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5-axis CNC milling drawing: Al 7075-T6 block with pockets, toolpath and dimensions
G10 · FR4 · Glass-Epoxy Laminate

Structural insulator. Stiffer than Delrin. FR-rated.

G10 (and its flame-retardant cousin FR4) combines glass fiber strength with epoxy dielectric properties. Tensile 260 MPa, flexural modulus 18 GPa — stiffer than most engineering thermoplastics. The backbone of the PCB industry, also valued for electrical standoffs and structural insulators.

Engineering plasticsWuxi, ChinaMOQ 1 partDFM review included
Technical plate for Structural insulator. Stiffer than Delrin. FR-rated.

At a glance

Density
1.80 g/cc
Tensile strength
260 MPa
Flexural modulus
18 GPa
Hardness
M 100 Rockwell
HDT
140 °C
Dielectric strength
20 kV/mm
Water absorption
0.2 %
Flame (FR4 only)
UL 94 V-0
G10 · FR4 · Glass-Epoxy Laminate

Key data

Density
1.80 g/cc
Tensile strength
260 MPa
Flexural modulus
18 GPa
Hardness
M 100 Rockwell
HDT
140 °C
Dielectric strength
20 kV/mm
Water absorption
0.2 %
Flame (FR4 only)
UL 94 V-0
01 · Grades & variants

G10/FR4 variants.

G10

Glass-cloth epoxy laminate. Standard grade with excellent mechanical and electrical properties. Not flame retardant — used where FR isn't required.

FR4

Flame-retardant variant of G10. Bromine-based or halogen-free FR package. Standard PCB substrate, electrical enclosures, insulators near electrical components.

FR5

Higher Tg version for elevated-temperature PCB applications (190 °C vs 140 °C for FR4). Lead-free solder reflow compatible.

G11

High-temperature G10 with improved performance at elevated temperature. Used for mechanical parts needing temperature stability without FR requirement.

Halogen-free FR4

Phosphorus or nitrogen-based FR instead of bromine. RoHS and halogen-free compliance for European and Asian markets.

Rogers / Taconic

Specialty high-frequency PCB laminates (PTFE-glass, ceramic-filled). For RF circuit boards above 1 GHz. Machined through specialty partners.

Four common variants of glass-epoxy laminate cover most applications. Differences primarily in flame retardancy, thermal performance, and frequency characteristics.

02 · Why this material

Why G10/FR4.

Electrical insulation

20 kV/mm dielectric strength — high-voltage standoffs, bus-bar separators, transformer insulation. Volume resistivity 10^14 Ω·cm.

Mechanical stiffness

18 GPa flexural modulus — 4× nylon, 5× Delrin. Structural insulator bars, mounting plates for electrical and transformer applications.

Dimensional stability

0.2% water absorption, minimal thermal expansion. Critical for PCB registration and multi-layer board stability.

Machinability

Cuts cleanly with carbide tooling. Dusty (glass fibers airborne) — requires dust extraction. Fast to machine relative to engineering thermoplastics.

The combination of electrical insulation, mechanical stiffness, and machinability makes G10/FR4 unique. No single-material alternative offers all three.

03 · Applications

G10/FR4 applications.

PCB substrate prototypes

Custom PCB shapes and mechanical features for specialty applications

Electrical standoffs

High-voltage insulator standoffs for electrical panel builds

Transformer insulators

Bobbins, spacers, insulation bars for power transformers

Battery separator plates

Non-conductive separator plates between battery cells

Busbar insulators

High-current bus-bar separator bars for switchgear

Knife handle scales

G10 handles for high-end knives — durable, dimensionally stable, cosmetic

Aerospace structural

FR5 structural components for avionics and high-temp insulators

Test fixtures

Electrical test fixtures requiring insulation and dimensional stability

Firearm grip panels

G10 textured grip panels for handguns and tactical firearms

04 · Finishing

G10/FR4 finishing.

As-machined

Visible glass fiber surface. Dark green (FR4), yellowish (G10 natural). Functional finish.

Beveled edges

Sharp edges chip readily — chamfer or radius edges improves handling.

Textured

G10 is often surface-textured (knife handles) for grip. Machined texture patterns possible.

Machined threads

Threads hold in G10/FR4 but are subject to breakdown under repeated cycling. Heli-coils recommended for critical fasteners.

Pressed inserts

Threaded inserts pressed into G10 for assembly hardware.

Painted

Accepts standard paints. Smooth surface requires light sanding for adhesion.

Laminate orientation

Stacking direction matters — specify fiber orientation for critical mechanical properties.

Sealed edges

Machined edges can wick moisture — seal with epoxy or conformal coat for humid service.

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FAQ

Structural insulator — questions

G10 vs FR4 — what is the difference?

G10 and FR4 are nearly identical glass-epoxy laminates. The only difference: FR4 contains flame retardant (usually bromine-based) to achieve UL 94 V-0 rating. G10 burns if ignited. For electronics applications, FR4 is mandatory for safety. For mechanical applications where fire rating doesn't matter (knife handles, standoffs outside electronics), G10 is slightly cheaper and mechanically similar.

Is G10 machining hazardous?

Glass fiber dust is a respiratory and skin irritant. Machining G10/FR4 requires: dust extraction (HEPA or better filtering), protective clothing and gloves, eye protection, and dedicated tooling (dust contaminates other shop equipment). Our G10 machining is in dedicated area with proper ventilation. For customers: handling finished G10 parts is safe — the hazard is during machining only.

Can G10 be used structurally?

Yes — G10 is a true structural composite. Tensile 260 MPa, flexural modulus 18 GPa. Used for battery separator plates, test fixtures, knife handles. Loads are anisotropic (varies with fiber direction), so specify fiber orientation on drawings. Limitations: brittle failure mode vs tough thermoplastics, glass-fiber dust hazards during machining.

Does G10 handle high voltage?

Yes — dielectric strength 20 kV/mm (short-term). For sustained high-voltage service, derate to 5–10 kV/mm. Standard for medium-voltage electrical insulation, transformer bobbins, and switchgear components. For applications above 100 kV, specialty insulating ceramics or silicone elastomers are preferred.

Can you machine PCB material to specialty shapes?

Yes. We regularly machine FR4 to custom PCB shapes for specialty applications: spacecraft PCBs with weight cutouts, automotive PCBs with mechanical interlocks, industrial control PCBs with custom mounting features. We also machine PCB substrates for mechanical brackets that happen to also be conductive pathways. Non-standard PCB mechanical shapes are our specialty.

5-axis CNC milling drawing: Al 7075-T6 block with pockets, toolpath and dimensions

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