RO4003C and RO4350B are related thermoset RF laminate candidates, but they are not identical design inputs. Start with flame-performance requirements, then compare the electrical construction and the cost of qualifying the chosen build.
Apply required constraints before preferences
The official RO4000 datasheet differentiates the flame-performance status of the grades. When a project requires a particular recognized construction, verify that exact grade, thickness and foil configuration rather than treating the family as one approval. LoPro constructions also deserve their own qualification check. Read the grade records for RO4003C and RO4350B with the datasheet footnotes attached.
Keep the dielectric inputs consistent
Process Dk supports material characterization and production control; design Dk serves a different circuit-model purpose. Comparing one grade’s process value with the other’s design value exaggerates or obscures the actual difference. Set the same dielectric thickness, copper and line topology before recalculating geometry. If the model is calibrated to a measured baseline, retain that baseline and document how the candidate’s dielectric input was chosen.
Example: changing a matching network
Suppose an existing RF amplifier board is being revised to meet a new material requirement. Replacing the laminate name on the drawing is insufficient: transmission-line widths, electrical lengths, coupled sections and the package launch need review. Use the microstrip tool for an initial width check, then update the circuit or electromagnetic model. Include a line coupon that lets the prototype separate stackup error from device matching behavior.
Compare practical costs on equal terms
Request the same panel quantity, stackup, foil and acceptance package for both candidates. Ask whether either construction requires additional procurement or process qualification at the selected fabricator; do not assume a universal price premium from the grade name. Check the bonding route if the board is multilayer. Select the candidate that meets mandatory constraints with adequate measured margin, and prevent silent substitutions by recording the complete material callout.
A useful approval note records why the selected grade won: a mandatory material requirement, adequate loss margin, a supported multilayer build, or another stated reason. It should also identify which property would trigger reconsideration if the circuit or operating environment changes later.
Source-aware property comparison
RO4003C
| 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.
RO4350B
| Property | Reported value | Conditions / source |
|---|---|---|
| Process dielectric constant | 3.48 ± 0.05 | Typical, 10 GHz, 23°C; IPC-TM-650 2.5.5.5 clamped stripline; thickness direction. Source |
| Design dielectric constant | 3.66 | Typical, 8–40 GHz; differential phase length method. Average across the common constructions in the cited datasheet. Source |
| Dissipation factor | 0.0037 | Typical, 10 GHz, 23°C; IPC-TM-650 2.5.5.5; thickness direction. Source |
| Thermal conductivity | 0.69 W/(m·K) | Typical; ASTM C518, 80°C; through-thickness thermal conduction. Source |
| CTE, X axis | 10 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 | 12 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 | 32 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 | 50 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 | 1.86 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.
Choose required flame status first, then revalidate geometry and the complete fabrication construction.