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PCB introduction-the most comprehensive knowledge in PCBA industry

PCB introduction
Printed circuit board (PCB) refers to a printed circuit board that forms point-to-point connections and printed components on a common base material according to a predetermined design. PCB plays the role of transmission and is an important electronic component and a support for electronic components. The supplier of electrical connection of electronic components, known as the “mother of electronic products”. Because it is made using electronic printing, it is called a “printed” circuit board. With the continuous development of electronic equipment, the demand for production technology and equipment in the electronic industry is getting higher and higher. PCB, as one of the important carriers and parts ofPCBA, its industry market scale has been expanding in recent years, and moving towards high-end and intensive direction continuous development. The following article will analyze several aspects of PCB to help you know more about PCB thoroughly–PCB Introduction, classification, materials, production process, features, functions, components, application fields, etc. PCB-introduction

PCB Introduction

Almost every electronic device, ranging 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, all of them need PCB. The PCB consists of an insulating base plate, connecting wires and pads for assembling and soldering electronic components, and has the dual functions of a conductive circuit and an insulating base plate. PCB can replace complex wiring and realize the electrical connection between components in the circuit, which can simplifies the assembly and welding of electronic products, reduces the workload of wiring in the traditional way, and greatly reduces the labor intensity of workers. Besides it can reduce the size of the whole machine. volume, reduce product cost, and improve the quality and reliability of electronic equipment. At present, printed circuit boards have been widely used in the manufacture of electronic products.

Classification

PCB-layers

1. Flexible PCB A flexible PCB ( referred to as “FPC”) is a printed circuit board with a single-layer, double-layer or multi-layer circuit made of a flexible substrate. It has the characteristics of light, thin, short, small, high density, high stability and flexible structure. In addition to static bending, it can also be dynamically bent, rolled and folded.

2. Rigid PCB A rigid PCB (referred to as “PCB”) is a printed circuit board made of a rigid substrate material that is not easily deformed, and is in a flat state during use. It has the advantages of high strength, not easy to warp, and firm installation of SMD components.

3.Rigid flex board Rigid flex board is a special flexible printed circuit board composed of rigid-flex and flexible substrates selectively laminated together, with a tight structure and electrical connections formed by metallized holes. It has the characteristics of high density, thin wire, small aperture, small size, light weight and high reliability, and its performance is still very stable under vibration, shock and wet environment. Flexible, three-dimensional installation, effective use of installation space, is widely used in mobile phones, digital cameras, digital video cameras and other portable digital products. Rigid-flex boards will be used more in areas that reduce packaging, especially in consumer areas.

4.Single layer PCB Single-layer board is the most basic type of pcb board, also called single-sided board. Because the wires only appear on one side, we call this pcb board a single-sided board.

5.Double layer PCB The wiring on both sides of the board is called double-sided board. When we prohibit wiring on one side, it becomes a single-layer board again.

6.Multilayer PCB In order to increase the area that can be wired, more single or double-sided wiring boards are used for multilayer boards. Multi-layer boards use several double-layer boards, and put a layer of insulating layer between each layer of boards and then glue them (pressed). The number of layers of the board represents several independent wiring layers, usually the number of layers is even, and includes the outermost two layers. Most motherboards are 4 to 8 layers of structure, but technically it is possible to achieve nearly 100 layers of PCB boards.

Material

copper-PCB-material

1、Conductive Medium: Copper (CU) ﹣Copper foil: Rolled copper (RA), Electrolytic copper (ED), High ductility electrolytic copper (HTE) ﹣Thickness: 1/4OZ, 1/3OZ, 1/2OZ, 1OZ, 2OZ, these are the more common thickness – OZ (ounces): copper foil thickness unit; 1OZ = 1.4 mil

2、Insulation layer: Polyimide, Polyester, polyethylene naphthalene (PEN) ﹣The most commonly used is polyimide (referred to as “PI”) ﹣PI thickness: 1/2mil, 1mil, 2mil, these are the more common thickness -1 mil = 0.0254mm = 25.4um = 1/1000 inch

3、 Adhesive: epoxy resin, acrylic. ﹣ The most commonly used is epoxy resin, the thickness varies with different manufacturers

4. Cuclad laminates, referred to as “CCL”: ﹣Single-sided CCL: 3LCCL (with glue), 2LCCL (without glue) ﹣ Double-sided CCL: 3LCCL (with glue), 2LCCL (without glue)

5、Coverlay (referred to as “CVL”): It is composed of an insulating layer and an adhesive, which covers the wire and plays the role of protection and insulation.

PCB production process

PCB process

1、 Cutting

2、CNC Drilling

3、Plating Through Hole

4、DES process

DES is the abbreviation of developing, etching, and stripping. Etching consists of three parts: developing, etching, and stripping. Simply put, D stands for development, which is to display the graphics on the previous film on the PCB. E stands for etching, whic h is to etch out the line. S stands for film stripping, the film is removed, and the part covered by the film does not need to be etched. In fact, both the inner and outer layers have DES. ” Here refers to five steps. ⑴.Dry film lamination ⑵.Exposure ⑶.Develop ⑷.Etching ⑸.Stripping 5.AOI Automatic optical inspection is a device that detects common defects encountered in welding production based on optical principles. 6.Pre-lamination 7.thermo-compression (hot press lamination) 8.surface treatment 9.Silk Screen Printing Screen printing is to stretch silk fabric, synthetic fiber fabric or metal mesh on the screen frame, and use the method of hand-carved paint film or photochemical plate making to make screen printing plate. Modern screen printing technology uses photosensitive materials to make screen printing plates by means of photolithography. 10.Testing(O/S Testing) Full functional inspection of the circuit board with test fixture + test software. 11.punching 12.assembly To assemble ingredients or components according to customer requirements 13.Testing Inspection items: appearance, size, reliability 14.Packaging i. Plastic bag + cardboard ii. low-adhesion packaging iii.Standard vacuum box iv.Special vacuum box (antistatic)

Features

The reason why PCB can be used more and more widely is because it has many unique advantages, which are roughly as follows:

● High density possible Over the years, the high density of printed boards has been able to develop correspondingly with the improvement of integrated circuit integration and the advancement of mounting technology.

● High reliability Through a series of technical means such as inspection, testing and aging tests, the PCB can be guaranteed to work reliably for a long time (usually 20 years).

● Designability The requirements for various properties of the PCB (electrical, physical, chemical, mechanical, etc.) can be achieved through design standardization, normalization, etc. In this way, the design time is short and the efficiency is high.

● manufacturability PCB adopts modern management, which can realize standardization, scale (quantization) and automatic production, so as to ensure the consistency of product quality.

● Testability A relatively complete test method and test standard have been established, and various test equipment and instruments can be used to detect and identify the qualification and service life of PCB products.

● Assemblability PCB products not only facilitate the standardized assembly of various components, but also enable automated and large-scale mass production. In addition, the overall assembly of the PCB and various other components can also form larger components, systems, and even complete machines.

● maintainability Since the components of PCB products and various components are assembled in a standardized design and large-scale production, these components are also standardized. Therefore, once the system occurs errors, then it can be replaced quickly, conveniently and flexibly, and be quickly restored. PCB also has some other advantages, such as making the system smaller and lighter, and speeding up signal transmission.

Functions

PCB has the following functions in electronic equipment. (1) Provide mechanical support for fixing and assembling various electronic components such as integrated circuits, wiring. Besides, it provides electrical connection or electrical insulation between various electronic components such as integrated circuits. (2) Provide identification characters and graphics for component insertion, inspection, and maintenance. (3) After the electronic equipment adopts printed boards, manual wiring errors are avoided due to the consistency of similar printed boards. Then electronic components can be automatically inserted or mounted, automatic soldering, and automatic detection, which can ensure electronic products quality, improve labor productivity, reduce costs, and facilitate maintenance. (4) Provide the required characteristics of electrical, impedance and electromagnetic compatibility for the circuit in high-speed or high-frequency circuits. (5) The printed board with passive components embedded inside provides certain electrical functions, which simplifies the electronic installation procedure, and improves the reliability of the product. (6) In large-scale and ultra-large-scale electronic packaging components, PCB provides an effective chip carrier for the miniaturized chip packaging of electronic components.

Components

Components are one of the important components of PCBA ( PCB assembly). PCB boards are assembled through processes such as SMT or DIP. About the specific PCBA process, you can read our other articles in website.

Resistors

resistors

Resistor is one of the most commonly used electronic components on pcb boards. It is represented by the letter R, and the unit is ohm Ω, which represents the resistance of the conductor to the current. It plays the role of shunt, current limit, voltage divider and bias in the circuit.

Capacitors

Capacitors

Capacitors are represented by the letter C and are used to store charge and electrical energy in circuits. Its main feature is to pass AC and block DC. The resistance of capacitors to AC is called capacitive reactance, which is a type of reactance (the other is called inductive reactance). The size of the capacitive reactance is related to the frequency of the alternating current and its own capacity. In the circuit, the capacitor mainly plays the role of coupling, filtering, resonance, bypass, compensation, frequency division and so on.

Crystal diode

Crystal-diode

The crystal diode is represented by the letter D, which belongs to a kind of semiconductor device. It has nonlinear volt-ampere characteristics and its main function is unidirectional conductivity. Its core part is a PN junction, which is widely used in various electronic circuits.

Inductors

inductor

The inductor is represented by the letter L, and its structure is similar to that of a transformer. It is a device that converts electrical energy into magnetic energy and stores it. Its main functions in the circuit are: filtering, oscillation, delay, trapping, filtering signals, filtering noise, stabilizing current and suppressing electromagnetic waves interference, etc.

Transistor

transistors

The full name of the triode is a semiconductor triode. It is a semiconductor device that controls current. It is a core component in an electronic circuit. It is also called a bipolar transistor and a transistor. It has a current amplifying effect. Variation to control the larger variation of collector current. Its magnification is represented by the symbol “β”. The triode is made of two PN junctions that are very close to each other on a semiconductor substrate. The two PN junctions divide the whole semiconductor into three parts. The middle part is the base region, and the two sides are the emitter region and the collector region. The arrangement is PNP and NPN.

Field effect transistor

Field-effect-transistor

Field effect transistor, English abbreviation FET, referred to as field effect transistor. There are mainly two types of JFET (junction type) and metal-oxide semiconductor field effect transistor (MOS-FET). A field effect transistor, also called a unipolar transistor, is a voltage-controlled semiconductor device. The function is to be used for amplification. Since the input impedance of the FET amplifier is very high, the coupling capacitor can have a small capacity, and it is not necessary to use an electrolytic capacitor.

Applications

Medical industry

medical-PCB

The rapid development of medicine is closely related to the electronics industry. Many medical devices requires special PCB, such as pH meters, heartbeat sensors, temperature measurement, electrocardiograph, EEG, MRI, X-ray machine, CT scanners, blood pressure machines, blood sugar level measuring equipment, etc.

Industrial equipment

industry-PCB

PCB boards are widely used in manufacturing, especially those industries with high-power mechanical equipment. These equipment operation needs high-power and require high-current circuit, such as arc welding, large servo motor drives, lead-acid battery chargers, etc.

Lighting

LED--PCB

LED lights and high-intensity LEDs are mounted on a PCB based on an aluminum substrate. Aluminum has the property of absorbing heat and dissipating it in the air.

Automotive and aerospace industries

AutoAero-pcbFlexible PCB is lightweight but can withstand high vibrations, also because of this, the overall weight of the spacecraft can be reduced. Flexible PCB can be adjusted even in tight spaces. These flexible PCB is used as connectors, interfaces, and can be assembled even in tight spaces, such as behind panels, under dashboards, etc.

conclusion

The development of the PCB industry can reflect the development and technical of the electronic information industry in a country or region. In the current environment of accelerated evolution of 5G network construction, big data, artificial intelligence, new energy vehicles, Industry 4.0, and the Internet of Things, the PCB industry has become the basic force linking the entire electronics industry chain. If you want to know more about PCB introduction or PCBA knowledge, you can visit our website to read more articles, which will help you understanding of the industry comprehensively. If you are interested in PCB/PCBA, browse our website and contact us immediately. With the 17 years PCBA experience, IBE has supplied one-stop service for customers all over the world from PCB design, assembly, to testing, package.

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