The application of vacuum technology in the 5G industry chain.

With the official launch of 5G commercial use in our country, 5G has become a key infrastructure for the transformation of the digital economy, gradually spreading and penetrating into various fields of society. The 5G industrial chain is very broad, including components, main equipment, operators, and downstream applications. The initial investment mainly includes wireless equipment, transmission equipment, base station equipment, small base stations, optical communication equipment, network planning and implementation, etc. From the application perspective, 5G applications include three major directions: industrial digitalization, intelligent life, and digital governance. Vacuum technology, as a modern basic science closely related to applied science, has a wide range of applications in the 5G industrial chain. From the preparation process of materials and devices in 5G base stations, vacuum leak detection of optical communication devices in the backbone network, to the preparation of core components in 5G mobile phones, VR/AR devices, and autonomous vehicles, vacuum technology is involved and widely applied. Below, I will take you into the 5G industrial chain to explore the application of vacuum technology in the 5G industrial chain.

　　1. 5G Industrial Chain

From a hardware perspective, the 5G industrial chain is mainly divided into two categories: 5G networks and 5G terminals. 5G Network: The 5G network can be divided into three areas: access network (including 5G base stations and supporting power supplies, antennas, RF devices, etc.), backbone network (including optical fibers, optical cables, optical modules, optical communication equipment, etc.), and core network (including servers, switching equipment, etc.).

Figure 1: Three areas of the 5G network industrial chain

5G Terminals: 5G terminals refer to the application end of 5G technology, including 3D communication, ultra-high-definition video, online AR/VR, cloud office, cloud gaming, etc., as well as a series of new application scenarios suitable for mobile internet and the Internet of Things, such as IoT, autonomous vehicles, industrial automation, and electronic medical care.

　2. Application of Vacuum Technology in 5G Access Network

1) Substrate Isolators and Circulators

The frequency usage plan for the 5G system in our country clearly stipulates the frequency bands of 3300-3400MHz (generally limited to indoor use), 3400-3600MHz, and 4800-5000MHz as the working frequency bands for the 5G system; it stipulates that the 5G system must use the above working frequency bands and must not cause harmful interference to radio astronomy services and other radio services legally conducted in the same or adjacent frequency bands. Therefore, the substrate isolators and circulators used in the original 4G base stations need technical upgrades to meet the 5G usage requirements. The substrate isolators/circulators used in 5G base stations currently involve vacuum coating technology in two aspects: one is the production of metal bottom electrodes on the ceramic surface, and the other is the preparation of YIG films using vacuum coating technology (such as PLD laser pulse deposition).

Figure 2: 5G Substrate Isolator

2) Ceramic Dielectric Filters

As 5G base stations develop towards miniaturization, lightweight, and high integration, the technology of base station antennas continues to upgrade, leading to a significant increase in the demand for filters. Ceramic dielectric filters, with advantages such as low insertion loss, high dielectric constant, small size, lightweight, and low cost, are gradually becoming the mainstream filters for 5G base stations, replacing the metal cavity filters widely used in 4G base stations. Currently, the metallization schemes for ceramic dielectric filters mainly include silver paste technology and vacuum coating technology. The vacuum coating technology involves placing clean multi-cavity microwave dielectric ceramic substrates in pollution-free, zero-emission vacuum coating equipment, using high-energy ion PVD technology to coat a dense layer of metallic silver on the ceramic surface, achieving the metallization of ceramic filters.

Figure 3: Comparison before and after the vacuum silver coating process of ceramic dielectric filters

3) Lithium Iron Phosphate Batteries

Due to the use of larger array antennas and higher bandwidth in 5G base stations, the full-load power of a single station approaches 3800W, which is 3.5 times that of 4G base stations. Considering the energy consumption of other equipment in the machine room, the energy consumption of 5G base stations will reach 5300W. Based on a backup time of 4 hours, the backup power capacity for a single base station needs to be 21.2KWh. Due to the significant increase in power consumption of 5G base stations, using backup power to peak shaving and filling valleys to reduce electricity costs will become a standard feature of 5G base stations. Lithium iron phosphate batteries have a cycle life four times that of lead-acid batteries, good rate performance, support for fast charging, and a wide temperature range, making them more suitable for use with backup power for 5G base stations. Therefore, the large-scale construction of 5G base stations will lead to an increase in the demand for lithium iron phosphate batteries. During the preparation of lithium batteries, it is necessary to leak test the welding points of the shell. If the electrolyte inside the lithium battery leaks due to the non-sealing of the shell, it not only affects the service life of the equipment but may also pose a hazard to the operators. Therefore, it is essential to conduct leak testing during the assembly and sealing of lithium batteries (cylindrical and prismatic cells through welding). Depending on the production process, either a helium mass spectrometer leak detector or a helium leak detection system can be chosen.

Figure 4: A helium mass spectrometry leak detection scheme for a lithium iron phosphate battery shell

　3. Application of Vacuum Technology in 5G Backbone Network

1) Optical Passive Devices

Optical passive devices refer to a general term for optical functional devices that do not contain optical energy. They mainly perform functions such as connection, energy attenuation, reverse isolation, branching or combining, signal modulation, and filtering in the optical path. Optical passive devices have very high sealing requirements; if there are leaks, it will affect their performance and accuracy. The leak rate standard in the optical communication industry is less than 5×10-9 Pa*m3/s, so leak detection is necessary. The helium mass spectrometry leak detection method uses helium gas as a tracer gas, which can accurately locate leak points, replacing traditional foam leak detection methods and differential pressure leak detection methods, and is now widely used in the production process of optical devices.

Figure 5: Optical passive devices to be leak tested

2) Thin Film Filters (TFF)

One advantage of fiber optic communication is the ability to transmit dozens of wavelengths simultaneously through a single fiber, known as Wavelength Division Multiplexing (WDM). The basic components for WDM transmission are optical filters, which can be realized through technologies such as Fiber Bragg Grating (FBG), Thin Film Filters (TFF), Arrayed Waveguide Gratings (AWG), and optical comb filters. TFF and AWG are the two most commonly used WDM technologies. Devices based on thin film filters are widely used in front-haul and mid-haul WDM schemes. Currently, thin film filters are mainly produced using Ion-Assisted Deposition (IAD) or Ion Beam Sputtering (IBS) techniques. The thin film filters used in 5G backhaul networks are produced by alternating the deposition of SiO2 and Ti2O5 on the filter surface through coating processes, with a deposition thickness at the molecular layer level, ranging from a few layers to hundreds of layers as needed. The more layers there are, the closer the response spectrum curve approaches a rectangle, resulting in superior filter performance.

Figure 6: Structure of a certain thin film filter

　4 Vacuum technology in 5G terminals

1) 5G smartphones

· Coating of 5G smartphone back panels

5G communication uses high-frequency signals, and metal smartphone back panels that significantly shield high-frequency signals will gradually exit the market, replaced by glass and ceramic back panels. Since traditional anodized aluminum alloy dyeing processes cannot be used, optical decorative coating has become the preferred process for glass dyeing. In the manufacturing process of ceramic back panels, magnetron sputtering coating has also gradually become the preferred solution for printing logos and decorative stripes.

Figure 7: Aurora color glass back panel of a certain brand smartphone

· Electromagnetic shielding film for 5G smartphones

5G smartphones have a large number of Massive MIMO antennas, and the trend towards high frequency and high speed significantly increases the demand for electromagnetic shielding. Typically, 5G smartphone manufacturers will laminate a cover film and an electromagnetic shielding film onto the FPC (Flexible Printed Circuit Board) to address electromagnetic shielding issues. The electromagnetic shielding film is a type of electromagnetic shielding material, currently mainly applied in FPC and related components, with broad application space in electromagnetic shielding and wave absorption fields. The electromagnetic shielding film needs to have high shielding effectiveness, thin thickness, light weight, bend resistance, high peel strength, and low grounding resistance. The electromagnetic shielding film in 5G smartphones is mainly produced using vacuum roll-to-roll magnetron sputtering.

Figure 8: Electromagnetic shielding film on FPC

· OLED display screens for 5G smartphones

In terms of the back panel process of smartphone displays, 5G displays are mainly divided into four categories: flexible OLED, rigid OLED, low-temperature polycrystalline silicon LTPS-LCD, and amorphous silicon α-Si-LCD. OLED screens, with their fast response speed and energy-saving advantages, have become core components of 5G smartphones. The preparation of OLED materials is closely related to vacuum coating technology, where vacuum evaporation is a key process in OLED manufacturing, directly affecting the display of OLED screens. The working of the evaporation machine is to accurately, uniformly, and controllably evaporate OLED organic light-emitting materials onto the substrate; at the same time, the preparation of OLED organic light-emitting materials also needs to be conducted in a vacuum environment.

Figure 9: Schematic diagram of OLED vacuum evaporation

· Cameras and filters for 5G smartphones

From 3G to 4G to 5G, each generation of communication network upgrades means a larger volume of information throughput. Currently, mainstream 5G smartphones have all increased the number of cameras, and the pixel enhancement of individual cameras has also become a significant trend. Under this trend, the number of camera lenses and infrared cutoff filters in smartphone cameras has significantly increased, greatly increasing the demand for optical coatings.

Figure 10: Structure of smartphone camera

2) VR/AR devices

In the 4G era, smartphones developed rapidly. With the arrival of the 5G era, people cannot help but speculate about what the next generation of consumer electronic terminals will be. Among them, the most anticipated are VR/AR devices. Whether VR or AR devices, their core feature is a new type of display system. In addition to image display devices, the more critical component is the Near-eye Display optical lens group. The lens solutions for AR and VR devices differ, which will be introduced separately below. The AR lens solutions currently mainly include prisms, freeform surfaces, and optical waveguides, with planar optical waveguides being the mainstream. Currently, optical devices based on planar optical waveguide technology solutions are mainly manufactured through optical coating. The VR lens solutions mainly use Fresnel lenses, where vacuum coating technology is mainly applied to the anti-fog film on the inner side of the lens and the anti-reflection film of the lens.

Figure 11: VR/AR devices (rendering)

3) Smart home

5G technology will promote the rapid development of the Internet of Things, providing communication infrastructure for smart homes. Currently, a series of smart home products have emerged in China, such as smart table lamps, smart security systems, smart curtains, smart temperature control systems, and smart audio systems. Whether in the production process of smart home products themselves or in the communication systems that achieve "thing-to-thing" connectivity, vacuum technology is indispensable.

Figure 12: Schematic diagram of smart home

　　5 Developing vacuum technology to support the 5G industry

As a new generation of mobile communication technology, 5G expands its service targets from person-to-person communication to person-to-thing and thing-to-thing communication, and its application fields extend from mobile internet to mobile IoT, opening up a new journey of ubiquitous connectivity, deep human-machine interaction, and intelligent-led transformation. It represents the development direction and strategic high ground of the new generation of information communication technology. Vacuum technology, as a continuously developing modern basic science, is widely applied in various aspects of the 5G industry. In the future, Zhongke Keyi will continue to strengthen its leading advantages in vacuum technology, focusing on cutting-edge technologies such as 5G, artificial intelligence, and the Internet of Things, and contributing to the continuous development of 5G technology and its industrialization.