Materials Used in 5G Communication

Introduction

5G communication technology promises significant advancements, such as faster speed, lower latency, improved connection density and wider coverage; thus enabling implementation of Internet of Things (IoT), augmented reality (AR) or virtual reality (VR) applications, factory automation, vehicular communications and other applications where security, reliability, quality of service and efficiency are critical. While the lucrative 5G industry is preparing businesses to experience digital transformation, electronic manufacturers behind the scenes are at the forefront of developing high performance components to support reliable implementation. Major challenges to be addressed by electronic manufacturers include managing extreme thermal conditions within increasing smaller encapsulated components and delivering high performance at low power. These challenges can be overcome through the use of high-performance materials [1].

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Antenna:

5G technology antennas need greater capacity, wider wireless spectrum utilization, high gain and steer-ability. Given that the conventional small-size antennas will be unable to meet the requirement of high frequency during fabrication and installation, the new antenna technology offers challenges with respect to the dynamic structure, adaptive array configuration and extended performance, along with energy-friendly operation at affordable costs. The different types of antennas such as MIMO, Microstrip, Patch antennas, Monopole and Dipole antennas with varying functionalities use different high-performance materials [2]. For example, graphene provides high frequency and bandwidth, excited by coplanar waveguide [3], [4]. Materials generally used for manufacturing 5G antennas are advanced ceramic materials, starting with raw materials such as barium carbonate, silicon dioxide, yttrium oxide and others taken in stoichiometric ratios and synthesized using appropriate sintering techniques to impart desired performance. Other materials include meta-materials for manufacturing MIMO antenna, dielectric substrate materials such as those available from Roger Corporation (RT Duroid 5880) with dielectric constant (Dk) of 2.2 for microstrip antenna, non-metallic substrate materials used in antenna circuits such as Polyphenylene Sulfide (PPS), Polyphenylene ether (PPE), UV photosensitive resin liquid and electro-conductive resin powder as cladding materials for 5G mobile phone antenna [5]. Further, a compact 5G antenna can be printed on manganese zinc ferrite substrate material [6].

Antenna Radome:

Radomes are protective enclosures for equipment such as antennas. Protecting the antenna from winds, rain or ice improves the system availability. Other benefits include reduced structural requirements resulting in reduced fabrication, installation and maintenance costs. In the fast roll-out of 5G services, cost-effective materials are being considered. The key performance targets for the composite material radome are low permittivity and low loss tangent at GHz frequencies, whilst also satisfying cost reduction and processing requirements.

Plastics used for making radome shells typically include Polypropylene (PP), Polycarbonates (PC), Polyvinyl chloride (PVC) and Sheet Molding Compound (SMC). Their better processability and lower dielectric constant (Dk) make them more suitable for manufacturing radome shells. Radomes may also be formed of a material that enables communication of RF signals without significant reduction in gain such as fiberglass, resin, composite materials, etc.

Antenna radomes require critical UV resistance, low temperature mechanical strength and stable dielectric constant (Dk)/dissipation factor (Df) value. Dyneema® from DSM is a lightweight, super-strong, Ultra-High Molecular Weight Polyethylene (UHMWPE) with the widest range of frequencies. LNPTM copolymers from Sabic offer weatherability for outdoor applications, such as for macrocell antenna and tiny cell cover. LNP Copolymers can meet these design requirements, even at an outdoor working environment of -60 degree Celsius [6], [7], [8], [9], [10], [11], [12].

Microwave Circuits:

To enable increased wireless data transfer needed for the new 5G wireless standard, a spectrum in the millimeter wave (mmWave) range is required. The mmWave range is largely unregulated with wide chunks of available bandwidth, making it ideal for data transfer applications. Just as in lower frequency applications in the RF/microwave bands, control of electromagnetic interference (EMI) is critical in mmWave bands too. Traditional shielding techniques are comparitively less effective due to smaller wavelengths. EMI control in the mmWave range is critical, and hence the need for absorbers.

Microwave circuits such as oscillator module and dielectric resonator modules are made up of Ultra/ super – conducting materials and ceramic materials that offer improved frequency, stability, supply current and voltage, operating temperature etc. Absorbers are available in various forms, including polyurethane foams, silicone or urethane elastomers, and also a range of thermoset forms. Polyurethane foam may be chosen based on cost or low weight. An elastomer may be chosen for material toughness or other environmental properties as desired. A thermoset material may be chosen for a complex shaped part, which is best made using injection molding techniques.

Among the circuit materials that provide desirable characteristics for 5G amplifiers, Rogers Corp. offers materials with different thicknesses and other characteristics as needed for different frequency ranges. RO4385™ circuit laminates are low-cost circuit materials that maintain consistent performance across wide temperature ranges. The materials have dielectric constant (Dk) of 3.48 in the z-axis at 10 GHz, tightly controlled within ±0.05. They are ideal for competitive applications and can be fabricated with standard epoxy/glass (FR-4) processes. RO3003™ laminates consist of PTFE with ceramic filler. They have dielectric constant (Dk) of 3.0 in the z-axis at 10 GHz tightly controlled within ±0.04. They feature extremely low loss at higher frequencies that helps get the maximum gain from the active devices in an amplifier circuit, even at the various millimeter-wave bands expected to serve the many backhaul links of future 5G wireless networks [13], [14], [15], [16].

Isolators used in 5G communication are made up of magnetic materials. For 3-6 GHz, Triplate or Stripline (below the resonance values of Yttrium Iron Garnet-Based Materials) and for mmWaves, Microstrip or SIW are used (High Magnetization Ni-Zn Ferrite and Li-based Spinels). Dielectric substrates used in filters are based on materials such as liquid crystal material, ceramic materials and Roger Corp’s Rogers5880. These are used in manufacturing filters such as cascade high-pass filter, low-pass filter, bandpass filter.

Power Amplifiers:

Earlier, wireless communication with complex modulation schemes had high peak to average power ratio, and therefore, maintaining the efficiency and linearity of power amplifiers was a tough task. The power amplifiers’ specifications on output power, energy efficiency, and linearity are challenging to meet. Power amplifiers for 5G communications are made up of semiconductor gallium nitride and polybutylene PBT-package power amplifier for 28GHz. Other materials such as Silicon-germanium (SiGe) power amplifiers too operate at higher frequencies, albeit at lower power rates than gallium-based devices. Indium phosphide (InP) offers an alternative to gallium arsenide (GaAs) in providing increased performance at higher frequencies while consuming lower power [17], [18], [19], [20], [21], [22].

Cables:

Nexan, Corning and Prysmian are major players in the manufacture and supply of cables used in 5G applications. Nexan’s Cat 6A 5G SxTP® cables are specifically designed for indoor and outdoor 5G applications, and can also support voice, data, CATV while sharing application installations up to 600 MHz. The high-density tinned copper braids offer the right EMC performance required for 5G networks. Heat-conducting, flame retarding, foaming and sealing materials are used in 5G communications. The sealing material is a composite material comprising liquid silicone rubber base glue, a foaming agent, heat-conducting powder and an auxiliary agent, according to required weight percentage [23].

Circuit Board Substrates:

Alkali-free glass fiber base cloth and polytetrafluoroethylene (PTFE) are used for 4G and 5G network circuit board substrates. The substrate materials should have very low values of dielectric constant (Dk), dissipation factor (Df) and moisture absorption, at low material and manufacturing costs. The alternative materials that may be used to improve the substrate characteristics are Polyimides (PI), Polytetrafluoroethylene (PTFE), Liquid crystal polymers (LCP) and Low Temperature Co-fired Ceramics (LTCC) etc. Further materials that can be used in substrates are modified epoxy, phenolic resins, Polyphenol Ether (PPE), Polyether Ether Ketone (PEEK), glass and flexible ceramics [24]. PolyOne announced it has developed new polymer Edgetek™ Formulations using Polyphenylene Ether (PPE) for 5G base station applications [25].

LG Chemical’s key material for 5G IC package substrate is Copper Clad Laminate/Pre Preg (CCL/PPG). PPG is manufactured by impregnating glass fibers with resin and then hardening them, and this plays the role of a bonding sheet in the stacking process of package substrate. CCL, a laminated Cu foil layer formed by coating both sides of PPG with copper, plays the role of an insulator. This product provides high-speed/low-loss substrate with low dielectric constant (Dk)& dissipation factor (Df), and has wide process margin and excellent processability [26], [27], [28].

Other Components:

Electronic components in 5G communications require improved signal transmission and device miniaturization. Ferrite materials and new spin-ferrite materials (based on ferric oxide, bismuth tetroxide, yttrium oxide, cupric oxide, calcium carbonate, gadolinium (III) oxide, indium (III) oxide, vanadium (V) oxide and manganese (III) oxide are used to improve signal transmission and device miniaturization. Wireless charging in 5G communication can be achieved using Iron-based micro / nano magnetic powder material (combination of iron, silicon, boron niobium, molybdenum, nickel and copper). Chip material comprises gallium nitride wafer.

Base Station Bricks:

Low penetration loss in 5G base stations is managed using special brick material consisting of coal residue, phosphogypsum, desulfurization gypsum, quartz sand and clay. Shenzhen Xingshengdi New Materials Co., Ltd, a manufacturer of communication equipment, electronics and electrical appliances in China, has used BASF’s plastic additives to produce 5G base stations for major international telecommunications companies. Tinuvin® 360, a very low volatile ultraviolet light absorber (UVA) of the hydroxyphenyl benzotriazole class, imparts outstanding light stability to a variety of polymers and will withstand weathering and degradation by intense sunlight, thus maintaining stable service with an extended life span [29], [30].

5G Material Suppliers:

A few suppliers of 5G materials are listed below.

• Nokia Bell Labs has developed a 5G-ready lithium nanotube battery. The electrodes use a composite of carbon nanotubes and lithium storage materials. This design enables energy to be transferred at near-theoretical peak efficiency levels [31].
• Tokuyama Corp. engages in the manufacturing of chemicals and supplies aluminum nitride for 5G devices, particularly for semiconductors and heat dissipation materials [32].
• Japan’s Furuya Metal works on processing technologies for Iridium and Ruthenium used for high-resolution OLED panels. It supplies materials for China’s BOE Technology Group, as well as South Korea’s Samsung Electronics and LG Electronics [33].
• Preperm® is a tradename of the Finnish Premix group, a technology leader in electrical conducting plastics and RF materials. Patented PREPERM® technology and PREPERM® low-loss dielectric materials boost antenna efficiency to new levels even at very high frequencies [34], [35].
• Murata Manufacturing is a supplier of multilayer ceramic condensers for 5G base stations. Taiyo Yuden recently opened a third manufacturing facility for MLCC (Multilayer Ceramic Chip Capacitor) [36].
• Soitec (Euronext Paris), a world leader in designing and manufacturing innovative semiconductor materials, announced that it is the first materials supplier to join the China Mobile 5G Innovation Center (“Center”), an international alliance chartered to develop 5G communication solutions for China, the world’s largest wireless communications market with 925M mobile subscribers. Both silicon and non-silicon engineered substrates are essential in bringing to mass deployment 5G mobile communications for various applications, including self-driving cars, industrial connectivity and virtual reality [37].

Patents:

A few interesting patents disclosing different materials used in 5G communication are listed below.

US20200008163A1 – Pivotal Commware
The method involves providing external antennas to communicate radio frequency (RF) wireless signals with remote wireless devices. The direction or shape of waveform provided by the external antennas is adjusted selectively for the communication of RF wireless signals. The wide-angle impedance match (WAIM) material or metamaterial is incorporated in a radome to increase the gain for upload RF wireless signal and download of RF wireless signal communicated by the external antennas. The internal antennas are provided to communicate the download RF wireless signal to local wireless devices and the upload RF wireless signal from the local wireless devices. The authorized communication of local wireless devices with the remote wireless devices is determined in response to a power value of the upload RF wireless signal.

CN110342903A – XINHUA
Invention relates to low penetration loss in 5G, in particular to a method for making a brick material and base station.

It discloses brick-making method using materials such as, phosphogypsum, desulfurized gypsum quartz sand and clay. The bricks are used for the construction of 5G base station, to reduce the loss of signal during transmission.

CN110400742A – JINAN SHITONG BUILDING MACHINERY
The invention relates to manufacturing of radio frequency chip material useful in the field of 5G networking and intelligent automotive. The preparation process includes the following steps: after preliminary cutting, and grinding of the gallium nitride wafer, fine polishing is performed; The surface of the wafer is washed with a cleaning agent and then dried to obtain a radio frequency chip material. The polishing liquid used in the polishing treatment includes the following weight percentage components: 20-30 wt% mixed abrasive grains, 0.4-0.8 wt% etchant, 0.3-0.7 wt% oxidant, and 0.001-0.01 wt% promotion Agent and balance water. Preferably, the mixed abrasive particles are composed of purified silica sol and modified boron carbide in a mass ratio of 1: 1; the particle size of the purified silica sol ranges from 60 to 90 nm and that of the modified boron carbide, 100-130 nm.

Collaborations:

• Novoset Technology Center in Berkeley Heights, NJ (USA) has collaborated with Shin-Etsu Chemical in Japan for the manufacture of new hydrocarbon resins, and also to commercialize 5G related products to address material gaps and make difficult-to-process current 5G materials such as Liquid-Crystal Polymers (LCP), Polyimides (PI) and Polytetrafluorethylene (PTFE) targeted at mm-Wave substrates and antennas [38].
• Covestro has partnered with Tongji University to develop 5G materials as part of its open innovation approach. The polycarbonates manufactured by Covestro for antenna casings offer perfect signal transmission and design flexibility [39].

Conclusion

Materials used for designing 5G systems mostly focus on preventing the system from signal losses, safeguarding signal integrity and improving performance. Different material combinations have been studied by players in the market. Materials such as synthesis of aromatic allyl ether are used for preparing high frequency low dielectric materials required for 5G and above communication technologies. Microwave dielectric ceramic material with High Quality Factor (Q-Value) is useful for electronic components like 5G filter. Iron-based micro / nano magnetic powder material is used in microwave 5G communication. Gallium nitride is used for making power amplifiers and RFID chips used in 5G communication. The research advancement in materials is paving the way for a substantial opportunity to provide potent communication systems.

It is accepted that 5G will reach its limits by 2030 and the chase will continue. It is anticipated that 6G will be AI-led and high computational power will be required to run the AI algorithms. According to scientists, there will be a need to develop modulators that operate on plasmonic nanophotonics, which is a nano-scale, light-trapping technology that will directly couple the receiver antenna to a glass fiber. This will enable terahertz connections with very high data rates. All these will be made possible only by the birth of a new generation of materials.

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