Six reasons F4B earns its place between FR-4 and premium PTFE laminates — electrical performance, thermal stability, mechanics, processing and cost.
The selection of F4B as a high-frequency PCB laminating material is primarily based on its low dielectric constant, low dielectric loss, excellent temperature stability, good mechanical properties, and chemical stability. These characteristics enable it to meet the stringent requirements of high-frequency signal transmission, ensuring signal integrity and circuit reliability. The following is a detailed analysis.
High-frequency signal transmission requirements: In high-frequency (above GHz) applications, signal transmission speeds are extremely fast, making the dielectric properties of materials highly sensitive. The dielectric constant (Dk) affects signal propagation speed, while the dielectric loss factor (Df) determines signal energy loss.
Advantages of F4B:
High-frequency application environment: High-frequency circuits (such as 5G communication and radar systems) typically operate in high-temperature or extreme temperature environments, requiring stable material performance.
Mechanical properties: F4B is based on polytetrafluoroethylene (PTFE) composite material, possessing excellent mechanical strength and impact resistance, capable of withstanding high-frequency vibration and mechanical stress. Its bending resistance and fatigue resistance are superior to ordinary FR-4, making it suitable for complex high-frequency PCB designs.
Chemical stability: F4B exhibits high resistance to acids, alkalis, and organic solvents, reducing the impact of environmental factors on circuit performance and extending service life.
Lamination process: F4B employs a high-temperature, high-pressure lamination process, ensuring tight interlayer bonding, reducing the risk of bubbles and delamination, and improving PCB flatness and dimensional stability. Its low resin flowability requires precise control of lamination temperature and pressure, but high-quality lamination can be achieved by optimizing process parameters (such as stepped pressure increase and extended holding time).
Drilling and surface treatment: Drilling of F4B requires laser or special mechanical drilling techniques to ensure hole wall smoothness and precision, reducing signal transmission loss. Surface treatment is preferably electroless nickel-gold (ENIG) or immersion silver to avoid introducing additional losses and improve soldering reliability — see our comparison of ENIG, immersion silver and immersion tin for the trade-offs.
Performance matching: F4B’s low loss, high stability, and environmental resistance perfectly meet the needs of these fields, making it one of the preferred materials for high-frequency PCB applications.
Performance and cost balance: Compared to top-tier high-frequency materials like PTFE (such as the Rogers RO4000 series), F4B has slightly lower performance (though Dk is slightly higher), but it is more cost-effective and has a more mature manufacturing process, making it suitable for scenarios with high performance requirements but limited budgets.
Compared to improved FR-4: F4B offers superior high-frequency performance, meeting more demanding application requirements.
Overall cost-effectiveness: F4B achieves a good balance between performance, cost, and manufacturability, making it a widely adopted intermediate solution in high-frequency PCB design.
Common questions about choosing F4B laminate.
F4B's Df can be as low as 0.0009–0.002 versus about 0.02 for FR-4, and its Dk varies little with frequency or temperature. That means far lower signal attenuation and more stable impedance above 1 GHz.
RO4000 series materials offer slightly better performance, but F4B is more cost-effective with a mature manufacturing process. For projects with tight budgets and solid high-frequency requirements, F4B is the balanced choice.
F4B's CTE is close to copper foil's, reducing interlayer stress, and its Dk/Df remain stable from about -55°C to +125°C (up to +200°C for some variants), preventing warping and delamination.
ENIG or immersion silver are preferred. Both avoid introducing the additional losses that some other finishes cause, improving soldering reliability on high-frequency traces.
Send us your stack-up and performance targets. We will confirm whether F4B fits your design — or recommend a better-matched laminate — and quote your high-frequency PCB.
Send Us Your Stack-Up → Fast Reply on WhatsApp