Common green FPC flexible circuit boards are mainly made of copper foil wrapped with polyimide (PI) materials. In order to be thinner, the thickness of copper foil used to transmit data on the circuit board is gradually compressed from 12 μ m to 6~9 μ m ultra-thin calendered copper foil. The data interface of high-speed transmission requires that the circuit board must be able to withstand the transmission speed of 5G per second. In high-speed transmission, ultra-thin copper foil will produce high temperature. Due to the difference between the thermal conductivity of polyimide (PI) film and copper foil, the FPC flexible circuit board substrate will eventually warp, affecting the transmission speed.
As a new material, LCP (liquid crystal polymer material) has the following characteristics:
1) It has the characteristics of low dielectric constant (Dk=2.9) and low dielectric loss (Df=0.001-0002). In the future, mobile phones will develop towards 5G (higher and higher frequency), and LCP materials will have less dielectric loss and conductor loss;
2) With high plasticity, LCP will become like water when it is at high temperature. This feature makes it easier for LCP to form thin-walled and miniaturized connector parts, with better flexibility and sealing (water absorption less than 0.004%);
3) LCP antenna can also replace some RF connectors, which conforms to the trend of reducing the internal clearance of mobile phones.
LCP antenna represents one of the development directions of terminal antenna in 5G era. Compared with traditional antenna, LCP antenna has significantly improved in processing difficulty and value.