JPH0126295B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic probe for an electronic scanning type ultrasonic diagnostic apparatus. These probes have a structure in which a large number of piezoelectric vibrators shaped like short fences are arranged in a line, and these are electronically switched and driven to scan an ultrasonic beam.

Conventionally, zircon-lead titanate (PZT)-based ceramics have been widely used as materials for piezoelectric vibrators in ultrasonic probes. However, these piezoelectric ceramics (i) have an extremely large acoustic impedance compared to the human body, so for diagnostic purposes, it is necessary to use a matching layer, etc., and (ii) their dielectric constant is extremely large, so the piezoelectric voltage constant g is small, making it difficult to use ultrasonic waves. (iii) It is difficult to create a curvature that matches the shape of the human body. In order to solve these problems, so-called composite piezoelectric materials, which are composites of organic matter and piezoelectric materials, have been proposed. As an example, Newnham et al. of the United States have reported that a composite structure in which fiber-like PZT12 is embedded in organic material 11 is effective as shown in Figure 1 (Materials Research Bulletin, Vol. 13). pp. 525-536 (1978)). In fact, by combining PZT with an organic material such as silicone rubber, a material with low acoustic impedance and a large piezoelectric voltage constant g has been obtained. Moreover, at this time, the piezoelectric strain constant d, which is a measure of the ultrasonic wave generation efficiency, hardly decreases.

An object of the present invention is to provide an electronic scanning type ultrasound probe using such a composite material.
As shown in FIG. 2, the composite material used in the ultrasonic probe of the present invention is, for example, a plate-shaped organic material 2
1 has a structure in which columnar piezoelectric bodies 22 are regularly arranged two-dimensionally. Such a composite material can be regarded as a substantially uniform material if the size of the columnar piezoelectric body 22 is sufficiently small. The ultrasonic probe of the present invention has a large number of strip-shaped thin film electrodes 31 (indicated by diagonal lines in FIG. 3) on such a composite piezoelectric material, and a gap 32 between each electrode. It is characterized in that it is formed so as to correspond to the portion of organic substance 21 between 22 (FIG. 3).
Since the gaps between the strip-shaped electrodes are organic parts, the vibration energy is small, and the area under each strip-shaped electrode can be regarded as an independent vibration region (sound source). Therefore, the ultrasound probe of the present invention has a function as an electronic scanning type ultrasound probe.

The present invention will be explained in detail below with reference to Examples.
FIGS. 4A to 4E are diagrams for explaining the method of manufacturing an ultrasonic probe according to the present invention. As shown in Figure 4A, the length l uniformly polarized in the thickness direction is 20
A PZT ceramic plate 41 with a width w of 10 mm and a thickness t of 0.5 mm is mounted on a ferrite substrate 43 with an adhesive 42 that can be melted later, such as electron wax. 4
As shown in Figure B, the ceramic part is cut into a mesh shape with a pitch of 300 μm, and a 150 μm square columnar PZT45 is made.
I made it. After cutting, the resulting groove 44 is filled with silicone rubber 46 as shown in FIG. 4C, dried, the adhesive 42 is dissolved, and the ceramic plate is attached to the ferrite substrate 4.
Separated from 3. In this way, a flexible composite piezoelectric plate 47 in which 150 μm square columnar PZT 46 is regularly embedded in silicone rubber 46 is formed.
I got it. Chromium and gold were deposited on the entire surface of one side of the composite piezoelectric plate 47 as a ground electrode. Then the fourth
Using a molybdenum metal mask 49 in which slits 48 each having a length l' of 0.5 mm and a width w' of 10 mm are lined up at a pitch of 0.6 mm in the length direction as shown in Fig. D, a composite piezoelectric plate is formed as shown in Fig. 4E. A strip-shaped electrode 50 was deposited on the other surface of 47. At this time, the 0.1 mm wide gap between the strip electrodes is made of silicone rubber 46
The masks were matched to correspond to the part.

In this way, under each strip electrode 50,
A probe 60 having a structure in which two rows of 150 μm square PZT45 columns were arranged was obtained. Each strip electrode 50
By attaching lead wires (not shown) to the electrodes, we conducted an experiment to generate ultrasonic waves, and as a result, it was confirmed that mutual crosstalk was small and that the area under each electrode operated as an almost independent sound source. . Although no packing material was used in this experiment, a short pulse width was obtained because the Q value was sufficiently reduced by the influence of the silicone rubber. In addition, the acoustic impedance is reduced to about 1/3 that of PZT ceramics, making it possible to efficiently send ultrasound into the human body without paying much attention to the matching layer. Furthermore, the ultrasonic probe 60 obtained here is flexible enough to be deformed almost arbitrarily, and can be adapted to the curvature of the human body.

[Brief explanation of drawings]

FIG. 1 is a three-dimensional diagram showing an example of a composite piezoelectric material.
FIG. 2 is a plan view showing an example of a composite piezoelectric plate used in the ultrasonic probe of the present invention. FIG. 3 is an enlarged plan view showing one embodiment of the ultrasonic probe of the present invention. 4th A~
FIG. 4E is a diagram for explaining the method of manufacturing an ultrasonic probe according to the present invention.

Claims (1)

[Claims] 1. A composite piezoelectric plate having a shape in which a large number of columnar ceramics whose length direction is perpendicular to the plate surface are regularly arranged and embedded in a network-like organic substance, and the composite piezoelectric plate It has electrodes formed on both sides, and at least one of the electrodes is separated into a plurality of strip electrodes by a plurality of gaps in one direction, with a large number of columnar ceramics under each strip electrode. An ultrasonic probe characterized in that the plurality of gaps are arranged and each of the plurality of gaps is located at a position of the organic substance.