JP4609586B2 - Piezoelectric vibrating piece, method for manufacturing piezoelectric vibrating piece, piezoelectric vibrator, and electronic device equipped with piezoelectric vibrator - Google Patents

Description

  The present invention relates to a piezoelectric vibrating piece, a method for manufacturing a piezoelectric vibrating piece, a piezoelectric vibrator, and an electronic device on which the piezoelectric vibrator is mounted.

Conventionally, a piezoelectric vibrator, for example, a tuning fork type quartz vibrator, is known. This crystal resonator is used as a time standard for a clock, a piezoelectric gyro sensor as an angular velocity sensor, and the like. Accordingly, the piezoelectric vibrator (quartz crystal vibrator) is also required to be downsized.
The vibration frequency of the piezoelectric vibrating piece, which is the vibrating body of the piezoelectric vibrator, is determined by the cross-sectional shape (vibration direction width and thickness) and length of the vibrating arm, when the same material is used. That is, in order to reduce the size of the piezoelectric vibrator, shortening the length of the vibrating arm has the highest contribution rate, and accordingly, it is required to reduce the cross-sectional shape of the vibrating arm.
However, it is also known that when this is done, the vibration state tends to become unstable, such as the occurrence of a higher-order vibration mode.

  In order to suppress the occurrence of this higher-order vibration mode or to obtain a stable vibration state, a weight part (balance head) formed larger than the width of the arm part of the vibrating arm is provided at the tip of the vibrating arm of the vibrating piece. A formed piezoelectric vibrating piece (quartz crystal vibrating piece) is known (see, for example, Patent Document 1).

JP-A-54-37488 (2nd to 3rd pages, FIGS. 3 and 4)

In Patent Document 1, by extending the width of the tip of the vibrating arm (oscillation piece) of the crystal vibrating piece, a weight portion (balance head) is formed at the tip of the vibrating arm as a result. Only the higher-order vibration mode, which is likely to occur when the crystal resonator element is miniaturized, can be particularly suppressed.
However, simply forming the weight portion at the tip of the vibrating arm can shorten the vibrating arm, but increases the amount of displacement, so there is a limit to downsizing, and it is insufficient for further downsizing.
Further, as the miniaturization proceeds, higher accuracy is required for the shapes of the vibrating arm, the weight portion, and the base portion. In particular, there was a problem that a slight imbalance in the left / right symmetry of the vibrating arm affects the stability and excitation of vibration.

  An object of the present invention is to provide a piezoelectric vibrating piece, a method for manufacturing the piezoelectric vibrating piece, a piezoelectric vibrator, and an electronic device having the piezoelectric vibrator mounted thereon, which can obtain a small and stable vibration characteristic.

The piezoelectric vibrating piece according to the present invention includes a vibrating arm having a plurality of rod-shaped arm portions, a first weight portion that is wider than the arm portion and formed at one end of the arm portion, and the arm. And a base part that joins the other end of the part, and a groove part is formed on the front surface and the back surface along the vibration center line of the vibration arm.
Here, a quartz crystal vibrating piece can be adopted as the piezoelectric vibrating piece.
In one embodiment, a protruding portion is provided that extends from the first weight portion and is provided via the arm portion and a gap.
In another embodiment, a second weight portion having a width wider than the protruding portion is provided at the tip of the protruding portion.

According to the present invention, since the groove portion is formed on both the front surface and the back surface of the vibrating arm of the piezoelectric vibrating piece, a cross section in the width direction of the vibrating arm is formed in, for example, a substantially H shape.
As a result, the electric field efficiency of the vibrating arm is greater than when the groove is not formed. Therefore, when obtaining the same vibration frequency, even if the piezoelectric vibrating piece is downsized, the vibration loss is small and the CI value (crystal impedance or equivalent series resistance) can be kept low.
In addition, since the weight portion is formed at the end portion (tip portion) of the arm portion, it is possible to obtain the stability of the vibration frequency when the piezoelectric vibrating piece is downsized. A plurality of vibrating arms (for example, two tuning fork types) are formed. However, since the moment of inertia is increased due to the weight portion, there is also an effect that the influence of variation among the vibrating arms can be reduced.

In the piezoelectric vibrating piece of the present invention, it is preferable that the first weight portion is formed symmetrically with respect to the vibration center of the vibrating arm, and is formed at the same position and the same size.
According to such a structure, for example, in the case of a tuning-fork type crystal vibrating piece, the mass and the moment of inertia of the two vibrating arms are the same, so that stable vibration can be obtained.
In addition, since the two vibrating arms are balanced, vibration leakage at the base can be reduced.

In addition, the piezoelectric vibrating piece according to the present invention includes a tapered portion symmetrical to a vibration center of the vibrating arm at a coupling portion between the arm portion and the first weight portion and a coupling portion between the arm portion and the base portion. It is characterized by having.
At this time, the tapered portion may be formed with a straight line or a curved line.

By providing the taper portion in this way, when the vibrating arm vibrates, no stress is concentrated on the joint between the arm portion and the weight portion, and the basic vibration mode is not affected. Can be obtained.
Further, since the taper portion is also provided at the joint portion between the arm portion and the base portion, a more stable vibration can be obtained.
Furthermore, by providing the tapered portion at each of the above-mentioned parts, there is an effect that it is possible to prevent problems such as destruction when the piezoelectric vibrating piece receives an impact force and deterioration of the vibration mode.

In the piezoelectric vibrating piece of the present invention, it is preferable that the length of the first weight portion is substantially the same as the effective length of the arm portion.
For example, when the vibration arm is lengthened, the vibration frequency is lowered, and when the vibration arm is shortened, the vibration frequency is increased. At this time, when the length of the vibrating arm is fixed in order to reduce the size of the piezoelectric vibrating piece, the vibration frequency is increased by increasing the length of the weight portion. Therefore, if the length of the weight portion is made substantially the same as the effective length of the arm portion, the effect of forming the weight portion is maximized.

  In the piezoelectric vibrating piece according to the aspect of the invention, the groove is formed symmetrically with respect to the vibration center of the vibrating arm, the distal direction is greater than the coupling portion of the first weight portion and the arm portion, and the arm portion and the base portion. It is preferable that it is formed so as to extend in the base direction rather than the joint portion.

As described above, the vibrating arm is formed with grooves on the front and back surfaces, and the cross-sectional shape of the vibrating arm is substantially H-shaped.
At this time, the groove portion is formed symmetrically at the vibration center of the vibrating arm and extends to a position where it enters the weight portion and the base portion. A vibrating arm with such a shape can secure the arm length necessary to obtain the fundamental vibration mode of the vibrating arm, and eliminates stress concentration with the groove at the joint between the arm, weight and base, and is stable. Vibration can be obtained. A further effect can be obtained by combining with the aforementioned tapered portion.

  The piezoelectric vibrating piece according to the present invention may have a polygonal or circular hole formed in the first weight portion substantially symmetrically with respect to the vibration center on a substantial extension of the vibration center line of the vibrating arm. desirable.

  As will be described later, a driving electrode for driving the piezoelectric vibrating piece and a detection electrode for detecting the driving state are formed on the surface of the piezoelectric vibrating piece. At this time, the same electrode is formed on the front and back surfaces of the piezoelectric vibrating piece, but a hole (through hole) penetrating the front and back is formed in the weight portion in order to connect the electrodes on the front and back. Electrodes can be formed on the front and back electrodes more easily than when the side portions of the piezoelectric vibrating piece are divided into electrodes, and when the piezoelectric vibrating piece is, for example, a quartz vibrating piece and formed by an etching method, the crystal is a crystal. It is known that there is anisotropy. As will be described later, there may be a difference in etching speed depending on the location. By making the hole polygonal or circular, the shape error due to the difference in etching speed can be reduced.

The method for manufacturing a piezoelectric vibrating piece according to the present invention preferably includes a step of forming an outer shape of the piezoelectric vibrating piece by etching and a step of forming the groove by etching.
In one embodiment, when manufacturing the piezoelectric vibrating piece, the groove portion is formed symmetrically with respect to the vibration center of the vibrating arm, and the distal end direction and the arm portion are more than the connecting portion of the weight portion and the arm portion. It is formed so as to extend in the direction of the base than the joint with the base.
In another embodiment, the outer shape of the piezoelectric vibrating piece and the hole are formed by etching.

  In such a manufacturing method, the outer shape and the hole of the piezoelectric vibrating piece are an etching process that penetrates the thickness, and the groove is a half-etching process. As a result, the outer shape, the hole, and the groove can be formed with appropriate shapes and dimensions.

  In the method of manufacturing a piezoelectric vibrating piece according to the present invention, the piezoelectric vibrating piece is a quartz crystal vibrating piece, and is formed by shifting an etching base point with respect to the shape of the piezoelectric vibrating piece, or the vibration center of the vibrating arm. It is characterized by being manufactured using an etching mask formed asymmetrically with respect to.

  As described above, when the piezoelectric vibrating piece is a quartz vibrating piece, it is known that there is crystal anisotropy. Due to the crystal anisotropy, the etching speed varies depending on the etching location in the etching process. In view of this, a place where the etching speed is slow or a place where the etching speed is fast is corrected in advance so that the completed shape after etching can be formed into a predetermined shape. As a result, stable vibration can be obtained.

The piezoelectric vibrator of the present invention is characterized in that the piezoelectric vibrating piece is accommodated in a package.
The piezoelectric vibrating piece is housed in a package formed of, for example, ceramic. The inside of the package is preferably in a vacuum state, and the vibration piece is vibrated in a vacuum environment, so that more stable vibration can be maintained over a long period of time.
Further, by being housed in the package, it is easy to handle and the piezoelectric vibrator piece can be protected from the external environment such as humidity.

The electronic device of the present invention is characterized in that a piezoelectric vibrator manufactured by the above-described configuration and manufacturing method is mounted.
Such a piezoelectric vibrator can obtain a stable vibration mode. This piezoelectric vibrator is used, for example, in a time standard such as a watch or a piezoelectric gyro sensor, and is used as a reference transmitter for a communication device, an attitude control device for an automobile, a car Electronic devices such as navigation devices and camera shake prevention devices such as cameras can be provided.

FIG. 3 is a plan view showing the piezoelectric vibrating piece according to the embodiment of the invention. The principal part top view of the weight part of a piezoelectric vibrating piece. The perspective view which shows the modification of the piezoelectric vibrating piece of this invention. The perspective view which shows the other modification of the piezoelectric vibrating piece of this invention. The perspective view which shows the electrode structure of a piezoelectric vibrating piece. The partial cross section which shows a piezoelectric vibrating piece manufacturing process. The polar coordinate figure which shows the etching rate in quartz crystal substrate XY plane. The principal part top view of the weight part when not considering an etching rate. The principal part top view of the weight part at the time of considering an etching rate. The hole part top view in the case of not considering an etching rate. The hole part top view of the weight part at the time of considering an etching rate. FIG. 3 is a schematic cross-sectional view showing a configuration of a ceramic package type vibrator. FIG. 2 is a schematic cross-sectional view showing a configuration of a cylinder type piezoelectric vibrator.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 3 show a piezoelectric vibrating piece 100 of the present embodiment.
FIG. 1 is a plan view of a piezoelectric vibrating piece 100 according to the present embodiment, FIG. 2 is a plan view of a principal part of a weight 110 of the piezoelectric vibrating piece 100, and FIG. 3 is a perspective view of the piezoelectric vibrating piece 100 according to the present embodiment.
1A and 1B, in this embodiment, a pair of thin rod-shaped vibrating arms 120 are formed from the end of the base 130 of the piezoelectric vibrating piece 100. A substantially square weight portion 110 that is set to be larger than the width of the arm portion 121 of the vibrating arm 120 is formed at the longitudinal end portion of the vibrating arm 120.

The pair of vibrating arms 120 has a similar shape, and the length, width, and mass are the same. The weight part 110 is symmetrical with respect to the vibration center B of the vibrating arm 100. As a result, the pair of vibrating arms 120 are vibrated with exactly the same vibration frequency and amplitude.
A groove portion 122 is formed along the vibration center B in the arm portion 121 of the vibrating arm 120. The groove 122 is formed symmetrically with respect to the vibration center B, and starts from a position where it enters from the end 131 of the base 130 on the vibrating arm 120 side and extends to a position where it enters the weight 110.

  FIG. 1B shows an A-A ′ cross section of the arm 121. As described above, the groove 122 is formed on the back surface of the piezoelectric vibrating piece 120 with the same width, length, and depth, and has a substantially H-shaped cross-sectional shape.

A tapered portion 132 is formed at a joint portion between the arm portion 121 and the base portion 130, and a tapered portion 112 is formed at a joint portion between the arm portion 121 and the weight portion 110.
These tapered portions 132 and 112 are symmetrical with respect to the vibration center B, and are set so as to reduce stress concentration when the vibrating arm 121 is vibrated in the X direction in each of the coupling portions described above. . At this time, the tapered portions 132 and 112 do not need to be set in the same shape, and can be appropriately set in accordance with a predetermined vibration mode.
In this embodiment, the piezoelectric vibrating piece is a quartz vibrating piece, and as shown in FIG. 1A, X is a mechanical axis, Y is an electric axis, and Z is an optical axis.

A substantially rectangular hole 113 that penetrates from the front surface to the back surface is provided at the center in the width direction of the weight portion 110. As will be described later, the hole 113 is a through hole for connecting electrodes formed on the front and back surfaces of the piezoelectric vibrating piece 100 (FIG. 3).
The hole 113 is positioned on the extension of the vibration center B of the vibrating arm 120 and is symmetrical. In FIG. 1A, it is a quadrangle, but it is set so that the vibration balance of the left and right vibrating arms 120 is balanced regardless of whether it is a polygon such as another hexagon or a circle.
At this time, the weight portion length Lw and the effective vibration length La of the arm portion are set to substantially the same length. That is, the lengths Lw and La of the weight part 113 and the arm part 121 with respect to the entire length of the vibrating arm 120 are each approximately ½ of the length.

FIG. 2 shows a modification of the shape of the weight part 110 of the present embodiment. Except for the shape of the weight part 110, the description is omitted because it is the same as FIG.
In FIG. 2A, an orthogonal part between the end face of the tip of the weight part 110 and the side surface in the outer shape longitudinal direction (Y-axis direction) is formed in a continuous shape with a curve. This shape may be a shape in which the tip is continuous with one curve, or may be a chamfered shape with a straight line.

  FIG. 2B is a modification of the tapered portion shape of the joint portion between the weight portion 110 and the arm portion 121. In FIG. 2B, the taper portion 114 is formed in a shape in which the outer shape in the longitudinal direction (Y-axis direction) of the weight portion 110 and the arm portion 121 are continuous in a straight line.

  FIG. 2C shows another modification of the connecting portion between the weight part 110 and the arm part 121 shown in FIG. As shown in FIG.2 (c), the coupling | bond part of the weight part 110 and the arm part 121 is continuously formed in the curve (it shows by 115 in a figure). Here, it is good also as a shape which put the straight line between the curve by the side of the weight part 110, and the curve by the side of the arm part 110. FIG.

  At this time, the shape of the tip portion of the weight portion 110 (for example, FIG. 2A) and the shape of the joint portion of the weight portion 110 and the arm portion 121 (for example, FIGS. 2B and 2C). These may be formed in combination.

3 and 4 are perspective views showing modifications of the weight portion 110 of the piezoelectric vibrating piece 100 according to the present embodiment.
In FIG. 3 (a), the weight part 110 has a pair of protrusions extending along the arm part 121 at both sides in the width direction of the arm part 121 toward the base part 130 at positions away from the arm part 121. A portion 116 is formed. The protrusions 116 (four in the figure) are all the same size.

  FIG. 3B shows a modification of the piezoelectric vibrating piece 100 of FIG. In FIG. 3B, a second weight portion 117 wider than the width of the protruding portion 116 is formed at the tip of the protruding portion 116 described above. The second weight portions 117 are also the same size.

  FIG. 4 shows another modification of the piezoelectric vibrating piece 100 of the present embodiment. In FIG. 4, a pair of substantially U-shaped notches 131 are formed on both sides of the base portion 130 in the width direction between the connecting portion of the arm portion 121 of the base portion 130 and the other end portion. These notches 131 are symmetrical with respect to the center line (not shown) of the base portion 130 in the width direction.

FIG. 5 is a perspective view of the piezoelectric vibrating piece 100 according to the present embodiment, and shows the configuration of the electrode 140 formed on the surface of the piezoelectric vibrating piece 100.
In the tuning fork type piezoelectric vibrating piece 100 having a substantially H-shaped cross section formed in this way, an electrode 140 is formed at a portion indicated by hatching in FIG. The electrode 140 is formed from the base portion 130 to the arm portion 121 and the weight portion 110 of the two vibrating arms 120, and is also formed on the side surfaces of the arm portion 121 and the weight portion 110 and the inner surface of the groove portion 122.
The electrode 140 is also formed on the back surface of the piezoelectric vibrating piece 100 not shown in FIG. 5 in the same manner as the front surface. Here, it is also formed on the hole side surface of the hole 113 provided in the weight part 110, and the front electrode and the back electrode are connected.

  The electrode 140 arranged and formed in this way generates an electric field when an electric current is applied from the outside, and vibrates the vibrating arm 120 of the piezoelectric vibrating piece 100 that is a piezoelectric body.

For example, when the vibration frequency used as a time standard for a timepiece or the like is 32,768 kz, the piezoelectric vibration piece 100 formed in this way is formed smaller than a conventional piezoelectric vibration piece having the same vibration frequency without a groove. .
On the other hand, the thickness of the piezoelectric vibrating piece 100 having a substantially H-shaped cross section is, for example, about 0.1 mm, and is formed to be equal to the thickness of a piezoelectric vibrating piece without a conventional groove.
That is, since the groove part 122 is formed in the piezoelectric vibrating piece 100 and the electrode 140 is formed in the groove part 122, the generated electric field is widely distributed inside the vibrating arm 120. The vibration loss is small and the CI value can be suppressed.
Accordingly, a piezoelectric vibrating piece having a small CI value and a low CI value is formed as compared with the piezoelectric vibrating piece having no groove as described above.

Next, a manufacturing method of the substantially H-shaped piezoelectric vibrating piece 100 having the weight 110 will be described with reference to FIG.
FIG. 6 schematically shows an AA ′ cross section (shown in FIG. 1) of the arm portion 121 of the piezoelectric vibrating piece 100 of the present embodiment.
When the piezoelectric vibrating piece 100 of the present embodiment is a quartz vibrating piece, although not shown, it is cut out from a single crystal of quartz and processed into a tuning fork type. As shown in FIG. 1, a piezoelectric substrate 100 having a tuning fork type and an H-shaped cross section is formed by etching or the like on a quartz substrate cut out so that the X axis is an electric axis, the Y axis is a mechanical axis, and the Z axis is an optical axis. It is formed.

In FIG. 6, a corrosion resistant film 151 is formed on both the front and back surfaces of the quartz substrate 150 cut out as described above by vapor deposition or the like, and a resist film 152 is applied on the upper surface of the corrosion resistant film 151 (FIG. 6A). .
Subsequently, external pattern exposure and external pattern development are performed using a mask (not shown) that matches the external shape of the piezoelectric vibrating piece 100 and the shape of the hole 113 of the weight portion 110 (FIG. 6B).
Next, the developed exposed portion of the corrosion-resistant film 151 is peeled off by the etching solution (FIG. 6C), and the resist 152 is peeled off (FIG. 6D). At this time, only the corrosion-resistant film 151 having a shape close to the outer shape of the piezoelectric vibrating piece 100 is left.

Next, the entire surface of the quartz substrate 150 including the remaining surface of the corrosion-resistant film 151 is coated with a resist film 152 (FIG. 6E), pattern exposure and development of the groove 122 are performed (FIG. 6F), Subsequently, the outer shape of the piezoelectric vibrating piece 100 is etched (FIG. 6G). At this time, although not shown, a hole 113 provided in the weight 110 is also formed at the same time.
The resist film 152 is left in accordance with the outer shape of the groove 122.

Next, the corrosion-resistant film 151 is peeled off, and only the groove 122 is exposed on the surface of the crystal substrate 150, and then the groove 122 is etched. This etching process is half-etched, and is etched down to a predetermined depth while managing the etching time and the like, so that a groove is formed to a predetermined shape and depth (FIG. 6 (i)).
Thereafter, the resist film 152 and the corrosion-resistant film 151 are peeled off to form a grooved piezoelectric vibrating piece (FIG. 6 (j)).

After the outer shape, the hole 113, and the groove 122 of the piezoelectric vibrating piece 100 are formed in such a process, the electrode 140 as shown in FIG. 5 is formed, and the shape of the piezoelectric vibrating piece 100 is completed.
The electrode 140 is formed by depositing a metal film having good electrical conductivity such as gold on the surface of the piezoelectric vibrating piece 100 by a method such as vapor deposition or sputtering, and dividing the electrode into a predetermined shape by an etching method.

  When the piezoelectric vibrating piece 100 is formed of quartz, it is known that the quartz has crystal anisotropy. As a result, etching anisotropy exists when the quartz substrate 150 is etched, and the etching speed varies depending on the portion of the substrate even if etching is performed under the same conditions. This etching speed is called an etching rate.

FIG. 7 is a polar coordinate diagram showing the etching rate of the quartz crystal substrate 150 in the XY plane.
In FIG. 7, the center of the circle has an etching rate of 0, and the etching rate is displayed faster as it goes outward.
In particular, the in-plane etching speeds in the + X direction, the + 120 ° direction with respect to the X axis, and the −120 ° direction are high, and conversely, the inner surface etching speeds in the + 30 ° direction and the −30 ° direction with respect to the −X direction and the X axis. Becomes slower.
On the other hand, the etching speed in the Z direction increases in the −30 ° direction and the −30 ° direction, and decreases in the + X direction and the + 120 ° direction and the −120 ° direction with respect to the X axis.

  Since there is anisotropy in the etching processability as described above, an optimal mask shape is baked and photolithography is performed in order to accurately form the shape of the piezoelectric vibrating piece 100. For example, for the tip portion of the weight portion 110, the joint portion between the weight portion 110 and the arm portion 121, the joint portion between the weight portion arm portion 121 and the base portion 130, the hole portion 113 provided in the weight portion 110, etc. The mask shape is corrected in accordance with the etching rate.

The relationship between the mask shape and the shape of the piezoelectric vibrating piece 100 will be described with reference to FIGS.
8 is a plan view of the main part of the weight part 110 when the etching rate is not considered, FIG. 9 is a plan view of the main part of the weight part 110 when the etching rate is considered, and FIG. 10 is a case where the etching rate is not considered. FIG. 11 is a plan view of the hole 113 in consideration of the etching rate.

In FIG. 8, the etching mask 150 is formed in accordance with a predetermined shape of the piezoelectric vibrating piece 110 (without correcting the shape). That is, it is formed symmetrically with respect to the vibration center B ′ of the vibrating arm 120 (shown by a solid line in the figure). When the etching process is performed using this mask, a straight line B connecting the center of gravity of the weight part 110 and the arm part 121 is originally formed like the weight part 110 indicated by a two-dot chain line in the figure due to the difference in the etching rate. The center of vibration (B ′ in the figure) is deviated.
Further, the left corner 110A in the figure of the tip corner of the weight portion 110 has a chamfered shape, and the other corner 110B has a similar shape.
Further, the −X direction taper portion 112A of the taper portion 112 formed between the weight portion 110 and the arm portion 121 is formed smaller, and the + X side taper portion 112B is formed larger.

FIG. 9 shows the shape of the weight portion 110 when the etching mask 150 is formed by correcting the shape in advance according to the above-described etching rate.
In FIG. 9, the shape indicated by the solid line is the mask 150, and the shape indicated by the two-dot chain line is the shape of the weight part 110 formed by the etching process. The X-direction center line B ′ of the mask 150 has a shape corrected in the + X-axis direction with respect to the vibration center B of the vibrating arm 120, and the tip 150 of the weight portion 110 in the −X direction (left side in the drawing) corner 150 A is + Y A projection is formed in the direction, and a similar projection 150B is also formed in the -Y direction in the -Y direction (lower left side in the figure).
The taper part 112A on the −X direction side of the mask 150 is also formed larger than the + X side taper part 112B side.
As described above, when the etching process is performed using the mask 150 whose etching base point and shape are corrected in advance according to the etching rate, the center line B of the weight portion 110 coincides with the initially targeted vibration center, and the center line B Symmetrical vibrating arm 120 is formed.
At this time, in FIG. 8 and FIG. 9, the hole 113 formed in the weight 110 is omitted.

10 and 11 are enlarged plan views schematically showing the hole 113 formed in the weight part 110. FIG.
In FIG. 10, the mask 150 has an opening 151 through which light is transmitted corresponding to the shape of the hole 113. The opening 151 is formed in a quadrangular shape symmetrically with respect to the vibration center of the vibrating arm 120. In this case, the vibration center coincides with the center line B ′ of the mask opening 151.
When an etching process is performed using such a mask, as shown by the two-dot chain line in the figure (113A), it is formed large in the -X direction, and the corners 113B and 113C having a low etching rate are not formed properly. Etching remains.
Therefore, the etched vibrating arm 120 is formed in an asymmetric shape with respect to the center line B, and the hole 113 center line B moves to a position shifted from the vibration center.
At this time, the hole 113 and the outer shape of the piezoelectric vibrating piece 100 can be formed by the same etching process.

FIG. 11 shows the hole portion 113 of the weight portion 110 when a mask 150 whose shape is corrected in advance for the predetermined hole portion 113 is used.
In FIG. 11, the mask 150 has an opening 151 through which light is transmitted corresponding to the shape of the hole 113. The center line of the opening 151 is shifted to B ′ with respect to the vibration center of the vibrating arm 120, and the upper −X side corner in the drawing of the opening 151 of the mask 150 has a recess 151 </ b> A in the −X direction. A recess 151B similar to the recess 151A is formed at the -Y side corner of the recess 151A.
In the hole 113 subjected to the etching process using the mask 150 formed in this way, the hole center line B coincides with the vibration center of the vibrating arm 120 as shown by a two-dot chain line in the figure, and Are formed symmetrically with respect to the center line B.

As shown in FIGS. 9 and 10, since the etching process is performed using the mask 150 formed in consideration of the etching rate, the piezoelectric vibrating piece 100 can balance the left and right of the two vibrating arms 120. In addition, the weight part 110 also has a center line B that coincides with the vibration center, and both the outer shape and the hole 113 are formed symmetrically with respect to the vibration center (center line B).
The piezoelectric vibrating piece 100 manufactured in this way is used by being housed in a package.

12 and 13 show a state in which the piezoelectric vibrating piece 100 of the present embodiment is housed in a package.
FIG. 12 is a schematic cross-sectional view showing the configuration of the ceramic package type resonator 200. As shown in FIG. 12, the ceramic package 210 is a box-shaped package 210 having a space inside. The package 210 has a base portion 211 at the bottom thereof. The base portion 211 is made of ceramic such as alumina, for example.

  A sealing portion 212 is provided on the base portion 211, and the sealing portion 212 is formed from the same material as the base portion 211. Further, a lid 213 is placed on the upper portion of the sealing portion 212, and a hollow box is formed by the base portion 211, the sealing portion 212, and the lid 213.

A package-side electrode 214 is provided on the base 211 of the package 210 formed in this way. An end portion of the piezoelectric vibrating piece 100 in which the electrode 140 is formed on the package side electrode 214 via a conductive adhesive or the like is fixed. The package 210 is preferably in a vacuum state in order to maintain stable bending vibration.
The piezoelectric vibrator piece 100 is vibrated accurately when a constant driving voltage is applied from the package-side electrode 214.
Although not shown, a semiconductor chip for vibration control is placed in the gap in the cross section between the bottom portion 211 of the package 210 and the piezoelectric vibrating piece 100 and connected to the electrode 140 of the piezoelectric vibrating piece 100 to be connected to a transmitter or the like. It is set as the structure which can also be used.

FIG. 13 is a schematic cross-sectional view showing the configuration of the cylinder-type piezoelectric vibrator 500.
In FIG. 13, a cylinder type piezoelectric vibrator 500 has a metal cap 530 for housing the piezoelectric vibrating piece 100 therein. The cap 530 is press-fitted into the stem 520, and the inside is kept in a vacuum state.
Two leads 510 are provided through the stem 520. The electrode 140 at the end of the piezoelectric vibrating piece 100 is fixed and held on the lead 520 with a conductive adhesive or the like.
When a constant drive voltage is applied from the lead 510 to the piezoelectric vibrating piece 100 configured as described above, the vibrating arm 120 vibrates accurately and functions as the piezoelectric vibrator 500.

The piezoelectric vibrators 200 and 500 configured as described above and manufactured by the above-described manufacturing method are used as a time standard for a timepiece or an electronic device.
Further, such a piezoelectric vibrating piece 100 is used in a piezoelectric gyro sensor as an angular velocity sensor by rotating the Z-axis as a rotation axis, generating a Coriolis force, and detecting it. It is installed in electronic devices such as car navigation devices and camera shake prevention devices such as cameras.

  Therefore, according to the present embodiment, the following effects can be obtained.

(Effect 1)
According to the present embodiment, since the groove portion 122 is formed on both the front surface and the back surface of the arm portion 121 of the piezoelectric vibrating piece 100, the cross section in the width direction of the arm portion 121 is formed in, for example, a substantially H-shaped cross section. Yes. As a result, the section modulus of the arm 121 is larger than when the groove 122 is not formed. Therefore, when obtaining the same vibration frequency, even if the piezoelectric vibrating piece 100 is downsized, the vibration loss is small and the CI value (crystal impedance or equivalent series resistance) can be kept low.
Further, since the weight portion 110 is formed at the end portion (tip portion) of the vibrating arm 120, the stability of the vibration frequency when the piezoelectric vibrating piece 100 is reduced in size can be obtained. A plurality of vibrating arms 120 (two tuning fork types in the present embodiment) are formed. However, since the moment of inertia increases because of the weight 110, there is also an effect that the influence of variation of the vibrating arms can be reduced. .

(Effect 2)
The piezoelectric vibrating piece 100 of the present invention has such a structure because the weight portion 110 is formed symmetrically with respect to the vibration center B of the vibrating arm 120 and is formed at the same position and size. Therefore, for example, in the case of a tuning-fork type crystal vibrating piece, the mass and the moment of inertia of the two vibrating arms 120 are the same, so that stable vibration can be obtained.
In addition, since the two vibrating arms 120 are balanced, vibration leakage at the base can be reduced.

(Effect 3)
By providing the tapered portion 112 as in the present embodiment, when the vibrating arm 120 vibrates, stress concentration is not caused at the joint portion between the arm portion 121 and the weight portion 110, and the basic vibration mode is affected. Therefore, stable vibration can be obtained.
Further, since the tapered portion 132 is provided also in the joint portion between the arm portion 121 and the base portion 130, more stable vibration can be obtained. By providing the tapered portion 132 in this manner, even if the shapes of the weight portion 110 and the arm portion 121 are slightly symmetric, the influence of the relative balance difference can be reduced.
Furthermore, by providing the tapered portion at each of the aforementioned portions, there is an effect that it is possible to prevent problems such as destruction when the piezoelectric vibrating piece 100 receives an impact force or deterioration of the vibration mode.

(Effect 4)
As described above, the groove 121 is formed on the front surface and the back surface of the arm 121, and the cross-sectional shape of the arm is substantially H-shaped.
At this time, the groove 122 is formed symmetrically with respect to the vibration center B of the vibrating arm 120 and extends to a position where it enters the weight 110 and the base 130. The vibrating arm 120 having such a shape can secure the arm length necessary to obtain the basic vibration mode of the vibrating arm 120 without being affected by the base point position of the groove portion 122, and the arm portion 121 and the weight portion 110. In the joint portion with the base portion 130, stress concentration with the groove portion 122 is eliminated, and stable vibration can be obtained. A further effect can be obtained by combining with the aforementioned tapered portion.

(Effect 5)
In the present embodiment, the length of the weight part 110 is about ½ of the effective length of the vibrating arm. For example, when the vibrating arm 120 is lengthened, the vibration frequency is decreased, and when the vibration arm 120 is shortened, the vibration frequency is increased. At this time, when the length of the vibrating arm 120 is fixed in order to reduce the size of the piezoelectric vibrating piece 100, the vibration frequency is increased by increasing the length of the weight portion 110. Therefore, when the length of the weight part 110 is set to ½ of the effective length of the vibrating arm 120 (that is, the length of the weight part 110 and the length of the arm part 121 are substantially the same), the weight part 110 is The effect formed is utilized to the maximum.

(Effect 6)
In this embodiment, in order to connect the electrodes 140 formed on the front and back of the piezoelectric vibrating piece 100, a hole portion (through hole) 113 penetrating the front and back is formed in the weight portion 110. Compared with the case where the front and back electrodes 140 are formed on the side surface portions of the piezoelectric vibrating piece 100, there is an effect that it is easier to connect the electrodes to the weight portion 110 having a large area by through holes.
In addition, since the hole (through hole) 113 has a difference in etching rate depending on the location as described above, the correction amount of the mask can be reduced by making it a hexagon, an octagon or a circle as well as a square. There is also an effect that the setting becomes easy.

(Effect 7)
In the manufacturing method of the present embodiment, the outer shape of the piezoelectric vibrating piece 100 and the hole 113 are formed by an etching process penetrating in the thickness direction, and the groove 122 is formed by a half-etching process, and is formed by another selected process. Is done. Thus, the outer shape of the piezoelectric vibrating piece 100, the hole 113, and the groove 122 can be formed with appropriate shapes and dimensions.

(Effect 8)
In the present embodiment, as described above, it is known that when the piezoelectric vibrating piece 100 is a crystal vibrating piece, there is crystal anisotropy. Due to the crystal anisotropy, the etching speed (etching rate) varies depending on the etching location in the etching process. Therefore, the place where the etching speed is slowed down and the place where it is fastened are symmetric with respect to the vibration center after etching by shifting the etching base point in advance or correcting the shape in advance corresponding to each place. Therefore, a more stable vibration mode and vibration frequency can be obtained.

(Effect 9)
In the modification of the present embodiment (shown in FIG. 3), since the protruding portion 116 is provided on the base portion 130 side of the weight portion 110, the vibration arm 120 can be vibrated without changing the mass of the weight portion 110. Since the arm length of the next moment can be shortened, the stability of vibration due to the difference in etching rate can be increased, and the CI value can be lowered.
Further, by providing the second weight portion 117 at the tip of the protruding portion 116, these effects can be further enhanced.
Furthermore, as shown in FIG. 4, by providing the notch 131 in the base portion 130, the bending vibration of the vibrating arm 120 can reduce the vibration leakage from the base portion 130, and the CI value can be kept low.

(Effect 10)
The piezoelectric vibrating piece 100 of this embodiment is housed in a package 210 formed of ceramic or the like. Since the package 210 is held in a vacuum state, a more stable vibration can be maintained over a long period of time.
Moreover, since it is housed in the package 210, it is easy to handle and the piezoelectric vibrator piece 100 can be protected from the external environment such as humidity.

(Effect 11)
The electronic apparatus according to the present embodiment includes the piezoelectric vibrators 200 and 500 manufactured by the above-described configuration and manufacturing method.
Such piezoelectric vibrators 200 and 500 can obtain a stable vibration mode and vibration frequency, and are used for, for example, time standards such as watches and piezoelectric gyro sensors, and are used as reference transmitters for communication devices, attitude control devices for automobiles, cars. Electronic devices such as navigation devices and camera shake prevention devices such as cameras can be provided.

It should be noted that the present invention is not limited to the above-described embodiment, but includes modifications and improvements as long as the object of the present invention can be achieved.
For example, in the above-described embodiment, the tuning fork type piezoelectric vibrating piece 100 has been described as an example. However, in addition to the tuning fork type piezoelectric vibrator, for example, a planar H type piezoelectric vibrator in which a drive arm and a detection arm are configured separately. It can also be applied to a piezoelectric vibrator called a double T-type vibrator.

  According to the present invention as described above, a piezoelectric vibrating piece capable of obtaining a small and stable vibration characteristic, a method for manufacturing the piezoelectric vibrating piece, a piezoelectric vibrator having the piezoelectric vibrating piece, and an electronic device equipped with the piezoelectric vibrator are provided. be able to.

  DESCRIPTION OF SYMBOLS 100 ... Piezoelectric vibrating piece, 110 ... Weight part, 116 ... Projection part, 117 ... Second weight part, 120 ... Vibrating arm, 121 ... Arm part, 122 ... Arm part, 130 ... Base part.

Claims (12)

A vibrating arm having a plurality of rod-shaped arm portions and a first weight portion that is wider than the arm portions and formed at one end of the arm portions;
A base for joining the other end of the arm,
A projecting portion extending from the first weight portion and provided through the arm portion and a gap;
With
A piezoelectric vibrating piece, wherein grooves are formed on a front surface and a back surface along a vibration center of the vibrating arm. The piezoelectric vibrating piece according to claim 1,
A piezoelectric vibrating piece having a second weight portion wider than the protruding portion at a tip of the protruding portion. The piezoelectric vibrating piece according to claim 1 or 2,
The piezoelectric vibrating piece, wherein the first weight portion is formed symmetrically with respect to a vibration center of the vibrating arm, and is formed at the same position and the same size. The piezoelectric vibrating piece according to any one of claims 1 to 3,
A piezoelectric vibrating piece having a tapered portion symmetrical with respect to a vibration center of the vibrating arm at a connecting portion between the arm portion and the first weight portion and a connecting portion between the arm portion and the base portion. . The piezoelectric vibrating piece according to any one of claims 1 to 4,
The piezoelectric vibrating piece, wherein a length of the first weight portion is substantially the same as an effective length of the arm portion. In the piezoelectric vibrating piece according to any one of claims 1 to 5,
The groove portion is formed symmetrically with respect to the vibration center of the vibrating arm, and the base portion is more distal than the connecting portion between the first weight portion and the arm portion and the connecting portion between the arm portion and the base portion. A piezoelectric vibrating piece formed by extending in a direction. The piezoelectric vibrating piece according to any one of claims 1 to 6,
A piezoelectric vibrating piece having a polygonal or circular hole portion formed symmetrically with respect to a vibration center on the first weight portion on substantially an extension of a vibration center line of the vibration arm. A method for manufacturing the piezoelectric vibrating piece according to any one of claims 1 to 7, wherein an outer shape of the piezoelectric vibrating piece is formed by etching,
And a step of forming the groove part by etching. The method of manufacturing a piezoelectric vibrating piece according to claim 8,
The groove portion is formed symmetrically with respect to the vibration center of the vibrating arm, and the base portion is more distal than the connecting portion between the first weight portion and the arm portion and the connecting portion between the arm portion and the base portion. The method of manufacturing a piezoelectric vibrating piece, wherein the piezoelectric vibrating piece is formed extending in a direction. The method of manufacturing a piezoelectric vibrating piece according to claim 9,
The piezoelectric vibrating piece is a quartz vibrating piece,
Piezoelectric vibration characterized in that it is formed using an etching mask formed by shifting an etching base point with respect to the shape of the piezoelectric vibrating piece or asymmetrically with respect to the vibration center of the vibrating arm. A manufacturing method of a piece.   A piezoelectric vibrator, wherein the piezoelectric vibrating piece according to any one of claims 1 to 7 is housed in a package.   An electronic device, wherein the piezoelectric vibrator according to claim 11 is mounted.

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