Base Station Communication Backplane PCB Board Solution

With the large-scale deployment of 5G and the trial commercialization of 6G, base stations have increasingly high requirements for signal transmission and equipment miniaturization. As the core of signal interaction in base stations, the communication backplane PCB board undertakes the core responsibilities of data transmission, power supply and signal distribution among various functional modules (CU/DU/AU), and its performance directly determines the operational efficiency, anti-interference ability and service life of the base station. Based on the harsh requirements of the base station communication scenario and combined with the latest industry technical standards, this solution provides a high-reliability, high-compatibility and low-cost overall solution for base station communication backplane PCB boards, which is suitable for various types of base station equipment such as macro base stations and micro base stations, helping the efficient upgrading of communication networks.

Analysis of Core Requirements for Base Station Communication Backplane PCB Boards

Base stations are mostly deployed in outdoor open-air scenarios or closed computer rooms, facing multiple challenges such as high and low temperatures, humidity changes, electromagnetic interference, vibration and impact. At the same time, they need to meet the requirements of high-speed signal transmission and high-density integration. The core requirements are focused on the following points, which are specific as follows in combination with the particularity of the base station operation scenario:

• High-speed signal transmission: Supports data exchange above 100Gbps, signal delay ≤ 10ns, adapts to the U6G frequency band (6425MHz–7125MHz), and avoids signal attenuation and crosstalk.

• High reliability: Can withstand a wide temperature range of -40℃~85℃, no failure after 500 temperature cycle tests; has excellent anti-electromagnetic interference ability, electromagnetic shielding efficiency ≥ 40dB, and can resist outdoor environments such as vibration and salt spray.

• High-density integration: Integrates more interfaces and lines in a limited space, supports multi-layer wiring, the line width/line spacing reaches refined standards, and balances the layout rationality of power modules and signal modules to reduce the impact of parasitic parameters.

• Low-cost and mass production: Uses cost-effective domestic materials and mature processes to reduce the difficulty of mass production, and ensures consistency during mass production to meet the cost control needs of large-scale base station deployment.

The above requirements jointly determine the design direction and process standards of the base station communication backplane PCB board, which is the core premise for the implementation of the solution.

Core Design of Base Station Communication Backplane PCB Board Solution

Combined with the needs of different base station units, differentiated domestic high-frequency and high-speed substrates are selected, and the specific selection is shown in the following table:

Adapted Base Station Unit	Substrate Type	Core Parameters	Selection Advantages
CU (Central Unit)	High-speed Copper Clad Laminate	Dielectric Constant Dk 3.6–4.0, Dielectric Loss Df≤0.003, Heat Resistance Tg≥240℃	Suitable for high-speed digital processing, with prominent cost performance of domestic materials
DU (Distributed Unit)	Medium and High-frequency Copper Clad Laminate	Dielectric Constant Dk 3.9–4.5, Dielectric Loss Df≤0.0025, Heat Resistance Tg≥250℃	Balances high-frequency and high-speed digital signal transmission without mutual interference, mature and stable
AU (Antenna Unit)	High-frequency Copper Clad Laminate	Dielectric Constant Dk 3.8–4.2, Dielectric Loss Df≤0.002, Heat Resistance Tg≥260℃	Suitable for low-loss transmission of U6G high-frequency signals, mature domestic substitution

The substrates are all selected from domestic leading enterprises such as Shengyi Technology and Huazheng New Materials, realizing the localization of core materials, reducing supply chain risks, and their performance reaching the level of international similar products, with the cost about 30% lower than that of imported substrates.

Details of Layer and Wiring Design

A multi-layer wiring structure is adopted, and differentiated design is adapted to different base stations, focusing on signal stability. The specific details are as follows:

• Layer design: 16-32 layers for macro base stations, 8-16 layers for micro base stations, and 10-20 layers for AU unit-related backplanes, which are respectively adapted to different transmission needs.

• Wiring specifications: High-speed signal lines adopt differential wiring design, impedance is controlled at 50Ω (single-ended) and 100Ω (differential), impedance tolerance ≤ ±7% to reduce signal reflection; high-frequency signal lines and power lines are laid separately with a spacing of not less than 2mm to avoid electromagnetic coupling interference; laser etching technology is used to process lines, and the minimum line width/line spacing can reach 0.06mm/0.06mm to improve wiring density.

• Hole design: HDI three-order blind and buried hole technology is adopted, the laser drilling aperture is as low as 50μm, reducing signal stubs, the residual length is controlled within 50μm, and high-frequency signal reflection is avoided; key signal holes are silver-plated to reduce contact resistance and improve signal transmission efficiency.

The scientific layer and wiring design effectively avoids problems such as signal crosstalk and reflection, and ensures the stable transmission of high-speed and high-frequency signals.

Key Points of Heat Dissipation and Protection Design

In view of the environmental characteristics of outdoor base station deployment and the heat generation during operation, the key points of heat dissipation and protection design are as follows:

• Heat dissipation design: A composite heat dissipation structure of “copper base + heat pipe embedding” is adopted, the copper foil thickness is 2oz, and 4oz thick copper is used in key areas, the thermal conductivity is increased to more than 5W/(m·K); a heat dissipation via array is set in the area corresponding to the power module to quickly conduct heat to the heat sink, ensuring that the chip junction temperature is controlled below 85℃; the surface is treated with a heat dissipation coating to enhance the heat dissipation effect.

• Protection design: The surface is treated with Electroless Nickel Immersion Gold (ENIG), the gold immersion thickness ≥ 0.8μm, improving oxidation resistance and corrosion resistance; the outdoor base station backplane is additionally coated with conformal coating to resist salt spray and humid environments, no corrosion after 48-hour neutral salt spray test; the edge is designed with rounded corners to avoid mechanical damage and enhance vibration resistance.

The complete heat dissipation and protection measures greatly improve the environmental adaptability of the PCB board and extend the service life of the base station equipment.

Requirements for Core Production Processes

Strict control is exercised over each process in the production link, and the specific requirements for the core production processes are as follows:

• Inner layer production: LDI laser imaging technology is adopted with a positioning accuracy of ±2μm to ensure the accuracy of the line pattern; acid etching process is used in the etching process to control the etching speed and temperature, ensuring that the line edges are smooth without burrs, disconnections and other defects.

• Lamination process: High-temperature and high-pressure lamination technology is adopted, the lamination temperature is controlled at 200-220℃, and the pressure is 30-40MPa to ensure tight interlayer bonding without delamination, bubbles and other problems; interlayer insulation test is carried out after lamination to ensure that the insulation performance meets the standard.

• Drilling and copper plating: CNC drilling machine is used to accurately control the hole position and aperture, and deburring treatment is carried out after drilling; chemical copper plating + electrolytic copper plating process is used for hole wall copper plating to ensure uniform copper layer with a thickness of 15-20μm, improving the conductivity and reliability of the hole position.

• Solder mask and silk screen: High-temperature resistant and corrosion-resistant epoxy resin material is selected for the solder mask, and the silk screen process ensures clear patterns without missing printing; the thickness of the solder mask layer is controlled at 10-15μm, which not only plays an insulating and protective role, but also does not affect the heat dissipation effect.

The standardized core production processes provide a solid guarantee for the performance consistency and reliability of the PCB board.

Finished Product Testing Standards

Before leaving the factory, the finished products undergo multi-dimensional testing, and the specific standards are shown in the following table:

Testing Item	Testing Standard	Testing Method
Signal Integrity Test	Signal Delay ≤ 10ns, Crosstalk ≤ -30dB, Impedance Tolerance ±7%	Tested by TDR Time Domain Reflectometer and Network Analyzer
Environmental Adaptability Test	Wide Temperature -40℃~85℃, No Failure After 500 Temperature Cycles; No Corrosion After 48-hour Salt Spray Test	Tested by High and Low Temperature Test Chamber and Salt Spray Test Chamber
Electrical Performance Test	Insulation Resistance ≥ 10^12Ω, Withstand Voltage ≥ 2000V, No Short Circuit or Open Circuit	Tested by Insulation Resistance Tester and Withstand Voltage Tester
Mechanical Performance Test	Anti-vibration, Anti-impact, No Delamination or Disconnection	Tested by Vibration Test Bench and Impact Test Bench

Core Advantages of the Solution

Compared with traditional solutions, this solution has significant advantages in localization, performance, reliability and other aspects, which are specific as follows:

• Localization adaptation: The entire industrial chain is domestic, the cost is 25%-30% lower than that of imported solutions, reducing supply chain risks and adapting to large-scale deployment.

• High-performance adaptation: Matches the 5G/6G base station CU/DU/AU architecture, supports high-speed and high-frequency signal transmission, with strong anti-interference ability and high stability.

• High reliability: Full-process quality control and strict environmental design ensure long-term stable operation in harsh outdoor environments, with a service life of more than 15 years, reducing base station maintenance costs.

• High compatibility: Suitable for various types of base station equipment such as macro base stations and micro base stations, supports the docking of functional modules from different manufacturers, and can be customized.

The superposition of multiple core advantages enables this solution to efficiently adapt to various base station scenarios and meet the needs of communication network upgrading.

Application Scenarios of the Solution

This solution is suitable for 5G macro base stations, 5G micro base stations, 6G trial commercial base stations and distributed base stations. It can be used as the core backplane of the base station to carry the functions of CU unit computing power transmission, DU unit intermediate frequency processing, and AU unit radio frequency signal transmission. It is widely used in various base station deployment scenarios such as cities, rural areas, industrial parks and remote areas. At the same time, it can adapt to the expansion needs of emerging communication scenarios such as integrated communication and sensing, and space-air-ground integration, providing reliable hardware support for the upgrading of communication networks.