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What is Printed Circuit Board? Definition, Types and Composition

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What is PCB Board

A printed circuit board called PCB is an assembly board that selectively processes and manufactures conductive patterns on an insulating substrate. Specifically, the electrical connection diagram is “printed” on the copper-clad laminate, the copper foil outside the circuit is removed through the corrosive solution, and the copper foil of the connection graphic part is reserved as the connecting plate for the wire and the installation component. Printed circuit boards install and connect circuit components such as miniaturized components and transistor integrated circuits. Because it is produced using electronic printing, it is also called a “printed” circuit board.

The insulating substrate that has been processed and assembled can be called a PCB, and its wide application benefits from its unique advantages such as high reliability, designability, and manufacturability. Next, let’s take a look at what are the common PCBs?

History of PCBs

The PCB history is both interesting and extensive. In the early days, circuits and electrical components would be manually connected using wires. This was labor-intensive and prone to errors, not to mention the lack efficiency and scalability.

However, in 1936, an Austrian engineer named Paul Eisler invented the first printed circuit board. This marked the start of the PCB revolution. In subsequent years, advances in technology have seen more efficient and reliable boards being developed.

In the present day, printed circuit boards are used to construct various electronic devices, from intricate aerospace controllers to the small cell phone motherboards.

How is a PCB Made?

A PCB is made in 2 main stages: the design stage and the fabrication stage. The two stages of PCB production involve a complex process that requires precision and expertise, as explained below. Note that this is a general overview of the process; the complete PCB manufacturing process is explained in our subsequent posts.

PCB Design

In the PCB design stage, an engineer creates a schematic diagram of the circuit board. This is done using PCB design software. The software produces the board’s layout or drawing in 3D, exporting it as what is known as a Gerber file.

The PCB schematic diagram shows how all the components are connected together and provides essential details such as the number of conductive traces needed and their widths.

PCB manufacturing

This is the actual making of PCBs. The PCB fabrication stage involves putting together the board layers and creating the desired circuitry pattern. Finally, the board is inspected for defect before it can be ready for assembly with electronic components. Here is what happens.

  • The PCB making process starts with a piece of copper sheet or foil
  • The copper sheet is then laminated onto a fiberglass board. The board’s function is to provide support to the foil.
  • Next, PCB etching is done. This is where a resistive mask is printed onto the sheet to recreate the desired circuitry.
  • The board is then dipped into an alkaline solution which dissolves the unmasked parts to leave out the intended circuit traces.
  • Using an optical inspection machine, the board is checked for broken copper traces and other problems.
  • Next, a protective solder mask coating is applied to the board.
  • Finally, the board is printed with what’s called a silk screen for the component symbols and other markings such as logos.

The PCB fabrication process is complex and exacting, requiring a high level of precision in order to ensure that all components are correctly connected and that the circuit functions properly.

How Does a PCB Work?

A PCB works by providing an electrical pathway between the various components of a circuit using conductive pathways and pads that form a pattern on the surface of the board.

When power is supplied to the PCB circuit board, electricity flows through these traces, enabling it to reach its intended component(s). The design of the printed circuit board also determines the placement of components, ensuring that their functioning is not affected by other components.

PCB Vs. Breadboard

A breadboard is a type of electronic device used to quickly prototype electronic circuits. Unlike a PCB board, a breadboard allows components to be connected and disconnected easily in order to test different circuit configurations. This makes it an ideal device for experimenting with different designs.

PCB Vs. Motherboard

A motherboard is simply a main PCB circuit board that contains the necessary components of an electronic device. The term is mainly used in relation to the main circuit boards of computers and smaller products such as mobile phones. In contrast, a PCB is any printed circuit board, whether main or secondary.

Types of PCB

The PCB, known as the “mother of electronic products”, is the key electronic interconnection of electronic products. Its main function is to make various electronic components form a predetermined circuit connection and play the role of relay transmission. Common PCB can be divided into the following 4 categories:

Single-sided printed circuit board

Single-sided printed circuit boards usually use phenolic paper-based single-sided copper-clad boards. By printing and etching, printed wires are made on the copper-clad side of the insulating substrate.

Applicable to: radios, tape recorders, televisions, instruments, and meters that do not require high electrical performance.

Single-sided PCB
Single-sided PCB

Double-sided printed circuit board

double-sided printed circuit boards are printed circuit boards with printed wires on both sides. Epoxy resin glass cloth copper foil board or epoxy phenolic glass cloth copper foil board is usually used. Since there are printed wires on both sides, metalized holes are generally used to connect the printed wires on both sides.

Applicable to: communication equipment, computers, instruments, meters, etc., that require high electrical performance.

Feature: Its wiring density is higher than single-sided board, and it is more convenient.

Double-sided PCB
Double-sided PCB

Multilayer printed circuit board

A multilayer printed circuit board is a printed circuit board made of more than two layers of printed wires on an insulating substrate. It is laminated and pressed by several layers of thinner single-sided or double-sided printed circuit boards (each layer’s thickness is less than 0.4mm). To lead out the printed wires sandwiched in the insulating substrate, the holes for mounting components on the multilayer printed circuit board need to be metalized to communicate with the printed wires sandwiched in the insulating substrate. Four, six, and eight layers are widely used, and more are also used.

Multi-layer PCB
Multi-layer PCB

Flexible printed circuit board

Flexible printed circuit board is a printed circuit board made of soft layered plastic or other soft insulating materials. It can be divided into three categories: single-sided, double-sided, and multi-layer.

Applicable to: Widely used in electronic computers, automation instruments, and communication equipment.

Feature: Besides light weight, small size, and high reliability, the most prominent feature is its flexibility, which can be folded, bent, and rolled.

Flexible PCB
Flexible PCB

The above four common PCBs have their own characteristics and scope of application, and it is precisely because different types of PCBs are made of different materials that they have different characteristics and functions. General PCBs are mostly composed of materials such as copper foil, adhesives and additives.

PCB Uses

The PCBs can be found in many different types of electronic devices today, from mobile phones and computers to satellites and robots. In these many situations, they allow for increased miniaturization of circuitry, improved signal integrity, and higher performance. Here is a mention of some of the most common PCB uses.

  • PCBs are used in the manufacture of computers and cell phones, as well as other digital devices such as televisions and gaming consoles.
  • Printed circuit boards are also used extensively for powering industrial machinery, controlling medical equipment and providing navigation data in aircrafts.
  • PCB uses in the automotive industry include engine, airbag, and transmission controllers.
  • PCBs are also extensively used in defense systems to provide vital control functions to military equipment.
  • In addition to the mentioned PCB applications, these devices are also used in various other industries, such as energy production, medical technology and industrial automation.

PCB boards provide a reliable way for components to be connected together quickly and easily. Furthermore, PCBs can also reduce costs by decreasing the number of components needed to build a device, as well as reducing the amount of labor required.

PCB layout
An example of a PCB layout
Resource: https://www.researchgate.net

PCB Composition

There are many substrates used for PCB, which can be mainly divided into two categories, namely organic and inorganic. Organic substrates are made of reinforcing materials such as glass fiber cloth, which are also called copper clad laminates, while inorganic substrates are mainly ceramic plates and enamel-coated steel substrates. Subdivided PCBs are mainly composed of copper foil, reinforcing materials, adhesives and additives.

Copper foil is a thin, continuous metal foil deposited on the base layer of the circuit board. As a conductor of the PCB, it is easily bonded to the insulating layer and etched to form a circuit pattern. Reinforcement materials include glass fiber cloth (felt), fiber paper, etc.; adhesives include phenolic, epoxy, polyester, polyimide, polytetrafluoroethylene, silicone, etc.; additives include solid agents, stabilizers, flame retardants, etc.

construction of single sided PCb

Conclusion

PCBs are important electronic components. Almost every electronic device, regardless of size, as long as there are electronic components, such as integrated circuits and printed circuit boards, are used for the electrical interconnection between them. Through the introduction of this article, I hope it can help you get a general understanding of PCB and it will be helpful to you. In the following article, we will continue to introduce typical applications, design methods, and production processes of PCBs.

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