JPH0759768A - Ultrasonic probe - Google Patents

Abstract

PURPOSE:To provide an ultrasonic probe easy in miniaturization and connection and enhanced in the reliability of the close adhesiveness of a resin bonded to a piezoelectric element by providing a pair of first electrodes to both surfaces of the piezoelectric element in opposed relationship and arranging second electrodes to the side surface parts of the piezoelectric element in the state electrically connected to the first electrodes. CONSTITUTION:A pair of strip like electrodes 7, 8 are formed to both surfaces of a piezoelectric element 5 as first electrodes in opposed relationship in the thickness direction thereof so as to be positionally shifted each other. Silver paste is applied to the both surfaces of the piezoelectric element 5 by a screen printing method and baked to form the electrodes 7, 8 and polarization is performed to form the piezoelectric element 5. Next, surface treatment is applied to the piezoelectric element 5 by ion bombardment to perform vapor deposition at temp. not deteriorating spontaneous polarization and silver electrodes are bonded to the side surfaces of the piezoelectric element to form side surface electrodes 22 being second electrodes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic probe used for an ultrasonic endoscope used for medical purposes.

[0002]

2. Description of the Related Art In recent years, ultrasonic probes have been rapidly used as not only nondestructive inspection devices but also ultrasonic diagnostic devices for medical use. For example, a probe such as an ultrasonic endoscope emits high-frequency acoustic vibrations from an ultrasonic transducer into a living body,
The ultrasonic wave reflected and returned is received by the ultrasonic transducer, and different information is processed due to a slight difference in the interface characteristic, thereby obtaining a cross-sectional image of the inside of the living body. The vibrator of the ultrasonic transducer is roughly divided into a piezoelectric element, an acoustic matching layer, and a back load material, which are sequentially stacked. This ultrasonic transducer uses an electrode formed on its surface to apply a high-frequency voltage pulse to a piezoelectric element to cause the piezoelectric element to resonate and rapidly change to generate an ultrasonic pulse.

However, when high frequency and miniaturization are required as in the case of an ultrasonic probe for blood vessels, the shape of the piezoelectric element is small and the thickness is very thin, which makes it difficult to arrange the so-called electrodes by a wiring method. Came. Further, the electrode material also has a strong adhesion strength to the resin or the piezoelectric ceramic, but does not have completely satisfactory characteristics such as the piezoelectric characteristics not being sufficiently drawn out.

FIG. 9 shows a conventional ultrasonic probe disclosed in Japanese Patent Laid-Open No. 3-173547. The ultrasonic probe is in contact with a non-conductive case 100, a piezoelectric element 110 fitted into one end of the case 100 and not subjected to polarization treatment, and one surface of the piezoelectric element 110. Good conductivity back load material 120 filled in the case 100
And a thin film electrode 130 formed on the other surface of the piezoelectric element 110 and the outer surface of the case 100, and the piezoelectric element 110.
And an acoustic matching layer 140 laminated on the other surface of the. This ultrasonic probe uses the back load material 120 as a positive electrode and the thin-film electrode 130 as a negative electrode, and applies a voltage to the piezoelectric element 110 to polarize it to impart a piezoelectric effect.

[0005]

A conventional ultrasonic probe using a back load material 120 in which a thin film electrode 130 is provided on a non-polarized piezoelectric element 110 and conductivity is provided as one electrode is After the thin-film electrode 110 and the back load material 120 of good conductor are bonded or directly formed on the piezoelectric element 110, the polarization operation is performed. The piezoelectric element 110 tends to deform due to this polarization operation, but the back load material 120 mainly regulates this deformation, so stress is applied to the piezoelectric element, and discharge breakdown or microcracks occur during polarization. However, there is a problem that the life is greatly shortened.

Further, the thin film electrode 130 is likely to be cracked as the piezoelectric element is deformed during polarization. Furthermore, the back load material 120 that also serves as an electrode and a thin-film electrode has a problem in that it is easily peeled between the piezoelectric elements 110 due to strain during polarization, which causes characteristic deterioration.

The present invention has been developed in view of the above points, and it is an object of the present invention to provide an ultrasonic probe which is easy to miniaturize and connect, and which has high reliability of adhesion of resin to be bonded to a piezoelectric element. To aim.

[0008]

The ultrasonic probe of the present invention comprises a laminated body in which a back load material, a piezoelectric element and an acoustic matching layer are laminated in order, and a housing to which the laminated body is attached. The piezoelectric element has a pair of first electrodes that oppose each other in the thickness direction, and a second electrode that is arranged in a side surface portion in a state of being electrically connected to each of the first electrodes. And

In the above structure, the piezoelectric element is formed with the electrode in the thickness direction and the electrode on the side surface portion, the adhesion strength of the electrode to the resin is increased, and the reliability is improved.

[0010]

[Embodiment 1] FIGS. 1 to 4 show a procedure for manufacturing electrodes of a piezoelectric element according to Embodiment 1 of the present invention. As shown in Figure 1,
A plurality of strip-shaped electrodes 7 and 8 facing each other in the thickness direction are formed on both surfaces of the piezoelectric element 5. These electrodes 7 and 8 serve as first electrodes and are formed so as to be displaced from each other. Specifically, the thickness is 0.11mm and the resonance frequency is 20M.
A piezoelectric element 5 is obtained by lapping a lead titanate (PT) -based material of Hz. The temperature at which the spontaneous polarization in the piezoelectric element 5 disappears is 320 ° C. Silver paste is applied to the piezoelectric element 5 by a screen printing method, baked to form electrodes 7 and 8 having a thickness of about 7 μm, and polarized to produce the piezoelectric element 5 shown in FIG. Then, FIG.
A piezoelectric element 5 having a cross section shown in FIG. 3 is produced by cutting along a wavy line shown in FIG. Here, one end of each of the electrodes 7 and 8 reaches one corner of the surface of the piezoelectric element 5, but the other end is interrupted at a midway portion, and this portion serves as an electrode slit 26. Next, the piezoelectric element 5 is subjected to surface treatment such as ion bombardment, vapor deposition is performed at a temperature at which spontaneous polarization does not deteriorate, for example, 150 ° C., and a silver electrode is attached to a side surface which is a cut surface. The side electrode 22 which is the second electrode is formed. In this case, the side surface electrode 22 on each side surface is formed so as to be electrically connected to the respective electrodes 7 and 8.

5 and 6 show a state in which the acoustic matching layer 4 and the back load material 3 are laminated on the piezoelectric element 5 to form the vibrating portion 25 of the ultrasonic probe. The acoustic matching layer 4 and the back load material 3 are attached to the piezoelectric element 5 by the anaerobic adhesive 21.
Are bonded and laminated on both sides of.

The back load material 3 has the function of acoustically dampening and shortening the ultrasonic pulse waveform, and the function of attenuating the ultrasonic waves radiated to the back surface so that the reflected ultrasonic waves do not reach the piezoelectric element. It is composed of an epoxy resin portion 1 containing tungsten powder as a filler for the purpose of preparation and an insulating layer 2 on the side surface and the bottom surface made of only an epoxy resin for improving the insulating property. The insulating layer 2 on the side surface is a back load material. Three
It is laminated according to the position of the electrode slit 26 of the piezoelectric element 5 on the surface contacting with.

FIG. 7 shows an ultrasonic probe 18 manufactured by using the vibrator section 25. In this ultrasonic probe 18, the vibrator portion 25 is fixed to the housing 6 in which a metal pipe is processed with an adhesive, and the positive and negative electrodes 7 and 8 are connected to the lead wires 10 and 11 with a conductive resin 9. At that time, the lead wire 1 on the GND side
1 is connected to the housing 6 with a conductive resin 9 and is connected from the housing 6 with the conductive resin 9, and then the conductive resin 9 portion is sealed with an insulating resin 12.

In the illustrated example, the housing 6 is brazed using the flexible shaft 24 and the silver brazing 14, while the coaxial cable 13 is used as the lead wire. Since the ultrasonic probe 18 is provided with the planar first electrode and then positioned and cut using a precision cutting machine, the electrode slit 26 between the positive and negative electrodes can be easily manufactured with high precision. A plurality of piezoelectric elements having side electrodes can be manufactured at one time. In addition, when polarization is performed after manufacturing a piezoelectric element having a side surface electrode, distortion occurs at the corner of the planar electrode and the side surface electrode due to strain during polarization, and conduction failure occurs when cut into an ultrasonic probe. However, in this embodiment, since the side surface electrode is attached after the polarization, the conduction failure does not occur.

Further, the pair of electrodes in the thickness direction is made by baking a silver paste, and since glass frit or the like is mixed therein, the adhesion strength with the ceramic and the adhesion strength with the resin are high. On the other hand, the silver vapor-deposited electrode provided on the side surface is more elastic than the baking electrode, and the durability as a transducer is improved. The method of attaching the side surface electrode may be sputtering instead of vapor deposition, and the same material can be used as long as it can easily expand and contract, such as gold, silver, copper or an alloy containing these. Furthermore, by using solderable silver, silver alloy, etc. as the material of the side electrodes, the reliability of the connection is also improved.

[0016]

Second Embodiment FIG. 8 shows a transducer portion of an ultrasonic probe according to a second embodiment of the present invention, and the same elements as in the first embodiment are designated by the same reference numerals. In this embodiment, the resonance frequency 25 in which the strip electrodes 7 and 8 are formed by baking the silver paste is used.
On the negative electrode surface 8 of the piezoelectric element 5 having a frequency of MHz and a thickness of about 90 μm, an epoxy resin 15 having a thickness of ¼ wavelength is printed as the first acoustic matching layer 4 and further made of soft polyethylene to a thickness of about 1 /. A sheet 23 having a thickness of 4 wavelengths is adhered. Further, a back load material 16 made of a resin containing alumina as a filler is laminated on the positive electrode side of the piezoelectric element 5 to form a vibrator portion.

Then, it is cut in the Y direction indicated by the broken line by a precision cutting machine, and a silver alloy is vapor-deposited on the side surface portion having the exposed electrode to form a side surface electrode. Then, the transducer part 25 is cut by cutting in the X direction, adhered to the housing in the same manner as in Example 1, and connected to make an ultrasonic probe (see FIG. 7).

In this embodiment, since the acoustic matching layer is laminated on the piezoelectric element and then cut, an acoustic matching layer having a desired thickness and a uniform thickness and having the same shape as the piezoelectric element can be manufactured. As a result, high sensitivity can be obtained, and an ultrasonic probe without distortion of the ultrasonic beam can be obtained.

Further, since the acoustic matching layer and the back load material are laminated on the piezoelectric element and then cut and the side electrodes are attached, there is no wraparound of the adhesive, the resin forming the acoustic matching layer and the back load material, and the wiring is connected. The ultrasonic probe can have high reliability.

In this embodiment, the acoustic matching layer has a three-layer structure, but the same effect can be obtained if at least one acoustic matching layer or one acoustic lens is provided. Furthermore, the electrode deposited on the side surface is not limited to the piezoelectric element portion, but even if it extends to a part of the side surface of the back load material and the side surface of the acoustic matching layer, it does not reach the bottom surface of the back load material, resulting in insulation. Since it suffices to secure the electrodes, it is easy to apply electrodes even to a piezoelectric element having a high frequency and a small thickness.

[0021]

As described above, according to the present invention,
Since the electrodes are formed on the side surfaces of the piezoelectric element, it is possible to use an acoustic matching layer which is likely to be peeled off at the boundary surface and an electrode material having a high adhesion strength with the resin of the back load material. Further, since the electrode material having high elasticity is used for the electrodes on the side surfaces, it is possible to obtain an ultrasonic probe having high product reliability. Moreover, in a piezoelectric element of an ultrasonic probe that requires a wraparound electrode, polarization is performed with only a pair of electrodes in the thickness direction being applied, and then electrodes are applied to the side faces, so that polarization is performed in the lateral direction. It is possible to provide a high-resolution ultrasonic probe in which there is no part to be generated, an unnecessary vibration mode does not occur when a pulse is applied, and noise is reduced.

[Brief description of drawings]

FIG. 1 is a perspective view showing the production of a piezoelectric element in Example 1 of the present invention.

FIG. 2 is a side view showing the manufacture of the piezoelectric element according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view of a piezoelectric element before an electrode is provided on a side surface.

FIG. 4 is a cross-sectional view of a piezoelectric element having electrodes on its side surface.

5A and 5B are cross-sectional views showing manufacturing of a vibrator portion.

FIG. 6 is a cross-sectional view of a vibrator portion.

FIG. 7 is a cross-sectional view of the ultrasonic probe according to the first embodiment.

FIG. 8 is a perspective view of the second embodiment.

FIG. 9 is a cross-sectional view of a conventional ultrasonic probe.

[Explanation of symbols]

 5 Piezoelectric element 7,8 electrode

Claims (2)

[Claims] 1. A laminated body in which a back load material, a piezoelectric element, and an acoustic matching layer are laminated in order, and a housing to which the laminated body is attached, wherein the piezoelectric element is a pair of first opposing members in the thickness direction. And an second electrode disposed on a side surface portion in a state of being electrically connected to each of the first electrodes. 2. The ultrasonic probe according to claim 1, wherein the first electrode and the second electrode are made of different materials.