How long do you allow the caps to cool before testing them on ATE.  We
have found on some caps that it takes as long as 8 hours for them to
cool down and pass.

In addition, we have found that on electrolytic caps the fluid in the
wash gets into the caps and makes them fail.

Just two suggestions.

Max Bernhardt
Woodward Governor Co.
970-962-7376
 ----------
From: Dhawan, Ashok        CA-WINPO2
To: IPC TechNet
Subject: Bowing off Tantulam Caps
Date: Monday, June 09, 1997 9:42AM



We are facing acute problem on blowing off caps . Specifically, these
caps
are tantulam caps with high capacitance range of 220 MICROFARADS , rated
at

10 voltage and tolerance in capacitance value is 20%.We have tried more
than
one vendor: one vendor was worse than the present one--however failures
are

always there.

These caps are processed ( assembled) alongwith other tantulum caps and
 usually go through two heat cycles: first one on gluecure  and second
one
at wave. The standards (temp profiles) followed at reflow and wave are
as
per process guidelines .

These caps when tested after wave pass 100% at 5v test. Fails 20 to 25%
for

voltages above 7v . Dwell between wave and ATE does not matter much.
Tried
with and without wash -- it does not make significant difference.

It is expected that the cap should pass 100% at rated voltage. Clearly
there
is deterioration after assembly process. we ran DOE and observed caps
failing after wave. however our wave process does not seem to out of
control.

any one having experience on such a behaviour of Tantulum Caps -- we
will
appreciate your technical advise on this problem as we are running out
of
ideas and thinking to change process  to bypass wave solder operation
altogether.But that is not easy to do in short time.

Please send your advise on this mail or email directly to me.

[log in to unmask]
Tel: 204-257-9199




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