However, a large proportion of ceramic multichip modules are of the cofired** variety, in which case they are formed from a material such as aluminum nitride or beryllium oxide and can contain hundreds of layers. (**I???m sure it won???t surprise you to learn that topics like thick-film, thin-film, and co-fired ceramics are more fully explained in Bebop to the Boolean Boogie [grin])Ceramic, glass,