It appears that the OEM wanted to evaluate a board fabricator's ability to
produce a board with thick copper on the surface - in addition to any other
attributes.  When a drawing takes exception to the various specification
"minimums" then I consider that to be a critical element.  The fact that
there are areas where the surface conductor thickness does not meet the
minimum of the range means that the board is not compliant.  By stating a
range for thickness - it indicates that a minimum value is
needed on all surface features.  The thickness of a hole copper is slightly
diminished by adding HASL coating, but board fabricators plan for this and
should make certain the thickness is adequate for this variation.  Scrubbing
prior to solder mask application is also another process that can remove some
of the surface copper plating, but again - the fabricator should make certain
the amount of copper on the surface will result in compliance with the
drawing minimums after this process.

By "fair" doesn't either apply.  The sample either meets the drawing
requirements or it doesn't.  The fact that an view of the overall thickness
at the plated through holes - I am assuming that was made with a micrometer -
does not meet the minimum is also a concern as to whether the sample produced
meets the drawing requirement.

Unlike hole wall thickness that has a requirement of an average - the surface
thickness requirement was given as a range and anything less than the minimum
of that range would be non-compliant.

Susan Mansilla
Robisan Lab

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