Peter

This is most probably silver sulfide you are seeing. Electrically it is
not harmful, it is even conductive, but a thick deposit can reduce
solderability, unless you are using a very active flux. My advice is
that, if it causes no problem in manufacture, ignore it.

It is caused by the presence of sulfur compounds present as atmospheric
pollution, particularly hydrogen sulfide and sulfur dioxide. These are
present everywhere, but particularly in large cities where
un-desulfurised fuels are available or near any place where coal is
burnt.

Brian

peter lee wrote:
>
> Has anyone seen ceramic components displaying
> brownish/ tarnish after being stored for a period of
> time? These components have silver finish. I do not
> know for sure if it's silver oxide or not.
>
> Could this be atmosphere condition (eg. humidity, air
> circulation) related? It appears to be cosmetic only
> and does not affect the functional requirement.
>
> But how would one go about removing such layer on the
> surface.
>
> Rgds,
> Peter
>
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