Printed circuit board is the most important part of electronics. Alternately, the acronym has also accounted for printed wiring boards and printed wiring cards, which are essentially the same thing. Due to the crucial role of these boards in everything from computers to calculators, PC board material selection should be undertaken with care and knowledge for electrical necessities of a given piece of equipment.
Before the development of the PCB, circuit board materials were mostly covered by nests of entangled, overlapping wires that could easily fail at certain junctures. They could also short circuit once age took hold and certain wires started to crack. As could be expected, the manual process that went into the wiring of these early boards was confusing and painstaking.
As an increasing variety of everyday electronic components began to rely on circuit boards, the race was on to develop simpler, more compact alternatives, and this led to the development of the material, PCB. With PCB materials, circuits can be routed between a host of different components. The metal that facilitates the transfer of current between the board and any attached components is known as solder, which also serves a dual purpose with its adhesive qualities.
PCB generally consists of four layers, which are heat laminated together into a single layer. The material used in PCB from top to bottom includes Silkscreen, Soldermask, Copper and Substrate.
The last of those layers, substrate, is made of fiberglass and is also known as FR4, with the FR letters standing for "fire retardant." This substrate layer provides a solid foundation for PCBs, though the thickness can vary according to the uses of a given board.
A cheaper range of boards also exist on the market that don't utilize the same aforementioned PCB materials, but instead consist of phenolics or epoxies. Due to the thermal sensitivity of these boards, they tend to lose their lamination easily. These cheaper boards are often easy to identify by the smell they give off when being soldered.
PCB second layer is copper, which is laminated onto the substrate with a mixture of heat and adhesive. The copper layer is thin, and on some boards there are two such layers - one above and one below the substrate. PCBs with only one layer of copper tend to be used for cheaper electronics devices.
The massively-used copper clad laminate (CCL) can be classified into different categories according to different classification standards including reinforcing material, used resin adhesive, flammability, CCL performance. The brief classification of CCL is shown in the following table.