This project shows the creation of a large array of UV LEDs. They are used to expose a presensititised blank circuit board. Another common method is to use UV tubes. Alfredo has translated it to English as well as he could (English is not his first language). This is great since for some reason the good old Google translator could not do much with it. Thanks Alfredo!
"Why if we make PCBs under 160x100mm we need to use big insolators size legal or A4? We can make an insolator box little, portable,cheap and really cool. We are going to use UV leds with wavelength of 400nm that are the most indicated for our presensibilited PCBs for its high component of UV and nearest to visible light spectrum ( an important part of actinic light ). Usual 6w UV tubes seems that provides more UV power than leds UV of about 60mw, but not all power in UV tubes is light intensity, the most power is disipated as heat. We used to make the isolation box: 54 UV leds buyed from E-bay for about 15 $ 18 resistors 68ohms, 1/4Watt for 0,60 $ 1 two pole connector for about 0,85 $ 1 Electrolitic capacitor of 2200uF and 30v recover from a F.A. 1 Eurocard presensibilized PCB of 160x100mm The insolator is powered with 12Vcc. Leds goes in groups of 3 conected in serial with a resistor of 68 ohms. As the cone light angle of LEDs is 20º, we need a box that have about 80 mm of height to put the leds in a grid of 18mm. We have founded a metal box with 85 mm of height in a chinesse bazar for about 12$ that is perfect for the project. Later, we proceed soldering the leds on PCB. It’s very important that the leds are perfectly vertical to PCB.You can see this great solder job!!! After of solder process, we applied 12Vcc to PCB and… voila!!! Warning!!! Don’t see directly to the UV leds!!! We changed 5 leds that don’t brighted than others. Next we buyed a glass cutted in a form to put into Box for about 1,5$ and put a piece of foam on box cover for tight the PCB with glass for a good insolation without shadows. You can see a PCB made with this insolator box with 6 minutes of exposure. The best thing taht you can make with this portable insolator is that you can bring it at your friend’s home for make little elctronic projects. The next thing to do is a timer with LCD ,4 buttons and PWM intensity UV control for don’t flame some strange PCBs."