JPH06237025A - Laminated type piezoelectric element - Google Patents

Abstract

PURPOSE:To provide a piezoelectric element, in which there is no defective connection between an internal electrode and an external electrode and defective insulation, etc., in the laminated type piezoelectric element used as an actuator. CONSTITUTION:In a laminated type piezoelectric element, in which piezoelectric materials and internal electrodes 12 are laminated alternately and which has an insulating layer continuously formed onto the side faces of the laminate and an external electrode 63 continuously formed onto the insulating layer and electrically connected to the internal electrodes 12, sections, in which the internal electrodes 12 and the external electrode 63 are bonded electrically, are shaped thinly and sections, in which the internal electrodes 12 and the external electrode 63 are not bonded, thickly in the insulating layer having multiple structure consisting of an epoxy electrodeposition layer 61 and an insulating film 62. The internal electrodes 12 corresponding to the thin sections of the insulating layer and the external electrode 63 are connected by nickel plated layers 71.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated piezoelectric element in which a large number of thin films of piezoelectric material are laminated and a longitudinal displacement can be obtained by applying a voltage.

[0002]

2. Description of the Related Art When manufacturing a laminated piezoelectric element, it is common to dispose internal electrodes on the entire surface of the piezoelectric element in order to obtain efficient displacement and prevent damage during driving. In this case, it is necessary to connect the internal electrodes to the positive electrode and the negative electrode every other layer outside the device.

For example, as shown in FIG. 8, in a piezoelectric element in which an internal electrode 82 is arranged on the entire surface between a film or a thin plate 81 made of a piezoelectric material, an insulating layer formed continuously on one side surface of the element. 83 and an external electrode 84 continuously formed on the insulating layer 83 with the same width. The end of the internal electrode 82 exposed on the side surface of the element and the external electrode 84 are separated by a nickel plating layer 85. Electrically connected to.
On the other hand, the insulating layer and the external electrode 84 are similarly formed on the other side surface, and the end of the internal electrode 82 where the nickel plating layer 85 is not formed on one side surface and the external electrode 84 are formed by the nickel plating layer 85. The structure is such that the internal electrodes 82 are electrically connected to every other layer, and the layers are shifted on a pair of side faces facing each other as a whole, and the internal electrodes 82 are connected to every other layer.

[0004]

However, there are the following problems when the above connection method is used. That is, as is clear from FIG. 8, the nickel plating layer 85 is grown from the side surface of the element where the internal electrode 82 is exposed, and the nickel plating layer 85 is grown up to the external electrode 84 by at least the thickness of the insulating layer 83. However, there is variation in the growth of the nickel plating layer 85, and in order to connect all the internal electrodes 82 of every other layer, the thickness of the insulating layer 83 is made thin, and the internal electrode 82 and the external electrode are connected. It is necessary to reduce the distance from 84.

However, although the internal electrodes 82 that are not connected are formally insulated, a voltage of several hundreds of volts is applied through the insulating layer 83 during actual driving, so the insulating layer 8
If the thickness of 3 is thin, dielectric breakdown may occur. As described above, the thickness of the insulating layer 83 has contradictory effects on the relationship between the connection during manufacturing and the withstand voltage during driving,
It has been difficult to set the conditions, resulting in poor connection and dielectric breakdown, which has been a cause of reduced yield.

The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a highly reliable piezoelectric element by preventing defects such as connection defects and insulation breakdown.

[0007].

In order to achieve this object, the laminated piezoelectric element of the present invention is an insulating layer having different thicknesses between a portion where an internal electrode and an external electrode are electrically connected and a portion where they are not electrically connected. With layers. Further, the insulating layer has at least a layer for adjusting the thickness, and has a multi-layered structure.

[0008]

In the laminated piezoelectric element of the present invention having the above-mentioned structure, the insulating layer is thin at the portion where the internal electrode and the external electrode are connected and can be easily and surely connected, and the insulating layer is thick at the portion which is not connected. Insulation can be ensured.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall view of a laminated piezoelectric element according to the present invention, in which a film of a piezoelectric material 11 containing PZT as a main component and a P film are formed.
An insulating layer 13 is formed on the opposite side surfaces 14 and 15 of the stacked body in which the internal electrodes 12 containing d as a main component are alternately overlapped so as to continuously extend over the entire piezoelectric material 11 in the stacking direction of the element. Copper foil 6 as an external electrode on the insulating layer 13
3 are similarly formed continuously in the stacking direction of the element, and the internal electrodes 12 exposed on the side surfaces of the element and the copper foil 63 are electrically connected by the nickel plating layer 71 as a conductive material. The layers are shifted by 15 and connected to the internal electrodes 12 of every other layer.

A method of manufacturing the laminated piezoelectric element having such a structure will be described below with reference to FIGS.

First, a piezoelectric material powder containing PZT as a main component was mixed to a desired composition, and then 5 parts by weight of a binder and a small amount of a plasticizer and a defoaming agent were added to the powder which was calcined at 850 ° C. Disperse in a solvent to make a slurry. This slurry is formed into a green sheet by a doctor blade method to a predetermined thickness. Pd paste is screen-printed as the internal electrodes 12 on the green sheet, and a predetermined number of punched out pieces are stacked and integrated by hot pressing.

After degreasing, sintering was performed at about 1200 ° C.
As shown in FIG. 4, the temporary external electrodes 22, 2 are added to the sintered body 21 cut at positions where the internal electrodes 12 are exposed every other layer.
3 is applied and baked, and further cut so that another pair of side surfaces 24 and 25 are exposed. After masking one side surface 25, it is dipped in an epoxy cation electrodeposition paint, and a DC-power source is connected to the temporary external electrode 22 and electrodeposition is carried out at 50 V for 5 minutes. Then, the temporary external electrode 23 is connected to the power source, and 3
When electrodeposition is performed at 0 V for 2 minutes, epoxy electrodeposition layers 61a and 61b having different heights are formed every other layer as shown in FIG.

When heat-treated at 150 ° C. for 30 minutes in this state, the paint (epoxy electrodeposited layers 61a, 61) is heated by heat.
When b) flows, it gradually hardens, and as shown in FIG. 4, it is continuously connected while maintaining the relationship of the high bottom difference in the electrodeposition state, and an insulating layer (epoxy electrodeposition layer) for the purpose of adjusting the thickness. )
61, and is formed on substantially the entire side surface 24 of the sintered body 21. On this epoxy electrodeposition layer 61, an insulating film 62 having a predetermined width and a copper foil 63 are overlapped with each other and pasted at predetermined intervals, and shot blasting treatment is performed. As a result, as shown in FIG. Epoxy electrodeposition layer 61 on the part not attached
Is peeled off, and the end faces of the piezoelectric material 11 and the internal electrode 12 are exposed again.

FIG. 6 is a view showing the insulating layer portion formed in this way. Epoxy electrodeposition in which thick layers and thin layers are alternately provided on the inner surface of the internal electrode 12 on the side surface of the device. A layer 61 is formed, an insulating film 62 having a constant thickness is formed on the layer 61, and the insulating layer 13 (see FIG. 1) having a multiple structure is formed by these two layers. Copper foil 63 is formed as.

Next, the external electrode (copper foil 63) and the internal electrode 1
A nickel plating bath for making electrical connection with 2 is created. That is, 750 g of nickel sulfamate, 5 g of nickel chloride, 30 g of boric acid, and 5 ml of a brightening agent are added to a total amount of 1 liter to prepare a plating bath, and an appropriate amount of sulfamic acid is added to adjust the pH to around 4.0.

Then, a titanium cage containing nickel balls is used for the positive electrode, and a temporary external electrode 23 connected to the internal electrode 12 corresponding to the thin portion of the epoxy electrodeposition layer 61 is connected to the negative electrode. When a direct current of about 50 mA is applied for 20 minutes, the nickel plating layer 71 grows on the internal electrode 12 exposed on the side surface of the device as shown in FIG. The copper foil 63 is connected to the copper foil 63 that has grown until the height of the thin portion of the adhesion layer 61 and the insulating film 62) is exceeded.

Then, the nickel plating layer 71 grows also from the copper foil 63 which is electrically connected to the temporary external electrode 23, and is sequentially connected to the slow-growing nickel plating layer 71a (see FIG. 7). As a result, the copper foil 63, which is an external electrode, and the internal electrode 12 are connected to each other through the nickel plating layer 71 at the thin portion of the insulating layer 13. Further, the internal electrode 12 which is not connected is completely insulated by the thick portion of the insulating layer 13.

Next, also on the opposite side surface 25, similarly, the layers are shifted to perform electrodeposition treatment, external electrode attachment and nickel plating connection.

In this way, the sintered body 21 in which the internal electrodes 12 are connected to each other by shifting the layers on the pair of side surfaces facing each other, is cut at the position shown by the broken line in FIG. 5, and is shown in FIG. It becomes a single element like this. A power supply is connected to the copper foil (external electrode) 63 extending from the element body, and the nickel plating layer 7
When a voltage is applied to the internal electrode 12 via 1, the internal electrode 12 arranged on the entire surface of the element causes uniform displacement.
The element itself is further packaged with epoxy resin or the like and then subjected to polarization treatment to be a finished product.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention. For example, when the driving voltage is low, the epoxy electrodeposition layer 61 alone may form a single insulating layer, and a conductive film may be bonded instead of the copper foil 63 to be used as an external electrode. Further, a fluororesin or the like can be used instead of the epoxy resin.

[0022]

As is apparent from the above description, in the laminated piezoelectric element of the present invention, the insulating layer having different thicknesses is formed between the portion where the internal electrode and the external electrode are electrically connected and the portion where they are not connected. Since it has, it is easy to connect the internal electrode and the external electrode, and moreover, the portion which is not connected is surely insulated even if a voltage is applied. Therefore, it is possible to prevent a decrease in yield due to poor connection or poor insulation, and to obtain a highly reliable piezoelectric element.

[Brief description of drawings]

FIG. 1 is a perspective view of a laminated piezoelectric element showing an embodiment of the present invention.

FIG. 2 is a perspective view of a cut laminated sintered body.

FIG. 3 is a diagram showing an epoxy electrodeposition layer immediately after electrodeposition.

FIG. 4 is a diagram showing an epoxy electrodeposition layer in a state where it is connected by being subjected to heat treatment.

FIG. 5 is a perspective view of a laminated sintered body on which a temporary external electrode is formed and shot blasting is performed.

FIG. 6 is a diagram showing a state in which an insulating film and a copper foil are attached on an epoxy electrodeposition layer.

FIG. 7 is a diagram showing a process of growing a nickel plating.

FIG. 8 is a perspective view of a conventional laminated piezoelectric element.

[Explanation of symbols]

 11 Piezoelectric material 12 Internal electrode 13 Insulating layer 61 Epoxy electrodeposition layer 62 Insulating film 63 Copper foil (external electrode) 71 Nickel plating layer

Claims (2)

[Claims] 1. A piezoelectric material and an internal electrode are alternately laminated, and an insulating layer continuously formed on a side surface of the piezoelectric material and an internal electrode continuously formed on the insulating layer are electrically connected to the internal electrode. A multilayer piezoelectric element including an external electrode, wherein the insulating layer has different thicknesses between a portion where the internal electrode and the external electrode are connected and a portion where the external electrode is not connected. 2. The multi-layer piezoelectric element according to claim 1, wherein the insulating layer has at least a layer for adjusting the thickness and has a multiple structure.