Differences in Frequency Range Between F4B and FR-4
F4B Frequency Range
F4B is a polytetrafluoroethylene (PTFE) composite material designed specifically for high-frequency applications, with a typical frequency range covering 1 GHz to 40 GHz and beyond. At 10 GHz, F4B’s dielectric loss factor (Df) is as low as 0.0013; at 20 GHz, it is 0.0019; and at 40 GHz, it maintains an extremely low loss of 0.0019. Furthermore, its dielectric constant (Dk) varies minimally with frequency (e.g., F4BM265 has a Dk of 2.65 ± 0.05 at 10 GHz). This stability makes it an ideal choice for ultra-high-frequency applications such as millimeter-wave communications (24 GHz, 28 GHz, 39 GHz), automotive radar (77 GHz), and satellite communications.
Frequency Range of FR-4
FR-4 is a traditional epoxy-glass fiber material that is low-cost but has limited high-frequency performance. Its dielectric constant (Dk) is approximately 4.3–4.7 at 1 GHz and decreases significantly as frequency increases (e.g., dropping to around 3.7 at 10 GHz), while its dielectric loss factor (Df) ranges from 0.015 to 0.035 at 1 GHz, with losses increasing sharply at higher frequencies. Therefore, FR-4 is only suitable for low-frequency applications below 1 GHz. Significant loss and phase issues begin to appear between 1 GHz and 3 GHz, performance drops sharply between 3 GHz and 8 GHz, and its use is not recommended above 8 GHz.
Performance Comparison and Selection Criteria
High-Frequency Loss: F4B has a dielectric loss tangent of 0.0023 dB/cm at 10 GHz, far lower than FR-4’s 0.095 dB/cm, and its conductor loss tangent is also lower (0.0357 dB/cm for F4B vs. 0.0499 dB/cm for FR-4), significantly reducing signal attenuation.
Stability: The Dk and Df values of F4B vary very little with frequency, ensuring impedance consistency and signal integrity; in contrast, FR-4 exhibits significant fluctuations in Dk (over ±10%), which can easily lead to impedance mismatch and signal distortion.
Application Scenarios: F4B is suitable for high-frequency applications such as 5G communications, radar, and satellites; FR-4 is only suitable for low-frequency fields such as consumer electronics and industrial control.
