JP2008272438A - Ultrasonic probe and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic probe which realizes a high degree of sensitivity and a wide area while miniaturizing vibrators and considers also measures against heat generation. <P>SOLUTION: The ultrasonic probe is provided with: a packing material; a vibrator array as a laminated structure in which a plurality of vibrators arranged in a first direction form a group of vibrators and a plurality of vibrators are arranged in a second direction different from the first direction; a first layer of a conductive resin for electrically interconnecting first electrode layers of adjacent vibrators in each group of vibrators; a second layer of a conductive resin for electrically interconnecting internal electrodes of adjacent vibrators in each group of vibrators; and insulating resins arranged in prescribed areas between a plurality of vibrators in each group of vibrators. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ultrasonic probe used for transmitting and receiving ultrasonic waves in an ultrasonic diagnostic apparatus, and further relates to a method for manufacturing such an ultrasonic probe.

  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 an elastic wave is 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 about 1/8 to 1/10 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.

  As a related technique, the following Patent Document 1 discloses an ultrasonic probe using a highly reliable and low-cost composite piezoelectric body having a fine structure. In this composite piezoelectric material, a plurality of composite sheets in which a plurality of fine wire-like sintered piezoelectric elements are arranged in a fixed direction on the surface of the resin layer are arranged so that each fine wire-like sintered piezoelectric material is between the resin layers. They are laminated and integrated, and are cut in a direction perpendicular to the length direction of the fine-line sintered piezoelectric body.

  Further, Patent Document 2 below discloses a method for manufacturing a composite piezoelectric body corresponding to ultrasonic vibration in a high frequency band. In this manufacturing method, a composite piezoelectric body is formed by forming a unit composite sheet and laminating it. The manufacturing method of the unit composite sheet includes a step of preparing a composite plate in which a resin layer is formed on one surface of a plate-like piezoelectric body, and without completely dividing the resin layer with respect to the plate-like piezoelectric body of the composite plate. Forming a plurality of fine wire-like piezoelectric bodies from the plate-like piezoelectric body by forming a plurality of grooves.

  Further, in Patent Document 3 below, a composite piezoelectric body that has a plurality of fine columnar piezoelectric bodies having a high aspect ratio and has a low electrical impedance can be provided at low cost without degrading performance. A method is disclosed. This manufacturing method includes a step of preparing a composite plate in which a plurality of piezoelectric bodies extending in one direction and a plurality of conductors are alternately arranged on a resin layer, and the length of the piezoelectric body relative to the plate-like piezoelectric body of the composite plate. Forming a plurality of columnar piezoelectric bodies and a plurality of internal conductors extending across the plurality of columnar piezoelectric bodies on the resin layer by forming a plurality of grooves extending in a direction intersecting with the direction. .

  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. For example, the size in the elevation direction of a convex array transducer for FNA (fine needle aspiration) is about 4 mm to 5 mm.

  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 at the time of reception decreases in synergy with the reduction in size of the vibrator.

In order to compensate for such a decrease in sensitivity, it is also practiced to reduce the electrical impedance by increasing the capacitance of the vibrator by connecting the vibrators in each layer in parallel with a laminated structure.
Japanese Patent Laying-Open No. 2003-70096 (page 1-2, FIG. 6) Japanese Patent Laying-Open No. 2003-174698 (page 1-2, FIG. 5) JP 2003-189395 A (page 1-2, FIG. 7)

  Therefore, in view of the above points, an object of the present invention is to provide an ultrasonic probe that realizes high sensitivity and a wide band while miniaturizing a vibrator and also considers heat generation countermeasures.

  In order to solve the above-described problem, an ultrasonic probe according to one aspect of the present invention is an ultrasonic probe including a plurality of transducers for transmitting and / or receiving ultrasonic waves, wherein (i ) A backing material, and (ii) a plurality of vibrators arranged in the first direction constitute a vibrator group, and the plurality of vibrator groups are arranged in a second direction different from the first direction. Each of the transducers is common to the first electrode layer formed on the main surface of the backing material, the plurality of piezoelectric layers, at least one internal electrode layer, and each transducer group. A transducer array having a laminated structure including a second electrode layer; and (iii) a first layer of conductive resin that electrically connects the first electrode layers of adjacent transducers in each transducer group; (Iv) Conductivity of the second layer that electrically connects internal electrode layers of adjacent vibrators in each vibrator group And (v) an insulating resin disposed in a predetermined region between a plurality of vibrators in each vibrator group.

  Also, an ultrasonic probe manufacturing method according to one aspect of the present invention is an ultrasonic probe manufacturing method including a plurality of transducers for transmitting and / or receiving ultrasonic waves. (A) forming a laminated structure including a first electrode layer, a plurality of piezoelectric layers, at least one internal electrode layer, and a second electrode layer on the main surface of the material; Forming a plurality of grooves reaching the backing material on the main surface of the body to separate the laminated structure into a plurality of vibrators arranged in the first direction; and forming in the step (b) A step (c) of filling the plurality of grooves with the conductive resin, a step (d) of removing a part of the conductive resin filled in the step (c), and a removal of the conductive resin in the step (d). Filling the plurality of grooves with insulating resin (e) and filling in the step (e) The step (f) of removing a part of the insulating resin and the steps (c) to (f) are repeated as necessary to electrically connect the first electrode layers of the adjacent vibrators to each other. Forms one layer of conductive resin, second layer of conductive resin that electrically connects internal electrode layers of adjacent vibrators, and insulating resin disposed in a predetermined region between the vibrators Step (g), forming a common electrode layer on the main surface of the laminated structure (h), forming at least one acoustic matching layer on the common electrode layer (i), and a laminated structure By forming a plurality of grooves reaching the backing material in the first direction on the main surface of the body, each vibrator is separated into a plurality of vibrators arranged in a second direction different from the first direction. Step (j).

  According to the present invention, a high-sensitivity and wide-band ultrasonic probe is obtained by improving the electromechanical coupling coefficient and reducing the acoustic impedance by making the vibrator 1-3 composite, and by reducing the electric impedance by stacking the vibrator. A tentacle can be realized.

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 plan view schematically showing an ultrasonic transducer array (vibrator array) used in the ultrasonic probe according to the first embodiment of the present invention. 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 included. In FIG. 1, the upper electrode layers of the vibrators 1 and the insulating resin between the vibrators 1 are omitted in order to show the arrangement of the vibrators 1. In the plurality of vibrators 1, in particular, the leftmost vibrator in the figure is 1a, and the rightmost vibrator in the figure is 1b.

  As shown in FIG. 1, the plurality of vibrators 1 are arranged two-dimensionally, but the electrodes of one row of vibrators 1 arranged in the X-axis direction (elevation direction) are made of conductive resin 2. Since they are connected in parallel, one row of transducers 1 constitutes one transducer group 10 that operates simultaneously. Therefore, a plurality of transducer groups 10 arranged in the Y-axis direction (azimuth direction) constitute a one-dimensional transducer array. In this way, by dividing the vibrator in the X-axis direction, the piezoelectric body included in each vibrator has a 1-3 composite shape, so the vibrator is not divided in the X-axis direction. Compared to the case, the electromechanical coupling coefficient can be increased.

  FIG. 2 is a front view showing the internal structure of the ultrasonic probe according to the first embodiment of the present invention. As shown in FIG. 2, a vibrator group 10 including a single row of vibrators 1 is formed on the backing material 3. Each vibrator 1 has a laminated structure, and a plurality of layers of conductive resins 2a to 2c are arranged to connect electrodes of two vibrators adjacent in the X-axis direction in parallel. The backing material 3 is formed of a material having a large acoustic attenuation, such as an epoxy resin containing ferrite powder, metal powder or PZT powder, or rubber containing ferrite powder, and is not generated from the plurality of vibrators 1. Speeds up the attenuation of ultrasound. Further, in a region where the conductive resins 2a to 2c are not present between or around the plurality of vibrators 1, the vibration between the vibrators is reduced and the vibrators are longitudinally controlled by suppressing the vibrations in the horizontal direction of the vibrators. Insulating resin 4 is arranged to vibrate only.

  On the plurality of transducers 1, at least one acoustic matching layer (two acoustic matching layers 5 and 6 are shown in FIG. 2) is formed. Moreover, you may make it form the acoustic lens 7 on an acoustic matching layer as needed. The acoustic matching layers 5 and 6 are made of, for example, Pyrex (registered trademark) glass that easily propagates ultrasonic waves, an epoxy resin containing metal powder, or the like, and an acoustic impedance between a subject such as a living body and the vibrator 1. Improve matching. Thereby, the ultrasonic wave transmitted from the transducer 1 propagates efficiently into the subject. The acoustic lens 7 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 5 and 6 at a predetermined depth in the subject. These portions 1 to 7 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 body via a cable.

  FIG. 3 is an enlarged perspective view showing the laminated structure of the vibrators. (A) shows the leftmost vibrator 1a in the vibrator group 10 shown in FIG. The rightmost vibrator 1b in the figure in the vibrator group shown in FIG. 2 is shown. Each vibrator has a lower electrode layer 11, a plurality of piezoelectric layers 12, at least one internal electrode layer, and an upper electrode layer 14 that is normally connected in common to a ground potential.

  Desirably, the internal electrode layer includes at least one first internal electrode layer and at least one second internal electrode layer alternately formed with the piezoelectric layer interposed therebetween. FIG. 3 shows a first internal electrode layer 13a and a second internal electrode layer 13b formed with the piezoelectric layer 12 interposed therebetween. Here, the lower electrode layer 11, the lowermost piezoelectric layer 12 and the internal electrode layer 13a constitute a first piezoelectric element, and the internal electrode layer 13a, the intermediate piezoelectric layer 12 and the internal electrode layer 13b. A second piezoelectric element is configured, and the third piezoelectric element is configured by the internal electrode layer 13b, the uppermost piezoelectric layer 12, and the upper electrode layer.

  Furthermore, the vibrator 1a at the left end in the figure has a side insulating film 15a and a side electrode 16a. The side electrode 16a is connected to the internal electrode layer 13a and the upper electrode layer 14, and is insulated from the internal electrode layer 13b by the side surface insulating film 15a. Further, the vibrator 1b at the right end in the figure includes a side insulating film 15b and a side electrode 16b. The side electrode 16b is connected to the internal electrode layer 13b and the lower electrode layer 11, and is insulated from the internal electrode layer 13a by the side insulating film 15b.

  2 and 3, the lower electrode layers 11 of a plurality of vibrators included in one vibrator group 10 are electrically connected to each other by the first layer of the conductive resin 2a, so that one vibration The internal electrode layers 13a of the plurality of vibrators included in the child group 10 are electrically connected to each other by the second-layer conductive resin 2b, and the plurality of vibrators included in the single vibrator group 10 The internal electrode layers 13b are electrically connected to each other by the third layer of conductive resin 2c.

  Thereby, in each vibrator, the laminated first to third piezoelectric elements are connected in parallel, whereby the capacity of the vibrator is increased and the electrical impedance is lowered. Further, when a plurality of vibrators in one vibrator group 10 are connected in parallel, the capacity of the vibrator is further increased and the electrical impedance is further lowered. Thereby, matching of the electrical impedance with the electronic circuit in the ultrasonic diagnostic apparatus main body is improved.

  Furthermore, by composing the piezoelectric element, the ratio of the volume of the piezoelectric element to the entire volume of the vibrator is reduced, and the volume ratio of the piezoelectric body that is a heat source is reduced. An increase in surface temperature can be suppressed. In particular, when the piezoelectric element has a laminated structure, the amount of heat generation is very high compared to the case where the piezoelectric element has a single layer structure, which is more effective.

In this embodiment, a piezoelectric ceramic is used as the material of the piezoelectric body. Piezoelectric ceramics have a high electrical / mechanical energy conversion capability, so that they can generate powerful ultrasonic waves that can reach deep inside the body and have high reception sensitivity. Specific materials include PZT (lead zirconate titanate: Pb (Ti, Zr) O ₃ ), a metamorphic material having a similar perovskite crystal structure, and a material generally called a relaxor material Etc. can be used.

  In the present embodiment, the hardness of the conductive resin 2 is higher than the hardness of the insulating resin 4. As a material for the conductive resin and the insulating resin, for example, the material shown in FIG. 4 is used. As the insulating resin, it is possible to use an epoxy resin such as EPOTECH 310 (EPO-TEK310), EPOTECH 310-2FL (EPO-TEK310-2FL), EPOTECH 330 (EPO-TEK330) manufactured by Epoxy Technology. it can. On the other hand, as the conductive resin, conductive pastes such as H20S and H20E manufactured by the same Epoxy Technology can be used.

  FIG. 4 shows the Shore hardness of those materials. Shore hardness represents the measured value of the indentation depth of a predetermined indentation needle that is pushed into the material under the conditions specified in ISO 868. The D standard is harder than the A standard. Moreover, it represents that it is so hard that a numerical value is large in each specification. For example, when Epotec 310 is selected as the insulating resin from the materials shown in FIG. 4, H20S may be selected as the conductive resin, or H20E may be selected. The standard of Shore hardness is also defined in ASTM D2240-97e1 (Standard Test Method for Rubber Property-Durometer Hardness), JIS K7215 (Testing Method for Durometer Hardness of Plastics) and the like.

  When the vibrator is formed in a columnar shape and has a 1-3 composite shape, even if a flexible resin is filled between the vibrators, the vibration of the vibrator becomes large. Mechanical conversion characteristics cannot be obtained, and there are disadvantages such as occurrence of a plurality of resonance peaks. On the other hand, if a resin having high hardness is filled in the whole of a plurality of vibrators, vibrations of the vibrators are suppressed, and similarly, desired electromechanical conversion characteristics cannot be obtained.

  Therefore, in this embodiment, a resin having a high hardness is partially arranged in the soft resin so that vibration is not suppressed while vibration of the vibrator is prevented. That is, as shown in FIG. 2, the above structure is realized by disposing the conductive resin 2 having a relatively high hardness and the insulating resin 4 having a relatively low hardness between the plurality of vibrators 1. . Further, since the conductive resin 2 having a relatively high hardness is inserted into the groove formed in the backing material 3 like a pile, vibration of the vibrator is further prevented.

  Next, a method for manufacturing the ultrasonic probe according to the first embodiment of the present invention will be described. 5A to 5H are views for explaining the method of manufacturing the ultrasonic probe according to the first embodiment of the present invention.

  In the first step, as shown in FIG. 5A, a laminate including a lower electrode layer 11, a plurality of piezoelectric layers 12, internal electrode layers 13 a and 13 b, and an upper electrode layer 14 on the main surface of the backing material 3. A structure 20 is formed.

  Furthermore, a side surface insulating film 15a covering the internal electrode layer 13b is formed on the left side surface of the multilayer structure 20 in the drawing, and a side surface insulating film 15b covering the internal electrode layer 13a is formed on the right side surface of the laminated structure 20 in the drawing. The electrodeposition method, the dispensing method, or the printing method is used. As a material for the side insulating films 15a and 15b, epoxy resin, glass paste, or the like is used.

  Thereafter, the side electrode 16a connected to the internal electrode layer 13a and the upper electrode layer 14 on the left side surface of the multilayer structure 20, and the internal electrode layer 13b and the lower portion on the right side surface of the multilayer structure 20 in the figure. The side electrode 16b connected to the electrode layer 11 is formed by a plating method, a sputtering method, or the like. As the material of the side electrodes 16a and 16b, metals such as platinum, gold, palladium, nickel, chromium, titanium, cobalt, alloys containing at least one of them, and the like are used.

  In the second step, as shown in FIG. 5B, a plurality of grooves 17 reaching the backing material 3 are formed in the main surface of the laminated structure 20 in the elevation direction (X-axis direction in FIG. 1). Thereby, the laminated structure 20 is divided into a plurality of vibrators 1 ′ that are long in the X-axis direction.

  In the third step, as shown in FIG. 5C, the plurality of grooves 17 are filled with the conductive resin 2. Furthermore, in a 4th process, as shown to FIG. 5D, along the some groove | channel 17, at least one part of the conductive resin 2 is cut and removed by dicing. As a result, the first layer of conductive resin 2a is formed from below the lowermost piezoelectric layer 12 to about 1/3.

  In the fifth step, as shown in FIG. 5E, the insulating resin 4 is filled in the portions of the plurality of grooves 17 from which the conductive resin 2 has been removed in the fourth step. Further, in the sixth step, as shown in FIG. 5F, along the plurality of grooves 17, at least a part of the insulating resin 4 is cut and removed by dicing.

  By repeating the third to sixth steps as necessary, and finally cutting the protruding portion of the insulating resin 4 in the sixth step, as shown in FIG. 5G, the first layer of conductive resin 2a. A structure in which the conductive resin 2c and the insulating resin 4 of the third layer are arranged is completed. Further, since a part of the upper electrode layer 14 is cut by dicing, a common electrode layer 21 that supplements the upper electrode layer 14 is formed on the main surface of the multilayer structure 20 as shown in FIG. 5H. .

  Further, at least one acoustic matching layer is formed on the common electrode layer 21, and a plurality of grooves reaching the backing material 3 are formed in the first direction on the main surface of the laminated structure 20 on which the acoustic matching layer is formed. Are formed in a second direction different from (for example, the Y-axis direction shown in FIG. 1). Thereby, as shown in FIG. 1, each transducer group 10 including a plurality of transducers 1 arranged in the X-axis direction is formed. Thereafter, wiring to the electrode layer is performed, the acoustic lens 7 is attached, and the ultrasonic probe shown in FIG. 2 is completed.

  As a modification of the above manufacturing method, in the sixth step (FIG. 5F) of cutting a part of the insulating resin 4 by dicing, the width of the dicing blade is gradually increased or a plurality of dicing processes are performed. As shown in FIG. 6, the width of the groove 17 may be increased stepwise. As a result, the width of the first-layer conductive resin 2a to the third-layer conductive resin 2c also increases stepwise. As a result, the vibration of the vibrator is stabilized because the side shape of the vibrator is a trapezoid having a large lower side in the figure and a smaller upper side. In addition, since the acoustic impedance of the transducer gradually decreases toward the subject, the acoustic impedance matching between the subject such as a human body and the transducer is improved, and the sensitivity and bandwidth of the ultrasonic probe are improved. Etc. The performance is improved.

Next, a second embodiment of the present invention will be described.
FIG. 7 is a front view showing an internal structure of an ultrasonic probe according to the second embodiment of the present invention. In the second embodiment, in each vibrator group 10, as shown in FIG. 7, the third layer conductive resin 2c is not formed in the groove at the left end in the figure, and the first layer conductivity is not formed. Only the resin 2a and the second-layer conductive resin 2b are formed, and the second-layer conductive resin 2b is not formed in the groove at the right end in the figure, but the first-layer conductive resin 2a and the third-layer Only the conductive resin 2c is formed.

  The internal electrode layer includes at least one first internal electrode layer and at least one second internal electrode layer that are alternately formed with the piezoelectric layers interposed therebetween. FIG. 7 shows a first internal electrode layer 13a and a second internal electrode layer 13b formed with the piezoelectric layer 12 interposed therebetween.

  A side electrode 8 electrically connected to the internal electrode layers 13a and 13b and the upper electrode layer 14 is formed on the left side surface of each transducer group 10 in the drawing. A side electrode 9 electrically connected to the internal electrode layers 13 a and 13 b and the lower electrode layer 11 is formed.

  A groove for separating at least the internal electrode layer 13b is formed at the left end of each transducer group 10 in the drawing, and the insulating resin 4 is filled between the separated internal electrode layers 13b. Further, at least the groove for separating the internal electrode layer 13a is formed at the right end of each transducer group 10 in the drawing, and the insulating resin 4 is filled between the separated internal electrode layers 13a. The other points are the same as in the first embodiment.

  As described above, in the second embodiment, the conductive resins 2a to 2c and the insulating resin 4 are arranged in the left and right grooves in the drawing without forming the side insulating films 15a and 15b shown in FIG. 5A. By changing, the connection state of the electrode in a laminated body is ensured.

  Next, a method for manufacturing an ultrasonic probe according to the second embodiment of the present invention will be described. The ultrasonic probe according to the second embodiment is manufactured by changing a part of the method of manufacturing the ultrasonic probe according to the first embodiment described with reference to FIGS. 5A to 5H. The

  In the first step, as shown in FIG. 5A, a laminated structure including a lower electrode layer 11, a plurality of piezoelectric layers 12, internal electrode layers 13 a and 13 b, and an upper electrode layer 14 on the main surface of the backing material 3. 20 is formed. However, the side insulating films 15a and 15b shown in FIG. 5A are not formed, and are connected to the internal electrode layers 13a and 13b and the upper electrode layer 14 on the left side surface of the laminated structure as shown in FIG. The side electrode 8 is formed, and the side electrode 9 connected to the internal electrode layers 13a and 13b and the lower electrode layer 11 is formed on the right side surface of the multilayer structure.

  In the second step, as shown in FIG. 7, at the left end of the multilayer structure, a groove separating at least the internal electrode layer 13b is formed in the azimuth direction (Y-axis direction in FIG. 1). A groove for separating at least the internal electrode layer 13a is formed in the azimuth direction at the right end in the drawing of the laminated structure.

  Furthermore, by repeating the third to sixth steps as necessary, the first to third layers of the conductive resins 2a to 2c and the insulating resin 4 are formed. Here, as shown in FIG. 7, the insulating resin 4 is filled between the internal electrode layers 13a separated in the leftmost groove in the drawing of the laminated structure, and separated in the rightmost groove in the drawing of the laminated structure. The insulating resin 4 is filled between the internal electrode layers 13b.

Next, a third embodiment of the present invention will be described.
FIG. 8 is a front view showing the internal structure of an ultrasonic probe according to the third embodiment of the present invention. In the third embodiment, the specific shape of the transducer group in the ultrasonic probe according to the first embodiment is determined, the transducer group is actually manufactured, and the electrical impedance characteristics of the transducer are measured. is doing.

  In the present embodiment, chlorinated polyethylene mixed with ferrite powder is used as the backing material 3, and its acoustic impedance is about 6 MRayl. In addition, H20S, which is a silver (Ag) paste manufactured by Epoxy Technology, is used as the conductive resins 2a to 2c, and Epotech 330 (EPO-TEK330), which is an epoxy resin manufactured by Epoxy Technology, is used as the insulating resin 4. Used.

  As the piezoelectric body 12, three layers of piezoelectric ceramics (specifically, PZT) having a green sheet-molded thickness of 100 μm are stacked with the internal electrodes 13 a and 13 b interposed therebetween. The relative dielectric constant of this piezoelectric ceramic is 4500 at 1 kHz. The volume ratio between the piezoelectric body 12 and the resin region (the conductive resins 2a to 2c and the insulating resin 4) is about 1: 2.

  In FIG. 8, the length (elevation direction) of one transducer group 10 is 5.0 mm, the width (azimuth direction) is 0.11 mm (110 μm), and the height is 0.3 mm (300 μm). is there. The arrangement pitch of the conductive resins 22a to 22c and the insulating resin 4 is 550 μm, the length of one electrode in the lower electrode layer 11 is 250 μm, and the length of one electrode in the upper electrode layer 14 is 200 μm. is there. Each of the side electrodes 16a and 16b has a two-layer structure of chromium (Cr) and gold (Au), and the total thickness is about 450 nm.

  FIG. 9 is a diagram illustrating an image obtained by photographing a part of the cut surface of the transducer group manufactured on the backing material with a scanning electron microscope (SEM). FIG. 9A shows a vibrator group including seven vibrators. FIG. 9B is an enlarged view of a part of the transducer group shown in FIG. As shown in FIG. 9B, each vibrator has an internal electrode between the piezoelectric bodies, and an insulating resin is used to connect the internal electrodes of two adjacent vibrators. A conductive resin (silver paste H20S) is arranged surrounded by (Epotek 330). FIG. 9C is an enlarged view showing a part of the vibrator and the resin region shown in FIG. In FIG. 9C, it can be seen that the internal electrode and the conductive resin are well connected.

  FIG. 10 is a diagram showing the results of measuring the electrical impedance characteristics of the vibrator manufactured in the third embodiment of the present invention. 10A and 10B, the horizontal axis indicates the frequency (MHz), and the vertical axis in FIG. 10A indicates the absolute value | Z | (ohms) of the electrical impedance. The vertical axis in (B) of FIG. 10 represents the deflection angle φ (degree) of the electrical impedance. The number of samples of the transducer for measurement is three. When the apparent dielectric constant of the piezoelectric body was calculated based on the measured value of the electrical impedance of the vibrator at 2 MHz, it was about 12570.

As in this embodiment, when a piezoelectric material having a relative dielectric constant of 4500 and a resin having a relative dielectric constant of about 5 are composited at a volume ratio of 1: 2, the relative dielectric constant of the composite material is about 1500. In general, in a vibrator having a laminated structure formed by laminating N layers of piezoelectric bodies, the capacitance is N ² times that of a vibrator having a single-layer structure of the same size. It is considered that the apparent relative dielectric constant converted to the above vibrator is also N ² times. Therefore, when a vibrator having a three-layer structure is manufactured using a composite material having a relative dielectric constant of 1500, the apparent relative dielectric constant is expected to be 1500 × 3 ² = 13500. The measured value of the apparent relative dielectric constant in the present embodiment is 12570, which is 93% of the expected value, and can be said to be in good agreement with the expected value. Moreover, the measured values of the deflection angle of the electrical impedance in the present embodiment are also as expected, and these measurement results indicate that the three-layer structure vibrator using the composite material has been successfully manufactured.

  According to the above-described embodiment, the electromechanical coupling coefficient is improved by the 1-3 composite of the vibrator and the acoustic impedance is lowered, and the electrical impedance is lowered by the lamination of the vibrator. An acoustic probe can be realized. As a result, image quality and diagnostic performance in harmonic imaging and contrast Doppler imaging are improved as compared with conventional ultrasonic probes. Also, heat generation by the vibrator is reduced. Furthermore, by arranging a conductive resin having a relatively high hardness and an insulating resin having a relatively low hardness between a plurality of vibrators, a structure that prevents vibrations of the vibrators and prevents vibrations is provided. be able to. The present invention can be applied to any shape of ultrasonic probe such as a sector type, a linear type, a convex type, and a radial type.

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

1 is a plan view schematically showing an ultrasonic transducer array used in an ultrasonic probe according to a first embodiment of the present invention. It is a front view which shows the internal structure of the ultrasonic probe which concerns on the 1st Embodiment of this invention. It is a perspective view which expands and shows the lamination structure of a vibrator. It is a table | surface which shows the material of conductive resin and insulating resin. It is a figure for demonstrating the manufacturing method of the ultrasonic probe which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the manufacturing method of the ultrasonic probe which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the manufacturing method of the ultrasonic probe which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the manufacturing method of the ultrasonic probe which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the manufacturing method of the ultrasonic probe which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the manufacturing method of the ultrasonic probe which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the manufacturing method of the ultrasonic probe which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the manufacturing method of the ultrasonic probe which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the modification of the manufacturing method of the ultrasonic probe which concerns on the 1st Embodiment of this invention. It is a front view which shows the internal structure of the ultrasonic probe which concerns on the 2nd Embodiment of this invention. It is a front view which shows the internal structure of the ultrasonic probe which concerns on the 3rd Embodiment of this invention. It is a figure which shows the image | video which image | photographed a part of cut surface of the vibrator group manufactured on the backing material with the scanning electron microscope. It is a figure which shows the result of having measured the electrical impedance characteristic of the vibrator | oscillator manufactured in the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a, 1b Vibrator 2, 2a-2c Conductive resin 3 Backing material 4 Insulating resin 5, 6 Acoustic matching layer 7 Acoustic lens 8, 9 Side electrode 10 Vibrator group 11 Lower electrode layer 12 Piezoelectric body 13a, 13b Electrode layer 14 Upper electrode layer 15a, 15b Side insulating film 16a, 16b Side electrode 17 Groove 20 Laminated structure 21 Common electrode layer

Claims (12)

An ultrasound probe including a plurality of transducers for transmitting and / or receiving ultrasound,
Backing material,
A plurality of transducers arranged in a first direction constitute a transducer group, and a plurality of transducer groups are arranged in a second direction different from the first direction, and each transducer The child includes a first electrode layer formed on the main surface of the backing material, a plurality of piezoelectric layers, at least one internal electrode layer, and a second electrode layer common to each vibrator group. The transducer array having a laminated structure; and
A conductive resin of a first layer that electrically connects the first electrode layers of adjacent vibrators in each vibrator group;
A conductive resin of a second layer that electrically connects internal electrode layers of adjacent vibrators in each vibrator group;
Insulating resin disposed in a predetermined region between the plurality of vibrators in each vibrator group,
An ultrasonic probe comprising:   The ultrasonic probe according to claim 1, wherein the conductive resin of the first layer and the conductive resin of the second layer have hardness higher than that of the insulating resin.   The ultrasonic probe according to claim 1, wherein the conductive resin of the first layer has a hardness higher than that of the conductive resin of the second layer.   A plurality of grooves are formed in the main surface of the backing material, and a part of the conductive resin of the first layer is filled in the plurality of grooves. The described ultrasonic probe.   5. The ultrasonic probe according to claim 1, wherein the conductive resin of the second layer is formed in a region wider than a region where the conductive resin of the first layer is formed. Child. Each vibrator includes at least one first internal electrode layer and at least one second internal electrode layer that are alternately formed with the piezoelectric layers interposed therebetween,
A first side surface insulating film formed on the first side surface of each transducer group and covering the second internal electrode layer;
A second side surface insulating film formed on the second side surface of each transducer group and covering the first internal electrode layer;
Formed on the first side surface of each transducer group, connected to the first internal electrode layer and the second electrode layer, and insulated from the second internal electrode layer by the first side surface insulating film A first side electrode formed;
Formed on the second side surface of each transducer group, connected to the second internal electrode layer and the first electrode layer, and insulated from the first internal electrode layer by the second side surface insulating film A second side electrode formed;
The ultrasonic probe according to claim 1, further comprising: Each vibrator includes at least one first internal electrode layer and at least one second internal electrode layer that are alternately formed with the piezoelectric layers interposed therebetween,
A first side electrode formed on the first side surface of each transducer group and connected to the first and second internal electrode layers and the second electrode layer;
A second side surface electrode formed on a second side surface of each transducer group and connected to the first and second internal electrode layers and the first electrode layer;
And a groove for separating at least the second internal electrode layer is formed at an end portion on the first side surface of each vibrator group, and the groove is formed between the separated second internal electrode layers. Insulating resin is filled, and a groove for separating at least the first internal electrode layer is formed at the second side surface end of each vibrator group. The ultrasonic probe according to claim 1, wherein the insulating resin is filled in between. A method of manufacturing an ultrasound probe including a plurality of transducers for transmitting and / or receiving ultrasound,
Forming a laminated structure including a first electrode layer, a plurality of piezoelectric layers, at least one internal electrode layer, and a second electrode layer on the main surface of the backing material;
Separating the stacked structure into a plurality of vibrators arranged in a first direction by forming a plurality of grooves reaching the backing material on the main surface of the stacked structure;
Filling the plurality of grooves formed in the step (b) with a conductive resin (c);
A step (d) of removing a part of the conductive resin filled in the step (c);
Filling the plurality of grooves from which the conductive resin has been removed in step (d) with insulating resin (e);
A step (f) of removing a part of the insulating resin filled in the step (e);
By repeating steps (c) to (f) as necessary, the first layer conductive resin that electrically connects the first electrode layers of the adjacent vibrators to each other, and the internal electrodes of the adjacent vibrators Forming a second layer conductive resin that electrically connects the layers to each other, and an insulating resin disposed in a predetermined region between the plurality of vibrators;
Forming a common electrode layer on the main surface of the laminated structure (h);
Forming at least one acoustic matching layer on the common electrode layer (i);
A plurality of vibrations in which the vibrators are arranged in a second direction different from the first direction by forming a plurality of grooves reaching the backing material in the first direction on the main surface of the laminated structure. Separating into children (j);
A method of manufacturing an ultrasonic probe comprising:   The method for manufacturing an ultrasonic probe according to claim 8, wherein the conductive resin of the first layer and the conductive resin of the second layer have a hardness higher than that of the insulating resin.   10. The method of manufacturing an ultrasonic probe according to claim 8, wherein the conductive resin of the first layer has a hardness higher than that of the conductive resin of the second layer. The multilayer structure includes at least one first internal electrode layer and at least one second internal electrode layer alternately formed with a piezoelectric layer interposed therebetween,
Step (a) is
A first side insulating film that covers the second internal electrode layer is formed on a first side surface of the multilayer structure, and the first internal electrode layer is covered on a second side surface of the multilayer structure. Forming a second side surface insulating film;
A first side surface of the multilayer structure is connected to the first internal electrode layer and the second electrode layer, and is insulated from the second internal electrode layer by the first side surface insulating film. Forming a first side electrode; connected to the second inner electrode layer and the first electrode layer on the second side surface of the multilayer structure; and by the second side surface insulating film, Forming a second side electrode that is insulated from one internal electrode layer;
The manufacturing method of the ultrasonic probe of any one of Claims 8-10 containing these. The multilayer structure includes at least one first internal electrode layer and at least one second internal electrode layer alternately formed with a piezoelectric layer interposed therebetween,
Step (a) forms, on the first side surface of the multilayer structure, the first and second internal electrode layers and the first side electrode connected to the second electrode layer, and the multilayer structure. Forming, on the second side of the body, the first and second internal electrode layers and the second side electrode connected to the first electrode layer;
Step (b) forms a groove separating at least the second internal electrode layer at an end portion on the first side surface side of the multilayer structure, and an end portion on the second side surface side of the multilayer structure body Forming a groove separating at least the first internal electrode layer,
Step (g) includes filling the insulating resin between the separated first internal electrode layers and filling the insulating resin between the separated second internal electrode layers.
The manufacturing method of the ultrasonic probe of any one of Claims 8-10.