UV curable solder mask

Didn't make a homemade PCB for quite long time, nearly forget how to make one correctly. Recently this type of UV curable solder mask seem to get very easily available.

After a few round of failure, finally find out the way to make it work correctly.

This is summary of some tips to make it work:

1. Apply only thin layer of paint, excessive paint will cause the paint underneath have difficulty to cure and the paint may become easily peeled off during removing the transparency.
2. Preheat the PCB, release moisture or gas absorbed by the board, or else it can cause bubble during soldering, I preheat it with a laminator.
3. Cure long enough time under UV, the period is depending on UV light strength, 1 hours is normally more than enough and cured.
4. Reheat after exposure, this will strengthen the paint.
5. The UV curable paint doesn't seem to survive high temperature, solder only with ~250-300 degree Celsius.
6. This solder mask have some conductivity, which is not a good thing to know, long trace should not be too close, or else please consider few mega-ohm shorted circuit which may affect some high precision circuit such as high gain op-amp or delta-sigma ADC.