A printed circuit board, or PCB, is used to create a circuit by grouping electronic components. Most appliances like televisions, radios, computers and even your mobile phones have an electronics board inside them. This article will teach you how to use a light-sensitive photoresist for masking. It will also discuss the etching process, so that your board would be ready for component assembly.
Before you start etching a PCB, you must first create a schematic diagram. If a schematic diagram is already available, then you must test the circuit by either using a breadboard, or simulations software. You can use a breadboard to physically test if your connection is working. You must test your circuit against shorts and other faults, as well. Testing the electronics components should be also included in your list of tasks.
After the testing process, you can now mask the copper that you will exclude in the etching process. You can use a simple technique by using a permanent marker or a more advanced one called the photoengraving process.
A photoengraving process uses a special-purpose printed circuit board, which is called a light-sensitive photoresist. This technique uses a photomask to mark a portion of the copper excluded for etching, and a developer to remove the portion of the photomask coating. A photomask is just a plastic film where the PCB layout is printed. The developer dissolves the portion that the mask leaves unshielded.
In order to mask a photoresist PCB, its protective covering must first be peeled off. The photomask is then placed on top of the special PCB. An intense light source is directed at the top of the photomask, while the board is at the bottom. After a few minutes of exposure, the PCB is detached from the mask.
The board is submerged into a basin that contains water and the developer. Through constant agitation of the basin, an image has been revealed. The printed circuit board has formed an image similar to the mask. The parts which are unshielded were eaten away by the developer. The board is now developed using photoengraving, and is now ready for etching.
In the etching process, you must submerge the board in a mixture of Hydrochloric acid and hydrogen peroxide. A one-to-one (1:1) ratio of the two chemicals is recommended. It is also recommended to add a modest amount of salt to the mix.
Just make sure that you understand the health hazards of mixing these chemicals, because it will form a toxic chlorine gas. Wear gloves to protect your hands. You can also use a chemical called ferric chloride. Studies, however, suggest that this chemical is more harmful to you and the environment. Nevertheless, this iron variant is still the traditional and faster way to etch a copper board. Other studies suggest that you use a mixture of muriatic acid and hydrogen peroxide.
You must put the printed circuit board in a basin together with your chosen mixture. You must agitate the PCB in the basin until all exposed copper (those that are not marked) have all been dissolved by the acid. Remove the board from the basin, and use running water to remove any chemicals left in the board. Remove the mask that hides the copper. You can rub a piece of cotton (dipped in isopropyl alcohol) to the surface of the copper. You should now see that the copper circuit is etched in the board.
Do remember though, that a photoresist PCB is used for creating an electronics circuit layout. This is a more advanced procedure than just using a permanent marker in masking the copper lines. Still, you now know how to etch your printed circuit board. So, the last thing that you should do now is to assemble the circuit.
