LAMINATES: DK, DF AND TRACE WIDTH
What are the Dk and Df of Rogers RO4835?
Rogers RO4835 has a dielectric constant (Dk) of 3.48 and a loss factor (Df) of 0.0037 at 10 GHz, as published by its maker. A 50 ohm surface microstrip over a 0.2 mm dielectric comes out about 0.422 mm wide on it, against 0.353 mm on standard FR-4.
- Rogers RO4350B publishes the same Dk at 10 GHz; the two differ in Thermal Cond. (W/m·K): 0.66 against 0.69 for RO4350B.
- Dielectric loss on that microstrip is about 0.121 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 0.163 mm wide.
50 ohm surface microstrip, 1 oz copper
| Dielectric height | Trace width on RO4835 | On standard FR-4 |
|---|---|---|
| 0.1 mm | 0.200 mm | 0.166 mm |
| 0.2 mm | 0.422 mm | 0.353 mm |
| 0.5 mm | 1.10 mm | 0.920 mm |
| 1.6 mm | 3.58 mm | 3.02 mm |
As published
| Property | Value |
|---|---|
| Series | RO4000 |
| Dk @ 10GHz | 3.48 |
| Df @ 10GHz | 0.0037 |
| Thermal Cond. (W/m·K) | 0.66 |
| Key Application | Outdoor antennas, 5G infra |
Nearest grades in the catalogue by Dk at 10 GHz
| Laminate | Dk | Df | Tg |
|---|---|---|---|
| Rogers RO4350B | 3.48 | 0.0037 | not published |
| Shengyi S7136H | 3.48 | 0.003 | not published |
| AGC/Taconic RF-35 | 3.5 | 0.0019 | 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).