JP2008244859A - Array type ultrasonic wave probe and ultrasonic diagnosis device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an array type ultrasonic wave probe with an acoustic matching layer having three or more layers, in contact with a piezoelectric device, and is superior in dicing workability with a low attenuation ratio, heat resistance, adhesion between upper and lower layers, and conductivity, and is composed of magnesium alloy having an adequate acoustic impedance. <P>SOLUTION: An array type ultrasonic wave probe has a backing, a plurality of channels respectively having a piezoelectric device and an acoustic matching layer having three or more layers formed on the piezoelectric device arranged on the backing, and an acoustic lens. The piezoelectric device is composed of a piezoelectric body and electrodes formed on a backing side and an acoustic matching layer side respectively of the piezoelectric body, and has an acoustic impedance of 25-40 MRayls at 25°C. The electrode on the acoustic matching layer side of the piezoelectric device has a thickness of 5 μm or less. In the acoustic matching layer having three or more layers, the acoustic impedance is gradually reduced for the acoustic lens, and the acoustic matching layer in contact with the electrode is composed of a magnesium alloy of Mg-Sn system or Mg-Cu system having an acoustic impedance of 11-19 MRayls at 25°C. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an array-type ultrasonic probe that transmits and receives an ultrasonic signal to and from a subject and the like and an ultrasonic diagnostic apparatus having the array-type ultrasonic probe.

  A medical ultrasonic diagnostic apparatus or ultrasonic image inspection apparatus transmits an ultrasonic signal to an object, receives a reflection signal (echo signal) from the object, and images the inside of the object It is. In this medical ultrasonic diagnostic apparatus and ultrasonic image inspection apparatus, an electronically operated array ultrasonic probe having an ultrasonic signal transmission / reception function is mainly used.

  The array-type ultrasonic probe has a structure including a backing, a plurality of channels that are bonded onto the backing and arranged in an array with a desired space, and an acoustic lens that is bonded onto the channels. . Each of the plurality of channels is formed on the backing, for example, a piezoelectric element having a structure in which electrodes are attached to both surfaces of a piezoelectric body made of a lead zirconate titanate (PZT) -based piezoelectric ceramic material or a relaxor-based single crystal material; And an acoustic matching layer formed on the piezoelectric element. In some cases, a groove is formed in the backing corresponding to the space of each channel.

  Conventionally, the acoustic matching layer has a one-layer structure, a two-layer structure, or a multilayer gradient structure having three or more layers. In particular, three or more acoustic matching layers have recently been suitably used to increase the bandwidth and increase the sensitivity (see Non-Patent Document 1). In addition, since a two-dimensional array type ultrasonic probe in which piezoelectric elements are arranged two-dimensionally can obtain a three-dimensional moving image, a one-dimensional array type ultrasonic probe in which piezoelectric elements are arranged in a one-dimensional form can be used. It is designed to be used instead.

  On the other hand, in a general manufacturing method of an ultrasonic probe, a piezoelectric element having electrodes formed on both sides of a piezoelectric material made of a piezoelectric material such as PZT is attached to a rubber plate as a backing, and an acoustic matching layer is further formed on the piezoelectric element. Are bonded to form a laminate. Subsequently, the laminated body is cut from the acoustic matching layer side with a dicer to a width of about 50 to 300 μm to form a plurality of channels. In the two-dimensional array type ultrasonic probe, the array is cut in the x and y directions with a dicer. By cross-cutting the acoustic matching layer, crosstalk between the channels is prevented. For this reason, it is important that the acoustic matching layer is diced with high workability. Subsequently, a relatively soft resin such as low acoustic impedance and high damping silicone rubber is filled in the dancing grooves between the channels to maintain the mechanical strength. Then, an ultrasonic probe is manufactured by adhering an acoustic lens on the acoustic matching layer of a plurality of channels.

  As the acoustic matching layer, a layer having a thickness of 1/4 of the frequency (λ) to be used is usually used. An acoustic matching layer made of a material having a speed of sound of about 5000 m / s is, for example, about 400 μm when the operating frequency is 3 MHz. Since the acoustic matching layer is used with substantially the same thickness as the piezoelectric element, the use of a material having a large attenuation factor reduces the ultrasonic signal. The desired attenuation factor is 20 dB / m / MHz or less, more preferably 2 dB / m / MHz or less.

  When such an array-type ultrasonic probe is applied to an ultrasonic diagnostic apparatus for medical use, the acoustic lens side is brought into contact with the subject at the time of diagnosis, and the piezoelectric element of each channel is driven from the front surface of the piezoelectric element. An ultrasonic signal is transmitted within the subject, that is, to the human body. This ultrasonic signal is focused at a required position in the subject by electronic focusing based on the driving timing of the piezoelectric element and focusing by the acoustic lens. At this time, an ultrasonic signal can be transmitted to a required range in the subject by controlling the drive timing of the piezoelectric element, and an ultrasonic image (tomographic image) of the required range can be received by receiving an echo signal from the subject. Image). In driving the piezoelectric element of the ultrasonic probe, an ultrasonic signal is also emitted to the back side of the piezoelectric element. For this reason, a backing is placed on the back side of the piezoelectric element of each channel, and the ultrasonic signal to the back side is absorbed (attenuated) by this backing, and the normal ultrasonic signal is an ultrasonic signal (reflected signal) from the back side. At the same time, the adverse effect of being transmitted into the subject is avoided.

  Further, when the array ultrasonic probe is driven, ultrasonic energy radiated from the piezoelectric elements of the plurality of channels is absorbed and attenuated by the acoustic matching layer and the acoustic lens. Since a part of the ultrasonic energy is converted into heat, for example, in the ultrasonic probe for a circulator, the temperature of the acoustic matching layer may be 60 ° C. or higher. Further, during use of the ultrasonic probe, a considerable pressure is always applied to the acoustic matching layer through the acoustic lens. Due to the difference in thermal expansion and mechanical pressure between the acoustic lens and the acoustic matching layer due to these thermal effects, the acoustic matching layer between the acoustic lens and the uppermost acoustic matching layer, and the acoustic matching layer below the uppermost acoustic matching layer Peeling may occur between the layers. As a result, the sensitivity in the ultrasonic probe varies and the reliability is lowered. In severe cases, the ultrasound probe stops functioning. These phenomena become a serious problem particularly in a two-dimensional array type ultrasonic probe having many connection points.

  Patent Documents 1 to 4 specifically illustrate characteristics and the like of an ultrasonic probe including an acoustic matching layer made of metal or the like. For example, Patent Documents 1 and 2 describe examples in which metal aluminum is used as the acoustic matching layer. Patent Document 3 describes an example in which a conductive adhesive, tin oxide, gold, or aluminum is used as the acoustic matching layer. However, these materials have a low attenuation factor required for an acoustic matching layer, characteristics such as dicing workability, heat resistance, adhesion to upper and lower layers, and appropriate for forming three to four acoustic matching layers. Not all acoustic impedances are met.

  Patent Document 4 discloses an ultrasonic probe using single crystal silicon as an acoustic matching layer. However, the acoustic impedance of silicon is 19.5 MRayls, which is too large compared with 35 MRalys which is the acoustic impedance of a normal PZT-based piezoelectric material. For this reason, it is not suitable for an ultrasonic probe having two to three acoustic matching layers that are practical. In addition, silicon has a defect that processability and conductivity are not sufficient.

  On the other hand, Patent Document 5 shows an example of a piezoelectric broadband transducer having an additional elastic layer having the same acoustic impedance as that of a piezoelectric material. In Patent Document 5, as an example, when a composite piezoelectric vibrator in which a bulk piezoelectric material having an acoustic impedance of 12 to 10 MRayls and a resin are combined is used, metallic magnesium having an acoustic impedance of 10 MRAlys as an additional layer and a matching layer. And the use of alloys. However, there is no disclosure of a specific composition of a magnesium alloy excellent in acoustic impedance, attenuation rate, and dicing processability.

  Conventionally, the acoustic matching layer may be made of a material in which the density is adjusted by adding tungsten powder or the like to an epoxy resin. Specifically, an acoustic matching layer made of a composite resin in which 30% by volume of tungsten is filled in an epoxy resin and having an acoustic impedance of 12 MRAlys is known. However, this composite resin not only has a large attenuation rate of 1000 dB / m / MHz or more, but is inferior in dicing workability.

  Non-Patent Document 1 shows an example in which glass is used as the material of the acoustic matching layer. Glass has an acoustic impedance of about 12 MRAlys, but since it is insulative, when channels are arranged in a two-dimensional array by dicing, it is difficult to route the electrodes on the upper side of the piezoelectric element to the outside by wiring.

Furthermore, the density, sound velocity, and acoustic impedance of each of substantially pure metallic magnesium, metallic aluminum, and metallic zinc are 1.74, 5800 m / s, 10 MRayls, 2.7, 6400 m / s, 17.4 MRayls, 7.6, respectively. 4200 m / s, 30 MRayls. However, these pure metals have extremely low processability by dicing or polishing. In particular, when these pure metals are applied to the acoustic matching layer in the production of a two-dimensional array type ultrasonic probe, it is difficult to process the fine area of 0.2 mm ² or less by polishing or dicing.
JP-A-56-143149 JP 58-053755 A JP 59-174099 A JP2003-125494A Published patent publication 2004-518319 (USP 6,645,150) T. Inoue et al., IEEE, UFFC, vol.34 No.1,1987, pp.8-15

  The present invention is a magnesium which is in contact with a piezoelectric element among three or more acoustic matching layers, has a low attenuation rate, is excellent in dicing workability, heat resistance, adhesiveness to upper and lower layers, and has conductivity, and has an appropriate acoustic impedance. An object of the present invention is to provide an array type ultrasonic probe having an acoustic matching layer made of an alloy.

  An object of the present invention is to provide an ultrasonic diagnostic apparatus including the array type ultrasonic probe.

According to the invention, a backing;
A plurality of channels arranged on the backing and having a piezoelectric element and three or more acoustic matching layers formed on the piezoelectric element; and formed to cover at least the surface of the uppermost acoustic matching layer of each channel. Acoustic lens;
Comprising
The piezoelectric element is composed of a piezoelectric body and electrodes formed on the backing side and the acoustic matching layer side of the piezoelectric body, and has an acoustic impedance of 25 to 40 MRayls at 25 ° C.,
The electrode on the acoustic matching layer side of the piezoelectric element has a thickness of 5 μm or less,
The three or more acoustic matching layers have an acoustic impedance that decreases stepwise toward the acoustic lens, and the acoustic matching layer that contacts the electrode has an acoustic impedance of 11 to 19 MRayls at 25 ° C. An array type ultrasonic probe is provided which is made of a Mg alloy or Mg—Cu magnesium alloy.

  According to the present invention, there is provided an ultrasonic diagnostic apparatus comprising the array-type ultrasonic probe having the above-described configuration and an ultrasonic probe controller connected to the ultrasonic probe through a cable.

  According to the present invention, out of three or more acoustic matching layers, the piezoelectric element is in contact with the piezoelectric element, has a low attenuation rate, is excellent in dicing workability, heat resistance, adhesion to upper and lower layers, and conductivity, and has an appropriate acoustic impedance. To provide a high-performance, high-reliability array-type ultrasonic probe that is equipped with an acoustic matching layer made of magnesium alloy and that can be connected to the wiring from the acoustic matching layer side, and is capable of widening the ultrasonic bandwidth. Can do. In particular, it is possible to provide a two-dimensional array ultrasonic probe for a medical ultrasonic diagnostic apparatus in which channels are two-dimensionally arranged.

  Further, according to the present invention, it is possible to provide an ultrasonic diagnostic apparatus in which crosstalk is small, a high-performance, high-reliability array type ultrasonic probe is incorporated, and image quality improvement and sensitivity improvement of a tomographic image are achieved. .

  Hereinafter, an array type ultrasonic probe and an ultrasonic diagnostic apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

  The array type ultrasonic probe according to the embodiment includes a backing. The plurality of channels are arranged on the backing. Each of these channels includes a piezoelectric element disposed on the backing and three or more acoustic matching layers formed on the piezoelectric element. The acoustic lens is formed so as to cover at least the uppermost acoustic matching layer surface of each channel.

  The piezoelectric element is composed of a piezoelectric body and electrodes formed on the backing side and the acoustic matching layer side of the piezoelectric body, respectively, and has an acoustic impedance of 25 to 40 MRayls at 25 ° C. The electrode on the acoustic matching layer side of the piezoelectric element has a thickness of 5 μm or less. The acoustic matching layers of three or more layers have an acoustic impedance that decreases stepwise toward the acoustic lens. The acoustic matching layer in contact with the piezoelectric element is composed of a Mg—Sn based or Mg—Cu based magnesium alloy having an acoustic impedance of 11 to 19 MRayls at 25 ° C.

  Examples of such an array-type ultrasonic probe include a structure in which channels are arranged in a one-dimensional direction and a structure in which channels are arranged in a two-dimensional direction. Hereinafter, a two-dimensional array type ultrasonic probe having three acoustic matching layers will be described in detail with reference to FIGS. 1 is a perspective view showing a two-dimensional array type ultrasonic probe according to the embodiment, FIG. 2 is a cross-sectional view of a main part of the two-dimensional array type ultrasonic probe of FIG. 1, and FIG. 3 is a two-dimensional array type ultrasonic probe of FIG. It is a principal part perspective view of a sound wave probe.

The two-dimensional array type ultrasonic probe 1 includes a backing 2. The piezoelectric element 3 is fixed on the backing 2 with, for example, an epoxy resin adhesive layer (not shown). As shown in FIGS. 2 and 3, the piezoelectric element 3 includes, for example, a lead zirconate titanate (PZT) -based piezoelectric ceramic material, a relaxor-based single crystal, a barium titanate-based ceramic, and a piezoelectric body 4 made of a single crystal. The first and second electrodes 5 ₁ and 5 ₂ are formed on both surfaces of the piezoelectric body 4. The piezoelectric body 4 may be a composite made of the piezoelectric material and an organic resin. The first acoustic matching layer 6 made of Mg-Sn-based or Mg-Cu alloy containing having an acoustic impedance of 11~19MRayls at 25 ° C. is on the second electrode 5 _{and second} piezoelectric elements 3, for example, an epoxy resin adhesive It is fixed with an agent layer (not shown). The second acoustic matching layer 7 made of a conductive material such as carbon having an acoustic impedance of 2.7 to 8 MRayls at 25 ° C. is, for example, an epoxy resin adhesive layer (not shown) on the first acoustic matching layer 6. ). The first and second acoustic matching layers 6 and 7 are two-dimensionally arranged with a space 8 formed by dicing, for example, as shown in FIGS. The piezoelectric element 3, the groove 9 which reaches the piezoelectric elements 4 are respectively formed, the second electrode 5 ₂ are also two-dimensionally separated in correspondence with the space 8. These spaces and grooves are allowed to be filled with a relatively soft resin such as low acoustic impedance, high damping silicone rubber. The flexible printed wiring board 21 is connected to the plurality of second acoustic matching layers 7 via the pads 22 of the wiring board 21 to form signal electrodes. That is, since the second acoustic matching layer 7 is made of a conductive material such as carbon, and the first acoustic matching layer 6 is made of a specific magnesium alloy, the pads 22 of the flexible printed wiring board 21 are two-dimensionally arranged. electrically conductive second is connected to the second electrode 5 ₂ and which are two-dimensionally separated through the first acoustic matching layer 7 and 6. The flexible printed wiring board 21 is formed, for example, on a film 23 made of, for example, polyimide or silicone epoxy resin that approximates the acoustic impedance of the second acoustic matching layer 24, and is formed on the film 23 corresponding to each second acoustic matching layer 7. A plurality of pads 22, one end connected to each pad 22 on the film 23, the other end extending to the periphery of the film 23, and each film 23 including each wire on the film 23. A solder resist film (not shown) is formed so that the pad 22 is exposed. The third acoustic matching layer 10 made of a material having an acoustic impedance of 1.8 to 2.5 MRayls at 25 ° C. (for example, silicone epoxy resin) is formed on the flexible printed wiring board 21 by, for example, an epoxy resin adhesive layer (not shown). )).

  The piezoelectric element 3, the plurality of first and second acoustic matching layers 6 and 7 and the third acoustic matching layer 10 that are two-dimensionally arranged constitute a plurality of channels 11. These channels 11 are provided on the piezoelectric element 3 having an acoustic impedance of 25 to 40 MRayls at 25 ° C., the first to third acoustic matching layers 6, 7, 10, that is, 25 ° C. A first acoustic matching layer 6 made of an Mg-Sn or Mg-Cu magnesium alloy having an acoustic impedance of 11 to 19 MRayls, and a conductive material such as carbon having an acoustic impedance of 2.7 to 8 MRayls at 25 ° C. A second acoustic matching layer 7 made of a material and a third acoustic matching layer 10 made of a material (for example, silicone epoxy resin) having an acoustic impedance of 1.8 to 2.5 MRayls are laminated.

In each channel 11, since the piezoelectric element 3 is a longitudinal wave vibration, the first electrode 5 ₁ and the common electrode (ground electrode), first from the flexible printed wiring board 21 is a signal electrode conductive individual channels 11 2, by applying a first of the second electrode 5 ₂ to the voltage two-dimensionally separated through the acoustic matching layer 7 and 6, be vibrated at a frequency corresponding to the piezoelectric element 3 of each channel 11 to the voltage Is possible.

  The acoustic lens 12 is fixed on the third acoustic matching layer 10 of each channel 11 by, for example, a rubber-based adhesive layer (not shown). The rubber-based adhesive is preferably a modified silicone-based adhesive having an acoustic impedance of 1.3 to 1.8 MRayls at 25 ° C.

The backing 2, the plurality of channels 11, and the acoustic lens 12 are housed in a case (housing) 13 having an opening at the upper end so that the backing 2 is placed on the support base 14. The case 13 includes a signal processing circuit (not shown) including a control circuit for controlling the driving timing of the piezoelectric element 3 of each channel 11 and an amplifier circuit for amplifying the received signal received by the piezoelectric element 3. Has been. The other end of the flexible printed wiring board 21 as the signal electrode is connected to a control circuit. Ground side printed wiring board (not shown) has one end connected to the first electrode 5 ₁ of the piezoelectric element 3 is connected to the other end signal processing circuitry. The cable 15 is inserted from the case 13 portion opposite to the acoustic lens 12, and the tip thereof is connected to a signal processing circuit and a control circuit (both not shown).

In the two-dimensional array type ultrasonic probe 1 having such a configuration, a voltage is applied between the _first and _second electrodes 5 ₁ and 5 ₂ of the piezoelectric element 3 in each channel 11 to resonate the piezoelectric body 4. Thus, the ultrasonic wave is radiated (transmitted) through the first to third acoustic matching layers 6, 7, 10 and the acoustic lens 12 of each channel 11. At the time of reception, the piezoelectric body 4 of the piezoelectric element 3 of each channel 11 is vibrated by ultrasonic waves received through the acoustic lens 12 and the first to third acoustic matching layers 6, 7, and 10 of each channel 11. Electrically converted into a signal to obtain an image.

The piezoelectric element 3 has an acoustic impedance of 25 to 40 MRayls at 25 ° C., and the electrode (second electrode 5 ₂ ) on the first acoustic matching layer 6 side has a thickness of 5 μm or less. When the thickness of the electrode (second electrode 5 ₂ ) exceeds 5 μm, not only the resonance frequency of the piezoelectric element changes, but also the first acoustic matching with the piezoelectric element 3 with the electrode (second electrode 5 ₂ ) as a boundary. There is a possibility that the reflection of the ultrasonic wave due to the difference in acoustic impedance between the layers 6 cannot be ignored. A more preferable thickness of the electrode (second electrode 5 ₂ ) is 2 μm or less.

  The first acoustic matching layer 6 is made of a Mg—Sn-based or Mg—Cu-based magnesium alloy, and has an acoustic impedance of 11 to 19 MRayls at 25 ° C.

  The magnesium alloy is represented by the following general formula (I), and preferably has a three-point bending strength of 150 MPa or more and an elongation at break of 2% or less.

Mg _x M1 _y M2 _z (I)
In the formula, M1 is Sn or Cu, M2 is at least one metal selected from the group consisting of Al, Zn, Sn, Cu, Ni, Mn, Si, Ti, Sb, Zr, Ca, Li, Y and rare earth elements. , X, y, z are x = 40 to 80% by weight, y = 20 to 60% by weight, and z = 0 to 5% by weight. The magnesium alloy is Mg _x Sn _y X _z (X is Ca, Y, Zr, Al, x, y, z is x = 40 to 80% by weight, y = 20 to 60% by weight, z = 0 to 5% by weight) %.) Is most preferable.

  When the amount of Mg in the magnesium alloy of the general formula (I) is less than 40% by weight, it is brittle and difficult to process, and the first sound is generated in the channel configuration having the acoustic impedance of the piezoelectric element and the three acoustic matching layers. It becomes difficult to obtain 11 to 19 MRayls which is the optimum acoustic impedance of the strong matching layer. On the other hand, when the amount of Mg in the magnesium alloy exceeds 80% by weight, not only does the attenuation rate increase, but there is a risk of ignition due to sharp oxidation of the cutting powder during dicing, and the surface is more likely to oxidize, resulting in corrosion resistance. May be inferior. A more preferable amount of Mg in the magnesium alloy is 45 to 65% by weight. A magnesium alloy containing Mg in such a range has not only a smaller attenuation factor required for the first acoustic matching layer but also excellent corrosion resistance, dicing characteristics, and long-term stability.

  If the amount of the M2 component in the magnesium alloy of the general formula (I) exceeds 5% by weight, the damping rate may increase or the workability may decrease, and the corrosion resistance may further decrease. A more preferable amount of the M2 component is 2% by weight or less.

  When the three-point bending strength of the magnesium alloy of the general formula (I) is less than 150 MPa, when forming a fine channel (for example, 50 μm square to 200 μm square) like a two-dimensional array ultrasonic probe, There is a risk that defects due to bending of one acoustic matching layer frequently occur. A more preferable three-point bending strength is 200 MPa or more.

  If the breaking elongation of the magnesium alloy of the general formula (I) exceeds 2%, the linearity of the diamond blade during dicing is impaired, and not only the defects with different areas for each channel frequently occur, but also damage during the dicing. There is a risk of frequent occurrence. A more preferable elongation at break is 0.5% or less.

  The magnesium alloy of the general formula (I) further has a damping rate of 0.3 dB / m / MHz or less at a measurement rate of 5 MHz, a longitudinal wave velocity of 4000 to 6000 m / s at 25 ° C., and a density of 2.0 to 3 .5 g / cm @ 3 is preferable.

  The magnesium alloy of the general formula (I) preferably has an average crystal grain size of 200 μm or less in order to improve dicing properties. If the average crystal grain size of the magnesium alloy exceeds 200 μm, the first acoustic matching layer made of the magnesium alloy may be frequently broken during dicing. A more preferable average grain size of the magnesium alloy is 100 μm or less.

  The first acoustic matching layer is allowed to have a metal layer selected from Ni, Au and Sn having a thickness of 1/100 or less of the thickness of the acoustic matching layer on the upper and lower surfaces.

  The first to third acoustic matching layers preferably have a thickness of λ / 5 to λ / 2 due to vibration of the piezoelectric element.

  In the two-dimensional array type ultrasonic probe according to the embodiment, the extraction of the electrodes is not limited to the structure shown in FIGS. For example, a piezoelectric element having first and second electrodes is separated and arranged in a two-dimensional space together with first and second acoustic matching layers thereon, and a groove reaching the backing corresponding to the space. The piezoelectric elements may be separated two-dimensionally, and through holes reaching the first electrode contacting the upper surface of the backing from the lower surface of the backing may be formed, and a flexible printed wiring board may be connected to each through hole. According to such a configuration, not only voltage control at the flexible printed wiring board connected to the second electrode separated two-dimensionally through the conductive first and second acoustic matching layers, but also two-dimensionally. It is possible to control the voltage with another flexible printed wiring board connected to the separated first electrode through a through hole. That is, it is possible to independently control the voltage of each channel having the piezoelectric element and the first to third acoustic matching layers.

  Next, a manufacturing method of the two-dimensional array type ultrasonic probe according to the above-described embodiment will be described.

  First, the piezoelectric element, the first acoustic matching layer, and the second acoustic matching layer described above are laminated on the backing in this order, for example, by interposing a low-viscosity epoxy resin adhesive between these members. Subsequently, the laminate is heated at, for example, 120 ° C. for about 1 hour to cure the epoxy resin adhesives, thereby backing and piezoelectric elements, piezoelectric elements and first acoustic matching layers, first acoustic matching layers and first acoustic matching layers. Two acoustic matching layers are bonded and fixed, respectively.

  Next, using a diamond blade, for example, a dicing process is performed to a depth of 50 to 200 μm square from the second acoustic matching layer to the piezoelectric body of the piezoelectric element to divide into a two-dimensional array. The flexible printed wiring board is aligned with the plurality of divided second acoustic matching layers, and the plurality of pads are connected to the second acoustic matching layers. If necessary, the spaces and grooves may be filled with a relatively soft resin such as low acoustic impedance, high damping silicone rubber. Next, a plurality of channels having a piezoelectric element, a plurality of first and second acoustic matching layers, and a third acoustic matching layer by bonding and fixing the third acoustic matching layer to the flexible printed wiring board with an epoxy resin adhesive. Form. Thereafter, the acoustic lens is bonded and fixed to the third acoustic matching layer with a silicone rubber-based adhesive layer, and the backing, the plurality of channels, and the acoustic lens are housed in the case to manufacture a two-dimensional array type ultrasonic probe.

  The array-type ultrasonic probe according to the embodiment has three or more acoustic matching layers, and may have a laminated structure of, for example, four acoustic matching layers in addition to the above-described three acoustic matching layers. In the case of four acoustic matching layers, the first acoustic matching layer in contact with the piezoelectric element is an Mg—Sn or Mg—Cu based magnesium alloy having an acoustic impedance of 12 to 19 MRayls at 25 ° C., two layers The acoustic matching layer of the eye is a magnesium alloy having an acoustic impedance of 7 to 12 MRayls at 25 ° C., and the third acoustic matching layer is in contact with a conductive material having an acoustic impedance of 3 to 5 MRayls at 25 ° C., the acoustic lens. The fourth acoustic matching layer is preferably composed of a material containing a resin having an acoustic impedance of 1.8 to 2.5 MRayls at 25 ° C. In such an ultrasonic probe, each acoustic matching layer preferably has a thickness of λ / 5 to λ / 2 due to vibration of the piezoelectric element.

  An ultrasonic diagnostic apparatus including the ultrasonic probe according to the embodiment will be described with reference to FIG.

  A medical ultrasonic diagnostic apparatus (or ultrasonic image inspection apparatus) that transmits an ultrasonic signal to an object, receives a reflection signal (echo signal) from the object, and images the object, An array type ultrasonic probe having a sound wave signal transmission / reception function is provided. This ultrasonic probe has, for example, the two-dimensional array structure shown in FIGS. The ultrasonic probe 1 is connected to an ultrasonic diagnostic apparatus main body 31 through a cable 15. In the ultrasonic diagnostic apparatus main body 31, an ultrasonic probe controller (not shown) that performs transmission and reception processing of ultrasonic signals of the ultrasonic probe, a display 32, and the like are provided.

  The array-type ultrasonic probe according to the embodiment described above includes a backing and a plurality of channels arranged on the backing, each having a piezoelectric element and three or more acoustic matching layers formed on the piezoelectric element. And an acoustic lens formed so as to cover at least the surface of the uppermost acoustic matching layer of each channel. The piezoelectric element includes a piezoelectric body and electrodes formed on the backing side and the acoustic matching layer side of the piezoelectric body, and has an acoustic impedance of 25 to 40 MRayls at 25 ° C., and the piezoelectric element The electrode on the acoustic matching layer side has a thickness of 5 μm or less. Three or more acoustic matching layers have an acoustic impedance gradually decreasing toward the acoustic lens, and the acoustic matching layer in contact with the piezoelectric element is an Mg-Sn system having an acoustic impedance of 11 to 19 MRayls at 25 ° C. Made of Mg-Cu based magnesium alloy. By adopting such a configuration, the following effects can be obtained.

  (1) The piezoelectric element has an acoustic impedance of 25 to 40 MRayls at 25 ° C., and the thickness of the electrode in contact with the acoustic matching layer is 5 μm, so that the piezoelectric element can be vibrated at a stable resonance frequency. Become. The acoustic matching layers of three or more layers gradually decrease in acoustic impedance toward the acoustic lens, and the acoustic matching layer in contact with the electrode has a low attenuation factor and the acoustic impedance of 11 to 19 MRayls appropriately matched with the piezoelectric element. Have As a result, ultrasonic waves generated by vibrating the piezoelectric element in each channel are transmitted from the acoustic lens through three or more acoustic matching layers including the first acoustic matching layer, and three or more acoustic matching layers from the acoustic lens. The ultrasonic energy loss can be reduced and the ultrasonic wave passing performance can be improved and the bandwidth can be increased while receiving through the piezoelectric element through the piezoelectric element. Therefore, it is possible to provide a high-performance array type ultrasonic probe capable of efficient transmission and reception. .

  In particular, in an ultrasonic probe having an acoustic matching layer having a three-layer structure, the first acoustic matching layer in contact with the piezoelectric element is a magnesium alloy having an acoustic impedance of 11 to 15 MRalys at 25 ° C., and the second acoustic layer. The matching layer has a conductive material having an acoustic impedance of 2.7 to 8 MRayls at 25 ° C., and the third acoustic matching layer in contact with the acoustic lens has an acoustic impedance of 1.8 to 2.5 MRayls at 25 ° C. By making the thickness of each acoustic matching layer to be λ / 5 to λ / 2 of the frequency due to vibration of the piezoelectric element, the energy loss of ultrasonic waves at the time of transmission and reception is more effective Therefore, it is possible to further improve the performance of passing ultrasonic waves and increase the bandwidth.

  Further, in the ultrasonic probe having the acoustic matching layer of the four-layer structure, the first acoustic matching layer in contact with the piezoelectric element is made of Mg—Sn or Mg—Cu having an acoustic impedance of 12 to 19 MRayls at 25 ° C. Magnesium alloy, magnesium alloy having a second acoustic matching layer having an acoustic impedance of 7 to 12 MRayls at 25 ° C, and conductive material having an acoustic impedance of 3 to 5 MRayls in a third acoustic matching layer at 25 ° C The material and the fourth acoustic matching layer in contact with the acoustic lens are each composed of a material containing a resin having an acoustic impedance of 1.8 to 2.5 MRayls at 25 ° C., and the thickness of each acoustic matching layer Is set to a thickness of λ / 5 to λ / 2 of the frequency due to vibration of the piezoelectric element, so that the energy loss of ultrasonic waves during transmission and reception Can be more effectively reduced, and the ultrasonic wave passing performance can be further improved and the bandwidth can be increased.

  Furthermore, in the structure in which the three or four acoustic matching layers are stacked, the first and second acoustic matching layers are made of a conductive material, so that the first and second acoustic matching layers are two-dimensionally formed by dicing, for example. If the electrodes that contact the first acoustic matching layer are also two-dimensionally separated by forming grooves that reach the piezoelectric body of the piezoelectric element below it, the second acoustic matching layer is It becomes possible to function as an electrode on the upper side. As a result, it is possible to easily realize a two-dimensional array type ultrasonic probe capable of easily connecting a flexible printed wiring board as a signal electrode to the second acoustic matching layer arranged two-dimensionally and routing it to the outside.

  (2) The acoustic matching layer in contact with the piezoelectric element is made of an Mg—Sn-based or Mg—Cu-based magnesium alloy and has excellent dicing workability, and thus has a desired width by, for example, dicing with a diamond saw. The channel can be precisely formed. As a result, since crosstalk between channels can be reduced, a high-resolution array ultrasonic probe can be realized.

  (3) The acoustic matching layer (first acoustic matching layer) in contact with the piezoelectric element has excellent heat resistance and is an epoxy adhesive layer interposed between the upper and lower layers (piezoelectric element and second acoustic matching layer). On the other hand, since it has high adhesiveness, peeling from the upper and lower layers can be prevented even when the acoustic matching layer is heated due to absorption and attenuation of ultrasonic energy and mechanical pressure is applied. As a result, it is possible to provide an array ultrasonic probe having high long-term reliability with uniform sensitivity between channels.

In particular, an acoustic matching layer made of a Mg—Sn-based or Mg—Cu-based magnesium alloy represented by the general formula Mg _x M1 _y M2 _z , having a three-point bending strength of 150 MPa or more and a breaking elongation of 2% or less, Since it has more stable dicing workability, it is possible to form a channel having a fine area of 0.03 mm ² or less by dicing with a diamond saw, for example, and it is possible to provide a much smaller array type ultrasonic probe.

Mg _x Sn _y X _z (X is Ca, Y, Zr, Al, x, y, z is x = 40 to 80% by weight, y = 20 to 60% by weight, z = 0 to 5% by weight) The acoustic matching layer made of a ternary Mg—Sn or Mg—Cu based magnesium alloy is capable of precise workability at 50 μm square or less by dicing, and has excellent plating characteristics and corrosion resistance. . In addition, the acoustic matching layer made of a magnesium alloy has a sound velocity as low as 5500 m / s or less and can be made thin, so that a lightweight array-type ultrasonic probe can be realized.

  The ultrasonic diagnostic apparatus according to the embodiment includes a high-performance, high-reliability array-type ultrasonic probe with low crosstalk, and thus can improve image quality and sensitivity of a tomographic image.

  In the following, embodiments of the present invention will be described in more detail.

Example 1
Magnesium and tin were weighed so that the constituent ratios were Mg = 78.25 wt% and Sn = 21.75 wt%. This was put into a vacuum melting furnace and mixed and stirred in an atmosphere of sulfur hexafluoride (SF ₆ ) gas at 600 to 800 ° C., and then the molten metal was molded into a 60 mm × 60 mm square ingot and cooled. A test piece having a width of 30 mm, a length of 30 mm, and a thickness of 1.0 mm was processed from the obtained ingot using a normal electric discharge machine to produce a first acoustic matching layer material.

(Example 2)
Magnesium and tin were weighed so that the constituent ratios were Mg = 43.33 Wt% and Sn = 56.67 wt%. This was put into a vacuum melting furnace, mixed and stirred and dissolved in an atmosphere of sulfur hexafluoride (SF ₆ ) gas at 600 to 800 ° C., and the molten water was molded into a 60 mm × 60 mm square ingot and cooled. A test piece having a width of 30 mm, a length of 30 mm, and a thickness of 1.0 mm was processed from the obtained ingot using a normal electric discharge machine to produce a first acoustic matching layer material.

(Example 3-11)
Magnesium, tin, copper, calcium, aluminum, yttrium, zirconium, manganese and zinc were weighed as shown in Table 1 below. These were put into a vacuum melting furnace, mixed and dissolved in an atmosphere of sulfur hexafluoride (SF ₆ ) gas at 600 to 1000 ° C., and the molten metal was molded into nine ingots of 60 mm × 60 mm square and cooled. A test piece having a width of 30 mm, a length of 30 mm, and a thickness of 1.0 mm was processed from each of the obtained ingots using an ordinary electric discharge machine to produce a first acoustic matching layer material.

(Comparative Examples 1-5)
Aluminum, magnesium and zinc were weighed as shown in Table 1 below. These were put into a vacuum melting furnace, mixed and stirred and melted in an atmosphere of sulfur hexafluoride (SF ₆ ) gas at 600 to 1000 ° C., and the molten metal was molded into 5 types of 60 mm × 60 mm square ingots and cooled. A test piece having a width of 30 mm, a length of 30 mm, and a thickness of 1.0 mm was processed from each of the obtained ingots using an ordinary electric discharge machine to produce a first acoustic matching layer material.

  The first acoustic matching layer material of Examples 1-11 and Comparative Examples 1-5, the first acoustic matching layer material (Comparative Example 6) made of a composite epoxy resin containing 30% by volume of tungsten, and silicate glass The material for the first acoustic matching layer (Comparative Example 7) was evaluated for density, sound speed, acoustic impedance (z), attenuation rate, and workability by the following methods.

1) Density Density was determined using a characteristic evaluation sample having a width of 30 mm, a length of 30 mm, and a thickness of 1.0 mm obtained by polishing the first acoustic matching layer material. The density was measured by measuring the weight of a sample at 25 ° C. in the air and in water and using the Archimedes method.

2) Sound velocity and attenuation rate 30 mm in width, 30 mm in length, 1.0 mm in thickness, 50 mm square, and 80 mm in length obtained by polishing the first acoustic matching layer material were used as samples.

  The acoustic characteristics were performed using a measurement probe of 5 MHz at 25 ° C. The speed of sound was measured using a sample having a width of 30 mm, a length of 30 mm, and a thickness of 1.0 mm, and the sound speed was determined from the time difference of the reflected echo depending on the presence or absence of the sample in water and the sample thickness. The speed of sound (C) was calculated using the following formula using the time difference between the transmission waveforms of water and the sample on the basis of the sound speed of water at each temperature.

C = C ₀ / [L−C ₀ (Δt / d)]
Here, C ₀ is the speed of sound of water, d is the thickness of the sample, and Δt is the time difference between the zero cross points after passing the first peak of the transmission waveform of water and the sample.

  The attenuation factor was measured in air using a 5 MHz probe at 25 ° C. in accordance with JIS Z 2354-2005 “Method for measuring ultrasonic attenuation factor of solid by ultrasonic pulse half oblique”. The sample used was a 50 mm square and a length of 80 mm. Both ends are polished to a surface roughness of 25S, a small amount of glycerin aqueous solution is applied to the top surface, a 5MHz probe is placed, the reflection from the bottom surface is measured, and the intensity difference of the reflected echo and the sample thickness are measured. The attenuation rate was obtained by this method.

3) Acoustic impedance (z)
z was determined as the product of density and sound velocity measured at room temperature of 25 ° C.

4) Elongation at break The elongation at break was measured according to JIS Z2241. The size of the sample was measured using an Instron apparatus using specified dimensions of length 50 mm, width 10 mm, and thickness 2.0 mm.

5) Three-point bending strength A 3 mm square, 30 mm long square bar obtained by polishing the first acoustic matching layer material was used as a sample, and a bending test was performed at n = 5 using an Instron testing machine. The bending strength was determined by a predetermined method defined in JIS-R1601.

6) Workability A width of 30 mm, a length of 30 mm, and a thickness of 1.0 mm obtained by polishing the first acoustic matching layer material were cut using a diamond blade with a thickness of 50 μm. 5 pitches of 250 μm, 200 μm, 150 μm, and 100 μm, and a depth of 400 μm, and further rotated 90 degrees, and again with the same pitch of 250 μm, 200 μm, 150 μm, and 100 μm, the depth is A cut was made so as to be 400 μm. This processing is called a cross dicing test.

  The remaining part (200 μm × 200 μm square to 50 μm × 50 μm square) after cutting by the above test was observed with a microscope. In this observation, the workability confirmed from the fall of the workability evaluation sample (first acoustic matching layer) and the linearity was evaluated. Samples with inferior processability were cut five times in one direction and the remaining part was evaluated.

Judgment of workability
・ When there is no problem with the remaining 50 μm square processing: 10,
・ When there is no problem with the remaining 100 μm square processing: 9,
・ When there is no problem with the remaining 150 μm square processing: 8,
・ When there is no problem with the remaining 200 μm square processing: 7,
・ When there is no problem in processing the remaining 50 μm × 30 mm strip: 6,
When there is no problem in processing the remaining 100 μm × 30 mm strip: 5,
When there is no problem in processing the remaining 150 μm × 30 mm strip: 4,
・ When there is no problem in processing the remaining 200 μm × 30 mm strip: 3,
・ When the remaining 500 μm × 30 mm can be grooved: 2
・ When grooving to the remaining 500 μm × 30 mm is not possible: 1
10 stages.

These results are shown in Table 2 below.

  As apparent from Table 1 and Table 2, the first acoustic matching layers (acoustic matching layers in contact with the electrodes of the piezoelectric element) of Examples 1 to 13 made of a magnesium alloy having a specific composition have an acoustic impedance (z) of the piezoelectric element. It can be seen that despite having the appropriate 11-19 MRayls in relation to the above, it has a low attenuation factor and excellent workability.

  On the other hand, the first acoustic matching layers of Comparative Examples 1 to 7 may not satisfy all of these characteristics such as a large attenuation rate, poor workability, or no electrical conductivity. Recognize.

  The array type ultrasonic probe having the first acoustic matching layer of Examples 1 to 11 can effectively transmit and receive ultrasonic energy, has uniform sensitivity between channels, and has crosstalk between channels. It can be reduced and has high resolution and long-term reliability.

(Example 12)
A PZT piezoelectric body, a piezoelectric element having a thickness of 0.4 mm with Ni electrodes formed on both sides thereof, a Mg alloy plate (first acoustic matching layer) of Example 3 having a thickness of 0.4 mm, and a thickness of 0.2 mm A strip vibrator was produced by cutting three laminated vibrators composed of a carbon plate (second acoustic matching layer) with a width of 0.15 mm, a height of 1.0 mm, and a length of 10 mm.

  The impedance and phase characteristics with respect to the frequency of the obtained strip resonator were examined. The result is shown in FIG. As is clear from FIG. 5, peaks due to the first acoustic matching layer and the second acoustic matching layer are clearly observed at the positions indicated by arrows A and B, and the first acoustic matching layer made of this Mg alloy has good acoustic characteristics. You can see that

(Example 13)
A first acoustic material made of a Mg—Sn—Ca alloy of Example 3 having a piezoelectric element with a thickness of 400 μm, a thickness of 420 μm, and z of 13.9 MRayls on a backing obtained by adding ferrite to chloroprene rubber having an acoustic impedance (z) of 4 MRayls. A matching layer, a carbon plate having a thickness of 200 μm and z of 5.2 MRayls (second acoustic matching layer), a silicone epoxy resin layer having a thickness of z of 2.1 MRayls and a thickness of 180 μm (third acoustic matching layer) in this order, And after interposing an epoxy resin adhesive between them, they were cured by heating at 120 ° C. for about 1 hour while being pressurized and adhered to each other. The piezoelectric element has first and second electrodes made of Ni / Au (thickness 0.1 μm / 0.2 μm) on both sides. The first to third acoustic matching layers were formed by forming a metal layer made of Ni / Au (thickness 0.1 μm / 0.2 μm) on each side. The ground electrode and the signal electrode were constructed by attaching a well-known wrap-around electrode around the piezoelectric element and attaching a flexible printed wiring board to the lower part thereof.

  Next, dicing was performed from the third acoustic matching layer toward the backing with a diamond blade having a width of 50 μm so that the width was 200 μm and the depth of cut into the backing was 200 μm. This dicing made 200 μm one channel, and a total of 64 channels were formed. Subsequently, liquid silicone rubber was filled in the space between the channels and cured at 125 ° C. for 1 hour. On each channel, an acoustic lens made of silicone rubber and having a z of 1.5 MRayls was fixed with a modified silicone rubber adhesive. Finally, a backing, a plurality of channels and an acoustic lens are housed in a case (housing), and a control circuit for controlling the driving timing of the piezoelectric element of each channel and a received signal received by the piezoelectric element are stored in the case. A one-dimensional array type ultrasonic probe of 3.5 MHz was assembled by incorporating a signal processing circuit including an amplifier circuit for amplification.

(Example 14)
A piezoelectric element having a thickness of 500 μm on a backing obtained by adding ferrite to chloroprene rubber having an acoustic impedance (z) of 4 MRayls, a Mg—Sn—Ca alloy shown in Example 3 having a thickness of 420 μm and z of 13.9 MRayls After stacking the first acoustic matching layer, carbon plate having a thickness of 200 μm and z of 5.2 MRayls (second acoustic matching layer) in this order and interposing an epoxy resin adhesive therebetween, at 120 ° C. They were heat-cured under pressure for about 1 hour and adhered to each other. The piezoelectric element has first and second electrodes made of Ni / Au (thickness 0.1 μm / 0.2 μm) on both sides. The first and second acoustic matching layers were formed by forming a metal layer made of Ni / Au (thickness 0.1 μm / 0.2 μm) on both surfaces. The ground electrode was configured by connecting a flexible printed wiring board to the lower electrode (first electrode) of the piezoelectric element.

  Next, dicing was performed from the second acoustic matching layer toward the piezoelectric element by a diamond blade having a width of 30 μm so that the width was 200 μm and the depth of cut into the piezoelectric element was 300 μm. Further, the two-dimensional array of 64 × 64 = 3900 channels was formed by this dicing. Subsequently, liquid silicone rubber was filled in the space between each channel and cured at 125 ° C. for 1 hour. Next, a flexible printed wiring board is prepared by forming a plurality of wirings and pads connected to these wirings on a silicone epoxy resin film having an acoustic impedance of 2.0 MRayls and a thickness of 180 μm. A signal electrode was formed on each second acoustic matching layer separated in a plurality of dimensions by being aligned and attached so that each pad was connected to each acoustic matching layer. After a silicone epoxy resin layer (third acoustic matching layer) having a thickness of 2.1 μMayls and a thickness of 180 μm is laminated on the flexible printed wiring board with an epoxy resin adhesive interposed therebetween, it is heated at 120 ° C. for about 1 hour. It was heat-cured with pressure and adhered to each other. A resinous acoustic lens having z of 1.55 MRayls was fixed on the third acoustic matching layer with a modified silicone rubber adhesive. Finally, a backing, a plurality of channels and an acoustic lens are housed in a case (housing), and a control circuit for controlling the driving timing of the piezoelectric element of each channel and a received signal received by the piezoelectric element are stored in the case. A 3 MHz two-dimensional array type ultrasonic probe was assembled by incorporating a signal processing circuit including an amplifier circuit for amplification.

  When the obtained array-type ultrasonic probe of Examples 13 and 14 was connected to an image diagnostic apparatus and its characteristics were evaluated, a better image was obtained as compared with the conventional product.

  Furthermore, the array type ultrasonic probes of Examples 13 and 14 were put in a heat cycle tester at −10 ° C. and 85 ° C., and images were confirmed before and after the 100 cycle test. However, there was no reduction in channel failure or reduction in image quality.

A perspective view showing a two-dimensional array type ultrasonic probe concerning an embodiment. FIG. 2 is a cross-sectional view of a main part of the two-dimensional array type ultrasonic probe of FIG. 1. The principal part perspective view of the two-dimensional array type ultrasonic probe of FIG. 1 is a schematic diagram showing an ultrasonic diagnostic apparatus according to an embodiment. The figure which shows the characteristic of the impedance with respect to the frequency of the strip vibrator of Example 12, and a phase.

Explanation of symbols

1 ... dimension array type ultrasonic probe, 2 ... backing, 3 ... piezoelectric elements, 5 _1, 5 ₂ ... electrode, 6 ... first acoustic matching layer, 7 ... second acoustic matching layer, 10 ... third acoustic matching layer, DESCRIPTION OF SYMBOLS 11 ... Channel, 12 ... Acoustic lens, 13 ... Case (housing), 15 ... Cable, 21 ... Flexible printed wiring board, 31 ... Ultrasonic diagnostic apparatus main body.

Claims (10)

backing;
A plurality of channels arranged on the backing and having a piezoelectric element and three or more acoustic matching layers formed on the piezoelectric element; and formed to cover at least the surface of the uppermost acoustic matching layer of each channel. Acoustic lens;
Comprising
The piezoelectric element is composed of a piezoelectric body and electrodes formed on the backing side and the acoustic matching layer side of the piezoelectric body, and has an acoustic impedance of 25 to 40 MRayls at 25 ° C.,
The electrode on the acoustic matching layer side of the piezoelectric element has a thickness of 5 μm or less,
The three or more acoustic matching layers have an acoustic impedance that decreases stepwise toward the acoustic lens, and the acoustic matching layer that contacts the electrode has an acoustic impedance of 11 to 19 MRayls at 25 ° C. An array-type ultrasonic probe comprising an Mg-based or Mg—Cu-based magnesium alloy. The array-type ultrasonic probe according to claim 1, wherein the magnesium alloy is represented by the following general formula (I), and has a three-point bending strength of 150 MPa or more and an elongation at break of 2% or less.
Mg _x M1 _y M2 _z (I)
In the formula, M1 is Sn or Cu, M2 is at least one metal selected from the group consisting of Al, Zn, Sn, Cu, Ni, Mn, Si, Ti, Sb, Zr, Ca, Li, Y and rare earth elements. , X, y, z are x = 40 to 80% by weight, y = 20 to 60% by weight, and z = 0 to 5% by weight.   The array type ultrasonic probe according to claim 1, wherein the magnesium alloy has an average crystal grain size of 200 μm or less.   The array type ultrasonic probe according to claim 1, wherein the acoustic matching layer made of the magnesium alloy has a longitudinal wave velocity of 4000 to 6000 m / s at 25 ° C. and a density of 2.0 to 3.5. .   2. The acoustic matching layer made of a magnesium alloy has a metal layer selected from Ni, Au and Sn having a thickness of 1/100 or less of the thickness of the acoustic matching layer on the upper and lower surfaces. The array type ultrasonic probe as described.   The acoustic matching layer has a three-layer structure, and the first acoustic matching layer in contact with the piezoelectric element is an Mg—Sn based or Mg—Cu based acoustic impedance of 11 to 15 MRayls at 25 ° C. Magnesium alloy, the second acoustic matching layer is a conductive material having an acoustic impedance of 2.7-8 MRayls at 25 ° C., and the third acoustic matching layer in contact with the acoustic lens is 1.8- 2. A material having an acoustic impedance of 2.5 MRayls, and each acoustic matching layer has a thickness of λ / 5 to λ / 2 of a frequency caused by vibration of the piezoelectric element. The array type ultrasonic probe as described.   The acoustic matching layer has a laminated structure of four layers, and the first acoustic matching layer in contact with the piezoelectric element is made of Mg—Sn or Mg—Cu having an acoustic impedance of 12 to 19 MRayls at 25 ° C. Magnesium alloy, the second acoustic matching layer is a magnesium alloy having an acoustic impedance of 7 to 12 MRayls at 25 ° C., and the third acoustic matching layer is a conductive material having an acoustic impedance of 3 to 5 MRayls at 25 ° C., The fourth acoustic matching layer in contact with the acoustic lens is made of a material including a resin having an acoustic impedance of 1.8 to 2.5 MRayls at 25 ° C., and each acoustic matching layer is formed of the piezoelectric element. 2. The array type ultrasonic probe according to claim 1, having a thickness of [lambda] / 5 to [lambda] / 2 of a frequency caused by vibration.   The array type ultrasonic probe according to claim 1, wherein the channels are arranged two-dimensionally.   The piezoelectric body of the piezoelectric element is composed of at least one material selected from the group consisting of lead zirconate titanate ceramic materials, relaxor single crystals and barium titanate ceramics, and single crystals. 2. The array-type ultrasonic probe according to 1.   An ultrasonic diagnostic apparatus comprising: the array-type ultrasonic probe according to claim 1; and an ultrasonic probe controller connected to the ultrasonic probe through a cable.

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