FR-4
ASTM D709
FR-4 is a thermoset laminate of woven E-glass cloth in brominated or halogen-free epoxy, the standard copper-clad PCB substrate and insulating structural material under ASTM D709 and the NEMA grade family.
Values for the Epoxy Matrix condition
FR-4 grades and fills
FR-4 is supplied in 19 conditions, soft to hard. Epoxy Matrix is the default FabDigit quotes; the values on this page are for it.
- NEMA-C
- NEMA-CE
- GPO-3
- GPO-1
- NEMA-L
- NEMA-LE
- NEMA-XXX
- NEMA-XX
- NEMA-X
- NEMA-G7
- NEMA-G3
- NEMA-G5
- NEMA-G9
- High-CTI
- Epoxy Matrix
- Halogen-Free
- High-Tg
- NEMA-FR5
- NEMA-G11
Compare all 19 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
NEMA Grade C | Coarse-weave cotton fabric / phenolic laminate — mechanical grade with high impact strength and good machinability; poor electricals. | 70 | 105 HRM | ||
NEMA Grade CE | Coarse cotton fabric / phenolic laminate with improved moisture and electrical performance over Grade C. | 70 | 105 HRM | ||
NEMA GPO-3 | Flame-retardant glass-mat polyester sheet with high arc and tracking resistance (CTI ≥ 600 V); standard switchgear insulation board. | 75 | 100 HRM | ||
NEMA GPO-1 | Glass-mat reinforced polyester sheet, general-purpose mechanical/electrical grade, non flame-retardant (UL 94 HB). | 80 | 100 HRM | ||
NEMA Grade L | Fine-weave linen/cotton fabric phenolic laminate — smoother finish and finer machined detail than Grade C, mechanical grade. | 85 | 108 HRM | ||
NEMA Grade LE | Fine-weave fabric phenolic laminate of electrical quality — best machining/finish of the cotton grades with usable dielectric strength. | 85 | 110 HRM | ||
NEMA Grade XXX (PBE) | Paper/phenolic electrical-grade laminate with minimum cold flow and low loss under humidity — classic radio/terminal-board material. | 100 | 105 HRM | ||
NEMA Grade XX | Paper/phenolic laminate of mechanical-and-electrical quality — better moisture resistance and dielectric behaviour than Grade X. | 110 | 105 HRM | ||
NEMA Grade X | Paper-reinforced phenolic laminate, mechanical grade — highest strength of the paper grades, electrical properties not guaranteed. | 125 | 105 HRM | ||
NEMA G-7 (GSG) | Silicone-resin / woven glass laminate — Class H thermal endurance (~220 °C), excellent arc resistance and low dielectric loss, modest strength. | 145 | 100 HRM | ||
NEMA G-3 (GPG) | Phenolic-resin / woven glass laminate — tough and impact resistant with fair electricals; largely superseded by G-10/FR-4. | 170 | 100 HRM | ||
NEMA G-5 (GMG) | Melamine-resin / woven glass laminate — very hard, high arc- and track-resistance, self-extinguishing; used for arc barriers and switchgear. | 205 | 120 HRM | ||
NEMA G-9 (GME) | Electrical-grade melamine / woven glass laminate — G-5 mechanicals with better dielectric performance under humidity and high arc resistance. | 215 | 120 HRM | ||
tracking-resistant grade (CTI ≥ 600 V) | Specify for high-voltage / EV / solar boards where creepage distances are set by IEC 60664 material group I. | 300 | 1.7 | 110 HRM | |
Epoxy MatrixDefault standard difunctional FR-4 (Tg 130–140 °C) | Default choice for general PCB substrates, insulating plates, spacers and fixtures below ~130 °C. | 310 | 1.8 | 110 HRM | |
phosphorus/nitrogen flame retarded | Use when RoHS-plus / halogen-free (Br, Cl < 900 ppm) declarations are required by the customer or end market. | 310 | 1.7 | 110 HRM | |
High-Tg FR-4 | Pick for lead-free reflow, multilayer/HDI boards or parts running above 130 °C where Z-axis expansion and via reliability matter. | 320 | 1.7 | 112 HRM | |
NEMA FR-5 (GEB-F) | Heat-resistant multifunctional epoxy / woven E-glass laminate, flame-retardant (UL 94 V-0), retains strength to ~155 °C. | 320 | 112 HRM | ||
NEMA G-11 (GEB) | High-temperature epoxy / woven E-glass laminate (non flame-retardant, UL 94 HB) retaining ≥50 % of flexural strength at 150 °C. | 340 | 112 HRM |
Supply forms, finishes and certifications
Ways FR-4 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
CCL | Copper-clad FR-4 | Coating |
G10 | Same glass/epoxy laminate without flame retardant | Certification |
What is FR-4?
FR-4 is a thermoset laminate of woven E-glass cloth in brominated or halogen-free epoxy, the standard copper-clad PCB substrate and insulating structural material under ASTM D709 and the NEMA grade family. It is specified for stiffness (22 GPa modulus, 310 MPa tensile, 1.8% elongation, 1.85 g/cm³ density), high dielectric strength, UL94 V-0 flammability rating, low water absorption and dimensional stability at low cost, supplied as pressed sheet, rod, tube and clad laminate. Standard Tg is 130–140 °C (135 °C typical) with about 130 °C continuous service, Z-axis CTE is high, and the glass abrades tooling and generates hazardous dust; the cured resin cannot be remelted or recycled. Use high-Tg FR-4 or NEMA G11/FR-5 for hotter service, G10 where flame retardancy is not required. FR-4 has a density of 1.85 g/cm³ (0.0668 lb/in³), heavier than 67% of composite grades. Its glass-transition temperature is 135°C (275 °F). FR-4 has a tensile strength of 310 MPa (45 ksi), stronger than 56% of composite grades. Elongation at break is 1.8% and the elastic modulus is 22 GPa (3.19 Msi).
What is FR-4 used for?
- Printed circuit board substrate
- Electrical insulators, standoffs and barriers
- Terminal boards and switchgear panels
- Transformer and busbar spacers
- Motor and battery pack insulation plates
- Test fixture and bed-of-nails plates
- Knife handles and scales
Advantages
- Low moisture uptake — 0.12%, better than 78% of composite grades
FR-4 properties
Typical room-temperature values for FR-4-Epoxy Matrix; bars are the position among composite grades.
Physical4
FR-4 has a density of 1.85 g/cm³ (0.0668 lb/in³), heavier than 67% of composite grades. Its glass-transition temperature is 135°C (275 °F).
Mechanical12
FR-4 has a tensile strength of 310 MPa (45 ksi), stronger than 56% of composite grades. Elongation at break is 1.8% and the elastic modulus is 22 GPa (3.19 Msi).
Thermal8
FR-4 is rated for continuous service to 130°C (266 °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 16 µm/m·K (8.89 µin/in·°F).
Electrical7
FR-4 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 excellent (85/100), better than 65% of composite grades. UV resistance is fair.
Sustainability4
Producing a kilogram of FR-4 takes about 95 MJ of energy and emits 6 kg of CO₂ — less than 72% of composite grades. Typical recycled content is 0%.
Manufacturability2
FR-4'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-4 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with FR-4
Is FR-4 easy to machine?
Machine dry with carbide or diamond-coated tools at high speed/low feed; glass is highly abrasive, so expect rapid tool wear, and capture the dust (respirable glass/epoxy) with local extraction.
Can FR-4 be welded?
Not weldable — a thermoset; join by adhesive bonding (epoxy), riveting or threaded inserts.
Can FR-4 be formed, bent or molded?
Supplied only as pressed flat sheet/rod/tube; no post-forming — parts are machined, routed, drilled or laser/water-jet cut, and layer count is set during lamination.
Manufacturability
The process limits FabDigit's quote engine applies to FR-4. Design inside these and the part quotes instantly; outside them it routes to an engineer.
CNC machining
| Machinability | Poor45 / 100 |
|---|---|
| Cutting speed (rough / finish) | — / — |
| Minimum wall | — |
| Minimum internal radius | — |
| Drill depth limit | |
| Best surface (machined / polished) | Ra — / — |
| Hardenable after machining | — |
Sheet metal
| Formability | Not Recommend1 / 100 |
|---|---|
| Weldability | Not Recommend1 / 100 |
FR-4 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 fabric (7628/2116/1080 styreinforcement, wt % | 50 – 65 | 58 |
| brominated flame retardant (TBBPA-derivewt % of the resin phase; absent in halogen-free grades | 12 – 20 | 17 |
| inorganic filler (silica / ATH)grade dependent | 0 – 10 | 3 |
| epoxy resin (DGEBA / multifunctional, cumatrix incl. hardener (dicy or phenolic) | ≥ 30 (balance) |
What surface finishes work on FR-4?
Deburr edges to avoid delamination and glass splinters; can be silkscreened, epoxy-painted, copper-etched and plated (through-hole Cu/Ni/Au), but never anodized or polished to a mirror finish.
Surface treatments FabDigit runs on composite parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Equivalent designations
Standards and trade names that resolve to FR-4 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- D709
- Also called
- NEMA FR-4
How much does FR-4 cost?
FR-4 is a standard-cost composite ($$), cheaper than about 60% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
FR-4 — frequently asked
What is FR-4 used for?
FR-4 is typically used for printed circuit board substrate, electrical insulators, standoffs and barriers, terminal boards and switchgear panels, transformer and busbar spacers, motor and battery pack insulation plates and test fixture and bed-of-nails plates. In short: bullet-proof glass alternative.
What is the tensile strength of FR-4?
FR-4 has a typical tensile strength of 310 MPa (45 ksi) — stronger than 56% of composite grades. Strength varies by condition: see the 19 listed tempers.
Is FR-4 easy to machine?
Reasonably — machinability is rated fair (45/100, better than 63% of composite grades). Machine dry with carbide or diamond-coated tools at high speed/low feed; glass is highly abrasive, so expect rapid tool wear, and capture the dust (respirable glass/epoxy) with local extraction.
Can FR-4 be welded?
Not weldable — a thermoset; join by adhesive bonding (epoxy), riveting or threaded inserts.
What surface finishes work on FR-4?
Deburr edges to avoid delamination and glass splinters; can be silkscreened, epoxy-painted, copper-etched and plated (through-hole Cu/Ni/Au), but never anodized or polished to a mirror finish.
Can FR-4 be formed, bent or molded?
Supplied only as pressed flat sheet/rod/tube; no post-forming — parts are machined, routed, drilled or laser/water-jet cut, and layer count is set during lamination.
What is the maximum service temperature of FR-4?
FR-4 is rated for continuous use to about 130°C (266 °F), and briefly to 180°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does FR-4 cost?
FR-4 is a standard-cost composite ($$), cheaper than about 60% 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.
Can FabDigit make parts in FR-4?
Yes — FR-4 is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- IPC-4101 Specification for Base Materials for Rigid and Multilayer Printed Boards — IPC (2021)
- NEMA LI-1 Industrial Laminating Thermosetting Products — NEMA (1998)
- Isola / Shengyi / ITEQ FR-4 laminate datasheets (S1141, S1000-2, IT-180A) — Isola, , ITEQ (2023)
- Garolite FR-4 / G-10 sheet property tables — McMaster-Carr / Röchling (2024)
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.