JP3317219B2 - Piezoelectric resonance components with built-in capacitance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a built-in capacitive type piezoelectric resonance component used as, for example, a piezoelectric oscillator, and more particularly to a built-in capacitive type piezoelectric resonance device having an improved laminated structure of a piezoelectric resonant element and a capacitive element. Related to parts.

[0002]

2. Description of the Related Art Hitherto, there has been known a piezoelectric oscillator having a built-in capacitor formed by combining a piezoelectric resonance element and a capacitor.
There is also known a chip type piezoelectric oscillator in which the built-in capacitance type piezoelectric oscillator is housed in a case configured by joining a cap material having an opening below to a case substrate from the opening side. .

In the above-mentioned chip type piezoelectric oscillator, a plurality of terminal electrodes for connection to the outside are formed on a case substrate made of an insulating material such as alumina. Further, on the case substrate, a three-terminal capacitance element formed by forming a plurality of capacitance extraction electrodes on both main surfaces of the dielectric substrate is bonded via a conductive bonding material. Further, a piezoelectric resonance element is bonded and laminated above the rectangular plate-shaped capacitance element via a conductive bonding material, for example, solder or conductive paste. By joining the cap material to the case substrate from the lower opening side of the cap material,
A laminated structure composed of the above-mentioned capacitive element and piezoelectric resonance element is hermetically sealed in an internal space formed by a case substrate and a cap material.

[0004]

In the above-described conventional piezoelectric resonator component with a built-in capacitor, a rectangular plate-shaped capacitor laminated on a case substrate and a rectangular plate-shaped piezoelectric resonator laminated on the capacitor are provided. , Those having the same dimensions, particularly those having the same width dimension, have been used. Therefore, the frequency of the width mode generated when the piezoelectric resonance element is driven substantially matches the natural frequency in the width direction of the capacitive element, and both elements resonate with each other in the width mode, and a spurious response caused by the width mode is generated. There was a problem that it became large.

Therefore, it is sometimes difficult to reliably oscillate at a target frequency. In particular, spurious due to the width mode becomes too large, and abnormal oscillation may occur at the frequency of the spurious response.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks of the conventional piezoelectric resonator component with a built-in capacitor and effectively suppress unnecessary spurious components due to the width mode.
An object of the present invention is to provide a built-in capacitance type piezoelectric resonance component that can stably oscillate at a target frequency.

[0007]

According to a first aspect of the present invention, there is provided a piezoelectric resonance component having a built-in capacitor, wherein the piezoelectric resonance component has a rectangular plate shape, and is laminated to the piezoelectric resonance element via a conductive material. A rectangular plate-shaped capacitance element, wherein the width dimension of the capacitance element is Wc, the frequency constant in the width direction is Nc, the width dimension of the piezoelectric resonance element is We, and the frequency constant in the width direction is Ne.
1.3 ≦ (Ne / We) / (Nc / W
c).

In the invention according to the second aspect, a case substrate is further provided in which the laminated structure including the capacitive element and the piezoelectric resonance element is joined to the upper surface from the capacitive element side via a conductive material and laminated.

According to the third aspect of the present invention, the laminated structure including the capacitive element and the piezoelectric resonance element is surrounded by
A cap material fixed to the case substrate is further provided.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be clarified by describing non-limiting embodiments of the present invention with reference to the drawings.

FIG. 1 is an exploded perspective view of a built-in capacitance type piezoelectric resonance component according to an embodiment of the present invention. In the built-in capacitance type piezoelectric resonance component of the present embodiment, a case is constituted by the case substrate 1 and the cap material 2. The capacitor 3 and the piezoelectric resonance element 4 are housed in this case.

The case substrate 1 is made of a plate-like insulating material having a substantially rectangular planar shape. As the insulating material, an insulating ceramic such as alumina, a synthetic resin, or the like can be used.

A plurality of cutouts are formed in the opposing long side surfaces 1a and 1b of the case substrate 1, respectively. Terminal electrodes 5a to 5c are formed on the upper surface 1c of the case substrate 1, as shown in a plan view in FIG. Each of the terminal electrodes 5a to 5c is formed on the upper surface 1c of the case substrate 1 so as to reach both ends in the width direction, and further extends into cutouts formed on the side surfaces 1a and 1b.

The terminal electrodes 5a to 5c are connected to the case substrate 1
As a conductive material, for example, Ag, Cu, Ag-Pd
And the like. The method for forming the conductive film is not particularly limited, and an appropriate method such as application and baking of a conductive paste, evaporation, plating, and sputtering can be used.

Returning to FIG. 1, the capacitive element 3 is bonded on the case substrate 1 via conductive bonding materials 6a, 6b, 6c. A known conductive adhesive can be used as the conductive bonding materials 6a to 6c.

The capacitive element 3 is a rectangular plate-shaped dielectric substrate 3a.
1 is formed by forming a capacitance extracting electrode 3b on the lower surface as shown by an imaginary line in FIG. 1 and a pair of capacitance extracting electrodes 3c and 3d on the upper surface. Capacitance extraction electrode 3
c and 3d face each other at a predetermined distance in the center of the upper surface of the dielectric substrate 3a. In addition, the capacitance extraction electrode 3
b is formed so as to partially oppose the capacitance extraction electrodes 3c and 3d via the dielectric substrate 3a.

Each end of each of the capacitance extracting electrodes 3c and 3d is extended to reach the lower surface through the end surface of the dielectric substrate 3. Therefore, on the lower surface of the dielectric substrate 3,
The capacitance extraction electrode 3b and the electrode extension portions 3c ₁ and 3d ₁ are formed.

As the dielectric substrate 3a, a rectangular plate-shaped material made of an appropriate dielectric ceramic or synthetic resin can be used. Further, the capacitance extraction electrodes 3b,
3c and 3d can be made of the same metal material as the terminal electrodes 5a to 5c described above.

The capacitive element 3 constitutes a three-terminal capacitor, and the conductive bonding materials 6a, 6b and 6c are respectively bonded to the electrode extension 3c ₁ , the capacitance extraction electrode 3d and the electrode extension 3d _1. And are electrically connected to these. The conductive bonding materials 6a to 6c are bonded to the terminal electrodes 5a to 5c on the lower surfaces, respectively.

An insulating adhesive 7 is applied to the upper surface of the case substrate 1 as shown by hatching in FIG. The insulating adhesive 7 is provided except for the portions to which the conductive bonding materials 6a to 6c are applied, that is, the rectangular regions 7a and 7c.
It is applied except for b and 7c. This insulating adhesive 7
Is applied to join the capacitive element 3 to the case substrate 1 and to join a cap material 2 described later to the case substrate 1. As the insulating adhesive 7, an appropriate insulating adhesive such as an epoxy adhesive or a silicone adhesive can be used.

The piezoelectric resonator 4 is an energy-trap type piezoelectric resonator utilizing harmonics in the thickness longitudinal vibration mode,
It has a rectangular plate-shaped piezoelectric plate 4a. The piezoelectric plate 4a can be made of a piezoelectric ceramic such as a lead zirconate titanate-based ceramic, or a piezoelectric single crystal such as quartz or LiNbO ₃ . When the piezoelectric plate 4a is made of piezoelectric ceramics, it is polarized in the thickness direction.

The first excitation electrode 4 is provided on the upper surface of the piezoelectric plate 4a.
b is formed. The first excitation electrode 4b is a piezoelectric plate 4
a extends from the center of the upper surface toward one end.
Further, a second excitation electrode 4c is formed on the lower surface of the piezoelectric plate 4a. The second excitation electrode 4c extends from the center of the lower surface of the piezoelectric plate 4a to one end of the piezoelectric plate 4a. The excitation electrodes 4b and 4c are electrically connected by a conductive film 4d on one end surface of the piezoelectric plate 4a.

On the other hand, inside the piezoelectric plate 4a, an internal electrode 4e is formed at an intermediate height position. The inside 4e is arranged so as to overlap the excitation electrodes 4b and 4c via the piezoelectric layer, and is drawn out to the other end of the piezoelectric plate 4a. At the other end of the piezoelectric plate 4a, an extraction electrode 4f is formed so as to cover the end surface and reach the upper and lower surfaces.

By applying an AC voltage between the first and second excitation electrodes 4b and 4c and the internal electrode 4e, the piezoelectric resonator 4 is excited in the thickness longitudinal vibration mode, Resonance characteristics utilizing the higher harmonics can be obtained.

The piezoelectric resonance element 4 is made of a conductive bonding material 8.
a and 8b, and are electrically connected to the capacitive element 3. That is, the conductive bonding material 8a electrically connects the capacitance extraction electrode 3c and the extraction electrode 4f formed on the piezoelectric resonance element 4, and the conductive bonding material 8b
The capacitance extraction electrode 3d and the second excitation electrode 4c are electrically connected.

Further, the piezoelectric resonance element 4 is mechanically joined to the capacitance element 3 by the conductive joining materials 8a and 8b. The feature of this embodiment is that when the width of the piezoelectric resonance element 4 is We, the frequency constant in the width direction is Ne, the width of the capacitive element 3 is Wc, and the frequency constant in the width direction is Nc,
That is, the dimensions of the capacitive element 3 and the piezoelectric resonance element 4 are determined so as to satisfy the relationship of 1.3 ≦ (Ne / We) / (Nc / Wc).

In the piezoelectric resonance element 4 of the present embodiment, the dimensions of the piezoelectric resonance element 4 and the capacitance element 3 are determined so as to satisfy the above equation.
Unnecessary spurious due to the width mode can be effectively suppressed, and it is possible to stably oscillate harmonics of the thickness longitudinal vibration.

In FIG. 1, reference numeral 2 denotes a cap material, which is made of, for example, a metal material such as stainless steel or aluminum or an appropriate synthetic resin. The cap member 2 has an opening at the bottom, and the peripheral edge of the opening is joined to the case substrate 1 via an insulating adhesive 7. Therefore,
A closed space is constituted by the case substrate 1 and the cap material 2,
The above-described laminated structure of the capacitive element 3 and the piezoelectric resonance element 4 is housed in the sealed space, and is sealed from the outside.

FIG. 3 is a perspective view showing the appearance of the built-in capacitance type piezoelectric resonance component 9 according to the present embodiment obtained as described above. In the piezoelectric resonance component 9, the terminal electrodes 5a, 5
The piezoelectric resonance element 4 is connected between the terminals c and c, and a capacitor is inserted between the terminal electrode 5b and the terminal electrodes 5a and 5c. That is, the circuit configuration shown in the circuit diagram of FIG.

In the built-in capacitance type piezoelectric resonance component 9 of this embodiment, the terminal electrodes 5a to 5c are extended so as to reach the notches formed in the side surfaces 1a and 1b of the case substrate 1. Therefore, like other chip-type electronic components, surface mounting can be easily performed on, for example, a printed circuit board using an automatic machine.

Next, the fact that unnecessary spurious due to the width mode can be suppressed in the piezoelectric resonator component 9 with a built-in capacitor will be described based on specific experimental examples. Now, the built-in capacitance type piezoelectric resonance component 9 according to the above-described embodiment was manufactured with the following specifications. That is, the capacitance element 3 has a length of 2.2.
X Dielectric substrate 3a made of lead zirconate titanate having a thickness of 0.15 mm (the width W was changed as described later).
Are formed on the upper surface of the capacitor, and the capacitance extracting electrodes 3c and 3d having an area of 0.8 × Wmm ² are formed on the lower surface.
A capacitor extraction electrode 3b was formed so as to face each of the electrodes d in a region of 0.1 × Wmm ² . As the piezoelectric resonance element 4, a piezoelectric plate 4a made of lead titanate and having a thickness longitudinal vibration mode of 2.2 × 0.3 mm (the width was changed as described later) is used. In the central region of the piezoelectric plate 4a, a plate was prepared in which the first and second excitation electrodes 4d and 4c and the internal electrode 4e faced ^each other in a region of 0.24 mm ² via the piezoelectric layer.

The capacitive element 3 and the piezoelectric resonance element are sequentially laminated on the case substrate 1 using an epoxy-based conductive adhesive as conductive bonding materials 6a to 6c, 8a, 8b, and a cap material made of a nickel-iron alloy 2 was joined to the case substrate 1. In this way, the built-in capacitance type piezoelectric resonance component 9 of the embodiment
Was prepared.

In the piezoelectric resonance component 9, the capacitive element 3
And the width dimension of the piezoelectric resonance element 4 is changed, that is, (N
e / We) / (Nc / Wc) were variously changed, and the magnitude of the phase of the spurious response caused by the width mode was measured.
FIG. 5 shows the results.

As apparent from FIG. 5, the above ratio (Ne /
If We) / (Nc / Wc) is 1.3 or more, it is understood that the spurious phase caused by the width mode is 60 ° or less. Normally, in a piezoelectric resonator using harmonics in the thickness longitudinal mode, when the phase of the spurious response due to the width mode exceeds 60 °, abnormal oscillation is caused, which is a problem in practical use. Therefore, as is apparent from FIG. 5, when the above ratio is set to 1.3 or more, a piezoelectric resonator component with a built-in load capacitance capable of stably oscillating harmonics of the thickness longitudinal vibration without causing abnormal oscillation is provided. It can be understood that it can be done.

FIGS. 6 and 7 are diagrams showing impedance-frequency characteristics of a comparative example and an example for explaining spuriousness caused by the width mode. In the comparative example shown in FIG. 6, Ne = 2200 Hz · m and We = 0.4
mm, Nc = 1800 Hz · m, Wc = 0.4 mm, that is, the above ratio (Ne / We) / (Nc / Wc) = 1.2
The characteristics of a piezoelectric resonance component with a built-in load capacitance configured in the same manner as in the example, except that it is set to 2, are shown. In FIG. 6, the arrow A indicates the response of the third harmonic of the thickness longitudinal vibration, and the arrow B indicates the spurious response caused by the width mode. As is apparent from FIG. 6, a response B caused by a relatively large width mode occurs near the response A of the thickness longitudinal vibration mode harmonic.

On the other hand, FIG. 7 shows that in the above embodiment, Ne = 2200 Hz.m, We = 0.4 mm, Nc
= 1800 Hz · m, Wc = 0.6 mm, that is, impedance-frequency characteristics when the ratio (Ne / We) / (Nc / Wc) = 1.83 is shown. As is clear from FIG. 8, in the present embodiment, it is understood that the response due to the width mode indicated by the arrow C is extremely small.

In the above-described embodiment, the case is constituted by the case substrate 1 and the cap member 2, but the cap member 2 is not necessarily used. Further, instead of the cap member 2, a flat case substrate similar to the case substrate 1 may be laminated above the piezoelectric resonance element 4 via the conductive adhesive or the insulating adhesive.

Further, as the case substrate 1, the capacitive element 3 and the piezoelectric resonance element 4 are laminated on the bottom surface instead of the plate-like member, and the periphery of the portion where these elements are laminated is located from the upper surface of the piezoelectric resonance element 4. Alternatively, a bottomed case substrate having an opening that opens upward, which has a side wall that extends upward, may be used. In this case, by using a flat cover material or the like so as to close the upper opening, it is possible to configure a case in which the piezoelectric resonance element 4 and the capacitance element 3 can be hermetically sealed.

The piezoelectric resonance element 4 is not limited to the one using the harmonics of the thickness longitudinal vibration described above, but may be a device using a fundamental wave of the thickness longitudinal vibration, or a thickness longitudinal vibration mode or a width mode. A vibration mode other than the above may be used.

As described above, the capacitance element 3 is also
Capacitance extraction electrodes 3b on both surfaces of a single dielectric substrate 3a,
The structure is not limited to the one having the 3c and 3d formed therein, and may have another structure such as a multilayer capacitor having internal electrodes as long as it has a rectangular plate shape.

[0041]

According to the first aspect of the present invention, in a piezoelectric resonance component having a structure in which a rectangular plate-shaped piezoelectric resonance element and a rectangular plate-shaped capacitance element are joined via a conductive material, Since Ne / We) / (Nc / Wc) is equal to or greater than 1.3, unnecessary spurious due to the width mode can be effectively suppressed, and therefore, a capacitor capable of stably oscillating at a desired frequency. It is possible to provide a built-in piezoelectric resonance component.

According to the second aspect of the present invention, since the laminated structure including the capacitive element and the piezoelectric resonance element is joined and laminated from the capacitive element side to the upper surface of the case substrate via a conductive material, the laminated structure is formed on the case substrate. By providing a terminal electrode and electrically connecting the terminal electrode to a capacitor with a conductive material,
A piezoelectric resonance component that can be surface-mounted on a printed circuit board or the like from the case substrate side can be provided.

According to the third aspect of the present invention, since the cap member is fixed to the case substrate so as to surround the laminated body composed of the capacitive element and the piezoelectric resonance element, the cap material is fixed to the case substrate. The laminate is sealed, thus
A piezoelectric resonance component having excellent environmental resistance, impact resistance, and the like can be obtained.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view for explaining a built-in capacitance type piezoelectric resonance component according to an embodiment of the present invention.

FIG. 2 is a plan view of a case substrate used in the piezoelectric resonance component shown in FIG.

FIG. 3 is a perspective view showing the appearance of the built-in capacitance type piezoelectric resonance component of the embodiment shown in FIG. 1;

FIG. 4 is a diagram showing a circuit configuration of the built-in capacitance type piezoelectric resonance component shown in FIG. 3;

FIG. 5 is a diagram showing a change in the phase of the response caused by the width mode when the ratio (Ne / We) / (Nc / Wc) is changed in the piezoelectric resonator component with a built-in capacitor according to the embodiment.

FIG. 6 is a diagram showing impedance-frequency characteristics of a built-in capacitance type piezoelectric resonance component prepared for comparison.

FIG. 7 is a diagram showing impedance-frequency characteristics of the piezoelectric resonator component with a built-in capacitor according to the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Case board 2 ... Cap material 3 ... Capacitance element 4 ... Piezoelectric resonance element 6a-6c ... Conductive joining material 8a, 8b ... Conductive joining material 9 ... Capacitance built-in type piezoelectric resonance component

Claims (3)

(57) [Claims] 1. A rectangular plate-shaped piezoelectric resonance element, and a rectangular plate-shaped capacitance element bonded and laminated to the piezoelectric resonance element via a conductive material, wherein the width dimension of the capacitance element is Wc. The frequency constant in the width direction is N
c, when the width dimension of the piezoelectric resonance element is We and the frequency constant in the width direction is Ne, 1.3 ≦ (Ne / We) /
(Nc / Wc). A piezoelectric resonance component with a built-in capacitor. 2. The case according to claim 1, further comprising a case substrate in which the laminated structure including the capacitive element and the piezoelectric resonance element is joined and laminated on the upper surface from the capacitive element side via a conductive material. A piezoelectric resonance component with a built-in capacitor as described. 3. The piezoelectric device with a built-in capacitor according to claim 2, further comprising a cap material fixed to the case substrate so as to surround a laminated structure including the capacitor element and the piezoelectric resonance element. Resonant components.