The printed circuit board is the key electronic interconnection of electronic products, and is known as the “mother of electronic products”. With the rapid development, iteration, and integration of electronic product-related technology applications, PCB, as a bridge to carry electronic components and connect circuits, will face huge challenges and development opportunities in order to meet the needs of new technologies and new applications in the field of electronic information.
According to the Prismark report forecast, the global PCB output value was 80.449 billion US dollars in 2021, an increase of 23.4% over the previous year, and the PCB industry in all regions has shown a continuous growth trend. From 2021 to 2026, the compound annual growth rate of the global PCB output value is expected to reach 4.8%, and the output value of the global PCB industry will reach 101.559 billion US dollars in 2026.
Benefiting from 5G commercial use, base stations as wireless communication infrastructure will be built on a large scale, and the demand for PCBs for communication equipment such as switches, routers, and optical transport networks used in 5G networks will increase accordingly, and the output value and added value of communication PCBs will be doubled. In 2021, the industrial output value of the communication field was 631 billion U.S. dollars, and it is expected to reach 828 billion U.S. dollars in 2026, with a compound annual growth rate of 5.58% from 2021 to 2026.
What challenges communication PCBs are facing?
With the development of 5G technology, 5G communication products have strict requirements on the reliability, reliability, electrical performance, thermal performance and product quality of PCB, and require the service life of products to reach more than ten years, which puts forward higher requirements for PCB board factory process and technology.
1. Requirements for hole technology of PCB factory
Blind and buried vias: 5G product functions have been improved, and the requirements for high-density PCBs have increased. At present, in most PCB factories, 1-3 levels of HDI tend to be mature, but the ability of higher-level buried blind vias needs to be improved.
Stub: The short pile effect of 112G products cannot be ignored. Back-drilled stubs put forward stricter requirements, and ostub will be the trend.
Embedded copper: The heat dissipation of high-frequency and high-power devices in 5G communication requires copper blocks to be embedded in the PCB to improve the heat dissipation capacity of the PCB.
2. Requirements for surface technology of PCB factory
Accuracy and consistency: 5G products increase the data signal transmission rate from 25Gbps to 56Gbps, and put forward stricter requirements for product impedance and loss. The product impedance requirement is increased from 10% to 5%, and the line width tolerance needs to be increased from 20% to 10%.
From the perspective of the influencing factors of impedance control, the size of impedance tolerance is affected by dielectric thickness tolerance, copper thickness tolerance, and current control accuracy. The impedance tolerance of the inner layer is reduced from 10% to 5%, the dielectric thickness tolerance should be controlled at ±7%, the copper thickness tolerance should be controlled at ±3, the line width tolerance should be controlled at ±8%, and the outer layer impedance is also the same. This is closely related to board materials, PCB engineering design, process technology, process control, etc.
Inner layer: In the case of high-speed or high-frequency 5G communication, it is mainly affected by the skin effect. The impedance felt by the signal transmission in the conductor will be much greater than the resistance of the conductor under DC conditions. The roughness of the traditional inner layer is as low as Ra<0.5um.
Interlayer: 5G high speed, the uniformity of the thickness of the dielectric layer will also affect the signal transmission characteristics, and the requirement for the uniformity of the dielectric layer is 15%.
3. Requirements for PCB board technology
Dissipation factor Df: With the increase of 5G communication rate and frequency, the loss factor D of the plate will become smaller and smaller.
Insertion loss & consistency: With the increase of 5G communication rate and frequency, the requirements for insertion loss & consistency are getting higher and higher.
Temperature resistance: thin substrate materials, high thermal conductivity, smooth copper foil surface, low loss factor and other materials, increasing PCB working temperature, require PCB to have higher RTI, higher thermal conductivity Tc.
CTE: PCB size ≥ 1100mm, chip size ≥ 100mm, the demand for compatibility between packaging materials and PCB is improved, and the CTE (X, Y) of PCB board is required to be ≤ 12PPM.
High CTI: Powerboards have high requirements for CTI.
4. Technical Requirements for Excipients
Solder resist ink: The main factors affecting signal transmission quality are not only PCB design and material selection (plate, copper foil, glass fiber collocation, etc.), but also the selection of PCB solder mask oil black has a greater impact on the outer layer of high-speed lines. Conventional solder-resist ink has become a bottleneck, and the research and application of ultra-low loss ink is urgent.
Browning potion: Due to the skin effect of current, in the high-frequency and high-speed field, the surface roughness of copper foil greatly affects the circuit loss, and low-roughness browning potion is more and more widely used in high-speed board processing.
Conclusion
In today’s fast-paced technological landscape, communication PCBs face challenges related to speed, miniaturization, security, and compatibility. However, with advancements in technology and innovative designs, these challenges can be certainly addressed to enable faster, more compact, secure, and interoperable communication systems for people!
