JP2006295700A - Piezoelectric device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric device which is excellent in impact resistance and can keep an excellent current square value characteristic by increasing the area of a main electrode. <P>SOLUTION: In this piezoelectric device, an approximately rectangular piezoelectric vibrating element 31 is bonded and fixed to the inner bottom surface of a package 36 with a conductive adhesive in at least three bonding parts of bonding parts in both terminal parts at the side of its drawing electrodes 31a, 31a and a bonding part of a distal end part 31b. A driving main electrode 51 of the piezoelectric vibrating element is formed into a notched shape so as to keep away the coating area 43-1 of the conductive adhesive in the bonding part of the distal end part 31b. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an improvement of a piezoelectric device in which a piezoelectric vibrating piece is accommodated in a box-shaped package.

Piezoelectric devices such as piezoelectric vibrators and piezoelectric oscillators in small information devices such as HDDs (hard disk drives), mobile computers, IC cards, and mobile communication devices such as mobile phones, car phones, and paging systems Is widely used.
A conventional piezoelectric device accommodates, for example, a piezoelectric vibrating piece formed of a piezoelectric material in a package.
The piezoelectric vibrating piece is formed, for example, by etching a quartz wafer into a rectangular shape and providing a driving electrode.

A piezoelectric device having such a structure is known (see Patent Document 1). In this piezoelectric device, a raised electrode is formed on the bottom plate of a container body that is a package, and a crystal piece base is formed thereon. Both ends in the width direction of the end are fixed (see Patent Document 1, FIG. 1B, and FIG. 2).
On the other hand, the tip of the crystal piece is placed on a holding table, so that the crystal piece can be held horizontally in the package.

JP-A-2005-33479

In the above-mentioned Patent Document 1, since the tip of the crystal piece is merely placed on the holding base, if such a configuration can be maintained, the crystal piece is held horizontally in the package, but is fixed at the tip. It is not vulnerable to external impacts.
Therefore, a structure as shown in FIG. 6 is also conceivable.
FIG. 6 is a plan view of the piezoelectric device 1 in which the above-described drawbacks are improved with the lid body removed.
In the drawing, connection electrode portions 5 and 5 are formed at one end portion of the inner bottom surface of the package 2 so as to be spaced apart from each other in the width direction. The electrode portions 5 and 5 are routed around the package 2 and connected to mounting terminals provided on a bottom surface (not shown).

  The piezoelectric vibrating reed 4 is a rectangular AT vibrating reed, and excitation electrodes 9 serving as driving electrodes are formed on the front surface and the back surface serving as the main surface. The electrode arrangement of the piezoelectric vibrating reed 4 is exactly the same on the front and back sides, and the excitation electrode 9 is routed to the end in the width direction at one end (base end side) to be provided with an extraction electrode 9a. Is extended to the side surface, and an extraction electrode having the same shape is formed on the back side (not shown). Note that the extraction electrode 9b extends from the excitation electrode on the back surface, goes around the side surface, and is exposed to the front surface side.

Conductive adhesives 6 and 6 are applied to the electrode portions 5 and 5 on the package 2 side, and the extraction electrodes 9a and 9b are placed thereon, and the conductive adhesive is cured, so that the piezoelectric adhesive is applied. One end of the vibrating piece 4 is electrically and mechanically joined to the package 2.
Further, a metallized portion 7 is formed on the inner bottom surface of the package 2 corresponding to the tip portion of the piezoelectric vibrating reed 1, and the same material as the conductive adhesive 6 is used on the metallized portion 7. In the same process, the conductive adhesive 8 is applied, and the tip portion of the piezoelectric vibrating reed 4 is placed thereon and cured.
Thereby, since the piezoelectric vibrating reed 4 is fixed not only at one end but also at the tip, it is joined and fixed at three convenient points, and the impact resistance is improved.

However, according to such a structure, the conductive adhesive 8 may short-circuit the front and back excitation electrodes unless the excitation electrode 9 is made sufficiently small as shown in the drawing and positioned inside the tip portion.
However, if the excitation electrode, that is, the main electrode for excitation of the piezoelectric vibrating reed 4 is made small, the following problems occur.
7 shows the relationship between current and frequency when the area of the excitation electrode 9 is 0.96 square millimeters, for example, and FIG. 8 shows the relationship between the current and frequency when the area of the excitation electrode 9 is 0.72 square millimeters, for example. It is.

In FIGS. 7 and 8, the vertical axis represents frequency change and the horizontal axis represents the square value of current, which is a so-called current square value characteristic. The smaller the slope of the graph, the more stable the frequency with respect to the current value, and the larger the area of the main electrode, the better the current square value characteristic.
FIG. 9 is a graph in which the vertical axis represents the slope of FIGS. 7 and 8 in terms of the current square value, and the horizontal axis represents the area of the main electrode. As shown in FIG. Is small, and the current square value characteristic is excellent.

  The present invention has been made to solve the above-described problems, and provides a piezoelectric device that is excellent in impact resistance and that can maintain a good current square value characteristic by increasing the area of the main electrode. For the purpose.

  According to the first aspect of the present invention, the substantially rectangular piezoelectric vibrating piece is at least 3 of the joining portion at both ends on the lead electrode side and the joining portion at the tip end portion with respect to the bottom surface inside the package. A piezoelectric device that is bonded and fixed by a conductive adhesive at a junction of points, wherein the main electrode for driving the piezoelectric vibrating piece avoids the conductive adhesive application region at the junction of the tip This is achieved by a piezoelectric device having a cut-out shape.

According to the configuration of the first invention, since the piezoelectric vibrating piece is fixed at least at three points, the impact resistance is improved. Further, the driving main electrode is not cut in the region where the conductive adhesive is applied, so that it does not come into contact with the conductive adhesive. As a result, the main electrode can prevent a short circuit while securing a necessary area.
Thus, it is possible to provide a piezoelectric device that is excellent in impact resistance and that can maintain the current square value characteristic by increasing the area of the main electrode.
The “substantially rectangular piezoelectric vibrating piece” is not limited to a rectangle but includes a shape close to a square.

A second invention is characterized in that, in the configuration of the first invention, the joint portion of the tip portion is provided at a central portion in the width direction of the piezoelectric vibrating piece.
According to the structure of 2nd invention, the junction part of the said front-end | tip part will be located in the position of equidistance from each junction part by the side of the drawer | drawing-out of a piezoelectric vibrating piece, and a junction structure will be stabilized more.

According to a third aspect of the invention, in the configuration of the first aspect of the invention, the joint portion of the tip portion is provided at an end portion in the width direction of the piezoelectric vibrating piece.
According to the configuration of the third aspect of the invention, the area of the main electrode can be maximized by providing the joint portion at the front end portion of the piezoelectric vibrating piece at the end portion in the width direction, and the current square value characteristic is more favorable. Can be.

According to a fourth aspect of the invention, in the configuration of the third aspect of the invention, at a predetermined height along the width direction of the piezoelectric vibrating piece, at a position corresponding to the tip portion of the piezoelectric vibrating piece on the inner bottom surface of the package. And a joint portion of the tip portion is provided at one end portion in the width direction of the piezoelectric vibrating piece.
According to the configuration of the fourth aspect of the invention, the area of the main electrode can be maximized while reliably preventing the main electrode of the piezoelectric vibrating piece from touching the inner bottom surface of the package.

1 to 3 show a first embodiment of a piezoelectric device according to the present invention. FIG. 1 is a schematic plan view of a piezoelectric device with an internal structure excluding a lid, and FIG. FIG. 3 is a schematic cross-sectional view taken along line -A, showing a lid disposed, and FIG. 3 is a schematic plan view of the package.
In these drawings, the piezoelectric device 30 shows an example in which a piezoelectric vibrator is configured, and the piezoelectric device 30 accommodates a piezoelectric vibrating piece in a package 36.
Specifically, as shown in FIG. 3, the piezoelectric device 30 houses the piezoelectric vibrating piece 31 in a package 36 including a first substrate 34 and a second substrate 35 laminated on the first substrate 34. is doing.

The first substrate 34 constituting the package 36 is an insulating base, and the electrode part 32 is formed thereon. In FIG. 1, as indicated by reference numerals 32 and 32, a pair of electrode portions is provided at both end portions in the width direction of the first substrate 34 at the end portion of the package 36.
The first substrate 34 and the second substrate 35 are formed of an insulating material, and ceramic is suitable. In particular, a material having a thermal expansion coefficient that matches or is very close to the thermal expansion coefficient of the piezoelectric vibrating piece 31 or a lid described later is selected as a preferable material. In this embodiment, for example, a ceramic green sheet is used. ing. The green sheet is obtained, for example, by dispersing a ceramic powder in a predetermined solution, forming a kneaded product formed by adding a binder into a sheet-like long tape shape, and cutting it into a predetermined length Is.

  The first substrate 34 and the second substrate 35 can be formed by laminating and sintering green sheets molded into the illustrated shape. In this case, the first substrate 34 is a substrate that constitutes the bottom of the package 36, and the second substrate 35 that is stacked on the first substrate 34 has a frame shape by removing the internal material from the above-described green sheet as a plate shape. As shown, the internal space S of FIG. 2 is formed, and the piezoelectric vibrating piece 31 is accommodated using the internal space S (see FIG. 3). A lid 37 made of a metal such as ceramic, glass, or kovar is joined to the package 36 via low-melting glass, nickel 47, or the like. Thereby, the package 36 is hermetically sealed.

  On the first substrate 34, for example, after forming a required conductive pattern using a conductive paste such as silver or palladium or a conductive paste such as tungsten metallization, the first and second substrates are sintered. Thereafter, nickel and gold or silver are sequentially plated to form the electrode portions 32 and 32 described above. As shown in FIG. 2, the electrode portion 32 is connected to mounting terminals 41 and 41 exposed on the bottom surface of the package 36 by a conductive pattern (not shown). The conductive pattern for connecting the electrode portion 32 and the mounting terminal 41 may be formed on the surface of a castellation (not shown) used when the package 36 is formed, and the outer surface of the package 36 may be routed. Alternatively, the connection may be made by a conductive through hole (not shown) penetrating the first substrate 34.

  As shown in FIG. 2, the piezoelectric vibrating piece 31 is formed by, for example, a so-called AT-cut vibrating piece obtained by processing a wafer formed of a piezoelectric material into a thin rectangular shape, so that a vibrating piece piece that is a piezoelectric chip is formed. Yes. As the piezoelectric material, for example, quartz is used in this embodiment, and other piezoelectric materials such as lithium tantalate and lithium niobate can be used. Further, the shape of the piezoelectric chip is not limited to the flat type, and a convex type or a reverse mesa type resonator element can be used.

  In FIG. 1, an excitation electrode 51 is formed as a main electrode for driving on the surface of a piezoelectric chip which is an individual piece of a vibrating piece. The excitation electrode 51 is formed in a region where the piezoelectric chip is actively vibrated, and applies a driving voltage to the piezoelectric material, thereby efficiently generating an electric field in the material and exciting the material. The excitation electrode 51 is also formed in the same form on the back surface of a piezoelectric chip (not shown), and is an extraction electrode that is a connection electrode formed at each end in the width direction at the end in the length direction of the piezoelectric vibrating piece 31. 51a and 51a are connected separately. Each extraction electrode 51a, 51a goes around the side surface of the piezoelectric chip and is also formed on the back surface.

As shown in FIG. 1, such a piezoelectric vibrating piece 31 is formed by applying conductive adhesives 43 and 43 on the respective electrode portions 32 and 32 on the package 36 side, and then on the piezoelectric vibrating piece 31. The base end portion or one end portion 31a on which the respective extraction electrodes 51a and 51a described in FIG. 1 are formed are placed, and the conductive adhesives 43 and 43 are cured to be joined in a cantilever manner. Yes.
As a result, the drive voltage supplied from the outside of the package 36 via the mounting terminals 41, 41 is transmitted from the electrode portions 32, 32 on the package 36 side to the conductive adhesives 43, 43 and the extraction electrodes 51 a of the piezoelectric vibrating reed 31. It is applied to the excitation electrode 51 via 51a. Accordingly, the distal end side 31b of the piezoelectric vibrating piece 31 is driven by being vibrated by a piezoelectric action.

Here, as the conductive adhesives 43, 43, a binder component made of a predetermined synthetic resin to which conductive particles such as silver particles are added can be used. In addition, the piezoelectric vibrating piece 31 is not necessarily a cantilever type, and a part of the tip end side 31b may be joined to the package 36 side.
In addition, the piezoelectric substrate 31 is hermetically sealed by a shallow box-shaped lid (not shown) without forming the electrode using the first substrate 34 as an insulating base and laminating the second substrate 35. It is also possible to use a package that stops. Alternatively, a plug connected to an external drive voltage source is connected to the piezoelectric vibrating piece 31, the piezoelectric vibrating piece 31 is inserted into a metal cylindrical case with one end closed, and the case is hermetically sealed with this plug. You may make it (not shown).

The excitation electrode 51 has a concave cutout 45 at the center in the width direction at the tip 31b of the piezoelectric vibrating piece 31 so as to avoid an adhesive application region, for example, as shown in the figure.
That is, a metallized portion (metal covering portion) 46 is formed on the inner bottom surface of the package 36 (the surface of the first substrate 34) at a location corresponding to the tip portion 31 b of the piezoelectric vibrating piece 31. The metallized portion 46 may be a simple metal film or may have a shape as shown in FIG. As shown in FIG. 1, a conductive adhesive 43-1 is applied on the metallized portion 46, and the tip end portion 31b of the piezoelectric vibrating piece 31 is placed and bonded thereto.
That is, the metallized portion 46 is simultaneously formed in the same process as the electrode portions 32 and 32 of the package 31, and the conductive adhesive 43-1 is also the same as the conductive adhesive 43 and 43 applied to the electrode portions 32 and 32. Things are applied in the same process. As a result, the piezoelectric vibrating piece 31 is joined at a total of three locations including two locations of the one end portion 31a and one location of the tip portion 31b.

The present embodiment is configured as described above, and the piezoelectric vibrating piece 31 is fixed to the package 36 at three points, so that the impact resistance is improved. Moreover, since the notch part 45 was formed so that the excitation electrode 51 might avoid this about the area | region where the conductive adhesive 43-1 was apply | coated, there exists a possibility that the excitation electrode 51 may contact with the conductive adhesive 43-1. There is no. Since it was set as such a structure, the excitation electrode 51 can ensure sufficient area required, and can prevent a short circuit.
Thus, it is possible to provide the piezoelectric device 30 that is excellent in impact resistance and that can maintain the current square value characteristic favorably by increasing the area of the excitation electrode 51.
In particular, in this embodiment, since the joint portion of the tip end portion 31b of the piezoelectric vibrating piece 31 is provided at the center portion in the width direction of the piezoelectric vibrating piece 31, from each joint portion of the one end portion 31a of the piezoelectric vibrating piece 31, etc. The joint portion of the tip portion is positioned at the distance position, and the joint structure is further stabilized.

4 and 5 show a second embodiment of the piezoelectric device.
FIG. 4 is a schematic plan view of the piezoelectric device 30-1 according to the second embodiment, and FIG. 5 is an end view taken along the line BB of FIG.
In these drawings, the portions denoted by the same reference numerals as those in the first embodiment have a common configuration, and therefore, overlapping description will be omitted, and hereinafter, differences will be mainly described.

  In this piezoelectric device 30-1, as clearly shown in FIGS. 4 and 5, the inner bottom surface of the package 36 corresponding to the tip 31b of the piezoelectric vibrating piece 31 has a predetermined height along the width direction. A support portion 56 is formed. The support part 56 is provided by forming the metallized part thickly. However, the present invention is not limited thereto, and a step part is formed of a ceramic material or the like at a corresponding part of the first substrate 34, and a thin metallized part is formed thereon. It may be formed.

The excitation electrode 51-1 of the piezoelectric vibrating piece 31 is formed with a concave notch 55 at the end in the width direction of the tip 31b of the piezoelectric vibrating piece 31.
The notch 55 is substantially ¼ as shown in FIG. 4, whereas the notch 45 in the first embodiment of FIG. 1 is substantially semicircular. Thereby, the area of the excitation electrode 51-1 of the second embodiment is larger than that of the excitation electrode 51 of the first embodiment.

This embodiment is configured as described above, and by providing the joint portion of the tip portion 31b of the piezoelectric vibrating piece 31 at the end portion in the width direction, the area of the excitation electrode 51-1 can be maximized, Accordingly, the current square value characteristic can be improved.
Further, the tip portion 31b of the piezoelectric vibrating piece 31 is supported by the support portion 56 having a predetermined height. For this reason, the front end portion of the piezoelectric vibrating piece 31 can be fixed while maintaining an appropriate horizontal posture. For this reason, since the excitation electrode on the lower surface of the piezoelectric vibrating piece 31 does not touch the inner bottom surface of the package 36 and appropriate excitation is not hindered, good performance can be obtained.

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.
The present invention can be used not only for an AT-cut piezoelectric vibrating piece, but also for a so-called convex type piezoelectric vibrating piece, an inverted mesa-shaped piezoelectric vibrating piece, and the like.
In addition, the present invention is applicable to all piezoelectric devices regardless of the names of piezoelectric vibrators, piezoelectric oscillators, etc., as long as they use a package as a box-shaped container and accommodate a piezoelectric vibrating piece inside. can do.

1 is a schematic plan view of a piezoelectric device according to a first embodiment of the present invention. The AA cut | disconnection end elevation of FIG. The schematic plan view of the package of the piezoelectric device of FIG. The schematic plan view of the piezoelectric device which concerns on the 2nd Embodiment of this invention. The BB line | wire cut end elevation of FIG. The schematic plan view which shows an example of the piezoelectric device which does not contain this invention. The graph which shows the electric current square value characteristic of a piezoelectric device. The graph which shows the electric current square value characteristic of a piezoelectric device. The graph which shows the electric current square value characteristic of a piezoelectric device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 30 ... Piezoelectric device, 31 ... Piezoelectric vibrating piece, 36 ... Package, 45 ... Notch part, 51 ... Excitation electrode, 55 ... Notch part

Claims (4)

A substantially rectangular piezoelectric vibrating piece is bonded and fixed to the inner bottom surface of the package by a conductive adhesive at at least three junctions between the junction at both ends on the lead electrode side and the junction at the tip. A piezoelectric device,
The piezoelectric device characterized in that the main electrode for driving the piezoelectric vibrating piece has a cut-out shape so as to avoid the conductive adhesive application region at the joint of the tip.   2. The piezoelectric device according to claim 1, wherein a joint portion of the tip portion is provided at a center portion in a width direction of the piezoelectric vibrating piece.   The piezoelectric device according to claim 1, wherein a joint portion of the tip portion is provided at an end portion in a width direction of the piezoelectric vibrating piece.   A support portion having a predetermined height along the width direction of the piezoelectric vibrating piece is formed at a position corresponding to the tip portion of the piezoelectric vibrating piece on the inner bottom surface of the package, and The piezoelectric device according to claim 3, wherein a joint portion is provided at one end portion in the width direction of the piezoelectric vibrating piece.

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