LCP Printed Circuit Boards (Liquid Crystal Polymer Circuit Boards)
LCP printed circuit boards refer to liquid crystal polymer circuit boards.
Liquid crystal polymer (LCP) is widely used in high-frequency multilayer circuit boards due to its excellent microwave and millimeter-wave properties. In multilayer circuit board structures, designing via interconnect structures with superior electrical characteristics is particularly important to achieve efficient interconnections between electronic components and transmission line structures across different layers. In recent years, as the operating frequencies of multilayer circuit boards continue to increase, the discontinuity issues of via interconnect structures have become more prominent. Therefore, rapid and accurate electromagnetic modeling of these structures can significantly improve the design efficiency of microwave and millimeter-wave circuits. Based on a 4-layer LCP circuit board, an efficient and fast via modeling method for multilayer circuits is proposed, specifically for the grounded coplanar waveguide-stripline-grounded coplanar waveguide (GCPW-SL-GCPW) structure. By segmenting the multilayer structure for modeling and introducing a fast convergence algorithm during parasitic parameter extraction, a lumped parameter equivalent circuit structure for the via is established. Using the microwave network cascade method, the equivalent circuit model of the GCPW-SL-GCPW structure is quickly constructed. Compared with full-wave simulation results from 3D high-frequency electromagnetic software (HFSS), this modeling method is found to be simple and fast. A GCPW-SL-GCPW circuit structure was fabricated using LCP multilayer technology, and test results showed high consistency between the measured results and the equivalent circuit analysis results over a broad frequency range of 10 MHz to 40 GHz, validating the effectiveness of this via interconnect modeling method.
As a special thermoplastic material, LCP can achieve high-frequency and high-speed flexible boards while ensuring high reliability. LCP possesses excellent electrical characteristics:
(1) Its dielectric constant remains nearly constant across the entire radio frequency range up to 110 GHz, demonstrating good consistency.
(2) Its loss tangent is very small, only 0.002, and increases to just 0.0045 even at 110 GHz, making it highly suitable for millimeter-wave applications.
(3) It exhibits minimal thermal expansion properties, making it an ideal material for high-frequency packaging. Currently, LCP is mainly used in high-frequency circuit substrates, COF substrates, multilayer boards, IC packaging, μ-BGA, high-frequency connectors, antennas, speaker substrates, and other fields. With the rise of high-frequency and high-speed applications, LCP is set to replace PI as a new flexible board technology.
As a special material, liquid crystal polymer, with the continuous advancement of its theoretical foundations, will play an increasingly significant role in high-performance structural materials, information recording materials, functional films, and nonlinear optical materials.
LCP (liquid crystal polymer material), as a new material, is highly suitable for microwave and millimeter-wave devices, showing promising application prospects. LCP materials exhibit lower dielectric and conductor losses, effectively reducing signal loss. Additionally, with the trend toward full-screen displays, the clearance space for antennas is reduced. The excellent flexibility of LCP flexible boards allows for free-form design, making full use of the limited space in smartphones and further improving space utilization efficiency.
Laser—The Best Method for Processing LCP Materials
Strictly speaking, "LCP antennas" refer to FPC flexible boards using LCP as the substrate, which carry certain antenna functions. LCP is the abbreviation for liquid crystal polymer, a high-molecular material highly susceptible to liquefaction under thermal influence. Cutting and processing with ultrafast lasers with pulse durations of less than 10 picoseconds perfectly avoids the generation and diffusion of heat (simply put, the laser operates so quickly that the entire cutting process is completed before any heat is generated).
Therefore, only ultrafast picosecond laser processing can effectively address the challenges of cutting LCP antennas. Metals can shield signals, and in the 5G era, "demetalization" will become a trend in mobile phone development. Non-metallic back covers such as glass, ceramics, sapphire, and synthetic materials will become industry hotspots. At the same time, laser processing of brittle materials will become increasingly common and widespread.
Ultrafast lasers, in particular, can focus on ultra-fine spatial regions while offering extremely high peak power and ultrashort laser pulses. During processing, they do not affect the surrounding materials in the involved spatial range, achieving "ultra-precision" in manufacturing.
