JP2013026425A - Multilayer piezoelectric, multilayer piezoelectric element using the same, and manufacturing method of multilayer piezoelectric element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer piezoelectric in which energization failure of an external electrode does not occur when a multilayer piezoelectric element is diced, and to provide a multilayer piezoelectric element using the multilayer piezoelectric, and a manufacturing method of the multilayer piezoelectric element.SOLUTION: In a multilayer piezoelectric 1 laminating n layers (n is an integer of 2 or more) of piezoelectric 5 and (n-1) layers of internal electrode 2 alternately, a groove 8 is formed in the lamination direction at an end of the multilayer piezoelectric 1. Since the groove 8 is formed at an end of the multilayer piezoelectric 1, an external electrode can be formed up to the inner surface of the groove 8 in the process of manufacturing a multilayer piezoelectric element by forming an external electrode on the outer periphery of the multilayer piezoelectric 1.

Description

  The present invention relates to a laminated piezoelectric body and a laminated piezoelectric element, and more specifically, from a plate-like laminated piezoelectric element after forming an external electrode in a processing step for mounting the laminated piezoelectric element on an ultrasonic probe or the like. The present invention relates to a laminated piezoelectric element that does not cause a failure in energization of an external electrode at the time of cutting into a laminated piezoelectric element such as an array, a laminated piezoelectric element using the laminated piezoelectric element, and a method for manufacturing the laminated piezoelectric element.

Conventionally, a piezoelectric element used for an ultrasonic probe used for medical imaging, industrial nondestructive inspection, and the like has been required to have a high sensitivity and a wide band.
Here, one of the problems that hinders realization of high sensitivity of a piezoelectric element is a problem of transmission loss of an electric signal between the piezoelectric element and a cable or system connected thereto.

  Among these, a so-called matching problem between the piezoelectric element and the cable is caused by a difference in impedance between the piezoelectric element and the cable, and is described in Patent Document 1 in order to solve such a problem. Multilayer piezoelectric elements have been developed. Since this laminated piezoelectric element has a structure in which a piezoelectric body and an electrode are laminated, as described in the background art column of Patent Document 2 and the abstract column of Non-Patent Documents 1 and 2, a single-layered piezoelectric element is used. This is because the impedance can be lower than that of the piezoelectric body and a high capacitance can be realized.

  The applicant of the present application also pays attention to this characteristic, and has developed a multilayer piezoelectric element that stably exhibits an electromechanical coupling coefficient of 65% or more after being processed into an array as shown in Patent Document 3.

  Non-Patent Document 3 discloses a multilayer piezoelectric element that can improve the 6 dB bandwidth by 12% during transmission and 15% during reception by using piezoelectric bodies having different thicknesses.

  Further, Non-Patent Document 4 discloses a laminated piezoelectric element in which a so-called composite piezoelectric material composed of a piezoelectric material and an organic polymer material is laminated. It is also disclosed that a laminated piezoelectric element in which this composite piezoelectric material is laminated can reduce internal heat generation and improve transmission power.

Japanese Patent No. 3280677 US Pat. No. 6,822,374 Japanese Patent No. 4175535

X.MingLu, T.L.Proulx, 2005 IEEE Ultrasonics Symposium, P227-230 MihaiState, Andrea Grandoni, Lorenzo Spicci, Peter Kerkhof, Peter J. Brands, Frans N. vande Vosse, 2009 IEEE International Ultrasonics Symposium Proceedings, P2704-2707 MihaiState, Andrea Grandoni, Lorenzo Spicci, Peter Kerkhof, Peter J. Brands, Frans N. vande Vosse, 2009 IEEE International Ultrasonics Symposium Proceedings, P2730-2733 MichaelJ. Zipparo, Kristin F. Bing, Kathryn R. Nightingale, IEEE Transactionson Ultrasonics, Ferroelectrics, and Frequency Control, vol. 57, no. 9, September 2010, P2076-2090

Here, as shown in FIGS. 3 to 8 of Patent Document 2 and FIGS. 1 to 5 of Patent Document 3, such a laminated piezoelectric element is a laminated piezoelectric element in which a piezoelectric body and an internal electrode are laminated using an adhesive or the like. It is produced by forming external electrodes on the outer periphery of the body.
The plate-shaped laminated piezoelectric element thus fabricated is cut into an array after a backing material or an acoustic matching layer is pasted, for medical imaging, industrial nondestructive inspection, etc. It is used as the sensing part of the ultrasonic probe used.

  However, in recent years, the piezoelectric elements used in these ultrasonic probes are required to have fine pitch processing with a cutting interval of about 0.2 mm or less in the above cutting processing in order to improve the image quality. Therefore, when such a precise cutting process is performed in a multilayer piezoelectric element having a complicated structure, there has been a problem in that external electrodes are peeled off or disconnected, resulting in poor conduction.

  The present invention has been made in view of the above-described problems, and includes a laminated piezoelectric element that does not cause poor conduction of external electrodes at the time of cutting the laminated piezoelectric element, a laminated piezoelectric element using the laminated piezoelectric element, and An object of the present invention is to provide a method for manufacturing the laminated piezoelectric element.

  In order to achieve this object, a laminated piezoelectric material according to claim 1 of the present invention is a laminated piezoelectric material in which n layers (n is an integer of 2 or more) and n-1 layers of internal electrodes are alternately laminated. In this embodiment, the end portion of the multilayer piezoelectric body has a groove formed in the stacking direction.

  The laminated piezoelectric body according to claim 2 of the present invention has a structure in which the groove is formed at least at the laminated interface between the piezoelectric body and the internal electrode at the end portion.

  In the multilayer piezoelectric body according to claim 3 of the present invention, the shape of the groove is any one of a substantially concave shape, a substantially U shape, a substantially V shape, and a substantially W shape in a cross-sectional view parallel to the laminated interface. It is configured.

  The laminated piezoelectric element according to claim 4 of the present invention is connected to the internal electrode at least on the inner surface of the groove at the end of the laminated piezoelectric body of claims 1 to 3, and the internal electrodes are electrically parallel to each other. An external electrode formed so as to be connected to is provided.

  According to a fifth aspect of the present invention, there is provided a method for manufacturing a laminated piezoelectric element comprising producing a laminated piezoelectric material in which n layers (n is an integer of 2 or more) and n-1 layers of internal electrodes are alternately laminated. Then, in the method for manufacturing a laminated piezoelectric element having a step of forming an external electrode at the end of the laminated piezoelectric body, the method further includes a step of forming a groove in the stacking direction of the end of the laminated piezoelectric body.

  According to a sixth aspect of the present invention, there is provided a multilayer piezoelectric element manufacturing method comprising: a first step of forming electrodes on the surface of an n-layer (n is an integer of 2 or more) piezoelectric material; and an adhesive layer between the electrodes. A second step of forming a laminated body as an internal electrode by bonding so as to exist, a third step of forming a groove at the end in the stacking direction of the laminated body obtained by bonding the electrodes together, And a fourth step of forming an external electrode on the inner surface.

  Next, the laminated piezoelectric material of the present invention will be described below.

(Laminated piezoelectric body)
The laminated piezoelectric material used in the present invention has a structure in which piezoelectric materials and internal electrodes are alternately laminated.
Specifically, as shown in FIG. 1, piezoelectric bodies are positioned on the uppermost layer and the lowermost layer, and piezoelectric bodies and internal electrodes are alternately laminated, and are bonded by synthetic resin or heat fusion or co-fired. It is the structure produced by.

Further, the internal electrodes are laminated so that the electrodeless portion appears on the laminated surface of the piezoelectric body. By laminating internal electrodes in such an arrangement, when an external electrode is formed at the end of a laminated piezoelectric material described later, a laminated piezoelectric element in which the internal electrodes are electrically connected in parallel can be produced. is there.
Further, the structure of the internal electrode and the external electrode is determined according to the design of the ultrasonic probe using the multilayered piezoelectric element of the present invention, the workability at the time of manufacturing the ultrasonic probe, and the like. For example, as shown in FIG. 1, the electrodeless portions of the internal electrodes may be stacked so as to appear alternately in a sectional view of the stacked piezoelectric body.

  Next, main parts constituting the multilayer piezoelectric body of the present invention will be described.

  The piezoelectric body used in the multilayer piezoelectric body of the present invention is not particularly limited as long as it can convert mechanical energy applied from the outside into electrical energy, or vice versa. In particular, the material and type are not limited. And, for example, barium titanate ceramics, lead titanate ceramics, lead zirconate titanate (PZT) ceramics, lead niobate ceramics, lithium niobate single crystals, lead zinc titanate niobate (PZNT) single crystals , Lead magnesium niobate titanate (PMNT) single crystals, bismuth titanate ceramics, lead metaniobate ceramics, and the like can be used.

  As the piezoelectric body used in the multilayer piezoelectric body of the present invention, a so-called composite piezoelectric body in which an organic polymer body is filled between arranged columnar piezoelectric ceramics can also be used. Further, as the organic polymer filled between the arranged columnar piezoelectric ceramics, an organic polymer in which bubbles are dispersed as invented by the applicant of the present invention in Japanese Patent No. 4222467 may be used.

  Examples of the internal electrode used in the multilayer piezoelectric material of the present invention include metals such as gold, platinum, nickel, silver, palladium, and copper. Examples of the method for forming the internal electrode in the multilayer piezoelectric body of the present invention include sputtering, vapor deposition, electrolytic plating, and electroless plating. Of these, from the viewpoint of cost and electrode adhesion, it is preferable to perform an electroless plating method using nickel, copper, or the like. Furthermore, after performing the electroless plating process, an electrode forming process by electrolytic plating using gold, copper, or the like can be performed as necessary.

As a method for stacking the piezoelectric body and the internal electrode, a conventionally known method can be employed. For example, as shown in FIG. 2, first, a plurality of piezoelectric bodies having electrodes formed on a laminated surface are prepared, and the surfaces on which the electrodes of each piezoelectric body are formed are laminated by using an epoxy resin adhesive or the like. The method of doing is mentioned.
In addition, as shown in FIG. 3, the inner electrode is formed by applying and laminating silver-palladium alloy paste, platinum paste, copper paste, etc., which are electrode materials, to one of the laminated surfaces of the piezoelectric body and then firing. In addition, a method of manufacturing by laminating at the same time can also be mentioned.

  In addition, when laminating with an adhesive, the used adhesive remains as an adhesive layer after lamination. The thickness of the adhesive layer is not particularly limited. If the thickness is 1 μm or more, the laminated electrode is interposed between the layers when the backing material or the acoustic matching layer is pasted and cut into an array or the like. It is preferable because peeling can be more effectively prevented.

The laminated piezoelectric material according to the present invention is characterized in that after the piezoelectric material and the internal electrode are laminated, a groove portion is provided at the end portion in the lamination direction of the laminated piezoelectric material. By forming such a groove portion at the end of the laminated piezoelectric material, the external electrode can be formed even on the inner surface of the groove portion in the step of forming a laminated piezoelectric element by forming an external electrode on the outer periphery of the laminated piezoelectric material described later. it can.
As a result, when a backing material or acoustic matching layer is applied to the laminated piezoelectric element and then cut into an array, etc., the external electrode near the cut surface has defects, disconnection, or peeling due to cutting. However, since the defects and the like are suppressed from progressing to the inner surface of the groove portion, the inner surface of the groove portion can maintain the state in which the external electrode is formed, and therefore, it is possible to prevent a failure of the external electrode. is there.

  In addition, the groove portion is suitable not only because the degree of freedom in width and depth is widened, but also in forming the external electrode described later, the external electrode can be easily formed on the inner surface of the groove.

  In addition, as for the formation position of the groove at the end of the laminated piezoelectric material, the groove extends from the uppermost layer to the lowest layer of the laminated piezoelectric material as long as it is formed at least at the laminated interface between the piezoelectric material and the internal electrode. It is not necessary to provide However, it is necessary to pay attention not to form a groove in the cut portion when cutting into an array shape which is a subsequent process. The reason for this is that if a groove is formed at the cut portion when cutting, the backing material or the acoustic matching layer is applied to the laminated piezoelectric element as described above, and then cut into an array or the like. This is because when a defect, disconnection, peeling, or the like associated with cutting occurs in the external electrode near the cut surface, the external electrode formed in the groove also causes a defect, disconnection, peeling, or the like.

  The specific method for forming the groove is not particularly limited. However, when the piezoelectric body and the internal electrode are alternately stacked, and then cut into a predetermined position by a dicing machine or the like, the stacked piezoelectric body is obtained. Since a groove portion extending from the uppermost layer to the lowermost layer can be easily formed, it is preferable in terms of productivity.

In FIG. 1, the shape of the groove is substantially concave when viewed in a cross section parallel to the stacking interface, but is not limited to this, and in the cross section of the cross section parallel to the stacking interface. Various shapes such as a substantially U-shape, a substantially V-shape, and a substantially W-shape can also be used.
Further, the depth and width of the groove can also be appropriately determined according to the dimensions and laminated state of the actually used laminated piezoelectric element and the arrangement state of the internal electrodes.

Furthermore, in the end part of the laminated piezoelectric material, a through hole can be provided instead of the groove part. Also by providing such a through hole, it is possible to form the external electrode up to the inner surface of the through hole in the step of forming a laminated piezoelectric element by forming the external electrode on the outer periphery of the laminated piezoelectric body described later.
In the subsequent cutting process into an array or the like, the external electrode was formed on the inner surface of the through-hole even when a defect, disconnection, peeling, or the like associated with the cutting occurred in the external electrode near the cut surface. It is possible to maintain the state, and thus it is possible to prevent an energization failure of the external electrode.

  The shape of the through hole is not particularly limited as long as it penetrates from the uppermost layer to the lowermost layer of the laminated piezoelectric body. For example, various shapes such as a cylindrical shape, a prismatic shape, and a conical shape can be used.

  Also, the depth and width of the through-hole can be appropriately determined according to the dimensions and the laminated state of the actually used laminated piezoelectric element and the arrangement state of the internal electrodes.

  Next, the laminated piezoelectric element of the present invention will be described below.

(Laminated piezoelectric element)
The multilayer piezoelectric element used in the present invention is manufactured by forming external electrodes on the outer periphery of a multilayer piezoelectric body having grooves and through holes formed at the end portions described above.
Specifically, as shown in a sectional view of the laminated piezoelectric element shown in FIG. 4, separate external electrodes are provided for the internal electrode appearing at one end of the laminated piezoelectric body and the internal electrode appearing at the other end. It is produced by forming. In this case, external electrodes are formed not only on the uppermost surface and the lowermost surface of the multilayer piezoelectric element but also on the inner surfaces of the groove and the through hole. Then, by forming the external electrodes in such a form, a laminated piezoelectric element in which the internal electrodes are electrically connected in parallel is manufactured.

  Next, the manufacturing method of the multilayer piezoelectric element of the present invention will be described below.

(Manufacturing method of laminated piezoelectric element)
The method for manufacturing a laminated piezoelectric element of the present invention is characterized by including a step of forming a groove or a through hole in the lamination direction at the end of the laminated piezoelectric material. By having such a process, even when the plate-shaped multilayered piezoelectric element is cut into an array or the like, it is possible to produce a multilayered piezoelectric element that prevents the external electrode from being poorly energized.

  The order of the step of forming the groove and the through hole in the stacking direction at the end of the multilayer piezoelectric body is not particularly limited as long as it is before the step of forming the external electrode. For example, as described above, it may be performed after the piezoelectric material and the internal electrode are laminated, or a step of forming a groove or a through hole in advance may be performed, and then the lamination may be performed.

Further, when a plurality of piezoelectric bodies having electrodes formed on a laminated surface as shown in FIG. 2 are prepared and the surfaces on which the electrodes of the respective piezoelectric bodies are formed are bonded and laminated, a laminated piezoelectric body is produced. Can also be produced mainly through the following four steps.
1st process: The process which forms an electrode on the surface of the piezoelectric material of n layer (n is an integer greater than or equal to 2), 2nd process: It adheres to an internal electrode by adhere | attaching electrodes so that an adhesive layer may exist between electrodes Forming a laminated body, third step: forming a groove at the end of the laminated body obtained by bonding the electrodes together, and fourth step: forming an external electrode on the inner surface of the groove.

  According to the multilayer piezoelectric body and the multilayer piezoelectric element using the multilayer piezoelectric body of the present invention, a groove or a through hole is provided at the end of the multilayer piezoelectric body, and the internal electrodes are electrically connected in parallel to the inner surface. Since external electrodes are provided, it is possible to effectively prevent defects, disconnection, and peeling of external electrodes at the interface of the laminate when cutting plate-like laminated piezoelectric elements into arrays, etc. Can be prevented.

  In addition, it is possible to easily prevent poor conduction of the external electrode by making the shape of the groove portion substantially concave, substantially U-shaped, substantially V-shaped, or substantially W-shaped in a cross-sectional view parallel to the lamination interface. It is possible to provide a laminated piezoelectric material that can be produced and a laminated piezoelectric element using the laminated piezoelectric material.

It is a schematic diagram which shows the laminated piezoelectric material of this invention. It is a cross-sectional schematic diagram which shows the lamination | stacking method of the piezoelectric material and internal electrode in the laminated piezoelectric material of this invention. It is a cross-sectional schematic diagram which shows another lamination | stacking method of the piezoelectric material and internal electrode in the multilayer piezoelectric material of this invention. It is a schematic diagram which shows the laminated piezoelectric element of this invention. It is a figure which shows the manufacturing process of 1st Embodiment in the multilayer piezoelectric element of this invention. It is a microscope picture in the side view of the edge part of the laminated piezoelectric element which formed the groove part and formed the external electrode after that. It is a figure which shows the manufacturing process of 2nd Embodiment in the multilayer piezoelectric element of this invention. It is a figure which shows the manufacturing process of 3rd Embodiment in the multilayer piezoelectric element of this invention. It is a figure which shows the manufacturing process of 4th Embodiment in the multilayer piezoelectric element of this invention. 4 is a time signal waveform of an arrayed transducer element produced from the laminated piezoelectric element of Example 1. 2 is an FFT spectrum of an arrayed transducer element produced from the laminated piezoelectric element of Example 1. It is a schematic diagram which shows the conventional laminated piezoelectric material.

  Next, the laminated piezoelectric material of the present invention and the laminated piezoelectric element using the laminated piezoelectric material will be described in detail with reference to the drawings. In addition, although all the following embodiments are about a laminated piezoelectric element having three layers of piezoelectric bodies, the present invention is not limited to this.

(First Embodiment of Multilayer Piezoelectric Element)
First, a first embodiment of the multilayer piezoelectric element of the present invention will be described. FIG. 5 is a diagram showing a manufacturing process of the first embodiment of the multilayer piezoelectric element of the present invention. Hereinafter, the laminated piezoelectric element according to the first embodiment will be described with reference to FIG.

  First, as shown in FIG. 5 (a), a piezoelectric material having a predetermined shape is obtained by forming and firing a material such as lead zirconate titanate (PZT) ceramic powder into a plate shape and then performing thickness processing and outer shape cutting processing. 5 is prepared.

Next, as shown in FIG. 5B, the internal electrode 2 is formed by performing electroless plating using nickel and electrolytic plating using gold on the laminated surface 6 of the piezoelectric body 5.
Here, the internal electrode 2 of each layer is formed by forming the internal electrode 2 over the entire laminated surface 6 and then removing unnecessary portions as shown in FIG. Two narrow internal electrodes 2b are provided, and the internal electrode 2a having a large area and the internal electrode 2b having a small area are formed so as to appear alternately in a cross-sectional view in the stacking direction.
The same internal electrodes 2a and 2b can also be formed by previously masking a portion where the internal electrode is not required and performing the above plating process on the entire laminated surface 6 and then removing the masking.

  Next, as shown in FIG. 5C, the laminated piezoelectric body 1 is manufactured by bonding the internal electrodes 2 with an adhesive or the like.

Next, as shown in FIG. 5D, the groove 8 is formed in the end 7 of the multilayer piezoelectric body 1 so as to be cut at a predetermined position by a dicing machine or the like.
Here, in FIG. 5D, six groove portions 8 are provided in each end portion 7, but the number of groove portions 8 is not limited to this, and is required in actual manufacturing. The array division number of the laminated piezoelectric element is designed according to the performance of the ultrasonic probe, and a large number of groove portions 8 such as 64, 96, 128, etc. are provided according to the division number.

Further, FIG. 6 shows a micrograph in a side view of the end of the laminated piezoelectric element in which the groove is actually formed and then the external electrode is formed. A dotted line in FIG. 6 indicates a cutting position 9 when an external electrode is formed to form a laminated piezoelectric element and a backing material or an acoustic matching layer is further pasted and then actually cut into an array.
Therefore, FIG. 6 also shows that the groove 8 must be provided so as to avoid such a cutting position 9 as described in paragraph [0029].

  Next, as shown in FIG. 5E, the outer electrode 10 is formed by performing electroless plating using nickel and electrolytic plating using gold on the outer periphery of the multilayer piezoelectric body 1 provided with the groove 8.

Next, as shown in FIG. 5 (f), the internal electrode 2 a and the internal electrode 2 b are electrically separated by removing unnecessary portions of the external electrode 10 formed on the outer periphery of the multilayer piezoelectric body 1. Are connected to the external electrode 10a and the external electrode 10b, respectively.
Finally, the multilayer piezoelectric element 11 of the first embodiment is manufactured by performing a polarization process in which a DC voltage is applied to the processed external electrode 10a and external electrode 10b. In the present embodiment, the polarization treatment is performed after the lamination. However, in the case of lamination using an adhesive or the like, the polarization treatment can be performed before the lamination. In this case, a laminated piezoelectric element made of a piezoelectric material having an arbitrary polarization direction can be obtained.

(Second Embodiment of Multilayer Piezoelectric Element)
Next, a second embodiment of the multilayer piezoelectric element of the present invention will be described. FIG. 7 is a diagram showing a manufacturing process of the second embodiment of the multilayer piezoelectric element of the present invention. Hereinafter, the laminated piezoelectric element according to the second embodiment will be described with reference to FIG.

  First, as shown in FIG. 7A, a green sheet 12 prepared by kneading materials such as lead zirconate titanate (PZT) ceramic powder and a binder into a plate shape is prepared. Here, with respect to the multilayer piezoelectric element of the second embodiment, a multilayer piezoelectric body is formed by simultaneously firing the green sheet and the applied internal electrode paste as described later. Only the surface accuracy of the uppermost and lowermost piezoelectric bodies is not sufficient. Therefore, in the present embodiment, a green sheet 12a serving as a sacrificial layer is prepared, and after simultaneous firing, the green sheet 12a is polished and removed to obtain surface accuracy of the uppermost and lowermost piezoelectric bodies. I am doing so.

Next, as shown in FIG. 7B, an internal electrode paste 4 such as a silver-palladium alloy paste, a platinum paste, or a copper paste is applied to one laminated surface 6 of the green sheet 12 by a screen printing method or the like.
Specifically, the internal electrode paste 4 is applied using a printing plate (not shown) in which the emulsion is fixed to a portion where the internal electrode is not formed in advance. By coating the internal electrode paste 4 using such a method, two locations of the internal electrode paste 4a having a large area and the internal electrode paste 4b having a small area are provided. The wide internal electrode paste 4a and the narrow internal electrode paste 4b are formed so as to appear alternately.

  Next, as shown in FIG. 7C, the laminated surface 6 coated with the internal electrode paste 4 of one green sheet 12 and the laminated surfaces 6 of the other green sheet 12 not coated with the internal electrode paste are laminated. To do. The sacrificial green sheet 12a is also laminated.

  Next, as shown in FIG. 7D, the stacked green sheet 12 and internal electrode paste 4 are fired simultaneously.

  Next, as shown in FIG. 7E, the sacrificial layer portion is removed by polishing, whereby the laminated piezoelectric body 1 is manufactured.

  Next, as shown in FIG. 7 (f), a groove 8 is formed in the end 7 of the multilayer piezoelectric body 1 so as to be cut at a predetermined position by a dicing machine or the like.

  Next, as shown in FIG. 7G, the outer electrode 10 is formed by performing electroless plating using nickel and electrolytic plating using gold on the outer periphery of the multilayer piezoelectric body 1 provided with the groove 8.

Next, as shown in FIG. 7 (h), the internal electrode 2a and the internal electrode 2b are electrically separated by removing unnecessary portions of the external electrode 10 formed on the outer periphery of the multilayer piezoelectric body 1. Are connected to the external electrode 10a and the external electrode 10b, respectively.
Finally, the laminated piezoelectric element 11 according to the second embodiment is manufactured by performing a polarization process in which a DC voltage is applied to the processed external electrode 10a and external electrode 10b.

(Third Embodiment of Multilayer Piezoelectric Element)
Next, a third embodiment of the multilayer piezoelectric element of the present invention will be described. FIG. 8 is a diagram showing manufacturing steps of the third embodiment of the multilayer piezoelectric element of the present invention. Hereinafter, the laminated piezoelectric element according to the third embodiment will be described with reference to FIG.
As shown in FIG. 8D, the laminated piezoelectric element 11 according to the third embodiment of the present invention is replaced with a laminated piezoelectric body in place of the step of forming the groove portion 8 according to the first embodiment shown in FIG. This is manufactured in the same manner as the manufacturing process of the first embodiment except that the through hole 13 is provided in the end portion 1 of 1 by machining (mechanical drilling) and laser processing.

(Fourth Embodiment of Multilayer Piezoelectric Element)
Next, a fourth embodiment of the multilayer piezoelectric element of the present invention will be described. FIG. 9 is a diagram showing a manufacturing process of the fourth embodiment of the multilayer piezoelectric element of the present invention. The laminated piezoelectric element according to the fourth embodiment will be described below based on FIG.

  First, as shown in FIGS. 9A to 9C, after the internal electrode 2 is formed on the laminated surface 6 of the piezoelectric body 5 having a predetermined shape, it is left as it is without removing the unnecessary portion of the internal electrode 2. The laminated piezoelectric body 1 is manufactured by laminating in the state.

Next, as shown in FIG. 9D, unnecessary portions of the internal electrodes are cut together with the piezoelectric body by cutting the unnecessary portions of the internal electrodes from the uppermost layer and the lowermost layer of the laminated piezoelectric body 1 by a dicing machine or the like. Remove by cutting. Then, by filling the cut and removed portion with an insulating resin 14 such as an epoxy resin, two locations of the internal electrode 2a having a large area and the internal electrode 2b having a small area are provided, as in FIG. The internal electrodes 2a having a large area and the internal electrodes 2b having a small area are formed so as to appear alternately in a cross-sectional view in the stacking direction.
As for the depth of this cutting removal, it is necessary to remove unnecessary portions of the internal electrode from the uppermost layer and the lowermost layer of the multilayered piezoelectric body 1, but unwanted vibrations when the multilayered piezoelectric element is formed. In order to reduce the thickness, as shown in FIG. 9D, it is preferable to cut and remove as deeply as possible without cutting the internal electrode of the next layer.

  Next, as shown in FIGS. 9E and 9F, the groove 8 to the end 7 of the multilayer piezoelectric body 1 is obtained by the same method as in FIGS. 5D and 5E in the first embodiment. The external electrode 10 is formed on the outer periphery of the multilayer piezoelectric body 1.

  Next, as shown in FIG. 9G, unnecessary portions of the external electrode 10 formed on the outer periphery of the multilayer piezoelectric body 1 are removed. Here, in this embodiment, the unnecessary portion of the external electrode is configured to be removed up to the end portion in the plan view of the laminated piezoelectric element. The form of such an external electrode is as described in paragraph [0020]. Furthermore, it is selected according to the design of the ultrasonic probe to be obtained and the workability at the time of manufacturing the ultrasonic probe.

  Finally, as shown in FIG. 9 (h), the laminated piezoelectric element 11 of the fourth embodiment is manufactured by performing a polarization process in which a DC voltage is applied to the processed external electrode 10.

  Next, the multilayer piezoelectric element of the present invention and the multilayer piezoelectric element using the multilayer piezoelectric element will be described in detail based on examples. In addition, this invention is not limited to a following example.

Example 1
First, a soft lead zirconate titanate ceramic (Taika Co., Ltd .: L-155N, electromechanical coupling coefficient k33: 77%, relative dielectric constant: 5700, Curie temperature: 155 ° C.) dicing machine and double-side polishing machine To obtain a piezoelectric body having a length of 23 mm, a width of 14 mm, and a thickness of 0.17 mm.

  Next, for the purpose of forming internal electrodes on the obtained piezoelectric body, a 0.5-μm-thick nickel electroless plating was applied to the piezoelectric laminate surface, and a 0.5-μm-thick gold electrolytic plating was further applied. Thereafter, unnecessary portions of the internal electrode were removed by a dicing machine. Then, the internal electrodes were bonded to each other with an epoxy adhesive to produce a laminated piezoelectric material having three piezoelectric material layers of 23 mm × 14 mm × 0.51 mm.

  Next, a dicing machine was used to cut the both ends of the multilayer piezoelectric body at intervals of 0.17 mm to form 128 grooves each having a width of 0.03 mm and a depth of 0.05 mm.

  Next, an outer electrode was formed by applying nickel electroless plating with a thickness of 0.5 μm to the outer periphery of the laminated piezoelectric body provided with the groove, and further applying gold electrolytic plating with a thickness of 0.5 μm. Thereafter, unnecessary portions of the external electrode were removed by a dicing machine.

  Finally, the laminated piezoelectric element of Example 1 was fabricated by applying a direct current voltage between both external electrodes of the laminated piezoelectric element after the processing to perform polarization treatment.

(Example 2)
First, hard lead zirconate titanate ceramic powder (manufactured by Teika Co., Ltd .: H-8, electromechanical coupling coefficient k33: 70%, mechanical quality factor: 2500, Curie temperature: 320 ° C.), binder, plastic The slurry obtained by mixing the agent and the organic solvent was molded by the doctor blade method to obtain a green sheet having a thickness of 0.21 mm.

Next, a 2 mg / cm ² pattern of silver-palladium alloy paste was applied to one laminated surface of the green sheet by a screen printing method.
Next, the laminated surface of the green sheet on which the silver-palladium alloy paste is applied and the laminated surface of the other green sheet on which the silver-palladium alloy paste is not applied are laminated, and the silver-palladium alloy paste is placed on the laminated surface. Laminate 1 sheet of green sheet that has not been coated, and further laminate 1 sheet of green sheet that has not been coated with silver-palladium alloy paste one above the other as a sacrificial layer. did. Thereafter, the upper and lower sacrificial layers were evenly polished and removed to produce a laminated piezoelectric material having three piezoelectric material layers of 23 mm × 14 mm × 0.51 mm.
And the subsequent process performed the process similar to Example 1, and produced the laminated piezoelectric element of Example 2. FIG.

(Example 3)
A laminated piezoelectric element of Example 3 was manufactured by performing the same process as in Example 1 except that a through hole having a diameter of 0.06 mm was formed by machining at the end of the laminated piezoelectric body.

Example 4
First, a plate-like piezoelectric body having a length of 60 mm, a width of 16 mm, and a thickness of 0.8 mm was obtained by performing the same process as in Example 1.

  Next, a groove having a depth of 0.60 mm is formed at a pitch of 100 μm using a blade having a width of 30 μm on a dicing machine parallel to one side of the piezoelectric body, and a plurality of prisms of 70 μm × 60 mm × 0.6 mm are formed. This upright piezoelectric body was produced.

Next, the groove formed in the piezoelectric body is filled with acrylonitrile copolymer resin in which normal hexane and normal pentane are encapsulated, heat-treated at 160 ° C. for 5 minutes, and then the organic polymer body and the piezoelectric are bonded with a double-side polishing machine. By removing the excess of the body and adjusting the thickness, the organic polymer, which is a solidified acrylonitrile copolymer resin in which bubbles are dispersed, was filled, length 23 mm, width 14 mm, thickness 0.17 mm A composite piezoelectric body of the dimensions was prepared.
And the subsequent process performed the process similar to Example 1, and produced the laminated piezoelectric element of Example 4. FIG.

(Example 5)
In the same manner as in Example 1, soft lead zirconate titanate ceramics (manufactured by Teika Co., Ltd .: L-155N, electromechanical coupling coefficient k33: 77%, relative dielectric constant: 5700, Curie temperature: 155 ° C.) A piezoelectric body having a length of 23 mm, a width of 14 mm, and a thickness of 0.17 mm was obtained by processing with a dicing machine and a double-side polishing machine.

  Next, for the purpose of forming internal electrodes on the obtained piezoelectric body, a 0.5-μm-thick nickel electroless plating was applied to the piezoelectric laminate surface, and a 0.5-μm-thick gold electrolytic plating was further applied.

  Next, the laminated surfaces were bonded with an epoxy-based adhesive to produce a laminated piezoelectric material having three piezoelectric material layers of 23 mm × 14 mm × 0.51 mm.

  Next, for the purpose of forming an electrodeless portion in the internal electrode, the width is 0.2 mm by cutting away in the stacking direction using a dicing machine at a position of 0.4 mm from both end portions of the multilayer piezoelectric body. A groove having a depth of 0.32 mm was formed, and the groove was filled with an epoxy adhesive.

  Next, a dicing machine was used to cut the both ends of the multilayer piezoelectric body at intervals of 0.17 mm to form 128 grooves each having a width of 0.03 mm and a depth of 0.05 mm.

  Next, an outer electrode was formed by applying nickel electroless plating with a thickness of 0.5 μm to the outer periphery of the laminated piezoelectric body provided with the groove, and further applying gold electrolytic plating with a thickness of 0.5 μm. Thereafter, unnecessary portions of the external electrode were removed by a dicing machine.

  Finally, the laminated piezoelectric element of Example 5 was manufactured by applying a direct current voltage between both external electrodes of the laminated piezoelectric element after the processing to perform polarization treatment.

(Comparative example)
A laminated piezoelectric element of a comparative example was fabricated by performing the same process as in Example 1 except that the process of forming the groove portion in Example 1 was omitted.

(Investigation of defective rate)
Next, with respect to the laminated piezoelectric elements obtained in Examples 1 to 5 and Comparative Example obtained above, an acoustic matching layer is attached to the ultrasonic radiation surface, and a backing material is attached to the surface opposite to the ultrasonic radiation surface, Further, a wiring member was attached. Thereafter, using a dicing machine, a blade having a blade thickness of 0.03 mm was fed at a feed rate of 3 mm / sec, whereby each groove was cut at a pitch of 0.17 mm to produce 128 array transducer elements.
Then, the capacitance of each arrayed transducer element obtained was measured, and the number of transducer elements (number of defects) in which capacitance abnormality due to disconnection was recognized was investigated. The results are shown in Table 1.

As a result, for the laminated piezoelectric elements of Examples 1 to 5, the defect rate of the external electrodes was 3% or less, whereas the laminated piezoelectric element of the comparative example in which no groove or through hole was provided at the end of the laminated piezoelectric element. Regarding the element, the defect rate of the external electrodes was about 26%, which was significantly higher than the laminated piezoelectric elements of Examples 1 to 5.
Also from this, it was found that the multilayered piezoelectric body of the present invention, the multilayered piezoelectric element using the multilayered piezoelectric body, and the method of manufacturing the multilayered piezoelectric element are effective for preventing defects of the external electrodes.

(Measurement of time signal waveform and FFT spectrum)
Furthermore, an acoustic lens was attached to the arrayed transducer element group obtained in Example 1, and among them, one of the elements in which no capacitance abnormality was observed due to disconnection was obtained from Panametrics Pulsar Receiver (model 5800PR). ), A single pulse was applied, and a time signal waveform and an FFT spectrum were measured.
FIG. 10 shows the measurement result of the time signal waveform, and FIG. 11 shows the measurement result of the FFT spectrum. As a result, the peak to peak voltage was 79.4 mV, the center frequency was 2.49 MHz, and the 6 dB bandwidth was 88.9%.

  The multilayer piezoelectric body of the present invention, the multilayer piezoelectric element using the multilayer piezoelectric body, and the method of manufacturing the multilayer piezoelectric element include medical ultrasonic equipment, aerial ultrasonic equipment, underwater ultrasonic equipment, solid ultrasonic equipment, other It can be used for sensing materials such as ultrasonic equipment.

DESCRIPTION OF SYMBOLS 1 Laminated piezoelectric body 2 Internal electrode 2a Internal electrode 2b Internal electrode 3 Adhesive layer 4 Internal electrode paste 4a Internal electrode paste 4b Internal electrode paste 5 Piezoelectric body 6 Laminated surface 7 End part 8 Groove part 9 Cutting position 10 External electrode 10a External electrode 10b External Electrode 11 Multilayer piezoelectric element 12 Green sheet 12a Green sheet 13 Through hole 14 Insulating resin

Claims (6)

In a laminated piezoelectric material in which n layers (n is an integer of 2 or more) and n-1 internal electrodes are alternately laminated,
At the end of the laminated piezoelectric material,
A laminated piezoelectric body having a groove formed in a lamination direction. The groove is
The multilayer piezoelectric body according to claim 1, wherein the multilayer piezoelectric body is formed at least at a multilayer interface between the piezoelectric body and the internal electrode at the end portion. The shape of the groove is
3. The laminated piezoelectric element according to claim 1, wherein the laminated piezoelectric element has any one of a substantially concave shape, a substantially U shape, a substantially V shape, and a substantially W shape in a cross-sectional view of a cross section parallel to the laminated interface. body. In the end portion of the multilayer piezoelectric body according to claim 1,
At least on the inner surface of the groove,
A laminated piezoelectric element comprising an external electrode connected to the internal electrode and formed so that the internal electrodes are electrically connected in parallel. A step of producing a laminated piezoelectric material in which n-layer (n is an integer of 2 or more) piezoelectric materials and n-1 layer internal electrodes are alternately laminated, and thereafter forming an external electrode at the end of the laminated piezoelectric material. In the manufacturing method of the laminated piezoelectric element having
A method of manufacturing a laminated piezoelectric element comprising a step of forming a groove in the lamination direction of an end of the laminated piezoelectric material. a first step of forming an electrode on the surface of a piezoelectric body of n layers (n is an integer of 2 or more);
A second step of forming a laminate as an internal electrode by adhering the electrodes so that an adhesive layer exists between the electrodes;
A third step of forming a groove at an end in the stacking direction of the laminate obtained by bonding the electrodes;
And a fourth step of forming an external electrode on the inner surface of the groove.