Communication is the most important downstream application area of PCB. According to Prismark's data, communication accounted for 27.30% of the total output value of PCB in 2017, which is the first downstream application area of PCB. PCB is widely used in wireless network, transmission network, data communication and fixed network broadband, and is usually high value-added products such as backplane, high-frequency high-speed board, multi-layer board. 5G is the next generation of mobile communication network, there will be a large number of infrastructure construction needs, which is expected to dramatically boost the demand for communication boards. The number of 5G base stations is expected to increase substantially. The peak rate of 4G is 100 Mbps to 1 Gbps, while 5G will provide bandwidth with a peak value of 10 Gbps or more, 1ms delay and ultra-high density connection, with mobility of 500 km/h and traffic density of 10 Mbps/m2. At present, China's three major operators have entered the stage of large-scale acceleration of 5G construction. Pilot tests have been carried out on 5G scale test and application test. Local governments have set a timetable for 5G coverage and accelerated infrastructure construction in order to achieve the goal of large-scale commercial use in 2020. Because 5G needs a lot of connections, the number of base stations in 5G era will be larger than that in 4G era. By the end of 2017, the number of 4G macro base stations in China has reached about 3.6 million, while the planning of 5G macro base stations of the three major operators is 1.5 times that of 4G, with a total number of about 5.4 million. The peak period of construction of 5G base stations will be from 2019 to 2023. 5G will also drive the construction of tens of millions of micro-base stations. Due to the high frequency of spectrum used in 5G communication, the transmission process will produce a greater degree of attenuation, so it is necessary to use micro-base station as a supplement to macro-base station to achieve ultra-dense network. According to Saidi's forecast, the number of 5G micro-base stations is expected to be 4-5 times that of macro-base stations, corresponding to about 25 million micro-base stations. 5G will bring significant changes to the base station structure, and the amount and unit price of communication PCB are expected to increase substantially. In the 4G era, a standard macro base station is mainly composed of baseband processing unit BBU (Base Band Unit), radio frequency processing unit RRU (Remote Radio Unit) and antenna. Because the 10Gbps transmission capacity of traditional CPRI (public radio interface connecting RRU and BBU) is not enough in 5G era, the 5G base station structure needs to be reconstructed in order to reduce transmission bandwidth. In 5G base station, because of the need to use Massive MIMO antenna, some BBU functions are combined with RRU and antenna, forming a new active antenna unit AAU (Active Antenna Unit). The remaining BBU is divided into two levels of CU-DU architecture, in which DU (Distributed Unit) is a distributed unit responsible for meeting the real-time requirements, and has part of the underlying baseband protocol processing power. Yes; CU (Centralized Unit) is a central unit with non-real-time wireless high-level protocol processing functions.