JPH11168344A - Piezo-resonator and piezoelectric resonance component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration of resonance characteristics and filter characteristics even when components are mounted on a supporting substrate and made into a package by forming the edge of an extraction electrode in the lower face of the piezoelectric substrate in projecting and recessed parts. SOLUTION: The edge of the parts of the input electrode and the output electrode 8 of the piezoelectric filter 2, which are led to the lower face of the piezoelectric substrate 3, is formed in a comb type and it has the projecting and recessed parts. Namely, the edges 6a and 8a are formed to be connected to the projecting and recessed parts. The parts of the input electrode and the output electrode 8, which are led to the lower face of the piezoelectric substrate 3, are jointed to conductive paste and a ground electrode 9 is jointed to an outer electrode with conductive paste. This, undesired electrostatic capacitance generated with ground potential can be reduced. The projecting/recessed parts at the edge of the an extraction electrode in the lower face of the piezoelectric substrate 3 are formed into the comb shape or waveform.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric resonance element such as a piezoelectric resonator or a piezoelectric filter and a piezoelectric resonance component obtained by laminating a piezoelectric resonance element on the substrate. The present invention relates to a piezoelectric resonance element and a piezoelectric resonance component in which the structure of an extraction electrode for connection to the outside is improved.

[0002]

2. Description of the Related Art For commercialization of a piezoelectric resonance element such as a piezoelectric resonator or a piezoelectric filter, a structure in which a piezoelectric resonance element is housed in a case is widely used. As an example of such a case structure, a case is known in which a piezoelectric resonance element is bonded on a support substrate and a cap is attached to the support substrate so as to surround the piezoelectric resonance element.

Referring to FIGS. 11 and 12, the structure of a conventional piezoelectric resonance component will be described. FIG. 11 (a) and (b)
FIG. 1 is a plan view and a bottom view showing a piezoelectric filter as an example of a conventional piezoelectric resonance element. The piezoelectric filter 51 is configured using a rectangular piezoelectric substrate 52. Piezoelectric substrate 5
2 is polarized in the direction of arrow P, that is, in the direction parallel to the piezoelectric substrate 52. On the upper surface of the piezoelectric substrate 52, the resonance electrodes 53a and 53b face each other with a predetermined gap. A common electrode 53c is formed on the lower surface of the piezoelectric substrate 52 so as to face the resonance electrodes 53a and 53b. The resonance electrodes 53a and 53b and the common electrode 53c constitute a first resonance section.

On the other hand, a second resonance section is formed on the piezoelectric substrate 51 at a position separated from the first resonance section. The second resonating portion includes a resonating electrode 54a,
54b is formed by forming a common electrode 54c on the lower surface.

The resonance electrode 53a is connected to an input electrode 56 formed near one end on the upper surface of the piezoelectric substrate 52 by a connection conductive portion 55a. Also, the resonance electrode 53
b and the resonance electrode 54a are electrically connected by the connection conductive part 55b. The resonance electrode 54b is connected to the connection conductive portion 5
5c, the output electrode 5 formed near the end of the piezoelectric substrate 52 opposite to the side on which the input electrode 56 is formed.
7 is connected.

The common electrode 53c and the common electrode 54c are connected to the piezoelectric substrate 52 by connecting conductive portions 55d and 55e, respectively.
Is connected to a ground electrode 58 formed at the center of the lower surface of the. In addition, as shown in FIG.
It is mounted on a support substrate 60. Therefore, the input electrode 56 and the output electrode 57 are formed from the upper surface of the piezoelectric substrate 52 to the lower surface via the end surface (FIG. 11).
(B)).

As shown in FIG. 12, when a piezoelectric filter 51 is commercialized, conductive pastes 61 a to 61 c are applied to external electrodes 60 a to 60 c formed on a support substrate 60.
The piezoelectric filter 51 is joined via the line c. Thereafter, a cap (not shown) is fixed to the support substrate 60 to surround the piezoelectric filter 51.

[0008]

As described above, in a conventional piezoelectric resonance component in which the piezoelectric filter 51 is mounted on the support substrate 60, and a cap or the like is bonded and packaged, the obtained filter waveform has a symmetry. There was a problem that it was not enough. That is, the characteristics of the piezoelectric filter 51 may be deteriorated by packaging.

Further, even when the piezoelectric resonator is packaged, the characteristics of the piezoelectric resonator may be similarly deteriorated by the packaging. An object of the present invention is to solve the above-mentioned drawbacks of the conventional piezoelectric resonance element, and to mount the piezoelectric resonance element on a support substrate and package the same, so that the resonance characteristic and the filter characteristic hardly deteriorate,
Another object of the present invention is to provide a piezoelectric resonance component in which such a piezoelectric resonance element is mounted on a support substrate, and has excellent resonance characteristics and filter characteristics.

[0010]

According to a first aspect of the present invention, there is provided a piezoelectric substrate, a resonating portion formed on the piezoelectric substrate, and a plurality of piezoelectric substrates formed on a lower surface of the piezoelectric substrate for connection to the outside. In a piezoelectric resonance element including an extraction electrode, an edge of the extraction electrode on the lower surface of the piezoelectric substrate has a shape having irregularities.

The shape of the edge of the extraction electrode in the lower surface of the piezoelectric substrate having irregularities is not particularly limited, and the edge may be comb-shaped as described in claim 2, or A third aspect of the present invention may be configured to have a corrugated shape.

Further, the piezoelectric resonance element according to the present invention can be applied to an appropriate piezoelectric resonance element such as a piezoelectric resonator or a piezoelectric filter. In a specific aspect of the present invention, as described in claim 4, In order to form a filter, a plurality of resonance units are formed on the piezoelectric substrate.

According to a fifth aspect of the present invention, there is provided the piezoelectric resonance element according to any one of the first to fourth aspects, wherein the piezoelectric resonance element is bonded to a supporting substrate via a conductive bonding material. Parts. In this case, the conductive bonding material is not particularly limited, but a conductive paste can be suitably used as described in claim 6.

[0014]

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 a perspective view showing a main part of a piezoelectric resonance component according to one embodiment of the present invention. The piezoelectric resonance component of the present embodiment has a structure in which a piezoelectric filter 2 as a piezoelectric resonance element is mounted on a rectangular plate-shaped support substrate 1.

The piezoelectric filter 2 is made of, for example, a piezoelectric ceramic such as a piezoelectric ceramic made of lead zirconate titanate or a piezoelectric single crystal such as a quartz crystal. As shown by the arrow, it is parallel to the longitudinal direction of the piezoelectric substrate 3.

The piezoelectric substrate 3 has first and second resonance sections 4
5 are configured. The first resonance section 4 includes a resonance electrode 4
a, 4b and a common electrode 4c (see FIG. 2) formed on the lower surface. The resonance electrodes 4a and 4b are opposed on the piezoelectric substrate 3 with a predetermined gap therebetween. The common electrode 4c is formed so as to face the resonance electrodes 4a and 4b and the piezoelectric substrate 3 from front to back. Similarly, in the second resonance section 5, the resonance electrodes 5a and 5b and the common electrode 5c are formed.

The resonance electrode 4a is electrically connected to the input electrode 6 by a connection conductive portion 7a. The input electrode 6 is formed from the upper surface of the piezoelectric substrate 3 to the lower surface via the end surface.

Further, the resonance electrode 4b and the resonance electrode 5a are electrically connected by the connection conductive portion 7b. The resonance electrode 5b is electrically connected to the output electrode 8 via the connection conductive part 7c. The output electrode 8 is formed so as to extend from the upper surface of the piezoelectric substrate 3 to the lower surface via the end surface, similarly to the input electrode 6.

The input electrode portion and the output electrode portion on the lower surface of the piezoelectric substrate 3 correspond to the extraction electrodes in the present invention.

As shown in the bottom view of FIG. 2, in the portions of the input electrode and the output electrode 8 which reach the lower surface of the piezoelectric substrate 2, the edges in the lower surface have a comb-like shape. It is comprised so that it may have. That is, the end edges 6a and 8a have a shape in which a concave portion and a convex portion are connected as shown in FIG.

On the lower surface of the piezoelectric substrate 3, an earth electrode 9 is formed at the center. The ground electrode 9 is connected to the common electrodes 4c and 5c by connection conductive portions 7c and 7d. The various electrodes described above, that is, the resonance electrodes 4a, 4b,
5a, 5b, common electrodes 4c, 5c, connection conductive portions 7a to 7
The d and the input / output electrodes 6 and 8 are all formed by applying an appropriate conductive material by a method such as application and curing of a conductive paste, vapor deposition, plating, and sputtering.

Returning to FIG. 1, the support substrate 1 is made of an appropriate insulating material such as an insulating ceramic such as alumina or a synthetic resin, and has a substantially rectangular planar shape. The external electrodes 10 a to 10 a
10c is formed. The external electrodes 10a to 10c
The support substrate 1 is formed so as to reach both end edges 1a and 1b.

On the other hand, as shown in a schematic sectional view in FIG.
The piezoelectric filter 2 is joined to the support substrate 1 via conductive pastes 11a to 11c. That is, portions of the input electrode 6 and the output electrode 8 of the piezoelectric filter 2 reaching the lower surface of the piezoelectric substrate 3 are formed by the conductive pastes 11a and 11c.
The ground electrode 9 is joined to the external electrodes 10a and 10c by the conductive paste 11b.

In place of the conductive pastes 11a to 11c, an appropriate conductive bonding material such as solder or silver solder may be used.

As shown by a dashed line A in FIG. 3, a cap is attached to the upper surface of the support substrate 1, whereby the piezoelectric filter 2 is housed in a case composed of the cap and the support substrate 1.

In this embodiment, a package having a cap and a supporting substrate 1 is used as a case forming a package. However, a rectangular frame-shaped case material is laminated on the supporting substrate 1 to form a rectangular frame-shaped case material. The case may be configured by fixing the lid material so as to close the opening. That is, the members forming the case are not particularly limited, and the support substrate 1 is not limited to a flat plate, but has a three-dimensional shape having a concave portion in which the piezoelectric resonance element is housed. There may be.

The feature of the piezoelectric resonance component of the present embodiment is that the edges 6a, 8a in the lower surface of the portion reaching the lower surfaces of the input electrode 6 and the output electrode 8 of the piezoelectric resonance element 2 are formed to have irregularities. Is to be. That is, the edges 6a,
8a is configured so as to have irregularities, so that it is securely in contact with the conductive pastes 11a, 11c, and is not only securely bonded to the external electrodes 10a, 10c on the support substrate 1, but also between the ground potential. The resulting unwanted capacitance can be reduced, thereby improving the symmetry of the filter waveform.

In the above embodiment, the piezoelectric resonance element is used.
In the lower surface of the input / output electrode on the lower surface of all the piezoelectric filters 2
Edges 6a, 8a of the two protruding portions 6a₁, 6a_Two, 8
a₁, 8a_TwoIs configured to have
The shape of the edge having irregularities is not particularly limited. An example
For example, as shown in FIG.
Outgoing part 6a_ThreeWith protrusions 6a at both ends_ThreeSmaller than the width of
Protruding part 6a_Four, 6a _FiveAs having teeth like
Is also good. In addition, as shown in FIG.
6a₆~ 6a₈The edge 6a is comb-shaped so as to have
You may.

Further, the present invention is not limited to the one having a comb tooth shape, and the edge 6a may have a corrugated shape as shown in FIG.

In the conventional piezoelectric filter 51, as shown in FIG. 6, an edge 56a of the input electrode in the lower surface of the piezoelectric substrate is provided.
Is linear, but in this embodiment and the modified examples shown in FIGS. 4 and 5, the electrode edge 6a in the lower surface has irregularities. The capacity can be reduced, and the filter characteristics can be improved.

Next, based on specific experimental examples, a description will be given of how the filter waveform is improved when a piezoelectric resonance section is formed using the piezoelectric filter 2 of the present embodiment. As the piezoelectric filter 2, a length of 6.7 × a width of 1.25 × a thickness of 0.2 [m
m], and a piezoelectric filter 2 having a center frequency of 6.0 MHz was formed using a piezoelectric substrate 3 made of lead zirconate titanate having an external dimension of [m]. In the portion of the input / output electrode reaching the lower surface of the piezoelectric substrate 3, the dimensions B to D in FIG.
m, C = 0.30 mm, D = 0.35 mm, and the shape was a comb tooth shape. As for the output electrode 8, the input electrode 6
The same as above.

For comparison, an input / output electrode edge located on the lower surface of the piezoelectric substrate is separated from the edge surface of the piezoelectric substrate by 0.4 mm, and each input / output electrode has a linear input / output electrode. A conventional piezoelectric filter was prepared.

As shown by the broken line in FIG.
The piezoelectric filter of the above embodiment and the piezoelectric filter of the related art were bonded on the support substrate 1 and packaged, with the piezoelectric filter interposed between the support substrate so as to have a diameter of 0.6 mm. The filter characteristics of each piezoelectric resonance component were measured. The results are shown in FIGS.

FIGS. 7A and 7B and FIGS.
(B) is a diagram showing attenuation-frequency characteristics and group delay time-frequency characteristics of four conventional piezoelectric filters. The dashed line indicates the attenuation-frequency characteristics, and the solid line indicates the group delay time-frequency characteristics.

On the other hand, FIGS. 9A and 9B and FIG.
(A) and (b) show the attenuation-frequency characteristics (dashed-dotted line) and the group delay time-frequency characteristics (solid line) of the piezoelectric filters of the four embodiments.

As is clear from the comparison between the characteristics shown in FIGS. 7 and 8 and the characteristics shown in FIGS. 9 and 10, the edges of the input / output electrodes on the lower surface of the piezoelectric substrate are linear. It can be seen that in the conventional example, the symmetry of the filter waveform is impaired, whereas in the piezoelectric filter of the embodiment, the symmetry of the filter waveform is enhanced.

Table 1 below shows the electrical characteristics when the piezoelectric filters of the above-described embodiments and the conventional example are mounted on a supporting substrate.

[0039]

[Table 1]

The values in Table 1 show the average values of 30 samples in each of the embodiment and the conventional example. The upper part shows the average value, and the lower part shows the standard deviation σ. Also, 3 dBW in Table 1 indicates a 3 dB attenuation width, that is, an insertion loss of 3 dB.
B indicates a frequency bandwidth within B, Lo-sp indicates a magnitude of a spurious component on a low frequency side (5.0 to 6.0 MHz), and Hi-sp indicates a high frequency side (that is, 6.0 to 6.0 MHz).
In the passband, the ripple indicates the magnitude of the ripple (the difference between the largest peak and the smallest valley in the passband), and D-GDT indicates the magnitude of the ripple in the passband. , Group delay time deviation (difference between the maximum value and the minimum value of the group delay time within the pass band).

As is clear from Table 1, from the measurement results of 30 samples in each of the conventional example and the comparative example, the 3 dB band was obtained by forming the edge on the lower surface of the portion reaching the lower surface of the output electrode into a comb-like shape. It can be seen that the width can be increased, the variation in the filter characteristics can be reduced, the in-band ripple can be significantly reduced, and the group delay time characteristics are also improved.

In the embodiment shown in FIG. 1, a double mode piezoelectric filter utilizing a thickness-shear vibration mode is shown as the piezoelectric resonance element. However, the present invention is applicable to a piezoelectric resonator other than the piezoelectric filter. The vibration mode to be used is not limited to the thickness-shear vibration mode.

[0043]

According to the first aspect of the present invention, in a piezoelectric resonance element having a lead electrode for connection to the outside on the lower surface of a piezoelectric substrate on which a resonating portion is formed, the lead electrode in the lower surface of the piezoelectric substrate is provided. Since the edge has a shape having irregularities, stray capacitance between the extraction electrode and the ground potential can be reduced, for example, when mounted on a printed circuit board or a support substrate for commercialization, It is possible to improve resonance characteristics and filter characteristics. Therefore,
It is possible to provide a piezoelectric resonance element having good resonance characteristics and filter characteristics.

According to the fifth aspect of the present invention, since the piezoelectric resonance element is bonded to the supporting substrate via the conductive bonding material, the lead electrode is connected to the supporting substrate via the conductive bonding material. Even when the connection is made to the connection electrode, the capacitance between the extraction electrode and the ground potential can be reduced, so that it is possible to provide a piezoelectric resonance component having good resonance characteristics.

[Brief description of the drawings]

FIG. 1 is a perspective view for explaining a piezoelectric resonance component according to one embodiment of the present invention.

FIG. 2 is a bottom view of a piezoelectric filter as a piezoelectric resonance element used in the piezoelectric resonance component of FIG.

FIG. 3 is a schematic sectional view of the piezoelectric resonance component shown in FIG. 1;

FIGS. 4A and 4B are partial cutaway plan views showing modified examples of a structure in which the edge of the extraction electrode in the lower surface of the piezoelectric substrate has a comb shape.

FIG. 5 is a partially cutaway plan view showing an example in which the edge of the extraction electrode in the lower surface of the piezoelectric substrate is corrugated.

FIG. 6 is a partially cutaway plan view for explaining an edge of a lead electrode on a lower surface of a piezoelectric substrate in a conventional piezoelectric filter prepared for comparison.

7A and 7B are diagrams showing attenuation-frequency characteristics and group delay time-frequency characteristics of a conventional piezoelectric filter.

FIGS. 8A and 8B are diagrams showing attenuation-frequency characteristics and group delay time-frequency characteristics of a conventional piezoelectric filter.

FIGS. 9A and 9B are diagrams showing filter characteristics and group delay time-frequency characteristics in the piezoelectric resonance component of the example.

FIGS. 10A and 10B are diagrams showing filter characteristics and group delay time-frequency characteristics in the piezoelectric resonance component of the example.

11A and 11B are a plan view and a bottom view of a conventional piezoelectric filter.

FIG. 12 is a cross-sectional view illustrating a main part of a conventional piezoelectric resonance component in which the piezoelectric filter shown in FIG. 11 is mounted on a support substrate.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Support substrate 2 ... Piezoelectric filter as a piezoelectric resonance element 3 ... Piezoelectric substrate 4a, 4b, 5a, 5b ... Resonance electrode 4c, 5c ... Common electrode 4,5 ... Resonance part 6,8 ... Input / output electrode 6a, 8a ... Edges of extraction electrodes from which input / output electrodes are extended to the lower surface 9 ... Earth electrodes 11a to 11c ... Conductive paste as conductive bonding material

Claims (6)

[Claims] 1. A piezoelectric resonance element comprising: a piezoelectric substrate; a resonance section formed on the piezoelectric substrate; and a plurality of extraction electrodes formed on a lower surface of the piezoelectric substrate and connected to the outside. Wherein the edge within the lower surface of the piezoelectric substrate has an uneven shape. 2. The piezoelectric resonance element according to claim 1, wherein an edge of the extraction electrode in the lower surface of the piezoelectric substrate has a comb-like shape, so that the edge has irregularities. 3. The piezoelectric resonance element according to claim 1, wherein an edge of the extraction electrode in the lower surface of the piezoelectric substrate has a waveform shape, so that the edge has irregularities. 4. The piezoelectric resonance element according to claim 1, wherein a plurality of resonance parts are formed on the piezoelectric substrate to form a filter. 5. A piezoelectric resonance component, wherein the piezoelectric resonance element according to claim 1 is bonded to a support substrate via a conductive bonding material. 6. The piezoelectric resonance component according to claim 5, wherein the conductive bonding material is a conductive paste.