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PCB solder mask making using UV resin (discuss.tchncs.de)
submitted 7 months ago by Rolive@discuss.tchncs.de to c/askelectronics@discuss.tchncs.de
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It appears to me that UV resin, used for SLA printers should be quite convenient for making PCBs with a laser etcher. You can spread a thin layer of resin on the board and quickly expose it using a laser engraver. It should be most convenient for silkscreen layers that are otherwise difficult to apply.

I think the common method of applying UV mask and spreading it using a piece of plastic sheet is messy and I can never guess how much resin to apply. It's always too much or too little and it's always unevenly spread. And then the UV light exposure is another guessing game.

I have a 500mw 405nm laser module attached to my 3D printer and could easily 'print' some PCB layouts on a thin layer of SLA resin.

Does anyone have experience with this?

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[-] Rolive@discuss.tchncs.de 1 points 7 months ago* (last edited 7 months ago)

Tooting my own horn. I have something to add. With the UV "Mechanic" solder mask that gets sold on Chinese webshops pre-heating the solder mask makes a HUGE difference. Apparently it contains some volatile components that interfere with the curing process.

Heating it to about 80-ish C for a few minutes and optionally letting it cool down causes the laser to almost instantly cure the mask. Any non-exposed mask will be easily washed off with some IPA.

[-] GooseFinger@sh.itjust.works 1 points 6 months ago

Honestly, interesting thought.

My first concern is fidelity - you can only get as detailed as the diameter of your laser, which I imagine is pretty big relative to the tiny features on PCBs. A 10 mil diameter sounds pretty good for a home job to me.

How well does cured resin hold up to copper etchants? I would assume pretty well.

What benefit does this have over other methods, such as transferring a laser print on glossy paper to a blank PCB? The resin/laser method sounds very similar, but more automated and essentially the same, minus the transfer step.

Now I want to try this haha.

[-] Rolive@discuss.tchncs.de 1 points 6 months ago

For my use case fidelity is no problem at all. My spot size is minimally about 0.1mm and I've increased it to 0.5mm to increase speed.

For photosensitive dry film you don't need much power so you don't need max focus. In fact you're likely to burn through the film with the smallest spot size.

Toner transfer has been messy and unpredictable for me. Also alignment with double-sided PCBs is more difficult this way.

this post was submitted on 01 Apr 2024
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