RadioBanter - View Single Post

December 5th 03, 07:53 PM

in article , Dick at
wrote on 11/28/03 11:30 AM:

Has anyone home brewed a UV exposure box for making PC boards ?
I've got a couple of 8w UV tubes & a 0-30min timer and looking at
pictures of commercial designs I think all I have to do is:

1. Mount the tubes & timer in a light proof box.
2. Fix a sheet of glass 1-2" above them to act as a flat mount for the
photo sensitised PC board & photo master.
3. Fix a mask to the glass, blanking off all but a working area directly
above the UV tubes.
4. Make a lid for the box & fit a foam pad inside it that'll press the
PC board and master firmly down onto the sheet of glass thus stopping
those sneaky photons from getting round the corners of the PC master.

Is it as simple as this or am I missing something blindingly
obvious ?? Is 1-2" a suitable spacing between the tubes & glass plate &
will normal, thin, glass sheet be suitable ??

I use regular 2-3 mm window glass, I place the pcb board with the artwork on
my washing machine (nice flat white surface, good in low light), cover it
with the glass and place the light, a 12 cm long unit, on two wooden blocks
about 6 cm above the PCB board.
Hit the switch, leave the room and come back when the time is up.
For large boards I have to shift the lamp every few minutes for an even
exposure.

I have done quite a few exposures this way and would recommend this
primitive appraoch before I set out to build anything. Experience will then
guide you how to do your "final" exposure box.
Besides, my approach is dirt cheap and dissappears completely when I am
done, nothing much to store.

regards Uwe