JPH03212981A - Method for polarization of piezoelectric substrate - Google Patents

Abstract

PURPOSE:To polarize a piezoelectric substrate simply and well without damaging it by a method wherein one pair of faced polarization electrodes are formed on both main faces of the piezoelectric substrate and a required DC voltage is applied between the polarization electrodes. CONSTITUTION:Three pairs of polarization electrodes 12a 13a to 12c and 13c are formed so as to be faced with both main faces 11a, 11b of a piezoelectric substrate 11; a + DC voltage is applied to the electrodes 12a, 13a, 12c, 13c; a-DC voltage is applied to the electrodes 12b, 13b. Then, electric-field components (C) become parallel with the respective main faces 11a, 11b; the substrate 11 is not damaged by a warp; the substrate 11 can be polarized simply and well by using a small voltage. After this treatment, the polarization electrodes are removed and a resonance circuit or the like can be formed on the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for polarizing a piezoelectric substrate suitable for constructing a piezoelectric device using BGS waves.

[Conventional technology]

Conventionally, piezoelectric resonant elements that utilize BGS waves (piezoelectric surface shear waves) have been proposed. BGS waves propagate along the surface of the piezoelectric body parallel to the surface of the piezoelectric body, but in order to excite the BGS waves, the wave propagates parallel to the piezoelectric substrate and perpendicular to the propagation direction of the BGS waves. It is necessary to apply a voltage to the polarization process.

Polarization as described above has conventionally been carried out by the methods shown in FIGS. 2 and 3.

In the first method, a block-shaped piezoelectric body 1 shown in FIG. 2 is prepared. Polarization electrodes 2.3 are provided on both end faces of the piezoelectric body 1. Then, apply a voltage between electrodes 2.3 and arrow A
The piezoelectric body 1 is polarized in the direction shown by . Thereafter, the piezoelectric body 1 is sliced along the dashed line B to obtain a piezoelectric substrate polarized parallel to the main surface.

The second method is as shown in FIG. j, a plurality of polarization electrodes 58 to 5d are formed on one main surface of the substrate 4; As shown in the figure, the electrodes 5a to 5d are filled with
Potentials of opposite polarity are applied alternately to polarize the pressure@substrate 4 in the direction shown by arrow B. In this method, pressure TM, group +7
Since the polarization electrodes 5a to 5d are directly formed on i4 for polarization processing, there is no need to perform a process such as slicing after polarization.

[Technical problem to be solved by the invention] In the first polarization method, when the length of the block-shaped piezoelectric body 1 is L, the polarization process is performed unless a voltage of 2 to 3 kV is applied per unit length. Therefore, in order to polarize a piezoelectric material L with length L = 50 m, for example, a small voltage (at least 100 kV) is required. Breakage was apt to occur.Furthermore, it was necessary to perform a complicated cutting process of slicing the piezoelectric body 1 after polarization, which caused problems in terms of productivity.

On the other hand, in the second polarization method, the polarization electric currents Fi5a to 5d
Since they are not very far apart, high voltages as in the first polarization method are not required.

However, during polarization, one main surface 48 of the piezoelectric substrate 4
Since voltage is applied only from the side, the piezoelectric ceramic is distorted b and curved so that the main surface 4a is inward, and in extreme cases, the piezoelectric substrate 4 may break.

Therefore, an object of the present invention is to reduce the possibility of damage to the piezoelectric substrate;
And relatively easy pressure T! j. The object of the present invention is to provide a method capable of polarizing a substrate parallel to its main surface.

[Means for solving technical problems]

The piezoelectric substrate polarization method of the present invention includes forming a plurality of pairs of electrodes arranged on both main surfaces of the piezoelectric substrate so as to face each other with the piezoelectric substrate interposed therebetween, and forming each pair of electrodes facing each other with the piezoelectric substrate interposed therebetween. By applying a DC voltage between the plurality of pairs of electrodes so that a potential of the same polarity is applied to the electrodes that are It is characterized by subjecting the substrate to polarization treatment.

[Effect]

Voltage 211 = A DC voltage is applied between each pair so that potentials of the same polarity are applied to pairs of polarizing electrodes facing each other across the plate, that is, the polarizing electrodes are connected to the piezoelectric substrate. Since it is formed on both main surfaces of the piezoelectric substrate, the electric field component is only parallel to the main surface of the piezoelectric substrate. That is, the electric field component on both the upper surface and the lower surface of the piezoelectric substrate is substantially parallel to the main surface of the piezoelectric substrate. Therefore, since the distortion due to polarization is uniform on both main surfaces of the piezoelectric substrate, warping of the piezoelectric TL substrate is less likely to occur.

[Explanation of Examples]

FIG. 1 is a schematic side view for explaining a polarization method according to an embodiment of the present invention. On the upper surface 11a and lower surface 11b of the piezoits plate 11 made of a piezoelectric material such as piezoelectric ceramics,
Electrodes 12a to 12c and 13a to f for polarization, respectively.
Form 3c.

As shown in FIG. 4, the electrodes 12a to 12c are formed in a rectangular shape extending from one edge of the piezoelectric substrate 11 to the other edge. Although not particularly illustrated, the electric ttN 13 a ~
13 c is formed in the same shape as the electrodes 12 a - 12 c and at a position facing them with the piezoelectric substrate 11 interposed therebetween.

Accordingly, in the configuration shown in FIG.
c constitutes another pair of electrodes.

Next, as shown in FIG.
c, 13a, +3c to a potential of 10, electrodes 12b, 13b
A DC voltage is applied to the electrodes between each pair so that a negative potential is applied to the electrodes, and the pressure polarizes the substrate 11. In this case, polarization electrode 12a=12c.

Since 13a to 13c are not far apart from each other, a relatively low voltage can be applied thereto.

As shown enlarged in FIG. 5, due to polarization, the electrodes 12a,
The electric field component extending from the side of the electrode 13a to the side of the electrodes 12b and 13b is applied to the piezoelectric substrate 11 in the region between the electrodes 12a and 13a and the electrodes 12b and 13b, as shown by the dashed line C in the figure.
almost parallel to the principal plane of In other words, it can be seen that near both the upper surface 11a and the lower surface 11b of the piezoelectric substrate 11, the polarization process is performed almost parallel to the soil surface of the piezoelectric substrate.

Although not particularly shown, the piezoelectric substrate portions between the polarization electrodes 12c and +3C and the electrodes 12b and 13b are similarly polarized in parallel to the main surface of the piezoelectric substrate.

In the case of the polarization method of this embodiment, the polarization electrodes are arranged on both main surfaces of the piezoelectric substrate 11 so as to face each other with the piezoelectric substrate 11 in between. are equivalent. Therefore, warping and cracking of the piezoelectric substrate in the case of the conventional second polarization method is unlikely to occur in the method of this embodiment.

As an application example of the above embodiment, a method for obtaining a piezoelectric resonant element using the piezoelectric substrate 11 polarized as described above will be described.

Electrodes 12a to 12 on the polarized pressure 1 Fill
c and 13a to 13c are removed, and then the piezoelectric substrate 11
Affi is deposited on the entire upper surface of the substrate to form an electrode on the entire surface.

Thereafter, as shown in FIG. 6, a plurality of interdigital transducers I4 and terminal electrodes 15a and 15b electrically connected to the interdigital transducers 14 are formed by etching.

Note that the interdigital transducer 14 is formed in the above-described polarized portion.

That is, polarization electrodes 12a-12c, 13a-13c
Interdigital transducer 1 in the area between
4 is formed. On the other hand, the terminal electrodes 15a and 15b are formed in the regions where the polarization electrodes 12a to 12c and 13a to 13c described above were formed.

In order to facilitate understanding, in FIG. 6, the direction of polarization performed by the above-mentioned polarization treatment is indicated by an arrow P.

Next, the piezoelectric substrate 11 is moved along the dashed line H in FIG.
By cutting the piezoelectric resonant element 16 shown in FIG.
can be obtained. In the piezoelectric resonant element 16, the piezoelectric base F
Since the polarization direction of i, 11' is the direction shown by arrow P,
If voltage is applied from the terminal electrodes 15a and 15b, BO3
It can excite waves, and operates as a resonator using reflection of BO3 waves at both end faces of the piezoelectric substrate 11'.

Note that the polarization method of the present invention is not limited to obtaining piezoelectric resonant elements as described above, but can also be used to obtain surface wave devices-C such as surface wave filters and delay lines that utilize BO3 waves. .

〔Effect of the invention〕

According to the present invention, polarization electrodes to which potentials of the same polarity are applied during polarization are arranged facing each other on both main surfaces of a piezoelectric substrate, and a DC voltage is applied between each pair of electrodes arranged facing each other to perform polarization processing. Therefore, the electric field components are equivalent in the vicinity of both principal surfaces of the piezoelectric substrate portion between the polarization electrode pair. Therefore, cracks are less likely to occur when the piezoelectric substrate warps. In addition, in the case of the first conventional polarization method, a large block-shaped piezoelectric material was polarized and required a high voltage for polarization, but the method of the present invention does not require the application of a very large voltage. Both can be polarized. Therefore, there is less risk of damage to the piezoelectric body, which tends to occur when a high voltage is applied.

Therefore, by utilizing the present invention, it becomes possible to easily and reliably obtain a piezoelectric element using BO3 waves.

[Brief explanation of drawings]

1 is a schematic side view for explaining a polarization method according to an embodiment of the present invention, FIG. 2 is a perspective view for explaining a first example of a conventional polarization method, and FIG. 3 is a schematic side view for explaining a polarization method according to an embodiment of the present invention. A schematic side view for explaining the second example of the polarization method, FIG. 4 is a plan view of the pressure shown in FIG. 1 and the substrate, and FIG. FIG. 6 is a schematic partially cutaway enlarged side view for explaining the direction of polarization, FIG. 6 is a plan view for explaining the process of forming an interdigital transducer and terminal electrodes after polarization, and FIG. 7 is a polarization method of the present invention. FIG. 2 is a plan view showing a piezoelectric resonant element that utilizes BO2 waves obtained using . In the figure, 11 is a piezoelectric substrate, Ila and llb are the upper and lower surfaces of the piezoelectric substrate, 12a to 12c, 13 a = l
3c indicates an electrode for polarization.

Claims (1)

[Claims] (1) A plurality of pairs of electrodes are formed on both main surfaces of the piezoelectric substrate so as to face each other with the piezoelectric substrate interposed therebetween, and potentials of the same polarity are applied to both electrodes forming each pair. A method for polarizing a piezoelectric substrate, characterized in that the piezoelectric substrate is polarized by applying a DC voltage between the plurality of pairs of electrodes, thereby applying a voltage parallel to the main surface of the piezoelectric substrate. .