Toner transfer method (DIY etching)

[Mads Barnkob]

The toner transfer method is a cheap and easy method to create prototype industry quality boards in your own home, what just items and apparatuses that you can find in almost any home.

Stuff needed:
Bare circuit board material
Cleaning remedies like pan sponge, steel wool or very fine grit sand paper
Glossy paper that can range from magazines to photo paper for the printer
Laser printer, ink jet does not work, a photocopier machine might work, I have not tried it
Iron for clothes, do not steal your mothers, find a old discarded one
Etchant, the widely used and easy to handle Iron(III) chloride, also called ferric chloride have been my favorite for many years
Cleaning agent, acetone works very well for quickly removing toner in one swipe.

Things to consider and experiment with:
Iron temperature has to be just right to the toner your printer uses, not too cold and not too hot. If you have a IR termometer it is easy to hit around 130 degree Celsius, which is the reported good temperature from others doing toner transfers and corresponds good with a iron set for hottest possible results in smeared toner and too cold the toner does not melt enough to spread out properly and you get a noise like pattern instead of filled surfaces.


Printer settings like DPI, image resolution in printing, toner saver options, tricks like dotted or interleaved image print, PCL drivers differences etc, there are many fall pits in laser printers that can result in less smooth edges, corners etc.
My own printer does not have a problem with printing a BMP export from ExpressPCB, but some might have, other users have described that exporting to SVG and printing it from a proper vector image program can help a lot on this, as the printer driver gets a proper set of information about the graphics.


Step 1: It does not matter how old or how dirty/oxidized your copper circuit board material is, it can easily be cleaned with regular dish washing soap and a pan sponge/steel wool. No fancy or harmful cleaning agents are needed.


Step 2: As long as the oxidized copper layer and greasy surface is gone, it does not matter that it has visible polishing directions.


Step 3: I prepare for the transfer by cutting out the print on the glossy paper on 3 sides, which leaves me a snippet to control it with. Underneath I use a cork pan holder as it is hard, but yet soft for pressure and can help distribute the pressure evenly when transfering the toner.


Step 4: I use a additional layer of paper between the one that is printed on and the iron, this is to avoid "browning" the printed on paper from the heat from the iron and get a more indirect heating to the bottom layer against the copper. First I heat it all up like in the picture and then use the nose of the iron to rub all over the print, to ensure all tracks have been under pressure.


Step 5: After ironing the paper is fused to the copper through the toner, leave it to cool down on the cork pad before putting it in a water bath, leave it in the water bath until the paper is soaked and it can be pealed off easily.


Step 6: Some times it has to be done in more than one step and a additional soaking is needed.


Step 7: Here I have only rubbed the print with the soft part of my thumb, you can even use your nails to remove the paper pulp. without scratching off the toner, for the centre holes in the components pads I use a needle or tweezers to scratch it out. If there are any holes in the toner, it can be touched up with a permanent marker, this will withstand ferric chloride.


Step 8: I have been using the well known ferric chloride, mostly harmless (do not get it on your clothes, unless its already a curry yellow shirt) and it is not releasing any harmful fumes while etching. For a faster etching you can also use Sodium persulfate. If we go back to only using house hold items, clog drainer can also be used, but take care with strength of solution, reaction and gasses.


Step 9: Even the most simple container can used for etching. I put a cable binder through a hole, to be able to move the print while etching it. Improvements could be a heating element from aquariums, circulation pumps (expect heavy wear as the etchant passes through it) and even better a small bubbles membrane pump, also known from oxidizing aquariums.


Step 10: The result after etching and rinsing with water. Notice the few tracks that I had to touch up with a permanent marker, they are still intact.


Step 11: Acetone, a plastic bag and kitchen towels is all it takes to remove the toner from the remaining copper tracks. Only swipe once with the kitchen towel, then turn it and use a clean part of it. I use a plastic bag to waste as little acetone as possible and keep the toner out of my kitchen drain.


Step 12: After cleaning the toner away, there can still be some residue, I have not yet had problems with this. The tracks on the small board to the right are for a SO8 SMD IC (0.15in)

[NEYi]

That method's super popular in my country, called "laser ironing".
Personally though – I prefer using lithography, a.k.a. photoresist method since it gives better quality and doesn't require heating up a huge iron...
But the method definitely has it's place since it doesn't require any unusual chemicals.
I know a few tips regarding the topic, maybe somebody will find them useful.

1. Softening up the paper with regular water can take some time, and still – peeling the remaining paper off can damage the traces.
Instead of water I usually used powerful caustic soda solution – it's super aggressive against cellulose and quickly dissolves it, especially when the solution is heated up.
For heating the microwave oven is really handy to use, just don't do it with the PCB floating in the liquid.
After 1-2 minutes in a caustic bath most of the paper's gone, and the remaining one can be washed off under a water faucet.
That's useful not really for saving time, but mostly if you're trying to make PCB with small details, like 0.3 mm traces and TQFP chips – undissolved paper bridges between traces mess up the etching process.
However, that's definitely the limit of this technology – for good precision and chance of success photoresist works much better.

2. In theory – it's possible to make PCBs without the huge heated iron, using only acetone and a towel.
Just water-up the PCB and print-out with little acetone, then push them against each other with force using a soft towel, after 5 seconds release and peal off the paper piece.
Toner will be transferred to the PCB surface. What's cool about this method is that it can be used with plastic or heatsinks as well – that either can be melted with ironing, or radiate too much heat and the ironing method works poorly.
This method isn't very reliable, but it works – anyone can just try it out. Here it's mostly used not for PCB manufacturing, but for making writings/logos on plastic cases or keyboard keys.
Of course, after being transferred to plastic – toner should be covered with some lacquer, otherwise it'll peel off fairly quickly.

Hope some of it was useful, cheers.

[T3sl4co1l]

Paper can also be hydrolyzed with 50% sulfuric acid.  The toner may be affected in the process, however.  (Use with caution -- sulfuric acid is the one that heats up when mixed with water.  "Do as you ought'er, add acid to water."  HCl/muriatic acid doesn't have this hazard.)

I never had good results myself (with iron-on), and also found that Sharpie(R) markers don't survive well in the bath.  Get a good grease or paint pen for touchup work.

But most of all, with PCBs being so ludicrously cheap these days, it's nothing more than a curiosity.  Do a few if you like, then tire of all the labor spent fiddling with them to make an inferior product.  Then, grab a beverage from the 'fridge, press the order button on a fab run, wait two weeks and enjoy.  You'll only be out two beers worth of money -- one of which you just drank!

Tim

[T3sl4co1l]

Proof of experience (not that anyone will doubt it ):





Only my best example, of course... the layer registration managed to be incredibly good, +/- 5 mils maybe?  Others I did were more like 20 (lots of partial annular rings..).

Using paper substrate, dimensional stability better than maybe 10 mils over 6" simply isn't possible.  The paper itself doesn't expand and contract evenly as it's heated and cooled, and exposed to whatever ambient humidity is.  This severely limits the practical size range.

(Note: 1 mil == 0.254 mm.)

Tim

[Mads Barnkob]

Thanks for the tip with the caustic soda, that is one of the mute points of the process that you have to wait for the paper to dissolve in water and yes I have also ruined traces from being impatient, so I would have to touch it up again with a permanent marker, which ofcause never gives a good result

Any other chemicals that are good for removing the toner? As you can see in my pictures it will often leave a faint large black surface where the copper has been removed, when rubbing off the toner with acetone.

[T3sl4co1l]

I never had a problem -- sanded away or wiped off with acetone (or both).  Maybe my stock just had a cleaner surface than yours does?   (Depends on the surface prep of the foil before laminating -- usually, rough and oxidized for better strength.  Mine doesn't look obviously different, so who knows.)

Tim

[Mads Barnkob]

I never had a problem -- sanded away or wiped off with acetone (or both).  Maybe my stock just had a cleaner surface than yours does?   (Depends on the surface prep of the foil before laminating -- usually, rough and oxidized for better strength.  Mine doesn't look obviously different, so who knows.)

Tim

You are properly right about just sanding it off with a fine grit, I only used acetone and maybe its just my "white" PCB that has this problem with toner getting stuck on the fiberglass, as you can see in this detailed picture, not even more acetone can remove those stains, so sanding it the way to go!

 

[T3sl4co1l]

Yeah, for sure it's there once it's there!

I think I usually sanded it, because I'm sanding it anyway to clean up the surface (which was usually rough and pitted, because... Sharpies).  Think I did wet sanding with 220 grit, or else, steel wool or Scotchbrite if you have it also sound great.

Mechanistically.. I suppose removing the plastic-and-black particles keeps it rolling over the surface, whereas solvent frees the black (soot, dye?) and it's gonna settle on everything it touches.

Sanding also smooths some of the fiberglass surface, for whatever that's worth I guess.

Tim

[Twospoons]

https://www.techniks.com/
If you want the best results invest in the press'n'peel blue toner transfer film. Magazine paper works OK, but this stuff is far better. No scrubbing and no pinholes. I've done double-sided Kapton flex pcbs with it, on 5mil/5mil track and space.  You do have to keep everything absolutely clean and free of dust though, for best results.
Its also worth modifying a laminator to use instead of an iron - more consistent temperature and pressure.
Or go further, like I did, and upgrade a portable kitchen hotplate with a good temperature controller, then use a silicone sheet and vacuum pump to apply pressure - that system worked brilliantly.