JP2006191149A - Manufacturing method of laminated type piezoelectric element, and the laminated type piezoelectric element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a laminated type piezoelectric element superior in durability, having no disconnection of an external electrode and an internal electrode, even when being driven continuously over a long period of time in a high field and under a high pressure. <P>SOLUTION: The manufacturing method comprises processes of: manufacturing a columnar laminate for which the end parts of the plurality of internal electrodes are exposed alternately on two side faces; applying conductive paste containing 50-95 vol.% of conductive metal powder and 5-50 vol.% of glass powder, to at least a part where the end part of the internal electrode is exposed on the side face of the columnar laminate; and forming the external electrode, by thermally treating the conductive paste in the temperature range of 90-120% of the softening point of glass. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a laminated piezoelectric element and a laminated piezoelectric element, and, for example, to produce a laminated piezoelectric element used for a precision positioning device such as an automobile fuel injection device and an optical device, a driving element for preventing vibration, and the like. The present invention relates to a method and a multilayer piezoelectric element.

  Conventionally, as a multilayer piezoelectric element, a multilayer piezoelectric actuator in which piezoelectric bodies and internal electrodes are alternately stacked is known. Multilayer piezoelectric actuators are classified into two types: the simultaneous firing type and the stack type in which piezoelectric ceramics and internal electrode plates are alternately laminated. Since the multilayer piezoelectric actuator of the type is advantageous for thinning, its superiority is being shown.

  FIG. 4 shows a conventional laminated piezoelectric actuator. In this actuator, piezoelectric bodies 51 and internal electrodes 52 are alternately laminated to form a columnar laminated body 53, which is inactive on both end faces in the laminating direction. Layer 55 is laminated.

The internal electrode 52 is formed so that one end thereof is alternately covered with the insulator 61 on the left and right sides, and the strip-like external electrode 70 is electrically connected to the internal electrode 52 every two layers on the left and right.

On the strip-shaped external electrode 70, a lead wire 76 is further fixed with solder 77.

By the way, in recent years, in order to ensure a large amount of displacement under a large pressure with a small piezoelectric actuator, a higher electric field is applied to continuously drive for a long time.
Japanese Patent No. 3250918

  However, in the above-described piezoelectric actuator, when continuously driven for a long time under a high electric field and high pressure, peeling occurs between the internal electrode 52 formed between the piezoelectric bodies 51 and the external electrode 70 for the positive electrode and the negative electrode. There is a problem that the voltage is not supplied to some of the piezoelectric bodies 51 and the displacement characteristics change during driving. Further, when the external electrode is continuously driven for a long time, there is a problem that the voltage is not supplied due to disconnection due to the repeated stress.

  An object of the present invention is to provide a multi-layer piezoelectric element having excellent durability without disconnection of an external electrode and an internal electrode even when continuously driven for a long time under a high electric field and high pressure. .

  The method for manufacturing a laminated piezoelectric element of the present invention has a columnar laminate in which a plurality of piezoelectric bodies and a plurality of internal electrodes are alternately laminated, and a pair of external electrodes are formed on two side surfaces of the columnar laminate, respectively. A method of manufacturing a laminated piezoelectric element, comprising: producing a columnar laminated body in which end portions of the plurality of internal electrodes are alternately exposed on the two side surfaces; and at least the inner side of the side surface of the columnar laminated body A step of applying a conductive paste containing 50 to 95% by volume of conductive metal powder and 5 to 50% by volume of glass powder on the exposed portion of the electrode; and 90 to 120% of the softening point of the glass And heat-treating the conductive paste in a temperature range to form an external electrode.

  The softening point of the glass in the present invention is preferably in the range of 400 to 930 ° C., and the heat treatment temperature is higher than the softening point of the glass and not more than the melting point of the conductive metal powder. Good.

  The multilayer piezoelectric element of the present invention includes a pair of columnar laminates formed by alternately laminating piezoelectric bodies and internal electrodes, and a pair of the internal electrodes connected alternately every other layer. A plurality of external electrodes, and a protruding conductive terminal protruding from the side surface of the columnar stacked body is provided at every other end of the internal electrode. The terminal is embedded in an external electrode containing a conductive material and glass, and the porosity of the external electrode is 30 to 70%.

  In the multilayer piezoelectric element of the present invention, the projecting conductive terminal is provided at the end of the internal electrode, and this projecting conductive terminal is embedded in the external electrode. The external electrode is firmly bonded to the internal electrode, and even when operated continuously for a long time under a high electric field and high pressure, the disconnection between the external electrode and the internal electrode can be suppressed, greatly improving durability. Can be improved.

  Conventionally, an external electrode is bonded to the end of the internal electrode, and the bonding area with the external electrode is small, the conductivity is low, and the connection reliability is low. Since the conductive terminal is embedded in the external electrode, the joint area between the protruding conductive terminal and the external electrode is large, the conductivity between the external electrode and the internal electrode can be improved, and the connection between the external electrode and the internal electrode can be improved. Connection reliability can also be improved.

  In the present invention, the protruding conductive terminal is embedded in an external electrode containing a conductive material and glass, and the porosity of the external electrode is 30 to 70%. In addition, it is possible to suppress the destruction of the external electrode due to the repeated stress caused by driving and improve the reliability.

  According to the method for manufacturing a multilayer piezoelectric element of the present invention, a step of producing a columnar laminated body in which ends of a plurality of internal electrodes are alternately exposed on two side surfaces, and at least the end of the internal electrode on the side surface of the columnar laminated body A conductive paste containing 50 to 95% by volume of conductive metal powder and 5 to 50% by volume of glass powder on the exposed part, and conductive in a temperature range of 90 to 120% of the softening point of the glass. And a step of forming an external electrode by heat-treating a functional paste, and a laminated piezoelectric element having excellent durability can be provided.

  1A and 1B show one embodiment of a multilayer piezoelectric element comprising a multilayer piezoelectric actuator of the present invention. FIG. 1A is a perspective view, and FIG. 1B is a longitudinal sectional view taken along the line AA 'in FIG. , (C), (d) are enlarged views of the vicinity of the joint between the internal electrode and the external electrode.

  As shown in FIG. 1, the multilayer piezoelectric actuator has a side surface of a quadrangular columnar laminated body 1 a in which a plurality of piezoelectric bodies 1 and internal electrodes 2 are alternately laminated. A protruding conductive terminal 5 is provided at the end of the internal electrode 2 that is covered with the insulator 3 and is not covered with the insulator 3, and the protruding conductive terminal 5 is made of a conductive material mainly composed of silver and glass. The external electrodes 4 are embedded and bonded, and lead wires 6 are connected and fixed to the external electrodes 4.

  The piezoelectric body 1 is made of, for example, a lead ceramic zirconate titanate Pb (Zr, Ti) O3 (hereinafter abbreviated as PZT) or a piezoelectric ceramic material mainly composed of barium titanate BaTiO3. This piezoelectric ceramic desirably has a high piezoelectric strain constant d33 indicating its piezoelectric characteristics.

  The thickness of the piezoelectric body 1, that is, the distance between the internal electrodes 2 is preferably 50 to 250 μm.

In order to obtain a larger displacement amount by applying a voltage to the laminated piezoelectric actuator, a method of increasing the number of laminated layers is used. By adopting the thickness of the piezoelectric body 1 as described above, This is because a reduction in size and height can be achieved, and dielectric breakdown of the piezoelectric body 1 can be prevented.

  An internal electrode 2 is disposed between the piezoelectric bodies 1, and the internal electrode 2 is formed of a metal material such as silver-palladium, and a predetermined voltage is applied to each piezoelectric body 1. It acts to cause displacement due to the reverse piezoelectric effect.

  Further, grooves having a depth of 30 to 500 μm and a width of 30 to 200 μm in the stacking direction are formed on the side surface of the columnar laminated body 1a on which the protruding conductive terminals 5 are formed, and glass is filled in the grooves. Thus, the insulator 3 is formed. The glass in the groove preferably has a low Young's modulus.

  The protruding conductive terminals 5 and the insulators 3 are alternately formed at the end portions of the internal electrodes 2 exposed on one side surface of the columnar laminated body 1a on which the external electrodes 4 are formed. That is, the end portions of the internal electrodes 2 are alternately insulated by the insulators 3 filled in the grooves, and the other non-insulated end portions of the internal electrodes 2 are connected via the protruding conductive terminals 5. It is joined to a conductive material mainly composed of silver and an external electrode 4 made of glass.

  The protruding conductive terminal 5 is diffusion bonded to the end of the internal electrode 2. That is, when the internal electrode 2 contains silver as a main component, contains palladium, and the protruding conductive terminal 5 has silver as a main component, the silver of the internal electrode 2 and the protruding conductive terminal 5 diffuses mutually. The palladium of the internal electrode 2 diffuses into the projecting conductive terminal 5, whereby the projecting conductive terminal 5 is diffusion bonded to the end of the internal electrode 2.

  The opposite side surfaces of the columnar laminate 1 a are formed by applying a conductive paste, and a conductive material mainly composed of silver and an external electrode 4 made of glass are bonded to each other. Are embedded with protruding conductive terminals 5, whereby the internal electrodes 2 are electrically connected to the external electrodes 4 every other layer.

  The external electrode 4 made of a conductive material mainly composed of silver and glass serves to commonly supply a voltage necessary for displacing the piezoelectric body 1 to the connected internal electrodes 2 by the inverse piezoelectric effect.

  The conductive material of the external electrode 4 and the protruding conductive terminal 5 is mainly composed of silver, and is composed of a metal having conductivity such as nickel, copper, gold, and aluminum and alloys thereof. However, the conductive material of the external electrode 4 and the protruding conductive terminal 5 are mainly composed of the same metal or the same alloy.

  The conductive material of the external electrode 4 and the protruding conductive terminal 5 are preferably silver or an alloy containing silver as a main component because they have oxidation resistance, are easy to diffuse and move at a relatively low temperature, and have a low Young's modulus.

  Further, in the present invention, a glass rich layer 4b having a glass component larger than that of the other portion 4a is formed on the surface layer portion of the external electrode 4 on the piezoelectric body side, and this glass rich layer 4b is bonded to the surface of the piezoelectric body 1. ing.

  As described above, the glass-rich layer 4b of the external electrode 4 in contact with the piezoelectric body 1 contains more glass components than the other portion 4a of the external electrode 4, so that the external electrode 4 and the columnar laminated body 1a are formed. The bonding strength can be made strong.

  In the glass rich layer 4 b, glass is present at a ratio of 1.1 times or more than the other portion 4 a of the external electrode 4.

  The glass-rich layer 4b of the external electrode 4 is easily formed on the portion corresponding to the periphery of the projecting conductive terminal 5, but the projecting conductive terminal 5 is connected to the conductive material of the external electrode 4 and further conductive. In order to improve, it is desirable that the amount of the conductive material in the glass rich layer 4b is large.

  The shape of the protruding conductive terminal 5, the shape and thickness of the glass rich layer 4 b in contact with the protruding conductive terminal 5 and the glass rich layer 4 b in contact with the piezoelectric body 1 are shown in FIGS. 1 (c) and 1 (d). As shown, it need not be uniform.

  Further, the conductive material in the external electrode 4 is 50 to 95% by volume, and the remaining glass component is 5 to 50% by volume. Thereby, since an appropriate amount of glass component can be secured, the bonding strength between the external electrode 4 and the columnar laminate 1a and the protruding conductive terminal 5 can be effectively increased, and the resistance value of the external electrode 4 can be increased. Therefore, local heat generation of the external electrode 4 can be suppressed, and disconnection of the external electrode 4 can be prevented.

  The porosity of the external electrode 4 is desirably 30 to 70%. When the porosity in the external electrode is less than 30%, the external electrode 4 is densified, the Young's modulus becomes high, and when it is driven for a long period of time, a crack is generated due to the repeated stress and the wire is disconnected. When the porosity exceeds 70%, the strength as an external electrode is lowered, and the element is broken due to disconnection or local heat generation.

  In order to adjust the porosity of the external electrode 4, the amount of binder added in the silver glass conductive paste is changed, the heat treatment temperature during baking is changed, the heat treatment time is increased, the glass softening point is changed. This can be achieved by changing.

  For example, when the heat treatment is performed at a temperature higher than the softening point of the glass, the porosity is decreased. Conversely, when the heat treatment is performed at a low temperature, the porosity is increased. The porosity can be adjusted to 30 to 70% by heat treatment in the range of 90% to 120% with respect to the softening point.

  It is also effective to reduce the density of the paste by increasing the amount of binder in the conductive paste, or to add a pore material made of organic matter that decomposes and scatters during the baking process of the electrode.

  Moreover, as glass which comprises the external electrode 4, the working temperature at the time of forming the external electrode 4 is 400-930 degreeC, soda lime glass, lead alkali silicate glass, alumino borosilicate glass, It is preferable to use borosilicate glass, aluminosilicate glass, borate glass, phosphate glass, or the like.

  For example, as the borosilicate glass, the total amount of alkaline earth metal oxides such as SiO 240 to 70 wt%, B 2 O 32 to 30 wt%, Al 2 O 30 to 20 wt%, MgO, CaO, SrO, BaO is 0 to 20 wt%. Those containing 0 to 10% by weight in total of alkali metal oxides such as wt%, Na2O, K2O and Li2O can be used.

Moreover, it is good also as glass which contains 5-30 weight% ZnO in said borosilicate glass. ZnO has the effect of lowering the temperature of the softening point of borosilicate glass.

  Examples of the phosphate glass include P2O540 to 80% by weight, Al2O 30 to 30% by weight, B2O 30 to 30% by weight, ZnO 0 to 30% by weight, alkaline earth metal oxide 0 to 30% by weight, alkali metal oxide 0 Glasses containing up to 10% by weight can be used.

  Moreover, as lead glass, PbO 30-80 weight%, SiO20-40 weight%, Bi2O30-30 weight%, Al2O30-20 weight%, ZnO0-30 weight%, alkaline-earth metal oxide 0-30 weight%, alkali Glasses containing 0 to 10% by weight of metal oxide can be used.

  A lead wire 6 is connected and fixed to the external electrode 4 with solder. The lead wire 6 serves to connect the external electrode 4 to an external voltage supply unit.

  A method for producing the multilayer piezoelectric element of the present invention will be described. First, the columnar laminate 1a is produced.

A slurry is prepared by mixing calcined powder of piezoelectric ceramics such as PZT, a binder made of an organic polymer such as acrylic or butyral, and a plasticizer such as DBP (diethyl phthalate) or DOP (dibutyl phthalate). The ceramic green sheet which becomes the piezoelectric body 1 is produced by tape molding methods such as a known doctor blade method and calendar roll method.

  Next, a conductive paste is prepared by adding a binder, a plasticizer, and the like to silver-palladium powder, and this is printed on the upper surface of each green sheet to a thickness of 1 to 40 μm by screen printing or the like.

  Then, a plurality of green sheets with conductive paste printed on the top surface are laminated, and a plurality of green sheets with no conductive paste printed are laminated on the top and bottom surfaces of the laminate. After debinding, it is produced by firing at 900 to 1200 ° C.

  Thereafter, as shown in FIG. 2A, grooves are formed on every other side of the columnar laminate 1a by a dicing apparatus or the like. And as shown in FIG.2 (b), it fills with the paste which disperse | distributed glass powder to this groove part, and it bakes at 700-1000 degreeC, a glass is filled into a groove | channel, and the columnar laminated body 1a is formed.

  Thereafter, as shown in FIG. 2 (c), 50 to 95% by volume of silver powder (melting point: 960 ° C.) having an average particle size of 0.1 to 10 μm is formed on the side surface where the groove of the columnar laminate 1a is formed. A silver glass conductive paste 21 prepared by adding a binder to a mixture of 5 to 50% by volume of glass powder having an average particle size of 0.1 to 10 μm and a softening point of 400 to 930 ° C. containing silicon as a main component is applied. Then, by baking at a temperature higher than the softening point of the glass and below the melting point of silver, the silver in the silver glass conductive paste 21 gathers at the end of the internal electrode 2, and FIG. As shown, the protruding conductive terminals 5 are formed, and the external electrodes 4 can be formed.

  That is, the glass component is dispersed in the silver glass conductive paste 21, and the glass is softened by heat treatment at a temperature higher than the softening point of the glass and below the melting point of silver. Silver that is difficult to diffuse gathers at the end of the internal electrode 2 to form the projecting conductive terminal 5, and at the same time, glass components gather near the projecting conductive terminal 5 and the piezoelectric body 1.

In this manner, the protruding conductive terminals 5 and the external electrodes 4 can be formed.

  At the same time, silver and palladium constituting the internal electrode 2 are diffused into the protruding conductive terminal 5, and the bonding between the protruding conductive terminal 5 and the internal electrode 2 becomes strong. The protruding height of the protruding conductive terminals 5 from the columnar laminate 1a is preferably 1 μm or more, and particularly preferably 3 μm or more. Thus, increasing the protrusion height can be achieved by increasing the heat treatment temperature during baking, increasing the heat treatment time, or lowering the softening point of the glass.

  The baking temperature of the silver glass conductive paste is preferably equal to or lower than the baking temperature of the glass filled in the groove.

  As described above, after forming the projecting conductive terminals 5 and the external electrodes 4, the lead wires 6 are connected to complete the multilayer piezoelectric element of the present invention.

  Then, by applying a direct current voltage of 0.1 to 3 kV / mm to the pair of external electrodes 4 via the lead wires 6 to polarize the columnar laminated body 1a, a laminated piezoelectric actuator as a product is completed, When the lead wire 6 is connected to an external voltage supply unit and a voltage is applied to the internal electrode 2 via the lead wire 6 and the external electrode 4, each piezoelectric body 1 is greatly displaced by the inverse piezoelectric effect.

  In the multilayer piezoelectric element configured as described above, the protruding conductive terminal 5 is provided at the end of the internal electrode 2, and the protruding conductive terminal 5 is embedded in the external electrode 4. The external electrode 4 is firmly bonded to the internal electrode 2 due to the anchor effect of the protruding conductive terminal 5, and even when operated continuously for a long time under a high electric field and high pressure, the external electrode 4 and the internal electrode 2 Disconnection can be suppressed and durability can be greatly improved.

  Further, since the protruding conductive terminal 5 is embedded in the external electrode 4, the bonding area between the protruding conductive terminal 5 and the external electrode 4 is large, and the conductivity between the external electrode 4 and the internal electrode 2 is improved. In addition, the connection reliability between the external electrode 4 and the internal electrode 2 can be improved.

  Further, the protruding conductive terminal is embedded in an external electrode containing a conductive material and glass, and the porosity of the external electrode is set to 30 to 70%, thereby generating cracks due to a difference in thermal expansion and driving. It is possible to suppress the destruction of the external electrode due to the repeated stress caused by the above and improve the reliability.

  In the present invention, a conductive auxiliary member 7 may be formed outside the external electrode 4 as shown in FIG. In this case, by providing a conductive auxiliary member 7 on the outer surface of the external electrode 4, a large current can be supplied to the conductive auxiliary member 7 even when a large current is input to the actuator and driven at high speed. The current flowing through the external electrode 4 can be reduced, the external electrode 4 can be prevented from causing local heat generation and disconnection, and the durability can be greatly improved.

  The conductive auxiliary member 7 is composed of one or a composite of a plate-like conductive member, a conductive adhesive, a conductive coil, a conductive corrugated plate, a conductive fiber assembly (wool-like).

  The multilayer piezoelectric element of the present invention is not limited to these, and various modifications can be made without departing from the gist of the present invention. Moreover, although the example which formed the external electrode 4 in the side surface which the columnar laminated body 1a opposes was demonstrated in the said example, in this invention, you may form a pair of external electrode in the side surface provided adjacently, for example.

  First, a columnar laminate was produced. The piezoelectric body was formed of PZT having a thickness of 150 μm, the internal electrode was formed of a silver-palladium alloy having a thickness of 3 μm, and the number of stacked piezoelectric bodies and internal electrodes was 300 layers.

  After that, as shown in FIG. 2A, grooves having a depth of 50 μm and a width of 50 μm were formed at every other end portion of the internal electrode on the side surface of the columnar laminate by a dicing apparatus. Then, as shown in FIG. 2B, the groove was filled with a paste in which glass powder was dispersed, and baked at 900 ° C. to fill the groove with glass.

  Next, an amorphous borosilicate glass (Si, Al, B) having 90% by volume of silver powder having an average particle diameter of 5 μm and a balance of 600 ° C. with a softening point of silicon having an average particle diameter of 5 μm as the main component. 2) A binder is added to a mixture of 10% by volume of powder and mixed well to prepare a silver glass conductive paste. As shown in FIG. 2 (c), on the side surface on which the grooves of the columnar laminate are formed. This was applied and baked at 700 ° C. to form protruding conductive terminals and external electrodes as shown in FIG.

  The thickness of the protruding conductive terminals in the stacking direction was 3 μm on average, and the height of protrusion from the side surface of the columnar stacked body was 5 μm on average. At this time, the main component of the protruding conductive terminal was silver, and it was confirmed that palladium was diffused from the internal electrode into the protruding conductive terminal.

  In addition, a glass-rich layer having a glass component larger than that of other external electrodes is formed on the portion of the external electrode that contacts the projecting conductive terminal and the piezoelectric body, and the average thickness of the glass-rich layer is It was about 2 μm.

  Thereafter, a lead wire is connected to the external electrode, a 3 kV / mm DC electric field is applied to the positive and negative external electrodes via the lead wire for 15 minutes to perform polarization treatment, and the laminated piezoelectric actuator as shown in FIG. Was made.

  As a result of applying a DC voltage of 150 V to the obtained multilayer piezoelectric actuator, a displacement of 40 μm was obtained in the stacking direction. Furthermore, as a result of applying a driving test by applying an AC voltage of 0 to +150 V at a frequency of 150 Hz to this actuator at a room temperature, a displacement of 40 μm was obtained when driving up to 1 × 108 cycles, and abnormalities of the external electrodes were observed. I couldn't.

Sample No. in Table 1 It is described in 1.

  Next, the same configuration as in Example 1 except that the silver content and the glass softening point in the silver glass conductive paste were changed, the heat treatment temperature for baking the external electrode 4 was changed, and the porosity was changed. No. 2 to No. 8 were produced. In the samples 1 to 7, protruding conductive terminals mainly composed of silver were formed at the end portions of the internal electrodes of the columnar laminate.

  The porosity was measured by mirror-processing the cross section of the external electrode 4 and performing image analysis. In addition, No. Samples 6 to 8 are comparative examples. In the sample No. 6, the protruding conductive terminals were formed, but the porosity of the external electrode 4 was 15%, which is outside the scope of the present invention. In the samples 7 to 8, no projecting conductive terminals were formed.

An AC voltage of 0 to 150 V was applied to the obtained multilayer piezoelectric actuator at room temperature at a frequency of 150 Hz, and a driving test was performed. The amount of displacement obtained in the initial stage was 40 μm in all samples (Nos. 1 to 8). In addition, a driving test was performed with an AC voltage of 0 to 200 V at a frequency of 150 Hz at room temperature. The obtained results are shown in Table 1.

  Sample No. In all the samples other than the sample in which the protruding conductive terminal 8 was not formed, a displacement of 40 μm was obtained when driving at 150 V up to 1 × 10 8 cycles, and no abnormality of the external electrode was observed. In addition, the sample No. in which the protruding conductive terminal was formed. In 1 to 6, since the external electrode and the internal electrode are electrically and firmly joined via the projecting conductive terminal, a spark occurs between the external electrode and the internal electrode up to 1 × 10 8 cycles. There was no.

  On the other hand, no. In the case of samples 7 to 8, the connection between the external electrode and the internal electrode was weak, and sparking occurred at the contact point between the external electrode and the internal electrode.

  Furthermore, as a result of driving at 200 V, which has strict driving conditions, No. 1 within the scope of the present invention. In the samples 1, 2, 3, 4, and 5, no abnormality such as disconnection or sparking of the external electrode was observed even when driving at 200 V or driving up to 1 × 10 8 cycles. On the other hand, no. In the sample No. 6, since the porosity of the external electrode 4 was low, the external electrode was disconnected.

  That is, by continuously setting the silver content in the external electrode to 50 to 95% by volume, the softening point of the glass component to the melting point of silver or less, and the porosity of the external electrode to 30 to 70%, continuous driving at a high electric field and high speed. Even in this case, the protruding conductive terminal strongly bonds the internal electrode and the external electrode electrically, and the external electrode is firmly bonded to the columnar laminate. There was no problem of sparking at the electrode contacts.

The laminated piezoelectric element of this invention is shown, (a) is a perspective view, (b) is a longitudinal cross-sectional view along the AA 'line of (a), (c) And (d) is (b). It is sectional drawing which expands and shows a part of. (A)-(d) is process drawing for demonstrating the manufacturing method of the lamination type piezoelectric element of this invention. FIG. 4 shows another embodiment of the multilayer piezoelectric element of the present invention, where (a) is a perspective view and (b) is a cross-sectional view taken along line A-A ′ of (a). It is a longitudinal cross-sectional view of a conventional multilayer piezoelectric actuator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric body 1a ... Columnar laminated body 2 ... Internal electrode 4 ... External electrode 4b ... Glass rich layer 5 ... Projection-like conductive terminal

Claims (4)

A method of manufacturing a laminated piezoelectric element having a columnar laminated body in which a plurality of piezoelectric bodies and a plurality of internal electrodes are alternately laminated, and having a pair of external electrodes formed on two side surfaces of the columnar laminated body. ,
Producing a columnar laminate in which end portions of the plurality of internal electrodes are alternately exposed on the two side surfaces;
Applying a conductive paste containing 50 to 95% by volume of conductive metal powder and 5 to 50% by volume of glass powder on at least an end portion of the internal electrode on the side surface of the columnar laminate;
And a step of heat-treating the conductive paste in a temperature range of 90 to 120% of the softening point of the glass to form an external electrode.   The method for producing a multilayer piezoelectric element according to claim 1, wherein the glass has a softening point in the range of 400 to 930 ° C.   The method for manufacturing a multilayer piezoelectric element according to claim 1 or 2, wherein the heat treatment temperature is higher than a softening point of the glass and not higher than a melting point of the conductive metal powder. A columnar laminated body formed by alternately laminating piezoelectric bodies and internal electrodes, and a pair of external electrodes provided on the side surfaces of the columnar laminated body and having the internal electrodes alternately connected every other layer. In the multilayer piezoelectric element, a protruding conductive terminal protruding from a side surface of the columnar stacked body is provided at every other end of the internal electrode, and the protruding conductive terminal contains a conductive material and glass. A multilayer piezoelectric element embedded in an external electrode, wherein the porosity of the external electrode is 30 to 70%.

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