There are provided a piezoelectric vibrator capable of suppressing vibration leakage while securing mounting strength of a piezoelectric vibrating reed and an oscillator, an electronic apparatus, and a radio-controlled timepiece each using the piezoelectric vibrator. The piezoelectric vibrator includes: a package that accommodates a piezoelectric vibrating reed; and a bump that mounts the base portion of the piezoelectric vibrating reed on a package. The bump includes a plurality of main bumps which is arranged in a line in the width direction of the base portion so as to be bonded to the base portion; and an auxiliary bump which is bonded to the base portion in an area between the main bumps disposed at both ends in the width direction of the base portion and an area between the main bumps and base ends of the vibrating arms in the longitudinal direction of the base portion.

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2010-022407 filed on Feb. 3, 2010, the entire content of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a piezoelectric vibrator, an oscillator, an electronic apparatus, and a radio-controlled timepiece.

2. Description of the Related Art

In recent years, piezoelectric vibrators using crystal or the like have been used in mobile phones or portable information terminals as a time source, a control signal timing source, a reference signal source, and the like. Various piezoelectric vibrators are available as such kinds of piezoelectric vibrators, and a piezoelectric vibrator in which a so-called tuning fork-type piezoelectric vibrating reed is sealed in a package is also known as one of the piezoelectric vibrators.

A tuning-fork-type piezoelectric vibrating reed is a thin plate-like crystal reed which includes a pair of vibrating arms arranged in a line in a width direction thereof and a base portion that integrally fixes base end sides in the longitudinal direction of the pair of vibrating arms. A pair of excitation electrodes is formed on both the upper and lower surfaces of each of the vibrating arms of the piezoelectric vibrating reed with a predetermined gap therebetween. Moreover, a pair of mount electrodes is formed on both the upper and lower surfaces of the base portion and electrically connected to a pair of excitation electrodes through a pair of extraction electrodes. On the other hand, bumps made of gold or the like are formed on the inner electrodes of the package.

The mount electrodes of the piezoelectric vibrating reed are mounted on the inner electrodes of the package, whereby a piezoelectric vibrator is formed. Specifically, the piezoelectric vibrating reed is mounted in the package by a so-called flip-chip bonding method in which the mount electrodes of the piezoelectric vibrating reed are pressed against the bumps on the inner electrodes to cause ultrasonic vibration, whereby the mount electrodes and the bumps are ultrasonically bonded to each other.

However, when the piezoelectric vibrating reed is mounted in the package by the flip-chip bonding method, the mounting strength of the piezoelectric vibrating reed decreases if the number of bumps being bonded is small. Moreover, when an impact load is applied to the piezoelectric vibrator, there is a problem in that the piezoelectric vibrating reed falls off the mounting surface of the package, and accordingly, an oscillation stops. In order to obviate such a problem, a method of increasing the number of bumps to improve the mounting strength of the piezoelectric vibrating reed may be considered.

JP-A-2007-096899 discloses a piezoelectric vibrating reed in which two bumps are formed on each of a pair of connection electrodes (corresponding to the lead-out electrodes of the present invention) in the package along the longitudinal direction of the piezoelectric vibrating reed, and the respective bumps are bonded to pad electrodes (corresponding to the mount electrodes of the present invention). In the piezoelectric vibrating reed disclosed in JP-A-2007-096899, since the piezoelectric vibrating reed is mounted on the package using four bumps in total, even when an impact load is applied to the piezoelectric vibrator, stress resulting from the impact load applied to the bonding portion of the piezoelectric vibrating reed can be distributed to a plurality of bumps. Therefore, the mounting strength of the piezoelectric vibrating reed can be improved.

However, since the piezoelectric vibrating reed disclosed in JP-A-2007-096899 is firmly mounted on the package by means of a plurality of bumps, there is a possibility that, when the piezoelectric vibrating reed is operated, so-called vibration leakage may occur. That is, vibration energy of the piezoelectric vibrating reed may leak to the outside through the plurality of bumps. When vibration energy of the piezoelectric vibrating reed leaks to the outside when vibration leakage occurs, there is a possibility that the energy efficiency of the piezoelectric vibrator will decrease. Moreover, when the piezoelectric vibrator with vibration leakage is mounted on a substrate of an electronic apparatus or the like, since the degree of binding of the piezoelectric vibrator is different in accordance with solid variations in the mounting state such as the amount of solder, there is a problem in that the vibration properties of the piezoelectric vibrator fluctuate.

SUMMARY OF THE INVENTION

The invention has been made in view of the above problems. An object of the present invention is to provide a piezoelectric vibrator capable of suppressing vibration leakage while securing a mounting strength of a piezoelectric vibrating reed and an oscillator, an electronic apparatus, and a radio-controlled timepiece each using the piezoelectric vibrator.

In order to solve the problems, according to an aspect of the present invention, there is provided a piezoelectric vibrator including: a piezoelectric vibrating reed including a pair of vibrating arms arranged in a line along a width direction thereof, and a base portion that integrally fixes base end sides in a longitudinal direction of the pair of vibrating arms; a package that accommodates the piezoelectric vibrating reed; and a bump that mounts the base portion of the piezoelectric vibrating reed on the package, wherein the bump includes: a plurality of main bumps which is arranged in a line in the width direction of the base portion so as to be bonded to the base portion; and an auxiliary bump which is bonded to the base portion in an area between the main bumps disposed at both ends in the width direction of the base portion and an area between the main bumps and base ends of the vibrating arms in the longitudinal direction of the base portion.

According to this configuration, since the base portion of the piezoelectric vibrating reed is bonded to the package by the plurality of main bumps and the auxiliary bump, it is possible to improve the mounting strength of the piezoelectric vibrating reed. Moreover, the auxiliary bump is bonded to the base portion in an area between the main bumps disposed at both ends in the width direction of the base portion and an area between the main bumps and base ends of the vibrating arms in the longitudinal direction of the base portion. These areas are near the nodal point of vibration as disclosed in the Journal of IEICE (The Institute of Electronics, Information and Communication Engineers), Volume J72-A, No. 11, Page 1736, November 1989. Therefore, the magnitude of vibration of the piezoelectric vibrating reed is small in these areas. Since the auxiliary bump is bonded to the base portion in the areas near the nodal point of vibration where the magnitude of vibration is small, the vibration of the piezoelectric vibrating reed will rarely leak to the outside through the auxiliary bump. In this way, it is possible to suppress the vibration leakage of the piezoelectric vibrator. Therefore, it is possible to suppress the vibration leakage of the piezoelectric vibrator while securing the mounting strength of the piezoelectric vibrating reed.

The auxiliary bump is preferably disposed approximately at the center in the width direction of the base portion.

According to this configuration, since the auxiliary bump is disposed approximately at the center in the width direction of the base portion, the auxiliary bump is disposed at a position closer to the nodal point of vibration. Therefore, it is possible to further suppress the vibration leakage of the piezoelectric vibrator while securing the mounting strength of the piezoelectric vibrating reed.

The auxiliary bump is preferably disposed at a position which is separated from a tip end of the base portion toward the base end side by a distance corresponding to approximately a half of the width of the vibrating arm.

As disclosed in the Journal of IEICE (The Institute of Electronics, Information and Communication Engineers), Volume J72-A, No. 11, Page 1736, November 1989, the position which is separated from the tip end of the base portion toward the base end side by a distance corresponding to approximately a half of the width of the vibrating arm corresponds to the nodal point of the vibration of the piezoelectric vibrating reed. With this configuration, since the auxiliary bump is disposed at the nodal point of vibration, the vibration of the piezoelectric vibrating reed will rarely leak to the outside through the auxiliary bump. Therefore, it is possible to further suppress the vibration leakage of the piezoelectric vibrator while securing the mounting strength of the piezoelectric vibrating reed.

A recess portion is preferably formed on a side surface in the width direction of the base portion, and the recess portion is preferably disposed between the main bumps and the auxiliary bump in the longitudinal direction.

With this configuration, since the recess portion is formed on the side surface in the width direction of the base portion, the vibration of the vibrating arm is more rarely transmitted to the base end side than the recess portion. Moreover, since the recess portion is disposed between the main bumps and the auxiliary bump in the longitudinal direction, the vibration of the piezoelectric vibrating reed will rarely be transmitted to the main bump. As a result, the vibration of the piezoelectric vibrating reed will rarely leak to the outside through the main bumps. Therefore, it is possible to further suppress the vibration leakage of the piezoelectric vibrator while securing the mounting strength of the piezoelectric vibrating reed.

According to another aspect of the invention, there is provided an oscillator in which the above-described piezoelectric vibrator is electrically connected to an integrated circuit as an oscillating piece.

According to still another aspect of the invention, there is provided an electronic apparatus in which the above-described piezoelectric vibrator is electrically connected to a clock section.

According to still another aspect of the invention, there is provided a radio-controlled timepiece in which the above-described piezoelectric vibrator is electrically connected to a filter section.

Since each of the oscillator, electronic apparatus, and radio-controlled timepiece of the above aspects of the present invention includes the piezoelectric vibrator capable of suppressing the vibration leakage while securing the mounting strength of the piezoelectric vibrating reed, an oscillator, an electronic apparatus, and a radio-controlled timepiece having superior reliability and excellent performance can be provided.

According to this configuration, since the base portion of the piezoelectric vibrating reed is bonded to the package by the plurality of main bumps and the auxiliary bump, it is possible to improve the mounting strength of the piezoelectric vibrating reed. Moreover, the auxiliary bump is bonded to the base portion in an area between the main bumps disposed at both ends in the width direction of the base portion and an area between the main bumps and base ends of the vibrating arms in the longitudinal direction of the base portion. These areas are near the nodal point of vibration as disclosed in the Journal of IEICE (The Institute of Electronics, Information and Communication Engineers), Volume J72-A, No. 11, Page 1736, November 1989. Therefore, the magnitude of vibration of the piezoelectric vibrating reed is small in these areas. Since the auxiliary bump is bonded to the base portion in the areas near the nodal point of vibration where the magnitude of vibration is small, the vibration of the piezoelectric vibrating reed will rarely leak to the outside through the auxiliary bump. In this way, it is possible to suppress the vibration leakage of the piezoelectric vibrator. Therefore, it is possible to suppress the vibration leakage of the piezoelectric vibrator while securing the mounting strength of the piezoelectric vibrating reed.

DESCRIPTION OF PREFERRED EMBODIMENT

Hereinafter, a piezoelectric vibrator and a piezoelectric vibrating reed according to an embodiment of the present invention will be described with reference to the accompanying drawings.

Moreover, in the following description, it is assumed that the mounting surface of a base substrate bonded to a lid substrate is an upper surface U and the opposite surface is a lower surface L.

Moreover, it is assumed that the longitudinal direction of the piezoelectric vibrator is a longitudinal direction X, a base end side of the vibrating arm is a positive X direction, and a tip end side of the vibrating arm is a negative X direction. Moreover, it is assumed that the width direction of the piezoelectric vibrating reed is a width direction W.

FIG. 1is a perspective view showing an external appearance of a piezoelectric vibrator according to an embodiment of the present invention.

FIG. 2is a top view showing an inner structure of the piezoelectric vibrator, showing a state where a lid substrate is removed.

FIG. 3is a sectional view of the piezoelectric vibrator taken along the line A-A inFIG. 2.

FIG. 4is an exploded perspective view of the piezoelectric vibrator shown inFIG. 1. InFIG. 4, for better understanding of the drawings, illustrations of the excitation electrode15, extraction electrodes19and20, main mount electrodes16and17, auxiliary mount electrode25, and weight metal film21are omitted.

As shown inFIGS. 1 to 4, a piezoelectric vibrator1according to the present embodiment is a surface mount device-type piezoelectric vibrator1which includes a package9, in which a base substrate2and a lid substrate3are anodically bonded to each other with a bonding film35disposed therebetween, and a piezoelectric vibrating reed4which is accommodated in a cavity C of the package9.

Piezoelectric Vibrating Reed

FIG. 5is a top view of a piezoelectric vibrating reed.

FIG. 6is a bottom view of the piezoelectric vibrating reed.

FIG. 7is a sectional view taken along the line B-B inFIG. 5.

InFIGS. 5 to 7, it is assumed that the mounting surface of the piezoelectric vibrating reed4is a lower surface Q and the opposite surface is an upper surface P.

Hereinafter, the piezoelectric vibrating reed4will be described with reference to the drawings.

As shown inFIGS. 5 to 7, the piezoelectric vibrating reed4is a turning-fork type vibrating reed which is made of a piezoelectric material such as crystal, lithium tantalate, or lithium niobate and is configured to vibrate when a predetermined voltage is applied thereto.

As shown inFIGS. 5 and 6, the piezoelectric vibrating reed4according to the present embodiment includes a pair of vibrating arms10and11arranged in a line in the width direction W and a base portion12that integrally fixes the base end sides in the longitudinal direction X of the pair of vibrating arms10and11. The piezoelectric vibrating reed4further includes an excitation electrode15which is formed on the outer surfaces of the pair of vibrating arms10and11so as to vibrate the pair of vibrating arms10and11and which includes a first excitation electrode13and a second excitation electrode14.

On both the upper surface P and the lower surface Q of each of the pair of vibrating arms10and11, a pair of vertically long groove portions18is formed to have a fixed width along the longitudinal direction X. The groove portions18are formed in a range exceeding intermediate portions from the base end sides of the vibrating arms10and11. As a result, each of the pair of vibrating arms10and11has an H-shaped section when seen along the line B-B as shown inFIG. 7.

As shown inFIGS. 5 and 6, the pair of excitation electrodes13and14is formed on both the upper surface P and the lower surface Q of each of the pair of vibrating arms10and11. The pair of excitation electrodes13and14is an electrode that allows the pair of vibrating arms10and11to vibrate at a predetermined resonance frequency in a direction of moving closer to or away from each other when a voltage is applied thereto. The pair of excitation electrodes13and14is patterned on the surfaces of the pair of vibrating arms10and11in an electrically isolated state. Specifically, as shown inFIG. 7, one excitation electrode13is mainly formed in the groove portion18of one vibrating arm10and on the side surfaces of the other vibrating arm11. On the other hand, the other excitation electrode14is mainly formed on the side surfaces of one vibrating arm10and in the groove portion18of the other vibrating arm11.

In addition, as shown inFIGS. 5 and 6, a weight metal film21configured to include a rough tuning film21aand a fine tuning film21bfor adjusting (frequency adjustment) the vibrating states of the pair of vibrating arms10and11to vibrate within a predetermined frequency range is formed at the distal ends of the vibrating arms10and11. By performing frequency adjustment using the weight metal film21, the frequency of the pair of the vibrating arms10and11can be set to fall within the nominal frequency range of the device.

Base Portion

As shown inFIGS. 5 and 6, the base portion12is adjacent to the vibrating arms10and11and supports the base ends of the vibrating arms10and11. A pair of recess portions41and42is formed on both side surfaces43and44in the width direction W of the base portion12. In the present embodiment, the width of the base portion12in the positive X direction with respect to the recess portions41and42is larger than the width of the base portion12in the negative X direction with respect to the recess portions41and42.

The recess portions41and42are formed between the main mount electrodes16and17and the auxiliary mount electrode25so that the recess portions41and42are disposed between the main bumps and the auxiliary bump in the longitudinal direction X when the piezoelectric vibrating reed4is mounted on the base substrate. The depths of the recess portions41and42are equal to the width W1of each of the vibrating arms10and11in the base portion12in the positive X direction, and the bottom surfaces of the recess portions41and42are formed approximately in parallel along the central axis O. Moreover, the recess portions41and42penetrate the piezoelectric vibrating reed4in the thickness direction from the upper surface P to reach the lower surface Q. In this way, by forming the recess portions41and42while increasing the width of the base portion12in the positive X direction, it is possible to secure the strength of the base portion12. In addition, since the vibration of the piezoelectric vibrating reed4is more rarely transmitted in the positive X direction than towards the recess portions41and42, the vibration of the piezoelectric vibrating reed4is rarely transmitted to the main bumps B1disposed closer to the positive X direction than the recess portions41and42. Therefore, it is possible to suppress the vibration leakage of the piezoelectric vibrator.

Main Mount Electrode and Auxiliary Mount Electrode

The pair of main mount electrodes16and17and the pair of extraction electrodes19and20are formed on both the upper surface P and the lower surface Q of the base portion12. The main mount electrodes16and17are electrically connected to the excitation electrodes13and14through the extraction electrodes19and20, respectively. Therefore, a voltage is applied to the pair of excitation electrodes13and14through the pair of main mount electrodes16and17and the pair of extraction electrodes19and20. In addition, in addition to the main mount electrodes16and17and the extraction electrodes19and20, the auxiliary mount electrode25is formed on both the upper surface P and the lower surface Q of the base portion12. Since the main mount electrodes16and17and the auxiliary mount electrode25are formed on both the upper surface P and the lower surface Q, it becomes unnecessary to distinguish the front and rear sides of the piezoelectric vibrating reed4at the time of mounting. Thus, it is possible to prevent assembling errors of the piezoelectric vibrating reed4. In addition, although the auxiliary mount electrode25of the present embodiment is formed in an approximately rectangular shape in top view, a circular shape, for example, is also possible.

The main mount electrodes16and17and the auxiliary mount electrode25are formed by forming a chromium (Cr) film as a base layer and forming a gold (Au) film thereon as a finishing layer. By forming the main mount electrodes16and17and the auxiliary mount electrode25so as to have the same structure, it is possible to form the main mount electrodes16and17and the auxiliary mount electrode25at the same time. In addition, in a mounting step described later, the auxiliary mount electrode25can be bonded to the auxiliary bump under the same conditions as the bonding of the main mount electrodes16and17to the main bumps.

As shown inFIG. 6, the auxiliary mount electrode25is formed between the main mount electrodes16and17and the base ends of the vibrating arms10and11in the longitudinal direction X and between the main mount electrodes16and17in the width direction W.

As disclosed in the Journal of IEICE (The Institute of Electronics, Information and Communication Engineers), Volume J72-A, No. 11, Page 1736, November 1989, in the longitudinal direction X of the piezoelectric vibrating reed4, the nodal point G of the vibration of the piezoelectric vibrating reed4is disposed at the position which is separated from the tip end of the base portion12toward the base end side by a distance corresponding to approximately ½ of the width W1of the vibrating arms10and11. Moreover, the nodal point G of the vibration of the piezoelectric vibrating reed4is disposed approximately at the center in the width direction W of the piezoelectric vibrating reed4.

The auxiliary mount electrode25is disposed so as to include the nodal point G of the vibration described above. By doing so, since the auxiliary bump can be bonded to the base portion12in the area near the nodal point G of vibration where the magnitude of vibration is small, the vibration of the piezoelectric vibrating reed4will rarely leak to the outside through the auxiliary bump. Furthermore, in the present embodiment, the auxiliary mount electrode25is disposed so that the center of the auxiliary mount electrode25is identical to the nodal point G of the vibration described above. Since the nodal point G of the vibration does not vibrate, by bonding the auxiliary bump with the center of the auxiliary mount electrode25identical to the nodal point G of the vibration, the vibration of the piezoelectric vibrating reed4will yet more rarely leak to the outside. Therefore, it is possible to further suppress the vibration leakage of the piezoelectric vibrator while securing the mounting strength of the piezoelectric vibrating reed4.

The auxiliary mount electrode25of the present embodiment is formed in a state of being electrically isolated from the main mount electrodes16and17and the extraction electrodes19and20which are formed in the base portion12. Therefore, short-circuiting between the electrodes can be prevented. Since the auxiliary mount electrode25is not electrically connected to the outer electrodes of the piezoelectric vibrator described later, no power is supplied from the outer electrodes to the auxiliary mount electrode25. Therefore, when the auxiliary mount electrode25is electrically connected to only one main mount electrode, there will be no short-circuit between the electrodes. Thus, the auxiliary mount electrode25can be formed to be connected to one extraction electrode which is adjacent to the auxiliary mount electrode25. In this way, it is unnecessary to form electrodes with a small gap around the auxiliary mount electrode25.

Piezoelectric Vibrator

As shown inFIGS. 1,3, and4, the lid substrate3is a substrate that can be anodically bonded and that is made of a glass material, for example, soda-lime glass, and is formed in a plate-like form. On a bonding surface side of the lid substrate3to be bonded to the base substrate2, a recess portion3afor a cavity is formed in which the piezoelectric vibrating reed4is accommodated. The recess portion3afor a cavity serves as a cavity C that accommodates the piezoelectric vibrating reed4when the two substrates2and3are superimposed onto each other.

The base substrate2is a substrate that is made of a glass material, for example, soda-lime glass, and is formed in an approximately plate-like form having the same outer shape as the lid substrate3as shown inFIGS. 1 to 4. Moreover, the base substrate2is formed with a pair of penetration holes30and31penetrating through the base substrate2in the thickness direction thereof and a pair of penetration electrodes32and33.

As shown inFIGS. 2 and 3, the penetration holes30and31are formed so as to be received in the cavity C when the piezoelectric vibrator1is formed. More specifically, the penetration holes30and31of the present embodiment are formed such that one penetration hole30is positioned at a corresponding position close to the base portion12of the mounted piezoelectric vibrating reed4which is mounted in a mounting step described later, and the other penetration hole31is positioned at a corresponding position close to the tip end sides of the vibrating arms10and11.

As shown inFIG. 3, the penetration electrode32is formed by a cylindrical member6made of glass and a conductive member7which are disposed at the inner side of the penetration hole30.

In the present embodiment, the cylindrical member6is obtained by baking a paste-like glass frit. The cylindrical member6has a shape of which both ends are flat and which has approximately the same thickness as the base substrate2. The conductive member7is disposed at the center of the cylindrical member6so as to penetrate through the cylindrical member6. The cylindrical member6is tightly attached to the conductive member7and the penetration hole30.

The cylindrical member6and the conductive member7serve to maintain airtightness of the inside of the cavity C by completely closing the penetration hole30and also to make a lead-out electrode36and an outer electrode38described later electrically connected to each other. The penetration electrode33is formed similarly to the penetration electrode32. Moreover, the same relationship between the penetration electrode32, the lead-out electrode36, and the outer electrode39applies to the relationship between the penetration electrode33, the lead-out electrode37, and the outer electrode39.

As shown inFIGS. 2 to 4, a pair of lead-out electrodes36and37is formed on the upper surface U side of the base substrate2. In addition, an auxiliary electrode34which is separated from the lead-out electrodes36and37is formed on the upper surface U side of the base substrate2. Moreover, the lead-out electrodes36and37and the auxiliary electrode34are formed of a material having high conductivity and high resistance to corrosion. In the present embodiment, the lead-out electrodes36and37and the auxiliary electrode34are formed by forming a Cr film as a base layer and forming an Au film thereon as a finishing layer. Since a Cr film having high adhesion to a glass-based substrate is used as the base layer, the lead-out electrodes36and37and the auxiliary electrode34can be firmly attached to the upper surface U of the base substrate wafer40which is made of a glass-based material. By forming the lead-out electrodes36and37and the auxiliary electrode34so as to have the same structure, it is possible to form the lead-out electrodes36and37and the auxiliary electrode34at the same time. In addition, when bumps are formed by wire bonding in an electrode pattern forming step described later, the auxiliary bump can be formed on the auxiliary electrode34with the same condition as the forming of the main bumps on the lead-out electrodes36and37.

As shown inFIG. 4, one lead-out electrode36among the pair of lead-out electrodes36and37is formed so as to be disposed right above one penetration electrode32. Moreover, the other lead-out electrode37is formed so as to be disposed right above the other penetration electrode33after being led out from a position near one lead-out electrode36towards the tip end sides of the vibrating arms10and11along the vibrating arms10and11.

Moreover, the auxiliary electrode34is positioned in the negative X direction of the penetration electrodes32and33in the longitudinal direction X and between the penetration electrodes32and33in the width direction W and is formed at a position corresponding to the auxiliary mount electrode25of the piezoelectric vibrating reed4. The auxiliary electrode34is not electrically connected to the penetration electrodes32and33.

Moreover, as shown inFIGS. 1,3, and4, a pair of outer electrodes38and39is formed on the lower surface L of the base substrate2. The pair of outer electrodes38and39is formed at both ends in the longitudinal direction of the base substrate2and is electrically connected to the pair of penetration electrodes32and33, respectively.

Main Bump and Auxiliary Bump

A pair of main bumps B1is formed on the pair of lead-out electrodes36and37described above. Moreover, an auxiliary bump B2is formed on the auxiliary electrode34. The main bumps B1and the auxiliary bump B2are formed in a tapered form by gold material.

In a mounting step described later, the pair of main mount electrodes16and17of the piezoelectric vibrating reed4is bonded to the pair of main bumps B1. When the pair of main mount electrodes16and17is bonded to the pair of main bumps B1, one main mount electrode16is electrically connected to one penetration electrode32through one lead-out electrode36, and the other main mount electrode17is electrically connected to the other penetration electrode33through the other lead-out electrode37.

The auxiliary mount electrode25is bonded to the auxiliary bump B2at the same time as the bonding of the main mount electrodes16and17to the main bumps B1. The auxiliary mount electrode25of the base portion12is bonded to the auxiliary bump B2in an area between the main bumps B1in the width direction W of the base portion12and an area between the main bumps B1and the base ends of the vibrating arms10and11in the longitudinal direction X of the base portion12.

When the piezoelectric vibrator1configured in this manner is operated, a predetermined drive voltage is applied between the outer electrodes38and39formed on the base substrate2. In this way, since a voltage can be applied to the excitation electrode15including the first and second excitation electrodes13and14, of the piezoelectric vibrating reed4through the main bumps B1, the pair of vibrating arms10and11can be allowed to vibrate at a predetermined frequency in a direction of moving closer to or away from each other. This vibration of the pair of vibrating arms10and11can be used as the time source, the timing source of a control signal, the reference signal source, and the like.

In the present embodiment, the auxiliary bump B2is bonded to the nodal point G of the vibration of the piezoelectric vibrating reed4described above. When the piezoelectric vibrating reed4vibrates, since the nodal point G of the vibration does not vibrate, the vibration of the piezoelectric vibrating reed4rarely leaks to the outside through the auxiliary bump B2. Therefore, it is possible to suppress the vibration leakage of the piezoelectric vibrator1while securing the mounting strength of the piezoelectric vibrating reed4.

Piezoelectric Vibrator Manufacturing Method

Next, a method for manufacturing the above-described piezoelectric vibrator will be described with reference to a flowchart.

FIG. 8is a flowchart of the manufacturing method of a piezoelectric vibrator according to the present embodiment.

FIG. 9is an exploded perspective view of a wafer assembly. The dotted line shown inFIG. 9is a cutting line M along which a cutting step performed later is achieved.

The manufacturing method of the piezoelectric Vibrator according to the present embodiment mainly includes a piezoelectric vibrating reed manufacturing step (S10), a lid substrate wafer manufacturing step (S20), a base substrate wafer manufacturing step (S30), and an assembling step (S50and subsequent steps). Among the steps, the piezoelectric vibrating reed manufacturing step (S10), the lid substrate wafer manufacturing step (S20), and the base substrate wafer manufacturing step (S30) can be performed in parallel.

Piezoelectric Vibrating Reed Manufacturing Step

In the piezoelectric vibrating reed manufacturing step S10, the piezoelectric vibrating reed4shown inFIGS. 5 to 7is manufactured. Specifically, first, a rough quartz crystal Lambert is sliced at a predetermined angle to obtain a wafer having a constant thickness. Subsequently, the wafer is subjected to crude processing by lapping, and an affected layer is removed by etching. Then, the wafer is subjected to mirror polishing processing such as polishing to obtain a wafer having a predetermined thickness. Subsequently, the wafer is subjected to appropriate processing such as washing, and the wafer is patterned so as to have the outer shape of the piezoelectric vibrating reed4by a photolithography technique. Moreover, a metal film is formed and patterned on the wafer, thus forming the excitation electrode15, the extraction electrodes19and20, the main mount electrodes16and17, the auxiliary mount electrode25, and the weight metal film21. In this way, a plurality of piezoelectric vibrating reeds4can be manufactured. Subsequently, rough tuning of the resonance frequency of the piezoelectric vibrating reed4is performed. This rough tuning is achieved by irradiating the rough tuning film21aof the weight metal film21with a laser beam to evaporate in part the rough tuning film21a, thus changing the weight of the vibrating arms10and11.

Lid Substrate Wafer Manufacturing Step

In the lid substrate wafer manufacturing step S20, as shown inFIG. 9, the lid substrate wafer50later serving as the lid substrate is manufactured. First, a disk-shaped lid substrate wafer50made of a soda-lime glass is polished to a predetermined thickness and cleaned, and then, the affected uppermost layer is removed by etching or the like (S21). Subsequently, in a cavity forming step S22, a plurality of recess portions3afor cavities is formed on a bonding surface of the lid substrate wafer50to be bonded to the base substrate wafer40. The recess portions3afor cavities are formed by heat-press molding, etching, or the like. After that, in a bonding surface polishing step S23, the bonding surface bonded to the base substrate wafer40is polished.

Subsequently, in a bonding film forming step S24, a bonding film35shown inFIGS. 1,3, and4is formed on the bonding surface to be bonded to the base substrate wafer40. The bonding film35may be formed on the entire inner surface of the cavity C in addition to the bonding surface to be bonded to the base substrate wafer40. In this way, patterning of the bonding film35is not necessary, and the manufacturing cost can be reduced. The bonding film35can be formed by a film-formation method such as sputtering or CVD. Since the bonding surface polishing step S23is performed before the bonding film forming step S24, the flatness of the surface of the bonding film35can be secured, and stable bonding with the base substrate wafer40can be achieved.

Base Substrate Wafer Manufacturing Step

In a base substrate wafer manufacturing step S30, as shown inFIG. 9, the base substrate wafer40later serving as the base substrate is manufactured. First, a disk-shaped base substrate wafer40made of a soda-lime glass is polished to a predetermined thickness and cleaned, and then, the affected uppermost layer is removed by etching or the like (S31).

Penetration Electrode Forming Step

Subsequently, a penetration electrode forming step S32is performed where the pair of penetration electrodes32and33is formed on the base substrate wafer40. In the following description, although only the step of forming the penetration electrode32is described, the same applies to the step of forming the penetration electrode33.

First, penetration holes30are formed in the base substrate wafer40by performing press working or the like in a direction from the lower surface L towards the upper surface U. Subsequently, the conductive member7is inserted into the penetration holes30and a paste material made of glass frit is filled therein. After that, the paste material is baked so that the cylindrical member6made of glass, the penetration holes30, and the conductive member7are integrated with each other. Finally, both the upper surface U and the lower surface L of the base substrate wafer40are polished to obtain a flat surface while exposing the conductive member7to both the upper surface U and the lower surface L, whereby the penetration electrodes32are formed in the penetration holes30. With the penetration electrodes32, electrical connection between the upper surface U side and the lower surface L side of the base substrate wafer40is secured, and airtightness of the inside of the cavity C can be secured.

Electrode Pattern Forming Step

Subsequently, as shown inFIGS. 4 and 9, an electrode pattern forming step S34is performed where the lead-out electrodes36and37and the auxiliary electrode34are formed on the upper surface U of the base substrate wafer40. In the present embodiment, since the lead-out electrodes36and37and the auxiliary electrode34are made of the same material, it is possible to form the lead-out electrodes36and37and the auxiliary electrode34at the same time. The lead-out electrodes36and37and the auxiliary electrode34are formed by patterning a coating formed by a sputtering method, a vacuum deposition method, or the like using a photolithography technique.

Moreover, as shown inFIGS. 2 to 4, a pair of main bumps B1is formed on the pair of lead-out electrodes36and37, and an auxiliary bump B2is formed on the auxiliary electrode34. Specifically, the bumps are formed as follows.

First, the tip end of an ultrafine gold wire is welded using a wire bonder, and a gold ball is formed on the tip end of the gold wire. Subsequently, the gold ball at the tip end of the gold wire is bonded to the bump formation positions of the lead-out electrodes36and37and the auxiliary electrode34, and then, the gold wire is pulled and cut, whereby the main bumps B1and the auxiliary bump B2are formed. InFIG. 9, for better understanding of the drawing, illustrations of the main bumps and the auxiliary bump are omitted. The base substrate wafer manufacturing step S30ends at this point in time.

Mounting Step

Subsequently, a mounting step S50is performed where the piezoelectric vibrating reeds4are bonded to the lead-out electrodes36and37and the auxiliary electrode34of the base substrate wafer40by the main bumps B1and the auxiliary bump B2. In the present embodiment, the piezoelectric vibrating reeds4are mounted on the base substrate wafer40by a flip-chip bonding method.

Specifically, first, the piezoelectric vibrating reeds4are picked up by performing vacuum suction or the like using a bonding head of a flip chip bonder (not shown), and the piezoelectric vibrating reeds4are moved onto the base substrate wafer40. Subsequently, the main mount electrodes16and17are pressed against the main bumps B1formed on the lead-out electrodes36and37, and the auxiliary mount electrode25is pressed against the auxiliary bump B2formed on the auxiliary electrode34. After that, the bonding head is heated so that a bonding interface between the main mount electrodes16and17and the lead-out electrodes36and37and the bonding interface between the auxiliary mount electrode25and the auxiliary electrode34are heated to a predetermined temperature. Then, the bonding head is ultrasonically vibrated in the horizontal and vertical directions. In this way, the main mount electrodes16and17can be ultrasonically bonded to the main bumps B1, and the auxiliary mount electrode25can be ultrasonically bonded to the auxiliary bump B2. Moreover, as shown inFIG. 3, the base portion12, the main bumps B1, and the auxiliary bump B2are mechanically fixed in a state where the vibrating arms10and11of the piezoelectric vibrating reed4are floated from the upper surface U of the base substrate wafer40.

Superimposition Step and Subsequent Steps

After the mounting of the piezoelectric vibrating reed4is completed, as shown inFIG. 9, a superimposition step S60is performed where the lid substrate wafer50is superimposed onto the base substrate wafer40. Specifically, the two wafers40and50are aligned at a correct position using reference marks or the like not shown in the figure as indices. In this way, the piezoelectric vibrating reed4mounted on the base substrate wafer40is accommodated in the cavity C which is surrounded by the recess portion3afor cavities of the lid substrate wafer50and the base substrate wafer40.

After the superimposition step S60is performed, a bonding step S70is performed where the two superimposed wafers40and50are inserted into an anodic bonding machine (not shown) to achieve anodic bonding under a predetermined temperature atmosphere with application of a predetermined voltage. Specifically, a predetermined voltage is applied between the bonding film35and the base substrate wafer40. Then, an electrochemical reaction occurs at an interface between the bonding film35and the base substrate wafer40, whereby they are closely and tightly adhered and anodically bonded. In this way, the piezoelectric vibrating reed4can be sealed in the cavity C, and a wafer assembly60in which the base substrate wafer40and the lid substrate wafer50are bonded to each other can be obtained as shown inFIG. 9. InFIG. 9, for better understanding of the drawing, the wafer assembly60is illustrated in an exploded state, and illustration of the bonding film35is omitted from the lid substrate wafer50.

Subsequently, an outer electrode forming step S80is performed where a conductive material is patterned onto the lower surface L of the base substrate wafer40so as to form a plurality of pairs of outer electrodes38and39(seeFIG. 3) which is electrically connected to the pair of penetration electrodes32and33. By this step, the piezoelectric vibrating reed4is electrically connected to the outer electrodes38and39through the main bumps B1, the lead-out electrodes36and37, and the penetration electrodes32and33.

Subsequently, a fine tuning step S90is performed on the wafer assembly60where the frequencies of the individual piezoelectric vibrators sealed in the cavities C are tuned finely to fall within a predetermined range. Specifically, a predetermined voltage is continuously applied to the outer electrodes38and39shown inFIG. 4to allow the piezoelectric vibrating reeds4to vibrate, and the vibration frequency is measured. In this state, a laser beam is irradiated onto the base substrate wafer40from the outer side so as to evaporate the fine tuning film21bof the weight metal film21shown inFIGS. 5 and 6. In this way, since the weight on the tip end sides of the pair of vibrating arms10and11decreases, the frequency of the piezoelectric vibrating reed4increases. By so doing, the frequency of the piezoelectric vibrator can be finely tuned so as to fall within the range of the nominal frequency.

After the fine tuning of the frequency is completed, a cutting step S100is performed where the bonded wafer assembly60is cut along the cutting line M shown inFIG. 9. Specifically, first, a UV tape is attached on the surface of the base substrate wafer40of the wafer assembly60. Subsequently, a laser beam is irradiated along the cutting line M from the side of the lid substrate wafer50(scribing). Subsequently, the wafer assembly60is divided and cut along the cutting line M by a cutting blade pressing against the surface of the UV tape (breaking). After that, the UV tape is separated by irradiation of UV light. In this way, it is possible to divide the wafer assembly60into a plurality of piezoelectric vibrators. The wafer assembly60may be cut by other methods such as dicing.

Moreover, the fine adjustment step S90may be performed after cutting the wafer assembly into pieces of individual piezoelectric vibrators in the cutting step S100. However, as described above, the fine adjustment can be performed on the form of the wafer assembly60by performing the fine adjustment step S90first. Therefore, in the case of performing the fine adjustment step S90first, a plurality of piezoelectric vibrators can be finely adjusted more efficiently. This is preferable since the throughput can be improved.

Then, an inner electrical property test S110is performed. That is, resonance frequency, resonant resistance value, drive level characteristics (excitation power dependency of resonance frequency and resonant resistance value), and the like of the piezoelectric vibrating reed4are checked by measurement. Moreover, an insulation resistance characteristic and the like are checked together. Finally, visual inspection of the piezoelectric vibrator is performed to finally check the dimensions, quality, and the like. Thus, the manufacturing of the piezoelectric vibrator ends.

According to the present embodiment, as shown inFIGS. 2 to 4, since the base portion12of the piezoelectric vibrating reed4is bonded to the base substrate2by the plurality of main bumps B1and the auxiliary bump B2, it is possible to improve the mounting strength of the piezoelectric vibrating reed4. Moreover, the auxiliary bump B2is bonded to the base portion12in an area between the main bumps B1disposed at both ends in the width direction W of the base portion12and an area between the main bumps B1and the base ends of the vibrating arms10and11in the longitudinal direction X of the base portion12. These areas are near the nodal point G of vibration as disclosed in the Journal of IEICE (The Institute of Electronics, Information and Communication Engineers), Volume J72-A, No. 11, Page 1736, November 1989. Therefore, the magnitude of vibration of the piezoelectric vibrating reed4is small in these areas. Since the auxiliary bump B2is bonded to the base portion12in the areas near the nodal point G of vibration where the magnitude of vibration is small, the vibration of the piezoelectric vibrating reed4will rarely leak to the outside through the auxiliary bump B2. In this way, it is possible to suppress the vibration leakage of the piezoelectric vibrator1. Therefore, it is possible to suppress the vibration leakage of the piezoelectric vibrator1while securing the mounting strength of the piezoelectric vibrating reed4.

Moreover, according to the present embodiment, the auxiliary bump B2is disposed at the nodal point G of the vibration which is separated from the tip end of the base portion12of the piezoelectric vibrating reed4towards the base end side in the positive X direction by a distance corresponding to ½ of the width W1of the vibrating arm. Since the nodal point G of the vibration does not vibrate, the vibration of the piezoelectric vibrating reed4will rarely leak to the outside through the auxiliary bump B2. Therefore, it is possible to further suppress the vibration leakage of the piezoelectric vibrator1while securing the mounting strength of the piezoelectric vibrating reed4.

Furthermore, according to the present embodiment, since the recess portions41and42are formed on the side surfaces43and44in the width direction W of the base portion12, the vibration of the vibrating arms10and11is more rarely transmitted to the base end side than the recess portions41and42. Moreover, since the recess portions41and42are disposed between the main bumps B1and the auxiliary bump B2in the longitudinal direction X, the vibration of the piezoelectric vibrating reed4will rarely be transmitted to the main bumps B1. As a result, the vibration of the piezoelectric vibrating reed4will rarely leak to the outside through the main bumps B1. Therefore, it is possible to further suppress the vibration leakage of the piezoelectric vibrator1while securing the mounting strength of the piezoelectric vibrating reed4.

Oscillator

Next, an oscillator according to another embodiment of the invention will be described with reference toFIG. 10.

In an oscillator110according to the present embodiment, the piezoelectric vibrator1is used as an oscillating piece electrically connected to an integrated circuit111, as shown inFIG. 10. The oscillator110includes a substrate113on which an electronic component112, such as a capacitor, is mounted. The integrated circuit111for an oscillator is mounted on the substrate113, and the piezoelectric vibrating reed of the piezoelectric vibrator1is mounted near the integrated circuit111. The electronic component112, the integrated circuit111, and the piezoelectric vibrator1are electrically connected to each other by a wiring pattern (not shown). In addition, each of the constituent components is molded with a resin (not shown).

In the oscillator110configured as described above, when a voltage is applied to the piezoelectric vibrator1, the piezoelectric vibrating reed in the piezoelectric vibrator1vibrates. This vibration is converted into an electrical signal due to the piezoelectric property of the piezoelectric vibrating reed and is then input to the integrated circuit111as the electrical signal. The input electrical signal is subjected to various kinds of processing by the integrated circuit111and is then output as a frequency signal. In this way, the piezoelectric vibrator1functions as an oscillator piece.

Moreover, by selectively setting the configuration of the integrated circuit111, for example, an RTC (real time clock) module, according to the demands, it is possible to add a function of controlling the operation date or time of the corresponding device or an external device or of providing the time or calendar in addition to a single functional oscillator for a clock.

As described above, since the oscillator110according to the present embodiment includes the piezoelectric vibrator1capable of suppressing vibration leakage while securing mounting strength of the piezoelectric vibrating reed, the oscillator110having superior reliability and excellent performance can be provided.

Electronic Apparatus

Next, an electronic apparatus according to another embodiment of the invention will be described with reference toFIG. 11. In addition, a portable information device120including the piezoelectric vibrator1will be described as an example of an electronic apparatus.

The portable information device120according to the present embodiment is represented by a mobile phone, for example, and has been developed and improved from a wristwatch in the related art. The portable information device120is similar to a wristwatch in external appearance, and a liquid crystal display is disposed in a portion equivalent to a dial pad so that a current time and the like can be displayed on this screen. Moreover, when it is used as a communication apparatus, it is possible to remove it from the wrist and to perform the same communication as a mobile phone in the related art with a speaker and a microphone built in an inner portion of the band. However, the portable information device120is very small and light compared with a mobile phone in the related art.

Next, the configuration of the portable information device120according to the present embodiment will be described. As shown inFIG. 11, the portable information device120includes the piezoelectric vibrator1and a power supply section121for supplying power. The power supply section121is formed of a lithium secondary battery, for example. A control section122which performs various kinds of control, a clock section123which performs counting of time and the like, a communication section124which performs communication with the outside, a display section125which displays various kinds of information, and a voltage detecting section126which detects the voltage of each functional section are connected in parallel to the power supply section121. In addition, the power supply section121supplies power to each functional section.

The control section122controls an operation of the entire system. For example, the control section122controls each functional section to transmit and receive the audio data or to measure or display a current time. In addition, the control section122includes a ROM in which a program is written in advance, a CPU which reads and executes a program written in the ROM, a RAM used as a work area of the CPU, and the like.

The clock section123includes an integrated circuit, which has an oscillation circuit, a register circuit, a counter circuit, and an interface circuit therein, and the piezoelectric vibrator1. When a voltage is applied to the piezoelectric vibrator1, the piezoelectric vibrating reed vibrates, and this vibration is converted into an electrical signal due to the piezoelectric property of crystal and is then input to the oscillation circuit as the electrical signal. The output of the oscillation circuit is binarized to be counted by the register circuit and the counter circuit. Then, a signal is transmitted to or received from the control section122through the interface circuit, and current time, current date, calendar information, and the like are displayed on the display section125.

The communication section124has the same function as a mobile phone in the related art, and includes a wireless section127, an audio processing section128, a switching section129, an amplifier section130, an audio input/output section131, a telephone number input section132, a ring tone generating section133, and a call control memory section134.

The wireless section127transmits/receives various kinds of data, such as audio data, to/from the base station through an antenna135. The audio processing section128encodes and decodes an audio signal input from the wireless section127or the amplifier section130. The amplifier section130amplifies a signal input from the audio processing section128or the audio input/output section131up to a predetermined level. The audio input/output section131is formed by a speaker, a microphone, and the like, and amplifies a ring tone or incoming sound to a louder volume or collects the sound.

In addition, the ring tone generating section133generates a ring tone in response to a call from the base station. The switching section129switches the amplifier section130, which is connected to the audio processing section128, to the ring tone generating section133only when a call arrives, so that the ring tone generated in the ring tone generating section133is output to the audio input/output section131through the amplifier section130.

In addition, the call control memory section134stores a program related to incoming and outgoing call control for communications. Moreover, the telephone number input section132includes, for example, numeric keys from 0 to 9 and other keys. The user inputs a telephone number of a communication destination by pressing these numeric keys and the like.

The voltage detecting section126detects a voltage drop when a voltage, which is applied from the power supply section121to each functional section, such as the control section122, drops below the predetermined value, and notifies the control section122of the detection. In this case, the predetermined voltage value is a value which is set beforehand as a lowest voltage necessary to operate the communication section124stably. For example, it is about 3 V. When the voltage drop is notified from the voltage detecting section126, the control section122disables the operation of the wireless section127, the audio processing section128, the switching section129, and the ring tone generating section133. In particular, the operation of the wireless section127that consumes a large amount of power should be necessarily stopped. In addition, a message informing that the communication section124is not available due to insufficient battery power is displayed on the display section125.

That is, it is possible to disable the operation of the communication section124and display the notice on the display section125by the voltage detecting section126and the control section122. This message may be a character message. Or as a more intuitive indication, a cross mark (X) may be displayed on a telephone icon displayed at the top of the display screen of the display section125.

In addition, the function of the communication section124can be more reliably stopped by providing a power shutdown section136capable of selectively shutting down the power of a section related to the function of the communication section124.

As described above, since the portable information device120according to the present embodiment includes the piezoelectric vibrator1capable of suppressing vibration leakage while securing a mounting strength of the piezoelectric vibrating reed, the portable information device120having superior reliability and excellent performance can be provided.

Next, a radio-controlled timepiece according to still another embodiment of the invention will be described with reference toFIG. 12.

As shown inFIG. 12, a radio-controlled timepiece140according to the present embodiment includes the piezoelectric vibrators1electrically connected to a filter section141. The radio-controlled timepiece140is a clock with a function of receiving a standard radio wave including the clock information, automatically changing it to the correct time, and displaying the correct time.

In Japan, there are transmission centers (transmission stations) that transmit a standard radio wave in Fukushima Prefecture (40 kHz) and Saga Prefecture (60 kHz), and each center transmits the standard radio wave. A long wave with a frequency of, for example, 40 kHz or 60 kHz has both a characteristic of propagating along the land surface and a characteristic of propagating while being reflected between the ionospheric layer and the land surface, and therefore has a propagation range wide enough to cover the entire area in Japan through the two transmission centers.

Hereinafter, the functional configuration of the radio-controlled timepiece140will be described in detail.

An antenna142receives a long standard radio wave with a frequency of 40 kHz or 60 kHz. The long standard radio wave is obtained by performing AM modulation of the time information, which is called a time code, using a carrier wave with a frequency of 40 kHz or 60 kHz. The received long standard wave is amplified by an amplifier143and is then filtered and synchronized by the filter section141having the plurality of piezoelectric vibrators1.

In the present embodiment, the piezoelectric vibrators1include crystal vibrator sections148and149having resonance frequencies of 40 kHz and 60 kHz, respectively, which are the same frequencies as the carrier frequency.

In addition, the filtered signal with a predetermined frequency is detected and demodulated by a detection and rectification circuit144.

Then, the time code is extracted by a waveform shaping circuit145and counted by the CPU146. The CPU146reads the information including the current year, the total number of days, the day of the week, the time, and the like. The read information is reflected on an RTC147, and the correct time information is displayed.

Because the carrier wave is 40 kHz or 60 kHz, a vibrator having the tuning fork structure described above is suitable for the crystal vibrator sections148and149.

Moreover, although the above explanation has been given for the case in Japan, the frequency of a long standard wave is different in other countries. For example, a standard wave of 77.5 kHz is used in Germany. Therefore, when the radio-controlled timepiece140which is also operable in other countries is assembled in a portable device, the piezoelectric vibrator1corresponding to frequencies different from the frequencies used in Japan is necessary.

As described above, since the radio-controlled timepiece140according to the present embodiment includes the piezoelectric vibrator1capable of suppressing vibration leakage while securing mounting strength of the piezoelectric vibrating reed, the radio-controlled timepiece140having superior reliability and excellent performance can be provided.

FIG. 13is a bottom view of a piezoelectric vibrating reed in which three main mount electrodes are formed on a base portion.

In the present embodiment, a pair of main mount electrodes is provided in the width direction of the base portion, and the pair of main mount electrodes is bonded to a pair of main bumps, whereby the piezoelectric vibrating reed is mounted on the substrate. However, as shown inFIG. 13, in addition to the pair of main mount electrodes16and17of the present embodiment, another main mount electrode26may be provided so that three main mount electrodes16,17, and26in total are formed in the width direction W of the base portion. By doing so, since the piezoelectric vibrating reed can be mounted on the substrate by bonding three main mount electrodes to three main bumps, the piezoelectric vibrating reed can be firmly mounted. However, since the number of main bumps increases as compared to the present embodiment, there is a possibility that the vibration of the piezoelectric vibrating reed can be easily transmitted to the outside. Therefore, the present embodiment is superior in terms of suppression of the vibration leakage.

In the present embodiment, only one auxiliary electrode and only one auxiliary bump are provided on the base substrate. However, two auxiliary electrodes and two auxiliary bumps may be provided at the corresponding positions near the center in the width direction of the base portion. By doing so, the mounting strength can be further improved compared with the present embodiment. However, since the number of auxiliary bumps increases as compared to the present embodiment, and the piezoelectric vibrating reed is mounted at a position separated from the nodal point of vibration, there is a possibility that the vibration of the piezoelectric vibrating reed can be easily transmitted to the outside. Therefore, the present embodiment is superior in terms of suppression of the vibration leakage.

In the present embodiment, the main mount electrodes and the auxiliary mount electrode are formed on both the upper and lower surfaces of the base portion of the piezoelectric vibrating reed. However, the main mount electrodes and the auxiliary mount electrode may be formed only on the lower surface of the base portion serving as the mounting surface of the piezoelectric vibrating reed. However, in this case, since it is necessary to distinguish the upper and lower surfaces of the piezoelectric vibrating reed, the present embodiment is superior in terms of prevention of the assembling errors in the mounting step.

In the present embodiment, the recess portions are formed so as to penetrate through the piezoelectric vibrating reed in the thickness direction from the upper surface to reach the lower surface. However, openings of the recess portions may be provided only on the side surfaces in the width direction of the base portion of the piezoelectric vibrating reed so that the recess portions do not penetrate through the piezoelectric vibrating reed in the thickness direction from the upper surface to reach the lower surface. However, the present embodiment is superior from the fact that vibration is made less easily be transmitted to the base end side than the recess portions.

In the present embodiment, the base portion is divided into a part close to the base end side with respect to the recess portions and a part close to the tip end side, and the width of the base portion on the base end side is larger than the width of the base portion on the tip end side. However, the width of the base portion on the base end side may be the same as the width of the base portion on the tip end side. However, the present embodiment is superior from the fact that the base portion on the base end side is formed to have a larger width so as to secure the strength of the base portion.