JPS60135858A - Ultrasonic probe and manufacture thereof - Google Patents

Abstract

PURPOSE:To enable the transmitting and receiving of ultrasonic pulses at the highest efficiency by integrating a unit element electrode with lambda/4 plate to prevent the ringing of the ultrasonic pulse excited from a piezo-electric body. CONSTITUTION:Metal thin film electrodes 1 and 2 are provided entirely on one side of a high molecular piezo-electric film 3 by evaporation or the like while a resist material 10 is applied on the other side thereof corresponding to the size of clearance in a lambda/4 plate 2' concurrently serving as a strip-shaped electrode by screen printing or the like. Then, an exposing mask 11 is used to expose the material to light. In this case, the mask 11 is allowed to shield ultraviolet rays from the portion for the plate 2' to be set of the piezo-electric body 3, leaving a positive type photoresist on the clearance portion of the plate 2' only. A metal film 2' is set by plating using the metal thin film electrode of the piezo-electric body 3 thus obtained as plating electrode and after that, the material 10 and an access plate 2' and the like are removed. Then, the strip- shaped electrode and lambda/4 plate integrated type piezo-electric body 3 obtained via such a process is fastened on a support with an adhesive.

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, and a method for manufacturing the same.

[Technical background of the invention and its problems]

Ultrasonic diagnosis, ultrasonic flaw detection, and video using ultrasound!
As the ultrasonic wave emitting/receiving element of the device, an inorganic piezoelectric material such as PZT or a polymeric piezoelectric material such as polyvinylidene fluoride or polyvinylidene fluoride copolymer is used. In particular, polymer piezoelectric materials have a small mechanical Q and large mechanical loss, so they have the advantage of being able to emit and receive shorter ultrasonic pulses than inorganic piezoelectric materials. For this purpose, a plurality of unit ultrasonic wave emitting/receiving elements are arranged using a polymeric piezoelectric material. In the so-called linear array type annular array type ultrasonic probe.

It is unnecessary to cut the piezoelectric element, which was necessary with inorganic piezoelectric materials, and the desired function can be achieved by providing a divided electrode on at least one side of the polymer piezoelectric material in one continuous sheet. can.

Furthermore, the polymer piezoelectric material has a characteristic acoustic impedance of PZT.
Because it is smaller than other inorganic piezoelectric materials, its characteristic acoustic impedance is thicker than that of the polymer piezoelectric material (and one quarter of the wavelength of the ultrasonic waves emitted and received by the polymer piezoelectric material or less). It is known that ultrasonic waves can be emitted and received more efficiently by lining the opposite side of the acoustic device with an intermediate substrate that is an odd number times thicker (hereinafter referred to as λ/4 plate). (
JP-A-5353-2539 0) Figure 1 shows a cross-sectional view of a near-array type ultrasonic probe using a polymer piezoelectric material as an example.

A polymer piezoelectric material (3) having a common electrode (1) and a rectangular unit electrode (2) is connected to a λ/4 plate (5) via a contact material (41).
), and then the λ/4 plate (51, is the adhesive (6)
is adhered to the support material (7). The adhesive materials 141 and +61 at this time may be of the same type.

However, in the above ultrasonic probe.

It is important that the adhesive joint of the adhesive material (4) is as thin as possible (and has a uniform thickness; preferably, the strip-shaped unit electrode (2) and the λ/4 plate (5) are integrated. As a result, a good ultrasonic probe can be obtained.

That is, due to the adhesive (4), the ultrasonic waves emitted and received from the polymer piezoelectric material (31) due to excitation voltage pulses are caused to ring and become shorter than the interface between the adhesive (4) and the λ/4 plate (5). It becomes difficult to generate a single ultrasonic pulse; ■ Mechanical Q1 mechanical loss of the adhesive (4) causes attenuation of the ultrasonic pulse from the polymer piezoelectric material (31), reducing efficiency; ■ The input of the excitation voltage pulse decreases due to the electrical constant, dielectric loss, etc. of the adhesive (4).

In addition to a reduction in the ultrasonic output, there are other problems such as the fact that it is extremely difficult to make the thickness of the adhesive (4) uniform.

For this purpose, as a method of integrating the strip-shaped unit electrode (2) and the λ/4 plate (5), the polymer piezoelectric material (3)
λ/4 plate (5) Lamecki method, vapor deposition method, sputtering method,
It is conceivable to install it by a method such as thermocompression bonding, and if necessary, to provide a strip-shaped unit electrode (2) and λ/4 plate (4) by a method such as etching. however.

This method requires a long time to form a λ/4 plate with a desired thickness (evaporation method, sputtering method), causes a decrease in the properties of the polymer piezoelectric material (thermocompression bonding method), During etching, the shape of the λ/4 plate changes due to the side etching phenomenon, resulting in problems such as deterioration of ultrasonic pulse characteristics (occurrence of ringing). □ [Object of the invention] The present invention eliminates the above-mentioned drawbacks and achieves high performance.

Ultrasonic probe with excellent SlN ratio The purpose is to provide the following.

[Summary of the Invention] The present invention provides an ultrasonic probe in which a plurality of unit ultrasonic wave emitting/receiving elements are arranged, characterized in that a unit element electrode and a λ/4 plate are integrally configured. This invention relates to a sound wave pulse and its manufacturing method.

The outline of the present invention will be explained using CIs shown in FIGS. 2 and 3 (a) to (CI). FIG. 3) In terms of acoustic operation, kl,
41. A metal thin film electrode (1) made of Ni, Cr, etc. is provided on the entire surface by known means such as vapor deposition or sputtering, and a rectangular electrode and A /4 plate (2) is provided as an integral structure, and a λ/4 plate (21 is a support material (7) that also functions as an electrode) is provided.
) with an adhesive 16). Further, a polymer film for electrical insulation and acoustic matching is fixed to the upper surface of the metal thin film electrode +11 with an adhesive (not shown).

Next, the manufacturing method of the present invention will be explained with reference to FIG. First, a known metal thin film electrode (1) (21) made of Aj, Aj, Ni, Or, etc. is formed on at least one side of the polymer piezoelectric film (3) such as the 3rd V (al) by a known means such as vapor deposition or sputtering. Apply resist material (1) to the entire surface, and then apply resist material (1) to one side. When applying the resist material, apply it by screen printing or the like in a manner that corresponds to the gap size between the rectangular flat electrodes and the λ/4 plate. I'll do it like that.

Alternatively, a photoresist may be applied or a photoresist polymer film may be laminated or the like. In this case, the thickness of the resist film should be approximately one-fourth of the wavelength of the excitation ultrasonic wave of the polymer piezoelectric material, or an odd number multiple thereof. In the case of a photoresist polymer film, the desired thickness can be achieved by repeating the process several times to get close to the desired thickness.

When using a photoresist, it can be used regardless of its type, such as negative type or positive type, by selecting an exposure mask.

Diagram 3 of the nest (bl is a strip-shaped electrode of a polymer piezoelectric material and λ/4λ
A process diagram is shown in which a positive photoresist polymer film (10) is laminated on a /4 plate, and the positive photoresist polymer film (10) is exposed to light using an exposure mask (11), for example, irradiated with ultraviolet rays (exposure). In this case, the part where the strip-like electrode and λ/4 plate (2) is installed on the polymer piezoelectric material is blocked from ultraviolet rays by the exposure V-splash (11). After the phenomenon treatment, the positive photoresist polymer film (11) in this area is removed, and the positive photoresist remains only in the gap between the strip electrodes and the λ/4 plate.

FIG. 3 1cl uses the above-obtained thin metal electrode of the piezoelectric polymer as a plating electrode, and has Aj+, 12, and Cu.

An example is shown in which a metal film (21) such as Ni is installed by plating.In this case, the selected metal needs to be higher than the specific acoustic impedance of the polymer piezoelectric material. The specific acoustic impedance of polyvinylidene fluoride is approximately 4 Xi O@ky/m”・
sec, and the specific acoustic impedance of metals that can be plated is several 10XIO'y/m'sec, and most metals can be cited.

Regarding this plating, different metals may be provided in layers as necessary.

After the plating process is completed, the positive photoresist polymer is removed with an appropriate solvent, and the excess strip-shaped electrode/λ/4 plate (
bulges at the electrode ends that tend to occur especially during plating),
Unnecessary parts of the metal thin film electrode used in the plating operation are removed by etching or the like.

The ultrasonic probe shown in FIG. 2 is obtained by fixing the polymeric piezoelectric material integrated with a strip-shaped electrode and λ/4 plate through the above steps to a support material using an adhesive.

The plating of the rectangular flat electrode and λ/4 plate in the present invention is not particularly limited, and usual known conditions can be applied. However, in order to maintain the piezoelectric properties of the polymer piezoelectric material, it is desirable to set the temperature as close to room temperature as possible. Further, in the present invention, an example has been described in which a metal thin film is previously provided on the plating electrode of a rectangular flattened plate and a λ/4 plate by vapor deposition or the like; however, for example, the necessary electrode portion may be provided by electroless plating or the like.

〔Effect of the invention〕

According to the present invention, an ultrasonic probe having the following effects can be obtained.

In other words, the ultrasonic probe obtained by the present invention has an integrated structure of an electrode and a λ/4 plate, so that it can generate ultrasonic pulses excited from a piezoelectric material, as seen in conventional ultrasonic probes. Also, depending on the plating conditions, the thickness of the λ/4 plate should be precisely one-fourth of the wavelength emitted or received from the piezoelectric material, or an odd number multiple thereof (this will reduce the thickness due to management, so the highest efficiency can be achieved). It becomes possible to emit and receive ultrasonic pulses.

Furthermore, in the present invention, since the electrode and λ/4 plate are integrated, the conventional alignment due to the electrical and mechanical properties of the adhesive can be eliminated, making it possible to fully utilize the inherent properties of the piezoelectric material. In addition, the electrode-cum-λ/4 plate in the present invention (for example, when used in a linear array type ultrasonic probe with a strip-shaped electrode) has a configuration as shown in Fig. 2, and has an appropriate electrode shape. Since n is obtained, and the gap between adjacent electrode/λ/4 plates can be maintained in good alignment, electrical crosstalk to adjacent electrode/λ/4 plates can be prevented.

Since the electrode/λ/4 plate according to the present invention is integrally constructed using a plating method, 1, for example, a polymer piezoelectric material is processed into a cylindrical or circular shell shape, and a so-called focused ultrasonic probe that focuses an ultrasonic beam on a specific position is used. It can also be applied to the case of tentacles. In this case, the electric material/V4 plate has good precision (in addition to being able to obtain a predetermined curvature, bending processing of the viewing pole/λ/4 plate is not required, so bending distortion is completely removed, and the ultrasonic beam has high precision). can be focused.

[Embodiments of the invention]

Silver was deposited to a thickness of about 1 μm on both sides of a uniaxially stretched polyvinylidene fluoride film having a thickness of 65 μm by vacuum deposition, and the film was further polarized to obtain a polymer piezoelectric material. A photopolymer film resist (trade name: Liston ■) is placed on one side of this polymeric piezoelectric material.

N13420. (manufactured by Depon) at 70℃ 160 kg/
cm ” laminated under conditions of summer and applied photopolymer film resist. Next, a length of 1.3 m was preliminarily
A strip-shaped WL pole (64 poles) consisting of a width of 0.9 mm and an adjacent element gap Q of 1 mm was brought into close contact with a patterned metal-glass exposure mask, exposed to light using an ultra-high pressure mercury lamp, and developed with Liston ■ developer. Then, the photopolymer resist was removed from the area where the electrode/λ/4 plate was to be installed.

Next, the silver electrode film of the polymer piezoelectric material that had been installed in advance was used as an electrode.
A λ/4 plate was formed by plating in a sulfuric acid steel plating bath. In this case, the thickness of the λ/4 plate is.

The wavelength was set to be equivalent to 1/4 of the wavelength excited by polyvinylidene fluoride.

After copper plating treatment 1. Liston installed in a polymer piezoelectric material■
The film was peeled off, and the film thickness of the λ/4 plate was adjusted for λ/4 excitation, and the silver electrodes in the electrode gap were removed by selective etching to produce an ultrasonic probe element.

Connect the lead wire from a part of the electrode and λ/4 plate part of the element, and then apply epoxy adhesive (trade name Kobotech 301-
2. (manufactured by Evotech) and fixed it to a ferrite rubber support material to form a linear array type ultrasonic probe.

On the other hand, for comparison, a rectangular rectangular electrode pattern with one side having the same shape as the above example, and a λ/4 equivalent copper plate (thickness 150μ , copper λ/ cut with a dicer
4 plates) with epoxy adhesive (product name Kobotech 301-
2. (manufactured by Ebotek Co., Ltd.) and further fixed to a ferrite rubber support material to obtain a 1J near array type ultrasonic probe for comparison.

The entire thin film electrode part on the acoustically active side of the two prototype linear array type ultrasonic probes was used as the ground electrode, and eight strip-shaped electrode elements were simultaneously connected via lead wires to the rectangular lay-down part. Driven by Aerotic UTA
-3 (input/output impedance 50Ω) connected to 150V
A strike pulse was applied. At this time, the ultrasonic reflected wave from the linear array type ultrasonic probe (reflected wave from the surface of the methacrylic resin block placed at a depth of 70 mm underwater) exhibited 45 dB in the example of the present invention.

On the other hand, in the case of the S-A array type ultrasonic probe of the comparative example, the intensity of one reflected wave was 38 dB, which showed a decrease in sensitivity of 7 dB compared to the example of the present invention. Furthermore, as shown in Figure 2, 1
In the linear array type ultrasonic probe according to the present invention, the polymeric piezoelectric material and the λ/4 plate are in direct contact with each other by plating to form an integral structure.

It was confirmed that there was very little ringing from the interface between the polymer piezoelectric material and the λ/4 plate, and that a good reflected wave waveform was exhibited.

As described in the above embodiments, one aspect of the present invention is to generate a plurality of unit ultrasonic waves.
In an ultrasonic probe in which receiving elements are arranged, by integrally configuring the unit element electrode and the λ/4 plate, ringing of the ultrasonic pulse excited from the polymer piezoelectric material is prevented and a good waveform, that is, resolution is achieved. can provide excellent ultrasonic probes.

Furthermore, the ultrasonic probe of the present invention makes it possible to eliminate alignment (loss) due to the electrical and mechanical properties of the adhesive, making it possible to provide a highly sensitive ultrasonic probe.

The present invention is based on a piezoelectric element having thin film electrodes on one surface.
Mainly concerning so-called linear Φ array type ultrasonic probes in which one electrode is divided into a plurality of rectangular flat electrodes, or the piezoelectric element is divided into a plurality of rectangular elements having electrodes on both sides. However, the present invention can also be applied to a piezoelectric element having thin film electrodes on both sides (one electrode is divided into a plurality of circular electrodes, or the piezoelectric element is a plurality of circular elements having electrodes on both sides). It goes without saying that '' can also be applied to the so-called Aniera array type ultrasonic probe, which is divided into two types.

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

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a conventional linear array type ultrasonic probe using a piezoelectric polymer, and Fig. 2 is a cross-sectional view of an IJ near array ultrasonic probe using a piezopolymer, which shows one example of the present invention. A cross-sectional view of a type ultrasonic probe, Fig. 3 (al to Fig. 3 (C1 is a diagram of the manufacturing process of an IJ near array type ultrasonic probe using a polymer piezoelectric material according to the present invention, Fig. 4) 1al and tbl show characteristic diagrams of linear array type ultrasound probes according to the present invention and a conventional example, respectively. 1... Electrode, 2... Electrode, 2'... Electrode and λ/4
Plate, 3... Polymer piezoelectric material, 4.6... Adhesive material, 5.
...λ/4 plate. 7... Supporting material, 10... Resist material, 11... Mask. Representative Patent Attorney Nori Chika @ (and 1 other person) Figure 2 Figure 3 (Power Figure 3 (Mun Figure 4 (0L)

Claims (1)

[Scope of Claim] An ultrasonic probe in which a plurality of unit ultrasonic wave emitting/receiving elements made of an ill polymer piezoelectric material are arranged, in which a unit element electronic electrode and a λ/4 plate are integrated. An ultrasonic probe featuring: (2) a step of applying a resist corresponding to the strip-shaped or ring-to-flat electrode gap on the non-acoustic operation surface of the polymer piezoelectric material;
Alternatively, it is characterized by comprising the steps of: installing a photoresist in a portion corresponding to the gap between the strip-shaped or ring-shaped electrodes; plating the portion corresponding to the strip-shaped or ring-shaped electrode; and removing the resist. A method for manufacturing an ultrasonic probe.