Photoresists are sensitive (I thin) to NEAR ultraviolet, which is less
dangerous and more compatible with standard optics than the shorter
wavelengths.  Presumably some are "somewhat sensitive" to visible light, and
one of the current crop of high-intensity blue LEDs might be interesting to
experiment with.  (white LEDs, as I understand them, are basically a blue
emitter with some blue-stimulated wide spectrum phosphors in front, so
they're likely to be less useful than the bare blue LED...)

Note that optical storage is extremely likely to drive the technology toward
lasers in shorter wavelengths becomming rather common.  If your circuit
board happens to look like a DVD, you ought to be in fat city :-)

BillW

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