Composite Epoxy Materials (CEM) are a group of composite materials typically made from woven glass fabric surfaces and non-woven glass core combined with epoxy synthetic resin. They are typically used in printed circuit boards. CEM-1 and CEM-3, designated by NEMA, are PCB base materials.
According to “k. Continuous Filament Glass Cloth, Epoxy-Resin Binder” of MIL-I-24768 (25 February 1992),
CEM-1 – Glass Cloth Base, Epoxy-Resin, Cellulose Core
CEM-3 – Glass Cloth Base, Epoxy-Resin, Nonwoven Core
NEMA LI-1 Industrial Laminated Thermosetting Products was revised in 1999 to mirror MIL-I-24768 with the intention of replacing this Military Specification. According to Composite-Base Laminates in NEMA LI 1-1998 (R2011) Industrial Laminating Thermosetting Products,
Grade CEM-1: Laminated with continuous-filament glass cloth surfaces and a cellulose core, all with a flame-resistant epoxy resin binder. With good punching practice, sheets up to and including 0.094 inch in thickness may be punched at temperatures not less than 23℃ (73℉) and in thickness over 0.094 inch up to and including 0.125 inch, when warmed to a temperature not exceeding 66℃ (150℉). Meets UL 94 V-0 when tested in accordance with UL 94.
Grade CEM-3: Laminated with continuous-filament glass cloth surfaces and a non-woven glass core, all with a flame-resistant epoxy resin binder. Property values approach those of FR-4. With good punching practice, sheets up to and including 0.062 inch in thickness may be punched at temperatures not less than 23℃ (73℉) and in thickness over 0.062 inch, up to and including 0.125 inch when warmed to a temperature not exceeding 66℃ (150℉). Meets UL 94 V-0 when tested in accordance with UL 94.
CEM-1 is used to fabricate single-sided boards, and CEM-3 is used to fabricate double-sided boards. Click below to find your CEM-1 and CEM-3 base materials from Kingboard (KB).