Tuning fork-type piezoelectric vibration device

Abstract

Provided is a tuning fork-type piezoelectric vibrator (1) having at least a tuning fork-type piezoelectric vibrating piece (2) mounted in a container (3). The fork-type piezoelectric vibrating piece (2) comprises: a base part (20); a pair of vibrating arm parts (21, 22) extending in a first direction from one end side of the base part (20); and metal bumps (7a, 7b) joined to the container (3). The pair of vibrating arm parts (21, 22) have: widening parts (212, 222) having weights at the respective leading end sections; and widened parts (211, 221). The center (P) of the container (3) in a plan view is disposed in a region surrounded by a virtual outer peripheral frame (H1) of the widened parts (211, 221) and the widening parts (212, 222).

Description

Tuning fork type piezoelectric vibration device

[0001] The present invention relates to a tuning-fork type piezoelectric vibrating device equipped with a tuning-fork type piezoelectric vibrating piece in which a pair of vibrating arms vibrates in a flexural vibration mode.

[0002] Tuning-fork type piezoelectric vibrating pieces have been widely used as frequency sources for reference signals in clocks, etc. Such piezoelectric vibrating pieces are used as surface-mount tuning-fork type piezoelectric vibrators, for example, by bonding them to the inside of a recessed insulating base (container) and hermetically sealing the recessed portion with a lid.

[0003] One such tuning fork-type piezoelectric vibrator has been disclosed, in which a tuning fork-type piezoelectric vibrating piece having a metal film for frequency adjustment formed on the wide portion formed at the tip of the vibrating arm is bonded to the upper surface of a step portion provided inside a container (see, for example, Patent Document 1).

[0004] Patent Publication No. 2021-141368

[0005] However, as described in Patent Document 1, when the tuning-fork-type piezoelectric vibrating piece is arranged inside the container so that the wide portion on which the metal film for frequency adjustment is formed is near the longitudinal end of the container, there is a risk that the vibration change of the tuning-fork-type piezoelectric vibrating piece in a vibrating state will be biased depending on the direction of the impact applied to the container. In other words, there has been a demand for a tuning-fork-type piezoelectric vibrating device that suppresses the bias of the vibration change of the tuning-fork-type piezoelectric vibrating piece caused by the direction of the impact applied to the tuning-fork-type piezoelectric vibrating device and has improved stability of vibration characteristics.

[0006] The present invention has been made in view of the above-mentioned problems, and has an object to provide a tuning-fork type piezoelectric vibration device with improved stability of vibration characteristics.

[0007] The present invention is a tuning fork-type piezoelectric vibration device having at least a tuning fork-type piezoelectric vibration piece mounted inside a container, wherein the tuning fork-type piezoelectric vibration piece comprises a base, a pair of vibrating arms extending in a first direction from one end side of the base, and a joining member joined to the container, and the pair of vibrating arms have vibration characteristic adjustment parts with weights attached to their respective tips, and the tuning fork-type piezoelectric vibration device is characterized in that the center of the container in a planar view is located within an area surrounded by the virtual outer frames of the pair of vibration characteristic adjustment parts.

[0008] That is, the tuning-fork-type piezoelectric vibrating device of the present invention has a pair of vibrating arms each having a weighted vibration characteristic adjustment unit at its tip, and the center of the container in a planar view is located within a region surrounded by the virtual outer frame of the pair of vibration characteristic adjustment units. With this configuration, when an external impact is applied to the tuning-fork-type piezoelectric vibrating device, the bias in the vibration of the vibrating arms of the mounted tuning-fork-type piezoelectric vibrating reed can be suppressed. More specifically, in the tuning-fork-type piezoelectric vibrating reed, the weighted vibration characteristic adjustment unit at the tip of the vibrating arm is more affected by the vibration caused by the impact on the container. Therefore, depending on the direction of the impact on the container, the closer the position of the impact is to the vibration characteristic adjustment unit, the greater the change in the vibration state of the vibration characteristic adjustment unit and the vibrating arms having the vibration characteristic adjustment unit. With this configuration, the vibration characteristic adjustment unit is located near the center of the container, which is least displaced by the external impact in a planar view, and this suppresses bias in the vibration change of the tuning-fork-type piezoelectric vibrating reed depending on the direction of the impact on the container. That is, a tuning fork type piezoelectric vibration device with improved stability of vibration characteristics can be obtained.

[0009] The vibration characteristic adjusting section may be configured to be wide on the vibrating arm section, and this configuration allows the area of ​​the vibration characteristic adjusting section in a plan view to be increased, thereby widening the adjustment range of the vibration characteristics.

[0010] Furthermore, the tuning-fork-type piezoelectric vibrating piece may include a support arm extending from the other end of the base in a direction opposite to the first direction, the bonding member being provided on the support arm, the container having a step therein, the step having a mounting portion on its upper surface that is bonded to the bonding member, and an edge of the step in the first direction overlapping the base in a plan view. With this configuration, when the tuning-fork-type piezoelectric vibrating device receives an external impact, a relatively weak portion of the internal tuning-fork-type piezoelectric vibrating piece comes into contact with the step of the container, preventing the tuning-fork-type piezoelectric vibrating piece from breaking (breaking) due to the "leverage principle" with the contact portion as a fulcrum.

[0011] The bonding member may also be formed of a metal bump. With this configuration, the tuning-fork-type piezoelectric vibrating piece and the container can be bonded using a metal bump. Metal bump bonding can improve the bonding strength between the container and the tuning-fork-type piezoelectric vibrating piece compared to bonding using an adhesive. Furthermore, improved bonding strength can make it easier for vibrations caused by an impact on the tuning-fork-type piezoelectric vibrating device to be transmitted to the tuning-fork-type piezoelectric vibrating piece, which, together with internal displacement caused by the impact, can significantly change the vibration characteristics. However, with a configuration such as the present invention, in which the center of the container in a plan view is located within an area surrounded by the outer frames of a pair of vibration characteristic adjusters, changes in the vibration state of the tuning-fork-type piezoelectric vibrating piece due to internal displacement caused by the impact can be suppressed, thereby suppressing changes in the vibration characteristics of the tuning-fork-type piezoelectric vibrating piece. In other words, a tuning-fork-type piezoelectric vibrating device with improved stability of vibration characteristics can be achieved.

[0012] The bonding member may be formed of a plurality of the bumps, and with this configuration, the tuning-fork type piezoelectric vibrating piece can be bonded to the container more firmly.

[0013] According to the present invention, it is possible to provide a tuning fork type piezoelectric vibration device with improved stability of vibration characteristics.

[0014] FIG. 1 is a plan view of a tuning fork type piezoelectric vibrator according to a first embodiment. FIG. 2 is a cross-sectional side view taken along line A-A of the tuning fork type piezoelectric vibrator in a state where it is hermetically sealed with a lid in FIG. 1. FIG. 3 is a schematic plan view of one main surface side of a tuning fork type piezoelectric vibrating piece according to the first embodiment. FIG. 4 is an enlarged plan view of the vicinity of the wide portion in FIG. 1. FIG. 5 is an enlarged plan view of the vicinity of the support arm and base in FIG. 1. FIG. 6 is a schematic plan view of one main surface side of a tuning fork type piezoelectric vibrating piece according to another embodiment 1. FIG. 7 is a schematic plan view of one main surface side of a tuning fork type piezoelectric vibrating piece according to another embodiment 2. FIG. 8 is a schematic plan view of one main surface side of a tuning fork type piezoelectric vibrating piece according to another embodiment 3.

[0015] An example of an embodiment will be described in detail below with reference to the drawings. Note that in this specification, the various electrodes formed on the piezoelectric vibrating reed (tuning fork-type piezoelectric vibrating reed) are omitted. Also, the X-axis direction (X-direction) in each drawing and this specification is the same as the X-axis direction of the quartz crystal axis, the Y-axis direction (Y-direction) is the same as the Y-axis direction of the quartz crystal axis (or the Y' direction tilted a few degrees from the Y-axis), and the Z-axis direction (Z-direction) is the same as the Z-axis direction of the quartz crystal axis (or the Z' direction tilted a few degrees from the Z-axis).

[0016] Fig. 1 is a plan view of a tuning fork type piezoelectric vibrator 1 according to the first embodiment, and Fig. 2 is a cross-sectional side view taken along line A-A of the tuning fork type piezoelectric vibrator 1 in a state where it is hermetically sealed with a lid 4 in Fig. 1. In this specification, the bottom and top are described with the depth direction in Fig. 1 being the bottom side of the tuning fork type piezoelectric vibrator 1 and the front direction being the top side of the tuning fork type piezoelectric vibrator 1.

[0017] The tuning fork type piezoelectric vibrator 1 (crystal vibrator 1) in the first embodiment (present embodiment) is a surface-mount type crystal vibrator having a substantially rectangular parallelepiped package structure. The external dimensions of the crystal vibrator 1 are not particularly limited, and various known dimensions can be used depending on the application.

[0018] 2, in the quartz crystal resonator 1 according to this embodiment, a tuning-fork type piezoelectric vibrating piece 2 (quartz crystal vibrating piece 2) is housed in a recess 5 of a container 3 made of an insulating material, and then a flat lid 4 is bonded to the open end of the container 3 so as to cover the recess 5, thereby airtightly sealing the quartz crystal vibrating piece 2 in the internal space. The container 3 and the lid 4 are bonded together via a sealing material (not shown).

[0019] The container 3 is a box-shaped body made of an insulating material primarily composed of a ceramic such as alumina. For example, the container 3 is formed by stacking three ceramic green sheets and sintering them together to form a lower layer 3a, a middle layer 3b, and an upper layer 3c. In this embodiment, the rectangular frame-shaped middle layer 3b is stacked on the bottommost lower layer 3a, and the rectangular frame-shaped upper layer 3c is stacked on top of the middle layer 3b. Therefore, the container 3 has a rectangular recess 5 in plan view, with the top surface of the lower layer 3a as its bottom and the middle layer 3b and upper layer 3c as a frame-shaped bank portion 30. The middle layer 3b protrudes from the top surface of the lower layer 3a toward the recess 5, and a portion of it forms a step 31 on which the quartz crystal vibrating piece 2 is mounted. A sealing material (not shown) is formed in a frame shape in a plan view on the upper surface 300 of the bank portion 30 (upper layer portion 3 c ), and the sealing material corresponds to the outer peripheral portion of the lid 4 .

[0020] The step portion 31 forms an edge 32 as an end surface that protrudes relative to the recess 5 in a plan view. The step portion 31 also has two mounting pads 6a, 6b on its upper surface that are conductively bonded to the quartz crystal vibrating piece 2. The mounting pads 6a, 6b are formed in parallel with a gap between them and are connected to metal bumps 7a, 7b on the quartz crystal vibrating piece 2 by bump bonding, respectively. In other words, the mounting pads 6a, 6b correspond to the mounting portion in the present invention. The two mounting pads 6a, 6b have opposite polarities and are electrically connected to multiple external connection terminals 8 provided on the outer bottom surface of the container 3 via internal wiring and vias (not shown).

[0021] In this embodiment, the two mounting pads 6 a and 6 b are formed by laminating nickel and gold in this order on the upper surface of a tungsten metallization layer using a method such as plating. Note that molybdenum may be used as the metallization layer instead of tungsten.

[0022] The lid 4 may be, for example, a metal lid body having a rectangular shape in plan view and made of Kovar as a base. Furthermore, the lid 4 may have, for example, a nickel-plated layer on the outer periphery of the surface to be joined with the container 3, on which a metallic brazing material is formed in a circumferential direction. Furthermore, the lid 4 and the container 3 may be joined by brazing or seam welding.

[0023] 3 is a schematic plan view of one main surface of a tuning-fork type piezoelectric vibrating piece (quartz crystal vibrating piece) 2 according to an embodiment of the present invention. For ease of explanation, of the two opposing main surfaces of the quartz crystal vibrating piece 2, the main surface that faces the mounting pads 6a and 6b when mounted on the container 3 will be referred to as the back surface, and the other main surface will be referred to as the front surface. In other words, FIG. 3 is a plan view of the quartz crystal vibrating piece 2 as seen from the front surface side.

[0024] The quartz crystal vibrating piece 2 is a thin quartz crystal Z-plate having a thickness in the Z direction. The quartz crystal vibrating piece 2 includes a base 20, a pair of vibrating arms 21 and 22 that are parallel to one another and protrude (extend) in the Y direction (first direction) from one end of the base 20, and a support arm 23 that protrudes in the -Y direction (the opposite direction to the vibrating arms 21 and 22) from the other end opposite the one end of the base 20 and further protrudes (extends) in the X direction (second direction) by bending. Therefore, the quartz crystal vibrating piece 2 is a tuning-fork-shaped piezoelectric vibrating piece in a planar view, and the end opposite the longitudinal vibrating arms 21 and 22 is formed into a substantially L-shape in a planar view by the support arm 23. Furthermore, because the support arm 23 is formed in an L-shape, a constriction is formed between the base 20 and the extending portion of the L-shape. In this embodiment, the vibrating arms 21 and 22 are formed to extend in the +Y direction, but they may also be formed to extend in the -Y direction. Also, in this embodiment, the support arm 23 is formed to extend in the +X direction, but it may also be formed to extend in the -X direction. It is preferable that the support arm 23 is formed to extend in the +X direction.

[0025] The shape of the quartz crystal vibrating piece 2 of this embodiment (the vibrating arms 21, 22, base 20, and support arms 23 that constitute the quartz crystal vibrating piece 2) is formed, for example, by wet etching a quartz crystal blank (not shown), which is a quartz crystal piece made of anisotropic material.

[0026] In this embodiment, the base 20 has a bilaterally symmetrical shape (symmetrical in the X direction) in a planar view. The base 20 is wider (longer in the X direction) than the vibrating arms 21 and 22. The other end of the base 20 (near the boundary with the support arm 23) is gradually narrower from the vibrating arms 21 and 22 toward the support arm 23. The base 20 may also have one or more through holes penetrating in the Z direction (see FIGS. 7 and 8). Such a configuration with through holes ensures electrical continuity of the extraction electrodes, described below. Furthermore, by efficiently attenuating mechanical vibrations of the tuning fork vibrating arms during operation and suppressing propagation of vibrations to the support arm 23, acoustic leakage and the equivalent series resistance (Crystal Impedance, CI) can be reduced.

[0027] The pair of vibrating arms 21, 22 are formed continuously from the base 20. The pair of vibrating arms 21, 22 include arm portions 214, 224 formed continuously from the base 20 to extend in the first direction, widened portions 212, 222 formed continuously from the arm portions 214, 224 and gradually widening in the first direction, and widened portions 211, 221 (weight portions) formed continuously from the widened portions 212, 222 and wider than the arm portions 214, 224. That is, the widened portions 211, 221 form the tip portions of the vibrating arms 21, 22 in the first direction (Y direction). Each corner of the widened portions 211, 221 on the tip side is chamfered. The vibrating arms 21, 22 have a pair of main surfaces facing each other in the Z direction and a pair of side surfaces facing each other in the X direction.

[0028] Long grooves are formed on the main surfaces of the pair of vibrating arms 21 and 22 to further reduce the equivalent series resistance (Crystal Impedance, CI value). More specifically, a long groove 213 is formed on the surface of the vibrating arm 21, and a long groove (not shown) is formed on the back surface, with the long grooves facing each other. A long groove 223 is formed on the surface of the vibrating arm 22, and a long groove (not shown) is formed on the back surface, with the long grooves facing each other. The long grooves 213 and 223 formed on the surface of each of the vibrating arms 21 and 22, and the long groove (not shown) formed on the back surface, are formed with a predetermined depth (length in the Z direction) and width (length in the X direction) on the front and back surfaces of each of the vibrating arms 21 and 22. One end of each long groove in the Y direction extends to the region of the base 20, and the other end is formed at the boundary between the arm 214, 224 and the widened portion 212, 222. That is, all of the long grooves have a longitudinal direction along the protruding direction of the vibrating arms 21, 22 (first direction, Y direction) and a width direction along the juxtaposed direction of the vibrating arms 21, 22 (second direction, X direction). Furthermore, excitation electrodes (not shown) described below are formed inside each long groove. Furthermore, each long groove is formed by wet etching.

[0029] In this embodiment, the combined portion of the widened portions 212, 222 and the widened portions 211, 221 is weighted by being wider than the arm portions 214, 224. That is, the widened portions 212, 222 and the widened portions 211, 221 serve as vibration characteristic adjustment portions in the present invention. When the quartz crystal vibrating piece 2 is formed by wet etching, its vibration characteristics change depending on the widthwise size of the widened portions 212, 222 and the widened portions 211, 221.

[0030] The support arm 23 is formed to protrude in the -Y direction from the other end side of the base 20 (the side opposite to where the vibrating arms 21 and 22 protrude). That is, the support arm 23 is formed to protrude in the first direction from the other end side of the base 20. The support arm 23 also has an L-shape that extends in the X direction from the end opposite the base 20 side.

[0031] In this embodiment, the support arm 23 has a metal bump 7a on the rear main surface of one end in the X direction, and a metal bump 7b on the rear main surface of the other end, at the end opposite the base 20 in the Y direction. The metal bumps 7a and 7b are plated bumps formed by electrolytic plating. The metal bump 7a is bonded to the mounting pad 6a of the container 3 when the quartz crystal vibrating piece 2 is mounted on the container 3, and the metal bump 7b is bonded to the mounting pad 6b. In other words, the metal bumps 7a and 7b correspond to the bonding members of the present invention. Note that in this embodiment, the metal bumps 7a and 7b are provided at both ends of the support arm 23 in the X direction, respectively. However, the position, shape, and number of the metal bumps on the support arm 23 are not particularly limited as long as multiple metal bumps are bonded to both the mounting pads 6a and 6b of the container 3. That is, in this embodiment, the metal bumps 7a, 7b have an elliptical shape and the same size, but the shapes of the metal bumps 7a, 7b are not particularly limited and can be various shapes, and the metal bumps 7a and 7b may have shapes that are different in size or outline from each other. Also, in this embodiment, the support arm 23 is configured to have two metal bumps 7a, 7b, but it is sufficient that the support arm 23 has at least two metal bumps of opposite polarities. That is, the support arm 23 may have three or more metal bumps (see FIG. 8 ).

[0032] The quartz crystal vibrating piece 2 also includes first and second excitation electrodes configured at different potentials, and lead electrodes extending from the first and second excitation electrodes via lead electrodes. The first excitation electrodes are formed on the front and back principal surfaces, including the inner circumferential surfaces of the long grooves of one vibrating arm 21, and on the outer and inner surfaces of the other vibrating arm 22 via lead electrodes. Similarly, the second excitation electrodes are formed on the front and back principal surfaces, including the inner circumferential surfaces of the long grooves of the other vibrating arm 22, and on the outer and inner surfaces of one vibrating arm 21 via lead electrodes. The lead electrodes extending from the first excitation electrode are connected to metal bump 7b, and the lead electrodes extending from the second excitation electrode are connected to metal bump 7a. Note that the electrode patterns are not shown in the drawings. By applying an electric field to the first excitation electrode and the second excitation electrode, which are configured at different potentials, the pair of vibrating arms 21, 22 flexurally vibrate with predetermined vibration characteristics. At this time, the vibration gradually increases from a position close to the base 20 of the vibrating arms 21, 22 toward the tip, and the vibration is greatest at the wide portions 211, 221 that form the tip of the vibrating arms 21, 22.

[0033] The first excitation electrode, the second excitation electrode, and the routing electrode are formed by laminating a gold layer on the upper surface of a base metal layer, which is the base. The metal that forms the base metal film can be, for example, chromium or titanium. The first excitation electrode, the second excitation electrode, and the routing electrode can be formed by sputtering and photolithography. The metal bumps 7a and 7b are formed by further plating the upper surfaces of the routing electrodes with gold. The metal bumps 7a and 7b can be formed by electrolytic plating.

[0034] Additionally, frequency-adjustment metal films 215, 225, which function as frequency-adjustment weights, are formed on the major surfaces of the wide portions 211, 221. The frequency-adjustment metal films 215, 225 are, for example, metal films containing gold, and are formed by laminating them on the excitation electrodes by vapor deposition after the first and second excitation electrodes are formed. The frequency, which is one of the vibration characteristics of the quartz crystal vibrating piece 2, varies slightly depending on the amount of the frequency-adjustment metal films 215, 225. Therefore, fine adjustment of the vibration characteristics (frequency) of the quartz crystal vibrating piece 2 is performed by varying the amount of the frequency-adjustment metal films 215, 225. Fine frequency adjustment is performed, for example, by reducing the mass of the frequency-adjustment metal films 215, 225 by ion beam irradiation or ion milling, or by depositing a larger amount of metal by vapor deposition. The frequency-adjustment metal films 215, 225 are also provided on the wide portions 211, 221, which constitute the vibration characteristic adjustment section. Therefore, the frequency adjustment metal films 215, 225 are part of the vibration characteristic adjustment section. The frequency adjustment metal films 215, 225 may be formed on only one of the front and back surfaces of the wide portions 211, 221, or may be formed on both surfaces. When the frequency adjustment metal films 215, 225 are formed on both the front and back surfaces, the weight balance of the vibration characteristic adjustment section of the quartz crystal vibrating piece 2 can be improved. Furthermore, when the frequency adjustment metal films 215, 225 are formed on only one of the front and back surfaces, the generation of foreign matter can be suppressed when the frequency adjustment metal films 215, 225 are irradiated with a laser for frequency adjustment. In this embodiment, the frequency adjustment metal films 215, 225 are formed on the front surface (the main surface on the front side).

[0035] FIG. 4 is an enlarged plan view of the vicinity of the wide portions 211 and 221 in FIG. 1 , and FIG. 5 is an enlarged plan view of the vicinity of the support arm 23 and base 20 in FIG. 1 . In the quartz crystal resonator 1, the quartz crystal resonator piece 2 is mounted on the container 3 by bonding the metal bumps 7a and 7b of the quartz crystal resonator piece 2 to the mounting pads 6a and 6b. The metal bumps 7a and 7b and the mounting pads 6a and 6b are each conductively bonded using FCB (flip chip bonding). That is, the quartz crystal resonator piece 2 is bonded to the container 3 by bumps formed by metal plating (plated bumps). More specifically, the top layer of the metal film forming the mounting pads 6a and 6b is diffusion bonded to the metal bumps 7a and 7b. Therefore, in this embodiment, the gold film forming the top layer of the mounting pads 6a and 6b is diffusion bonded to the metal bumps 7a and 7b. More specifically, the metal bumps 7 a, 7 b are made of gold (Au), and the metal bumps 7 a, 7 b and the mounting pads 6 a, 6 b are conductively bonded to each other by gold-to-gold diffusion bonding. Note that although the bump bonding is performed using plated bumps in this embodiment, bump bonding using stud bumps may also be used.

[0036] In this case, the center P of the container 3 in plan view is located within an area surrounded by a virtual outer peripheral frame H1 of the pair of vibration characteristic adjustment portions (the widened portions 212, 222 and the widened portions 211, 221) of the mounted quartz crystal vibrating piece 2. The virtual outer peripheral frame H1 is a virtual frame set along the outer edges of the widened portions 211, 221 and the widened portions 212, 222 so as to surround all of the widened portions 211, 221 and the widened portions 212, 222. Therefore, the center P of the container 3 in plan view overlaps the widened portions 212, 222 and the widened portions 211, 221, is located between the pair of widened portions 212, 222, or is located between the pair of widened portions 211, 221.

[0037] Furthermore, the center P of the container 3 in plan view is preferably located within an area surrounded by an imaginary outer peripheral frame H2 of the pair of frequency adjustment metal films 215, 225 of the mounted quartz crystal vibrating piece 2. The imaginary outer peripheral frame H2 is an imaginary frame set along the outer edges of the pair of frequency adjustment metal films 215, 225 so as to surround the pair of frequency adjustment metal films 215, 225. Therefore, the center P of the container 3 in plan view is preferably overlapped with the pair of frequency adjustment metal films 215, 225 or located at the pair of frequency adjustment metal films 215, 225.

[0038] In addition, in a plan view, the base 20 of the quartz-crystal vibrating piece 2 and the edge 32 of the step 31 are arranged to overlap. Therefore, in a plan view, the edge 32 of the step 31 does not overlap the support arm 23 and the vibrating arms 21 and 22, and does not overlap the constriction in the quartz-crystal vibrating piece 2. In other words, the edge 32 of the step 31 is arranged between the constriction of the quartz-crystal vibrating piece 2 and the vibrating arms 21 and 22 in the Y direction. Note that the overlap position of the base 20 and the edge 32 is preferably the position at which the width of the base 20 is greatest.

[0039] The above configuration can provide a tuning-fork piezoelectric vibrator 1 that suppresses biased changes in vibration characteristics due to impact and improves the stability of vibration characteristics. The quartz crystal vibrator 1 has a pair of vibrating arms 21, 22 of a quartz crystal vibrating piece 2 mounted therein, each of which has weighted widened portions 212, 222 and widened portions 211, 221 (vibration characteristic adjustment units) at their respective tips, and the center P of the container 3 in a plan view is located within an area surrounded by the outer frame H1 of the pair of vibration characteristic adjustment units. This configuration can suppress biased effects on the vibration of the vibrating arms 21, 22 of the mounted quartz crystal vibrating piece 2 when an external impact is applied to the quartz crystal vibrator 1. More specifically, the weighted widened portions 212, 222 and widened portions 211, 221, which are at the tips of the vibrating arms 21, 22 of the quartz crystal vibrating piece 2, are more affected by vibrations caused by the impact on the container 3. Therefore, depending on the direction of the impact on the container 3, the closer the position of the impact is to the positions of the widened portions 212, 222 and the widened portions 211, 221, the greater the change in the vibration state of the vibrating quartz crystal vibrating piece 2. With the configuration of the present invention, the widened portions 212, 222 and the widened portions 211, 221 are positioned near the center P of the container 3, which is the area least displaced by an external impact in a plan view. This prevents bias in the change in vibration of the quartz crystal vibrating piece 2 depending on the direction of the impact on the container 3, resulting in a quartz crystal resonator 1 in which bias in the change in vibration characteristics due to impact is suppressed. In other words, the quartz crystal resonator 1 has improved stability in the vibration characteristics.

[0040] Furthermore, in this embodiment, the center P of the container 3 in plan view is located within the area surrounded by the outer periphery H2 of the pair of frequency-adjusting metal films 215, 225 provided on the wide portions 211, 221 of the mounted quartz crystal vibrating piece 2. This configuration allows the most heavily weighted portion of the quartz crystal vibrating piece 2 to be located near the center P of the container 3, which is least displaced by an external impact in plan view. This makes it possible to further suppress bias in the change in vibration of the quartz crystal vibrating piece 2 depending on the direction of the impact received by the container 3, resulting in a quartz crystal resonator 1 in which bias in the change in vibration characteristics due to impact is further suppressed. In other words, the quartz crystal resonator 1 can be provided with improved stability in its vibration characteristics.

[0041] In this embodiment, the widened portions 212, 222 and the widened portions 211, 221 are wider than the arm portions 214, 224 in the vibrating arms 21, 22. This configuration allows for a larger planar area for forming the frequency-adjusting metal films 215, 225 when fine-tuning the frequency (vibration characteristics) of the quartz crystal vibrating piece 2, thereby widening the adjustable range of vibration characteristics. Furthermore, while it becomes difficult to adjust the frequency lower when the quartz crystal vibrating piece 2 is made smaller, the configuration of this embodiment allows for easy adjustment of the frequency lower by adjusting the shape (weight) of the widened portions.

[0042] Furthermore, in this embodiment, the support arm 23 is formed to extend in the +X direction. When the support arm 23 is formed in an L-shape as in this embodiment, a constriction with the lowest strength is formed in the support arm 23 between the base 20 and the extending portion of the L-shape, and wet-etching residue is formed on the side of the constriction. With the configuration of this embodiment, the edge (end surface in the +X direction) of the wet-etching residue can be made linear. In other words, the wet-etching residue can improve the strength of the constriction of the support arm 23, thereby improving the strength of the quartz-crystal vibrating piece 2.

[0043] Furthermore, in this embodiment, the edge 32 of the step 31 of the container 3 overlaps the base 20 of the quartz vibrating piece 2 in a plan view. With this configuration, even if the quartz vibrating piece 2 comes into contact with the container 3 when the quartz vibrator 1 receives an external impact, the base 20 of the quartz vibrating piece 2, which has a relatively strong physical strength, will come into contact with the step 31 of the container 3. This prevents the quartz vibrating piece 2 from breaking (breaking) due to the "leverage principle," with the edge 32, which is the contact portion with the container 3, serving as a fulcrum. In other words, the edge 32 does not overlap the vibrating arms 21 and 22 or the constrictions of the support arms 23, which have a relatively weak physical strength, of the quartz vibrating piece 2. Therefore, even if the quartz vibrating piece 2 comes into contact with the container 3, the quartz vibrating piece 2 can be prevented from breaking (breaking).

[0044] Furthermore, in this embodiment, the overlapping position between the base 20 and the edge 32 is the position where the width of the base 20 is greatest. With this configuration, even if the quartz crystal resonator 1 receives an external impact and the quartz crystal vibrating piece 2 comes into contact with the container 3, the position of the base 20 of the quartz crystal vibrating piece 2 that has the greatest physical strength will come into contact with the step 31 of the container 3. Therefore, it is possible to more reliably prevent the quartz crystal vibrating piece 2 from breaking (breaking) due to the "leverage principle" with the edge 32, which is the contact portion with the container 3, as a fulcrum.

[0045] In this embodiment, the metal bumps 7a and 7b, which serve as the bonding members, are formed of metal. This configuration allows the crystal vibrating piece 2 and the case 3 to be bonded using metal bump bonding. Metal bump bonding can improve the bonding strength between the case 3 and the crystal vibrating piece 2 compared to bonding using adhesive. Furthermore, improved bonding strength can more easily transmit vibrations caused by an impact on the crystal resonator to the crystal vibrating piece 2, which, combined with internal displacement caused by the impact, can significantly change the vibration characteristics. However, in this embodiment, the center P of the case 3 in a plan view is located within the area surrounded by the virtual outer frame H1 of the widened portions 212 and 222 and the widened portions 211 and 221. This can suppress changes in the vibration state of the crystal vibrating piece 2 due to internal displacement caused by the impact, thereby suppressing changes in the vibration characteristics of the crystal resonator 1. In other words, the crystal resonator 1 can have improved stability in its vibration characteristics.

[0046] Other Embodiments The present invention is not limited to the configurations of the above-described embodiments, and many other embodiments are possible. Figure 6 is a schematic plan view of one main surface of a tuning-fork-type piezoelectric vibrating piece (quartz crystal vibrating piece) 2 according to another embodiment 1. For example, in the above embodiment, the vibrating arms 21, 22 of the quartz crystal vibrating piece 2 include widened portions 212, 222 that extend from the arm portions 214, 224 and gradually widen in the first direction, and widened portions 211, 221 that extend from the widened portions 212, 222 and are wider than the arm portions 214, 224. However, the widened portions 212, 222 and the widened portions 211, 221 may not be included. In other words, the vibrating arms 21, 22 may have a uniform width. In this configuration, frequency-adjusting metal films 215, 225, which are weights for adjusting the frequency, are formed on the front and back principal surfaces near the tips of the uniformly-sized vibrating arms 21, 22. The frequency-adjusting metal films 215, 225 correspond to the vibration characteristic adjuster of the present invention, and the center of the container (not shown) containing the quartz crystal vibrating piece 2 in a plan view is located within the region of the outer peripheral frame H3 of the frequency-adjusting metal films 215, 225.

[0047] In the above embodiment, the support arm 23 has the metal bump 7a at one end in the X direction and the metal bump 7b at the other end. However, one or both of the metal bumps 7a and 7b may be provided at a more inward position rather than at the end. For example, as shown in Figure 6, the metal bump 7a may be configured to be located closer to the metal bump 7b than an imaginary center line that passes through the center in the X direction between the pair of vibrating arms 21 and 22 and is parallel to the Y direction. Alternatively, the center of the metal bump 7a may be located on an imaginary center line that passes through the center in the X direction between the pair of vibrating arms 21 and 22 and is parallel to the Y direction.

[0048] In addition, in the above embodiment, an example of a tuning fork type piezoelectric vibration device is a tuning fork type piezoelectric vibrator 1 in which a tuning fork type piezoelectric vibrating piece is sealed in a container 3, but it may also be a tuning fork type piezoelectric vibration device that is equipped with an IC (integrated circuit) in addition to the tuning fork type piezoelectric vibrating piece, for example.

[0049] FIG. 7 is a schematic plan view of one main surface of a tuning-fork type piezoelectric vibrating piece (quartz crystal vibrating piece) 2 according to another embodiment 2. In the above embodiment, the base 20 of the quartz crystal vibrating piece 2 does not have any openings such as through-holes. However, as shown in FIG. 7 , the base 20 of the quartz crystal vibrating piece 2 may have openings 21c and 22c. The openings 21c and 22c can be formed simultaneously when the outer shape of the quartz crystal vibrating piece 2 is formed by wet etching. In this example, the openings 21c and 22c are through-holes (penetrating holes) that penetrate the base 20 in the Z-axis direction. In this case, the openings 21c and 22c are formed by wet etching both main surfaces of the quartz crystal vibrating piece 2 that are relatively thick in the Z-axis direction. The openings 21c and 22c may also be recesses with bottoms. In this case, the openings 21c and 22c are formed by wet etching one or both main surfaces of the quartz crystal vibrating piece 2 that are relatively thin in the Z-axis direction.

[0050] 7, the openings 21c and 22c are used to route the extraction electrodes 21b and 22b that are respectively extracted from the pair of excitation electrodes 21a and 22a. Specifically, as shown in FIG. 7, a first excitation electrode 21a and a second excitation electrode 22a that are configured at different potentials are formed on the pair of vibrating arms 21 and 22 of the quartz crystal vibrating piece 2, and extraction electrodes 21b and 22b that are respectively extracted from the first excitation electrode 21a and the second excitation electrode 22a are formed on each of the base 20, the pair of vibrating arms 21 and 22, the support arm 23, etc. of the quartz crystal vibrating piece 2. The pair of excitation electrodes 21a and 22a and the extraction electrodes 21b and 22b are formed on both the front and back main surfaces of the quartz crystal vibrating piece 2.

[0051] The openings 21c, 22c are formed in the base 20 of the quartz crystal vibrating piece 2 in the formation areas of the extraction electrodes 21b, 22b, and conductive electrodes (not shown) are formed inside the openings 21c, 22c. The conductive electrodes formed inside the openings 21c, 22c may be formed only on the wall surfaces S1, S2 of the openings 21c, 22c, or may be formed with the conductive electrodes filled in the openings 21c, 22c. This configuration of the openings 21c, 22c allows the extraction electrodes 21b, 22b formed on the front main surface of the quartz crystal vibrating piece 2 to be routed to the extraction electrodes 21b, 22b of the same polarity on the back main surface. The extraction electrode 21b, which is extracted from the first excitation electrode 21a, is connected to the metal bump 7a formed on the back main surface of the quartz crystal vibrating piece 2. Furthermore, an extraction electrode 22 b that is extracted from the second excitation electrode 22 a is connected to a metal bump 7 b formed on the main surface on the back side of the quartz crystal vibrating piece 2 .

[0052] In this way, by providing the openings 21c, 22c in the quartz crystal vibrating piece 2, the openings 21c, 22c can efficiently block the propagation of vibration energy, preventing vibration leakage and resulting in a quartz crystal vibrating piece 2 with good characteristics. Note that when the openings 21c, 22c are recessed portions with bottoms, the extraction electrodes 21b, 22b are not routed to the front and back surfaces via the openings 21c, 22c, but the openings 21c, 22c can efficiently block the propagation of vibration energy, as in the case when the openings 21c, 22c are through holes, preventing vibration leakage and resulting in a quartz crystal vibrating piece 2 with good characteristics.

[0053] FIG. 8 is a schematic plan view of one main surface of a tuning-fork type piezoelectric vibrating piece (quartz crystal vibrating piece) 2 according to another embodiment 3. In the above embodiment, the support arm 23 of the quartz crystal vibrating piece 2 is provided with one metal bump 7a, 7b of opposite polarity as a bonding member for bonding to the mounting pads 6a, 6b of the container 3 (see FIG. 3). However, as shown in FIG. 8, for example, two metal bumps 7a, 7b of opposite polarity may be provided on the support arm 23 of the base 20 of the quartz crystal vibrating piece 2. Furthermore, three or more metal bumps 7a, 7b of opposite polarity may be provided on the support arm 23 of the base 20 of the quartz crystal vibrating piece 2. The metal bumps 7a, 7b are simultaneously bonded to the mounting pads 6a, 6b of the container 3 by the FCB method described above. Furthermore, it is preferable that the arrangement patterns of the multiple metal bumps 7a and the multiple metal bumps 7b are the same, and it is more preferable that the shapes and sizes of the metal bumps 7a, 7b at positions corresponding to the arrangement patterns are the same. Furthermore, it is more preferable that the metal bumps 7 a, 7 b are formed to have the same shape (e.g., circular) and the same size, since this configuration makes it possible to make uniform the bonding strength between the metal bump 7 a and the mounting pad 6 a and the bonding strength between the metal bump 7 b and the mounting pad 6 b, thereby achieving a more stable bonding state.

[0054] In this way, by forming the bonding member formed on the support arm portion 23 at the base 20 of the quartz vibrating piece 2 with multiple metal bumps 7a, 7b, the quartz vibrating piece 2 can be more firmly bonded to the container 3.

[0055] In the above, the quartz crystal vibrating piece 2 is bonded to the container 3 by bump bonding using the metal bumps 7a and 7b. However, this is not a limitation; the quartz crystal vibrating piece 2 may also be bonded to the container 3 using an adhesive. While silicone adhesives, epoxy adhesives, and other adhesives can be used as such adhesives, silicone adhesives are preferred because they allow for flexible mounting of the quartz crystal vibrating piece 2 and reduce the risk of gas generation during heating. As mentioned above, when mounting a relatively small quartz crystal vibrating piece 2 on the container 3, the mounting area for the quartz crystal vibrating piece 2 is small. Therefore, bump bonding is preferable to adhesive bonding in terms of increasing the bonding strength. Furthermore, when mounting a relatively small quartz crystal vibrating piece 2 on the container 3, bump bonding allows the metal bumps 7a and 7b to be formed on the quartz crystal vibrating piece 2 by photolithography, allowing the position and size of the metal bumps 7a and 7b to be precisely determined.

[0056] The embodiments disclosed herein are illustrative in all respects and are not intended to be limiting. Therefore, the technical scope of the present invention should not be interpreted solely by the above-described embodiments, but should be defined by the scope of the claims. Furthermore, all modifications within the scope and meaning equivalent to the claims are included.

[0057] This application claims priority based on Japanese Patent Application No. 2023-198103, filed on November 22, 2023, the entire contents of which are incorporated herein by reference.

[0058] The tuning-fork type piezoelectric vibration device of the present invention can be used in the industry of manufacturing and selling piezoelectric vibration devices that have a tuning-fork type piezoelectric vibration piece mounted inside a container.

[0059] DESCRIPTION OF SYMBOLS 1... tuning fork type piezoelectric vibrator (piezoelectric vibrating device) 2... quartz crystal vibrating piece (tuning fork type piezoelectric vibrating piece) 20... base 21, 22... vibrating arm portion 211, 221... wide portion (vibration characteristic adjusting portion) 212, 222... widened portion (vibration characteristic adjusting portion) 213, 223... long groove 214, 224... arm portion 215, 225... frequency adjusting metal film 23... supporting arm portion 3... container 31... step portion 32... edge 6a, 6b... mounting pad (mounting portion) 7a, 7b... metal bump (bonding member)

Claims

1. A tuning fork type piezoelectric vibration device having at least a tuning fork type piezoelectric vibration piece mounted inside a container, wherein the tuning fork type piezoelectric vibration piece comprises a base, a pair of vibrating arms extending in a first direction from one end side of the base, and a joining member joined to the container, wherein the pair of vibrating arms have vibration characteristic adjustment parts with weights added to their respective tips, and the center of the container in a planar view is positioned within an area surrounded by the virtual outer frames of the pair of vibration characteristic adjustment parts.

2. A tuning-fork type piezoelectric vibration device according to claim 1, characterized in that the vibration characteristic adjustment section is formed wide on the vibrating arm section.

3. A tuning-fork-type piezoelectric vibration device as described in claim 1, characterized in that the tuning-fork-type piezoelectric vibration piece has a support arm extending from the other end side of the base in a direction opposite to the first direction, the joining member is provided on the support arm, the container has a step therein, the step has a mounting portion on its upper surface which is joined to the joining member, and the edge of the step in the first direction overlaps with the base in a planar view.

4. A tuning fork type piezoelectric vibration device according to claim 1, 2 or 3, characterized in that the joining members are formed of bumps made of metal.

5. A tuning fork type piezoelectric vibration device according to claim 4, characterized in that the joining member is formed of a plurality of the bumps.

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