JPH0212882A - Laminated displacement element - Google Patents

Abstract

PURPOSE:To obtain a layer-built displacement element having external electrodes with high bond strength and capable of preventing migration completely by forming internal electrodes of a non-silver material and forming the external electrodes by stacking a layer consisting of at least one of Pd and Pt and grass frit and a layer consisting of at least one of Ni and Cu. CONSTITUTION:A plurality of sheets 1 of an electromechanical converting material and internal electrodes 2 of a conductive metallic material are stacked alternately, and a pair of external electrodes 3 are provided on the sides of the layer-built body so that they are connected with alternate layers of the internal electrodes 2. In a layer-built displacement element thus constructed, the internal electrodes 2 are formed of a non-silver material while the external electrodes 3 are formed by stacking a layer consisting of at least one of Pd and Pt and glass frit and a layer consisting of at least one of Ni and Cu. According to an embodiment, palladium paste for forming the internal electrodes 2 is screen printed on the surface of each green sheet and the printed sheets are stacked and baked. Then, the external electrodes 3 are provided as described in the above.

Description

[Detailed description of the invention] [Industrial application field] The present invention is a 7-cut unit for industrial Kawaguchi bots.

This relates to an electromechanical transducer used in ultrasonic motors, etc., and in particular, by laminating multiple thin plates made of electromechanical *lA material via electrodes.

This invention relates to an improvement of a laminated displacement element that increases the amount of displacement.

(Prior Art) Conventionally, laminated piezoelectric elements used for displacement elements used in positioning mechanisms of x-y stages, brakes, etc. are made by attaching electrodes to a thin plate made of piezoelectric ceramic material processed into a predetermined shape. The method used is to attach the electrodes directly or through a thin metal using an organic adhesive after polarization. However, when stacking layers using adhesive as described above, depending on the usage conditions, the adhesive layer may absorb displacement due to vibration of the piezoelectric element, or the adhesive may deteriorate due to high temperature environment or long-term use. There are drawbacks.

For this reason,? Recently, a multilayer piezoelectric element with a multilayer chip capacitor structure has been put into practical use. That is, 2 For example, as described in Japanese Patent Publication No. 59-32040 f [1, a paste-like piezoelectric ceramic material obtained by adding a binder to raw material powder and kneading it is formed into a thin plate of a predetermined thickness, and one side of this thin plate is An internal electrode is formed by applying a conductive material such as silver-palladium to the inside or both sides. A predetermined number of the above-mentioned thin plates were laminated and pressed together, further processed into a predetermined shape, and then fired to form a ceramic, and external electrodes were formed on both sides of the 111 body. The laminated piezoelectric element with the above structure has excellent adhesion between the thin plate made of piezoelectric ceramic material and the internal electrode, and has stable thermal properties, so it can be used satisfactorily even in high-temperature environments, and can be used for long periods of time. It has the advantage of extremely little deterioration over time.

[Problem to be solved by the invention]

In the laminated piezoelectric element having the above structure, when a DC high voltage is applied between the 11 electrodes to obtain displacement, using root thread material as the electrode material prevents so-called migration in a high humidity atmosphere. There is a problem in that this may occur and eventually lead to dielectric breakdown. In other words, at 1rt, Ag constituting the pole is ionized (Ag+) in a high humidity atmosphere.
However, it is attracted to the negative electrode by the applied voltage and is deposited on the negative electrode side.

Over time, these deposits grow into cedar leaf shapes and form '1! This lowers the insulation resistance between the electrodes and eventually causes a short circuit. The occurrence of such migration is particularly remarkable in the external electrodes exposed to the outside air. As a means to prevent the above-mentioned migration, it is possible to form the electrodes from a non-silver material, but this is not preferable as it would result in an increase in cost. There has also been a proposal to form the external "N, +ffi" by baking a silver paste with high adhesion strength, and then apply electrolytic nickel plating or the like to isolate it from the outside air (for example, see Japanese Patent Laid-Open No. 62-62571). However, since the IW formed by electrolytic nickel plating has many pinholes, it allows moisture to enter from the outside.

There is a problem that migration of silver forming the external electrode occurs. Furthermore, 1Rffi pole is used.

Twelve methods have also been proposed for directly forming external electrodes on the side surfaces of the laminate using nickel coatings (for example,
3-. (See Publication No. 1327). However, when applied to a type 1 piezoelectric element, the product J (adhesion strength is low).

There is a problem that reliability is unsatisfactory.

The present invention solves the problems existing in the prior art described above, and has an external electrode with high adhesion strength.

It is an object of the present invention to provide a laminated displacement element that can completely prevent migration.

[Means to solve the problem]

In order to achieve the above object, in the present invention, a plurality of thin plates made of an electromechanical conversion material are alternately laminated with internal electrodes made of a conductive metal material interposed therebetween, and a plurality of thin plates made of an electromechanical conversion material are stacked alternately with the internal electrodes on the side surfaces thereof. In a laminated displacement element having a pair of external electrodes to be connected every other layer, five internal electrodes are formed of a non-silver material, and the external electrodes are made of Pd or Pd.
a layer consisting of at least one of t and glass frit;
Alternatively, it is formed by laminating a layer made of at least one of Cu. A technical method was adopted.

As the electromechanical conversion material in the present invention, it is preferable to use a piezoelectric material or an electrostrictive material.

[Effect]

With the above configuration, a chemical bonding state can be created between the glass frit and the electromechanical conversion material, and the adhesion strength can be increased.

Note that the conductive function as an external electrode can be protected by a plating layer of Pd and/or PL and Ni or Cu in the glass frit.

〔Example〕

The figure is a perspective explanatory view of essential parts schematically showing an embodiment of the present invention. In the figure, l is )111 plate, and piezoelectric ceramic material is used to make I12710mIII, l'i[sa1
00 p m square shape. Reference numeral 2 denotes an internal electrode, which is made of palladium and is interposed between the thin plates 1. First, Pb(Zr,Ti)O, powder, PVB as an organic binder, and Br'BC as a plasticizer.

After adding trichlene as an organic solvent and mixing thoroughly, the mixture is processed into a sheet with a thickness of 100 μm using a doctor blade method. Next, a palladium paste for forming the internal electrodes 2 is screen printed on the surface of this sheet material. in this case.

Providing a non-printed portion on one edge of the sheet-like material to form a non-printed portion is effective in constructing a so-called alternating electrode as shown in FIG. For example, 1 piece of the sheet-like material formed as described above
After laminating 00 sheets and pressing them together, they are cut into a predetermined size and shape to form a laminate. Next, this laminate was heated to 1150-1250°C.
By baking for 1 to 5 hours at
A corner sintered laminate.

In the figure, reference numeral 3 denotes external electrodes, which are formed into a pair by connecting one end edge of the internal electrodes 2 every other layer. That is, the internal electrodes 2 of the laminate are formed every other layer by screen printing a cellulose-based paste containing 1% by weight of at least one of Pd or PL and 2% by weight of lead-based glass frit having a melting point of 580°C. After printing on the exposed side.

The Pb (Zr) material is dried at 80 to 100°C for 10 minutes, placed in an electric furnace, and subjected to baking treatment at 600°C for 20 minutes.Thin plate 1 is formed by this baking process.

T'i) O, and glass frit I.
can produce a uniformly deposited layer. After the above-mentioned baking treatment, a pair of external electrodes 3 shown in Fig. 2 can be formed by immersing the nickel film or copper film in 80°C electroless nickel solution or electroless copper solution for 10 minutes.
, 3 can be formed. Reference numeral 4 denotes a lead wire, which is electrically connected to the external electrode 3 formed as described above via a solder 5. For comparison, the external electrode 3 is
A conventional type of silver paste coating and baking followed by nickel plating was manufactured and the characteristics were compared. As a result,
In the conventional type, the adhesion strength of the external electrode 3 is 38 k.
g/cJ, whereas in the case of this example, Ni
It was confirmed that 50 J/ad or more was exhibited in both cases of Cu and Cu. In addition, in an atmosphere of 40°C and 90% relative humidity, we applied a DC voltage of 150 V and investigated the state after 1000 hours, and found that 18 out of 20 of the conventional products suffered dielectric breakdown due to migration silane generation. In contrast, it was confirmed that there was no dielectric breakdown in the case of this example.

In this embodiment, an example has been described in which the hv provisional planar contour shape is a square, but the same effect can be obtained even if the shape is a circle, another quadrilateral, or any other geometric shape other than a square. As for the type of internal electrodes, it goes without saying that in addition to the alternating electrodes used in the three embodiments, so-called full-surface electrodes may also be used. Next, the electromechanical conversion material that forms the thin plate is 1
Not only piezoelectric ceramic materials such as lead zirconate titanate shown in this embodiment, but also other piezoelectric materials can be used.

Since the Curie temperature is lower than room temperature, there is no need for single polarization.
Moreover, a laminated displacement element using an electrostrictive material, which has characteristics such as a large displacement amount and low hysteresis, has exactly the same effect as described above! IJI samurai can do it. One example of such an electrostrictive material is:

(P bo, qIb Lao, aua) (Zro
, &, Ti6,25)o, qqq O1・ (Pbo,, as Sro, +s) (Zro, s
+ Tlo, saZ no, o+zs N! o
, osri5 Nbo, +e)Ox.

(P lla, es S ro, +s) (Z r
6,5a T io, a.

Z n6.6s Ni a, os N bo, +
o) Oi + etc. can be used. In addition to palladium, other materials for forming the internal electrodes include l) t
Non-silver based materials including other refractory metals can be used.

〔Effect of the invention〕

Since the present invention has the structure and operation as described above, it is possible to completely prevent migration of the laminated displacement element, and the adhesion strength of the external electrode to the laminated body can be increased by chemical bonding by glass lift. It is possible to significantly improve the reliability of the multilayer displacement element by
The effect is that it can be dramatically increased.

[Brief explanation of the drawing]

The figure is a perspective explanatory view of essential parts schematically showing an embodiment of the present invention. l: thin plate, 2: internal electrode, 3: external electrode.

Claims (3)

[Claims] (1) A plurality of thin plates made of an electromechanical conversion material are alternately stacked with internal electrodes made of a conductive metal material interposed therebetween, and a pair of external electrodes to be connected to the internal electrodes alternately every other layer is attached to the side surfaces of the thin plates. In the multilayer displacement element provided, the internal electrodes are made of a non-silver material, and the external electrodes are made of Pd.
Alternatively, a laminated displacement element characterized in that it is formed by laminating a layer made of at least one of Pt and glass frit, and a layer made of at least one of Ni or Cu. (2) Claim (1) in which the electromechanical conversion material is a piezoelectric material
The laminated displacement element described above. (3) Claim (1) in which the electromechanical conversion material is an electrostrictive material.
The laminated displacement element described above.