JPH0870496A - Ultrasonic transducer and its manufacture - Google Patents

Abstract

PURPOSE: To realize the structure of an ultrasonic wave transducer suitable for miniaturization and its manufacture. CONSTITUTION: In the ultrasonic transducer 11 whose basic components are a piezoelectric element 1, a sound matching layer 12 formed on the surface of one side of the piezoelectric element 1, a back damping member 13 formed on the surface of the other side of the piezoelectric element 1, and a package board 9 provided with, at least, two electrode terminals 22, 23 and one wiring pattern two electrode terminals 22, 23 on the package board of the ultrasonic transducer 11 are insulated from each other, and simultaneously, one side is of the same potential as the wiring pattern, and the first electrode terminal 22 on the package board and a surface electrode 3 formed on the surface of one side of the piezoelectric element 1 are connected electrically to each other, and the second electrode terminal 23 on the package board and the surface electrode 4 formed on the surface of the other side of the piezoelectric element 1 are connected electrically to each other through the wiring pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic transducer used in a medical or nondestructive ultrasonic diagnostic apparatus and a method for manufacturing the same.

[0002]

2. Description of the Related Art As a conventional technique, there is JP-A-4-126136 filed by the present applicant. In the same application, a preformed ultrasonic transducer is mounted on a preformed housing in the same manner, and then a piezoelectric element surface electrode of the ultrasonic transducer and an electrode terminal or lead wire on the housing are made of a conductive resin or By connecting with solder,
Wiring to the ultrasonic transducer is done.

In the current situation, there is an increasing demand for realizing a medical ultrasonic endoscope capable of diagnosing the pancreatic duct / circulatory organ and an industrial ultrasonic diagnostic apparatus for performing nondestructive inspection of a thin tube. In this case, since the outer diameter of the probe inserted into the internal organs or the narrow tube becomes very small, about 1 to several mm,
At the same time, it is necessary to reduce the size of the ultrasonic transducer mounted on it. Further, for the circulation system, the probe needs to be disposable from the viewpoint of infection prevention. Due to these circumstances, it is necessary to manufacture a microminiature ultrasonic transducer at low cost.

[0004]

However, in the above-described structure and manufacturing method, when a small ultrasonic transducer of about 1 mm or less is mounted, each member is extremely small, so that a micro assembly technique is required. At the same time, positioning of each component becomes extremely difficult. As a result, problems such as an increase in manufacturing cost, a relative decrease in assembly accuracy, and a decrease in product quality typified by an increase in performance distribution width are caused.

Similarly, it is only possible to mount the transducers one by one, and it is not possible to meet the demand for cost reduction, which is compatible with the disposable structure.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a structure of an ultrasonic transducer suitable for miniaturization and a manufacturing method thereof.

[0007]

In order to achieve the above object, the ultrasonic transducer of the present invention according to claim 1 is
A piezoelectric element, an acoustic matching layer formed on one surface of the piezoelectric element, a back damping material formed on the other surface of the piezoelectric element,
In an ultrasonic transducer having a mounting substrate having at least two electrode terminals and one wiring pattern as a basic constituent element, the two electrode terminals of the ultrasonic transducer on the mounting substrate are insulated from each other at the same time. Has the same potential as the wiring pattern, the first electrode terminal on the mounting substrate and the surface electrode formed on one surface of the piezoelectric element are electrically connected, and the second electrode on the mounting substrate is connected. It is characterized in that the electrode terminal and the surface electrode formed on the other surface of the piezoelectric element are electrically connected via a wiring pattern.

An ultrasonic transducer according to a second aspect of the present invention is characterized in that, in the first aspect, the mounting substrate is the same as the housing in which the transducer is to be mounted.

Further, the ultrasonic transducer of the present invention according to claim 3 is the ultrasonic transducer according to claim 1 and claim 2,
At least a part of the drive electric circuit of the transducer is mounted on the mounting board.

In the ultrasonic transducer manufacturing method of the present invention according to claim 4, the piezoelectric element, the acoustic matching layer formed on one surface of the piezoelectric element, and the back surface formed on the other surface of the piezoelectric element. In a method of manufacturing an ultrasonic transducer, which comprises a damping material and a mounting board having at least two electrode terminals and one wiring pattern as basic components,
The ultrasonic transducer is integrated with the laminated body of the acoustic matching layer, the piezoelectric element, and the back damping material on the mounting board, and then the first electrode terminal on the mounting board and the surface electrode formed on one surface of the piezoelectric element. And a wiring pattern on the mounting substrate and a surface electrode formed on the other surface of the piezoelectric element are electrically connected to each other by a conductive thin film, thereby wiring the piezoelectric element. To do.

Further, an ultrasonic transducer manufacturing method according to a fifth aspect of the present invention is characterized in that, in the fourth aspect, the conductor thin film is made of Ti, Cr, W alone or contains them.

[0012]

The operation of the ultrasonic transducer and the method of manufacturing the same of the present invention having the above-described structure is as follows.

According to the first aspect of the present invention, the piezoelectric element surface electrode constituting the ultrasonic transducer is electrically connected to the electric terminal by the conductor thin film via the wiring pattern formed on the mounting substrate, and through both electric terminals, The ultrasonic transducer can be driven.

In the second aspect, the ultrasonic transducer is formed integrally with the housing.

In the third aspect, a part of the drive circuit for the ultrasonic transducer is formed integrally with the transducer.

In the fourth aspect, the ultrasonic transducer having the above structure is manufactured.

In the fifth aspect, the strength of the conductor thin film is increased.

[0018]

Embodiments of an ultrasonic transducer and a method of manufacturing the same according to the present invention will be described below with reference to the accompanying drawings.

(Embodiment 1) This embodiment will be described with reference to FIGS.

(Structure) The piezoelectric element 1 is a rectangular plate-shaped PZ.
It is constituted by forming a radiation surface side surface electrode 3 and a back surface side surface electrode 4 on both surfaces of the T piezoelectric ceramic 2 by Ag baking, and is polarized. An acoustic matching layer 12 is formed on one surface (radiation surface) of the PZT piezoelectric ceramics 2, and a back braking material 13 is formed on the other surface (back surface) thereof.

The acoustic matching layer 12 is made of a hard epoxy resin, and the back damping material 13 is made of an epoxy resin in which tungsten particles are dispersed.

The size of the piezoelectric element 1 is equal to or greater than the length of the ultrasonic transducer after completion, and its width is the same as the width of the ultrasonic transducer after completion, or a width corresponding to a plurality of widths. That is all. At the same time, the sizes of the acoustic matching layer 12 and the backside braking material 13 are determined by the piezoelectric element
Shall match. Here, the width direction of the piezoelectric element 1 will be described as a direction orthogonal to the paper surface.

Apart from these, on the surface of the glass epoxy substrate 9 having a wiring pattern made of copper foil on both sides, a concave portion 27 having a size approximately corresponding to the back braking material 13,
The first electrode terminal 22 is formed on a portion of the surface near the recess 27, and the second electrode terminal 23 is formed on a portion electrically insulated from the first electrode terminal 22 by the insulating portion 7. At the same time, the back conductor 24 is formed on the entire back surface. Back conductor 2
4 and the second electrode terminal 23 are electrically connected by a connection conductor 25.

The width of the substrate 9 is equal to that of the piezoelectric element 1.

(Manufacturing Method) The manufacturing method will be described below.

As shown in FIG. 1, the piezoelectric element 1 in which the back surface side electrode 4 is integrated with the back surface braking material 13 and the radiation surface side surface electrode 3 is integrated with the acoustic matching layer 12 is formed in the concave portion of the substrate 9. It is joined to 27 by an epoxy adhesive (not shown).

After joining both members, as shown in FIG. 2, among the exposed portions of the piezoelectric element back surface electrode 4, the first electrode terminal 2 is formed.
Insulation material 1 made of epoxy resin
Seal with 9.

After the sealing step is completed, a thin film of Ti having a thickness of about 1 μm is formed on the conductor thin film forming portions 10a and 10b shown in FIG. 3 by the sputtering method. At this time, portions other than the conductor thin film forming portions 10a and 10b are masked (not shown) so that the Ti thin film is not formed. At this time, the temperature of the piezoelectric element or the like is set to 120 ° C. or lower by adjusting the film forming condition so that the piezoelectric element does not depole.

After the film formation, when the width of the piezoelectric element 1 was made wider than the width of a plurality of ultrasonic transducers, it was cut by a precision cutting grindstone or the like in a plane parallel to the paper surface, as shown in FIG. An ultrasonic transducer having such a structure is manufactured.

(Function) Backside surface electrode 4 of the piezoelectric element 1
Is electrically connected to the second electrode terminal 23 via the back surface conductor 24 and the connection conductor 25 by the Ti thin film. At the same time, the emission surface side surface electrode 3 is made of a Ti thin film, and the first electrode terminal 2 is formed.
2 is electrically connected. Ultrasonic transducer 11
Transmits and receives signals by connecting a pulsar / observer (both not shown) to both terminals 22 and 23.

(Effect) It is suitable for downsizing and mass production, and since it is not necessary to directly connect the lead wire to the surface electrode of the piezoelectric element, the mechanical load of the lead wire and the heat applied to the piezoelectric element at the time of joining the lead wire. Since no stress or the like is applied to the piezoelectric element, the piezoelectric element is not stressed, and an ultrasonic transducer having high performance and high reliability can be configured.

By forming the conductor thin film using Ti, a conductor thin film having excellent adhesion and strength can be obtained. Thereby, the reliability of the wiring can be improved, and the reliability and the yield of the entire product including the transducer can be improved.

By using a large piezoelectric element,
When the process of cutting after film formation is adopted, since it is the process of cutting after assembling each component member, the handling of the members becomes easier, and the assembly accuracy can be improved, and the compact and high performance Sound wave transducers can be manufactured more easily.

Since the wiring of the lead wire is performed on the terminal provided on the substrate, by optimizing the material of the terminal,
The bonding strength of the lead wire can be increased. For example, when soldering a copper lead wire, a terminal based on copper and supplied with solder by plating is suitable, and when wiring an aluminum wire by the wire bonding method, copper is used as a base and a soft wire is used. Gold plated terminals are suitable. With these, it is possible to improve the reliability of the entire system including the wiring.

In this embodiment, PZ is used as the piezoelectric element.
Although the case of using T-based piezoelectric ceramics is shown, other perovskite-type piezoelectric ceramics such as PT-based, PLZT-based, and lead niobate-based, polymer piezoelectric materials typified by PVDF, and piezoelectric ceramics-resin composite materials can be used. It is also possible to use a typical composite piezoelectric material, a crystalline piezoelectric material typified by LiNbO ₃ .ZnO, and lead niobate. When a polymer and a composite piezoelectric material are used, since the acoustic impedance thereof is close to that of water and the human body, it is possible to reduce the transmission loss and to omit the acoustic matching layer, especially when used for medical purposes. is there. Further, in the case of a crystalline piezoelectric material, there is no deterioration in piezoelectric characteristics due to temperature, so that an ultrasonic transducer excellent in environmental resistance (under high temperature) can be obtained particularly when applied to industrial applications.

Similarly, for the surface electrode, in addition to Ag shown in this embodiment, Au, Cu, Ni, Cr,
Metals such as Ti / Mo / W / Ta / Zr / Al and their alloys, metal oxides such as indium oxide / ITO, borides such as TiB ₂ / ZrB ₂ , WC / SiC
A carbide such as MoSi ₂ or a silicide such as WSi ₂ can be used, and as a forming method, in addition to the baking method, sputtering, vacuum deposition, electroless plating, ion plating, CVD, or the like can be used. . It is also possible to form the above materials as a multilayer thin film having two or more layers. For example, by forming the Ag thin film after forming the Cr thin film, it is possible to secure both the adhesion of the film and good electrical conductivity.

Also, the shape of the piezoelectric element is not fixed to a rectangular flat plate. For example, a circular flat plate as shown in FIG. 5, a conical or spherical shell cut out in a circular shape as shown in FIGS. 6 and 7, or a combination thereof, FIGS. A curved surface plate represented by various cylindrical concave plates such as the cylindrical curved surface type piezoelectric element 15, the curved surface-flat surface type piezoelectric element 16 and the biconcave curved surface type piezoelectric element 17 as shown in 10 can be used.
Also, at this time, the acoustic matching layer and the backside damping material have the same planar shape as that of the piezoelectric element or the shape of the joint with the piezoelectric element, or are formed integrally with the piezoelectric element by a casting method as described later. There is a need.

Further, in this embodiment, both electrodes of the piezoelectric element are electrically insulated by masking them with an insulating material or the like after integrating the respective members, but it is possible to partially insulate them as shown in FIG. Masking can be partially omitted by using the piezoelectric element whose electrodes are removed 20, 21 by patterning, etching, grinding or the like.

In this embodiment, the polarized piezoelectric element was used prior to the process. However, by setting the temperature at the time of forming the conductive thin film to a high temperature such as 150 ° C. or higher, the adhesion strength of the film is improved. It is also possible to increase the temperature and take a step of repolarizing the piezoelectric element depolarized by this temperature rise after the film formation.

Further, instead of a flat plate-like acoustic matching layer, an acoustic lens having a curved surface or having a sound velocity distribution therein is possible, a plurality of acoustic matching layers are used instead of a single layer, and A combination of these is also possible.

Similarly, in this embodiment, the conductor thin film is
Although the method of forming Ti by sputtering has been described,
Similar to the material of the piezoelectric element surface electrode described above, the material is not limited to this. The material of the conductor thin film is Ag · A
u ・ Cu ・ Ni ・ Cr ・ Ti ・ Zr ・ Ta ・ Mo ・ W ・
Metals such as Al and their alloys, indium oxide / I
Metal oxides such as TO, borides such as TiB ₂ · ZrB ₂ , carbides such as WC · SiC · MoSi ₂ · WSi
A silicide such as ₂ can be used. As a forming method, vacuum vapor deposition, ion plating, CVD, and thin film formation by a metal polymer are also possible, and it is also possible to form a multi-layer conductor film by combining these. It is also possible to mechanically and electrically strengthen the surface of the conductor thin film by covering the surface of the conductor thin film with a conductive resin after the formation of the conductor thin film.

As the matrix material of the acoustic matching layer and the backside damping material, epoxy-based, polyimide-based, phenol-based or silicone-based resins can be similarly used. Further, particularly for the back braking material, in addition to the above, a rubber-like material represented by silicone rubber / neoprene rubber can be used as the matrix. As the filler, ceramics such as alumina, tungsten oxide, tungsten nitride and piezoelectric ceramics, metals and metal compounds such as tungsten, silver and ferrite,
Ba-ferrite / samarium cobalt (SmCo ₅ ,
Magnetic particles such as Sm ₂ Co ₁₇ ) or inorganic particles coated with a magnetic material can be used.

Although the method of integrating the backside damping material and the acoustic matching layer is not particularly shown in this embodiment,
In addition to the bonding method, it is possible to directly cast and cure the liquid backside damping material and the acoustic matching layer on the piezoelectric element to integrate them. This method is particularly effective when a piezoelectric element other than the flat plate described above is used.

As for the material of the substrate, in addition to the glass epoxy substrate described in this embodiment, an alumina substrate, a flexible printed circuit board, a phenol substrate, etc., which are generally used as electric component mounting boards, can be used. Further, in the present embodiment, the case where the lead wire is joined only on the front surface of the substrate has been described. The connecting conductors on the front and back surfaces can be omitted. Further, in the present embodiment, it is assumed that the connecting conductor is formed by a method such as through-holes in advance, but the conductor thin film may be formed at the same time when the conductor thin film is formed.

In addition to the precision cutting grindstone, laser cutting such as pulse oscillation or continuous wave oscillation YAG laser / CO ₂ laser and wire cutting can be used for the cutting.

Further, the width of the piezoelectric element is set to be equal to or more than the width of the transducers, and in the cutting step, the piezoelectric element is completely separated, but the substrate is cut to such an extent that the substrate is integrated. It is also applicable to the manufacturing of.

(Embodiment 2) This embodiment will be described with reference to FIG. In the description of the drawings, the same elements as those in the above-described embodiment will be designated by the same reference numerals, and overlapping description will be omitted.

(Structure) In this embodiment, as shown in FIG. 12, unlike the first embodiment, the radiation surface side surface electrode 3 is electrically connected to the second electrode terminal 23 via the back surface conductor 24 and the connection conductor 25. Connected. At the same time, the back surface electrode 4
Are electrically connected to the first electrode terminal 22 by the Ti thin film.

Therefore, in this embodiment, the exposed portion of the back surface electrode 4 on the end face side is covered with the insulating material 19 and the outside of the insulating material 19 is used as the conductor thin film forming portion 10b.

(Function) The periphery of the transducer has the same potential as the surface electrode 3 of the piezoelectric element radiating surface side.

(Effect) In order to secure the safety of the non-measurement target, the entire transducer is wrapped with a conductor having the same potential as the surface electrode of the radiation surface of the piezoelectric element, which is generally grounded, so that the resistance to electromagnetic noise is increased. As a result, S / N
Since the ratio is improved, high performance can be achieved, and the sensitivity is low, which is suitable for miniaturization requiring improvement of the S / N ratio.

(Embodiment 3) This embodiment will be described with reference to FIG. In the description of the drawings, the same elements as those in the above-described embodiment will be designated by the same reference numerals, and overlapping description will be omitted.

(Structure) In this embodiment, the substrate 9 is formed by bonding the back braking material 13 with a conductor made of copper foil.
Here, the back braking material 13 is an epoxy resin in which zirconia particles are dispersed in order to ensure the insulation of each electrode. In this case, unlike the first embodiment, no recess is formed in the substrate 9.

(Operation) The substrate functions as a back braking material.

(Effect) Since the entire thickness of the substrate serves as the backside braking material, the braking is effectively performed and the transmission / reception pulse is shortened. Thereby, the resolution in the depth direction can be improved.

(Embodiment 4) This embodiment will be described with reference to FIG. In the description of the drawings, the same elements as those in the above-described embodiment will be designated by the same reference numerals, and overlapping description will be omitted.

(Structure) In this embodiment, the substrate 18 is
It was formed by a conductor typified by a metal such as SUS and a small-sized board 14 made of a single-sided electrical mounting board in which one surface of an insulator was made into a conductor.

(Operation) While the substrate itself functions as one terminal, the small substrate on the substrate functions as the other terminal.

(Effect) A material such as metal having excellent workability and mechanical strength can be used as the substrate. Therefore, the housing that houses the transducer can be used as a substrate, the structure can be simplified, and the positional accuracy between the transducer and the housing can be improved.
A highly accurate transducer can be easily obtained.

(Embodiment 5) This embodiment will be described with reference to FIG. In the description of the drawings, the same elements as those in the above-described embodiment will be designated by the same reference numerals, and overlapping description will be omitted.

(Structure) In this embodiment, on the substrate 9,
The matching coil 26 is mounted.

(Operation) A part of the driving circuit is integrated on the transducer.

(Effect) Since the sensitivity of the transducer can be improved and the pulse width can be shortened, a high performance transducer can be obtained.

In the present embodiment, only the matching coil, which is the easiest to illustrate, is shown, but the mounting of electric circuit parts such as amplifiers and ICs, pickup devices for encoders, semiconductor lasers for medical treatments, etc. You can do the same. When mounting these, it is necessary to provide a wiring pattern, a power supply line, and the like for that purpose on the substrate.

[0065]

As described above, according to the ultrasonic transducer and the method of manufacturing the same of the present invention, it is possible to provide an ultrasonic transducer suitable for miniaturization.
That is,

In the invention described in claim 1, it is possible to provide an ultrasonic transducer having a structure suitable for miniaturization.

According to the invention described in claim 2, it is possible to provide an ultrasonic transducer which can be mounted in a housing with high accuracy.

According to the invention described in claim 3, it is possible to provide a high-performance ultrasonic transducer in which a part of the drive circuit is integrated.

According to the invention described in claim 4, it is possible to produce the ultrasonic transducer having the above structure.

In the invention described in claim 5, it is possible to produce a highly reliable ultrasonic transducer.

[Brief description of drawings]

FIG. 1 is a first sectional view showing a method of manufacturing an ultrasonic transducer according to a first embodiment of the present invention in the order of steps.

FIG. 2 is a second cross-sectional view showing the method of manufacturing the ultrasonic transducer according to the first embodiment of the present invention in the order of steps.

FIG. 3 is a third cross-sectional view showing the method of manufacturing the ultrasonic transducer according to the first embodiment of the present invention in the order of steps.

FIG. 4 is a fourth cross-sectional view showing the method of manufacturing the ultrasonic transducer according to the first embodiment of the present invention in the order of steps.

FIG. 5 is a perspective view showing another example of a piezoelectric element that can be used in the ultrasonic transducer of the first embodiment.

FIG. 6 is a perspective view showing still another example of a piezoelectric element that can be used in the ultrasonic transducer of the first embodiment.

FIG. 7 is a perspective view showing still another example of a piezoelectric element that can be used in the ultrasonic transducer of the first embodiment.

FIG. 8 is a perspective view showing still another example of a piezoelectric element that can be used in the ultrasonic transducer of the first embodiment.

FIG. 9 is a perspective view showing still another example of a piezoelectric element that can be used in the ultrasonic transducer of the first embodiment.

FIG. 10 is a perspective view showing still another example of a piezoelectric element that can be used in the ultrasonic transducer of the first embodiment.

FIG. 11 is a perspective view showing a modified example of the ultrasonic transducer of the first embodiment.

FIG. 12 is a sectional view showing an ultrasonic transducer according to a second embodiment of the present invention.

FIG. 13 is a sectional view showing an ultrasonic transducer according to a third embodiment of the present invention.

FIG. 14 is a sectional view showing an ultrasonic transducer according to a fourth embodiment of the present invention.

FIG. 15 is a sectional view showing an ultrasonic transducer according to a fifth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric element 2 Piezoelectric ceramics 3 Radiation surface side surface electrode 4 Back surface side electrode 5 Radiation surface side conductor layer 6 Back surface conductor layer 7 Insulating part 9 Glass epoxy substrate 10a Conductor thin film forming part 10b Conductor thin film forming part 11 Ultrasonic transducer 12 Acoustic Matching Layer 13 Back Damping Material 14 Small Substrate 15 Cylindrical Curved Piezoelectric Element 16 Curved-Plane Piezoelectric Element 17 Biconcave Curved Piezoelectric Element 18 Substrate 19 Insulating Material 20 Radiation Side Surface Electrode Unformed Part 21 Back Side Surface Electrode Unformed portion 22 First electrode terminal 23 Second electrode terminal 24 Back surface conductor 25 Connection conductor 26 Matching coil 27 Recess

Claims (5)

[Claims] 1. A piezoelectric element, an acoustic matching layer formed on one surface of the piezoelectric element, a back braking material formed on the other surface of the piezoelectric element, at least two electrode terminals, and one wiring pattern. In a ultrasonic transducer having a mounting substrate having a and a basic component, the two electrode terminals of the ultrasonic transducer on the mounting substrate are insulated from each other, and at the same time, one has the same potential as the wiring pattern, The first electrode terminal on the mounting board and the surface electrode formed on one surface of the piezoelectric element are electrically connected to each other, and the second electrode terminal on the mounting board and the other surface of the piezoelectric element are formed. An ultrasonic transducer, wherein the ultrasonic transducer is configured by being electrically connected to the formed surface electrode via a wiring pattern. 2. The ultrasonic transducer according to claim 1, wherein the mounting substrate is the same as the housing on which the transducer is to be mounted. 3. The ultrasonic transducer according to claim 1, wherein at least a part of a drive electric circuit of the transducer is mounted on the mounting board. 4. A piezoelectric element, an acoustic matching layer formed on one surface of the piezoelectric element, a back braking material formed on the other surface of the piezoelectric element, at least two electrode terminals, and one wiring pattern. In a method of manufacturing an ultrasonic transducer having a mounting substrate having a base component, the ultrasonic transducer is integrated with a laminated body of an acoustic matching layer, a piezoelectric element, and a rear damping material on the mounting substrate, and then the mounting substrate The upper first electrode terminal and the surface electrode formed on one surface of the piezoelectric element, and the wiring pattern on the mounting substrate and the surface electrode formed on the other surface of the piezoelectric element are electrically connected by a conductive thin film. A method for manufacturing an ultrasonic transducer, characterized in that the ultrasonic transducer is manufactured by connecting to the piezoelectric element and wiring to the piezoelectric element. 5. The conductor thin film according to claim 4, wherein the conductor thin film is made of Ti or C.
A method of manufacturing an ultrasonic transducer, characterized in that r or W is used alone or is included.