Characterization of CEM-1 Boards
One of the more common substrates used in low-cost electronic packaging is composite epoxy material (CEM) laminate. This paper presents some of the key thermohygro-mechanical properties of CEM laminates used in printed circuit board (PCB) fabrication. CEM laminates are defined by material composition with some minimum performance specifications. NEMA1 grade CEM-1 laminates are composed of a cellulose paper core, sandwiched between two layers/ plies of continuous woven glass fabric, infiltrated with a flame-resistant epoxy resin binder NEMA grade CEM-3 laminates are similar, but with a chopped glass fiber core.
The thermal, mechanical, chemical, and electrical properties of CEM substrates can vary depending upon the type of epoxy resin used by the manufacturer, and the fiber selected for reinforcement of the surface layers. This range in material properties can necessitate characterization of the CEM substrate received from the vendor before eventual use.