FR-1, like FR-2, typically specified to 105 °C, some grades rated to 130 °C. Room-temperature punchable. Similar to cardboard. Poor moisture resistance. Low arc resistance.
FR-3, cotton paper impregnated with epoxy. Typically rated to 105 °C.
FR-5, woven fiberglass and epoxy, high strength at higher temperatures, typically specified to 170 °C.
FR-6, matte glass and polyester
G-10, woven glass and epoxy - high insulation resistance, low moisture absorption, very high bond strength. Typically rated to 130 °C.
G-11, woven glass and epoxy - high resistance to solvents, high flexural strength retention at high temperatures.Typically rated to 170 °C.
CEM-1, cotton paper and epoxy
CEM-2, cotton paper and epoxy
CEM-3, non-woven glass and epoxy
CEM-4, woven glass and epoxy
CEM-5, woven glass and polyester
PTFE, ("Teflon") - expensive, low dielectric loss, for high frequency applications, very low moisture absorption (0.01%), mechanically soft. Difficult to laminate, rarely used in multilayer applications.
PTFE, ceramic filled - expensive, low dielectric loss, for high frequency applications. Varying ceramics/PTFE ratio allows adjusting dielectric constant and thermal expansion.
RF-35, fiberglass-reinforced ceramics-filled PTFE. Relatively less expensive, good mechanical properties, good high-frequency properties.
Alumina, a ceramic. Hard, brittle, very expensive, very high performance, good thermal conductivity.
Polyimide, a high-temperature polymer. Expensive, high-performance. Higher water absorption (0.4%). Can be used from cryogenic temperatures to over 260 °C.