JP2009072349A - Ultrasonic transducer, its manufacturing method and ultrasonic probe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic transducer which achieves high sensitivity and a wide band, and has excellent sound consistency with a human body and is excellent in ultrasonic propagation characteristics. <P>SOLUTION: The ultrasonic transducer includes a first piezoelectric body with a recessed part and a projected part, formed on the first surface, a second piezoelectric body with a recessed part and a projected part, formed on the first surface, a first internal electrode formed along the recessed part and projected part of the first piezoelectric body, a second internal electrode formed along the recessed part and projected part of the second piezoelectric body, and a filler having a sound impedance smaller than the sound impedance of the first and second piezoelectric bodies. The length of the recessed part of the first and second piezoelectric bodies is longer than the length of the projected part, the recessed part and projected part of the first piezoelectric body and the projected part and recessed part of the second piezoelectric body are fitted at prescribed intervals so as to fill the filler between the first internal electrode and the second internal electrode, and a laminate piezoelectric complex is formed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ultrasonic transducer (piezoelectric vibrator) used for transmitting and receiving ultrasonic waves in an ultrasonic diagnostic apparatus, and a manufacturing method thereof. Furthermore, the present invention relates to an ultrasonic probe using such an ultrasonic transducer.

  In an ultrasonic probe, as an ultrasonic transducer for transmitting and / or receiving ultrasonic waves, a piezoelectric ceramic represented by PZT (Pb (lead) zirconate titanate) is generally used. A vibrator (piezoelectric vibrator) in which electrodes are formed on both ends of a piezoelectric material such as a polymer piezoelectric material represented by PVDF (polyvinyliden difluoride) is used.

  When a voltage is applied to the electrodes of such a vibrator, the piezoelectric body expands and contracts due to the piezoelectric effect, and elastic waves are generated. In particular, by applying a broadband signal voltage to the electrodes of the vibrator, a resonant elastic wave having a wavelength corresponding to the thickness of the piezoelectric body is generated. In particular, when the thickness of the ceramic piezoelectric body is several mm or less, ultrasonic waves are generated from the piezoelectric body. Furthermore, an ultrasonic beam can be formed in a desired direction by arranging a plurality of transducers in a one-dimensional or two-dimensional manner and driving with a plurality of drive signals given a predetermined delay. On the other hand, the vibrator expands and contracts by receiving propagating ultrasonic waves and generates an electrical signal. This electrical signal is used as an ultrasonic detection signal.

  The ultrasonic diagnostic apparatus uses an ultrasonic probe to transmit an ultrasonic wave to a subject such as a human body and receive an ultrasonic echo reflected from the subject, based on an ultrasonic detection signal. Display an image. Thereby, the internal organs and blood vessels are examined. However, when a piezoelectric ceramic is used in the vibrator, there is a large difference between the acoustic impedance of the vibrator and the acoustic impedance of the human body, etc. Reflection occurs, resulting in propagation loss.

Here, the acoustic impedance is a material-specific constant represented by the product of the acoustic medium density and the sound velocity. Generally, MRayl (mega rail) is used as the unit, and 1 MRayl = 1 × 10 ^6. kg · m ⁻² · s ⁻¹ . A typical piezoelectric ceramic has an acoustic impedance of about 25 MRayl to about 35 MRayl, and a human body has an acoustic impedance of about 1.5 MRayl.

If the acoustic impedance of the vibrator is Z ₀ and the acoustic impedance of the human body is Z _M , the ultrasonic wave reflectance R at the contact interface is given by the following equation (1).
R = | Z ₀ −Z _M | / (Z ₀ + Z _M ) (1)
In Equation (1), if Z ₀ = 35 MRayl and Z _M = 1.5 MRayl, R = 0.92, so most of the ultrasonic waves are reflected at the contact interface, and the ultrasonic waves do not propagate by 10%. I understand that.

  In order to solve this problem, an acoustic matching layer is inserted between the transducer and the subject to achieve acoustic impedance matching. Furthermore, if the acoustic matching layer has a multi-layer structure, the propagation efficiency of ultrasonic waves is improved. However, for the convenience of manufacturing, the acoustic matching layer is limited to two to three layers.

  Therefore, in order to further improve the propagation efficiency of ultrasonic waves, it is conceivable to reduce the acoustic impedance of the vibrator itself. For example, it is effective to form a lattice-like groove in the piezoelectric body to form an array, and to fill the groove with a material having an acoustic impedance of about 2 MRayl to 4 MRayl. At that time, the interval between the grooves is made sufficiently smaller than the wavelength of the ultrasonic wave propagating in each transducer separated by the grooves. In general, it is desirable that the interval between the grooves be 1/8 to 1/10 or less of the wavelength of the ultrasonic wave. As such an array transducer, for example, a composite piezoelectric body in which a rod-like PZT long in one direction is arranged in a resin is used, and this composite piezoelectric body is called a 1-3 composite.

  In the case of 1-3 composite, each vibrator has a rod shape, and therefore its vibration mode is 33 vibration mode. The 33 vibration mode refers to a vibration mode when a piezoelectric body that has been subjected to polarization processing (polling processing) in the third direction (Z-axis direction) is vibrated by applying an electric field in the same third direction. . Generally, in the vibrator, since the electromechanical coupling coefficient k33 in the 33 vibration mode is larger than the electromechanical coupling coefficient kt in the plate shape or the electromechanical coupling coefficient k33 ′ in the bar shape, each vibrator has a rod shape. Therefore, high conversion efficiency can be expected.

  Also, the large electromechanical coupling coefficient k33 contributes to the expansion of the bandwidth of the vibrator. Furthermore, by adopting 1-3 composite, a part of the piezoelectric body with high acoustic impedance is replaced with resin with low acoustic impedance, so that the acoustic impedance of the vibrator is lowered and the propagation efficiency of ultrasonic waves is improved. The However, since the effective area of the piezoelectric body having a large dielectric constant is reduced, the capacitance of the vibrator is electrically reduced and the electrical impedance is increased.

  On the other hand, in recent years, an ultrasound probe is inserted into the body through the mouth (oral endoscope), the endoscope inserted into the body through the nose (transnasal endoscope), Since it is used in blood vessel catheters and the like, miniaturization of ultrasonic probes is required. Since the diameter of the oral endoscope is about 8 mm to 11 mm and the diameter of the transnasal endoscope is about 4 mm to 5 mm, it is necessary to reduce the size of the vibrator.

  However, the electrical impedance of the vibrator increases with the miniaturization of the vibrator. When the electrical impedance of the transducer in the frequency band of ultrasonic waves to be transmitted / received becomes larger than the electrical impedance of the receiving circuit of the ultrasonic diagnostic apparatus body or the characteristic impedance of the connection cable, the transmission characteristics of the detection signal deteriorate. In addition, the sensitivity is reduced in synergy with the reduction in size of the vibrator.

  In order to compensate for such a decrease in sensitivity, the vibrator (piezoelectric body and electrode) has a laminated structure, and the vibrator of each layer is connected in parallel, thereby increasing the capacitance of the vibrator and lowering the electrical impedance. Has been done. However, it seems that no attempt has been made to achieve both the 1-3 composite of the vibrator and the lamination of the vibrator. The reason is that the internal electrode structure orthogonal to the ultrasonic radiation direction required for lamination and the formation of grooves parallel to the ultrasonic radiation direction required for 1-3 composite are contradictory in structure and processing. This is because it is difficult to achieve both.

  In addition, quadrangular columnar vibrators that vibrate in 33 vibration modes are stacked, electrodes are formed so as to operate as a single vibrator by arranging them in an array, and a plurality of such vibrators are arranged in a one-dimensional manner. Although it can be a child array, the process of manufacturing this is similar to the process of manufacturing a stacked two-dimensional transducer array, and requires a great deal of labor.

As related techniques, the following Patent Document 1 and Patent Document 2 disclose a method of manufacturing a composite piezoelectric body. In this method of manufacturing a composite piezoelectric body, two piezoelectric bodies having a plurality of concave portions and a plurality of convex portions on the surface are fitted together by sandwiching a resin, and the bonded piezoelectric bodies are cut out along a straight line. Thus, a composite piezoelectric body in which a plurality of piezoelectric bodies and a plurality of resins are alternately arranged is formed. However, Patent Document 1 and Patent Document 2 do not disclose that the 1-3 composite of the vibrator and the lamination of the vibrator are compatible.
US Pat. No. 5,239,736 US Pat. No. 6,984,284

  Therefore, in view of the above points, the present invention provides an ultrasonic transducer that achieves high sensitivity and a wide band, has excellent acoustic matching with a human body, and has excellent ultrasonic propagation characteristics, and such an ultrasonic transducer. An object is to provide an ultrasonic probe to be used.

  In order to solve the above-described problem, an ultrasonic transducer according to one aspect of the present invention includes a first piezoelectric body in which a plurality of concave portions and a plurality of convex portions are formed on a first surface, and a plurality of piezoelectric transducers on the first surface. A second piezoelectric body having a plurality of concave portions and a plurality of convex portions, a first internal electrode formed along the plurality of concave portions and the plurality of convex portions of the first piezoelectric body, and a second piezoelectric body. A second internal electrode formed along the plurality of concave portions and the plurality of convex portions, and a first electrode formed on the second surface facing the first surface of the first piezoelectric body, A second electrode formed on the second surface facing the first surface of the second piezoelectric body, and a filler having an acoustic impedance smaller than that of the first and second piezoelectric bodies; And the length of the concave portions of the first and second piezoelectric bodies is larger than the length of the convex portions, The plurality of concave portions and the plurality of convex portions of the first piezoelectric body and the plurality of convex portions and the plurality of concave portions of the second piezoelectric body are set at predetermined intervals so that the filler is filled between the inner electrodes of the first piezoelectric body. Are joined together to form a laminated piezoelectric composite.

  An ultrasonic transducer manufacturing method according to an aspect of the present invention is a method of manufacturing an ultrasonic transducer for transmitting and / or receiving ultrasonic waves, and includes a first surface of a first piezoelectric body. A plurality of concave portions and a plurality of convex portions are formed on the first surface of the second piezoelectric body, and a plurality of concave portions and a plurality of convex portions are formed on the first surface of the second piezoelectric body. Forming the first internal electrode along the plurality of concave portions and the plurality of convex portions of the first piezoelectric body, and a plurality of second piezoelectric bodies. Forming a second internal electrode along the concave portion and the plurality of convex portions, and forming the first electrode on the second surface facing the first surface of the first piezoelectric body. And a step of forming a second electrode on the second surface opposite to the first surface of the second piezoelectric body (c) And the filling material having an acoustic impedance smaller than the acoustic impedance of the first and second piezoelectric bodies is filled between the first internal electrode and the second internal electrode. A step (d) of forming a laminated piezoelectric composite by fitting the plurality of recesses and the plurality of protrusions with the plurality of protrusions and the plurality of recesses of the second piezoelectric body with a predetermined interval; To do.

  Furthermore, an ultrasonic probe according to one aspect of the present invention includes a transducer array formed by arranging a plurality of ultrasonic transducers according to the present invention, a backing material provided on the back surface of the transducer array, and a transducer array. And at least one acoustic matching layer provided on the front surface.

  According to the present invention, it is possible to improve electromechanical coupling coefficient and reduce electrical impedance by achieving both 1-3 composite and lamination, and achieve high sensitivity and wide bandwidth, and reduce acoustic impedance. In addition, it is possible to provide an ultrasonic transducer that has excellent acoustic compatibility with the human body and excellent ultrasonic propagation characteristics. Furthermore, an ultrasonic probe using such an ultrasonic transducer can be provided.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. The same constituent elements are denoted by the same reference numerals, and the description thereof is omitted.
FIG. 1 is a perspective view schematically showing the internal structure of the ultrasonic probe according to the first embodiment of the present invention, and FIG. 2 is an ultrasonic wave used in the ultrasonic probe shown in FIG. It is sectional drawing when a transducer array (vibrator array) is cut | disconnected by the surface parallel to XY plane. This transducer array expands and contracts when a drive signal is supplied and transmits an ultrasonic wave toward the subject, and outputs an electrical signal (detection signal) by receiving the ultrasonic wave reflected by the subject. A plurality of ultrasonic transducers (vibrators) 1 are provided.

  Each vibrator 1 has a piezoelectric body 2a having a plurality of concave portions and a plurality of convex portions formed on the first surface (lower surface), and a plurality of concave portions and a plurality of convex portions formed on the first surface (upper surface). Piezoelectric body 2b, internal electrodes 3a formed along the plurality of concave portions and the plurality of convex portions of the piezoelectric body 2a, and internal electrodes formed along the plurality of concave portions and the plurality of convex portions of the piezoelectric body 2b 3b, an upper electrode 5 formed on the second surface facing the first surface of the piezoelectric body 2a, and a lower electrode formed on the second surface facing the first surface of the piezoelectric body 2b 6 and a laminated piezoelectric composite composed of a filler 4 having an acoustic impedance smaller than that of the piezoelectric bodies 2a and 2b.

  Here, the lengths of the concave portions of the piezoelectric bodies 2a and 2b are larger than the length of the convex portions, and the plurality of concave portions of the piezoelectric body 2a are filled with the filler 4 between the internal electrodes 3a and 3b. The plurality of convex portions and the plurality of convex portions and the plurality of concave portions of the piezoelectric body 2b are fitted with a predetermined interval. Furthermore, a plurality of transducers 1 constitute a transducer array 8.

  As shown in FIG. 1, the ultrasonic probe has a backing material 11, and the transducer array 8 is provided on the backing material 11. On the transducer array 8, one or a plurality of acoustic matching layers (in FIG. 1, two acoustic matching layers 12a and 12b are shown), and an acoustic lens 13 is provided on the acoustic matching layer as necessary. It is done. The acoustic matching layers 12a and 12b are formed of, for example, Pyrex (registered trademark) glass that easily propagates ultrasonic waves, epoxy resin containing metal powder, or the like, and an acoustic impedance between a subject such as a living body and the vibrator 1 is used. Improve matching. Thereby, the ultrasonic wave transmitted from the transducer 1 propagates efficiently into the subject. The acoustic lens 13 is made of, for example, silicone rubber, and focuses ultrasonic waves transmitted from the plurality of transducers 1 and propagated through the acoustic matching layers 12a and 12b at a predetermined depth in the subject. These parts are housed in a housing, and wiring drawn from the plurality of transducers 1 is connected to an electronic circuit in the ultrasonic diagnostic apparatus main body via a cable.

  FIG. 3 is a cross-sectional view for conceptually explaining that the ultrasonic transducer according to the first embodiment of the present invention constitutes a 1-3 composite. As shown in FIG. 3A, each of the two piezoelectric bodies 2a and 2b has a plurality of concave portions and a plurality of convex portions on the first surface facing each other. Internal electrodes 3a and 3b are formed along the concave and convex portions. An upper electrode 5 is formed on the second surface of the piezoelectric body 2a, and a lower electrode 6 is formed on the second surface of the piezoelectric body 2b. As shown in FIG. 3B, a laminated piezoelectric composite is formed by laminating the piezoelectric body 2a on which electrodes are formed and the piezoelectric body 2b.

  Here, it can be seen that the plurality of convex portions of the piezoelectric bodies 2a and 2b are arranged in one direction (X-axis direction shown in FIG. 1) to form a row of transducer groups that operate simultaneously. . As a result, the transducer group in one row has the characteristic of 1-3 composite, and the individual transducers (convex portions) constituting the transducer group in one row vibrate in the 33 vibration mode. In general, in the piezoelectric vibrator, since the electromechanical coupling constant k33 in the 33 mode is larger than the electromechanical coupling constant kt in the plate shape and the electromechanical coupling constant k33 ′ in the bar shape, high conversion efficiency can be realized. . In addition, a large electromechanical coupling constant k33 also leads to expansion of the bandwidth of the vibrator. Therefore, adopting 1-3 composite results in high sensitivity and wide bandwidth of the piezoelectric vibrator. Furthermore, by laminating the piezoelectric body and the electrodes, the capacitance increases and the electrical impedance decreases, so that the transmission efficiency of the detection signal is improved.

  4A and 4B are diagrams showing an ultrasonic transducer according to the first embodiment of the present invention. As shown in FIG. 4A, each of the two piezoelectric bodies 2a and 2b has a plurality of concave portions and a plurality of convex portions on the first surface facing each other. As shown in FIG. 4A, if the lengths of the convex portions of the piezoelectric bodies 2a and 2b are L1, the length of the concave portions is L2, and the thicknesses of the internal electrodes 3a and 3b are sufficiently small, the concave portions and the convex portions are , L1 <L2 is established, and the piezoelectric body 2a and the piezoelectric body 2b are formed at the same pitch. Specific values of L1 and L2 are, for example, L1 = 150 μm and L2 = 300 μm.

  An internal electrode 3a is formed along the concave and convex portions of the piezoelectric body 2a, and an internal electrode 3b is formed along the concave and convex portions of the piezoelectric body 2b. An upper electrode 5 is formed on the second surface of the piezoelectric body 2a, and a lower electrode 6 is formed on the second surface of the piezoelectric body 2b. Each electrode is formed, for example, as a chromium / gold (Cr / Au) electrode in which the base adhesive layer is chromium (Cr) and the surface conductive layer is gold (Au), and the thickness of the electrode is, for example, 300 nm. .

  As shown in FIG. 4B, the plurality of concave portions and the plurality of convex portions of the piezoelectric body 2a and the plurality of convex portions and the plurality of concave portions of the piezoelectric body 2b have an acoustic impedance smaller than the acoustic impedance of the piezoelectric bodies 2a and 2b. A laminated piezoelectric composite is formed by fitting with the filler 4 sandwiched therebetween. Here, since the relationship of L1 <L2 is established between the length L1 of the convex portions and the length L2 of the concave portions of the piezoelectric bodies 2a and 2b, the internal electrodes are arranged in the longitudinal direction of the laminated piezoelectric composite. A gap is formed between 3a and the internal electrode 3b, and the filler 4 is also filled in this gap.

  The piezoelectric bodies 2a and 2b are formed of, for example, Fuji Ceramics C-91H, which is a relaxor piezoelectric body. The material of the filler 4 is selected from materials having an acoustic impedance lower than that of piezoelectric ceramics, that is, 25 Mrayl to 35 Mrayl, and having adhesive ability.

  Examples of such a material include resin materials such as epoxy resin, urethane resin, silicone resin, melamine resin and the like having an acoustic impedance of about 2.0 Mrayl to 3.5 Mrayl, and a silver paste having an acoustic impedance of 11.7 Mrayl (30% silver, epoxy resin). 70%), polyimide with an acoustic impedance of 2.61 Mrayl, solder with an acoustic impedance of about 18 Mrayl, glycerin with an acoustic impedance of 2.38 Mrayl, glass with an acoustic impedance of about 13.0 Mrayl to 15.0 Mrayl, organic glass with an acoustic impedance of 3.21 Mrayl, acoustic Polystyrene having an impedance of 2.5 Mrayl, hard rubber having an acoustic impedance of 2.80 Mrayl, soft rubber having an acoustic impedance of 1.46 Mrayl, and the like.

  For example, Epoxy Technology 301-2FL manufactured by Epoxy Technology is used as the resin. Moreover, when giving heat dissipation effect to resin, Chemitech Co., Ltd. product Keshmir S-8586 or Idemitsu Kosan XE11-C2148 is used.

  In FIG. 4B, the vibrator 1 may be driven by connecting the upper electrode 5 and the lower electrode 6 to the ground potential and applying a drive voltage to the internal electrodes 3a and 3b. Alternatively, the vibrator 1 may be driven by connecting the internal electrodes 3 a and 3 b to the ground potential and applying a drive voltage to the upper electrode 5 and the lower electrode 6. By arranging the vibrators 1 formed in this way in one direction (Y direction shown in FIG. 1), a one-dimensional vibrator array is formed. The overall size of the transducer array is, for example, 5 mm in length, 5 mm in width, and 600 μm in thickness.

  In the present embodiment, since the resin having a lower acoustic impedance than the piezoelectric body is filled between the piezoelectric bodies 2a and 2b, the acoustic impedance of the vibrator 1 is lowered, and the ultrasonic wave is reflected at the interface. Can be reduced. Thereby, an ultrasonic wave can be efficiently propagated to the subject. In addition, filling the resin between the vibrators 1 reduces the capacitance and increases the electrical impedance. However, increasing the capacitance by stacking the piezoelectric body and the electrodes realizes the electrical impedance. Is reduced. Further, by appropriately determining the thickness t1 (excluding the electrodes) of the vibrator and the thicknesses t2 and t3 of the piezoelectric bodies in the recesses of the piezoelectric bodies 2a and 2b, a desired plurality of resonance frequencies can be obtained. In addition, the frequency sensitivity characteristics can be balanced by appropriately determining the area ratio of these regions. Therefore, it is possible to realize a wide band of the vibrator, which is particularly advantageous when performing harmonic imaging or contrast Doppler imaging.

  In this embodiment, the electrical impedance when the thickness t1 of the laminated piezoelectric composite and the thicknesses t2 and t3 of the piezoelectric bodies in the recesses of the piezoelectric bodies 2a and 2b are t1 = 600 μm and t2 = t3 = 150 μm, respectively. The measured value of the phase will be described. FIG. 5A is a diagram showing the frequency dependence of the measured value of the electrical impedance, and FIG. 5B is a diagram showing the frequency dependence of the measured value of the phase. From the measured values of electrical impedance and phase, it can be seen that a peak value corresponding to t1 = 600 μm exists in the vicinity of 2.5 MHz, and a peak value corresponding to t2 = t3 = 150 μm exists in the vicinity of 10.5 MHz.

  FIG. 6 shows the thickness t1 of the laminated piezoelectric composite, the thickness t2 of the concave portion of the piezoelectric body 2a, and the thickness t3 of the concave portion of the piezoelectric body 2b in the vibrator of this embodiment, respectively, t1 = 200 μm and t2. It is a figure which shows the frequency dependence of the transmission-and-reception gain measured when it is set to = t3 = 135 micrometers and average acoustic impedance Zave is set to Zave = 15Mrayl.

  The transmission / reception gain corresponding to the thickness t1 = 200 μm of the multilayer piezoelectric composite exhibits a large transmission / reception gain value in a relatively low frequency band with a peak at the center frequency of 8.0 MHz. On the other hand, the transmission / reception gain corresponding to the thickness t2 = t3 = 135 μm of the recesses of the piezoelectric bodies 2a and 2b shows a large transmission / reception gain value in a relatively high frequency band with the center frequency being 11.0 MHz. The transmission / reception gain of the laminated piezoelectric composite formed by laminating the piezoelectric body 2a and the piezoelectric body 2b is wide by superimposing the transmission / reception gain corresponding to the thickness t1 and the transmission / reception gain corresponding to the thickness t2. A flat transmission / reception gain value in the frequency band is shown.

Next, a second embodiment of the present invention will be described.
7 and 8 are diagrams showing an ultrasonic transducer and an ultrasonic probe according to the second embodiment of the present invention, and manufacturing steps thereof. As shown in FIG. 8D, the ultrasonic transducer according to this embodiment includes a side electrode 10a connected to the internal electrodes 3a and 3b, an upper electrode 5 and a lower part on the left and right side surfaces of the laminated piezoelectric composite. And a side electrode 10 b connected to the electrode 6.

  A manufacturing process of the ultrasonic transducer and the ultrasonic probe according to this embodiment will be described. First, as shown in FIG. 7A, piezoelectric bodies 2a and 2b that are materials for forming a vibrator are prepared. For example, PZT is used as the piezoelectric bodies 2a and 2b. Next, as shown in FIG. 7B, a plurality of recesses and a plurality of projections are formed on the first surfaces of the piezoelectric bodies 2a and 2b by forming a plurality of grooves using a dicer or the like.

  As shown in FIG. 7C, the internal electrode 3a and the upper electrode 5 are integrally formed on the surface of the piezoelectric body 2a by a method such as plating, sputtering, or vapor deposition, and the internal surface is formed on the surface of the piezoelectric body 2b. The electrode 3b and the lower electrode 6 are integrally formed. As these electrodes, it is preferable to form a chromium / gold (Cr / Au) electrode in which the base adhesive layer is chromium (Cr) and the surface conductive layer is gold (Au). The thickness of the chromium / gold electrode is, for example, 300 nm. The upper electrode 5 and the lower electrode 6 may be formed in a later process.

  As shown in FIG. 7D, the filler 4 is filled in the first surfaces of the piezoelectric bodies 2a and 2b. As the filler 4, for example, Epochec 301-2FL manufactured by Epoxy Technology is used. Next, as shown in FIG. 7E, the piezoelectric body 2a and the piezoelectric body 2b are bonded together with the filler 4 interposed therebetween, and the filler 4 is cured while pressing the piezoelectric bodies 2a and 2b. Thereby, a laminated piezoelectric composite is formed. After the adhesive resin is cured, as shown in FIG. 7F, unnecessary portions on the side surfaces of the laminated piezoelectric composite are removed using a method such as cutting. At this time, the internal electrode 3a and the upper electrode 5 are separated, and the internal electrode 3b and the lower electrode 6 are separated.

  As shown in FIG. 8A, an insulating film 9 is formed at a location where the internal electrodes 3a and 3b on the right side surface of the laminated piezoelectric composite are exposed. This insulating film 9 is used to insulate the internal electrodes 3a and 3b from the side electrode 10b in a later step. Next, as shown in FIG. 8B, a side electrode 10a is formed on the left side surface of the multilayered piezoelectric composite by a method such as plating, sputtering, or vapor deposition, and the side surface is formed on the right side of the multilayered piezoelectric composite. The electrode 10b is formed. The side electrode 10a is connected to the internal electrodes 3a and 3b. The side electrode 10b is formed so as to bridge over the insulating film 9, is connected to the upper electrode 5 and the lower electrode 6, and is separated from the internal electrodes 3a and 3b by the insulating film 9. As these side electrodes, it is preferable to form chromium / gold (Cr / Au) electrodes in which the base adhesive layer is chromium (Cr) and the surface conductive layer is gold (Au). The thickness of the chromium / gold electrode is, for example, 300 nm.

  Next, as shown in FIG. 8C, the electrodes are removed at the upper left corner and the lower left corner of the laminated piezoelectric composite. Thereby, the upper electrode 5 and the lower electrode 6 are insulated from the side electrode 10a. The internal electrodes 3a and 3b are connected to the side electrode 10a and connected to the outside through the side electrode 10a. The upper electrode 5 and the lower electrode 6 are connected to the side electrode 10b and connected to the outside through the side electrode 10b. In this process, the piezoelectric vibrator 1 is completed.

  Next, as shown in FIG. 8D, the piezoelectric vibrator 1 is disposed on the backing material 11. On the piezoelectric vibrator 1, acoustic matching layers 12a and 12b and an acoustic lens 13 are provided. A ground lead paste 14 and a ground wire 15 are provided on the left side surface of the ultrasonic probe, and the internal electrodes 3 a and 3 b of the vibrator 1 are connected via the side electrode 10 a, the ground lead paste 14, and the ground wire 15. Connected to ground potential.

  On the right side surface of the ultrasonic probe, an extraction paste 16, an address extraction line 17, a solder 18, and an address extraction FPC (flexible circuit board) 19 are provided, and the upper electrode 5 and the lower electrode 6 are extracted. It is connected to the address lead FPC 19 via the paste 16, the address lead line 17, and the solder 18. The ground drawing paste 14 and the drawing paste 16 contain, for example, silver (Ag) as a main component. The address lead line 17 is made of, for example, copper (Cu). This process completes the assembly of the ultrasound probe.

Next, a third embodiment of the present invention will be described.
FIG. 9 is a cross-sectional view showing a laminated piezoelectric composite in an ultrasonic transducer according to the third embodiment of the present invention. In the third embodiment, the laminated piezoelectric composite is obtained by fitting the piezoelectric bodies 2a and 2b in which a plurality of concave portions having a trapezoidal side shape and a plurality of convex portions are formed with the filler 4 interposed therebetween. It is formed. By making the side surfaces of the piezoelectric bodies 2a and 2b trapezoidal, unnecessary vibrations generated at the corner portions of the plurality of concave portions and the plurality of convex portions are suppressed. Thus, the side surface shape of the plurality of concave portions and the plurality of convex portions formed on the first surface of the piezoelectric body is not limited to a rectangle.

Next, a fourth embodiment of the present invention will be described.
In the fourth embodiment, the shapes of the first surfaces of the piezoelectric bodies 2a and 2b facing each other are made different from each other. For example, FIG. 10A shows a piezoelectric body having a first surface constituted by concave portions formed in a lattice shape and convex portions surrounded by such concave portions, and FIG. ) Is a piezoelectric body having a first surface constituted by a plurality of concave portions formed in a groove shape long in one direction and a plurality of convex portions formed in a mountain shape sandwiched between the concave portions. Is shown. A laminated piezoelectric composite is formed by fitting the concave and convex portions of the piezoelectric body shown in FIG. 10 (a) with the convex and concave portions of the piezoelectric body shown in FIG. 10 (b).

  The plurality of concave portions and / or the plurality of convex portions formed on the first surfaces of the piezoelectric bodies 2a and 2b are not limited to a rectangular parallelepiped, and may be rounded at least at the corner portions. FIG. 11A shows a piezoelectric body in which a plurality of cylindrical convex portions arranged in a lattice shape are formed on the first surface, and FIG. 11B shows a corner portion arranged in a groove shape. 2 shows a piezoelectric body in which a plurality of concave portions having roundness are formed on the first surface. By imparting roundness to the corners of the recesses and / or protrusions, unwanted resonance in the lateral direction can be reduced.

Next, a fifth embodiment of the present invention will be described.
FIG. 12A is a cross-sectional view showing an example of an apodization structure of an ultrasonic transducer according to the fifth embodiment of the present invention in a cross section parallel to the XY plane (see FIG. 1). FIG. 12B is a cross-sectional view showing an example of an apodization structure of an ultrasonic transducer according to the fifth embodiment of the present invention in a cross section parallel to the XZ plane (see FIG. 1). In FIG. 12, electrodes are omitted for the sake of simplicity.

  Unnecessary vibration occurs at the end of the vibrator. In this embodiment, in order to reduce this unnecessary vibration, by adopting an apodization structure, the vibrator is configured so that the acoustic impedance and the sound pressure output gradually decrease as the end of the vibrator is approached. Has been. In other words, the apodization structure is realized by reducing the length of the convex portion of the piezoelectric body and increasing the length of the filler as it approaches the end of the vibrator. In addition, the apodization structure may be realized by reducing the electrode, reducing the amount of polarization of the piezoelectric body, or changing the pitch length.

  Next, a modification of the fifth embodiment of the present invention will be described. FIG. 13A is a cross-sectional view showing an example of an apodization structure of an ultrasonic transducer according to a modification of the fifth embodiment of the present invention in a cross section parallel to the XY plane (see FIG. 1). FIG. 13B is a diagram showing the relationship between the position in the longitudinal direction of the ultrasonic transducer according to the modification of the fifth embodiment of the present invention and the volume ratio of the piezoelectric body to the resin. In FIG. 13A, electrodes are omitted for the sake of simplicity.

In the vibrator according to the present embodiment, the volume ratio of the piezoelectric body is maximized at the center of the vibrator in the longitudinal direction of the vibrator (X-axis direction in FIG. 1), and the piezoelectric becomes closer to the end of the vibrator. By reducing the volume ratio of the body according to the Gaussian distribution, an apodization structure is realized. The Gaussian distribution f (x) is expressed by the following equation, where m is the average and σ is the standard deviation.
f (x) = 1 / sqrt (2π) σ × exp (− (x−m) ² / 2σ ² )
In this embodiment, the volume ratio of the piezoelectric body is determined by discretizing the Gaussian distribution f (x).

  FIG. 13B shows the distribution of the volume ratio of the piezoelectric body to the resin in each section by dividing the length in the longitudinal direction of the vibrator into 11 sections and dividing the section into a plurality of sections. PZT is used as the piezoelectric body. The distribution shown in FIG. 13B is a standard normal distribution. In this case, if the length of the vibrator in the elevation direction is 5.00 mm, the length of one section is about 0.45 mm. The ultrasonic transducer according to the present embodiment has a sound pressure distribution close to a Gaussian distribution (normal distribution) that becomes maximum at the center in the longitudinal direction of the transducer and decreases as it approaches the end when a uniform drive signal is applied. Have Thereby, it becomes possible to reduce a virtual image. In addition, artifacts due to side lobes can be reduced and contrast resolution can be improved.

  As described above, according to the embodiment of the present invention, by adopting 1-3 composite, high sensitivity and wide bandwidth of the piezoelectric vibrator are realized, and by stacking the vibrator, Impedance is lowered and the transmission efficiency of the detection signal is improved. In addition, since heat can be radiated to the housing by using the filler filled between the piezoelectric bodies, it is possible to reduce the temperature rise of the vibrator due to the increase in heat generated by stacking the vibrators.

  Although there are materials that are difficult to make a laminated piezoelectric body by simultaneous firing by the green sheet method or the like, according to an embodiment of the present invention, a laminated piezoelectric body is formed by laminating individual piezoelectric bodies. Can do. Further, in the ultrasonic transducer and the ultrasonic probe according to the embodiment of the present invention, initial reliability and temporal reliability are improved as compared with the conventional side surface insulation method. Furthermore, the method for manufacturing an ultrasonic transducer according to the embodiment of the present invention is simple and excellent in reproducibility as compared with the case of using an electrodeposition method, a printing method, and a dispensing method.

  The present invention can be used in an ultrasonic transducer array and an ultrasonic probe used for transmitting and receiving ultrasonic waves in an ultrasonic diagnostic apparatus.

1 is a perspective view showing an ultrasonic probe according to a first embodiment of the present invention. It is sectional drawing which shows the internal structure of the ultrasonic probe which concerns on the 1st Embodiment of this invention. It is sectional drawing for demonstrating notionally that the ultrasonic transducer which concerns on the 1st Embodiment of this invention comprises 1-3 composite. 1 is a cross-sectional view showing an ultrasonic transducer according to a first embodiment of the present invention. 1 is a cross-sectional view showing an ultrasonic transducer according to a first embodiment of the present invention. It is a figure which shows the impedance of the ultrasonic transducer which concerns on the 1st Embodiment of this invention. It is a figure which shows the change of the frequency dependence of the transmission / reception gain by the thickness of each part of a laminated piezoelectric material. It is a figure which shows the manufacturing process of the ultrasonic transducer and ultrasonic probe which concern on the 2nd Embodiment of this invention. It is a figure which shows the manufacturing process of the ultrasonic transducer and ultrasonic probe which concern on the 2nd Embodiment of this invention. It is sectional drawing which shows the laminated piezoelectric composite in the ultrasonic transducer which concerns on the 3rd Embodiment of this invention. It is sectional drawing which shows the piezoelectric material in the ultrasonic transducer which concerns on the 4th Embodiment of this invention. It is sectional drawing which shows the modification of the piezoelectric material in the ultrasonic transducer | vibrator which concerns on the 4th Embodiment of this invention. It is sectional drawing which shows the lamination | stacking composite piezoelectric material in the ultrasonic transducer | vibrator which concerns on the 5th Embodiment of this invention. It is a figure which shows the laminated piezoelectric composite in the ultrasonic transducer which concerns on the modification of the 5th Embodiment of this invention, and its structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vibrator 2a, 2b Piezoelectric body 3a, 3b Internal electrode 4 Filler 5 Upper electrode 6 Lower electrode 8 Vibrator array 9 Insulating film 10a, 10b Side electrode 11 Backing material 12a, 12b Acoustic matching layer 13 Acoustic lens 14 Ground extraction paste 15 Ground Line 16 Lead Paste 17 Address Lead Line 18 Solder 19 Address Lead FPC

Claims (9)

A first piezoelectric body having a plurality of concave portions and a plurality of convex portions formed on the first surface;
A second piezoelectric body having a plurality of concave portions and a plurality of convex portions formed on the first surface;
A first internal electrode formed along the plurality of concave portions and the plurality of convex portions of the first piezoelectric body;
A second internal electrode formed along the plurality of concave portions and the plurality of convex portions of the second piezoelectric body;
A first electrode formed on a second surface facing the first surface of the first piezoelectric body;
A second electrode formed on a second surface opposite to the first surface of the second piezoelectric body;
A filler having an acoustic impedance smaller than the acoustic impedance of the first and second piezoelectric bodies;
The length of the concave portions of the first and second piezoelectric bodies is greater than the length of the convex portions, and the filler is filled between the first internal electrode and the second internal electrode. As described above, the plurality of concave portions and the plurality of convex portions of the first piezoelectric body and the plurality of convex portions and the plurality of concave portions of the second piezoelectric body are fitted to each other with a predetermined interval, and a laminated piezoelectric An ultrasonic transducer in which a composite is formed. An insulating film formed on the first side surface of the multilayer piezoelectric composite from which the first and second internal electrodes are exposed, and covering the first and second internal electrodes;
A first side electrode formed on the first side surface of the multilayered piezoelectric composite, bridged on the insulating film and connected to the first electrode and the second electrode;
A second side electrode formed on the second side surface of the multilayer piezoelectric composite and connected to the first internal electrode and the second internal electrode;
The ultrasonic transducer according to claim 1, further comprising:   The filler is a resin material including at least one of epoxy resin, urethane resin, silicone resin, melamine resin, silver paste, polyimide, solder, glycerin, glass, organic glass, poly The ultrasonic transducer according to claim 1, comprising at least one of polystyrene, hard rubber, and soft rubber.   The ultrasonic transducer according to any one of claims 1 to 3, wherein a volume ratio of the piezoelectric body to the filler decreases from a central portion to an end portion in a longitudinal direction of the laminated piezoelectric composite.   The plurality of concave portions and / or the plurality of convex portions formed in the first piezoelectric body and / or the second piezoelectric body have curved surfaces at least at the corner portions. Ultrasonic transducer. A transducer array formed by arranging a plurality of ultrasonic transducers according to any one of claims 1 to 5,
A backing material provided on the back surface of the transducer array;
At least one acoustic matching layer provided in front of the transducer array;
An ultrasonic probe comprising: A method of manufacturing an ultrasound transducer for transmitting and / or receiving ultrasound comprising:
Forming a plurality of concave portions and a plurality of convex portions on the first surface of the first piezoelectric body, and forming a plurality of concave portions and a plurality of convex portions on the first surface of the second piezoelectric body; A step (a) of making the length of the concave portions of the first and second piezoelectric bodies larger than the length of the convex portions;
A first internal electrode is formed along the plurality of concave portions and the plurality of convex portions of the first piezoelectric body, and a second interior is formed along the plurality of concave portions and the plurality of convex portions of the second piezoelectric body. Forming an electrode (b);
Forming a first electrode on a second surface facing the first surface of the first piezoelectric body, and forming a first electrode on the second surface facing the first surface of the second piezoelectric body; A step (c) of forming an electrode of 2;
The first piezoelectric material is filled between the first internal electrode and the second internal electrode with a filler having an acoustic impedance smaller than that of the first and second piezoelectric bodies. A step (d) of fitting a plurality of recesses and a plurality of projections of the body with a plurality of projections and a plurality of recesses of the second piezoelectric body with a predetermined interval to form a laminated piezoelectric composite; When,
A method of manufacturing an ultrasonic transducer comprising:   The method of manufacturing an ultrasonic transducer according to claim 7, further comprising a step (e) of removing both ends of the laminated piezoelectric composite. Forming an insulating film covering the first and second internal electrodes on the first side surface of the multilayered piezoelectric composite from which the first and second internal electrodes are exposed; and
Forming a first side electrode connected to the first electrode and the second electrode by bridging the insulating film on the first side surface of the multilayer piezoelectric composite; Forming a second side electrode connected to the first internal electrode and the second internal electrode on the second side surface of the composite (g);
The method of manufacturing an ultrasonic transducer according to claim 8, further comprising:

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