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I've recently started having problems with etching my PCBs.

I use a permanent marker to do the traces and etch them in a stainless steel cup, heated with a tea light (small candle.)

The PCBs come out very badly, the traces have holes in them and some thinner ones have completely disappeared.

Pictures:

Trace side

Component side

It's before removing the marker, BTW.

I also sandpapered the board before.

This is my setup, the tea light goes in the can under the cup:

Setup

What can be the cause of it coming out so badly?

Should I use some different etching compound? I'm thinking about either ferric chloride or vinegar (or bleach?) + peroxide.

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    \$\begingroup\$ I doubt your permanent marker is a good idea \$\endgroup\$ – PlasmaHH Jun 10 '18 at 8:26
  • \$\begingroup\$ Perhaps it reacted with sodium persulfate since sodium persulfate is a strong oxidizing agent. \$\endgroup\$ – Long Pham Jun 10 '18 at 8:35
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    \$\begingroup\$ Did they ever come out well? If so, what have you changed? If they have all come out bad (you've never gotten a good board using this method) then maybe the whole method is bad. \$\endgroup\$ – JRE Jun 10 '18 at 9:18
  • \$\begingroup\$ How old is your marker pen? If its a bit old then the output won't be as thick as when its new and juicy. \$\endgroup\$ – Criggie Jun 11 '18 at 3:52
  • \$\begingroup\$ There's quite a variety of permanent markers out there. If you have a well-stocked office supplier nearby, look for a 'paint marker', something like an Edding 751. They're a bit more expensive, but will get you much better coverage. \$\endgroup\$ – AkselA Jun 11 '18 at 12:09
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Your main problem is coverage with the permanent marker. They do work as an etch stop, but it is hard to get uniform coverage - you end up with more ink in the middle, and less at the edges (it flows). For very large plane areas you will also get blotchy coverage.

Any areas where the pen puts down less ink will let some of the etchant through, giving you the patchy results you are seeing. This is especially the case for thin traces.

If you want to keep trying PM, try going over the areas multiple times. You could also switch to a different pen such as sharpie, as they tend to give better coverage.

Failing that, another option is to switch to the toner transfer method - which in short uses laser printer toner as an etch stop rather than permanent marker. This tends to give slightly better coverage. There are also companies that offer special paper that bonds to the toner to fill in small gaps.



When it comes to etching, if you were thinking of switching to Ferric-Chloride, don't submerge the board in it. Instead wear a rubber glove and put a tiny amount of the etchant on a sponge (like you would use for washing dishes, but not the same one you use for washing dishes!). Wipe the sponge back and forth gently over the board. Once the sponge goes green, add a drop more etchant.

This approach is far faster because you use mechanical action to keep fresh etchant on the board surface. It doesn't require heating to speed up the reaction. And the best bit is, your storage jar of etchant stays at full strength because you never put the copper into the storage jar.

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  • \$\begingroup\$ About the toner transfer method. Will an office photocopier work? Laser printing here is unreasonably expensive. I was thinking of printing the PCB design on copy paper using an inkjet printer at home, then having it photocopied somewhere on some glossy magazine paper. \$\endgroup\$ – Gene Dela Rosa Jun 10 '18 at 14:32
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    \$\begingroup\$ @pandalion98 photocopiers that use toner will work just as well. \$\endgroup\$ – Tom Carpenter Jun 10 '18 at 14:39
  • \$\begingroup\$ I think marker should only be used to fill up the imperfect. \$\endgroup\$ – Long Pham Jun 10 '18 at 15:02
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Main problem is indeed that the permanent marker is coming off for some reason.

It's difficult to say for sure, but two general tips:

  1. Wash the board before applying the marker, and let it dry longer than you think it'd need. It seems that the copper surface easily retains a bit of water on it even after it appears dry. Heating with e.g. hair dryer helps it dry off faster. You mention sandpapering the board, which can also work, but if there is anything oily on the surface, might not be as good as washing.

  2. Let the marker also dry longer than you'd think it would need. It will keep forming more chemical bonds for a while after all the solvent has dried off.

These apply equally for any kind of coating, be it marker, photoresist etc. Even for toner transfer, 1. is important (toner hardens quite fast because it has no solvent, so 2. is irrelevant).

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    \$\begingroup\$ When I was doing toner transfer a few years back, I found cleaning boards with acetone prior to using them helped a lot. I guess any general purpose solvent would give similar results. \$\endgroup\$ – Jules Jun 10 '18 at 12:24
  • \$\begingroup\$ most markers are acetone soluble. I remember using it to wash off the marker after etching. acetone is excellent to remove fat (fingerprints...) but be sure to have none left before you start drawing with the marker. \$\endgroup\$ – dlatikay Jun 11 '18 at 11:22
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Had similar problems with etching. First thing would be to buy a new set of markers and use them only for PCBs to prevent any contamination with oils and fats. You don't need to sand the board it's better to take some steel wool or a wire brush, because it won't remove so much copper. After cleaning, wipe the board down with some isopropyl alcohol, then draw the traces.

Also, you can do the etching on the kitchen stove, as persulfate isn't toxic. use a plastic container with persulfate solution and put it into a bigger pot, which I fill with water and then set on the stove. This way, you can regulate how much heat gets to the solution and keep it at its optimal etching temperature, which is around 50°C for persulfate.

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Thanks for all your help! I used 2/5 peroxide and 3/5 vinegar and a bit of salt and my pcb etched no problem! I also retraced my pernament marker traces and look at the results! PCB

Btw, I used edding 142, M size.

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