PCB Components – Everything You Need to Know about the Basic Composition
PCBs are an essential part of fundamental electronics. As the technology advanced from gigantic vacuum tubes to relays, the pressure upon engineers and scientists increased for further miniaturizing the devices. Reduction in sizes came with the advent of the semiconductor technology. With the development of integrated circuits and silicon devices electronics became prevalent in consumer goods which brought about the inception of PCBs. People are aware of what a PCB does but seldom do they know about what composes a printed circuit board.
PCB Components
The PCB is analogous to a layered cake – how? Well, there are multiple layers composed of different materials. Heat and adhesive materials are used to laminate the individual PCB components together to form a single circuit board.
What’s in the middle?
The middle portion of a PCB is called the substrate, or the base material. This material more often than not is fiberglass also termed as FR4. The rigidity of fiberglass provides the PCB thickness and sturdiness. However, rigid PCB is not the only type of printed circuit boards available. Flexible PCBs are also available in the market. These are composed of polyimide film called Kapton (or its equivalent). Cheap PCBs are made up of materials like phenolics and epoxies.
These materials do not have the resilience of FR4, obviously, but these are still used in low end consumer electronics because of the low cost. A typical way of identifying the phenolic paper substrate is the pungent smell that comes out when the circuit board is being soldered. It is because phenolic circuit boards delaminate, releasing smoke when charred with solder iron.
What sandwiches the substrate?
Upon the substrate is a fine copper layer. In case of a 2 layer PCB or double sided PCB, there are two layers of copper in the printed circuit board. PCBs may have a single layer of copper up till 16 and even more! The copper foil’s thickness varies which is specified by its weight. Normally a single ounce of copper over a square foot is adequate but sometimes, high power PCBs requires 2 to 3 ounces per square foot of copper.
What’s on Top of Copper Layer?
Lying above the copper layers is the green colored soldermask layer. Sometimes red, blue and even purple colored soldermask is applied for insulation. The layer is applied for the insulation of the copper traces against mishaps that might lead copper to get into contact with conductive bits, solder or other metallic substances. The layer covers up the diminutive copper traces. However, it leaves behind pads and silver rings exposed for soldering PCB electronic components.
What’s the White Layer on PCBs?
The white colored layer that you see on the PCB used for lettering, symbols and numbers is called the silkscreen. The silkscreen is an integral PCB component which clarifies the understanding of the board to the users regarding the PCB assembly. Although white is the common color for silkscreen, other colors such as red, black, yellow and gray are also used for the ilk screen.
PCB electronic components
Various electronic components are either surface mounted on the PCB or soldered through the holes. Some of the essential PCB components are transistors, ICs, batteries, controllers, resistors, capacitors, inductors, relays, oscillators, regulators, diodes and logic gates.