JP6591910B2 - Piezoelectric element and manufacturing method thereof - Google Patents

Description

  The present invention relates to a laminated piezoelectric element that expands and contracts by application of a voltage and a method for manufacturing the same.

  Conventionally, as shown in FIG. 3A, piezoelectric ceramics 210 and internal electrodes 221 and 222 are alternately stacked, and the internal electrodes 221 and 222 are connected in parallel every other layer by the external electrodes 271 and 272 on the side surface of the element. A piezoelectric element 200 is known. On the other hand, there is also known a piezoelectric element in which internal electrodes are connected to each other through through-hole electrodes inside the element when it is inappropriate to provide external electrodes (see, for example, Patent Document 1).

JP 2008-211047 A

  In recent years, there are increasing demands for miniaturization and thinning of the multilayer piezoelectric element as described above, and as shown in FIG. The thickness of the layer may be reduced (for example, up to about 50 μm). In this case, the external electrodes 371 and 372 on the side surfaces protrude from the end face in the element stacking direction, and a flat surface cannot be secured. In such a piezoelectric element 300, it is impossible to accurately extract the displacement with respect to the reference plane.

  Moreover, even if it does not protrude temporarily, as shown in FIG. 3C, if there are external electrodes 471 and 472 on the side surfaces, the external electrodes 471 and 472 and the metal member when the piezoelectric element 400 is installed on the metal member 900. It becomes difficult to ensure insulation between the two.

  The present invention has been made in view of such circumstances. Even when the device is miniaturized or thinned, a reference plane is secured on the element so that the displacement can be accurately taken out, and insulation is provided when the device is installed on a metal member. An object of the present invention is to provide a piezoelectric element that can be secured and a method for manufacturing the same.

  (1) In order to achieve the above object, the piezoelectric element of the present invention is a stacked piezoelectric element that expands and contracts by application of voltage, and is alternately stacked with piezoelectric layers formed of piezoelectric ceramics and the piezoelectric layers. A through-hole electrode that penetrates the element body and is connected in parallel to every other layer, and is connected to both ends of the internal electrode provided at both ends in the stacking direction. The thickness of the protective layer, which is the piezoelectric layer on the part side, is less than 100 μm.

  As a result, even if the device is downsized and thinned, a reference plane can be secured on the element so that the displacement can be accurately taken out, and insulation can be secured when it is installed on the metal member. In addition, the external electrode is not provided on the side surface of the element, and it is only necessary to provide the external electrode only on one end face in the stacking direction, so that wiring is easy.

  (2) Further, the piezoelectric element of the present invention is characterized in that it further includes an external electrode connected to the through-hole electrode and provided on only one of the pair of end faces in the stacking direction. Thereby, since the external electrode is only on one end face, wiring with the outside becomes easy. Moreover, since the other end surface can be used as a reference surface, the displacement can be taken out accurately. Further, since the external electrode is only on one end face, there is no danger of short circuit even if the other end face is installed on the metal member.

  (3) Further, the piezoelectric element of the present invention is characterized in that the distance between adjacent electrodes among the internal electrodes is less than 50 μm. Despite such a structure, electrical connection is made with the through-hole electrode, and wiring is facilitated because the external electrode is only on one of the end faces.

  (4) A method for manufacturing a piezoelectric element according to the present invention is a method for manufacturing a stacked piezoelectric element that expands and contracts by application of a voltage, and includes a hole for a through-hole electrode formed on a green sheet laminate on which an electrode pattern is printed. The solid content is adjusted so that the metal particles for the electrode occupy 20 to 50 vol% in the through-hole electrode hole, and the solid content is adjusted to 45 to 55 vol%. The method includes a step of injecting an electrode paste, and a step of firing the laminated body filled with the electrode paste.

  By using the electrode paste as described above, the metal particles occupy 20 to 50 vol% after the paste is dried, and the electrodes are filled with the metal particles by subsequent firing. As a result, even if the piezoelectric element is reduced in size and thickness, the reference plane can be secured on the element, the displacement can be accurately taken out, and insulation can be ensured when it is installed on the metal member. In addition, the adjustment of the electrode paste as described above does not cause swell that affects the element thickness in the firing process for the through-hole electrode portion.

  According to the present invention, even when the piezoelectric element is downsized or thinned, it is possible to secure a reference plane on the element to accurately extract the displacement, and to ensure insulation when the element is installed on a metal member.

(A), (b), (c) is the top view, side view, and side sectional view of the piezoelectric element of the present invention, respectively. It is a sectional side view of the piezoelectric element of this invention arrange | positioned on a metal member. (A), (b), (c) is a sectional side view of a conventional piezoelectric element.

  Next, embodiments of the present invention will be described with reference to the drawings. In order to facilitate understanding of the description, the same reference numerals are given to the same components in the respective drawings, and duplicate descriptions are omitted.

(Piezoelectric element)
1A, 1B, and 1C are a plan view, a side view, and a side sectional view of the piezoelectric element 100, respectively. FIG.1 (c) has shown sectional drawing of the cross section 1c of Fig.1 (a). FIG. 2 is a side sectional view of the piezoelectric element 100 disposed on the metal member 900. The piezoelectric element 100 is a stacked piezoelectric element that is formed in a rectangular body and has one main surface bonded to a metal member 900. The piezoelectric element 100 includes a piezoelectric layer 110, internal electrodes 121 and 122, and through-hole electrodes 171 and 172, and expands and contracts when a voltage is applied to the through-hole electrodes 171 and 172.

  The piezoelectric layer 110 is formed in a layer shape with piezoelectric ceramics such as PZT and barium titanate. The piezoelectric layer 110 is polarized in the stacking direction with the internal electrodes 121 and 122.

  The internal electrodes 121 and 122 are made of a metal such as Ag—Pd or Ag—Pt, and are stacked alternately with the piezoelectric layers 110. The internal electrodes 121 and 122 are connected to every other layer in parallel by through-hole electrodes 171 and 172, respectively. Thereby, it is not necessary to provide an external electrode on the side surface of the piezoelectric element 100.

  The distance between adjacent electrodes among the internal electrodes 121 and 122 is preferably less than 50 μm. With such a thinned structure, the piezoelectric element can be operated with high efficiency. Wiring is facilitated by providing the through-hole electrodes 171 and 172 in a thinned state.

  The through-hole electrodes 171 and 172 penetrate the element body and are connected to the internal electrodes 121 and 122, respectively. As a result, the external electrodes 171a and 172a for taking out the internal electrodes 121 and 122 do not exist on the side surfaces. Accordingly, since the electrodes on the side surfaces do not protrude from the end surface 150 in the stacking direction, even if the size and the thickness of the layer are reduced, a reference surface (equivalent to the end surface 160) is secured as shown in FIG. Can be taken out. And insulation can be ensured when installing in the metal member 900. FIG. For example, a high effect can be expected when the thickness t of the piezoelectric element 100 is less than 500 μm.

  The protective layers 110a and 110b are regions from the pair of end surfaces 150 and 160 perpendicular to the stacking direction of the internal electrodes 121 and 122 to the nearest electrode of the internal electrodes 121 and 122 (in other words, more end than the internal electrode at the end). Part piezoelectric layer). The thicknesses t1 and t2 of the protective layers 110a and 110b are less than 100 μm and preferably less than 30 μm. The smaller the layers that do not contribute to expansion and contraction, such as the protective layers 110a and 110b, the higher the efficiency.

  The external electrodes 171a and 172a are preferably connected to the through-hole electrodes 171 and 172 and provided only on one of the pair of end surfaces 150 and 160 (the end surface 150 in the example of FIGS. 1 and 2). Thereby, wiring becomes easy, and even if the other end surface 160 is installed on the metal member 900, there is no possibility of short circuit.

  The piezoelectric element 100 configured as described above can be used for, for example, a precision positioning piezoelectric actuator, a piezoelectric transformer, and a medical probe using a stage or a mass flow controller valve as a driven body.

(Piezoelectric element manufacturing method)
A manufacturing process of the piezoelectric element 100 will be described. First, a piezoelectric material, a solvent, a binder and the like are mixed in a predetermined composition, and a green sheet is formed by extrusion molding. An electrode pattern is printed on the obtained green sheet with an electrode paste, they are laminated, and the laminate is punched with a mold. And the hole for through-hole electrodes is provided in the punched-out laminated body, and electrode paste is inject | poured to predetermined amount.

  At this time, the electrode metal particles such as Ag / Pd are adjusted so as to occupy 20 to 50 vol% of the solid content, and the solid content of the electrode paste is adjusted to 45 to 55 vol%. And it is preferable to inject | pour electrode paste into a hole so that it may fully fill with respect to the volume of a hole. Since the ceramic compact shrinks during pressing and firing, the filling rate of the original metal powder itself is kept low. When injecting the electrode paste, an external electrode connected to the through-hole electrode may also be provided.

  When the filled electrode paste is dried, drying shrinkage occurs, and both ends of the main surface of the electrode filling the hole are recessed in a funnel shape. The electrode paste after drying forms a structure like a porous body in which metal particles are dispersed in an organic resin (binder), and the metal particles are dispersed in an organic network. At this time, only solid content remains, and the occupation ratio of the metal particles to the organic matter is 20 to 50%.

  The laminate thus prepared is fired while being pressed. A fired body can be produced. The external electrode on the end face in the stacking direction may be fired simultaneously with the piezoelectric ceramic. When firing, the electrode shrinks to about 50% by volume due to firing shrinkage compared to when dried. As a result, the swell that affects the element thickness does not occur in the through-hole electrode portion. The fired body is processed by grinding, and a lead wire is connected to the external electrode of the fired body obtained by the processing. Then, the piezoelectric element 100 is obtained by polarizing the piezoelectric layer in the active region. By adjusting the components of the electrode paste in advance as described above, it is possible to prevent the swelling that affects the element thickness and to form a thin piezoelectric element having a through-hole electrode.

DESCRIPTION OF SYMBOLS 100 Piezoelectric element 110 Piezoelectric layer 110a, 110b Protective layer 121,122 Internal electrode 150,160 End surface 171,172 Through-hole electrode 171a, 172a External electrode 900 Metal member

Claims (1)

A method of manufacturing a laminated piezoelectric element that expands and contracts by applying a voltage,
Providing a hole for a through-hole electrode in a laminate of green sheets printed with an electrode pattern;
An electrode paste in which the solid content is adjusted so that the metal particles for the electrode occupy 20 to 50 vol% and the solid content is adjusted to 45 to 55 vol% is injected into the through-hole electrode hole. Process,
Firing the laminate filled with the electrode paste. A method of manufacturing a piezoelectric element, comprising:

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