UV exposure box with UV LEDs?

[Kain]

Recently I was using the photo-exposure method to do some boards (I like the tonner transfer but sometimes I need to get more acurate ;D). I used my friend's exposure room to do it - he's having some huge lamps which emmit 75% light in the UV spectrum. However, I've seen that there are UV LEDs available on the market, and it's been a while. Actually when I checked on different manifactors it seems that there are high intensity UV LEDs now, so I wonder if a small exposure box can be built using those? The wave-lenght of most types is arround 380~400nm with power rating 80mW. Some have even 3000mCD rating but this is kind a not right since UV light is not visible. Anyways, do you think that this would be enough to expose a board well enough?

[Guest Alun]

What's wrong with just using good old fashioned UV tubes? - black lights, you know the violet coloured lights used to read bank notes or the ones you see in night clubs also those blue coloured tubes used in insect killers work well.

Just don't use germicidal lamps used in ROM erasers as their UV wavelength is to short is also very dangerous and can burn your skin and eyes. These tubes are made of quaz and are transparent, and they are also more expensive.

[Kain]

Well I didn't say that there is anything wrong with using good old fashioned UV tubes, but this doesn't answer the question. Thanks for the suggestion anyways :). Since it seems nobody had tryed it (no answers to the topic) I decided to try it myself. I got one UV LED from the local electronics store. They told me it's high intensity, and I can actually see it is when I feed it with 3.5V at 30mA. I don't know what is the rating of this LED but I know I've seen more powerful than those. It is extremely irritating to eyes as well - I can look at it for no longer than 2 sec and this is not looking stright in the lense - I don't advise you to do so anyways ;D. Anyways, I tryed the exposure and I exposed precoated board for 5 min. Worked just fine. The distance that illuminated from was about 150mm for I can get more uniform patern over the board as well as illuminate larger area. I'm looking for a way to distribute the light more evenly now using more LEDs. Any ideas how I can spread the LED's beam uniformly, or close to uniformly since I plan to use more than 1 LED? :)