JPS59178378A - Ultrasonic probe - Google Patents

Abstract

PURPOSE:To prevent danger of electric leakage to a sample (organism) by providing an insulating intermediate layer on the opposite side of an acoustic operation surface of a piezo-electric element. CONSTITUTION:A metal thin film electrode 1 is provided on an acoustic operation surface employing a high molecular piezo-electric body as a piezo-electric body 3 while a strip-shaped electrode 2 on a non-acoustic operation surface thereof. An insulating intermediate layer 5 which is higher than the natural acoustic impedance of the piezo-electric element and about quarter or odd times the wavelength of excitation ultrasonic wave in the thickness is applied on the non-acoustic operation surface and fixed on a support 4. The intermediate layer uses glass, a ceramic substrate or a substrate obtained by mixing epoxy resin or the like with an insulating powder such as Al2O3, SiO2. As a high voltage pulse for excitation can be applied to the non-acoustic operation surface, the electrode on the side of a sample (organism) as acoustic operation surface can be grounded thereby preventing danger of electric leakage or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to an ultrasonic probe in which a plurality of unit ultrasonic wave emitting/receiving elements are arranged.

[Prior art and its problems]

1) Inorganic piezoelectric materials such as ZT and polymeric piezoelectric materials such as polyvinyritine fluoride are used as ultrasonic emitting/receiving elements in imaging equipment that uses ultrasound for ultrasound diagnosis, ultrasonic flaw detection, etc. . In particular, polymer piezoelectric materials have a small Young's modulus and large vibration damping, so they have the advantage of being able to emit and receive shorter pulses than inorganic piezoelectric materials such as PZT. For this purpose, so-called linear
In the array canopy ultrasonic probe, there is no need to cut the piezoelectric element, which is always necessary with inorganic piezoelectric materials such as PZT, and a strip-shaped By providing electrodes, the desired function can be achieved.

That is, in a linear array type ultrasonic probe using an inorganic piezoelectric material such as PZT, as shown in FIG.
, (2+ piezoelectric body (3) with backing material (4)
The sheet is pasted on the sheet and divided into m pieces using a dicing saw.

In this case, there are problems such as the piezoelectric vibrator cracking or peeling off from the backing material when it is divided with a dicing saw, and the workability is also difficult. - In the case of a long polymer piezoelectric material, the electrode (1
), (2>) on a support (
4) Just by pasting it on the surface, it will perform the same function as a linear array type ultrasonic probe using an inorganic piezoelectric material such as PZT.

Furthermore, the polymer piezoelectric material has a characteristic acoustic impedance of PZT.
Because it is smaller than other inorganic piezoelectric materials, the polymer piezoelectric material also has a large specific acoustic impedance, and is one quarter of the wavelength of the ultrasonic waves emitted and received by the polymer piezoelectric material or an odd number thereof. It is known that ultrasonic waves can be emitted and received more efficiently by lining the opposite side of the acoustically active substrate with an intermediate substrate that is twice as thick (hereinafter referred to as a λ/4 plate). (
JP-A-53-25390) When this method is applied to a linear array type ultrasonic probe using a polymer piezoelectric material, as shown in Fig. 3(a), the electrode (1) on the acoustically active surface is The piezoelectric material (
The electrode (2) on the non-acoustic operation surface of 3) is provided as a common electrode (2), and a support (
4), or as shown in Fig. 3(b), the electrode (1) on the acoustically active surface is used as a common electrode,
A conceivable method is 3) in which the electrode (2) on the non-acoustic operating surface is shaped like a strip and the supporting body (4) is provided via an opposing λ/4 plate (5) of the same shape. Regarding the manufacture of linear array type ultrasound, the configuration shown in FIG. 150-600■ element excitation
Since a high voltage pulse of about 100 mL is applied, it cannot be said to be practical if we take into account electrical leakage, etc. For this reason, in the configuration of a linear array type ultrasonic probe, the configuration shown in Figure 3 ( As shown in b), the electrode on the acoustically active side, that is, the living body side, is grounded when the piezoelectric element is excited, and the excitation is carried out via a strip-shaped electrode or a λ/4 plate that also serves as an electrode provided on the non-acoustically active side. Apply a high-voltage electric pulse.

In this case, the λ/4 plate of the linear array type ultrasonic probe is divided into the same shape as the strip-shaped electrode installed on the polymer piezoelectric film, so when manufacturing the probe, the λ/4 plate is divided into strip-shaped electrodes and λ /
It is difficult to align the patterns of the four plates, and the polymer piezoelectric film is easily deformed along the spacing between the strip-shaped λ/4 plates.
As a result, problems arise such as the ultrasonic waves emitted and received from the strip-shaped electrodes are scattered, leading to a decrease in resolution.

[Object of the present invention]

The present invention relates to an ultrasonic probe in which a strip-shaped thin film electrode is formed on at least one side of a piezoelectric vibrator, and a plurality of unit ultrasonic wave emitting/receiving elements are arranged. The object of the present invention is to provide an ultrasonic probe that eliminates the risk of electric leakage of Ill, simplifies the manufacture of the ultrasonic probe, and provides high resolution.

[Summary of the invention]

The present invention provides an ultrasonic probe comprising a piezoelectric element having a thin film electrode divided into strips on at least one side thereof, wherein a side opposite to an acoustically active surface of the piezoelectric element has a characteristic impedance higher than the intrinsic impedance of the piezoelectric element. It is characterized by providing a continuous insulating intermediate layer having a thickness of approximately one-fourth of the wavelength of the ultrasonic wave of the piezoelectric element used or an odd multiple thereof.

The present invention will be explained using FIG. 4.

Ag
, A4. A metal thin film electrode (1) made of Ni, Cr, etc. is provided on the entire surface by vapor deposition, Spangoo method, or plating method. 2) is provided. In this case, the strip-shaped electrode (2) is made by covering unnecessary parts with a mask or the like in advance in a vapor deposition method, sputtering method, plating method, etc.

Strip-shaped electrodes may be provided only in important parts, or thin film metal electrodes may be provided on the entire surface and then unnecessary parts of the thin film electrodes may be removed by etching or the like.

Next, on the non-acoustic operating surface of the piezoelectric element, a continuous insulator having a thickness higher than the characteristic acoustic impedance of the piezoelectric element and approximately one quarter of the wavelength of the ultrasonic wave used to excite the piezoelectric element or an odd number multiple thereof is applied. A transparent intermediate layer (5) is applied and further fixed to the support (4). This intermediate layer insulates the high-voltage transducer excavation pulse applied to the strip-shaped electrode (2), prevents electrical crosstalk to adjacent piezoelectric elements, and efficiently uses the ultrasonic energy of the transducer. The purpose is to radiate the sound to the operating surface, and the following intermediate layers may be used.

That is, the specific acoustic impedance of polyvinylidene fluoride, which is useful as a polymeric piezoelectric material, is approximately 4X10#/-sec.
glass/ceramic substrates with a higher specific acoustic impedance than that, or various metal plates with an insulating oxide film formed on their surfaces, or various metal substrates whose surfaces are coated with highly insulating fluororesin or the like; At
20s, SiC, Si.

A substrate obtained by mixing insulating powder such as N4, 5i02 into epoxy resin or the like is used.

[Effects of the present invention]

In the present invention, the piezoelectric element has a thickness that is higher than the intrinsic impedance of the piezoelectric element and approximately one-fourth of the wavelength of the ultrasonic wave of the piezoelectric element used, or an odd number multiple thereof, on the opposite side of the elevated operating surface of the piezoelectric element. By providing a continuous insulating intermediate layer, the following effects can be produced.

That is, by using a continuous insulating intermediate layer, it is possible to apply a high voltage pulse for excitation to the non-acoustic active surface of the piezoelectric element, so the electrode on the subject side (living body side), which is the acoustic active surface, is grounded. It is possible to prevent dangers such as electrical leakage. In addition, since this insulating intermediate layer is continuous, there is no need to match it with the strip-shaped electrode pattern installed on the non-acoustic operation surface, and it can function simply by pasting the piezoelectric element and the insulating intermediate layer. is possible.

This simplifies manufacturing. Furthermore, since the insulating intermediate layer can be used in the form of a continuous flat plate, the unevenness of the rectangular pattern that tends to occur when using a polymeric piezoelectric film is completely eliminated, and as a result, the piezoelectric element can transmit and receive signals. The ultrasonic beam generated will no longer be scattered or bent,
This brings about advantages such as being able to obtain a high-resolution ultrasonic probe.

[Embodiments of the invention]

Next, a specific example will be described.

Example 1 Ag was vacuum-deposited (thickness: 01 to 02 μm) on both sides of a uniaxially stretched polyvinylidene fluoride film having a thickness of 65 μm, and a piezoelectric element was obtained by separating the films. This one side is 13mm long,
64 strip-shaped electrodes with a width of 0.9 and a pitch of 0.1
It was formed using this Etch Song method.

Next, a quartz glass substrate acoustic impedance polished to a thickness of 100 μm was attached to the piezoelectric element side on which the strip electrode was installed using epoxy adhesive (Evotech 301-2), and the other side of this quartz glass substrate was attached to an acrylic substrate (5t). A linear array type ultrasonic probe was created by attaching it to the

The entire thin film electrode part on the acoustically active side of the linear array type ultrasonic probe is used as a ground electrode, and the strip-shaped electrode part is connected to a lead wire so that each element can be driven simultaneously. 3 (input/output impedance 50Ω
) and driven by a 150V strike pulse, the ultrasonic reflected wave from the methacrylic resin block placed at a depth of 70 degrees underwater was 45 dB.

Next, under the same underwater conditions, we measured the ultrasonic beam emitted from the linear array ultrasonic probe using a hydrophone installed 50 mm underwater, and found that the width of the ultrasonic beam was 8.5 cm (- 10 (IB).

However, no ultrasonic beam oscillation was observed from the elements adjacent to the piezoelectric element being driven.

Example 2 S + 0 was formed by applying an organic silane compound to the piezoelectric element used in Example 1 on a copper plate with a thickness of 100μ and firing it.
An intermediate layer with a 20μ thick dioxide coating on all tracks, and a thickness of 1 which has been treated with corona treatment on both sides to improve adhesion.
Two types of ultrasonic probes were similarly obtained using an intermediate layer in which a 2μ 47 fluoride ethylene film was attached to a 100μ thick copper plate.

When these two types were evaluated using the same foot measurement method used in Example 1, the sensitivity was 43 dB and 42 dB, respectively.
No scattering or bending of the ultrasound beam was observed.

It was confirmed that the intermediate layer used in the water-saving example exhibited the effect of a λ/4 plate. Further, even when a direct current filling pressure of 700 V was applied to one element of these two types of ultrasonic probes for 30 seconds, no electrical leakage to the adjacent element was observed.

In the present invention, at least one electrode of a piezoelectric element having thin film electrodes on both sides is divided into a plurality of strip-shaped electrodes, or
Alternatively, although the so-called linear array type ultrasonic probe in which the piezoelectric element is divided into a plurality of strip-shaped elements having electrodes on both sides has been mainly described, the present invention also includes a so-called linear array type ultrasonic probe having thin film electrodes on both sides. Also regarding a so-called annular array type ultrasonic probe in which at least one electrode of a piezoelectric element is divided into a plurality of circular electrodes, or the piezoelectric element is divided into a plurality of circular elements having electrodes on both sides. It goes without saying that it can be applied.

The intermediate layer according to the present invention can be processed into a circular shape or an internal shape, and can be applied to a so-called focusing type ultrasonic probe that focuses an ultrasonic beam on a specific position.

Further, in this embodiment, the case where there is only one piezoelectric element has been described, but similar effects can be obtained in a stacked array probe formed by stacking a large number of piezoelectric elements.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a linear array type ultrasound probe using a conventional inorganic piezoelectric material, and Figure 2 is a cross-sectional view of a conventional linear array type ultrasound probe using a polymer piezoelectric material. Figure 3 is a cross-sectional view of a linear array type ultrasonic probe made of polymer piezoelectric material when a λ/4 intermediate layer is used, - Figure 4 is a cross-sectional view of a linear play type ultrasonic probe according to the present invention. It is a sectional view of a feeler. 1.2... Electrode, 3... Piezoelectric body, 4... Knocking material (support body), 5... λ/4 plate.

Claims (4)

[Claims] (1) Is the electrode on at least one side of a piezoelectric element having thin film electrodes on both sides divided into a plurality of strip-shaped electrodes?
Alternatively, in an ultrasonic probe in which the piezoelectric element is divided into a plurality of strip-shaped elements having electrodes on both sides, the opposite side of the acoustic operation surface of the piezoelectric element (1!I is the characteristic sound W of the piezoelectric element An ultrasonic probe comprising a continuous insulating intermediate layer having a thickness higher than an impedance and having a thickness of approximately one quarter of the wavelength of the ultrasonic wave of the piezoelectric element used or an odd number multiple thereof. (2) The ultrasonic probe according to item 1 of the scope of patent Bl'f, characterized in that a ceramic substrate is used as the insulating intermediate layer. (3) The ultrasonic probe according to claim 1, characterized in that an insulating metal oxide or a metal substrate provided with an insulating substrate is used as the insulating intermediate layer. (4) The ultrasonic probe according to claim 1, characterized in that the insulating intermediate layer is made of plastic mixed with insulating powder.