FR4 介电常数表
Use this reference chart to estimate how standard FR4 dielectric constant and dissipation factor shift with frequency before final impedance and material decisions.
在使用 FR4 设计高速或射频 PCB 时，必须了解 介电常数 (Dk, εr) 和 耗散因数 (Df, 损耗角正切) 不是静态值。它们随频率变化，通常随着频率升高，Dk 降低而 Df 升高。请参考此图表作为标准 FR4 材料 (Tg 130-140°C) 的一般参考。
| 频率 | 介电常数 (Dk) | 耗散因数 (Df) |
|---|---|---|
| 1 MHz | 4.7 | 0.015 |
| 10 MHz | 4.6 | 0.018 |
| 100 MHz | 4.5 | 0.020 |
| 1 GHz | 4.35 | 0.022 |
| 2.5 GHz | 4.30 | 0.023 |
| 5 GHz | 4.25 | 0.025 |
| 10 GHz | 4.20 | 0.028 |
| 20 GHz | 4.15 | 0.030 |
These values are directional engineering reference data for standard FR4 only. Actual dielectric behavior depends on laminate family, resin system, glass style, copper profile, processing, and test method. Final controlled-impedance work should use exact material data from your PCB manufacturer.
When to use this tool
Check whether your assumed dielectric constant is directionally reasonable before estimating controlled impedance and trace geometry.
Use it to understand where standard FR4 starts to become a weak fit for loss-sensitive or higher-frequency routing.
Bring this into stackup discussions when you need to compare standard FR4 assumptions with real laminate data and fabrication capability.
Practical notes
• Standard FR4 can work for many digital and general-purpose boards, but it is not automatically the right material for every impedance-critical design.
• Dk shifts affect propagation speed and impedance; Df shifts affect insertion loss and signal attenuation.
• At higher frequencies, simplified assumptions become less reliable and material selection becomes more important.
为什么 Dk 很重要？
为什么 Df 很重要？
Related resources & next steps
Use dielectric assumptions from this reference to estimate single-ended impedance targets.
Cross-check geometry decisions when signal and current requirements need to coexist on the same board.
Move from generic FR4 assumptions to stackup, laminate, and fabrication-ready review.
Send your target impedance, frequency range, and material questions to engineering.
常见问题解答
FR4 适合 5G 天线设计吗？
通常不适合。对于 5G 毫米波频率，标准 FR4 的信号损耗 (Df) 太高，且 Dk 稳定性差。您应该考虑专门的高频层压板。然而，对于 6GHz 以下频段，取决于走线长度，高性能 FR4 可能仍然可以接受。
温度会影响 Dk 吗？
是的。Dk 通常随温度升高而增加。如果您的设备在极端热环境下工作，一致的阻抗需要具有稳定“介电常数热系数”(TcDk) 的材料。