Wednesday 6 January 2010

Home-made (bodged) PCBs!

For a little while now, I've been interested in trying to make my own PCBs using the laserprinter method discussed on MAKE. I finally got around to trying the method today, and I'm really impressed with the results! For my first attempt, it worked well.

I needed a temperature controlled waterbath for a separate project, and I found a suitable circuit on the internet, courtesy of a Make article.
Instructions and comments below:

It had a PCB diagram, so I didn't need to mess about with designing my own.
Print out the PCB diagram, at the correct size, mirrored, then use it to cut a copper PCB to the right size. For my first attempt, I made a couple.Make it as dark (as much toner) as you can.
From PCB
Clean the surface of the copper as well as you can. Any grease stops the toner sticking. I used a green scourer and some 'Cif'.
From PCB
Take your dark laserprinted PCBs, and tape the copper side of the PCBs to the stencil.
From PCB
I then ironed the back of paper (setting on 3 dots), letting the heat soak into the copper. The heat causes the toner to melt and to stick to the copper. Spraying water on the back of the paper, you can see the toner stuck to the copper:
From PCB
Using water and rubbing, most of the paper can be removed, leaving the toner on the PCB. It seemed to be pretty well stuck on, and only a couple of little gaps.
From PCB
When you've got the paper off you can see the layout on the copper board. Any gaps or tidying up can be done with a sharpie marker - apparently they are also etch-resistant, like the toner.
From PCB

Now, it's time for the etching. I got a standard bottle of etching solution from Maplins. Note that this can be messy and this stuff is nasty chemicals - treat with care. It will stain pretty much anything it comes into contact with (including stainless steel sinks!). Wear rubber gloves and take care.
I poured some into an old plastic container, and used a soaked tissue to dab and rub it onto the board. The toner works pretty well as a stencil, resisting the etching - and dabbing it by hand allows you to pay extra attention to the edges or places where it needs more.
No pictures, I'm afraid, as my hands were all dirty.
After a few minutes, it's fairly obvious when the copper is etched away. I was able to rub over a few areas that weren't quite done yet to finish it off, then I dunked them in a big bucket of water to clean them up.
The black toner can then be scrubbed off using a green scourer, leaving a completed board:
From PCB
This left a pretty good result. It still needs drilling (a chance to use my new Dremmel! Yay!) and a little repair where the toner didn't stick, but I'm pleased with the first attempt.

This technique looks suitable for the few 'one-off' boards for specific projects now and again.

The final result:
From PCB