How 5G affects PCB design and manufacturing
5G wireless technology is characterized by high speed, wide access range and short 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 latency. The spectrum extends into the millimeter waveband (mmWave), and these extremely high frequencies are one of the toughest challenges facing the PCB manufacturing industry.
As such, 5G impacts many aspects of design and manufacturing, including PCB assembly. There are multiple challenges in designing a PCB that can take advantage of 5G devices. Assembly shops also require new process methods, advanced testing and inspection facilities.
5G-related PCB design challenges
Here are some of the main issues engineers facing when designing and manufacturing PCBs for 5G applications.
As design complexity increases, 5G devices will likely use high-density interconnect (HDI) PCBs with finer traces and a higher density of connection pads. And these thinner traces often cause signal integrity problems when transmitting high-speed signals.
Impedance irregularities can occur on HDI PCBs due to various factors such as trace size, width, and cross-section. If the traditional negative etching process is used to form the cross section of the trace, the problem of signal loss due to abnormal impedance can easily occur.
To integrate multiple antenna array units (AAUs), PCB manufacturers must deal with more complex technologies such as multiple-input multiple-output (MIMO). Additionally, 5G designs will require more base stations and antenna arrays to operate effectively at very high operating frequencies. Therefore, it is not surprising that EMI, crosstalk and parasitic capacitance are key issues in 5G RF PCB design.
Thermal management is also a key task in 5G PCB design. Since high-speed signals generate a lot of heat, the chosen substrate and dielectric constant should be sufficient to handle heat dissipation. Otherwise, issues such as copper wire peeling, delamination, and board warping can degrade PCB performance.
These 5G-related challenges mentioned above greatly impact the PCB assembly process and push the limits of traditional PCB manufacturing methods.
Advanced technology in 5G PCB design
New technologies continue to emerge in the area of PCB design for 5G applications . Here are two techniques that PCB designers are using to meet emerging 5G technology needs :
- Improved Semi-Additive Process (MSAP): To achieve high circuit density and minimal signal degradation, 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. The copper present between the conductors is further etched away. The lithography technique here is used to ensure high-precision etching, resulting in minimal signal loss.
- Automatic Optical Inspection (AOI): For 5G designs, manufacturers will use advanced AOI systems during PCB manufacturing and identify potential failures by measuring the continuity of the top and bottom signal lines in through-hole or SMD assemblyto improve the accuracy of AOI fault detection, reduce false alarms and shorten production line delays. New approaches using artificial intelligence (AI) focus on those actual errors that can be fixed using automatic optical shaping (AOS) systems. The integrated AOI system can provide the data needed to analyze the efficiency of the production line.
Signal frequencies in 5G applications are high, so their mixed-signal PCB design is rather complex. In addition to manufacturing and testing using the new technologies discussed above, there are some best practices for efficient 5G PCB design. Below is a brief introduction to best practices for 5G PCB implementation.
5G PCB design guidelines
Choose a substrate material with as low a dielectric constant (Dk) as possible because Dk loss increases proportionally with frequency. Most solder masks are highly hygroscopic and may absorb moisture if used in large quantities. Therefore, it is recommended to use less solder mask to avoid any failure due to moisture.
The skin effect of traces increases with frequency and it impedes current flow. Therefore, it is highly recommended to properly design traces with a uniform copper surface in 5G-enabled PCBs. Even the copper planes should be sure to be smooth and symmetrical throughout the PCB stackup to avoid any resistive losses.
Correct selection of laminate thickness is critical for 5G PCBs. If the thickness is higher than recommended, the laminate will resonate and propagate vibration waveforms, causing interference.
The transmit and receive components used in 5G designs are very sensitive. Accurate installation of these components is critical to proper operation of these components and requires adherence to tight trace tolerances. Antennas used in 5G circuits should be impedance matched to the traces. The recommended no-wiring area should be preserved to avoid EMI issues.
Choosing the right transmission line is important in high frequency PCB design. In microstrip, stripline, and grounded coplanar waveguide (GCPW), stripline may be a better option, but it is difficult to manufacture and may increase production costs. Additionally, microvias are used to connect the striplines to the outer layers with minimal signal reflections. It requires a certain amount of expertise and discussions with the contract manufacturer in advance to avoid possible problems during the PCB manufacturing process.
5G-growth opportunities for PCB designers
5G technology is still evolving and features are being added every day. Therefore, PCB manufacturer 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 requirements of 5G technology should be a huge development opportunity.
The consumer industry is rapidly adapting to 5G networks as it offers innovative features with powerful performance. The PCB industry will continue to expand as the demand for powerful and flexible 5G equipment continues to grow. However, PCB assembly suppliers must provide the tools and process flow to accommodate the rapid development of 5G technology.
In conclusion, understanding the design requirements and development trends of 5G is very helpful in maintaining a competitive advantage in the PCB manufacturing industry.