Homebrew PCBs

tboneuk_2000 wrote:

> Hello all,
>   I would like to make my own uv exposure box, but I am having some 
> trouble locating a suitable tube. Could anyone tell me if replacement 
> aquariam uv tubes would work (do they opperate at a different 
> wavlength), also can you use disco uv tubes?
> 
> If anyone knows of a supplier in the uk other than maplin I would 
> appreciate it (RS do sell them but they are very expensive, maplin 
> are out of stock)
> 
> Thanks for your help
> 


For fluro tubes type lamps then you need standard BL (blacklight) lamps 
used for attracting insects to "insect zappers". Phillips make them and are 
very common. The filtered blacklights used for special effects will equally 
produce the 365nm emission from mercury , but much more expensive.

You can get 175W HID (High Intensity Discharge) mercury vapor lamps pretty 
cheap. Due to the HID lamps high intensity point like source they will 
eliminate most photomask light undercutting problems. The mercury vapor 
lamp are almost always made with a white phosphorous outer shell, but I 
found that doesn't seem to attenuate too much of the long wave UV (330nm to 
400nm) which is the wavelengths standard photoresists are most sensitive 
too. A home made exposure box using a single HID lamp is better than an 
array of fluorescent tubes in terms of cost, performance and construction 
simplicity.

I use 400W HID mercury lamp, with white phosphor shell, and exposure time 
is about 150 seconds at 40 cm distance, using Epson inkjet transparency, 3 
mm window glass and negative dry film photoresists from Macdermid.

The other common HID lamp is the metal halide. These lamps are manufactured 
with a clear outer shell since the arc tube is designed to produces mostly 
visible light. I'm not sure how much long wave UV is produced from metal 
halide HID lamps compared to phosphorized mercury vapor HID lamps. Has 
anyone tried a metal halide HID lamp for photoresist exposure ?

Motto: There is no need to waste your money on specialty lamps.

Adam