JPH0998062A - Monolithic crystal filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress higher harmonic modes of undesired flection and contour vibrations and to secure satisfactory band-pass characteristics. SOLUTION: A thin AT-cut crystal plate is machined into a rectangular crystal plate 1, and an input electrode 11 and an output electrode 12 are provided close to each other in the Z' axis direction on the plate 1 with a prescribed space secured between them. Then the lead-out electrodes 111 and 121 are led out to the end face of the plate 1 from both electrodes 11 and 12 respectively. A common electrode 13 including the parts corresponding to the electrodes 11 and 12 is provided on the rear surface of the plate 1. The electrode 13 has an approximately rhombic shape and has the width that is gradually reduced toward the end part of every side of the plate 1 centering on the parts corresponding to both electrodes 11 and 12. Thus the electrode 13 is formed up to the points near the end part of every side of the plate 1 and forms the lead-out electrodes 131 and 132 at the end parts of upper and lower sides of the plate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monolithic crystal filter using thickness type vibration used in communication equipment and the like.
The present invention relates to a monolithic crystal filter that suppresses the influence of a higher-order bending or contour vibration mode.

[0002]

2. Description of the Related Art Due to the miniaturization of communication devices and the like, the piezoelectric vibrating components used in these devices are also required to be miniaturized, and a chip type is required for ease of mounting. Figure 10 shows a conventional chip-type ultra-miniaturized monolithic crystal filter.
This will be described with reference to FIG. FIG. 10 is an exploded perspective view of a chip-type monolithic crystal filter using a rectangular crystal plate, and FIG. 11 is a plan view of the crystal plate mounted on a package. An input electrode is provided on the surface of the rectangular quartz plate 8.
Output electrodes 81 and 82 are formed, and extraction electrodes 81a and 82a are provided from these electrodes toward the ends of the quartz plate. On the back surface, a common electrode 83 (not shown) is formed at a position corresponding to the input electrode and the output electrode 81, 82, and the extraction electrodes 83a, 83 from this electrode toward the edge of the quartz plate.
a (not shown). The package 9 is made of ceramics, has a thin rectangular parallelepiped shape with an open upper surface, a metal ring 91 is formed in the opening, and external lead-out electrodes 92, 93, 94, and 95 for leading electrodes from the inside of the package to the outside. It is formed integrally. The quartz plate 8 is mounted on such a package 9, necessary conductive bonding is performed with a conductive bonding material S, the cap C made of a metal plate is covered on the opening, and the metal ring and the cap are connected to each other. Hermetically sealed by means such as seam welding.

[0003]

In a monolithic quartz filter having such a structure, thickness shear vibration is excited by using an input / output electrode and a common electrode formed opposite to each other with a quartz plate interposed therebetween as a resonance region, and is generally symmetric. Mode vibration (fs)
And obliquely symmetric mode vibration (fa) are excited, and these are acoustically coupled to form a main vibration, which constitutes an electromechanical filter having a predetermined frequency pass band.

If the external dimensions of such a monolithic crystal filter are reduced, unnecessary vibration modes are generated in addition to the main vibrations of the symmetric mode and the obliquely symmetric mode, and these modes are strongly coupled to the main vibrations to generate spurious components. Sometimes. In particular, in the case of a small rectangular crystal plate, such spurious may be noticeable. This unnecessary vibration mode may be high-order thickness shear vibration, or is considered to be a bending vibration mode determined by the external dimensions of the crystal plate or each harmonic mode of the contour vibration mode. This is because as the external dimensions become smaller, the order of the harmonics of these unwanted vibration modes to be coupled is lowered, and acoustic coupling is likely to be performed. Therefore, it is necessary to design the external dimensions in consideration of suppression of these unnecessary vibration modes for each frequency used.

[0005] However, even when a design is made in consideration of the above circumstances, depending on the error in the processing technology of the quartz plate and the temperature range in which the monolithic quartz filter is used, etc.
The unnecessary vibration modes described above were sometimes excited. In some cases, such unnecessary vibration modes can be suppressed by subjecting the quartz plate to convex processing or bevel processing.However, when a thickness-based vibration is used, its frequency is inversely proportional to the thickness of the quartz plate. Due to the increase in the frequency of the crystal plate, the quartz plate has become extremely thin, so that the above-mentioned processing cannot be performed in practice.

The present invention has been made to solve the above problems, and suppresses unnecessary harmonic modes of unnecessary bending vibration and contour vibration generated near the main vibration (nominal frequency).
An object of the present invention is to provide a monolithic crystal filter capable of obtaining a good pass band as an electromechanical filter.

[0007]

In order to solve the above problems, a monolithic crystal filter according to claim 1 is formed by forming an input electrode and an output electrode close to one main surface of a crystal plate at a predetermined interval. , And a resonance electrode is formed on the other main surface by providing a common electrode having at least the portions corresponding to the input electrode and the output electrode, respectively, and an extraction electrode for leading out each electrode to the outside is formed. In a monolithic crystal filter using system vibration,
The common electrode is characterized in that its width gradually decreases toward the end face of the crystal plate around the portions corresponding to the input electrode and the output electrode, and is formed up to the vicinity of the end face.

For example, the common electrode described above has a rhombus shape as shown in FIG. 1. By adopting such a shape, the main vibration of the thickness system gradually converges toward the end face of the quartz plate, It can be reduced, and acoustic coupling with higher-order bending vibrations and contour vibration modes is less likely to occur.

Further, as described in claim 2, in the monolithic crystal filter according to claim 1, the main surface portion corresponding to the input electrode and the extraction electrode led out from the output electrode on one main surface is provided on the other main surface portion. The common electrode may not be formed.

According to this structure, it is possible to eliminate the formation of a resonance region composed of the common electrode and the extraction electrode led out from the input electrode and the output electrode, and to facilitate the design of the filter. .

According to a third aspect of the present invention, an input electrode and an output electrode are formed close to each other on a main surface of the quartz plate at a predetermined distance, and the input electrode and the output electrode are formed on the other main surface. In the monolithic crystal filter using thickness-based vibration, a resonance region is formed by providing a common electrode corresponding to each of the electrodes, and an extraction electrode that leads each of the electrodes to the outside is formed. Weighting is performed from the periphery of the input electrode and the output electrode to the vicinity of the end face of the quartz plate, and this weighting is such that the weight near the end face is smaller than the weight around the input electrode and the output electrode. It may be a characteristic configuration.

As a concrete structure of this weighting, as shown in claim 4, a structure in which the weight gradually decreases toward the end face of the quartz plate around the periphery of the input electrode and the output electrode, and in claim 5, As shown, the area near the end face is smaller than the area around the input electrode and the output electrode, or as shown in claim 6, the area around the end face is closer than the thickness around the input electrode and the output electrode. Examples include a structure having a small thickness or a combination of these.

According to the third to sixth aspects, the main vibration of the thickness system can be gradually converged and reduced toward the end face of the crystal plate, and can be combined with higher-order thickness shear vibration, bending vibration, and contour vibration mode. Acoustic coupling can be suppressed.

Further, as described in claim 7, in the monolithic crystal filter according to claims 1 to 6, the crystal plate may have a small rectangular shape.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment A first embodiment of the present invention will be described with reference to the drawings. This embodiment relates to claims 1 and 2. FIG. 1 is a plan view of a front surface of a quartz plate showing a first embodiment of the present invention, and FIG. 2 is a plan view of the back surface thereof. The crystal plate 1 is formed by processing a thin AT-cut crystal plate into a rectangular shape, and the input electrode 11,
The output electrodes 12 are arranged side by side in the Z′-axis direction and are arranged close to each other at a predetermined interval, and the extraction electrodes 111 and 121 are drawn out from the respective electrodes to the end faces of the crystal plate. A common electrode 13 including portions corresponding to the input electrodes and output electrodes 11 and 12 is provided on the back surface. The common electrode 13 has a rhombic shape as a whole, and is configured such that its width gradually decreases toward the end of each side of the crystal plate 1 around the portion corresponding to the input electrode 11 and the output electrode 12, and in the vicinity of the end. Is formed up to the end of the upper and lower sides of the crystal plate.
1, 132 are formed.

Such a crystal plate is housed in a package as shown in the conventional example, and each extraction electrode of the crystal plate and the electrode pad of the package are bonded with a conductive bonding material. With the above electrode structure, the main vibration of the thickness system can be gradually converged and reduced toward the end face of the crystal plate, and acoustic coupling with an unnecessary vibration mode can be suppressed. Further, the conductive bonding material can further absorb the attenuated vibration and suppress an unnecessary vibration mode.

FIG. 3 is a plan view showing another embodiment on the common electrode side of the above embodiment. The common electrode 14 has a rhombic shape as a whole, and is configured such that its width gradually decreases toward the end portions of the respective sides of the crystal plate 1 around the portion corresponding to the input electrode 11 and the output electrode 12 on the surface. Extraction electrodes 111, 121 extending from the input / output electrodes to the ends of the crystal plate
The electrodeless portion 1 in which no electrode is formed in the portion corresponding to
It is configured to have 4a and 14b. By adopting such an electrode configuration, it is possible to eliminate the formation of a resonance region composed of the common electrode and the extraction electrode derived from the input electrode and the output electrode, in addition to the above advantages, and to design the filter. It has the advantage that it can be facilitated.

Second Embodiment A second embodiment of the present invention will be described with reference to the drawings. This embodiment relates to claims 3 to 5 and 7.
FIG. 4 is a plan view of the front surface of a quartz plate showing a second embodiment of the present invention, and FIG. 5 is a plan view of the back surface thereof. The structure of the crystal plate and the electrode structure constituting the monolithic crystal filter are the same as those in the above-described embodiment, the thin AT-cut crystal plate 1 is processed into a rectangular shape, and the input electrode 11 and the output electrode 12 are formed on the surface.
Are provided adjacent to each other at a predetermined interval along the Z′-axis direction,
Extraction electrodes 111, 1 from each electrode to the end face of the quartz plate
21 is pulled out. A common electrode 15 corresponding to the input electrodes and output electrodes 11 and 12 is provided on the back surface. The extraction electrode 15 is also connected to the end of the quartz plate from the common electrode 15.
1,152 are pulled out. The lead-out direction of the common electrode and the lead-out direction of the common electrode may be different from the lead-out direction of the input / output electrode to prevent a short circuit between the two.

Peripheral electrodes 21, are provided on the upper and lower portions of the input / output electrodes.
22 are formed respectively. These peripheral electrodes 21,
22 has a line-symmetrical shape with respect to the direction in which the input / output electrodes are arranged.
2, 222. The narrow tip of the peripheral electrode extends to near the edge of the quartz plate. The peripheral electrodes 23 and 24 are formed similarly on the common electrode side of the back surface, and the wide electrodes 231 and 241 are formed near the common electrode.
In addition, the narrow electrodes 232 and 242 are gradually formed in the vicinity of the extraction electrode that is away from the input / output electrodes.

With this structure, the main vibration of the thickness system excited by the input / output electrodes and the common electrode propagates to the periphery of these electrode portions and also to the peripheral electrodes. With the configuration, the vibration propagated to the peripheral electrodes gradually converges toward the end surface of the crystal plate, and the energy thereof can be reduced. Therefore, it is possible to suppress acoustic coupling with higher-order bending vibrations and contour vibration modes.

FIG. 6 is a plan view showing another embodiment on the common electrode side of the second embodiment. The common electrode 16 is drawn out to one long side of the rectangular crystal plate 1 by the extraction electrode 161. A peripheral electrode 25 having a substantially rhombic outer shape is formed around the common electrode 16 and includes a wide electrode 251 portion and a narrow electrode 252 portion. By adopting such an electrode configuration, it is possible to efficiently reduce the vibration energy propagating from the short side portion of the excitation electrode and prevent a short circuit with the extraction electrode on the surface.

The electrode structure is not limited to the above-mentioned embodiment, and the peripheral electrode structure as shown in FIGS. 7 and 8 may be adopted. Peripheral electrodes 26, 27, 28,
By providing a curvature on the outer circumference of 29, there is an effect that the unnecessary vibration is gradually converged more smoothly. Also, FIG.
It is also possible to apply to a configuration in which the input / output electrodes are arranged in the X-axis direction as shown in FIG.

Third Embodiment A third embodiment of the present invention will be described with reference to the drawings. This embodiment relates to claims 6 and 7. FIG. 9 is a plan view of the surface of a quartz plate showing a third embodiment of the present invention, and FIG.
11 is a rear view of the same, and FIG. 11 is a side view of the same. Input / output electrodes 11 and 12 are formed on the front surface of the rectangular crystal plate 1 and a common electrode is formed on the back surface thereof, and both electrodes constitute an excitation electrode. The extraction electrodes 111, 121, and 171 form crystal electrodes from the respective electrodes. It is pulled out to the edge of the board. Peripheral electrodes 31, 32, 33, 34 are formed around these electrodes. As shown in FIG. 11, each of these peripheral electrodes is formed thick in the vicinity of the excitation electrode, and gradually becomes thinner as the distance from the excitation electrode increases. Although the electrode film thickness is gradually reduced in FIG. 11, there is no problem even if the electrode thickness is gradually reduced. Note that such a configuration in which the electrode film thickness at the end of the crystal plate is thinner than the electrode film thickness in the vicinity of the input / output electrodes is adopted simultaneously for the input / output electrodes, the common electrode, and the extraction electrode drawn from these. Good. That is, the film thickness in the vicinity of the crystal plate of the extraction electrode may be smaller than the film thickness of the input / output electrode and the common electrode. Further, by applying the configuration of this embodiment together with the configuration in which the area of the peripheral electrode is changed as shown in the second embodiment, the vibration energy can be reduced more efficiently. Furthermore, the same effect can be obtained even with a configuration in which the electrode thickness on only one side of the crystal plate is changed.

[0024]

[Comparison Data] FIGS. 12 and 13 show comparison verification data of the frequency characteristics of the conventional product and the product of the present invention. The crystal plate used for the comparative verification is a 3 × 4 mm rectangular AT-cut crystal plate, and the center frequency is set to 21.4 MHz. The basic structure of the electrode is the electrode structure described in the second embodiment (the structure shown in FIG. 4 on the front surface and the structure shown in FIG. 6 on the back surface), and the peripheral electrode is not formed in the conventional product. The length of each electrode is 1.45mm on the long side and 0.75m on the short side.
m, the distance between the electrodes is 0.55 mm, and the common electrode on the back surface has a size substantially corresponding to this input / output electrode.
FIG. 12 is a graph showing frequency characteristics of the conventional product,
FIG. 13 shows, as a product of the present invention, a peripheral electrode having a substantially diamond outer shape is formed around the excitation electrode (the input / output electrode and the common electrode), and the distance between the excitation electrode and the peripheral electrode is 0.3 to 0.5 mm.
4 is a graph showing frequency characteristics of the above configuration.

From these graphs, it can be understood that the product of the present invention suppresses the spurious vibration (high-order contour system vibration) appearing on the left side of the main vibration as compared with the conventional product. Since the spurious suppression effect changes depending on the thickness of the peripheral electrodes, the spacing between the above-mentioned electrodes and the weighting electrodes and the thickness are taken into consideration in consideration of the design accuracy of the mechanical mask means during the vacuum deposition used when forming the electrodes. Etc. need to be decided.

Attention must be paid to the dimension design of the electrodeless portion between the input / output electrode and the peripheral electrode or between the common electrode and the peripheral electrode. That is, the main vibration of the thickness system is excited between the input / output electrode and the common electrode (hereinafter referred to as an excitation electrode), and the vibration energy is concentrated in this portion, but the vicinity of these electrodes also vibrates. Therefore, if the peripheral electrodes are formed too close to these excitation electrodes, the vibration energy may be greatly attenuated. Therefore, these dimensional designs need to be set to dimensions that do not suppress the energy of the main vibration.

[0027]

According to the first aspect of the present invention, in a monolithic crystal filter using thickness type vibration, the width of the common electrode is gradually increased toward the end face of the crystal plate around the portion corresponding to the input electrode and the output electrode. Since the structure is made small and is formed near the end face, the main vibration of the thickness system can be gradually converged and reduced as it goes to the end face of the quartz plate. The acoustic coupling of can be suppressed. As a result, it is possible to suppress the generation of spurious due to the coupling between the main vibrations of the thickness system and these higher-order vibration modes, and it is possible to obtain a monolithic crystal filter having stable electric characteristics.

Further, according to the second aspect of the invention, it is possible to eliminate the formation of the resonance region composed of the common electrode and the extraction electrode led out from the input electrode and the output electrode, and it is possible to eliminate the resonance region of the filter. The design can be facilitated.

According to the third to sixth aspects, in the monolithic crystal filter using the thickness-based vibration, at least one main surface is weighted from around the input electrode and the output electrode to near the end surface of the crystal plate. And this weighting is more than the weight around the input and output electrodes.
Since the weight in the vicinity of the end face is small, the main vibration of the thickness system can be gradually converged and reduced as it goes toward the end face of the crystal plate. It is possible to suppress physical coupling. As a result, it is possible to suppress the generation of spurious due to the coupling between the main vibrations of the thickness system and these higher-order vibration modes, and it is possible to obtain a monolithic crystal filter having stable electric characteristics.

Further, according to the seventh aspect, since the boundary condition is formed by a straight line in the related art, the above-mentioned weighting configuration is applied to the quartz crystal plate even for a rectangular quartz plate in which unnecessary vibration is likely to occur. By applying it to the plate, unnecessary vibration can be surely suppressed, and a monolithic crystal filter having stable electric characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a plan view showing an electrode configuration on the surface of a quartz plate according to a first embodiment.

FIG. 2 is a plan view of the back surface of FIG.

FIG. 3 is a plan view of the back surface of the crystal plate showing another embodiment of the first embodiment.

FIG. 4 is a plan view showing an electrode configuration on the surface of a crystal plate of a second embodiment.

5 is a plan view of the back surface of FIG.

FIG. 6 is a plan view of the back surface of a crystal plate showing another embodiment of the second embodiment.

FIG. 7 is a plan view of the surface of a quartz plate showing another embodiment of the second embodiment.

FIG. 8 is a plan view of the surface of a quartz plate showing another embodiment of the second embodiment.

FIG. 9 is a plan view showing an electrode configuration on the surface of a crystal plate of a third embodiment.

FIG. 10 is a plan view of the back surface of FIG.

FIG. 11 is a side view of FIG. 7.

FIG. 12 is an exploded perspective view of a surface-mounted monolithic crystal filter showing a conventional example.

FIG. 13 is a plan view of the assembled lid of FIG.

FIG. 14 is a diagram showing comparative data.

FIG. 15 is a diagram showing comparison data.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Crystal plate 11,12 Input / output electrode 13,14,15,16,17 Common electrode 21,22,23,24,25,26,27,28,2
9, 31, 32, 33, 34 Peripheral electrodes (weighting)

Claims (7)

[Claims] 1. An input electrode and an output electrode are formed close to each other on a main surface of a quartz plate at a predetermined interval, and the other main surface has at least portions corresponding to the input electrode and the output electrode, respectively. In the monolithic crystal filter using the thickness type vibration, the resonance region is formed by providing the common electrode, and the extraction electrode that leads each of the electrodes to the outside is formed, and the common electrode corresponds to the input electrode and the output electrode. A monolithic crystal filter having a structure in which the width is gradually reduced toward the end face of the crystal plate around the portion to be formed and is formed up to the vicinity of the end face. 2. The main surface portion of the other main surface corresponding to the lead-out electrode derived from the input electrode and the output electrode on one main surface,
The monolithic crystal filter according to claim 1, wherein a common electrode is not formed. 3. An input electrode and an output electrode are formed close to each other on a main surface of a quartz plate at a predetermined interval, and common electrodes corresponding to the input electrode and the output electrode are provided on the other main surface. In this way, a resonance region is formed, and extraction electrodes that lead out each of the electrodes are formed, and in a monolithic crystal filter using a thickness-based vibration, at least one main surface is provided around the input electrode and the output electrode. A monolithic crystal filter, wherein weighting is performed over the vicinity of the end face of the crystal plate, and this weighting is such that the weight near the end face is smaller than the weight around the input electrode and the output electrode. 4. The monolithic crystal filter according to claim 3, wherein the weighting is configured such that the weight gradually decreases toward the end surface of the crystal plate around the periphery of the input electrode and the output electrode. . 5. The monolithic crystal filter according to claim 3, wherein the weighting is such that an area near the end face is smaller than an area around the input electrode and the output electrode. 6. The monolithic crystal filter according to claim 3, wherein the weighting is such that the thickness in the vicinity of the end face is smaller than the thickness in the periphery of the input electrode and the output electrode. 7. The monolithic crystal filter according to claim 1, wherein the crystal plate has a small rectangular shape.