Piezoelectric vibrating reed, piezoelectric vibrator, and piezoelectric vibrator intermediate

Abstract

To secure an area of a vibration part to the maximum in a piezoelectric vibration piece having a structure in which a fixed part is thicker than the vibration part.SOLUTION: A piezoelectric vibrating reed according to an aspect of the present invention is a piezoelectric vibrating reed that vibrates in a thickness shear mode and has a substantially rectangular shape in a plan view, the piezoelectric vibrating reed including a vibrating portion, an inclined portion, and a fixing portion that are integrally formed and are disposed in this order along a first direction, in which a pair of adhering and fixing portions to which an adhesive for adhering and fixing the piezoelectric vibrating reed to a container is applied are formed in regions in the vicinity of both end portions in a second direction intersecting the first direction in a plan view on a rear surface of the fixing portion. The fixed portion is thicker than the vibrating portion in a third direction intersecting both the first direction and the second direction, the inclined portion becomes thicker in the third direction from the vibrating portion side toward the fixed portion side, and a boundary line between the vibrating portion and the inclined portion is convex toward the fixed portion side in a plan view.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a piezoelectric vibrating piece in which a vibrating portion and a fixed portion that is thicker than the vibrating portion are integrally formed, and to a piezoelectric vibrator and a piezoelectric vibrator intermediate that use this piezoelectric vibrating piece. [Background technology]

[0002] 2. Description of the Related Art In various electronic devices such as mobile phones and personal computers, piezoelectric vibrators such as crystal oscillators and crystal oscillators are widely used for frequency selection and control.

[0003] Known types of such piezoelectric vibrators include those that use an AT-cut quartz crystal piece and those that use a so-called twice-rotated quartz crystal piece, such as an SC-cut. Patent Document 1 shows a type of piezoelectric vibrating piece that uses quartz crystal, in which a vibrating part and a fixed part that is thicker than the vibrating part are integrally formed.

[0004] The schematic configuration of the quartz crystal vibrating piece disclosed in Patent Document 1 is shown in Figure 7. Figure 7(a) is a plan view of the quartz crystal vibrating piece disclosed in Patent Document 1, Figure 7(b) is a cross-sectional view taken along line AA in Figure 7(a), and Figure 7(c) is a cross-sectional view taken along line BB in Figure 7(a). Note that this quartz crystal vibrating piece uses an AT-cut quartz crystal piece.

[0005] As shown in Fig. 7(a), the quartz crystal vibrating piece 100 shown in Patent Document 1 has a substantially rectangular planar shape and is composed of a vibrating portion 101, a fixed portion 102, and a pair of buffer portions 103 located between them and spaced apart in the short-side direction of the quartz crystal vibrating piece 100 across a through-hole 104. Furthermore, in the quartz crystal vibrating piece 100, the thickness of the vibrating portion 101 is set to a thickness corresponding to the target vibration frequency, and the thickness of the fixed portion 102 is made considerably thicker than the vibrating portion 101, as shown in Fig. 7(b). Furthermore, the thickness of the buffer portions 103 increases from the vibrating portion 101 toward the fixed portion 102, as shown in Fig. 7(c).

[0006] In addition, excitation electrodes 201 are formed on the front and back surfaces of the vibrating part 101 to apply a voltage to the vibrating part 101 to vibrate the quartz crystal vibrating piece 100, and connection electrodes 202 are formed on the front and back surfaces of the fixing part 102 to connect the quartz crystal vibrating piece 100 to an external terminal (not shown), and the excitation electrodes 201 and the connection electrodes 202 are electrically connected by wiring parts 203.

[0007] According to Patent Document 1, the disclosed quartz crystal vibrating piece 100 has a sloped portion with a varying thickness in the buffer portion 103 located between the vibrating portion 101 and the fixed portion 102, which can suppress the influence of the fixed portion 102 on the vibrating portion 101. This prevents the crystal impedance (CI) value from increasing. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-34061 Summary of the Invention [Problem to be solved by the invention]

[0009] The fixing portion 102 of the quartz crystal vibrating piece 100 in Patent Document 1 is also required to adhesively fix the quartz crystal vibrating piece 100 to a container (not shown). Furthermore, due to the need for overall device miniaturization, a configuration is generally adopted in which the adhesive is conductive, thereby simultaneously achieving electrical connection from an external terminal. In the quartz crystal vibrating piece 100 in Patent Document 1, a conductive adhesive is applied to the adhesive fixing portion 102a (see FIG. 7(c)) on the back surface of the portion that overlaps the connection electrode 202 formed on the fixing portion 102 in a plan view, thereby simultaneously achieving adhesive fixing of the quartz crystal vibrating piece to the container and electrical connection to the external terminal. The adhesive fixing portion 102a must have a certain area. Therefore, the length of the vibrating portion 101 in the direction along the long sides of the piezoelectric vibrating piece 100 is shorter than the length of the long sides of the piezoelectric vibrating piece 100, resulting in L0, as shown in FIG. 7(c). On the other hand, as shown in FIG. 7(b), even in the region where the through-hole 104 is present, the length of the vibrating portion 101 in the direction along the long side of the quartz crystal vibrating piece 100 is L0, as in FIG. 7(c), even though there is no need to secure an adhesive fixing portion. In the case of a quartz crystal vibrating piece, the larger the effective area of ​​the vibrating portion, the more advantageous it generally is in terms of characteristics and design freedom. In the piezoelectric vibrating piece of Patent Document 1, as described above, more area than necessary is secured for part of the fixing portion, and it cannot be said that the area of ​​the vibrating portion is maximized.

[0010] The present invention has been made in view of the above-mentioned problems, and its object is to maximize the area of ​​the vibrating portion in a piezoelectric vibrating piece having a structure in which the fixed portion is thicker than the vibrating portion. [Means for solving the problem]

[0011] In order to solve the above problem, one embodiment of the piezoelectric vibrating piece of the present invention vibrates in a thickness-shear mode, is a piezoelectric vibrating piece that is approximately rectangular in a planar view, and is composed of a vibrating portion, an inclined portion, and a fixed portion that are integrally formed and arranged in this order along a first direction, and on the back surface of the fixed portion, in the area near both ends in a second direction that intersects with the first direction in a planar view, a pair of adhesive fixing portions are formed to which adhesive is applied for adhesively fixing the piezoelectric vibrating piece to a container, and the fixing portion is thicker than the vibrating portion in a third direction that intersects with both the first and second directions, and the inclined portion becomes thicker in the third direction as it moves from the vibrating portion side to the fixed portion side, and the boundary line between the vibrating portion and the inclined portion is convex toward the fixed portion side in a planar view.

[0012] A piezoelectric vibrator according to an embodiment of the present invention includes the above-described piezoelectric vibrating piece and a container that accommodates the piezoelectric vibrating piece.

[0013] Furthermore, a piezoelectric vibrator intermediate according to one embodiment of the present invention is the above-mentioned piezoelectric vibrating piece, in which a pair of excitation electrodes, an extraction electrode, and a wiring portion electrically connecting the excitation electrodes and the extraction electrode are formed on the front and back surfaces of the piezoelectric vibrating piece, respectively, and the pair of extraction electrodes are formed in an area on the back surface of the fixing portion that overlaps with the adhesive fixing portion, and the wafer is made up of a plurality of piezoelectric vibrating pieces arranged in a matrix. [Effects of the Invention]

[0014] According to the present invention, in a piezoelectric vibrating piece having a structure in which the fixed portion is thicker than the vibrating portion, it is possible to maximize the area of ​​the vibrating portion. Further features related to the present invention will become apparent from the description of the present specification and the accompanying drawings. Furthermore, problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0015] [Figure 1] 1A and 1B are diagrams illustrating a piezoelectric vibrator and a piezoelectric vibrating reed according to an embodiment of the present invention. [Figure 2] FIG. 10 is a diagram for explaining the effect of the present invention. [Figure 3] 10A and 10B are diagrams illustrating a piezoelectric vibrating reed according to a modified example of the present invention. [Figure 4] 5A to 5C are diagrams illustrating an example of a method for manufacturing a piezoelectric vibrator according to an embodiment of the present invention. [Figure 5] 5A to 5C are diagrams illustrating an example of a method for manufacturing a piezoelectric vibrator according to an embodiment of the present invention. [Figure 6] 5A to 5C are diagrams illustrating an example of a method for manufacturing a piezoelectric vibrator according to an embodiment of the present invention. [Figure 7] 1A and 1B are diagrams illustrating a piezoelectric vibrating reed according to a conventional technique. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that each drawing used for the description is merely a schematic illustration to enable understanding of the present invention. In addition, in each drawing used for the description, similar components are designated by the same numerals, and their explanation may be omitted.

[0017] [Example] 1A and 1B are diagrams illustrating a piezoelectric vibrator 10 including a piezoelectric vibrating piece 20 according to an embodiment of the present invention and a container 40 that accommodates the piezoelectric vibrator 10. FIG. 1A is a plan view of the piezoelectric vibrator 10, FIG. 1B is a cross-sectional view taken along line AA in FIG. 1A, and FIG. 1C is a cross-sectional view taken along line BB in FIG. 1A. In each diagram, the coordinate axes defining the directions are set as an X-axis along the long side of the piezoelectric vibrating piece 20, a Y-axis along the short side, and a Z-axis along the thickness direction, but these are not the same as so-called quartz axes.

[0018] 1, the piezoelectric vibrator 10 in this embodiment includes a piezoelectric vibrating piece 20 and a container 40 that houses the piezoelectric vibrating piece 20. Note that a lid member 42, which is part of the container 40, is not shown in the plan view of FIG.

[0019] The piezoelectric vibrating reed 20 is an AT-cut piezoelectric vibrating reed 20 that has a substantially rectangular planar shape and vibrates in a thickness-shear mode. The piezoelectric vibrating reed 20 is composed of a vibrating portion 21, an inclined portion 23, and a fixed portion 22 that are arranged in this order along the X direction.

[0020] The vibrating portion 21 has a thickness (in the Z direction) that corresponds to the vibration frequency required for the piezoelectric vibrating piece 20, and when a predetermined voltage is applied, it stably outputs the required vibration frequency.

[0021] 1(b) and 1(c), the fixing portion 22 has a predetermined thickness that is thicker than the vibrating portion 21 in the Z direction, and has adhesive fixing portions 24 formed on its lower surface (the back surface of the piezoelectric vibrating piece 20) in the areas near both ends in the Y direction, to which adhesive is applied for adhesively fixing the piezoelectric vibrating piece 20 to a container (described later). Note that in FIG. 1(a), the adhesive fixing portions 24 are formed in areas that overlap at least with extraction electrodes 32 (described later).

[0022] 1(a), in this embodiment, the inclined portion 23 located between the vibrating portion 21 and the fixed portion 22 is a crescent-shaped region in plan view, in which the boundary line with the vibrating portion 21 is represented by reference symbol 23a and the boundary line with the fixed portion 22 is represented by reference symbol 23b. Also, as shown in FIGS. 1(b) and 1(c), the inclined portion 23 has the same thickness (in the Z direction) at the boundary with the vibrating portion 21 and at the boundary with the fixed portion 22, and becomes thicker in the Z direction from the vibrating portion 21 toward the fixed portion 22.

[0023] The piezoelectric vibrating piece 20 also has a pair of excitation electrodes 31 formed on the front and back surfaces in the region of the vibrating portion 21. In the region of the fixing portion 22, a pair of extraction electrodes 32 are formed in regions near both ends in the Y direction and overlapping with the adhesive fixing portion 24. Then, on each of the front and back surfaces of the piezoelectric vibrating piece 20, wiring portions 33 are formed to electrically connect the excitation electrodes 31 and the extraction electrodes 32.

[0024] The excitation electrode 31, extraction electrode 32, and wiring portion 33 described above are integrally formed, and have a laminated structure in which, for example, the base film is a chromium film and the main film on the base film is a gold film.

[0025] The container 40 includes a base 41 and a lid member 42 connected to the base 41 to form a sealed space in cooperation with the base 41. The base 41 defines a space for mounting the piezoelectric vibrating piece 20, and the piezoelectric vibrating piece 20 is mounted on the bottom surface of the space (the inner bottom surface of the base 41) via connection pads 50. The piezoelectric vibrating piece 20 and the connection pads 50 are bonded and fixed together with a conductive adhesive 60 applied to the adhesive fixing portion 24. The conductive adhesive 60 is an adhesive made of an organic binder resin (e.g., epoxy resin) containing conductive particles (e.g., silver particles). An external connection terminal 70 is disposed on the outer bottom surface of the base 41 for connecting the piezoelectric vibrator 10 to an external device. The connection pads 50 and the external connection terminals 70 are connected by via wiring or castellation (not shown). The base 41 can be formed, for example, as a ceramic container. The lid member 42 is flat and can be formed of any structure and material depending on the sealing method.

[0026] 1(a), in the present embodiment, the boundary line 23a between the vibrating portion 21 and the inclined portion 23 has a convex shape toward the fixed portion 22 side in a plan view. In the present embodiment, the boundary line 23a has an arc shape that convex toward the fixed portion 22 side.

[0027] Here, in this specification, "boundary line 23a is convex toward fixed portion 22" means that when a line segment is drawn between any two points on boundary line 23a, all boundary lines 23a at any position between the two points are located closer to fixed portion 22 than boundary line 23a.

[0028] However, in the present invention, the main focus is to expand the area of ​​the vibrating part more than conventionally in the region where the adhesive fixing part is not formed on the fixed part, as will be described later, so it is sufficient that the vibrating part is convex toward the fixed part 22 at least in the region that does not overlap with the region where the adhesive fixing part is formed when viewed in the Y direction.

[0029] As described above, in this embodiment, the adhesive fixing portions 24 are formed spaced apart in regions near both ends of the fixing portion 22 in the Y direction. Under these circumstances, by setting the boundary line 23a between the vibrating portion 21 and the inclined portion 23 to have a shape that is convex toward the fixing portion 22 as shown in FIG. 1A, a sufficient area is ensured for the adhesive fixing portion 24, which is the region necessary for adhesively fixing the piezoelectric vibrating reed 20 to the container 40. In this case, as shown in FIG. 1C, the length of the vibrating portion 21 in the X direction in this region is L2. Meanwhile, as shown in FIG. 1B, in regions where no adhesive fixing portions are formed on the fixing portion 22, the length of the vibrating portion 21 in the X direction is L1, which is longer than L2. Therefore, by ensuring that the length of the vibrating portion 21 in the X direction is longer in regions where no adhesive fixing portions are formed than in regions where adhesive fixing portions are formed, it is possible to maximize the area of ​​the vibrating portion 21, thereby improving the characteristics and design flexibility of the piezoelectric vibrating reed 20.

[0030] FIG. 2 is a diagram specifically illustrating the effects of the present invention. In FIG. 2, only the piezoelectric vibrating piece 20 is shown, and the electrodes, container, and the like are omitted. As described above, in this embodiment, the boundary line 23a between the vibrating portion 21 and the inclined portion 23 is convex toward the fixed portion 22 in a plan view. On the other hand, in the prior art, the length of the vibrating portion in the long side direction is a constant value L0 in all regions. Therefore, in the prior art, the end edge of the vibrating portion on the fixed portion side can be represented as 23c. For these reasons, in this embodiment, it is possible to increase the area of ​​the vibrating portion 21 by the shaded area surrounded by the boundary lines 23a and 23c compared to the prior art.

[0031] [Variations] A piezoelectric vibrating reed according to a modified example of the present invention will be described with reference to FIG. In the above example, the fixed portion 22 existed as an integral region defined by an end edge on the +X side, a boundary line 23b with the inclined portion 23, and a pair of end edges facing each other in the Y direction. Both the boundary lines 23a and 23b were arc-shaped.

[0032] However, the shape of the region of the vibrating portion 21 is not limited to the above, and may be, for example, as shown in Figure 3(a), a shape in which the fixed portion 22 is divided in the Y direction by a boundary line 23b with the inclined portion 23, or as shown in Figure 3(b), a convex shape in which the boundary lines 23a, 23b protrude at an acute angle toward the fixed portion 22 (a so-called L-shape in Figure 3(b)).

[0033] 3, it is also possible to maximize the area of ​​vibrating section 21. In particular, by adopting a configuration in which fixed section 22 is separated in the Y direction by boundary line 23b with inclined section 23 (with boundary line 23b being moved as close to the +X side as possible), it is possible to move boundary line 23a between vibrating section 21 and inclined section 23 closer to the +X side by that amount, and it is possible to further increase the area of ​​vibrating section 21.

[0034] However, in a configuration in which the fixed portion 22 is divided in the Y direction by the boundary line 23a between the inclined portion 23 and the fixed portion 22, the boundary line 23a moves closer to the +X side, thereby reducing the area of ​​the fixed portion 22. As described above, the fixed portion 22 is also required to have an area for the adhesive fixing portion formed on the lower surface, so it is preferable to ensure that the area of ​​the fixed portion 22 is at least a predetermined ratio to the area of ​​the piezoelectric vibrating piece 20.

[0035] In the above embodiment, the container 40 is an example of a container including a base 41 having an internal space and a lid member 42 joined to the base. However, the container may have another structure. For example, although not shown, the container may be a container including a plate-shaped base and a cap-shaped lid member having a recess that accommodates the piezoelectric vibrating piece 20.

[0036] Furthermore, in the above embodiment, an example was shown in which an AT-cut quartz crystal piece was used as the piezoelectric vibrating piece, but the present invention can also be applied to a so-called two-turn piezoelectric vibrating piece, such as an SC-cut.

[0037] [Piezoelectric vibrator intermediate] To deepen understanding of the piezoelectric vibrating piece and piezoelectric vibrator described above, an example of a method for manufacturing the piezoelectric vibrator 10 will be described with reference to Figures 4 to 6. The following description will focus on the case where quartz crystal is used as the piezoelectric vibrator. Many piezoelectric vibrators 10 can be manufactured from a quartz crystal wafer using photolithography and wet etching techniques. Therefore, some of the figures used in the following description of the manufacturing method show a plan view of the quartz crystal wafer 10w and an enlarged plan view of a portion M of the quartz crystal wafer. Each figure also shows the surface of the quartz crystal wafer 10w.

[0038] First, prepare a quartz crystal wafer 10w as shown in Figure 4(a). As is well known, the oscillation frequency of an AT-cut piezoelectric vibrating piece 10 is largely determined by the thickness of the main surface (XZ' plane) of the quartz crystal piece. However, in the case of the present invention, since a fixing portion is provided that is thicker than the vibrating portion, the prepared quartz crystal wafer 10w is thicker than the final vibrating portion.

[0039] Next, as shown in Figure 4(b), wet-etching-resistant masks 80 for defining the outlines of the quartz crystal pieces are formed on both the front and back surfaces of the quartz crystal wafer 10w using well-known film-forming and photolithography techniques. In this embodiment, the wet-etching-resistant masks 80 are shaped to cover the portions corresponding to the outlines of the quartz crystal pieces and the frame portions 10x that hold the quartz crystal pieces.

[0040] Next, the quartz crystal wafer with the wet-etching-resistant mask 80 formed thereon is immersed in a wet etching solution for a predetermined period of time. This allows the outline of the quartz crystal piece to be formed. Next, as shown in Figure 5(a), a vibrating portion forming mask 82 is formed on the front and back of the wafer after the outline has been formed, exposing the portion that will become the vibrating portion. However, the vibrating portion forming mask 82 has a long, narrow opening 82a between the frame portion and the fixed portion (see reference numeral 22 in Figure 1) that allows the etchant to penetrate but does not penetrate all the way through the quartz crystal wafer. The reason for this is to form a recess 82a that will serve as the starting point for breaking off the quartz crystal piece when it is separated from the frame portion.

[0041] Next, as shown in Figure 5(b), the quartz crystal wafer with the wet-etching-resistant mask 82 formed thereon is immersed in a wet etching solution for a predetermined time. After that, the wet-etching-resistant mask 82 is removed. This allows the vibrating portion 21, the fixed portion 22, and the break-off starting point portion 84 to be formed. At this time, the inclined portion 23 is also formed on the back surface.

[0042] Next, as shown in Figure 6(a), excitation electrodes 31 and extraction electrodes 32 are formed using known film formation and photolithography techniques. This results in a piezoelectric vibrator intermediate 90 including a large number of crystal pieces according to the embodiment of the present invention. At this time, inspection electrode pads 86 are formed on the frame portion to enable characteristic inspection of the piezoelectric vibrator in wafer form. Thereafter, electrical characteristic inspections and the like are carried out in wafer form as needed.

[0043] Finally, as shown in Figure 6(b), an appropriate force is applied to an appropriate location on the crystal blank 10 to break it off, and the crystal blank 10 is broken off from the frame using the break-off starting point 84. Of course, the intermediate product 90 can also be traded commercially.

[0044] The present invention is not limited to the above-described embodiments, and various design modifications may be made without departing from the spirit of the present invention as defined in the claims. For example, the above-described embodiments have been described in detail to facilitate understanding of the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0045] 10 Piezoelectric vibrator (quartz crystal vibrator), 10w quartz crystal wafer, 20 Piezoelectric vibrating piece (quartz crystal vibrating piece), 21 Vibrating part, 22 Fixing part, 23 Sloping part, 23a, 23b Boundary line, 24 Adhesive fixing part, 31 Excitation electrode, 32 Extraction electrode, 33 Wiring part, 40 Container, 90 Piezoelectric vibrator intermediate body

Claims

1. A piezoelectric vibrating piece that vibrates in a thickness shear mode and has a substantially rectangular shape in a plan view, a vibration portion, an inclined portion, and a fixed portion that are integrally formed and arranged in this order along a first direction; a pair of adhesive fixing portions to which an adhesive is applied for adhesively fixing the piezoelectric vibrating piece to a container are formed in a rear surface of the fixing portion and in a region near both ends in a second direction intersecting the first direction in a plan view; the fixed portion is thicker than the vibrating portion in a third direction that intersects both the first direction and the second direction, the inclined portion becomes thicker in the third direction from the vibrating portion side toward the fixed portion side, a boundary line between the vibration portion and the inclined portion that is convex toward the fixed portion in a plan view; A piezoelectric vibrating piece characterized by:

2. The piezoelectric vibrating piece according to claim 1 , A pair of excitation electrodes, a pair of extraction electrodes, and a wiring portion electrically connecting the excitation electrodes and the extraction electrodes are formed on the front and back surfaces of the piezoelectric vibrating piece, respectively; the pair of extraction electrodes are formed on the rear surface of the fixing portion in an area overlapping with the adhesive fixing portion; A piezoelectric vibrating piece characterized by:

3. The piezoelectric vibrating piece according to claim 1 , The boundary line is an arc that is convex toward the fixed portion in a plan view. A piezoelectric vibrating piece characterized by:

4. The piezoelectric vibrating piece according to claim 1 , The boundary line has a convex shape protruding toward the fixed portion in a plan view. A piezoelectric vibrating piece characterized by:

5. The piezoelectric vibrating piece according to claim 1 , the fixed portion is divided in the second direction by a boundary line between the fixed portion and the inclined portion; A piezoelectric vibrating piece characterized by:

6. A piezoelectric vibrating piece according to claim 2, comprising: a container for accommodating the piezoelectric vibrating piece; A piezoelectric vibrator characterized by:

7. A wafer in which a plurality of the piezoelectric vibrating pieces according to claim 2 are arranged in a matrix. A piezoelectric vibrator intermediate body characterized by:

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