JPS60145717A - Ultrasonic transducer and its production - Google Patents

Abstract

PURPOSE:To make it easy to generate bulk waves in the direction vertical to the surface and improve independence of each pair of cross finger electrodes by forming a notched groove between cross finger electrodes. CONSTITUTION:Notched grooves 4 are provided between cross finger electrodes 2 and 3 from the surface of a piezoelectric material plate 1. When the piezoelectric material plate 1 is polarized in both sides of these notched grooves 4, distribution of polarization is across these notched grooves 4. Distribution of polarization has a sharp angle to the surface of the piezoelectric material plate 1. Thus, it is difficult to generate surface waves, and surface waves are prevented from being propagated on the surface of the piezoelectric material plate 1 by these notched grooves 4, and required bulk waves are generated efficiently in the direction of an arrow.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides electrodes that cross each other on the surface of a piezoelectric body,
The present invention relates to an ultrasonic transducer that polarizes near the surface of the piezoelectric body using the electrode and generates bulk waves in a direction perpendicular to the surface of the piezoelectric body, and a method for manufacturing the same.

(Prior Art) Surface acoustic wave elements, in which an excitation transducer and a reception transducer called interdigital electrodes or interdigital electrodes are formed on a piezoelectric plate, are used in filters, delay lines, oscillators, and the like. This type of surface acoustic wave device is IDT (Int
The excitation transducer and reception transducer, called interdigital electrodes or interdigital electrodes, are formed on an already polarized piezoelectric plate or a plate made of a natural piezoelectric material such as crystal. Manufactured by This surface acoustic wave element converts an electric signal into a surface acoustic wave signal using an excitation converter, and receives this surface acoustic wave signal and converts it into an electric signal using a receiving converter. Bulk waves are difficult to generate for
Furthermore, even if this bulk wave occurs, it is suppressed using some kind of -L stage to improve spurious characteristics.

By the way, in addition to the surface acoustic wave element described in L, interdigital electrodes are formed on the surface of a plate-shaped ferroelectric material that has not been subjected to polarization treatment, such as piezoelectric ceramic fuchs, niobium oxide, tantalum oxide, etc. After polarization treatment is performed between these interdigital electrodes, when the electrodes are excited with a DC or AC power supply, unlike the surface acoustic wave element described above, a bulk of longitudinal or transverse waves is generated in the direction perpendicular to the surface. It can generate waves. Such a transducer is called a single surface excitation type ultrasonic transducer. This surface excitation type ultrasonic transducer will be further explained.

FIG. 1(a) is a surface view showing a state in which interdigital electrodes 2.3 are provided on the surface of the piezoelectric plate 1, FIG. 1(b) is a cross-sectional view of the same, and FIG. 1(C) FIG. 2 is a cross-sectional view showing the state of polarization in the piezoelectric plate l. As can be seen from FIG. 1(C) in this surface-excited ultrasonic transducer, the polarization distribution of the piezoelectric plate 1 is such that the polarization is extremely parallel to the surface near the surface.

(Problems with the Prior Art) The surface-excited ultrasonic transducer described above tends to generate unnecessary surface waves and transverse waves, as can be seen from FIG. 1(C). In addition, interdigital electrodes 2.
It is necessary to provide a non-electrode portion b (hereinafter referred to as a space) between the width a of 3 and the interdigital electrodes 2 and 3. This becomes a problem when the electrode structure is made smaller, and surface waves are more likely to propagate through that portion, causing interference between adjacent electrodes. Furthermore, in the conventional method, interdigital electrodes are formed by etching, etc., and a special etching mask must be prepared each time, which is time consuming and costly.

(Objective of the Invention) The object of the present invention is to eliminate the conventional drawbacks as described above, to facilitate the generation of bulk waves in the direction perpendicular to the surface, and to improve the independence of each interdigital electrode pair. The objective is to reduce the manufacturing cost of an excitation type ultrasonic transducer.

(Summary of the Invention) - In order to achieve the object of the present invention as described above, the present invention provides a pair of interdigital electrodes on the surface of a piezoelectric plate, and a bulk electrode arranged in a direction substantially perpendicular to the surface of the piezoelectric plate. In an ultrasonic transducer that generates waves, an ultrasonic transducer is provided in which a 9J groove is formed between interdigital electrodes. Furthermore, the present invention provides a step of forming interdigital electrodes on the surface of the ferroelectric plate and providing cut grooves between the interdigital electrodes;
A method of manufacturing an ultrasonic transducer is also provided, which includes the step of polarizing the ferroelectric plate after the above steps.

(Example) Next, embodiments of the present invention will be described in detail using the drawings.

FIG. 2(a) is a sectional view showing the first embodiment of the surface-excited ultrasonic i-tenshusser according to the present invention;
Figure (b) is a front view showing the electrode arrangement. In addition,
The same parts as those in the conventional example shown in Fig. 1 are designated by the same reference numerals.
The explanation will be omitted.

In FIG. 2, a cut groove 4 is provided from the surface of the piezoelectric plate 1 between the interdigital electrodes 2 and 3. When polarization is applied to the piezoelectric plate 1 across this notch IR4, the polarization distribution will straddle this notch 4, as shown in FIG. Since the angle is sharp with respect to the surface of the piezoelectric plate l, surface waves are less likely to be generated.The cut grooves 4 prevent the surface waves from propagating on the surface of the piezoelectric plate l, and direct the required bulk waves to the second wave. It can be efficiently generated in the direction of the arrow in Figure (a).

The intensity of polarization can be adjusted by adjusting the depth d and width g of this cut groove 4. If the polarization voltage is constant, the strength (or degree) of polarization tends to decrease as the depth d and width g increase.

FIG. 3(a) is a sectional view showing a second embodiment of the surface-excited ultrasonic transducer according to the present invention, and FIG. 3(b) is a front view showing the electrode arrangement thereof. In FIG. 3, notch grooves 4 are provided from the surface of the piezoelectric plate 1 between interdigital electrodes 2 and 3 constituting each interdigital electrode pair A, A... , A is provided with a separation groove 5 which is deeper than the cut groove 4. In this embodiment as well, when polarization is applied to the piezoelectric plate l across the notch 4, the polarization distribution will straddle the notch 4, as shown in FIG. 3(a), and the polarization distribution will be is at a sharp angle with respect to the surface of the piezoelectric plate 1, surface waves tend to occur, and the cut grooves 4 prevent the surface waves from propagating on the surface of the piezoelectric plate 1. It is possible to efficiently generate bulk waves in the direction of the arrow in FIG. Moreover, since the separation groove 5 is provided, each interdigital electrode pair A.
The independence between A is improved. Note that the state in which the depth of the separation groove 5 is extended to the maximum limit is considered to be a state in which the interdigital electrode pairs are separated.

FIG. 4(a) is a front view showing the electrode arrangement of the third embodiment of the surface-excited ultrasonic transducer according to the present invention, and FIG. 4(b) is a sectional view thereof. . Figure 4 (a
) and (b), a cut groove 4 is provided in the piezoelectric plate 1 between the interdigital electrodes 2 and 3 without providing a space between them where the surface of the piezoelectric plate 10 is atomized.

This embodiment is very easy to manufacture since there is no space between the interdigital electrodes. That is, FIGS. 4(a) and (b)
), a uniform length and width W electrode is formed on the piezoelectric plate 1, and as shown in FIG. 4(b), the required electrode width a and the required width W are formed. The cut groove 4 is formed with +ilJ depth g and the required depth d of the cut groove 4 to obtain a desired interdigital electrode structure. Then, by polarizing the piezoelectric plate 1, a surface-excited ultrasonic transducer is completed. Note that this manufacturing method will be explained in detail later.

In this embodiment as well, when polarization is applied to the pressure plate 1 across the cut grooves 4, the polarization distribution will straddle the cut grooves 4, as shown in FIG. 4('b). Since the polarization distribution forms a sharp angle with respect to the surface of the piezoelectric plate 1, surface waves are less likely to be generated, and the grooves 4 prevent surface waves from propagating on the surface of the piezoelectric plate 10. ,
The required bulk wave can be efficiently generated in the direction of the arrow in FIG. 4(b). The size of the interdigital electrodes is the same as the size of the piezoelectric plate 1 (length LL, width W).
It may be configured as follows.

FIG. 5(a) is a sectional view showing a fourth embodiment of the surface-excited ultrasonic transducer according to the present invention, and FIG. 5(b) is a front in-1 view showing the electrode arrangement thereof. Fifth
In the figure, a νj deep groove 4 is formed from the surface of the piezoelectric plate l between the interdigital electrodes 2 and 3 constituting each interdigital electrode pair A...-A.
and +) between each interdigital electrode pair A, A.
A separation groove 5 deeper than the J groove 4 is provided. In this embodiment as well, when polarization is applied to the piezoelectric plate l across the cut groove 4, the distribution of one polarization will straddle the cut groove 4, as shown in FIG. 5(a), and the polarization distribution is at a sharp angle with respect to the surface of the piezoelectric plate 1, making it difficult for surface waves to occur.The cut grooves 4 prevent the surface waves from propagating on the surface of the piezoelectric plate 1, and the required / Herck waves can be efficiently generated in the direction of the arrow in FIG. Moreover, since the separation groove 5 is provided, the independence between each interdigital electrode pair A-A is improved.

Next, a method for manufacturing the ultrasonic transducer shown as the first embodiment will be described.

First, as shown in FIG. 6(a), the well-known P
An electrode pattern structure 7.8 consisting of a set of five interdigital electrodes is formed on the surface of an elongated piezoelectric plate 1'' such as ZT using photolithography. However, this piezoelectric plate 1' is unpolarized and, strictly speaking, can be called a ferroelectric material.

Next, a wiring board 1, OO is made, which will serve as an extraction lead for the interdigital electrodes and also serve as a supporter for the piezoelectric plate during the polarization process. FIG. 6(b) is a front view showing this wiring board 100, and in the same figure, 10 is an insulating board made of polyimide resin or the like with heat resistance and flexibility, and on this is a wiring pattern made of copper foil. Form 11.12. A punch hole 14 is formed in the center of the wiring board 100. A connecting portion 11 connected to the wiring pattern 11.12 is provided on the longitudinal edge of the hole 14.
a, 12a are formed. Note that in FIG. 6(b), wiring patterns 11 and 12 are formed on the back side of wiring board lOO.

Thereafter, as shown in FIG. 6(C), the side of the piezoelectric plate 1' on which the electrode pattern structure 7.8 is formed is brought into contact with the back side of the wiring board 100, and the electrode pattern structure 7.8 is The root portion and the connecting portions 11a, 12a are connected using reflow solder or the like. Then, using a cutter, cut grooves 4 are formed between the top of the wiring board 100 and the electrode pattern structure 7.8 (as shown by the two-dot chain line in FIG. A slit 15 is provided which penetrates from the front surface of the wiring board 100 to the back surface of the piezoelectric board 1''. In this step, notch grooves 4 are formed between the electrode pattern structures 7 and 8, and the piezoelectric plates 1' are each cut into individual pieces.

Then, while applying a voltage between the wiring patterns 11 and 12, the piezoelectric plate l.

The piezoelectric plate l° is immersed in, for example, silicone oil heated to a temperature below the Curie point of the piezoelectric material. In this step, the piezoelectric plate l' is polarized.

After this process is completed, cut the part indicated by the dashed-dotted line.
A separate ultrasound transducer is formed. In addition,
This ultrasonic transducer chip has a wiring board lO
Since a part of O is attached to the end as a terminal,
Thereafter, the terminal forming step is omitted.

In the above embodiment, after the cut groove 4 is provided in the area shown by the two-dot chain line in FIG. 6(C), the slot 7) l. , 5, and the piezoelectric plate 1' is cut along with the wiring board 100 by extending the dotted line part 15 without cutting the dotted line part, thereby forming an ultrasonic transducer element. The manufacturing process may also be taken.

Afterwards, a method for manufacturing the ultrasonic transducer shown as the third embodiment will be explained.

First, as shown in FIG. 7(a), for example, the well-known P
A -polar electrode 21 is formed on the surface of an elongated unpolarized piezoelectric plate 1'' made of ZT or the like.

Next, a wiring board 200 is made which will serve as an extraction lead for the interdigital electrodes and will also serve as a supporter for the piezoelectric plate during the polarization process.

FIG. 7(b) is a front view showing this wiring board 200,
In the figure, 20 is an insulating plate made of polyimide resin or the like having heat resistance and flexibility, on which wiring patterns 21 and 22 made of copper foil are formed. A punch hole 24 is formed in the center of the wiring board 200. A connecting portion 21a connected to the wiring pattern 21, 22 is provided on the longitudinal edge of the hole 24,
22a is formed. In addition, in FIG. 7(b),
Wiring patterns 21 and 22 are formed on the back side of wiring board 200.

After that, as shown in FIG. 7(C), the side on which the negative electrode 21 of the piezoelectric plate 1', which has a uniform electrode 21 formed on its surface, is brought into contact with the back side of the wiring board 200, The negative electrode 21
and the connecting portions 21a, 22a' are connected using reflow solder or the like. Then, using a cutter, the wiring board 20
Cut groove 4 into the uniform electrode 21 and piezoelectric plate 1' from -L of 0.
will be established.

In this step, the interdigital electrodes 27 and 28 are formed on the piezoelectric plate 1°t, and the cut grooves 4 are formed between the interdigital electrodes 27 and 28. And wiring pattern 21.2
While applying a voltage between the two, the piezoelectric plate 1' is immersed in, for example, silicone oil heated to a temperature below the Curie point of the piezoelectric plate l°. In this step (1) and (2), the piezoelectric plate l' is polarized.

Finally, when the portion indicated by the one-dot chain line is cut, the surface of the piezoelectric plate has ultrasonic transducer elements arranged in parallel. Note that since a part of the wiring board 200 is cut out at the end of this ultrasonic transducer element as a terminal, the terminal forming step will be omitted from now on.

In this embodiment as well, as in the previous embodiment, polarization is performed after the cut grooves 4 are provided in FIG. A manufacturing process may be used in which the body plate 1' is cut to form each ultrasonic transducer element.Incidentally, as shown in FIG. 8.9, a set of interdigital electrodes 2
．． It is also possible to provide a notch groove 4 between each set of interdigital electrodes instead of providing a notch groove between each set of interdigital electrodes.

Further, although the above embodiments all use PZT for the piezoelectric plate, it is of course possible to use a plate made of other piezoelectric material such as LiNbO3.

(Effects of the Invention) As explained in detail, in the present invention, the cut grooves are formed between the interdigital electrodes, so that the pair of interdigital electrodes are formed on the surface of the piezoelectric plate. In ultrasonic transducers that generate bulk waves in a direction almost perpendicular to the surface, Herck waves are more likely to be generated in a direction perpendicular to the surface.

Further, according to the present invention, in an ultrasonic transducer that generates bulk waves in a direction substantially perpendicular to the surface of the piezoelectric plate, a set of interdigital electrodes is provided on the surface of the piezoelectric plate. Ultrasonic transducers that easily generate bulk waves can be manufactured in a cylinder.

[Brief explanation of drawings]

FIG. 1(a) is a surface view showing a state in which interdigital electrodes 2.3 are provided on the surface of the piezoelectric plate 1, FIG. 1(b) is a cross-sectional view of the same, and FIG. 1(C) is a piezoelectric plate 1. 2(a) is a sectional view showing one embodiment of the surface-excited ultrasonic transducer according to the present invention, and FIG. 2(b) is the electrode arrangement thereof. 3(a) is a sectional view showing a second embodiment of the surface-excited ultrasonic transducer according to the present invention, FIG. 3(b) is a front view showing the electrode arrangement, FIG. 4(a) is a front view showing the electrode arrangement of the third embodiment of the surface-excited ultrasonic transducer according to the present invention, FIG. 4(b) is a cross-sectional view thereof, and FIG. ) is a sectional view showing the fourth embodiment of the surface-excited ultrasonic transducer according to the present invention, FIG. 5(b) is a front view showing the electrode arrangement thereof, and FIGS. 6('a) to C ) is a process explanatory diagram showing the manufacturing process of an embodiment of the surface-excited ultrasonic transducer according to the present invention, and FIGS. 7(a) to c)
8 is a process explanatory diagram showing the manufacturing process of another embodiment of the surface-excited ultrasonic transducer according to the present invention, and FIG. 8 and FIG. 9 are sectional views showing other embodiments. l... Piezoelectric plate, 2.3... Interdigital electrode 4... Notch groove 5... Separation groove A... Interdigital electrode pair 100
... Wiring board 11.12 ... Wiring pattern patent applicant Hiki Denpa Kogyo Co., Ltd. agent Patent attorney Minoru Tsuji (1 other person) Figure 1 1--1 Ultrasound No. Figure 2 (α) (b) 2 Figure 3 (a + ++ 10 (A) (A) (A) (A) (70 Figure 4 (θ) (b) Figure 5 (θ) (b ) Figure 6 (,b)

Claims (5)

[Claims] (1) In an ultrasonic transducer in which a pair of interdigital electrodes are provided on the surface of a piezoelectric plate and a bulk wave is generated in a direction substantially perpendicular to the surface of the piezoelectric plate, cut grooves are formed between the interdigital electrodes. An ultrasonic transducer characterized by: (2) The ultrasonic transducer according to claim (i), wherein the width between the interdigital electrodes is the width of the cut groove. (3) The ultrasonic transducer according to claim (1), wherein a cut groove having a width narrower than the width of the space is provided in the space between the interdigital electrodes. (4) The ultrasonic transducer according to claim (1), characterized in that a separation groove is provided between adjacent sets of interdigital electrode sets. (5) In a method for manufacturing an ultrasonic transducer in which a pair of interdigital electrodes are provided on the surface of a piezoelectric plate and a bulk wave is generated in a direction substantially perpendicular to the surface of the piezoelectric plate, the interdigital electrodes are provided on the surface of one ferroelectric plate. A method for manufacturing an ultrasonic transducer, comprising the steps of forming electrodes and providing cut grooves between the interdigital electrodes, and after the step is completed, polarizing a strong electric plate.