JP2009285257A - Ultrasonic transducer and ultrasonic probe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic transducer which is simply constructed to prevent its electrode from corrosion without reducing sonic power of an ultrasonic wave. <P>SOLUTION: The ultrasonic transducer 30 includes a piezoelectric device 40 in which a piezoelectric body 43 is sandwiched between an upper electrode 44 and a lower electrode 45, wherein the upper electrode 44 has the upper surface the end of which is covered with a wire protection layer 47, and also has all the other surfaces covered with a sonic adjustment layer 41; and a corrosion-proofing layer 49 is disposed just beneath the boundary between the sonic adjustment layer 41 and the wire protection layer 47 to prevent an electric material-corrosive factor from penetrating. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ultrasonic transducer for obtaining an ultrasonic image and an ultrasonic probe using the ultrasonic transducer.

  In recent years, ultrasonic inspection has been performed in the medical field. In the ultrasonic inspection, an ultrasonic probe, for example, an ultrasonic probe is inserted into the body of the subject, and the observation site is scanned with ultrasonic waves. This ultrasonic probe has a plurality of ultrasonic transducers arranged at the tip of a long insertion portion to be inserted into the body. Each ultrasonic transducer emits an ultrasonic wave to a site to be observed in the body and receives an echo signal while being driven by an electronic switch. The received echo signal is transmitted to an external ultrasonic observation device via a lead wire extracted from each ultrasonic transducer, and after various signal processing is performed, it is displayed as an ultrasonic image on a monitor or the like.

  The ultrasonic transducer is configured by laminating a piezoelectric element and an acoustic matching layer on the upper surface of a backing material. The piezoelectric element is obtained by sandwiching the upper and lower sides of a piezoelectric body with a pair of electrodes, and is connected to an ultrasonic observation apparatus via a lead wire bonded to a surface end portion of each electrode. When a pulse voltage is applied from this ultrasonic observation apparatus, the piezoelectric body is rapidly deformed by the inverse piezoelectric effect, and ultrasonic waves are generated. The acoustic matching layer is formed so as to cover the upper surface of the piezoelectric element, that is, the surface of the electrode on the upper side of the piezoelectric body (hereinafter referred to as the upper electrode), and improves the propagation efficiency of ultrasonic waves. Ultrasound generated by the piezoelectric element is radiated to the outside through the acoustic matching layer and reaches the site to be observed in the body. Then, the ultrasonic wave reflected from the observation site is incident again on the ultrasonic transducer and received as an echo signal.

  As is well known, ultrasonic waves and echo signals are significantly attenuated in the air. Therefore, at the time of ultrasonic inspection, an elastic bag-like balloon is attached to the tip of the ultrasonic probe. And after inserting an insertion part in a test subject's body, deaerated water as an ultrasonic transmission medium is inject | poured in this balloon in the circumference | surroundings of a to-be-observed site | part. Thereby, since the balloon is inflated and comes into contact with the site to be observed, the ultrasonic scanning region is filled with deaerated water, and attenuation of the ultrasonic wave and the echo signal is prevented.

  While having such advantages, the balloon is also a factor that corrodes the piezoelectric element. Balloons are generally made of rubber that is vulcanized to provide the desired elasticity and contain a sulfur component that is a corrosive factor for electrical components. Therefore, if deaerated water is poured into the balloon for a long time, the sulfur component of the balloon is gradually dissolved in the deaerated water. The deaerated water containing the sulfur component may enter the ultrasonic transducer and corrode the upper electrode of the piezoelectric element. In particular, when silver, which is weak against corrosion of sulfur components, is used as the upper electrode, the corrosion progresses remarkably and the upper electrode may become non-conductive. The upper surface of the upper electrode is almost entirely covered with the acoustic matching layer, but only the joint portion of the lead wire is covered with the wiring protective layer. It is considered that deaerated water containing a sulfur component reaches the upper electrode from the boundary between the acoustic matching layer and the wiring protective layer.

In order to prevent the corrosion of the electrode due to the sulfur component, the ultrasonic probe described in Patent Document 1 wraps the upper surface of the vibrator (ultrasonic transducer) with a film that does not transmit the sulfur component. According to this configuration, even if the sulfur component penetrates from the tip of the ultrasonic probe, the ultrasonic transducer and the sulfur component are isolated by the film, so that the electrode of the piezoelectric element does not corrode.
Japanese Patent Laid-Open No. 10-5227

  However, in the above configuration, the upper surface of the ultrasonic transducer that is the ultrasonic scanning surface is covered with the film. As a result, there has been a problem that the image quality of the ultrasonic image is deteriorated due to a decrease in the acoustic power of the ultrasonic wave or noise in the received echo signal.

  The present invention has been made in view of the above problems, and an ultrasonic transducer capable of preventing corrosion of electrodes of a piezoelectric element with a simple configuration and without reducing the acoustic power of the ultrasonic wave, and the use thereof An object of the present invention is to provide an ultrasonic probe.

  In order to achieve the above object, the ultrasonic transducer of the present invention is provided at the upper end of the electrode so as to cover the piezoelectric element in which the electrode is arranged on the piezoelectric body and the wiring electrically connected to the electrode. A wiring protective layer, an acoustic matching layer adjacent to the wiring protective layer and covering the upper surface of the electrode, and a corrosion prevention layer covering a portion of the upper surface of the electrode located under the boundary between the acoustic matching layer and the wiring protective layer It is characterized by that.

  It is preferable to form the corrosion prevention layer with a material that does not allow the sulfur component to permeate. Furthermore, the corrosion prevention layer preferably has conductivity. In this case, it is preferable to extend the corrosion prevention layer below the wiring.

  In addition, the corrosion prevention layer is preferably formed of a material having a higher degree of solder fixing than the electrode. The degree of solder fixing is synonymous with so-called solder wettability or solder riding.

  Furthermore, the corrosion prevention layer is preferably a thin film layer. In a preferred embodiment of the present invention, the corrosion prevention layer is formed by gold vapor deposition. In addition, a thin film is a film | membrane formed by vapor deposition, sputtering, etc., and means the thing of thickness about several micrometers.

  The ultrasonic probe of the present invention includes any one of the above-described ultrasonic transducers. This ultrasonic probe is preferably an ultrasonic endoscope in which an image sensor is integrated.

  According to the present invention, the upper surface of the electrode disposed on the piezoelectric body is locally covered by the corrosion prevention layer that does not allow the corrosion factors such as the sulfur component and the water component to permeate. Thereby, the corrosion factor which penetrate | invaded the boundary of an acoustic matching layer and a wiring protective layer does not reach | attain an electrode, and corrosion of an electrode is prevented. In addition, since the corrosion prevention layer does not cover the ultrasonic scanning surface, the ultrasonic acoustic power does not decrease or noise is not generated in the echo signal, and the image quality of the ultrasonic image may deteriorate. Absent. Furthermore, since it has a simple structure in which a thin film layer is formed on a part of the upper surface of the electrode, it can be introduced easily and at low cost. Further, since gold is used as the corrosion prevention layer, the degree of fixing of solder for connecting the wiring is good. Accordingly, it is difficult for the wiring to be peeled off, and deterioration of the image quality of the ultrasonic image due to poor contact of the wiring is prevented.

  In FIG. 1, an ultrasonic endoscope 10 includes an insertion portion 11 to be inserted into the body, an operation portion 12 connected to a proximal end portion of the insertion portion 11, and a cord 13 connected to a lower portion of the operation portion 12. It consists of and. The code 13 is connected to an ultrasonic observation apparatus 14 that generates an ultrasonic tomographic image, and the ultrasonic tomographic image generated here is displayed on the monitor 21. Further, the code 13 branches in the middle, and an endoscope processor device 22 that generates an endoscope image, and a light source that supplies illumination light for illuminating an observed site in the body to the ultrasonic endoscope 10 It is connected to the device 23.

  The insertion portion 11 includes a thin and long flexible portion 15 whose screw tube is covered with an exterior jacket, and a distal end hard portion 16 located at the distal end of the flexible portion 15. Inside the insertion portion 11, an air / water supply channel for sending air and water to an objective lens, which will be described later, a forceps channel for passing a treatment instrument, and the like are inserted. The flexible portion 15 has a bending portion obtained by connecting a plurality of bending pieces, and is bent according to the operation of the practitioner so that the distal end hard portion 16 faces a desired site in the body.

  The operation unit 12 is provided with an air / water supply button 17, a suction button 18, an angle knob 19, a forceps port 20, and the like. The air / water supply button 17 is operated when air or water is supplied to the air / water supply channel. The suction button 18 is operated when sucking air, moisture, or the like accumulated in the organ through the forceps channel. The angle knob 19 is operated when the bending portion is bent in a desired direction.

  As shown in FIG. 2, the distal end hard portion 16 has, for example, a hollow cylindrical shape, and is an imaging unit (not shown) including a CCD or the like for capturing an endoscopic image by imaging a site to be observed in the body. Is built-in. On the end surface of the distal end hard portion 16, there are two illumination windows 26 that irradiate illumination light toward the observation site, and an observation window 27 in which an objective lens that forms an image of the observation site on the CCD is arranged at the back. An air / water supply port 28 that is an outlet of the air / water supply channel and a forceps outlet 29 that is an outlet of the forceps channel are provided. A plurality of ultrasonic transducers 30 for obtaining an ultrasonic tomographic image are juxtaposed along the circumferential direction on the outer peripheral surface of the distal end hard portion 16. Each ultrasonic transducer 30 radiates an ultrasonic wave toward the site to be observed and receives the echo signal. When performing an ultrasonic tomographic examination, a balloon 31 is attached to the outer peripheral surface of the distal end hard portion 16 so as to cover the ultrasonic transducer 30.

  The balloon 31 is made of a stretchable rubber and has a cylindrical shape in which the vicinity of the center swells. Both ends of the balloon 31 are open, and elastic rings 32a and 32b are integrally formed in these openings. On the outer peripheral surface of the distal end hard portion 16, annular grooves 33a and 33b are formed so as to sandwich the ultrasonic transducer 30 in accordance with the positions of the elastic rings 32a and 32b. The elastic rings 32a and 32b It fits into each of the grooves 33a and 33b. The diameters of the elastic rings 32 a and 32 b are slightly narrower than the diameter of the distal end hard portion 16, and are crimped to the outer peripheral surface of the distal end hard portion 16 when the balloon 31 is attached to the distal end hard portion 16. Deaerated water as an ultrasonic transmission medium is injected into the balloon 31 thus mounted. The deaerated water is injected from a balloon water supply port 34 formed on the distal end side of the groove 33b, and the balloon 31 is inflated and brought into contact with a site to be observed in the body. As a result, air is excluded from the site to be observed and the ultrasonic transducer 30, that is, from the ultrasonic scanning region, and attenuation of the ultrasonic waves and echo signals is prevented. When the insertion portion 11 is pulled out from the body of the subject, the deaerated water in the balloon 31 is discharged from the balloon water supply port 34 and the balloon 31 is deflated.

  FIG. 3 is a cross-sectional view of the distal end hard portion 16 cut along the line AA in FIG. As shown in FIG. 3, the ultrasonic transducer 30 is configured by integrally stacking a backing material 39, a piezoelectric element 40, and an acoustic matching layer 41. Further, an acoustic lens 42 made of, for example, silicon rubber and for converging the ultrasonic wave to the observation site is attached to the upper surface of the acoustic matching layer 41 that is an ultrasonic wave transmitting / receiving surface. The backing material 39 is made of, for example, ferrite rubber, and restricts free vibration of the piezoelectric element 40 when radiating ultrasonic waves, thereby improving the resolution in the traveling direction of the ultrasonic waves. The acoustic lens 42 has a length W1 in the width direction (arrow direction) of about 5 mm and a thickness of about 1 mm.

  The piezoelectric element 40 is made of PZT (lead zirconate titanate) or the like, and includes a piezoelectric body 43 having a thickness of about 0.1 mm, and an upper electrode 44 and a lower electrode 45 that sandwich the piezoelectric body 43 from above and below. . The upper electrode 44 and the lower electrode 45 are, for example, silver thin film layers, and lead wires 46a and 46b are electrically connected to end portions of the upper surface thereof. The connecting portions of the lead wires 46a and 46b are covered with thin film protective layers 47 and 48 made of epoxy resin or the like, respectively. One of the lead wires 46 a and 46 b is grounded, and the other is connected to the ultrasonic observation apparatus 14. The ultrasonic observation device 14 has a built-in pulse generation circuit (not shown). When a pulse voltage is applied to the piezoelectric element 40 from the pulse generation circuit, the piezoelectric body 43 is rapidly deformed and an ultrasonic wave having a predetermined frequency is obtained. Is excited.

  The acoustic matching layer 41 is formed between the tip edge of the upper electrode 44 (edge on the tip side in the insertion direction) and the wiring protection layer 47 so as to cover the upper surface of the upper electrode 44. That is, the upper surface of the upper electrode 44 is covered with the wiring protective layer 47 from the base edge (edge facing the front edge) to a predetermined range, and all the remaining portions are covered with the acoustic matching layer 41. Yes. The acoustic matching layer 41 is made of, for example, an epoxy resin, has a length W2 in the width direction of about 3.5 mm, and the thickness is the same as that of the wiring protective layer 47 and is extremely thin. The acoustic matching layer 41 has an acoustic impedance lower than that of the piezoelectric body 43. Thereby, the difference in acoustic impedance between the piezoelectric element 40 having high acoustic impedance and the living body having low acoustic impedance is alleviated, and the transmission efficiency of ultrasonic waves is improved. The ultrasonic wave emitted from the piezoelectric element 40 passes through the acoustic matching layer 41, is converged by the acoustic lens 42, and is radiated to the site to be observed in the body.

  A corrosion prevention layer 49 that locally covers the upper surface of the upper electrode 44 is provided immediately below the boundary between the acoustic matching layer 41 and the wiring protective layer 47. The corrosion prevention layer 49 is a conductive thin film layer deposited with a material such as a sulfur component or a water component that does not transmit a corrosion factor of an electrical member, such as gold, and has a thickness of about several micrometers. The corrosion prevention layer 49 has a width direction length W3 of about 1 mm, and extends from the base end edge of the upper electrode 44 to a position beyond the boundary between the acoustic matching layer 41 and the wiring protection layer 47. Further, a lead wire 46a is joined to the surface of the corrosion prevention layer 49 near the base end edge by, for example, solder. The corrosion prevention layer 49 can be formed by sputtering or the like in addition to vapor deposition.

  The corrosion prevention layer 49 reaches the upper electrode 44 by the corrosive factor of the electrical member, in particular, deaerated water from which the sulfur component of the balloon 31 is dissolved invades from the boundary between the acoustic matching layer 41 and the wiring protective layer 47. To prevent it. Therefore, the upper electrode 44 is not corroded by the sulfur component, and deterioration of the image quality of the ultrasonic tomographic image, disconnection of the electrode, and the like are prevented. Further, since the corrosion prevention layer 49 is extremely thin and only locally covers the upper surface of the upper electrode 44 that is an ultrasonic scanning surface, the ultrasonic acoustic power is reduced and noise is generated in the echo signal. There is nothing to do. The corrosion prevention layer 49 has a simple structure in which gold is vapor-deposited on the surface of the upper electrode 44, and can effectively prevent corrosion of the upper electrode 44 while being easily and inexpensively introduced. Furthermore, gold, which is the material of the corrosion prevention layer 49, has a higher degree of fixing of the solder used for joining the lead wire 46a than the upper electrode 44 made of silver. Therefore, the lead wire 46a is difficult to peel off, and deterioration of the image quality of the ultrasonic tomographic image due to poor contact at the joint is prevented.

  Next, the operation of the above configuration will be described. When performing an ultrasonic tomography with the ultrasonic endoscope 10, first, the balloon 31 is attached to the distal end hard portion 16, and the insertion portion 11 is inserted into the body of the subject. And after making the front-end | tip hard part 16 arrive to the vicinity of a to-be-observed site | part, deaerated water is inject | poured from the balloon water supply port. Thereby, the balloon 31 is inflated and comes into contact with the site to be observed, and the ultrasonic scanning region is filled with deaerated water. In this state, a pulse voltage is applied from the ultrasonic observation device 14 to the piezoelectric element 40. The pulse voltage is applied to the piezoelectric body 43 via the lead wire 46 a, the corrosion prevention layer 49 and the upper electrode 44, and the lead wire 46 b and the lower electrode 45. As a result, the piezoelectric element 40 is rapidly deformed and ultrasonic waves are generated. The ultrasonic wave is reflected at the site to be observed, then enters the ultrasonic transducer 30 as an echo signal, and is received by the piezoelectric body 43. The received echo signal is input to the ultrasonic observation apparatus 14 through the upper electrode 44, the corrosion prevention layer 49, the lead wire 46a, and the lower electrode 45 and the lead wire 46b through a path opposite to the pulse voltage. The And after various image processing, it displays on the monitor 21 as an ultrasonic tomographic image.

  In this way, while performing the ultrasonic tomography, the sulfur component of the balloon 31 is gradually dissolved in the deaerated water. The deaerated water containing the sulfur component enters the ultrasonic transducer 30 from the acoustic lens 42 and reaches the acoustic matching layer 41 or the wiring protection layer 47. Then, it enters the boundary between the acoustic matching layer 41 and the wiring protection layer 47 and goes toward the upper electrode 44. However, a corrosion prevention layer 49 is provided immediately below the boundary between the acoustic matching layer 41 and the wiring protection layer 47 so as to cover the upper electrode 44. As described above, the corrosion prevention layer 49 is formed by gold vapor deposition and is impermeable to the sulfur component, so that the deaerated water containing the sulfur component reaches the upper electrode 44. There is nothing. Therefore, the upper electrode 44 is not corroded by the sulfur component. Further, since the corrosion prevention layer 49 only covers the upper surface of the upper electrode 44 only locally, it does not reduce the acoustic power of the ultrasonic waves or generate noise. Furthermore, since the corrosion prevention layer 49 has a better degree of solder fixation than the upper electrode 44, the lead wire 46a is less likely to peel off, and image quality deterioration of the ultrasonic tomographic image due to poor contact of the lead wire 46a is prevented. .

  In the above embodiment, the corrosion prevention layer 49 is formed by gold vapor deposition, but the corrosion prevention layer may be formed of an insulating thin film. For example, as shown in FIG. 4, the ultrasonic transducer 55 includes a corrosion prevention layer 56 made of, for example, a polyimide insulating film. The corrosion prevention layer 56 is formed only immediately below the boundary between the acoustic matching layer 41 and the wiring protection layer 47, and the lead wire 46 a is joined to the upper electrode 44. According to this configuration, since expensive gold is not used, corrosion of the upper electrode 44 can be prevented while suppressing costs.

  In the above-described embodiment, the radial scanning type ultrasonic endoscope has been described as an example. However, the present invention can also be applied to a linear scanning type or sector scanning type ultrasonic endoscope.

  In the above embodiment, an ultrasonic endoscope in which an ultrasonic transducer and an imaging unit are integrated has been described as an example. However, the present invention is effective even when applied to an ultrasonic probe that does not include an imaging unit. is there.

It is the schematic which shows the structure of the ultrasonic endoscope apparatus of this invention. It is explanatory drawing which shows the front-end | tip hard part of an ultrasonic endoscope. It is sectional drawing of the front-end | tip hard part cut | disconnected by the AA line of FIG. It is sectional drawing of the front-end | tip hard part which shows the ultrasonic transducer which provided the insulating corrosion prevention layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Ultrasonic endoscope 30, 55 Ultrasonic transducer 40 Piezoelectric element 41 Acoustic matching layer 43 Piezoelectric body 44 Upper electrode 45 Lower electrode 47, 48 Wiring protection layer 49, 56 Corrosion prevention layer

Claims (8)

A piezoelectric element having electrodes disposed on a piezoelectric body;
A wiring protective layer provided on the upper surface end of the electrode so as to cover the wiring electrically connected to the electrode;
An acoustic matching layer adjacent to the wiring protective layer and covering the upper surface of the electrode;
An ultrasonic transducer comprising: a corrosion preventing layer covering a portion of the upper surface of the electrode located under the boundary between the acoustic matching layer and the wiring protective layer.   The ultrasonic transducer according to claim 1, wherein the corrosion prevention layer is made of a material that does not allow a sulfur component to pass therethrough.   The ultrasonic transducer according to claim 1, wherein the corrosion prevention layer has conductivity and extends to the lower side of the wiring.   4. The ultrasonic transducer according to claim 1, wherein the corrosion prevention layer is formed of a material having a higher degree of solder fixation than the electrode.   The ultrasonic transducer according to claim 1, wherein the corrosion prevention layer is a thin film layer.   6. The ultrasonic transducer according to claim 1, wherein the corrosion prevention layer is formed by gold vapor deposition. A piezoelectric element having electrodes disposed on a piezoelectric body;
A wiring protective layer provided on the upper surface end of the electrode so as to cover the wiring electrically connected to the electrode;
An acoustic matching layer adjacent to the wiring protective layer and covering the upper surface of the electrode;
An ultrasonic probe comprising: an ultrasonic transducer having a corrosion prevention layer covering a portion of the upper surface of the electrode located under the boundary between the acoustic matching layer and the wiring protective layer.   The ultrasonic probe according to claim 7, which is an ultrasonic endoscope in which an imaging element is integrated.

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