What Is the Difference Between FR4 and G10 Epoxy Sheets?

FR4 and G10 epoxy sheets are both fiberglass-reinforced epoxy laminates widely used in electrical, electronic, and industrial applications. At first glance, they appear very similar in structure, machining behavior, and mechanical strength. In practice, the key difference lies in fire performance certification and electrical compliance, which directly affects where each material is used.

Understanding this difference helps engineers and manufacturers select the correct laminate for safety, reliability, and regulatory alignment.

What FR4 and G10 Have in Common

Both FR4 and G10 epoxy sheets are produced by impregnating woven fiberglass cloth with epoxy resin and curing it under heat and pressure. As a result, they share many core properties:

• High mechanical strength and stiffness

• Excellent electrical insulation

• Good dimensional stability after machining

• Resistance to moisture and many industrial chemicals

• Suitability for CNC machining, drilling, and tapping

From a structural and processing standpoint, FR4 and G10 can often be machined into the same types of parts, such as insulation plates, spacers, supports, and fixtures.

The Core Difference: Flame Retardancy

The defining difference between FR4 and G10 epoxy sheets is flame resistance.

FR4 Epoxy Sheets

FR4 is a flame-retardant grade of epoxy laminate. The “FR” designation indicates that the material meets specific flame-retardancy requirements, commonly associated with UL94 V-0 performance. When exposed to flame, FR4 is designed to self-extinguish within a controlled time frame.

Because of this behavior, FR4 is commonly specified in:

• Electrical and electronic assemblies

• Power distribution equipment

• Control cabinets and switchgear

• Applications where fire safety compliance is required

G10 Epoxy Sheets

G10 is a non-flame-retardant epoxy laminate. It does not include flame-retardant additives and is therefore not intended to meet fire-resistance standards. However, the absence of these additives can slightly improve certain mechanical characteristics.

G10 is often selected for:

• Mechanical and structural insulation parts

• Industrial tooling and fixtures

• Spacers and supports where flame rating is not mandatory

• Applications prioritizing strength and cost efficiency over fire compliance

Electrical and Mechanical Performance Comparison

In most practical designs, FR4 and G10 offer very similar electrical insulation and mechanical strength. Differences are usually secondary and application-dependent rather than absolute.

How the Choice Affects Real Applications

Electrical Equipment and Safety-Critical Assemblies

In power distribution, control systems, and electrical enclosures, FR4 epoxy sheets are usually preferred or specified. Flame retardancy reduces risk in fault conditions and supports internal or customer compliance requirements.

Industrial Machinery and Structural Parts

For mechanical spacers, supports, wear plates, and tooling components, G10 epoxy sheets are often sufficient. When fire rating is not part of the design criteria, G10 can deliver reliable performance with optimized material cost.

Long-Term Reliability Considerations

The decision is not only about initial performance. Flame-retardant requirements can influence material approval processes, internal audits, and downstream customer acceptance. Selecting FR4 where fire behavior matters can reduce redesign and requalification later in the product lifecycle.

Selection Guidance from a Manufacturing Perspective

When deciding between FR4 and G10 epoxy sheets, manufacturers typically evaluate:

• Whether flame retardancy is required by design or internal standards

• Operating voltage and insulation distance requirements

• Continuous and peak operating temperatures

• Mechanical load and fastening stress

• Production volume and machining complexity

• Cost targets and supply consistency

A clear definition of these parameters allows the epoxy sheet grade to be selected efficiently without over-specifying the material.

About SENKEDA Epoxy Sheets

As an epoxy laminate manufacturer, SENKEDA supplies both FR4 and G10 epoxy sheets for industrial and electrical applications. Based on the material range presented on skdepoxysheet.com, SENKEDA focuses on consistent laminate quality, stable thickness control, and suitability for machining into insulation and structural parts.

For manufacturers sourcing epoxy sheets, working with a supplier that understands the practical differences between FR4 and G10 helps ensure the selected material aligns with safety expectations, processing requirements, and long-term performance goals.

Summary

FR4 and G10 epoxy sheets are structurally similar but functionally distinct in one critical area: flame retardancy.

• Choose FR4 when fire safety and electrical compliance are part of the design requirements.

• Choose G10 when mechanical strength, insulation performance, and cost efficiency are the primary concerns without flame-rating obligations.

Selecting the correct grade early supports safer designs, smoother approvals, and more predictable production outcome