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