What are the challenges of 5G communication for PCB design
5G wireless technology is characterized by fast speed, wide access range and low latency. Compared with 4G networks, 5G can provide 10-20 times the transmission rate, about 100 times the data capacity and less than 1 millisecond delay. The spectrum extends into the millimeter wave band (mmWave), and this extremely high frequency is one of the toughest challenges facing the PCB manufacturing industry.
As such, 5G impacts many aspects of PCB design and manufacturing, including PCB assembly. Designing a PCB that can take advantage of the benefits of a 5G device presents several challenges. Assembly shops also require new process methods and advanced testing and inspection facilities.
5G communication has an increasing impact on people’s lives, and newly developed mobile phones will gradually enter the 5G era. Let’s take a look at what challenges 5G communication brings to the PCB industry today!
The challenge of 5G communication to PCB process
5G communication is a huge and complex integrated technology. Its challenges to the PCB process mainly focus on: large size, high multi-layer, high frequency, high speed and low loss, high density, rigid-flexible combination, high and low frequency mixed voltage, etc. So many process technologies put forward new or higher requirements for PCB materials, design, processing, and quality control. PCB manufacturers need to understand changing needs and propose comprehensive solutions.
Requirements for materials: A very clear direction for 5G PCB is high-frequency and high-speed materials and board manufacturing. In terms of high-frequency materials, it can be clearly seen that leading material manufacturers in the traditional high-speed field such as Lianmao and Panasonic have begun to deploy high-frequency plates and launched a series of new materials.
This will break the current dominance of Rogers in the field of high-frequency sheet materials. After healthy competition, the performance, convenience, and availability of materials will be greatly enhanced. Therefore, the localization of high-frequency materials is an inevitable trend.
Requirements for quality monitoring: Due to the increase in the 5G signal rate, the deviation of the board manufacturing has a greater impact on the signal performance, which requires stricter control of the production deviation of the board. However, the existing mainstream board-making process and equipment are not updated much, which will become the bottleneck of future technological development. How PCB manufacturers break through is crucial.
Requirements for process technology: The functional improvement of 5G-related application products will increase the demand for high-density PCBs, and HDI will also become an important technical field. Multi-stage HDI products and even products interconnected in any order will be promoted, and new technologies such as buried resistors and buried capacitors will be more and more applied.
PCB copper thickness uniformity, line width accuracy, interlayer alignment, interlayer dielectric thickness, backdrill depth control accuracy, and plasma desmear capability are all worthy of further study.
Requirements for PCB design: The type selection of the board must meet the requirements of high frequency and high speed, and the impedance matching, stacking planning, wiring spacing/holes must meet the signal integrity requirements. Specifically, we can start from six aspects: loss, embedding, high-frequency phase/amplitude, mixed voltage, heat dissipation, and PIM.
Requirements for equipment and instruments: high-precision equipment and pre-processing lines with less roughening of copper surfaces are currently ideal processing equipment; and testing equipment includes passive intermodulation testers, flying probe impedance testers, loss test equipment, etc.
Precise pattern transfer and vacuum etching equipment, real-time monitoring and feedback data change line width and coupling spacing detection equipment. Electroplating equipment with good uniformity and high-precision lamination equipment can also meet the production needs of 5G PCB.
Advanced technology in 5G PCB design
New technologies continue to emerge in the field of PCB design for 5G applications . Below are two techniques that PCB designers are employing to meet the emerging 5G technology demands.
Modified Semi-Additive Process (MSAP): To achieve high circuit density with minimal signal attenuation, PCB manufacturers use the MSAP process instead of the usual negative etch method.
This process applies a thin layer of copper to a laminate without photoresist. Copper present between the conductors is further etched away. Here photolithography is used to ensure high-precision etching, resulting in minimal signal loss.
Automated Optical Inspection (AOI): For 5G designs, manufacturers will use advanced AOI systems in the PCB manufacturing process to identify potential faults by measuring the conduction of the top and bottom signal lines in through-hole or patch assembly, thereby improving Accuracy in AOI fault detection, reducing false alarms and shortening production line delays.
The new approach, using artificial intelligence (AI), focuses on actual errors that can be fixed using automated optical shaping (AOS) systems. An integrated AOI system can provide the data needed to analyze the efficiency of the production line.
The signal frequency in 5G applications is very high, so its mixed-signal PCB design is quite complex. In addition to manufacturing and testing with the new technologies discussed above, there are some best practices for efficient 5G PCB design. The following is a brief introduction to the best practical methods for 5G PCB implementation.
5G PCB design guidelines
Choose a substrate material with as low a dielectric constant (Dk) as possible, since Dk losses increase proportionally with frequency.
Most solder masks are highly hygroscopic and may absorb moisture if used in large quantities. Therefore, sparing solder mask is recommended to avoid any failure due to moisture.
The skin effect of the trace increases with frequency, which hinders the flow of current. Therefore, it is highly recommended to properly design traces with uniform copper surface in 5G capable PCBs. Even the copper planes should be smooth and symmetrical throughout the PCB stackup to avoid any resistive losses.
Correct selection of laminate thickness is crucial for 5G PCB. If the thickness is higher than recommended, the laminate will resonate and propagate the vibration wave, causing interference.
The transmit and receive components used in 5G designs are very sensitive. Accurate mounting of these components is critical to proper operation of these components, requiring adherence to tight trace tolerances.
Antennas used in 5G circuits should be impedance matched to traces. The recommended no-wiring areas should be preserved to avoid EMI problems.
Choosing the right transmission line is important in high frequency PCB design. In microstrip, stripline, and grounded coplanar waveguides (GCPW), using stripline may be a better choice, but it is difficult to manufacture and may increase production costs.
In addition, use microvias to connect the stripline to the outer layers with the least signal reflections. It requires some expertise and discussions with contract manufacturers in advance to avoid possible problems during PCB fabrication.
Growth opportunities for 5G PCB designers
5G technology is still evolving and features are being added every day. Therefore, PCB manufacturers must understand the requirements in terms of raw materials and equipment upgrades. In addition, investing in the research and development of PCB assembly processes that meet the technical requirements of 5G should be a huge development opportunity.
The consumer industry is quickly adapting to 5G networks because it offers innovative features with powerful performance. With the growing demand for powerful and flexible 5G devices, the PCB industry will also continue to expand. However, PCB assembly suppliers must provide tools and processes that adapt to the rapid development of 5G technology.
In conclusion, understanding the design requirements and development trends of 5G is very helpful to maintain a competitive advantage in the PCB manufacturing industry.