There are two layers of each and every PCB. The first layer or the bottom layer is a conductive one and the second one is an insulating layer. The first layer is made of copper foils and the second one is made of prepared resin. The board is usually coated with a green color solder mask. Other colors such as blue, white, red and black are used in place of green. You can use different materials to provide different insulating values to your device.
Most of the boards are made by combining the copper layer with the entire substrate on both sides. Then the unwanted copper is removed by virtue of a temporary mask, leaving only the copper traces. Some of the PCB’s are built by adding the traces to bare substrates. The manufacturing method of PCB varies depending on the purpose of the circuit board. It may be for a small sample or a production volume.
Etching is a chemical procedure where ammonium persulfate or ferric chloride is used to etch off the unwanted copper. After the unwanted copper is removed, only bare copper remains. Some of the PCB’s do posses trace layers inside it and those layers are called multi layer and the PCB is called a multilayer PCB.
There are many small holes on the circuit board and they are drilled with a little drill bit. It is an automated drill machine and is controlled with a drill tape. Vias allow the thermal and electrical connection of the conductors on the other sides of PCB.
The board is usually plated with tin, solder or gold that helps to etch away unnecessary underlying copper.
There are some areas that are not soldered and those areas should be covered with polymer solder resist. This prevents the board from short circuiting. Various tests are done on unpopulated boards, namely the bare board test, flying grid testers, rigid needle adapter and many more.
After all those procedures have been done, then the electronic components are attached to the boards. You can use different soldering techniques in order to attach the components of the board. Some parts can be soldered automatically and others are done manually. PCB’s that are built for the extreme environments often do have conformal coating. Previously wax was used as a conformal coating but in modern time’s, solutions of silicon rubber and polyurethane are used for the coating of the board, although it also has some disadvantages as servicing of the PCB becomes extremely difficult.
Many PCB’s are static sensitive and should therefore be placed in an antistatic bag and the components of the board should be handled carefully.
These are the basic parts and the basic strategies of the PCB boards that are found everywhere in the world.
