Piezoelectric filter in a casing sealed by an insulating filler and having cranked connecting legs

Claim 1

A piezoelectric filter device comprising at least one pair of piezoelectric resonators, a plurality of terminal plates, including input and output terminal plates, which are electrically connected to and mechanically support respective resonators of the at least one pair of resonators at oscillation nodes thereof, the input and output terminal plates being respectively provided with connecting legs having a configuration which is in the shape of a crank and which, in use, provide mounting of the piezoelectric filter device on a surface of a printed circuit board, a casing which houses the piezoelectric resonators and the terminal plates, at least one insulating plate disposed within said casing between one of said terminal plates and said casing, said resonators and terminal plates being connected together in stacked relation so as to define a ladder-type filter circuit, and said casing having an opening through which the connector legs externally project, and an insulating filler closing off the opening of the casing, the opening of the casing being provided with an inner peripheral rough surface which is bonded to the insulating filler, said casing including a lower wall and a connecting extension which extends from said lower wall, said connecting legs each having a free end, and said extension having a free end and being of a length, measured from the free end of said extension to said insulating filler, greater than the perpendicular distances between the free ends of the connecting legs of the terminal plates and the insulating filler.