G10 vs FR4 Fiberglass Board: Industrial Insulation Material Selection Guide

G10 vs FR4 Fundamentals
Composition & Structure
Performance Comparison Table
Typical Industrial Applications
Selection Decision Tree
Pricing & Lead Time
Summary & Recommendations

G10 and FR4 fiberglass/epoxy laminate are the two most frequently compared insulation materials in industrial equipment design. Despite their similar appearance and overlapping properties, they differ significantly in flame retardancy, mechanical strength, application suitability, and certification requirements. This article provides a thorough comparison from composition to practical selection guidance.

1. G10 vs FR4 Fundamentals

Both G10 and FR4 are glass epoxy laminate sheets, but they follow distinct standard systems:

G10: Derived from U.S. military standard (MIL-SPEC), classified as MIL-I-24768 Type GEE — non-flame-retardant (NH grade);
FR4: Conforms to NEMA LI 1-1998; "FR" stands for Flame Retardant — meets UL94 V-0 rating.

In China's market, type "3240" epoxy board falls between G10 and FR4 in performance, using a phenolic epoxy system.

2. Composition & Structure Comparison

Item	G10	FR4
Base Resin	Pure epoxy (Bisphenol-A type)	Brominated epoxy (flame-retardant)
Reinforcement	E-glass woven fabric	E-glass woven fabric
Flame Retardancy	NH (Non-Flame-Retardant)	UL94 V-0 (Self-extinguishing)
Standard Color	Natural (tan/light green/brown)	Standard: dark green; custom: yellow/white/black
Standard Thickness	0.3mm – 100mm	0.3mm – 100mm

3. Performance Comparison

Property	G10	FR4	Test Method
Flexural Strength (vertical)	≥340 MPa	≥415 MPa	IPC-4101
Flame Retardancy	NH (non-FR)	V-0 (extinguishes within 10s)	UL94
Dielectric Strength	≥20 MV/m	≥20 MV/m	ASTM D149
Water Absorption (24h)	≤0.15%	≤0.10%	ASTM D570
Max Operating Temp	130°C – 155°C	130°C – 155°C	—
CTI (Comparative Tracking Index)	≥175V	≥175V	IEC 60112
Insulation Resistance	≥10⁶ MΩ	≥10⁶ MΩ	IEC 60093

4. Typical Industrial Applications

G10 Preferred Transformer Oil Insulation

G10 maintains stable performance in transformer oil environments, making it suitable for transformer clamping insulation, insulating spacers, and other wet/oil-exposed electrical equipment applications.

FR4 Required Markets Requiring Flame Retardancy

UL94 V-0 rated FR4 is mandatory for electrical equipment exported to North America, Europe, and other markets requiring CE/UL certification. This includes industrial power supplies, EV chargers, and power electronics enclosures.

Either Works PCB Test Jigs (Test Fixtures)

PCB test jigs represent one of the largest application markets for both G10 and FR4. Both offer high flatness, rigidity, and machinability. The choice depends on whether the end customer requires flame retardancy.

Either Works Automation Equipment Insulation

CNC machine insulation pads, automation limit blocks, and FPC stiffener plates can use either material. When flame retardancy is not required, G10 offers better cost efficiency.

5. Selection Decision Tree

    Quick Selection Guide:

    ① Exporting to North America/Europe/Japan/Korea? → FR4 mandatory (UL/CE requirements)

    ② Customer specifies UL certification or brominated flame-retardant? → FR4

    ③ General domestic industrial use, no FR requirement? → G10 — better value

    ④ Used in transformer oil environment? → G10 or 3240 preferred

    ⑤ Cost-sensitive bulk order? → Compare G10 vs FR4 pricing first

6. Pricing & Lead Time

In China's domestic market, G10 typically costs 5%~15% less than FR4. Key factors affecting price:

Thickness: Thin sheets (<1mm) and extra-thick sheets (>20mm) show larger price gaps;
Custom sizes: Non-standard dimensions incur additional machining fees;
Color customization: Non-green FR4 requires separate production or dyeing;
Certification requirements: UL-certified materials carry a quality premium.

7. Summary & Recommendations

The core distinction between G10 and FR4 lies in flame retardancy and certification compliance. For export-oriented industrial customers, FR4 is non-negotiable; for high-volume domestic applications where performance requirements are met, G10 provides a meaningful cost advantage.

Chaorong Electronics supplies both G10 and FR4 fiberglass boards in custom sizes, thicknesses, and colors, with material certificates and UL yellow card support. Contact us for selection assistance and competitive pricing.

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