JPS62178100A - piezoelectric vibrator - Google Patents

Abstract

PURPOSE:To prevent the damage of acoustic characteristics and to facilitate the lead-out of lead wires by forming an electrode of the second layer through an electric insulating layer on an electrode of one face of a piezoelectric vibrator where electrodes are provided on both faces of a piezoelectric body. CONSTITUTION:A shield electrode 14 is formed on one electrode 11 through an insulating layer 13. Since acoustic impedances of electrodes 11 and 12, a piezoelectric body 10, the insulating layer 13, and the electrode 14 are easily equalized approximately by this constitution, a fundamental frequency can be handled as a lambda/2 resonance frequency calculated at an average acoustic velocity for the thickness of the whole and acoustic characteristics are not damaged. With respect to the insulating layer, a metallic oxide film consisting of alumina, silicon oxide, or the like whose acoustic impedance approximates that of materials of electrodes is formed by vapor deposition or printing. Lead wires are led out similarly to essential lead wires of electrodes 11 and 12 and conventional special considerations of the forming process of a matching layer and an acoustic lens are made unnecessary.

Description

[Detailed Description of the Invention] [Summary] The present invention is a piezoelectric vibrator such as an ultrasonic transducer, in which an electrode for shielding external electromagnetic noise is formed on the original electrode with an insulating layer interposed therebetween. It is characterized by

[Industrial application field]

The present invention relates to the improvement of piezoelectric vibrators used in probes of ultrasonic diagnostic equipment, ultrasonic flaw detection equipment, etc., and enables highly accurate measurements by removing external electromagnetic noise.

[Conventional technology]

A conventional piezoelectric vibrator generally consists of a backing material 41, a piezoelectric material 40, and a matching layer 42, as shown in FIG.
0 consists of a piezoelectric ceramic 40-1, a back electrode 40-2, and a front electrode 40-3. In this figure, observation ultrasonic waves are transmitted from the front electrode side to the measurement target via the matching layer, and reflected waves from the target are received through the opposite path, signal processed, and displayed.

The received signal is generally extremely weak, and the influence of external electromagnetic noise picked up by signal cables cannot be ignored. For this reason, signal cables and connectors are often shielded, but shielding of the opening surface of the piezoelectric vibrator has become a problem. In contrast, an example has been proposed in which a shield electrode is provided on the matching layer 42, as shown in FIG.
207138 etc.).

Note that 43 is an acoustic lens.

[Problem to be solved by the invention]

However, in the example of FIG. 5, the shield electrode is connected to the matching layer 4.
2, the thickness must be extremely thin so as not to adversely affect the acoustic characteristics of the ultrasonic waves, and there are also problems such as difficulty in drawing out the lead wire from this shield electrode. Ta.

[Means for solving problems]

In the present invention, as shown in the principle diagram in Fig. 1, one electrode 1)
It is characterized in that a shield electrode I4 is formed on top of the insulating layer 13 via an insulating layer 13.

[Operation] By adopting such a configuration, electrode 1). Since it is easy to make the acoustic twinpedances of the 12° piezoelectric body 10, the insulating layer 13, and the shield electrode 14 approximately the same, the fundamental frequency is the /2 resonance frequency calculated from the average sound speed of the entire thickness. It can be treated as such, without damaging the abutment characteristics. The insulating layer 13 may be made of alumina (AlzO3) or silicon oxide (S), which has an acoustic impedance close to that of the electrode material.
A fully bent oxide film such as iOz) may be formed by vapor deposition or baking.

Also, regarding the lead wire extraction, the original electrode 1). 1
This can be done in the same way as lead wire No. 2, and there is no need for special considerations in the process of forming the matching layer and acoustic lens as in the conventional method.

〔Example〕

FIG. 2 shows an ultrasonic transducer according to an embodiment of the present invention, in which 20 is a piezoelectric vibrator, 20-1 is a piezoelectric ceramic, 20-2 is a back electrode, 20-3 is a front electrode, 20-
4 is an insulating layer, 20-5 is a shield electrode, 21 is a matching layer,
22 is a banking material, and 23 is a driving/receiving circuit.

The shield electrode 20-5 is grounded, and electromagnetic waves from the direction of the arrow are reflected and absorbed by this electrode, so that the energy reaching the front electrode 20-3 is attenuated.

FIG. 3 shows an array type ultrasonic transducer according to another embodiment of the present invention, in which the same symbols as in FIG. 2 mean the same things, and 24 is a sound 3 lens.

The difference from FIG. 2 is that the piezoelectric ceramic is divided into multiple parts, and the front electrodes are commonly connected to each other, and the front electrode 20-3 and the shield electrode 20-5 are connected together for lead wire extraction. part is exposed.

〔Effect of the invention〕

As described above, according to the present invention, since the shield electrode is formed on the front electrode via the insulating layer, the acoustic characteristics are not impaired, and lead wires can be easily drawn out.

Incidentally, the shield electrode can be provided not only on the front side but also on the back side.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing the principle of the present invention, Fig. 2 is a perspective view showing one embodiment of the invention, Fig. 3 is a perspective view showing another embodiment of the invention, and Fig. 4 is a conventional example. FIG. 5 is a sectional view showing another conventional example. In FIG. 1, 10 is a piezoelectric ceramic, 1) is a front electrode, 12 is a back electrode, 13 is an insulating layer, and 14 is a shield electrode. Demonstration of the principle of the present invention 1 gen n Ding Miryo 1 crime 8 (饅1 grounding invention 0-laughing paddle i1 nMzu5゛dayΣ1ρai ed)
3

Claims (3)

[Claims] (1) A piezoelectric vibrator having electrodes on both sides of a piezoelectric body, characterized in that a second layer of electrodes is formed on at least one side of the electrodes with an electrically insulating layer interposed therebetween. (2) The piezoelectric vibrator according to claim (1), wherein mutually independent lead wires are drawn out from the two layers of electrodes formed on one surface. (3) The piezoelectric vibrator according to claim 1 or 2, wherein a metal oxide film is used as the insulating layer.