FR4 Thickness and Selection Guide for Electrical Insulation Applications

Time: 10-15 2025 Auther: Xujue Electrical

1. Introduction to FR4 Material FR4 Material (Flame Retardant 4) is a composite material made of epoxy resin and fib...

1. Introduction to FR4 Material

FR4 Material (Flame Retardant 4) is a composite material made of epoxy resin and fiberglass cloth. It features:
Excellent electrical insulation performance
High mechanical strength
Good heat resistance (typically 130–140°C)
UL94 V-0 flame retardant rating
Therefore, FR4 is widely used in electrical insulation components, PCB boards, transformer partitions, switchgear barriers, and EV charging equipment.

fr4 material

2. Common FR4 Thickness Specifications

Below are the typical FR4 sheet thicknesses (unit: mm):

Thickness (mm)	Typical Application
0.2 – 0.5	Thin insulation layers, flexible boards, insulation spacers
0.8 – 1.6	Standard PCB thickness
2.0 – 3.2	Insulation gaskets, mechanical support plates
5.0 – 10.0	Power equipment partitions, transformer insulation barriers
12.0 – 20.0	Structural insulation components for heavy-duty use

Customized thickness (0.1–50 mm) is available from manufacturers and can be cut or CNC-machined to required sizes.

3. Key Factors for FR4 Material Selection

(1) Electrical Performance

For high-voltage equipment (transformers, switchgear), focus on:
Dielectric strength ≥ 14 kV/mmInsulation resistance ≥ 10¹² Ω
For low-voltage PCB applications, standard FR4 PCB-grade material is sufficient.

(2) Mechanical Strength

For load-bearing or structural parts → thickness ≥ 5 mm
For insulation spacers or connection parts → thickness 1–3 mm

(3) Thermal Properties

Continuous operating temperature ≤ 130°C
For higher temperature environments, consider FR5 (up to 150°C+).

(4) Size & Machinability

Excellent for CNC machining, drilling, cutting, and tapping.
Leave machining allowance to avoid cracks or burrs.

(5) Flame Retardancy & Certifications

Choose UL94 V-0 flame-retardant grade.
For export products, ensure compliance with RoHS, REACH, CE, UL standards.

4. Selection Examples

Application	Recommended Thickness	Type	Note
PCB Board	1.6 mm	FR4 Standard	Most common
Transformer Insulation Barrier	3–10 mm	FR4 Electrical Grade	High insulation strength
Switchgear Partition	5–15 mm	FR4 Industrial Grade	High mechanical strength
EV Charger Support Plate	5 mm	FR4 Epoxy Glass	Excellent bending strength
Motor Insulation Pad	2 mm	FR4 Sheet	CNC processable

5. Recommendation from Xujue Electrical

Xujue Electrical is a professional manufacturer of electrical insulation materials, providing:

FR4 epoxy glass sheets, rods, and tubes

Custom sizes and precision machining

Certified by UL, RoHS, ISO9001, and IEC

Widely used in transformers, switchgear, EV chargers, motors, and power systems

Leave us a message to get quotation and sample!

If you are interested in our products,, please send us a message and we will contact you as soon as we receive it. Email: info@ztaero.com whatsApp: +8616650273778