- FR4 is the cost-effective workhorse for PCB and general electrical insulation up to 130°C, with excellent flame retardance (UL94 V-0) and the lowest price per sheet.
- G10 offers superior mechanical strength and machinability vs FR4, handles up to 150°C, but lacks the brominated flame retardant — choose it when strength and precision matter more than fire rating.
- G11 is the high-temperature champion, rated to 180°C continuous service, with mechanical properties that hold up where FR4 and G10 soften — at roughly 2× the cost of FR4.
- For most general electrical applications, FR4 hits the sweet spot; for structural components or elevated-temperature environments, step up to G10 or G11 based on your thermal budget.
When you open a material spec sheet for an electrical insulation project, three names keep showing up: FR4, G10, and G11. All three are glass-reinforced epoxy laminates manufactured under the NEMA LI 1 standard. All three use woven fiberglass cloth impregnated with epoxy resin. Yet the performance gap between them can be the difference between a decade of reliable service and a field failure in six months.
At SIDA, we supply all three grades to transformer manufacturers, PCB fabricators, switchgear builders, and motor repair shops across 40+ countries. The most common question we get from procurement engineers is not “do you have it?” but “which one should I actually order?”
This comparison cuts through the datasheet noise. We will walk through what the three laminates share, where they diverge on temperature and strength, which application each grade owns, and what you should expect to pay per sheet — including real shipping lead times for customers in Bangladesh and South Asia.
What Do FR4, G10, and G11 Have in Common?
Before focusing on the differences, it helps to understand the shared foundation. FR4, G10, and G11 all belong to the NEMA glass epoxy laminate family. Each grade starts with woven E-glass fabric — the same fiberglass cloth used across the composite industry — and saturates it with an epoxy resin system under heat and pressure.
The manufacturing process is functionally identical across all three: layers of glass cloth are stacked, impregnated with resin, and consolidated in a heated hydraulic press. The resulting sheet, tube, or rod has a characteristic pale green (FR4), light green-to-tan (G10), or amber-brown (G11) appearance. All three can be CNC-machined, drilled, tapped, and waterjet-cut into finished components.
Shared properties include: excellent electrical insulation (dielectric strength typically above 20 kV/mm), low moisture absorption (under 0.2% after 24-hour immersion per ASTM D570), and good chemical resistance to transformer oils, coolants, and mild acids. All three grades also offer dimensional stability across a wide humidity range — a critical factor for precision spacer blocks, busbar supports, and PCB substrates where warpage equals scrap.
In practice, if your application is strictly room-temperature electrical isolation with no structural load, any of the three will work. The selection decision becomes urgent only when temperature, mechanical stress, or flammability enters the picture.
What Are the Key Differences in Temperature Rating and Mechanical Strength?
The single biggest differentiator is thermal class. FR4 is rated for continuous service at 130°C (Class B). G10 pushes that to 150°C (Class F). G11 reaches 180°C (Class H) — a full 50°C above FR4, which in thermal aging terms translates to roughly 4× longer life at a given elevated temperature.
The reason is chemistry. FR4 uses a standard brominated epoxy system optimized for flame retardance. G10 uses a non-brominated, higher-crosslink-density epoxy that sacrifices some flame resistance for mechanical integrity. G11 goes further with a high-temperature epoxy formulation designed specifically to resist thermal degradation. Our testing data shows G11 retaining over 80% of its room-temperature flexural strength at 150°C, while FR4 drops below 50% at the same temperature.
| Property | FR4 | G10 | G11 |
|---|---|---|---|
| Continuous Operating Temp | 130°C | 150°C | 180°C |
| Flexural Strength (LW, MPa) | 415 | 450 | 415 |
| Compressive Strength (MPa) | 350 | 380 | 360 |
| Dielectric Breakdown (kV/mm) | 22 | 23 | 22 |
| Water Absorption (24h, %) | 0.15 | 0.15 | 0.15 |
| Flame Rating (UL94) | V-0 | HB | HB |
| NEMA Specification | LI 1-FR4 | LI 1-G10 | LI 1-G11 |
On mechanical strength, G10 is the standout. Its non-brominated epoxy achieves higher crosslink density, giving it roughly 8–10% higher flexural and compressive strength than FR4. This makes G10 the preferred choice for structural insulating components — threaded rods, nut-and-bolt sets, and heavy busbar supports — where mechanical load, not just voltage, is the design driver.
FR4’s defining advantage is its UL94 V-0 flame rating. The brominated epoxy extinguishes itself when the flame source is removed. G10 and G11 rate only HB (horizontal burn), meaning they will continue to burn. For enclosed electronics, PCB fabrication, and any application governed by fire safety codes, this single data point often makes FR4 non-negotiable. Read more about FR4 in PCB fabrication and why its flame retardance matters.
Which Applications Suit Each Grade?
Understanding the thermal and mechanical profiles lets you map each grade to its natural application territory. Here is how we see the market segmentation based on 20+ years of supplying all three grades:
FR4 applications: PCB substrates (over 90% of all rigid PCBs globally use FR4), switchgear panel insulation, terminal boards, electrical enclosure backplates, and general-purpose insulating sheets where cost matters and temperatures stay below 130°C. If you are building control panels, instrumentation housings, or low-voltage distribution equipment, FR4 is almost certainly your starting point. Its FR4 density (1.85 g/cm³ typical) also makes it the lightest of the three.
G10 applications: High-strength structural insulators, transformer coil supports, busbar clamping plates, precision-machined spacers and washers, and threaded fasteners that must maintain torque under vibration. G10’s superior machinability — it chips less and holds tighter tolerances than FR4 — makes it the go-to for CNC-machined insulating components. See our detailed G10 vs G11 comparison for structural use cases.
G11 applications: High-temperature transformer internals, motor slot wedges in Class H windings, aerospace electrical isolation panels, and any environment where continuous exposure exceeds 150°C. If your equipment operates near oil-filled transformer windings at full load, G11’s thermal headroom provides a safety margin that FR4 and G10 cannot match. Our article on G11 high-temperature performance covers the chemistry in more depth.
A practical decision flow: Start with FR4. If the temperature exceeds 130°C, move to G10. If it exceeds 150°C, go to G11. If you need UL94 V-0, stay with FR4 or consider FR5 (the V-0-rated G11 equivalent).
Cost Comparison: FR4 vs G10 vs G11 Pricing Per Sheet
Let us talk numbers — because spec sheets do not issue purchase orders, budgets do. Pricing for epoxy glass laminates follows the thermal-performance curve almost exactly.
Taking a standard 1.6 mm × 1,020 mm × 1,220 mm sheet as our reference (the most commonly ordered format for general fabrication), here is the approximate pricing tier as of mid-2026:
| Grade | Price per Sheet (USD) | Relative Cost | Typical MOQ |
|---|---|---|---|
| FR4 | $18 – $28 | 1.0× (baseline) | 50 sheets |
| G10 | $28 – $42 | 1.5 – 1.6× | 30 sheets |
| G11 | $40 – $58 | 2.0 – 2.2× | 20 sheets |
Several factors move these numbers. Thickness is the biggest lever — a 0.4 mm FR4 sheet for PCB lamination costs far less per unit area than a 50 mm G11 block for machining. Sheet size matters too: non-standard dimensions (e.g., 1,500 mm × 2,000 mm) carry a premium. Order volume can swing pricing by ±15% at MOQ thresholds. And surface finish — whether you need standard press-finish or a ground/machined surface — adds processing cost.
For procurement teams, the practical takeaway is: G10 costs roughly 50–60% more than FR4, and G11 costs roughly 100% more than FR4. Unless your application genuinely requires the elevated thermal rating, over-specifying to G11 is simply leaving money on the table. Conversely, under-specifying to FR4 when you actually need G10’s temperature margin creates a far more expensive problem down the line — field failures, warranty claims, and reputational damage.
Real Customer Question: Shipping Time for FR4/G10 to Bangladesh
One of the most frequent inquiries we receive from South Asian buyers is about logistics lead times. A recent customer in Dhaka asked: “We need 200 sheets of FR4 and 100 sheets of G10 for transformer bushing plates. How fast can you ship to Chittagong port, and what is the freight cost?”
This is a representative scenario for many of our procurement partners. Here is the realistic breakdown based on current (Q2 2026) shipping conditions from our Ningbo consolidation warehouse:
Sea freight to Chittagong: 14–18 days transit, plus 2–3 days for customs clearance and documentation. Total door-to-port is typically 18–22 days. For LCL (less than container load) shipments of 200–500 sheets, freight runs approximately $180–$280 depending on total volume and the carrier’s current bunker surcharge.
Air freight option: For urgent orders, we ship via Shanghai Pudong to Dhaka Hazrat Shahjalal. Transit is 3–5 days door-to-door. Air freight for 300 sheets of 1.6 mm material (roughly 350 kg packaged) costs approximately $1,200–$1,800. This is typically reserved for time-sensitive maintenance shutdowns or prototype builds.
Our recommendation: For planned production, sea freight is the clear choice. We advise placing orders 4–5 weeks ahead of your required production date to absorb any port congestion or customs delays. SIDA handles all export documentation — Certificate of Origin, packing list, commercial invoice, and bill of lading — so your customs broker in Bangladesh receives a complete document package before the vessel arrives. For G10 material equivalents and cross-referencing with Chinese standard 3240 epoxy sheet, review our technical reference page.
Frequently Asked Questions
Can I substitute FR4 for G10 in a transformer busbar support?
Not if the busbar operates above 130°C or carries significant mechanical load. FR4 has lower flexural strength (415 vs 450 MPa) and softens at a lower temperature than G10. For indoor, low-voltage, ambient-temperature busbar supports, FR4 is adequate. For oil-filled transformer internals or outdoor switchgear exposed to solar heating, step up to G10 or G11. When in doubt, share your operating conditions with our engineering team — we will recommend the grade that matches your thermal and mechanical envelope without over-specifying.
What is the difference between G10 and 3240 epoxy sheet?
3240 is the Chinese national standard (GB/T 1303) equivalent that occupies a middle ground between G10 and FR4. It uses an epoxy resin system similar to G10 but typically with slightly lower glass transition temperature (Tg) and mechanical properties closer to FR4. The practical difference: 3240 sheets cost about 15–20% less than NEMA-grade G10 and are widely available from Chinese manufacturers. For non-certified applications, 3240 is a capable, budget-friendly alternative. For projects requiring NEMA traceability, IEC compliance documentation, or UL recognition, genuine G10 is the safer choice. SIDA supplies both grades — we help you determine which documentation trail your end customer actually requires.
Does G11 require special machining tools compared to FR4?
G11’s higher crosslink density and thermal resistance make it slightly harder on tooling than FR4. Carbide-tipped drill bits and router cutters are recommended for production runs; HSS tooling wears roughly 30–40% faster on G11 than on FR4. Feed rates should be reduced by about 15–20% compared to FR4 parameters to avoid chipping at the cut edge. Coolant is generally not required for thin sheets (under 3 mm), but for thicker sections (10 mm+), a mist coolant or compressed air helps maintain dimensional accuracy and extends tool life. The good news: any shop that machines FR4 or G10 already has the equipment to machine G11 — it is a parameter adjustment, not a capital investment.
Summary: Choosing the Right Epoxy Laminate for Your Application
The FR4 vs G10 vs G11 decision ultimately reduces to three questions: What is your continuous operating temperature? Do you need UL94 V-0 flame retardance? What is your budget?
FR4 answers the call for probably 70% of electrical insulation applications — it is affordable, flame-retardant, and widely available in sheets, tubes, rods, and machined components. G10 is the choice when mechanical strength, machinability, or a 150°C thermal ceiling is required. G11 is the specialist: pay roughly double the FR4 price and get a material that holds its properties at temperatures where the others fail.
At SIDA, we stock all three NEMA grades plus the Chinese standard 3240 epoxy sheet in our Ningbo warehouse. We supply in full sheets, cut-to-size panels, and CNC-machined finished components per customer drawings. Our product range includes FR4/G10 epoxy glass sheets, tubes, and rods, G11/FR5 high-temperature sheets and rods, and 3240 epoxy glass fiber laminate in thicknesses from 0.2 mm to 100 mm.
Need help selecting the right grade for your specific application? Contact our engineering team — we review your thermal, mechanical, and compliance requirements and recommend the optimal material. No charge for the consultation.
📞 Phone/WhatsApp: +86-15958243831
📧 Email: jessie.feng@sidanm.com
🌐 Web: sidanm.com
