Chapter 40 – Hermeticity Tests

Microelectromechanical systems (MEMS) often contain sensitive structures whose operating response strongly depends on ambient conditions. The demand for an hermetic package is therefore vital. Ideally, such a package should guarantee stable environmental conditions for more than 10 years. The small package size of most microsystems puts severe demands on the requirements of encapsulation methods. Hermeticity testing has therefore become a key technology driven by the rising demands in the development of sealing bond processes and end-of-line testing. This chapter deals with the details of hermeticity testing and discusses aspects of the kinetic gas theory and vacuum physics. The basics of leakage measurement, pressure measurement based test methods and test methods based on the direct measurement of the amount of gas inside a cavity are discussed and the requirements for getters in modern MEMS enclosures are covered briefly.