Learning how to etch a pcb

On this tutorial we show how to print a PCB using chemicals.

The first step is to design the desired circuit. We use Eagle by Cadsoft, which provides a free to use version with only board's size limitation. The following picture shows our schematic: It's a simple test board for Atmega328p MCUs.

 After designing the schematic, board designing comes. Next picture correspond to: a) Complete board ; b) Bottom side ; c) Top side.

We put some text on both sides of the board for two reasons: First one because... It's cool ;), but mainly because it helps us checking if the footprint has the right orientation.

We are going to expose a photosensitive double sided cooper board with an UV box, so firstly we need to print the board and make paper transparent with a transparent spray (Pausklar 21 by Kontakt Chemie. It's also possible to use some kind of uncolored body oil but Pausklar is better).

Take care about aligning properly both side of the board:

Then introduce the cooper board between both papers, use the transparent spray and put it into the UV box. The exposure time is ~3 minutes (But it sometimes varies depend on the manufacturer). Don't forget to expose both sides!

After exposition, introduce the board into a solution of caustic sosa (Dissolve 15g into 1 L of water) and wait until the footprint appears.

Clean the board and prepare a mixture of chlorhydric acid (HCl)  and peroxide (H2O2). We recommend you to add progressively the peroxide to the HCl in order to control the speed of the etching (Slowly etching is recommended if there are thin traces in the board):