Choose a specific laminate and construction against a circuit budget. FR4 is a broad material category, while Rogers supplies several distinct material systems. Neither label, by itself, predicts the performance or cost of a finished board.
Replace the frequency rule with a budget
There is no universal frequency above which every circuit requires a Rogers laminate. A short interconnect and a long antenna feed can operate at the same frequency yet tolerate very different loss. Start with allowable insertion loss, phase error or impedance variation, then allocate part of that budget to the PCB. Include connectors, vias and assembly transitions so the laminate is not asked to solve an unrelated discontinuity.
Compare the actual baseline
For FR4, identify the manufacturer, grade, glass style, resin content and finished spacing. For a Rogers candidate, record the same construction detail plus the relevant design Dk and copper option. Compare Df only when frequency and method make the comparison meaningful. A generic simulation default called FR4 is not a measured material specification and should not become the reference for a purchasing decision.
Use two different example decisions
A short radio-module feed that already meets margin may gain little from a material change; connector launch and ground continuity could be the more useful improvements. A long distribution network with tight amplitude and phase balance deserves a more detailed low-loss-material investigation. These are engineering examples, not measured results. In either case, estimate the improvement over the actual route length using the dielectric-loss tool, while remembering that conductor and other losses remain.
Consider a selective hybrid construction
A hybrid stackup can place an RF material where it is needed and retain a suitable conventional material elsewhere. It also introduces bonding, registration and thermal-compatibility decisions. Request comparable quotations for an agreed build, including coupons and acceptance testing. Compare total development and verification effort as well as board price. The right answer may be to keep the baseline, redesign one layer or qualify a different complete stack.
For a redesign, state the improvement required before collecting quotes. An objective such as recovering a defined amount of channel margin makes the experiment actionable; simply asking for a higher-frequency board leaves both design scope and acceptance ambiguous.
Source-aware property comparison
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.
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.
Change materials when the measured or modeled circuit budget justifies it, and verify the exact construction you will buy.