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

摘要

A piezoelectric filter device having one or more pairs of piezoelectric resonators for forming a ladder-type filter circuit, a plurality of terminal plates including an input and output terminal plates for electro-mechanically holding respective resonators at oscillation nodes, and a casing for containing the piezoelectric resonators and the terminal plates and having an opening which is closed by an insulating filler, in which the opening has an inner peripheral rough surface with which the insulating filler is securly bonded. The casing has a connecting extention extending from the bottom wall thereof which is longer than cranked or bent connecting legs of the input and output terminal plates. Alternatively, each cranked or bent connecting leg has a width larger than that of its tip portion to be connected to a printed-circuit board.