JP2011199608A - Piezoelectric vibrator, electronic component and oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric vibrator in which the vibration property is excellent, an electronic component and an oscillator.SOLUTION: In a mesa-shaped or inverse-mesa-shaped crystal piece 2 in which heights of a principal surface 21 and of an edge 22 are different, a first exciting electrode and a second exciting electrode are respectively formed on both sides of the principal surface 21, a plurality of first and second lead-out electrodes are provided to radially extend from the first and second exciting electrodes, and first and second arcuate electrodes are formed to respectively connect the first and second lead-out electrodes with each other. The second lead-out electrode is then disposed at a position that is not overlapped with a projection area of the first lead-out electrode, and the second arcuate electrode is formed at a position that is not overlapped with a projection area of the first arcuate electrode.

Description

  The present invention relates to a piezoelectric vibrator having good vibration characteristics, an electronic component including the piezoelectric vibrator, and an oscillator technology.

  By making the crystal piece a mesa type or inverted mesa type structure in which the main surface part and the peripheral part surrounding the main surface part have different heights, the excitation energy is confined in the main surface part, so this excitation energy is attenuated. It is known that the crystal impedance (CI) value decreases if the crystal piece is pulled out as compared with a structure having a uniform crystal piece thickness.

  However, in a mesa-type or inverted mesa-type crystal piece, the thickness of the region where the extraction electrode is formed and the region where the excitation electrode is provided are different, so the extraction electrode on one side of the crystal piece and the extraction electrode on the other side As shown in FIG. 7, in the mesa type, spurious vibration f1 is generated at a frequency higher than the excitation frequency of the main vibration f0 of the excitation electrode, and in the reverse mesa type, the excitation frequency of the main vibration f0 is exceeded. The spurious vibration f2 is generated at a low frequency.

  Incidentally, a crystal resonator including an inverted mesa type crystal vibrating piece having a small thickness at the center is described in Patent Document 1. FIG. 2 of the patent document 1 shows a configuration of a conventional crystal resonator. In this example, excitation electrodes are formed on both surfaces of a crystal piece, and a front-side extraction electrode and a back-side extraction electrode are provided so as to be opposed to each other in the length direction of the crystal piece. Accordingly, since there is no overlap of the extraction electrodes, it is possible to suppress the occurrence of spurious vibrations, but the extraction electrode is connected to a part of the excitation electrode, and the excitation energy is locally extracted. The excitation energy is attenuated by the resistance of the extraction electrode, resulting in a high CI value. Moreover, since both the one end side and the other end side of the crystal piece in the length direction are fixed, vibration hardly occurs and vibration characteristics are deteriorated. Further, in the configuration of FIG. 1 of Patent Document 1, one end side of the crystal resonator is fixed, and the other end side is a free end, so that the vibration characteristics are favorably maintained. However, even in this configuration, a slight overlapping portion is generated in the extraction electrode, and therefore a configuration for further reducing the overlap of the extraction electrode is being studied.

JP 2006-33165 A (FIG. 1)

  The present invention has been made under such circumstances, and an object of the present invention is a mesa-type or inverted-mesa-type piezoelectric vibrator having a low CI value and capable of reducing spurious vibration, and the piezoelectric vibration. An object is to provide an electronic component and an oscillator using a child.

The piezoelectric vibrator of the present invention is a mesa-type or reverse mesa-type piezoelectric piece having a different height between a main surface portion and a peripheral portion surrounding the main surface portion;
A first excitation electrode and a second excitation electrode respectively formed on a main surface portion on one surface side of the piezoelectric piece and a main surface portion on the other surface side of the piezoelectric piece;
A plurality of first extraction electrodes formed on a peripheral portion on one surface side of the piezoelectric piece, extending radially from the first excitation electrode, and formed in a circumferential direction of the piezoelectric piece;
A first arc-shaped electrode formed by connecting the first lead electrodes to each other along a circle centered on the central portion of the piezoelectric piece;
A plurality of second extraction electrodes formed on a peripheral portion on the other surface side of the piezoelectric piece, extending radially from the second excitation electrode, and formed in a circumferential direction of the piezoelectric piece;
These second lead electrodes are connected to each other, a second arc-shaped electrode formed along a circle having a diameter different from the diameter of the circle centered on the central portion of the piezoelectric piece;
A first connection electrode and a second connection electrode electrically connected to the first arc-shaped electrode and the second arc-shaped electrode, respectively, for connecting to an external conductive path;
The second extraction electrode is arranged at a position not overlapping the projection area of the first extraction electrode so as to be alternately arranged with the projection area of the first extraction electrode along the circumferential direction of the excitation electrode,
The second arcuate electrode is formed at a position that does not overlap the projection area of the first arcuate electrode.

  In the piezoelectric vibrator, it is preferable that the first extraction electrode and the second extraction electrode are formed at equal intervals along the circumferential direction of the piezoelectric piece. Moreover, it is preferable that the sum of the lengths of the contact portions of the first lead electrode and the second lead electrode with the piezoelectric piece is ½ or less of the circumferential length of the piezoelectric piece.

The electronic component of the present invention includes a package,
The piezoelectric vibrator provided in the package;
An external electrode formed on the outer surface of the package and electrically connected to the first connection electrode and the second connection electrode of the piezoelectric vibrator, respectively.

  Furthermore, an oscillator according to the present invention includes the electronic component and an oscillation circuit.

  In the present invention, mesa-type or inverted-mesa-type piezoelectric pieces are used, and a plurality of first and second extraction electrodes are radially extended from first and second excitation electrodes provided on both surfaces of the main surface portion, respectively. The first lead electrodes are electrically connected by a first arc-shaped electrode, and the second lead electrodes are electrically connected by a second arc-shaped electrode. . For this reason, the uniformity of the electric field distribution (electric energy distribution) of the circumferential direction in a main surface part is high, and CI value can be reduced as a result.

  In the mesa-type or inverted-mesa-type piezoelectric vibrator, the first and second extraction electrodes are arranged at positions where the projection areas do not overlap with each other, and the first and second arc-shaped electrodes are arranged in the projection areas. By forming at a position where they do not overlap, spurious vibration can be reduced. Thus, since the CI value and spurious vibration can be reduced, the vibration characteristics are good.

1 is a plan view, a cross-sectional view, and a bottom view showing a crystal resonator according to an embodiment of the present invention. 1 is a plan view showing a crystal resonator according to an embodiment of the present invention. It is a schematic sectional drawing which shows the manufacturing method of the crystal oscillator based on embodiment of this invention. FIG. 6 is a plan view, a cross-sectional view, and a bottom view showing a crystal resonator according to another example of the present invention. It is a schematic sectional drawing which shows the electronic component which concerns on embodiment of this invention. It is explanatory drawing which shows the outline of the oscillator which concerns on embodiment of this invention. It is a characteristic view which shows the spurious vibration of a mesa type | mold and a reverse mesa type crystal piece.

  A structure of a crystal resonator that is a piezoelectric resonator according to an embodiment of the present invention will be described with reference to the drawings. 1A is a plan view of the crystal resonator, FIG. 1B is a cross-sectional view taken along the line AA of FIG. 1, and FIG. 1C is a bottom view of the crystal resonator. This crystal resonator includes a crystal piece 2 which is a piezoelectric piece having different heights between a main surface portion 21 and a peripheral edge portion 22 surrounding the main surface portion 21. In this example, the main surface portion 21 is formed in a circular shape, and the peripheral edge portion 22 is formed in a rectangular shape. The crystal piece 2 in this example is a mesa type, and the main surface portion 21 is higher than the peripheral edge portion 22. For example, the diameter L1 of the main surface portion 21 is set to about 0.5 mmφ, the thickness L2 of the main surface portion 21 is set to about 50 μm, and the thickness L3 of the peripheral portion 22 is set to about 40 μm, for example. In FIG. 1, reference numeral 20 denotes a line indicating the outline of the main surface portion 21.

  A first excitation electrode 31 is formed on the main surface portion 21 on one surface side (front surface side) of the crystal piece 2, and a second excitation is formed on the main surface portion 21 on the other surface side (back surface side) of the crystal piece 2. An electrode 32 is formed. The first and second excitation electrodes 31 and 32 are formed in the same shape as each other, and are provided so as to face each other with the main surface portion 21 therebetween. In this example, the first and second excitation electrodes 31 and 32 are formed in a circular shape centered on the central portion of the main surface portion 21, for example, approximately the same size as or slightly smaller than the main surface portion 21.

  In addition, a plurality of, for example, eight first shapes having the same shape are formed at equal intervals in the circumferential direction of the crystal piece 2 so as to radially extend from the first excitation electrode 31 to the peripheral edge portion 22 on one surface side of the crystal piece 2. The lead electrode 41 is formed. These extraction electrodes 41 are formed in a fan shape having a larger outer edge 44 than the side 43a connected to the excitation electrode 31, and the total length of the sides 43a connected to the excitation electrode 31 in the plurality of extraction electrodes 41 is: It is set to be equal to or less than ½ of the circumference of the excitation electrode 31.

  Furthermore, the one surface side of the crystal piece 2 includes a first arc-shaped electrode 51 formed along a circle centered on the center of the crystal piece 2 so as to connect the first lead electrodes 41 to each other. ing. In this example, eight first extraction electrodes 41 are connected by eight first arc-shaped electrodes 51.

  On the other hand, the peripheral portion 22 on the other surface side of the crystal piece 2 also has a plurality of, for example, eight pieces of the same shape at equal intervals in the circumferential direction of the crystal piece 2 so as to extend radially from the second excitation electrode 32. Two extraction electrodes 42 are formed. The total length of the sides 43b connected to the excitation electrode 32 in the plurality of extraction electrodes 42 is set to be equal to or less than ½ of the circumferential length of the excitation electrode 32.

  In addition, the second lead electrode 42 is also connected to the other surface side of the crystal piece 2 along a circle having a diameter different from the diameter of the circle, with the center of the crystal piece 2 being the center. In this example, eight second extraction electrodes 42 are connected by eight second arc-shaped electrodes 52.

  FIG. 2 shows an arrangement example of the first and second extraction electrodes 41 and 42 and the first and second arc-shaped electrodes 51 and 52. This figure is a plan view seen from one surface side of the crystal piece 2, and the projection areas of the second extraction electrode 42 and the second arc-shaped electrode 52 are indicated by dotted lines. Thus, the first extraction electrode 41 is disposed at a position that does not overlap the projection area of the second extraction electrode 42, and the first arc-shaped electrode 51 is projected from the second arc-shaped electrode 52. It is formed at a position that does not overlap with the region.

  Therefore, in this example, the second extraction electrode 42 is formed so as to have a length in the radial direction larger than that of the first extraction electrode 41, and the second circle is formed outside the first arc-shaped electrode 51. An arcuate electrode 52 is formed. That is, the first arc-shaped electrode 51 is formed along a circle having a radius R1 centered on the center portion O of the crystal piece 2, and the second arc-shaped electrode 52 has a radius centered on the center portion O. It is formed along a circle having a radius R2 larger than R1.

  Further, the first extraction electrode 41 and the second extraction electrode 42 are configured in a shape in which the dimensions in the circumferential direction overlap when the phases are matched. That is, if the second extraction electrode 42 is rotated, the shape in the circumferential direction is the same so that the eight first extraction electrodes 41 and the eight second extraction electrodes 42 overlap each other in the circumferential direction. It is formed to become.

  In this example, the first extraction electrode 41 and the second extraction electrode 42 are formed so that the lengths in the radial direction are different from each other. However, the first extraction electrode 41 is formed of the second extraction electrode 42. If the first arc-shaped electrode 51 can be formed at a position that does not overlap with the projection area, and the first arc-shaped electrode 51 can be formed at a position that does not overlap with the projection area of the second arc-shaped electrode 52, the first extraction electrode 41 and the second The lead electrode 42 may be configured to have the same shape in the circumferential direction and the radial direction.

  The first and second excitation electrodes 31 and 32, the first extraction electrode 41 and the second extraction electrode 42, the first arc-shaped electrode 51 and the second arc-shaped electrode 52 are formed on, for example, chromium (Cr). And a metal film in which gold (Au) is laminated. In FIG. 1, for convenience of explanation, a solid line is drawn between the excitation electrode 31, the extraction electrode 41, and the arc-shaped electrode 51, and between the excitation electrode 32, the extraction electrode 42, and the arc-shaped electrode 52. Although they are distinguished, they are actually formed integrally.

  A first connecting electrode 61 is electrically connected to the first arc-shaped electrode 51 to connect to an external conductive path, and a second arc-shaped electrode 52 is connected to an external conductive path. In addition, the second connection electrode 62 is electrically connected. The first and second arc-shaped electrodes 51 and 52 are also formed of a metal film in which, for example, Au is laminated on Cr.

  Such a crystal oscillator oscillates in the following manner: an external conductive path, first and second connection electrodes 61 and 62, first and second arc-shaped electrodes 51 and 52, and first and second lead electrodes. This occurs when a voltage is applied to the first and second excitation electrodes 31 and 32 via 41 and 42.

  Next, a method of manufacturing the crystal unit shown in FIG. 1 will be briefly described with reference to FIG. Note that FIG. 3 illustrates one crystal resonator formed on a part of one crystal substrate. First, after cutting and cleaning a cut crystal substrate 7 such as a crystal wafer (FIG. 3 (a)), as shown in FIG. 3 (b), a region other than the main surface portion 21 is dug down by etching. , Forming a mesa structure. This etching is formed by wet etching or dry etching. When forming by wet etching, it is performed as follows. For example, a metal film is formed on both surfaces of the quartz substrate 7, and a positive resist film is formed on the metal film. Next, a predetermined pattern is exposed on the positive resist film, developed, immersed in a KI (potassium iodide) solution, and metal etched to form a mask pattern in which the metal film and the resist film are laminated. Next, the quartz substrate 7 having a mask pattern formed on the surface is etched by immersing it in a hydrofluoric acid solution to form a mesa structure on the quartz substrate 7.

In the case of forming by dry etching, for example, a mask pattern is formed on the surface of the quartz substrate 7 by the same method as the above-described wet etching. Next, the quartz substrate 7 having a mask pattern formed on the surface is etched using an etching gas such as CHF ₃ gas to form a mesa structure on the quartz substrate 7.

  Next, as shown in FIG. 3C, a metal film 71 in which Au is laminated on Cr is formed on the entire surface of the quartz substrate 7 by, for example, sputtering or vacuum evaporation. Next, after forming a resist pattern on the metal film 71, it is immersed in a KI solution to form an electrode pattern as shown in FIGS. 1A and 1C (FIG. 3D). As a result, the first excitation electrode 31, the first extraction electrode 41, the first arc-shaped electrode 51, and the first connection electrode 61 are integrally formed on one surface side of the crystal substrate 7. On the other surface side, the second excitation electrode 32, the second extraction electrode 42, the second arc-shaped electrode 52, and the second connection electrode 62 are integrally formed. Thereafter, by cutting along a dicing line using a dicing saw, the crystal resonators are separated from the crystal substrate 7 one by one, thereby completing the crystal resonator shown in FIG. )).

  As shown in FIG. 4, the above-described crystal piece 2 may be an inverted mesa type. In the crystal resonator using the inverted mesa type crystal piece 2, the height of the main surface portion 21 is higher than that of the peripheral portion 22. Is the same as that of the quartz crystal resonator using the mesa-type quartz piece 2 except that it is low. 4A is a plan view of the crystal resonator, FIG. 4B is a cross-sectional view along BB, and FIG. 4C is a bottom view.

  Next, an electronic component incorporating the above-described crystal resonator will be described with reference to FIG. In FIG. 5, reference numeral 8 denotes a package in which the crystal resonator is housed. The package 8 includes a base body 81 made of ceramics such as glass or crystal, and a metal lid body 82. The base body 81 and the lid body 82 are seam welded by a seal material made of, for example, a welding material, and the inside thereof is in a vacuum state.

  The base body 81 is formed of a laminate of a bottom portion 81A and a side wall portion 81B, and internal terminals 83A and 83B made of a metal film are formed on the surface of the bottom portion 81A. These internal terminals 83A and 83B are arranged side by side in the Y direction in FIG. 5. In FIG. 5, the internal terminal 83A is provided on the inner side of the internal terminal 83B. The internal terminal 83A corresponds to the first connection electrode 61, and the internal terminal 83B corresponds to the second connection electrode 62, respectively. Furthermore, external terminals 84A and 84B made of a metal film are formed on the outer surface of the base body 81 from the side to the bottom. These external terminals 84A and 84B correspond to external electrodes formed on the outer surface of the package 8 and electrically connected to the first connection electrode 61 and the second connection electrode 62, respectively. In this example, the internal terminal 83B and the external terminal 84B are electrically connected, and the internal terminal 83A and the external terminal 84A are electrically connected through a conductive path (not shown) provided on the surface of the bottom 81A. ing.

  The crystal resonator is stored horizontally in the base body 81 with the first connection electrode 61 connected to the internal terminal 83A and the second connection electrode 62 connected to the internal terminal 83B. In this example, the first connection electrode 61 is electrically connected to the internal terminal 83A by wire bonding 85, and the second connection electrode 62 is connected to the internal terminal 83B by a conductive adhesive 86. Thus, the first connection electrode 61 of the crystal resonator is electrically connected to the external terminal 84A via the internal terminal 83A, and the second connection electrode 62 is electrically connected to the external terminal 84B via the internal terminal 83B. Connected.

  In such an electronic component, for example, after a crystal resonator is mounted on the base body 81 and bonded, the excitation electrodes 31 and 32 are shaved with an electron beam or the like and controlled to a constant frequency, and then the lid 82 is fixed to the base body. It is manufactured by vacuum seam sealing to 81.

  In the above-described embodiment, a mesa-type or inverted-mesa-type crystal piece 2 is used, and a plurality of first and second excitation electrodes 31 and 32 provided on both surfaces of the main surface portion 21 are used. The first extraction electrodes 41 and 42 are formed so as to extend radially, the first extraction electrodes 41 are electrically connected to each other by the first arc-shaped electrode 51, and the second extraction electrode 41 is electrically connected to each other. The electrodes 42 are electrically connected.

  For this reason, the electric field distribution (electric field energy distribution) in the circumferential direction in the main surface portions 21 and 22 is highly uniform, and this electric field can be drawn out as it is through the extraction electrodes 41 and 42 and the arc-shaped electrodes 51 and 52 as they are. , CI value can be reduced. At this time, since the first and second lead electrodes 41 and 42 are formed with the same electrode pattern so that the dimensions in the circumferential direction overlap each other when the phases are matched, the main surface portions 21 and 22 are formed. On both sides, the electric field energy distribution is aligned, and the uniformity of the electric field distribution (electric field energy distribution) in the circumferential direction is increased.

  If the first and second lead electrodes 41, 42 are electrically connected by the first and second arc-shaped electrodes 51, 52, the first connection electrode 61 and the second connection electrode 62 are provided. Irrespective of the shape, a uniform excitation energy can be extracted radially.

  Further, the second extraction electrode 42 is disposed at a position not overlapping the projection area of the first extraction electrode 41, and the second arc-shaped electrode 52 does not overlap the projection area of the first arc-shaped electrode 51. Since it is formed at the position, the overlap between the electrode pattern on the one surface side of the crystal piece 2 and the electrode pattern on the other surface side can be suppressed, and spurious vibrations other than the main vibration can be reduced. As a result, the CI value is reduced. can do.

  In the present invention, the crystal oscillator 9 is configured by mounting the crystal resonator shown in FIG. 1 or FIG. 4 on the wiring substrate 91 on which the circuit components of the oscillation circuit 90 are mounted as shown in FIG. May be.

  In the crystal piece 2 described above, the shape of the main surface portion 21 is preferably circular, but the crystal piece of the peripheral portion 22 may be circular, elliptical, or rectangular, and the number of extraction electrodes can be selected as appropriate. It is. Furthermore, the arc-shaped electrode is not limited to the configuration in which the outer peripheral portions of the extraction electrode in the radial direction are connected to each other, and the center side may be connected to the outer peripheral portion of the extraction electrode. Further, in the electronic component of the present invention, the package structure is not limited to the example shown in the figure, and the first connection electrode 61 is made to wrap around to the back surface side of the crystal piece 2 and the back surface connection electrode 61 is connected to the internal terminal 63A. A structure in which a conductive adhesive is used for connection may be used, or a structure in which power is supplied to the crystal resonator using a through hole may be used.

2 crystal piece 21 main surface portion 22 peripheral portion 31 first excitation electrode 32 second excitation electrode 41 first extraction electrode 42 second extraction electrode 51 first arc-shaped electrode 52 second arc-shaped electrode 61 first Connection electrode 62 Second connection electrode

Claims (5)

A mesa-type or reverse mesa-type piezoelectric piece having a different height between the main surface portion and the peripheral edge surrounding the main surface portion;
A first excitation electrode and a second excitation electrode respectively formed on a main surface portion on one surface side of the piezoelectric piece and a main surface portion on the other surface side of the piezoelectric piece;
A plurality of first extraction electrodes formed on a peripheral portion on one surface side of the piezoelectric piece, extending radially from the first excitation electrode, and formed in a circumferential direction of the piezoelectric piece;
A first arc-shaped electrode formed by connecting the first lead electrodes to each other along a circle centered on the central portion of the piezoelectric piece;
A plurality of second extraction electrodes formed on a peripheral portion on the other surface side of the piezoelectric piece, extending radially from the second excitation electrode, and formed in a circumferential direction of the piezoelectric piece;
These second lead electrodes are connected to each other, a second arc-shaped electrode formed along a circle having a diameter different from the diameter of the circle centered on the central portion of the piezoelectric piece;
A first connection electrode and a second connection electrode electrically connected to the first arc-shaped electrode and the second arc-shaped electrode, respectively, for connecting to an external conductive path;
The second extraction electrode is arranged at a position not overlapping the projection area of the first extraction electrode so as to be alternately arranged with the projection area of the first extraction electrode along the circumferential direction of the excitation electrode,
The piezoelectric vibrator, wherein the second arcuate electrode is formed at a position that does not overlap with a projection area of the first arcuate electrode.   2. The piezoelectric vibrator according to claim 1, wherein the first lead electrode and the second lead electrode are formed at equal intervals along the circumferential direction of the piezoelectric piece.   2. The sum of the lengths of contact portions of the first lead electrode and the second lead electrode with the piezoelectric piece is ½ or less of the circumferential length of the piezoelectric piece, respectively. Or the piezoelectric vibrator of 2. Package and
The piezoelectric vibrator according to any one of claims 1 to 3 provided in the package,
An electronic component comprising: an external electrode formed on an outer surface of the package and electrically connected to the first connection electrode and the second connection electrode of the piezoelectric vibrator, respectively.   An oscillator comprising the electronic component according to claim 4 and an oscillation circuit.

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