5G communication arrow on the string, low dielectric plastic ready to go

First, 5G communication arrow on the string

The fifth generation mobile phone communication is abbreviated as 5G. 5G communication is not a simple upgrade of 4G communication, but a qualitative leap in communication mode. With the gradual improvement of 5G in baseband, chip, terminal, standard level, and the acceleration of the 5G commercial deployment process of the three major operators, 5G has become the focus and core of technology development in 2019-2020.

The " 13th Five-Year Plan" outlines that we must actively promote the development of 5G and start 5G commercial use in 2020.

The Outline of the National Informatization Development Strategy puts forward the strategic goal of making breakthroughs in 5G technology R&D and standards by 2020; the 863 Program and the major special three-phase start-up 5G R&D projects actively support technological innovation; " Made in China 2025" indicates that We will comprehensively break through the fifth-generation mobile communication (5G) technology and promote the systematic development and scale application of core information communication equipment. In January 2016, we launched the 5G technology research and development test, which was organized and implemented by the IMT-2020 (5G) promotion group.

5G communication has been on the string, and it is coming out. New era, new requirements, new pattern. "Materials and horses have not moved grain and grass first", materials are the cornerstone of the realization of the technological revolution, and the realization of 5G technology is no exception.

Modified plastics are one of the essential raw materials for 5G technology, in smartphones, tablets (Ipads), personal digital assistants (PDAs), laptops, e-book readers, wearable devices, handheld game consoles and smart financial terminals. Machines (La Cala, POS), smart home, smart home appliances, smart media, smart cars, intelligent transportation, intelligent logistics and transportation, smart cities and other fields are widely used. The dramatic changes in communication methods have made it necessary for materials people to delve into and design the dielectric properties of modified plastics.

Second, the insulating properties and characterization of modified plastics

In the 5G era, the modified plastic can be used for the outer frame, keyboard, back cover, middle frame, bracket and other components of the device, and has the functions of covering, decorating, supporting and connecting the outer casing. Common modified plastic resins are shown in Figure 1.

In electricians, it is generally believed that a material having a resistivity of more than 1010 cm and exhibiting electrical properties in an electric field in an induced rather than conductive manner is a dielectric, commonly known as an insulating material. Most polymer resins are large molecular weight synthetic materials mainly composed of carbon, hydrogen, oxygen, nitrogen and sulfur through covalent bonds in a specific sequence and stereo configuration. There are no mobile free electrons in the molecule, even in In the case of applied voltage, the directional movement of electrons cannot be formed. At the same time, most polymer resins do not contain metal elements or molecular structures that absorb and reflect electromagnetic waves; and polymer resins are the most important and proportion of modified plastics. The highest substrate, so we default to the vast majority of modified plastics as insulating materials.

The insulating properties of modified plastics are generally expressed by three terms of volume resistivity, dielectric constant and dielectric loss, and breakdown voltage.

Volume resistivity is the impedance of a material per unit volume to current and is used to characterize the electrical properties of a material. Generally, the higher the volume resistivity, the higher the effectiveness of the material as an electrically insulating component. The so-called resistivity is the volume resistivity.

The dielectric constant is the most basic parameter characterizing a dielectric. The physical quantity that characterizes the material's ability to polarize and store charge is called the dielectric constant, expressed as ε, dimensionless.

Dielectric loss (tgδ): refers to the part of the energy that the dielectric material generates heat when it is heated by an external electric field. Dielectric loss is usually referred to as AC loss. Often under the action of an electric field, the electrical energy consumed per unit time is called dielectric loss. In engineering, the dielectric loss is often expressed by the dielectric loss tangent tgδ. Tgδ is the ratio of the energy consumed by the insulator to the effective input. It represents the ratio of the thermal power loss to the storage in a period, and is the physical quantity that measures the degree of material loss.

Dielectric loss is of particular importance for materials and devices used in high-voltage devices, high-frequency devices, especially in high-voltage, high-frequency, etc., and the dielectric loss is too large, which not only reduces the performance of the whole machine, but even causes the insulation material. Thermal breakdown.

Breakdown voltage and breakdown electric field strength: is the most important parameter to characterize the insulation properties of a material. The breakdown electric field strength is also referred to as dielectric strength. The relationship between the two is:

Breakdown electric field strength

The typical modified plastic is a complex composite material made of polymer resin as the substrate, adding fiber, auxiliary agent and filler and high temperature extrusion granulation process. The dielectric constant ε has more influencing factors. It is closely related to the dielectric constant of the polymer resin substrate, and also to the microscopic structure formed by the physicochemical reaction process of the fibers, the auxiliaries and the granules added thereto.

Relationship between 5G communication and dielectric constant of modified plastics

The higher the electromagnetic wave frequency, the shorter the wavelength. China's 5G initial IF frequency band is 3.3-3.6GHz and 4.8-5GHz, and the 24.75-27.5GHz and 37-42.5GHz high frequency bands are collecting opinions; while the international frequency is mainly used for testing at 28GHz. This means that 5G communication uses the millimeter wave band. The shorter the wavelength of the electromagnetic wave, the worse the diffraction ability, and the greater the attenuation of the electromagnetic wave during the propagation process, which means that the electromagnetic wave coverage capability and transmission signal strength of the 5G communication are greatly reduced compared with the 4G communication era, and the material needs We regulate dielectric properties to reduce this effect.

Maxwell's equations are the basic equations of electromagnetism and the link between electromagnetics and dielectric constants. According to Maxwell's equations and its derivation, the influence of the electrical properties of modified plastics on the transmission characteristics of electromagnetic signals is manifested in four aspects:

Relationship between dielectric constant and electromagnetic signal transmission speed ν

Relationship between dielectric constant and electromagnetic signal delay Td

Transmission signal loss and electrical performance

Relationship between dielectric constant and antenna length

The higher the dielectric constant value, the higher the wavelength at which the electromagnetic signal is transmitted in the antenna. According to the characteristics of the antenna, the length of the antenna should be proportional to the wavelength λ, which is approximately 1/10~1/4 of λ.

5G communication uses millimeter-wave electromagnetic signals, and the length of the antenna is also shortened to millimeters. Intelligent terminals use multiple antenna arrays to ensure signal transmission. However, antenna characteristics require that multiple antenna arrays require that the distance between the antennas be kept above half a wavelength. Adjusting and controlling the dielectric constant εr of the antenna material can control the capacity and arrangement of the antenna array in the smart terminal.

Fourth, low dielectric constant modified plastics ready to go

From the above analysis, the dielectric constant of the modified plastic has a great influence on the signal transmission speed, signal delay, signal loss, etc. of the 5G communication millimeter wave. Lowering the dielectric constant of the modified plastic is beneficial to improve the signal transmission of the intelligent terminal. Speed, reduce signal delay, and reduce signal loss. Therefore, low dielectric constant modified plastics are ready to be developed, and it is extremely urgent to study, design and prepare low dielectric constant modified plastics suitable for various industries.

Six application areas for low dielectric constant modified plastics:

5G base station, micro base station system housing and cladding and protective materials;

Supporting, covering, and protective materials for housings and middle frames of intelligent terminals such as data communication terminals and multimedia terminals;

Antenna and RF module covering and protective materials;

Protection and coating materials for outer casings, middle frames, etc. of wearable devices such as VR and AR;

Wisdom ecological Internet of Things, car shells, shells, frames and other supporting and protective materials;

Housing and frame materials for industrial automation, telemedicine, and autonomous driving instruments and equipment.