JPH0352312A - Piezoelectric resonator - Google Patents

Abstract

PURPOSE:To prevent the deterioration in the resonance characteristic by arranging 1st and 2nd capacitor electrodes opposite to each other with a prescribed interval from 1st and 2nd resonance electrodes on a piezoelectric substrate, opposing the 1st and 2nd capacitor electrodes on the front and rear sides with the piezoelectric substrate inbetween and connecting them electrically. CONSTITUTION:A 1st resonance electrode 22a is formed to nearly the center of an upper face of a piezoelectric substrate 21, a 2nd resonance electrode 22b is formed to a lower side of the piezoelectric substrate 21 and the resonance electrodes 22a, 22b form the resonance section. A couple of first capacitor electrodes 25, 26 are formed to the upper face of the piezoelectric substrate 21 at a prescribed interval with the resonance electrode 22a and similarly, a couple of 2nd capacitor electrodes 27, 28 are formed to positions opposite to front and rear sides with the resonance electrodes 22a, 22b via the piezoelectric substrate 21 with a prescribed interval with the resonance electrode 22b via the piezoelectric substrate 21. Thus, a capacitor is formed so that capacities are taken out respectively between the 1st and 2nd resonance electrodes 22a, 22b and the 1st and 2nd capacitor electrodes 25-28. Thus, the piezoelectric substrate part on which the capacitor electrodes 25-28 are formed is does not resovate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a piezoelectric resonator with a built-in capacitance, and particularly to a piezoelectric resonator with an improved electrode structure for exerting capacitance. [Prior art] The oscillator with built-in load capacitor shown in the circuit diagram in Fig. 2 is as follows.
Conventionally, a structure in which a piezoelectric resonator is combined with a capacitive electrode has been used.

An example of the conventional structure of a resonator with built-in load capacitance is shown in Figure 3 (a).
) and (b). A first resonant electrode 2 is formed on the upper surface la of the piezoelectric substrate l, and a second resonant electrode 3 is formed on the lower surface 1b. The first and second resonant electrodes 2 and 3 are formed so as to face each other with the piezoelectric substrate 1 interposed therebetween.

Resonant electrodes 2.3 are connected to input/output terminal electrodes 4a. 4
It is electrically connected to b by a conductive pattern. Here, the terminal electrodes 4a, 4b are given a certain extent, and capacitive electrodes 5a, 5b facing the terminal electrodes 4a, 4b are formed on the upper surface 1a and lower surface tb of the piezoelectric substrate 1, respectively. The capacitive electrodes 5a, 5b are electrically connected to a connecting electrode 6 formed on the side surface of the piezoelectric substrate 1 via a conductive pattern. Therefore, by using the terminal electrodes 4a and 4b as input/output terminals and the connecting electrode 6 as a ground terminal, it can be used as the resonator with built-in load capacitance shown in FIG. Further, in the piezoelectric resonator 7 shown in FIG. 4, protective substrates 9a and 9b made of dielectric ceramics are attached to the upper and lower surfaces of the piezoelectric resonator unit 8 in which resonant electrodes are formed so as to face each other. First and second resonant electrodes that control the piezoelectric resonant unit are connected to external electrodes 10a and 10b.

A capacitive electrode 11 is formed so as to surround the piezoelectric resonator 7 at a predetermined distance from the external electrodes 10a and 10b. Here, external electrodes 10a and 1 which serve as human output terminal electrodes are shown.
0b and the capacitive electrode 11, each capacitance is taken out.

[Technical problem to be solved by the invention] In the piezoelectric resonator shown in FIG. It had to be relatively large.

In addition, since the capacitance is taken out between a pair of electrodes facing each other via the piezoelectric substrate 1, piezoelectric vibrations such as thickness vibrations are excited between the opposing T electrodes as charges are charged and discharged, resulting in deterioration of resonance characteristics. There was also the problem of However, if the polarization of the piezoelectric substrate 1 is removed in the portion from which the capacitance is taken out, the resonance characteristics can be improved, but in that case, the steps such as polarization treatment become complicated, resulting in poor yield and reduced mass productivity.

On the other hand, in the conventional example shown in FIG. 4, since the protective substrates 9a and 9b made of dielectric ceramics are attached to the piezoelectric substrate 8, it is difficult to match the capacitance-temperature characteristics of the piezoelectric substrate 8 and the protective substrates 9a and 9b, and the frequency There were stability issues. In addition, complicated manufacturing processes such as attaching the protective substrates 9a and 9b are required. An object of the present invention is to provide a small-sized piezoelectric resonator with built-in capacitance, which is unlikely to suffer from deterioration of resonance characteristics and has excellent stability of characteristics against temperature changes.

[Effect]

In the present invention, first. A resonant section is defined by the second resonant electrode, and the capacitance is extracted between the first and second resonant electrodes and the first and second capacitor electrodes.

Since the first and second capacitive electrodes, which are electrically connected to each other, are arranged so as to face each other with the piezoelectric substrate in between, the portion of the piezoelectric substrate where the capacitive electrodes are formed does not resonate. In addition, leakage of vibrations from the resonant part is effectively damped in the piezoelectric substrate part where the capacitive electrodes are placed facing each other. In addition, since the first and second capacitive electrodes formed on both main surfaces of the piezoelectric substrate are electrically connected by the connecting electrode, the capacitive electrode also functions to electromagnetically shield the resonant part. .

[Explanation of Examples]

FIG. 1 is a plan view of a piezoelectric resonator according to an embodiment of the present invention. The piezoelectric substrate 21 is made of a suitable piezoelectric material and is polarized uniformly in the thickness direction.

A first resonant electrode 22a is provided approximately at the center of the upper surface of the piezoelectric substrate 21.
is in great shape. As is clear from FIGS. 5(a) and 5(b), there is a second resonant electrode 2 on the bottom surface of the piezoelectric substrate 2l.
2b is taking shape. The second resonant electrode 22b
It has the same shape as the resonant electrode 22a.

The first resonant electrode 22a is electrically connected to an input terminal electrode 24a shaped along the edge of the piezoelectric substrate 2l via a conductive pattern 23a. Similarly, on the lower surface side of the piezoelectric substrate 2l, the second common
The lii electrode 22b is electrically connected to the output terminal electrode 24b (see FIG. 5(a)) via a conductive pattern 23b. In addition, as shown in FIG. 5(a), the input side terminal electrode 24
A is shaped so as to reach the bottom surface of the piezoelectric substrate 21 via the side surface thereof. The output side terminal electrode 24b is also arranged in the same manner and is formed so as to reach the upper surface of the pressure-tight substrate 21.

With the first and second resonant electrodes 22a and 22b described above,
In this embodiment, a resonator is configured.

Next, the configuration of the capacitor section will be explained.

On the upper surface of the piezoelectric substrate 2l, a pair of first capacitive electrodes 25 and 26 are formed at a predetermined distance from the first resonant electrode 22a. That is, the resonant electrode 22a and the capacitive electrode 2
The capacity is taken out between 5.5 and 26, respectively.

Similarly, a second resonant electrode 2 is also provided on the lower surface side of the piezoelectric substrate 2l.
2b and a pair of second capacitive electrodes 27.2 separated by a predetermined distance.
8 is formed (see FIG. 5(b)). Although the planar shape of the second capacitor electrodes 27 and 28 is not particularly illustrated, the planar shape of the second capacitor electrodes 27 and 28 is the same as that of the first capacitor! It has the same shape as the electrodes 25 and 26,
And the first volume through the piezoelectric substrate 2l! i electrode 25.26
It is depicted in a position where the front and back are opposite each other. Therefore, also on the lower surface side of the piezoelectric substrate 21, capacitance is taken out between the second resonance electrode 22b and the second capacitance electrodes 27 and 28, respectively. The first capacitor electrodes 25 and 26 are electrically connected to the second capacitor electrodes 27 and 28 on the lower surface side through connecting conductive parts 29a and 29b, respectively. In other words, the first container on the top side! 11t pole 25
, 26 and the second capacitor electrodes 27, 28 on the lower surface side, connection conductive portions 29a, 29b are formed through the side surface of the piezoelectric base Fi21.

Therefore, in the piezoelectric resonator of this embodiment, the connecting conductive portion 29a
, 29b, all the capacitor electrodes are connected to the same potential. Then, by making this capacitive electrode part the ground terminal, the human power side terminal electrode 24a as the input terminal, and the output side terminal electrode 24b as the output terminal, a piezoelectric oscillator with a built-in load capacitance corresponding to the circuit shown in FIG. It can be realized. In the piezoelectric resonator of this example, the first capacitive electrode 25.26
and the second capacitive electrodes 2L and 28 are opposed to each other with the piezoelectric substrate 21 in between, but since the first and second capacitive electrodes are connected to the same potential, the first and second capacitive electrodes 25-2
The pressure that 8 is facing front and back! The substrate part does not resonate. In addition, leakage of vibration from the resonant portion is effectively damped because the charge generated by the vibration is short-circuited between the opposing capacitance tt poles.

Furthermore, the input side terminal electrode 24a and the output side terminal electrode 24b
The first . Since the second capacitor electrodes 25 to 28 are formed, the electromagnetic shield between the input and output terminal electrodes is also provided by the capacitor electrodes 25 to 28.
~28.

Note that if the shape of the connecting conductive parts 29a and 29b or the piezoelectric resonator is used as a chip component, it can be used simultaneously with the external electrodes if this is done at the time of forming the external electrodes. Moreover, the piezoelectric substrate 21 of the input/output side terminal electrodes 24a, 24b
and the first and second capacitor electrodes 2
For 5-2 days, mother's pressure! In the state of the board, the first
, second resonant electrode 22a. It can be formed at the same time as 22b. Therefore, it can be seen that the piezoelectric resonant element of this example is also excellent in mass productivity. Note that in the above embodiment, the first. second resonant electrode 22a,
First capacitive electrodes 25, 26 on both sides of 22b, respectively.
and second capacitor electrodes 27, 28, but only on one side are the first capacitor electrode and the second capacitor! You can also use poles. That is, the structure may be such that only the first capacitor electrode 25 and the second capacitor electrode 27 are used, or only the first capacitor electrode 26 and the second capacitor electrode 28 are used. ．． When the piezoelectric resonant element is a chip-shaped component, the sixth
As shown in the figure, protective substrates 30a and 30b made of an insulating material are attached to the upper and lower surfaces of the piezoelectric base Fi21 to form a closed space that does not hinder the vibration of the resonant part, and the external electrodes 31a, 3lb, 31c All you have to do is formulate a precept. In addition,
Safe! ! Since the substrates 30a and 30b are not used to form capacitance, there is no need to select dielectric ceramics with a focus on capacitance. Therefore, in the piezoelectric resonator of this embodiment, the problem that the capacitance temperature characteristics of the portion from which the capacitance is extracted does not match the capacitance temperature characteristics of the resonant portion does not occur. In the embodiment of FIG. 1 in which the first and second capacitive electrodes are shaped like
, a rectangular shape extending in the longitudinal direction of the piezoelectric substrate 21 is shown. However, the first and second
The planar shape of the capacitor electrode can be configured into any suitable shape in the remaining region excluding the region formed by the resonance electrode and the input/output terminal electrode. For example, as shown in FIG. 7, curved edges 32 similar to the outer peripheral edge of the resonant electrode 22a are formed on both sides of the resonant electrode 22a.
A first capacitive electrode 32.33 having electrodes 32 and 33a may be formed. In this case, the second capacitor electrode is the first capacitor! It has the same shape as the electrodes 32 and 33, and has a pressure of 1t and the substrate 21.
The front and back sides are arranged to face the first capacitance 1t poles 32 and 33 through the capacitors. Further, in the piezoelectric resonator shown in FIG. 8, the conductive pattern 23a connecting the resonant electrode 22a and the input terminal electrode 24a is formed from the center of the piezoelectric substrate 2l toward one end edge 2lb. Then, the curved edge 34a of the first capacitor electrode 34
However, it is made longer than the curved edge 32a in FIG. 7 by the amount that the conductive pattern 23a is gathered together. Further, the connecting conductive portion 35 that electrically connects the first capacitive electrode and the second capacitive electrode (not shown) is shaped to extend the entire length of one edge of the piezoelectric substrate 21, so that a shielding effect is achieved. It's expensive. In the example shown in FIG. 9, the first electrode is arranged so as to cover most of the area other than the resonant electrode 22a formed on the top surface of the piezoelectric substrate 21, the conductive pattern 23a, and the input/output side terminal electrodes 24a and 24b.
A capacitive electrode 36 is formed. Therefore, the resonant portion is electromagnetically shielded more effectively by the first capacitor electrode 36 and the second capacitor electrode on the back side. In addition, the curved edge portion 36a
Since the length of is also made longer than in the examples shown in FIGS. 7 and 8, the part facing the resonant electrode 22a is made wider, so the value of the capacitance extracted from the capacitance part is also made thicker. There is.

Further, as shown in FIG. 10, a container IJ having a comb-tooth electrode shape at both ends has a plurality of electrode fingers 37a, 38a at both ends.
Electrodes 37, 38 may be arranged on both sides of the resonant electrode 22a. Here, a plurality of electrode fingers 37a, 38a and input/output side terminal electrodes 24a. A plurality of electrode fingers 39a, 39a protruding inward from the piezoelectric substrate 21 from 24b are arranged so as to be interposed with each other. [Effects of the Invention] As described above, according to the present invention, the first and second capacitive electrodes face each other at a predetermined distance from the first and second resonant electrodes that control the resonant portion on the piezoelectric substrate. The first,
Since the second capacitor electrodes face each other through the piezoelectric substrate and are electrically connected to each other, the remaining area of the piezoelectric substrate where the resonance electrode, input/output terminal electrode, etc. are formed is You can use the area efficiently and take care of the capacity. Therefore, it is possible to downsize the piezoelectric resonator with built-in capacitance.

In addition, since the first and second capacitor electrodes are electrically connected, the piezoelectric substrate portion where the capacitor electrodes are placed facing each other does not resonate, and leakage of vibration from the resonant portion is effectively damped. Ru. Not only the first. The second capacitor electrode also makes it possible to provide electromagnetic shielding of the resonant portion.

Furthermore, the capacitance is extracted using a piezoelectric substrate,
Figure 4: Unlike the conventional example, there is no need to laminate a dielectric substrate different from the piezoelectric substrate in order to extract the capacitance. Therefore, frequency stability can also be improved.

[Brief explanation of drawings]

FIG. 1 is a plan view of a piezoelectric resonator according to an embodiment of the present invention, and FIG.
The figure shows a circuit diagram of a piezoelectric resonator with a built-in capacitor, Figures 3 (a) and (b) are perspective views and bottom views of a conventional piezoelectric resonator with a built-in capacitor, and Figure 4 shows a conventional piezoelectric resonator with a built-in capacitor. 5(a) and 5(b) are sectional views taken along line A-A and line B-B of FIG. 1, and FIG. 6 is a perspective view of FIG. , an external perspective view of the chip-type piezoelectric resonator constructed according to the embodiment, and FIGS. FIG. 6 is a plan view showing an example in which the shape is modified. In the figure, 21 is a piezoelectric substrate, 22a. 22b is the first.
a second resonant electrode, 25.26 a first capacitive electrode, 27.
28 is a second capacitor electrode, 29a. 29b indicates a connecting conductive part. Figure 2 Figure 3 Figure 4 Figure 5 (Q)

Claims (1)

[Claims] a piezoelectric substrate; first and second resonant electrodes formed on both principal surfaces of the piezoelectric substrate so as to face each other with the piezoelectric substrate interposed therebetween; and first and second resonance electrodes formed on the principal surfaces of the piezoelectric substrate; The first and second capacitive electrodes are arranged opposite to each other at a predetermined distance from the electrode, and the first and second capacitive electrodes are arranged so as to face each other with a piezoelectric substrate interposed therebetween. 1st,
A piezoelectric resonator further comprising a connection conductive part that electrically connects the second capacitor electrode.