JP4301140B2 - Piezoelectric vibrating piece and piezoelectric device - Google Patents

Description

  The present invention relates to an improvement of a piezoelectric vibrating piece and a piezoelectric device in which the piezoelectric vibrating piece is accommodated in a package or case.

Piezoelectric vibrators and piezoelectrics in 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 piezoelectric gyro sensors Piezoelectric devices such as oscillators are widely used.
FIG. 7 is a schematic plan view showing an example of a piezoelectric vibrating piece conventionally used in a piezoelectric device.

In the figure, a piezoelectric vibrating reed 1 is formed by etching a piezoelectric material such as quartz to form the outer shape shown in the figure. A rectangular base 2 attached to a package (not shown) or the like, A pair of vibrating arms 3 and 4 extending upward is provided, and long grooves 3a and 4a are formed on the main surfaces (front and back surfaces) of these vibrating arms, and necessary driving electrodes are formed ( Patent Document 1).
In such a piezoelectric vibrating piece 1, when a driving voltage is applied via a driving electrode, the piezoelectric vibrating piece 1 is flexibly oscillated so that the distal ends of the vibrating arms 3 and 4 approach and separate from each other. The signal of the frequency of is extracted.

By the way, in such a piezoelectric vibrating piece 1, an extraction electrode is formed at a location indicated by reference numerals 5 and 6 of the base portion 2, and an adhesive is applied to this portion and is fixedly supported, for example, on a package.
And, after the fixing support by this adhesive, the residual stress remaining due to the difference in the linear expansion coefficient between the material constituting the piezoelectric vibrating piece and the material such as the package does not hinder the bending vibration of the vibrating arm, Cut portions 7 and 7 are formed in the base 2.

JP 2002-261575 A

By the way, in the conventional piezoelectric vibrating piece 1, when the driving power to be applied is gradually increased along the horizontal axis in FIG. 8, the frequency shown on the vertical axis may shift to minus as shown in the figure, which is not satisfactory. May show characteristics.
This is considered to be because in the piezoelectric vibrating reed 1, the vibrations of the vibrating arms 3 and 4 leak a relatively large amount to the base 2 side, and the notches 7 and 7 formed in the base 2 are not sufficiently effective. .

  The present invention has been made to solve the above-described problems, and appropriately prevents the leakage of vibration from the vibrating arm side to the base side, and has such a piezoelectric vibrating piece with good drive level characteristics. An object of the present invention is to provide a piezoelectric device using a piezoelectric vibrating piece.

A piezoelectric vibrating piece according to the present invention includes a base formed of a piezoelectric material and a plurality of vibrating arms formed integrally with the base and extending in parallel to each other, and an end of the base opposite to the vibrating arm side. In the tuning-fork type piezoelectric vibrating piece fixedly supported in the vicinity of the portion, a cut portion provided so as to reduce the dimension in the width direction of the base portion is formed at a side edge of the base portion, and the cut portion is The position K to be provided is a position that exceeds the arm width dimension W of the vibrating arm from the root of the vibrating arm and is on the root side with respect to the fixedly supported portion. Comprises a long groove formed along these longitudinal directions and a driving electrode formed in the long groove, and the width dimension of each vibrating arm is the root of the vibrating arm with respect to the base. Toward the tip of each vibrating arm What has a reduced width portion that is condensation width, said long groove is located in the reduced width portion, from said end of the reduced width portion of each of the vibration arms, the width dimension toward a distal end side of the respective vibrating arms The change point P of the width change that extends in the same size or starts to increase is located at the tip of each vibrating arm further than the tip of the long groove .

According to such a configuration of the invention, in the piezoelectric vibrating piece of the present invention, the cut portion is provided in the base portion to be supported and fixed.
Here, the present inventor paid attention to the fact that the vibration leakage range of the tuning fork-type vibrating piece undergoes flexural vibration, and has a correlation with the arm width dimension W of the vibrating arm. It was found that the notch of the resonator element was not provided at an appropriate position. Therefore, in the present invention, the position K where the cut portion is provided is a position exceeding the arm width dimension W of the vibrating arm from the root of the vibrating arm and the base side of the fixed and supported portion. It was decided that. As a result, the cut portion can have a structure that can more reliably suppress propagation of vibration leakage from the vibrating arm to the base side.
Therefore, according to the present invention, it is possible to appropriately prevent the leakage of vibration from the vibrating arm side to the base side, and provide a piezoelectric vibrating piece with good drive level characteristics.

Further, the reduced width portion of each vibrating arm includes a first reduced width portion that is reduced from a base portion with respect to the base portion toward a distal end side of each of the vibrating arms, and an end of the first reduced width portion. And a second reduced width portion that is reduced in width toward the distal end side of each vibrating arm,
  The reduced width of each vibrating arm in the first reduced width portion is more abrupt than the reduced width of each vibrating arm in the second reduced width portion.

In addition, from the end of the reduced width portion of each vibrating arm, the width dimension has a change point P of the width change in which the width dimension extends in the same size toward the tip side of each vibrating arm, or starts to increase, The change point P is located at the tip of each vibrating arm further than the tip of the long groove.

Further, the present invention is further characterized in that the position K of the cut portion is formed at a position away from the base portion by the arm width dimension W × 1.2 or more.
In such a configuration, the position K of the cut portion is formed at a position separated from the base portion by the arm width dimension W × 1.2 or more, so that the drive level characteristic is set to the level of a normal piezoelectric vibrating piece. It was confirmed experimentally that it can be adapted.

The piezoelectric device of the present invention is a piezoelectric device in which a piezoelectric vibrating piece is accommodated in a package or a case, and the piezoelectric vibrating piece is formed integrally with the base portion made of a piezoelectric material and parallel to each other. A tuning-fork type piezoelectric vibrating piece that is fixedly supported near an end of the base opposite to the vibrating arm side, on a side edge of the base, in the width direction of the base A cut portion provided so as to reduce the dimension is formed, and the position K where the cut portion is provided is a position exceeding the arm width dimension W of the vibrating arm from the root of the vibrating arm, And each of the resonating arms is provided with a long groove formed along the longitudinal direction thereof and a driving electrode formed in the long groove. And each of the above Width of Doude is, the has a reduced width portion to width reduction toward the base of the portion on the tip side of each vibrating arm with respect to the base of each vibrating arm, said long groove is located in the reduced width portion Each of the vibrating arms has a change point P of a width change in which the width dimension extends from the end of the reduced width portion toward the tip side of each vibrating arm with an equal size or starts to increase. The change point P is located at the tip of each vibrating arm further than the tip of the long groove .

In addition, each of the vibrating arms has a change point P of a width change in which the width dimension extends from the end of the reduced width portion toward the distal end side of each of the vibrating arms or increases. The change point P is located at the tip of each vibrating arm further than the tip of the long groove.

  Further, in the piezoelectric device according to the present invention, the position K of the cut portion may be formed at a position away from the base portion by the arm width dimension W × 1.2 or more.

1 to 4 show an embodiment of the piezoelectric device of the present invention, FIG. 1 is a schematic plan view thereof, FIG. 2 is a schematic sectional view taken along line BB of FIG. 1, and FIG. 3 is a piezoelectric device of FIG. 4 is a schematic plan view showing an embodiment of a piezoelectric vibrating piece used in FIG. 4, and FIG. 4 is an end view taken along the line CC of FIG.
In these drawings, the piezoelectric device 30 shows an example in which a piezoelectric vibrator is configured. As shown in FIGS. 1 and 2, the piezoelectric device 30 accommodates a piezoelectric vibrating piece 32 in a package 37. Yes. As shown in FIG. 2, the package 37 is formed by laminating a first substrate 55 and a second substrate 56. For example, an aluminum oxide ceramic green sheet is formed as an insulating material. After forming the shape, it is formed by sintering.

  As shown in FIG. 2, the package 37 forms a space of the internal space S by removing the material inside the second substrate 56. This internal space S is a housing space for housing the piezoelectric vibrating piece 32. Then, on the electrode portions 31, 31 formed on the first substrate 55, the positions of the extraction electrodes 37 a, 38 a provided on the base portion 51 of the piezoelectric vibrating piece 32 are placed using the conductive adhesives 43, 43. And joined.

  The electrode portions 31 are connected to the mounting terminals 41 on the back surface of the package through conductive through holes. The package 37 is hermetically sealed by housing the piezoelectric vibrating piece 32 and then bonding a transparent glass lid 40 using a sealing material 38. Thus, after the lid 40 is sealed, the frequency can be adjusted by trimming the electrodes of the piezoelectric vibrating piece 32 by irradiating laser light from the outside.

The piezoelectric vibrating piece 32 is formed of, for example, quartz, and a piezoelectric material such as lithium tantalate or lithium niobate can be used in addition to quartz. As shown in FIG. 3, the piezoelectric vibrating piece 32 includes a base 51 fixed to the package 37 side, and a pair of vibrations extending in parallel with the base 51 as a base end and splitting into two forks upward in the figure. Arms 35 and 36 are provided.
Long grooves 33 and 34 extending in the length direction are preferably formed on the front and back of the main surfaces of the vibrating arms 35 and 36, respectively. As shown in FIGS. 3 and 4, driving electrodes are formed in the long grooves. Excitation electrodes 37 and 38 are provided. The tuning fork-shaped outer shape of the piezoelectric vibrating piece 32 and the long groove provided in each vibrating arm should be precisely formed by wet etching a material such as a quartz wafer with a hydrofluoric acid solution or dry etching, for example. Can do.

  The excitation electrodes 37 and 38 are formed in the long grooves 33 and 34 and on the side surfaces of the vibrating arms, and the electrodes in the long grooves and the electrodes provided on the side surfaces of each vibrating arm are paired. The excitation electrodes 37 and 38 are respectively routed to the extraction electrodes 37a and 38a described with reference to FIG. As a result, when the piezoelectric device 30 is mounted on a mounting substrate or the like, an external driving voltage is transmitted from the mounting terminals 41 to the extraction electrodes 37a and 38a of the piezoelectric vibrating piece 32 via the electrode portions 31 and 31. Are transmitted to the excitation electrodes 37 and 38.

Then, by applying a driving voltage to the excitation electrodes in the long grooves 33 and 34, the electric field efficiency inside the region where the long grooves of the respective vibrating arms are formed can be increased during driving.
Further, preferably, in the base 51, similarly to the resonator element of FIG. 3, recesses or notches 61 and 62 formed on the both side edges of the base 51 by partially reducing the width in the width direction of the base 51. Is provided. The cut portions 61 and 62 are separated from the base position T of the vibrating arms 35 and 36 of the base 51 by a predetermined distance toward the lead electrodes 37a and 38a, which are locations where the piezoelectric vibrating reed 32 is supported and fixed. It is formed at a position indicated by K (lower right enlarged view of FIG. 3). It is preferable that the depths of the cut portions 61 and 62 are reduced to such an extent that they coincide with the outer side edges of the adjacent vibrating arms 35 and 36, respectively.

  The notches 61 and 62 are provided in order to greatly reduce the leakage of the vibration due to the bending vibration of the vibrating arms 35 and 36 to the base 51 side and to suppress the CI value. In this embodiment, In order to achieve this effect, the following measures are taken for the position of the symbol K.

That is, the position K at which the notches 61 and 62 are provided is a position exceeding the arm width dimension W of the vibrating arms 35 and 36 from the base T of the vibrating arm, and the piezoelectric vibrating piece 32 is The base electrode is located on the base T side with respect to the extraction electrodes 37a and 38a that are fixedly supported.
That is, it is known that the range in which the vibration leakage is transmitted toward the base 51 when the vibrating arms 35 and 36 of the tuning fork type vibrating piece are flexibly vibrated is correlated with the arm width dimension W of the vibrating arms 35 and 36. It has been. The inventor pays attention to this point, and has the knowledge that the cut portion of the conventional piezoelectric vibrating piece is not provided at an appropriate position. Therefore, in the present embodiment, the position K where the notches 61 and 62 are provided is a position that exceeds the distance corresponding to the arm width dimension W of the vibrating arm, starting from the root T of the vibrating arm, and The root T side of the extraction electrodes 37a and 38a is selected. As a result, the notches 61 and 62 have a structure that more reliably suppresses vibration leakage from the vibrating arms 35 and 36 from propagating to the base 51 side.
Thereby, in this embodiment, the leakage of the vibration from the vibrating arm side to the base side can be appropriately prevented, and a piezoelectric vibrating piece with good drive level characteristics can be provided.

FIG. 5 shows the value of K (the distance from the root T to the cuts 61 and 62) where the cut portions 61 and 62 are provided on the horizontal axis, and the frequency deviation when the drive level characteristics are viewed on the vertical axis. It is a graph taken.
In a normal piezoelectric vibrating piece, a positive frequency shift of about 6 ppm is observed in the drive level characteristic.
In this embodiment, the width W of the vibrating arm in FIG. 3 is 50 μm. However, in FIG. 5, when the cut portion is 50 μm, the frequency is shifted by 4 ppm, and the size of the vibrating arm W is 1.2. When the cut portion is formed at the multiplied value of 60 μm, the drive level characteristic is approximately plus 6 ppm, which matches the value of a normal piezoelectric vibrating piece.

FIG. 6 is a graph showing the drive level characteristics of the piezoelectric vibrating piece 32 of the present embodiment, in which the horizontal axis indicates the drive power to be applied and the vertical axis indicates the corresponding frequency deviation. In this case, the driving power is changed from 0.5 microwatts (μW) to 3.0 microwatts (μW).
Compared with the conventional example of FIG. 8, in the example of FIG. 8, the frequency deviation is negative, and the energy is leaked during bending vibration of the vibrating arm, that is, vibrates due to unstable bending vibration. Is. On the other hand, in FIG. 6, the frequency deviation is positive, and it can be seen that the notches 61 and 62 sufficiently exhibit their functions and realize stable vibration.

Further, in the piezoelectric vibrating piece 32, the vibrating arms 35 and 36 are formed to have a shape as shown in FIG.
Since each resonating arm has the same shape, the resonating arm 36 will be described. The resonating arm width is the widest at the base end portion (same as the root portion) T extending from the base 51. Then, a first reduced width portion TL that is suddenly reduced in width is formed between U positions that are separated from the position of T, which is the root of the vibrating arm 36, by a slight distance toward the distal end side of the vibrating arm 36. Yes. Then, from the position of U, which is the end of the first reduced width portion TL, to the position of P toward the distal end side of the vibrating arm 36 further, that is, with respect to the vibrating arm, the reduced width gradually and continuously over the distance of CL. A second reduced width portion CL is formed.

For this reason, the vibrating arm 36 is provided with high rigidity in the vicinity of the base close to the base 51 by providing the first reduced width portion TL. Further, as the second reduced width portion CL is formed from the end U of the first reduced width portion TL toward the tip, the rigidity is continuously reduced. The portion P is an arm width change point P, which is a constricted position in terms of the form of the vibrating arm 36, and can be expressed as a constricted position P. In the resonating arm 36, the arm width extends at the tip side further than the constricted position P, or the arm width is enlarged as shown in the figure.
Here, as the long grooves 33 and 34 in FIG. 3 are longer, the electric field efficiency of the material forming the vibrating arms 35 and 36 is improved, and the length of the long grooves 33 and 34 from the base 51 with respect to the entire length L of the vibrating arms. It is known that the CI value of the tuning fork type resonator element decreases as PL becomes longer at least up to about PL / L = 0.7. In this embodiment, in FIG. 3, the total length L of the vibrating arm 36 is, for example, about 1200 μm.

With the above structure, the rigidity of the base portion of the vibrating arm 36, that is, the vicinity of the base is enhanced by the first reduced width portion TL. Thereby, the flexural vibration of the vibrating arm can be further stabilized and the CI value can be suppressed.
In addition, by providing the second reduced width portion CL, the rigidity of the vibrating arm 36 gradually decreases from the vicinity of the base toward the constriction position P toward the distal end side, and further from the constriction position P to the distal end side. Then, since there is no long groove 34 and the arm width is gradually expanded, the rigidity is increased toward the tip side.
For this reason, it is considered that the “node” of vibration at the time of vibration in the second harmonic can be positioned on the more distal end side of the vibrating arm 36, which makes the long groove 34 longer and the piezoelectric material Even if the electric field efficiency is increased and the CI value is increased, the CI value of the second harmonic can be prevented from being lowered while the CI value of the fundamental wave is suppressed. Thus, even if the size is reduced, the CI value of the fundamental wave can be kept low, and a piezoelectric vibrating piece that does not deteriorate the drive characteristics can be provided.

The present invention is not limited to the above-described embodiment. Each configuration of the embodiment can be appropriately combined or omitted, and can be combined with other configurations not shown.
Further, the present invention is not limited to the case where the piezoelectric vibrating piece is accommodated in the box-shaped package, the case where the piezoelectric vibrating piece is accommodated in the cylindrical container, the piezoelectric vibrating piece functioning as a gyro sensor, Can be applied to any piezoelectric device using a piezoelectric vibrating piece regardless of the name of a piezoelectric vibrator, a piezoelectric oscillator, or the like.

The schematic plan view which shows embodiment of the piezoelectric device of this invention. BB schematic sectional drawing of FIG. FIG. 2 is a schematic plan view of a piezoelectric vibrating piece used in the piezoelectric device of FIG. 1. The CC sectional view taken on the line of FIG. The graph which shows the relationship between the position of the notch of the piezoelectric vibrating piece of FIG. 3, and a drive level characteristic. The graph which shows the frequency change at the time of changing the drive power applied to the piezoelectric vibrating piece of FIG. FIG. 6 is a schematic plan view of a conventional piezoelectric vibrating piece. The graph which shows the frequency change at the time of changing the drive power applied to the piezoelectric vibrating piece of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 30 ... Piezoelectric device, 32 ... Piezoelectric vibrating piece, 33, 34 ... Long groove, 35, 36 ... Vibrating arm, TL ... First reduced width part, CL ... Second Reduced width portion, 61, 62 ... cut portion

Claims (5)

A tuning fork comprising a base formed of a piezoelectric material and a plurality of vibrating arms formed integrally with the base and extending in parallel to each other, and fixedly supported near an end of the base opposite to the vibrating arm side Type piezoelectric vibrating piece,
The side edge of the base is formed with a cut portion provided to reduce the width dimension of the base.
The position K at which the cut portion is provided is a position exceeding the arm width dimension W of the vibrating arm from the root of the vibrating arm, and is closer to the root side than the fixedly supported location.
Each of the vibrating arms includes a long groove formed along the longitudinal direction thereof, and a driving electrode formed in the long groove, and the width dimension of each of the vibrating arms is equal to each of the vibrating arms. Having a reduced width portion that is reduced in width toward the tip side of each vibrating arm from the base of the base portion of
The long groove is located in the reduced width portion ,
From the end of the reduced width portion of each vibrating arm, the width dimension extends at the same size toward the distal end side of each vibrating arm, or has a change point P of a width change that turns to increase. The point P is located at the tip of each vibrating arm further than the tip of the long groove . The reduced width portion of each of the vibrating arms includes a first reduced width portion that is reduced in width from a base portion with respect to the base portion toward a distal end side of each of the vibrating arms, and an end of the first reduced width portion. A second reduced width portion that is reduced in width toward the distal end side of each vibrating arm,
2. The piezoelectric device according to claim 1, wherein the contracted width of each vibrating arm in the first contracted width portion is sharper than the contracted width of each vibrating arm in the second contracted width portion. Vibrating piece. 3. The piezoelectric vibrating piece according to claim 1, wherein the position K of the cut portion is formed at a position away from the base portion by the arm width dimension W × 1.2 or more. A piezoelectric device containing a piezoelectric vibrating piece in a package or case,
The piezoelectric vibrating piece is
A tuning fork comprising a base formed of a piezoelectric material and a plurality of vibrating arms formed integrally with the base and extending in parallel to each other, and fixedly supported near an end of the base opposite to the vibrating arm side Type piezoelectric vibrating piece,
The side edge of the base is formed with a cut portion provided to reduce the width dimension of the base.
The position K at which the cut portion is provided is a position exceeding the arm width dimension W of the vibrating arm from the root of the vibrating arm, and is closer to the root side than the fixedly supported location.
Each of the vibrating arms includes a long groove formed along the longitudinal direction thereof, and a driving electrode formed in the long groove, and the width dimension of each of the vibrating arms is equal to each of the vibrating arms. Having a reduced width portion that is reduced in width toward the tip side of each vibrating arm from the base portion of the base portion, and the long groove is located in the reduced width portion ,
Each vibrating arm has a change point P of a width change in which the width dimension extends from the end of the reduced width portion toward the front end side of each vibrating arm or increases. The change point P is located at the tip of each vibrating arm further than the tip of the long groove . 5. The piezoelectric device according to claim 4 , wherein a position K of the cut portion is formed at a position away from the base portion by the arm width dimension W × 1.2 or more.

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