LAMINATES: DK, DF AND TRACE WIDTH
What are the Dk and Df of Rogers RO4450F?
Rogers RO4450F has a dielectric constant (Dk) of 3.52 and a loss factor (Df) of 0.004 at 10 GHz, as published by its maker. A 50 ohm surface microstrip over a 0.2 mm dielectric comes out about 0.418 mm wide on it, against 0.353 mm on standard FR-4.
- The nearest grade in the catalogue by Dk is AGC/Taconic RF-35, at Dk 3.5 and Df 0.0019 at 10 GHz.
- Dielectric loss on that microstrip is about 0.132 dB per inch at 10 GHz, and the signal travels at about 138 ps per inch.
- Buried as a stripline between planes 0.4 mm apart, 50 ohms needs a trace about 0.161 mm wide.
50 ohm surface microstrip, 1 oz copper
| Dielectric height | Trace width on Rogers RO4450F | On standard FR-4 |
|---|---|---|
| 0.1 mm | 0.198 mm | 0.166 mm |
| 0.2 mm | 0.418 mm | 0.353 mm |
| 0.5 mm | 1.09 mm | 0.920 mm |
| 1.6 mm | 3.55 mm | 3.02 mm |
As published
| Property | Value |
|---|---|
| Prepreg Grade | RO4450F |
| Chemistry | Hydrocarbon/Ceramic |
| Dk @ 10 GHz | 3.52 |
| Df @ 10 GHz | 0.0040 |
| Tg (°C) | >280 (post-cure) |
| Td (°C) | 390 |
| Target Data Rate | RF/MW, 10–25 Gbps |
Nearest grades in the catalogue by Dk at 10 GHz
| Laminate | Dk | Df | Tg |
|---|---|---|---|
| AGC/Taconic RF-35 | 3.5 | 0.0019 | not published |
| Rogers RO4350B | 3.48 | 0.0037 | not published |
| Rogers RO4835 | 3.48 | 0.0037 | not published |
How this was counted
Dk and Df are the maker's published values at 10 GHz, from the MPBxChange material catalogue, which keeps each source's test frequency and method. Where a maker publishes a range, the midpoint is used. Widths are solved with the Hammerstad and Jensen microstrip equations and Wadell's stripline form, for 1 oz copper, and are a starting point: Dk moves with frequency, resin content and glass style, and a fabricator's field solver is the authority. Standard FR-4 here is the median of 22 FR-4 grades in the catalogue (Dk 4.4).