FR4 Epoxy Sheet Properties and Industrial Applications

2026,10,13

What is FR4 epoxy sheet used for?

FR4 epoxy sheet is used for rigid electrical insulation in motors, transformers, switchgear, busbar supports, battery modules, electronic fixtures and CNC-machined insulating parts. It is selected when the part needs stiffness, electrical separation and, for suitable grades, flame-retardant performance.

Quick answer: Is FR4 a good insulator?

Yes. FR4 combines glass-cloth reinforcement with epoxy resin, giving the sheet high electrical insulation, good mechanical strength and stable dimensions. For UL94 V-0 applications, specify the correct flame-retardant grade rather than using G10 by default.

What Is FR4 Material?

FR4 is a glass-cloth-reinforced epoxy laminate. It is supplied as sheet, rod or blank and can be cut, drilled, milled and machined into custom insulation parts.

What Are the Main FR4 Sheet Properties?

The table below answers the most common technical questions about FR4 epoxy sheet. Values are typical references; confirm the exact grade and batch COA for production use.

Property	Typical value	Test method or condition
Density	1.85–1.95 g/cm³ (115.5–121.7 lb/ft³)	ISO 1183
Flexural strength	≥340 MPa (≥49,300 psi), lengthwise ≥300 MPa (≥43,500 psi), crosswise	IEC 60893-2
Tensile strength	≥280 MPa (≥40,600 psi)	ISO 527
Compressive strength	≥350 MPa (≥50,800 psi), perpendicular to the laminate layers	IEC 60893-2
Interlaminar shear strength	≥45 MPa (≥6,530 psi)	Grade-dependent
Impact strength	≥33 kJ/m²	IEC 60893-2, parallel to the layers
Breakdown voltage	≥40 kV at 1.0 mm thickness	IEC 60243, 90°C oil, perpendicular to the layers
Insulation resistance	≥5.0 × 1010 Ω	IEC 60167, after 24-hour water immersion
Dielectric constant	4.3–4.8	IEC 60250, at 1 MHz
Dissipation factor, tan δ	≤0.035	IEC 60250, at 1 MHz
Water absorption	≤0.15%	ISO 62, 1.6 mm specimen, 24 hours
Flame rating	UL94 V-0 for flame-retardant grades	Confirm the exact grade and supporting documents
Continuous service temperature	Typically 130–155°C (266–311°F)	Grade and application dependent

Typical values are not a substitute for a grade-specific datasheet or batch COA. Test direction, thickness and conditioning can change the reported result.

Why Use FR4 for Electrical Insulation?

High-voltage insulation

Use FR4 for rigid barriers, supports, spacers and electrical clearance parts.

Strong insulating structure

Glass reinforcement helps the part resist bending while maintaining electrical separation.

FR4 flame-retardant grade

Specify the exact grade when UL94 V-0 performance is required.

FR4 CNC machining

Suitable for cut-to-size sheets and drawing-based insulating components.

What Are the Industrial Applications of FR4?

Motors and transformers: spacers, barriers, supports and other custom insulating parts.

Power distribution: busbar supports, switchgear insulation and electrical cabinet partitions.

New-energy equipment: battery-module barriers, fixtures and insulating brackets.

Electronics manufacturing: drilling fixtures, test fixtures and assembly tooling. Bare FR4 sheet should not be confused with copper-clad laminate (CCL).

Industrial machinery: rigid guides, spacers, guards and custom-machined components where electrical insulation is also required.

Rail and transportation equipment: custom insulation parts, subject to the project’s specific fire and certification requirements.

FR4 vs G10 vs 3240: Which Sheet Should You Choose?

Material	When it is usually considered	Important point
FR4	Structural electrical insulation with a flame-retardant requirement	Confirm the exact grade, UL94 scope and working temperature
G10	Rigid glass-epoxy insulation where flame retardancy is not required	Do not use G10 as a substitute when V-0 is specified
3240	Cost-sensitive industrial insulation, especially in GB-grade applications	3240 and FR4 are different systems; they should not be described as identical
G11 or FR5	Higher-temperature applications beyond the normal FR4 range	Confirm the continuous temperature, peak temperature and flame requirement

How to Order FR4 Epoxy Sheet

To receive a useful recommendation and quotation, include:

Material grade: FR4, G10, G11, FR5 or 3240.

Thickness and sheet size, using mm and inches where useful.

Working temperature, voltage, CTI requirement and flame rating.

Quantity, expected repeat demand and preferred surface finish.

A PDF or DWG drawing for machined parts, including critical tolerances and hole locations.

Can I Get a Free FR4 Sample?

Yes. A free FR4 sample is available for suitable enquiries so your team can check fit, surface condition and initial machining behaviour before production.

Send the grade, thickness, size or drawing, application and estimated quantity. Sample availability and shipping arrangements will be confirmed by our sales team.

Frequently Asked Questions About FR4

Can FR4 be used as a mechanical support?

Yes. FR4 is often selected when a part needs both structural rigidity and electrical insulation. The actual load, span, temperature and mounting method still need to be reviewed.

Is FR4 the same as 3240 Epoxy Sheet?

No. They use different material systems and standards. FR4 is generally more suitable when a NEMA or IEC grade and flame-retardant performance are required.

Can XYH machine FR4 from a drawing?

Yes. XYH can review cut-to-size and CNC-machined FR4 parts from PDF, DWG, STEP or IGES files. Include the quantity and critical tolerances with the drawing.

Technical recommendations are based on the information provided and typical material data. Final suitability must be verified by the buyer under the actual operating conditions. Values shown in this article are typical reference values and are subject to the applicable batch COA.

Author:

Ms. Shelby Luo

E-mail:

shelby@xiongyihua-plastic.com

Phone/WhatsApp:

+86 133 6054 9300