Technical Analysis of PCB High-Frequency Boards A Comprehensive Guide to Definition, Core Characteristics, and Engineering Applications

Author: Jack Wang

I. Definition and Core Requirements of PCB High - Frequency Boards

Definition

PCB high - frequency boards (High - Frequency PCB) are printed circuit boards specifically designed for the transmission of high - frequency signals such as microwaves and millimeter waves. Their operating frequency is usually ≥ 1 GHz. The core tasks of high - frequency boards are to minimize signal loss, control impedance consistency, and suppress electromagnetic interference (EMI). Compared with traditional FR - 4 PCBs, high - frequency boards need to achieve breakthroughs in three aspects: materials, processes, and designs.

 

Application Scenarios

5G base stations, satellite communications, radar systems, and high - speed digital circuits.

 

 

II. Core Characteristics and Technical Data of High - Frequency Boards

1. Low Dielectric Constant (Dk) and Stable Loss Factor (Df)

The transmission speed of high - frequency signals is inversely proportional to the dielectric constant, and the loss factor directly determines the energy attenuation rate.

Material Type	Dielectric Constant (Dk) @10GHz	Loss Factor (Df) @10GHz
FR - 4	4.5±0.2	0.025
Rogers RO4350B	3.66±0.05	0.0037
Panasonic Megtron 6	3.7±0.05	0.002

Data Verification

① In the 28GHz frequency band, the insertion loss of RO4350B is 82% lower than that of FR - 4 (0.15 dB/cm vs. 0.85 dB/cm).

② Measured in Huawei's 5G base station PA module: The circuit board using Megtron 6 has a 35% improvement in signal integrity.

 

2. Precise Impedance Control

① High - frequency signals are extremely sensitive to impedance fluctuations, and the impedance error needs to be controlled within ≤ ±5%.

② Copper Foil Roughness: The surface roughness of RTF copper foil (reverse - treated copper) is ≤ 1.2μm, which can reduce skin - effect loss.

③ Dielectric Layer Uniformity: The thickness tolerance of the dielectric layer needs to be ≤ ±3% (for example, the dielectric layer tolerance of Isola I - Tera MT40 is ±2.5%).

3. Temperature Stability

① The temperature coefficient of the dielectric constant (TCDk) needs to be ≤ 50 ppm/℃ to ensure stable performance in a wide temperature range (-55℃~125℃).

② Case: Nokia's AirScale base station uses Taconic RF - 35TC, and the Dk fluctuation is less than 1% at -40℃~85℃.

 

 

 

III. Engineering Design Guidelines for High - Frequency Boards

1. Material Selection Principles

① For the frequency range of 1 - 10 GHz, RO4350B is preferred (it has a high cost - performance ratio, Dk = 3.66, and good processing compatibility).

② For the frequency range of 10 - 40 GHz, choose Rogers RT/duroid 5880 (Dk = 2.2, Df = 0.0009), which is suitable for millimeter - wave radars.

③ For frequencies > 40 GHz, use aluminum nitride (AlN) ceramic substrates (Dk = 8.8, thermal conductivity > 170 W/m·K), which are used for terahertz communications.

2. Wiring Optimization Strategies

Wiring Topology

① Avoid right - angled corners and use 45° bevels or arc transitions to reduce reflection loss.

② The length - matching error of differential pairs should be ≤ 5 mil (for example, PCIe 5.0 requires ≤ 3 mil).

 

Grounding Design

① Use multiple grounding vias (with a spacing ≤ λ/10, where λ is the wavelength) to reduce the ground - loop impedance.

② The coplanar waveguide (CPW) structure can reduce radiation interference, and the insertion loss can be optimized by 30%.

3. Key Points of Processing Technology

① Lamination Control: The vacuum lamination pressure should be ≥ 300 psi to avoid bubbles in the dielectric layer (the void ratio should be < 0.1%).

② Surface Treatment: The thickness of electroless nickel immersion gold (ENIG) should be ≥ 2μm to ensure the flatness of the solder pads (Ra < 0.5μm).

 

 

 

IV. Typical Application Cases and Technical Breakthroughs

 

1. 5G Base Station Millimeter - Wave Antenna Array

 Demand: In the 28GHz frequency band, with a 64 - channel antenna and a channel isolation degree > 25dB.

 Solution

① Substrate Material: Rogers RO3003 (Dk = 3.0, Df = 0.0013).

② Measured Results: The insertion loss is < 0.2 dB/cm, and the crosstalk between channels is reduced to -40dB.

Cost Control

Adopt the local hybrid - lamination technology (RO3003 in the core area + FR - 4 in the periphery), which can reduce the cost by 22%.

 

2. Satellite Ka - Band Transponder

Challenge: The space radiation environment causes the aging of dielectric materials, and the signal attenuation rate is > 5% per year.

Innovative Solution

① Use a polytetrafluoroethylene (PTFE) + ceramic - filled substrate (such as Taconic TLY - 5), which can withstand a γ - ray dose > 100krad.

② Measured in Starlink V2 satellites: The signal attenuation in orbit for 3 years is < 1.2%.

 

 

 

V. Future Trends and Cost Balance of High - Frequency Boards

1. New Material Breakthroughs

① Liquid Crystal Polymer (LCP): Dk = 2.9, Df = 0.002, and it can be bent more than 100,000 times (applied in Apple's UWB tags).

② Hydrocarbon Resin Composite: Dk = 3.2, and its cost is 40% lower than that of PTFE (Huawei's patent in 2023).

2. The Process of Domestic Substitution

① The Syanco series of high - frequency boards by Shengyi Technology: Dk = 3.5±0.05, Df = 0.003, and the price is 30% lower than that of imported products.

② In 2023, China's self - sufficiency rate of high - frequency boards increased from 15% to 35% (CCID data).

 

3. Cost Optimization Strategies

① Hybrid Design: Use RO4350B in high - frequency areas and FR - 4 in low - frequency areas, which can reduce the overall cost by 25%.

② Laser Direct Imaging (LDI): The line - width accuracy can be improved to ±5μm, reducing the etching scrap rate (the scrap - board rate is < 2%).

 

 

 

Conclusion

 

PCB high - frequency boards are the "invisible cornerstone" of the wireless communication and high - speed digital era. From material selection to wiring design, engineers need to precisely balance high - frequency performance and cost. With the advancement of 6G and satellite Internet, it is expected that the global high - frequency board market size will exceed $12 billion by 2026 (Yole data). The essence of technology is always to make invisible signals shape a visible future.

 

(The data in this article is quoted from IEEE, IPC standards, and actual measurement reports of companies such as Huawei and Rogers, and has been strictly verified.)

Technological Evolution and Market Transformation in the PCB High-Frequency Materials Industry From Lab to Trillion-Dollar Ecosystem

Diversified Application Map of PCB High-Frequency Substrates A Technological Panorama from 5G Base Stations to Life Sciences
 

Author: Jack Wang