When it comes to making a homemade PCB, you can find several methods online: from the most rudimentary, using only a pen, to the more sophisticated using 3D printers and other equipment. And this tutorial falls on that last case!
In this project I show how to fabricate a printed circuit board using a low cost and low power laser cutter.
Until recently, you would only find one of those machines in makerspaces or other comercial facilities. They would cost thousands of dollars, so that an ordinary maker wouldn’t be able to have one for himself. Luckily now there are several laser engraving machines available online! Most of them have low power laser and might be used only for etching and engraving drawing in different surfaces (glass, metal or wood for instance). Their surface area and laser power are only a fraction of professional machines, but it would be a good start for makers and hobbyists.
In this tutorial I’ll show you how you I used a low power laser engraver to produce a printed circuit board (PCB). It would be a good alternative if you want to make your first prototype of a circuit board (at least until you order a better version from an online manufacturer!).
You can find the laser cutter I’ve used in the following links:
The following tools and materials were used in this tutorial:
10W laser engraver (link / link / link). It was used for printing the circuit drawing on a blank copper PCB board.
Copper PCB (link / link / link). Homemade circuit boards are usually printed on copper coated phenolic plates. The whole surface of the board is coated (on one side or both). Copper is a conductive material, while the phenolic substrate can't conduct electricity. By removing parts of the copper layer, one can create tracks between the components, creating the circuit board.
Latex PVA water based ink. As you will see later on this tutorial, I used water based ink to create a mask on the surface of a copper PCB. This mask prevents parts of the copper layer from being removed by the ferric chloride solution.
Paint brush. A thick layer of paint will have to be applied on the circuit board, and a paint brush will be usefull here.
Ferric chloride. This comes as a salt and should be dissolved in water before it's used. This solution is able to corrode copper, removing it from it's phenolic substrate. Apply a mask and only the parts of the copper plate exposed to the solution will be dissolved.
Sandpaper. In the end, you'll have to remove the remaining mask from the board. This can be done easily using a sandpaper.
Homemade PCB Manufacturing Process
The manufacturing process of homemade PCB usually consists of the following steps:
1. PCB design
In this step the drawing of the board to be produced is made. It is possible to both design a new board and make copies of opensource projects. Different CAD software can be used (Fritzing, KiCAD, Proteus, Eagle, etc.).
2. Apply a mask on the PCB
Once the printed circuit board is designed, it must be transferred to the circuit board. There are several ways to do this: using the thermal method (by transferring toner from a sheet of paper to the plate, by applying heat), manually (by drawing the circuitry with a suitable pen) and even using a 3D printer. In this project, I used a laser engraver to transfer the design to the plate.
3. Chemical etching the PCB
Once the mask is transferred to the plate, corrosion of parts of the plate is performed to remove parts of the copper. At the end of the process, the board should only be with the tracks that make up the circuit.
4. Cleaning and finishing
Once the corrosion is complete, the plate will be ready to be cleaned, drilled and the components welded. After that, just check everything, power it up and be happy!
PCB Design and Creating the Mask
Once you have a PCB design (designed using any CAD software of your choice) you can export it in SVG format for reading in other graphic editing software. Several layers can be exported in this process: top view, bottom view, mask, silk, etc. All layers are available in normal or mirrored format. The fabrication process described in this tutorial requires that a mask be applied to the PCB. The part of the cover plate that is covered by the mask will not be corroded and will therefore be retained on the end plate. Parts that are not covered with the mask will be exposed to the iron chloride, being corroded and removed from the printed circuit board.
In this process it is necessary to coat the entire plate with a layer of paint, and remove only a few sections using the laser engraver.
In this way, the mask generated by most software should have its colors inverted (invert the black pixels to white and vice versa). To perform the mask inversion, two softwares were used:
- Inkscape: used to convert SVG files into image format (PNG). Also used to transform the drawing into a black and white image (if the CAD export in color format);
- Gimp: used to invert the mask color (white pixels in black pixels).
The resulting image is then loaded into the laser engraver software for printing to the surface of the plate.
Pay attention to the dimensions of the image: check that the output dimensions of the laser engraver software are the desired ones for the actual prototype.
In the case of this tutorial, the design of a specific board was not done. Instead, I tried to replicate an opensource board, developed by Fábio Souza: Franzininho. This incredible board can be easily assembled and programmed by users of all levels, it is compatible with the Arduino IDE and entirely designed in Brazil!