Talk about the difference between high frequency PCB board and high-speed PCB board in detail!
With the development and construction of 5G communication, the demand for high-frequency high-speed boards in the electronic equipment industry is growing. Due to different use environments, high-frequency boards and high-speed boards have many common features and some differences. In this paper, the characteristics of high frequency plate and high speed plate are described, and the future development of high frequency plate and high speed plate is prospected.
1、 The demand of 5G network for high-frequency high-speed segment 5G, the fifth generation mobile communication. Cellular mobile communication has experienced four upgrades from analog communication (1G) to LTE (4G), which is now popular. Since 2012, the research and testing of 5G networks have made rapid progress. In the past, from 1G to 4G, the main scene was the network communication between people, while the 5G network would meet the interconnection of everything and start a new round of information network revolution. The 5G communication industry chain mainly includes the following five important links:
(1) Network planning and design (preliminary technical research and network construction planning);
(2) Main wireless equipment (core network, base station antenna, RF devices, optical devices/optical modules, small base stations, etc., wireless supporting, network coverage and optimization links are deployed);
(3) Transmission equipment (wireless equipment needs wired transmission link, followed by optical fiber and cable, system integration, IT support, value-added services, etc.);
(4) Terminal equipment (chip matching with terminal);
(5) Operator. In addition to the above five important links, the following two links are also important:
(6) PCB/CCL industrial chain (used for base station RF, baseband processing unit, IDC and core network router, etc.);
(7) Dielectric waveguide filter (base station RF). In the process of 5G construction, the frequency bands used by products in different industries are different, which leads to different requirements for high-frequency high-speed plates for different products in different industries. It can be seen that 5G network is a comprehensive application of multi band microwave. Therefore, the choice of high-speed board and high-frequency board will be different in different industries.
2、 Characteristics of high frequency high-speed plate 2.1 Dielectric constant Dk and dielectric loss Df When talking about high frequency high-speed plate, it is inevitable to talk about two concepts "dielectric constant Dk" and "dielectric loss Df". The PCB dielectric layer used for high-speed digital signal transmission not only plays the role of insulating layer between conductors, but also plays the role of "characteristic impedance", and also affects signal transmission speed, signal attenuation and heating The size of dielectric loss (Df) indicates the attenuation degree of signal transmission. The attenuation of this signal transmission is often generated by heat consumption. With the high frequency and high speed digital signal transmission, the signal attenuation and heat consumption will inevitably increase rapidly with the high frequency and high speed digital signal transmission. For high-frequency and high-speed digital signal transmission, the smaller the dielectric loss (Df), the better. In the development process of high-speed products and high-frequency products, the dielectric constant (Dk) and dielectric loss (Df) of plates are required to be smaller. However, there are still some differences between high-frequency products and high-speed products in the demand for plates. 2.2 High speed material characteristics High speed products pay more attention to the dielectric loss (Df) of plates.
The grades of high-speed materials commonly used in the market are also classified according to the dielectric loss (Df). Different substrate materials are divided into conventional loss, medium loss, low loss, extremely low loss and ultra-low loss according to the dielectric loss of the substrate.) Five corresponding levels of transmission signal loss. 2.3 Characteristics of high-frequency materials Compared with high-speed materials, high-frequency materials pay more attention to the size and change of dielectric constant (Dk) of materials. High frequency products are very sensitive to the change of dielectric constant (Dk) of materials. Therefore, the emphasis of high-frequency materials is on the stability of dielectric constant (Dk), the thickness of the material medium, the temperature drift coefficient of the material and the stroboscopic performance of the material. There is no clear classification standard for high-frequency materials in the industry, but many
PCB manufacturer
The high-frequency plates are roughly classified according to the dielectric constant (Dk) of the materials. Materials with the same dielectric constant (Dk) are considered to be similar and can be substituted for each other. In the field of high-frequency materials, there is also a common way to divide materials into PTFE materials and non PTFE materials. This is closely related to the application field of high-frequency products. The current RF field can be divided into two parts. First, the common frequencies below 6GHZ are 3.5GHZ, 2.7GHZ and 1.8GHZ. The main products are power amplifiers, antenna calibrators, arrays and other products. The other part is that the common frequencies in the millimeter wave field above 20GHz are 24GHZ, 66GHZ and 77GHZ, and the main products are radar products. This is mainly because with the increase of frequency, the stroboscopic effect and dielectric loss of non PTFE products have a sharp increase in the impact on signal transmission, while PTFE materials have better performance characteristics.
3、 Development Prospect of High Frequency High Speed Plate
Traditional CCL materials have large transmission loss and cannot meet the requirements of high frequency signal transmission quality. Therefore, the most important performance of PCB substrate materials used in 5G communication is to meet the requirements of high frequency and high speed, as well as the requirements of integration, miniaturization, lightweight, multi-function and high reliability. In particular, resin materials require low dielectric constant (Dk), low dielectric loss (Df), low coefficient of thermal expansion (CTE) and high thermal conductivity. At present, hard copper clad laminate represented by polytetrafluoroethylene (PTFE) thermoplastic materials and hydrocarbon resin (PCH) thermosetting materials has occupied most of the high-frequency/high-speed PCB substrate market due to its incomparable low dielectric properties. In recent years, high-frequency/high-speed PCB substrates of new resin materials such as polyphenylene oxide (PPO or PPE), bismaleimide (BMI), cyanate ester (CE), triazine resin (BT), benzoxazine (BOZ), benzocyclobutylene (BCB) and related modifications have been developed. Polyphenylene oxide (PPO or PPE), whose dielectric property is second only to PTFE, has attracted the attention of the industry in recent years. In addition, the processability of PPO materials is much better than that of PTFE materials. Therefore, at present, the very low loss (Very Low Loss) and ultra low loss (Ultra Low Loss) in high-speed boards mostly use modified PPO resins, such as Panasonic M6, M7N, Lianmao IT968 and IT988GSE. The resin system of high-frequency plate mainly consists of polytetrafluoroethylene (PTFE) thermoplastic material and hydrocarbon resin (PCH). Although extremely low dielectric loss (Df) and stable dielectric constant (Dk) can be obtained, the poor processability of materials is not suitable for high multilayer boards, let alone
HDI board
Processed products. With the development of 5G communication, the PCB complexity of high-frequency products is also getting higher and higher (traditional high-frequency PCBs are mainly single and double sided, and the development of multilayer boards even has HDI design requirements). In recent years, material developers also use PPO resin to make high-frequency boards. While ensuring that the board has extremely low dielectric loss (Df) and stable dielectric constant (Dk), good PCB processability can be obtained. For example, the IT-88GMW, IT-8300GA, IT-8350G, IT-8338G, IT-8615G and other high-frequency plates launched by Lianmao adopt a mixed system of modified PPO resin and hydrocarbon resin. While meeting the requirements of high frequency signal transmission, the machinability of materials is greatly enhanced. On the one hand, 5G communication is developing towards higher speed and higher frequency, which inevitably requires that the dielectric loss (Df) and dielectric constant (Dk) of materials be developed towards smaller direction; On the other hand, 5G products require miniaturization and more unified corresponding PCBs, which will inevitably develop towards high multilayer and even HDI, which requires good processability of materials. At present, the use of polyphenylene oxide (PPO or PPE) resin is a good development direction, whether from the perspective of high-frequency materials or high-speed materials.
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