JP2000252536A - Multilayer piezoelectric actuator and method of manufacturing the same - Google Patents

Abstract

(57) [Abstract] [Problem] To securely join a piezoelectric plate and a metal thin plate,
Provided is a highly reliable laminated piezoelectric actuator that prevents cracks in a piezoelectric plate. Kind Code: A1 A ceramic piezoelectric plate and a thickness of 1 to 2 on both sides.
Ni— such as Kovar coated with a 0 μm Ag metal layer 4
By alternately laminating the metal thin plates 2 made of an alloy containing Fe as a main component, and by thermocompression bonding at 400 to 700 ° C. while applying a load of 700 to 2000 kgf, A
The g metal layer 4 is pressed between crystal grains on the surface of the ceramic piezoelectric plate 1, and the ceramic piezoelectric plate 1 and the thin metal plate 2 are joined and integrated via the Ag metal layer 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated piezoelectric actuator, and is used, for example, as a precision positioning device such as an optical device, a drive element for preventing vibration, a drive element for fuel injection of an automobile engine, and the like. The present invention relates to a multilayer piezoelectric actuator.

[0002]

2. Description of the Related Art Conventionally, a piezoelectric plate has an inverse piezoelectric effect that expands and contracts when a voltage is applied. However, since the amount of expansion and contraction of each piezoelectric plate is very small, a laminated piezoelectric actuator formed by laminating a plurality of piezoelectric plates has been manufactured.

[0003] In this laminated piezoelectric actuator, a voltage is applied to a piezoelectric plate to extend the piezoelectric plate by several to several tens of μm, and this is used as a driving force source of the actuator. As a known example, there is JP-B-7-40613.

In such a laminated piezoelectric actuator, for example, a conductive adhesive layer having a thickness of several μm is formed on both surfaces of a piezoelectric plate by printing or vapor deposition of an electrically conductive paste. It has a structure in which a metal sheet is interposed between the conductive adhesive layers, heated and pressed, and integrated.

According to such a laminated piezoelectric actuator, for example, according to Japanese Patent Application Laid-Open No. 60-121784, a conductive adhesive formed by printing and baking a mixed paste of Ag powder and glass powder on both surfaces is disclosed. A plurality of piezoelectric plates on which the layers are formed are laminated with a metal thin plate disposed between the conductive adhesive layers, and connection projections formed on the metal thin plate are axially moved so as to leave a predetermined gap with respect to the outer peripheral surface of the piezoelectric plate. A stacked piezoelectric actuator is disclosed in which the connecting projections are bent in the same direction, and connection projections having the same polarity are overlapped and joined by spot welding or the like.

In Japanese Utility Model Publication No. 60-3589,
A ribbon-shaped metal plate in which thin metal plates are connected by a connection member and soldering is unnecessary is disclosed as a wiring member, and a large number of laminated piezoelectric actuators using such a ribbon-shaped metal plate have been proposed (Japanese Patent Application Laid-Open No. Sho. 60-103885, JP-A-61-276278, JP-B-4-16
029, JP-A-7-283455, etc.).

In recent years, a multilayer piezoelectric actuator has been driven by applying a high voltage at a high frequency in order to utilize a high response characteristic of the multilayer piezoelectric actuator while securing a large displacement. In addition, a thinner piezoelectric plate has been used to promote further miniaturization.

[0008]

However, a conductive adhesive layer is formed on both surfaces of the piezoelectric plate disclosed in Japanese Patent Publication No. 7-40613, and the piezoelectric plate and the metal thin plate are connected via the conductive adhesive layer. In a laminated piezoelectric actuator that performs thermocompression bonding,
When laminating a piezoelectric plate and a metal thin plate, the conductive adhesive layer on the surface of the piezoelectric plate and the metal thin plate are displaced, and therefore, when driving at a high voltage and a high frequency, the metal thin plate is displaced in the laminating direction. The stress generated at the joint between the piezoelectric plate and the metal sheet becomes uneven due to the expansion and contraction movement in the radial direction accompanying the displacement, and high stress is generated at the misalignment between the conductive adhesive layer on the piezoelectric plate and the metal sheet, There is a problem that cracks are generated in the piezoelectric plate during driving, and the reliability of the actuator is reduced.

[0009] When the laminated piezoelectric actuator is incorporated into a device under a state where a high load is applied, stress concentrates due to the load at a position shift portion between the conductive adhesive layer and the metal thin plate, and cracks are generated on the piezoelectric plate. Had been promoted.

Further, connecting projections having the same polarity are overlapped and joined by soldering or the like.
Japanese Patent Application Laid-Open No. 7-2 using a laminated piezoelectric actuator disclosed in Japanese Patent Application Publication No.
In the multilayer piezoelectric actuator disclosed in Japanese Patent No. 83455 or the like,
When a metal having a low Young's modulus is used as a thin metal plate, the connection projections and the connecting portion of the ribbon-shaped metal plate are easily deformed, and stress deformation occurs in the connection projections and the connection portion deformed by the displacement operation, resulting in fatigue disconnection. In the case of a laminated piezoelectric actuator in which connection projections of the same polarity are overlapped with each other and joined by spot welding, there is a problem that the joint is fatigued by high stress accompanying high displacement, and peeling and disconnection are likely to occur. .

In addition, Japanese Patent Application Laid-Open No. Sho 60-121784 describes A
In the case of bonding via a conductive adhesive layer made of g and glass, the glass component preferentially diffuses into the porcelain grain boundaries of the piezoelectric body during thermocompression bonding, thereby deteriorating the electrical characteristics and durability of the piezoelectric ceramic. .

As means for solving these problems, Japanese Patent Publication No. Hei 7-118554 discloses a method of manufacturing a laminated piezoelectric actuator without compressing a thin metal plate and a piezoelectric plate. According to this, a relatively hard material such as stainless steel is used as a metal thin plate, and electrode materials such as copper, silver, and aluminum, which are softer than the metal thin plate, are formed on both surfaces of the metal thin plate by a method such as plating. Later, by contact between the soft electrode formed on the electrode thin plate and the piezoelectric plate, the electrode functions as an electrode of the piezoelectric plate, and a voltage can be applied to the piezoelectric plate.

However, in such a laminated piezoelectric actuator, the piezoelectric plate and the thin metal plate are not substantially joined, and it is difficult to maintain the laminated state. For this reason, the laminated piezoelectric actuator having this structure must be sealed in a case immediately after lamination, and handling in the process is very difficult.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a highly reliable laminated piezoelectric actuator that can reliably connect a piezoelectric plate and a metal thin plate and that prevents the piezoelectric plate from cracking.

[0015]

Means for Solving the Problems As a result of repeated studies on the above-mentioned problems, the present inventors have found that a stacked type formed by alternately stacking a plurality of piezoelectric plates and a plurality of thin metal plates. In the piezoelectric actuator, an Ag metal layer substantially containing no glass is coated on the surface of the metal thin plate, and the Ag metal layer is pressed between crystal grains on the surface of the ceramic piezoelectric plate to thereby form the ceramic piezoelectric plate. A plate and the metal thin plate are joined and integrated via the Ag metal layer.

As a method for manufacturing such a laminated piezoelectric actuator, a plurality of ceramic piezoelectric plates and a thin metal plate having an Ag metal layer substantially containing no glass on both surfaces are alternately laminated. Later, 700-200
By heating at a temperature of 400 to 700 ° C. while applying a load of 0 kgf, and pressing the Ag metal layer between crystal grains on the surface of the ceramic piezoelectric plate, the ceramic piezoelectric plate and the metal thin plate are brought into contact with the Ag metal. It is characterized in that it is joined and integrated via a layer.

In the above structure, the thin metal plate is preferably made of an alloy containing Ni-Fe as a main component, and the thickness of the Ag metal layer is preferably 1 μm or more.

[0018]

According to the multilayer piezoelectric actuator of the present invention,
After alternately laminating a plurality of ceramic piezoelectric plates and thin metal plates having an Ag metal layer formed on both surfaces, 700 to 2000
By heating at a temperature of 400 to 700 ° C. while applying a load of kgf, the ceramic piezoelectric plate shown in FIG.
As shown in the schematic diagram of the bonding interface with the metal layer, the Ag metal layer coated on both surfaces of the thin metal plate is pressed into the space between the crystal grains on the surface of the ceramic piezoelectric plate. Therefore, the laminated piezoelectric actuator can obtain a bonding strength enough to withstand handling in a process. Since the conductive adhesive layer is not formed on the ceramic piezoelectric plate, the process can be simplified.

Further, since the conductive adhesive layer is not formed on the piezoelectric plate side, the problem of displacement between the conductive adhesive layer and the metal thin plate, which has occurred during the lamination as described above, is eliminated, and a high load is applied. Of the conductive adhesive layer and the metal sheet by the driving at a high voltage and a high frequency.
For this reason, it is possible to suppress the generation of cracks in the piezoelectric plate that has occurred due to the stress concentration.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A laminated piezoelectric actuator according to the present invention has a basic structure in which a plurality of ceramic piezoelectric plates 1 and a plurality of thin metal plates 2 are alternately laminated as shown in the schematic diagram of FIG. Become.

The ceramic piezoelectric plate 1 is generally made of Pb (Z
Ceramics containing rTi) O ₃ (hereinafter abbreviated as PZT) as a main component are used, but are not limited thereto, and any ceramic having piezoelectricity may be used. As the piezoelectric material constituting the piezoelectric plate 1, those piezoelectric strain constant d ₃₃ is high is preferable. In particular, in addition to Pb, Zr, and Ti as metal components, Zn, Sb, Ni, Te,
A piezoelectric ceramic composition comprising a composite perovskite compound containing at least one of Sr and Ba is desirable.

The thickness t of the ceramic piezoelectric plate 1 is in the range of 0.2 to 0.2 in terms of miniaturization and application of a high voltage.
It is preferably 6 mm.

The metal sheet 2 is a disk-shaped metal sheet 2 for a positive electrode.
a and the negative electrode metal sheet 2b.
a and 2b are also alternately stacked. Further, as shown in the connection structure of the metal thin plates in FIG. 3, the metal thin plates 2 are connected in series by being connected by connecting members 3 (3a, 3b) for each polarity. As shown in FIG. 1 and FIG. 2, the connecting portions 3 protruding in the radial direction of the piezoelectric plate 1 laminate are bent, and the metal thin plates 2 connected in series are bent for the positive electrode and the negative electrode. And the exposure location is set differently. Further, the metal sheet 2 is desirably smaller than the piezoelectric sheet 1 so as not to be exposed on the outer peripheral surface of the piezoelectric sheet 1 in order to prevent a short circuit or discharge with the metal sheet 2 having a different polarity.

The multi-layer piezoelectric actuator of the present invention is characterized in that, in the above-described actuator structure, an Ag metal layer 4 substantially containing no glass is formed on at least both surfaces of the thin metal plate 2. . Then, as shown in the schematic view of the joining portion between the metal thin plate 2 and the ceramic piezoelectric plate 1 in FIG. 4, the Ag metal layer 4 is pressed into the gap between the crystal grains 1a on the surface of the ceramic piezoelectric plate 1 to press the ceramic piezoelectric plate. The plate 1 and the thin metal plate 2 can be firmly joined and integrated via the Ag metal layer 4.

As the thin metal plate 2, for example, stainless steel or an alloy foil containing Ni-Fe as a main component is used. In particular, N
An alloy containing i-Fe as a main component has high conductivity, and furthermore, Kovar (52Fe) having a thermal expansion coefficient close to that of a piezoelectric plate.
-31Ni-17Co, 42 alloy (58Fe-42N
Metals such as i) are most preferred. The thickness of the metal sheet 2 is preferably as thin as possible so as not to contribute to the amount of displacement, and particularly preferably 20 to 50 μm.

When the thickness of the Ag metal layer 4 coated on both surfaces of the metal thin plate 2 is less than 1 μm, the contact of the Ag metal layer 4 with the surface of the ceramic piezoelectric plate 1 tends to be insufficient, so that the bonding strength is low. There is. When the thickness is larger than 20 μm, the Ag metal layer 4 may hinder the displacement of the actuator.
-20 μm, particularly preferably 2-15 μm.

In the present invention, the Ag metal layer 4 is generally formed by coating the surface of a thin metal plate by plating or vapor deposition, or by using a clad material obtained by sandwiching a thin metal plate between two Ag foils and simultaneously rolling them. Can also.

According to the present invention, the Ag metal layer 4
May be formed on both surfaces of the metal sheet 2 and formed on the surface of the connecting member 3 connecting the metal sheets 2. In this case, oxidation of the connecting member 3 during heat treatment at 400 to 600 ° C. during thermocompression bonding can be suppressed, and a decrease in strength can be prevented.

As shown in FIG. 1, an inactive body 5 that is piezoelectrically inactive and transmits mechanical energy is provided on the uppermost surface and the lowermost surface of the laminate of the ceramic piezoelectric plate 1 and the metal thin plate 2. Is bonded to the uppermost metal sheet 2 by an adhesive such as glass.

The above-described laminated piezoelectric actuator of the present invention is manufactured by the following method. First, the ceramic piezoelectric plate 1 is made of, for example, Pb (ZrTi) O ₃ (hereinafter referred to as PZ).
It is manufactured by forming a piezoelectric composition containing (mainly, T) as a main component into the shape of each piezoelectric plate 1 and firing at a temperature of 1100 to 1300 ° C.

On the other hand, the metal thin plate 2 is formed into a predetermined shape as shown in FIG. 3 by punching a metal plate made of a predetermined metal. Thereafter, the surface of the metal thin plate 2 is coated with an Ag metal layer by the plating method and the vapor deposition method as described above, or a clad material is used.

As shown in FIGS. 1 and 2, the ceramic piezoelectric plate 1 manufactured as described above and the positive and negative metal thin plates 2 having an Ag metal layer 4 adhered to the surface thereof were formed as shown in FIGS. Then, the metal thin plates 2 are alternately sandwiched and laminated between the ceramic piezoelectric plates 1 so that the connecting portions 4 of the metal thin plates 2 are located at the same position every other layer, and then a thermocompression bonding is performed by applying a load from above.

The load at this time is 700 to 2000 k.
gf, particularly 700 to 1000 kgf, and as is clear from the examples described later, 700 g
If the load is smaller than gf, a strong bond between the ceramic piezoelectric plate and the thin metal plate cannot be obtained. If the load exceeds 1000 kgf, a strong bond can be obtained, but problems such as cracking of the ceramic piezoelectric plate occur.

Further, the temperature at this time is 400 to 700
C., especially 450-650.degree. This means that if the temperature is lower than 400 ° C., good bonding strength cannot be obtained,
If the temperature is higher than 700 ° C., the strength of the metal sheet is reduced, and the reliability of the electrode for extracting the metal sheet is reduced.

By performing thermocompression bonding under the above conditions, it is possible to press-fit between crystal grains on the surface of the ceramic piezoelectric plate 1 as shown in FIG. 4 due to the ductility of the Ag metal layer. 1 and the metal sheet 2 can be reliably connected to each other.

The inert body 5 installed on the uppermost surface and the lowermost surface of the laminated body may be made of a lead borosilicate glass or the like at the same time as or after the joint integration of the ceramic piezoelectric plate and the metal thin plate. By baking at 400 to 600 ° C., and the inert body 5 is laminated and integrated above and below the laminate.

In the laminated piezoelectric actuator laminated and integrated as described above, the outer peripheral surfaces of the ceramic piezoelectric plate 1 and the connecting member 3 are covered with an insulating silicon resin 6 or the like. Similarly, the gap between the piezoelectric plate 2 and the outer peripheral portion of the piezoelectric plate 2 and the connecting portion 4 is filled with the insulating silicon resin 6 so that no gap is generated.

As a method for filling such a resin, it is sufficient to adjust the conditions such as viscosity and fill the void with the insulating silicon resin under reduced pressure such as a vacuum removal method. It is desirable that the insulating silicon resin 6 be filled with a material having a low elastic modulus.

[0039]

EXAMPLE 1 Both surfaces of a PZT piezoelectric ceramic were polished to a diameter of 20.
A disc-shaped ceramic piezoelectric plate 1 having a thickness of 0.3 mm and a thickness of 0.3 mm was produced.

A metal member formed by punching a metal plate made of Kovar having a thickness of 30 μm and connecting 50 thin metal plates made of a circle having a diameter of 19 mm as shown in FIG. 3 at a connecting portion having a width of 2 mm and a length of 2 mm. Was prepared. Then, an Ag plating layer 5 having a thickness of 5 μm was formed on both surfaces of the metal member.

Then, among the above-mentioned metal members, a circular metal thin plate is successively sandwiched between ceramic piezoelectric plates, and a positive metal thin plate and a negative metal thin plate are alternately laminated between each of the 99 piezoelectric plates. Thus, a laminate was formed.

A PZT-based ceramic similar to the ceramic piezoelectric body was used as the inert body, and both surfaces thereof were polished to form a cylindrical inert body having a diameter of 20 mm and a thickness of 5 mm. A glass paste of lead borosilicate glass was printed on one surface of these inert materials to a thickness of 10 μm, dried at 100 ° C., and baked at 500 ° C.

A load of 1000 kgf was applied from above to the laminated body prepared as described above using a pressing machine while lightly applying pressure so as not to cause misalignment.
Pressure bonding was carried out at a temperature of 1 hour.

Thereafter, the whole of the above-mentioned laminated body was covered with insulating silicone rubber, and this was covered with silicone oil at 80 ° C. for 3 hours.
Polarization treatment was performed by applying a DC voltage of kv / mm for 30 minutes to produce a multilayer piezoelectric actuator of the present invention.

Further, on both surfaces of the ceramic piezoelectric plate, Ag powder 97 wt%, was printed glass 3 wt% of the conductive paste mainly composed of PbO-SiO ₂ -B ₂ O ₃ so that the thickness of 10μm After drying at 100 ° C, 500
A ceramic piezoelectric plate having a conductive adhesive layer formed by baking at a temperature of ° C was produced. Then, a piezoelectric actuator for comparison was produced in exactly the same manner as above except that the ceramic piezoelectric plate and the metal thin plate 3 made of Kovar were laminated and thermocompression-bonded at 500 ° C. for 1 hour.

Observation of the bonding state between the ceramic piezoelectric body and the metal thin plate with respect to the obtained four types of laminated piezoelectric actuators by a scanning electron microscope showed that the product of the present invention had an Ag plating layer on the surface of the ceramic piezoelectric plate. It was confirmed that the particles were press-fitted and bonded firmly.

Next, in order to compare the durability of each sample,
A set voltage to be applied to each of the laminated piezoelectric actuators is determined so that the generated displacement becomes 50 μm under an applied load of 440 kgf, and a set voltage is applied 1 × 10 ⁹ times at a frequency of 50 Hz from an applied load of 440 kgf and an applied voltage of 0 V. A durability test was performed. The displacement was measured by fixing the sample on an anti-vibration table, attaching aluminum foil to the upper surface of the sample, and evaluating the average value of the values measured at the central part and the peripheral part of the element using a laser displacement meter. did.

Further, with respect to the layer structure of each actuator, one piezoelectric body is sandwiched between a pair of thin metal plates.
A voltage was applied between the metal thin plates, and a voltage when a spark was generated between the metal thin plates was measured as a withstand voltage.

As a result, it was confirmed that the product of the present invention could be driven without problems even at 1 × 10 ⁹ times. The withstand voltage is 15KV
/ Mm and a high value. Furthermore, as a result of observing the bonding interface between the metal thin plate and the piezoelectric plate, it was confirmed that the Ag metal layer was pressed into the space between the crystal grains on the surface of the piezoelectric body and was firmly bonded.

On the other hand, in the laminated piezoelectric actuator thermocompression-bonded to a thin metal plate made of Kovar via a conductive adhesive layer containing glass as a comparative product, the driving was stopped at 2 × 10 ⁸ times. The withstand voltage was 11 KV / mm, which was lower than that of the product of the present invention. In addition, as a result of observing the interface between the metal sheet and the piezoelectric body of this actuator, diffusion of the glass component was observed. Further, as a result of observing the broken portion of the actuator, it was confirmed that sparking occurred between the conductive adhesive layers formed on the piezoelectric body. Furthermore, as a result of performing a cross-sectional observation near the damaged portion, it was confirmed that a crack was generated in the piezoelectric plate starting from the outermost peripheral portion at the joint interface between the metal thin plate and the piezoelectric plate. This phenomenon was observed not only in the damaged part but also in most piezoelectric plates.

Example 2 FIG. 5 shows the relationship between the applied load at the time of thermocompression bonding and the bonding strength between a ceramic piezoelectric plate and a thin metal plate in producing the product of the present invention of Example 1. In this test, the diameter was 14 m.
m, ceramic piezoelectric plate with thickness 0.5mm and diameter 12m
m, a 70 μm-thick metal sheet made of Kovar having 70 μm Ag-plated layers on both sides alternately laminated 70 sheets, and thermocompression-bonded with each load, then lower span 30 m
It was determined by performing a three-point bending of m. The results are shown in the relationship between the applied load and the bonding strength in FIG.

As is apparent from the results shown in FIG.
It can be seen that a bonding strength of 35 MPa, which is substantially equal to that of the ceramic piezoelectric plate at gf or more, is obtained. At an applied load of 1000 kgf or more, the bonding strength is almost saturated. However, with an applied load exceeding 2000 kgf, it was confirmed that stress was concentrated on the outer peripheral portion of the metal thin plate 3 in the ceramic piezoelectric plate 2 and microcracks were generated on the piezoelectric plate.

Therefore, the applied load during thermocompression bonding is 700 to 2
It is understood that 000 kgf, particularly 700 to 2000 kgf, is good.

[0054]

As described above in detail, in the laminated piezoelectric actuator of the present invention, after alternately laminating a metal thin plate having both surfaces coated with an Ag metal layer and a ceramic piezoelectric plate,
The Ag metal layer is pressed between crystal grains on the surface of the ceramic piezoelectric plate by thermocompression bonding while applying a load of ~ 2000 kgf, whereby the ceramic piezoelectric plate and the metal thin plate are joined together via the Ag metal layer. Therefore, the laminated piezoelectric actuator can obtain a bonding strength that can sufficiently withstand handling in a process. Further, since it is not necessary to form a conductive adhesive layer on the piezoelectric plate, the process can be simplified.

Further, since the conductive adhesive layer is not formed on the ceramic piezoelectric plate, the conductive adhesive layer and the metal thin plate, which have been generated at the time of lamination, are not displaced from each other. Due to the stress concentration on the misaligned portion between the conductive adhesive layer and the metal sheet accompanying the displacement, and the expansion and contraction in the radial direction accompanying the displacement in the stacking direction when driving at high voltage and high frequency, the piezoelectric plate Unevenness of the stress generated at the joint between the metal plate and the thin metal plate can be prevented, so that generation of cracks in the piezoelectric plate can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a basic configuration of a laminated piezoelectric actuator of the present invention.

FIG. 2 is an enlarged sectional view showing a part of FIG. 1;

FIG. 3 is a plan view showing a metal member in which thin metal plates are connected by a connecting member.

FIG. 4 is a schematic view of a bonding interface between a ceramic piezoelectric plate and a thin metal plate in a multilayer piezoelectric actuator according to the present invention.

FIG. 5 is a graph showing a relationship between an applied load and a bonding strength during thermocompression bonding of a multilayer piezoelectric actuator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceramic piezoelectric plate 2 Metal thin plate 3 Connecting member 4 Ag metal layer 5 Inactive body 6 Insulating silicon resin

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tomohiro Kawamoto 1-4-4 Yamashita-cho, Kokubu-shi, Kagoshima Inside the Kyocera Research Institute (72) Inventor Katsuhiko Onizuka 1-4-4 Yamashita-cho, Kokubu-shi, Kagoshima Kyocera 3G066 BA33 BA46 BA54 BA54 CD21 CD28 CD30 CD27 CE27 CE31

Claims (6)

[Claims] 1. A laminated piezoelectric actuator formed by alternately laminating a plurality of ceramic piezoelectric plates and a plurality of metal thin plates, wherein an Ag metal layer substantially containing no glass is formed on the surface of the thin metal plates. While forming a coating, the above A
A multi-layer piezoelectric actuator, wherein the ceramic piezoelectric plate and the thin metal plate are joined and integrated via the Ag metal layer by pressing a g metal layer between crystal grains on the surface of the ceramic piezoelectric plate. 2. The multilayer piezoelectric actuator according to claim 1, wherein said thin metal plate is made of an alloy containing Ni-Fe as a main component. 3. The multilayer piezoelectric actuator according to claim 1, wherein the thickness of the Ag metal layer is 1 μm or more. 4. After alternately laminating a plurality of ceramic piezoelectric plates and thin metal plates having an Ag metal layer substantially free of glass formed on both surfaces, apply a load of 400 to 700 kgf while applying a load of 700 to 2000 kgf. And heated at a temperature of
a multi-layer piezoelectric actuator characterized in that the ceramic piezoelectric plate and the thin metal plate are joined and integrated via the Ag metal layer by pressing a metal layer between crystal grains on the surface of the ceramic piezoelectric plate. Manufacturing method. 5. The method according to claim 4, wherein the thin metal plate is made of an alloy containing Ni—Fe as a main component. 6. The method according to claim 4, wherein the thickness of the Ag metal layer is 1 μm or more.