JP2009297118A - Ultrasonic transducer and ultrasonic probe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the corrosion of the electrode of an ultrasonic transducer without lowering the acoustic power of an ultrasonic wave by a simple constitution. <P>SOLUTION: The ultrasonic transducer 30 is equipped with a piezoelectric element 40 wherein the upper and under sides of a piezoelectric body 43 are held between upper and lower electrodes 44 and 45. The upper and lower electrodes 44 and 45 are formed so that the length related to the insertion direction of them is longer than the piezoelectric body 43 and each keep one end protruded to the outside from the region just under an acoustic lens 42. A dummy substrate 49 having the same thickness as the piezoelectric body 43 and having no piezoelectric function is held between the protruded upper and lower electrodes 44 and 45. A wiring protecting layer 47 is formed to the upper surface end part of the protruded part of the upper electrode 44 and an acoustic matching layer 41 is adjacent to the wiring protecting layer 47 to cover the upper surface of the upper electrode 44. The boundary of the acoustic matching layer 41 and the wiring protecting layer 47 is positioned outside the region just under the acoustic lens 42. <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 tomography has been performed in the medical field. In ultrasonic tomography, an ultrasonic probe, for example, an ultrasonic probe, is inserted into the body of a 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 tomographic image on a monitor or the like. .

  The ultrasonic transducer includes a piezoelectric element in which a piezoelectric body is sandwiched between 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. By applying a pulse voltage from the ultrasonic observation apparatus, ultrasonic waves are generated from the piezoelectric element. The upper surface of the piezoelectric element, that is, the surface of the electrode (hereinafter referred to as the upper electrode) on the upper side of the piezoelectric body is covered with an acoustic matching layer that improves the propagation efficiency of ultrasonic waves. Further, an acoustic lens for converging the ultrasonic waves is disposed on the acoustic matching layer. The ultrasonic wave generated by the piezoelectric element is radiated toward the observed site in the body through the acoustic matching layer and the acoustic lens. In addition, the ultrasonic wave reflected from the site to be observed is received by the ultrasonic transducer as an echo signal through a path reverse to the above.

  As is well known, ultrasonic waves and echo signals are significantly attenuated in the air. Therefore, at the time of ultrasonic tomography, an elastic bag-like balloon is attached to the tip of the ultrasonic probe. After inserting the ultrasonic probe into the body of the subject, deaerated water as an ultrasonic transmission medium is injected into the balloon. 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. This sulfur component is gradually dissolved in the deaerated water injected into the balloon. Thus, the deaerated water containing the sulfur component may reach the ultrasonic transducer through the acoustic lens 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.

Therefore, in order to prevent corrosion of the electrode due to the sulfur component, in the ultrasonic probe described in Patent Document 1, the vibrator (ultrasonic transducer) is wrapped with a film that does not allow the sulfur component to pass therethrough and disposed behind the acoustic lens. According to this configuration, even if the sulfur component penetrates from the tip of the ultrasonic probe or the acoustic lens, since the ultrasonic transducer and the sulfur component are separated by the film, the electrode of the piezoelectric element is corroded by the sulfur component. There is no.
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 tomographic image is deteriorated due to a decrease in the acoustic power of the ultrasonic waves or noise in the received echo signal.

  Further, in the conventional configuration in which the upper surface of the ultrasonic transducer is exposed, as described above, the deaerated water that has passed through the acoustic lens reaches the upper electrode, and the upper electrode is corroded. 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.

  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, an ultrasonic transducer according to the present invention is disposed below an acoustic lens that converges ultrasonic waves, covers a piezoelectric body that generates ultrasonic waves, and covers at least one end of the piezoelectric body. An electrode protruding outward from directly below the lens; a wiring protection layer provided on the upper surface of the protruding portion of the electrode; covering the wiring connected to the electrode; and adjacent to the wiring protection layer at the protruding portion of the electrode; And an acoustic matching layer covering the upper surface of the substrate.

  Moreover, it is preferable to arrange the piezoelectric body inside the acoustic lens. Furthermore, it is preferable to arrange the piezoelectric body so that the center of the piezoelectric body coincides with the center of the acoustic lens.

  In a preferred embodiment of the present invention, a dummy substrate having the same thickness as the piezoelectric body and not having a piezoelectric function is provided under the protruding portion of the electrode.

  In another preferred embodiment of the present invention, a backing material is provided that supports the piezoelectric body from below and contacts the side surface of the piezoelectric body and the bottom surface of the protruding portion of the electrode.

  In still another embodiment of the present invention, the piezoelectric body extends to the side edge of the protruding portion of the electrode.

  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 boundary between the acoustic matching layer and the wiring protective layer, which is an intrusion route of the corrosive component, is disposed outside the direct underside of the acoustic lens. Therefore, the corrosion factor that has passed through the acoustic lens does not easily reach the electrode that covers the piezoelectric body, and corrosion of the electrode is prevented. In addition, since no film or member for preventing the invasion of corrosion factors is used, the ultrasonic sound power does not decrease and noise is not generated in the echo signal, and the image quality of the ultrasonic image is deteriorated. There is nothing. Further, since the center of the piezoelectric body can be made coincident with the center of the acoustic lens by using a dummy substrate or a backing material, it is possible to improve the ultrasonic resolution and obtain an ultrasonic image with excellent image quality. . Furthermore, since it has a simple structure in which one end of the electrode protrudes, it can be introduced easily and at low cost.

  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 in which a plurality of bending pieces are connected to the proximal end side of the distal end hard portion 16. This bending portion is bent according to the operation of the practitioner, and makes the distal end hard portion 16 face 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 laminating a backing material 39, a piezoelectric element 40, and an acoustic matching layer 41, and generates ultrasonic waves generated by the piezoelectric element 40. The acoustic matching layer 41 is radiated to the outside. 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. In addition, an acoustic lens 42 is attached to the upper surface of the acoustic matching layer 41 for converging the ultrasonic wave to the site to be observed. The acoustic lens 42 is made of, for example, silicon rubber, and has a length W in the insertion direction of the insertion portion 11 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 (electrode) 44 and a lower electrode 45 that sandwich the piezoelectric body 43 from above and below. Has been. The upper electrode 44 and the lower electrode 45 are, for example, silver thin film layers, and lead wires 46a and 46b are connected to end portions of the upper surface on the proximal side in the insertion direction. Connection portions of these lead wires 46a and 46b are covered with thin-film wiring 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, and has the same thickness as 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.

  The upper electrode 44 and the lower electrode 45 of the piezoelectric element 40 have a length in the insertion direction that is longer than that of the piezoelectric body 43, and one end of each of the upper and lower electrodes 45 protrudes outward from directly below the acoustic lens 42 toward the proximal direction in the insertion direction. Yes. Lead wires 46a and 46b are connected to the protruding portions. Here, the piezoelectric body 43 is arranged at an optimal position with respect to the acoustic lens 42 in order to improve the resolution of the ultrasonic waves. In other words, the piezoelectric body 43 is arranged so that the center of the piezoelectric body 43 in the insertion direction and the center of the acoustic lens 42 (both indicated by a one-dot chain line) coincide. Then, a gap is formed between the protruding upper and lower electrodes 44 and 45. Therefore, a dummy substrate 49 having the same thickness as that of the piezoelectric body 43 is provided between the gaps. The dummy substrate 49 fills the space between the projecting upper and lower electrodes 44 and 45 to maintain the shape of the piezoelectric element 40 and does not have a piezoelectric function.

  Thus, by projecting one end of the upper and lower electrodes 44, 45, the boundary between the acoustic matching layer 41 and the wiring protection layer 47 is disposed outside the direct lower side of the acoustic lens 42. The path through which the corrosive factor that has passed through the acoustic lens 42 reaches the upper electrode 44 is mainly the boundary between the acoustic matching layer 41 and the wiring protective layer 47. It becomes difficult to reach the upper electrode 44. As a result, corrosion of the upper electrode 44 can be prevented. Further, since the piezoelectric body 43 is positioned optimally with respect to the acoustic lens 42 by the dummy substrate 49, an ultrasonic image with excellent image quality can be obtained. Further, since one end of each of the upper and lower electrodes 44 and 45 protrudes outward from directly below the acoustic lens 42, the conventional manufacturing method can be implemented easily and at low cost without greatly changing.

  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 propagation path is filled with deaerated water. In this state, a pulse voltage is applied from the ultrasonic observation device 14 to the piezoelectric element 40. As a result, the piezoelectric element 40 is rapidly deformed and ultrasonic waves are generated. This ultrasonic wave is reflected by the observation site, received as an echo signal by the ultrasonic transducer 30, subjected to various image processing by the ultrasonic observation device 14, and then displayed 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 gradually passes through the acoustic lens 42 and reaches the acoustic matching layer 41 located immediately below the acoustic lens 42. However, since the boundary between the acoustic matching layer 41 and the wiring protective layer 47 is located outside the area directly below the acoustic lens 42, deaerated water containing a sulfur component does not immediately enter the boundary. Moreover, since the acoustic matching layer 41 is made of resin, it does not easily allow the deaerated water containing the sulfur component to pass therethrough. Therefore, the sulfur component does not reach the upper electrode 44, and the upper electrode 44 is not corroded. In addition, since a dedicated layer or member for preventing the invasion of corrosion factors such as sulfur components is not used, the acoustic power of the ultrasonic wave is not reduced and noise is not generated in the echo signal. Further, by adjusting the size of the dummy substrate 49, the center of the piezoelectric body 43 can be made to coincide with the center of the acoustic lens 42, so that the ultrasonic resolution is improved and the ultrasonic tomographic image with excellent image quality. Can be obtained.

  In the above embodiment, the dummy substrate 49 is disposed between the protruding upper and lower electrodes 44 and 45, but a piezoelectric body may be extended to the end portions of the upper and lower electrodes 44 and 45. For example, in the ultrasonic transducer 55 shown in FIG. 4, the length in the insertion direction of the piezoelectric body 56 is the same as that of the upper and lower electrodes 44 and 45. According to the piezoelectric element 57, it is not necessary to arrange the dummy substrate 49 between the upper and lower electrodes 44 and 45, and the process of creating the dummy substrate 49 can be omitted. Therefore, it can be introduced more easily and at a lower cost, and the corrosion of the upper electrode 44 due to a sulfur component or the like can be effectively prevented as in the above embodiment.

  Further, in each of the above embodiments, one end of each of the upper and lower electrodes 44 and 45 is projected, but only the upper electrode may be projected and the bottom surface of the upper electrode may be supported by the backing material. For example, as shown in FIG. 5, the piezoelectric element 61 of the ultrasonic transducer 60 includes a lower electrode 62 whose length in the insertion direction is the same as that of the piezoelectric body 43. A lead wire 46b is connected to the surface end of the lower electrode 62 on the proximal side in the insertion direction, and the wiring protective layer 48 covers this. A backing material 63 is formed so as to support the piezoelectric body 43 from below the lower electrode 62 and to be in contact with the side surfaces of the lower electrode 62 and the piezoelectric body 43 and the bottom surface of the upper electrode 44. According to this configuration, it is possible to effectively prevent corrosion of the upper electrode 44 due to a sulfur component or the like as in the above embodiments, while forming the lower electrode 62 by the same manufacturing method as in the prior art. Further, by adjusting the size of the backing material 63, the center of the piezoelectric body 43 in the insertion direction can be matched with the center of the acoustic lens 42.

  As mentioned above, although each embodiment was described according to drawing, this invention is not limited to these embodiment. In other words, the boundary between the acoustic matching layer 41 and the wiring protection layer 47 may be outside the area directly below the acoustic lens 42, and any form may be used without departing from the gist of the present invention.

  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 enlarged the piezoelectric material. It is sectional drawing of the front-end | tip hard part which shows the ultrasonic transducer which enlarged only the upper electrode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Ultrasonic endoscope 30, 55, 60 Ultrasonic transducer 39, 63 Backing material 40, 57, 61 Piezoelectric element 41 Acoustic matching layer 42 Acoustic lens 43, 56 Piezoelectric body 44 Upper electrode (electrode)
45, 62 Lower electrode 47, 48 Wiring protection layer

Claims (8)

A piezoelectric body disposed on the lower side of the acoustic lens for converging ultrasonic waves, and generating the ultrasonic waves;
An electrode that covers the piezoelectric body and at least one end of which protrudes outward from directly below the acoustic lens;
A wiring protective layer that is provided on the upper surface of the protruding portion of the electrode and covers the wiring connected to the electrode;
An ultrasonic transducer comprising: an acoustic matching layer that is adjacent to the wiring protective layer at a protruding portion of the electrode and covers an upper surface of the electrode.   The ultrasonic transducer according to claim 1, wherein the piezoelectric body is disposed directly inside the acoustic lens.   The ultrasonic transducer according to claim 2, wherein the piezoelectric body is arranged so that a center of the piezoelectric body coincides with a center of the acoustic lens.   4. The ultrasonic transducer according to claim 2, further comprising a dummy substrate provided below the protruding portion of the electrode and having the same thickness as the piezoelectric body and having no piezoelectric function.   The ultrasonic transducer according to claim 2, further comprising a backing material that supports the piezoelectric body from below and contacts a side surface of the piezoelectric body and a bottom surface of the protruding portion of the electrode.   The ultrasonic transducer according to claim 1, wherein the piezoelectric body extends to a side edge of a protruding portion of the electrode. A piezoelectric body disposed on the lower side of the acoustic lens for converging ultrasonic waves, and generating the ultrasonic waves;
An electrode that covers the piezoelectric body and at least one end of which protrudes outward from directly below the acoustic lens;
A wiring protective layer that is provided on the upper surface of the protruding portion of the electrode and covers the wiring connected to the electrode;
An ultrasonic probe comprising an ultrasonic transducer having an acoustic matching layer adjacent to the wiring protective layer and covering an upper surface of the electrode at a protruding portion of the electrode.   The ultrasonic probe according to claim 7, which is an ultrasonic endoscope in which an imaging element is integrated.

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