JP2011191091A - Tuning-fork type vibrator element, vibrator, and sensor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the load at formation of electrodes or wirings which accompanies miniaturization of a vibrator element. <P>SOLUTION: A tuning-fork type vibrator element includes a base portion 10; a vibrating arm 20 that extends in a first direction from the base portion in a prescribed surface, has a prescribed width in a second direction perpendicular to the first direction in the prescribed surface, and has a prescribed thickness, in a third direction perpendicular to the first direction and the second direction and perpendicular to the prescribed surface; and electrode 41a, 41b, disposed at least ON one of a first surface or a second surface, facing the first surface of the vibrating arm to generate an electric field in the first direction, wherein the vibrating arm 20 is made to vibrate in the third direction by stretching or contracting the vibrating arm in the first direction, by the use of electric field in the first direction. If the prescribed width of the vibrating arm 20 in the second direction is w, and the prescribed thickness in the third direction is t, the condition: w>t is satisfied. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a tuning fork type resonator element, a vibrator, a sensor device, and the like.

  A tuning fork type vibrating piece (tuning fork type piezoelectric vibrating piece) is a vibrating member that can be a constituent element of a vibrator, a vibration type sensor element, or the like. For example, at least one base part and at least one base connected (connected) to the base part. And a vibrating arm (vibrating beam) using a piezoelectric material.

  For example, when a voltage (electric field) is applied to a crystal that is a piezoelectric body (piezoelectric material), the crystal is deformed. Quartz develops an inductive reactance characteristic like a coil only in a specific frequency band close to its natural frequency. An electronic component that applies this principle is a crystal resonator. A tuning fork type crystal resonator is manufactured by housing a tuning fork type crystal resonator element in a package and, for example, vacuum-sealing the inside of the package. A crystal resonator is used as a component of an oscillation circuit, for example.

  In addition, a double tuning fork type vibrating piece (a vibrating piece having a structure in which both ends of the vibrating piece are supported by a base), which is a kind of tuning fork type vibrating piece, is a sensor element for detecting a physical quantity (acceleration, pressure, etc.) (Force sensing element). Since quartz has excellent temperature stability and a high Q value, a highly reliable vibration type sensor (sensor device) having high accuracy and high stability is realized by using a crystal resonator.

  An example of a tuning fork vibrator is described in Patent Document 1, for example. In the tuning fork type vibrator described in Patent Document 1, the vibrating piece has a width direction of the vibrating piece (that is, when the vibrating piece extends in the first direction, the first piece is perpendicular to the first direction in the same plane. Vibrates in two directions. Examples of using a comb electrode in a vibrator are described in Patent Document 2 and Patent Document 3, for example. The comb electrodes described in Patent Document 2 and Patent Document 3 are electrodes having a special shape that also serves as a drive electrode and a detection electrode for a gyro sensor, and the polarization direction of a predetermined portion of the piezoelectric single crystal is determined by piezoelectricity. The shape is such that it is easy to reverse (invert) the polarization direction of the entire single crystal.

  In recent years, it has been studied to significantly reduce the size of the vibrator using a MEMS technique or the like.

JP 2001-144581 A JP 2004-151031 A JP 2003-114127 A

  The resonance frequency when the vibrating arm of the vibrating piece, which is a constituent element of the vibrator, vibrates in the direction of the width (lateral width) of the vibrating arm (example described in Patent Document 1) is expressed by the following equation (1). Is done.

  When reducing the arm length l of the vibrating arm by reducing the arm length l of the vibrating arm under the condition that the resonance frequency fn is kept constant, the arm width w of the vibrating arm is obtained from the above equation (1). Need to be small. When the arm width w is reduced along with the miniaturization of the vibrator, the width of each electrode and the interval between the electrodes are reduced. Therefore, for example, when aiming at ultra-miniaturization of the vibrator, it may be difficult to form electrodes, and the yield may be reduced. This is a problem common to the vibrators described in Patent Documents 1 to 3.

  Further, in the case of the specially shaped comb-teeth electrodes described in Patent Document 2 and Patent Document 3, when the arm width w of the vibration piece is further reduced, the vibration arm is more than the electric field in the extending direction of the vibration arm. This causes an inconvenience that the electric field in the width direction becomes dominant, the electric field efficiency decreases, and the CI value (crystal impedance value) increases.

  According to at least one aspect of the present invention, it is possible to reduce a burden in forming electrodes and wirings accompanying the downsizing of the vibrator.

  (1) An aspect of the tuning-fork type resonator element of the invention includes a base and a second direction extending from the base in a first direction within a predetermined plane and perpendicular to the first direction within the predetermined plane. A vibrating arm having a predetermined width in a third direction that is perpendicular to each of the first direction and the second direction and perpendicular to the predetermined surface; An electrode for generating an electric field in the first direction provided on at least one of the first surface and the second surface facing the first surface, and expansion and contraction in the first direction on the vibrating arm by the electric field in the first direction When the vibrating arm is vibrated in the third direction, the predetermined width in the second direction of the vibrating arm is w, and the predetermined thickness in the third direction is t, w> t holds.

  In this aspect, the vibrating arm of the vibrating piece vibrates in a third direction perpendicular to the predetermined plane (out-of-plane direction: thickness direction of the vibrating arm). That is, the vibration of the walk mode is excited on the vibrating arm. In this case, the resonance frequency of the resonator element (vibrator) is expressed by the following equation (2).

As apparent from the above equation (2), when the arm length l of the vibrating arm is reduced on condition that the resonance frequency is kept constant, the thickness t of the vibrating arm may be reduced. Thereby, downsizing of the vibrating arm without difficulty is realized. The thickness t of the vibrating arm can be controlled with high accuracy, for example, by adjusting the thickness of the piezoelectric material plate constituting the vibrating piece.

  On the other hand, the arm width w of the vibrating arm does not need to be reduced in accordance with the scale down of the arm length l. Therefore, the arm width w of the vibrating arm can form, for example, an electrode and wiring with high reliability. It can be maintained to a certain extent. Therefore, in this aspect, the width of the vibrating arm (arm width) w> the thickness t of the vibrating arm is established. On the other hand, since the arm width of the vibrating arm can be set to an appropriate size while reducing the thickness of the vibrating arm, there is no need to worry about defective formation of wiring and electrodes (disconnection, contact, etc.). Therefore, it is possible to reduce the burden when forming electrodes and wirings accompanying the downsizing of the vibrator.

  Further, since the thickness t of the vibrating arm can be controlled with high accuracy, the resonance frequency of the vibrator can also be adjusted with high accuracy. For example, when a piezoelectric material plate is cut out from a piezoelectric single crystal (quartz or the like), the thickness t of the piezoelectric material plate can be adjusted, and the thickness t is also adjusted by polishing after the piezoelectric material plate is cut out. be able to. In any case, the parallelism between the front surface (first surface) and the back surface (second surface) of the piezoelectric material plate is high, and the thickness t itself can be controlled with high accuracy.

  (2) In another aspect of the tuning-fork type resonator element of the invention, the vibrating arm is formed of a piezoelectric material plate having a predetermined crystal plane, and the predetermined plane is a plane including the predetermined crystal plane; A strain in the first direction is generated by the electric field in the first direction of the piezoelectric material plate, and vibration in the third direction is generated.

  In this aspect, the resonator element vibrates out of plane in a direction (third direction) perpendicular to a plane including a predetermined crystal plane (for example, Z plane) of the piezoelectric material plate. The out-of-plane vibration causes a piezoelectric constant (for example, a strain Sx in the X-axis direction with respect to an electric field in the X-axis direction of crystal) that causes distortion in the first direction (extension direction of the vibrator) included in the piezoelectric material. It can be excited using the piezoelectric constant d11).

  (3) In another aspect of the tuning-fork type vibrating piece of the present invention, the electrode is a comb electrode provided on at least one of the first surface and the second surface of the vibrating arm.

  In this aspect, the comb-tooth electrode (IDT (interdigital transducer) electrode) can generate an electric field along the extending direction (first direction) of the vibrating arm for exciting the vibrating arm in the out-of-plane direction. .

  (4) In another aspect of the tuning-fork type resonator element according to the invention, the comb-tooth electrode includes a first facing portion including a pair of electrodes disposed to face each other at a predetermined distance, and the first facing portion. And a second opposing portion composed of a pair of electrodes arranged to face each other at a predetermined distance, and the first opposing portion and the second opposing portion are: It is arranged along the first direction which is the extending direction of the vibrating arm, and the predetermined distance is L1, and the distance between the first facing portion and the second facing portion is L2. Sometimes L1 <L2 holds.

  In this aspect, the comb-tooth electrodes are separated from each other by a predetermined distance, and are opposed to each other by a first opposed portion, which is adjacent to the first opposed portion, and spaced apart from each other by a predetermined distance. And a second facing portion composed of a pair of electrodes disposed to face each other. In each of the first facing portion and the second facing portion, an electric field (effective electric field) is generated between a pair of electrodes facing each other, and this electric field (effective electric field) is applied to the vibrating arm. On the other hand, an electric field (invalid electric field) is also generated between the electrode on the second facing portion side of the first facing portion and the electrode on the first facing portion side of the second facing portion. If the direction of the effective electric field generated in each of the first opposing portion and the second opposing portion is opposite to the reactive electric field generated between the first opposing portion and the second opposing portion, a part of the effective electric field is ineffective There is a disadvantage that it is canceled out by the electric field.

  For this reason, in this aspect, rather than the distance (L1) between the electrodes in each of the first facing portion and the second facing portion, the distance between the first facing portion and the second facing portion (L2: specifically, , The distance between the electrode on the second facing portion side of the first facing portion and the electrode on the first facing portion side of the second facing portion is set large. As a result, it is possible to reduce adverse effects caused by the reactive electric field generated between the first opposing portion and the second opposing portion (that is, a part of the effective electric field is canceled out by the reactive electric field).

  (5) In another aspect of the tuning-fork type resonator element of the invention, the comb electrode is provided adjacent to the second facing portion and is disposed to face each other at a predetermined distance. A third opposing portion comprising the electrodes, wherein the distance from the base portion increases in the order of the first opposing portion, the second opposing portion, and the third opposing portion; and When the distance between the facing portion and the third facing portion is L3, L2 <L3 is established.

  In order to generate out-of-plane vibration in the vibrating arm, it is necessary to cause stress (distortion) of contraction (compression) and extension (tensile) on the main surface (for example, at least one of the front surface and the back surface) of the vibrating arm. Since the vibrating arm vibrates in the out-of-plane direction with the base that is the fixed end as a reference, the strain that is most effective for bending the vibrating arm is a strain at a location close to the base. Distortion at a location far from the base (near the tip) has little effect on the bending of the vibrating arm.

  Based on this consideration, in this aspect, the interval between each of the three opposing portions included in the comb electrode is changed according to the distance from the base. That is, the interval (L3) between the second opposing portion and the third opposing portion is set larger than the interval (L2) between the first opposing portion and the second opposing portion. In this way, the number of opposing portions arranged along the extending direction of the vibrating arm can be reduced as compared with the case where the opposing portions are arranged at equal intervals. This means that the total amount of electric field generated in the vibrating arm is reduced, so that the effect of reducing power consumption can be obtained. On the other hand, even if the electric field at a location far from the base is reduced, the degree to which the electric field contributes to the bending of the vibrating arm is small. Therefore, the vibrating arm can generate drive vibration with a necessary amplitude.

  (6) In another aspect of the tuning-fork type resonator element of the invention, a convex portion is provided on at least one of the first surface and the second surface of the vibrating arm, and the convex portion is arranged in the first direction. A pair of electrodes constituting the comb electrode are provided so as to have a predetermined thickness and sandwich the convex portion.

  According to this structure, since the useless electric field is reduced, the strength of the electric field generated between the opposing electrodes can be increased. Therefore, the out-of-plane vibration can be excited more efficiently. Further, the invalid electric field generated between the opposing portions is weakened because the dielectric constant of air is smaller than the dielectric constant of the vibrating arm material (quartz or quartz). Therefore, canceling out the effective electric field by the reactive electric field is effectively reduced. This point also contributes to efficient excitation of out-of-plane vibration.

  (7) In another aspect of the tuning-fork type vibrating piece of the present invention, n (n is a natural number of 2 or more) vibrating arms extending in the first direction from the base are provided as the vibrating arms.

  By providing a plurality of vibrating arms and causing each vibrating arm to vibrate so as to achieve a dynamic balance, for example, the out-of-plane vibration of the vibrating arm can be further stabilized.

  (8) In another aspect of the tuning fork type vibrating piece according to the present invention, m (m is an odd number of 3 or more) vibrating arms are provided as the n vibrating arms, and each of the m vibrating arms is provided. The first vibrating arm to the m-th vibrating arm are arranged in the second direction in ascending order of the value of m, and the m vibrating arms include three vibration arms. The first group of vibrating arms is divided into arm groups, and the first group of vibrating arms to the (m / 3) vibrating arm is the first group of vibrating arms, and the {(2m / 3)} vibration from the {(m / 3) +1} vibrating arm. Up to the arm is the second group of vibrating arms, the {(2m / 3) +1} vibrating arm to the mth vibrating arm is the third group of vibrating arms, and the third direction is a positive third direction. And a negative third direction opposite to the positive third direction, wherein each of the first group of vibrating arms and the third group of vibrating arms is displaced in the positive third direction. When you are The second group of vibrating arms is displaced in the negative third direction, and each of the first group of vibrating arms and the third group of vibrating arms is displaced in the negative third direction. The vibrating arms of the second group are displaced in the positive third direction.

  In this aspect, an odd number of vibrating arms that vibrate in the walk mode are provided (that is, m (m is an odd number of 3 or more) are provided). In order to stably maintain the vibration of the walk mode, it is preferable to suppress the walk mode vibration of the vibrating arm from leaking to the base. The base portion of the tuning fork type vibrating piece is fixed to, for example, a base member (a member constituting a part of the package) with an adhesive, for example. If the walk mode in which the vibrating arm vibrates in the thickness direction of the vibrating arm is employed, the vibration may leak from the vibrating arm to the base, disturb the vibration, and cause inconvenience such as peeling of the adhesive. In order to prevent such a situation from occurring, an odd number (odd group) of vibrating arms are arranged in parallel, and the vibrating arms at both ends (vibrating arm groups at both ends) of each vibrating arm are in phase. It is preferable that the center vibrating arm (center vibrating arm group) is vibrated in reverse phase. When such a configuration is adopted, the vibration of the vibrating arm of the tuning fork-type vibrating piece is mechanically balanced in the width direction of the vibrating arm (second direction: for example, the left-right direction) in a plan view, and is vibrated. A mechanical balance in the thickness direction of the arm (the third direction that is the vibration direction: e.g., the vertical direction) is established, so that the base supporting each vibrating arm is not overburdened and vibration leakage occurs. It is suppressed.

  That is, the case where the 1st group, the 2nd group, and the 3rd group of vibrating arms arranged in order along the 2nd direction are provided is assumed. When the second region of the vibrating arms of the first group and the third group is displaced in the positive third direction, the second region of the vibrating arm of the center second group is displaced in the negative third direction. In this case, since the first group and the third group, which are groups at both ends, are displaced in phase, a balance in the second direction (left-right direction) can be obtained in plan view. In addition, since the first group, the third group, and the second group are displaced in opposite phases, stress due to displacement in the third direction (vibration direction) of each group (stress applied to the base portion that supports the vibrating arm of each group) ) Is canceled out, and thus a balance in the vibration direction (vertical direction) is also ensured.

  (9) One aspect of the vibrator according to the present invention includes any of the tuning fork type vibrating pieces described above and a housing that houses the tuning fork type vibrating piece.

  As a result, a small-sized vibrator capable of highly accurate oscillation can be realized.

  (10) In another aspect of the tuning fork type vibrating piece of the present invention, the tuning fork type vibrating piece includes a first base and a second base as the base, and one end of the vibrating arm is the first. It is a double tuning fork type resonator element that is connected to a base and the other end of the vibrating arm is connected to the second base.

  The vibration piece of this aspect is a double tuning fork type vibration piece whose both ends are supported by the base. This double tuning fork type resonator element can be used as a component of an acceleration sensor or a pressure sensor, for example.

  (11) In another aspect of the tuning-fork type resonator element according to the invention, the resonating arm includes a first area, a second area, and a third area, which are sequentially arranged in the first direction, and the first area and the second area. A first knot region provided between the second region and a second knot region provided between the second region and the third region, and the first surface or the second surface of the vibrating arm. When contraction stress is generated in the first region and the third region in the above, extension stress is generated in the second region of the first surface or the second surface of the vibrating arm, and the first of the vibrating arm is generated. When tensile stress is generated in the first region and the third region on the surface or the second surface, contraction stress is generated in the second region on the first surface or the second surface of the vibrating arm.

  In this aspect, in order to vibrate the vibrating arm in the thickness direction (third direction) in a well-balanced manner, one vibrating arm is divided into a first area, a second area, and a third area. A first node region is provided between the two regions, and a second node region is provided between the second region and the third region. Each of the first node region and the second node region includes a vibration node. Specifically, the vibration node is a point where the secondary differential coefficient becomes 0 when the displacement of the vibrating arm is obtained as the secondary differential coefficient. When the vibrating arm contracts, for example, in the first region and the third region of the first surface, the second region expands. Similarly, when the first arm and the third region expand. Shrinkage occurs in the second region. Thereby, a stable resonance vibration can be realized.

  (12) In another aspect of the tuning-fork type resonator element of the invention, n vibrating arms (n is a natural number of 2 or more) are provided as the vibrating arms.

  By providing a plurality of vibrating arms and vibrating each vibrating arm so that, for example, a mechanical balance is achieved, it is possible to excite more stable out-of-plane vibration to the vibrating arms in the double tuning fork type vibrating piece. .

  (13) In another aspect of the tuning fork type vibrating piece of the present invention, m (m is an odd number of 3 or more) vibrating arms are provided as the n vibrating arms, and each of the m vibrating arms is provided. The first vibrating arm to the m-th vibrating arm are arranged in the second direction in ascending order of the value of m, and the m vibrating arms include three vibration arms. The first group of vibrating arms is divided into arm groups, and the first group of vibrating arms to the (m / 3) vibrating arm is the first group of vibrating arms, and the {(2m / 3)} vibration from the {(m / 3) +1} vibrating arm. Up to the arm is the second group of vibrating arms, the {(2m / 3) +1} vibrating arm to the mth vibrating arm is the third group of vibrating arms, and the third direction is a positive third direction. And a negative third direction opposite to the positive third direction, and each of the first surface or the second in each of the first group of vibrating arms and the third group of vibrating arms surface When contraction stress is generated in the first region and the third region and extension stress is generated in the second region, the first surface or the second surface of the second group of vibrating arms is the first surface. Tensile stress is generated in the first region and the third region, and contraction stress is generated in the second region, and the first surface or the third group of vibrating arms in each of the first group and the third group of vibrating arms When the extension stress is generated in the first region and the third region of the second surface and the contraction stress is generated in the second region, the first surface or the second surface of the second group of vibrating arms. Shrinkage stress is generated in the first region and the third region of the surface, and tensile stress is generated in the second region.

  In this aspect, an odd number of vibrating arms is provided in the double tuning fork type vibrating piece. Similarly to the above aspect (8), the vibration of the vibrating arm of the double tuning fork type vibrating piece in this aspect is balanced mechanically in the width direction (second direction: for example, left-right direction) of the vibrating arm in plan view. In addition, a mechanical balance is obtained in the thickness direction of the vibrating arm (the third direction that is the vibrating direction: for example, the vertical direction). Therefore, an excessive load is not applied to the base portion that supports each vibrating arm, and vibration leakage is suppressed.

  (14) According to one aspect of the sensor device of the present invention, an elastic part that is displaced according to a change in a physical quantity of a measurement target, or a mass part connected to the elastic part, and at least one base are the elastic part or The tuning-fork type vibration according to any one of (10) to (13), wherein the vibration arm is connected to the mass part, and the elastic arm or the mass part is caused to expand and contract in the extending direction of the vibrating arm. And a container for housing the tuning-fork type vibration piece.

  As a result, a small and highly accurate sensor (such as a pressure sensor or an acceleration sensor) using a small vibrator capable of highly accurate oscillation can be realized. For example, a pressure sensor can be formed by fixing a double tuning fork type vibrating piece to a diaphragm which is an elastic part. Further, the acceleration sensor can be formed by fixing one end of the double tuning fork type vibrating piece to the mass part (weight part).

FIG. 1A to FIG. 1D are diagrams for explaining an example of the configuration and operation of a tuning fork type resonator element according to the first embodiment. 2 (A), 2 (B), and 2 (C) are diagrams showing examples of the configuration of comb electrodes. Diagram for explaining excitation of out-of-plane vibration in vibrating arm The figure which shows the other structural example of a comb-tooth electrode The figure which shows the other example of a comb-tooth electrode 6A and 6B are diagrams showing an example in which an odd number (three in this case) of vibrating arms are provided. A figure showing an example of a manufacturing process of a vibrator using a tuning fork type resonator element FIGS. 8A and 8B are diagrams for explaining an example of out-of-plane vibration in a double tuning fork type vibrating piece and electrode arrangement in the double tuning fork piece. 9A to 9C are diagrams showing a configuration example of a double tuning fork type resonator element. 10A and 10B are diagrams showing examples of arrangement of electrodes and wirings in a double tuning fork type vibrating piece having three vibrating arms. FIGS. 11A and 11B are diagrams illustrating an example of the structure of an acceleration sensor element and an acceleration sensor device using a double tuning fork type resonator element.

  Hereinafter, preferred embodiments of the present invention will be described in detail. The present embodiment described below does not unduly limit the contents of the present invention described in the claims, and all the configurations described in the present embodiment are indispensable as means for solving the present invention. Not always.

(First embodiment)
(Example of structure and operation of a resonator element using out-of-plane vibration)
FIG. 1A to FIG. 1D are diagrams for explaining an example of the configuration and operation of a tuning fork type resonator element according to the first embodiment. As shown in FIG. 1A, a tuning fork type vibrating piece 100 includes a base 10 and a vibrating arm 20 extending from the base in a first direction (X-axis direction) within a predetermined plane (in the XY plane). Have.

  The tuning fork type vibrating piece 100 is formed of, for example, a piezoelectric material plate having a predetermined surface. Specifically, for example, a quartz crystal Z plate (including a substantially Z plate) is used. The predetermined plane (XY plane) is a plane including a predetermined crystal plane (for example, a Z plane of quartz) of a piezoelectric material plate, for example. Hereinafter, a case where a quartz Z plate is used will be described as an example.

  The vibrating arm 20 has a predetermined width w in a second direction (Y-axis direction) perpendicular to the first direction (X-axis direction) within a predetermined plane, and the first direction (X-axis direction) and the second direction. It has a predetermined thickness t in a third direction (Z-axis direction) perpendicular to each of the (Y-axis direction) and perpendicular to the predetermined surface. A relationship of w> t is established with respect to the predetermined width w in the second direction and the predetermined thickness t in the third direction of the vibrating arm 20.

  The vibrating arm 20 vibrates in the third direction (Z-axis direction: specifically, the + Z-axis direction and the −Z-axis direction). That is, the vibrating arm 20 vibrates out of plane in a direction perpendicular to the predetermined plane. This out-of-plane vibration is excited by using a piezoelectric constant d11 that causes a strain Sx in the X-axis direction with respect to the electric field in the first direction (X-axis direction) of the quartz crystal as the piezoelectric material.

  FIG. 1B is a diagram showing the relationship between the piezoelectric constant, electric field, and strain of the quartz plate. As shown in FIG. 1B, with respect to the electric field Ex in the first direction (X-axis direction), the piezoelectric constant d11 (+2.308850823) that causes the strain Sx in the first direction (X-axis direction) and the second direction And a piezoelectric constant d12 (−2.30885023) that generates a strain Sy in the (Y-axis direction). Since the sign of the piezoelectric constant d11 corresponding to the strain Sx is +, an extension stress (tensile stress) is generated when the electric field + Ex is generated in the positive first direction (+ X-axis direction). Since the value of the piezoelectric constant d11 corresponding to the strain Sx is sufficiently large, a desired out-of-plane vibration can be excited in the vibrating arm 20 using this piezoelectric constant d11.

  FIG. 1C shows the shape of the tuning fork-type vibrating piece in plan view (the shape of the vibrating arm viewed from the positive third direction). FIG. 1D is a cross-sectional view of the tuning-fork type vibration piece taken along the line AA in FIG.

  In order to excite out-of-plane vibration in the vibrating arm 20, the electric field Ex in the first direction (X-axis direction) is applied to a pair of main surfaces (a first surface as a front surface and a second surface as a back surface) of the vibrating arm 20. Therefore, it is necessary to alternately generate an extension stress (tensile stress) and a contraction stress (compression stress) in the vibrating arm 20. In the present embodiment, a comb electrode (IDT (interdigital transducer) electrode) is used to generate the electric field Ex in the first direction. Comb electrodes are provided on at least one of a pair of opposing main surfaces (a first surface as a front surface and a second surface as a back surface) of the vibrating arm 20.

  In the example of FIG. 1C and FIG. 1D, comb electrodes are provided on each of the first surface (front surface) and the second surface (back surface) of the vibrating arm 20. As shown in FIG. 1C, the comb electrode provided on the first surface (front surface) of the vibrating arm 20 includes a first electrode 41a and a second electrode 41b. The first electrode 41a and the second electrode 41b have opposing electrode portions (intersecting finger electrode portions) that face each other at a predetermined interval.

  Further, as shown in FIG. 1D, the comb electrode provided on the second surface (back surface) of the vibrating arm 20 includes a first electrode 41c and a second electrode 41d. Although not shown in FIG. 1D, the first electrode 41c and the second electrode 41d also have opposing electrode portions (intersecting electrode portions) that face each other at a predetermined interval.

  The first electrode 41a in the comb electrode on the front surface and the first electrode 41c in the comb electrode on the back surface are connected via a through hole (not shown) provided in the base 10, for example. Connected to the point is a wiring drawn from a first external connection terminal (not shown) such as a bonding pad provided on the base 10. Similarly, the second electrode 41b in the comb electrode on the front surface and the first electrode 41d in the comb electrode on the back surface are also electrically connected via, for example, a through hole provided in the base 10, and the common connection thereof The point is connected to a wiring drawn from a second external connection terminal such as a bonding pad provided on the base 10. A predetermined voltage is supplied to each of the first external connection terminal and the second external connection terminal. As a result, an electric field (Ex1, Ex2) for generating out-of-plane vibration of the vibrating arm 20 is generated between the first electrode and the second electrode.

  1D, the electric field Ex1 generated by the comb-tooth electrodes (41a, 41b) provided on the first surface (front surface) of the vibrating arm 20 and the second surface (back surface) of the vibrating arm 20 are provided. The direction of the electric field Ex2 generated by the comb-tooth electrodes (41c, 41d) provided in () is opposite. Therefore, in the example of FIG. 1D, tensile stress is generated on the first surface (front surface), and compressive stress is generated on the second surface (back surface). If the directions of the electric field Ex1 and the electric field Ex2 are reversed, compressive stress is generated on the first surface (front surface), and tensile stress is generated on the second surface (back surface). Thereby, the vibrating arm 20 can be vibrated in the third direction (Z direction).

  Thus, in this embodiment, the vibrating arm vibrates in the third direction (out-of-plane direction: thickness direction of the vibrating arm) perpendicular to the predetermined plane. That is, the vibration of the walk mode is excited on the vibrating arm 20. In this case, the resonance frequency of the resonator element (vibrator) is expressed by the following equation (2).

  As apparent from the above equation (3), when the arm length l of the vibrating arm 20 is reduced on condition that the resonance frequency fn is kept constant, the thickness t of the vibrating arm 20 may be reduced. Thereby, downsizing of the vibrating arm without difficulty is realized. That is, the main design parameter for downsizing the resonator element (vibrator) while keeping the resonance frequency of the resonator element (vibrator) constant by vibrating the vibrating arm 20 out of plane is that the arm width w is the arm design parameter. The thickness t is changed. Here, the thickness t of the vibrating arm can be controlled with high accuracy, for example, by adjusting the thickness of the piezoelectric material plate constituting the vibrating piece.

  On the other hand, the arm width w of the vibrating arm does not need to be reduced in accordance with the scale down of the arm length l. Therefore, the arm width w of the vibrating arm can form, for example, an electrode and wiring with high reliability. It can be maintained to a certain extent. Therefore, in the present embodiment, the width of the vibrating arm 20 (arm width) w> the thickness t of the vibrating arm is satisfied.

  Since the arm width of the vibrating arm 20 can be set to an appropriate size, there is no need to worry about poor wiring or electrode formation (disconnection, contact, etc.), and the electrodes and The burden when forming the wiring can be reduced.

  Further, since the thickness t of the vibrating arm can be controlled with high accuracy, the resonance frequency of the vibrator can also be adjusted with high accuracy. For example, when a piezoelectric material plate is cut out from a piezoelectric single crystal (quartz or the like), the thickness t of the piezoelectric material plate can be adjusted, and the thickness t is also adjusted by polishing after the piezoelectric material plate is cut out. be able to. In any case, the parallelism between the front surface (first surface) and the back surface (second surface) of the piezoelectric material plate is high, and the thickness t itself can be controlled with high accuracy. This contributes to realizing a highly accurate and ultra-small vibrator.

(Combination electrode configuration example)
FIG. 2A, FIG. 2B, and FIG. 2C are diagrams showing examples of the configuration of the comb electrode. 2A is a plan view, and FIG. 2B is a cross-sectional view taken along the line AA in FIG. 2A. As shown in FIGS. 2A and 2B, comb electrodes (41 a and 41 b) are provided on the first surface (front surface) of the vibrating arm 20, and the second surface (back surface) of the vibrating arm 20 is provided. Comb electrodes (41c and 41d) are provided. Since the shape of the comb electrode is not a special shape, it is easy to form. Further, there is an advantage that even when the size is reduced, there is no inconvenience that the reactive electric field becomes dominant.

  Here, reference is made to FIG. The comb electrode provided on the first surface (surface) is a first facing portion 42 (1) composed of a pair of electrodes (a first electrode 41a and a second electrode 41b) disposed to face each other with a predetermined distance L1. ) And a second opposing portion 42 (2) composed of a pair of electrodes (41a, 41b) provided adjacent to the first opposing portion 42 (1) and opposed to each other at a predetermined distance L1. ) And a second facing portion 42 (2), and a third facing portion 42 (3) composed of a pair of electrodes (41a, 41b) disposed opposite to each other at a predetermined distance L1. ) And.

  A first counter part (also referred to as a first counter electrode part or a first cross finger electrode) 41 (1) and a second counter part (also referred to as a second counter electrode part or a second cross finger electrode) 41 ( 2) and a third counter portion (also referred to as a third counter electrode portion or a third cross finger electrode) 41 (3) are each in a first direction (X-axis direction) that is the extending direction of the vibrating arm 20 Are arranged along. Further, the distance between the first facing portion 42 (1) and the second facing portion 42 (2) (or the distance between the second facing portion 42 (2) and the third facing portion 42 (3)). When L2 is L2, L1 <L2 is established.

  Similarly, the comb-teeth electrode (having the pair of electrodes 41c and 41d) provided on the second surface (back surface) also includes the first opposing portion 42 (1) ′, the second opposing portion 42 (2) ′, 3 opposing portions 42 (3) ′. L1 <L2 is also established for the comb electrode provided on the second surface (back surface).

  The reason why L1 <L2 is set is as follows. In the following description, attention is focused on the first facing portion 42 (1) and the second facing portion 42 (2). In each of the first facing portion 42 (1) and the second facing portion 42 (2), an electric field (effective electric field) Ex (1) is generated between the pair of electrodes (41a, 41b) facing each other. ) Ex (1) is applied to the vibrating arm 20 and compressive or expansion (tensile) stresses are generated in the vibrating arm 20.

  On the other hand, an electric field (reactive electric field) Ex () also exists between the electrode 41b on the second opposing portion side in the first opposing portion 42 (1) and the electrode 41a on the first opposing portion side in the second opposing portion 42 (2). 2) occurs. The direction Ex (1) of the effective electric field generated in each of the first opposing portion 42 (1) and the second opposing portion 42 (2), and the first opposing portion 42 (1) and the second opposing portion 42 (2) When the direction of the reactive electric field Ex (2) generated between them is reverse, there arises a disadvantage that a part of the effective electric field Ex (1) is canceled out by the reactive electric field Ex (2).

  For this reason, in the example shown in FIG. 2B, the first facing portion 42 (1) is more than the distance L1 between the electrodes in each of the first facing portion 42 (1) and the second facing portion 42 (2). (L2: specifically, the electrode 41b on the second opposing portion side of the first opposing portion and the electrode 41a on the first opposing portion side of the second opposing portion) between the second opposing portion 42 (2) and the second opposing portion 42 (2) (Distance between) is set large. As a result, an adverse effect due to the reactive electric field Ex (2) generated between the first opposing portion 42 (1) and the second opposing portion 42 (2) (that is, a part of the effective electric field Ex (1) becomes the reactive electric field Ex ( 2) can be reduced.

  In addition, arrangement | positioning of the comb-tooth electrode shown by FIG. 2 (B) is an example, and is not limited to this. Here, reference is made to FIG. FIG. 2C shows another example of the arrangement of the comb electrodes.

  In the example of FIG. 2C, one electrode 41 b (black electrode) of the pair of comb electrodes provided on the first surface (A surface) of the vibrating arm 20 and the second surface of the vibrating arm 20. One electrode 41d (black electrode: electrode having the same potential as the electrode 41b) of the pair of comb-tooth electrodes provided on the (B surface) is provided so as to face.

  For example, the potential polarity of the electrode 41b and the electrode 41d (black electrode) is +, and the potential polarity of the electrode 41a and the electrode 41c (shaded electrode) is −. The arrangement of the polarities of the comb electrodes provided on the first surface (A surface) is +, −, +, −, + along the direction away from the base (left end in the figure) starting from the electrode 41b. . In addition, the arrangement of the polarities of the comb electrodes provided on the second surface (B surface) is +, −, − along the direction away from the base (the left end in the figure) starting from the electrode 41d facing the electrode 41b. +,-, +,-. Thus, considering the electrodes facing each other as the starting point, the polarity sequence of the comb-shaped electrodes on the first surface (A surface) matches the polarity sequence of the comb-shaped electrodes on the second surface (B surface). Will be.

  Such an electrode arrangement makes it difficult to generate a useless vertical electric field between the first surface (A surface) and the second surface (B surface). Therefore, unnecessary distortion in the vibrating arm 20 is suppressed. In addition, since a useless electric field is reduced, power consumption can be suppressed.

  FIG. 3 is a diagram for explaining excitation of out-of-plane vibration in the vibrating arm. A plan view of the vibrating arm 20 is shown on the upper side of FIG. 3, a sectional view taken along the line AA of the vibrating arm is shown in the middle stage, and a state of the vibrating arm vibrating in the out-of-plane direction is shown on the lower side. It is shown. As shown in the drawing, strain (stress) is generated on the first surface (A surface) and the second surface (B surface) of the vibrating arm by the electric field Ex in the first direction (X-axis direction) by the comb-tooth electrode. When contraction stress is generated on the first surface (A) and extension (tensile) stress is generated on the second surface, the vibrating arm 20 bends in the positive third direction (+ Z direction). On the other hand, when an extension (tensile) stress is generated on the first surface (A) and a contraction stress is generated on the second surface, the vibrating arm 20 bends in the negative third direction (−Z direction). . Bending in the positive third direction (+ Z direction) and bending in the negative third direction (−Z direction) occur alternately. Therefore, drive vibration (out-of-plane vibration or walk mode vibration) in the third direction (Z direction perpendicular to the XY plane) is steadily generated.

  FIG. 4 is a diagram illustrating another configuration example of the comb electrode. In the example of FIG. 2B described above, the distance between the opposing portions in the comb electrode is equal. However, in the example of FIG. 4, the distance between the opposing portions is changed from the base 10. Different depending on the distance.

  In FIG. 4, each of the first facing portion 42 (1), the second facing portion 42 (2), and the third facing portion (42 (3) of the comb-tooth electrode is far from the base 10 in the order described. The distance between the first facing portion 42 (1) and the second facing portion 42 (2) is L2, and the distance between the second facing portion 42 (2) and the third facing portion 42 (3). When L3 is L3, L2 <L3 is satisfied for the following reason.

  In order to generate drive vibration (out-of-plane vibration) in the vibrating arm 20, it is necessary to cause a compression or expansion (tensile) distortion (stress) on the main surface (for example, at least one of the front surface and the back surface) of the vibrating arm 20. There is. Since the vibrating arm 20 vibrates in the out-of-plane direction with the base 10 that is a fixed end as a reference, the distortion that is most effective for bending the vibrating arm is distortion at a location close to the base 10. Distortion at a location far from the base (near the tip) has little effect on the bending of the vibrating arm.

  Based on this consideration, in this embodiment, the interval between each of the three facing portions included in the comb electrode is changed according to the distance from the base. That is, the distance L3 between the second facing portion 42 (2) and the third facing portion 42 (3) is set to be larger than the distance L2 between the first facing portion 42 (1) and the second facing portion 2 (2). Set larger.

  In the example of FIG. 4, when the distance from the first point N1 to the second point N2 is L4, the distance L5 from the second point N2 to the third point N3 is set to be 2 · L4. . In this way, the number of facing portions arranged along the extending direction of the vibrating arm 20 can be reduced as compared with the case where the facing portions are arranged at equal intervals (particularly, the vibrating arm is long). In some cases, the effect of reducing the number of opposing parts becomes obvious). This means that the total amount of the electric field generated in the vibrating arm 20 is reduced, so that the effect of reducing power consumption can be obtained. On the other hand, even if the electric field at a location far from the base 10 is reduced, the degree to which the electric field contributes to the bending of the vibrating arm is small, so that the vibrating arm 20 can generate drive vibration with a necessary amplitude.

  FIG. 5 is a diagram showing another example of a comb electrode. A plan view of the vibrating arm 20 is shown on the upper side of FIG. 5, and a sectional view taken along the line AA of the vibrating arm 20 is shown on the lower side.

  As shown in the lower cross-sectional view of FIG. 5, convex portions 60 a to 60 c are provided on the first surface (front surface) of the vibrating arm 20. A pair of opposing electrodes 41a and 41b constituting the comb electrode are formed so as to sandwich each of the convex portions 60a to 60c. Similarly, convex portions 60 a ′ to 60 c ′ are provided on the second surface (back surface) of the vibrating arm 20. A pair of opposing electrodes 41c and 41d constituting the comb electrode are formed so as to sandwich each of the convex portions 60a 'to 60c'.

  According to this structure, since the useless electric field is reduced, the intensity of the electric field Ex generated between the opposing electrodes (41a and 41b, 41c and 41d) can be increased. Therefore, drive vibration can be excited more efficiently. In addition, an invalid electric field (indicated by a dotted line in the figure) generated between the opposing portions is such that the dielectric constant of air (such as near vacuum in a reduced pressure package) is a dielectric such as a vibrating arm material (crystal or quartz). It is weakened because it is smaller than the rate. Therefore, canceling out the effective electric field by the reactive electric field is effectively reduced. This point also contributes to efficient excitation of out-of-plane vibration. This contributes to lower power consumption of the vibrator.

(Second Embodiment)
In the present embodiment, a plurality of vibrating arms (that is, n (n is a natural number of 2 or more)) extending from the base portion 10 in the first direction (X-axis direction) are provided. By providing a plurality of vibrating arms and causing each vibrating arm to vibrate so as to achieve a dynamic balance, for example, the out-of-plane vibration of the vibrating arm can be further stabilized.

  FIGS. 6A and 6B are diagrams illustrating an example in which an odd number (three in this case) of vibrating arms are provided. FIG. 6A is a plan view, and FIG. 6B is a perspective view.

  As shown in FIG. 6A, three vibrating arms (first vibrating arm 20a, second vibrating arm 20b, and third vibrating arm 20c) extending from the base 10 in the first direction (X-axis direction). Further, an electrode for forming an electric field in the first direction (preferably both) on the first surface (front surface) and the second surface (back surface) of each of the vibrating arms 20a to 20c (preferably both) For example, a comb electrode) is formed.

  The comb electrode formed on the first surface (front surface) of the first vibrating arm 20a includes a first electrode 41a (1) and a second electrode 41b (1). The comb electrode formed on the first surface (front surface) of the second vibrating arm 20b includes a first electrode 41a (2) and a second electrode 41b (2). The comb electrode formed on the first surface (front surface) of the third vibrating arm 20c includes a first electrode 41a (3) and a second electrode 41b (3). What should be noted here is that the electrode arrangement of the second vibrating arm 20b is opposite to the electrode arrangement of the other vibrating arms (the first vibrating arm 20a and the third vibrating arm 20c). That is, the direction of the electric field generated at the portion of the second vibrating arm 20b facing the comb electrode is the direction of the electric field generated at the portion of the other vibrating arm (the first vibrating arm 20a and the third vibrating arm 20c) facing the comb electrode. The opposite is true.

  Therefore, as shown in FIG. 6B, the first vibrating arm 20a and the third vibrating arm 20c have the same displacement direction in the out-of-plane vibration (in-phase vibration), and the second vibrating arm 20b is out of plane. The direction of displacement in vibration is reversed (reverse phase vibration).

  When such a configuration is adopted, the vibration of each of the first vibrating arm 20a to the third vibrating arm 20c of the tuning fork type vibrating piece has a mechanical balance in the width direction (second direction) of the vibrating arm in plan view. And a mechanical balance in the thickness direction of the vibrating arms (the third direction that is the vibrating direction) is taken, and therefore, an excessive burden is not applied to the base 10 that supports each vibrating arm, Vibration leakage via the base is suppressed.

  That is, in the example of providing an odd number of vibrating arms that vibrate in the walk mode as in the present embodiment, in order to stably maintain the vibration in the walk mode, the walk mode vibrations of the respective vibrating arms (20a to 20c) are provided. Is preferably prevented from leaking to the support that supports the base 10 via the base 10. The base 10 of the tuning-fork type vibrating piece is fixed to, for example, a base member (a member constituting a part of the package) with an adhesive, for example. When the walk mode in which each vibrating arm (20a to 20c) vibrates in the thickness t direction of each vibrating arm (20a to 20c) is adopted, the vibration is generated from each vibrating arm (20a to 20c) to the base 10. It is possible that there will be inconveniences such as leakage of vibration and disturbance of the vibration and peeling of the adhesive. In order to prevent such a situation from occurring, an odd number of vibrating arms are arranged in parallel, and the vibrating arms at both ends (vibrating arms at both ends) of each vibrating arm are vibrated in the same phase. It is preferable to vibrate the vibrating arm (center vibrating arm) in reverse phase.

  In the above description, the case where the number of vibrating arms is three has been described. However, in a broad sense, the number of vibrating arms can be six, nine,. That is, in a broad sense, “m vibrating arms (m is an odd number of 3 or more) are provided as n vibrating arms, and each of the n vibrating arms is defined as a first vibrating arm to an mth vibrating arm. The first to m-th vibrating arms are arranged in the second direction (Y-axis direction) in ascending order of the value of m, and the m vibrating arms are divided into three vibrating arm groups. From the vibrating arm to the (m / 3) vibrating arm is the first group of vibrating arms, and from the {(m / 3) +1} vibrating arm to the {(2m / 3)} vibrating arm is the second group of vibrations. The third group of vibrating arms is from the {(2m / 3) +1} vibrating arm to the mth vibrating arm, and the third direction is a positive third direction (+ Z-axis direction) and a positive Each of the first group of vibrating arms and the third group of vibrating arms is displaced in the positive third direction, including a negative third direction (-Z-axis direction) opposite to the third direction. When the second group of vibrating arms is When the first group of vibrating arms and the third group of vibrating arms are displaced in the negative third direction when the first group of vibrating arms is displaced in the negative third direction, the second group of vibrating arms is positive third It can be expressed as “displaced in the direction”.

  When odd-numbered vibrating arms are arranged in parallel, considering the mechanical balance of the vibrating arms, the vibrating arm groups at both ends of each vibrating arm are vibrated in the same phase, and the central vibrating arm group is reversed. It is preferable to vibrate in phase. When such a configuration is adopted, the vibration of the vibrating arms of the tuning fork-type vibrating piece is mechanically balanced in the width direction (second direction) of each vibrating arm in plan view, and A mechanical balance is obtained in the thickness direction (the third direction which is the vibration direction). Therefore, an excessive load is not applied to the base portion supporting each vibration arm, and vibration leakage is suppressed.

  That is, the case where the 1st group, the 2nd group, and the 3rd group of vibrating arms arranged in order along the 2nd direction are provided is assumed. When the second region of the vibrating arms of the first group and the third group is displaced in the positive third direction, the second region of the vibrating arm of the center second group is displaced in the negative third direction. In this case, since the first group and the third group, which are groups at both ends, are displaced in phase, a balance in the second direction (left-right direction) can be obtained in plan view. In addition, since the first group, the third group, and the second group are displaced in opposite phases, stress due to displacement in the third direction (vibration direction) of each group (stress applied to the base portion that supports the vibrating arm of each group) ) Is canceled out, and thus a balance in the vibration direction (vertical direction) is also ensured.

(Third embodiment)
FIG. 7 is a diagram illustrating an example of a manufacturing process of a vibrator using a tuning fork type vibrating piece. In addition, the tuning fork type vibrating piece 100 used in the example of FIG. 7 includes a base 10 and two vibrating arms 20a and 20b. The plug 30 has an internal terminal 31 and an external terminal 33.

  In the mounting process, the internal terminal 31 of the plug 30 is soldered to the base 10 of the tuning fork type vibrating piece 100. In the next frequency adjustment step, the resonance frequency of the tuning fork type vibrating piece 100 is adjusted. In the next sealing step, the plug 30 is sealed in the case 35 in the vacuum chamber. The case 35 and the plug 30 constitute a sealed body (airtight package). Through the inspection process, the vibrator 1 is completed.

(Fourth embodiment)
In the present embodiment, a double tuning fork type vibrating piece (a vibrating piece having a structure for supporting a vibrating arm on both sides) is used as the tuning fork type vibrating piece. Also in the double tuning fork type resonator element, the vibration in the walk mode can be excited as in the above-described embodiment. However, in the case of a double tuning fork vibrating piece, since the vibrating arm is supported on both sides, the vibrating form of the vibrating arm is different from a single tuning fork type vibrating piece in which only one side of the vibrating arm is supported. In addition, in the double tuning fork resonator element, it is desired to employ an appropriate electrode arrangement from the viewpoint of exciting efficient walk mode vibration (out-of-plane vibration). Hereinafter, a specific description will be given with reference to FIGS.

  FIG. 8A and FIG. 8B are diagrams for explaining an example of out-of-plane vibration in a double tuning fork vibrating piece and an example of electrode arrangement in the double tuning fork vibrating piece. 8A shows the vibration state of the vibrating arm 20, the left side in FIG. 8B is a plan view of the double tuning fork vibrating piece, and the right side shows the vibration state of the double tuning fork vibrating piece. FIG.

  As shown in FIG. 8B, the double tuning fork type vibrating piece 101 has a first base portion 10a and a second base portion 10b as base portions. One end of the vibrating arm 20 is connected to the first base 10a, and the other end of the vibrating arm 20 is connected to the second base 10b. The double tuning fork resonator element 101 can be used as a component of an acceleration sensor or a pressure sensor, for example.

  As shown in FIG. 8A, one vibrating arm 20 (width w, thickness t (<w)) includes the first area ZA, the second area ZB, the third area ZC, and the first area ZC. The region is divided into a first node region Qab provided between the region ZA and the second region ZB, and a second node region Qbc provided between the second region ZB and the third region ZC. When contraction stress occurs in the first region ZA and the third region ZC on the first surface (front surface) or the second surface (back surface) of the vibrating arm 20, the first surface (front surface) or the second surface of the vibrating arm 20 is obtained. An extension stress is generated in the second region ZB on the surface (back surface). In FIG. 8A, the stress is indicated by an arrow. Further, when tensile stress is generated in the first region ZA and the third region ZC on the first surface (front surface) or the second surface (back surface) of the vibrating arm 20, the first surface (front surface) or the second surface of the vibrating arm 20 is obtained. Shrinkage stress is generated in the second region ZB on the surface (back surface).

  That is, in order to vibrate the vibrating arm 20 in a balanced manner in the thickness direction (third direction), one vibrating arm 20 is divided into a first area ZA, a second area ZB, and a third area ZC. A first node region Qab is provided between the region ZA and the second region ZB, and a second node region Qbc is provided between the second region ZB and the third region ZC. Each of the first node region Qab and the second node region Qbc includes vibration nodes FC1 and FC2 (see the diagram on the right side of FIG. 8B). Specifically, the vibration node is a point where the secondary differential coefficient becomes 0 when the displacement of the vibrating arm 20 is obtained as the secondary differential coefficient. For example, when contraction occurs in the first area ZA and the third area ZC on the first surface of the vibrating arm 20, expansion occurs in the second area ZB. Similarly, in the first area ZA and the third area ZC. When the expansion occurs, the contraction occurs in the second region ZB. As a result, stable resonance vibration (out-of-plane vibration) can be realized.

  As shown in the diagram on the left side of FIG. 8B, comb-shaped electrodes are formed on the first surface (front surface) of the vibrating arm 20. The comb electrode has a first electrode 41a and a second electrode 41b. The relative positional relationship between the first electrode 41a and the second electrode 41b in the second region ZB is opposite to the relative positional relationship between the first electrode 41a and the second electrode 41b in the first region ZA and the third region ZC. . Therefore, the direction of the electric field generated in the second region ZB is opposite to the direction of the electric field generated in the first region ZA and the third region ZC. The stress generated in each of the first region ZA, the second region ZB, and the third region ZC is indicated by a solid line arrow and a dotted line arrow in the left side of FIG. 8B.

  The vibration state of the vibrating arm 20 indicated by the solid line shown on the right side of FIG. 8B corresponds to the case where the stress indicated by the solid line arrow is generated in the left side of FIG. 8B. Similarly, the vibration state of the vibrating arm 20 indicated by the dotted line corresponds to the case where the stress indicated by the dotted arrow is generated in the left side of FIG. 8B.

  9A to 9C are diagrams illustrating a configuration example of a double tuning fork type vibrating piece. 9A includes a first base portion 10a, a second base portion 10b, and a single vibrating arm 20. The double tuning fork vibrating piece 101b in FIG. 9B has two vibrating arms 20a and 20b. The twin tuning fork type vibrating piece 101c in FIG. 9C has three vibrating arms 20a, 20b, and 20c. Note that GL1 and GL2 indicate grooves between the vibrating arms. When n (n is a natural number of 2 or more) vibrating arms are provided, it is preferable to vibrate each vibrating arm so as to achieve a dynamic balance. As a result, more stable out-of-plane vibration can be excited on each vibrating arm (20a to 20c, etc.) in the double tuning fork type vibrating piece.

  When three vibrating arms are provided (example in FIG. 9C), the vibrating arms 20a and 20c at both ends are vibrated in the same phase and the central vibrating arm is vibrated in the opposite phase as in the example in FIG. It is preferable to do so. The number of vibrating arms is not limited to three, but may be an odd number (3, 6, 9,...).

  In other words, in a broad sense, in the case where m (m is an odd number of 3 or more) vibrating arms are provided as n vibrating arms, each of the m vibrating arms is divided into the first vibrating arm to the mth vibrating arm. The first vibrating arm to the m-th vibrating arm are arranged side by side in the second direction in ascending order of the value of m, and the m vibrating arms are divided into three vibrating arm groups. To the (m / 3) vibrating arm is the first group of vibrating arms, and the {(m / 3) +1} vibrating arm to the {(2m / 3)} vibrating arm is the second group of vibrating arms. , From the {(2m / 3) +1} vibrating arm to the m-th vibrating arm are the third group of vibrating arms, and the third direction is a positive third direction (+ Z-axis direction) and a positive third A negative third direction (-Z-axis direction) opposite to the direction, and the first surface (or second surface) of each of the first group of vibrating arms and the third group of vibrating arms. 1 area ZA When the contraction stress is generated in the third region ZC and the extensional stress is generated in the second region ZB, the first region ZA and the third region of the first surface (or the second surface) of the second group of vibrating arms. A tensile stress is generated in the region ZC, and a contraction stress is generated in the second region ZB. Further, the first surface (or the second surface) of each of the first group of vibrating arms and the third group of vibrating arms is formed. When extension stress is generated in the first region ZA and the third region ZC and contraction stress is generated in the second region ZB, the first region of the first surface (or the second surface) of the second group of vibrating arms The contraction stress is generated in the ZA and the third region ZC, and the extension stress is generated in the second region ZB ”.

  In this way, the mechanical arm is balanced in the width direction (second direction: Y-axis direction) of the vibrating arm in a plan view, and the thickness direction of the vibrating arm (the out-of-plane vibration direction is the first direction). (3 directions: Z-axis direction) is balanced mechanically. Therefore, the base (the first base 10a and the second base 10b) that supports the vibrating arms (20a to 20c, etc.) is not overloaded, and vibration leakage is suppressed.

  FIG. 10A and FIG. 10B are diagrams showing an arrangement example of electrodes and wirings in a double tuning fork type vibrating piece having three vibrating arms. FIG. 10A is a diagram showing the arrangement of electrodes and wirings on the surface of the vibrating arm. FIG. 10B is a diagram (a perspective view seen from the front surface side) showing the arrangement of electrodes and wirings on the back surface of the vibrating arm. 10A and 10B, the stress generated in each vibrating arm is indicated by a thick arrow.

  As described in the example of FIG. 8, each of the vibrating arms 20a to 20c (width w, thickness t (<w)) includes the first region ZA, the second region ZB, the third region ZC, The first node region Qab is provided between the first region ZA and the second region ZB, and the second node region Qbc is provided between the second region ZB and the third region ZC.

  As shown in FIG. 10A, the first surface (front surface) of the first vibrating arm 20a is provided with a first electrode 41a (1) and a second electrode 41b (1) that constitute a comb electrode. It is done. Similar to the example of FIG. 8, for example, when tensile stress is generated in the first region ZA and the third region ZC, contraction stress is generated in the second region ZB.

  Similarly, on the first surface (front surface) of the second vibrating arm 20b, a first electrode 41a (2) and a second electrode 41b (2) constituting a comb-tooth electrode are provided. For example, when contraction stress is generated in the first region ZA and the third region ZC, extension stress is generated in the second region ZC.

  Similarly, a first electrode 41a (3) and a second electrode 41b (3) constituting a comb electrode are provided on the first surface (front surface) of the third vibrating arm 20c. For example, when tensile stress is generated in the first region ZA and the third region ZC, contraction stress is generated in the second region ZB.

  In FIG. 10A, L1 to L6 indicate wirings formed on the first surface (front surface) of the resonator element. TH1 is a through hole for connecting the first electrode on the front surface and the first electrodes on the back surface. TH2 is a through hole for connecting the second electrode on the front surface and the first electrode person on the back surface. In addition, bonding pads P1 and P2 as external connection terminals are provided on the surface (first surface) of the first base portion 10a.

  Further, as shown in FIG. 10B, on the second surface (back surface) of the first vibrating arm 20a, the first electrode 41a (1) ′ constituting the comb-tooth electrode and the second electrode 41b (1) 'And will be provided. For example, when contraction stress (compression stress) occurs in the first region ZA and the third region ZC, extension stress (tensile stress) occurs in the second region ZB.

  Similarly, on the second surface (back surface) of the second vibrating arm 20b, a first electrode 41a (2) 'and a second electrode 41b (2)' constituting a comb electrode are provided. For example, when tensile stress is generated in the first region ZA and the third region ZC, contraction stress is generated in the second region ZC.

  Similarly, a first electrode 41c (3) 'and a second electrode 41b (3)' constituting a comb electrode are provided on the second surface (front surface) of the third vibrating arm 20c. For example, when a contraction stress is generated in the first region ZA and the third region ZC, an extension stress is generated in the second region ZB.

  In FIG. 10B, L8 to L12 indicate wirings formed on the second surface (back surface) of the resonator element.

(Fourth embodiment)
FIG. 11A and FIG. 11B are diagrams showing an example of the structure of an acceleration sensor element and an acceleration sensor device using a double tuning fork type resonator element.

  An acceleration sensor element 500 (a kind of vibration type sensor element) in FIG. 11A includes a double tuning fork type vibration piece 101c (an example shown in FIG. 9C) having three vibration arms (20a to 20c). It is configured using.

  The first base portion 10a of the double tuning fork type vibrating piece 101c is fixed to the first surface of the base portion 502 with an adhesive, for example. Further, the second base portion 10b of the double tuning fork type vibrating piece 101c is fixed to the first surface of the weight portion (mass portion) 506 with, for example, an adhesive. Each of the vibrating arms 20a to 20c vibrates at a predetermined frequency in the walk mode.

  The weight portion (mass portion) 506 is connected (linked) to the base portion 502 via, for example, an elastic portion (including elastic beams, springs, and the like) 504. When acceleration is applied in the Z-axis direction, the weight part (mass part) 506 is displaced in the Z-axis direction. As a result, the frequency of vibration in each of the vibrating arms 20a to 20c changes, and the magnitude of acceleration can be detected (specified) by detecting the change in frequency.

  An acceleration sensor device 600 shown in FIG. 23B includes an acceleration sensor element 500 shown in FIG. 11A, a hermetically sealed package (accommodating body) 602 that accommodates the acceleration sensor element 500, and a physical quantity detection circuit 604. And having. The inside of the package is in a decompressed state (for example, in a vacuum state).

  In this embodiment, the base of the double tuning fork type vibrating piece is connected to the mass part (weight part), but the base of the double tuning fork type vibrating piece is fixed to an elastic partition wall (wide elastic part) such as a silicon diaphragm. Thus, a pressure sensor can be formed. That is, when the partition wall (elastic portion) is deformed in the Z-axis direction according to the pressure difference between the two spaces separated by the partition wall, the frequency of vibration in each of the vibrating arms 20a to 20c changes, and this change in frequency is detected. Thus, a change in pressure can be measured.

  As described above, the elastic part that is displaced according to the change in the physical quantity of the measurement target, or the mass part connected to the elastic part and at least one base is connected to the elastic part or the mass part, and the elastic part or the mass part The above-mentioned tuning fork type vibrating piece (double tuning fork type vibrating piece), in which at least one vibrating arm expands and contracts in the extending direction of the vibrating arm, and a housing for housing the double tuning fork type vibrating piece, Thus, a sensor device for measuring physical quantities can be realized.

  As a result, a small and highly accurate sensor (such as an acceleration sensor or a pressure sensor) using a small vibrator that can oscillate with high accuracy can be realized.

  As described above, according to the tuning fork type resonator element according to at least one embodiment of the present invention, since out-of-plane vibration (walk-mode vibration) is used, compared to the case of using conventional in-plane vibration. The tuning fork type resonator element can be downsized without difficulty. That is, it is possible to cope with downsizing by reducing the thickness t of the vibrating arm, and it is not necessary to reduce the width of the vibrating arm so much, so the burden on forming electrodes and wiring accompanying the downsizing of the vibrator is reduced. Can be reduced.

  Although the present invention has been described using several embodiments, the present invention is not limited to these embodiments, and various modifications can be made without departing from the technical idea of the present invention. It can be easily understood by the contractor. Accordingly, all such modifications are intended to be included in the scope of the present invention. For example, a term described at least once together with a different term having a broader meaning or the same meaning in the specification or the drawings can be replaced with the different term in any part of the specification or the drawings.

10 base, 20 (20a to 20c) vibrating arm, 100 tuning fork type vibrating piece,
A pair of electrodes (first electrode and second electrode) constituting the comb electrodes on the surfaces of 41a and 41b,
41c and 41d A pair of electrodes (first electrode and second electrode) constituting the comb electrodes on the surface
42 (1) to 42 (3), 42 (1) ′ to 42 (3) ′ Opposite portions of the comb-teeth electrodes (opposite electrode portions or cross finger electrodes)

Claims (14)

The base,
The base extends in a first direction within a predetermined plane and has a predetermined width in a second direction perpendicular to the first direction within the predetermined plane, and the first direction and the second direction A vibrating arm having a predetermined thickness in a third direction perpendicular to each of the predetermined directions and perpendicular to the predetermined plane;
An electrode that is provided on at least one of the first surface of the vibrating arm and the second surface facing the first surface, and that generates an electric field in the first direction;
Causing the vibrating arm to expand and contract in the first direction by the electric field in the first direction, causing the vibrating arm to vibrate in the third direction;
In addition, the tuning fork type resonator element, wherein w> t is established, where w is the predetermined width in the second direction of the vibrating arm and t is the predetermined thickness in the third direction. The tuning fork type resonator element according to claim 1,
The vibrating arm is formed of a piezoelectric material plate having a predetermined crystal plane,
The predetermined plane is a plane including the predetermined crystal plane,
A tuning-fork type vibration piece, wherein the piezoelectric material plate is distorted in the first direction by an electric field in the first direction to generate vibration in the third direction. It is a tuning fork type vibration piece according to claim 1 or 2,
The tuning fork-type vibrating piece according to claim 1, wherein the electrode is a comb electrode provided on at least one of the first surface and the second surface of the vibrating arm. It is a tuning fork type vibration piece according to claim 3,
The comb electrode is
A first opposing portion consisting of a pair of electrodes arranged facing each other at a predetermined distance;
A second opposing portion comprising a pair of electrodes provided adjacent to the first opposing portion and disposed to face each other at the predetermined distance;
The first facing portion and the second facing portion are disposed along the first direction, which is the extending direction of the vibrating arm, and the predetermined distance is L1, and the first facing portion and the second facing portion are When the distance between the second facing portion is L2, L1 <L2 is established.
A tuning fork type vibration piece characterized by the above. It is a tuning fork type vibration piece according to claim 3,
The comb electrode is
A third opposing portion comprising a pair of electrodes provided adjacent to the second opposing portion and disposed opposite to each other by the predetermined distance;
The distance from the base increases in the order of the first facing portion, the second facing portion, and the third facing portion, and the distance between the second facing portion and the third facing portion is When L3, L2 <L3 holds,
A tuning fork type vibration piece characterized by the above. It is a tuning fork type vibration piece according to claim 3,
A convex portion is provided on at least one of the first surface and the second surface of the vibrating arm, and the convex portion has a predetermined thickness in the first direction, and sandwiches the convex portion. A pair of electrodes constituting the comb electrode is provided,
A tuning fork type vibration piece characterized by the above. It is a tuning fork type vibration piece in any one of Claims 1-6,
A tuning-fork type vibrating piece, wherein n vibrating arms (n is a natural number of 2 or more) extending from the base portion in the first direction are provided as the vibrating arms. The tuning fork type vibrating piece according to claim 7,
As the n vibrating arms, m (m is an odd number of 3 or more) vibrating arms are provided,
Each of the m vibrating arms is a first vibrating arm to an mth vibrating arm, and the first vibrating arm to the mth vibrating arm are arranged side by side in the second direction in ascending order of the value of m.
The m vibrating arms are divided into three vibrating arm groups. The first vibrating arm to the (m / 3) vibrating arm are defined as the first vibrating arm, and the {(m / 3) +1} vibrating arm. To {(2m / 3)} vibrating arm is the second group vibrating arm, {(2m / 3) +1} vibrating arm to mth vibrating arm is the third group vibrating arm, and The third direction includes a positive third direction and a negative third direction opposite to the positive third direction,
When each of the first group of vibrating arms and the third group of vibrating arms is displaced in the positive third direction, the second group of vibrating arms is displaced in the negative third direction. ,
When each of the first group of vibrating arms and the third group of vibrating arms is displaced in the negative third direction, the second group of vibrating arms is displaced in the positive third direction. ,
A tuning fork type vibration piece characterized by the above. The tuning fork type vibrating piece according to any one of claims 1 to 8,
A housing for housing the tuning-fork type resonator element;
A vibrator characterized by comprising: It is a tuning fork type vibration piece in any one of Claims 1-6,
The tuning fork type vibrating piece is
A double tuning fork in which a first base and a second base are provided as the base, one end of the vibrating arm is connected to the first base, and the other end of the vibrating arm is connected to the second base. A tuning-fork type vibration piece characterized by being a type vibration piece. The tuning fork type resonator element according to claim 10,
The vibrating arm is
A first region, a second region, and a third region arranged in order in the first direction;
A first knot region provided between the first region and the second region;
A second knot region provided between the second region and the third region;
Have
When contraction stress is generated in the first region and the third region of the first surface or the second surface of the vibrating arm, the second region of the first surface or the second surface of the vibrating arm is applied to the second region. When tensile stress is generated and tensile stress is generated in the first region and the third region of the first surface or the second surface of the vibrating arm, the tensile force is applied to the first surface or the second surface of the vibrating arm. Shrinkage stress is generated in the second region,
A tuning fork type vibration piece characterized by the above. The tuning fork type resonator element according to claim 11,
A tuning fork-type vibrating piece having n (n is a natural number of 2 or more) vibrating arms provided as the vibrating arms. The tuning fork type resonator element according to claim 12,
As the n vibrating arms, m (m is an odd number of 3 or more) vibrating arms are provided,
Each of the m vibrating arms is a first vibrating arm to an mth vibrating arm, and the first vibrating arm to the mth vibrating arm are arranged side by side in the second direction in ascending order of the value of m.
The m vibrating arms are divided into three vibrating arm groups. The first vibrating arm to the (m / 3) vibrating arm are defined as the first vibrating arm, and the {(m / 3) +1} vibrating arm. To {(2m / 3)} vibrating arm is the second group vibrating arm, {(2m / 3) +1} vibrating arm to mth vibrating arm is the third group vibrating arm, and The third direction includes a positive third direction and a negative third direction opposite to the positive third direction,
In each of the first group of vibrating arms and the third group of vibrating arms, contraction stress is generated in the first region and the third region of the first surface or the second surface, and in the second region. When tensile stress is generated, tensile stress is generated in the first region and the third region of the first surface or the second surface of the second group of vibrating arms, and in the second region. Contraction stress occurs,
In each of the first group of vibrating arms and the third group of vibrating arms, tensile stress is generated in the first region and the third region of the first surface or the second surface, and in the second region When contraction stress is generated, contraction stress is generated in the first region and the third region of the first surface or the second surface in the second group of vibrating arms, and expansion is performed in the second region. Stress occurs,
A tuning fork type vibration piece characterized by the above. An elastic part in which displacement occurs according to a change in a physical quantity of a measurement object, or a mass part connected to the elastic part;
The at least one base is connected to the elastic part or the mass part, and the elastic arm or the mass part is displaced to cause expansion and contraction of the vibrating arm in the extending direction of the vibrating arm. A tuning-fork type vibrating piece according to any one of
A housing for housing the tuning-fork type resonator element;
A sensor device comprising:

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