JP3368213B2 - Piezoelectric resonators, electronic components and communication equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric resonator, an electronic component and a communication device, and in particular, for example, a piezoelectric resonator utilizing mechanical resonance of a piezoelectric body, an oscillator using the same,
The present invention relates to electronic components such as discriminators and filters, and communication devices.

[0002]

2. Description of the Related Art FIG. 23 is a perspective view showing an example of a conventional piezoelectric resonator. The piezoelectric resonator 1 includes, for example, a plate-shaped piezoelectric substrate 2 having a rectangular shape in plan view. The piezoelectric substrate 2 is polarized in the thickness direction. Electrodes 3 are formed on both surfaces of the piezoelectric substrate 2. By inputting a signal between the electrodes 3,
An electric field is applied in the thickness direction of the piezoelectric substrate 2, and the piezoelectric substrate 2 vibrates in the length direction. In addition, as shown in FIG.
There is a piezoelectric resonator 1 in which electrodes 3 are formed on both surfaces of a plate-shaped piezoelectric substrate 2 having a square shape in plan view. Also in this piezoelectric resonator 1, the piezoelectric substrate 2 is polarized in the thickness direction. In this piezoelectric resonator 1, an electric field is applied in the thickness direction of the piezoelectric substrate 2 by inputting a signal between the electrodes 3, and the piezoelectric substrate 2 expands and vibrates.

[0003]

These piezoelectric resonators utilize the piezoelectric lateral effect in which the electric field direction, the polarization direction, and the vibration direction are different. The electromechanical coupling coefficient of the piezoelectric resonator utilizing the lateral piezoelectric effect is smaller than that of the piezoelectric resonator utilizing the longitudinal piezoelectric effect in which the electric field direction, the polarization direction, and the vibration direction match. Therefore, in the piezoelectric resonator using the piezoelectric lateral effect, the difference ΔF between the resonance frequency and the anti-resonance frequency is relatively small. This leads to the drawback that the bandwidth is small when the piezoelectric resonator is used as an oscillator or a filter. Therefore, the degree of freedom in designing characteristics of the piezoelectric resonator and electronic parts using the piezoelectric resonator is low.

In the piezoelectric resonator shown in FIG. 23, the primary resonance of length vibration is used, but structurally,
Spurious in high-order modes such as third-order and fifth-order, which are odd multiples, and in width modes also occur. In order to suppress this spurious, measures such as polishing the piezoelectric resonator, adding mass, and changing the electrode shape can be considered, but these lead to an increase in manufacturing cost.

Further, in the case of the piezoelectric resonator shown in FIG.
Since the piezoelectric substrate has a rectangular plate shape in a plan view, it is not possible to make the thickness too thin due to strength restrictions. Therefore, the distance between electrodes cannot be reduced and the capacitance between terminals cannot be increased. This is extremely inconvenient when performing impedance matching with an external circuit. When a plurality of piezoelectric resonators are alternately connected in series and in parallel to form a ladder filter, the capacitance ratio between the series resonator and the parallel resonator should be increased in order to increase the amount of attenuation other than the pass band width. Need to be bigger. However, there is a limit in shape as described above, and it may not be possible to obtain a large attenuation amount.

In the piezoelectric resonator shown in FIG. 24, the primary resonance of the spreading vibration is used, but structurally there is a high possibility that spurious waves such as the third harmonic of the spreading and the thickness mode will occur. . Further, this piezoelectric resonator has a larger size in order to obtain the same resonance frequency as compared with a piezoelectric resonator using length vibration, and it is difficult to downsize.
Further, when forming a ladder type filter using a plurality of piezoelectric resonators, in order to increase the capacitance ratio of the series resonator and the parallel resonator, not only to increase the thickness of the resonator connected in series, A method is adopted in which an electrode is formed only on a part of the piezoelectric substrate to reduce the capacitance. In this case, the partial electrodes reduce not only the capacitance but also the difference ΔF between the resonance frequency and the anti-resonance frequency. Accordingly, the piezoelectric resonators connected in parallel also have ΔF
Therefore, there is a problem that the piezoelectric property of the piezoelectric substrate cannot be effectively utilized and the pass band width of the filter cannot be increased.

Therefore, as a piezoelectric resonator having a small spurious and a large difference ΔF between the resonance frequency and the anti-resonance frequency,
For example, the applicant proposed a piezoelectric resonator having a laminated structure as shown in Japanese Patent Application No. 8-110475. FIG. 25 is an illustrative view showing an example of a piezoelectric resonator having such a laminated structure. In the piezoelectric resonator 4 shown in FIG. 25, a plurality of piezoelectric layers 6 and a plurality of electrodes 7 constituting a base 5 having a longitudinal direction are alternately laminated, and the plurality of piezoelectric layers 6 are polarized in the longitudinal direction of the base. The piezoelectric resonator having the laminated structure excites the fundamental vibration of the length vibration. In the piezoelectric resonator 4 having the laminated structure, the polarization direction, the electric field direction, and the vibration direction of the piezoelectric layer 6 are the same, and the piezoelectric longitudinal effect is used. The electromechanical coupling coefficient becomes larger and the difference ΔF between the resonance frequency and the anti-resonance frequency becomes larger than that of the piezoelectric resonator. Furthermore, in the piezoelectric resonator 4 having the laminated structure, by utilizing the piezoelectric vertical effect,
Vibrations in modes different from the basic vibration such as width mode and thickness mode are less likely to occur.

In the piezoelectric resonator 4 having this laminated structure, the substrate 5
The ends of the electrodes 7 are exposed on all side surfaces of the. Therefore, on one side surface of the substrate 5, every other end of the electrode 7 is covered with the insulating resin film 8a, and then the external electrode 9a is formed.
Are formed so as to be connected to every other electrode 7. In addition, on the other side surface facing the one side surface of the base body 5, every other electrode 7 having an insulating resin film 8a formed thereon.
In order to connect the external electrode 9b to the external electrode 9b, every other end of the electrode 7 is covered with the insulating resin film 8b, and then the external electrode 9b is formed. In the piezoelectric resonator 4 having this laminated structure, the area of the cross section orthogonal to the longitudinal direction of the substrate 5 or the area of the main surface of the piezoelectric layer 6 is S, and the thickness of the piezoelectric layer 6 or the distance between the electrodes 7 is T. , And the number of piezoelectric layers sandwiched by the electrodes 7 is n, the electrostatic capacitance C between the external electrodes 9a and 9b is represented by C∝nS / T. Therefore, in the piezoelectric resonator 4 having this laminated structure, in order to obtain the same electrostatic capacitance C while reducing the area S and reducing the size, it is sufficient to reduce T or increase n. However, since it is difficult to form the insulating resin films 8a and 8b with a small piezoelectric resonator in which the distance between the electrodes 7 is, for example, 100 μm or less with high positional accuracy by a method such as printing, it is possible to reduce the size of the piezoelectric vibrator itself. Is difficult.

Further, in the piezoelectric resonator 4 having this laminated structure,
FIG. 25 shows the external electrodes 9a and 9b formed on the insulating resin films 8a and 8b due to expansion and contraction of the insulating resin films 8a and 8b due to a temperature change such as heat shock or heat cycle in the subsequent process. As described above, there is a risk of disconnection on the insulating resin films 8a and 8b.

In the laminated piezoelectric resonator 4 shown in FIG. 25, the external electrodes 9a on the insulating resin films 8a, 8b,
As shown in FIG. 26, the conductive resin layer 9 is formed on the surfaces of the external electrodes 9a and 9b in order to prevent the disconnection of 9b.
It is possible to form c and 9d.

However, when the insulating resin films 8a and 8b and the conductive resin layers 9c and 9d are formed on the side surfaces of the base body 5 as described above, a large load mass is formed on the side surfaces of the base body 5, and the mechanical quality is increased. The coefficient Qm is deteriorated and the voltage dependence of the resonance frequency is increased.

Therefore, the main object of the present invention is to reduce the spurious and to reduce the difference Δ between the resonance frequency and the anti-resonance frequency.
Piezoelectric resonator with large F, easy miniaturization, breakage of external electrodes, deterioration of mechanical quality factor Qm, and large voltage dependence of resonance frequency, electronic component and communication device using the same Is to provide.

[0013]

A piezoelectric resonator according to the present invention comprises a base having a longitudinal direction and a first base which is disposed orthogonal to the longitudinal direction of the base and spaced apart in the longitudinal direction of the base. And a second electrode, and is connected to the first or second electrode, and is formed on one side surface of the base body at one end side and the other end side from the center in the width direction of the base body, respectively, along the longitudinal direction of the base body. And a pair of external electrodes, the base includes a plurality of piezoelectric layers laminated in the longitudinal direction of the base, and the plurality of piezoelectric layers are polarized in the longitudinal direction of the base to form a plurality of piezoelectric layers. The first and second electrodes are arranged between the layers, and the first electrode connected to one of the pair of external electrodes is
The second electrode, which is formed so as not to be exposed at a portion of one side surface of the base body where the other of the pair of external electrodes is formed, and is connected to the other side of the pair of external electrodes is , The first and second electrodes are formed so as not to be exposed in a portion where one of the pair of external electrodes is formed.
Te, the individual piezoelectric layers, by applying an AC electric field <br/> longitudinal direction of the base member through a pair of external electrodes, the piezoelectric longitudinal effect in the entire substrate
Ru is excited the fundamental vibration of longitudinal vibration mode using a piezoelectric resonator. In the piezoelectric resonator according to the present invention, for example, a groove is formed along the longitudinal direction of the base body in a substantially central portion in the width direction of the side surface of the base body on which the pair of external electrodes are formed,
The pair of external electrodes are formed on one side and the other side of the side surface of the base separated by the groove. In the piezoelectric resonator according to the present invention, each of the first and second electrodes is formed in plural. Further, the piezoelectric resonator according to the present invention may include a mounting member arranged substantially at the center of the base in the longitudinal direction. Further, an electronic component according to the present invention is an electronic component using the above-mentioned piezoelectric resonator, wherein a base is mounted on a substrate having electrodes formed on its surface via a mounting member, and the base is covered on the substrate. The electronic component is characterized in that the cap is arranged as described above. Furthermore, an electronic component according to the present invention is an electronic component using the above-described piezoelectric resonator, in which a plurality of bases are mounted on a substrate having electrodes formed on its surface so as to form a ladder type filter. The electronic component is characterized in that a cap is disposed on the substrate so as to cover the base body while being mounted via the electronic component. The communication device according to the present invention,
A communication device having a detector, wherein the piezoelectric resonator according to the present invention is used as the detector. The communication device according to the present invention is a communication device having a bandpass filter, and the electronic component according to the present invention is used for the bandpass filter.

In the piezoelectric resonator according to the present invention, the polarization direction and electric field direction of the piezoelectric layer coincide with the vibration direction, and the piezoelectric longitudinal effect is utilized. Therefore, the electromechanical coupling coefficient becomes larger and the difference ΔF between the resonance frequency and the anti-resonance frequency becomes larger than that of the piezoelectric resonator using the piezoelectric lateral effect whose vibration direction is different from the polarization direction and the electric field direction. Further, by utilizing the piezoelectric longitudinal effect, it becomes difficult to generate vibration in a mode different from the basic vibration of the length vibration such as the width mode and the thickness mode. Further, in the piezoelectric resonator according to the present invention, the first electrode connected to one of the pair of external electrodes should not be exposed at the portion of one side surface of the substrate where the other of the pair of external electrodes is formed. The second electrode that is formed and is connected to the other of the pair of external electrodes is formed so as not to be exposed at the portion where one of the pair of external electrodes is formed on one side surface of the substrate. On the side, the first
Alternatively, it is not necessary to form an insulating resin film for insulating the end portion of the second electrode. Therefore, the distance between the first and second electrodes can be narrowed, which facilitates miniaturization. Further, in the piezoelectric resonator according to the present invention, since the insulating resin film is not formed, the external electrode is less likely to be disconnected due to temperature change such as heat shock or heat cycle. Further, in the piezoelectric resonator according to the present invention, since the load mass such as the insulating resin film and the conductive resin layer is not formed on the side surface of the base body, the mechanical quality factor Qm does not deteriorate and the resonance frequency does not increase in voltage dependency. . Using the piezoelectric resonator according to the present invention, an oscillator, a discriminator,
When manufacturing electronic components such as filters and communication devices, the piezoelectric resonator can be mounted on the substrate on which electrodes are formed, etc., through the mounting member arranged in the central portion of the base in the longitudinal direction, and at the node portion. The piezoelectric resonator can be surely held. Also, by covering the substrate with a cap, a chip-type electronic component can be obtained.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments of the invention with reference to the drawings.

[0016]

1 is an illustrative view showing an example of a piezoelectric resonator according to the present invention. Piezoelectric resonator 1 shown in FIG.
0 includes a rectangular parallelepiped base 12 having a size of, for example, 3.8 mm × 1 mm × 1 mm. The substrate 12 includes twelve piezoelectric layers 14 that are made of, for example, a piezoelectric ceramic and are stacked. The piezoelectric layers 14 have the same dimensions. In addition, the middle eight piezoelectric layers 14 of the piezoelectric layers 14 are arranged so that the adjacent piezoelectric layers 14 have opposite polarization directions as shown by arrows in FIG.
Is polarized in the longitudinal direction.

The first electrode 16 and the second electrode 18 are alternately formed on the main surface of the middle eight piezoelectric layers 14 to be polarized, which are orthogonal to the longitudinal direction of the substrate 12. Therefore, these first electrode 16 and second electrode 18
Are arranged at right angles to the longitudinal direction of the base 12 and at intervals in the longitudinal direction of the base 12. In addition, the first electrode 16
2A is formed on a portion of the main surface of the piezoelectric layer 14 excluding the middle portion of the upper side and one end side portion thereof, as shown in FIG. 2A, and the second electrode 18 is formed as shown in FIG. 2B. In addition, the piezoelectric layer 14 is formed on the main surface of the piezoelectric layer 14 at a portion except the middle portion of the upper side and the other end side portion. Therefore, the first electrode 16
Is formed on one side surface on the upper side of the base 12 so as not to be exposed at one end side portion from the middle portion in the width direction but to be exposed at the other end side portion. In addition, the second electrode 18
Is formed on one upper side surface of the base 12 so as to be exposed at one end side portion in the width direction but not exposed from the intermediate portion to the other end side portion.

On one side surface on the upper side of the substrate 12, the substrate 1
2 to the one end side and the other end side from the center in the width direction.
The external electrodes 20 and 22 are formed in two rows along the longitudinal direction of. In this case, one external electrode 20 is connected to the first electrode 16 and the other external electrode 22 is connected to the second electrode 1.
8 is connected.

Next, an example of a method of manufacturing the piezoelectric resonator 10 will be described.

First, as shown in FIG. 3, a plurality of piezoelectric ceramic mother substrates 15 to form a large number of piezoelectric layers 14 are formed.
Two pieces are prepared. A plurality of mother electrodes 17 to be the first electrodes 16 are formed on one main surface of each of the five mother substrates 15. Further, a large number of mother electrodes 19 to be the second electrodes 18 are formed on one main surface of the other four mother substrates 15. No electrodes are formed on the remaining three mother substrates 15. Then, a laminated body is formed by laminating these mother substrates 15. Then, the laminated body is cut at a portion indicated by a chain line extending in the lateral direction in FIG.

Then, as shown in FIG. 4, electrodes 21 to be the external electrodes 20 and 22 are formed on the cut surface of the laminate thus cut. Then, by applying a high DC voltage between the adjacent electrodes 21 and 21, each mother substrate 15 or each piezoelectric layer 14 is polarized. Then, the piezoelectric resonator 10 is manufactured by cutting the laminated body at a portion indicated by a chain line in FIG.
It should be noted that other piezoelectric resonators described later than the piezoelectric resonator shown in FIG. 1 can be manufactured in the same manner.

In this piezoelectric resonator 10, the external electrodes 20,
22 is used as an input / output electrode. At this time, by applying a signal to the external electrodes 20 and 22, an electric field is applied between the adjacent first and second electrodes 16 and 18,
The intermediate eight piezoelectric layers 14 excluding the four piezoelectric layers 14 on both ends of the base 12 are piezoelectrically active. In this case, mutually opposite voltages are applied to the piezoelectric layers 14 of the base 12 that are polarized in opposite directions, so that the piezoelectric layers 14 tend to expand and contract in the same direction as a whole. That is, the external electrode 2
First and second electrodes 16, 18 connected to 0, 22
By applying an AC electric field in the longitudinal direction of the substrate 12 to each of the piezoelectric layers 14 to generate an expansion / contraction driving force in each of the piezoelectric layers 14, the piezoelectric resonator 10 as a whole has The fundamental vibration of the length vibration having the center in the longitudinal direction as a node is excited.

In this piezoelectric resonator 10, the polarization direction of the piezoelectric layer 14, the electric field direction according to the input signal, and the piezoelectric layer 14 are used.
The vibration directions of are the same. That is, this piezoelectric resonator 10
Is a resonator utilizing the piezoelectric vertical effect. The piezoelectric resonator 10 has a larger electromechanical coupling coefficient than a piezoelectric resonator utilizing the piezoelectric lateral effect in which the polarization direction and the electric field direction are different from the vibration direction. Therefore, in this piezoelectric resonator 10, as compared with the conventional piezoelectric resonator utilizing the piezoelectric lateral effect,
The difference ΔF between the resonance frequency and the anti-resonance frequency is large. Therefore, in this piezoelectric resonator 10, it is possible to obtain a characteristic having a larger bandwidth as compared with the conventional piezoelectric resonator utilizing the lateral piezoelectric effect.

In order to measure the difference between the piezoelectric longitudinal effect and the piezoelectric lateral effect, the piezoelectric resonator shown in FIGS. 5, 6 and 7 was produced. The piezoelectric resonator shown in FIG. 5 has a size of 4.0 mm × 1.0 m.
Electrodes are formed on both surfaces in the thickness direction of a piezoelectric substrate of m × 0.38 mm. The piezoelectric substrate is polarized in the thickness direction, and the length vibration is excited by applying a signal to the electrodes. The piezoelectric resonator shown in FIG. 6 has the same dimensions as the piezoelectric resonator shown in FIG. 5, and has electrodes formed on both surfaces in the longitudinal direction of the piezoelectric substrate. The piezoelectric substrate is polarized in the longitudinal direction, and by applying a signal to the electrodes,
Length vibration is excited. Further, the piezoelectric resonator shown in FIG. 7 is one in which electrodes are formed on both surfaces in the thickness direction of a piezoelectric substrate of 4.7 mm × 4.7 mm × 0.38 mm. The piezoelectric substrate is polarized in the thickness direction, and the spreading vibration is excited by applying a signal to the electrodes. That is, the piezoelectric resonator shown in FIGS. 5 and 7 utilizes the lateral piezoelectric effect, and the piezoelectric resonator shown in FIG. 6 utilizes the longitudinal piezoelectric effect.

The resonance frequency Fr and the electromechanical coupling coefficient K of these piezoelectric resonators were measured, and the results are shown in Table 1.
The results are shown in Tables 2 and 3. Table 1 shows the measurement results of the piezoelectric resonator shown in FIG. 5, Table 2 shows the measurement results of the piezoelectric resonator shown in FIG. 6, and Table 3 shows the measurement results of the piezoelectric resonator shown in FIG.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

As can be seen from these measurement results, the piezoelectric resonator utilizing the piezoelectric longitudinal effect has a larger electromechanical coupling coefficient K than the piezoelectric resonator utilizing the transverse piezoelectric effect, and therefore the resonance frequency and the anti-resonance frequency are different. The difference ΔF is large.
Further, regarding the largest spurious in the piezoelectric resonator utilizing the piezoelectric longitudinal effect, the electromechanical coupling coefficient K is 12.2% at the third harmonic of the length. Moreover, the electromechanical coupling coefficient K in the width mode different from the fundamental vibration is as small as 4.0%.
On the other hand, in the piezoelectric resonator of length vibration utilizing the piezoelectric lateral effect, the electromechanical coupling coefficient K in the width mode is 2
It is as large as 5.2%, and in the piezoelectric resonator of the spreading vibration utilizing the piezoelectric lateral effect, the electromechanical coupling coefficient K in the thickness mode is as large as 23.3%. Therefore, it can be seen that the piezoelectric resonator utilizing the piezoelectric longitudinal effect has a smaller spurious than the piezoelectric resonator utilizing the piezoelectric lateral effect.

Further, in the piezoelectric resonator 10 shown in FIG. 1, the first electrode 16 connected to one external electrode 20 is different from the other external electrode in comparison with the laminated piezoelectric resonator 4 shown in FIG. The second electrode 18 is formed so as not to be exposed at one end side portion in the width direction of one side surface of the base 12 on which the 22 is formed, and further connected to the other external electrode 22.
Since one outer electrode 20 is formed so as not to be exposed at the other end side portion in the width direction of one side surface of the base 12 on which the external electrode 20 is formed, the side surface of the base 12 has the first or second electrode 16, It is not necessary to form an insulating resin film for insulating the end portions of 18. Therefore, the first and second electrodes 1
The interval between 6 and 18 can be narrowed, which facilitates miniaturization.

Further, in this piezoelectric resonator 10, FIG.
In comparison with the piezoelectric resonator 4 having the laminated structure shown in FIG.
Since the insulating resin film is not formed between 0 and 22 and the base 12, the external electrodes 20 and 22 are less likely to be disconnected due to temperature changes such as heat shock or heat cycle.

Further, in this piezoelectric resonator 10, the substrate 12
Since a load mass such as an insulating resin film or a conductive resin layer is not formed on the side surface of, the mechanical quality factor Qm does not deteriorate and the voltage dependence of the resonance frequency does not increase.

Furthermore, in this piezoelectric resonator 10, in order to maintain the insulating properties of the end portions of the first and second electrodes 16 and 18, the first and second electrodes 16 and 16 are formed on the main surface of the piezoelectric layer 14. Even if the size of the resonator in the width direction is reduced while the width of the portion where 18 is not formed is kept constant, the first and second electrodes 1 with respect to the area of the main surface of the piezoelectric layer 14 are formed.
Since the ratio of the facing areas of 6 and 18 does not change, it is possible to reduce the driving force generated in the piezoelectric layer 14 in the width direction without reducing the efficiency.

Further, in this piezoelectric resonator 10, the first and second electrodes 16 and 18 are partially formed on the main surface of the piezoelectric layer 14, so that the first and second electrodes 16 and 18 are not formed. By adjusting the facing area, ΔF can be adjusted and the degree of freedom in designing the characteristics is large.

Further, in this piezoelectric resonator 10, for example, the areas where the first and second electrodes 16 and 18 face each other, the number of the piezoelectric layers 14 and the first and second electrodes 16 and 18, the piezoelectric layer 14 are provided. The capacitance of the resonator can be adjusted by adjusting the dimension of the substrate 12 in the longitudinal direction. That is, the first and second electrodes 1
By increasing the areas of the electrodes 6 and 18 facing each other, increasing the number of the piezoelectric layer 14 and the first and second electrodes 16 and 18, or shortening the dimension of the base 12 in the piezoelectric layer 14 in the longitudinal direction, The capacitance of the resonator can be increased, and conversely, the opposing areas of the first and second electrodes 16 and 18 can be narrowed, and the piezoelectric layer 14 and the first and second electrodes 16 and 18 can be reduced. The capacitance of the resonator can be reduced by reducing the number or increasing the dimension of the piezoelectric layer 14 in the longitudinal direction of the substrate 12. Therefore, the first and second electrodes 16 of the piezoelectric resonator 10,
18 facing areas, the number of the piezoelectric layer 14 and the first and second electrodes 16 and 18, the base 1 in the piezoelectric layer 14.
The capacitance can be adjusted by adjusting the dimension of 2 in the longitudinal direction, and the degree of freedom in designing the capacitance is large. Therefore, when the piezoelectric resonator 10 is mounted on a circuit board or the like, it is easy to achieve impedance matching with an external circuit.

In the piezoelectric resonator 10 shown in FIG. 1, the first electrode 16 is, as shown in FIG. 8A, on the main surface of the piezoelectric layer 14 from the middle portion of the upper side to the one end side portion and the lower side. The second electrode 1 which is not formed on the part
8 is a mirror image of the first electrode 16 and is shown in FIG.
As shown in, the piezoelectric layer 14 may not be formed on the main surface from the middle portion of the upper side to the other side portion and the lower side portion. In the piezoelectric resonator 10 shown in FIG. 1, as shown in FIG. 9, since the facing portions of the first and second electrodes 16 and 18 that constitute the capacitance are displaced from the central axis of the base 12, The driving force generated in the piezoelectric layer 14 may deviate from the central axis of the base 12, and the base 12 may bend during vibration. Therefore, when the spurious occurs due to the bending of the substrate 12, and the resonance frequency of the spurious is between the resonance point of the main vibration and the anti-resonance point, the characteristics may be deteriorated. In contrast, FIG. 8 (a) and FIG.
In the piezoelectric resonator 10 having the first and second electrodes 16 and 18 shown in (b), as shown in FIG. 10, the central axis L1 of the overlapping shape of the first and second electrodes 16 and 18 or Since the center point P1 is formed so as to coincide with the center axis L2 or the center point P2 on the plane perpendicular to the longitudinal direction of the base 12, the driving force generated in the piezoelectric layer 14 does not shift from the center axis of the base 12. The base 12 is difficult to bend. Therefore, spurious effects due to the bending of the substrate 12 are less likely to occur, and the characteristics are less likely to be defective, which is another effect.

Further, in the piezoelectric resonator 10 shown in FIG. 1, the first electrode 16 is not formed on the three side portions other than the upper side of the piezoelectric layer 14 as shown in FIG. The second electrode 18 forms a mirror image of the first electrode 16, and as shown in FIG. 11B, on the main surface of the piezoelectric layer 14, other than the upper side where the external electrodes 20 and 22 are formed. It may not be formed on the three sides. By forming the first and second electrodes 16 and 18 in this manner, the first and second electrodes are formed.
Of the electrodes 16 and 18 are not exposed at all on the surface of the piezoelectric resonator 10, the moisture resistance of the first and second electrodes 16 and 18 is improved, and the insulation resistance between the first and second electrodes 16 and 18 is improved. Another effect is that it is less likely to deteriorate.

Further, in the piezoelectric resonator 10 shown in FIG. 1, the first electrode 16 has a main surface of the piezoelectric layer 14 from the middle portion of the upper side to one end side portion thereof and the first electrode 16 as shown in FIG. The second electrode 18 is formed in a portion excluding the adjacent one of the vertical sides, and the second electrode 18 has a mirror image shape with the first electrode 16. As shown in FIG. It may be formed on the main surface except the middle part of the upper side except the other end side part and the other vertical side part adjacent thereto.

In the piezoelectric resonator 10 shown in FIG. 1, the first electrode 16 is, as shown in FIG. 13 (a), one of the first surface of the piezoelectric layer 14 which is adjacent to the middle portion of the upper side of the main surface. The second electrode 18 is formed over the middle portion of the vertical side, and further, the second electrode 18 forms a mirror image of the first electrode 16, and as shown in FIG. It may be formed from the middle portion to the middle portion of the other vertical side adjacent to the middle portion.

Further, in the piezoelectric resonator 10 shown in FIG. 1, the first electrode 16 has one vertical side, one upper side and one side from the central portion in the main surface of the piezoelectric layer 14 as shown in FIG. 14A. It is formed over each middle part of the lower three sides,
The second electrode 18 has a shape of a mirror image with the first electrode 16, and as shown in FIG. 14B, in the main surface of the piezoelectric layer 14, from the central portion to the other vertical side, the upper side and the lower side. It may be formed over each middle part of the side.

Further, in the piezoelectric resonator 10 shown in FIG. 1, the first electrode 16 is, as shown in FIG. 15 (a), the middle portion of the main surface of the piezoelectric layer 14 from the central portion to the upper side and the lower side. And is not formed on the vertical side portions on both sides of the piezoelectric layer 14, and further the second electrode 18 is formed.
Has a mirror image shape with the first electrode 16, and is shown in FIG.
As shown in, the piezoelectric layer 14 may be formed from the central portion to the intermediate portions of the upper side and the lower side on the main surface of the piezoelectric layer 14, and may not be formed on the vertical side portions on both sides of the piezoelectric layer 14.

Further, in the piezoelectric resonator 10 shown in FIG. 1, the first electrode 16 is formed from the central portion to the vertical side portions on both sides of the main surface of the piezoelectric layer 14 as shown in FIG. 16 (a). In addition, the second electrode 18 is
16B, it may be formed in a mirror image shape and may be formed from the central portion to both vertical side portions on the main surface of the piezoelectric layer 14 as shown in FIG. 16B.

If the first and second electrodes 16 and 18 are formed as shown in FIG. 8 or 16, in order to maintain the insulating properties of the end portions of the first and second electrodes 16 and 18. The first and second electrodes 1 are formed on the main surface of the piezoelectric layer 14.
While keeping the width of the part where 6 and 18 are not formed constant,
The piezoelectric layer 1 is formed even if the width of the resonator is reduced.
The first and second electrodes 16, 1 with respect to the area of the principal surface of No. 4
Since the ratio of the opposing areas of 8 does not change, the piezoelectric layer 1
4 can be reduced in the width direction without lowering the efficiency of the driving force generated.

If the first and second electrodes 16 and 18 are formed as shown in FIG. 11, FIG. 13, FIG. 14, FIG. 15 or FIG. 16, the first and second electrodes 16 and 18 are overlapped. Since the central axis or the central point of the combined shape is formed to coincide with the central axis or the central point on the plane perpendicular to the longitudinal direction of the substrate 12, the driving force generated in the piezoelectric layer 14 is the center of the substrate 12. The base body 12 is hard to bend without being displaced from the axis. Therefore, spurious effects due to the bending of the substrate 12 are less likely to occur, and the characteristics are less likely to be defective, which is another effect. In these examples, the piezoelectric layer 14
The shapes of the facing portions of the first and second electrodes 16 and 18 with respect to the main surface are vertically symmetrical.

In the above-described piezoelectric resonator 10, the intermediate portion in the longitudinal direction of the base body 12 is configured to be piezoelectrically active and vibrates, and both end portions in the longitudinal direction of the base body 12 are inactive portions that are not piezoelectrically active. Is formed by.
When the piezoelectric layer is polarized and an electric field is applied, it becomes piezoelectrically active, and otherwise it becomes piezoelectrically inactive. , Other structures may be used.

Electronic components such as an oscillator and a discriminator are manufactured by using the piezoelectric resonator 10 described above. Figure 1
FIG. 7 is a perspective view showing an example of the electronic component 60. The electronic component 60 includes an insulating substrate 62 as a supporting member. Two recesses 64 are formed at each of opposite ends of the insulating substrate 62. 2 on one surface of the insulator substrate 62
Two pattern electrodes 66 and 68 are formed. One of the pattern electrodes 66 is formed between the facing concave portions 64 and has a portion extending in an L shape from one end side thereof toward the central portion of the insulating substrate 62. The other pattern electrode 68
Has a portion that is formed between the other opposed concave portions 64 and that extends in an L shape from the other end side toward the central portion of the insulator substrate 62. These pattern electrodes 66 and 68 are formed so as to wrap around from the recess 64 of the insulating substrate 62 toward the other main surface. A well-known substrate such as a glass epoxy substrate or an alumina substrate can be used as the insulator substrate 62. Further, as the substrate, a multilayer substrate, a dielectric substrate or the like may be used.

Protrusions 70, 70 as attachment members made of a conductive material such as a conductive adhesive are formed at the center of the base 12 in the lengthwise direction of the piezoelectric resonator 10, respectively. Then, as shown in FIG. 18, the piezoelectric resonator is mounted on the pattern electrodes 66 and 68 of the insulating substrate 62 via the protrusions 70 and 70. At this time, the external electrodes 20 and 22 of the piezoelectric resonator 10 are connected to the pattern electrodes 66 and 68 via the protrusions 70 and 70, respectively.
An adhesive that bonds the protrusions 70, 70 may be applied on the pattern electrodes 66, 68 of the insulating substrate 62.

Further, as shown in FIG. 17, a metal cap 74 is placed on the insulating substrate 62. At this time, the insulating substrate 62 and the pattern electrode 6 are arranged so that the metal cap 74 and the pattern electrodes 66 and 68 are not electrically connected.
Insulating resin is applied onto 6, 68. Then, the electronic cap 60 is covered with the metal cap 74.
Is created. In this electronic component 60, the insulating substrate 62
The pattern electrodes 66 and 68 formed so as to wrap around from the concave portion 64 to the back surface are used as input / output terminals for connecting to an external circuit.

In this electronic component 60, since the projection 70 is formed in the central portion of the piezoelectric resonator 10, the piezoelectric resonator 1
The central part, which is the node point of 0, can be reliably supported, and the length vibration excited is not hindered.

The electronic component 60 is used by being attached to a circuit board together with an IC or the like, and is used as, for example, an oscillator or a discriminator. Since the electronic component 60 having such a structure is hermetically sealed and protected by the metal cap 74, it can be used as a chip component that can be attached by reflow soldering or the like.

When the electronic component 60 is used as an oscillator, since the piezoelectric resonator 10 described above is used, spurious can be suppressed to be small and abnormal oscillation due to spurious can be prevented. Moreover, since the capacitance value of the piezoelectric resonator 10 can be freely set, impedance matching with an external circuit can be easily achieved. In particular, when used as an oscillator for a voltage controlled oscillator, since the resonator has a large ΔF, it is possible to obtain a wide frequency variable range that has not been heretofore available.

When the electronic component 60 is used as a discriminator, the feature that the ΔF of the resonator is large leads to the feature that the peak separation is wide. Further, since the capacitance design range of the resonator is wide, it is easy to achieve impedance matching with an external circuit.

FIG. 19 is a plan view of a main part showing an example of a ladder type filter as an electronic component using the piezoelectric resonator according to the present invention, and FIG. 20 is an exploded perspective view of the main part.
In the electronic component 60 shown in FIGS. 19 and 20, four pattern electrodes 9 are provided on an insulating substrate 62 as a supporting member.
0, 92, 94, 96 are formed. These pattern electrodes 90 to 96 are arranged in a line at a distance 5
Two lands are formed. In this case, the first land from one end of the insulating substrate 62 is formed on the pattern electrode 90, the second land and the fifth land are formed on the pattern electrode 92, and the third land is formed on the pattern electrode 94.
And the fourth land is formed on the pattern electrode 96.

On these pattern electrodes 90 to 96,
The external electrodes 20, 22 of the piezoelectric resonators 10a, 10b, 10c, 10d are attached, respectively. As these piezoelectric resonators 10a to 10d, for example, the piezoelectric resonator 10 in which external electrodes 20 and 22 are formed on one side surface of a substrate 12 as shown in FIG. 1 is used.

The piezoelectric resonators 10a, 10b, 10
When mounting the c and 10d on the pattern electrodes 90 to 96, the external electrodes 20 of the piezoelectric resonators 10a to 10d,
The projection 70, which is a mounting member disposed on the wiring 22, is connected to a conductive adhesive (not shown) applied on the pattern electrodes 90 to 96 of the insulating substrate 62. Then, on the insulating substrate 62, a metal cap (not shown)
It is covered.

The electronic component 60 shown in FIGS. 19 and 20.
Is used as a ladder type filter having a ladder type circuit as shown in FIG. At this time, the two piezoelectric resonators 10a and 10c are used as series resonators, and the other two piezoelectric resonators 10b and 10d are used as parallel resonators. In such a ladder type filter, the capacitance of the parallel piezoelectric resonators 10b and 10d is equal to that of the series piezoelectric resonator 1
It is designed to be larger than the capacitance of 0a and 10c.

The amount of attenuation of the ladder type filter depends on the capacitance ratio between the series resonator and the parallel resonator. 19 and 2
In the electronic component 60 shown in 0, the piezoelectric resonators 10a to 10d
The capacitance can be adjusted by changing the number of laminated layers. Therefore, by adjusting the capacitance of the piezoelectric resonators 10a to 10d, a ladder-type filter having a smaller number of resonators and a larger attenuation amount as compared to the case of using a conventional piezoelectric resonator utilizing the lateral piezoelectric effect. Can be realized. Further, since ΔF of each of the piezoelectric resonators 10a to 10d is larger than that of the conventional piezoelectric resonator, it is possible to achieve a pass band width wider than that using the conventional piezoelectric resonator.

Further, in the electronic component 60 shown in FIGS. 19 and 20, since two electrodes of adjacent piezoelectric resonators are attached to the same land, there is no need to insulate between the two electrodes of adjacent piezoelectric resonators. The adjacent piezoelectric resonators can be brought close to each other, and the size can be reduced.

Although each of the electronic components described above is formed in the shape of a chip, in the present invention, the electronic component may have a shape other than the shape of a chip.

In the piezoelectric resonator 10 described above, the plurality of piezoelectric layers 14 are alternately polarized in opposite directions, but the polarization directions of the plurality of piezoelectric layers 14 are not limited to this.

In the piezoelectric resonator 10 described above, the substrate 1
The respective dimensions of the piezoelectric layer 14 in the longitudinal direction of 2 and the respective intervals between the adjacent first and second electrodes 16 and 18 are formed to be the same, but they may not be formed to be the same.

Further, in the piezoelectric resonator 10 described above, one piezoelectric layer 14 is provided between the adjacent first and second electrodes 16 and 18, but a plurality of piezoelectric layers are provided. You may be asked.

In each of the piezoelectric resonators 10 described above, the first and second electrodes 1 connected to the external electrodes 20 and 22 are also included.
Although 6 and 18 are formed alternately, the first and second electrodes 16 and 18 may not be formed alternately. Also,
The first and second electrodes 16 and 18 do not necessarily have to be formed in plural, and may be formed one by one.

FIG. 22 is a block diagram showing an example of a double superheterodyne receiver according to the present invention. The double superheterodyne receiver 100 shown in FIG. 22 includes an antenna 102. The antenna 102 is the input circuit 10
4 is connected to the input terminal. As the input circuit 104, a tuning circuit or a bandpass filter that performs impedance matching between the antenna 102 and a high-frequency amplifier 106 described later and selects a desired wave is used. The output end of the input circuit 104 is connected to the input end of the high frequency amplifier 106. The high frequency amplifier 106 is for amplifying a weak radio wave with low noise to improve the sensitivity and also to improve the image frequency selectivity. The output terminal of the high frequency amplifier 106 is connected to the input terminal of the first frequency mixer 108. The first frequency mixer 108 is for mixing the desired wave and the first local oscillation wave to generate a first intermediate frequency of sum or difference. The other input of the first frequency mixer 108 has a first
The output terminal of the local oscillator 110 is connected. The first local oscillator 110 is for oscillating a first local oscillation wave for producing a first intermediate frequency. The output terminal of the first frequency mixer 108 is connected to the first bandpass filter 1
It is connected to 12 input terminals. The first bandpass filter 112 is for passing the first intermediate frequency. The output end of the first bandpass filter 112 has a second end
Is connected to the input end of the frequency mixer 114. The second frequency mixer 114 is for mixing the first intermediate frequency and the second local oscillation wave to generate a second intermediate frequency of sum or difference. The output terminal of the second local oscillator 116 is connected to another input terminal of the second frequency mixer 114. The second local oscillator 116 is for oscillating a second local oscillation wave for creating a second intermediate frequency. The output terminal of the second frequency mixer 114 is connected to the input terminal of the second bandpass filter 118. The second bandpass filter 118 is for passing the second intermediate frequency. The output terminal of the second bandpass filter 118 is connected to the input terminal of the intermediate frequency amplifier 120. The intermediate frequency amplifier 120 is for amplifying the second intermediate frequency. The output terminal of the intermediate frequency amplifier 120 is connected to the input terminal of the detector 122. Detector 122
Is for obtaining a signal wave from the second intermediate frequency. The output end of the detector 122 is connected to the input end of the low frequency amplifier 124. The low frequency amplifier 124 is for amplifying a signal wave to a level capable of driving a speaker. The output terminal of the low frequency amplifier 124 is connected to the speaker 126.

In the present invention, in the double superheterodyne receiver 100, the above-mentioned piezoelectric resonator may be used as the detector 122, and the first bandpass filter 112 and the second bandpass filter may be used. The ladder filter described above may be used for each 118. Such a receiver is small in size and has excellent reception characteristics.

Further, in the present invention, in the single super-heterodyne receiver, the above-mentioned piezoelectric resonator may be used for the wave detector, and the above-mentioned ladder filter may be used for the band pass filter. Such a single super-heterodyne receiver is also small in size and has excellent reception characteristics, like the double super-heterodyne receiver described above.

[0067]

According to the present invention, the spurious is small, the difference ΔF between the resonance frequency and the anti-resonance frequency is large, the miniaturization is easy, the external electrode is hard to be broken, and the mechanical quality factor Qm is deteriorated. As a result, a piezoelectric resonator in which the voltage dependence of the resonance frequency does not increase can be obtained. Further, when an electronic component is manufactured using the piezoelectric resonator according to the present invention, it can be a chip-type electronic component, so that it can be easily mounted on a circuit board or the like. Further, according to the present invention, the spurious is small, the difference ΔF between the resonance frequency and the anti-resonance frequency is large, the miniaturization is easy, the external electrodes are not easily broken, the mechanical quality factor Qm does not deteriorate, and the resonance It is possible to obtain an electronic component and a communication device using a piezoelectric resonator in which the frequency voltage dependency does not increase.

[Brief description of drawings]

FIG. 1 is an illustrative view showing an example of a piezoelectric resonator according to the present invention.

FIG. 2 is a plan view showing first and second electrodes used in the piezoelectric resonator shown in FIG.

FIG. 3 is an illustrative view of a main part showing an example of a mother substrate or the like for manufacturing the piezoelectric resonator shown in FIG.

FIG. 4 is an essential part schematic view showing an example of an external electrode or the like for manufacturing the piezoelectric resonator shown in FIG.

FIG. 5 is a perspective view showing a piezoelectric resonator that vibrates in length using a piezoelectric lateral effect as a comparative example.

FIG. 6 is a perspective view showing a piezoelectric resonator that vibrates in length utilizing a piezoelectric longitudinal effect.

FIG. 7 is a perspective view showing a piezoelectric resonator vibrating in a spreading manner using a lateral piezoelectric effect as a comparative example.

FIG. 8 is a plan view showing a modification of the first and second electrodes used in the piezoelectric resonator shown in FIG.

9 is an illustrative view showing a central axis of a base body and a central axis of a portion where first and second electrodes face each other in the piezoelectric resonator shown in FIG. 1. FIG.

10 shows a center axis and a center point of a base body and a center axis and a center point of opposing portions of the first and second electrodes in the piezoelectric resonator using the first and second electrodes shown in FIG. It is an illustration figure.

11 is a plan view showing another modification of the first and second electrodes used in the piezoelectric resonator shown in FIG.

FIG. 12 is a plan view showing still another modification of the first and second electrodes used in the piezoelectric resonator shown in FIG.

13 is a plan view showing still another modified example of the first and second electrodes used in the piezoelectric resonator shown in FIG.

FIG. 14 is a plan view showing still another modification of the first and second electrodes used in the piezoelectric resonator shown in FIG.

15 is a plan view showing still another modified example of the first and second electrodes used in the piezoelectric resonator shown in FIG. 1. FIG.

16 is a plan view showing still another modified example of the first and second electrodes used in the piezoelectric resonator shown in FIG. 1. FIG.

FIG. 17 is an illustrative view showing one example of an electronic component using the piezoelectric resonator according to the present invention.

18 is a side view solution diagram showing a mounting structure of a piezoelectric resonator in the electronic component shown in FIG.

FIG. 19 is a main part plan view showing an example of a ladder type filter using the piezoelectric resonator according to the present invention.

20 is an exploded perspective view of a main part of the ladder type filter shown in FIG.

21 is a circuit diagram of the ladder filter shown in FIGS. 19 and 20. FIG.

FIG. 22 is a block diagram showing an example of a double super-heterodyne receiver according to the present invention.

FIG. 23 is a perspective view showing an example of a conventional piezoelectric resonator.

FIG. 24 is a perspective view showing another example of a conventional piezoelectric resonator.

FIG. 25 is an illustrative view showing one example of a piezoelectric resonator having a laminated structure which is the background of the present invention.

FIG. 26 is an illustrative view showing a state where a conductive resin layer is formed on the surface of the external electrode of the piezoelectric resonator shown in FIG. 25.

[Explanation of symbols]

10 Piezoelectric resonator 12 Base 14 Piezoelectric layer 16 First electrode 18 Second electrode 20,22 External electrode 60 electronic components 62 Insulator substrate 64 recess 66,68 pattern electrodes 70 Protrusion 72 Conductive wire 74 Metal Cap 90,92,94,96 pattern electrodes 100 double superheterodyne receiver 112 First Bandpass Filter 118 second bandpass filter 122 detector

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshihiko Unami               2 26-10 Tenjin, Tenjin, Nagaokakyo, Kyoto Prefecture               Murata Manufacturing Co., Ltd. (72) Inventor Mamoru Ogawa               2 26-10 Tenjin, Tenjin, Nagaokakyo, Kyoto Prefecture               Murata Manufacturing Co., Ltd. (72) Inventor Jiro Inoue               2 26-10 Tenjin, Tenjin, Nagaokakyo, Kyoto Prefecture               Murata Manufacturing Co., Ltd.

Claims (8)

(57) [Claims] 1. A base body having a longitudinal direction, first and second bodies arranged inside the base body orthogonal to the longitudinal direction of the base body and spaced apart in the longitudinal direction of the base body.
Of electrodes, and connected to said first or second electrode,
On one side surface of the base, a pair of external electrodes respectively formed along the longitudinal direction of the base is provided at one end side and the other end side from the center in the width direction of the base, and the base is the base A plurality of piezoelectric layers laminated in the longitudinal direction of the plurality of piezoelectric layers, the plurality of piezoelectric layers being polarized in the longitudinal direction of the base, and the first and second electrodes between the plurality of piezoelectric layers. And the first electrode connected to one of the pair of external electrodes is
A second electrode is formed so as not to be exposed at a portion of one side surface of the base body where the other of the pair of external electrodes is formed, and further connected to the other of the pair of external electrodes.
The piezoelectric body is formed so as not to be exposed at a portion of one side surface of the base body where one of the pair of external electrodes is formed, and is formed by the first and second electrodes.
An AC electric field is applied to the layer through the pair of external electrodes in the longitudinal direction of the base to exert a piezoelectric vertical effect on the entire base.
The fundamental vibration of longitudinal vibration mode with use Ru is excited, the piezoelectric resonator. 2. A groove is formed along a longitudinal direction of the base body in a widthwise central portion of a side surface of the base body on which the pair of external electrodes are formed, and the pair of external electrodes are separated by the groove. The piezoelectric resonator according to claim 1, wherein the piezoelectric resonator is formed on one side and the other side of the formed base, respectively. 3. The piezoelectric resonator according to claim 1, wherein a plurality of the first and second electrodes are formed, respectively. 4. The piezoelectric resonator according to claim 1, further comprising a mounting member arranged substantially at the center of the base in the longitudinal direction. 5. An electronic component using the piezoelectric resonator according to claim 4, wherein the base is mounted on the substrate having an electrode formed on the surface via the mounting member, and the substrate is mounted on the substrate. An electronic component, wherein a cap is arranged so as to cover the base body. 6. An electronic component using the piezoelectric resonator according to claim 4, wherein a plurality of the bases are mounted on a substrate having electrodes formed on the surface thereof so as to form a ladder type filter. An electronic component, characterized in that a cap is arranged on the substrate so as to cover the base body while being mounted via the electronic component. 7. A communication device having a wave detector, wherein the piezoelectric resonator according to claim 1 is used in the wave detector. 8. A communication device having a bandpass filter, wherein the electronic component according to claim 6 is used for the bandpass filter.