High Speed PCB

A. High-speedPCBis A Special Type of Printed Circuit Board, Usually Used in High-speed Digital Circuits

1. a, PCB is A Key Electronic Interconnection for Electronic Products.
2. Circuit Board is abbreviated as PCB (Printed Circuit Board), the PCB substrate consists of conductive copper foil and insulating insulation material in the middle, and utilizes a mesh of tiny lines to form a predetermined circuit connection between various electronic components. This connection function makes PCB become the key electronic interconnections of electronic products, therefore, PCB is known as the "mother of electronic products". PCB can be divided into organic and inorganic materials according to materials, rigid, flexible, rigid-flex and package substrate according to structure, and single-side, double-side and multi-layer according to the number of layers. The upstream of the PCB industrial chain mainly involves the manufacturing of relevant raw materials, such as copper-clad laminates, semi-solidified sheets, copper foils, copper spheres, gold salts, dry films and inks, etc.; the midstream mainly involves the manufacturing of PCB; the downstream is the wide application of PCB, which is the main reason why PCB are so widely used. The midstream is mainly PCB manufacturing; while the downstream is the PCB's wide range of applications, including communications, consumer electronics, automotive electronics, industrial control, medical, aerospace, defense and semiconductor packaging and other fields.
3. The development trend of PCB technology is mainly reflected in miniaturization, high-level, flexibility and intelligence. Miniaturization refers to the miniaturization of consumer electronics products and the development of functional diversification, PCB needs to carry more components and reduce the size of the PCB requires PCB has a higher degree of precision and microfabrication capabilities. High-levelization means that with the high-speed and high-frequency development of computer and server fields in the 5G and AI era, PCB need to work at high frequency and high speed, have stable performance, and take on more complex functions, which requires PCB to have a greater number of layers and a more complex structure. Flexibility refers to the rise of wearable devices and flexible displays and other emerging applications, PCB need to have good flexibility and bendability to adapt to different shapes and spaces, requiring PCB to have better flexibility and reliability. Intelligent means that with the development of Internet of Things, smart cars and other fields, PCB need to have stronger data processing capabilities and intelligent control capabilities to achieve interconnectivity between devices and automated management, requiring PCB to have a higher degree of integration and intelligence.

1. b, High-speed PCB is A Special Kind of Printed Circuit Boards.
2. High-speed PCB are mainly used in high-speed digital circuits, which need to ensure the integrity of signal transmission. High-frequency PCB are mainly used in high-frequency (frequency above 1 GHz) and ultra-high-frequency (frequency above 10 GHz) electronic devices, such as RF chips, microwave receivers, RF switches, space tuners, frequency selection networks, and so on. Unlike high-frequency PCB, the design of high-speed PCB requires more consideration of signal integrity, impedance matching, signal coupling, and signal noise. In order to meet these requirements, high-speed PCB require special materials and processes. In high-speed PCB design, selecting the right high-speed CCL material is crucial. Data center switches and AI servers are important application areas for high-speed PCB, and AI servers are usually characterized by large memory and high-speed storage, multi-core processors, etc., which require PCB specifications and performance to match. Domestic mainstream data center switches are upgrading from 10G/40G to 400G/800G port rate. According to the report released by Dell' Oro, it is expected that by 2027, 400Gbps and higher speeds will account for nearly 70% of the sales of data center switches, which cannot be separated from the application of high-speed PCB.

   The demand for high-speed PCB is increasing due to automotive intelligence. Driven by electrification, intelligence and network connectivity, the demand for medium and high-end PCB in the fields of ADAS (Advanced Driver Assistance System), intelligent cockpit, power system electrification, and automotive electronic function architecture continues to increase. Electronic control units (ECUs) with integrated, multi-functional, and high-efficiency features will drive the demand for related high-end automotive boards.

B. High-speed CCL is the core material for high-speed PCB, and the high-end field is mainly dominated by Taiwanese and Japanese enterprises.

CCL is one of the main materials for PCB

CCL, known as Copper Clad Laminate (CCL) in Chinese, is a kind of electronic fiberglass cloth or other reinforcing materials impregnated with resin, covered with copper foil on one or both sides, and then hot-pressed and made into a kind of plate material with good dielectric and mechanical properties, etc., whose upper reaches include copper foil, resin, fiberglass cloth and other raw materials, and lower reaches include communication equipment, consumer electronics, automotive electronics and other fields. Its upstream mainly includes copper foil, resin, glass fiber cloth and other raw material industries, and its downstream mainly includes communication equipment, consumer electronics, automotive electronics and other fields.

The performance, quality, processability, manufacturing level, manufacturing cost, and long-term reliability and stability of PCB depend to a large extent on CCL, which, as the core substrate material in PCB manufacturing, mainly plays the role of interconnecting, insulating and supporting PCB, and has a great influence on the transmission speed, energy loss and characteristic impedance of the signals in the circuits, etc. The technology development trend of CCL is in line with the technology development trend of PCB, and the development trend of CCL is in line with the technology development trend of PCB. The technical development trend of CCL is consistent with that of PCB, which is mainly embodied in the aspects of miniaturization, high-level, flexibilization and intelligence. For example, HDI boards and carrier-like boards require higher microminiaturization capability of CCL; high multilayer through-hole boards and backplanes require higher number of layers and structure of CCL; flexible boards and rigid-flexible combination boards require higher flexibility and reliability of CCL; package substrates and embedded component boards require higher integration and intelligence of CCL. According to the different reinforcing materials, CCL can be divided into fiberglass cloth-based CCL, paper-based CCL, composite-based CCL, of which the reinforcing material used in fiberglass cloth-based CCL is fiberglass cloth, which is suitable for the manufacturing of consumer electronics products, and the fiberglass is able to absorb most of the stresses during the bending of the PCB main board, so that the fiberglass cloth-based CCL has very good mechanical properties. Paper-based CCL is made of wood pulp fiber paper, which is mainly used in the manufacture of computers, communication equipment and other electronic industrial products. Composite-based CCL uses wood pulp fiber paper or cotton pulp fiber paper as the core reinforcing material and glass fiber cloth as the surface reinforcing material, which is widely used in the manufacture of high-grade home appliances and electronic equipment. According to the different insulating resins, CCL can be divided into epoxy resin CCL, polyvinyl acetate resin CCL, phenolic resin CCL, and according to the different mechanical properties, CCL can be divided into rigid CCL, flexible CCL.

According to the size of dielectric loss (Df) and dielectric constant (Dk) of CCL, CCL can be classified into high speed CCL and high frequency CCL. High-speed CCL emphasizes its own dielectric loss (Df), and the grades of high-speed CCL commonly used in the market are also classified according to the magnitude of dielectric loss (Df). Compared with high-speed CCL, high-frequency CCL emphasizes the size and change of dielectric constant (Dk) and the stability of dielectric constant (Dk). CCL accounts for about 30% of PCB production costs, and its dielectric constant (Dk) and dielectric loss factor (Df) values directly determine the PCB performance. The lower the dielectric constant (Dk), the faster the signal transmission speed; the smaller the quality loss factor (Df), the smaller the signal transmission loss.

High-speed CCL refers to copper-clad laminates with high signal transmission speed, high characteristic impedance accuracy, low dispersion of transmitted signals, and low loss (Df). High-speed CCLs are divided into many grades, and are generally compared with Panasonic's M series, such as M4, M6, M7, etc., with the larger number being the more advanced and adapted to a higher transmission rate; the M4 grade is a low-loss material, corresponding roughly to a transmission rate of 16 Gbps; the M6 grade is a very low-loss material; and the M7 grade is a super ultra low-loss material, corresponding roughly to a transmission rate of 16 Gbps. M4 is a low loss material, M6 is a very low loss material, and M7 is super ultra low loss, which corresponds to a transmission rate of 32Gbps.

The core requirement for high speed boards is a low dielectric loss factor (Df), the smaller the Df the more stable and the better the high speed performance. Dielectric loss factor (Df) is a characteristic of the resin, in general, to reduce the Df is mainly through the resin, substrate and substrate resin content to achieve. The epoxy resin used in ordinary CCL is mainly FR-4, and its Df value is above 0.01. High-speed CCL needs to be modified or added with resin materials such as PPO/PPE on this basis, and the Df values of PTFE and hydrocarbon resin (two typical high-frequency materials) are the lowest among all kinds of resin materials and below 0.002. The Df of the resin used in the final high-speed material is between the high-frequency material and FR-4. The Df of the resins used in the final high-speed material is between that of the HF materials and FR-4.

High-frequency CCL refers to copper-clad laminates with ultra-low dielectric constants (Dk) for ultra-high frequencies above 5 GHz, where the dielectric loss factor (Df) is as small as possible.

PCB made of CCL as the core raw material can be regarded as a capacitive device. When a signal is transmitted in a wire, part of the energy is accumulated by the PCB, resulting in a delay in transmission, which is more pronounced the higher the frequency. Similar to high-speed CCL, the main method to reduce Dk is to modify the insulating resin, glass fiber, and overall structure. At present, the mainstream high-frequency CCL on the market is mainly realized through the use of polytetrafluoroethylene (PTFE) and hydrocarbon resin material process, of which the use of PTFE CCL is the most widely used, with low dielectric loss, small dielectric constant and small change with temperature and frequency, and close to the coefficient of thermal expansion of the metal copper foil and other advantages.