During the early development of commercial microelectromechani-

cal systems (MEMS) products, the reduction of costs was inhibited

by the wide variety of non-standard manufacturing processes, ma-

terials and packaging. In many cases, packaging was the dominant

cost. In recent years, much of theMEMS industry hasmoved to using

silicon as a material, with silicon processes and standard integrated

circuit (IC)-like plastic packages (Gilleo, 2005). For example, MEMS

accelerometers are silicon-based and typically use quad flat no.

(QFN) (see Fig. 6.3) plastic packages. The QFN form is known as an

open-cavity package and is completed by the bonding of a plastic lid

to form a hermetic seal.