JPH04245898A - Piezoelectric board for probe and ultrasonic probe using said board - Google Patents

Abstract

PURPOSE:To facilitate the manufacture of the fine probe of a high frequency and a wide band by making a piezoelectric board for probe in which one main surface of a piezoelectric board is set to be a reference surface and the other surface to be an inclined surface to be a disk shape. CONSTITUTION:The piezoelectric board 8 of PZT is installed on a case for probe 6. Rod-like PZT is cut and worked in the size of a prescribed diameter, is cut in round slices and the plural disk-like piezoelectric boards 8 are obtained. One main surface in both cut surfaces is set to be the reference surface 8a and the other main surface to be the inclined surface 8b which is inclined to the surface 8a by a prescribed angle, whereby both surfaces 8a and 8b are ground. Exciting electrodes 9 are formed on the both main surfaces 8a and 8b and a polarization processing is executed. Lead lines 10 are connected to the electrodes 9. The case 6 is made cylindrical and the piezoelectric board 8 is inserted with the side of the surface 8b as the inside, and the surface 8a is fixed to the opening end surface of the case 6. Paste-like hardening rubber and the like is filled and hardened on the side of the surface 8b so as to form a back member 11. Resin is applied on the face 8a and the opening end surface of the case 6, is ground, and an acoustic matching layer 12 which is lambda/4 of an ultrasonic wave is formed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small ultrasonic probe for accurately diagnosing minute parts of the body, and more particularly to a piezoelectric plate for a probe which is a source of ultrasonic waves.

0002

BACKGROUND OF THE INVENTION Ultrasonic probes are useful as ultrasound transmitting/receiving units in medical ultrasound diagnostic equipment. Among them,
A small ultrasound probe is inserted into a body cavity such as the esophagus, anus, or urethra or into a blood vessel. It is also considered a means of diagnosing the affected area from a closer distance and making highly accurate diagnoses. In the future, it is hoped that these devices will be further miniaturized to reduce the burden on patients and improve the safety of medical procedures. At the same time, it is also desired to improve high frequency and broadband frequency characteristics to obtain more detailed information inside the body.

0003

2. Description of the Related Art FIGS. 7 and 8 are a sectional view and a plan view of an ultrasonic probe illustrating a conventional example of this type. The ultrasonic probe is configured with a single piezoelectric plate 1 made of, for example, lead zirconate titanate (PZT) as an ultrasonic generation source. Excitation electrodes 2 are formed on both principal surfaces of the piezoelectric plate 1, and an acoustic matching layer 3 is further provided on one principal surface to serve as a wave surface for transmitting and receiving ultrasonic waves. A backing material 4 is provided on the other main surface, and the device is housed in a case 5. In particular, for example, for intravascular diagnosis, the piezoelectric plate 1
The outer shape of the acoustic matching layer 3 is made minute and its thickness is made small, and the acoustic matching layer 3 is made into a multilayer structure (3a, 3b) (FIG. 9). Furthermore, it is designed to be ultra-compact, capable of high frequency, and have wideband characteristics. Note that by multilayering the acoustic matching layer 3, the damping effect is enhanced and broadband characteristics are obtained. Further, each acoustic matching layer 3 (ab) has a wavelength of λ/4 of the ultrasonic frequency.

0004

[Problems with the prior art] However, in the ultrasonic probe with the above configuration, the ultrasonic frequency is high, especially 15 MH.
In the case of z or more, the thickness becomes extremely small, and it is technically difficult to form the acoustic matching layer 3 into multiple layers. For example, when using a material with a sound velocity of 3000 m/s, the thickness of the acoustic matching layer 3 (λ/4) is 0.0 at 15 MHz.
At 5 mm and 20 MHz, it is 0.035 mm. For this reason, there was a problem in that the yield was low and the method could not be put to practical use. Therefore, instead of making the acoustic matching layer 3 multi-layered, there is a method in which the piezoelectric plate 1 is curved into a concave or convex lens shape and the thickness is varied to achieve a wide band (FIG. 10). However, in this case, during manufacturing (polishing work), the center axis B-B line of the curved surface is likely to deviate from the center axis A-A line of the piezoelectric plate 1. Therefore, for example, it is difficult to assemble the device accurately to the cross section of the opening end face of the case 1, and the ultrasonic wave transmission/reception direction P is shifted from the center of the case (line A-A) (FIGS. 11 and 12). This problem becomes especially serious during mass production. Also, especially in small size, 10
At frequencies above MHz, it is difficult to obtain a desired thickness due to manufacturing problems, resulting in a problem of errors in band characteristics. For this reason, a rectangular wedge-shaped piezoelectric plate 1, as shown in FIG. 13, has attracted attention (
Reference publication: Japanese Unexamined Patent Publication No. 1-302999). This has the advantage that it is easier to polish and design than curved surface machining because it only needs to be inclined in one direction from one end in the width direction to the other end. However, in this case, the polishing must be done in such a way that the thickness gradually decreases starting from one end, which makes positioning, etc. difficult. For example, the first
As shown in Figure 4, if one end, which is the starting point, is polished with a deviation, for example, the thickness ab of each end on the other end
CD is different, causing an error from the original characteristics, and especially in the case of mass production, there is a problem of mutual variation.

[0005]

[Object of the Invention] The present invention provides a piezoelectric plate for a probe that can reduce the difficulty in manufacturing and can be easily processed even though it is a small high-frequency, broadband probe, and an ultrasonic wave using the same. The purpose is to provide a probe.

[0006]

[Solution and Operation] The basic solution of the present invention is that one main surface of the piezoelectric plate is a flat reference surface, the other main surface is an inclined surface, and the shape is disc-shaped. As a result, it is possible to polish the inclined surface starting from an arbitrary outer circumferential end, and an effect is produced in which the directionality during polishing can be ignored.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 6. In addition, Fig. 1 is a cross-sectional view of the ultrasonic probe, Fig. 2 is a plan view of the same excluding the acoustic matching layer, Fig. 3 is a drawing of a round bar-shaped PZT, Fig. 4 is a drawing of a piezoelectric plate, and Fig. 5 is a drawing of a piezoelectric plate. Figure, 6th
The figure is a sectional view of the same. The ultrasonic probe mainly includes a piezoelectric plate 8 made of PZT, which is attached to a probe case 6. In this example, PZT7 sintered into a round bar shape is used.
(FIG. 3) is cut to a desired outer diameter dimension, and then cut in the orthogonal direction so as to cut into rings to obtain a plurality of disc-shaped piezoelectric plates 8. Leave an allowance for the cutting width (thickness) relative to the final finished dimensions. One of the two cut surfaces (both main surfaces) of the piezoelectric plate 8 is used as a reference surface 8a, and is subjected to a flat surface finish polishing process so as to be perpendicular to the outer peripheral end surface. The other main surface is an inclined surface 8b that is inclined at a predetermined angle with respect to the reference surface 8a.
Then, perform the same flat surface finish polishing process as described above (Figure 4).
. Then, excitation electrodes 9 are formed on both main surfaces of the piezoelectric plate 8 and polarization processing is performed. Furthermore, lead wires 10 are connected to the excitation electrodes 9 on both main surfaces (Fig. 6. The probe case 6 is cylindrical, and the inner diameter of the case is slightly larger than the outer diameter of the piezoelectric plate 8 to allow for loose fitting. Then, the inclined surface 8b of the piezoelectric plate 8
The piezoelectric plate 1 is inserted with the side facing inside, and the reference surface 8a of the piezoelectric plate 1 and the opening end surface of the case 6 are aligned on the same plane and fixed. Next, the back material 11 is attached to the inclined surface side of the piezoelectric plate 8. The backing material 11 is filled with, for example, a paste-like curable rubber or adhesive and then cured. Alternatively, attach the inside of the case and the piezoelectric plate 8 in advance.
Glue a solid object that fits the inclined surface 8b. Then, a resin is applied to the reference surface 8a of the piezoelectric plate 8 and the open end surface of the case 6 and polished to form a single acoustic matching layer 12 having an ultrasonic frequency of λ/4 (FIG. 1).

[0008] In such a product, the other main surface of the piezoelectric plate 8 is an inclined surface 8b, so that the thickness can be varied because the shape is simpler than that of a piezoelectric plate with a curved surface (concave or convex). At the same time, it is possible to suppress variations in size, shape, etc. even for minute objects. Moreover, since the shape is circular, polishing can be performed starting from either end, and the directionality during polishing can be ignored. Therefore, it is possible to eliminate the need for positioning, improve work efficiency, and expect a uniform finish, which is particularly effective in mass production. Furthermore, since the outer peripheral end surface of the piezoelectric plate 8 and the reference surface 8a are at right angles, when the piezoelectric plate 8 is assembled to the case 6, the ultrasonic wave transmitting/receiving surface of the piezoelectric plate 8 and one end surface of the case 6 are on the same plane. This makes it easy to match and ensures reliable alignment. Therefore, the direction of the ultrasonic wave transmitting/receiving layer can be reliably aligned with the center direction of the case 6. Furthermore, the ultrasonic wave transmitting/receiving surface and one end surface of the case 6 are aligned on the same plane, and the acoustic matching layer 3 is provided to cover both, thereby increasing the mechanical strength and making it solid.

[0009]

Effects of the Invention In the present invention, one main surface of the piezoelectric plate is a flat reference surface, the other main surface is an inclined surface, and the shape is disk-shaped. It is possible to provide a piezoelectric plate for a probe that can be polished onto an inclined surface as a starting point, which reduces the difficulty in manufacturing and can be easily processed, and an ultrasonic probe using the same, which has great practical advantages. It is.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of an ultrasonic probe illustrating an embodiment of the present invention. FIG. 2 is a plan view of an ultrasound probe illustrating an embodiment of the present invention, excluding an acoustic matching layer. FIG. 3 is a diagram of a round bar-shaped PZT explaining one embodiment of the present invention. FIG. 4 is a diagram of a piezoelectric plate illustrating an embodiment of the present invention. FIG. 5 is a cross-sectional view of a piezoelectric plate illustrating an embodiment of the present invention. FIG. 6 is a sectional view of a piezoelectric plate illustrating an embodiment of the present invention. FIG. 7 is a sectional view of an ultrasound probe illustrating a conventional example. FIG. 8 is a plan view of an ultrasound probe illustrating a conventional example. FIG. 9 is a sectional view of an ultrasound probe illustrating a conventional example. FIG. 10 is a sectional view of an ultrasound probe illustrating a conventional example. FIG. 11 is a diagram for explaining the drawbacks of the conventional example, and is a cross-sectional view of a piezoelectric plate for explaining axis misalignment. FIG. 12 is a cross-sectional view of an ultrasonic probe illustrating axis misalignment, which is a diagram illustrating the drawbacks of the conventional example. [Figure 1
3] A diagram of a piezoelectric plate explaining a conventional example. FIG. 14 is a diagram of a piezoelectric plate illustrating a drawback of a conventional example. [Explanation of symbols] 7 Round bar-shaped PZT 8 Disc-shaped piezoelectric plate 8a Reference surface 8b Inclined surface 10 Lead wire

Claims

[Claims] 1. A piezoelectric plate for a probe in which one principal surface of the piezoelectric plate is a flat reference surface and the other principal surface is an inclined surface, characterized in that the piezoelectric plate is disk-shaped. Piezoelectric plate for children. 2. An ultrasonic probe comprising an acoustic matching layer provided on the reference surface side of the piezoelectric plate for a probe to serve as an ultrasonic wave transmitting/receiving surface, and a backing material provided on the inclined surface side of the piezoelectric plate for the probe. Tentacles. 3. The outer peripheral end surface of the piezoelectric plate for a probe is set in a direction perpendicular to the reference plane, and the piezoelectric plate for a probe is loosely fitted into an open end of a cylindrical probe case, The reference surface of the piezoelectric plate for the probe and the open end surface of the probe case are aligned and fixed, and the open end of the probe case and the reference surface of the piezoelectric plate for the probe are integrated. An ultrasonic probe that has an acoustic matching layer covering it.