on video What is a PCB?



What is a PCB (printed circuit board)? The definition of PCB

PCB Definition

A printed circuit (or PCB in English) is an electrical circuit whose electronic components and conductors are integrated into a mechanical structure. A PCB is made up of several layers of copper covered with an insulating material.

In addition to many components, circuit boards require connectors such as copper traces, pads, and heat sinks.

The layers are etched by a chemical process. The main structure is plated, then covered with a non-conductive solder mask and silkscreen, which indicates the location of the electronic components on the board.

The printed circuit is constructed by alternating layers of conductive copper and layers of non-conductive insulating material.

During the manufacturing phase, the internal copper layers are etched to reveal the copper tracks that will be used to connect the circuit components. After etching, the insulating material is laminated to the surface of the copper layers until the printed circuit is completed.

The tracks electrically connect different areas of the circuit board. The pads, once perforated, establish an electrical connection, either between the components soldered through the printed circuit, or between the different layers of copper.

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Panneaux latéraux

Sometimes, non-perforated pads are used to solder so-called “surface mounted” (SMT) components. Heat sinks help ensure control of the circuit board temperature.

For the circuit board or PCB to perform optimally, it is very important to have a well-prepared and organized project, and this is where the best unified PCB design software Altium Designer comes in.

Once all the layers have been etched and assembled, the components are placed on the outer layers of the printed circuit. Surface mount components are placed automatically by robots while through-hole components are placed manually.

All of these parts are then soldered onto the board using techniques such as reflow soldering or wave soldering. Finally, the final assembly is plated, then solder mask and screen printing are applied.

The different types of PCBs

Several types of PCBs exist. They are suitable for different uses such as for industrial equipment, the medical environment, the aeronautical environment, for automobiles or even lighting.

As the name suggests, single-sided circuits have a single side of copper deposited on an insulating support. This type of circuit, which is inexpensive, does not make it possible to produce assemblies of high-density components, not very resistant to mechanical stresses, limits this type of circuit to applications for the general public.

In double-sided circuits, the insulating support is sandwiched between two layers of copper, with one side for the components and one for the solders. This arrangement allows the tracks of different potential to cross on the opposite faces, which makes it possible to increase the density of components.

Finally, in multilayer circuits, there is a stack of electrical layers (up to 22 layers in rare applications) separated by a very thin insulator. The layers must all be perfectly superimposed on each other and communicate via vias or metallized holes.

The tools for the latter are often quite expensive and often result in mass production to make the latter profitable.

PCBs can be rigid or flexible/soft. The latter are made from thin insulating material such as plastic and can be adapted to the housings of the devices. The flexibility saves space and reduces the cost of production.

They are often used in special applications with very high integration density such as computer keyboards, or in RFID tags.

Circuit board history

Before going further in the definition of a PCB, it is necessary to understand where these electronic boards come from. Because the latter have come a long way before the appearance of HDI designs with hundreds of holes and circuits whose electrical connections are now capable of powering everything from smartphones to rockets to heart monitors.

The journey that transformed our wiring boards into flexible printed circuits, and which will continue to evolve this technology, has given us a great adventure.

Before the emergence of printed circuit boards, electrical circuits were designed by attaching individual wires to components. To obtain conductive paths, the metal components were thus welded using wires.

The largest circuits, which accommodated many components, could therefore contain an impressive amount of wires. Thus, when the number of wires reached peaks, it was not uncommon for them to become entangled or for the space occupied by the circuit to have to be enlarged.

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