemblies, and experienced massive failures of
these
caps. They are PPS films. Unfortunately, this has been a first for
me...never
had to process these caps before. They are delaminating...the layers of
film
are flaking off from the caps.

Can anybody tell me how I should assemble these devils? Went to the web
page
of the manufacturer, and they have a recommended reflow profile that is
2-mins, 45-seconds long...to me, that violates the specifactions that
Kester
recommends for their paste to perform...

Is using SMT film caps a bad idea? ( I think I know the answer, but I just
want a confirming opinion...)

-Steve Gregory-

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