RO4003C is a glass-reinforced thermoset laminate for microwave interconnects, filters and matching networks where low dielectric loss and familiar PCB processing matter together. Its process Dk and Design Dk answer different questions: the former describes the acceptance test, while the latter is the more relevant starting point for a compatible transmission-line model.
Material system
Ceramic-filled hydrocarbon thermoset reinforced with woven glass
Technical properties
| Property | Reported value | Conditions / source |
|---|---|---|
| Process dielectric constant | 3.38 ± 0.05 | Typical, 10 GHz, 23°C; IPC-TM-650 2.5.5.5 clamped stripline; thickness direction. Source |
| Design dielectric constant | 3.55 | Typical, 8–40 GHz; differential phase length method. Average across the common constructions in the cited datasheet. Source |
| Dissipation factor | 0.0027 | Typical, 10 GHz, 23°C; IPC-TM-650 2.5.5.5; thickness direction. Source |
| Thermal conductivity | 0.71 W/(m·K) | Typical; ASTM C518, 80°C; through-thickness thermal conduction. Source |
| CTE, X axis | 11 ppm/°C | Typical; -55°C to 288°C, IPC-TM-650 2.4.41; average expansion over the interval, not necessarily linear. Source |
| CTE, Y axis | 14 ppm/°C | Typical; -55°C to 288°C, IPC-TM-650 2.4.41; average expansion over the interval, not necessarily linear. Source |
| CTE, Z axis | 46 ppm/°C | Typical; -55°C to 288°C, IPC-TM-650 2.4.41; average expansion over the interval, not necessarily linear. Source |
| Thermal coefficient of dielectric constant | 40 ppm/°C | Typical; -50°C to 150°C, IPC-TM-650 2.5.5.5 (modified temperature measurement); 10 GHz. Source |
| Water absorption | 0.06 % | Typical; 48 h at 50°C, 60 mil specimen, ASTM D570. Source |
| Density | 1.79 g/cm³ | Typical; 23°C, ASTM D792. Source |
Typical reported values are not a purchase specification. Process Dk, design Dk and values measured at different frequencies are not interchangeable.
Selection and design notes
- Consider it for an RF layer in a hybrid board when the fabricator already controls RO4000 processing and a flame-retardant grade is not mandatory.
- For a filter redesign, recalculate resonator lengths with the selected copper and actual core thickness; retaining an FR4 layout because the boards look similar can move the passband.
- Retain measured coupon results for future procurement comparisons.
Thickness and copper options
Datasheet standard dielectric thicknesses: 8, 12, 16, 20, 32 and 60 mil; tolerances depend on thickness. These are core dimensions before finished-board plating.
Standard ED copper includes 18 and 35 µm. LoPro is a separate construction; consult the RO4000 LoPro and CU4000 documents before changing foil.
Fabrication considerations
- Specify the glass construction, core thickness tolerance and foil designation in the fabrication drawing. Standard glass-epoxy style processing is an advantage, but the manufacturer must still qualify drilling, desmear, registration and the chosen bonding system for the complete stackup.
Application fit
- RF matching networks
- Microwave filters
- Hybrid RF boards
Limits and substitution checks
- RO4003C is not the flame-retardant counterpart of RO4350B. The datasheet also warns that prolonged hot oxidative exposure can change hydrocarbon dielectric properties, so a room-temperature loss comparison does not settle lifetime suitability.