Direct Answer
Use Rogers RO4003C when a PCB needs lower RF loss and tighter Dk control than FR-4, but the design does not require the UL 94 V-0 flame rating offered by RO4350B.
Specification Snapshot
| Property | RO4003C value | Engineering note |
|---|---|---|
| Material family | Hydrocarbon ceramic laminate with woven glass | Thermoset RF laminate |
| Process Dk | 3.38 +/- 0.05 at 10 GHz | Lower than RO4350B |
| Design Dk | 3.55 | Use for initial circuit modeling, then confirm stackup |
| Dissipation factor | 0.0027 at 10 GHz | Lowest loss in the common RO4000 comparison with RO4350B |
| Thermal conductivity | 0.71 W/m-K | Similar class to RO4350B |
| CTE, X/Y/Z | 11 / 14 / 46 ppm/C | Z-axis CTE is higher than RO4350B |
| Water absorption | 0.04 percent | Low moisture uptake supports RF repeatability |
| Flame rating | Not UL 94 V-0 | Check regulatory and customer requirements early |
Why Engineers Choose RO4003C
RO4003C is a cost-sensitive RF laminate. The reason to choose it is not simply that it is a Rogers material. The reason is that the RF path needs lower dielectric loss and better Dk control than standard FR-4, while the product does not require the flame-rating profile of RO4350B.
It is commonly used when antennas, matching networks, filters, and microwave traces need repeatable phase and impedance behavior. If the board only has short RF traces with generous link margin, the cost may not be justified.
Manufacturing Notes
RO4003C can be processed with methods closer to epoxy/glass laminates than PTFE-based laminates. That reduces fabrication friction, but it does not make the board electrically forgiving. Controlled impedance still depends on trace geometry, pressed dielectric thickness, copper foil roughness, etch compensation, and coupon correlation.
Specify the exact laminate, copper foil, dielectric thickness target, and impedance requirement. If the design is hybrid, the fabricator should review lamination compatibility, resin flow, layer registration, and warpage before quoting production.
Worked Example
A compact wireless sensor board includes a 5 GHz RF front end and short antenna feed. Standard FR-4 passes functional testing at room temperature but shows tuning drift across temperature and lot variation. RO4003C can reduce dielectric uncertainty and loss for the RF layer while keeping the rest of the board on conventional materials.
The key release decision is whether compliance requires UL 94 V-0. If it does, RO4350B may be the better RO4000-family choice even if RO4003C has lower Df.
Comparison
| Material | Best use | Main tradeoff |
|---|---|---|
| RO4003C | Cost-sensitive RF/microwave boards with low-loss needs | Not UL 94 V-0 rated |
| RO4350B | RF boards needing UL 94 V-0 and lower Z-axis CTE | Higher Dk and Df than RO4003C |
| FR4 Tg170 | Thermally robust multilayer digital and industrial boards | Higher RF loss and looser Dk behavior |
| MEGTRON 6 | High-speed digital channels and backplanes | Not usually selected for RF tuning |
Datasheet References
Summary
RO4003C is best treated as a targeted RF material, not a premium default. Use it when simulation or test data shows FR-4 is the limiting factor, and document the material, stackup, copper, impedance targets, coupon plan, and substitution rule before fabrication.