Toner Transfer Paper

Toner transfer paper is a method of making PCBs at home.

You can buy special paper for making PCBs. I was wondering if it was possible to make your own toner transfer paper. It turns out you can. The key point about these types of paper is that they are coated with a water soluble coating that makes it easy to remove the paper from the PCB after you have heat fused the paper to the PCB. I used regular copy paper or onion skin paper and coated it with dextrin (vegetable based glue, similar to the stuff that is on the back of stamps and envelopes). The dextrin is made from corn starch.

Making the dextrin

• Pour a thin layer of corn starch (You can find this in your local supper market with the baking supplies) on a cookie sheet or pan. I just made the small pan out of some aluminum foil.
• Toast the corn starch in the oven until it is just starting to turn golden brown. (stir often so it does not burn. I believe I was using about 350 deg. F)

• Let the powder dextrin cool then it can also be stored in powder form.
• I was mixing enough powered dextrin with water so I got a consistency of thin syrup. I have not tried other consistencies yet some so thicker or thinner could be better.
• Be sure to get all the lumps out. I usually mix as much as I will need than seal it in a container and let it set for a day. This will let the lumps absorb some to the water and they will be easier to mix. I also found that I had to mix some rubbing alcohol in with it to keep it from growing mold. I think I used about 1/4 alcohol and 3/4 water. You can see what it looks like mixed up below.

Coating the paper with dextrin

• I spread a thin layer of the dextrin on a piece of flat metal. I am using and old piece of brushed aluminum that is meant to cover a 19 inch rack. I also use an old dot matrix printer roller as a rolling pin to spread out the glue.

• Then lay the paper on the glue. Quickly smooth the paper quickly to get the air bubbles.

• Then peal the paper up and hang it up to dry. You have to be quick about these last two steps because the glue starts to dry very quickly.

• After a day or two take the paper down and flatten. I store them in a folder between some heavy books to help keep them flat. As long as they are kept dry I have not had a problem with them sticking together. It takes a little practice to get the right amount of the glue on the paper. To thick and the glue will want to crack and flake off to thin and it will not protect the paper from the toner. I just trim the paper to the size of the PCB that I am making.

Using the toner transfer paper for etching

I am using one of my projects as an example. Just as reference most of the traces on this PCB are 40mil, 80mil, or 100mil.

• I print out a copy of the PCB that I will be etching. I use this to check that things look OK and I will use this sheet to center the toner transfer paper when I print it.
• Now I will cut a piece of the toner transfer paper that will be a little bigger that the PCB that I will etch. See that I used masking tape and only on the top of the paper. DO NOT use plastic tape like scotch tape because it could melt to the fuser in your laser printer. If you tape the bottom it will wrinkle and not print as good.

• After it has been ran through the printer again it will look like this. I am using an HP LaserJet P1006 and it seems to be working pretty good.

• Then I heat press the toner paper with the image on to the copper clad with an iron. The key to getting the paper to stay stuck to the copper clad for me was to keep pressure on the paper and the copper clad while they were cooling. If I did not do this then the paper wanted to curl and bubble before the toner had a chance to cool enough to stick to the copper.

• Next I trimmed the PCB with a band saw.

• After that I soaked the PCB and paper in some warm water so the paper would release from the toner. most of it should release from the toner after a while (~30 min.). Some times I have to gently pull on the paper to get it to release the last little bit. Then the toner is left on the copper.

• Now the PCB can be cleaned up and fixed. I fix the places where the toner did not stick to the copper with a sharpie and clean up any areas where the toner smeared with an exacto knife.

• After it was etched it looked OK, it just needs a little cleaning.

For more information about etching chemistry take a look at this link.

http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/index.html

• After cleaning with a little acetone. There was a little bit of over etching in a few places but it was not to bad.