What Is PCB? Several Ways Of PCB Fault Detection

The creator of the PCB is the Austrian Paul eisler (Paul eisler), in 1936, he first used in the radio printed circuit boards. 1943, the Americans more than the technology used in military radios, in 1948, the United States officially recognized this invention can be used for commercial purposes. It was only since the mid 1950s that printed circuit boards began to be widely utilized. Printed circuit boards are found in almost every type of electronic device. If there are electronic parts in a certain kind of equipment, then they are also set in different sizes on the PCB. PCB's main function is to make a variety of electronic components to form a predetermined circuit connection, the role of relay transmission, is the key electronic interconnections of electronic products, "the mother of electronic products," as the name.

(1) To provide mechanical support for the fixing and assembly of various electronic components such as integrated circuits, to realize the wiring and electrical connection or electrical insulation between various electronic components such as integrated circuits, and to provide the required electrical characteristics.
(2) Provide soldermask graphics for automatic soldering, and identification characters and graphics for component insertion, inspection, and maintenance.
(3) electronic equipment using printed circuit boards, due to the consistency of similar printed circuit boards, to avoid errors in manual wiring, and can realize the automatic insertion or placement of electronic components, automatic soldering, automatic inspection, to ensure the quality of electronic products, improve labor productivity, reduce costs, and easy maintenance.
(4) In high-speed or high-frequency circuits to provide the circuit with the required electrical characteristics, characteristic impedance and electromagnetic compatibility characteristics.
(5) Printed boards with passive components embedded internally provide certain electrical functions, simplify electronic installation procedures, and improve product reliability.
(6) In large-scale and ultra-large-scale electronic packaging components, provides an effective chip carrier for miniaturized chip packaging of electronic components.

Electronic resins have different performance, each with its own advantages and disadvantages, downstream customers often according to the different uses of the product, the use of a variety of materials to complement the shortcomings in order to achieve the best overall performance.

Hydrocarbon resin: It refers to polyolefin homopolymers or copolymers, including butadiene styrene copolymer, butadiene homopolymer, styrene, homopolymer, styrene/divinylbenzene copolymer, styrene-butadiene-divinylbenzene copolymer, and so on.

Polytetrafluoroethylene: polytetrafluoroethylene PTFE has excellent dielectric properties, chemical resistance, heat resistance, flame retardant, high frequency range of dielectric constant and dielectric loss is small and small changes, but due to the polytetrafluoroethylene melt state has a high viscosity, and therefore commonly used molding and sintering and other methods of molding.

LCP: liquid crystal polymer LCP is a new high-performance special engineering plastics developed in the early 80's, with outstanding high-frequency dielectric properties, dimensional stability, heat resistance, is very ideal for 5G high-frequency high-speed circuit board substrate.

Polyphenylene ether: also known as polyphenylene oxide or polyphenylene ether, developed in the 1960s, high-strength engineering plastics, referred to as PPO or PPE, with good mechanical properties and excellent dielectric properties, such as dielectric constant Dk and dielectric loss Df, become the first choice of high-frequency printed circuit board substrate resin materials. Disadvantages are high melt viscosity, difficult to process molding; poor solvent resistance, in the printed circuit board production process of solvent cleaning environment is likely to lead to poor adhesion or fall off; melting point and the glass transition temperature Tg is similar to the printed circuit board process is difficult to withstand more than 250 ° C in the soldering operation. Therefore, PPE is thermoset modified to meet the requirements of printed circuit boards.

PI: also known as polyimide, is the molecular chain containing cyclic imide groups in the polymer polymer collectively, referred to as PI. polyimide film is the world's best performance of film-type insulating materials, the appearance of a yellow transparent, relative density of 1.39-1.45, with excellent resistance to high and low temperatures, electrical insulation, adhesion, resistance to radiation, media resistance.

PCB products can be categorized into single-layer boards, double-layer boards, flexible boards, HDI boards and packaging substrates. From the perspective of PCB's segmented product structure, multilayer board has occupied the main part of the global PCB product structure, in 2016 the global multilayer PCB output value of 21.1 billion U.S. dollars, accounting for 39% of the global PCB output value; in 2016, the global output value of flexible boards was 10.9 billion U.S. dollars, accounting for 20% of the global PCB output value, accounting for the year-on-year trend of increasing; in 2016, the global single-layer board output value of 8 billion U.S. dollars , accounting for 15% of the global PCB output value; global HDI output value of $7.7 billion in 2016, accounting for 14% of the global PCB output value; global packaging substrate output value of $6.6 billion in 2016, accounting for 12% of the global PCB output value.

HDI stands for High Power Density Interconnect Motherboard (High Density Inverter), a type of printed circuit board that produces printed circuit boards with a relatively high density of line distribution using micro-blind/buried hole technology. In the PCB industry on the definition of HDI board is usually the minimum line width / pitch in 75/75μm and below, the smallest through-hole aperture in the 150μm and below, containing blind or blind buried holes, the minimum pad in 400μm and below, the pad density is greater than 20/cm2 PCB board, belonging to the high-end PCB type.

HDI motherboards are mainly divided into first-order, second-order, third-order, Anylayer HDI, the feature size is gradually reduced, and the manufacturing difficulty is also gradually increased. Currently in the electronic terminal products on the application of more third-order, fourth-order or Anylayer HDI motherboards. Anylayer HDI is known as any order or any layer of HDI motherboards, also known as ELIC (Every Layer Interconnect) HDI. 12 layers. Apple's cell phone motherboard from the iPhone 4S first introduced the use of Anylayer HDI, and Huawei's current flagship series is mainly used for Anylayer HDI, for example, Huawei P30 series motherboards are divided into MainPCB and RF PCBs, both using Anylayer HDI, Mate20 and Mate30 series are also using Anylayer HDI motherboards. The Mate20 and Mate30 series also use Anylayer HDI.

manufacturing and storage
Similar to other electronics, PCBs are sensitive to different environmental factors such as temperature, humidity, and contamination, and various defects can occur during the manufacturing and storage of PCBs.

During storage and during component installation, PCBs are subject to temperature, which can fluctuate multiple times under extreme conditions and can potentially lead to component or connector failure.

The maximum and minimum operating temperatures of the PCB must be considered during the PCB design phase. Expansion and contraction of the PCB due to temperature fluctuations can lead to premature failure of the PCB.
 

Exposure to moisture during PCB manufacturing and storage can cause short circuits and can lead to defects in various components of the circuit. The presence of moisture in the air can damage solder, which in turn can lead to corrosion.

Contaminants can create defects in the manufacturing process and where PCBs are stored after the manufacturing process, and can weaken PCB performance when the PCB is exposed to dust, insects, contamination, and other factors.
Impacts

Impacts on PCBs can be catastrophic during the manufacturing, storage and transportation of PCBs. PCBs that are dropped violently or not manufactured in the normal manner can cause excessive vibration and therefore the PCB loses its flexibility, which in turn damages the PCB's alignment.