Since some of you are wondering how my UV exposure box looks like, I shot the photos below for your viewing pleasure. The unit uses 2x8W UV lights obtained from Farnell. The box was fabricated from HDF board (the same board used by picture frame shop) and the exposure area was lined with aluminum foil to improve reflectivity. The tubes are about 4" apart and 4" below the frosted glass. The frosted glass is intended to diffuse the UV so that there are no UV bright spots.
I've also made a simple PIC-based timer to time the exposure. Using the Kingsten PCB, exposure is 90 seconds. I use inkjet transparencies to make the exposure film. So far, I've managed to get 0.25mm track with 0.25mm separation with no problem. PCB are developed using NaoH developer and etches using Fe2Cl3. From exposure to PCB ready to drill in less than 20 minutes. I'll never go back to iron-on method... :-)
Tuesday, May 26, 2009