ABSTRACT
Microelectromechanical system (MEMS) devices, as they are defined, are both electrical and mechanical devices. Via microlevel mechanical operation, MEMS devices, as sensors, transform mechanical, chemical, optical, magnetic, and other nonelectrical parameters to electrical or electronic signals, and as actuators, MEMS devices transform electrical or electronic signals to nonelectrical or electronic operations. Therefore, MEMS devices very often interact with the environment electrically, magnetically, optically, chemically, and mechanically. In order to support these nonconventional device operations (i.e., the device’s mechanical operation and the nonelectrical interactions between a MEMS device and its environment), new packaging capabilities beyond those provided by conventional integrated circuit (IC) packaging technology are required [Madou, 1997]. A chemically inert, optically dark, and electromagnetically “quiet” environment for packaging conventional ICs, provided by hermetic sealing and electromagnetic screening, is no longer suitable for packaging most MEMS devices. Because MEMS devices have 12-2very specific requirements for their immediate packaging environment, it is expected that the design of MEMS packaging will be very device-dependent. This is in contradiction to the conventional IC packaging practice, in which a universal package design can accommodate many different ICs. Compared to conventional IC packaging, the most distinct issue of MEMS packaging is to meet the requirements imposed by device mechanical operability, nonelectrical signal exchange, and thermomechanical reliability of MEMS devices.
