5G communication equipment is facing higher requirements in terms of performance, size and functional integration, and multi-layer flexible circuit boards, with their excellent flexability, thin and light characteristics and high design flexibility, have become the key support components for 5G communication equipment to achieve miniaturization and high performance, showing a wide range of important applications in the field of 5G communication equipment.

一、Application of multilayer flexible circuit board in 5G communication equipment
（一）Base station equipment
In 5G base stations, multi-layer flexible circuit boards are widely used in RF modules. Because 5G base stations need to support higher frequency bands and larger bandwidth, the design of RF modules has become more complex, and the signal transmission performance and spatial layout of the circuit board are extremely demanding. The multi-layer flexible circuit board can realize the efficient transmission of RF signals through the precise circuit design, and its bendable characteristics can adapt to the complex spatial structure of the base station, effectively saving space and improving the integration of the equipment. For example, in the antenna array connection part of the base station, the multi-layer flexible circuit board can accurately connect multiple antenna units to the RF front-end module to ensure the stable transmission of signals and the normal operation of the antenna.
In the power module of the base station, the multi-layer flexible circuit board also plays an important role. It can realize efficient distribution and management of power supply, and accurately transport power of different voltage levels to various electronic components through reasonable line layout to ensure the stable operation of base station equipment. Moreover, the thin and light characteristics of the multi-layer flexible circuit board help to reduce the overall weight of the base station equipment and facilitate installation and maintenance.
（二）Terminal equipment
In 5G mobile phones and other terminal equipment, multi-layer flexible circuit boards are more widely used. First of all, in the connection between the motherboard and the display screen, the multi-layer flexible circuit board plays a key bridge role. It can not only realize the signal transmission between the motherboard and the display screen, but also adapt to the deformation needs of the mobile phone in the process of folding, bending and other operations. For example, the folding part of the folding screen mobile phone relies on multiple layers of flexible circuit boards to achieve a reliable connection between the display and the motherboard, ensuring that the display can normally display images and receive touch signals in the folded and unfolded state.
Secondly, in the camera module, a multi-layer flexible circuit board is used to connect the camera sensor to the motherboard. With the continuous improvement of 5G mobile phone camera pixels and increasingly rich functions, the requirements for data transmission speed and stability are becoming higher and higher. The multi-layer flexible circuit board can provide high-speed and stable data transmission channel, and ensure that the high-definition images and videos captured by the camera can be timely and accurately transmitted to the motherboard for processing.
In addition, in terms of battery connection and fingerprint recognition module connection of 5G mobile phones, multi-layer flexible circuit boards ensure the normal operation of various functional modules with their good flexibility and electrical performance, providing strong support for the thin and multi-functional design of 5G mobile phones.

二、Technical requirements of multilayer flexible circuit board in 5G communication equipment
（一）Signal transmission performance
The high speed and low delay characteristics of 5G communication put forward extremely high requirements for signal transmission performance of multilayer flexible circuit boards. The circuit board needs to have very low signal transmission losses to ensure the integrity and accuracy of 5G signals during transmission. This requires in the material selection, the use of low dielectric constant, low loss substrate materials, such as polyimide (PI), and strict control of the surface roughness of the material, reduce the scattering and reflection in the signal transmission process. At the same time, in line design, by optimizing the width, spacing and impedance matching of the line, the differential signal transmission and other technologies are adopted to improve the transmission speed and anti-interference ability of the signal, and meet the strict requirements of 5G communication for signal transmission.
（二）Reliability and stability
5G communication equipment usually needs to operate stably for a long time in a variety of complex environments, so multi-layer flexible circuit boards must have a high degree of reliability and stability. In terms of mechanical properties, it should be able to withstand multiple bending, twisting and other deformation without line breakage, solder joint falling off and other problems. This requires the use of advanced flexible material processing technology in the manufacturing process, such as laser drilling, electroplating, etc., to ensure the robustness of the line and the reliability of the connection. In terms of electrical performance, it is necessary to have good temperature and moisture resistance, to maintain stable electrical performance in harsh environments such as high temperature and high humidity, and to avoid faults such as abnormal signal transmission or short circuit caused by environmental factors.
（三）Thin and small
In order to meet the design needs of miniaturization and thinness of 5G communication equipment, multi-layer flexible circuit boards need to continuously reduce their thickness and size. In terms of thickness, the ultra-thin design of the circuit board is realized by using ultra-thin substrate materials and fine line processing technology. For example, the thickness of the substrate is controlled below 0.05mm, and the width and spacing of the line are reduced to improve the wiring density of the circuit board. In terms of size, by optimizing line layout and adopting advanced packaging technologies, such as chip-level packaging (CSP) and system-level packaging (SiP), more electronic components are integrated in a smaller space to achieve miniaturization of multi-layer flexible circuit boards, providing conditions for the thin and light design of 5G communication equipment.

Multilayer flexible circuit boards have a wide range of important applications in 5G communication equipment, from base station equipment to terminal equipment, can not be separated from its support. At the same time, in order to meet the high-performance needs of 5G communication equipment, multi-layer flexible circuit boards are facing strict technical requirements in terms of signal transmission performance, reliability and stability, lightness and miniaturization.