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| 4" Vertex Rotary Table CNC conversion |
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| sparky961:
Just as an aside, flourescent lamp tubes work to expose the board as well - at least with the brands I've used. They just need to be very close and provide fairly light perpendicular to the board. Exposure time will vary with your setup. -Sparky |
| andyf:
Another aside: I print a mirror image of the pattern on plain paper, improve any grey areas with a felt tip pen, and put it printed side down on the photosensitive PCB in a light box with a 12" UV fluorescent tube. Andy |
| raynerd:
Andy, just to clarify, you just print on paper? Chris |
| sparky961:
--- Quote from: andyf on January 05, 2012, 07:08:53 PM ---.... on plain paper .... --- End quote --- I'll second the quizical look from Chris.... if it works, I'll have to try that too. Do you still end up with nice crisp traces, or maybe you haven't tried really fine lines with this method? -Sparky |
| andyf:
Though I have used transparencies intended for overhead projectors, plain paper works fine for me if exposed to UV for a bit longer. If you can find flimsies (as were used for carbon copies) and your printer will handle them, so much the better. Because the printed side is in contact with the PCB, light doesn't bleed round the edges of the black areas to any appreciable extent. As I said, a bit of improvement with black ink helps, especially if your printer (like my old b/w laser one) produces a rather streaky black. Another trick is to make two prints, shifting the image a bit before doing the second one so any streaks come in different places, and use one on top of the other after taking care to ensure the patterns register. But having two layers extends the exposure time considerably. Andy |
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