Electronics > Beginners
Dry film photoresist developing
ogden:
--- Quote from: ZeroResistance on March 31, 2019, 09:51:20 am ---After washing I should see exposed areas of copper correct ? I don't see any.
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*During* development unexposed areas (light blue) shall dissolve in developer. When done, you see either copper or exposed (dark) resist. You wash using water only when you see that you are done with development and unexposed resist is removed completely.
ZeroResistance:
--- Quote from: ogden on March 31, 2019, 09:57:03 am ---
--- Quote from: ZeroResistance on March 31, 2019, 09:51:20 am ---After washing I should see exposed areas of copper correct ? I don't see any.
--- End quote ---
*During* development unexposed areas (light blue) shall dissolve in developer. When done, you see either copper or exposed (dark) resist. You wash using water only when you see that you are done with development and unexposed resist is removed completely.
--- End quote ---
Ok, currently the unexposed resist is not getting removed. I will try with 3% concentration of sodium carbonate.
ogden:
--- Quote from: ZeroResistance on March 31, 2019, 10:00:35 am ---Ok, currently the unexposed resist is not getting removed. I will try with 3% concentration of sodium carbonate.
--- End quote ---
Also make sure solution is not cold, bring it into 30..40 oC range.
ZeroResistance:
--- Quote from: ogden on March 31, 2019, 10:06:05 am ---
--- Quote from: ZeroResistance on March 31, 2019, 10:00:35 am ---Ok, currently the unexposed resist is not getting removed. I will try with 3% concentration of sodium carbonate.
--- End quote ---
Also make sure solution is not cold, bring it into 30..40 oC range.
--- End quote ---
3% concentraton of sodium carbonate slight difference. Its not dissolving the unexposed photoresist.
Looks like its still an issue of overexposure @ 2 to 3 min of sunlight.
Next I will try 30 sec of sunlight.
ZeroResistance:
--- Quote from: ogden on March 31, 2019, 09:20:25 am ---
--- Quote from: JackJones on March 31, 2019, 08:28:42 am ---I don't think regular fluorescent bulbs work, it should really be UV to develop properly.
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Nail polish lamp works and what's even more important - gives consistent results.
--- Quote ---It looks to me a bit overexposed, you could try leaving it outside for a little less time.
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Definitely overexposed. It is necessary to find correct exposure time, every UV resist beginner shall start with step wedge exposure test. Info from silksreen guys, but it's the same for PCB as well:
https://medium.com/@spotprintsonline/step-wedge-test-a-high-quality-print-requires-a-good-stencils-cb1fbaa11998
[edit] I find this guide well-written: https://sparks.gogo.co.nz/dry-film-tips.pdf. Pay attention to PCB "before/after" pictures in page 13 that shows how unexposed areas shall look like after expo - they look the same (color) as before expo.
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This is some pretty amazing info. Many Thanks!
I guess I'll try to calibrate the dry film with a bunch of fluorescent bulbs to get more control over the exposure.
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