All modern electronic devices now have a printed circuit board integrated within. These boards play very important roles in allowing interactive and intelligent services to users. Computers, TVs, coffee makers, refrigerators, washing machines and mobile phones all have PCBs that run their functions, allowing users for smart use. Most modern PCBs are made of laminated plastics that have soldered chips, metal circuits, sockets, different components and cables.
Types of printed circuit board
Over the years, there were many PCB types made in response to the growing need for increasingly sophisticated devices. There are various classifications, which includes according to type of substrate and how the layers were manufactures.
The different types according to substrate material include the FR-2 paper/phenolic, FR-4 epoxy, and FR-4 high and ultra-high performance.
The FR-2 Paper/Phenolic type of PCB uses synthetic resin bonded paper. This is a composite material produced from paper, which is impregnated with plasticized resin of phenol formaldehyde. The FR-2 sheet is most commonly used in the manufacture of low-end kinds of consumer electronic equipment.
The FR-4 Epoxy board is made of fiberglass cloth that is woven together using an epoxy resin as a binder. This binding material is flame-resistant, which means it has self-extinguishing capabilities. When electrical fires break out within the circuit, the natural characteristic of the substrate material discourages the fire from building up and spreading to other parts. The FR-4 material has nearly zero absorptive capacity, which means it does not absorb moisture that can be produced from the heat generated by electrical conduction. It also high values when it comes to mechanical strength. This means that the fiberglass substrate is able to withstand pressure and stress. Also, the high electrical insulating qualities as well as physical values are retained in both humid and dry operating conditions. Because of these characteristics, FR-4 epoxy PCBs function more often as electrical insulators.
Also, fiberglass has very high flammability values. This means that extremely high temperatures are needed before the material bursts into flames. For a fiberglass substrate to be considered as FR-4 and flame retardant, it must pass the standards of at least a UL 94 V-1a for plastics flammability.
Epoxies used should also be heat resistant, to avoid degradation when heat and moisture are generated when the device is used. The most common material used is brominated epoxy.
An FR-4 high and ultra-high performance printed circuit board is most often used for consumer electronics that are battery-powered and require circuit boards that are highly dependable. This maximizes the autonomy of the device, allowing for longer life and consistent function. These qualities are even more crucial for instruments and equipment used for military and aerospace applications, rapidly performing computer servers, and medical equipment and electronic instrument crucial for maintaining life. Most of these circuit boards used for these sensitive applications are PTFE-based. This is polytetrafluoroethylene, which allows for dielectric permitivity (Dk) and loss tangent (Df).
PCBs are also classified according to the layer of substrates used. This classification includes the single-sided board, double-sided board and the multi-layered board.
A single-sided printed circuit board is the simplest type. The substrate comes in a single layer. All of the electronic components and parts are grouped o one side of the side and all the copper traces in the other.
A double-sided PCB is the most commonly used type. Parts and components of the circuit are attached on both sides of the board’s substrate. There are connecting traces on the upper and lower surfaces of the substrate to ensure continuity of the connections.
There are multiple layers of substrate found in a multi-layered type of circuit board. The layers are separated by insulating material. These boards may have 4, 6, 8 or 10 layers. Some may even exceed 42 layers. Multi-layered boards are more commonly used in devices, equipment and instruments that require electronic circuits that are extremely complex.