Bob AZ wrote:

"David Farber" wrote:
I occasionally see this residue where the components are soldered. Is this
flux? Something else?

David

Conformal coating. Probably used for moisture protection among other
things. Like a varnish. Also some coatings were epoxy types.

It is NOT conformal coating. Besides you'll probably only ever see that on
high-end industrial or military gear.

Graham