Etching Printed Circuit Boards

Interactive installations often require electronics and ours is not an exception. One way to produce the needed electronics is to solder all your components onto experimental circuit boards. This means you have to create all the electrical circuits yourself using wire or solder. It’s a great way of making a quick prototype but the downside is that it often results in a chaotic mess that is hard to debug if something doesn’t work. When you’re making one prototype this is not a huge issue but when you’re mass producing the same board multiple times it can get very frustrating and slow you down considerably.

In order to make our lives easier we decided to design printed circuit boards. The first step is to create a schematic of your circuit. The schematic has nothing to do with the physical world but is just a drawing of how all the components should be connected in theory. To make this schematic we used the program ‘PCB Artist’.

When it’s finished, the schematic can be imported to another part of the same program where you can edit the physical appearance of the PCB. All the components and their connections are imported and displayed in their physical form.

This is where the design of the PCB really starts. You have to untangle all the crossing wires and draw the connections. Due to the complexity of the circuits it’s usually impossible to make the circuit without wires crossing each other. This can be remedied by making jumper wires on the other side of the PCB to cross over the printed circuit. This creates extra solder work though and is preferably kept to a minimum.

Once the design is complete the production can begin. PCB’s consist of a couple of layers. The first is a plastic non conductive layer that is only there to support the other layers. The second layer is a thin layer of copper over the entire surface of the board. The top layer is a photosensitive layer.

To produce your PCB the first thing to do is print your design on a transparent sheet in as dark and dense black as possible. We used a simple laser printer to do the job. The photosensitive layer on the PCB is effected by UV light. We used an old scanner in which we installed UV lights. We placed the printed transparent sheet on the scanner with the PCB on top. We switched the UV light on for 40 seconds. The photosensitive layer is affected by the UV light in such a way that afterwords only the parts exposed to UV light can be removed with an alkaline.

This is the next step in the process. The exposed PCB is placed in a an alkaline solution. We used drain cleaner for this. The parts of the photosensitive layer that were exposed to the UV light will dissolve. This is when you can see your design on the PCB for the first time.

Once the photosensitive layer is removed it no longer protects the copper layer underneath. To remove the copper we used ferric chloride which becomes acidic when dissolved in water. The acid eats away the copper where it isn’t protected by the photosensitive layer.

What remains after this is just the copper you need to make the circuit with a photosensitive layer on top. The last step is removing the remaining photosensitive layer by placing the PCB in in the UV light without any protection and back in the alkaline solution again. This removes the remaining photosensitive layer and you’re left with a (hopefully) working PCB.

One final effort is all that remains. All the components have to be soldered onto the PCB. Once this is done the PCB is finished and ready to use.

Designing the PCB’s takes time but once that’s done the are very easy to mass produce and the process will save you lots of time in the long run.