Homemade PCB with toner transfer method

 Author:   Posted on:   Updated on:  2017-10-27T19:16:27Z
The toner transfer method is a cheap and easy way to make your own printed circuit boards (PCBs) at home. A laser printer is used to print the design on paper. Not all paper types are suitable for this kind of usage. The paper is placed with the printed side over the copper side of the circuit board and then the whole thing is heated. Most people use with good results a common iron, but if you have a laminator, use it instead of the iron. When heated, toner melts and sticks to the surfaces. The idea is to make it stick to the copper layer. After heating, cold water is used to soften the paper which should be easily peeled off from the circuit board. A good transfer means no toner remains on the paper. Once this is done, the board can be etched using whatever method you want (ferric chloride for example).

This method is widespread among hobbyists because is cheap and easy. However, for some, the results are unsatisfactory and variable. I will share some of my experiences with this method.
Homemade PCB with toner transfer method incl. silkscreen
Homemade PCB with silkscreen
The first requirement is to have a PCB design. I got very confused about mirroring the design before printing. Well, in all CAD tools I know, you design the top layers normal and the bottom layers mirrored (the PCB is transparent - the traces are drawn in see-through mode). So, the following apply:
  • bottom layers (copper and silkscreen) must be printed as they are in the CAD software. The result will be a mirror of what you see when looking at the real PCB;
  • top layers (silkscreen and copper) must be mirrored because when you design them they are not mirrored.
Let's make a test. Write on the bottom copper layer and then on the top copper layer. You will see that the bottom text appears mirrored.
Top vs. bottom layers (green text in on bottom layer while the red text is on top layer)
Top vs. bottom layers (green text in on bottom layer while the red text is on top layer)
An important aspect of printing PCB designs is the real size. You must make sure the printer does not apply any zooming or shrinking to your design. If you are uncertain about your printer is always a good idea to draw some lines in the CAD software at a known distance, then print the design and use a ruler to measure that distance on real paper. If they don't match, you need to apply a zooming factor when printing.

Make sure you select individual layers when printing. You don't want the silkscreen overlaid on top of the copper layer. Also, I find it better to print very small drill marks or no drill marks at all. There is no need to etch the area of a hole. More, if you etch a very small area (small drill mark) this could help you if you make drills with a hand tool. The drill tip will slip into the small depression created in the copper layer (the etch mark) and holes will be centered with ease. So, I prefer to print designs with small drill marks. If you're using KiCAD, you have this option in Print and Plot dialog windows.

You already know the printer must be laser type. If you have large areas of copper it is recommended to set toner density to maximum (the printer will lay more toner on the paper). You can't use normal paper. I used with great success special paper which has a glossy side. This paper does not absorb toner and it does not stick to the PCB.
PCB design printed on special toner transfer paper
PCB design printed on special paper
You should know that this paper is very thin and once it passes through the printer it has a tendency to curl and you cannot feed it again to the printer. When I inserted one sheet in the paper tray, the printer recognized it as "vellum paper". The glossy side looks just like the backing paper from self-sticking labels. Avoid touching the glossy side of paper. Place the printed side over the copper side of the raw board. The copper should have been previously cleaned with some grease remover. You should not have to use sand paper, but if you do use one that's very fine.

Iron the paper over the copper layer. Apply uniform pressure and make circular moves with the iron. The iron should have a temperature of 150 ... 180 degrees Celsius (for the paper I used). When toner melts, it will appear to you that the paper sticks to the copper. Well, only the toner does that. After a few circular moves with the iron, take the PCB-paper thing and drop it in cold water. Some say you should wait for it to cool, but I usually drop the PCB in water just after I finish heating it. Move your finger over the paper to make sure the water soaks it and let it for no more than a minute to cool. Take it out and slightly peel the paper starting at one corner.

If you applied too much pressure or heat, this kind of paper will stick to the copper and you can't peel it off. Otherwise, if heat was not sufficient, the paper will peel off easy, but toner will remain on it.
After peeling off the paper: the toner print on copper
After peeling off the paper: the toner print on copper
This was the result for me. There are some small and unimportant imperfections where toner didn't stick to the copper, but overall the print looks good. This needs to be etched. I used ferric chloride (40% solution). Remember to use a plastic container. To speed up the etching process you should continuously move the container with the PCB soaked in chloride. Slightly heating the chloride also speeds up the process, but be aware of fumes it may generate. Heat it by placing it in hot water, not directly on heat source.

Check very often the progress of etching. It will look as if it's taking a lot of time, but once you see areas without copper the process will appear to speed up and you're almost done. Do not leave the PCB in chloride unless there is copper to etch. It will eventually pass through toner and etch tracks too.
Etched PCB with toner over tracks
Etched PCB with toner over tracks
After etching, wash the PCB with water, then use a harder sponge to clean toner. You could also use acetone, alcohol or cleaning products. Avoid sand paper. You don't want to make tracks thinner.
Copper tracks after cleaning the toner
Copper tracks after cleaning the toner
Now, all it remains to do is to drill the holes. The toner transfer method can also be used for printing the silkscreen. It looks good although it's not very scratch resistant. Using the same method (obviously without etching) I created the silkscreen shown in the top photo.

To prevent copper oxidation, I recommend covering the tracks with a mixture of rosin flux dissolved in isopropyl alcohol or acetone. If you used acetone, it will soften the toner on the silkscreen, so try to avoid the mixture getting on the other side.

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