JP6542660B2 - Piezoelectric element, method of manufacturing the same, and piezoelectric actuator - Google Patents

Description

  The present invention relates to a laminated piezoelectric element that expands and contracts by application of a voltage, a method of manufacturing the same, and a piezoelectric actuator.

  In recent years, piezoelectric actuators used in semiconductor manufacturing apparatuses and FPD manufacturing apparatuses are often driven by a high electric field in a high temperature environment. In such a use environment, a high electric field voltage is applied between the electrodes, so insulation failure due to ion migration is likely to occur. Ion migration occurs because the metal of the positive electrode is ionized to generate dendrites or to diffuse the glass phase. In the use environment of the piezoelectric actuator in recent years, suppression of such ion migration is made into the subject.

  On the other hand, conventionally, one using a different material for an internal electrode of a piezoelectric element is known. For example, Patent Document 1 describes a piezoelectric element in which a gold-palladium alloy is used for both the positive electrode and the negative electrode. Patent Document 2 describes a piezoelectric element in which internal electrodes on the same lamination surface are formed of a platinum portion and a silver-palladium portion.

JP 2001-250994 A Japanese Patent Application Laid-Open No. 05-110157

  In the piezoelectric element driven by a high electric field under the above-mentioned high temperature environment, ion migration is suppressed by using inactive platinum as an internal electrode. However, platinum is a scarce and expensive material which it is desirable to reduce its use for cost reduction. Ion migration is accelerated in proportion to the environmental temperature at which the piezoelectric actuator is used, and every 10 ° C. increase in average failure time decreases by 30 to 50%.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a piezoelectric element having a long life, high reliability and low cost even when used under high temperature, a method of manufacturing the same, and a piezoelectric actuator. To aim.

  (1) In order to achieve the above object, the piezoelectric element of the present invention is a laminated piezoelectric element that expands and contracts by application of voltage, and is connected to an external electrode provided on the surface of the element body and the external electrode The internal electrode and the piezoelectric layer alternately stacked with the internal electrode, wherein only the internal electrode on the positive electrode side of the internal electrode is made of platinum, and the internal electrode on the negative electrode side is made of silver-palladium alloy It is characterized by being done.

  Thereby, the cost of the electrode material can be reduced while preventing the internal electrode on the positive electrode side from ionizing and migrating. As a result, it is possible to realize a piezoelectric element having a long life and high reliability even when used under high temperature.

  (2) Further, the piezoelectric element of the present invention is characterized in that the internal electrode on the negative electrode side has an electrode pattern of a lead-out portion which is 1.5 times or more larger than the internal electrode on the positive electrode side. Thereby, in the manufacturing process, the electrode pattern on the positive electrode side and the electrode pattern on the negative electrode side can be distinguished, and the accuracy and efficiency of the work are improved.

  (3) Further, in the piezoelectric element of the present invention, a platinum powder in which the internal electrode on the positive electrode side has a particle diameter 20% or more smaller than the particle diameter of the silver-palladium mixed powder or alloy powder forming the internal electrode on the negative electrode It is characterized in that it is formed of As described above, since the internal electrode on the positive electrode side is formed of fine particles of Pt, the sintering temperature is lowered, and simultaneous firing with the Ag / Pd electrode becomes possible.

  (4) Further, according to the piezoelectric actuator of the present invention, a piezoelectric actuator main body formed by connecting a plurality of the piezoelectric elements according to (1) to (3) in series, and a seat for fixing one end of the piezoelectric actuator main body And a cap which is formed in a cylindrical shape with a bottom, and which accommodates the piezoelectric actuator main body inside, and whose open end is sealed in a seat. This makes it possible to suppress migration acceleration due to the humidity of the use environment, and can prevent the occurrence of insulation failure even when the piezoelectric actuator is driven by applying a high electric field in a high temperature environment.

  (5) Further, the piezoelectric actuator of the present invention is characterized in that it is used in an environment of medium to high temperature of 40 ° C. or more for opening and closing a gas flow valve of a mass flow controller. Thereby, the piezoelectric actuator which migration is hard to occur can be used for opening and closing the gas flow valve of the mass flow controller.

  (6) Further, the method of manufacturing a piezoelectric element according to the present invention is a method of manufacturing a laminated piezoelectric element that expands and contracts by application of a voltage, and the internal electrode on the negative electrode side contains silver-palladium mixed powder or alloy powder. Printing the electrode paste, and printing the electrode paste containing finely divided platinum powder on the positive electrode side internal electrode by making the particle diameter 20% or more smaller than that of the silver-palladium mixed powder or alloy powder, and And a step of laminating the printed green sheets and simultaneously firing them integrally. This makes it possible to manufacture a piezoelectric actuator having a long life and high reliability even when used under high temperature.

  According to the present invention, it is possible to realize a piezoelectric actuator which has long life, high reliability and low cost even when used at high temperature.

(A), (b) is the perspective view and front sectional view of the piezoelectric element of this invention, respectively. (A), (b) is the plane sectional view of the piezoelectric element of this invention, and the side view of the positive electrode side, respectively. (A), (b) is the plane sectional view of the piezoelectric element of this invention, and the side view of the negative electrode side, respectively. It is the schematic which shows the lamination | stacking state of the electrode in the piezoelectric element of this invention. It is a front sectional view showing a piezoelectric actuator of the present invention.

  Next, embodiments of the present invention will be described with reference to the drawings. In order to facilitate understanding of the description, the same reference numerals are given to the same components in the respective drawings, and the overlapping description will be omitted.

(Configuration of piezoelectric element)
FIGS. 1A and 1B are a perspective view and a front sectional view of the piezoelectric element 100, respectively. The stacked piezoelectric device 100 formed into a rectangular body has the piezoelectric layers 103 and the internal electrodes 104 and 105 alternately stacked in the stacking direction Z, and expands and contracts by application of a voltage to the internal electrodes 104 and 105. The piezoelectric layer 103 is made of, for example, a piezoelectric material such as PZT or barium titanate, and is polarized alternately in the thickness direction.

  The internal electrodes 104 and 105 are taken out on the side surfaces of the opposing elements and are connected to the external electrodes 106 and 107, respectively, and different voltages can be applied from the external electrodes 106 and 107 to the adjacent internal electrodes 104 and 105. By applying a voltage to the internal electrodes 104 and 105, each piezoelectric layer 103 expands and contracts, and the entire piezoelectric element expands and contracts.

  2A and 2B are a cross-sectional plan view of the piezoelectric element 100 and a side view of the positive electrode side, respectively. FIGS. 3A and 3B are a cross-sectional plan view of the piezoelectric element 100 and a side view of the negative electrode side, respectively. FIG. 4 is a schematic view showing the laminated state of the electrodes in the piezoelectric element 100. As shown in FIG.

  The electrode material used for the internal electrode 104 on the positive electrode side is Pt (platinum). The electrode material used for the internal electrode 105 on the negative electrode side or the external electrodes 106 and 107 is Ag / Pd (alloy of silver-palladium).

  By this configuration, it is possible to prevent the metal constituting the internal electrode 104 on the positive electrode side from being ionized, and suppress the ion migration which is likely to occur selectively in the vicinity of the internal electrode 104 on the positive electrode side. The cost of the electrode material can be reduced by setting the electrode to inexpensive Ag / Pd. And, even when used at high temperature, insulation deterioration can be prevented, the life of the piezoelectric element 100 can be extended, and the reliability can be improved.

  With regard to the electrode pattern, the lead-out portion 105a of the internal electrode 105 on the negative electrode side preferably has an area 1.5 times or more larger than the lead-out portion 104a of the internal electrode 104 on the positive electrode side, It is more preferable to have an electrode pattern of the takeout part of the area. Thereby, in the manufacturing process, the electrode pattern on the positive electrode side and the electrode pattern on the negative electrode side can be distinguished, and the accuracy and efficiency of the work are improved. In the example of the figure, the width W2 of the extraction portion 105a is 1.5 times or more larger than the width W1 of the extraction portion 104a.

  The internal electrode 104 on the positive electrode side is preferably formed of platinum powder having a particle diameter 20% or more smaller than the particle diameter of the silver-palladium alloy used in the internal electrode on the negative electrode side. Since the internal electrode 104 on the positive electrode side is composed of fine particles of Pt as described above, the sintering temperature can be lowered, and simultaneous firing with Ag / Pd, which is the electrode material of the internal electrode 105 on the negative electrode side, is possible. Become.

(Configuration of piezoelectric actuator)
FIG. 5 is a front sectional view showing the piezoelectric actuator. The piezoelectric actuator 190 is a positioning piezoelectric actuator 190, and expands and contracts by application of a voltage. The piezoelectric actuator 190 is formed by housing and sealing the piezoelectric actuator body 110 in the cap 160. In FIG. 5, only the cap 160 is shown in cross section, and the piezoelectric actuator body 110 is shown in front view.

  The piezoelectric actuator main body 110 is formed by connecting a plurality of piezoelectric elements 100 in series along the stacking direction Z. The lead members 121 and 122 are made of metal, respectively adhered to the external electrodes 106 and 107, and connected to the terminals 151 and 152 at the seat 140, respectively.

  The seat 140 fixes one end of the piezoelectric actuator body 110. The cap 160 is formed in a cylindrical shape with a bottom, and accommodates the piezoelectric actuator body 110 therein, and the open end is sealed to the seat 140. Even when the piezoelectric actuator 190 is driven by applying a high electric field at high temperature without causing the influence of the humidity of the use environment by sealing, the occurrence of ion migration is suppressed. The cap 160 can be formed, for example, in such a manner that the cylindrical portion is cylindrical, and the tip portion forming the bottom is a diaphragm whose center is hemispherical.

  In the piezoelectric actuator 190, when a voltage is applied to the terminals 151 and 152, the piezoelectric actuator body 110 expands and contracts, and the cap 160 in contact with the hemispherical chip 130 contacts a driven object such as a stage. As a result, precise alignment of the driven body can be performed, and a highly durable piezoelectric actuator 190 can be realized. The driven body may be a valve or a stage depending on the application.

(Application to mass flow controller)
It is required to vaporize and supply a liquid material at a high temperature in a manufacturing process of an IGZO semiconductor, an organic EL, or the like. In order to supply the vaporized high-temperature gas precisely, a high-temperature mass flow controller and a high-temperature compatible piezoelectric actuator serving as its driving source are required. When a conventional piezoelectric actuator is used at high temperature with a high electric field of up to 3 kV / mm, ion migration of the positive electrode internal electrode is accelerated, and a sufficient life can not be obtained. In the piezoelectric actuator 190, since the material of the internal electrode 104 on the positive electrode side is Pt, ion migration hardly occurs. Therefore, as opening and closing of the gas flow valve of the mass flow controller, it is suitable for use in a medium to high temperature environment of 40 ° C to 150 ° C.

  If Pt is uniformly used as the internal electrode, ion migration can be suppressed, but this also causes an increase in the cost of the piezoelectric actuator. There is a large difference in cost between Pt and Ag / Pd, and the cost is as low as about 1/10 of that of Pt, even with a high cost of 70:30 Ag / Pd. When the above-described piezoelectric actuator 190 is used, since the internal electrode 105 on the negative electrode side is Ag / Pd, the cost of the internal electrode can be almost halved compared to the case where both internal electrodes are Pt. In addition, it can be expected to be adopted as a piezoelectric actuator having high reliability even at normal temperature operation in the medical field etc. which was not used because the cost did not match.

(Piezoelectric element, method of manufacturing piezoelectric actuator)
A method of manufacturing the piezoelectric element 100 and the piezoelectric actuator 190 configured as described above will be described. Powders of Pt pulverized to an average particle size of 1 μm or less and coarse Ag / Pd powder alloyed by calcination are prepared in advance, and each organic material is mixed to form an electrode paste. The respective electrode materials generally have a difference of 50 ° C. in the firing temperature, but the simultaneous firing becomes easy by micronizing the Pt particles as described above. Then, first, the electrode pattern of the internal electrode on the positive electrode side is printed with a Pt electrode paste on a green sheet of piezoelectric ceramic, and the electrode pattern of the internal electrode on the negative electrode side is printed with an Ag / Pd electrode paste.

  At that time, it is preferable to print in a pattern having an area larger by 1.5 times or more of the extraction portion of the internal electrode 105 on the negative electrode side than the extraction portion of the internal electrode 104 on the positive electrode side. It is more preferable to make the portion 1.5 times or more twice or more.

  Then, the green sheets are stacked and pressed, and the piezoelectric layer 103 is co-fired at 1200 ° C. or less together with the internal electrodes 104 and 105. This makes it possible to manufacture a piezoelectric actuator 190 having a long life and high reliability even when used under high temperature. The external electrodes 106 and 107 can be formed by printing and baking an electrode paste on the side surface of the obtained sintered body so as to be connected to the internal electrodes 104 and 105 along the stacking direction. The piezoelectric element 100 is obtained by subjecting the fired body thus obtained to polarization treatment.

  Thus, an adhesive such as epoxy is applied and adhered to the end faces of the plurality of piezoelectric elements 100 thus obtained, and they are connected in the serial direction to produce the piezoelectric actuator main body 110. Then, the lead members 121 and 122 are fixed to the external electrodes 106 and 107 with adhesive members such as solder, and are connected to the terminals 151 and 152 at the seat 140 respectively. Then, the piezoelectric actuator body 110 can be housed in the cap 160 and sealed to make the piezoelectric actuator 190.

DESCRIPTION OF SYMBOLS 100 piezoelectric element 103 piezoelectric layer 104, 105 internal electrode 104a, 105a taking-out part 106, 107 external electrode 110 piezoelectric actuator main body 121, 122 lead member 130 chip 140 seat 151, 152 terminal 160 cap 190 piezoelectric actuator

Claims (5)

A laminated piezoelectric element that expands and contracts by application of a voltage, and
An external electrode provided on the surface of the element body;
An internal electrode connected to the external electrode;
And piezoelectric layers alternately stacked with the internal electrodes,
Of the internal electrodes, only the internal electrode on the positive electrode side is made of platinum, and the internal electrode on the negative electrode side is made of silver-palladium alloy ,
The internal electrode on the positive electrode side is formed of platinum powder having a particle diameter 20% or more smaller than the particle diameter of the silver-palladium mixed powder or alloy powder forming the internal electrode on the negative electrode side. .   2. The piezoelectric element according to claim 1, wherein the internal electrode on the negative electrode side has an electrode pattern of a lead-out portion larger by 1.5 times or more than the internal electrode on the positive electrode side. A piezoelectric actuator body formed of the piezoelectric element according to claim 1 or claim 2 in more connected in series,
A seat for fixing one end of the piezoelectric actuator body;
What is claimed is: 1. A piezoelectric actuator comprising: a bottomed tubular shape, the cap accommodating the piezoelectric actuator body therein, and having an open end sealed in a seat. 4. The piezoelectric actuator according to claim 3 , wherein the piezoelectric actuator is used in an environment of medium to high temperature of 40 [deg.] C. or higher for opening and closing a gas flow valve of a mass flow controller. A method of manufacturing a laminated piezoelectric element that expands and contracts by application of a voltage,
An electrode paste containing silver-palladium mixed powder or alloy powder is printed on the internal electrode on the negative electrode side, and a particle diameter is made 20% or more smaller than that of the silver-palladium mixed powder or alloy powder on the internal electrode on the positive electrode side. Printing an electrode paste containing stabilized platinum powder,
And laminating the green sheets on which the printing has been performed and simultaneously firing the sheets together.

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