1. Field of the Invention
The present invention relates to an energy trap type piezoelectric resonance component, and more particularly, it relates to a chip-type piezoelectric resonance component preferably utilizing a shear vibration mode of thickness shear vibration of width shear vibration, which can be surface-mounted on a printed circuit board or the like.
2. Description of the Background Art
FIG. 2 is a perspective view showing an exemplary piezo-resonator part of a conventional energy trap type piezoelectric resonance component utilizing a width shear vibration mode. A piezo-resonator 1 comprises an elongated rectangular piezoelectric substrate 2 and excitation electrodes 3 and 4 which are provided on both side surfaces thereof. The piezoelectric substrate 2 is polarized along arrow P. The excitation electrodes 3 and 4 are located to be opposed to each other through the piezoelectric substrate 2, so that vibration is excited by the opposed portions of the excitation electrodes 3 and 4. Further, the excitation electrodes 3 and 4 are arranged to reach different ends of the piezoelectric substrate 2, whereby the piezo-resonator 1 is electrically connected with the exterior and mechanically held on both ends of the piezoelectric substrate 2.
In order to form a chip-type piezoelectric resonance component for surface mounting by the aforementioned piezo-resonator 1, a pair of spacer plates are arranged on both side surfaces of the piezo-resonator 1 through clearances for allowing vibration of the piezoelectric substrate 2, while upper and lower portions thereof are held by a pair of case substrates through frame members etc. serving as spacers for allowing vibration, thereby preparing a chip-type laminate.
In the aforementioned energy trap type piezo-resonator 1, vibration as excited is trapped in a part between the opposed portions of the excitation electrodes 3 and 4, i.e., in a vibrating part, and this vibration is sufficiently damped in the vicinity of both ends of the piezoelectric substrate 2. Even if the piezoelectric substrate 2 is mechanically held on its both ends, therefore, resonance characteristics are hardly deteriorated.
A plurality of such piezo-resonators 1 are generally mass-produced by forming mother excitation electrodes on a mother piezoelectric substrate and thereafter cutting the mother substrate. In order to increase the number of piezo-resonators which can be manufactured from a single mother piezoelectric substrate thereby improving mass productivity, therefore, it is desirable to reduce the length L of each piezoelectric substrate 2. Further, miniaturization is required for piezo-resonators similarly to other electronic components, and it is desirable to reduce the length L of each piezoelectric substrate 2.
When the length L of the piezoelectric substrate 2 is reduced, however, vibration is insufficiently damped in the vicinity of both ends of the piezoelectric substrate 2. When the piezoelectric substrate 2 is mechanically held at both ends, thereof the resonance characteristics are disadvantageously deteriorated. Particularly in the piezo-resonator 1 shown in FIG. 2, the resonance characteristics are determined by the width of the piezoelectric substrate 2, while it is impossible to sufficiently damp vibration when the width of the piezoelectric substrate 2 is increased to implement a low frequency band, unless the length L thereof is also increased in response. In general, therefore, it has been extremely difficult to attain sufficient resonance characteristics while reducing the length L of the piezoelectric substrate 2.