To Richard Haynes

Hi Richard,

We have been having intermittent trouble with (what most people call) pits
in electrolytic Cu plating.  The location of these pits is always at the
resist sidewall, they are always perfectly round, as are caused by bubbles.
Popular opinion is that this has been caused by oxygen induction via
filtration system.  All four of the copper tanks we have are different in
physical construction and to have all the tanks cavitating air at one time
seems an outside possibility to me.  However, we have asked for vendor
guidance in new filtration system setup.

Your comment on cathode-hydrogen evolution and oxygen evolution interested
me and I have some questions:

A vendor told me that there is no hydrogen evolution in acid copper as it is
100% efficient.  I don't know.

 What physical characteristics do annodes exhibit when polizaration occurs?
Is there extremely irregular surface?

Can high chloride concentration also cause polizaration, i.e. 144 ppm?

When I pull a sample in a glass flask and look at the amount of bubbles
present, is turbidity the condition I'm looking for or the size/quantity of
the bubbles present?  I don't know what amount of bubbles should cause
concern.  Sorry if these are dumb questions.

Thanks very much
Sharon

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