JPH0245845B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a piezoelectric resonator such as a crystal resonator.

[Prior art and its problems] Conventionally, a crystal resonator that performs thickness-shear vibration has drive electrodes provided at the center of both principal surfaces. The oscillation frequency of this crystal resonator has been adjusted by adding silver or the like to the drive electrode by vacuum deposition, or by removing (trimming) the electrode film at the center of the drive electrode using a laser beam.

However, adjustment using the added mass effect has a problem in that workability is extremely poor because the atmosphere during adjustment must be kept in a vacuum.

In addition, trimming adjustment using a laser beam has the problem that thermal shock is applied to the center of the crystal piece, which is most sensitive to oscillation, so that changes over time due to thermal shock are unavoidable.

Furthermore, in the past, it has been known that the drive electrode is divided into two parts (for example,
Publication No. 49386, Japanese Unexamined Patent Publication No. 1983-13806, Japanese Unexamined Patent Publication No. 1987-13806
-157463, etc.), but in all of these known devices, the extraction electrodes from the split electrodes are connected to a holding member separately, and the oscillation frequency is adjusted by cutting the extraction electrodes in the middle. isn't it.

[Object of the Invention] An object of the present invention is to provide a piezoelectric vibrator that can easily adjust the oscillation frequency and maintain stable oscillation accuracy for a long period of time without applying thermal shock to the center of the piezoelectric element. It is something.

[Means for Achieving the Object] In order to achieve the above object, the piezoelectric vibrator according to the present invention has a pair of driving electrodes formed at the center of both main surfaces of the piezoelectric element so as to face each other. At least one of the electrodes is divided into a plurality of small electrodes, and from each of the small electrodes, lead electrodes extending to the outer periphery of the piezoelectric element are separated from each other and collected at one location. Each of the extraction electrodes is mechanically and electrically connected to the same holding member at the outer periphery of the piezoelectric element, and the oscillation frequency can be adjusted by cutting any of the extraction electrodes in the middle.

[Embodiments] Hereinafter, the present invention will be described in detail with reference to preferred embodiments shown in the accompanying drawings.

In FIGS. 1 and 2, reference numeral 1 denotes a piezoelectric vibrator that performs thickness-shear vibration, and drive electrodes 3 and 4 are provided on both main surfaces 2a and 2b of a crystal piece 2 that is a piezoelectric element, respectively, in a vacuum state. It is formed by a method such as vapor deposition.

On the other hand, the drive electrode 3 formed on the main surface 2a has a plurality of small electrodes 3A, 3B, . . . formed by horizontal slits.
It is divided into 3I. These small electrodes 3A, 3
B...3I has lead electrodes 3 each led to the outer peripheral edge of the crystal piece 2 so as to be electrically connected.
a, 3b...3i are formed.

The drive electrode 4 formed on the other main surface 2b of the crystal blank 2 is a single circular electrode.
From there, a lead electrode 4a is formed extending to the outer peripheral end.

The extraction electrodes 3a, 3b...3i and the extraction electrode 4a are each extracted in opposite directions,
The crystal piece 2 is mechanically and electrically connected and held to holding members (holding springs) 5 and 6 via a conductive adhesive (not shown) at these extraction electrode portions.

Generally, the oscillation frequency of the crystal resonator 1 that performs thickness-shear vibration is as follows: is given by In the above formula, t is the thickness of the crystal piece, C ₆₆ is the elastic constant, and ρ is the density.

Now, if the thickness t of the crystal piece is 0.42 mm = 0.42 × 10 ^-3 m, the density of the crystal piece is ρ = 2.34 × 10 ³ Kg/m ³ , and the electric field where all the extraction electrodes 3a, 3b...3i are connected is The elastic constant for a constant case is C ^E ₆₆ = 29.326×
By taking values close to 10 ⁹ N/m ² and substituting these into the above equation, fs ₁ =3.943MHz.

In addition, the elastic constant when the electrical displacement is constant when all the extraction electrodes 3a, 3b...3i are cut is C ^D ₆₆ =
Taking a value close to 28.967×10 ⁹ N/m ² and substituting this into the above equation yields fs ₂ =3.968MHz.

In other words, crystal oscillator 1 starts from 3.968MHz.
The oscillation frequency can be adjusted up to 3.943MHz as shown in the third diagram.

FIG. 4 shows a state in which the extraction electrodes 3a and 3i are cut in order to adjust the oscillation frequency of the crystal resonator 1.

In this case, the oscillation frequency will be higher than when all the extraction electrodes shown in the first figure are connected. The rate of change in oscillation frequency when one extraction electrode is cut is:
Measure it experimentally in advance. Then, by appropriately cutting the extraction electrode, the oscillation frequency can be brought close to the target oscillation frequency.

When cutting the extraction electrode with a laser beam,
Cutting can be done in air. Furthermore, since the thermal shock caused by the laser beam is applied to the outer periphery of the crystal piece 2, the center part, where vibrational displacement is large, is not affected, and oscillation accuracy can be stably maintained over a long period of time.

FIG. 5 shows another embodiment of the invention.

The crystal resonator 11 is composed of a crystal piece 12 that performs thickness-shear vibration, and drive electrodes 13 and 14 formed on both main surfaces of this crystal piece.
3 is constituted by small electrodes 13A, 13B, . These small electrodes 13A, 13B, 13E
From there, the extraction electrodes 13a and 1 are extended to the outer periphery, respectively.
3b...13e are formed to extend. The other drive electrode 14 is a single circular electrode, and an extraction electrode 14a is formed extending to the outer periphery of the other drive electrode 14.

This crystal resonator 11 also has extraction electrodes 13A, 1
The oscillation frequency is adjusted by cutting 3B...13E in the middle, but the cutting is done at the extraction electrodes 13e,
Perform steps 13d, 13c, and 13b in this order. By cutting in this manner, the remaining small electrode group becomes circular, so it matches well with the circular drive electrode on the other side, and efficient excitation can be performed.

Although a thickness-shear crystal vibrator is shown as an example of the piezoelectric vibrator, it is also possible to use other vibration modes and other piezoelectric elements. It is also possible to divide both drive electrodes into a plurality of small electrodes.

[Effects of the Invention] According to the piezoelectric vibrator of the present invention, the oscillation frequency can be adjusted by cutting the extraction electrode located on the outer periphery of the piezoelectric element in the middle using a laser beam or the like, and as a result, the piezoelectric element Since no thermal shock is applied to the central part of the piezoelectric vibrator, it is possible to provide a piezoelectric vibrator with stable oscillation accuracy.

[Brief explanation of drawings]

Fig. 1 is a front view of an embodiment of a piezoelectric vibrator according to the present invention, Fig. 2 is a rear view thereof, Fig. 3 is a characteristic diagram showing changes in the oscillation frequency, and Fig. 4 is a diagram after adjusting the oscillation frequency. FIG. 5 is a front view of another embodiment. 2, 12...Piezoelectric element (crystal piece), 3, 4, 1
3, 14... Drive electrode, 3A-3E, 13A-1
3E...Small electrodes, 3a to 3e, 13a to 13e...
...extraction electrodes of small electrodes, 4a, 4b...extraction electrodes of circular electrodes, 5, 6...holding members.

Claims (1)

[Scope of Claims] 1. At least one of a pair of drive electrodes formed in a mutually opposing relationship at the center of both main surfaces of a piezoelectric element is divided into a plurality of small electrodes; From each of them, extraction electrodes extending to the outer periphery of the piezoelectric element are formed separated from each other and collected in one place, and each of the extraction electrodes is mechanically and electrically extended to the outer periphery of the piezoelectric element. A piezoelectric vibrator, characterized in that the piezoelectric vibrator is connected to the same holding member at both ends thereof, and the oscillation frequency can be adjusted by cutting one of the lead-out electrodes midway.