homemade UV lightbox. LEDs or fluorescent tubes?

Other Hardware General Electronics
1

Hi,

I make my own PCBs. Currently I use an off-the-shelf UV lightbox, but I was thinking of making my own, double sided unit.

First question is should I use UV fluorescent tubes, or UV leds?

The second question is what are the critical criteria (i.e. power, wavelength, colour temperature etc) that I should be checking for?

Most commercial UV light bulbs seem to be advertised as 'fly killer' or 'black light', so they're either designed for attracting mosquitoes, or making nightclubs look good. What sort do I need for making PCBs?

UV leds seem to be available ranging in price from less than £1 to nearly £100, what sort are best for developing boards?

Some background info - My current UV lightbox is very large (A4 sized) and has no timer. All of my PCBs are designed using the free version of Eagle CAD, so in practice I need a UV light box not much bigger than an arduino mega. I want to build my own so that a) I can add an electronic timer, and b) I can make it no larger than I need, and c) I can make it double sided to eliminate the problems in aligning the 2nd side.
I've noticed that all the professional UV light-boxes are based around fluorescent tubes and only homemade lighboxes seem to use LEDs, not sure if this indcates that LEDS aren't as good, or just that professional manufacturers have long lead times!

Any advice appreciated.

Thanks

2

You are not going to get the right wave length with LEDs, unless you can get them around or below 300nm. High power UV LEDS will work, but take longer, because if the wave length (most I've had experience with are UVB or UVA).

You need (IMHO) a good UVC source. I use GT8U Sterilizer flourescent tubes (8Watt,unfiltered,mercury vapor(not really fluorescent). They give off UNFILTERED UVC light and will damage your eyes if you aren't carefull, and can give you a sunburn too.

Good luck and be carefull.

3

Since my original post I've done some more research.
Mega electronics (http://www.megauk.com/pcb_laminates.php) sell PCBs with this spec....
Spectral response............350-450nm
UV light energy required...approx. 50mJ/cm

The UV box they sell use these light bulbs....
Sylvania blacklight 350 F8W/T5/BL350
And these ballasts....
Tridonic Atco EC13 C102K

These bulbs are 8 watt, and looking at the figures for light energy required, I think I may have trouble getting these from a LED. RS do sell LEDs that operate at a similar frequency, but these are all relatively low power and very expensive.

Unless I can find some very small florescent UV bulbs, i think I'm going to have to make something much bigger than I actually want!