Flame-Retardant Glass-Reinforced Epoxy Laminate (NEMA FR-4)
FR-4 glass epoxy provides flame resistance, high mechanical strength, and reliable electrical insulation for printed circuit boards, electrical components, and industrial equipment.
Select a form factor to view real-time inventory, pricing, and custom cut-to-size options.
| Short Description | Color | Thickness | Width | Length | Stock | Price | Add to quote |
|---|---|---|---|---|---|---|---|
| FR4 - 0.005" 36 x 48 Natural Sheet | Natural | 0.005″ | 36″ | 48″ | In stock467 | $20.98per sheet | |
| FR4 - 0.005" 48 x 48 Natural Sheet | Natural | 0.005″ | 48″ | 48″ | Out of stock | $26.55per sheet | |
| FR4 - 0.005" 48 x 96 Natural Sheet | Natural | 0.005″ | 48″ | 96″ | Out of stock | $55.86per sheet | |
| FR4 - 0.007" 36 x 48 Natural Sheet | Natural | 0.007″ | 36″ | 48″ | In stock13 | $12.77per sheet | |
| FR4 - 0.007" 48 x 48 Natural Sheet | Natural | 0.007″ | 48″ | 48″ | Out of stock | $16.49per sheet | |
| FR4 - 0.007" 48 x 96 Natural Sheet | Natural | 0.007″ | 48″ | 96″ | Out of stock | $34.05per sheet | |
| FR4 - 0.008" 36 x 48 Natural Sheet | Natural | 0.008″ | 36″ | 48″ | In stock289 | $14.23per sheet | |
| FR4 - 0.008" 48 x 48 Natural Sheet | Natural | 0.008″ | 48″ | 48″ | Out of stock | $18.38per sheet | |
| FR4 - 0.008" 48 x 96 Natural Sheet | Natural | 0.008″ | 48″ | 96″ | Out of stock | $37.89per sheet | |
| FR4 - 0.009" 36 x 48 Natural Sheet | Natural | 0.009″ | 36″ | 48″ | Out of stock | $29.68per sheet |
Material Overview
FR4 sheet is the flat-panel form of NEMA FR-4 flame-retardant glass-epoxy laminate — a thermoset composite of woven fiberglass cloth impregnated with brominated epoxy resin, laminated under heat and pressure into rigid flat stock. FR-4 is the most widely used glass-epoxy grade in electrical and electronic industries, balancing high mechanical strength, reliable dielectric insulation, low moisture absorption, and a certified UL 94 V-0 flame rating. It is the standard substrate material for printed circuit boards and a preferred insulating structural material across industrial OEM applications.
FR4 sheet provides a tensile strength of 65,000 psi, flexural strength of 60,000 psi, and compressive strength of 38,000 psi. Rockwell M115 hardness and a shear strength of 21,500 psi reflect the material's structural rigidity. Water absorption over 24 hours is just 0.10%. The UL 94 V-0 flammability rating and maximum continuous operating temperature of 280°F (140°C) make FR4 sheet suitable for UL-listed enclosures, switchgear panels, and fire-rated electrical equipment.
Standards & compliance. FR4 sheet conforms to NEMA LI-1 Grade FR-4 and is tested per ASTM D709. The UL 94 V-0 rating is the defining compliance attribute of FR-4 versus G-10. Ready Plastics stocks FR4 sheet in standard thicknesses; custom-cut pieces are available on request.
Sister grades. G-10 glass-epoxy sheet is mechanically comparable but carries a 94HB flame rating — appropriate when flame retardancy is not required. G-11 glass-epoxy sheet and its flame-retardant counterpart FR-5 are rated to 355°F (180°C), offering higher thermal performance for elevated-temperature service. For extreme heat up to 425°F (220°C), see G-7 glass-silicone sheet.
Frequently Asked Questions
FR4 sheet is a flat thermoset laminate of woven fiberglass cloth and flame-retardant epoxy resin, cured under heat and pressure per NEMA LI-1. It is rated UL 94 V-0, offers 65,000 psi tensile strength, and absorbs only 0.10% moisture over 24 hours. It is the standard material for PCB substrates and electrical insulation panels requiring certified flame resistance.
Ready Plastics stocks FR4 glass-epoxy sheet in a range of standard thicknesses. Contact us for current inventory and custom-cut availability.
FR4 sheet is machined using carbide or diamond-coated tooling on routers, mills, and drill presses. The woven fiberglass reinforcement is abrasive, so carbide is strongly preferred over HSS. Sharp tools, adequate feed rates, and chip clearance minimize delamination at cut edges. Dust extraction is essential when routing or drilling FR4.
FR-4 and G-10 are both NEMA glass-epoxy laminates with very similar mechanical and electrical properties. The critical difference is flame rating: FR-4 is certified UL 94 V-0 (self-extinguishing), while G-10 carries only a 94HB rating. For UL-listed equipment, PCB production, or any application with a fire-safety requirement, FR-4 is the correct choice.
FR4 sheet is used for printed circuit board substrates, electrical insulation panels, switchgear barriers, motor terminal boards, enclosure panels in UL-listed equipment, and structural insulators where flame retardancy is required. Its combination of 65,000 psi tensile strength, UL 94 V-0 rating, and 0.10% moisture absorption makes it one of the most widely specified engineering laminates.
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