PCB fabrication is a complex process that often involves a lot of careful steps in order to achieve a fully-functional finished product. The first step often involves choosing the material to use for the base board. Most PCB manufacturers choose a flat sheet of fiberglass as the material for the base because this does not conduct electricity. It is then coated with a thin copper sheet that would serve as the surface where all the PCB components would be mounted on. The copper sheet also serves as the layer that holds the printed diagram for connecting all the components correctly.
During the initial stages of the PCB fabrication process, engineers already determine whether the PCB would be made as a single-layer or multi-layer circuit board. This would mostly depend on the type of device that the PCB would be used for. Determining the type of PCB beforehand also plays a big role in creating the schematic diagram for the design that would be etched onto the board’s copper plate.
The diagram is etched onto the plate in two different ways :
1. By manually drawing the design onto the plate using a permanent marker.
2. By drawing the diagram on the computer and printing it using a LaserJet printer either on the glossy side of a photo paper or on a piece of transparent paper. This printed diagram is transferred onto the circuit board by sticking the printed part of the paper onto the copper surface. It is then pressed with a pre-heated clothes iron for several minutes until the design transfers completely onto the copper surface.
The manually-drawn or computer-printed diagram is etched permanently onto the copper plate by dissolving the board in a basin that contains a mixture of water and hydrochloric (muriatic) acid. A lot of people who engage in do-it-yourself (DIY) PCB fabrication as a hobby often make use of this method since it is cheaper. However, it has to be noted that this process can be a bit risky since the fumes of the chemicals used for etching could cause permanent damage to the sensory receptors on the nose. Some precautions that have to be undertaken before the etching process include:
1. Make sure that there are enough openings in the workroom for the fresh to circulate. It is best to keep the windows open while the board is soaking on the acid-water mixture.
2. Make sure that the work area is free from clutter to avoid accidents. This precaution has to be taken not just while etching the diagram onto board but all throughout the entire PCB fabrication process.
3. Keep all the tools and materials away from children. It is best to create the PCB in a room where kids don’t normally go to.
4. Wear protective gloves when handling the copper plate, especially after it has been soaked on the etching solution.
5. Wear a mask especially when pouring the acid onto the basin to avoid inhaling the fumes.
Hobbyists who wish to avoid the risks posed by the chemicals used for etching the diagram onto the board can simply purchase a circuit board that already has a printed design on it. This way, they would only need to work on the component-mounting stage of the PCB fabrication. They can choose between either of the following methods for mounting the components onto the circuit board:
1. The traditional through-hole technology, or
2. The more recent surface mount technology
In some cases, a hobbyist might need to make use of both methods especially when mounting components on complex diagrams for circuit boards with multiple layers. Regardless of which method they choose to employ, as long as they have a sturdy soldering iron then they should be good to go.
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