5G communication is a communication technology that relies on semiconductor materials and devices to achieve wireless electromagnetic wave long-distance transmission, transceiver and processing.

Compared with traditional 4G and other communication technologies, 5G needs to meet the three basic performance requirements of full spectrum access, high frequency band and even millimeter wave transmission, and high spectral efficiency, so the device raw materials are also put forward higher performance and upgrade needs, such as large-scale integration, materials with high dielectric constant and low dielectric loss, and materials with high electron mobility.

According to the forecast of IHS research institute, by 2035, the 5G industry chain alone will reach 3.5 trillion US dollars of economic output, and will create 22 million jobs.

What is more noteworthy is that 5G will create a value of 12.3 trillion US dollars for global sales activities in multiple industries, which will account for 4% of the value of total global sales activities!

Which polymer materials are more popular?

Polytetrafluoron

Excellent high frequency PCB board material

High frequency PCB board material performance requirements, including dielectric constant (Dk) must be small and very stable, and the coefficient of thermal expansion of copper foil as much as possible.

At the same time, the water absorption should be low, otherwise the dielectric constant and dielectric loss will be affected by moisture. In addition, heat resistance, chemical resistance, impact strength, peeling strength, etc., must also be good.

thermoplastic material polytetrafluoroethylene (PTFE) has the characteristics of high temperature resistance, the use of working temperature of 250¡æ. In a wide frequency range, the dielectric constant and dielectric loss are very low, and the breakdown voltage, volume resistivity and arc resistance are high, is the ideal PCB board material.

PTFE can also be strengthened by various forms of fillers such as glass fiber or ceramic materials and can improve the coefficient of thermal expansion of the material, the material has the low temperature characteristics and electrical characteristics of the PTFE material itself, very suitable for the application of high frequency millimeter wave multi-layer board.

Mobile phone antenna

LCP liquid crystal polymer becomes a new favorite

As an important part of wireless communication, antenna technology innovation is the key driving force to promote the development of wireless connection. With the approach of 5G and the scale deployment of the Internet of Things era, the role of antenna in 5G network will be more and more important, and the development prospects are also good.

Taking smart phones as an example, due to the development of the industry and market, with the integration and highly integrated appearance design of mobile phones, the internal space is constantly reduced, which can be said to be extremely difficult for antenna design.

Multiple components of mobile phones need to use softboard to connect | Figure 1

Antenna of mobile phones has been developed from the early external antenna to the internal antenna, and softboard has become the mainstream technology, accounting for more than 70%.

At present, the mobile phone antenna soft plate substrate is mainly PI, but in view of the PI substrate dielectric constant and loss factor is large, and moisture absorption, high frequency transmission loss and poor structural characteristics, so that it can not well meet the needs of 5G material performance.

With the arrival of 5G technology, LCP(industrial liquid crystal polymer) has become an ideal antenna material. It is a new type of high-performance special engineering plastic developed in the early 1980s, which generally shows liquid crystal when it is molten.

LCP | Figure 2

LCP has excellent electrical insulation properties, its dielectric strength is higher than that of general engineering plastics, and good arc resistance. Even if the continuous use temperature of 200-300¡æ, it will not affect its electrical properties. The intermittent use temperature is higher up to about 316¡æ!

Compared with PI, LCP material has less dielectric loss and conductor loss, and is more flexible and sealable, so it has a promising prospect in the manufacture of high-frequency devices. As 4G moves towards high-frequency and high-speed 5G networks, LCP is also expected to become a new soft board process to replace PI.

For example, the iPhoneX launched by Apple used multi-layer Liquid Crystal Polymer antenna for the first time, while the iPhone XS/XS Max/XR all used multiple LCP antennas.

In terms of upstream production, the main manufacturers include Du Pont, Ticona, Sumitomo, Poly Plastics, Toray, etc. For example, Sumitomo, as one of the main manufacturers of LCP resin, said that it is optimistic about the key application of LCP resin in the 5G era, and believes that the application of LCP will be more and more important in the future.

MPI modified polyimide

5G mobile phone antenna material rising star

LCP as a mobile phone antenna material, although there are many advantages, but in practical application, also faces many challenges.

According to foreign media reports, analyst Guo Mingd ??1 pointed out in his report on the new iPhone in 2019 that in view of Apple's low bargaining power for LCP raw material suppliers and the shortage of new LCP soft board suppliers In 2019, Apple will combine LCP and the latest MPI(Modified PI) technology to cater to and promote 5G technology.

So what is MPI? Modified PI is actually a polyimide antenna with a modified formula. As an amorphous material, MPI has a wide operating temperature, is easy to operate under low-temperature pressed copper foil, and can easily connect with copper on the surface, so MPI material may also become a popular material for 5G equipment in the future.

Radome:

A variety of resin substrates come in handy

Because 5G antennas follow the MIMO(multiple-input multiple-output) concept, meaning Multiple Input Multiple Output, which means that multiple antennas can be installed in a base station, And the size of these antennas is very small, need the protection of radome.

The radome should have good electromagnetic wave penetration characteristics, and the mechanical properties should be able to withstand the erosion of the external harsh environment such as storms, snow and ice, sand and dust, and solar radiation.

In general, inflatable radomes are commonly coated with polyester fiber film of hypalon rubber or neoprene; Fiberglass reinforced plastic for rigid radomes; The sandwich in the sandwich structure is filled with honeycomb core or foam.

Under the trend of 5G, the composite material with superior performance has become a popular antenna cover material. The composite material can play the role of insulation, anti-corrosion, lightning protection, anti-interference, durable, etc., and the wave penetration effect is very good.

Wave transmittance composite material is composed of reinforcement fiber and resin matrix, usually, the mechanical properties and dielectric properties of the reinforcement material are better than the resin matrix, so the wave transmittance of the composite material mainly depends on the performance of the resin matrix.

Therefore, it is very important to choose the resin matrix with excellent electrical properties, and the resin also plays the role of an adhesive in the composite material, which is the basic component that determines the heat resistance of the composite material.

The main selection of resin matrix includes:

Traditional unsaturated polyester resin (UP), epoxy resin (EP), modified phenolic resin (PF) and in recent years began to research and application of cyanate resin (CE), organic silicone resin, bismaleimide resin (BMI), polyimide (PI), polytetrafluoroethylene (PTFE) and other new high temperature resistant resins.

PC/PMMA plastic composite

5G era, 5G application equipment materials put forward more stringent requirements. Because 5G is metal-sensitive millimeter wave, the use of metal shell will shield the signal. Taking mobile phone materials as an example, metalization under 5G conditions has become a trend.

and tend to use non-metallic materials such as glass, ceramics and composite plates, for example, plastic composite materials with superior performance, become the trend choice of mobile phone back cover.

Among them, the most popular number of PC/PMMA composite plate. This material is PMMA and PC through co-extrusion (non-alloy material), including PMMA layer and PC layer.

PMMA layer can reach more than 4H of pencil hardness after hardening, to ensure the scratch resistance of the product, and the PC layer can ensure that it has enough toughness to ensure the overall impact strength.

Ideal 5G equipment thermal conductivity and heat dissipation material

High frequency, upgrade of hardware parts and the number of networking equipment and antenna multiplying, electromagnetic interference between equipment and equipment and equipment itself is everywhere, The harm of electromagnetic interference and electromagnetic radiation to electronic equipment is also becoming increasingly serious.

At the same time, with the upgrading of electronic products, the power consumption of equipment is increasing, and the heat is also rising rapidly.

In the future, high frequency and high power electronic products should focus on solving the electromagnetic radiation and heat generated by them.

To this end, more and more electromagnetic shielding and thermal conduction devices will be added to the design of electronic products. Therefore, the role of electromagnetic shielding and heat dissipation materials and devices will become more and more important, and the future demand will continue to grow.

Taking thermal conductive graphene as an example, 5G mobile phones are expected to use customized thermal conductive graphene solutions in more key parts, and composite and multi-layer high thermal conductive films will be more used due to their better heat dissipation effect.

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