FR-4 vs Phenolic XX
Composite · grade comparison
FR-4 and Phenolic XX are both composite grades, both electrical insulation composite. FR-4 is the stronger of the two: tensile strength 310 MPa (45 ksi) against 90 MPa (13.1 ksi) for Phenolic XX, about 3.4 times as much. FR-4 is the more ductile: elongation 1.8% versus 1.5% for Phenolic XX. Phenolic XX is lighter (1.34 g/cm³ vs 1.85 g/cm³ for FR-4) and FR-4 is stiffer (22 GPa vs 7 GPa). On the shop floor, Phenolic XX machines more easily (very good vs fair) and FR-4 sits in a lower cost tier (standard, $$) than Phenolic XX (premium, $$$).
FR-4Choose it when strength drives the design, or when the part is bent, formed or impact-loaded.
Phenolic XXChoose it when weight is the constraint, or when the part is machined in volume.
FR-4 vs Phenolic XX: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all composite grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
How to read these bars
- One bar per material. A full bar is the highest value among all composite grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Shear Modulus
Poisson's Ratio
Tensile Strength (Ultimate)
Elongation at Break
Compressive Strength
Compressive Modulus
Flexural Strength
Flexural Modulus
Shear Strength
Izod Impact, Notched
Hardness, Rockwell M
Hardness, Shore D
Hardness, Rockwell R
Physical
Density and transition temperatures.
Density
Glass Transition (Tg)
Water Absorption (24 h)
Water Absorption (Saturation)
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Specific Heat Capacity
Thermal Expansion (CTE, 20–100 °C)
Max Service Temperature (continuous)
Limiting Oxygen Index
Max Service Temperature (short-term)
Heat Deflection Temp. @ 0.45 MPa
Heat Deflection Temp. @ 1.8 MPa
Same in both: Min Service Temperature -50°C-58 °F
Electrical
Conductivity and insulation.
Electrical Resistivity
Dielectric Strength
Dielectric Constant (1 MHz)
Dissipation Factor (1 MHz)
Volume Resistivity
Surface Resistivity
Comparative Tracking Index (CTI)
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
UV / Weathering Resistance
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Polishability
Weldability
Formability (cold)
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Carbon (primary production)
Embodied Water
Typical Recycled Content
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
Same in both: Thermal Diffusivity 0.1 mm²/s · Thermal Shock Resistance Index 0
Strength versus weight
Yield strength against density for every composite grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
Manufacturing and finishing
| Capability | FR-4 | Phenolic XX |
|---|---|---|
| Default condition | Epoxy Matrix | Phenolic Matrix |
| Relative cost | $$ Standard | $$$ Premium |
| Min. machined wall | — | — |
| Best machined surface | — | — |
Both are offered for CNC machining and Sheet metal. Both take the same 1 finish: Painting.
FR-4 vs Phenolic XX — frequently asked
Is FR-4 stronger than Phenolic XX?
Yes. FR-4 has a typical tensile strength of 310 MPa (45 ksi) against 90 MPa (13.1 ksi) for Phenolic XX — about 3.4 times as much.
Which is cheaper, FR-4 or Phenolic XX?
FR-4 is the lower-cost material: it sits in the standard tier ($$) while Phenolic XX is premium ($$$). Part price depends far more on geometry, tolerance and quantity than on raw stock — upload a CAD file for a live quote.
Which is easier to machine, FR-4 or Phenolic XX?
Phenolic XX. Its machinability rates very good (80/100) against fair (45/100) for FR-4.
Ready to make it?
Upload a CAD file and FabDigit prices the part in FR-4 and Phenolic XX side by side — material, machining time, tolerance and finish in one quote. Certified material data ships with the order on request.
Typical handbook values for the conditions named above, normalised for comparison. Hardness on non-Brinell scales is converted approximately for charting only. Request certified data with your order for design-critical properties.