A New High-Sensitivity Package-Leak Testing Method for MEMS Sensors

A new high-sensitivity package-leak testing method has been developed for micro electro mechanical system (MEMS) sensors such as a vibrating angular-rate sensor housed in a vacuum package. Procedures of the method to obtain high leak-rate resolution are as follows. (1) A package filled with helium gas is kept in a small and closed chamber to accumulate helium gas leaking out of the package. (2) The chamber is chilled with liquid-N₂ after the accumulation to reduce background gases except the helium gas. (3) The helium gas is transported to a mass spectrometer in a short time and recorded as a transient waveform. The leak-rate resolution of 1times10^-17 Pamiddotm³/s was obtained. This resolution was 10⁵ times superior to that of the conventional method.