JP2006086726A - Piezoelectric vibrating piece, piezoelectric device, and method of manufacturing piezoelectric device - Google Patents

Abstract

The present invention provides a piezoelectric vibrating piece, a piezoelectric device, and a method for manufacturing a piezoelectric device that can improve vibration balance and suppress a CI value to be low.
A base 51 made of a piezoelectric material, a plurality of vibrating arms 34 and 35 formed integrally with the base and extending in parallel from the base, and extending in a length direction formed on each of the vibrating arms. And a driving member formed in the long groove, and a lid member 41 made of a material whose strength is similar to that of the piezoelectric material is joined to end portions of both side walls sandwiching the long grooves. .
[Selection] Figure 3

Description

  The present invention relates to a piezoelectric vibrating piece to be housed in a package or case, a piezoelectric device in which the piezoelectric vibrating piece is housed in a package or case, and a method for manufacturing the same.

Packages such as small information devices such as HDDs (hard disk drives), mobile computers, IC cards, mobile communication devices such as mobile phones, car phones, and paging systems, and measuring devices such as gyro sensors Piezoelectric devices such as piezoelectric vibrators and piezoelectric oscillators that house a piezoelectric vibrating piece inside are widely used.
FIG. 7 is a schematic plan view schematically showing a known configuration example (see Patent Document 1) of a piezoelectric vibrating piece used in such a piezoelectric device.

In the figure, the piezoelectric vibrating reed 1 is made of, for example, a single crystal of quartz, and includes a wide base 2 and two vibrating arms 3 and 4 extending in parallel in the same direction from the base. FIG. 8 is a cross-sectional end view taken along the line AA of FIG. 7, and the vibrating arms 3 and 4 have long grooves 5 and 6 extending in the length direction on the front and back surfaces, respectively. Excitation electrodes as drive electrodes (not shown) are formed in the long grooves 5 and 6.
As a result, when a driving voltage is applied to the excitation electrode from the outside, an electric field is efficiently generated in the vibrating arms 3 and 4, and each vibrating arm 3 and 4 has its tip portion as shown in FIG. It bends and vibrates so as to approach and separate from each other. Then, by extracting the vibration frequency based on such vibration, it is used as a reference signal such as a clock signal for control.

The vibrating arms 3 and 4 of the piezoelectric vibrating piece 1 and the grooves 5 and 6 of the vibrating arms 3 and 4 are formed by etching a substrate made of a piezoelectric material in the form of a wafer. That is, generally, the wafer substrate is first etched to form a tuning fork-shaped outer shape as shown in FIG. 7, and then the grooves 5 and 6 described in FIG. 8 are half-etched.
JP2002-76806

However, in such a piezoelectric vibrating piece 1, in the wet etching in the outer shape etching process, there is a difference in the etching progress speed with respect to the mechanical axis X, the electric axis Y, and the optical axis Z shown in FIGS. As can be seen, a flat bottom surface cannot be formed in the long grooves 5 and 6 due to such etching anisotropy.
As a result, for example, when viewing the vibrating arm 3, the thicknesses of both side walls sandwiching the long groove 5 are different from each other on the left and right. As a result, the vibrating arm 3 is The rigidity is different. That is, the left side wall has high rigidity, and the right side wall has lower rigidity.

  For this reason, in the state in which the vibrating arms 3 and 4 are bent and vibrated as shown in FIG. 7, the degree of deformation at the time of bending left and right in the horizontal direction is different. Will collapse. As a result, the stress transmitted to the base 2 due to the deformation of the vibrating arms 3 and 4 cannot be canceled out because F1 and F2 are not balanced, causing displacement in the Z direction and displacement in the Y direction. It is thought that the crystal impedance) value increases.

  An object of the present invention is to provide a piezoelectric vibrating piece, a piezoelectric device, and a method for manufacturing the piezoelectric device, which can improve the vibration balance and keep the CI value low.

According to the first aspect of the present invention, a base portion formed of a piezoelectric material, a plurality of vibrating arms formed integrally with the base portion and extending in parallel from the base portion, and each vibrating arm are formed. A long groove extending in the length direction and a driving electrode formed in the long groove, and a lid member made of a material whose strength is similar to that of the piezoelectric material is bonded to the end portions of both side walls sandwiching each long groove. This is achieved by the piezoelectric vibrating piece.
According to the configuration of the first aspect of the invention, a lid member made of a material whose strength is similar to that of the piezoelectric material is joined to end portions of both side walls sandwiching the long grooves, and the lid member is joined to the piezoelectric material. Therefore, the vibrating arm and the lid member are integrated to form a pipe-shaped vibrating arm formed hollow with the piezoelectric material. For this reason, the rigidity of the vibrating arm is significantly improved, and the combined balance of the left and right of the vibrating arm is improved. Thereby, since the bending vibration of the vibrating arm is improved in terms of the bending balance, the displacement in the Z direction and the displacement in the Y direction can be suppressed, and the CI value can be suppressed low.
Accordingly, in the present invention, it is possible to provide a piezoelectric vibrating piece that can improve the vibration balance and keep the CI value low.

A second invention is characterized in that, in the configuration of the first invention, the material of the lid member is a material whose linear expansion coefficient approximates that of the piezoelectric material.
According to the configuration of the second invention, the portion where the lid member is joined to the vibrating arm due to a change in ambient temperature is less likely to break and has a strong structure.

A third invention is characterized in that, in the structure of either the first or second invention, the material of the lid member is quartz.
According to the configuration of the third aspect of the invention, the lid member is made of quartz, which is a representative material of the piezoelectric material constituting the vibrating arm, so that it is the same as the vibrating arm in terms of density, weight, strength, and the like. Therefore, the lid member is almost completely integrated with the vibrating arm.

According to a fourth aspect of the present invention, there is provided a piezoelectric device in which a piezoelectric vibrating piece is accommodated in a container, wherein the piezoelectric vibrating piece is integrally formed with a base portion made of a piezoelectric material. A plurality of resonating arms formed in parallel to the base, a long groove formed in each resonating arm, and a driving electrode formed in the long groove, on both sides of each long groove This is achieved by a piezoelectric device in which a lid member made of a material whose strength is similar to that of the piezoelectric material is bonded to the end of the wall.
According to the fourth invention, it is possible to provide a piezoelectric device that can improve the vibration balance and keep the CI value low by the same principle as described for the first invention.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a piezoelectric device in which a piezoelectric vibrating piece is accommodated in a container, and an outer shape forming step of forming an outer shape of a tuning fork type piezoelectric vibrating piece by etching. And a groove forming step of forming a long groove on the piezoelectric substrate corresponding to the position of the vibrating arm of the tuning fork type piezoelectric vibrating piece, an electrode forming step of forming a drive electrode in the long groove, and ends of both side walls sandwiching the long groove This is achieved by a method of manufacturing a piezoelectric device including a lid member joining step for positioning and joining a lid member made of a material whose strength is similar to that of the piezoelectric material.
According to the configuration of the fifth invention, the combined balance of the left and right of the vibrating arm is improved by the same principle as described in the first invention. Thereby, since the bending vibration of the vibrating arm is improved in terms of the bending balance, the displacement in the Z direction and the displacement in the Y direction can be suppressed, and the CI value can be suppressed low.
Thereby, in this invention, the manufacturing method of the piezoelectric device which can improve vibration balance and can keep CI value low can be provided.

A sixth invention is characterized in that, in the configuration of the fifth invention, the step of joining the lid member is performed by anodic bonding.
According to the configuration of the sixth aspect of the invention, in joining the lid member, the driving electrode in the long groove is extended to the end portions of both side walls sandwiching the long groove, so that the extended electrode is used for anodic bonding. By using this electrode, the lid member can be easily joined.

1 and 2 show a first embodiment of a piezoelectric device according to the present invention. FIG. 1 is a schematic plan view thereof, and FIG. 2 is a schematic cross-sectional view taken along line BB of FIG.
In the figure, the piezoelectric device 30 shows an example in which a crystal resonator is configured, and the piezoelectric device 30 houses a piezoelectric vibrating piece 32 in a package 36 as a housing container. The package 36 is formed, for example, by laminating a plurality of substrates formed by molding an aluminum oxide ceramic green sheet as an insulating material, and then sintering. Each of the plurality of substrates is formed with a predetermined hole on the inner side thereof, so that a predetermined internal space S2 is formed on the inner side when stacked. The internal space S2 is a housing space for housing the piezoelectric vibrating piece 32.

A piezoelectric vibrating piece 32 is mounted inside the package 36 and hermetically sealed with a lid 39. Here, the lid 39 is formed by selecting a material such as ceramic, metal, or glass.
When the lid 39 is made of metal, for example, there is an advantage that the strength is generally higher than that of other materials. An approximate thermal expansion coefficient with the package 36 is suitable, and for example, Kovar can be used.
Moreover, in order to enable frequency adjustment after sealing the lid, the lid 39 is made of a light transmitting material such as glass, for example. For example, a plate body such as borosilicate glass can be used.

  In the inner space S2 of the package 36, in the vicinity of the left end portion, the laminated substrate that is exposed to the inner space S2 and constitutes the inner bottom portion has, for example, electrode portions 31 and 31 formed by nickel plating and gold plating on tungsten metallization. Is provided. The electrode portions 31 are connected to the outside to supply a driving voltage. Conductive adhesives 43, 43 are applied on the electrode portions 31, 31, and the base 51 of the piezoelectric vibrating piece 32 is placed on the conductive adhesives 43, 43. 43 are hardened. In addition, as the conductive adhesives 43 and 43, a synthetic resin agent as an adhesive component exhibiting a bonding force and containing conductive particles such as fine silver particles can be used. A system-based or polyimide-based conductive adhesive can be used.

The piezoelectric vibrating piece 32 is formed by etching, for example, quartz as a piezoelectric material by a manufacturing process described later. In the case of the present embodiment, the piezoelectric vibrating piece 32 is formed in a small size to obtain necessary performance. Therefore, in particular, the structure shown in the schematic perspective view of FIG. 3 and the C-C line cut end view of FIG. 3 shown in FIG.
That is, the piezoelectric vibrating piece 32 has a base 51 fixed to the package 36 side, and a pair of vibrating arms 34 and 35 that extend in parallel to be divided into two forks diagonally rightward in the drawing with the base 51 as a base end. A so-called tuning fork type piezoelectric vibrating piece having a shape like a tuning fork is used.

As can be understood with reference to FIGS. 3 and 4, long bottomed long grooves 56 and 57 extending in the length direction are formed in the respective vibrating arms 34 and 35 of the piezoelectric vibrating piece 32. The long grooves 56 and 57 are formed on both front and back surfaces of the vibrating arms 34 and 35 as shown in FIG. 4 which is a cross-sectional end view taken along the line CC of FIG.
Further, in FIG. 3, lead electrodes 52 and 53 are formed near both ends in the width direction of the end portion (lower end portion in FIG. 3) of the base portion 51 of the piezoelectric vibrating piece 32. The lead electrodes 52 and 53 are similarly formed on the back surface (not shown) of the base 51 of the piezoelectric vibrating piece 32.

  These lead electrodes 52 and 53 are portions connected to the package-side electrode portions 31 and 31 shown in FIG. 1 by the conductive adhesives 43 and 43 as described above. As shown in FIGS. 3 and 4, the lead electrodes 52 and 53 are integrally connected to the excitation electrodes 54 and 55 provided in the long grooves 56 and 57 of the vibrating arms 34 and 35, respectively. Yes. Further, as shown in FIG. 4, the excitation electrodes 54 and 55 are also formed on both side surfaces of the vibrating arms 34 and 35. For example, with respect to the vibrating arms 34, the excitation electrodes 54 in the long groove 56. And the excitation electrode 55 of the side part is made to have a different polarity. Further, with respect to the vibrating arm 35, the excitation electrode 55 in the long groove 57 and the excitation electrode 54 on the side surface thereof are configured to have different polarities.

Between the base 51 of the piezoelectric vibrating piece 32 and the vibrating arms 34 and 35, a notch portion or a constricted portion (not shown) provided with a reduced width in the width direction of the base 51 may be provided.
Thereby, the leakage of the vibration of the piezoelectric vibrating piece 32 to the base 51 side can be prevented, and the CI (crystal impedance) value can be reduced.
Moreover, the piezoelectric vibrating piece 32 as a whole is extremely small. In FIG. 3, for example, the total length is about 1300 μm, the length of the vibrating arm is about 1040 μm, and the arm width is about 40 μm to 55 μm. Yes.

Further, as shown in FIG. 4, the end portions of both side walls at the positions sandwiching the long grooves 56, 57 of the vibrating arms 34, 35 are joined with lid members indicated by reference numeral 41, whereby the long grooves 56, 57 is blocked.
Since the vibrating arms 34 and 35 have the same structure, the vibrating arm 34 will be described. Joining electrodes 42 and 42 are formed on the upper and lower ends of both side walls sandwiching the long groove 56, respectively. The lid members 41, 41 are fixed by anodic bonding, for example, as shown in FIG.
Such a structure avoids the disadvantages described with reference to FIGS.
That is, when the long grooves 56 and 57 are formed in the respective vibrating arms 34 and 35, the bottoms in the long grooves are not formed flat, and the thickness of the walls on both sides sandwiching the long grooves is different, so that the vibrating arms 34 and 35 are It is possible to improve that the right and left stiffness balance is deteriorated.

For this reason, as a material selected as the lid member 41, it is necessary to be able to improve the rigidity balance between the left and right integrally with the piezoelectric material of the vibrating arm by joining them. In the case of the above-described piezoelectric material, this embodiment, a material whose strength and density are close to those of quartz is preferable. In addition, the use of a material having a linear expansion coefficient approximate to that of the piezoelectric material can prevent breakage due to thermal stress.
From this point, the most preferable as the lid member 41 is a thin crystal plate.

The piezoelectric device 30 according to the present embodiment is configured as described above, and the piezoelectric vibrating piece 32 is provided at the ends of both side walls sandwiching the long grooves 56 and 57 of the vibrating arms 34 and 35 of the piezoelectric vibrating piece 32. A lid member 41 made of a material whose strength is similar to that of the piezoelectric material to be formed is joined, and this lid member 41 has a strength similar to that of the piezoelectric material. Therefore, the vibrating arms 34 and 35 and the lid member 41 are integrated. Thus, a pipe-shaped vibrating arm is formed hollow with the piezoelectric material. For this reason, the rigidity of the vibrating arms 34 and 35 is significantly improved, and the combined balance of the left and right of the vibrating arms is improved. Thereby, since the bending vibration of the vibrating arm is improved in terms of the bending balance, the displacement in the Z direction and the displacement in the Y direction can be suppressed, and the CI value can be suppressed low.
Thereby, in this embodiment, a vibration balance can be improved and CI value can be restrained low.

(Piezoelectric device manufacturing method)
(Method for manufacturing lid and package)
Next, an embodiment of a method for manufacturing the piezoelectric device 30 will be described.
FIG. 5 is a simple flowchart for explaining an embodiment of the method for manufacturing the piezoelectric device 30 of the present embodiment.
The piezoelectric vibrating piece 32, the package 36, and the lid 39 of the piezoelectric device 30 are separately manufactured.
For example, the lid 39 is prepared as a lid having a size suitable for sealing a package 36 by cutting a glass plate having a predetermined size.
As described above, the package 36 is formed by laminating a plurality of substrates formed by molding an aluminum oxide ceramic green sheet and then sintering. At the time of molding, each of the plurality of substrates forms a predetermined hole on the inner side thereof, so that a predetermined inner space S2 is formed on the inner side when stacked.

(Method for manufacturing piezoelectric vibrating piece)
FIG. 6 is a process diagram showing the main steps of the embodiment of the manufacturing method by showing only the portion corresponding to the cross section of one vibrating arm in the piezoelectric vibrating piece 32 of the present embodiment. The following description will be made mainly with reference to FIGS.

  As the substrate 71, for example, a quartz crystal wafer having a size capable of separating a plurality or a large number of piezoelectric vibrating reeds 32 among piezoelectric materials is used. When the substrate 71 is made into a tuning fork type piezoelectric vibrating piece 32 by the progress of the process, the piezoelectric material, so that the X axis shown in FIG. 3 is the electric axis, the Y axis is the mechanical axis, and the Z axis is the optical axis, For example, it is cut out from a single crystal of quartz. In addition, when cutting out from a single crystal of crystal, the crystal Z cut out by rotating clockwise in the range of 0 degrees to 2 degrees around the Z axis in the orthogonal coordinate system composed of the X axis, Y axis and Z axis described above. It is obtained by cutting and polishing a plate to a predetermined thickness.

(Outline forming process)
In FIG. 6A, the quartz wafer as a piezoelectric substrate has a predetermined mask pattern (a fork-shaped outer shape of the piezoelectric vibrating piece 32 including the base 51 and the vibrating arms 34 and 35 described with reference to FIG. (Not shown) is formed by, for example, a corrosion-resistant film, and is formed by wet etching using a hydrofluoric acid solution or the like (ST11).

(Groove formation process)
Next, in FIG. 6B, a necessary corrosion-resistant film (not shown) is provided on the front surface (front and back surfaces) of the substrate 71 to form a mask, and a portion of the long groove 56 of the vibrating arm using a hydrofluoric acid solution or the like. Are formed by half etching (ST12).
In this case, the bottom of each long groove 56 does not become horizontal as shown in the figure due to the etching anisotropy of quartz.

(Electrode formation process)
Next, an excitation electrode as a drive electrode is formed (ST13).
That is, as shown in FIG. 6C, metal films to be electrodes are formed on both the front and back surfaces of the substrate 71. For example, the metal film is formed by a technique such as vapor deposition or sputtering of chromium as a base.
Thereafter, the metal film is etched by a photolithography technique to form excitation electrodes 54 and 55 as described with reference to FIG.

(Cover member joining process)
Next, as shown in FIG. 6D, lid members 41 and 41 made of, for example, a crystal thin plate are prepared. An electrode 42 is provided in advance in a region to be joined to the crystal thin plate serving as the lid member 41.
Then, as shown in the drawing, the electrodes 42 and 42 for bonding are brought into contact with the end portions of both side walls sandwiching each long groove 56, that is, the upper and lower end portions in the drawing, with the electrode 42 side facing the substrate 71 side. Position so that you can.
Next, as shown in FIG. 6 (e), bonding electrodes 42 and 42 are brought into contact with the end portions of both side walls sandwiching each long groove 56, that is, the upper and lower end portions in the drawing, and are described with reference to FIG. Thus, the lid member is fixed by anodic bonding (ST15).
Thus, the piezoelectric vibrating piece 32 of FIG. 3 is completed.

  Here, in the electrode formation step, the excitation electrode 54 in each long groove is extended to the end portions of both side walls sandwiching the long groove 56 so that the extended portion comes into contact with the lid member 41 and the substrate 71. Then, anodic bonding can be performed using the excitation electrode 54. This is advantageous because it is not necessary to previously provide the bonding electrode 42 on the lid member 41 side.

  As shown in FIGS. 1 and 2, the completed piezoelectric vibrating piece 32 is bonded to the electrode portions 31 and 31 using a conductive adhesive 43 (ST16). Next, in a vacuum atmosphere, the lid 39 is hermetically bonded to the end of the package 36 with a predetermined brazing material (ST17), and necessary inspection is executed (ST18), whereby the piezoelectric device 30 is sealed. Is completed.

The present invention is not limited to the above-described embodiment. Each configuration of each embodiment can be appropriately combined or omitted, and can be combined with other configurations not shown.
In addition, as long as the piezoelectric vibrating piece is accommodated in the package, the present invention includes all piezoelectric vibrating pieces and piezoelectric devices using the same regardless of the names of the crystal resonator, the crystal oscillator, the gyroscope, the angle sensor, and the like. Can be applied to.
Moreover, in the above-described embodiment, a box-shaped package using ceramics is used. However, the present invention is not limited to such a form, and a piezoelectric material may be used in a storage container equivalent to a package such as a metal cylindrical case. The present invention can be applied to any package or case that can accommodate a resonator element.

1 is a schematic plan view of a piezoelectric device according to an embodiment of the present invention. The schematic sectional drawing in the BB line of the piezoelectric device of FIG. FIG. 2 is a schematic perspective view of a piezoelectric vibrating piece used in the piezoelectric device of FIG. 1. FIG. 4 is an end view taken along the line C-C of the piezoelectric vibrating piece of FIG. The flowchart which shows embodiment of the manufacturing method of the piezoelectric device of FIG. Process drawing which shows the principal part of embodiment of the manufacturing method of the piezoelectric vibrating piece of FIG. FIG. 6 is a schematic plan view of a conventional piezoelectric vibrating piece. The AA cut | disconnection end elevation of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 30 ... Piezoelectric device, 36 ... Package, 32 ... Piezoelectric vibrating piece, 34, 35 ... Vibrating arm, 41 ... Lid member, 51 ... Base, 54, 55 ... Excitation Electrode, 56, 57 ... long groove

Claims (6)

A base formed of piezoelectric material;
A plurality of vibrating arms formed integrally with the base and extending in parallel from the base;
A long groove extending in the length direction formed in each of the vibrating arms and a driving electrode formed in the long groove,
A lid member made of a material whose strength is similar to that of the piezoelectric material is joined to end portions of both side walls sandwiching the long grooves.   2. The piezoelectric vibrating piece according to claim 1, wherein a material of the lid member is a material whose linear expansion coefficient approximates that of the piezoelectric material.   The piezoelectric vibrating piece according to claim 1, wherein a material of the lid member is quartz. A piezoelectric device in which a piezoelectric vibrating piece is accommodated in a container,
The piezoelectric vibrating piece is
A base formed of piezoelectric material;
A plurality of vibrating arms formed integrally with the base and extending in parallel from the base;
A long groove extending in the length direction formed in each of the vibrating arms and a driving electrode formed in the long groove,
The piezoelectric device is characterized in that a lid member made of a material whose strength is similar to that of the piezoelectric material is joined to end portions of both side walls sandwiching the long grooves. A method of manufacturing a piezoelectric device in which a piezoelectric vibrating piece is housed in a housing container,
An outer shape forming step for forming an outer shape of the tuning fork type piezoelectric vibrating piece by etching,
A groove forming step of forming a long groove on the piezoelectric substrate corresponding to the position of the vibrating arm of the tuning fork type piezoelectric vibrating piece;
An electrode forming step of forming a drive electrode in the long groove;
A step of positioning a lid member made of a material whose strength is similar to that of the piezoelectric material with respect to the end portions of both side walls sandwiching the long groove, and a joining process of the lid member to be joined. Production method.   The method for manufacturing a piezoelectric device according to claim 5, wherein the bonding step of the lid member is performed by anodic bonding.

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