Making Printed Circuit Boards
This project is about making printed circuit boards, check out the main project index for the rest.
I needed to attach some position sensors to the linear actuators I had made for Android 5 – Combotron.
These are sliding potentiometers which are in the style of faders on a mixing desk. the only way to mount them was with their PCB pins, so I decided to make some boards to fit them onto.
I could have just used a bit of stripboard (veroboard) but this is made of synthetic-resin-bonded paper (SRBP) which is quite brittle and likely to break with not too much force. I decided that I should use fibreglass board as it is much stronger – but they don’t make fibreglass stripboard so the only option was to make a printed circuit board (PCB).
This article is intended to show the easiest way of making PCBs for the minimum cost with virtually no specialist equipment. First you will need some etching solution.
DANGER: this is Ferric Chloride – it is corrosive to metals, skin, clothes etc:
Next you will need an ‘etch resist pen’. This is not a normal pen, but a special pen that will resist the effects of the etching solution for a limited time. You will also need some ‘copper clad board’. This is fibreglass board which is coated on one (or both) sides with copper.
All you have to do is draw on the board with the pen where you would like the conducting circuit board tracks to be:
REMEMBER: this is the bottom of the board so you must draw the track layout as a ‘mirror image’ otherwise it will be the wrong way round when you turn it over.
Right, now you are ready to etch the board. If you buy ready made etching solution then you should dilute it 1:1 with water. You can also buy ‘etch crystals’ which you mix with warm water to make the solution. Always read the directions on the packaging.
Use a PLASTIC container to put the solution in – not metal, keep everything away from metal. I put mine on the draining board which is a really bad example:
REMEBER: if you leave the solution lying around the house make sure it is in a sealed container and labelled clearly. If you get it on your skin it won’t burn you right away but make sure you wash it of with soap and water. USE GLOVES or a plastic stick to poke the board around with.
If you stir the solution so it moves over the surface of the board it will etch quicker, it should take around 20 mins. The solution will be good for several boards but it will get slower the more copper is removed from the boards and added to the solution.
Here are four of the finished boards, these are the left hand boards, the others shown above are the right hand boards which is why the tracks look totally different:
Next you will need to drill holes in the right place for the component legs and solder them on:
And here are the eight finished boards: