Fred,

Just an idea - could you specify black THERMAL CURE marking ink over your
regular LPI mask?   P in LPI stands for photoimageable, and black LPI mask may
not process thru UV exposure so easily as the pale green.  Black UV-cure marking
inks are a possible anwer, but they go down pretty thin - and use brute force
UV flood exposure of the UV marking ink for curing.

Black carbon particles in an LPI would block UV light in exposure and make
edge definition pretty hard in a black LPI.  Usually, mask suppliers have to
"trick" the human eye by using a combination of green and yellow pigments that
transmit some UV, but look black to us.

How close to the edge of the LPI would the black overcoat have to be printed?
  Screen mask is not as accurate as LPI, so there would be a slight offset
between the black marking ink and the edges of the LPI defining edges of
openings.  Just enlarging the "dots" of the LPI mask would give you the stencil for
the black overcoat, allowing for the difference in imaging tolerances - LPI and
screen print.

Denny Fritz
MacDermid, Inc

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