JP2010093598A - Piezoelectric vibrator and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thickness-shear mode piezoelectric vibrator which uses piezoelectric ceramics, has increased thickness, is mechanically strong and is excellent in high-frequency correspondency without requiring any process for directly bonding a piezoelectric ceramics veneer, and to provide a method of manufacturing the piezoelectric vibrator by which the piezoelectric vibrator can be efficiently manufactured. <P>SOLUTION: An electric field is applied in a predetermined direction using polarization electrodes 4, 5 formed on a pair of end faces 2, 3, which are opposed to each other, of a piezoelectric ceramics rectangular plate 1 to polarize piezoelectric ceramics constituting the piezoelectric ceramics rectangular plate as a whole, then a part of the polarization electrodes is removed. An electric field is applied reversely to a partial region R2 of the piezoelectric ceramics constituting the piezoelectric ceramics rectangular plate using remaining polarization electrodes 4a, 5a to polarize the partial region of the piezoelectric ceramics reversely to a direction of polarization in the overall polarization step. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a piezoelectric vibrator, and more particularly to a piezoelectric vibrator using thickness shear vibration and a method for manufacturing the same.

  As a piezoelectric vibrator, a piezoelectric vibrator using thickness longitudinal vibration or thickness shear vibration of piezoelectric ceramics is widely used in electronic devices. With the recent increase in processing speed and communication speed of electronic devices, piezoelectric vibrators that are capable of resonance driving at higher frequencies have been demanded.

  By the way, in such a piezoelectric vibrator, as an inexpensive piezoelectric vibrator having a stable and highly symmetric polarization reversal structure and having a good spurious suppression effect, for example, a thickness-shear mode piezoelectric vibrator as shown in FIG. Has been proposed (see Patent Document 1).

In this piezoelectric vibrator, two piezoelectric single crystal wafers (for example, Z-cut lithium niobate, etc.) 51 and 52 having the same thickness are directly joined by reversing the polarization axis, and integrated polarization reversal wafer 53. And drive electrodes 54 a and 54 b formed on the upper and lower surfaces of the domain-inverted wafer 53. In FIG. 6, the direction of polarization Ps is indicated by an arrow in the figure.
According to this piezoelectric vibrator, when a voltage is applied from the drive electrodes 54a and 54b arranged to face each other, the thickness shear vibration wave is excited and the second harmonic is excited.

  However, since this piezoelectric vibrator is manufactured by bonding a previously polarized piezoelectric single crystal wafer, when handling or bonding a thin piezoelectric single crystal wafer, the piezoelectric single crystal The crystal wafer may be damaged, and it is considered that the manufacture is not always easy.

In addition, it may be possible to use piezoelectric ceramics instead of the piezoelectric single crystal wafer to have the configuration as in the above conventional example, but the main surface of the piezoelectric ceramic single plate to be joined is as smooth as the piezoelectric single crystal wafer. This is not easy, and it is extremely difficult to produce a piezoelectric vibrator having a good response level by a direct bonding method. Therefore, in reality, it is not easy to produce a vibrator that excites harmonics of thickness shear having response characteristics equivalent to those of the fundamental wave, using piezoelectric ceramics that are less expensive than single crystals.
Japanese Patent Laid-Open No. 10-51262

  The present invention solves the above-mentioned problems, and is a piezoelectric vibrator using piezoelectric ceramics, which does not require a step of directly joining the piezoelectric ceramic single plates, is thick and mechanically strong, An object of the present invention is to provide a thickness-shear mode piezoelectric vibrator excellent in high-frequency compatibility, and a method of manufacturing a piezoelectric vibrator capable of efficiently manufacturing the piezoelectric vibrator.

In order to solve the above problems, a method for manufacturing a piezoelectric vibrator of the present invention includes:
(a) Applying an electric field in a predetermined direction using the electrodes for polarization formed on each of a pair of opposing end faces of the piezoelectric ceramic rectangular plate, the entire piezoelectric ceramic constituting the piezoelectric ceramic rectangular plate An overall polarization step for polarizing in a predetermined direction,
(b) an electrode removing step of removing a part of each of the polarization electrodes formed on the pair of end faces;
(c) Using the polarization electrode remaining without being removed in the electrode removal step of (b), in the partial region of the piezoelectric ceramic constituting the piezoelectric ceramic rectangular plate, in the step (a) A partial polarization step of polarizing the partial region of the piezoelectric ceramic in a direction opposite to the polarization direction in the step (a) by applying an electric field in a direction opposite to the direction of application of the electric field. It is characterized by that.

The piezoelectric vibrator of the present invention is
A piezoelectric element made of piezoelectric ceramics, comprising at least two regions whose directions of polarization are opposite to each other, the adjacent regions being integrally sintered;
Drive electrodes disposed on both main surfaces of the piezoelectric element so as to face each other through the at least two regions are provided.

  In the method for manufacturing a piezoelectric vibrator according to the present invention, an electric field is applied in a predetermined direction using polarization electrodes formed on a pair of opposing end surfaces of a piezoelectric ceramic rectangular plate to form the piezoelectric ceramic rectangular plate. After the entire piezoelectric ceramic is polarized, a part of the electrode for polarization is removed, and an electric field is applied in the reverse direction to a part of the piezoelectric ceramic constituting the piezoelectric ceramic rectangular plate using the remaining electrode for polarization. Since a part of the piezoelectric ceramic is polarized in a direction opposite to the direction of polarization in the overall polarization process, the thickness is increased without requiring a process of directly joining the piezoelectric ceramic single plates. A thickness-shear mode piezoelectric vibrator that is mechanically strong and excellent in high-frequency compatibility can be efficiently manufactured.

  That is, according to the present invention, the entire piezoelectric ceramic rectangular plate is polarized in a predetermined direction using the polarizing electrodes formed on the pair of end faces of the piezoelectric ceramic rectangular plate, and then each part of the polarizing electrode is removed. In addition, since the predetermined region of the piezoelectric ceramic rectangular plate is polarized in the reverse direction using the remaining electrode for polarization, a process of preparing a piezoelectric ceramic single plate that is thin and easily damaged is performed. Without requiring a direct bonding step, it is possible to efficiently manufacture a polarization inversion type thickness-shear mode piezoelectric vibrator.

  In addition, the piezoelectric vibrator of the present invention includes at least two regions whose polarization directions are opposite to each other between adjacent regions, and the adjacent regions are not joined after sintering, but are sintered together. A piezoelectric element that is connected, and drive electrodes that are disposed on both main surfaces of the piezoelectric element so as to face each other with at least the two regions, and each region is joined after sintering. Because it is sintered together, it does not require direct bonding of piezoelectric ceramic single plates, and has high mechanical strength and high reliability. Can provide a child.

  And this piezoelectric vibrator can be efficiently manufactured with the manufacturing method of the above-mentioned this invention.

  Embodiments of the present invention will be described below to describe the features of the present invention in more detail.

<Production of piezoelectric vibrator>
(1) Prepare Pb ₃ O ₄ , SrCO ₃ , ZrO ₂ , TiO ₂ , Nb ₂ O ₅ , La ₂ O ₃ , MnCO ₃ , Nd ₂ O ₃ , and Bi ₂ O ₃ as starting materials. It measured so that it might become each composition of the following [Composition 1], [Composition 2], and [Composition 3].
[Composition 1]
(Pb _0.9 Sr _0.1 ) (Zr _0.54 Ti _0.46 ) O ₃ +1 mol% Nb ₂ O ₅
[Composition 2]
(Pb _0.85 La _0.1 ) TiO ₃ +1 mol% MnCO ₃
[Composition 3]
(Sr _0.85 Nd _0.1 ) Bi ₂ Nb ₂ O ₉ +1 mol% MnCO ₃

  (2) The raw materials of Composition 1, Composition 2 and Composition 3 weighed in the above proportions were wet-mixed in ion exchange water for about 16 hours using a ball mill, and the resulting mixture was dried and calcined at 700 to 900 ° C. Thus, a calcined product was obtained.

  (3) After roughly pulverizing this calcined product, an appropriate amount of an organic binder was added, wet pulverized for 16 hours using a ball mill, and particle size was adjusted through a 40-mesh sieve.

(4) Next, at a pressure of 1000 kg / cm ² ,
Length (L): 20mm,
Width (W): 3 mm
Thickness (T): 2mm
After being molded into a block shape, it was degreased at 500 ° C. for 2 hours and sintered at a temperature of 1200 ° C. using a normal sintering method to obtain a sintered body (piezoelectric ceramic rectangular plate).

  (5) Then, as shown in FIG. 1A, a pair of piezoelectric ceramic rectangular plates 1 facing each other, defined by the side in the length (L) direction and the side in the thickness (T) direction. A pair of polarization electrodes 4 and 5 were formed by forming an Ag thin film on the end surfaces 2 and 3 of the substrate using a sputtering method.

  (6) Next, in insulating oil at 150 ° C., a DC voltage of 2 to 10 kV / mm is applied between the polarizing electrodes 4 and 5 in a predetermined direction for 30 to 120 minutes to thereby form the piezoelectric ceramic rectangular plate 1. The first polarization treatment was applied to the entire piezoelectric ceramic.

  (7) Thereafter, a part of the polarization electrodes 4 and 5 (in this embodiment, the upper half) is deleted as shown in FIG. 1B, and the remaining polarization electrodes 4a and 5a in the lower half are removed. In the above step (6), the second polarization is performed under the same conditions in the direction opposite to the direction of the first polarization process, the polarization directions are opposite to each other, and the layered layers adjacent to each other are used. A piezoelectric ceramic rectangular plate 1 having regions R1 and R2 was obtained.

  (8) Then, as shown in FIG. 2, the polarization electrodes 4a and 5a were deleted to obtain a polarized piezoelectric ceramic rectangular plate 1.

  (9) Next, as shown in FIG. 3, an Ag thin film is formed on the upper and lower main surfaces 6 and 7 of the polarized piezoelectric ceramic rectangular plate 1 by sputtering, and the drive electrodes 8 and 9 are formed. Formed.

  (10) Thereafter, the piezoelectric ceramic rectangular plate 1 on which the drive electrodes 8 and 9 are formed is parallel to the end face 10 defined by the sides of the piezoelectric ceramic rectangular plate 1 in the width (W) direction and the thickness (T) direction. Then, a piezoelectric vibrator (sample) 11 (see FIG. 4) having dimensions of 3 mm × 2.5 mm × 2 mm was obtained by cutting with a dicer at intervals of 2.5 mm.

  The piezoelectric vibrator 11 is made of piezoelectric ceramics, and has two layered regions R1 and R2 which are adjacent to each other and whose polarization directions are opposite to each other, and two layered regions R1 and R2 are interposed therebetween. Drive electrodes 8 and 9 are provided on the front and back main surfaces of the piezoelectric element 12 so as to face each other. The layered regions R1 and R2 adjacent to each other are integrally sintered as described above, and are not joined after sintering.

  Therefore, according to the method of the above embodiment, the thickness is thick, mechanically strong, and capable of exciting the second harmonic without requiring the step of directly joining the piezoelectric ceramic single plates. The mode piezoelectric vibrator can be efficiently manufactured.

  In Example 1, sample numbers 1, 2, and 3 using the piezoelectric ceramic raw materials of the above [Composition 1], [Composition 2], and [Composition 3] as the piezoelectric vibrator (sample) 11 were used. A total of three types of piezoelectric vibrators were manufactured.

  For comparison, after the first polarization process, all the electrodes for polarization are deleted, and after the process of forming and cutting the drive electrodes, the piezoelectric ceramic is polarized in only one direction as shown in FIG. A vibrator (sample for comparison) 11a was produced. That is, each sample of the comparative example is manufactured under the same conditions as the sample of the above example except that the second polarization is not performed, and the dimensions are also the same. In FIG. 5, the parts denoted by the same reference numerals as those in FIG. 4 indicate the same or corresponding parts.

  In addition, as a sample of this comparative example, a total of three types of piezoelectric vibrations of sample numbers 4, 5, and 6 using the piezoelectric ceramic raw materials of the above [Composition 1], [Composition 2], and [Composition 3] were used. A child was made.

<Evaluation of characteristics>
Comparison of Samples Nos. 1, 2, and 3 (Samples of Examples) having the requirements of the present invention prepared as described above and Sample Nos. 4, 5, and 6 that are not subjected to the second polarization. With respect to the samples, the resonance frequency, the electromechanical coupling coefficient, the piezoelectric d constant, and the mechanical quality factor were examined, and the piezoelectric characteristics were evaluated. The results are shown in Table 1.

  As shown in Table 1, the samples Nos. 1 to 3 (examples) having the requirements of the present invention have the same thickness as the samples of the comparative examples Nos. 4 to 6. Regardless, it can be seen that the resonance having the same response characteristic can be generated at the position of the double frequency.

  Moreover, regarding the electromechanical coupling coefficient, the piezoelectric d constant, and the mechanical quality factor, there is no significant difference between the sample of the example of sample numbers 1 to 3 and the sample of the comparative example of sample numbers 4 to 6, It was confirmed that there was no problem with the basic performance as a piezoelectric vibrator.

  In the above embodiment, in the second polarization treatment step, the polarization treatment in the opposite direction to the first is performed to produce a piezoelectric vibrator having two layered regions whose polarization directions are opposite to each other. The characteristics of the second-order harmonics were examined. In the step (7) of the above embodiment, the polarization electrodes were adjusted in the removal mode, and the polarization directions were opposite to each other in the adjacent regions. By forming three or more regions, it is possible to excite higher-order harmonics such as third-order, fourth-order, fifth-order, and so on.

  The present invention is not limited to the above embodiments in other respects, and various applications and modifications can be made within the scope of the invention with respect to the types of piezoelectric ceramics, polarization conditions, and the like.

(a) is a figure which shows the state which polarized the whole piezoelectric ceramic rectangular plate in the predetermined direction in 1 process of the manufacturing method of the piezoelectric vibrator concerning the Example of this invention, (b) is an Example of this invention. It is a figure which shows the state which polarized a part of piezoelectric ceramic rectangular plate in the reverse direction in 1 process of the manufacturing method of the piezoelectric vibrator concerning. It is a figure which shows the state which removed all the electrodes for polarization of the piezoelectric ceramic rectangular plate of FIG.1 (b). It is a figure which shows the state which formed the drive electrode in the upper and lower both main surfaces of the piezoelectric ceramic rectangular plate of FIG. 2 which removed all the electrodes for polarization. It is a figure which shows the piezoelectric vibrator concerning the Example of this invention obtained by cut | disconnecting the piezoelectric ceramic rectangular plate of FIG. 3 with a dicer. It is a figure which shows the piezoelectric vibrator for a comparison. It is a figure which shows the conventional piezoelectric vibrator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric ceramic rectangular plate 2,3 A pair of opposing end surfaces of the piezoelectric ceramic rectangular plate 4,5 A pair of polarization electrodes 4a, 5a The remaining polarization electrodes 6,7 Both upper and lower main surfaces of the piezoelectric ceramic rectangular plate 8,9 A pair of drive electrodes 10 End faces of a piezoelectric ceramic rectangular plate 11 Piezoelectric vibrator 12 Piezoelectric elements R1, R2 Layered regions polarized in mutually different directions

Claims (2)

(a) Applying an electric field in a predetermined direction using the electrodes for polarization formed on each of a pair of opposing end faces of the piezoelectric ceramic rectangular plate, the entire piezoelectric ceramic constituting the piezoelectric ceramic rectangular plate An overall polarization step for polarizing in a predetermined direction,
(b) an electrode removing step of removing a part of each of the polarization electrodes formed on the pair of end faces;
(c) Using the polarization electrode remaining without being removed in the electrode removal step of (b), in the partial region of the piezoelectric ceramic constituting the piezoelectric ceramic rectangular plate, in the step (a) A partial polarization step of polarizing the partial region of the piezoelectric ceramic in a direction opposite to the polarization direction in the step (a) by applying an electric field in a direction opposite to the direction of application of the electric field. A method of manufacturing a piezoelectric vibrator. A piezoelectric element made of piezoelectric ceramics, comprising at least two regions whose directions of polarization are opposite to each other, the adjacent regions being integrally sintered;
A piezoelectric vibrator comprising: drive electrodes disposed on both principal surfaces of the piezoelectric element so as to face each other with the at least two regions interposed therebetween.

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