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Topic: UV solder mask (Read 261 times) previous topic - next topic


I'm jumping feet first into making a setup for homebrew pcb's. I've printed a small lightbox (2.5"x4.5") that lets me expose top/bottom and a means of mounting the transparencies. So far it's fine. I've gone from 10min with an OTT light to 40sec for exposure.

Now comes the UV curable soldermask. I never messed with it before, but gave it a go a few times yesterday. I find it too thick to make it even, which also affects the cure/overcure times. I'm thinking of thinning it a bit to make it a dip-able viscosity using IPA or acetone. I'm thinking it will flash off the thinner quick enough before placing the artwork on it to cure. I'm hoping it allows for better consistency in thickness because of the fine line in timing when dealing with some of the pin spacings of smd ic's (32VQFN) . 

Anyone see any issues doing this, or am I just wasting my time and material?

Seems I have had an abundance of simple mistakes on this project. First try with a board, I went with 3 minutes. That didn't go well with single layer artwork. Dropped to 50sec, but slid the board under both pieces of artwork (2-sided). Oops.
  Had to open a new package of 6x9 double sided board from MG. Pulled it out of the wrapper and much to my surprise, there was no cover on the board on either side. Really??!!. After I just grabbed it with grubby fingers, I slid it back in, turned off the lights and had to cut it with siding shears in the dark. I put my artwork on, board in, exposed and developed it, so far so good. Nice and clean. Etched it and it looked pretty good with .01 traces. Looked closer and noticed my resonator on the wrong side of the board. Nuts. In the dark, I put the artwork on upside down.

Corrected that and did another board. Finally, a workable board. Tried some soldermask with so-so results, but in the important spots (328P and some 0402 capacitors, 0603 resistors in close proximity) were crisp and defined. I put the uC, caps, resistors, resonator, and 6 pin header and was sold on the soldermask making life easier. I figured I would plug it in with a FTDI programmer and give a whirl. The chips that were supposed to have a bootloader on them-don't. Nice. I say that because this was a specialty board where I didn't break out many pins-many meaning MOSI and MISO are still nicely tucked under the leadless chip. I think I have a plan for that though.

It's not a hobby if you're not having fun doing it. Step back and breathe


I bought some on eBay a while back:
The description says:
Notice: Don't dilute when using the ink
Wash away the extra paint by gasoline or oil base solvent
I actually never have used the stuff. It does seem awfully thick. I was also thinking to dilute it slightly but was unsure what the appropriate solvent would be.

I got it because the green color of protoboard I was using for some LED lighting projects was showing through so I wanted to make the side with the LEDs white. Now that I can get cheap custom PCBs with white soldermask I don't know whether I'll end up using it.

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