JP2012191299A - Piezoelectric vibration element, piezoelectric vibrator, piezoelectric oscillator, and electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means that prevents excitation electrodes from having contact with upper and lower surfaces of a package when a small piezoelectric vibration element is mounted on the package.SOLUTION: A piezoelectric vibration element 100 includes: a piezoelectric substrate 10; excitation electrodes 20 that are arranged on both main surfaces of the piezoelectric substrate 10 so as to face each other; lead-out electrodes 22; and pads 24. The piezoelectric substrate 10 has: an excitation portion 14 positioned in the center thereof; and a peripheral portion 12 that is thinner than the excitation portion 14 and is formed around the excitation portion 14. Two opposite side surfaces of the excitation portion 14 are flat surfaces, respectively, with no bump, and other two opposite surfaces of the excitation portion 14 have respective bumps in a thickness direction. At least one projection 11 that is perpendicular to a direction of the main surfaces of the piezoelectric substrate 10 is provided on both of the main surfaces in a range where vibration displacement is sufficiently damped when the piezoelectric vibration element 100 is excited.

Description

  The present invention relates to a thickness vibration mode piezoelectric vibrator, and more particularly to a piezoelectric vibration element, a piezoelectric vibrator, a piezoelectric oscillator, and an electronic device having a so-called mesa structure.

A crystal resonator element using an AT-cut crystal resonator element is used in various fields such as electronic equipment because its vibration mode is a thickness-shear vibration and exhibits a cubic curve having excellent frequency temperature characteristics.
Patent Document 1 discloses a so-called mesa-type piezoelectric vibrator (AT-cut crystal vibrator) in which the energy confinement effect is similar to that of a bevel structure or a convex structure.
If the side ratio (ratio of the length of the side to the thickness) is small, if the side ratio is not set appropriately, contour vibrations (bending vibration, etc.) due to the contour dimensions of the piezoelectric substrate will be coupled to the main vibration. However, it is known to deteriorate the characteristics of the main vibration.
In Patent Document 2, an AT-cut quartz resonator is formed with a mesa structure, and at the boundary of the boundary between the mesa portion and the thin-walled portion, it extends from the excitation electrode when the side wall of the boundary portion is 90 ° with respect to the main surface. In view of the problem that the extracted lead electrode (lead electrode) is disconnected, it is possible to prevent disconnection of the lead electrode by making the side wall of the boundary portion inclined or curved. It is disclosed that it can be done. Further, it is disclosed that the surface roughness of the vibration part is reduced to a surface roughness as small as 0.2 microns in average roughness, thereby reducing the CI value and suppressing side vibrations.
Patent Document 3 discloses a crystal in which an AT-cut quartz crystal resonator is formed with a mesa structure, and the side wall of the mesa portion is inclined at 63 ° and 35 ° to suppress the coupling between thickness shear vibration and bending vibration. An oscillator is disclosed.

In Patent Document 4, the frequency of the quartz resonator element is f, the length of the long side (X axis) of the quartz substrate is X, the thickness of the mesa portion (vibrating portion) is t, and the length of the long side of the mesa portion is Mx. When the length of the long side of the excitation electrode is Ex and the wavelength of the bending vibration generated in the long side direction of the quartz substrate is λ, the following four formulas:
λ / 2 = (1.332 / f) −0.0024 (1)
(Mx−Ex) / 2 = λ / 2 (2)
Mx / 2 = (n / 2 + 1/4) λ (where n is an integer) (3)
X ≧ 20t (4)
It is disclosed that the coupling between the thickness shear vibration and the bending vibration can be suppressed by setting the parameters f, X, Mx, and Ex so as to satisfy the above.

In Patent Document 5, the height of the mesa portion of the mesa-type piezoelectric substrate (the step height) y is the length of the long side of the piezoelectric substrate x, and the thickness of the mesa portion (vibration portion) is t. The following formula y = −0.89 × (x / t) + 34 ± 3 (%)
It is disclosed that the unnecessary mode can be suppressed by setting the side ratio to satisfy the above.
In Patent Document 6, when the length of the short side of the mesa-type piezoelectric substrate is Z, the thickness of the mesa part (vibration part) is t, and the electrode dimension in the short side direction of the mesa part is Mz,
15.68 ≦ Z / t ≦ 15.84 and 0.77 ≦ Mz / Z ≦ 0.82
It is disclosed that the unnecessary mode can be suppressed by setting various parameters so as to satisfy the above relationship.

However, in the piezoelectric vibrator having a smaller side ratio, the vibration displacement is not sufficiently attenuated at the end of the X axis, and an unnecessary bending mode is excited at the end face, which is coupled with the main vibration. It was.
Patent Document 7 discloses that the vibration energy of the main vibration can be more completely confined by using a multi-stage mesa structure.
In Patent Document 8, a piezoelectric substrate having a convex cross-sectional shape can be approximately replaced by constructing a stepped shape along an assumed convex-shaped envelope. It is disclosed that the degree of approximation increases if it is a slope.

Patent Document 9 and Patent Document 10 disclose that the mesa portion of a piezoelectric substrate having a mesa structure can be multi-staged to increase the energy confinement effect of main vibration and suppress unnecessary modes.
Patent Document 11 discloses a mesa vibration device in which a step portion of a mesa structure is used as a flow stopper for a conductive adhesive to prevent the adhesive from flowing into the mesa portion. As described above, Patent Documents 7 to 11 disclose that it is useful to suppress the coupling between the main vibration and the bending vibration by making the mesa structure of the piezoelectric substrate a multi-stage mesa structure and deepening the energy confinement. ing.

In recent small piezoelectric vibrators, when a piezoelectric vibration element having a mesa structure is accommodated in a surface mounting package and sealed with a lid member, one end portion of the piezoelectric vibration element is electrically conductive adhesive. It is supported by a so-called cantilever system in which the other edge part opposite to the one edge part is used as a free end, but it is necessary because the package shape is small. The amount of the conductive adhesive cannot be used, so that the adhesive force is liable to decrease, and the main surface of the piezoelectric vibration element is inclined to cause the excitation electrode to contact the bottom surface of the package, resulting in malfunction.
Patent Document 12 discloses a method of manufacturing an AT-cut quartz crystal resonator having a multistage mesa structure using a laser.
Patent Document 13 discloses that the vibrating portion has a mesa structure, one end edge of a thin portion sandwiching the mesa portion is a thick protrusion portion, and at least a part of the other end edge on the opposite side is a thick protrusion portion. A piezoelectric vibration element having a structure as a part is disclosed. When a thick protrusion on the other end edge is mounted on the device mounting pad of the package using a conductive adhesive, the thick protrusion provided on the one end edge remains in the cavity space of the package or Either contact with the bottom surface or contact with the lid member. For this reason, it is disclosed that there is no possibility that the excitation electrode formed in the mesa portion contacts the bottom surface or the lid member in the package, and the vibration of the piezoelectric vibration element is not hindered, so that stable characteristics can be obtained.

However, the vibration displacement energy of the crystal resonator element is maximum at the center of the excitation electrode and attenuates as the distance from the center increases. When a portion where the vibration displacement energy is equal is plotted, an ellipse called a plurality of substantially similar contour lines centering on the center is drawn. In the crystal resonator element of Patent Document 13, the thick protrusion provided at one end edge in the longitudinal direction (X-axis direction) has a function of preventing contact between the excitation electrode and the package, but the vibration displacement energy of the crystal resonator element There is a problem that a part of is lost due to interference with a thick protrusion provided at one end edge. This loss has a greater effect as the crystal resonator element is made smaller, and there is a problem that it is difficult to stabilize the electrical characteristics of the crystal resonator.
Patent Document 14 discloses a piezoelectric vibration element having a mesa structure in which a protrusion is provided on the other end opposite to one end supported in a cantilever manner. The protrusion is provided at at least one corner of the other end excluding the central portion in the width direction. Protrusions are provided at the corners farthest from the center of the mesa-type piezoelectric vibration element, and the protrusions are brought into contact with the housing member. Accordingly, it is disclosed that a piezoelectric vibrator having stable electrical characteristics can be obtained even if the piezoelectric vibration element is downsized.

JP 58-047316 A Japanese Utility Model Publication No. 06-052230 JP 2001-230655 A Japanese Patent No. 4341585 JP 2008-263387 A JP 2010-062723 A Japanese Patent Laid-Open No. 02-057009 Japanese Patent No. 3731348 JP 2008-236439 A JP 2010-109527 A JP 2009-130543 A Patent No. 4075893 Japanese Patent Laid-Open No. 2004-200777 JP 2010-114620 A

However, in a thickness shear vibration element using a quartz substrate having a multistage mesa structure in which the long side direction is parallel to the X axis (an electric axis that is one of crystal axes of the crystal), the X side ratio (thickness t When the ratio X / t of the long side dimension X with respect to is small, for example, X / t = 17 or less, the thickness-shear vibration and the Z ′ axis (the optical axis that is one of the crystal axes of the crystal is the X axis). There is a problem that coupling with contour vibrations (bending vibrations, etc.) in a direction parallel to the axis (when the shaft is rotated by a predetermined angle) is generated.
In addition, a pad provided at an end portion of a crystal resonator element having a multi-stage mesa structure is mounted on an element mounting pad formed on the inner bottom surface of the package, and is made conductive and fixed with a conductive adhesive to constitute a crystal resonator. At this time, it is difficult to keep both the main surface of the quartz crystal vibration element and the bottom surface of the package in parallel due to the amount of conductive adhesive applied to the element mounting pad and its viscosity. There is a problem that the excitation electrode of the crystal resonator element comes into contact with each other and the electrical characteristics of the crystal resonator are deteriorated.
The present invention has been made to solve the above-mentioned problems, and is a thickness-sliding piezoelectric element in which an excitation electrode is provided on an excitation part of a piezoelectric substrate having a small thickness to long side ratio and a multi-stage mesa structure formed in the long side direction. A vibration element that suppresses the coupling between thickness-shear vibration and contour vibration (bending vibration, etc.) in the Z′-axis direction, and protrusions orthogonal to the principal surface of the piezoelectric substrate on the front and back of the end portion of the piezoelectric substrate It is an object of the present invention to realize a piezoelectric vibration element in which each is formed, a piezoelectric vibrator using the same, and a piezoelectric device.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 A piezoelectric vibration element according to the present invention includes a piezoelectric substrate, excitation electrodes disposed opposite to the vibration regions of both main surfaces of the piezoelectric substrate, and one of the piezoelectric substrates from each excitation electrode. A piezoelectric vibration element comprising: an extraction electrode extending toward an end; and a pad electrically connected to the extraction electrode and formed at each of two corners of the piezoelectric substrate. And an excitation part located in the center and a peripheral part that is thinner than the thickness of the excitation part and provided at the periphery of the excitation part, and the two opposing side surfaces of the excitation part are stepless flat surfaces, respectively. The other two opposite side surfaces of the excitation part have step portions in the thickness direction, and protrusions are formed on both main surfaces in a region where vibration displacement is sufficiently attenuated when the excitation part is excited. A piezoelectric vibration element comprising at least one part

  When the piezoelectric vibration element is configured as described above, it is possible to suppress the coupling between the thickness shear vibration and the unnecessary mode such as the contour vibration in the direction orthogonal to the stepless plane, and the CI value can be reduced. There is. In addition, by providing protrusions on both main surfaces of the piezoelectric substrate on which the vibration displacement is sufficiently attenuated as described above, when mounting on the package, the excitation electrode formed on the excitation unit and the package There is an effect that there is a possibility that the inner surface comes into contact.

  Application Example 2 In the piezoelectric vibration element, the piezoelectric substrate includes a crystal axis of quartz, an X axis as an electric axis, a Y axis as a mechanical axis, and a Z axis as an optical axis. Centering on the X axis of the coordinate system, the Z axis is tilted in the −Y direction of the Y axis as the Z ′ axis, and the Y axis is tilted in the + Z direction of the Z axis as the Y ′ axis. A quartz substrate having a plane parallel to the X-axis and the Z′-axis and having a thickness in a direction parallel to the Y′-axis. The quartz substrate has a side parallel to the X-axis as a long side. An excitation part having a side parallel to the Z ′ axis as a short side and located at the center thereof, and a peripheral part formed thinner at the periphery of the excitation part than the excitation part, and the excitation part The two side surfaces parallel to the X axis are stepless planes, and the other two side surfaces parallel to the Z ′ axis of the excitation unit are thicker. A piezoelectric vibrating element according to Application Example 1, characterized in that has a step portion.

  When the piezoelectric vibration element is configured using quartz as described above, the frequency temperature characteristic of the piezoelectric vibration element is excellent, and the coupling between the thickness shear vibration and the contour vibration in the Z′-axis direction can be suppressed, and the CI value is reduced. There is an effect that can be done. In addition, by providing protrusions on both main surfaces of the piezoelectric substrate on which the vibration displacement is sufficiently attenuated as described above, when mounting on the package, the excitation electrode formed on the excitation unit and the package There is an effect that a possibility that the inner surface comes into contact is excluded.

  Application Example 3 In the piezoelectric vibration element, the piezoelectric vibration according to Application Example 1 or 2, wherein the protrusion is provided at a corner portion of the piezoelectric substrate facing the pads. It is an element.

  As described above, when the protrusions are provided at the corners of the piezoelectric substrate, the vibration displacement of the thickness shear vibration of the main vibration excited on the piezoelectric substrate is sufficiently attenuated, so that the operation is not hindered. There is no change in electrical characteristics. In addition, when mounting a piezoelectric vibration element having a protrusion on a package, the possibility of contact between the excitation electrode formed on the excitation portion and the inner surface of the package is eliminated. Is greatly improved.

  Application Example 4 Further, in the piezoelectric vibration element, in the application example 2, the protrusion is provided along an edge along the Z ′ axis facing the pad of the piezoelectric substrate. It is a piezoelectric vibration element of description.

  As described above, when the protrusion is formed along the edge along the Z ′ axis on the piezoelectric substrate, even if the protrusion is slightly deformed by etching or the like, its function, that is, when mounted on the package, Since the function of eliminating the possibility of contact between the excitation electrode and the inner surface of the package is not impaired, there is an effect that the yield is greatly improved when the piezoelectric vibrator is manufactured.

  Application Example 5 In the piezoelectric vibration element, the protrusion includes a first protrusion portion provided along an edge along the Z ′ axis facing the pad of the piezoelectric substrate, and the first protrusion portion. And a second projecting portion that is continuously bent from both ends in the longitudinal direction of the projecting portion in the direction along the X-axis. It is.

  As described above, when the U-shaped protrusion is formed at the end of the piezoelectric substrate, the excitation electrode contacts the inner surface of the package even when the piezoelectric vibration element rotates and adheres to the package in the X-axis direction. There is no risk that the yield will be greatly improved when the piezoelectric vibrator is manufactured.

  [Application Example 6] The piezoelectric vibration element according to any one of Application Examples 1 to 5, wherein the total thickness of the front and back protrusions and the thickness of the peripheral part is equal to the thickness of the excitation part. This is a piezoelectric vibration element.

  As described above, by making the thickness of the excitation portion equal to the total thickness of the thicknesses of the protrusions on the front and back sides and the thickness of the peripheral portion, it is easy to manufacture the piezoelectric substrate, and the excitation electrode is formed on the package. There is no risk of contact with the inner surface, and the yield is greatly improved when the piezoelectric vibrator is manufactured.

  Application Example 7 In the piezoelectric vibration element, the dimension of the piezoelectric substrate in the direction parallel to the Z′-axis is Z, the dimension of the short side of the excitation unit is Mz, and the thickness of the excitation unit is t. The piezoelectric vibration element according to any one of Application Examples 2 to 5, wherein a relationship of 8 ≦ Z / t ≦ 11 and 0.6 ≦ Mz / Z ≦ 0.8 is satisfied. .

  If the piezoelectric vibration element is configured in this way, the CI value can be further reduced, and since there is no contact between the excitation electrode and the inner surface of the package, the yield is greatly improved when the piezoelectric vibrator is manufactured. There is an effect that.

  Application Example 8 In addition, in the piezoelectric vibration element, the relationship of X / t ≦ 17 is satisfied, where X is a dimension in the direction parallel to the X axis of the piezoelectric substrate. It is a piezoelectric vibration element as described in any one.

  By configuring the piezoelectric vibration element in this way, it is possible to reduce the CI value while reducing the size, and since there is no contact between the excitation electrode and the inner surface of the package, the yield is reduced when the piezoelectric vibrator is manufactured. Is greatly improved.

  Application Example 9 A piezoelectric vibrator according to the present invention includes the piezoelectric vibration element according to any one of Application Examples 1 to 8, and a package that accommodates the piezoelectric vibration element. This is a piezoelectric vibrator.

  If the piezoelectric vibrator is configured as described above, since the piezoelectric vibration element according to the present invention is provided, the CI value can be reduced and the excitation electrode and the inner surface of the package are not in contact with each other. When producing a child, the yield is greatly improved.

  Application Example 10 A piezoelectric oscillator according to the present invention includes the piezoelectric vibration element according to any one of Application Examples 1 to 8, an oscillation circuit that drives the piezoelectric vibration element, and a package. A piezoelectric oscillator characterized by the following.

  If the piezoelectric oscillator is configured as described above, the package includes the piezoelectric vibration element having a small CI value according to the present invention and the oscillation circuit, and the piezoelectric oscillator is downsized and the oscillation current of the oscillation circuit is reduced. Therefore, there is an effect that power consumption can be reduced.

  Application Example 11 A piezoelectric oscillator according to the present invention includes the piezoelectric vibrator according to Application Example 9 and an oscillation circuit that drives the piezoelectric vibrator.

  If the piezoelectric oscillator is configured as described above, the piezoelectric vibrator having a small CI value according to the present invention is provided, and the oscillation frequency is stable and the current of the oscillation circuit can be reduced, so that the power consumption of the piezoelectric oscillator is reduced. There is an effect that can be done.

  Application Example 12 The piezoelectric oscillator according to the application example 10 or 11 is characterized in that the oscillation circuit according to the present invention is mounted on an IC.

  If the piezoelectric oscillator is configured as described above, since the oscillation circuit is made into an IC, the piezoelectric oscillator can be reduced in size and the reliability can be improved.

  Application Example 13 An electronic device according to the present invention is characterized in that a package includes the piezoelectric vibration element according to any one of Application Examples 1 to 8 and at least one electronic component. It is an electronic device.

  If the electronic device is configured as described above, the electronic device is configured by the piezoelectric vibration element and the electronic component of the present invention, and thus an electronic device having a piezoelectric vibration element with a small CI can be configured. There is an effect that can be done.

  Application Example 14 An electronic device according to the present invention is an electronic device characterized in that the electronic component according to Application Example 13 is any one of a thermistor, a capacitor, a reactance element, and a semiconductor element.

  If an electronic device is configured as described above, an electronic device is configured using at least one electronic component among a thermistor, a capacitor, a reactance element, and a semiconductor element, and a piezoelectric vibration element. There is an effect of becoming.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic which showed the piezoelectric vibration element of the mesa structure which concerns on this invention, Comprising: (a) is a top view, (b) is P1-P1 sectional drawing, (c) is P2-P2 sectional drawing. (A) is Q1-Q1 sectional drawing of FIG. 1, (b) is Q2-Q2 sectional drawing of FIG. FIG. 3 is a diagram in which isobaric lines formed by connecting points having equal vibration displacement energy on the plane of a mesa structure piezoelectric vibration element are overwritten. The figure which shows the relationship between the new orthogonal axis | shaft X, Y ', Z' axis | shaft formed by theta rotation of the crystal axes X, Y, and Z of quartz around the X-axis, and an AT cut quartz substrate. (A) thru | or (c) are the top views and sectional drawings which show typically the manufacturing method of the piezoelectric vibration element of this embodiment. (A) thru | or (c) are the top views and sectional drawings which show typically the manufacturing method of the piezoelectric vibration element of this embodiment. (A) thru | or (c) are the top views and sectional drawings which show typically the manufacturing method of the piezoelectric vibration element of this embodiment. (A) thru | or (c) are the top views and sectional drawings which show typically the manufacturing method of the piezoelectric vibration element of this embodiment. (A) thru | or (d) are the top views and sectional drawings which show typically the manufacturing method of the piezoelectric vibration element of this embodiment. (A) thru | or (d) are the top views and sectional drawings which show typically the manufacturing method of the piezoelectric vibration element of this embodiment. (A) thru | or (d) are the top views and sectional drawings which show typically the manufacturing method of the piezoelectric vibration element of this embodiment. (A) thru | or (c) are based on the modification of this embodiment, (a) is a top view, (b) is P4-P4 sectional drawing, (c) is P5-P5 sectional drawing. (A) is Q6-Q6 sectional drawing of FIG. 12, (b) is Q7-Q7 sectional drawing of FIG. (A) is a top view concerning other modification of this embodiment, (b) is Q2-Q2 sectional drawing. (A) is a top view concerning other modification of this embodiment, (b) is Q1-Q1 sectional drawing. (A) is a top view concerning other modification of this embodiment, (b) is Q2-Q2 sectional drawing. It is sectional drawing which showed typically the piezoelectric vibrator which concerns on this embodiment, (a) is sectional drawing of a longitudinal direction center part, (b) is sectional drawing of a longitudinal direction edge part, (c), ( d) is a sectional view for explanation. (A) And (b) is the top view and sectional drawing which showed typically the piezoelectric vibration element of the comparative example. (A) And (b) is the figure shown with the graph which shows distribution of CI value. The figure shown with the graph which shows the relationship between Mz (dimension of the short side of an excitation part) / Z (dimension of the short side of a piezoelectric substrate), and CI value. (A) is sectional drawing which shows embodiment of an electronic device, (b) is sectional drawing which shows embodiment of a modification. (A) is sectional drawing which shows embodiment of a piezoelectric oscillator, (b) is sectional drawing which shows embodiment of a modification, (c) is sectional drawing which shows embodiment of another modification.

  Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. The present invention is not limited to the following embodiments at all, and includes various modifications that are implemented within a range that does not change the gist of the present invention. Note that not all of the configurations described in the following embodiments are indispensable constituent requirements of the present invention.

1. Piezoelectric Vibration Element First, a piezoelectric vibration element according to this embodiment will be described with reference to the drawings. 1 and 2 are schematic views showing the configuration of a piezoelectric vibration element 100 according to an embodiment of the present invention. 1A is a plan view of the piezoelectric vibration element 100, FIG. 1B is a cross-sectional view taken along the line P1-P1 in FIG. 1A, and FIG. It is P2-P2 sectional drawing of. 2A is a Q1-Q1 cross-sectional view of FIG. 1A, and FIG. 2B is a Q2-Q2 cross-sectional view of FIG. 1A, or a Q2′-Q2 ′ cross-sectional view. .
The piezoelectric vibration element 100 according to the present invention includes a piezoelectric substrate 10 having a multi-stage mesa structure excitation portion 14 located in the center, and a thin peripheral portion 12 continuously formed at the periphery of the excitation portion 14, and both the excitation portions 14. Excitation electrodes 20 disposed opposite to each other on the main surface, an extraction electrode 22 extending from each excitation electrode 20 toward the end of the piezoelectric substrate 10, and two ends of the extraction electrode 22 and the two corners of the piezoelectric substrate 10 And a pad 24 formed at each corner.
The excitation part 14 is a thick part in which the central part of the piezoelectric substrate protrudes in both main surface directions, and the peripheral part 12 is formed to project from the intermediate part in the thickness direction of at least a part of the outer peripheral side surface of the excitation part 14 in the outer diameter direction. Has been.

The piezoelectric substrate 10 has an excitation part 14 that is located at the center and serves as a main vibration region, and a peripheral part 12 that is thinner than the excitation part 14 and is formed along the periphery of the excitation part 14. The two opposing side surfaces (both side surfaces along the longitudinal direction) of the excitation unit 14 having a substantially rectangular plane shape are each a stepless flat surface, and the other two opposite side surfaces (short) of the excitation unit 14 are short. Each of the two side surfaces along the side direction has a structure having a stepped portion in the thickness direction.
When an alternating voltage is applied to each excitation electrode 20, the piezoelectric vibration element 100 is excited at a specific vibration frequency. At least one protrusion 11 perpendicular to the main surface direction of the piezoelectric substrate 10 is formed on the front and rear surfaces of the peripheral portion 12 in the region where the excited vibration displacement is sufficiently attenuated.
In the example shown in FIGS. 1 and 2, the protrusion 11 has a corner (see FIG. 1) that faces the pad 24 formed on each of the two corners (left side of FIG. 1A) of the piezoelectric substrate 10. Two pieces each on the front and back sides are formed on the right side of (a). That is, two protrusions 11 formed on the front and back surfaces of the peripheral portion 12 are provided at each corner of the peripheral portion 12 of the piezoelectric substrate 10. The sum of the thicknesses of the protrusions 11 on the front and back sides and the thickness of the peripheral part 12 can be configured to be equal to the thickness at the center of the excitation part 14.

FIG. 3 is formed on the plan view of the piezoelectric vibration element 100 by connecting the points where the vibration displacement energy (product of the square of the vibration displacement and the mass of the position) generated when the piezoelectric vibration element 100 is excited is equal. The force line is indicated by a one-dot chain line. In the piezoelectric vibration element 100 shown in FIG. 3, since the excitation unit 14 has a rectangular shape that is long in the X-axis direction, the contour lines have an elliptical shape with a large major axis in the X-axis direction and a minor minor axis in the Z′-axis direction. It becomes. The magnitude of the vibration displacement is maximum at the central portion of the excitation unit 14 and decreases as the distance from the central portion increases. That is, both the X-axis direction and the Z′-axis direction are distributed on the cosine on the excitation electrode 20, and are attenuated exponentially in a region where the excitation electrode 20 is not present.
In the piezoelectric vibration element 100 shown in FIG. 1, the protrusion 11 is provided in a region where vibration displacement energy is sufficiently attenuated, that is, in a corner portion of the peripheral portion 12. For this reason, even if the protrusion 11 is provided, the vibration displacement portion of the piezoelectric vibration element 100 is hardly affected. That is, the electrical characteristics of the piezoelectric vibration element 100 are not changed at all.

By the way, piezoelectric materials such as quartz belong to the trigonal system and have crystal axes X, Y, and Z orthogonal to each other as shown in FIG. The X axis, the Y axis, and the Z axis are referred to as an electric axis, a mechanical axis, and an optical axis, respectively. The AT-cut quartz crystal substrate 101 is a flat plate cut out from quartz along a plane obtained by rotating the XZ plane around the X axis by an angle θ. In the case of the AT-cut quartz substrate 101, θ is approximately 35 ° 15 ′. Note that the Y-axis and the Z-axis are rotated by θ around the X-axis to be the Y′-axis and the Z′-axis, respectively. Accordingly, the AT-cut quartz crystal substrate 101 has crystal axes X, Y ′, and Z ′ that are orthogonal to each other. The AT-cut quartz substrate 101 has a thickness direction of the Y ′ axis, and an XZ ′ plane (a plane including the X axis and the Z ′ axis) orthogonal to the Y ′ axis is a main surface, and thickness shear vibration is excited. . The AT-cut quartz substrate 101 can be processed to obtain the piezoelectric substrate 10.
That is, as shown in FIG. 4, the piezoelectric substrate 101 is centered on the X axis of an orthogonal coordinate system composed of an X axis (electric axis), a Y axis (mechanical axis), and a Z axis (optical axis), and the Z axis is the Y axis. The axis tilted in the −Y direction is the Z ′ axis, the Y axis is the Y ′ axis is the axis tilted in the + Z direction of the Z axis, and is composed of surfaces parallel to the X and Z ′ axes. It consists of an AT-cut quartz substrate with the thickness in the parallel direction.

As shown in FIG. 1A, the piezoelectric substrate 10 has a direction parallel to the X axis (hereinafter referred to as “X axis”) with a direction parallel to the Y ′ axis (hereinafter referred to as “Y ′ axis direction”) as a thickness direction. It is possible to have a rectangular shape having a long side as a “direction” and a short side as a direction parallel to the Z ′ axis (hereinafter referred to as “Z ′ axis direction”). The piezoelectric substrate 10 has an excitation part 14 and a peripheral part 12 formed along the periphery of the excitation part 14. Here, the “rectangular shape” includes literally a rectangular shape and a shape in which a corner portion of the rectangle is chamfered.
As shown in FIGS. 1 and 2, the peripheral portion 12 is formed on at least a part of the peripheral surface (side surface) of the excitation portion 14 and has a thickness (thin wall) smaller than the excitation portion 14.

As shown in FIG. 1 and FIG. 2, the excitation unit 14 according to this example is surrounded by the peripheral part 12 on the entire circumference, and has a thickness (thickness) larger than the thickness of the peripheral part 12 in the Y′-axis direction. Have. That is, the excitation unit 14 protrudes in the Y′-axis direction with respect to the peripheral portion 12 as shown in FIGS. 1B and 2A. In the illustrated example, the excitation unit 14 protrudes toward the + Y ′ axis side and the −Y ′ axis side with respect to the peripheral portion 12. The excitation unit 14 may have, for example, a point (not shown) that is a center of symmetry and a shape that is point-symmetric with respect to the center point.
As shown in FIG. 1A, the excitation unit 14 has a rectangular shape with the long side in the X-axis direction and the short side in the Z′-axis direction. That is, the excitation unit 14 has a side parallel to the X axis as a long side and a side parallel to the Z ′ axis as a short side. Therefore, the excitation unit 14 has side surfaces 14a and 14b extending in the X-axis direction and side surfaces 14c and 14d extending in the Z′-axis direction. That is, the longitudinal direction of the side surfaces 14a and 14b extending in the X-axis direction is the X-axis direction, and the longitudinal direction of the side surfaces 14c and 14d extending in the Z′-axis direction is the Z′-axis direction. In the illustrated example, of the side surfaces 14a and 14b, the side surface 14a is a side surface on the + Z ′ axis side, and the side surface 14b is a side surface on the −Z ′ axis side. Of the side surfaces 14c and 14d, the side surface 14c is a side surface on the −X axis side, and the side surface 14d is a side surface on the + X axis side.

For example, as shown in FIG. 1B, the side surface 14a extending in the X-axis direction is formed so as to protrude from the peripheral portion 12 on the + Y′-axis side and the + Y′-axis side. The same applies to the side surfaces 14b, 14c, and 14d. Each of the side surfaces 14a and 14b extending in the X-axis direction has a stepless shape in one plane as shown in FIG. That is, the side surface 14a on the + Y′-axis side is in one plane, and the side surface 14a on the −Y′-axis side is in one plane. Similarly, the side surface 14b on the + Y′-axis side is in one plane, and the side surface 14b on the −Y′-axis side is in one plane.
In the description according to the present invention, “in one plane” includes the case where the side surface of the excitation unit 14 is a flat surface and the case where the crystal portion has irregularities corresponding to the anisotropy of crystal. . That is, when an AT-cut quartz substrate is processed using a solution containing hydrofluoric acid as an etchant, the side surface of the excitation unit 14 exposes the R plane of the quartz crystal and is parallel to the XY ′ plane, and the m plane of the quartz crystal is It may be exposed and have irregularities corresponding to the crystal anisotropy of quartz. In the description according to the present invention, such a side surface having irregularities due to the m-plane of the quartz crystal is also “in one plane”. For convenience, in FIG. 1 (a) and FIG. 2 (a), unevenness due to the m-plane is omitted. It is also possible to expose only the R plane of the quartz crystal by processing the AT-cut quartz substrate with a laser.

  Each of the side surfaces 14c and 14d extending in the Z′-axis direction has a step as shown in FIG. The excitation unit 14 includes a first portion 15 having a maximum thickness located at the center, and a second portion 16 having a thickness smaller than the first portion 15, and the step between the side surfaces 14 c and 14 d is defined by the first portion. 15 and the second portion 16 are formed by differences in thickness. In the illustrated example, the side surfaces 14 c and 14 d are formed by a plane parallel to the Y′Z ′ plane of the first portion 15, a plane parallel to the XZ ′ plane of the second portion 16, and a Y′Z ′ of the second portion 16. And a plane parallel to the plane.

  As shown in FIGS. 1A and 2A, for example, the second portion 16 is formed so as to sandwich the first portion 15 from both sides in the X-axis direction. Therefore, as illustrated in FIG. 1B, the side surfaces 14 a and 14 b extending in the X-axis direction are formed by the side surfaces of the first portion 15. Thus, the excitation unit 14 has two types of portions 15 and 16 having different thicknesses, and it can be said that the piezoelectric vibration element 100 has a two-stage (multi-stage) mesa structure.

The excitation unit 14 can vibrate with the thickness shear vibration as the main vibration. The piezoelectric vibration element 100 can have an energy confinement effect because the excitation unit 14 has a two-stage mesa structure.
Here, the dimension (short side dimension) in the Z′-axis direction of the piezoelectric substrate 10 is Z, the short side dimension of the excitation unit 14 is Mz, and the thickness of the excitation unit (the thickness of the first portion 15 of the excitation unit 14). ) Is t, it is preferable to satisfy the relationship of the following formula (1).
8 ≦ Z / t ≦ 11 and 0.6 ≦ Mz / Z ≦ 0.8 (1)
Thereby, the coupling between the thickness shear vibration and the unnecessary mode such as the contour vibration can be suppressed, and the CI value can be reduced and the frequency temperature characteristic can be improved. (Details will be described later). Such coupling between the thickness shear vibration and the contour vibration is generally difficult to suppress as the area of the piezoelectric substrate is smaller. Therefore, for example, in a small piezoelectric vibration element 100 that satisfies the relationship of the following formula (2), where X is the dimension in the X-axis direction (long side dimension) of the piezoelectric substrate 10, the formula (1) When designed to satisfy the relationship, the coupling between the thickness shear vibration and the contour vibration can be suppressed more remarkably.
X / t ≦ 17 (2)

  The excitation electrode 20 is formed on the excitation unit 14. In the example shown in FIG. 1B and FIG. 2A, the excitation electrode 20 is formed with the excitation part 14 sandwiched between the front and back. More specifically, the excitation electrode 20 is disposed so as to face the vibration region (excitation part 14) of both main surfaces (surfaces parallel to the XZ ′ surface) of the piezoelectric substrate 10 on both sides. The excitation electrode 20 can apply a voltage to the excitation unit 14. The excitation electrode 20 is connected to the pad 24 via the extraction electrode 22, for example. The pad 24 is electrically connected to an IC chip (not shown) for driving the piezoelectric vibration element 100, for example. As materials for the excitation electrode 20, the extraction electrode 22, and the pad 24, for example, a material obtained by laminating chromium and gold in this order from the piezoelectric substrate 10 side can be used.

The piezoelectric vibration element 100 according to this embodiment has the following features, for example.
Coupling between thickness shear vibration and unnecessary modes such as contour vibration in a direction orthogonal to the stepless plane can be suppressed, and the CI value can be reduced. (Details will be described later) Further, by providing the projections 11 on both main surfaces of the region where the vibration displacement on the piezoelectric substrate is sufficiently attenuated, when mounting the package, the excitation electrode formed on the excitation unit and the package There is an effect that there is no possibility that the inner surface comes into contact. Further, when the piezoelectric vibration element is configured using crystal as in the embodiment shown in FIG. 1, the frequency temperature characteristic of the piezoelectric vibration element is excellent. The coupling between the thickness shear vibration and the contour vibration in the Z′-axis direction can be suppressed, and the CI value can be reduced. In addition, by providing protrusions on both main surfaces of the piezoelectric substrate on which the vibration displacement is sufficiently attenuated, when mounting on the package, the excitation electrode formed on the excitation unit and the inner surface of the package There is an effect that there is no risk of contact.

As in the embodiment shown in FIG. 1, since the protrusions 11 are provided at the corners of the peripheral portion 12 facing the pads 24 of the piezoelectric substrate 10, the thickness of the main vibration excited on the piezoelectric substrate 10. The vibration displacement of the sliding vibration is sufficiently attenuated, and the electrical characteristics are not changed without impeding the operation. In addition, when the piezoelectric vibration element 100 having the protrusion 11 is mounted on the package, the possibility that the excitation electrode formed on the excitation portion and the inner surface of the package come into contact with each other is eliminated. The yield is greatly improved.
Further, according to the piezoelectric vibration element 100, as described above, the dimension Z of the short side of the piezoelectric substrate 10, the dimension Mz of the short side of the excitation unit 14, and the thickness t of the excitation unit 14 satisfy the relationship of Expression (1). By doing so, the CI value can be reduced.
According to the piezoelectric vibration element 100, as described above, the CI value can be reduced while reducing the size by satisfying the relationship of the X side ratio (X / t) of the formula (2).

2. Next, a method for manufacturing a piezoelectric vibration element according to this embodiment will be described with reference to the drawings. 5 to 11 are diagrams schematically showing a manufacturing process of the piezoelectric vibrating element 100 according to the present embodiment. 5 to 11, (a) is a plan view, (b) is a P3-P3 sectional view of (a), and (c) is a Q3-Q3 sectional view of (a). Moreover, in FIG. 9 thru | or FIG. 11, (d) is Q4-Q4 or Q4'-Q4 'sectional drawing.

As shown in FIG. 5, a corrosion-resistant film 30 is formed on the front and back main surfaces (surfaces parallel to the XZ ′ plane) of the AT-cut quartz crystal substrate 101. The corrosion resistant film 30 is formed by, for example, laminating chromium and gold in this order by a sputtering method, a vacuum deposition method, or the like, and then patterning the chromium and gold. The patterning is performed by, for example, a photolithography technique and an etching technique. The corrosion-resistant film 30 has corrosion resistance against a solution containing hydrofluoric acid that becomes an etching solution when the AT-cut quartz crystal substrate 101 is processed.
As shown in FIG. 6, after applying a positive photoresist film on the corrosion-resistant film 30, the photoresist film is exposed and developed to form a resist film 40 having a predetermined shape. The resist film 40 is formed so as to cover a part of the corrosion resistant film 30.

Next, as shown in FIG. 7, a part of the resist film 40 is exposed again using a mask M to form a photosensitive portion 42. As shown in FIG. 7A, the mask M is disposed so as to intersect the resist film 40 when viewed from the Y′-axis direction. That is, the dimension of the mask M in the X-axis direction is smaller than the dimension of the resist film 40 in the X-axis direction, and the dimension of the mask M in the Z′-axis direction is larger than the dimension of the resist film 40 in the Z′-axis direction. By exposing using such a mask M, as shown in FIG. 7C, the photosensitive portions 42 can be formed on both sides of the resist film 40 when viewed from the Z′-axis direction.
Next, as shown in FIG. 8, the AT cut quartz crystal substrate 101 is etched using the corrosion resistant film 30 as a mask. Etching is performed using, for example, a mixed liquid of hydrofluoric acid (hydrofluoric acid) and ammonium fluoride as an etching liquid. As a result, the outer shape of the piezoelectric substrate 10 (the shape when viewed from the Y′-axis direction) is formed as shown in FIG.

Next, as shown in FIG. 9, after etching the corrosion-resistant film 30 with a predetermined etching solution using the resist film 40 as a mask, the AT-cut quartz crystal substrate 101 is half-cut to a predetermined depth using the above-mentioned mixed solution as an etching solution. Etch. Thereby, the external shape of the excitation part 14 and the external shape of the projection part 11 are formed.
Next, as shown in FIG. 10, the photosensitive portion 42 of the resist film 40 is developed and removed. Thereby, a part of the corrosion-resistant film 30 is exposed. Before developing the photosensitive portion 42, for example, an altered layer (not shown) formed on the surface of the resist film 40 is ashed by oxygen plasma generated by discharge in a vacuum or a reduced pressure atmosphere. Thereby, the photosensitive part 42 can be reliably developed and removed.
Next, as shown in FIG. 11, using the resist film 40 as a mask, the exposed portion of the corrosion-resistant film 30 is etched away with a predetermined etching solution, and then the AT-cut quartz crystal substrate 101 is further formed with the above-mentioned mixed solution as an etching solution. Half-etch to the depth of. Thereby, each of the side surfaces 14a and 14b extending in the X-axis direction can be formed in one plane. Further, a step can be formed on each of the side surfaces 14c and 14d extending in the Z′-axis direction. In addition, protrusions 11 orthogonal to the peripheral portion 12 can be formed at the corners on the front and back sides of the peripheral portion 12 of the piezoelectric substrate 10, respectively.

Through the above steps, the piezoelectric substrate 10 having the peripheral portion 12, the excitation portion 14, and the protrusion 11 can be formed.
As shown in FIGS. 1 and 2, after removing the resist film 40 and the corrosion-resistant film 30, the excitation electrode 20, the extraction electrode 22, and the pad 24 are formed on the piezoelectric substrate 10. The excitation electrode 20, the extraction electrode, and the pad 24 are formed by, for example, laminating chromium and gold in this order by sputtering or vacuum deposition, and then patterning the chromium and gold.

Through the above steps, the piezoelectric vibration element 100 according to the present embodiment can be manufactured.
According to the method for manufacturing the piezoelectric vibration element 100, the resist film 40 used for forming the outer shape of the excitation unit 14 is developed to remove the photosensitive portion, and then the side surface extending in the X-axis direction using the resist film 40 again. 14a and 14b can be exposed. Here, the mask M for forming the photosensitive portion 42 has a dimension in the X-axis direction smaller than the dimension of the resist film 40 and a dimension in the Z′-axis direction larger than the dimension of the resist film 40. Therefore, each of the side surfaces 14a and 14b can be accurately formed in one plane. For example, when a resist film is applied twice to form the excitation portion 14 (for example, after forming the outer shape of the excitation portion using the first resist film, the first resist film is peeled off and When the second resist film is applied to expose the side surface of the excitation unit), misalignment occurs between the first resist film and the second resist film, and the side surface of the excitation unit is formed in one plane. There are things that cannot be done. Such a problem can be solved by the manufacturing method of the piezoelectric vibration element 100.
In addition, according to the method for manufacturing the piezoelectric vibration element 100, the protrusions 11 that are orthogonal to the front and back of the peripheral portion 12 are formed at the corner portions of the peripheral portion 12 facing the two pads 24 at the corner portions of the piezoelectric substrate 10. Can be formed.

3. Next, a piezoelectric vibration element according to a modification of the present embodiment will be described with reference to the drawings. FIG. 12A is a plan view schematically showing a piezoelectric vibration element 200 according to a modification of the present embodiment. 12B is a cross-sectional view taken along the line P6-P6 in FIG. 12A, and FIG. 12C is a cross-sectional view taken along the line P7-P7 in FIG. 13A is a Q6-Q6 cross-sectional view of FIG. 12A, and FIG. 13B is a Q7-Q7 cross-sectional view of FIG. 12A or a Q7′-Q7 ′ cross-sectional view. . Hereinafter, in the piezoelectric vibration element 200 according to the modification of the present embodiment, members having the same structure and function as those of the 100 constituent members according to the present embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

In the example of the piezoelectric vibration element 100, the two-stage mesa structure having the first portion 15 and the second portion 16 having different thicknesses has been described as illustrated in FIGS. 1 and 2.
On the other hand, the piezoelectric vibration element 200 has a three-stage mesa structure as shown in FIGS. That is, the excitation unit 14 of the piezoelectric vibration element 200 includes a third portion 17 having a thickness smaller than that of the second portion 16 in addition to the first portion 15 and the second portion 16. In the example shown in FIGS. 12 and 13, the third portion 17 is formed so as to sandwich the first portion 15 and the second portion 16 from the X-axis direction.
The steps of the side surfaces 14c and 14d extending in the Z′-axis direction are formed by the thickness differences of the first portion 15, the second portion 16, and the third portion 17, as shown in FIG. In the illustrated example, the side surfaces 14c and 14d include a surface parallel to the Y′Z ′ plane of the first portion 15, a surface parallel to the XZ ′ plane of the second portion 16, and Y′Z ′ of the second portion 16. A plane parallel to the plane, a plane parallel to the XZ ′ plane of the third portion 17, and a plane parallel to the Y′Z ′ plane of the third portion 17 are configured. Further, in the excitation unit 14 including the first portion 15, the second portion 16, and the third portion 17, a peripheral portion 12 that is thinner than the thickness of the third portion 17 is formed along the periphery of the third portion 17. . Excitation electrodes 20 formed opposite to the excitation unit 14, the extraction electrodes 22 from the excitation electrodes 20, and the two pads 24 that are the terminal ends of the extraction electrodes 22 are also formed in the same manner as the piezoelectric vibration element 100. Yes. Opposite the two pads 24 provided at the corners of the piezoelectric substrate 10, the projections 11 are formed on the front and back surfaces of the corners 12 of the peripheral part 12 at right angles to the peripheral part 12.

  The piezoelectric vibration element 200 can be manufactured by applying the method for manufacturing the piezoelectric vibration element 100. That is, as shown in FIG. 10, after developing and removing the photosensitive portion 42, the resist film 40 is exposed again to form a second photosensitive portion (not shown) having a predetermined shape. Next, the corrosion resistant film 30 and the AT-cut quartz crystal substrate 101 are etched using the resist film 40 having the second photosensitive portion as a mask. Next, ashing is performed to remove the deteriorated layer of the resist film 40, and then the second photosensitive portion is developed and removed. Next, the corrosion resistant film 30 and the AT-cut quartz substrate 101 are etched using the resist film 40 from which the second photosensitive portion has been removed as a mask. Through the above steps, the three-stage mesa structure and the protrusions 11 orthogonal to the peripheral part 12 can be formed on the front and back of the corners of the peripheral part 12 of the piezoelectric substrate 10. By forming an excitation electrode 20 facing the excitation part of the three-stage type mesa structure on the piezoelectric substrate 10, an extraction electrode 22 from each excitation electrode 20, and two pads 24 that are terminations of the extraction electrode 22, The piezoelectric vibration element 200 can be manufactured.

According to the piezoelectric vibration element 200, the energy confinement effect can be further enhanced as compared with the piezoelectric vibration element 100 having a two-stage mesa structure. Further, according to the piezoelectric vibration element 200, the protrusions 11 that are orthogonal to the front and back of the peripheral portion 12 are formed at the corners of the peripheral portion 12 facing the two pads 24 at the corners of the piezoelectric substrate 10, respectively. The yield can be greatly improved when mounted on a package.
In the above-described example, the piezoelectric vibration element 200 having the three-stage mesa structure has been described. However, the invention according to the present application has one multi-stage mesa structure in which each side surface extending in the X-axis direction of the excitation unit has one. As long as it is within the plane, the number of steps of the mesa structure (the number of steps) is not particularly limited.

  FIG. 14A is a plan view of another modified example 110 of the piezoelectric vibration element (shown based on the piezoelectric vibration element 100 but may be based on the piezoelectric vibration element 200). These are Q2-Q2 sectional drawing of (a), or Q2'-Q2 'sectional drawing. The piezoelectric vibration element 110 has a mesa-structured excitation portion 14 formed at the center, and a piezoelectric substrate 10 having a thin peripheral portion 12 formed at the periphery of the excitation portion 14 and the front and back surfaces of the excitation portion 14 facing each other. And an extraction electrode 22 extending from each excitation electrode 20 toward the end of the piezoelectric substrate 10, and a pad 24 that is a terminal end of the extraction electrode 22. Further, on the peripheral portion 12 facing the two pads 24 provided at the corners of the piezoelectric substrate 10, a first protruding portion 11 a provided along the edge along the Z ′ axis (short side); The U-shaped protrusions 11 are formed on the front and back sides of the first protrusions 11a and the second protrusions 11b that are continuously bent from both longitudinal ends of the first protrusions 11a in the direction along the X axis. Has been. The thickness obtained by adding the thickness of the peripheral portion 12 and the thickness of the protrusions 11 on the front and back sides can be made equal to the thickness at the center of the excitation portion 14.

  FIG. 15A is a plan view of another modification 120 of the piezoelectric vibration element, and FIG. 15B is a cross-sectional view taken along the line Q1-Q1 in FIG. Since the excitation part 14, the excitation electrode 20, the extraction electrode 22, and the pad 24 of the piezoelectric substrate 10 are the same as those of the piezoelectric vibration element 100 shown in FIG. 1 and FIG. On the front and back sides of the peripheral portion 12 facing the two pads 24 provided at the corners of the piezoelectric substrate 10, the strip-shaped protrusions 11 are formed along the edges along the Z ′ axis (short side), respectively. ing.

  FIG. 16A is a plan view of another modification 130 of the piezoelectric vibration element, and FIG. 16B is a Q2-Q2 cross-sectional view or a Q2′-Q2 ′ cross-sectional view of FIG. Since the excitation part 14, the excitation electrode 20, the extraction electrode 22, and the pad 24 of the piezoelectric substrate 10 are the same as those of the piezoelectric vibration element 100 shown in FIG. 1 and FIG. Along the long sides (X-axis direction) of the piezoelectric substrate 10 at the corners of the peripheral portion 12 facing the two pads 24 provided at the corners of the piezoelectric substrate 10 and on the front and back orthogonal to the peripheral portion 12. Short strip-like protrusions 11 are respectively formed.

As shown in the embodiment of FIG. 14, when the U-shaped protrusion 11 (11a, 11b) is formed at the end of the piezoelectric substrate 10, the piezoelectric vibration element rotates and adheres to the package in the X-axis direction. However, there is no possibility that the excitation electrode contacts the inner surface of the package, and there is an effect that the yield is greatly improved when the piezoelectric vibrator is manufactured.
As shown in the embodiment of FIG. 15, when the protrusion 11 is formed over the entire length along the edge along the Z ′ axis on the piezoelectric substrate, some deformation occurs in the protrusion due to etching or the like. However, when it is mounted on the package, it does not impair the function of eliminating the possibility of contact between the excitation electrode and the inner surface of the package, so the yield is greatly improved when the piezoelectric vibrator is manufactured. There is an effect that.
In addition, as shown in the embodiment examples of FIGS. 1, 2, 12, 13, and 14 to 16, the thickness of the excitation portion 14, the thicknesses of the protrusions 11 on the front and back sides, and the thickness of the peripheral portion 12 are set. By making the total thickness equal, it is easy to manufacture the piezoelectric substrate, and there is no possibility that the excitation electrode contacts the inner surface of the package, so that the yield is greatly improved when the piezoelectric vibrator is manufactured. There is an effect that.

4). Next, the piezoelectric vibrator according to the present embodiment will be described with reference to the drawings. FIG. 17 is a cross-sectional view schematically showing the piezoelectric vibrator 300 according to the present embodiment.
17A is a cross-sectional view in the longitudinal direction (X-axis direction) showing the configuration of the piezoelectric vibrator 300, and is a cross-sectional view at the same position as the cross-sectional view of the piezoelectric vibration element 100 shown in FIG. It is. FIG. 17B is a cross-sectional view in the longitudinal direction (X-axis direction) at the end of the piezoelectric vibrator 300 in the short-side direction (Z′-axis direction). As illustrated in FIG. 17A, the piezoelectric vibrator 300 includes a piezoelectric vibration element according to the present invention (the piezoelectric vibration element 100 in the illustrated example) and a package 50.
The package 50 can accommodate the piezoelectric vibration element 100 in the cavity 52. Examples of the material of the package 50 include ceramic and glass. The cavity 52 is a space for the piezoelectric vibration element 100 to operate. The cavity 52 is hermetically sealed and has a reduced pressure space or an inert gas atmosphere.
The piezoelectric vibration element 100 is accommodated in the cavity 52 of the package 50. In the illustrated example, the piezoelectric vibration element 100 is fixed in the cavity 52 in a cantilever shape with a conductive adhesive 60 interposed therebetween. As the conductive adhesive 60, for example, solder or silver paste can be used.

17A and 17B illustrate an example in which both main surfaces of the piezoelectric vibration element 100 are configured to be parallel to the inner bottom view (or lid member) of the package 50. Depending on the application amount and viscosity of the adhesive 60, as shown in the cross-sectional view of FIG. 17C, the adhesive may tilt toward the inner bottom surface of the package 50, or conversely warp toward the lid member. However, in the case of the piezoelectric vibration element of the present invention (the piezoelectric vibration element 100 in the illustrated example), the protrusions 11 are formed on the front and back of the corners of the peripheral part 12 facing the pads 24 provided at the corners of the piezoelectric substrate 10. Therefore, even when the piezoelectric vibration element 100 is inclined toward the inner bottom surface side of the package 50 or when the piezoelectric vibration element 100 is warped toward the lid member side, the excitation electrode 20 formed on the excitation portion 14 is formed on the inner bottom surface and the lid member. There is no contact with any of the above. As shown in FIG. 17 (d), when one side (left side in the figure) of the substrate 62 having a uniform thickness is fixed to the base 65 with the adhesive 60, the substrate 62 is inclined downward. Although the lower end A of the other side (right side in the figure) of the substrate 62 is in contact with the upper surface of the base 65, other portions of the substrate 62 are not easily in contact with the upper surface of the base 65. .
Although not shown, the package 50 may contain an IC chip for causing the piezoelectric vibration element 100 to oscillate. The IC chip is electrically connected to the pad 24 via the conductive adhesive 60.
As shown in the embodiment of FIG. 17, according to the piezoelectric vibrator 300, since the piezoelectric vibrator 100 according to the present invention is included, the CI value can be reduced. Further, according to the piezoelectric vibrator 300, since the protrusions 11 are provided along the corners facing the pads 24 of the piezoelectric vibration element 100 or the opposing edges, the piezoelectric vibration element 10 is accommodated in the package 50. At this time, since the excitation electrode 20 does not contact the bottom surface of the package or the lid member, the yield of the piezoelectric vibrator 300 is greatly improved.

5. Experimental Example An experimental example is shown below to describe the present invention more specifically. The present invention is not limited by the following experimental examples.
<5.1 Configuration of Piezoelectric Vibration Element>
As Example 1, a piezoelectric vibration element 100 having a two-stage mesa structure shown in FIGS. 1 and 2 was used. In Example 1, the AT-cut quartz crystal substrate was processed by wet etching using a solution containing hydrofluoric acid to form the piezoelectric substrate 10 having the peripheral portion 12 and the excitation portion 14. The piezoelectric substrate 10 was formed point-symmetrically with respect to a point (not shown) serving as the center of symmetry. The thickness t of the excitation unit 14 (first portion 15) was 0.065 mm, and the vibration frequency was set to 24 MHz. Further, the long side dimension X of the piezoelectric substrate 10 is 1.1 mm (that is, the X side ratio X / t is 17), and the short side dimension Z of the piezoelectric substrate 10 is 0.629 mm (that is, the Z side ratio Z / t). t was set to 9.7), the short side dimension Mz of the excitation unit 14 was set to 0.43 mm, and the side surfaces 14a and 14b extending in the X-axis direction were formed in one plane.

As a comparative example, a piezoelectric vibration element 1000 shown in FIG. 18 was used. 18A is a plan view, and FIG. 18B is a Q8-Q8 cross-sectional view of FIG.
In Comparative Example 1, the excitation unit 1014 was formed in the same shape as the excitation unit 14 of Example 1 except that each side surface extending in the X-axis direction had a step as shown in FIG. Note that the peripheral portion 1012, the excitation electrode 1020, the extraction electrode 1022, and the pad 1024 shown in FIG. 18 are the peripheral portion 12, the excitation electrode 20, the extraction electrode 22, and the pad 24 shown in FIGS. It corresponds to.

<5.2 CI measurement result of distribution>
200 pieces of each of the above-described Example 1 and Comparative Example 1 were manufactured, and these were housed in a package, and the CI value (room temperature) was measured. FIG. 19 is a graph showing the CI value with respect to the measured number, FIG. 19A shows the measurement result of Example 1, and FIG. 19B shows the measurement result of Comparative Example 1. That is, FIG. 19 shows the CI value distribution in Example 1 and Comparative Example 1.
From FIG. 19, it was found that in all samples in Example 1, the CI value was 80Ω or less, which was lower than that in Comparative Example 1. Furthermore, in Example 1, it turned out that the dispersion | variation in CI value is small compared with the comparative example 1. FIG. That is, the CI value can be reduced by forming each of the side surfaces of the excitation unit extending in the X-axis direction in one plane. This is presumably because the formation of each side surface extending in the X-axis direction in one plane can suppress the coupling between the thickness shear vibration in the Z′-axis direction and unnecessary modes such as contour vibration. .

<CI value evaluation for 5.3 Mz / Z>
In the piezoelectric vibration element of Example 1, the thickness t of the excitation unit 14 is fixed to 0.065 mm, the dimension of the short side Mz of the excitation unit 14 is fixed to 0.43 mm, and the dimension Z of the short side of the piezoelectric substrate 10 is set to 0. The CI value (room temperature) was measured by shaking with 46 mm, 0.5 mm, 0.54 mm, 0.59 mm, 0.65 mm, 0.72 mm, 0.81 mm, and 0.92 mm. The measurement was performed by housing the piezoelectric vibration element in a package. FIG. 20 is a graph showing the relationship between Mz / Z and CI value.
From FIG. 20, it was found that the CI value is as low as about 60Ω in the range where Mz / Z is 0.6 or more and 0.8 or less. At this time, Z is 0.54 mm or more and 0.72 mm or less, and the Z side ratio (Z / t) is 8 or more and 11 or less. From the above, by setting the range of the Z side ratio (Z / t) to 8 ≦ Z / t ≦ 11 and the range of Mz / Z to 0.6 ≦ Mz / Z ≦ 0.8 (that is, It was found that the CI value can be reduced by satisfying the above formula (1). This is because by designing Z / t and Mz / Z so as to satisfy Equation (1), the coupling between the thickness shear vibration in the Z′-axis direction and unnecessary modes such as contour vibration can be further suppressed. Inferred.
In addition, Mz was set to 0.4 mm and Z was set to 0.65 mm (that is, Mz / Z = 0.6), and Mz was set to 0.48 mm and Z was set to 0.6 mm (that is, Mz /Z=0.8) The CI value of the piezoelectric vibrating element was measured and found to be about 60Ω. From this, it can be said that the CI value can be reduced as long as the above formula (1) is satisfied without being limited to the case of Mz = 0.43 mm.

  Although the above experimental example was performed on the piezoelectric vibration element having the two-stage type mesa structure shown in FIGS. 1 and 2, the result of this experiment is, for example, a multistage mesa type as shown in FIGS. 12 and 13. The present invention can also be applied to a piezoelectric vibration element having a mesa structure.

FIG. 21A is a cross-sectional view of an example of an embodiment according to the electronic device 400 of the present invention. The electronic device 400 includes a piezoelectric vibration element 100 of the present invention (the piezoelectric vibration element 100 is shown in FIG. 21A, but may be another piezoelectric vibration element of the present invention), and a thermistor that is a temperature-sensitive element. 58 and a package 50 that accommodates the piezoelectric vibration element 100 and the thermistor 58. The package 50 includes a package main body 50a and a lid member 50c. The package body 50a has a cavity 52 for accommodating the piezoelectric vibration element 100 on the upper surface side, and a recess 54a for accommodating the thermistor 58 on the lower surface side. A plurality of element mounting pads 55 a are provided at the end of the inner bottom surface of the cavity 52, and each element mounting pad 55 a is electrically connected to the plurality of mounting terminals 53 by an internal conductor 57. The piezoelectric vibration element 100 is placed on the element mounting pad 55 a, and each pad 24 and each element mounting pad 55 a are electrically connected and fixed via the conductive adhesive 60. A seal ring ring 50b made of Kovar or the like is fired on the upper portion of the package body 50a. A lid member 50c is placed on the seal ring ring 50b and welded by using a resistance welder, and the cavity 52 is sealed. Seal tightly. The cavity 52 may be evacuated or filled with an inert gas.
On the other hand, a recess 54a is formed in the center of the lower surface side of the package body 50a, and an electronic component mounting pad 55b is baked on the upper surface of the recess 54a. The thermistor 58 is mounted on the electronic component mounting pad 55b using solder or the like. The electronic component mounting pad 55 b is electrically connected to the plurality of mounting terminals 53 by the internal conductor 57.

FIG. 21 (b) shows an electronic device 410 according to a modification of FIG. 21 (a), which is different from the electronic device 400 in that a recess 54b is formed on the bottom surface of the cavity 52 of the package body 50a. The thermistor 58 is connected to the electronic component mounting pad 55b fired on the bottom surface through a metal bump or the like. The electronic component mounting pad 55 b is electrically connected to the mounting terminal 53. That is, the piezoelectric vibration element 100 and the thermistor 58 of the temperature sensitive element are accommodated in the cavity 52 and hermetically sealed.
In the above, the example in which the piezoelectric vibration element 100 and the thermistor 58 are accommodated in the package 50 has been described. As an electronic component accommodated in the package 50, an electronic that accommodates at least one of a thermistor, a capacitor, a reactance element, and a semiconductor element. It is desirable to configure the device.

  The embodiment shown in FIGS. 21A and 21B is an example in which the piezoelectric vibration element 100 and the thermistor 58 are accommodated in a package 50. With this configuration, since the thermistor 58 of the temperature sensitive element is located very close to the piezoelectric vibration element 100, there is an effect that a temperature change of the piezoelectric vibration element 100 can be quickly detected. In addition, by configuring an electronic device with the piezoelectric vibration element of the present invention and the above-described electronic component, an electronic device having a piezoelectric vibration element with a small CI can be configured, so that there is an effect that it can be used for various applications.

Next, a piezoelectric oscillator can be constructed by assembling an IC component equipped with an oscillation circuit for driving and amplifying the piezoelectric vibrator to the package of the piezoelectric vibrator using the piezoelectric vibrator according to the present invention. it can.
FIG. 22A is a cross-sectional view of an example of an embodiment according to the piezoelectric oscillator 500 of the present invention. The piezoelectric oscillator 500 includes a piezoelectric vibration element 100 of the present invention (the piezoelectric vibration element 100 is shown in FIG. 22A, but may be another piezoelectric vibration element of the present invention) and a single-layer insulating substrate 70. And an IC (semiconductor element) 88 that drives the piezoelectric vibration element 100 and a convex lid member 80 that hermetically seals the surface space of the insulating substrate 70 including the piezoelectric vibration element 100 and the IC 88. The insulating substrate 70 includes a plurality of element mounting pads 74a and electronic component mounting pads 74b for mounting the piezoelectric vibration element 100 and the IC 88 on the front surface, and mounting terminals 76 for connection to an external circuit on the back surface. . The element mounting pad 74 a and the electronic component mounting pad 74 b and the mounting terminal 76 are electrically connected by a conductor 78 that penetrates the insulating substrate 70. Furthermore, the element mounting pad 74a and the electronic component mounting pad 74b are electrically connected by a conductor wiring (not shown) formed on the surface of the insulating substrate 70. After the IC 88 is mounted on the electronic component mounting pad 74b using a metal bump or the like, the conductive adhesive 60 is applied to the element mounting pad 74a, and the pad 24 of the piezoelectric vibration element 100 is mounted on the IC mounting pad 74a. Harden with to make it conductive and fixed. The convex lid member 80 and the insulating substrate 70 are sealed with a low-melting glass 85 applied to the periphery of the upper surface of the insulating substrate 70. At this time, the inside can be evacuated by performing the sealing step in a vacuum.

  FIG. 22B is a cross-sectional view of a piezoelectric oscillator 510 according to another embodiment of the present invention. The piezoelectric oscillator 510 roughly includes the piezoelectric vibration element 100 of the present invention, a package body 90, an IC 88 that drives the piezoelectric vibration element 100, and a lid member 90c that hermetically seals the piezoelectric vibration element 100. The package body 90 is a so-called H-shaped package body composed of an upper part 90 a having a cavity 52 for accommodating the piezoelectric vibration element 100 and a lower part 90 b having a recess 90 d for accommodating the IC 88. The piezoelectric vibration element 100 is conductively fixed by applying a conductive adhesive 60 to an element mounting pad 74a formed at the end of the bottom of the cavity 52, placing it on this, and thermosetting it. The IC 88 is connected and fixed to the electronic component mounting pad 74b formed on the upper surface of the recess 90d on the lower surface side of the package body 90 by the metal bumps 79. The element mounting pad 74 a and the electronic component mounting pad 74 b are conductively connected by an internal conductor 78. A lid member 90c is placed on a fired seal ring (not shown) on the upper part of the package body 90, welded using a resistance welding machine or the like, and hermetically sealed. The cavity 52 may be evacuated or filled with an inert gas.

FIG. 22C is a cross-sectional view of a piezoelectric oscillator 520 according to another embodiment of the present invention. The piezoelectric oscillator 520 roughly includes the piezoelectric vibrator 300 of the present invention, a package body 90, an IC 88 that drives the piezoelectric vibrator 300, and a lid member 90c that hermetically seals the piezoelectric vibrator 300. The package body 90 is a so-called H-type package body composed of an upper part 90a having a cavity 52 for accommodating the piezoelectric vibrator 300 and a lower part 90b having a recess 90d for accommodating an IC. The piezoelectric vibrator 300 is placed on element mounting pads 74a formed at both ends of the bottom of the cavity 52, and is connected and fixed by solder, metal bumps, or the like. The IC 88 is connected and fixed by a metal bump 79 to an element mounting pad 74 b formed on the upper surface of the recess 90 d on the lower surface side of the package body 90. The element mounting pad 74 a and the electronic component mounting pad 74 b are electrically connected by the internal conductor 78. A lid member 90c is placed on a fired seal ring (not shown) on the upper portion of the package body 90 and welded using a resistance welder. The piezoelectric vibration element is hermetically sealed twice.
The IC 88 includes an oscillation circuit that drives the piezoelectric vibrator 300, a temperature sensing element that senses the temperature around the piezoelectric vibrator 300, a compensation circuit that compensates the frequency temperature characteristics of the piezoelectric vibrator 300, a voltage variable capacitance element, and the like. Can be included.

A piezoelectric oscillator 500 according to the embodiment of FIG. 22A includes a piezoelectric vibration element 100 having a small CI value according to the present invention and an IC (including an oscillation circuit) 88 in a package, and the piezoelectric oscillator is downsized. In addition, since the oscillation current of the oscillation circuit can be reduced, the power consumption can be reduced.
The piezoelectric oscillator 510 of the embodiment of FIG. 22B includes the piezoelectric resonator element 100 having a small CI value according to the present invention and an IC (including an oscillation circuit) 88 in the package, and the piezoelectric oscillator has low power consumption. There is an effect that can be achieved. Further, since the IC 88 can be adjusted from the outside, the frequency temperature characteristic is more excellent, and a multifunctional piezoelectric oscillator can be configured.
Since the piezoelectric oscillator 520 of the embodiment of FIG. 22C uses the piezoelectric vibrator 300 housed in a package, it is possible to configure a piezoelectric oscillator having excellent frequency stability such as aging and having multiple functions and reliability. effective.

The present invention is not limited to the embodiments described above, and various modifications are possible. For example, the present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same purposes and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that achieves the same effect as the configuration described in the embodiment or a configuration that can achieve the same object. In addition, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.
In the electronic device such as the piezoelectric oscillator described above, the piezoelectric vibrator is described as having a configuration including an electronic component typified by a semiconductor element (IC). However, it is preferable to include at least one electronic component. . As the electronic component, a thermistor, a capacitor, a reactance element, or the like can be applied, and an electronic device using a piezoelectric vibrating piece as an oscillation source can be constructed.

DESCRIPTION OF SYMBOLS 10 ... Piezoelectric substrate, 11 ... Projection part, 11a, 11b ... Projection part, 12 ... Peripheral part, 14 ... Excitation part, 14a, 14b ... Side surface extended in X-axis direction, 14c, 14d ... Side surface extended in Z'-axis direction, DESCRIPTION OF SYMBOLS 15 ... 1st part, 16 ... 2nd part, 17 ... 3rd part, 20 ... Excitation electrode, 22 ... Extraction electrode, 24 ... Pad, 30 ... Corrosion-resistant film, 40 ... Resist film, 42 ... Photosensitive part, 50 ... Package 50a, 90 ... package main body, 50b ... seal ring ring, 50c, 80, 90c ... lid member, 52 ... cavity, 53 ... mounting terminal, 54a, 54b, 90d ... recess, 55a, 74a ... element mounting pad, 55b, 74b ... pads for mounting electronic components, 57 ... internal conductor, 58 ... thermistor, 60 ... conductive adhesive, 70 ... insulating substrate, 76 ... mounting terminal, 78 ... conductor, 79 gold ... metal bump, 85 Low melting point glass, 88 ... IC (semiconductor element), 100, 110, 120, 130 ... Piezoelectric vibration element, 101 ... AT-cut quartz substrate, 200 ... Piezoelectric vibration element, 300 ... Piezoelectric vibrator, 400, 410 ... Electronic device, 500, 510, 520 ... Piezoelectric oscillator

Claims (14)

A piezoelectric substrate; excitation electrodes disposed opposite to vibration regions of both principal surfaces of the piezoelectric substrate; an extraction electrode extending from each excitation electrode toward one end of the piezoelectric substrate; and the extraction electrode A piezoelectric vibration element comprising a pad electrically connected and formed at each of two corners of the piezoelectric substrate,
The piezoelectric substrate has an excitation part located in the center, and a peripheral part that is thinner than the thickness of the excitation part and provided at the periphery of the excitation part,
Two opposing side surfaces of the excitation unit are stepless flat surfaces, and the other two opposing side surfaces of the excitation unit each have a step portion in the thickness direction,
A piezoelectric vibration element comprising at least one protrusion on both main surfaces of a region where vibration displacement is sufficiently attenuated when the excitation unit is excited. The piezoelectric substrate is centered on the X axis of an orthogonal coordinate system consisting of an X axis as an electric axis, a Y axis as a mechanical axis, and a Z axis as an optical axis, which are crystal axes of quartz. The axis tilted in the -Y direction of the Y axis is the Z 'axis, the axis tilted in the + Z direction of the Z axis is the Y' axis, and is parallel to the X axis and the Z 'axis. A quartz substrate having a thickness in a direction parallel to the Y ′ axis,
The quartz substrate has a side parallel to the X axis as a long side and a side parallel to the Z ′ axis as a short side and is located in the center of the quartz substrate, and is thinner than the excitation unit on the periphery of the excitation unit. A formed peripheral portion, and
The two side surfaces parallel to the X axis of the excitation unit are stepless planes, and the other two side surfaces of the excitation unit parallel to the Z ′ axis each have a step portion in the thickness direction. The piezoelectric vibration element according to claim 1, wherein:   3. The piezoelectric vibration element according to claim 1, wherein the protrusion is provided at a corner portion on the other end side facing the pads of the piezoelectric substrate.   3. The piezoelectric vibration element according to claim 2, wherein the protrusion is provided along an edge along the Z′-axis facing the pad of the piezoelectric substrate.   The protrusions include a first protrusion portion provided along an edge along the Z ′ axis facing the pad of the piezoelectric substrate, and a longitudinal end portion of the first protrusion portion, respectively. The piezoelectric vibration element according to claim 2, further comprising: a second projecting portion that is bent and provided in a direction along the X axis.   6. The piezoelectric vibration element according to claim 1, wherein the total thickness of the thicknesses of the front and back protrusions and the thickness of the peripheral part is equal to the thickness of the excitation part. When the dimension of the piezoelectric substrate in the direction parallel to the Z ′ axis is Z, the dimension of the short side of the excitation part is Mz, and the thickness of the excitation part is t,
6. The piezoelectric vibration element according to claim 2, wherein the relationship of 8 ≦ Z / t ≦ 11 and 0.6 ≦ Mz / Z ≦ 0.8 is satisfied. When the dimension of the piezoelectric substrate in the direction parallel to the X axis is X,
The piezoelectric vibration element according to claim 2, wherein a relationship of X / t ≦ 17 is satisfied.   A piezoelectric vibrator comprising: the piezoelectric vibration element according to claim 1; and a package that accommodates the piezoelectric vibration element.   A piezoelectric oscillator comprising: the piezoelectric vibration element according to claim 1; an oscillation circuit that drives the piezoelectric vibration element; and a package.   A piezoelectric oscillator comprising the piezoelectric vibrator according to claim 9 and an oscillation circuit that drives the piezoelectric vibrator.   The piezoelectric oscillator according to claim 10 or 11, wherein the oscillation circuit is mounted on an IC.   An electronic device comprising: a package comprising the piezoelectric vibration element according to claim 1 and at least one or more electronic components.   14. The electronic device according to claim 13, wherein the electronic component is one of a thermistor, a capacitor, a reactance element, and a semiconductor element.

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