FS Technology's comprehensive analysis of 5G PCBA

Overview: Since 2012, 5G signals have entered our field of vision, and with the advent of the 5G era, the communications industry has undergone major changes. The 5G base station AAU high-frequency PCBA replaces the traditional grid isolation, and the 5G frequency band extends to high-frequency, increasing the global demand for high-frequency copper-clad laminates.

Introduction to 5G Signals

What is 5G

With the innovation of communication technology, we are talking more and more about 5G. However, most people, do not know the real meaning of 5G, they only know that 5G is faster and more expensive. For society as a whole, it is the key to driving technological progress. 5G has a wide range of applications, including driverless technology, telemedicine technology, and virtual projection technology.

5G is an acronym for the fifth generation mobile communication network. The biggest difference between wireless communication and wired communication (such as optical fiber) is whether the signal is transmitted through electric waves or a medium. In the iterative update from 1G to 5G, essentially we only changed the frequency of the airwaves. The 5G signal is fast because it uses higher frequency airwaves. The higher the frequency, the more resources can be obtained, enabling it to carry a greater amount of information at the same time, and ultimately achieve high-speed signals. The following FS technology will use driverless technology to show you how the 5G signal works:

The driverless technology collects road conditions through various sensors, transmits the collected data to the data management center, and finally returns the instructions to the car to realize automatic driving. In this series of activities, the speed and integrity of data transmission are the difficulties of the whole process. It is said that the self-driving car will generate about 1GB of data every second, and the traditional 4G network cannot download such a huge amount of information in a short period. However, with the advancement of 5G PCBA technology, technicians have increased the theoretical value of network data transmission speed to 10Gb/s, which means that 1.25GB of data content can be downloaded per second. Unmanned driving is thus possible.

5G PCB and unmanned driving

The difference between 5G signal and 4G signal

Speed difference:

This is the part where we feel the most obvious. The average speed of 4G is about 100Mbps, while the 5G network reaches an astonishing 10Gbps, which is 100 times that of 4G.

Delay difference:

Video calls or games appearing in games are caused by signal delay. The delay of 4G network is about 30-50ms while using 5G network will shorten the delay to 1ms.

Compatibility difference

4G mobile phones can only receive 4G networks, which has nothing to do with the network you use, but because the old version of 4G PCBA is used inside the mobile phone, so the network compatibility is not strong. In contrast, 5G mobile phones are more compatible, not only supporting 5G networks, but also 4G, 3G, and 2G networks. The problems that cause insufficient compatibility are explained in detail below.

Difference in cost

Many people mistakenly believe that downloading files of the same size, the cost of using 5G and 4G is the same. The amount of data downloaded is the same, but the cost of unit traffic of 5G network is higher than that of 4G.

Challenges posed by 5G PCBAs

5G printed circuit board

With the continuous breakthrough of 5G technology, based on cost factors, its application in high-end electronic equipment is larger. For applications that are closely related to human health, such as autonomous driving and telemedicine, people have almost zero tolerance for errors. However, as more devices are added to the network, the shortcomings of security performance are gradually exposed, and the risk of these applications increases exponentially. As the core end of the electronics manufacturing industry, we turnkey PBCA assembly companies are increasingly responsible. In terms of continuity of communication and accuracy of data transmission, 5G PCBA faces the following challenges.

Signal Transmission Integrity

As the threshold of 5G PCBA application scenarios is getting higher and higher, it brings dual challenges in manufacturing to circuit board manufacturers – higher frequency and smaller size. To cope with higher frequency board requirements, we had to optimize the I/O with thinner traces at the beginning of the design. At the high frequency PCBA board design level, thinner traces mean that manufacturers take the risk of signal degradation. When the physical characteristics of the manufactured circuit board do not meet the original design expectations, it may cause delays in the transmission of RF signals. Traditional etch detailing does not meet our expectations, as the cross-section of the trace can be weird when the board is fabricated, making it abnormally impedance.

To ensure the integrity of the signal output, we can improve the semi-finished product processing process, which essentially solves the above problems, making the traces more accurate and reducing this foreseeable risk.

To ensure that the manufacturing of 5G printed circuit board is foolproof, no matter what method is used, FS Technology recommends setting up multiple quality inspection links in the manufacturing process in China. To ensure the quality of production and assembly, FS Technology has set up manual visual inspection windows at multiple exits of the workshop, and AOI automatic optical inspection is carried out after SMT assembly is completed, and secondary visual inspection is carried out after the finished product is completed.

Signal acceptance compatibility issues of 5G PCBA

Many people’s biggest feeling about 5G signals is the leap in speed. In fact, to improve the speed of wireless networks, researchers have used many methods, and without exception, they all failed. But with the use of Massive MIMO technology, this problem is completely solved. Massive MIMO is a multi-antenna technology that increases the number of antennas used by base stations and terminals. But this technology is not perfect, it also brings a series of problems while solving problems. This chapter mainly focuses on 5G PCBAs, so only the issues affecting the compatibility of mobile phones are introduced here. Using Massive MIMO can solve the efficiency problem of signal transmission and reception, but it is devastating for 4G mobile phones.

The circuit boards used by 4G mobile phones to receive signals are old-fashioned 4G and 3G PCBAs. Although it will not affect our use, it limits the sending and receiving frequencies of electronic components. The receiving frequency range of 4G PCBA is 600 MHz to 5.925 GHz, the bandwidth channel is 20 MHz, and the IoT system is 200 kHz, which cannot meet the receiving conditions of 5G high-frequency signals. The circuit boards of 5G mobile phones are designed to increase the sending and receiving frequencies of components to 28GHz, 30GHz, and some even up to 77GHz millimeter wave frequencies. In terms of bandwidth channels, 5G information systems can handle frequencies below 6GHz and above 400MHz.

To adapt to the changes in signal reception, the turnkey PCBA company needs to update the substrate material used in addition to the impedance control of the copper wires of the printed circuit board. For ordinary printed circuit boards, its dielectric constant standard is usually 3.5 to 5.5, which is far from enough for 5G PCBAs that require high speed and high frequency. Therefore, PCBA companies are committed to finding new materials with a dielectric constant as low as 3 and hope to reduce signal loss and improve signal accuracy and reliability in this way.

EMI Issues (Electromagnetic Interference) of 5G PCBAs

EMI problems of PCB

EMI is the abbreviation of Electromagnetic Interference, which refers to the signal shielding or interference caused by electronic equipment at work to other electronic products. Almost any government in the world is trying to control the harmful EMI produced by electronic equipment in other countries, so the EMI problem is all electronic product manufacturers need to spend time to solve.

In modern high-speed systems, mechanical assembly companies are updating connectors to suppress conducted and radiated EMI. At present, the most used and most effective connectors in China include the following: TE DEUTSCH filter connectors, Smiths Interconnect filter connectors, and AVIC photoelectric rectangular filter connection series.

In terms of printed circuit boards, to avoid EMI leakage, FS Technology believes that it is necessary to comply with the following design rules for high-speed signal traces:

Trace shielding rules: In the traced design of 5G high-speed PCBA, in order to avoid EMI leakage, we need to shield key high-speed signal lines such as clocks. FS Technology recommends that the shielded wire be grounded with holes per 1000mil.

Routing closed-loop and open-loop rules: For a high-density circuit board such as 5G PCBA, whether the clock signal produces a closed-loop or an open-loop result in the traces of the multi-layer board, a loop antenna will be generated, resulting in enhanced EMI radiation.

Characteristic impedance continuity rule: For high-speed signals, different layers must ensure the continuity of characteristic impedance when switching, that is, the width of the same layer of wiring must be continuous, and the trace impedance of different layers must be continuous.

Wiring direction rules: To avoid crosstalk between lines, the wiring between two adjacent layers must follow the principle of vertical wiring, that is to say, adjacent wiring layers must comply with the horizontal and vertical wiring direction rules.

Resonance rule for trace length: When the trace length is an integer multiple of 1/4 wavelength, the trace will have a resonance effect, causing electromagnetic waves to be radiated, resulting in interference problems.

Return path rules: We know that the magnitude of radiation is related to the signal transmission path and the area enclosed by the return path. Therefore, it is also a strategy to keep the return path of 5G signals unobstructed and reduce the return path of high-speed signals.

The rules for placing decoupling capacitors on the device: If you find that the decoupling capacitors are not effective, it may be due to the wrong placement of the decoupling capacitors. The principle we need to follow is: close to the pins of the power supply, and make the capacitors The area enclosed by power and ground traces is minimal.

Thermal management problems of 5G PCBA

5G signals have extremely high-speed requirements, so printed circuit boards need to absorb more resources and generate more current. As the number of currents increases, a lot of heat will be generated on the surface of the PCBA board. In addition, to increase the function of the base station, most of the base station PCBAs are high-frequency, high-speed, multi-layer, high-density circuit boards. The overly dense component structure will accumulate heat, resulting in the problem of difficult heat dissipation of the circuit board. This can cause issues such as copper wire peeling, delamination, reduction, and warping. Traditional FR-4 cannot overcome this problem. It is necessary to use a circuit board with excellent thermal management performance such as IMS PCBA. Its thermal conductivity is 8 to 12 times that of FR-4, which can better cope with high-temperature applications.

Opportunities brought by 5G PCBA to the circuit board industry

We know that the development of 5G is based on the premise of large-scale data control centers. As mentioned earlier, the speed of the 5G signal is positively related to the frequency of the radio wave, and the speed of light = frequency × wavelength. Signals have a characteristic: the decay rate in the medium is frequency dependent. The lower the frequency, the less attenuation, and the better the propagation capability. This is not good for high-frequency 5G base stations, which make the signal attenuate quickly during propagation. That is to say, to completely solve the problem of 5G signal transmission, it is necessary to increase the number and density of base stations. In today’s electronic society, all electronic products are inseparable from printed circuit boards. Based on such a large environment, end users’ demand for high-end communication PCBA will be infinitely increased, and the quality requirements of PCBAs are also rising. This is a huge expense for the communications industry, but an opportunity for us PCBA manufacturers.

5G base stations promote the development of high-end PCBAs

We know that the development of 5G is based on the premise of large-scale data control centers. As mentioned earlier, the speed of the 5G signal is positively related to the frequency of the radio wave, and the speed of light = frequency × wavelength. The signal has a characteristic: the attenuation rate in the medium is related to the frequency. The lower the frequency, the less attenuation, and the better the propagation ability. This is not good for high-frequency 5G base stations, which make the signal attenuate quickly during propagation. That is to say, to completely solve the problem of 5G signal transmission, it is necessary to increase the number and density of base stations. In today’s electronic society, all electronic products are inseparable from printed circuit boards. Based on such a large environment, end users’ demand for high-end communication PCBA will be infinitely increased, and the quality requirements of PCBAs are also rising. This is a huge expense for the communications industry, but an opportunity for us PCBA manufacturers.

5G antenna PCB usage

Due to the extremely stringent requirements of 5G for high frequency bands, the circuit boards are forced to show a trend of high frequency. At present, the mainstream antenna PCB solution is to use hydrocarbon PCBA boards, and the price is about 3000-6000 yuan/square meter, which is 2-3 times that of ordinary printed circuit boards. According to the communication industry report released by the research institute industry, the number of Acer construction will be twice that of the 4G era, and the number of small base stations will increase by more than 10 times on the original basis. To improve the ability of signal reception, base stations began to use massive antenna technology “Massive MIMO”, which is the reason for the sharp increase in the demand for 5G antennas. While a large number of 5G base station antennas increase the amount of high-frequency PCBAs, the increase in IDCs and communication base stations will also bring about the demand for high-speed PCBAs.

Construction of base stations

To meet the needs of the society for signal transmission capabilities, in addition to using a large number of circuit boards to build base stations, it is also necessary to increase the number of RF front-end components and use more advanced high-speed substrates. This makes the PCBA cost of a single base station three times that of the 4G era.

Technical aspects

The signal transmitted by the base station is not directional but is transmitted around. Earlier we mentioned that high frequency means using more resources, which also causes a lot of waste of resources. Therefore, it is necessary to use beamforming technology to bundle resources when building base stations. Beamforming technology refers to laying 5G antenna arrays on base stations and using the advantages of RF PCBAs to control the phase of RF signals. This technology can transmit signals to the target more centrally, and adjust the direction with the movement of the target, maximizing the accuracy of the base station and expanding its capacity of the base station.

The impact of PCBA on 5G mobile phones

The arrival of the 5G era has not only increased the construction of base stations but also accelerated the iterative update of mobile phones. The reason for this phenomenon is not only to meet the needs of the market, but also the “Massive MIMO” mentioned above.

The relationship between 5G mobile phones and PCBAs is also symbiotic. PCBA guarantees the speed and accuracy of 5G signal transmission, and the mobile phone industry is expected to bring more than 60 billion incremental opportunities to the PCBA industry in 2022.

In the entire PCBA industry, the application fields of circuit boards are very wide, including 5G communication, aerospace, consumer electronics, military equipment, medical equipment, etc. Among all application terminals, communications, computers, and consumer electronics are the focus of our PCBA industry, accounting for 27%, 27%, and 14% respectively.

The innovation of PCBA technology and the arrival of the 5G era have promoted a worldwide upsurge in replacement. According to the statistics of the Ministry of Industry and Information Technology, since the second half of 2019, to manufacture more compatible 5G mobile phones, major manufacturers have begun to purchase high-frequency PCBA components and manufacture multi-layer HDI circuit boards on a large scale. It is expected that China’s shipments of mobile phones will increase to 574 million in 2022. With the promotion of the 5G market, FS Technology believes that communication will be the highlight of the PCBA industry.

The impact of 5G development on China’s PCBA industry

Since the demand for 5G PCBAs has increased, China’s PCBA market has ushered in a record high. From the data of market research institutions, since 2017, China’s PCB production has accounted for more than 50% of the global output, which means that more than half of the circuit boards are exported from China. Although we have made great achievements in exporting copper clad laminates, if you study the data carefully, you will find that China’s 5G PCBA market environment is still not optimistic.

The industrial chain of CCL is a segmented market, and its upstream includes electronic components such as capacitors, resistors, and integrated circuits. The midstream is the PCB manufacturing, assembly, and mechanical assembly industries. This globalized industrial chain of the division of labor is somewhat similar to TSMC introduced in the 1990s. At that time, the boss of TSMC used Western technology to conduct R&D and manufacturing of TSMC around Taiwan. With the progress of scientific research, TSMC’s manufacturing has shifted from a turnkey project to two industrial chains – burning and packaging, and testing. That is to say, nearly 70% of TSMC’s production process starts in developed countries in Europe and the United States, then transfers to Japan and South Korea, and finally to Taiwan China. As a result, the core technology is mastered in European and American countries, while Taiwan can only carry out mechanized assembly work. This is similar to our current global PCBA market environment.

Although China’s 5G PCBA exports account for 50% of the global total, most of the exported CCLs are low-end and simple products. High-frequency PCBA, DHI PCBA, and other advanced circuit board types, are still dominated by European and American countries. For these more advanced copper clad laminates, the annualized growth rate and compound growth rate in mainland China is about 5%, which is quite low in terms of the growth rate of the entire industry.

At present, the output of 5G copper-clad laminates in China is quite low, and its basic high-speed and high-frequency products still rely on imports from developed countries. In 2015, China’s import and export volume of high-frequency boards was about 20,000 tons.

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