Quick Answer
G11 and FR5 are the high-temperature members of the epoxy fiberglass laminate family. Both use a high-Tg epoxy resin that keeps mechanical and electrical properties at 155–180 °C — well above the ~130 °C limit of standard G10/FR4. FR5 is the flame-retardant version of G11 (UL94 V-0 class). IncomePultrusion CNC-machines washers, spacers, and custom parts from certified G11/FR5 laminate to your drawing, quoted within 24 hours.
What Are G11 and FR5?
G11 and FR5 share the same woven E-glass reinforcement as G10/FR4, but the epoxy resin system has a higher glass transition temperature (Tg). Above its Tg, a laminate softens and loses mechanical strength and dielectric margin — so the resin system, not the glass, sets the temperature limit of the material.
- G11 — high-Tg epoxy glass laminate, not flame rated. Typical continuous service in the 155–180 °C class.
- FR5 — the flame-retardant version of G11 (UL94 V-0 class), sometimes sold as “FR4 High Tg”. Typical continuous service around 155 °C.
Room-temperature strength is comparable to G10/FR4 — the value of G11/FR5 is property retention at temperature, not extra strength when cold.
G10 vs FR4 vs G11 vs FR5
| Grade | Resin System | Flame Retardant | Typical Continuous-Use Temperature | Choose It When |
|---|---|---|---|---|
| G10 | Standard epoxy | No | ~130 °C | General electrical insulation, no flame rating |
| FR4 | Standard epoxy + FR | Yes (UL94 V-0 class) | ~130 °C | Flame rating specified, normal temperatures |
| G11 | High-Tg epoxy | No | ~155–180 °C | High temperature, no flame rating required |
| FR5 | High-Tg epoxy + FR | Yes (UL94 V-0 class) | ~155 °C | High temperature and flame rating required |
For the full family background — properties, NEMA / IEC EPGC / 3240 equivalents, and naming pitfalls — see the G10 material guide. For the two standard grades in detail, see FR4 vs G10.
A Note on “FR11”
NEMA never defined an “FR11” laminate grade. Inquiries asking for FR11 almost always mean the high-temperature grades G11 or FR5 — and occasionally “FR10”, which similarly maps back to FR4/G10. If your drawing or RFQ mentions FR10/FR11, send the operating temperature and flame-rating requirement; we will confirm the correct NEMA grade with a datasheet before machining, so the parts match the intent rather than the typo.
When to Specify G11/FR5 Instead of FR4
- Sustained heat: the assembly runs continuously above ~120–130 °C — motor and generator insulation, transformer components, welding fixtures, solder pallets, and power-electronics mounting
- Hot spots with electrical load: busbar supports and terminal insulation near heat sources, where dielectric margin must survive the temperature, not just the voltage
- Thermal cycling: repeated heat-up/cool-down cycles where a standard laminate would age faster
- Code + heat: the specification demands both a flame rating and elevated-temperature service — that combination is FR5
If the assembly stays below 130 °C, standard G10/FR4 is usually the more economical choice; moving to G11/FR5 without a thermal reason adds material cost without adding performance.
Parts We Machine from G11/FR5
The same CNC processes used for G10/FR4 apply to the high-temperature grades — carbide or diamond tooling, ±0.1–0.3 mm typical tolerances, prototypes to production batches:
- High temperature insulating washers and shoulder washers — see the custom insulating washers hub for sizing
- Spacers, standoffs, and sleeves for hot assemblies
- Insulating panels, terminal boards, and busbar supports cut to drawing — see G10 & FR4 machined parts for capability detail
- Custom profiles — any geometry definable on a drawing
Frequently Asked Questions
What is the temperature limit of G11 and FR5?
G11 is typically rated for continuous service in the 155–180 °C class; FR5 around 155 °C. Exact limits depend on the laminate manufacturer, thickness, load, and exposure time — confirm with the datasheet for the specific lot.
Is FR5 the same as FR4?
No. Both are flame retardant (UL94 V-0 class), but FR5 uses a high-Tg resin for service to ~155 °C, while standard FR4 is rated around 130 °C. FR5 is sometimes called “FR4 High Tg”.
Is G11 stronger than G10?
At room temperature their strengths are comparable. G11’s advantage is retaining mechanical and electrical properties at elevated temperature, where G10 would already be past its limit.
Does “FR11” exist?
No — it is not a NEMA grade. Requests for FR11 almost always mean G11 or FR5. Send the temperature and flame requirements and we will map the correct grade.
Can G11/FR5 be CNC machined like FR4?
Yes — same tooling (carbide or diamond), same processes, same typical tolerances. The grade choice affects service temperature, not machinability.
When should I stay with standard FR4 instead?
When the assembly runs below ~130 °C and a flame rating is required, standard FR4 is the economical choice. Specify G11/FR5 only when sustained heat, hot spots, or thermal cycling justify the high-Tg resin.
Request a Quote for G11/FR5 Parts
Send your drawing with the operating temperature and any flame-rating requirement through the quote request page — we will confirm the correct grade (G11 or FR5) with a material datasheet and return a quotation within 24 hours.