Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

A low cost method for exposing dry film photoresist is to use a 300
watt quartz lamp. I purchased a complete fixture with lamp for less
than $10 (US) and it worked great. The exposure time was about one
minute with the lamp 12" from the exposure frame. There seems to be
enough UV from the quartz lamp to get the job done.

There is no need to break the glass envelope from a mercury vapor
lamp if they are used for exposing photoresist. The outer glass
envelope prevents excessive generation of ozone and should be left
intact. I have a large commercial exposure system that uses a 1500
watt mercury vapor lamp with the glass envelope and it will properly
expose 1.5 mil dry film in 17 seconds. Removing the glass from the
bulb probably wouldn't make much difference in the exposure time.
This system will also expose indirect silkscreen emulsions in 30
seconds. Either lamp type will give excellent results after the
exposure time and lamp distance is determined.

Tom