JPH0835954A - Ultrasonic probe - Google Patents

Abstract

PURPOSE:To stabilize and retain a high performance by reducing an upper electrode as compared with the diameter of a piezoelectric transducer, increasing a lower electrode as compared with the diameter of the transducer and folding back the side surface edge part to an upper electrode side, and then sealing a lead wire to the fold-back part and the upper electrode. CONSTITUTION:An upper electrode 2 is formed concentrically at the center of a circular piezoelectric transducer 1, a lower electrode 3 covers the lower surface and all side surfaces of the transducer 1 and then covers an upper- surface circumferential part concentrically, and a bonding pad for a conductor is formed at the upper-surface edge part of the transducer 1. Then, the upper edge surface of an acoustic lens 6 is bonded to the lower surface of the electrode 3, a lead wire 8 is connected to the surfaces of the electrodes 2 and 3 with a conductive adhesive, and a damper material 5 is filled and hardened onto the electrode 2 using a tool. With this configuration, ultrasonic waves are excited and received only at a region directly below the electrode 2, thus preventing an unneeded high harmonic oscillation from being excited.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic probe mainly used in an ultrasonic flaw detector.

[0002]

2. Description of the Related Art As ultrasonic flaw detectors, metal flaw detectors for the purpose of flaw detection in the same medium, ultrasonic microscopes for the purpose of examining the shape and properties of composite media, medical diagnostic equipment, etc. have been put to practical use. ing. In these devices, an ultrasonic element that generates an ultrasonic beam, detects an echo, and converts it into an electric signal, and an acoustic lens for beam focusing that is attached to the ultrasonic element and focuses the ultrasonic beam It is a major component. A concave lens surface is formed at the tip of the acoustic lens to focus the ultrasonic beam.

As the ultrasonic element, one utilizing a magnetostrictive effect and one utilizing a piezoelectric effect have been put into practical use, but the former cannot be used because of an excessive eddy current loss in a high frequency region, and the ultrasonic element of 50 KHz or less is used. It has been put to practical use in ultrasonic cleaners in the low frequency range. On the other hand, the latter has a characteristic that it can be used in a high frequency region without limitation, and thus has been widely industrialized in recent years, centering on a ceramic thin film piezoelectric transducer.

To drive the piezoelectric transducer, a pair of electrodes, which are electrically independent from each other, are provided on the upper and lower portions of the piezoelectric transducer, and a lead wire for power supply is connected to each electrode to connect to an external power source and a circuit. When used for flaw detection, the resolution in the thickness direction is about the wavelength of the ultrasonic wave. Therefore, in order to improve the resolution, a high frequency band is used, and an acoustic lens for beam focusing is combined to form an ultrasonic probe. The lower end surface of the acoustic lens is processed into a concave surface to form a lens, and the lower electrode of the piezoelectric transducer is closely arranged on the upper end surface (flat surface).

As a concrete configuration example of the ultrasonic element, the configurations shown in FIGS. 2 and 3 have been conventionally used. 2 shows the structure of the piezoelectric transducer and the upper and lower electrodes, and FIG.
The state which formed the ultrasonic probe using the structure of is shown. In the figure, 11 is a piezoelectric element, 12 is an upper electrode, 13 is a lower electrode, 14 is an insulating spacer, 15 is a damper material, 16 is an acoustic lens, 17 is a conductive adhesive, 18 is a lead wire, 1
Reference numeral 9 is an ultrasonic element.

As shown in the figure, in the conventional ultrasonic probe, the acoustic lens 16 and the piezoelectric transducer 11 are used.
Then, a part of the lower electrode 13 is extended to a part of the upper end through the side surface of the piezoelectric transducer 11 to form the bonding pad of the lead wire 18. The bonding pad of the lower electrode 13 is arranged so as to cover one end of the circular upper electrode 12, as shown in FIG. 2A (top view). In order to electrically insulate between the upper electrode 12 and the lower electrode 13, a thin-film insulating spacer 14 is arranged as shown. (B) of FIG. 2 is A- of (a).
It is an A'sectional view.

A pair of lead wires 18 are connected to the bonding pads of the upper electrode 12 and the lower electrode 13 by a conductive adhesive 17 as shown in the cross section of FIG. Thereafter, the damper material 15 is filled so as to protect the connecting portion of the lead wire 18. The lower electrode 13 is arranged in close contact with the upper end surface of the acoustic lens 16. As shown in FIG. 3, the ultrasonic probe includes a piezoelectric transducer 11, upper and lower electrodes 12 and 13, an insulating spacer 14, a damper material 15, an acoustic lens 16, a conductive adhesive 17, a lead wire 18, and the like. To be done. Piezoelectric transducer 11
Is an oxide ceramic such as quartz or ZnO, and the damper material 15 is a resin mixed with W powder.
6 is formed by using an appropriate acoustic medium, for example, quartz glass, metal, resin or the like. The insulating spacer 14 is usually resin paint. The ultrasonic element shown in FIGS. 2 and 3 is a high-resolution ultrasonic device such as an ultrasonic imaging device that mainly displays a two-dimensional image of defects such as voids and peeling inside the sample.
Used for probes up to 0MHz.

[0008]

According to the above-mentioned prior art, the adhesion between the ultrasonic element and the acoustic lens is high at the time of manufacturing the ultrasonic probe, and the lead wire connection to the electrode of the ultrasonic element is easy. It can be carried out. However, electrical insulation may be inadequate because the upper and lower electrodes of the piezoelectric transducer are separated only by a thin insulating spacer at the top surface of the piezoelectric transducer.
That is, in order to induce an ultrasonic beam in the piezoelectric transducer, if a pulse voltage of several to several tens of KV / cm is applied between the upper and lower electrodes, a short circuit accident may occur via a film defect of the insulating spacer. Further, as shown in FIGS. 2 and 3, since the lead wire connecting portion of the lower electrode is formed only on a part of the upper end surface of the piezoelectric transducer, the thickness of only a part of the ultrasonic excitation region becomes uneven. Therefore, there is a problem that unnecessary higher-order mode ultrasonic beams are excited in this region.

Further, when the lead wire connecting portion of the lower electrode is formed only on a part of the upper end surface of the piezoelectric transducer as described above, there is a structural difference between this area and the other area, so that the piezoelectric transducer At the time of excitation, non-uniform distortion occurs, which causes separation of the ultrasonic element and the acoustic lens. In the separated state, an air layer is interposed between the ultrasonic element and the acoustic lens, so that the propagation of ultrasonic waves is significantly hindered and the sensitivity of the ultrasonic probe is lowered. An object of the present invention is to provide an ultrasonic probe capable of stably exhibiting high performance while maintaining ease of manufacturing.

[0010]

In order to achieve the above object, according to the present invention, a cylindrical acoustic lens having a lens surface on the lower end surface, and a circular lower electrode on the upper end surface of the acoustic lens,
In an ultrasonic probe including a circular piezoelectric transducer and ultrasonic elements concentrically arranged in the order of a circular upper electrode, the upper electrode has a diameter smaller than that of the piezoelectric transducer, and the lower electrode has a diameter smaller than that of the piezoelectric transducer. It is made larger than the diameter and is folded back to the upper electrode installation surface side of the piezoelectric transducer through the side end portion of the piezoelectric transducer, and the lower electrode lead wire and the upper electrode lead wire are respectively attached to the folded lower electrode portion and upper electrode. A fixed ultrasonic probe is disclosed.

[0011]

Since the upper electrode of the ultrasonic element is electrically separated from the lower electrode only in the central portion of the upper surface of the piezoelectric transducer, the excitation area of the ultrasonic beam is limited to immediately below the upper electrode. As a result, even if the lower electrode is disposed around the outer peripheral portion of the upper surface of the piezoelectric transducer, the risk of exciting ultrasonic waves in unnecessary modes is significantly reduced. In addition, the gap between the upper and lower electrodes can be surely widened as compared with the conventional one, and a short circuit accident can be prevented. Since the lower electrode of the ultrasonic element is arranged around the upper surface evenly, the occurrence of local non-uniform strain is prevented. As a result, the possibility of breakage or peeling that occurs during probe manufacture or probe operation is reduced.

[0012]

EXAMPLES The present invention will be described in more detail based on the following examples. FIG. 1 shows an arrangement of electrodes for a piezoelectric transducer of the present invention corresponding to FIG. 2 (conventional example). 1A is a top view, and FIG. 1B is a sectional view taken along line BB ′ of FIG.
In the figure, 1 is a piezoelectric transducer, 2 is an upper electrode,
Reference numeral 3 indicates a lower electrode.

The upper electrode 2 for exciting the piezoelectric transducer 1 is formed concentrically only in the central region of the circular piezoelectric transducer 1. On the other hand, the lower electrode 3 covers all of the lower surface and the side surface of the piezoelectric transducer 1 and concentrically covers the upper surface of the piezoelectric transducer 1 to form a bonding pad for a conductive wire at the upper end of the piezoelectric transducer 1. In such a structure, an annular mask (not shown) is concentrically and closely arranged on the upper surface of a circular piezoelectric transducer made of piezoelectric ceramic, and then gold or gold is simultaneously applied from the upper surface side and the lower surface side of the piezoelectric element 1. This is achieved by depositing a metal such as chromium. If the mask is removed after the vapor deposition, the mask arrangement portion remains in a circular groove shape as the piezoelectric transducer 1 of FIG.

FIG. 4 shows an example in which an ultrasonic probe is constructed based on the ultrasonic element of the embodiment of the present invention shown in FIG. In the figure, 5 is a damper material, 6 is an acoustic lens, 7 is a conductive adhesive, 8 is a lead wire, and 9 is an ultrasonic element. After forming the upper and lower electrodes 2 and 3 on the piezoelectric transducer 1 by the method described above, the upper end surface of the acoustic lens 6 is bonded to the lower surface of the lower electrode 3. Then, the lead wires 8 are connected to the surfaces of the upper and lower electrodes 2 and 3 with a conductive adhesive. Then, on the upper electrode 2, a mixture of metal powder and resin, that is, the damper material 5 is filled and solidified by using a jig (not shown). As illustrated, the ultrasonic element 9 having the piezoelectric transducer 1, the upper electrode 2, and the lower electrode 3, the damper material 5, the conductive adhesive 7, and the lead wire 8 constitute an ultrasonic probe.

The lead wires 8 for the upper and lower electrodes are respectively connected to terminals of an RF pulse oscillator (not shown),
When a high frequency pulse voltage of 1 to 100 MHz is applied to the piezoelectric transducer 1, plane ultrasonic waves are radiated into the acoustic lens 6. The acoustic lens 6 is formed by shaping sapphire, for example, and has a concave surface at its lower end as shown in FIG. The concave surface acts as a lens on the plane ultrasonic wave, and the ultrasonic beam is focused at the focal position. A liquid coupler (for example, water) is arranged between the subject (not shown) and the concave surface,
It prevents the ultrasonic waves emitted from the lens from being attenuated.
The focused ultrasonic beam arriving at the focal point formed on the surface of or inside the subject is reflected, scattered, and absorbed. Then, the reflected wave returns from the acoustic lens 6 through the lower electrode 3 to the piezoelectric transducer 1 through the same path as the incident path, is converted into an electric signal, and is detected by an external measurement circuit.

With the electrode configuration of FIG. 4, the excitation of ultrasonic waves,
Reception occurs only in the region immediately below the upper electrode 2 (pulse voltage application region). Therefore, the surrounding area of the lower electrode 3 on the upper surface of the piezoelectric transducer 1 does not excite unnecessary harmonic oscillation. Moreover, since the upper electrode 2 and the lower electrode 3 are separated by a sufficient distance on the upper surface of the piezoelectric transducer 1, there is no electrical short circuit when the pulse voltage is applied. Since the upper and lower electrodes 2 and 3 are geometrically symmetrically arranged on the upper surface of the piezoelectric transducer 1, the strain is evenly distributed during ultrasonic excitation, and therefore the ultrasonic element 9 and the acoustic lens are deteriorated due to deterioration over time. The possibility that 6 and 6 are peeled off is significantly lower than in the past.

[0017]

As described above, according to the present invention,
Without impairing the workability of the ultrasonic probe manufacturing process, a short circuit between the upper and lower electrodes of the piezoelectric transducer, generation of unnecessary harmonic components during operation of the ultrasonic probe, and ultrasonic element / acoustic lens It is considered that the occurrence of peeling between them can be suppressed. As a result, it is considered that the manufacturing yield of the ultrasonic probe and the reliability of the flaw detection device can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an ultrasonic element and an electrode structure thereof according to an embodiment.

FIG. 2 is a diagram showing a structure of an ultrasonic element according to a conventional example.

FIG. 3 is a diagram showing an outline of a conventional ultrasonic probe structure using the ultrasonic element of FIG.

FIG. 4 is a diagram showing an outline of an ultrasonic probe structure in one embodiment of the present invention using the ultrasonic element structure of FIG.

[Explanation of symbols]

 1, 11 Piezoelectric transducer 2, 12 Upper electrode 3, 13 Lower electrode 5, 15 Damper material 6, 16 Acoustic lens 7, 17 Conductive adhesive 8, 18 Lead wire 9, 19 Ultrasonic element 14 Insulating spacer

Claims (2)

[Claims] 1. A cylindrical acoustic lens having a lens surface on a lower end surface, and ultrasonic elements in which a circular lower electrode and a circular piezoelectric transducer circular upper electrode are concentrically arranged in this order on the upper end surface of the acoustic lens. In the ultrasonic probe, the upper electrode has a diameter smaller than that of the piezoelectric transducer, the lower electrode has a diameter larger than that of the piezoelectric transducer, and the piezoelectric transducer is connected through the side end of the piezoelectric transducer. The ultrasonic probe in which the lower electrode lead wire and the upper electrode lead wire are fixed to the folded lower electrode portion and the upper electrode, respectively. 2. The ultrasonic probe according to claim 1, wherein a damper material is formed so as to cover only a part of the upper electrode lead wire fixed to the upper electrode.