FR-4 and G-10 are the most versatile all-around of the laminate grades and are made by impregnating an epoxy resin binder into continuous glass woven fabric. G10/FR4 has extremely high mechanical strength, good dielectric loss properties, and good electric strength properties, both wet and dry. G10/FR4 are widely used in the electronics field – primarily because water absorption is virtually nil, rendering it an excellent insulator.
The difference between G10 and FR4 is that FR4 is a fire-retardant grade of G10. FR4 can be safely substituted when G10 is called out, while G10 can never be substituted where FR4 is called for.
Color: yellowish to light green
G10 specifies to MIL-I-24768/2 (GEE), MIL-P-18177 GEE and LP-509)
FR4 specifies to MIL-I-24768/27 (GEE-F) and MIL-P-18177 GEE-F