On Sun, 12 Jan 2003, Herbert Graf wrote:

*>        Thanks for the info, however this completely contradicts what I
*>got from this site (supplied by a fellow PICLISTer):

1. The optimal wavelength for photoresist exposure is usually 350nm which
is near UV (400nm is visible purple). The 'blacklight' lamps output
maximum here, but are useless for EPROM erasing.

2. The Gxxx lamps emit far UV useful for erasing EPROMs bugs and your
eyes, but have enough emission at 350nm to expose photoresist (not to
mention that they are about 5 times more efficient than blacklight lamps
and that photoresist is also sensitive to 253nm).

Therefore a Gxxx will do both jobs, perhaps with slightly longer exposure
time (7 minutes instead of 5)  but a blacklight one will only be enough to
expose small pcbs.

Search the web for lamp light spectra and compare with the specs of your
chemicals. EPROMs need 253nm to get erased. This is the first strong UV
line of Mercury (emitted by Gxxx lamps).

Imho looking into either kind of source is unhealthy but Gxxx light will
also cause skin damage so shield it well.

Peter

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