JPS63294976A - Laminating type piezoelectric element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a laminated piezoelectric element for an actuator that utilizes stretching strain induced in a piezoelectric material layer by an electric field, and particularly relates to an internal electrode layer of a laminated piezoelectric element. The present invention relates to a structure of a laminated piezoelectric element that connects a layer and an external electrode layer simply and reliably.

[Conventional technology]

With the rapid development of mechatronic equipment, actuators used in this field are attracting attention. the current,
Since the majority of actuators are driven by electromagnetic force,
In addition to high power consumption, they generate heat and electromagnetic noise, and there is a desire to develop an actuator that can replace this. In contrast, actuators that utilize the piezoelectric effect of solids not only can essentially overcome the drawbacks of electromagnetic actuators, but also have the advantage of being small, lightweight, resistant to vibration and shock, and can also have sensor functions. are doing.

As a piezoelectric actuator, a piezoelectric bimorph, which is made by bonding two piezoelectric plates together, has been known for a long time, and is used as a transducer for a speaker, a body thinner for a VTR head, and the like. Bimorph is a relatively low voltage
Piezoelectric bimorphs have the advantage of being able to obtain a large displacement of 00-00 and being easily manufactured, but on the other hand, the generated force is small and the response speed is not very fast.Furthermore, piezoelectric bimorphs basically utilize piezoelectric transverse effects. Therefore, the electric-mechanical energy conversion efficiency is low, and therefore the characteristics are insufficient as actuators for recent highly developed mechatronics or electronics. As an improvement on this, a piezoelectric longitudinal effect drive actuator in which a large number of piezoelectric plates are stacked in layers has also been proposed. The voltage required to drive this laminated actuator (stack type) is determined by the thickness of each piezoelectric plate, but due to processing and assembly constraints, it is difficult to make the plate thickness thinner than 0.5 Tsuru. Therefore, a drive voltage of soo v or higher is usually required. For this reason, it is difficult to construct the drive circuit using an IC, and the field of application thereof is limited.

Recently, a multilayer piezoelectric element has been proposed that applies the manufacturing technology of multilayer ceramic capacitors called the green sheet method.The zero-wire piezoelectric element is ultra-small and inexpensive compared to the conventional stack-type piezoelectric actuator, and is a bimorph type piezoelectric element. It has excellent characteristics such as faster response speed (higher generated stress, and higher positioning accuracy) than the previous one, so it is expected to be applied in various fields.

As such piezoelectric elements, for example, those shown in FIG. 2 and those having the structure shown in FIG. 3 are known.

FIG. 2 is a cross-sectional view of the piezoelectric element, where 1 is a piezoelectric material layer and 2A is a piezoelectric material layer.

2B is a buried internal electrode layer. 3A is an external electrode layer electrically connected to the internal electrode layer 2A, and 3B is an external electrode layer electrically connected to the internal electrode layer 2B. Voltages of different polarities are applied to the external electrode layer 3A and the external electrode layer 3B. The portion of the piezoelectric material layer 1 sandwiched between the internal electrode layers 2A and 2B expands and contracts due to the electric field, and the piezoelectric element functions as an actuator. FIG. 3 is a sectional view of another piezoelectric element. 21 is a piezoelectric material layer, 22A, 22B
is internal 1! The pole layers 23A and 23B are external lead wires. The external lead wire 23A is electrically connected to the internal electrode layer 22A. The external lead wire 23B is electrically connected to the internal electrode layer 22B. External lead wire 23^.

The operation in which voltages of different polarities are applied to 23B is the same as in the case of FIG. The difference between the piezoelectric elements in FIG. 2 and FIG. 3 is that in the former, the internal electrode layer is partially buried, whereas in the latter, the internal electrode layer is completely buried.

[Problem that the invention seeks to solve]

However, in the case of the partial embedding method, either the internal electrode layer 2A or the internal electrode layer 2B is exposed on the side end surface of the piezoelectric element, so it is easy to form the external electrode layers 3A and 3B. , 2B show only a partial overlap inside the element, the overlapped part is the piezoelectric material layer 1.
expands and contracts, but the non-overlapping portions do not expand and contract, which causes stress to concentrate near the boundary between the overlapping and non-overlapping portions of the internal electrodes J12A, 2B, resulting in mechanical damage. On the other hand, an internal electrode layer 22A as shown in FIG.
In the completely embedded type 22B, the piezoelectric material layer 21 expands and contracts uniformly over the entirety, and the piezoelectric element is not mechanically damaged, but the piezoelectric material layer 21 is formed by the doctor blade method. Therefore, its thickness is 0.1 to 0.3 m.
There was a problem that electrical connection between 3A and 23B was difficult.

In addition, in the case of this completely embedded type, as a method of electrically connecting the internal electrode layer and the external electrode layer, an insulating material is applied to every other layer of the internal electrode layer exposed on the side end surface to electrically insulate it. Another method has been proposed in which the external electrode layer is applied uniformly over the entire surface of the side end surface, but since a fluid material is used when applying the insulating material, the insulating layer is applied every other layer to minute areas as described above. This invention was made in view of the above points, and its purpose is to provide a structure in which a flexible printed wiring board equipped with parallel conductors is attached to the side end surface of a laminated piezoelectric element. Thereby, the purpose is to electrically connect the internal electrode layer exposed on the side end surface and the external electrode layer formed on the insulating layer efficiently and with high reliability.

[Means for solving problems]

According to the present invention, the above object is a laminated piezoelectric device in which piezoelectric material layers and electrode layers are alternately laminated, and voltages of different polarities are alternately applied to the obtained internal electrode layers to cause the piezoelectric material layers to expand and contract. In the element, (a) internal electrode layers 46A and 46B that lie or are embedded in the entire surface between the piezoelectric material layers 47 and are exposed at the side end surfaces of the piezoelectric element; Piezoelectric material layer 4
(c) two insulating layers 41^, 41B formed over the entire length of the internal electrode layers 46A, 46B in the stacking direction; and (c) an external electrode layer 42A formed on the surface of the insulating layer.

42B and middle) conductors 43A and 43B formed in parallel at twice the interval of the internal electrode layers, and using these conductors to connect the internal electrode layers 46A and 46B to the external electrode layer 42A.
, 442B, and is bonded to the laminate of the piezoelectric material layer and the internal electrode layer with adhesive resins 45A, 45B.

This is achieved by having the following.

The internal electrode layers 46^, 46B are embedded over the entire surface of the piezoelectric material layer 47 between the eyebrows. The piezoelectric material layers 47 and internal electrode layers are alternately stacked. Regarding the internal electrode layer, 46^ and 4
6B are alternately stacked. Internal electrode layers 46A and 46B
are applied with voltages of different polarities. Piezoelectric material layer 47
expands and contracts due to the electric field. Prior to use, the piezoelectric element is subjected to a preliminary decentralization process. At this time, the piezoelectric material layer is polarized in the direction of the electric field, resulting in a predetermined strain. When the electric field is removed, piezoelectric elements exhibit hysteresis and leave a certain residual strain.
When an electric field is applied, the strain caused by this electric field is added. When such a piezoelectric element expands and contracts, the internal electrode layer 46A.

46B is completely buried, the electric field distribution in the piezoelectric material layer 47 is uniform, and the expansion and contraction occurs uniformly over the entire piezoelectric material layer 47, and the amount of expansion and contraction of the piezoelectric material layer is maximum, and the partial Stress concentration is also eliminated and damage to the piezoelectric element is prevented. The embedded internal electrode layer is exposed at the side end surface. A voltage is applied to the internal electrode layer through this exposed portion. The voltage is applied to the external electrode layer 4, which will be described later.
This is done by electrically connecting to 2A and 42B.

External electrode! 42A supplies voltage in parallel to internal electrode layer 46A. The external electrode layer 42B is parallel to the internal electrode layer 46B.

supply voltage to.

The insulating layers 41A and 41B are the external electrode layers 42A and 42B.
is formed on this surface to prevent the external electrode layers 42A, 42B from directly contacting the internal electrode layers 46A, 46B.

Voltages of different polarities are supplied to the external electrode layers 42A and 42B.

The flexible printed wiring board made of thermosetting resin has conductors 43 arranged in parallel at the same pitch as the pitch of the internal electrode layers 46A (twice the pitch between the internal electrode layers 46A and 46B).
A or 43B is formed. Conductor 438 is formed on flexible printed circuit board 44A, and conductor 43B is formed on flexible printed circuit board 44B. This conductor 4
3^ or 43B electrically connects the internal electrode layer and the external electrode layer. The conductor 43A connects the internal electrode layer 46A and the external electrode 42A, and the conductor 43B connects the internal electrode layer 46
B and the external electrode layer 42B are connected.

The flexible printed wiring board is pressure bonded to the laminate of the piezoelectric material layer 47 and the internal electrode layers 46A and 46B using a liquid adhesive resin. At this time, electrical connections are made between the conductors 43A, 43B and the internal electrode layers 46A, 46B and the external electrode layers 42A, 42B. The liquid adhesive resin dries, and the flexible printed circuit board and
The adhesion of the laminate becomes stronger.

[Effect]

The flexible printed wiring boards 44A and 44B are connected to the piezoelectric material layer 47 and the internal electrode layer 46A via a liquid adhesive resin.

It is pressure bonded to the 46B laminate. The adhesive on the conductor surfaces (projections) is removed by applying pressure, and electrical connection between the conductors 43A, 43B and the internal electrode layers 46A, 46B and the external electrode layers 42A, 42B is achieved.

The liquid adhesive resin is applied to the grooves (recesses) between the conductors 43A and the conductors 43A.
It accumulates in the groove (recess) between B and adheres the flexible printed wiring board and the laminate.

〔Example〕

Next, embodiments of the present invention will be described based on the drawings. Nickel lead niobate (Pb (Ni'A Nb'S4)
A slurry is prepared by dispersing calcined powder of a piezoelectric material containing lead titanate (PbTiOs) and lead zirconate (PbZrOs) as main components and an organic binder in an organic solvent.

The slurry is spread on a polyester film to a thickness of 250 tns using a doctor blade, air dried, and then heated using infrared rays. The green sheet of piezoelectric material was peeled off from the polyester film, and then platinum paste for internal electrodes was printed uniformly on the surface of the green sheet to a thickness of 10 mm, and then cut into squares, as shown in Figure 1 ( Piezoelectric material green sheet 3 as shown in al.
A lamination sheet 34 having a thick internal electrode paste film 32 adhered thereon is formed on the lamination sheet 34.
A laminate molded body is formed by stacking 0 sheets and pressing them together by hot pressing.

The laminate molded body is fired at a temperature of 1200° C. to 1250° C., and a laminate 33 as shown in FIG. 1 is formed.

At this time, the thickness of the piezoelectric material layer 47 is 200 mm.

The insulating layers 41A and 41B shown in FIG. 1(e) are formed as follows. A slurry is prepared by dispersing an insulating material powder mainly composed of powdered glass and a mobile binder in an organic solvent, and the slurry is prepared by a doctor blade method to a thickness of 50 to 60 μm.
Form an insulating layer green sheet.

This insulating layer green sheet is cut to a length equal to the length of the side end face by 2 of the length of one side of the square of the laminate 33, and approximately 1
Heat and press the center part of the side end face at 00°C.

A green sheet serving as an insulating layer is similarly pressed onto the opposite side end face, and is baked at a temperature of about 900° C. to be integrated with the laminate 33.

The external electrodes N42A, 42B can be formed by applying silver paste onto the insulating layers 41A, 41B so as not to protrude the insulating layers, and baking the paste at about 600° C., as shown in FIG. 1+d+.

Next, a flexible printed wiring board 44 made of polyimide
Prepare A and 44B. The size of this wiring board is wider than the above-mentioned insulating layers 41A and 41B, and the length is about the same. This wiring board has a line width of 100 and a pitch of 400.
- Parallel conductors 43A and 43B made of copper are formed.

4 parts by weight of an epoxy liquid adhesive (Araldite CY232 (Ciba Geigi)) and 1 part by weight of a hardening agent (HY956 (Ciba Geigi)) were mixed well, and then applied uniformly to the entire end surface on which the external electrode was formed. Later, the conductors 43^, 43B of the flexible printed circuit board and the internal electrode layer 46A,
46B so that they overlap each other, temporarily fasten with transparent adhesive tape, apply pressure with a pressure jig of about 50 kg/- through silicone rubber, and hold at room temperature for about 8 hours. . FIG. 1+el shows the state where the flexible printed wiring board 44A is bonded to the laminate 33, and the flexible printed wiring board 44B shows the state before bonding.
and the conductor 43 of the flexible printed circuit board 44A.
This is an enlarged view of the state of electrical connection with A. The liquid adhesive resin is bonded to the conductor 43A and the internal electrode layer 46A by pressure during adhesion.
is removed from the exposed portion of the terminal, and electrical continuity is established. The adhesive resin 45A obtained by drying the liquid adhesive resin serves not only to fix the flexible printed wiring board but also to insulate every other layer of the exposed internal electric bridge.

External electrode layer 4 of the multilayer piezoelectric element manufactured by the above method
When a DC voltage of 100V is applied between 2A and 428, a displacement of approximately 6- is obtained.

The manufacturing accuracy of the thickness of the piezoelectric material layer 47 obtained by the green sheet method is high, and the spacing between the conductors of the flexible printed wiring board is also highly accurate.Furthermore, since the conductors can be provided with a predetermined width, the internal electrode It can be said that the reliability of the electrical connection between the layer and the conductor is high. Furthermore, when this electrical connection is made at one point, other parts are automatically connected, so it can be said that the connection is easy.

The insulating layers 41A and 41B have a film quality because they are preformed into sheets as described above.

A film with a uniform thickness is prepared, and the piezoelectric element expands and contracts uniformly.

〔Effect of the invention〕

According to this invention, piezoelectric material layers and RFfiN are alternately laminated, and the resulting internal i! In a laminated piezoelectric element in which the piezoelectric material layers are expanded and contracted by applying voltages of different polarities to the electrode layers alternately, (a) internal electrodes are embedded over the entire surface between the piezoelectric material layers and exposed at the side end surfaces of the piezoelectric element; (b) two insulating layers formed on a part of the side edge periphery and over the entire length of the piezoelectric material layer and the internal electrode layer in the stacking direction; and (c) two insulating layers formed on the surface of the insulating layer. A function of having a conductor formed in parallel with an interval twice the interval between the outer electrode layer and the inner electrode layer, and electrically connecting the inner electrode layer and the outer electrode layer using this conductor. and a flexible printed wiring board bonded to a laminate of a piezoelectric material layer and an internal electrode layer with an adhesive resin; The conductors on the board are bonded under pressure using a liquid adhesive resin, which removes the adhesive resin on the conductor surface and causes contact with the internal and external electrode layers.As a result, the internal and external electrode layers are flexible. Electrical connection is easily and reliably made via the conductor of the printed wiring board.

[Brief explanation of drawings]

FIG. 1 (al~(fl shows the laminated piezoelectric element according to the embodiment of the present invention according to the manufacturing process; (al~+1
41 is a perspective view of a piezoelectric element, (fl is a partially enlarged view of a piezoelectric element, and FIGS. 2 and 3 are schematic cross-sectional views of a conventional laminated piezoelectric element. 41^, 418F insulating layer, 42A, 42B: External electrode layer, 43A. 43B: Conductor, 44A, 44B: Flexible printed wiring board, 45^: Adhesive resin, 46A, 468:
Internal electrode layer, 47: piezoelectric material layer. Agent I "111 upper Ill + - 1 Ru゛;) - part 31 E ≧ electricity + rice 1 group part part figure 1 figure 1 ts2 figure 3 drawing's pure lightning r snowyong No change) Figure 1 Procedural amendment form) % form % 3. Relationship with the person making the amendment Applicant Location Kawasaki-shi, Kawasaki-ku, Tanabeshin FB 1 No. 1- Name (5234 Fuji Electric Co., Ltd. 4, representative) person

Claims (1)

[Claims] 1) A laminated piezoelectric element in which piezoelectric material layers and electrode layers are alternately laminated, and voltages of different polarities are alternately applied to the resulting internal electrode layers to cause the piezoelectric material layers to expand and contract. (a) an internal electrode layer embedded over the entire surface between the piezoelectric material layers and exposed at the side end surface of the piezoelectric element; and (b) a part of the periphery of the side end and between the piezoelectric material layer and the internal electrode layer. two insulating layers formed over the entire length in the stacking direction; (c) an external electrode layer formed on the surface of the insulating layer;
d) A conductor formed in parallel at twice the interval of the internal electrode layer, and having a function of electrically connecting the internal electrode layer and the external electrode layer using the conductor, and an adhesive resin. A laminated piezoelectric element comprising: a flexible printed wiring board bonded to a laminated body of a piezoelectric material layer and an internal electrode layer;