FR4誘電率チャート
Use this reference chart to estimate how standard FR4 dielectric constant and dissipation factor shift with frequency before final impedance and material decisions.
誘電率 (Dk) と 誘電正接 (Df) は周波数により変化します。このチャートを参考にしてください。
| 周波数 | 誘電率 (Dk) | 誘電正接 (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.
Dkの重要性
Dfの重要性
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.
FAQ
5GにFR4は使える？
いいえ、損失が大きすぎます。
温度の影響は？
はい、温度とともにDkは上昇します。