Antenna materials introduction
Antenna materials have seen renewed attention since liquid crystal polymer (LCP) antennas were first used in iPhone models. LCP antennas adopted in LCP flexible circuits began to grow early. Beyond smartphones, LCP antennas are being applied across a range of smart devices and are a new growth area for FPC, with increasing demand expected from camera flex circuits, high-speed transmission lines in laptops, smartwatch antennas, and similar applications.
5G antenna materials overview
2013 marked the commercial start of 4G. With national regulators issuing commercial 5G licenses in 2019, 5G has entered broader deployment.
5G is expected to drive large infrastructure and产业 investment. Industry estimates project major new infrastructure investment concentrated on 5G and related sectors. IHS forecasts that by 2035, 5G-driven global economic activity could reach trillions of dollars and span many industry sectors.
5G refers to the fifth generation of mobile communication technology. Higher carrier frequencies are used compared with previous generations; China initially allocated mid-band frequencies of 3.3–3.6 GHz and 4.8–5 GHz, with higher bands such as 24.75–27.5 GHz and 37–42.5 GHz under development. International trials often use 28 GHz. These higher frequencies approach the millimeter-wave band, which offers very high throughput but poorer penetration and greater attenuation. Millimeter wave is generally defined as 30–300 GHz (wavelengths of 1–10 mm), overlapping microwave and far-infrared bands and sharing characteristics of both.
5G advantages
Very high throughput: 5G peak transmission rates are orders of magnitude higher than 4G; users can download large, high-definition files in under a second in ideal conditions.
Very low latency: 4G signal latency is on the order of tens to hundreds of milliseconds, while 5G target latency can approach 1 ms.
Higher attenuation: Because 5G uses higher frequencies, signals are more easily blocked, subject to external interference, and attenuate more rapidly in transmission media.
Material requirements for 5G
Because 5G moves to higher frequencies and faster data rates, materials used in transmission paths must exhibit low dielectric constant and low dielectric loss.
Due to reduced propagation capability at higher frequencies, materials should offer strong electromagnetic shielding where required.
Thin, tightly sealed components in 5G devices require good thermal management; therefore, materials with favorable thermal conductivity are important.
In summary, 5G demands polymer materials combining low dielectric constant, low dielectric loss, good thermal conductivity, and effective electromagnetic shielding.
Categories of 5G antenna materials
Materials used in 5G communications span metals, ceramics, engineering plastics, glass, composites, and functional materials. The 5G rollout stimulates the entire supply chain and drives changes in material supply and manufacturing processes, presenting both opportunities and challenges for producers.
Technology evolution for 5G antenna materials
Common mobile terminal antennas built on flexible circuit boards (FPC) have typically used polyimide (PI) films wrapped around copper foil. At high frequencies and high data rates, heat accumulation and resulting temperature changes can deform the antenna, causing transmission loss and waveform distortion. To address these limitations, device makers have explored alternative material paths such as liquid crystal polymer (LCP) and modified polyimide (MPI).
LCP and MPI for 5G handset antennas
Higher radio frequencies in mobile communications shorten wavelengths and increase attenuation, so antenna materials must minimize loss at these frequencies. Early antennas were metal-based; with the advent of FPC processes, PI films became common in the 4G era. PI shows significant loss above roughly 10 GHz and does not meet 5G terminal requirements. LCP, with lower dielectric loss and conductor loss plus flexibility and sealing properties, has increasingly been applied.
LCP is relatively expensive and requires complex processing; MPI (modified polyimide) is a lower-cost, more process-friendly alternative and is a candidate to be a mainstream antenna material in the early 5G era.
Characteristics of LCP and MPI
iPhone X first used LCP antennas to improve high-frequency performance while saving space. The demonstration effect of leading handset vendors suggests other manufacturers may follow, potentially expanding the market for phone LCP antennas.
LCP
LCP (liquid crystal polymer) is a polymer whose rigid molecular chains can form a liquid crystalline state under certain conditions, combining fluidity with anisotropic crystalline properties. LCPs have unique molecular structures and thermal behavior. In the molten state LCP molecules can align under shear, producing strong anisotropy and a self-reinforcing effect. This yields excellent mechanical strength, dimensional stability, optical and electrical properties, chemical resistance, flame retardancy, and processability, along with low thermal expansion.
LCPs exhibit very low dielectric constant and dielectric loss at high frequencies because molecular motion in the main chain is constrained by the rigid, symmetric backbone and liquid crystal structure. Consequently, LCP materials are widely used in high-speed connectors, 5G base station radiators, 5G handset antennas, and high-frequency circuit boards.
MPI
MPI refers to modified polyimide formulations. As a polyimide-based material, MPI offers excellent chemical resistance, mechanical strength, and high electrical resistivity. It has been widely used in microelectronics and aerospace and offers advantages in planarization and manufacturability compared with some inorganic alternatives. MPI is non-crystalline, has a wide processing window, bonds well to copper at low lamination temperatures, and is comparatively cost-effective.
With fluorinated formulations, MPI now approaches LCP performance in the 10–15 GHz range. Some industry participants therefore consider MPI sufficient for many 5G use cases, with LCP not strictly required. Certain North American handset makers favor partial MPI adoption, in part due to LCP manufacturing capacity constraints.
In summary, LCP may be a long-term winner in 5G-era antenna materials, but MPI has a realistic opportunity to gain market share during the 4G-to-5G transition period.
Industry chain and competitive landscape for LCP antenna materials
Competitive landscape
The global antenna market shows oligopolistic characteristics, with the top suppliers occupying the majority of market share. Several Chinese firms are among the leading suppliers, and foreign vendors include established networking and RF infrastructure companies.
In mobile terminal antennas, major suppliers include Amphenol, Molex, Luxshare Precision, Sunway Communication, and others.
LCP antenna industry chain
The LCP antenna industry chain comprises upstream raw material suppliers and FCCL (flexible copper-clad laminate) manufacturers, midstream FPC soft-board manufacturers, and downstream antenna module makers. Upstream raw materials include LCP resin/film and rolled copper foil. FCCL manufacturers use these materials to produce FCCL; FPC manufacturers convert FCCL into flexible circuit boards; antenna module manufacturers then process those FPCs into antenna modules according to design requirements.
Multiple stages in the LCP antenna chain have high technical barriers; the most challenging steps are synthesis of film-grade LCP resin and film-casting. Key technical issues include:
- Synthesis of LCP resin is complex, often involving two to three monomers and requiring both melt and solid-phase polymerization steps. Strict control of impurities, molecular weight distribution, and specialized equipment is required. Certain synthesis routes are more suitable for film production.
- Film production is technically difficult and requires extensive process experience. Closed supply chains between resin producers and film manufacturers make it hard for new entrants to obtain film-grade resin or produce qualified films. Successful commercial film production has involved specific partnerships between resin and film makers, and post-processing steps such as heat treatment and coating include substantial proprietary know-how.
- Other steps present challenges as well: LCP's thermal behavior complicates copper lamination, requiring precise temperature control; drilling vias in multi-layer LCP flex boards is difficult because traditional mechanical punching methods are not suitable. Techniques such as filled vias and laser drilling are used by some manufacturers.
Companies mastering LCP film technology
LCP film production technology is concentrated in a few Japanese and U.S. firms. Film technology maturity can be viewed in stages from laboratory samples through qualifying products to fully commercialized materials. Companies with core LCP film capabilities include several U.S. and Japanese suppliers; among them, a smaller set has achieved full commercial readiness for antenna-grade films.
Global LCP resin production is concentrated in the U.S. and Japan. Major global suppliers include Celanese (U.S.), Polyplastics (Japan), and Sumitomo (Japan), whose combined capacity accounts for a large share of the market. After Celanese acquired the former DuPont LCP business, its global capacity reached about 22,000 tonnes, near 30% market share. The three leading suppliers together account for roughly 63% of production capacity. Within China, representative companies with scaled production capability include Kingfa Technology, Preter, Wote Co., and some Taiwanese suppliers.
LCP resin and film suppliers in China and commercialization progress
From an industry commercialization perspective, as of the latest reporting there were few China-based firms capable of independently mass-producing antenna-grade LCP film or film-grade LCP resin at scale.
The following summarizes several China-based or regional companies and their progress:
- Wote Co.: Film-grade LCP in testing; downstream applications are moving through customer qualification and into volume supply. The company focuses on modified engineering plastics and high-performance polymers including LCP, PTFE, PPE, carbon-fiber composites, and fluoropolymers. It completed an acquisition of a Samsung Precision Chemical LCP production line in 2014 and reports capabilities across multiple LCP grades. As of early 2020, its film-grade LCP was in customer testing and certification.
- Kingfa Technology: Small-batch exports of film-grade resin and collaborative development with 5G equipment vendors. Kingfa has developed low-dielectric, low-loss, high-dimension-stability film-grade LCP resins and reported small exports to Japan. The company has engaged with domestic 5G equipment manufacturers on flexible LCP antennas and has developed an LDS material based on LCP.
- Preter: Developed film-grade resin and is collaborating with downstream customers to develop LCP films. Preter has a history in TLCP (thermotropic liquid crystal polymer) and holds related patents and production systems, with injection-grade LCP already in volume supply and thin-film development underway.
- Ningbo JuJia New Materials: Claims film-grade LCP resin production capability with thin-film products in pilot scale. The company reports R&D teams and production lines targeting film-grade LCP resin capacity.
As domestic R&D investment and process improvements continue, the bottleneck for mass production of antenna-grade LCP films could be reduced. The industry should monitor these companies' progress on commercialization and customer qualification.
