FR-4 vs G-10: What Is the Difference and Which Should You Choose?

FR-4 and G-10 are both epoxy glass cloth laminates made by hot-pressing woven E-glass cloth impregnated with epoxy resin. They look similar and share excellent mechanical strength and electrical insulation, but there is one decisive difference.

The key difference: flame retardancy

FR-4 is flame-retardant and meets UL94 V-0, meaning it self-extinguishes when the flame source is removed. Standard G-10 is not flame-retardant. In fact, FR-4 began as the flame-retardant version of G-10 — the "FR" stands for flame retardant.

When to choose FR-4

Choose FR-4 whenever fire safety standards apply: printed circuit boards, electrical enclosures, switchgear and most electronic equipment. It is the global default for electrical insulation.

When to choose G-10

Choose G-10 when you need the absolute highest mechanical strength and fire safety is not a requirement — for example structural insulators, cryogenic supports, knife liners and precision machined parts. G-10 typically offers marginally higher mechanical strength because it is not loaded with flame-retardant additives.

Summary

If in doubt, FR-4 is the safer general-purpose choice. If you need maximum strength for a non-fire-rated structural part, G-10 is ideal. We supply both grades from 0.5 mm to 100 mm thick, cut to size, with factory-direct export worldwide.