JP2006086790A - Thickness slide piezoelectric vibrating piece and piezoelectric device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an AT cut vibrating piece having enhanced vibration characteristics by providing the large areas of excitation electrodes on the main plane of a piezoelectric element. <P>SOLUTION: The AT cut vibrating piece 20 comprises: the excitation electrodes 52a, 52b; and lead out electrodes 54a, 54b transferring a driving voltage to the excitation electrodes 52a, 52b on the surface of the rectangular piezoelectric element 22. The excitation electrodes 52a, 52b are formed on the main plane of the piezoelectric element 22. The lead out electrodes 54a, 54b are formed only on the end face of the piezoelectric element 22. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thickness-slip piezoelectric vibrating piece and a piezoelectric device using the same.

Piezoelectric devices are widely used in small information devices such as HDDs (hard disk drives), mobile computers, IC cards, and various electronic devices such as mobile phones, car phones, and paging systems.
FIG. 5 shows a configuration example of a piezoelectric vibrator as a conventional piezoelectric device (see Patent Document 1). In the figure, the piezoelectric device 1 is an AT-cut vibrating piece that is a thickness-sliding piezoelectric vibrating piece in a package 2. 3 is housed.

That is, the package 2 has electrode portions 4 and 4 that are electrically connected to mounting terminals (not shown) on the inner bottom surface exposed in the internal space.
The AT-cut vibrating piece 3 is formed of a piezoelectric element 8 such as quartz, for example, and an excitation electrode 5 for exciting the piezoelectric element 8 on an upper surface thereof, and an extraction electrode 6 for transmitting a driving voltage to the excitation electrode 5. Is provided. Although not shown, excitation electrodes and extraction electrodes are similarly formed on the lower surface of the AT-cut vibrating piece 3.
The portion of the extraction electrode 6 of the AT-cut vibrating piece 3 is electrically and mechanically joined to the electrode portion 4 in the package using the conductive adhesive 7.

Japanese Patent Laid-Open No. 2000-165176

  However, since the excitation electrode 5 and the extraction electrode 6 are provided on the same surface of the piezoelectric element 8, the area of the excitation electrode 5 is largely provided on the main surface of the piezoelectric element 8 because the extraction electrode 6 is provided. I couldn't. For this reason, in the conventional AT-cut vibrating piece 3, for example, when applied to a voltage-controlled oscillator, the frequency sensitivity to a change in series capacitance cannot be increased. It was difficult to improve the vibration characteristics, for example, because of the small size.

  An object of the present invention is to provide a thickness-slip piezoelectric vibrating piece having improved vibration characteristics by increasing the area of an excitation electrode on the main surface of a piezoelectric element, and a piezoelectric device using the same.

  According to the first aspect of the present invention, there is provided a thickness-slip piezoelectric vibrating piece including an excitation electrode and an extraction electrode for transmitting a drive voltage to the excitation electrode on a surface of a rectangular piezoelectric element, The excitation electrode is formed on a main surface of the piezoelectric element, and the extraction electrode is achieved by a thickness-slip piezoelectric vibrating piece formed only on an end surface of the piezoelectric element.

According to the configuration of the first invention, since the extraction electrode is formed only on the end surface of the rectangular piezoelectric element, the area of the excitation electrode can be reduced to the extent that the extraction electrode need not be provided on the main surface. Large on the main surface.
Thereby, for example, the energy per unit area of the excitation electrode is reduced, the energy is dispersed, and spurious is reduced. Further, even if the value of the current flowing through the thickness-slip piezoelectric vibrating piece increases, the frequency becomes difficult to change, and the variation in frequency with respect to the drive level becomes small. In addition, when this thickness-slip piezoelectric resonator element is used in a voltage-controlled piezoelectric oscillator that changes the frequency by changing the voltage, the sensitivity of the frequency to changes in series capacitance increases, and the oscillation frequency can be adjusted by the control voltage. The width can be increased. Further, even when the thickness-slip piezoelectric vibrating piece is mounted, even if the amount of the adhesive varies for each piezoelectric device to be manufactured, the extraction electrode and the excitation electrode are not arranged on the same surface. The distance is constant and the application area of the adhesive does not vary. Therefore, the variation in the vibration characteristics of the thickness-slip piezoelectric vibrating piece due to the variation in the adhesive application area can be reduced, and the variation in the CI value (crystal impedance value) for each manufactured piezoelectric device can be reduced. . In addition, since the excitation electrode can be formed wider than the conventional thickness-slip piezoelectric vibrating piece in which the excitation electrode and the extraction electrode are formed on the same surface, the CI value can be reduced.
Thus, according to the present invention, it is possible to provide a thickness-slip piezoelectric vibrating piece having improved vibration characteristics in various directions.

According to a second aspect of the present invention, in the configuration of the first aspect, the excitation electrodes are provided on the upper and lower surfaces of the piezoelectric element, and a first extraction electrode that supplies a driving voltage to the excitation electrodes on the upper surface; A second extraction electrode for supplying a driving voltage to the excitation electrode is formed on the opposite end faces of the piezoelectric element.
According to the configuration of the second invention, the first extraction electrode that supplies the driving voltage to the excitation electrode on the upper surface and the second extraction electrode that supplies the driving voltage to the excitation electrode on the lower surface are opposite to the piezoelectric element. It is formed on the side end face. For this reason, compared with the case where two extraction electrodes having different polarities are formed on the same end surface having a minimum area, the possibility of short-circuiting can be avoided and an extraction electrode having a large area can be formed. Therefore, it becomes easy to form the extraction electrode, and the bonding strength with the package can be increased.

According to a third aspect of the present invention, in any one of the first and second aspects, the piezoelectric element is an inverted mesa type formed such that a peripheral edge thereof is thicker than a vicinity of the center. .
According to the configuration of the third aspect of the invention, the piezoelectric element is an inverted mesa type formed so that the peripheral edge thereof is thicker than the vicinity of the center. For this reason, it has the same effect as the first and second inventions, and further increases the area of the end face of the piezoelectric element, which is the region where the extraction electrode is formed, thereby facilitating the formation of the extraction electrode. The bonding strength of can also be increased. Further, the strength of the peripheral edge that is easily damaged can be increased.

In addition, according to the fourth aspect of the present invention, the thickness-slip piezoelectric vibrating piece having an excitation electrode on the surface of a rectangular piezoelectric element and an extraction electrode for transmitting a drive voltage to the excitation electrode; A piezoelectric device comprising a package having a mount portion to which the thickness-slip piezoelectric vibrating piece is bonded, wherein the excitation electrode is formed on a main surface of the piezoelectric element, and the extraction electrode is an end surface of the piezoelectric element. This is achieved by a piezoelectric device formed only on the substrate.
According to the configuration of the fourth invention, since the extraction electrode is formed only on the end face of the rectangular piezoelectric element, the area of the excitation electrode can be reduced to the extent that the extraction electrode does not have to be provided on the main surface. It can be made large on the surface, and thereby the same effect as the first invention is exhibited.

According to a fifth invention, in the configuration of the fourth invention, a conductive adhesive is used as an adhesive for joining the thickness-slip piezoelectric vibrating piece to the mount portion, and the package is adjacent to the mount portion. It is the area | region, Comprising: It has the recessed part in the area | region outside the said excitation electrode, It is characterized by the above-mentioned.
According to the configuration of the fifth invention, the package has a recess in a region adjacent to the mount portion and outside the excitation electrode. For this reason, even if the conductive adhesive for mounting is applied more due to manufacturing variations, the concave portion accommodates excess conductive adhesive and prevents a short circuit with the excitation electrode.

According to a sixth aspect of the present invention, in the configuration according to the fourth or fifth aspect, the thickness-slip piezoelectric vibrating piece is mounted such that an end surface on which the extraction electrode is formed is close to an inner wall surface of the package. It is characterized by being.
According to the configuration of the sixth invention, since the end surface on which the extraction electrode is formed is mounted so as to be close to the inner wall surface of the package, the mounting adhesive includes the end surface on which the extraction electrode is formed. The space between the inner wall surface of the package and the inner wall surface of the package can be raised by capillary action, and the adhesive can be reliably applied to the entire extraction electrode.

According to a seventh invention, in any one of the fourth to sixth inventions, the piezoelectric element is made of quartz, and a silicone-based adhesive is used to bond the thickness-slip piezoelectric vibrating piece to the mount portion. A conductive adhesive is used, and the silicone-based conductive adhesive is in contact with the surface of the piezoelectric element not provided with the excitation electrode.
According to the structure of 7th invention, the silicone type electrically conductive adhesive is contacting the surface of the piezoelectric element in which the excitation electrode is not provided. Since the piezoelectric element is made of quartz, the silicone-based conductive adhesive is bonded to the quartz. Therefore, since the bonding strength between the silicone-based conductive adhesive and the crystal is high, the thickness-slip piezoelectric vibrating piece can be reliably bonded to the package.

1 and 2 show a first embodiment of a piezoelectric device of the present invention. FIG. 1 is a schematic plan view thereof, and FIG. 2 is a schematic cut end view taken along line AA of FIG.
In these drawings, the piezoelectric device 10 shows an example in which a piezoelectric vibrator is configured. The piezoelectric device 10 accommodates, for example, an AT-cut vibrating piece 20 in a package 30 as a thickness-slip piezoelectric vibrating piece.

  The package 30 is formed by, for example, laminating a plurality of substrates formed by molding an aluminum oxide ceramic green sheet as an insulating material, and then sintering. That is, as shown in FIG. 2, in this embodiment, the package 30 is formed by overlapping a first substrate 31, a second substrate 32, and a third substrate 33 from below.

  The third substrate 33 is configured to form a predetermined internal space S inside the package 30 when the third substrate 33 is stacked on the second substrate 32 by forming a predetermined through-hole inside thereof. Further, a lid body 46 is bonded to the upper end surface of the third substrate 33, that is, the open end surface opened above the package 30, via a brazing material 44 such as low melting point glass, for example, thereby sealing. It has been stopped.

The second substrate 32 is formed with a predetermined hole 32a on the inner side thereof so as to form a recess 50 exposed in the internal space S of the package 30 when the second substrate 32 is stacked on the first substrate 31. . The recess 50 will be described in detail later.
In addition, the hole 32 a of the second substrate 32 is formed to be smaller than the through hole of the third substrate 33, so that when the third substrate 33 is stacked on the second substrate 32, the second substrate 32. A mount portion 32b exposed to the internal space S is formed on the upper surface of the substrate.
More specifically, the mount portions 32b are formed at both ends in the longitudinal direction in the internal space S (at the left and right ends in FIG. 1), and have a length L1 that is equal to or greater than the width W1 of the AT cut vibrating piece 20. Thus, it is formed along the width direction of the package 30.

Mount electrodes 42, 42 formed of, for example, gold or a gold alloy are provided on the entire mount portions 32b, 32b provided at both ends in the longitudinal direction. The mount electrodes 42 and 42 are electrically connected to the mounting terminal portions 43 and 43 through through holes or the like to supply a driving voltage.
Conductive adhesives 40 and 40 are applied on the mount electrodes 42 and 42, and both ends in the longitudinal direction of the AT-cut vibrating piece 20 are placed on the conductive adhesives 40 and 40. The conductive adhesives 40 and 40 are bonded by being cured.
Here, an epoxy, polyimide, or silicone adhesive can be used as the conductive adhesive 40. However, in the present embodiment, the conductive adhesive 40 has more flexibility than the epoxy conductive adhesive. However, a silicone-based conductive adhesive that shrinks by drying and hardly warps the AT-cut vibrating piece 20 is used.

The AT-cut vibrating piece 20 can use a piezoelectric element 22 such as crystal, lithium tantalate, or lithium niobate. In the present embodiment, the AT-cut vibrating piece 20 uses a piezoelectric element 22 formed by cutting a thin quartz wafer cut out so as to vibrate in thickness into a rectangular shape.
An excitation electrode 52 and an extraction electrode 54 for transmitting a drive voltage to the excitation electrode 52 are formed on the surface of the rectangular piezoelectric element 22.

The excitation electrode 52 is an electrode provided on the main surface in order to efficiently vibrate the piezoelectric element 22, and is formed from the excitation electrode 52a provided on the upper surface in FIG. 2 and the excitation electrode 52b provided on the lower surface. Has been.
Further, the excitation electrode 52 of the present embodiment has an extraction electrode 54 disposed on the end face as will be described later, and as shown in FIG. 1, the central portion thereof is in the vicinity of the central portion O of the piezoelectric element 22 in a plan view. It is supposed to be arranged in.
The excitation electrode 52 is formed of, for example, a metal film obtained by applying a gold sputtering film on a chromium sputtering film.

The extraction electrode 54 is a metal film similar to the excitation electrode 52, is formed integrally with the excitation electrode 52, and serves as an electrode for supplying a drive voltage to the excitation electrode 52.
That is, the lead electrode 54 is electrically and mechanically bonded to the above-described mount electrode 42 on the package side and the conductive adhesive 40.

Here, the extraction electrode 54 is formed only on the end face of the piezoelectric element 22.
Specifically, the extraction electrode 54 includes a first extraction electrode 54a and a second extraction electrode 54b that have different polarities.
The first extraction electrode 54a is provided on the entire left end surface of the piezoelectric element 22 in the longitudinal direction, and supplies a driving voltage to the excitation electrode 52a on the upper surface through the connection electrode portion 53a having a narrow upper surface. The second extraction electrode 54b is provided on the entire right end surface of the piezoelectric element 22 in the longitudinal direction, and supplies a driving voltage to the excitation electrode 52b on the lower surface through the contact electrode portion 53b having a narrow lower surface. Yes.
Thus, the first extraction electrode 54 a and the second extraction electrode 54 b are formed on the opposite end surfaces of the piezoelectric element 22.

The longitudinal end surfaces on which the first and second extraction electrodes 54 a and 54 b are formed are mounted so as to be close to the inner wall surface 33 a of the package 30.
That is, in this embodiment, as shown in FIGS. 1 and 2, since the first and second extraction electrodes 54a and 54b are provided on the entire end face in the longitudinal direction, the first and second extraction electrodes 54a are provided. , 54b are mounted close to each other so as to face the inner wall surface 33a of the third substrate 33, respectively.

  Further, in the present embodiment, as shown in the partial enlarged view surrounded by the one-dot chain line in FIG. 2, the conductive adhesive 40 does not contact only the extraction electrode 54 but is not provided with the excitation electrode 52. The surface of the piezoelectric element 22 is also in contact. That is, as described above, the silicone-based conductive adhesive 40 that is softer than the epoxy-based adhesive has a higher bonding strength than that of the extraction electrode 54 from which gold or a gold alloy is exposed. The adhesive strength 40 is brought into contact with the piezoelectric element 22 so that the bonding strength between the AT-cut vibrating piece 20 and the package 30 can be further increased.

Further, as described above, the package 30 has the recess 50, and the recess 50 is formed in a region adjacent to the mount portion 32 b and outside the excitation electrode 52. That is, the recess 50 flows when the conductive adhesive 40 when mounting the AT-cut vibrating piece 20 flows toward the center as shown in the partial enlarged view surrounded by the one-dot chain line in FIG. It becomes a part which accommodates the conductive adhesive 40 which has come. Thereby, the short circuit which arises when the conductive adhesive 40 touches the excitation electrode 52 is prevented.
In the present embodiment, a recess 51 is also formed immediately below the excitation electrode 52 so that the excitation electrode 52 does not contact the inner surface of the package 30, and the recess 50 is continuous with the recess 51. It is integrally formed.

The piezoelectric device 10 according to the present embodiment is configured as described above, and the extraction electrode 54 is formed only on the end face of the rectangular piezoelectric element 22. Therefore, the excitation electrode does not need to be provided on the main surface. The area of 52 can be made large on the main surface of the piezoelectric element 22.
Thereby, the vibration characteristic of the AT cut vibrating piece 20 can be improved from various directions. For example, spurious generation has conventionally been a problem in a miniaturized AT-cut vibrating piece, but the energy per unit area of the excitation electrode 22 is reduced and the energy is dispersed, thereby reducing spurious. Further, even if the value of the current flowing through the AT-cut vibrating piece 20 is increased, the frequency is difficult to change. Therefore, the frequency variation with respect to the drive applied to the AT-cut vibrating piece 20 is reduced. Furthermore, since the conductive adhesive 40 and the excitation electrode 52 are not arranged on the same surface, even if the amount of the conductive adhesive 40 varies and is applied, the distance between the conductive adhesive 40 and the excitation electrode 52. Is fixed, and variation in CI value (crystal impedance value) for each manufactured piezoelectric device can be reduced. Furthermore, when a so-called piezoelectric oscillator of a type capable of changing the frequency by attaching a semiconductor element capable of changing the voltage to the piezoelectric device 10 described above, the variable width becomes large, so that the frequency is greatly changed. be able to.

  Further, the AT-cut vibrating piece 20 can oscillate at a higher frequency as the thickness is thinner. However, if the thickness is small, the area of the extraction electrode 54 becomes small and it becomes difficult to mount or easily breaks. It becomes difficult. However, in the present embodiment, as described above, the extraction electrodes 54a and 54b are formed on the entire end surface on the opposite side of the piezoelectric element 22, so that it is relatively possible to avoid the short circuit between the extraction electrodes 54a and 54b. A large electrode can be formed, and the bonding strength with the package 30 can be increased by applying a large amount of the conductive adhesive 40.

  Further, since the end surface in the longitudinal direction where the extraction electrodes 54a and 54b are formed is mounted so as to be close to the inner wall surface 33a of the package 30, the conductive adhesive 40 is formed between the extraction electrode 54 and the wall surface 33a. The conductive adhesive 40 can be reliably applied to the entire extraction electrode 54 by crawling up by the capillary phenomenon.

  In addition, since the recess 50 is formed in a region adjacent to the mount portion 32b and outside the excitation electrode 52, the conductive adhesive 40 comes into contact with the excitation electrode 52 as described above. Short circuit is prevented. Therefore, for example, a large amount of the conductive adhesive 40 can be applied without worrying about a short circuit between the extraction electrode 54 a and the excitation electrode 52 b, and the extraction electrode 54 can be reliably bonded to the package 30.

  Note that, as described above, the silicone-based conductive adhesive 40 is brought into contact with the surface of the piezoelectric element 22 made of quartz to further increase the bonding strength between the AT-cut vibrating piece 20 and the package 30. At this time, when the conductive adhesive 40 is brought into contact with the surface of the piezoelectric element 22, the area of the excitation electrode 52 is reduced by the amount of contact, but the extraction electrode 54 and the excitation electrode 52 are placed on the same surface. Compared with the arrangement, the area of the excitation electrode 52 can be increased, and at least the area of the excitation electrode 52 can be increased by the amount of the extraction electrode 54 provided on the end face.

3 and 4 show a piezoelectric device 60 according to a second embodiment of the present invention. FIG. 3 is a schematic plan view of the piezoelectric device 60, and FIG. 4 is a schematic cut end view taken along line BB of FIG. It is.
In these drawings, portions denoted by the same reference numerals as those used in the description of the piezoelectric device 10 described above have a common configuration, and therefore, redundant description will be omitted, and hereinafter, differences will be mainly described.

The piezoelectric device 60 of the second embodiment is different from the piezoelectric device 10 of the first embodiment in that a so-called reverse mesa type AT-cut vibrating piece is used for the thickness-slip piezoelectric vibrating piece.
That is, as shown in FIGS. 3 and 4, the piezoelectric element 22 is formed so that the peripheral edge 22a has a thickness larger than that of the reverse mesa portion 22b near the center.
More specifically, the piezoelectric element 22 has a reverse mesa portion 22b near the center, and the reverse mesa portion 22b and the peripheral edge 22a have step portions 22c on the upper and lower surfaces, respectively, and the thickness D of the peripheral edge 22a has a thickness D. It is formed to be large.

  The piezoelectric device 60 according to the second embodiment is configured as described above, exhibits the same operational effects as the piezoelectric device 10 according to the first embodiment, and further, the peripheral edge 22a of the piezoelectric element 22 is the center. The inverted mesa type is formed so as to have a thickness greater than the vicinity. For this reason, the area of the end face of the piezoelectric element (the thickness D of the peripheral edge 22a), which is the region where the extraction electrode 54 is formed, can be increased to increase the bonding strength with the package, and the strength of the peripheral edge 22a that is easily damaged. Can also be increased.

  The present invention is not limited to the above-described embodiment. Each configuration of the embodiment and each modified example can be appropriately combined or omitted, and can be combined with other configurations not shown.

1 is a schematic plan view showing a first embodiment of a piezoelectric device of the present invention. FIG. 2 is a schematic cut end view taken along line AA in FIG. 1. The schematic plan view which shows 2nd Embodiment of the piezoelectric device of this invention. FIG. 4 is a schematic cut end view taken along line BB in FIG. 3. The schematic perspective view which shows an example of the conventional piezoelectric device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10,60 ... Piezoelectric device, 20 ... AT cut vibration piece, 22 ... Piezoelectric element, 30 ... Package, 32b ... Mount part, 40 ... Conductive adhesive, 50 ... Recess, 52, 52a, 52b ... excitation electrode, 54 ... extraction electrode, 54a ... first extraction electrode, 54b ... second extraction electrode

Claims (7)

A thickness-sliding piezoelectric vibrating piece provided with an excitation electrode and an extraction electrode for transmitting a drive voltage to the excitation electrode on the surface of a rectangular piezoelectric element,
The excitation electrode is formed on the main surface of the piezoelectric element,
The lead-out electrode is formed only on the end face of the piezoelectric element. The excitation electrodes are provided on the upper and lower surfaces of the piezoelectric element,
A first extraction electrode that supplies a driving voltage to the excitation electrode on the upper surface and a second extraction electrode that supplies a driving voltage to the excitation electrode on the lower surface are formed on the opposite end surfaces of the piezoelectric element. The thickness-slip piezoelectric vibrating piece according to claim 1, wherein:   3. The thickness-shear piezoelectric vibrating piece according to claim 1, wherein the piezoelectric element is an inverted mesa type formed such that a peripheral edge thereof is thicker than a vicinity of a center. A package having an excitation electrode on the surface of a rectangular piezoelectric element, a thickness-slip piezoelectric vibrating piece having an extraction electrode for transmitting a driving voltage to the excitation electrode, and a mount portion to which the thickness-slip piezoelectric vibrating piece is joined A piezoelectric device comprising:
The excitation electrode is formed on the main surface of the piezoelectric element,
The extraction electrode is formed only on an end face of the piezoelectric element. A conductive adhesive is used as an adhesive for joining the thickness-slip piezoelectric vibrating piece to the mount part,
5. The piezoelectric device according to claim 4, wherein the package has a recess in a region adjacent to the mount portion and outside the excitation electrode. 6.   6. The thickness-sliding piezoelectric vibrating piece is mounted such that an end surface on which the extraction electrode is formed is close to an inner wall surface of the package. Piezoelectric device. The piezoelectric element is made of quartz,
A silicone-based conductive adhesive is used as an adhesive for joining the thickness-slip piezoelectric vibrating piece to the mount, and the silicone-based conductive adhesive is applied to the surface of the piezoelectric element on which the excitation electrode is not provided. The piezoelectric device according to claim 4, wherein the piezoelectric device is in contact.

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