Cap shorting Problem????

Failure Analysis Expert,

In a low voltage high impedance circuit we are finding ~700ohm short
across a .1uF capacitor in a low voltage, high impedance DC circuit.  We
find that over time the short develops, but a thermal cycle (touch-up) of
the location causes the problem to disappear.

We tried using X-ray of the cap's but proven inconclusive due to the density
of the ceramic cap body and the suspected low mass of the short.  Our initial
impression is that dendritic growth is occurring, and over time the two pads
short through this growth but we were not able to find any dendritic growth
(?) using microscope (30X). Is dendritic growth possible through epoxy which
porous in nature? This cap is glued on the bottom side using epoxy and goes
through wave soldering operation.

We are looking for any answer cum suggestion from anyone who has seen this
kind of problem were able to resolve.

Thanking you in advance.

Re,
Ken Patel

______________________________________________________
Ken Patel                       Phone:  (408) 490-6804
575 Cottonwood Dr.              Fax:    (408) 490-6859
Milpitas, CA 95035              Beeper: (888) 769-1808

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