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First time hobbyist here. Is it a common issue for closely placed track lines to end up touching each other during the toner transfer process (I'm assuming this is the correct term)? If so, are there any quick fixes I can do to my process to fix it? I'm just trying to avoid redesigning the PCB layout (unless that's the only option).

Please see attached pics -PCB board PCB layout design Yes some of the tracks are too close, but what I don't get is this - when I print it on paper, the lines are thin and the gap is reasonable. But when I use nail polish remover and place the paper on the copper board, at least 1-2 lines end up getting closer or nearly touching - see area marked in blue, bottom left. Track width is 0.25mm and gap is 0.5mm which I would think is reasonable. In the first two iterations I tried, these lines didn't end up touching, it was other lines. Is there anything I can try aside from redesigning the layout?

The process I'm following: I printed the layout on glossy paper on a laser printer. Cleaned the copper board and poured a really small amount of nail polish remover on it. Spread it evenly. Placed the layout paper on the wet surface and gave it about 5 seconds. Then using a paper towel, applied vertical pressure (not horizontal) for about 30-50 seconds. Then took the paper towel away and waited for the thing to settle for another 2 minutes. Finally dunked the board in water for another 2 minutes and tried peeling the paper. The toner transferred better than my previous attempts where I didn't give the process any time and also applied horizontal pressure/swipes.

Two major issues on this third iteration:

  1. The paper is stuck in some nooks and crannies. Trying to scratch it with my nails was clearly not a good idea because it erased away some of the track lines. Is there a better way to remove the paper bits?
  2. Two track lines at the bottom ended up touching each other. Yes I accidentally scratched them later, but they were reasonably apart pre transfer, but touching aftewards. Is there a way to prevent this from happening? does it just take practice?
    1. For track lines that didn't fully transfer, can I just use a black pen and write over it? if so, any particular type of pen/marker to use?

Also, here are the variable I think I could change to make this better. Experts, please share your thoughts:

  1. Use a different printer, but laser is supposed to be the most precise option from what I've heard. Not sure if I should be trying a different tech (e.g. digital printer) or just another better laser printer.
  2. Use a wood block instead of hand pressure directly over the paper. Maybe I inadvertently did a horizontal swipe thus causing the ink to smudge
  3. Fix the PCB layout design (most obvious but want to make sure the mistake isn't elsewhere in my process)
  4. Change the concentration of my nail polish remover. I don't even know how to do this. The one I have doesn't have any ingredients or concentrations listed on it.
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    \$\begingroup\$ Etching your own boards was worthwhile in the 1970s. We're not in the 1970s. Send your Gerber files off to itead.cc/open-pcb/pcb-prototyping.html or many others, wait a week or so. \$\endgroup\$
    – user16324
    Commented Mar 2, 2020 at 21:49
  • \$\begingroup\$ Almost any water-resistant marker will do. Remove the carbon with a scapel. But Brian is right. My etching equipment had centimeters of dust on it last time I cleaned up the attic. \$\endgroup\$
    – Janka
    Commented Mar 2, 2020 at 22:02
  • \$\begingroup\$ Is the option of using the photo-etch method with UV sensitized PCB open to you? In my experience, it's more reliable than toner transfer. \$\endgroup\$
    – user156429
    Commented Mar 3, 2020 at 0:20

2 Answers 2

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The toner "melts" a little when using the toner transfer method. You need to place your traces a little bit further apart.

Traces can also slide around a little. When you've got the whole thing soaked in acetone, all that is holding things in place is the liquid. When you go to soak it in water, it is very easy to accidentally wiggle the paper and smear your traces.

It takes some practice, and you need to allow more space on the board to get it to work out right.

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If you insist on the toner method, I suggest getting toner transfer paper.

Get a laminator which will (firmly) accept the thickness of your board + paper, and run it through that. Go as slow as possible, and use a high temperature. Let cool, peel off backer. That will transfer the toner without any of the drawbacks of liquid solvents (running, bridging.)

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