Although I’m a big fan of PCB-Pool, I’m trying to learn to make simple printed circuit boards at home instead of having to send out (and wait days or weeks). I’m attempting the toner-transfer method now; I don’t have it quite right yet, but it seems doable…with the right process. It sounds great in concept:
- Print the a mirror image of the pattern to be etched using a laser printer on suitable paper
- Transfer the toner image from the paper to a blank copper clad PCB using heat and pressure (iron-on)
- Etch the PCB with the toner acting as resist
- Use acetone to remove the toner leaving the desired copper pattern
- Optionally tin plate
- Drill and mount components!
So far, my main obstacle has been clean and heavy toner transfer. I’ve been able to transfer some fairly fine patterns (15 mil lines with 15 mil spacing), but invariably some of the toner doesn’t transfer and then touch-ups are required. Also, the toner appears to have some holes in it which results in pitting during etching. Using sharpie to touch up the toner seems to help a bit, but the sharpie often is removed in the etching process.
- Pages from a regular magazine (e.g. IEEE spectrum) that are thin and glossy seem to work better than expensive thick glossy paper. The toner transfers onto the page and the page releases it onto the circuit board fairly cleanly. The ink on the magazine page seems irrelevant to the process.
- Blank copper clad boards are cheap and plentiful on eBay.
- Preparing the blank board with a scrunge and tarn-x seems to help.
- I’m using a harbor-freight $30 laminator to do the toner transfer…I can’t yet tell if it works better than an iron…I need to do some head-to-head experiments. The PCB + paper just barely fits through the laminator and requires a bit of a push to get started. I make 6 or 7 passes through the laminator then soak the board in water to get the paper off.
- 2oz copper cladding takes a long time to etch…need to get some 1/2oz
- No success with sponge-etching…it mainly removed toner.
- Peroxide/vinegar/salt etchant seems to work, but slowly…I need to work more with this. It is certainly a much safer chemical process.
- Even the old standby ferric chloride seems to take a long time…I may need to get/build a more sophisticated etching tank (heater+agitator or sprayer)…and then there’s the disposal problem. I was mixing my own and may not have made it strong enough
- HCl (Muriatic acid) + H2O2 etching seems to work very fast, but it is quite aggressive and eats away a lot of the resist.
If I can’t get this to work reliably, I’m going to try a commercial toner transfer solution and then try using photoresist which may cost a bit more, but might save lots of time and aggravation. I also ordered a CNC machine which will, I hope, automate the drilling of vias and through-hole pads. (and can also be used for isolation routing of boards to eliminate etching entirely in some cases).