Composite Epoxy Materials (CEM) are group of composite material

Composite material

Composite materials, often shortened to composites or called composition materials, are engineered or naturally occurring materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct at the macroscopic or...

s typically made of woven glass fabric surfaces and non-woven glass core combined with epoxy resin. They are typically used in the printed circuit board

Printed circuit board

A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring...

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There are different types of CEMs:

CEM-1 is low cost, flame retardant, cellulose paper based laminate with only one layer of woven glass fabric.

CEM-2 has cellulose paper core and woven glass fabric surface.

CEM-3 is very similar to the most commonly used PCB material, FR4. Its color is white and it is flame retardant.

CEM-4 quite similar as CEM-3 but not flame retardant.

CEM-5 (also called CRM-5) has polyester woven glass core.