Hi, John
Don't know if you are the same John Anselmo I used to work with at ADC
Telecommunications?
Anyway, this varistor typically has a voltage present which changes as
the current increases/decreases dependant on temperature. If any flux
from the connector soldering operation, or for that matter any moisture
is present under the varistor, it greatly affects the performance of
that particular component.
You may wish to try and direct a de-ionized water spray directly at an
angle to get as much volume under the varistor as possible, followed by
a 15 minute bake at 105 deg. C to get the board clean and dry. Try this
on just one or two failed units first, and then re-test without
reworking. If this fixes the issue, your suspicions will be confirmed.
The other option is to mask off the area prior to the connector
soldering to prevent the flux from getting under there.
It may be flux remaining from the solder paste as well. I would start by
ensuring the board under the part is clean and dry and re-testing. If
that does not fix the issue, then you may have a problem with the test
heating up the part and getting a false fail. But based on the fact that
you can hand solder the part or re-solder the part and then it passes
test, my guess is you are removing the moisture under the part when you
do that, and then that portion of the circuit operates as it should
during subsequent testing, resulting in the assembly passing test.
R. Dean Stadem
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Anselmo
Sent: Tuesday, July 29, 2008 4:09 PM
To: [log in to unmask]
Subject: [TN] Ceramic Varistor Test Failures
Dear All,
We have been seeing an increase in test failures of the ceramic varistor
(AVX P/N VC060314A300) when these components are near a connector that
we hand solder.
I suspect it is contamination from the flux used for hand solder. We
fix the test failure by resoldering the varistor, and all is well at
retest.
We do a water wash after hand solder, but still see a 20% to 40% test
failure rate. Has anyone experienced this before? Waht was done to fix
the problem?
Thanks in advance for the help.
John Anselmo
Manufacturing Engineer
S&K Electronics, Inc.
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