JPH0397312A - Piezoelectric resonator component - Google Patents

Abstract

PURPOSE:To preclude the possibility of migration or solder bridge formation or the like by forming an enclosed vibration space with a piezoelectric base with a vibration electrode formed thereto and a dielectric base overlapped in the broadwise direction of the said piezoelectric base, forming a capacitor electrode to a face of the dielectric base toward the vibration space and connecting the vibration electrode and the capacitor electrode to an external terminal. CONSTITUTION:Vibration electrodes 3a, 3b are formed on the upper and lower faces of a piezoelectric base 2. Moreover, the electrode 3a connects to a lead electrode 4a formed to the left side of the base 2 and the electrode 3b connects to a lead electrode 4b formed to the right side of the base 2. A ceramic base of Pb(ZrTi)O3, BaTiO3 or the like ia used for the piezoelectric base 2. A dielectric base is used for protection bases 5, 8. Capacitor electrodes 6a, 6b, 6c are formed to the lower face of the protection base 5. The required capacitance is obtained by a gap formed between the electrodes 6a and 6b and between the electrodes 6b and 6c. The bases 2, 5, 8 prepared in this way are fixed with a distance by using an adhesives 9 so that they are not in direct contact with each other to form an enclosed vibration space.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to piezoelectric resonant components used in oscillators, filters, etc. For example, as an oscillator circuit using a piezoelectric resonator, the circuit shown in FIG. 8 is known. In this circuit, a piezoelectric resonator is connected between the input/output terminals (A) and (B), and a capacitor C1. C2 is connected.

Conventionally, to configure the circuit shown in FIG. 8, it is known that one piezoelectric substrate is provided with one resonator and two capacitors. However, in this case, the shape of the capacitor electrode needs to be made somewhat large in order to ensure the capacitance required for the capacitor section. Therefore, the size of the piezoelectric substrate increases, which is an obstacle to miniaturizing components.

In addition, if the region where the capacitor part is formed on the piezoelectric substrate is polarized, when a signal voltage is applied to the capacitive electrodes, the portion of the piezoelectric substrate sandwiched between the capacitive electrodes will become mechanical due to electrostriction. to excite. Therefore, the capacitor section acts as a resonator, degrading the electrical characteristics of the oscillator. Therefore, as a countermeasure to this problem, ■ A method in which polarization treatment is not applied only to the area where the capacitor part is formed on the piezoelectric substrate ■ A damping treatment by mounding solder or applying resin material on the surface of the capacitor electrode of the capacitor part We have adopted methods such as

However, these methods require complicated operations, resulting in poor productivity and a resulting deterioration in yield.

In order to solve these problems, an oscillator 30 with built-in capacitance shown in FIGS. 9 and 10 can be considered. In this oscillator 30, the formation position of the capacitor is changed from the piezoelectric substrate to the protective substrate.

As the piezoelectric substrate 31, a piezoelectric ceramic substrate or the like is used. Vibrating electrodes 32a. 32b
are formed facing each other. The vibrating electrodes 32a, 32b are connected to extraction electrodes 33a, 33b, respectively. This substrate 31 and a protective substrate 34 stacked in the thickness direction
．． 35 are fixed with adhesive to form a sealed vibration space. A dielectric substrate is used as the protection substrates 34 and 35.

FIG. 10 shows the appearance of the oscillator 30 fixed with adhesive. FIG. 10 is a view of the oscillator 30 viewed from the solder mounting surface side. External input/output terminals (A) and (B) are respectively connected to lead electrodes 33a. 33b. Similarly, an external common terminal (C) is formed in the shape of a band at the center of the oscillator 30. These external terminals (A),
(B) and (C) are used as electrodes for attachment to printed wiring boards, etc., and also have a function as capacitive electrodes. That is, between terminals (A) and (C) and between terminals (B) and
(C) between capacitor C1. C2 is formed.

Since the thus obtained oscillator 30 does not require a capacitive electrode to be provided on the piezoelectric substrate 31, complicated operations such as polarization treatment and damping treatment are not required, and productivity and yield are improved. . Further, the area where the capacitive electrode was formed can be omitted, and the size of the piezoelectric substrate 31 can be reduced.

In normal cases, the capacitance of the oscillator 3o with built-in capacitance is a capacitance that can be used practically.

By the way, if it is necessary to further increase the capacitance of the capacitors CI and C2, it is necessary to narrow the gaps between the terminals (A) and (C) and between the terminals (B) and (C).

However, if the gap is made narrower, migration is more likely to occur, and there is also a risk that solder bridges may occur during soldering, resulting in short circuits or solder holes. Furthermore, there is also the concern that it is unstable in terms of environmental resistance such as moisture absorption, dew condensation, rust, and corrosion.

Problems of the Invention Therefore, the problem of the present invention is to prevent migration, solder bridging, etc. from occurring even if the capacitor capacity is increased.
Furthermore, it is an object of the present invention to provide a piezoelectric resonant component that does not cause solder cracks in the capacitor electrode and has excellent environmental resistance characteristics.

Means for Solving a Problem In order to solve a problem that is more than just a problem, we have developed a piezoelectric resonant component according to the present invention, a piezoelectric substrate on which a vibrating electrode is formed, and a dielectric layer stacked in the thickness direction of the piezoelectric substrate. and the substrate form a sealed vibration space, a capacitive electrode is formed on a surface of the dielectric substrate on the vibration space side, and the vibrating electrode and the capacitive electrode are connected to an external terminal. It is characterized by

In the above structure, the required capacitance is obtained in the gap formed between the capacitor electrodes. Since the capacitor electrode is provided on the surface of the protection board facing the vibration space, even if the gap between the electrodes is narrowed to increase the capacitance, there is no need to worry about migration or solder bridges, and the capacitor is shielded from the outside world. Because of this, soldering during mounting, moisture absorption, dew condensation,
There is no risk of rust or corrosion.

On the other hand, the external terminal does not need to be considered as a capacitive electrode as in the conventional case, and is formed in a shape suitable for functioning as an electrode attached to a printed wiring board or the like, or with a sufficient gap.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the piezoelectric resonant component according to the present invention will be described below along with a manufacturing method thereof. In this embodiment, an oscillator with built-in capacitance will be described as a piezoelectric resonant component.

FIG. 1 shows an exploded perspective view of an oscillator 4 with built-in capacitance.

This oscillator 1 is a chip-type oscillator including one resonator and two capacitors. Vibrating electrodes 3a*3b are formed on the top and bottom surfaces of the piezoelectric substrate 2. Further, the electrode 3a is connected to an extraction electrode 4a formed on the left side of the substrate 2, and the electrode 3b is connected to an extraction electrode 4b formed on the right side of the substrate 2. The piezoelectric substrate 2 contains Pb
(ZrIi)Os, BaI'i0. Ceramic substrates, etc. are used.

Dielectric substrates are used as the protection substrates 5 and 8. Protection board 5
Capacitive electrodes 6a, 6b. 6c is formed. The required capacitance is between electrodes 6a and 6b and between electrodes 6
Obtained at the gap formed between b and 6c. That is, the capacitance value is determined by the width of the gap, the length of the gap, the dielectric constant of the substrate 5, etc.

In the actual mass production process, these substrates 2, 5.8 have a wide area and are cut into predetermined dimensions after being bonded.

The substrates 2, 5.8 prepared in this way are fixed by the applied adhesive 9 at a distance so as not to come into direct contact with each other, thereby forming a sealed vibration space (see Fig. 3).
. In this embodiment, the adhesive 9 covers the adhesive portions formed between the capacitor electrodes 6a and 6b and between 6b and 6c to further improve the protective effect. However, covering the gap portion with the adhesive 9 is not an essential component of the present invention.

FIG. 2 shows the appearance of the resonator 1. FIG. 2 is a view of the oscillator 1 viewed from the solder mounting surface side. External input/output terminals (A), (B) and an external common terminal (C) are formed at the left and right ends and the center of the oscillator 1, respectively. A lead electrode 4a and a capacitor electrode 6a are connected to the input/output terminal (A). The other input/output terminal (B) has a lead electrode 4b.
and the capacitor electrode 6c are connected. In addition, the common terminal (
C) is connected to the capacitor electrode 6b. Common terminal (C
) may be formed in a band shape at the center of the oscillator 1.

The oscillator 1 having the above configuration has the same electrical equivalent circuit as shown in FIG. A resonator is inserted between input and output terminals (A) and (B), and two capacitors C1. C2 is inserted between the input/output terminal (A) and the common terminal (C), and between the input/output terminal (B) and the common terminal (C). As shown in FIG. 3, the thus obtained oscillator 1 has capacitive electrodes 6a. 6b. 6c is provided, so even if the gap between the capacitor electrodes is narrowed, there is no risk of migration or solder bridges, resulting in high electrical reliability.Furthermore, since it is isolated from the outside environment, solder joints can be avoided. It has excellent environmental resistance without any fear. On the other hand, the external input/output terminals (A), (B) and the external common terminal (C) do not need to be considered as capacitive electrodes as in the past, and can be used for mounting on printed wiring boards, etc. It can be formed in a shape suitable for functioning as a pole or with a sufficient gap.

4 to 7 show other shapes of capacitive electrodes formed on the protective substrate 5. FIG. Each figure is a perspective view of the substrate 5 seen from the vibration space side.

FIG. 4 shows comb-shaped electrodes 16g, 16b. 16c and capacitor CI. This is intended to increase the capacity of C2.

In FIG. 5, capacitors C1 and C2 are formed independently on a protection substrate 5. In FIG. In FIG. 6, a vibration space forming recess 22 is formed in the center of the protective substrate 5, and a capacitive electrode 1 is formed around the recess 22.
8a. 18b. 18c is provided. The vibration space forming recess 22 is for preventing contact between the capacitor electrode and the vibration electrode. 7, similarly to FIG. 6, a vibration space forming recess 22 is formed in the center of the protective substrate 5, and capacitive electrodes 23a. 23b. 23c. 23d
It has been established.

Note that the piezoelectric resonator according to the present invention is not limited to the above-mentioned embodiments, and can be variously modified within the scope of the gist.

In the embodiment, a capacitive electrode is formed only on the substrate 5 of the two protective substrates 5 and 8, but if the capacitance is insufficient, the capacitive electrode may be formed on both protective substrates.

In the present invention, the capacitive electrode is provided on the side of the sealed vibration space formed by the piezoelectric substrate and the protection substrate, so even if the gap between the capacitive electrodes is narrowed to increase the capacitance, migration will not occur. This eliminates the risk of solder bridging, etc., and provides a piezoelectric resonant component with high electrical reliability.

Furthermore, the capacitive electrode is formed in a sealed vibration space,
Since it is isolated from the outside environment, there is no need to worry about solder cracks, and excellent environmental resistance properties can be obtained. Moreover, it is no longer necessary to consider the capacitive electrode as an electrode attached to a printed wiring board, etc., as in the past, and S! It is possible to design a shape suitable for the function.

On the other hand, external input/output terminals and external common terminals no longer need to be considered as capacitive electrodes as in the past, and can be formed in shapes suitable for functioning as electrodes for mounting on printed wiring boards, etc., or with sufficient gaps. Therefore, a piezoelectric resonant component with high reliability and productivity can be obtained.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of a piezoelectric resonant component that is an embodiment of the present invention, FIG. 2 is a perspective view showing the external appearance of the piezoelectric resonant component, and FIG.
The figure is a vertical sectional view taken along line xx' in FIG. 2. FIG. 4, FIG. 5, FIG. 6, and FIG. 7 are perspective views showing modified examples of the capacitive electrode. FIG. 8 is an electrical circuit diagram of the oscillator. Figure 9,
FIG. 10 shows a technique prior to the present invention, in which 9111 is an exploded perspective view of a piezoelectric resonant component, and FIG. 10 is a perspective view showing the external appearance of the piezoelectric resonant component. 1... Piezoelectric resonant component (capacitance built-in oscillator), 2...
... Piezoelectric substrate, 3a, 3b... Vibration electrode, 5...
・Dielectric substrate (protective substrate), 6ae 6b- 6c.
1 6a, 1 6b- 1 6ct 1 7a, 17
b, 17c, 17dt 18a, 18b. 18
c. 23a. 23b. 23ct 23d "" Capacitance electrode, (A>, (B)...external terminal (external input/output terminal), (C)...external terminal (external common terminal).

Claims (1)

[Claims] 1. A piezoelectric substrate on which a vibrating electrode is formed and a dielectric substrate overlaid in the thickness direction of the piezoelectric substrate form a sealed vibration space, and the capacitive electrode is connected to the vibration space of the dielectric substrate. A piezoelectric resonant component formed on a side surface, the vibrating electrode and the capacitive electrode being connected to an external terminal.