FR-3 HF
Grade
ASTM D709 Grade FR-3
HF = halogen-free flame-retardant FR-3
Choose for RoHS-plus/halogen-free customer specifications (Br+Cl each < 900 ppm) at a small price premium.
Values for the HF condition
Other FR-3 grades and fills
FR-3 is listed in 3 conditions; see the grade overview at FR-3.
Compare all 3 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Cold-punch grade | Pick when boards up to ~1.6 mm must be punched on unheated tooling in high-volume consumer production. | — | 85 | 1.4 | 100 HRM |
HFThis page Halogen-free flame-retardant FR-3 | Choose for RoHS-plus/halogen-free customer specifications (Br+Cl each < 900 ppm) at a small price premium. | — | 90 | 1.2 | 103 HRM |
Hot-punch grade | Pick for thicker sheet or the crispest hole edges; requires preheated blanks/dies but gives higher rigidity and Tg. | — | 105 | 1.1 | 110 HRM |
What is FR-3 HF?
FR-3 HF is FR-3 in the HF grade — choose for RoHS-plus/halogen-free customer specifications (Br+Cl each < 900 ppm) at a small price premium. FR-3 HF has a tensile strength of 90 MPa (13.1 ksi), weaker than 72% of composite grades. Elongation at break is 1.2% and the elastic modulus is 8.8 GPa (1.28 Msi). FR-3 HF has a density of 1.45 g/cm³ (0.0524 lb/in³), lighter than 59% of composite grades. Its glass-transition temperature is 115°C (239 °F).
Advantages
- Easy to machine — 80/100, better than 85% of composite grades
Limitations
- Limited service temperature — 105°C (221 °F), worse than 90% of composite grades
- Hard to polish — 20/100, worse than 90% of composite grades
- Degrades in UV without stabilisers — 25/100, worse than 86% of composite grades
FR-3 HF properties
Typical room-temperature values for FR-3 HF; 17 are specific to this condition. Other listed values are FR-3 reference data and may not represent this condition. Bars are the position among composite grades.
Physical4
FR-3 HF has a density of 1.45 g/cm³ (0.0524 lb/in³), lighter than 59% of composite grades. Its glass-transition temperature is 115°C (239 °F).
Mechanical10
FR-3 HF has a tensile strength of 90 MPa (13.1 ksi), weaker than 72% of composite grades. Elongation at break is 1.2% and the elastic modulus is 8.8 GPa (1.28 Msi).
Thermal8
FR-3 HF is rated for continuous service to 105°C (221 °F). It conducts heat at 0.29 W/m·K (0.168 BTU/hr·ft·°F), worse than 70% of composite grades. Thermal expansion is 20 µm/m·K (11.1 µin/in·°F).
Electrical7
FR-3 HF is an electrical insulator with a dielectric strength of 18 kV/mm (457.2 V/mil) and a resistivity of 5×10¹⁰ Ω·m.
Chemical & Environmental3
Corrosion resistance is good (68/100), worse than 69% of composite grades. UV resistance is poor.
Sustainability2
Producing a kilogram of FR-3 HF takes about 90 MJ of energy and emits 5 kg of CO₂ — less than 75% of composite grades.
Manufacturability2
FR-3 HF's machinability is very good (80/100, better than 85% of composite grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with FR-3 HF
Is FR-3 easy to machine?
Drills, routs and shears easily but the cured epoxy/paper is mildly abrasive — use carbide tools, high speed and vacuum dust extraction; edges fuzz if feeds are too low.
Can FR-3 be welded?
Not weldable; join by bonding with epoxy adhesive or by mechanical fastening/riveting.
Can FR-3 be formed, bent or molded?
Supplied as a fully cured thermoset laminate — it cannot be reformed; blanking and holes are made by cold or hot punching (hot punch 60–100 °C for thicker sheet) or by routing.
What surface finishes work on FR-3?
Cut edges should be sealed or varnished to limit moisture wicking into the paper core; clad grades take standard etch, HASL/OSP and solder mask, though bath temperatures must be kept moderate.
FR-3 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| cellulose (kraft) paper reinforcementmultiple plies of resin-impregnated paper | 45 – 60 | 55 |
| brominated flame retardant (TBBPA-based)absent in halogen-free HF variant | 2 – 6 | 4 |
| inorganic fillers / curing agents | 0 – 5 | 2 |
| copper foil (clad grades only)18–70 µm electrodeposited foil, one or both faces | 0 – 15 | 0 |
| epoxy resin binderoften DGEBA cured with dicy/novolac; may be phenolic-modified | ≥ 35 (balance) | — |
FR-3 HF — frequently asked
What is FR-3 HF used for?
FR-3 HF is typically used for single/double-sided PCBs, punched electrical insulation parts and terminal strips. In short: punchable epoxy-paper substrate; stronger than FR-2; cheaper than glass-epoxy FR-4.
What is the tensile strength of FR-3 HF?
FR-3 HF has a typical tensile strength of 90 MPa (13.1 ksi) — weaker than 72% of composite grades. Strength varies by condition: see the 3 listed tempers.
Is FR-3 HF easy to machine?
Yes — machinability is rated very good (80/100, better than 85% of composite grades). Drills, routs and shears easily but the cured epoxy/paper is mildly abrasive — use carbide tools, high speed and vacuum dust extraction; edges fuzz if feeds are too low.
Can FR-3 HF be welded?
Not weldable; join by bonding with epoxy adhesive or by mechanical fastening/riveting.
What surface finishes work on FR-3 HF?
Cut edges should be sealed or varnished to limit moisture wicking into the paper core; clad grades take standard etch, HASL/OSP and solder mask, though bath temperatures must be kept moderate.
Can FR-3 HF be formed, bent or molded?
Supplied as a fully cured thermoset laminate — it cannot be reformed; blanking and holes are made by cold or hot punching (hot punch 60–100 °C for thicker sheet) or by routing.
What is the maximum service temperature of FR-3 HF?
FR-3 HF is rated for continuous use to about 105°C (221 °F), and briefly to 150°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ASTM D709 — Standard Specification for Laminated Thermosetting Materials — ASTM International (2017)
- NEMA LI 1 — Industrial Laminated Thermosetting Products — NEMA (1998)
- UL 94 / UL 796 flammability and PCB material requirements — UL Solutions (2023)
- IPC-TM-650 test methods for laminate electrical and physical properties — IPC (2022)
- Paper-based copper clad laminate (FR-1/FR-2/FR-3) datasheets — Kingboard / Shengyi (2023)
- Printed Circuits Handbook — base material properties — McGraw-Hill (2016)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.