I am finally having success making single-sided PCBs at home using the toner transfer process. I am generally using traces no thinner than 12 mils (although I think I did 10 mils a few times and it worked fine) and 12-15 mil spacing. With modern surface-mount parts, it’s amazing how much of the circuit can be done in a single layer and without drilling.
I’m using products from PulsarFx that are specifically made for this process and they work much better. I came tantalizingly close many times using McGyver methods (magazine paper, clothes iron, etc.), but it never worked quite right and cost many hours of frustration. In particular, getting the paper to release from the toner was always a problem and I often experienced over-etching. I tried magazine, matte, and many varieties of glossy paper from Staples. In the end, the PulsarFx products are not that expensive and work perfectly.
I have no relationship with PulsarFx other than that I am a customer and am now a fan.
The current process:
- Print on PulsarFx toner transfer paper using an HP 1025nw printer. Printing did not work well with my Canon D420 printer (did not put enough toner down) and I couldn’t feed the thick transfer paper through my Samsung ML-1865W or ML-2160. The transfer paper is coated with a material that dissolves quickly in water, so after the toner is transferred to the copper board, the paper releases perfectly every time. Configure your printer for thick glossy paper, black or grayscale, and maximum toner output.
- Clean a blank copper board to a bright shine using steel wool. I get the blank copper-clad boards on eBay from seller abcfab; ideally you should use 1/2oz copper for much faster etching, but I’ve also had success etching 1oz and 2oz copper. After cleaning with steel wool, I’ve tried using tarn-x and/or acetone and they may help slightly but I’ve had good results without them. Once the board is bright and shiny everywhere, don’t touch it with your bare hands…use gloves to avoid getting skin oil on it. I use nitrile disposable gloves throughout this process; they cost $8 for 100 at Harbor Freight Tools.
- Place the printed pattern face down (toner touching the shiny copper) on the copper board and run it several times (like 10) through a laminator. I am using the PulsarFx “Applicator” which is just a big laminator. I also have a much cheaper Harbor Freight Tools laminator which I am going to try and report on. The board gets hot after a few passes through the laminator so I use leather work gloves.
- After lamination, soak the board with the transfer paper stuck to it in water, I use a plastic tupperware container. After a minute or two (sometimes within seconds), the paper’s coating dissolves and the paper just floats away from the copper board leaving the toner pattern on the copper. Throw away the paper and pat the board dry with a paper towel. The water and container gets used again later in this process so keep it handy.
- Follow the directions on the package and cut a sheet of PulsarFx Green Toner Reactive Foil a little larger than the copper board (2″ longer). Place the foil dull-side down on the board and wrap 2″ under the board. Place the side with the board with the 2″ wrapped under it in the laminator and try to keep apply some drag to the foil with your fingers as it goes through the laminator to prevent the foil from wrinkling. I don’t have this quite right yet, but it still works pretty well. I put it through the laminator a second time to make sure it has stuck. Then peel the foil back from the board at a 180-degree angle. What’s left is green foil covering most if not all of the toner. The foil creates a stronger barrier to the etchant; without it, the etchant sometimes eats through the toner in places before the etching is finished resulting in pitting or uneven edges. With the foil, I get perfect etching and nice clean edges, even with 2oz copper on the boards.
- In another plastic (e.g. tupperware) container, mix the etching solution using nitrile gloves and chemical protective glasses, and preferably wearing old clothes: pour 1 cup of hydogen peroxide (purchased at my local supermarket) into the tupperware then mix in 1 cup of muriatic acid (hydrochloric acid) which I get in 1 gallon containers from Lowes which costs around $5/gallon. I use a disposable styrofoam coffee cup as a measuring cup. Because this is a sadly litigious world: these are harsh chemicals; don’t get them on your skin, on your clothes, or in your eyes; it is acid, it’s dangerous. Use proper protective gear, if you don’t know how to handle chemicals, don’t do this. Proceed at your own risk. I do this in the back yard because the fumes (and liquid) can be corrosive to nearby metals. I am going to try this again with the white vinegar/peroxide/salt etching method and report back.
- Place the copper board in the etching solution with the pattern facing up; every minute or two gently brush the surface of the board with a foam paint brush (around $0.79 from Lowes). Brush it a few times to brush away the etched material and expose more shiny copper; this makes the etching process go much faster.
- When the copper is all gone and only the toner/transfer foil is showing, remove the board from the etchant and place it in the other tupperware container containing just water to stop the etching. Note: the etchant solution doesn’t seem to effect the nitrile gloves so I just take it out by hand.
- Carefully (gloves, chemical glasses) pour the etchant into a plastic container for storage and/or disposal. I use a plastic funnel and a plastic bottle that seals liquid tight (e.g. an iced tea or juice bottle). Take your time doing this so nothing splashes out. Seal the bottle, then rinse clean your brush, tupperware, circuit board, etc. You can’t just pour the used etchant down the drain (it is toxic and will probably ruin your pipes). Take it to your local recycling/waste disposal facility for proper disposal (I’m looking into ways to manage this better).
- The final step (for me, for now) is to remove the toner and foil from the board. This is done using a rag or paper towel and acetone (which also costs around $5/gallon at Lowes). Do this outside too, acetone is very smelly.
When you are done, you will have a nice shiny PCB ready to solder (or drill if you are still using through-hole parts). Total time is under 30 minutes.
- For drilling, I use an old Dremel model 380 rotary tool and an old Dremel model 210 drill press (purchased on eBay for ~$20 shipped – they are commonly available there – note, this press only fits tool models 245, 250, 260, 270, 280, 350, 370, and 380). I’ve read that the 210 press is much more precise than the newer ones but I can’t confirm that. I can confirm that this combination drills precise holes in the PCB. I get carbide drill bits that fit the rotary tool from Harbor Freight Tools. You can also get them from All Electronics or Ebay.
My next steps are to experiment with soldermask, silkscreen, photo-transfer, and multiple layers. I’m also going to look into more environmentally friendly etchants or good ways to make the left over etchant non-toxic.