A valuable item in a hardware enthusiast’s arsenal, an ultra violet LED exposure box can be used with good results in making quality PCBs. LEDs are cheaper and safer than usual fluorescent lamps and also have a longer life span, so using high brightness UV LEDs is a great choice for an exposure box. The only downside is the longer exposure time, but this is an acceptable trade-off for most hobbyists.
The Exposure Box described here is a double sided one, with 84 5 mm UV LEDs on each side which need 700mA at 12V (that means 8.4 Watts for each panel). Therefore, the Exposure Box possesses 168 LEDs that add up to 16.8 Watts. It is important that the LEDs have at least 2000mcd brightness, a peak wavelength of less than 400nm and a viewing angle of at least 20 degrees. Other important components are the resistors (you will need 56 of them), the boards on which the LEDs are mounted and a power supply unit (this design uses 2x 160mm x 100mm pieces of Veroboard and a 12 Volt 24 Watt switch mode power supply).
The box itself is made of 6mm MDF, which can be easily shaped to build the case. The walls of the box are glued together and you will also have to drill holes for screws and the PSU connector. Take precautions when soldering the LEDs (check the polarity and don’t look directly to them when powered). You will also need a power switch and wiring to connect both panels to the PSU. When everything is done you could test the Exposure Box to see how it works using a piece of metal with photo resist.
A great project for home use, the UV LED Exposure Box can come in handy when making PCBs. Details on the components, assembly, soldering as well as schematics and other useful information in the link.