JP3295926B2 - Monolithic crystal filter - Google Patents

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 a thickness vibration used for 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. A conventional chip type ultra-miniaturized monolithic crystal filter is shown in FIG.
This will be described with reference to FIG. FIG. 16 is an exploded perspective view of a chip type monolithic crystal filter using a rectangular crystal plate, and FIG. 17 is a plan view showing a state where the crystal plate is 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 and output electrodes 81 and 82, and the extraction electrodes 83a and 83 are drawn from the electrodes toward the ends 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, and a 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 a vibration called an oblique symmetric mode vibration (fa) are simultaneously excited, and these are acoustically coupled to form a main vibration, thereby constituting 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. This unnecessary vibration mode is considered to be a bending vibration mode determined by the external dimensions of the quartz plate, each harmonic mode of the contour vibration mode, or a harmonic of the thickness shear vibration,
This is because when the external dimensions of the quartz plate are reduced, the order of the harmonics of the unnecessary vibration modes to be coupled is reduced, and acoustic coupling is easily 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).
Obtaining good passband characteristics as an electromechanical filter,
It is an object of the present invention to provide a monolithic crystal filter having stable frequency-temperature characteristics.

[0007]

According to a first aspect of the present invention, there is provided a monolithic crystal filter in which an input electrode and an output electrode are formed close to one main surface of a quartz plate at predetermined intervals. And, by providing a common electrode corresponding to the input electrode and the output electrode on the other main surface, a resonance region is formed, and an extraction electrode for leading each electrode to the outside is formed, and a thickness-based vibration is used. A monolithic crystal filter, wherein at least one main surface is weighted from around the input electrode and the output electrode to near the end face of the quartz plate, and the weighting is performed around the input electrode and the output electrode. , The weight of which gradually increases toward the end face of the crystal plate.

With this configuration, 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 the weighting is performed on the end face of the quartz plate around the periphery of the input electrode and the output electrode. Since the weight gradually increases toward the front, it is possible to suppress the harmonics of bending vibration and contour vibration generated when the outer peripheral shape of the quartz plate becomes a boundary condition, and to prevent acoustic coupling with the main vibration. be able to.

As a specific configuration example of the weighting, as described in claim 2, a configuration in which the area near the end face is larger than the area around the input electrode and the output electrode, or as described in claim 3, A configuration in which the thickness near the end face is larger than the thickness around the input electrode and the output electrode, or a configuration in which these are combined.

According to the second or third aspect of the present invention, the weight of the weight gradually increases toward the end face of the quartz plate, so that a new boundary condition due to a sudden change in the weight is not created, and Propagation of the main vibration to the end face of the quartz plate can be suppressed, and higher-order bending vibration and contour vibration mode vibration can be suppressed by the weighting effect of the end portion.

According to a fourth aspect of the present invention, in the monolithic crystal filter according to any one of the first to third aspects, the crystal plate may have a rectangular shape.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment A first embodiment of the present invention will be described with reference to the drawings. This embodiment relates to claims 1, 2, 3, and 5. 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. Quartz plate 1 is thin A
A T-cut quartz plate is machined into a rectangular shape, and input electrodes 11 and output electrodes 12 are provided on the surface in a row at a predetermined interval in the Z′-axis direction. The extraction electrodes 111 and 121 are extracted. On the back surface, a common electrode 13 corresponding to the input electrode and the output electrodes 11 and 12 is provided. Extraction electrodes 131 and 132 are also extended from the common electrode 13 to the ends of the quartz plate.

Input / output electrodes 11 and 12 and common electrode 13
Electrodes 21 and 2 provided around an excitation electrode made of
2 are formed into narrow electrodes 211 and 221 having a small area around the excitation electrode, and become wide electrodes 212 and 222 having an area increasing with distance from the excitation electrode.
The weight is made different by gradually increasing the area. The same configuration is applied to the peripheral electrodes 23 and 24 on the back surface.

With the above-described configuration of the peripheral electrodes, the weight of the weight gradually increases toward the end face of the quartz plate, so that the propagation of the thickness-related main vibration to the end face of the quartz plate is suppressed, and With the weighting effect described above, it is possible to suppress higher-order bending vibration and contour vibration mode vibration.

Such a quartz plate is housed in a package as shown in the conventional example, and each lead electrode of the quartz plate and an electrode pad of the package are joined by a conductive bonding material. However, since the position of the extraction electrode is different from that of the conventional example, it is necessary to use a different position of the electrode pad of the package. The above electrode structure suppresses propagation of the thickness-based main vibration to the end face of the quartz plate, and suppresses acoustic coupling with higher-order bending vibration and contour vibration mode vibration due to the weighting effect of the end. Can be. Further, the damped vibration can be further absorbed by the conductive bonding material, and the excitation of unnecessary vibration modes can be suppressed.

FIGS. 3 and 4 show a modification of the first embodiment. The configuration of the peripheral electrodes 25, 26, 27, and 28 is such that the input / output electrodes and the common electrode side end faces are formed in an arc shape, whereby the weighting gradually changes. The input / output electrodes 14 and 15 and the common electrode 16 are formed in an elliptical shape as a whole. As a result, it is possible to obtain the effect of confining the thickness-shear vibration, which is the main vibration, to the excitation electrode portion, and to obtain the frequency characteristics that do not generate spurious vibrations, as well as the effect of suppressing higher-order bending vibrations and contour vibration modes by peripheral electrodes. Can be. In this embodiment, the extraction electrodes 141 and 151 are extended in the long side direction.
The configuration is such that the extraction electrode 161 of the common electrode is extended in the short side direction of the quartz plate. This can prevent a short circuit accident between the front and back extraction electrodes.

Second Embodiment A second embodiment of the present invention will be described with reference to the drawings. This embodiment relates to claims 1, 2, 3, and 5. FIG. 5 is a plan view of a front surface of a quartz plate showing a first embodiment of the present invention, and FIG. 6 is a plan view of the back surface thereof. Quartz plate 1 is thin A
A T-cut quartz plate is processed into a rectangular shape, and an input electrode 17 and an output electrode 18 are arranged on the surface in the Z′-axis direction and are provided close to each other at a predetermined interval. Peripheral electrodes 31, 31, 33, 34 are provided.
These peripheral electrodes are configured to have a small area and a small width around the excitation electrode, and have a large width with an area increasing as the distance from the excitation electrode is increased, so that the weights are different. An extraction electrode 171 is extracted from the input electrode 17 and connected to the peripheral electrode 31. Similarly, an extraction electrode 181 is extracted from the output electrode and the peripheral electrode 3
4 is connected. The peripheral electrodes 32 and 33 are commonly connected by a narrow connecting electrode 32a passing between the input and output electrodes, and are grounded together with a common electrode described later. On the back surface, common electrodes 19a and 19b corresponding to the input and output electrodes 11 and 12 are provided, and these common electrodes are commonly connected by a connection electrode 19c. Peripheral electrodes 35, 36, 37, and 38 are provided around the common electrode also on the back surface, and each has a narrow width portion and a wide width portion. An extraction electrode 191 is extracted from the common electrode 19a, is connected to the peripheral electrode 37, and is similarly connected to the common electrode 19b.
The extraction electrode 192 is extracted from the electrode and is connected to the peripheral electrode 36. These peripheral electrodes are grounded.

With the above structure, the peripheral electrode gradually changes its area from a narrow width to a wide width, so that the above-described effect of suppressing unnecessary vibration is obtained, and the peripheral electrode is used as an electrode leading portion. Since it can be used, it is possible to adopt a configuration in which an electrode connection portion with the outside is not selected.
A connection electrode 32a is connected between the input and output electrodes to ground.
Is passed, it is possible to suppress the generation of a direct wave where the signal input to the input electrode directly reaches the adjacent output electrode as an electromagnetic wave, and has an effect of improving the damping characteristics of the piezoelectric filter. Have.

Third Embodiment A third embodiment of the present invention will be described with reference to the drawings. This embodiment relates to claims 1, 2, 3, and 5. FIG. 7 is a plan view of the front surface of a quartz plate showing the first embodiment of the present invention, and FIG. 8 is a plan view of the back surface thereof. Quartz plate 1 is thin A
A T-cut quartz plate is processed into a rectangular shape, and an input electrode 41 and an output electrode 42 are provided on the surface side by side at a predetermined interval in the Z′-axis direction.
1,421 extend diagonally and are drawn out to the corners of the quartz plate. Around these input / output electrodes, a peripheral electrode 51,
52 are provided. These peripheral electrodes 51 and 52 are
Around the excitation electrode, the width is configured to be small with a small area, and the width becomes large as the distance from the excitation electrode is increased, and the weighting is varied. A common electrode 43 corresponding to the input and output electrodes 41 and 42 is provided on the back surface. Peripheral electrodes 53 and 54 are provided around the common electrode also on the back surface, and a narrow portion and a It has a configuration having a wide portion. Extraction electrodes 431 and 432 extend diagonally from the common electrode 43, are extracted to the corners of the quartz plate, and are grounded.

FIGS. 9 and 10 show another modification of the third embodiment.
It will be explained together. In the third embodiment, there is a possibility that each extraction electrode is short-circuited. In view of this, a configuration was adopted in which the direction in which the peripheral electrodes facing each other on the front and back became narrower from narrower was changed. That is, the peripheral electrodes formed around the common electrode 46 on the rear surface in the direction in which the peripheral electrodes 55 and 56 formed around the input electrode 44 and the output electrode 45 on the front surface gradually change from the narrow width to the wide width. The directions in which the electrode widths 57 and 58 change are made different. Note that the dotted lines in each figure indicate the peripheral electrode ends on the opposite surfaces. As a result, the gradually increasing weighting effect can be performed more efficiently, and the configuration can be such that the extraction electrode extraction directions are different from each other, so that an effect of preventing a short circuit accident can be achieved.

Fourth Embodiment A fourth embodiment of the present invention will be described with reference to the drawings. This embodiment relates to claims 1, 2, 3, and 5. FIG. 11 is a plan view of a front surface of a quartz plate showing a first embodiment of the present invention, and FIG. 12 is a plan view of the back surface thereof. The quartz plate 1 is formed by processing a thin AT-cut quartz plate into a rectangular shape, and on the surface, input electrodes 47 and output electrodes 48 are provided adjacent to each other at a predetermined interval in a line in the Z′-axis direction. Extraction electrode 4
71, 481 extend diagonally and are drawn out to the corners of the quartz plate. On the back surface, a common electrode 49 is formed to face these input / output electrodes, from which an extraction electrode 491 is extracted in a diagonal direction different from the above-mentioned extraction direction. Peripheral electrodes 61, 62 and 63, 64 are provided relatively close to the respective excitation electrodes formed by the input / output electrodes and the common electrode. By providing the peripheral electrodes close to the periphery of the excitation part in this way, unnecessary vibrations of the bending system and the contour system are suppressed by weighting, and are excited simultaneously with the main vibration.
A spurious vibration mode called in-harmonic vibration that is excited with the outer peripheral end surfaces of the respective electrodes as boundary conditions can be suppressed at the same time.

Fifth Embodiment A fifth embodiment of the present invention will be described with reference to the drawings. This embodiment relates to claims 1, 2, and 5. FIG.
Is a plan view of a surface of a quartz plate showing a first embodiment of the present invention,
FIG. 14 is a plan view of the back surface, and FIG. 15 is a sectional view taken along line AA of FIG. The quartz plate 1 is formed by processing a thin AT-cut quartz plate into a rectangular shape, and has an input electrode 71 and an output electrode 72 on the surface.
Are provided adjacent to each other at a predetermined interval along the Z′-axis direction,
Extraction electrodes 711 and 721 extend from each of these electrodes in the long side direction and are extended to the short side of the quartz plate. On the back surface, a common electrode 73 is formed so as to face these input / output electrodes, and lead electrodes 731 and 732 are drawn out from this electrode in the short side direction. Peripheral electrodes 65 and 6 surround the excitation portion formed by these input / output electrodes and the common electrode.
6, 67, 68 are formed. Each of these peripheral electrodes is configured to have a small thickness in the vicinity of the input / output electrode or the common electrode, and to have a gradually increasing thickness toward the edge of the quartz plate, so that the weighting is increased. The increase in the electrode thickness is not limited to a configuration in which the thickness gradually increases, and may be a configuration in which the thickness increases stepwise. Further, the direction of increase may be only in the long side direction, only in the short side direction, or a configuration in which both directions are combined.

[0023]

[Comparison Data] Comparison and verification data of the frequency characteristics of the conventional product and the product of the present invention are shown in the frequency characteristic graphs of FIGS.
The quartz plate used for comparative verification was a 4 x 2.8 mm rectangular AT
A cut quartz plate having a center frequency of 45 MHz was used. The basic configuration of the electrode is the same as that of the first embodiment (FIG. 1,
The electrode configuration described in 2) is used, and no peripheral electrode is formed for the conventional product. The dimensions of each electrode are
The long side of the input / output electrode is 0.8 mm, the short side is 0.5 mm, the interval between the electrodes is 0.00.3 mm, and the common electrode on the back surface has a size substantially corresponding to the input / output electrode. .

From these graphs, it can be understood that the product of the present invention suppresses spurious vibration (vibration of a higher-order contour system) that appears on the left side of the main vibration as compared with the conventional product. Since the spurious suppression effect varies depending on the thickness of the peripheral electrode and the like, the spacing and thickness of each electrode and the weighting electrode are taken into consideration in consideration of the design accuracy and the like of the mechanical mask means at the time of vacuum deposition used when forming the electrode. It is necessary to determine the degree.

Care must be taken when designing the dimension 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.

[0026]

According to the present invention, weighting is performed from the periphery of the input electrode and the output electrode to the vicinity of the end face in the quartz plate, and the weighting is performed centering on the periphery of the input electrode and the output electrode. Since the weight gradually increases toward the end face of the crystal plate, it is possible to suppress the harmonics of bending vibration and contour vibration that occur when the outer peripheral shape of the quartz plate becomes a boundary condition, and acoustic coupling with the main vibration Can be prevented. For this reason, it is possible to suppress unnecessary vibrations that have conventionally been caused by an error in the processing technology of the quartz plate or a temperature range in which the monolithic quartz filter is used, to obtain a good pass band characteristic, and to improve a frequency temperature characteristic. A stable and highly reliable monolithic crystal filter can be obtained.

Further, since the weight of the weighting gradually increases toward the end face of the quartz plate, no new boundary condition is created due to a sudden change in the weight, and the end face of the thickness-based main vibration quartz plate is not generated. While suppressing propagation to
Due to the weighting effect of the end portions, it is possible to suppress higher-order bending vibration and contour vibration mode vibration.

[Brief description of the 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 showing an electrode configuration on the back surface of the quartz plate of the first embodiment.

FIG. 3 is a plan view showing an electrode configuration on the surface of a quartz plate showing another example of the first embodiment.

FIG. 4 is a plan view showing an electrode configuration on the back surface of a quartz plate showing another example of the first embodiment.

FIG. 5 is a plan view showing an electrode configuration on the surface of a quartz plate according to a second embodiment.

FIG. 6 is a plan view showing an electrode configuration on the back surface of a quartz plate according to a second embodiment.

FIG. 7 is a plan view showing an electrode configuration on the surface of a quartz plate according to a third embodiment.

FIG. 8 is a plan view showing an electrode configuration on the back surface of a quartz plate according to a third embodiment.

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

FIG. 10 is a plan view showing an electrode configuration on the back surface of a quartz plate showing another example of the third embodiment.

FIG. 11 is a plan view showing an electrode configuration on the surface of a quartz plate according to a fourth embodiment.

FIG. 12 is a plan view showing an electrode configuration on the back surface of a quartz plate according to a fourth embodiment.

FIG. 13 is a plan view showing an electrode configuration on the surface of a quartz plate according to a fifth embodiment.

FIG. 14 is a plan view showing an electrode configuration on the back surface of a quartz plate according to a fifth embodiment.

FIG. 15 is a sectional view taken along line AA of FIG. 13;

FIG. 16 is a perspective view showing a conventional example.

FIG. 17 is a plan view showing a conventional example.

FIG. 18 is a graph showing comparison data.

FIG. 19 is a graph showing comparison data.

[Explanation of symbols]

1,8 Quartz plate 11,14,17,41,44,47,71,81 Input electrode 12,15,18,42,45,48,72,82 Output electrode 13,16,19a, 19b, 43,46 , 49,73
Common electrodes 21, 22, 23, 24, 25, 26, 27, 28, 3
1,32,33,34,35,36,37,38,5
1,52,53,54,55,56,57,58,6
1,62,63,64,65,66,67,68 Peripheral electrode

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H03H 9/19 H03H 9/56

Claims (4)

(57) [Claims] An input electrode and an output electrode are formed on one main surface of a quartz plate so as to be close to each other at a predetermined interval, and common electrodes respectively corresponding to the input electrode and the output electrode are provided on the other main surface. A monolithic crystal filter using a thickness-based vibration, in which a resonance region is formed and an extraction electrode for leading each electrode to the outside is formed, at least one main surface is formed from around the input electrode and the output electrode. Weighting is performed over the vicinity of the end face of the quartz plate .
This weighting is applied around the input and output electrodes.
A structure in which the weight gradually increases toward the end face of the quartz plate as a heart
Monolithic crystal filter, which is a formed. 2. The method according to claim 1, wherein the weighting is performed on an input electrode and an output electrode.
That the area near the end face is larger than the area around
2. The monolithic quartz crystal fill according to claim 1, wherein:
Ta. 3. The method according to claim 1, wherein the weighting is performed on an input electrode and an output electrode.
The thickness near the end face is larger than the thickness around the periphery.
The monolithic water according to claim 1 or 2,
Crystal filter. 4. A quartz plate having a rectangular shape.
4. A monolithic crystal fill according to claim 1
Ta.