The “Toner Transfer” method is probably the simplest and most cost effective method to make high quality PCBs at home. With a little practice, any one with access to a laser printer, or photocopier, can make a quality board in around an hour. For the purpose of this tutorial, I am assuming you already have the means to design, and print your PCB.
- Toner Transfer Paper
- Copper Clad Blank PCB
- Blue Painters Masking Tape
- Isopropyl Alcohol (contact cleaner)
- Lint Free Wipes ( coffee filters are cheap and work well)
- Fine Sandpaper (1200 or similar)
- Clothes Iron
- Ammonium Persulphate Or similar
I can’t stress enough that cleanliness is the key to success. Fingerprints, dust, oxidation, even fibres or a hair can cause problems.
Mark a piece of paper in your printers tray, so you can identify the direction easily then print your PCB design.
Cut a piece of Toner Transfer Paper a little larger than your artwork, and tape it to the sheet of paper you printed covering your design. You need to have the shiny side facing up. Tape it top and bottom, making sure that the corners are taped down and the tape is cleanly fixed to the paper. Folded back corners may cause the paper to jam or tear in the printer, or allow adhesive from the tape to stick to the print rollers.
At this stage I usually wipe the surface of the Toner Transfer Paper lightly with a lint free cloth that has been slightly dampened with Isopropyl Alcohol on. This is not always necessary, but will remove any fingermarks, and helps with some printers that struggle to print cleanly on the glossy surface.
Place the paper in the print tray and reprint your design. If you have put the paper in the printer the right way around, You will now have your pattern in the middle of your Toner Transfer Film, ready to be transfered to your board.
Your blank PCB should be cut to the correct size, and any rough edges and corners should be smoothed with sandpaper. It is essential that the top edges are not rough. Clean the copper surface under running water, first with detergent, then with fine sandpaper. I find 1200 grade wet and dry paper works well. Sand until the surface is shiny all over, but don’t sand away too much of the copper. Dry the board with a lint free cloth, and then clean the copper with acetone or isopropyl alcohol and another lint free cloth.
The iron will need to be heated quite high, and should NOT be set to steam. I use the “cotton” setting on mine .Place the blank on a heat resistant surface and position the toner transfer paper with the toner against the copper. Hold it in place and press down on one side with the iron. Around 20 seconds will stick the transfer paper in position. Now press the iron down over the entire board. Hold firm downwards pressure for 30 – 40 seconds before removing. Don’t slide the iron around or you will smudge your image, and firm pressure is all that is needed.
Cool the board and paper under running water then slowly peel the toner transfer film away from the board. Start with one corner and peel towards the other corner. Almost no toner should be left on the paper. If the image is coming away with the paper, stop and re iron.
At this stage you need to examine the PCB carefully for missing tracks or pads. If you have been meticulous, there shouldn’t be any, but it can difficult to keep everything spotless, especially if you are working in a dusty old shed. No worries though. Permanent markers also resist etchant, so you can touch up any gaps with a fine marker.
Once you are sattisfied, etch yor board following the instructions provided by the etchant manufacturer. I use Ammonium Persulphate. The instructions say to mix 400 grams of etchant crystals with 1.5 litres of water. For he board in this demonstration, I used One and a Half Tablespoons of crystals to 60 ml of near boiling water. I agitated it by shaking back and forth. Etching took around 4 minutes. With Ammonium Persulphate, the water needs to be hot. Agitation is also necessary to etch the board evenly. Etching causes bubbles of gas to form on the board, and these need to be disloged from between close together tracks or the copper will not be removed from those areas. If shaking does not clear the bubbles, I find a gentle wipe with a small paintbrush works. Etch untill all uncovered copper is gone. Then rinse with clean water.
Drill holes with appropriately sized drills.
After etching and drilling, use acetone and a rag to clean away the toner and expose the copper tracks. If you are not going to use the board immediately, you can leave the toner on to help protect the copper from oxidation. The labeling on the board pictured was also done using the toner transfer paper, and ironed on after etching.