G10 Grades — NEMA G10 vs FR4, G11, G7, G9 Laminates
NEMA LI 1 defines a family of industrial laminated thermosetting products using a letter-number designation system. G10 is one of nine glass-cloth-reinforced grades within that system, each distinguished by resin type and — in the case of FR4 — the presence or absence of flame-retardant additives. Selecting the correct grade requires matching the resin system, thermal class, flame rating, and reinforcement type to the application's electrical, mechanical, and regulatory requirements. This page covers G10 specifically, then places it in context relative to related grades.
At a glance:
- G10 = woven E-glass + standard epoxy, UL94 HB, Thermal Class B (130°C)
- FR4 = G10 chemistry + brominated flame retardant, UL94 V-0 — different grade, not interchangeable
- G11 = woven E-glass + higher-Tg epoxy, UL94 HB, improved elevated-temperature performance
- G7 = woven E-glass + silicone resin, Thermal Class H (180°C), superior high-temp insulation
- G9 = woven E-glass + melamine resin, arc-resistant applications
- G3 = woven E-glass + melamine resin (predecessor, less common)
The NEMA Laminate Designation System
NEMA LI 1 designates laminates by a prefix letter (reinforcement type) and a number (resin/grade sequence). The "G" prefix uniformly indicates woven glass-cloth reinforcement. Paper-based laminates use "X" and "C" prefixes; linen uses "L"; canvas uses "C." The number distinguishes the resin system and performance level within each reinforcement class.
| Prefix | Reinforcement |
|---|---|
| G | Woven E-glass cloth |
| X | Paper (cellulose) |
| C | Canvas (woven cotton) |
| L | Fine-weave linen |
Key reference standards:
- NEMA LI 1: Defines minimum properties for each grade (physical, electrical, thermal, dimensional)
- MIL-I-24768/2: Military procurement specification; Type GEE = G10, Type GEE/FR = FR4
- ASTM D709: Standard specification for laminated thermosetting materials; used for test method references
- IEC 60893: International equivalents (G10 ≈ EPGC 201/202 per IEC)
G10 Grade — Detailed Profile
G10 is the baseline woven-glass-epoxy laminate without flame-retardant modification. The epoxy resin system used in G10 is a standard bisphenol-A diglycidyl ether (BADGE) system, sometimes modified with anhydride curatives.
Key characteristics:
- Flame rating: UL94 HB (horizontal burn; material will sustain combustion)
- Thermal class: B — 130°C maximum continuous temperature for electrical insulation service
- Dielectric strength: ~500 V/mil short time
- Flexural strength: 60,000 psi (lengthwise), 50,000 psi (crosswise)
- Water absorption: 0.10% (24 hr, 1/8" specimen) — excellent for glass-reinforced thermoset
G10's absence of flame-retardant additives means it is halogen-free and avoids the brominated compounds (typically tetrabromobisphenol A, TBBPA) present in FR4. This is relevant in applications where halogen content is restricted by customer specifications, environmental regulations, or RoHS/REACH compliance requirements.
FR4 — The Flame-Retardant Counterpart
FR4 is not a separate material family — it is G10 with brominated flame-retardant chemistry added to the epoxy resin system. The two grades are essentially identical in mechanical properties, dielectric strength, and thermal class. The sole functional distinction is flame performance:
| Property | G10 | FR4 |
|---|---|---|
| Flame rating | UL94 HB | UL94 V-0 |
| Flame retardant | None | Brominated (TBBPA) |
| Halogen content | None | Contains bromine (~20% by weight in resin) |
| Mechanical properties | Equal | Equal |
| Electrical properties | Equal | Equal |
| Thermal class | B (130°C) | B (130°C) |
| Typical PCB substrate use | Legacy MIL, industrial | Standard commercial/consumer |
Substituting G10 for FR4 in a design that specifies FR4 may violate the UL94 V-0 requirement of the product safety certification (UL 94, IEC 60950, IEC 62368). Always verify the flame-rating requirement of your assembly before substituting. Conversely, substituting FR4 for G10 in a halogen-free design adds brominated compounds that may violate environmental or customer specifications.
For the full comparison, see the G10 vs FR4 comparison page.
G11 — Higher-Temperature Epoxy Variant
G11 uses the same woven E-glass reinforcement as G10 but a different epoxy resin system with a higher glass-transition temperature (Tg). The cured G11 laminate retains mechanical properties better at temperatures above 130°C.
| Property | G10 | G11 |
|---|---|---|
| Flame rating | UL94 HB | UL94 HB |
| Flexural strength (rt) | 60,000 psi | 65,000 psi |
| Heat deflection temp (264 psi) | 130–140°C | 150–160°C |
| Glass transition temperature | ~120–130°C | ~135–145°C |
| Dielectric strength | ~500 V/mil | ~500 V/mil |
| Relative cost | $ | $$ |
G11 is specified when G10 is marginal at operating temperature — for example, in transformers where winding hot-spot temperatures routinely approach or exceed 130°C, or in military electronics where temperature margins are required by specification.
G7 — Silicone-Glass Laminate
G7 replaces the epoxy binder with a silicone resin, which gives dramatically higher continuous-use temperature capability:
| Property | G10 | G7 |
|---|---|---|
| Resin system | Epoxy | Silicone |
| Thermal class | B (130°C) | H (180°C) |
| Flame rating | UL94 HB | UL94 HB |
| Flexural strength | 60,000 psi | 40,000 psi |
| Dielectric strength | ~500 V/mil | ~400 V/mil |
| Chemical resistance | Good | Moderate |
| Cost | $ | $$$ |
G7 is the laminate of choice for high-temperature motor insulation, traction motor components, and furnace equipment where operating temperatures exceed G10's Class B limit. It gives up some mechanical strength for the thermal upgrade. G7 is also less resistant to acids and solvents than the epoxy-based grades.
G9 and G3 — Melamine-Glass Laminates
G9 uses a melamine-triazine resin with glass-cloth reinforcement. Melamine resins provide good arc resistance and are specified in applications where arc-resistant insulation is the primary requirement:
- G9: Woven glass + melamine-triazine; higher arc resistance than G10; used in switchgear and arcing contact areas
- G3: Woven glass + melamine; older grade; largely supplanted by G9
These grades are less common in stock form than G10 or FR4 and are typically produced to order.
Grade Selection Guide
| Application | Recommended Grade | Reason |
|---|---|---|
| General electrical insulation, <130°C | G10 | Cost-effective, well-characterized |
| UL94 V-0 required | FR4 | Flame rating |
| Halogen-free, no FR required | G10 | No brominated additives |
| Elevated temp insulation, 130–160°C | G11 | Higher Tg epoxy |
| High-temp motors/transformers, >160°C | G7 | Silicone resin, Class H |
| Arc-resistant insulation | G9 | Melamine resin, arc-resistant |
| PCB substrate (commercial/consumer) | FR4 | IPC-4101 standard |
| PCB substrate (legacy MIL) | G10 | MIL-I-24768/2 Type GEE |
| Knife handles and mechanical parts | G10 | No FR needed; halogen-free |
Request G10 or G11 laminate sheet, rod, or tube
Request a Quote →More related guides
Applications
Industries
Compare to other materials
Frequently asked questions — G10 FAQ