JPH0794796A - Multilayer electrostrictive / piezoelectric element - Google Patents

Abstract

PURPOSE:To detect the existence of the breakages of via connection parts and the existence of the defective connections between the via connection parts and inner electrodes. CONSTITUTION:A number of material layers 32 which show an electrostriction/ piezoelectric effect are piled with inner electrodes 34 therebetween. The respective inner electrodes of every other layer are electrically connected to each other with the via connection parts and, further, the groups of the inner electrodes of every other layer which are connected to each other and have the same polarity are connected to outer terminal electrodes. The inner electrodes are connected to each other through the via connection parts in such a manner that each via connection part of the inner electrodes is shifted from the adjacent via connection part so as to have the adjacent via holes are connected to each other not directly but through the inner electrodes. Moreover, a pair of the outer terminal electrodes 38 are provided on each end part of the direction of lamination and the groups of the inner electrodes which have the same polarities respectively are connected to the corresponding outer terminal electrodes on both the end parts of the direction of lamination.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated electrostrictive / piezoelectric element having a via connection structure. More specifically, the position of the via connection portion is changed every time an internal electrode of the same polarity is connected to the via. The present invention relates to a laminated electrostrictive / piezoelectric element capable of inspecting the quality of via connection by electrical continuity by connecting to external terminal electrodes provided at both ends in the stacking direction while achieving electrical continuity via internal electrodes. is there. This element is useful as an actuator for, for example, printing of a dot printer and positioning of precision equipment.

[0002]

2. Description of the Related Art Laminated electrostrictive / piezoelectric elements have been publicly known. This is because a large number of material layers exhibiting an electrostrictive / piezoelectric effect are stacked via internal electrodes, and a large number of internal electrodes are alternately connected to each other, and two types of internal electrode groups corresponding thereto are respectively corresponded. This structure is connected to an external terminal electrode. Therefore, the external terminal electrode has the same structure as the capacitor formed at two locations. Conventionally, various techniques for electrically connecting internal electrodes have been developed, and one of them is a via connection structure. In the via connection structure, when ceramic green sheets (unsintered sheets) on which internal electrodes are printed are laminated, through holes called via holes are provided in the green sheets, and metal powder (actually This is a technique in which a conductive paste obtained by mixing metal powder such as silver particles and an organic binder is filled, laminated and integrated, and then sintered to achieve electrical connection between layers by the metal material in the via hole.

Usually, via connection portions are provided at two locations on a single green sheet, one of which is connected to an internal electrode and the other of which is not connected to the internal electrode due to escape, and they are arranged alternately. Then, the structure is such that the two via connection portions are continuous in the stacking direction. An example thereof is shown in FIGS. 4 and 5. FIG. 4 shows a cross section of the laminated body (Y _1-
The cross section at the Y ₂ position) is shown in FIG. 5, and FIG. In the element body portion 10, a large number of material layers 12 exhibiting an electrostrictive / piezoelectric effect are stacked via the internal electrodes 14, and two via connection portions 16 electrically connect the internal electrodes 14 to each other every other layer. In addition, the internal electrode groups having the same polarity by connecting every other layer in this manner are connected to the corresponding external terminal electrodes 18. At the upper and lower ends of the element body portion 10 are dummy portions (a laminated body in which the internal electrodes are not sandwiched) 20. Here, a pair of external terminal electrodes 18 are provided on the side surfaces of the dummy portion at the lower end.
In FIG. 4, a ring-shaped portion indicated by reference numeral 15 is a relief (a portion without an electrode material so that the via connection portion and the internal electrode are not connected). The via connection portion on the left side of FIG. 4 is drawn with a dotted line because it is connected to the internal electrode on the surface and is integrated.

The laminated electrostrictive / piezoelectric element of this structure is integrally sintered, and when a voltage is applied between the pair of external terminal electrodes 18, an internal solid (electrostrictive element sandwiched by the internal electrodes is formed). / Material exhibiting piezoelectric effect) causes abrupt displacement, and functions as an actuator.

In addition, the via connection portions are not arranged in a straight line along the stacking direction as described above, but are formed at different positions so as to be uniformly distributed as a whole when viewed from the stacking direction. A technique has also been proposed in which regions (relief portions and via connection portions, that is, regions where electrostriction / piezoelectric effect is not generated) are uniformly dispersed to relax stress (see Japanese Patent Laid-Open No. 2-79482).

[0006]

In such a laminated type electrostrictive / piezoelectric element having an integral sintered structure, the material layer 12 exhibiting the electrostrictive / piezoelectric effect can be made very thin, so that low voltage driving becomes possible, There is an advantage that it can be miniaturized. However, there is a problem in terms of reliability of electrical connection between internal electrodes by via connection. Usually, the contraction rate of the via connection part and the material exhibiting the electrostrictive / piezoelectric effect during sintering is different, and the contraction rate of the via connection part is smaller, so the via connection part becomes thinner than the via hole diameter. is there. As a result, poor connection may occur between the via connection portion and the internal electrode. This is schematically shown in FIG. In the portion of the cross section Z ₁ -Z ₂ , the internal electrodes are not electrically connected to the via connection portion. Further, in extreme cases, the via connection portion may be locally thinned and broken.

However, in the conventional structure, when the via connecting portion is broken or there is no conduction between the via connecting portion and the internal electrode, this cannot be clearly detected from the outside. There is a method of measuring the capacitance between external terminal electrodes as a method of inspecting such a connection failure point, but depending on the position and number of connection failure points, it is possible to accurately detect whether or not they are completely connected. Can not. Then, if there is such a defective connection portion, a desired electrostrictive / piezoelectric effect cannot be obtained when it is incorporated into the device.

An object of the present invention is to provide a laminated electrostrictive / piezoelectric element having a structure capable of completely and easily detecting the presence or absence of breakage of the via connection portion and the presence or absence of connection failure between the via connection portion and the internal electrode. Is to provide.

[0009]

The present invention provides a number of electrostrictive /
Material layers exhibiting a piezoelectric effect are laminated via internal electrodes, and each internal electrode is electrically connected to every other layer by a via connection part, and also corresponds to internal electrode groups of the same polarity connected to every other layer. Is a laminated electrostrictive / piezoelectric element having a structure connected to an external terminal electrode. Here, in the present invention, every time the internal electrodes are via-connected, the position of the via connecting portion is shifted so that the via electrodes are always connected via the internal electrodes, and a pair of external terminal electrodes is provided at both ends in the stacking direction. Are arranged to connect the internal electrode groups having the same polarity to the corresponding external terminal electrodes located at both ends in the stacking direction.

[0010]

The internal electrodes of the laminated electrostrictive / piezoelectric element are connected from the external terminal electrodes through the via connecting portions every other layer, but the positions of the via connecting portions are displaced each time the internal electrodes are connected. Therefore, each via connection portion is electrically connected so as to always pass through the internal electrode. And the internal electrode group that has the same polarity is
Since they are connected to the external terminal electrodes at both ends in the stacking direction, if they are non-defective, there is always continuity between the corresponding external terminal electrodes. Therefore, only by conducting a continuity check between a pair of external terminal electrodes of the same polarity, the presence or absence of breakage of the via connection part and the quality of the electrical connection between the via connection part and the internal electrode can be immediately and surely confirmed. Can be detected.

[0011]

1 is an exploded perspective view of an element body showing an embodiment of a laminated electrostrictive / piezoelectric element according to the present invention.
Is a cross-sectional view (position X ₁ -X _{2 in} FIG. 3), and FIG.
It is a development view of a vertical section in the F position. The basic structure is similar to the above-mentioned conventional one. In the element body 30,
A large number of material layers 32 exhibiting an electrostrictive / piezoelectric effect are laminated via internal electrodes 34, and the internal electrodes are electrically connected every other layer by the via connection portion 36, and each internal electrode 34 is electrically connected. The structure is such that every other layer is connected to a common external terminal electrode 38. Dummy portions (portions not sandwiching the internal electrodes) 40 are provided at both upper and lower ends. Reference numeral 35 is a relief for preventing the internal electrode and the via connecting portion from being connected.

In the present invention, the via connection portions are formed at four places as seen in the stacking direction. Two of them have the same polarity. Each internal electrode 34 is heteropolarly connected to every other layer 32 of the material having an electrostrictive / piezoelectric effect, but the positions of the via connection parts are displaced (zigzag arrangement) for each interlayer connection. Each via connection part 36 must be an internal electrode 34
It is configured to be connected through. Then, a pair of external terminal electrodes 38 is provided at both upper and lower ends in the stacking direction. This configuration is significantly different from the conventional one.

Therefore, as is apparent from FIG. 1, a continuity check between the external terminal electrodes having the same polarity is performed, and if there is no continuity, it can be immediately determined that the product is defective.
This is because conduction does not occur even if the via connection portion is broken, and conduction does not occur if there is even one defective connection point between the via connection portion and the internal electrode.

Manufacture of such a laminated electrostrictive / piezoelectric element can be basically performed in the same manner as in the prior art. For example, the internal electrode material is formed by screen printing on a thin (for example, about 80 μm) green sheet made of a ceramic material having a piezoelectricity such as lead zirconate titanate, and a via hole is formed at a predetermined via connection point. Is provided to fill the paste containing silver particles. Such green sheets are aligned and laminated in a predetermined order, and dummy layers are arranged on both ends to integrate under pressure, and then a degreasing / firing step is performed to integrate the green sheets. Usually, such an element can be produced in large numbers to improve the production efficiency. Thereafter, a pair of external terminal electrodes is provided on each of the dummy portions on both ends.

In the above embodiment, the via connection portions are provided at two locations on the same pole, but they may be arranged at three or more locations. However, it is the same that it is necessary to change the position of the via connecting portion each time the via connection is made to the internal electrodes having the same polarity so that the via electrodes are always connected via the internal electrodes.

[0016]

As described above, according to the present invention, each time an internal electrode having the same polarity is connected to a via, the position of the via connection portion is changed so that the via electrode is always connected via the internal electrode. By arranging a pair of external terminal electrodes at both ends and connecting them, it is only necessary to check the continuity between the external terminal electrodes of the same polarity, and there is no breakage of the via connection portion and the via connection. It is possible to confirm that there is no electrical connection between the connection portion and the internal electrode, and the defective product can be reliably detected. As a result, quality assurance is improved and a defective product can be found before finishing, so that it is possible to prevent an unnecessary increase in man-hours. Furthermore, since the external terminal electrodes are located at both ends in the stacking direction, the degree of freedom in assembling into the device is increased, and by utilizing them, the lead terminals can be connected in parallel to improve the reliability. it can.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of an element body showing an embodiment of a laminated electrostrictive / piezoelectric element according to the present invention.

FIG. 2 is a cross-sectional view of a laminated electrostrictive / piezoelectric element according to the present invention.

FIG. 3 is a development view showing a vertical cross section at the A-F position.

FIG. 4 is a cross-sectional view showing an example of a conventional technique.

FIG. 5 is a vertical sectional view thereof.

FIG. 6 is an enlarged explanatory view of a conventional via connection structure.

[Explanation of symbols]

 30 Element Main Body Part 32 Electrostrictive / Piezoelectric Effect Layer 34 Internal Electrode 35 Escape 36 Via Connection Part 38 External Terminal Electrode

Claims (1)

[Claims] 1. A large number of material layers exhibiting an electrostrictive / piezoelectric effect are laminated via internal electrodes, and each internal electrode is electrically connected by a via connection portion every other layer and connected every other layer. In an element with a structure in which a group of internal electrodes that have the same polarity are connected to the corresponding external terminal electrodes, each time the internal electrodes are connected to each other vias, the position of the via connection part is shifted so that the internal electrodes are always connected. In addition, a pair of external terminal electrodes are arranged at both ends in the stacking direction, and internal electrode groups having the same polarity are located at both ends in the stacking direction and connected to the corresponding external terminal electrodes. Characteristic multilayer electrostrictive / piezoelectric element.