I am trying to make a complete PCB with solder masking and silk screening, for creating a small PCB fabrication house of my own later.
I choose the process of screen printing for fabricating my pcb, I etched it successfully. I tried to make the solder-mask on it with the screen printing emulsion(UV Curable), but that didn't worked out quite well. After exposing it on sunlight for 40 min it dried successfully, but when I applied thinner to it, it got completely removed.
Solder-mask usually don't get removed by thinner nor the silkscreen. The actual solder-masking ink is not available in my area locally, the prices of solder-mask on ebay is about 33.33 times higher than that of the emulsion.
I think that this inks will work because even if the solder-mask got some special inks, the silkscreens are done by this screen-printing inks only, and they are not also removed by thinner.
So is there problem in my process?
Best Answer
Edit: You're using screen printing emulsion not the proper ink- it's usually pretty resistant to solvents, at least the industrial stuff is. There are some wimpy low-VOA products designed for the T-shirt industry that are probably not as good- more water based instead of manly carcinogenic (not really) stuff that actually works, but destroys your lungs etc. if not treated with respect.
It sounds like the UV-cured ink solvents simply dried out leaving a layer of dry (but not properly polymerized) ink.
I think you'll need a better UV source to get it to properly harden. If you exposed the solder mask ink to natural sunlight through a piece of glass or a window, that would usually absorb the UV that's needed to polymerize the ink.
The intensity of UV in even direct sunlight compared to a strong UV lamp is very low- maybe 1/10 or less so it may not be possible to use sunlight. An exposure lamp made with UV germicidal lamps (using conventional fluorescent lamp fixtures or ballasts) would work for sure.
When you do actually get this to work, you may well find that the screen printing emulsion does not withstand the high temperatures of solder, making it essentially useless. You really want an epoxy type product for this purpose.