JP6840535B2 - Piezoelectric vibrating elements and piezoelectric vibrating devices - Google Patents

Description

The present disclosure relates to piezoelectric vibrating elements and piezoelectric vibrating devices. The piezoelectric vibration device is, for example, a crystal oscillator or a crystal oscillator.

A crystal vibrating element used in a crystal oscillator or a crystal oscillator is, for example, a pair of excitations that overlaps a plate-shaped crystal piece and a pair of main surfaces (the widest surface. The front and back surfaces of the plate-shaped member) of the crystal piece. It has an electrode. In Patent Document 1, when a pair of excitation electrodes is viewed through a plane, one excitation electrode includes the other excitation electrode, and the distance between the outer edges of the pair of excitation electrodes is constant. The element is disclosed.

Japanese Unexamined Patent Publication No. 2014-230056

It is desired to provide a piezoelectric vibrating element and a piezoelectric vibrating device capable of improving the characteristics.

The piezoelectric vibrating element according to one aspect of the present disclosure has a plate-shaped piezoelectric piece and first and second excitation electrodes facing each other with the piezoelectric piece interposed therebetween, and is described in plan view. The second excitation electrode is wider than the first excitation electrode and overlaps the entire first excitation electrode, and the distance from the outer edge of the first excitation electrode to the outer edge of the second excitation electrode is the first excitation. It depends on the position along the outer edge of the electrode.

In one example, the outer edge of the second excitation electrode has a portion that is located outside the predetermined portion of the outer edge of the first excitation electrode and is inclined with respect to the predetermined portion in plan perspective. ing.

In one example, the first excitation electrode is rectangular in plan view, and the outer edge of the second excitation electrode has a curved portion that bulges outward with respect to one side of the rectangle in plan perspective.

In one example, the second excitation electrode has a pair of curved portions that bulge outward with respect to a pair of first sides of the rectangle facing each other and a pair of second pairs of the rectangle facing each other in plan perspective. It has a pair of straight lines that match the sides.

In one example, the rectangle is a rectangle, the pair of first sides is a pair of short sides of the rectangle, and the pair of second sides is a pair of long sides of the rectangle.

In one example, the rectangle is a rectangle, the pair of first sides is a pair of long sides of the rectangle, and the pair of second sides is a pair of short sides of the rectangle.

In one example, the outer edge of the second excitation electrode has a curved portion that bulges outward with respect to the four sides of the rectangle in plan perspective.

The piezoelectric vibration device according to one aspect of the present disclosure includes the above-mentioned piezoelectric vibration element and a package in which the piezoelectric vibration element is packaged.

According to the above configuration, the characteristics can be improved.

The exploded perspective view which shows the schematic structure of the crystal oscillator which concerns on 1st Embodiment. FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1 showing the configuration of the crystal oscillator of FIG. FIG. 3A is a perspective view of the crystal vibrating element of the crystal oscillator of FIG. 1 as viewed from the opposite side of FIG. 1, and FIG. 3B is a plan view showing the crystal vibrating element of FIG. 4 (a) to 4 (d) are plan views showing the crystal vibrating element according to the second to fifth embodiments. The perspective view of the crystal vibration element which concerns on 6th Embodiment.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The drawings used in the following description are schematic, and the dimensional ratios and the like on the drawings do not always match the actual ones. For convenience, the surface of the layered member (ie, the surface that is not a cross section) may be hatched.

The crystal oscillator or the crystal vibrating element of the present disclosure may be either upward or downward, but in the following, for convenience, the upper part of the paper surface (positive side in the Y'axis direction) of FIGS. 1 and 2 is used. Terms such as upper surface or lower surface may be used as the upper side. Further, in the case of simply plane view or plane perspective, unless otherwise specified, it means to view in the vertical direction defined for convenience as described above.

<First Embodiment>
(Overall configuration of crystal unit)
FIG. 1 is an exploded perspective view showing a schematic configuration of a crystal oscillator 1 (hereinafter, “crystal” may be omitted) according to the embodiment of the present disclosure. Further, FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1 showing the configuration of the oscillator 1.

The oscillator 1 is, for example, an electronic component having a substantially thin rectangular parallelepiped shape as a whole. The dimensions may be set as appropriate. For example, in a relatively small one, the length of the long side (X-axis direction) or the short side (Z'axis direction) is 1 to 2 mm, and the thickness (Y'axis direction) is 0.2 to 0.4 mm. Is.

The oscillator 1 includes, for example, an element mounting member 3 having a recess 3a formed therein, a crystal vibrating element 5 housed in the recess 3a (hereinafter, “crystal” may be omitted), and a lid for closing the recess 3a. Has 7 and.

The vibrating element 5 is a portion that generates vibration used for generating an oscillation signal. The element mounting member 3 and the lid 7 constitute a package 8 for packaging the vibrating element 5. The recess 3a of the element mounting member 3 is sealed by a lid 7, and the inside thereof is, for example, evacuated or filled with an appropriate gas (for example, nitrogen).

The element mounting member 3 mounts, for example, a base 9 which is a main body of the element mounting member 3, a pair of element mounting pads 11 for mounting the vibrating element 5, and an oscillator 1 on a circuit board (not shown) or the like. It has a plurality of (four in the illustrated example) external terminals 13 for the purpose.

The substrate 9 is made of an insulating material such as ceramic and constitutes the recess 3a described above. The element mounting pad 11 is formed of a conductive layer made of metal or the like, and is located on the bottom surface of the recess 3a. The external terminal 13 is composed of a conductive layer made of metal or the like, and is located on the lower surface of the substrate 9. The element mounting pad 11 and the external terminal 13 are connected to each other by a conductor (FIG. 2, reference numeral omitted) arranged in the substrate 9. The lid 7 is made of metal, for example, and is joined to the upper surface of the element mounting member 3 by seam welding or the like.

The vibrating element 5 includes, for example, a crystal piece 15, a first excitation electrode 17A (FIG. 2) for applying a voltage to the crystal piece 15, and a second excitation electrode 17B (hereinafter, these are simply “excitation electrodes” without distinction. 17 ”) and a pair of drawer electrodes 19 for mounting the vibrating element 5 on the pair of element mounting pads 11.

The vibrating element 5 has a substantially plate shape, and is housed in the recess 3a so as to face the bottom surface of the recess 3a. Then, the pair of extraction electrodes 19 are joined to the pair of element mounting pads 11 by the pair of bumps 21 (FIG. 2). As a result, the vibrating element 5 is supported by the element mounting member 3 like a cantilever. Further, the pair of excitation electrodes 17 are electrically connected to the pair of element mounting pads 11 via the pair of extraction electrodes 19, and are electrically connected to any two of the plurality of external terminals 13. To. The bump 21 is made of, for example, a conductive adhesive. The conductive adhesive is composed of, for example, a conductive filler mixed with a thermosetting resin.

The oscillator 1 configured in this way is arranged, for example, with the lower surface of the element mounting member 3 facing the mounting surface of a circuit board (not shown), and the external terminal 13 is joined to the pad of the circuit board by solder or the like. By doing so, it is mounted on the circuit board. An oscillation circuit 23 (FIG. 2) is configured on the circuit board, for example. The oscillation circuit 23 applies an AC voltage to a pair of excitation electrodes 17 via an external terminal 13 and an element mounting pad 11 to generate an oscillation signal. At this time, the oscillation circuit 23 uses, for example, the fundamental wave vibration of the thickness slip vibration of the crystal piece 15. Overtone vibration may be utilized.

(Structure of crystal vibrating element)
The crystal piece 15 is, for example, a so-called AT cut plate. That is, as shown in FIG. 1, in the crystal, the Cartesian coordinate system XYZ including the X-axis (electric axis), Y-axis (mechanical axis) and Z-axis (optical axis) is 30 ° or more and 40 ° or less around the X-axis. When the orthogonal coordinate system XY'Z'is defined by rotating (35 ° 15'as an example), the crystal piece 15 has a plate shape cut out parallel to the XZ'plane.

The crystal piece 15 is, for example, a flat plate. That is, the crystal piece 15 has a plate shape having a substantially constant thickness as a whole, and is not particularly marked, but a plurality of main surfaces connecting a pair of main surfaces (signs omitted) and a pair of main surfaces are connected. Has sides. The term main surface refers to the widest surface (front and back of the plate-shaped member).

When the outer shape of the crystal piece is formed by etching, a relatively large error (such as a systematic error) occurs due to the anisotropy of the crystal with respect to etching. The error may be used intentionally. In the description of the present disclosure, the existence of such an error shall be ignored. For example, in an actual crystal piece 15, the side surface may be inclined without being orthogonal to the main surface, or the side surface may be formed to bulge outward without being flat. / Or the illustration and description of the bulge will be omitted. Such errors may also be ignored when determining whether a third party product is involved in the technology of the present disclosure. Of course, things like random errors can be ignored.

As shown in FIG. 1, the shape of the crystal piece 15 in a plan view is rectangular. The rectangle is, for example, a rectangle (in the present disclosure, it is assumed that a square is not included. The same applies to the excitation electrode 17 and the like), and a pair of long sides and a pair connecting both ends of the pair of long sides are connected. Has a short side of. In the present disclosure, the rectangle or rectangle (shape having a pair of long sides and a pair of short sides) includes a shape with chamfered corners (the same applies to the excitation electrode 17 and the like). In the AT cut plate, the main surface is a surface substantially parallel to the XZ'plane, the long side is a side substantially parallel to the X axis, and the short side is a side substantially parallel to the Z'axis.

The thickness of the crystal piece 15 is set based on the desired natural frequency for the thickness slip vibration. For example, when the fundamental wave vibration is used and the natural frequency is F (MHz), the basic formula for obtaining the thickness t (μm) of the crystal piece 15 corresponding to the natural frequency F is t = 1670 / F. is there. Actually, the thickness of the crystal piece 15 is set to a value finely adjusted from the value of the basic formula in consideration of the weight of the excitation electrode 17 and the like.

Various dimensions of the crystal piece 15 may be appropriately set based on simulation calculations, experiments, and the like from various viewpoints such as reduction of equivalent series resistance. For example, the length of the long side is 550 μm or more and 1.1 mm or less, the length of the short side is 350 μm or more and 750 μm or less (however, it is shorter than the length of the long side), and the thickness is 20 μm or more and 70 μm or less.

The pair of excitation electrodes 17 and the pair of extraction electrodes 19 are composed of a conductive layer that overlaps the surface of the crystal piece 15. The conductive layer is, for example, a metal such as Au (gold), Ag (silver) or an Au-Ag alloy. The conductive layer may be composed of a plurality of layers whose materials are different from each other. The thickness of the conductive layer may be appropriately set, but as an example, it is 0.05 μm or more and 0.3 μm or less. In addition, in FIG. 2 and the like, the thickness of the conductive layer is shown to be thicker than the actual thickness.

The pair of excitation electrodes 17 are located on a pair of main surfaces of the crystal piece 15, and face each other with the crystal piece 15 interposed therebetween. The planar shape of the excitation electrode 17 will be described later.

The pair of extraction electrodes 19 extend from the pair of excitation electrodes 17 to one side in the X-axis direction (+ X side in the present embodiment), and at least one of the pair of main surfaces of the crystal piece 15 Has a pair of pads 19a joined to a pair of bumps 21 on the main surface of the. In the illustrated example, the pair of extraction electrodes 19 is a pair of pads 19a (in total) on each of the pair of main surfaces so that any of the pair of main surfaces may face the bottom surface of the recess 3a. It has two pairs of pads 19a).

The pads 19a and the excitation electrodes 17, which are located on the same main surface and should be connected to each other, are connected by a wiring portion 19b located on the main surface. The wiring portion 19b has a smaller width (Z'direction) than, for example, the pad 19a, and extends linearly in the X-axis direction with a substantially constant width. Two pads 19a, which are located on different main surfaces and should be connected to the same excitation electrode 17, are connected to each other via the side surfaces (short side and / or long side) of the crystal piece 15.

(Details of the shape of the excitation electrode)
In the following description, the code of the configuration related to the first excitation electrode 17A may be given an additional code of A, and the code of the configuration related to the second excitation electrode 17B may be given an additional code of B. In this case, the additional code of B may be added. A and B may be omitted as appropriate.

FIG. 3A is a perspective view showing the vibrating element 5 from the opposite side of FIG. FIG. 3B is a plan view of the vibrating element 5. In FIG. 3B, a portion of the outer edge of the first excitation electrode 17A that does not coincide with the outer edge of the second excitation electrode 17B is shown by a dotted line.

As shown in FIGS. 1, 3 (a) and 3 (b), the first excitation electrode 17A and the second excitation electrode 17B are different in shape (planar shape; the same applies hereinafter). Specifically, for example, it is as follows.

The shape of the first excitation electrode 17A is rectangular. The rectangle is, for example, a rectangle, and is a pair of long sides (a pair of long edges 29A) and a pair of short sides connecting both ends of the pair of long sides (free short edge 25A and fixed short edge 27A). ) And. The long edge 29A is, for example, parallel to the long side of the crystal piece 15, and the free short edge 25A and the fixed short edge 27A are parallel to the short side of the crystal piece 15. The free short edge 25A is a short side located on the free end side (opposite side of the extraction electrode 19) of the vibrating element 5, and the fixed short edge 27A is on the fixed end side (drawing electrode 19 side) of the vibrating element 5. It is the short side that is located.

For example, the center of gravity of the first excitation electrode 17A coincides with the center of gravity of the figure of the crystal piece 15 in the Z'direction and is displaced toward the free end side in the X direction. Therefore, the pair of long edges 29A is line-symmetric with respect to the center line Lx that is parallel to the X-axis and passes through the center of gravity of the crystal piece 15. On the other hand, the free short edge 25A and the fixed short edge 27A are, for example, asymmetric with respect to an unillustrated center line parallel to the Z'axis and passing through the center of gravity of the figure of the crystal piece 15. However, these may be line symmetric.

The center of gravity of the figure is a point at which the sum of the first-order moments in the figure becomes zero. In the present embodiment, the center line Lx is also the center line of the first excitation electrode 17A (and the second excitation electrode 17B), and may be referred to as the center line of the excitation electrode 17 in the following description.

The shape of the second excitation electrode 17B is a pair of long edges 29B corresponding to a pair of long edges 29A of the first excitation electrode 17A, and a free short edge 25A and a fixed short edge of the first excitation electrode 17A in plan perspective. It has a shape having a free short edge 25B and a fixed short edge 27B that bulge outward with respect to 27A. Therefore, the second excitation electrode 17B is wider than the first excitation electrode 17A and overlaps the entire first excitation electrode 17A.

When the corners of the rectangular or rectangular first excitation electrode 17A are chamfered, the pair of long edges 29B coincide with the pair of long edges 29A in plan perspective (the position, shape, and length are the same). Whether or not the chamfered part can be ignored. The same applies to the short edge and the like in other embodiments.

The free short edge 25B is, for example, a curved shape that bulges outward with respect to the free short edge 25A. Similarly, the fixed short edge 27B is, for example, a curved shape that bulges outward with respect to the fixed short edge 27A. Each curve of the free short edge 25B and the fixed short edge 27B has, for example, a line-symmetrical shape with the center line Lx as the axis of symmetry (however, the connection portion of the fixed short edge 27B with the extraction electrode 19 is excluded). Examples of such a line-symmetrical curve include an arc centered on a point (not shown) located on the center line Lx. The radius of the arc may be set as appropriate. Further, the shapes of the free short edge 25B and the fixed short edge 27B may be the same as each other (example in the figure) or may be different from each other.

In such a pair of excitation electrodes 17, the distance from the outer edge of the first excitation electrode 17A to the outer edge of the second excitation electrode 17B differs depending on the position along the outer edge of the first excitation electrode 17A. The distance here is, for example, the shortest distance from each position on the outer edge of the first excitation electrode 17A to the outer edge of the second excitation electrode 17B. Specifically, the distance differs depending on the position. For example, the distance from the long edge 29A to the long edge 29B is 0, whereas the distance from the free short edge 25A to the free short edge 25B, and The distance from the fixed short edge 27A to the fixed short edge 27B is not zero. Further, the distance from the free short edge 25A to the free short edge 25B and the distance from the fixed short edge 27A to the fixed short edge 27B are not constant with respect to the position in the Z'axis direction.

Focusing on the short edge, the outer edge of the second excitation electrode 17B is located outside a predetermined portion (assuming that it is a line, not a point) of the outer edge of the first excitation electrode 17A in plan perspective. However, it can be said that the portion is inclined with respect to the predetermined portion. Specifically, the free short edge 25B is a portion inclined with respect to the linear free short edge 25A (strictly speaking, one point on the center line Lx is excluded in this embodiment). Similarly, the fixed short edge 27B is a portion inclined with respect to the linear fixed short edge 27A (strictly speaking, one point on the center line Lx is excluded in this embodiment).

Although not particularly shown, at least one of the free short edge 25A and the free short edge 25B may be located at a node of a standing wave due to bending vibration (unnecessary vibration) with the X direction as the propagation direction. Similarly, at least one of the fixed short edge 27A and the fixed short edge 27B may be located at the node of a standing wave due to bending vibration with the X direction as the propagation direction. Similarly, the long edge 29 may be located at the node of a standing wave due to bending vibration with the Z'direction as the propagation direction. By locating the outer edge of the excitation electrode 17 at the node of the standing wave of the bending vibration in this way, the influence of the standing wave on the characteristics of the vibrating element 5 is reduced. Whether or not the curved portion of the outer edge (free short edge 25B or fixed short edge 27B in this embodiment) is located at the node of the standing wave is determined by, for example, the central position in the length direction (Z'direction). May be used as a reference.

The standing wave referred to here refers to a standing wave caused by bending vibration whose propagation direction is in the X direction or the Z'direction, which is most likely to be combined with the thickness slip vibration of the object to be used, and is obtained by simulation calculation or experiment. You can do it. The outer edge of the excitation electrode 17 may deviate from the node of the standing wave. For example, the deviation is λ / 8 or less or λ / 16 or less when the wavelength of the standing wave is λ. Of course, the position of the outer edge may be set independently of the antinodes or nodes of such standing waves.

As described above, in the present embodiment, the crystal vibrating element 5 has a plate-shaped crystal piece 15 and a pair of excitation electrodes 17 facing each other with the crystal piece 15 interposed therebetween. In planar fluoroscopy, the second excitation electrode 17B is wider than the first excitation electrode 17A and overlaps the entire first excitation electrode 17A, and the distance from the outer edge of the first excitation electrode 17A to the outer edge of the second excitation electrode 17B. Depends on the position along the outer edge of the first excitation electrode 17A.

From another viewpoint, in the present embodiment, the crystal oscillator 1 has the vibrating element 5 as described above and the package 8 in which the vibrating element 5 is packaged.

Therefore, for example, first, it is possible to reduce the influence of bending vibration, which is unnecessary vibration, on the characteristics of the vibrating element 5. This has been confirmed by an experiment conducted by the inventor of the present application on the vibrating element 5 having the configuration according to the present embodiment. The reason why such an action can be obtained is that, for example, the positions of the outer edges of the pair of excitation electrodes 17 are different from each other, and the distance between them changes according to the position along the outer edge. It is possible to reduce the possibility that the phases of bending vibrations, which depend on the position of the outer edge of the, are aligned. By reducing the influence of bending vibration, for example, the equivalent series resistance value can be reduced.

On the other hand, the capacitance of the pair of excitation electrodes 17 according to the present embodiment is compared with the capacitance in the embodiment in which the shape of the second excitation electrode 17B is the same as the shape of the first excitation electrode 17A. It doesn't make a big difference. As a result, for example, the design change of the vibrating element 5 is facilitated.

Specifically, for example, when the vibrating element 5 is miniaturized (for example, the length of the crystal piece 15 in the longitudinal direction is 1.1 mm or less), the influence of bending vibration, which is unnecessary vibration, becomes large. On the other hand, when the shape or size of a pair of excitation electrodes having the same shape is changed in order to reduce the influence of bending vibration, the electrical equivalent constant of the crystal vibration element changes. Especially the capacity is easy to change. As a result, for example, it is necessary to review the design of the crystal device (crystal oscillator). However, in the present embodiment, the shape and dimensions of the first excitation electrode 17A are left as they are, and the shape and / or dimensions of the second excitation electrode 17B are adjusted to reduce the influence of bending vibration and change the capacitance. It can be suppressed. As a result, the risk of having to redesign the crystal device is reduced.

Further, in the present embodiment, the outer edge of the second excitation electrode 17B is located outside the predetermined portion (25A and / or 27A) of the first excitation electrode 17A in plan perspective and is inclined with respect to the predetermined portion. Has a portion (25B and / or 27B).

Therefore, for example, it is possible to further reduce the influence of bending vibration on the characteristics of the vibrating element 5. Specifically, for example, the inclined portion (25B and / or 27B) of the outer edge of the second excitation electrode 17B is in a direction orthogonal to the linear portion (25A and / or 27A) of the first excitation electrode 17A. Since the position gradually changes with respect to the position in the direction along the straight line portion, the possibility that the phases of the bending vibrations propagating in the direction orthogonal to the straight line portion are aligned is more reliably reduced. .. Further, for example, since at least one of the straight portion and the inclined portion is inclined with respect to the outer edge of the crystal piece 15, the distance between the outer edge of the crystal piece 15 and the outer edge of the excitation electrode 17 is gradually increased. The bending vibration depending on the distance is reduced.

Further, in the present embodiment, the first excitation electrode 17A is rectangular in a plan view. The outer edge of the second excitation electrode 17B has a curved portion (25B and / or 27B) that bulges outward with respect to one side of the rectangle in plan perspective.

Therefore, for example, the various actions or effects described above can be obtained with respect to the first excitation electrode 17A having a relatively general shape. As a result, for example, the usefulness of the present embodiment is improved. Further, for example, in general, the energy distribution (energy contour line) of the thickness sliding vibration has an elliptical shape centered on the excitation electrode 17, so that the second excitation electrode 17B has a curved portion that bulges outward. Therefore, the shape of the second excitation electrode 17B can be made closer to the energy distribution. As a result, for example, an energy confinement effect can be efficiently obtained.

Further, in the present embodiment, the second excitation electrode 17B is a pair of curves that bulge outward with respect to a pair of first sides (25A and 27B) of the rectangles of the first excitation electrode 17A facing each other in plan perspective. It has portions (25B and 27B) and a pair of straight portions (29B) that coincide with a pair of opposite second sides (29A) of the rectangle.

Therefore, for example, as compared with a mode in which the entire outer edge of the second excitation electrode 17B is shifted with respect to the entire outer edge of the first excitation electrode 17A (this mode is also included in the technique according to the present disclosure), the pair of excitation electrodes has The amount of adjustment from the aspect of having the same shape as each other can be suppressed. As a result, for example, it is possible to reduce the possibility that the design of the device (oscillator 1) needs to be reviewed. On the other hand, for example, the influence of bending vibration propagating in the direction orthogonal to the first side (25A and 27B) of the pair can be reduced intensively. Therefore, for example, when the influence of bending vibration in the relevant direction is large, the characteristics can be preferably improved.

Further, in the present embodiment, the first side of the pair is a pair of short sides (25A and 27A), and the second side of the pair is a pair of long sides (29B).

Therefore, for example, the influence of bending vibration in the direction orthogonal to the short side can be reduced intensively. Further, for example, the radius of curvature can be reduced as compared with a mode in which the long side is curved outward (this mode is also included in the technique according to the present disclosure. See FIG. 4A), so that the first excitation is performed. It is easy to make the change in capacitance small with respect to the change in the distance from the outer edge of the electrode 17A to the outer edge of the second excitation electrode 17B. As a result, for example, it becomes easy to obtain the effect of improving the characteristics while reducing the possibility that the design of the device needs to be reviewed. In the experiment conducted by the inventor of the present application, it is equivalent series that the free short edge 25B and the fixed short edge 27B are curved outwards rather than the pair of long edges 29B are curved outwards. The resistance value could be reduced.

Further, in the present embodiment, the crystal piece 15 has a flat plate shape. In such a crystal piece 15, energy leaks to the vicinity of the outer edge of the crystal piece 15 and unnecessary vibration is likely to occur outside the excitation electrode 17 as compared with a mesa-shaped crystal piece (see FIG. 5). Therefore, the effect of suppressing unnecessary vibration is likely to appear due to the different shapes of the excitation electrodes 17.

<Second Embodiment>
FIG. 4A is a plan view similar to FIG. 3B showing the vibrating element 205 according to the second embodiment.

The vibrating element 205 differs from the vibrating element 5 of the first embodiment only in the shape of the second exciting electrode. Specifically, the second excitation electrode 217B of the vibrating element 205 has a shape in which the long edge bulges outward instead of the short edge. That is, the second excitation electrode 217B has a pair of free short edges 25A and a fixed short edge 27A of the first excitation electrode 17A, a free short edge 225B and a fixed short edge 227B, and a first excitation electrode 17A in plan perspective. It has a pair of long edges 229B that bulge outward with respect to a pair of long edges 29A.

Specifically, for example, the long edge 229B has a curved shape that bulges outward with respect to the long edge 29A. The curve has, for example, a line-symmetrical shape with the center line Lz parallel to the Z'axis as the axis of symmetry, passing through the center of gravity of the figure of the first excitation electrode 17A (or the second excitation electrode 17B). Examples of such a line-symmetrical curve include an arc centered on a point (not shown) located on the center line Lz. The radius of the arc may be set as appropriate. The shapes of the pair of long edges 229B are, for example, identical to each other. However, the shapes of the pair of long edges 229B may be different from each other.

Even in the vibrating element 205 having the above configuration, the second excitation electrode 217B is wider than the first excitation electrode 17A in plan perspective and overlaps the entire first excitation electrode 17A. The distance from the outer edge of the first excitation electrode 17A to the outer edge of the second excitation electrode 217B differs depending on the position along the outer edge of the first excitation electrode 17A. Focusing on the long edge, the outer edge of the second excitation electrode 217B is located outside the predetermined portion (29A) of the first excitation electrode 17A in plan perspective, and is inclined with respect to the straight line portion (229B). have.

As in the first embodiment, the free short edge 225B and the fixed short edge 227B are in the node of the standing wave due to the bending vibration propagating in the X direction (within the range of λ / 8 or λ / 16 from the node). May be located. Further, the long edge 229B (for example, the central position in the X direction) is located in the node of the standing wave due to the bending vibration propagating in the Z'direction (within the range of λ / 8 or λ / 16 from the node). Good.

As described above, also in the present embodiment, in the plan perspective, the second excitation electrode 217B is wider than the first excitation electrode 17A and overlaps the entire first excitation electrode 17A, from the outer edge of the first excitation electrode 17A. The distance to the outer edge of the second excitation electrode 217B differs depending on the position along the outer edge of the first excitation electrode 17A.

Therefore, for example, the same effect as that of the first embodiment can be obtained. For example, the influence of bending vibration on the characteristics can be reduced, while the change in capacitance can be suppressed.

Further, in the present embodiment, the second excitation electrode 217B has a pair of straight portions (225B and 227B) corresponding to a pair of short sides (25A and 27A) of the first excitation electrode 17A and the first excitation electrode 17A. It has a pair of curved portions (229B) that bulge outward with respect to a pair of long sides (29A) of the above.

Therefore, for example, the influence of bending vibration in the direction orthogonal to the long side can be reduced intensively. Further, for example, since the distance between the fixed short edge 227B and the extraction electrode 19 is secured in the same manner as the fixed short edge 27A, for example, it is not intended by the electric field formed between the fixed short edge 227B and the extraction electrode 19. The risk of spurious is reduced.

<Third Embodiment>
FIG. 4B is a plan view similar to FIG. 3B showing the vibrating element 305 according to the third embodiment.

The vibrating element 305 differs from the vibrating element 5 of the first embodiment only in the shape of the second exciting electrode. Specifically, the second excitation electrode 317B of the vibrating element 305 has a free short edge 25B and a fixed short edge 27B of the first embodiment and a pair of long edges 229B of the second embodiment.

From another viewpoint, the outer edge of the second excitation electrode 317B has a curved shape in which the entire outer edge (strictly speaking, excluding the apex of the first excitation electrode 17A) bulges outward with respect to the outer edge of the first excitation electrode 17A. The change at the connection point between the free short edge 25B and the fixed short edge 27B and the pair of long edges 229B may be made smoother. In other words, the second excitation electrode 317B may be elliptical (not necessarily a mathematical ellipse) or circular. Further, the outer edge of the second excitation electrode 317B may be separated from the apex of the first excitation electrode 17A.

As described above, also in the present embodiment, in the plan perspective, the second excitation electrode 317B is wider than the first excitation electrode 17A and overlaps the entire first excitation electrode 17A, from the outer edge of the first excitation electrode 17A. The distance to the outer edge of the second excitation electrode 317B differs depending on the position along the outer edge of the first excitation electrode 17A.

Therefore, for example, the same effect as that of the first embodiment can be obtained. For example, the influence of bending vibration on the characteristics can be reduced, while the change in capacitance can be suppressed.

Further, in the present embodiment, the outer edge of the second excitation electrode 317B has curved portions (25B, 27B and 229B) that bulge outward with respect to the four sides of the rectangle in plan perspective.

Therefore, for example, the influence of both the bending vibration propagating in the X direction and the bending vibration propagating in the Z'direction can be reduced. Further, for example, the shape of the second excitation electrode 317B becomes closer to the shape of the energy distribution of the thickness sliding vibration, and the energy confinement effect is further improved.

<Fourth Embodiment>
FIG. 4 (c) is a plan view similar to FIG. 3 (b) showing the vibrating element 405 according to the fourth embodiment.

The vibrating element 405 differs from the vibrating element 5 of the first embodiment only in the shape of the second exciting electrode. Specifically, the second excitation electrode 417B of the vibrating element 405 has a free short edge 25B and a pair of long edges 29B of the first embodiment, and a fixed short edge 227B of the second embodiment. That is, the second excitation electrode 417B has a shape in which only the free short edge 25B bulges outward with respect to the first excitation electrode 17A.

Even in such a configuration, the same effect as that of the first embodiment can be obtained. For example, the influence of bending vibration on the characteristics can be reduced, while the change in capacitance can be suppressed.

Further, since only the portion of the outer edge of the second excitation electrode 417B corresponding to one side of the first excitation electrode 17A is expanded outward, for example, the effect of suppressing the change in capacitance is high. Further, for example, since the distance between the fixed short edge 227B and the extraction electrode 19 is secured in the same manner as the fixed short edge 27A, for example, it is not intended by the electric field formed between the fixed short edge 227B and the extraction electrode 19. The risk of spurious is reduced.

<Fifth Embodiment>
FIG. 4D is a plan view similar to FIG. 3B showing the vibrating element 505 according to the fifth embodiment.

The vibrating element 505 differs from the vibrating element 5 of the first embodiment only in the shape of the second exciting electrode. Specifically, the second excitation electrode 517B of the vibrating element 505 has a fixed short edge 27B and a pair of long edges 29B of the first embodiment and a free short edge 225B of the second embodiment. That is, the second excitation electrode 517B has a shape in which only the fixed short edge 27B bulges outward with respect to the first excitation electrode 17A.

Even in such a configuration, the same effect as that of the first embodiment can be obtained. For example, the influence of bending vibration on the characteristics can be reduced, while the change in capacitance can be suppressed.

<Sixth Embodiment>
FIG. 5 is a perspective view corresponding to a part of FIG. 1, showing the vibrating element 605 according to the sixth embodiment.

The vibrating element 605 differs from the vibrating element 205 of the second embodiment only in the shape of the crystal piece. Specifically, the crystal piece 615 of the vibrating element 605 is a so-called mesa type. The first excitation electrode 17A (not shown here), the second excitation electrode 217B, and the extraction electrode 19 are basically the same as those in the second embodiment. However, since the vibrating element 605 is a mesa type, the extraction electrode 19 has a step. It goes without saying that specific dimensions may be appropriately set depending on the vibrating element 605 being a mesa type.

The mesa-shaped crystal piece 615 has a mesa portion 631 and an outer peripheral portion 633 that surrounds the mesa portion 631 in a plan view and has a thickness between a pair of main surfaces (in the Y'axis direction) thinner than that of the mesa portion 631. doing. Such a shape improves, for example, the energy confinement effect.

The shape of the mesa portion 631 is, for example, a plate shape having a pair of main surfaces parallel to each other. The planar shape of the mesa portion 631 is, for example, a rectangle (for example, a rectangle). However, the planar shape of the mesa portion 631 may be, for example, an ellipse or an oval (a shape in which the short side of the rectangle is an arc).

The shape of the outer peripheral portion 633 is, for example, a plate shape having a pair of main surfaces parallel to each other, ignoring the mesa portion 631. The shape of the outer edge of the outer peripheral portion 633 is the planar shape of the crystal piece 615 as a whole, and is the same as the planar shape of the crystal piece 15 in the first embodiment. That is, the outer peripheral portion 633 (crystal piece 615) is, for example, a rectangle.

In a plan view, the mesa portion 631 is located at the center of the outer edge of the crystal piece 615 (outer peripheral portion 633) in the Z'axis direction and on one side (opposite to the extraction electrode 19) in the X axis direction, for example. It is located off the side). However, the mesa portion 631 may be located at the center of the crystal piece 15 in the X-axis direction.

The outer peripheral portion 633 is located at the center of the mesa portion 631 in the Y'axis direction. That is, the height of the mesa portion 631 from the outer peripheral portion 633 (the amount of digging in the outer peripheral portion 633 for forming the crystal piece 615 into a mesa shape) is the same between the pair of main surfaces of the crystal piece 615.

The thickness of the mesa portion 631 is set based on a desired natural frequency for the thickness slip vibration, similarly to the thickness of the crystal piece 15 in the first embodiment. The thickness of the outer peripheral portion 633 is appropriately set from the viewpoint of the energy confinement effect and the like. For example, the difference in height between the main surface of the mesa portion 631 and the main surface of the outer peripheral portion 633 on one side of the pair of main surfaces of the crystal piece 615 (the amount of digging in the outer peripheral portion 633) is the difference in height of the mesa portion 631. It is 5% or more and 15% or less of the thickness, for example, about 20%.

Various dimensions of the crystal piece 615 may be appropriately set as in the first embodiment. For example, the length of the long side of the crystal piece 615 is 550 μm or more and 1.1 mm or less, the length of the short side of the crystal piece 615 is 350 μm or more and 750 μm or less (however, shorter than the length of the long side), and the mesa portion 631. The thickness is 20 μm or more and 70 μm or less, the length of the long side of the mesa portion 631 is 400 μm or more and 750 μm or less (however, it is shorter than the length of the long side of the crystal piece 615), and the length of the short side of the mesa portion 631 is 300 μm or more and 650 μm or less ( However, it is shorter than the length of the short side of the crystal piece 615 and the length of the long side of the mesa portion 631).

In a plan view, the first excitation electrode 17A and the second excitation electrode 217B are smaller than the mesa portion 631 and are contained in the main surface of the mesa portion 631. Further, in the pair of extraction electrodes 19, the pad 19a is located on the outer peripheral portion 633, and the wiring portion 19b extends from the mesa portion 631 to the outer peripheral portion 633. The second excitation electrode 217B, or the first excitation electrode 17A and the second excitation electrode 217B may be wider than the mesa portion 631.

Even in such a configuration, the same effect as that of the first embodiment can be obtained. For example, the influence of bending vibration on the characteristics can be reduced, while the change in capacitance can be suppressed.

Here, an embodiment in which the second excitation electrode 217B of the second embodiment is combined with the mesa-shaped crystal piece 615 has been described as an example, but instead of the second excitation electrode 217B, the second excitation electrode of another embodiment has been described. (17B, 317B, 417B and 517B) may be combined.

Further, in the present embodiment, the pair of first sides may be a pair of long sides and the pair of second sides may be a pair of short sides. Even in such a configuration, the same effect as that of the first embodiment can be obtained. For example, the influence of bending vibration on the characteristics can be reduced. Further, by doing so, the thickness sliding vibration, which is the main vibration of the mesa portion 631 sandwiched between the first excitation electrode and the second excitation electrode, is sandwiched between the first excitation electrode and the second excitation electrode. The vibration propagated from the leaked portion is reflected on the side surface of the mesa portion 631, and the vibration reflected by the leak propagated on the side surface of the mesa portion 631 is combined with the thickness slip vibration which is the main vibration to increase the equivalent series resistance value. It can be reduced.

The present invention is not limited to the above embodiments, and may be implemented in various embodiments.

The piezoelectric vibration device having the piezoelectric vibration element is not limited to the piezoelectric vibrator. For example, the piezoelectric vibration device may be an oscillator having an integrated circuit element (IC) that generates an oscillation signal by applying a voltage to the piezoelectric vibration element in addition to the piezoelectric vibration element. Further, for example, the piezoelectric vibration device (piezoelectric vibrator) may have other electronic elements such as a thermistor in addition to the piezoelectric vibration element. Further, the piezoelectric vibration device may be equipped with a constant temperature bath. In the piezoelectric vibration device, the structure of the package for packaging the piezoelectric vibration element may be an appropriate configuration. For example, the package may have an H-shaped cross section having recesses on the upper surface and the lower surface.

The piezoelectric piece is not limited to the crystal piece. For example, the piezoelectric piece may be made of a material obtained by injecting a dopant made of metal or the like into quartz. However, such a piezoelectric piece made of a material in which a dopant is injected into quartz may be regarded as a kind of quartz piece. Further, the piezoelectric piece may be made of, for example, ceramic.

The piezoelectric vibrating element is not limited to the one utilizing the thickness sliding vibration. When utilizing the thickness sliding vibration, the piezoelectric piece (quartz piece) is not limited to the AT cut plate. Regardless of the vibration mode used, it is possible to suppress the change in capacitance while reducing unnecessary vibration by changing the distance between the outer edges of the pair of excitation electrodes. For example, in the case of utilizing the thickness sliding vibration, the crystal piece may be a BT cut plate.

When the crystal piece is an AT cut plate, the relationship between the direction from the first excitation electrode to the second excitation electrode and the positive / negative of the Y'axis may be opposite to that of the embodiment. Further, the relationship between the direction in which the extraction electrode extends and the positive / negative of the X-axis may be opposite to that of the embodiment. In the embodiment, the pads 19a of the extraction electrode 19 are provided on both main surfaces of the crystal piece 15, and any of the pair of main surfaces of the vibrating element 5 can face the bottom surface of the recess 3a. As is clear from this, the relationship between the direction from the first excitation electrode to the second excitation electrode and the mounting direction with the vibrating element may be appropriately set.

The piezoelectric vibrating element is not limited to one in which a pair of pads (drawing electrodes) are provided on one main surface and supported in a cantilever shape. For example, a pair of extraction electrodes may extend from the pair of excitation electrodes in opposite directions to support both ends of the piezoelectric vibrating element. Further, the piezoelectric vibrating element may be supported in an upright state by a spring terminal or the like.

The shape of the first excitation electrode is not limited to a rectangle. For example, the shape of the first excitation electrode is similar to that of the second excitation electrode shown in the first to fifth embodiments, and the second excitation electrode is a rectangle wider than the first excitation electrode having such a shape. Alternatively, the shape may be different from that of the other first excitation electrode. Further, for example, both of the pair of excitation electrodes may be composed of only the outer edge of the curve. Even in these cases, the distance from the outer edge of the first excitation electrode to the outer edge of the second excitation electrode may be different depending on the position along the outer edge of the first excitation electrode, or the distance may be different with respect to a predetermined portion of the outer edge of the first excitation electrode. A part of the outer edge of the second excitation electrode located on the outside can be inclined with respect to the predetermined part.

When a part of the outer edge of the second excitation electrode has a shape that bulges outward with respect to the straight portion of the outer edge of the first excitation electrode, this bulging shape is limited to an arc (a curve whose curvature is constant throughout). Not done. For example, the bulging shape may include a straight line in part, or the curvature may change depending on the position in the length direction. Further, the bulging shape may be asymmetrical with respect to a line passing through a position intermediate between both ends thereof.

The crystal piece is not limited to a flat plate type and a mesa type. For example, the crystal piece may be of a so-called convex type or bevel type. The bevel type may be a kind of flat plate as long as the chamfering amount is small.

1 ... Crystal oscillator (piezoelectric vibration device), 5 ... Crystal vibration element (piezoelectric vibration element), 15 ... Crystal piece (piezoelectric piece), 17A ... First excitation electrode, 17B ... Second excitation electrode.

Claims (4)

Plate-shaped piezoelectric pieces and
The first and second excitation electrodes facing each other across the piezoelectric piece,
Have and
In plane perspective
The second excitation electrode is wider than the first excitation electrode and overlaps the entire first excitation electrode.
The distance from the outer edge of the first excitation electrode to the outer edge of the second excitation electrode differs depending on the position along the outer edge of the first excitation electrode .
The first excitation electrode is rectangular in a plan view and has a rectangular shape.
The second excitation electrode is used in planar fluoroscopy.
A pair of curved portions that bulge outward with respect to a pair of first sides of the rectangle that face each other,
A piezoelectric vibrating element having a pair of linear portions corresponding to a pair of second sides of the rectangle facing each other. The rectangle is a rectangle
The first side of the pair is a pair of short sides of the rectangle.
The piezoelectric vibrating element according to claim 1 , wherein the second side of the pair is the long side of the pair of rectangles. The rectangle is a rectangle
The first side of the pair is the long side of the pair of rectangles.
The piezoelectric vibrating element according to claim 1 , wherein the second side of the pair is the short side of the pair of rectangles. The piezoelectric vibrating element according to any one of claims 1 to 3 and
The package that packages the piezoelectric vibrating element and
Piezoelectric vibration device that has.

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