FR-5
ASTM D709 Grade FR-5
FR-5 is a flame-retardant woven-glass/epoxy laminate to ASTM D709 Grade FR-5, using a higher-temperature epoxy system that raises strength and heat resistance above FR-4 while keeping flame retardance.
Reference datasheet — FR-5 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
FR-5 grades and fills
FR-5 is supplied in one standard condition, HTG.
Supply forms, finishes and certifications
Ways FR-5 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
ROD | Rolled/moulded FR-5 epoxy-glass rod and tube | Supply form |
SHEETDefault | Standard FR-5 epoxy-glass laminate sheet/plate | Supply form |
CCL | Copper-clad FR-5 laminate | Coating |
What is FR-5?
FR-5 is a flame-retardant woven-glass/epoxy laminate to ASTM D709 Grade FR-5, using a higher-temperature epoxy system that raises strength and heat resistance above FR-4 while keeping flame retardance. Engineers specify it where G-11-class mechanical performance is required together with a flame rating: the default sheet is 340 MPa tensile, 1.85 g/cm³ density and 155 °C maximum service temperature, and it is stocked as sheet, high-Tg (HTG) grades, copper-clad laminate and rod. Being a thermoset it cannot be welded or post-formed, it is abrasive to machine, and it costs more than FR-4; where flame retardance is not needed, G-11 is the nearest alternative. FR-5 has a density of 1.85 g/cm³ (0.0668 lb/in³), heavier than 67% of composite grades. Its glass-transition temperature is 170°C (338 °F). FR-5 has a tensile strength of 340 MPa (49.3 ksi), stronger than 61% of composite grades. The elastic modulus is 22 GPa (3.19 Msi).
What is FR-5 used for?
- high-performance PCB substrates
- structural insulation under elevated temperature
- aerospace electrical components
Limitations
- Hard to polish — 25/100, worse than 76% of composite grades
FR-5 properties
Typical room-temperature values; bars are the position among composite grades.
Physical4
FR-5 has a density of 1.85 g/cm³ (0.0668 lb/in³), heavier than 67% of composite grades. Its glass-transition temperature is 170°C (338 °F).
Mechanical11
FR-5 has a tensile strength of 340 MPa (49.3 ksi), stronger than 61% of composite grades. The elastic modulus is 22 GPa (3.19 Msi).
Thermal8
FR-5 is rated for continuous service to 155°C (311 °F). It conducts heat at 0.3 W/m·K (0.173 BTU/hr·ft·°F), worse than 63% of composite grades. Thermal expansion is 14 µm/m·K (7.78 µin/in·°F).
Electrical7
FR-5 is an electrical insulator with a dielectric strength of 20 kV/mm (508 V/mil) and a resistivity of 1×10¹² Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (80/100), better than 54% of composite grades. UV resistance is fair.
Sustainability4
Producing a kilogram of FR-5 takes about 110 MJ of energy and emits 6.5 kg of CO₂ — less than 60% of composite grades. Typical recycled content is 0%.
Manufacturability2
FR-5's machinability is fair (45/100, better than 63% of composite grades).
Common Calculations4
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the composite family
Yield strength against density for every composite grade FabDigit runs. FR-5 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with FR-5
Is FR-5 easy to machine?
Machines like G-11/FR-4 but abrasive: use carbide or PCD tooling, high speed/low feed, vacuum dust extraction and support to avoid delamination and edge chipping.
Can FR-5 be welded?
Thermoset — cannot be welded; join by bonding with epoxy adhesives or mechanical fastening with washers to spread load.
Can FR-5 be formed, bent or molded?
Supplied as fully cured pressed sheet/rolled tube; no post-forming possible — cut, drill, rout or waterjet to shape.
FR-5 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 |
|---|---|---|
| E-glass woven fabric7628/2116 style cloth, silane finished | 50 – 65 | 58 |
| bromine (as flame retardant)wt % of resin fraction; gives UL 94 V-0 | 12 – 20 | 16 |
| inorganic filler / curing agentssilica or ATH in filled high-Tg versions | 0 – 8 | 3 |
| brominated epoxy resin (TBBPA-based)dicy or phenolic-novolac cured, high-Tg system | ≥ 30 (balance) |
What surface finishes work on FR-5?
Edges deburred/sealed with epoxy varnish for tracking resistance; paint or conformal coat for UV exposure; no plating except on copper-clad grades.
Equivalent designations
Standards and trade names that resolve to FR-5 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- D709 Grade FR-5
How much does FR-5 cost?
FR-5 is a premium-cost composite ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
FR-5 — frequently asked
What is FR-5 used for?
FR-5 is typically used for high-performance PCB substrates, structural insulation under elevated temperature and aerospace electrical components. In short: higher-temperature FR-4 upgrade; flame-retardant G-11 equivalent; 340 MPa epoxy-glass laminate.
What is the tensile strength of FR-5?
FR-5 has a typical tensile strength of 340 MPa (49.3 ksi) — stronger than 61% of composite grades.
Is FR-5 easy to machine?
Reasonably — machinability is rated fair (45/100, better than 63% of composite grades). Machines like G-11/FR-4 but abrasive: use carbide or PCD tooling, high speed/low feed, vacuum dust extraction and support to avoid delamination and edge chipping.
Can FR-5 be welded?
Thermoset — cannot be welded; join by bonding with epoxy adhesives or mechanical fastening with washers to spread load.
What surface finishes work on FR-5?
Edges deburred/sealed with epoxy varnish for tracking resistance; paint or conformal coat for UV exposure; no plating except on copper-clad grades.
Can FR-5 be formed, bent or molded?
Supplied as fully cured pressed sheet/rolled tube; no post-forming possible — cut, drill, rout or waterjet to shape.
What is the maximum service temperature of FR-5?
FR-5 is rated for continuous use to about 155°C (311 °F), and briefly to 200°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does FR-5 cost?
FR-5 is a premium-cost composite ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- ASTM D709 Standard Specification for Laminated Thermosetting Materials — ASTM International (2017)
- NEMA LI 1 Industrial Laminating Thermosetting Products — NEMA (1998)
- IPC-4101 Specification for Base Materials for Rigid and Multilayer Printed Boards — IPC (2021)
- Engineered Materials Handbook Vol.1: Composites — ASM International (1987)
- Epoxy glass laminate (G-10/FR-4/G-11/FR-5) property sheets — insulation laminate producers (2023)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.