There are two problems with having PCBs professionally made: firstly it costs a lot of money, especially if you only want one or two made, and secondly it takes a long time.
Making PCBs at home is cheap, quick and easy. I’ll now describe the ‘Toner Transfer’ method I use, based on other people’s methods from across the internet. The beauty of this method is that you probably already have everything you need to get started – the only likely exception being chemicals needed to etch the board… this really is the cheapest method possible!
Things you’ll need:
- Glossy photo paper.
- Copper clad board.
- A monochrome laser printer.
- A household iron.
- An etchant solution (more on this later!).
I’ll be etching the PCB for my Fermentation Controller.
Step 1 – Print your Design
Print your design onto the glossy side of the photo paper. Here I’m using Eagle. I like to print a test page onto plain paper first, to make sure the scale is correct. I’ll also check the components will fit etc., as this is the last chance to easily fix any mistakes!
Be very careful not to touch the printed design. Grease from your fingers will inhibit the adhesion of the toner onto the copper.
Step 2 – Clean your Copper Clad Board
We will soon be transferring the toner, which you printed onto the glossy paper, onto the copper clad board. To ensure the toner bonds nicely to the copper, the copper needs to be clean. I first use wire wool to remove the oxide layer of the board and then go over it again with some white spirit.
To the left is the printed design. Note, when cutting out the design, I left a small strip at the far end with which to hold the paper. This avoids touching the design itself. Note also the dirt on the white cotton wool!
You can see the white spirit is almost dried – once it has, move onto the next step.
Step 3 – Iron the Design onto the PCB
Position the design with the printed side touching the clean copper. Set your iron to maximum temperature and, once heated, place on top of the design. The goal of this step is to melt the toner whilst simultaneously applying pressure from above. This will make the toner stick like glue to the copper.
Press firmly down on the iron for several minutes – this will heat the board through and melt the toner as desired. The glossy paper will now be stuck to the board.
Step 4 – Removing the Glossy Paper
We now want to remove the glossy paper whilst leaving the toner stuck to the board. This is best done by soaking the board and paper in hot soapy water:
Leave the board in the water for 20 minutes or so – the longer the better. With any luck it should come out looking like this:
And the glossy paper will peal off with ease, leaving the toner stuck to the copper:
I generally find a glue-like residue is often left in places where the copper should be bear. For example, take a look at the white residue either side of the track in the bottom left hand corner of the following photo:
This can be removed by gently rubbing the surface with a toothbrush. Cut the board out and leave to dry – it should look something like this:
If there are any areas where the toner has come away from the copper, touch them up with a permanent pen. The board is now ready to etch!
Step 5 – Mixing the Etchant
I use a mix of Hydrogen Chloride (HCl) and Hydrogen Peroxide (H2O2). This is easier to use than Ferric Chloride, is less messy and is also easier to source. To learn about the chemistry, click here.
In the UK, H2O2 can be bought in small quantities from chemists. Boots often don’t stock it – I’ve found it’s best to ring and check first. Annoyingly, they often only let you buy one bottle at a time (good for an etch or two), due to anti-terrorist laws (buy enough and you can make a bomb!).
My source of HCl is brick cleaner. The bottle shown below contains 10% HCl. The bottle of H2O2 is 5%. At these concentrations, they should be mixed at 2 parts HCl to one part H2O2.
Step 6 – Etching the PCB
It’s time to etch the PCB! Obviously these chemicals are dangerous – use gloves and eye protection!
The etchant will dissolve the copper not covered by the toner, leaving you with your design. Swill the etchant over the board to speed up the process:
Here you can see the etching process is almost complete:
Note the etchant turns blue, due to the copper now in solution. Once finished, carefully remove the board with a pair of pliers and wash it off with some water. Finally, use some wire wool to remove the toner, revealing the copper tracks of the PCB!
Step 7 – Drill the Board
I use a pillar drill, set to high speed, to drill the board. Below are the drill bit and adaptor used.
You’re now ready to solder!