PCB (printed circuit board) is printed circuit board which is one of the important components in the electronics industry. Almost every kind of electronic equipment, from electronic watches and calculators to computers, communication electronic equipment and military weapon systems, as long as there are electronic components such as integrated circuits, in order to make the electrical interconnection between various components, we must use printed board.
A printed circuit board (PCB) is an electrical circuit whose components and conductors are contained within a mechanical structure.
The printed circuit board is composed of an insulating bottom plate, connecting wires and pads for assembling and soldering electronic components, and has the dual functions of conductive lines and insulating bottom plate.
Alternatives to PCBs include wire wrap and point-to-point construction, both once popular but now rarely used. PCBs require additional design effort to lay out the circuit, but manufacturing and assembly can be automated. Electronic computer-aided design software is available to do much of the work of layout.
Mass-producing circuits with PCBs is cheaper and faster than with other wiring methods, as components are mounted and wired in one operation. Large numbers of PCBs can be fabricated at the same time, and the layout only has to be done once. PCBs can also be made manually in small quantities, with reduced benefits.
PCBs can be single-sided (one copper layer), double-sided (two copper layers on both sides of one substrate layer), or multi-layer (outer and inner layers of copper, alternating with layers of substrate). Multi-layer PCBs allow for much higher component density, because circuit traces on the inner layers would otherwise take up surface space between components.
The rise in popularity of multilayer PCBs with more than two, and especially with more than four, copper planes was concurrent with the adoption of surface mount technology. However, multilayer PCBs make repair, analysis, and field modification of circuits much more difficult and usually impractical.
The world market for bare PCBs exceeded $60.2 billion in 2014. In 2018, the Global Single Sided Printed Circuit Board Market Analysis Report estimated that the PCB market would reach $79 billion by 2024.
Initially PCBs were designed manually by creating a photomask on a clear mylar sheet, usually at two or four times the true size. Starting from the schematic diagram the component pin pads were laid out on the mylar and then traces were routed to connect the pads.
Rub-on dry transfers of common component footprints increased efficiency. Traces were made with self-adhesive tape. Pre-printed non-reproducing grids on the mylar assisted in layout.
The finished photomask was photolithographically reproduced onto a photoresist coating on the blank copper-clad boards.
Modern PCBs are designed with dedicated layout software, generally in the following steps:
- Schematic capture through an electronic design automation (EDA) tool.
- Card dimensions and template are decided based on required circuitry and case of the PCB.
- The positions of the components and heat sinks are determined.
- Layer stack of the PCB is decided, with one to tens of layers depending on complexity. Ground and power planes are decided. A power plane is the counterpart to a ground plane and behaves as an AC signal ground while providing DC power to the circuits mounted on the PCB. Signal interconnections are traced on signal planes. Signal planes can be on the outer as well as inner layers. For optimal EMI performance high frequency signals are routed in internal layers between power or ground planes.
- Line impedance is determined using dielectric layer thickness, routing copper thickness and trace-width. Trace separation is also taken into account in case of differential signals. Microstrip, stripline or dual stripline can be used to route signals.
- Components are placed. Thermal considerations and geometry are taken into account. Vias and lands are marked.
- Signal traces are routed. Electronic design automation tools usually create clearances and connections in power and ground planes automatically.
- Gerber files are generated for manufacturing.
What is the Benefits of PCB ?
The reason why PCB can be more and more widely used is because it has many unique advantages, roughly as follows:
- High density – For many years, the high density of printed boards has been able to develop with the improvement of integrated circuit integration and advancement of mounting technology.
- High reliability – Through a series of technical measures such as inspection, testing and aging test, the PCB can be guaranteed to work reliably for a long time (usually 20 years of use).
- Designability – Requirements for various properties of PCB (electrical, physical, chemical, mechanical, etc.) can be achieved through design standardization and standardization. This design has short design time and high efficiency.
- Manufacturability – PCB adopts modern management, which can realize standardization, scale (quantity) and automatic production, thus ensuring the consistency of product quality.
- Testability – A relatively complete test method and test standard have been established, and the qualification and service life of PCB products can be detected and identified through various test equipment and instruments.
- Assemblability – PCB products are not only convenient for standardized assembly of various components, but also for automated, large-scale mass production. In addition, by assembling the PCB with various other components as a whole, larger parts and systems can be formed to the whole machine.
- Maintainability – Since the components assembled integrally with PCB products and various components are produced with standardized design and large-scale production, these components are also standardized. Therefore, once the system fails, it can be replaced quickly, conveniently and flexibly, and the work of the system can be quickly restored.
- PCB also has other advantages, such as miniaturization and lightening of the system, and high-speed signal transmission.
Fraser Innovation Inc have a group of high-quality PCB design engineers who have rich experience in the design of carrier-grade high-speed multilayer PCBs. Our team of engineers and CAD/CAM operators are available to discuss any project needs that our customer may have as we are fully licensed and utilize industry leading tools, including Cadence Allegro, Mentor Expedition, Mentor’s PADS, Altium, Valor for DFM Analysis.