Hey y'all:

We have seen some problems on SMD boards using 0805 package Rs and Cs.
These boards have soldermask and are silicone-coated twice.  They are used
in machine control products (machines such as bulldozers, motor graders,
drag scrapers), and so moisture presents a constant problem, as well as
temperature extremes (-20C to +70C).

We are having product failures after the product has been installed and
functioned normally for a few months.  A typical example would be a 4.75K
resistor on a failed unit would measure about 200 ohms after product
failure.  We take the part off; R between pads is in the meg-ohms (what we
expect).  Replace the part, problem goes away.

Does anyone know of a service that would help us find out what the probable
problem is, and maybe the cause and solution?  We think it might be
contamination left over from assembly process (vendor doesn't think so)
that moisture may affect after time in field.

Immense thanks.

Roger Stoops
Spectra Precision Inc.

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