Copper clad laminate industry is in the middle reaches of the whole PCB industry chain, providing raw materials for PCB products. Copper clad laminate (CCL) is a kind of board-like material, which is made by drying, cutting and laminating the electronic glass fiber cloth or other reinforced materials with resin adhesive, covering one side or both sides with copper foil and hot pressing. It is mainly used to make printed circuit boards, which can connect, insulate and support PCB. In the upstream of the industrial chain, raw materials such as electrolytic copper foil, wood pulp paper, glass fiber cloth and resin are in the upstream, PCB products are in the downstream, and the terminal industries are aerospace, automobile, household appliances, communication, computer, etc.
5G will be put into commercial use in 2019. The upstream raw materials of core materials such as high-frequency copper clad laminates are basically similar to those of traditional CCL. The high-frequency circuit boards suitable for high-frequency environment are produced by downstream PCB manufacturers and applied to base station antenna module, power amplifier module and other equipment components, and finally widely used in communication base station (antenna, power amplifier, low noise amplifier, filter, etc.) Automotive auxiliary system, aerospace technology, satellite communication, satellite TV, military radar and other high-frequency communication fields.
5G high frequency technology puts forward higher requirements for the circuit. The RF circuit with working frequency above 1GHz is generally called high-frequency circuit. In the process of mobile communication from 2G to 3G and 4G, the communication frequency band develops from 800MHz to 2.5GHz. In 5G era, the communication frequency band will be further improved. PCB board will be equipped with antenna oscillator, filter and other devices in 5G RF. According to the requirements of the Ministry of industry and information technology, it is expected that the early 5G deployment will adopt the 3.5GHz frequency band, and the 4G band will mainly be around 2GHz. The electromagnetic wave with the wavelength of 1-10mm in the frequency band of 30-300ghz is usually regarded as millimeter wave.
When 5G large-scale commercial use, millimeter wave technology ensures better performance: extremely wide bandwidth, available spectrum bandwidth of 28ghz band can reach 1GHz, available signal bandwidth of each channel in 60GHz band can reach 2GHz; corresponding antenna has high resolution, good anti-interference performance, and can be miniaturized; propagation attenuation in the atmosphere is fast, which can realize close range secure communication.
In order to solve the high frequency and high-speed demand, and to deal with the problems of poor penetration and fast attenuation speed of millimeter wave,5Gcommunication equipment has the following three points for PCB performance requirements:
1. low transmission loss;
2. low transmission delay;
3. precision control of high characteristic impedance. There are two ways to make PCB high frequency, one is that the processing process of PCB is required to be higher, the other is to use high frequency CCL, which is called high frequency copper clad plate, which can meet the high-frequency application environment.
There are two main indexes, namely, dielectric constant (DK) and dielectric loss factor (DF) to measure the properties of high frequency copper clad materials. The smaller the DK and DF, the more stable the high frequency and high-speed substrate. In addition, in RF PCB
, PCB board has larger area and more layers, which requires higher heat resistance (TG, high temperature modulus retention) and stricter thickness tolerance of the substrate.
There are several main high frequency high-speed materials in common circuit boards: hydrocarbon resin, PTFE
, LCP liquid crystal polymer, PPE/PPO, etc.