Piezoelectric resonator

Details Piezoelectric resonator Piezoelectric resonator

2000-11-06

2001-12-25

Ramirez, Nestor (Department: 2834)

Electrical generator or motor structure

Non-dynamoelectric

Piezoelectric elements and devices

C310S365000

Reexamination Certificate

active

06333591

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a piezoelectric resonator using the third harmonic of a thickness vertical vibration mode, and more particularly, the present invention relates to a piezoelectric resonator that effectively utilizes the resonance characteristics generated by the third harmonic while preventing the generation of a fundamental wave that produces spurious responses.
2. Description of the Related Art
Conventionally, an energy-trap type piezoelectric resonator has been widely used in piezoelectric oscillators and other devices. Japanese Unexamined Patent Application Publication No. 6-112756 discloses a piezoelectric resonator using the third harmonic of a thickness vertical vibration as a resonator which can be used in a higher frequency range.
As illustrated in
FIG. 10
, in a conventional piezoelectric resonator
51
, an excitation electrode
53
is located at the central portion of the upper surface of a piezoelectric substrate
52
made of a piezoelectric ceramic. At the central portion of the lower surface of the piezoelectric substrate
52
, another excitation electrode (not shown) is arranged so as to be opposed to the excitation electrode
53
with the piezoelectric substrate
52
disposed therebetween. These excitation electrodes disposed on both main surfaces define an energy-trap type piezoelectric resonance section utilizing a third harmonic of a vertical vibration mode.
On the upper surface of the piezoelectric substrate
52
, a lead-out electrode
54
is connected to the excitation electrode
53
, and a terminal electrode
55
is connected to the outside end of the lead-out electrode
54
. Likewise, on the lower surface of the piezoelectric substrate
52
, a lead-out electrode and terminal electrode are connected to the excitation electrode. The terminal electrode located on the lower surface is, however, disposed at the opposite end from the terminal electrode
55
located on the upper surface on the piezoelectric substrate
52
.
Also, the piezoelectric resonator
51
is coated with a damping material
56
consisting of resin. The damping material
56
is disposed outside of the area between the excitation regions of the fundamental wave and the third harmonic of the thickness vertical vibration when the piezoelectric resonator
51
is driven. That is, in the piezoelectric resonator
51
utilizing a thickness vertical vibration mode, the excitation region of the fundamental wave is located outside that of the third harmonic. Therefore, applying the damping material
56
to the area outside of the area between the two excitation regions permits utilization of the third harmonic by damping only the fundamental wave and weakly damping the third harmonic.
In this case, the diameter of a circular opening
56
a
where the damping layer is not applied is six to twelve times as long as the wavelength of the third harmonic used.
In the piezoelectric resonator
51
, however, the accuracy of applying and arranging the damping material
56
is not sufficient, and therefore, the piezoelectric resonator
51
cannot sufficiently damp the fundamental wave.
Also, since the damping material
56
is arranged to surround the excitation electrode
53
, the piezoelectric resonator
51
must have a much larger size than the diameter of the opening
56
a
of the damping material
56
. This makes it difficult to reduce the size of the piezoelectric resonator
51
.
In addition, since the damping material
56
is arranged to surround the excitation electrode
53
, there is a risk of a crack being generated in the piezoelectric substrate
52
when a thermal shock, an external force, or other stress is applied to the piezoelectric substrate
52
.
SUMMARY OF THE INVENTION
To overcome the problems described above, preferred embodiments of the present invention provide a much smaller energy-trap type piezoelectric resonator that maximizes damping of a fundamental wave of a thickness vertical vibration mode with ease and accuracy, while effectively utilizing the resonance characteristics generated by the third harmonic of the thickness vertical vibration mode.
The piezoelectric resonator according to a preferred embodiment of the present invention includes a piezoelectric substrate, first and second excitation electrodes located on portions of first and second main surfaces of the piezoelectric substrate, respectively, and opposed to each other via the first and second excitation electrodes on the top and bottom surfaces, first and second lead-out electrodes electrically connected to the first and second excitation electrodes, respectively, and located on the first and second main surfaces of the piezoelectric substrate, respectively, and first and second terminal electrodes arranged to establish external connections, located at the end portions of the respective first and second lead-out electrodes, the end portions being opposed to the sides where the respective first and second excitation electrode are connected. Each of the terminal electrodes is arranged to occupy an area not less than about 10% of the area of an annular region which extends over a normal-line distance of about 1.2 d to about 2 d from the outer peripheral edge of each of the excitation electrodes, where d is the diameter of each of the excitation electrodes.
In another aspect of various preferred embodiments of the present invention, solder is provided on at least a portion of the first and second main surfaces of the piezoelectric substrate, which occupies an area not less than about 10% of the area of the region between the excitation regions of the fundamental wave and the third harmonic in the terminal electrode.
In still another aspect of various preferred embodiments of the present invention, solder is provided over the entire upper surfaces of the terminal electrodes.
The piezoelectric resonator in accordance with another preferred embodiment of the present invention may further include first and second lead terminals bonded to the respective first and second terminal electrodes by soldering.
The piezoelectric resonator in accordance with other preferred embodiments of the present invention may be constructed as a chip type piezoelectric resonance component.
The above and other novel features, characteristics, advantages and elements of the present invention will become more apparent from the following detailed description of preferred embodiments thereof with reference to the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the present invention.


REFERENCES:
patent: 6-112756 (1994-04-01), None

Affiliated with

Also associated with

Rating

Piezoelectric resonator does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Piezoelectric resonator, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Piezoelectric resonator will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2594658