Todd,
John

I think the adhesion of a soldermask does not only depend on the
cleanliness of the board. Mechanical scrub does roughen the surface to a
certain extend. This has several effects :
- A rough surface is bigger than a flat one giving more opportunity to the
molecules to bind to each other.
- The irregular shape of the surface provides a certain mechanical fixture
of the coating.
- If a polymer is coated mechanical scrub will  break some molecule chains
on the surface. Since the open ends of the chains want to reassemble a
coating will adhere better than on a polymerized surface.

Regasds

Guenter Grossmann


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