METHOD FOR TESTING HERMETICAL SEAL OF PACKAGE FOR PIEZOELECTRIC ELEMENT

PROBLEM TO BE SOLVED: To perform a hermetical seal test of the interior of a package in a simple means with accuracy by changing ambient pressure and capturing the presence or absence of a change in pressure in the package with the changes of ambient pressure as a change in the impedance of a piezoelectric element. SOLUTION: The external terminals 11a and 11b of a package 6 for a piezoelectric element are mounted on the external terminals 5a and 5b of a measuring jig 3 so as to be connected to each other. Then through the use of an impedance measuring device 2, the impedance of the piezoelectric element (quartz oscillator) in atmospheric pressure is measured. Next, through the use of a vacuum pump, the inside of the measuring jig 3 is decompressed, and the impedance of the piezoelectric element at this time is measured. As air pressure in the package 6 does not change with the decompression of the interior of the package 6 in the case the sealing of the package 6 is complete, there is no change in impedance. On the other hand, in the case the sealing is incomplete and that the interior fails hermetically, the interior of the package 6 is decompressed with the decompression of the interior of the measuring jig 3, and the impedance changes with this.