Everything You Should Know About 5G PCB - NextPCB

5G PCB

5G(5th Generation) is the whole new global standard for broadband cellular networks. It follows the backward compatibility of 4G LTE networks. 5G network aims to connect everyone with everything globally including all the objects, machines, devices, etc. The major identity of 5G technology is the greater speed in gigabit and lower latency. The higher speed or higher increase in data transmission is due to the availability of more bandwidth and antenna technology. Improved efficiency and higher performance of 5G networks are expected to make businesses and industries more efficient and provide information access to users at a much faster rate. 

It is estimated that the 5G network provides 10 times faster communication with 1 millisecond of latency compared to that of the 4G network. Thus, to support this level of higher frequency and higher speed, PCBs have to simultaneously support the frequency and data rates higher compared to the current ones. A 5G network will have frequencies in the millimeter wave region (mmWave), centered around the frequencies 26 GHz, 30 GHz, and 77 GHz, while 4G networks use frequencies below 6 GHz (600 MHz to 5.925 GHz). 

One of the most challenging aspects of 5G technology is the use of the EHF (Extremely High Frequency) band. In addition to propagating only line-of-sight, millimeter waves are strongly attenuated by structures, foliage, rain, and humidity along the way. Due to this, 5G networks will require more base stations. Advanced 5G features such as beamforming will require multiple phased array antennas to support a large number of frequencies. Consequently, a PCB is integrated with a multiplicity of Antenna Array Units (AAU) on both mobile devices and base stations.

Importance of 5G to PCBs

5G has been growing in almost every section and is affecting the production process. 

Data Traffic

It is assumed that about one-quarter of the mobile data traffic will be handled by 5G due to its low latency, versatility, speed, and reliability. The data includes telecommunications, video and gaming sectors, etc. This increase in data traffic demands PCB manufacturers and designers and thus establishes a new process for managing reliable performance. 

Industry Applications

When discussing electronics and smart phones 5G terminologies are used more. These improvement has expanded the coverage of 5G including heat care, retail, and communication industries. 

Customer Awareness

The awareness of customers about the 5G coverage has made the readily available 5G PCB devices. Thus PCB manufacturers must be aware and thus fulfill the demands of this product from the market. The process and technologies should support them.

Types of 5G PCB Materials

Mixed high-speed and high-frequency signals must be managed when designing a printed circuit board for 5G applications. To prevent power losses and maintain signal integrity, it is important to select the material appropriately when designing PCBs with high-frequency signals. A board must also be designed to prevent EMI between analog and digital parts so that it meets the EMC requirements of the FCC. In choosing a material, two factors are taken into account: thermal conductivity and thermal coefficient of dielectric constant. Due to the component's ability to generate heat, it is obvious that a substrate with high thermal conductivity is preferable. An equally important parameter is the thermal coefficient of the dielectric constant. Variations in the dielectric constant can result in dispersions, which can change signal propagation speed, stretch digital pulses, and sometimes cause signal reflections on transmission lines.
 
As well as PCB geometry, transmission line characteristics, and laminate thickness play a key role in PCB performance. The laminate thickness for the first point must be between 1/4 and 1/8 of the highest operating frequency's wavelength. Waves can propagate through conductors if the laminate is too thin. Microstrip, stripline, or grounded coplanar waveguide are the three types of conductors that can use for transmission lines. 

Above 30 GHz, microstrips have problems with spurious mode propagation and radiation loss. It is possible to manufacture strip lines as well, but they are more expensive and difficult to manufacture. When deciding between microstrip, stripline, or grounded coplanar waveguide conductors for transmission lines, micro vias must be used. 

The substrate materials should have a lower dielectric constant compared to that of the FR4 materials that are used for making the PCB components. The boards should also follow the processors and amplifiers that could perform at high frequency and high speed. Heat management can be used for reducing the output disparities in the provided components.

After the selection of the substrate materials, the common rules should be followed by the designer. The rules should apply to high-frequency PCB designs. The rules include; routing the traces of the RF signal with an express track, use of the shortest tracks, check the distance and width of the tracks for keeping the impedance constant among all the interconnections. 

High-Frequency Millimeter-wave 5G PCB

5G Millimeter wave frequency has been developed to counter the limitation of 4G LTE latency. It has frequencies between 30GHz to 300GHz. Using millimeter wave frequencies, 5G provides ultra-high speeds, increased traffic, and high capacity with a cellular network that can accommodate more devices. Due to its relatively unused nature, the 5G short wavelength band presents an opportunity for increasing bandwidth and overcoming the congestion issues found in other mobile communication frequencies. Even with the much higher data transfer rates, the 5G millimeter wave can cover shorter distances. When 5G millimeter wave frequencies are used, it improves the user experience, especially in the IoT application and automation industry. 

The 5G mm PCB is the circuit board that makes use of the 5G millimeter wave frequencies. They are specially used for high-frequency applications. 

This kind of PCB offers higher speed with low latency. Besides, it has various other advantages including;

High bandwidth

With the increase in bandwidth, the speed rate would be higher. This is the quality of 5G MM PCB. With the higher speed, the latency of data transmission will also be decreased resulting in a better and fast quality of data.

Higher Return of Investment(RoI)

The 5G MM PCB provides better user experiences for consumers and businesses. This enhances the monetization potential for the operators. 

Application of 5G MM PCB

With 5G millimeter-wave frequencies, network speeds can reach multi-Gbps. With 5G MM wave technology, users can benefit from high-speed data transfer and wide bandwidth, as well as network efficiency. Data consumption on mobile devices is exponentially growing. The major property of 5G mm wave i.e. high bandwidth makes it the best candidate for short-distance wireless transmission of streaming videos and other multimedia contents. 

With the increase in the application of 5G mm-wave, there have been wide opportunities for 5G mm PCB. Some of its application areas include:

• Military Services
• Aerospace Industries
• Automation Industry
• Remote Sensing
• Image Processing
• Cryptography and security
• Telecommunication Industry

Besides, the high-speed rate and short distance propagation of PCB makes it ideal for data transmission between autonomous vehicles also.

Challenges of 5G PCB design

Although the 5G PCB provides a better solution and opens the door to various opportunities, there are still many challenges in designing these 5G PCBs since it is in their early phases. 
Some of the design challenges of this 5G PCB include:

Mixed Signal Acceptance Circuit Board Designs

Depending on the application, PCBs for 5G network systems will require Mm-wave frequencies. To capture and transmit both lower and higher signals at the same time without experiencing signal loss and EMI, a PCB must contain the appropriate materials. The devices will also become smaller, lighter, and more portable. PCB materials have to be flexible and light to accommodate the microelectronics that will be placed along the board while maintaining strict weight, size, and space limitations.

Copper traces on PCBs must have thinner traces and stricter impedance controls. Semi-additive processes can be used instead of subtractive etching for high-speed PCBs such as 3G and 4G. It will be possible to produce straighter walls and more precise trace lines with these modified semi-additive processes.

Most of the companies have the target of designing the PCB that has lower dielectric as 3. Low profile copper and lower dissipation factor loss materials are also the parameters that need to be considered for high-speed 5G PCB design for preventing signal losses.

EMI Shield Concerns

One of the major problems with any PCB board is electromagnetic interference, parasitic capacitors, and cross talk. The EMI and cross-talk results from the analog and digital frequencies on the board. Thus to counter this challenge, it is recommended to separate the traces. 

The multilayer board provides greater flexibility when deciding where to route the high-speed traces to ensure that the analog and digital return signals are kept apart, as well as AC and DC circuits. In addition to shielding and filtering components, adding shielding and filtering during PCB layout should also help reduce natural EMI.

For protecting the copper surface from defects and basics short circuits, 2D metrology and optical inspection are used. This not only measures the traces of conductors but also measures them. 

Thermal Management Challenges

A higher amount of heat is generated from a higher signal speed where current flows through the board. 5G technology will require PCB materials that are capable of handling high speeds. Copper trace peeling, warping, shrinkage, and delamination. These problems can damage the PCB if the materials are inadequate.

Thus in dealing with these challenges, one should be considered material selection. The materials should address the issue of thermal coefficients and thermal conductivity. Any materials that provide better transfer of heat, have better dielectric constant, and have higher thermal conductivity is selected. They provide all the requirements for managing the thermal requirement of the circuit. 

5 Tips for 5G PCB Design

While designing the 5G PCB designs, the designer must follow the rules that apply to the higher frequency PCB designs for better results. The design of the PCB system depends on the management of mixed high-frequency signals and high speed. The standard circuit board design practices must be followed regardless of materials used to design a PCB for a 5G applications. Besides, the regulation for measurement for producing the constant impedance should be regulated. Some of the tips that the designer should follow for PCB design are as follows:

1. Selection of materials with low dielectric constant

It is necessary to select the materials with a lower dielectric constant as the dielectric constant decreases with an increase in frequency and due to heat produced by the PCB operations. 

2. Limit using solder mask

Since most solder mask has a higher moisture absorbing capacity that leads to a higher loss of the circuit. Thus, the use of the solder mask should be limited to the 5G PCB board.

3. Smooth and regular copper traces 

The skin depth has the inverse proportion to that of the frequency. Thus, a high-frequency board will be pretty shallow. Besides, the rough surface could create a rough and irregular track that increases the resistive losses. 

4. Signal Integrity

For any integrated circuit designer, high frequency means the most challenging problems. Increasing I/O requires thinner tracks, which in turn can cause signal degradation, which in turn leads to further losses. High-density interconnections (HDI) optimize I/O by allowing for more I/O.

This loss can directly affect the RF signal transmission. This results in higher latency and causes a problem with the signal transmission chain. Signal integrity in higher frequencies is based on impedance. 

The substrate process, for example, produces the trapezoidal cross-section tracks. These tracks have an angle vertical perpendicular to the track and a horizontal perpendicular between 25-50 degrees. As a result, the 5G applications are limited by these cross sections, that modify the impedance of the track. With the Semi-Additive Fabrication Process, traces can be created more precisely, allowing photolithography to determine trace geometries. 

5. Automatic Inspection

It is necessary to perform automatic inspections of PCBs for high-frequency applications, both optically (AOI) and using automated test equipment (ATE). By highlighting possible errors and inefficiencies in the circuit, these procedures increase the quality of the product enormously.

The automatic monitoring and testing of the PCB is the latest and most recent progress in the PCB industry. This has led to time savings reducing the cost that could take in manual testing and verifications. The use of these automated inspection technologies can help counter the challenges of 5G. The use of automated inspection and monitoring methods can help in performance checks with higher rates of production. 

How Does a 5G PCB Antenna Work?

With the development of 5G technology, various 5G antennas are required for supporting the various frequency bands. The Advance Antenna System(AAS) is used by 5G which is the mixture of a set of AAS features and AAS radio. Multi-antenna techniques including MIMO(Multiple Input and Multiple Output) and beamforming are included in AAS. All bands in 5G require an antenna system for supporting them. 

The frequency band of the 5G network is higher compared to 4G. Thus the proper antenna system which could be multiple or multiband antennas needs to be used properly. The proper and correct antenna system can improve the transmission distance, and also improves the signal quality. Thus the optimized PCB design is the most that could use the 5G technology. The system performance of any PCB is affected by the use of the location of the antenna. Besides, the proximity of any other components could also affect the performance.  

A major benefit of 5G is that more people can assess the network while simultaneously maintaining high speeds. Massive MIMO antennas will be used to send and receive data simultaneously. The physical size of the antenna will be similar to that of the 4G network. MIMO antenna technology will also be built into 5G User Equipment including mobile phones and devices. 

For optimizing the circuit, Rf transmission lines and impedance matching must be considered.
Impedance matching for the PCB circuit is carried out at 50 Ohm. When the antenna is matched correctly, the RF source delivers most of its power to the antenna, and the antenna receives most of the power from the source. 

In addition to matching the antenna impedance and the remaining circuitry's impedance, the transmission line transmits radio frequency power along a structured path from the antenna to the load. 

The 5G PCB design optimization process must be followed by the selection of the antenna. Factors like ground plane length, device size, efficiency, and frequency bands need to be considered. This will determine the best antenna choice for your 5G applications. 

Technology Used in 5G PCB

Multi-layer boards(MLB) with high layer counts (HLC), such as cellular-based stations, high-performance computing systems, and data servers are becoming important in 5G infrastructure applications. There is an increase in demand for PCBs, high-density PCBs with advanced HDI, and any layer HDI caused by 5G antennas, display drivers, and camera modules. All the design requirements of PCB for 5G exceed the past technology of PCB manufacturing. Thus, the new and latest technology is used in the 5G PCB systems which are given below:

Imaging Technology

5G PCBs will require inspection and imaging capabilities based on several advanced manufacturing technologies. This includes automated optical shaping, automated optical inspection (AOI), and direct imaging. Although the manufacturing process of PCBs in 5G devices and 5G infrastructures are different. 

The tight impedance control is enabled in direct imaging (DI) technology in 5G infrastructure. The tight impedance control required high-frequency 5G like mm-wave, strict font-to-back accuracy, and higher accuracy in large panels. This DI technology which is also a high-capacity solder mask could support the large and warped panels fulfilling all the higher accuracy and resolution demands of 5G's network.

Automated Optical Inspection

5G infrastructure typically comprises HPCs and data servers that feature fine lines, which is why automated optical inspection (AOI) is ideal for detection and measurement, ensuring that the process does not require excessive handling.

DI system can enable high-quality imaging while maintaining the highest efficiency throughput and effectivity of modified semi-additive processes(mSAPs) and substrates like PCBs (SLPs) produced with modified semi-additive processes (mSAPs). FPCs(Flexible Printed Circuits) are becoming increasingly critical components in 5G electronics due to their small size, lighter weight, and higher functionality.

Using roll-to-roll DI systems in FPC manufacturing preserves the integrity and minimizes the damage and distortion commonly experiences by roll-based flex materials. 

The accurate top and bottom measurements are ensured by AOI with automatic 2D metrology. The accurate measurement is carried out for impedance control. 

Besides, there are other innovative technologies for 5G PCB design i.e. automated optical shaping and repair. 

In advance HDI(mSAP) PCBs and IC substrates, optical repair allows the manufacturer to quickly and accurately shape shorts and opens. This process helps in reducing the quality and production yield, saves time and labor, and reduces board and panes to be used in the process. Manufacturers may benefit from a competitive edge by automating optical repair as part of their 5G PCB mass production process. 

Conclusion

The new 5G protocol and demands require advanced manufacturing technologies to adapt infrastructure and devices. Using laser direct imaging, automated optical inspection, and automated optical shaping and repair, designers will no longer have to contend with low latency, high frequency, or complex and fragile materials. 5G technology is growing with various optimized features. Thus the PCB manufacturer should have to know the requirements in all terms of raw materials. In addition to this, the proper investment in R and D of PCB assembly for meeting all the 5G technological requirements can help to grow this industry. All most all the consumer industry is rapidly adapting to the 5G network as it provides robust performance and innovative features. 

With the growing demand for flexible 5G devices, the PCB industry will expand in near future as the consumers adapting the 5G PCB design have clear advantages. It has innovative features that perform better and aren't hindered by performance issues. Consumer demand may bring manufacturers similar benefits across various production equipment, but it is consumer demand that is the most significant.