Tuning-fork type quartz-crystal vibrating pieces and piezoelectric devices having low crystal impedance

摘要

Tuning-fork type quartz-crystal vibrating pieces are disclosed, of which the vibration frequency can be adjusted without increasing CI. An exemplary piezoelectric device has a pair of vibrating arms extending in a predetermined direction from a first edge of a base. Respective first grooves are defined in a first principal surface of the vibrating arms. The first grooves extend in the predetermined direction, and have first excitation electrodes extending from a back-edge surface but not completely to a front-edge surface of the grooves. Respective second grooves are defined in a second principal surface, opposite the first principal surface, of the vibrating arms. The second grooves extend in the predetermined direction, and have second excitation electrodes extending from a back-edge surface completely to a front-edge surface of the second grooves.

主权项

1. A tuning-fork type quartz-crystal vibrating piece, comprising:
first and second vibrating arms extending from a first edge of a base in a predetermined direction and having respective weights on distal tips thereof; respective first grooves defined on first principal surfaces of the vibrating arms, the first grooves being respective recesses extending in the predetermined direction and extending depthwise from the respective first principal surfaces; and respective second grooves defined on second principal surfaces, opposing the first principal surfaces, of the vibrating arms, the second grooves being respective recesses extending in the predetermined direction and extending depthwise from the respective second principal surfaces; the first and second grooves each having a respective length and sides, a respective lower main surface, a respective back-edge surface located toward the base and a respective front-edge surface located toward the weight; the first grooves include respective first excitation electrodes extending over the respective back-edge surface and on the respective sides and lower main surface toward the respective front-edge surface but not including the respective front-edge surface, the first excitation electrodes having a length that is less than the length of the first grooves; the second grooves include respective second excitation electrodes extending over the respective back-edge surface to the respective front-edge surface, including the respective front-edge surface, respective side surfaces and respective lower main surfaces, the second excitation electrodes each having a length equal to the length of the respective second groove; and the length of the first excitation electrodes is less than the length of the second excitation electrodes.