JPWO2006073024A1 - Conductive paste and piezoelectric electronic component using the same - Google Patents

Abstract

In a conductive paste suitable for forming an external electrode of a piezoelectric electronic component, comprising at least a conductive powder made of Ag powder, a glass frit, and an organic vehicle, the glass frit has a general formula: [xB2O3-ySiO2- zCaO] (unit of x, y, z is% by weight), in the ternary composition diagram of FIG. 1, (x, y, z) is A (75, 5, 20), B (15 , 65, 20), C (15, 45, 40) and D (55, 5, 40), and x + y + z = 100, and ZnO, Al2O3, alkali metal oxide The content of the oxide in the glass frit in the case where the alkali metal oxide is one or more selected from Li2O, Na2O, K2O, and contains any one of the oxides. But, Wt% ≦ ZnO ≦ 13 wt%, 1 wt% ≦ Al2 O3 ≦ 5 wt%, and 3 wt% ≦ alkali metal oxide ≦ 25% by weight in the range.

Description

  The present invention relates to a conductive paste suitable for forming an electrode of a piezoelectric electronic component, and a piezoelectric electronic component using the same.

  Conventionally, an electrode of a piezoelectric electronic component, particularly an external electrode, is applied or printed on the piezoelectric electronic component using a conductive paste obtained by kneading a conductive powder such as Ag, glass frit, and an organic binder, It was formed by baking.

  By the way, in the piezoelectric electronic component, if the ceramic laminated body repeats a minute expansion / contraction motion during the polarization process or by subsequent driving, the ceramic laminated body is fatigued and a crack is generated, and the crack propagates to the external electrode. As a result, the external electrode is broken, and as a result, there is a problem that the electric characteristics are deteriorated.

Therefore, for the purpose of maintaining the bonding strength between the ceramic body and the external electrode, in the conductive paste for external electrodes of electronic components, the glass frit contained in the conductive paste is (1) substantially free of lead oxide; and (2) in the glass frit, as an oxide units, B ₂ O _3: 9.0-20.0 wt%, SiO _2: 22.0 to 32.0 wt%, BaO: 35.0 to 45.0 Containing 0.1% by weight, ZnO: 0.1 to 30.0% by weight, Al ₂ O ₃ : 0.1 to 12.0% by weight, Na ₂ O: 0.1 to 15.0% by weight, and the conductive paste However, a method of forming an external electrode at a firing temperature of 600 to 670 ° C. (Patent Document 1) or a ZnO—Al ₂ O ₃ —B ₂ O ₃ —SiO ₂ glass insulating material having a heat resistant temperature of 150 ° C. or higher is formed. Furthermore, the external electrode material application part has a heat resistant temperature of 150 ° C. or higher and a composition of Manufacturing method of a piezoelectric actuator to form external electrode material made of _{Bi 2 O 3 -B 2 O 3} -PbO based glass Ag and junction components of the body (Patent Document 2), have been proposed.
Japanese Patent No. 3534684 JP 2000-31558 A

  However, when the glass frit described in Patent Document 1 or Patent Document 2 is used as a conductive paste, the bonding strength between the ceramic body and the external electrode is still insufficient, and cracks in the ceramic body and the external electrode The electrical characteristics deteriorated due to the breakage.

  Accordingly, an object of the present invention is to provide a conductive paste suitable for forming an external electrode of a piezoelectric electronic component that does not break by a minute stretching movement of the ceramic laminate while maintaining the bonding strength between the ceramic body and the external electrode, And it aims at providing a piezoelectric electronic component provided with the external electrode formed using it.

In order to achieve the above object, the conductive paste of the present invention comprises:
A conductive paste comprising at least conductive powder made of Ag powder, glass frit, and an organic vehicle,
The glass frit is
The general _{formula: [xB 2 O 3 -ySiO 2} -zCaO]
(However, the unit of x, y, z is% by weight)
In the three-component composition diagram shown in FIG. 1 of the accompanying drawings, the composition range represented by (x, y, z) is A (75, 5, 20), B (15, 65, 20), C (15, 45, 40) and D (55, 5, 40) and one or more oxides selected from ZnO, Al ₂ O ₃ , and alkali metal oxides, and x + y + z = 100 And the alkali metal oxide is at least one selected from Li ₂ O, Na ₂ O, and K ₂ O and contains any of the oxides, the inclusion of the oxides in the glass frit It is characterized in that the ratio is in the range of 2 wt% ≦ ZnO ≦ 13 wt%, 1 wt% ≦ Al ₂ O ₃ ≦ 5 wt%, 3 wt% ≦ alkali metal oxide ≦ 25 wt%.

Furthermore, the conductive paste of the present invention is characterized in that the conductive paste further includes 150% by volume or less of Bi ₂ O ₃ with respect to 100% by volume of the glass frit.

  According to another aspect of the present invention, there is provided a piezoelectric electronic component comprising an electrode made of a sintered body in which the conductive paste according to claim 1 or 2 and a conductive reinforcing material are integrally sintered.

  In the piezoelectric electronic component of the present invention, the conductive reinforcing material is formed of a base metal material as a core material and a surface of a noble metal material, and is formed in a mesh shape in the electrode.

  According to the conductive paste of the present invention, an external electrode that does not break can be formed while maintaining the bonding strength between the ceramic body and the external electrode. Furthermore, by providing the external electrode, it is possible to obtain a piezoelectric electronic component having no deterioration in electrical characteristics even by a minute expansion and contraction movement of the ceramic body.

In the glass frit contained in the conductive paste of the present invention, a three-component composition diagram showing the scope of the _{[xB 2 O 3 -ySiO 2 -zCaO} ] defines a composition represented by x, y and z. It is sectional drawing which shows typically one Embodiment of a laminated piezoelectric electronic component provided with the external electrode formed using the electrically conductive paste of this invention. It is the B section enlarged view of FIG. It is a top view which shows the state which formed the conductor pattern on the ceramic green sheet. It is a perspective view for demonstrating an example of the manufacturing method of the said multilayer piezoelectric electronic component. It is a principal part enlarged view which shows 2nd Embodiment of a lamination type piezoelectric electronic component. It is a principal part enlarged view which shows 3rd Embodiment of a lamination type piezoelectric electronic component. It is a principal part enlarged view which shows 4th Embodiment of a lamination type piezoelectric electronic component. It is a principal part enlarged plan view which shows 5th Embodiment of a lamination type piezoelectric electronic component.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ceramic body 2a-2g Internal electrode 3a, 3b External electrode 4a, 4b Lead wire 5a, 5b Coating film 6 Ag foil (conductive foil)
7 Ceramic Green Sheet 8 Conductor Pattern 8a Convex 9 Ag Wire (Conductive Linear Member)
10a, 10b Coating film 11 Coating film 12 Ag wire mesh (conductive reinforcement)
13 Conductive member (network member)
14 Ag wire mesh (conductive reinforcement)
30 crack

  Hereinafter, the conductive paste of the present invention will be described.

The conductive paste of the present invention is a conductive paste containing at least conductive powder made of Ag powder, glass frit, and an organic vehicle. The glass frit has a composition range represented by the general formula: [xB ₂ O ₃ —ySiO ₂ —zCaO], and (x, y, z) is A (75 in the three-component composition diagram shown in FIG. 5, 20), B (15, 65, 20), C (15, 45, 40) and D (55, 5, 40), and x + y + z = 100. Furthermore, it contains at least one oxide selected from ZnO, Al ₂ O ₃ and alkali metal oxides, and the alkali metal oxide is at least one selected from Li ₂ O, Na ₂ O and K ₂ O. In the case where any of the oxides is contained, the oxide content in the glass frit is 2 wt% ≦ ZnO ≦ 13 wt%, 1 wt% ≦ Al ₂ O ₃ ≦ 5 wt%, 3 wt% ≦ alkali It contains components within the range of metal oxide ≦ 25% by weight.

In addition, the conductive paste of the present invention further includes 150% by volume or less of Bi ₂ O ₃ with respect to 100% by volume of the glass frit.

  Hereinafter, experimental examples serving as the basis for selecting the above-described characteristic composition in the present invention will be described.

As a component of the glass frit, the composition range represented by the general formula: [xB ₂ O ₃ —ySiO ₂ —zCaO] is the three component composition diagram shown in the attached FIG. 1, where (x, y, z) is A (75, 5, 20), B (15, 65, 20), C (15, 45, 40) and D (55, 5, 40) are within the range of the polygon, and x + y + z = 100 This is because, in a glass frit outside the composition range, the bonding strength between the ceramic body and the external electrode is lowered, the number of driving cycles is reduced, and this causes a problem in actual use.

  Here, the number of driving cycles indicates the cumulative number of expansion / contractions performed until the piezoelectric electronic component breaks when the piezoelectric electronic component of the present invention is driven by applying a triangular wave having a frequency of 200 Hz and a voltage of 200V. . When measuring the number of driving cycles, each sample was driven by pressing the upper and lower sides with a metal plate in the stacking direction in order to suppress excessive transition during driving.

  Moreover, the addition amount of ZnO is limited to 2 to 13% by weight. If the addition amount of ZnO exceeds 13% by weight, the reactivity between the ceramic body constituting the piezoelectric electronic component and the glass frit increases. As a result, the generated reaction product reduces the bonding strength between the piezoelectric electronic component and the external electrode, and when the added amount of ZnO is less than 2% by weight, the softening temperature of the glass frit increases. This is because the affinity with the ceramic body constituting the piezoelectric electronic component is lowered, and as a result, the bonding strength between the ceramic body and the external electrode is lowered.

Further, The reason for limiting the addition amount of Al ₂ O ₃ 1 to 5 wt%, the softening temperature of the glass frit When the amount of Al ₂ O ₃ exceeds 5% by weight is high, the ceramic body and the external electrodes The bonding strength between the ceramic body and the external electrode decreases when the amount of Al ₂ O ₃ added is less than 1% by weight.

Further, the addition amount of alkali metal oxides (Li ₂ O, Na ₂ O, K ₂ O) is limited to 3 to 25% by weight when the addition amount of alkali metal oxides exceeds 25% by weight. The frit becomes crystallized glass, and the glass does not flow to the interface between the external electrode and the ceramic body due to the crystallization of the glass when baking the external electrode, and the bonding strength between the external electrode and the ceramic body decreases. Moreover, when the addition amount of the alkali metal oxide is less than 3% by weight, the softening temperature of the glass frit becomes high, and the effect of improving the fluidity of the glass in the external electrode at the time of baking the external electrode is reduced.

Further, the amount of Bi ₂ O ₃ added is limited to 150% by volume or less with respect to 100% by volume of the glass frit. When the amount of Bi ₂ O ₃ exceeds 150% by volume, the external electrode is baked. This is because the effect of improving the fluidity of the glass in the external electrode is reduced, which is not preferable.

  Next, the piezoelectric electronic component of the present invention will be described.

  FIG. 2 is a cross-sectional view showing an embodiment of a piezoelectric electronic component including external electrodes formed by baking the conductive paste of the present invention.

  The piezoelectric electronic component includes a ceramic body 1 mainly composed of lead zirconate titanate, a plurality of internal electrodes 2a to 2g embedded in parallel inside the ceramic body 1, and the ceramic body. 1 is composed of external electrodes 3a, 3b formed by baking the conductive paste of the present invention at both ends, and lead wires 4a, 4b connected to the external electrodes 3a, 3b.

  In the piezoelectric electronic component, one end of each of the internal electrodes 2a, 2c, 2e, and 2g is electrically connected to one external electrode 3a, and one end of each of the internal electrodes 2b, 2d, and 2f is electrically connected to the other external electrode 3b. Connected. When a voltage is applied between the external electrode 3a and the external electrode 3b via the lead wires 4a and 4b, the piezoelectric electronic component performs a minute expansion and contraction movement in the stacking direction indicated by the arrow A due to the piezoelectric longitudinal effect. .

  FIG. 3 is an enlarged view of part B of FIG. 2, and the external electrode 3b has an Ag foil (conductive foil) 6 as a conductive reinforcing material between coating films 5a and 5b made of Ag powder as a conductive material. It consists of a sintered body embedded in one piece.

  Since the external electrode 3a has the same configuration as the external electrode 3b, the description thereof is omitted.

  Thus, in the present embodiment, the Ag foil 6 is embedded between the coating films 5a and 5b containing Ag powder as a main component and integrated and baked to form the external electrode 3b. From this, the breakage of the external electrode 3 can be suppressed even if the piezoelectric electronic component repeats a minute expansion and contraction movement in the direction of arrow A for a long time due to the reinforcing effect of the Ag foil 6. Further, it is possible to prevent the external electrode from being short-circuited even when a high electric field is applied, and to obtain a piezoelectric electronic component having excellent durability.

  Further, since the strength of the external electrode 3b is improved by the Ag foil 6 which is a conductive reinforcing material, it is possible to suppress the occurrence of structural defects such as cracks in the ceramic body 1.

  Furthermore, the Ag powder 6 and the sintered body of the Ag powder contained in the coating films 5a and 5b are not only in contact with each other, but are firmly bonded to each other by baking, so that a long period of time under high temperature and high humidity. Even if it is left as it is, it is possible to prevent a decrease in conductivity and to improve moisture resistance.

  Next, a method for manufacturing a piezoelectric electronic component will be described.

First, a predetermined amount of a ceramic raw material such as Pb ₃ O ₄ , ZrO ₂ , TiO ₂ was weighed, and the weighed material was mixed with a grinding media such as zirconia beads and ground and mixed using a ball mill. Next, calcination or the like is performed to prepare a ceramic mixed powder, an organic binder or dispersant is added to the ceramic mixed powder, and the mixture is made into a slurry using water as a solvent, and zircon titanate using a doctor blade method. A ceramic green sheet mainly composed of lead acid was prepared.

  Next, for example, a conductive paste for internal electrodes in which the weight ratio Ag / Pd of Ag and Pd is adjusted to 70/30 is used, and as shown in FIG. A conductor pattern 8 having a portion 8a is formed.

  Next, as shown in FIG. 5, a predetermined number (for example, 500) of ceramic green sheets 7 on which the conductive pattern 8 is formed are stacked so that the convex portions 8a are staggered, and the conductive pattern 8 is not formed. The laminate was formed by sandwiching with ceramic green sheets. As a result, the external electrode 3a or the external electrode 3b is electrically connected to the conductive pattern 8 every other layer as indicated by a virtual line. Furthermore, after heating this laminated body to the temperature of 500 degrees C or less and performing a degreasing process, it baked at the temperature of 950-1100 degreeC, and the ceramic body 1 was obtained.

  Next, the conductive paste of the present invention is applied to both ends of the ceramic body 1 to form a coating film 5a, an Ag foil 6 is placed on the coating film 5a, and further on the surface of the Ag foil 6 The conductive paste of the present invention is applied to form the coating film 5b. Next, after drying this, baking is performed at a temperature of 700 to 850 ° C., and external electrodes 3a and 3b made of a sintered body in which the Ag foil 6 is integrally embedded in the coating films 5a and 5b are formed. A piezoelectric electronic component having a predetermined dimension (for example, length 7 mm × width 7 mm × thickness 35 mm) is formed.

  Further, a lead wire (enamel-coated Cu wire, wire diameter 250 μm) is soldered to the external electrodes 3a and 3b (Sn-3Ag-0.5Cu solder, soldering temperature: 350 ° C.). Next, in order to impart piezoelectric characteristics, oil polarization treatment was performed under conditions of an oil temperature of 80 ° C. and a voltage of 3 kV / mm. After the oil polarization, the piezoelectric electronic component was washed with a hydrocarbon-based cleaning agent, and then the hydrocarbon-based solvent was replaced with acetone and allowed to dry naturally.

  FIG. 6 is an enlarged view of a main part showing a second embodiment of the external electrode 3b.

  In the second embodiment, a piezoelectric electronic component including an external electrode made of a sintered body in which an Ag wire 9 is integrally embedded in a wave shape instead of an Ag foil is shown as a conductive reinforcing material.

  Also in the second embodiment, as in the first embodiment, the Ag wire 9 is embedded with the coating films 10a and 10b containing Ag powder as a main component, integrated, and baked, whereby the external electrode 3b. Therefore, even if the piezoelectric electronic component repeats a minute expansion and contraction movement in the direction of arrow A for a long time due to the reinforcing effect of the Ag wire 9, the external electrode 3 can be prevented from breaking and a high electric field is loaded. However, it is possible to prevent a short circuit and obtain a piezoelectric electronic component having excellent durability.

  In addition, since the strength of the external electrode 3b is improved by the Ag wire 9 which is a conductive reinforcing material, structural defects such as cracks can be prevented from occurring in the ceramic body 1.

  In addition, the Ag powder 9 and the sintered body of Ag powder contained in the coating films 10a and 10b are not simply in contact with each other, but are firmly bonded to each other by baking, so that they are left for a long time under high temperature and high humidity. Even so, a decrease in conductivity can be prevented, and moisture resistance can also be improved.

  The external electrode 3b can also be produced by the same method as in the first embodiment. That is, the conductive paste of the present invention is applied to both ends of the ceramic body 1 to form a coating film 10a, an Ag wire 9 is placed on the coating film 10a, and further on the surface of the Ag wire 9 The conductive paste of the present invention is applied to form 10b. Next, after drying this, a baking process is performed, whereby external electrodes 3a and 3b made of a sintered body in which the Ag wire 9 is integrally embedded in the coating films 10a and 10b can be formed. .

  FIG. 7 is an enlarged view of a main part showing a third embodiment of the external electrode 3b.

  In the third embodiment, the conductive reinforcing material is made of an Ag wire mesh (conductive wire member) 12 having a mesh shape, and the Ag wire mesh 12 is completely embedded in the coating film 11 made of Ag. Yes.

  That is, the external electrode 3b is made of a sintered body in which a mesh-like conductive linear member 12 is embedded and integrated in a coating film 11 made of Ag.

  In the third embodiment, for example, a crack 30 is generated as indicated by an imaginary line between the internal electrode 2d and the internal electrode 2e of the ceramic body 1, and the coating film 11 is cut as shown in part C in the figure. Even if it will be in a state, each internal electrode and the external electrode 3b are electrically connected via the Ag wire mesh 12, and can ensure electrical conductivity. In addition, since the contact area between the Ag wire mesh 12 and the coating film 11 is increased, peeling at the interface between the Ag wire mesh 12 and the coating film 11 is suppressed, thereby further improving durability.

  In addition, since the Ag wire mesh 12 and the sintered body of Ag powder contained in the coating film 11 are not simply in contact with each other, they are firmly metal-bonded by baking treatment, so that the first and second embodiments. Similarly to the above, even when left for a long time under high temperature and high humidity, the decrease in conductivity can be prevented and the moisture resistance can be improved.

  In the third embodiment, the external electrode 3b is formed as follows.

  That is, the conductive paste of the present invention is applied to both ends of the ceramic body 1 to form a coating film 11, which is naturally dried until the Ag wire mesh 12 is completely buried in the coating film 11, and then subjected to baking treatment. By performing, the external electrode 3b in which the coating film 11 made of Ag powder and the Ag wire mesh 12 are integrated is formed.

  FIG. 8 is an enlarged view showing a main part of a fourth embodiment of the external electrode 3b.

  In the fourth embodiment, the external electrode 3b is electrically connected to the external electrode 3b by welding after the mesh-like conductive member 13 is laminated on the external electrode 3b in addition to the third embodiment. Connected to.

  Specifically, the conductive member 13 has a core formed of Al or the like and a surface covered with a metal that melts at a soldering temperature, for example, Sn.

  As described above, since the surface of the conductive member 13 is melted at the soldering temperature, in addition to the effects described in the first to third embodiments, the solderability can be improved.

  Moreover, even if the Ag wire mesh 12 is broken, the coating film 11 can ensure conductivity through the conductive member 13 and can improve durability.

  FIG. 9 is an enlarged side view of an essential part showing a fifth embodiment of the external electrode 3b.

  In the fifth embodiment, the conductive reinforcing material is composed of an Ag wire mesh (conductive linear member) 14 as in the third and fourth embodiments, and the Ag wire mesh 14 is embedded in the coating film 11. In addition, at least one of the mesh rows of the Ag wire mesh 14 is exposed from the coating film 11 to the coating film surface.

  In this way, by exposing at least one or more of the mesh rows of the Ag wire mesh 14 from the coating film 11, the end of the Ag wire mesh 14 becomes a free end that is not fixed, thereby suppressing breakage of the Ag wire mesh 14. As a result, the durability can be dramatically improved.

  The present invention is not limited to the first to fifth embodiments. In the first to fifth embodiments, Ag is used as the conductive reinforcing material in consideration of moisture resistance, solderability, etc., but the specific resistance value is smaller than that of the conductive powder material in the conductive paste. It is preferable to use materials, and it is also preferable to use noble metal materials other than Ag, such as Pd, Au, Pt, etc., and use higher-strength base metal materials having heat resistance such as Ni. You can also.

  It is also preferable that the core material is formed of a base metal material having excellent heat resistance such as Ni, Ni alloy, Cr, and the surface is covered with an oxidation resistant material such as oxide glass or noble metal material. In this case, the oxide glass or the noble metal material having excellent oxidation resistance diffuses into the conductive powder during baking. Moreover, when it is inferior to oxidation resistance, it will fly out of a sintered compact at the temperature at the time of baking.

  Furthermore, it is also preferable to use a heat-resistant ceramic fiber or glass fiber that can withstand the baking temperature and maintain the shape as the core material of the conductive reinforcing material, and to form only the surface with the various metal materials having conductivity. .

  Further, in the first and second embodiments, the conductive reinforcing material is placed on the coating film, and then the coating film is formed on the conductive reinforcing material, and then the baking treatment is performed. As in the fifth to fifth embodiments, the external electrode may be formed by a method of embedding a conductive reinforcing material in the coating film. Conversely, the third and fifth embodiments also include the first and Similarly to the second embodiment, the conductive reinforcing material may be placed on the coating film, and then the coating film may be formed on the conductive reinforcing material, and then the baking treatment may be performed.

  Further, the shape of the conductive reinforcing material is not limited to the above embodiment, and for example, the conductive foil may be porous in addition to the shape as in the above embodiment. Further, the conductive linear member is not limited to the wave shape or the mesh shape, and may be a coil shape, a linear shape, or the like.

  In addition, for the connection state between the conductive reinforcing material and the external electrode, the external electrode may be formed integrally with the conductive powder by the baking process, in addition to the form embedded in the coating film as in the above embodiment, The conductive reinforcing material may be integrated by performing a baking process with the surface exposed.

  In the above embodiment, the piezoelectric electronic component has been described as an example. However, the present invention can also be applied to a ceramic electronic component such as a resistor component or a medium-high voltage ceramic capacitor. In particular, in the case of a ceramic electronic component that is baked to form an external electrode, the specific resistance value is higher than that of the metal constituting the external electrode. Therefore, by forming the external electrode using the conductive paste of the present invention, it is possible to obtain a ceramic electronic component including a low-resistance external electrode that is excellent in reliability and does not generate cracks. In addition, by providing a conductive reinforcing material joined so as to cover the external electrode or the external electrode, it is possible to obtain a highly reliable ceramic electronic component that does not cause cracks.

Next, experimental examples in the present invention will be described.
(Experimental example 1)
Here, as Experimental Example 1, a multilayer piezoelectric electronic component including an external electrode formed using the conductive paste of the present invention was evaluated.
(1) Production of Glass Frit for Conductive Paste Regarding Examples and Comparative Examples of the present invention, high purity boron oxide (B ₂ O ₃ ), silicon dioxide (SiO ₂ ) as a starting material for glass frit used for the conductive paste ₂ ), calcium oxide (CaO), bismuth oxide (Bi ₂ O ₃ ), barium oxide (BaO), lead oxide (PbO), zinc oxide (ZnO), aluminum oxide (Al ₂ O ₃ ), lithium oxide (Li ₂₎ Each powder of O) was prepared. Next, these powders were prepared so as to have the respective composition ratios shown in Table 1 to obtain mixed powders.

  Next, after putting the mixed powder in a crucible, the mixture was allowed to stand in a heating furnace and held at a maximum temperature of 1000 to 1600 ° C. for 60 minutes. After confirming that the mixed powder was completely melted, the crucible was taken out from the heating furnace, and the molten mixed powder was dropped into pure water to obtain a bead-shaped glass. The obtained bead-like glass was wet crushed for 16 hours using a ball mill, and then subjected to dehydration and drying treatment, thereby obtaining target glass frit samples Nos. 1 to 18. The obtained glass frit was confirmed to be amorphous by an X-ray diffraction method.

In Table 1, those marked with * are outside the scope of the present invention, and others are within the scope of the present invention.
(2) Production of conductive paste for evaluation Next, the glass frit of the sample numbers 1 to 18 obtained in (1) is 0.1 to 12.0% by weight and spherical Ag powder having an average particle size of 2.0 μm. An organic vehicle containing 50.0 to 90.0% by weight and the balance containing ethyl cellulose and terpineol was mixed and kneaded using a three-roll mill to obtain a target conductive paste for evaluation.

In the present invention, the conductive paste is manufactured using a three-roll mill. However, a media-less dispersing device such as a raikai machine or a kneader, or a dispersing device using a media such as a ball mill may be used as appropriate. .
(3) Fabrication of Evaluation Piezoelectric Electronic Component Next, a ceramic body having a length of 7 mm × width of 7 mm × thickness of 35 mm, mainly composed of lead zirconate titanate, in which an internal electrode made of Ag / Pd is formed. The conductive paste for evaluation obtained in the above (2) was printed on both side surfaces using a metal mask to form a raw coating film having a width of 4 mm and a film thickness of 400 μm. Next, an Ag wire mesh having a wire diameter of 150 μm and an opening of 40 mesh was placed on the raw coating film, and allowed to stand until the metal mesh was completely buried in the raw coating film. Next, the ceramic body was dried in an oven at a temperature of 150 ° C. for 10 minutes. Next, an external electrode in which an Ag wire mesh was included in a dry coating film was formed on both side surfaces of the piezoelectric electronic component by performing a baking process at 740 to 810 ° C. in an air atmosphere.

  In printing the conductive paste for evaluation, various printing methods such as screen printing, gravure printing, offset printing, gravure-offset printing, and ink jet printing are applied by adjusting the viscosity of the conductive paste. Can do.

Next, Sn wire containing 3 wt% Ag and 0.5 wt% Cu as a main component (Sn-3Ag-0.5Cu solder) is enamel-coated and the wire diameter is 250 μm. Was soldered to the external electrode, and a lead wire was connected to the external electrode. Next, polarization is performed in oil at an oil temperature of 80 ° C. and a voltage of 3 kV / mm to impart piezoelectric characteristics, and then washed with a hydrocarbon-based cleaning agent to obtain a target multilayer piezoelectric electronic component. It was.
[Characteristic evaluation of multilayer piezoelectric electronic components]
The adhesion strength, the electromechanical coupling coefficient k33, and the driving time of the external electrode of the multilayer piezoelectric electronic component produced as described above were evaluated.

  Regarding the adhesion strength of the external electrode, each sample was placed in a predetermined position of a tensile / compression tester (Imida Seisakusho, SV-201), and the lead wire soldered to the external electrode of each sample was pulled with a jig. And the strength value when the said lead wire peeled from the external electrode was measured. Further, 10 samples were measured for each sample, and the average value was taken as the adhesion strength of the external electrode of each sample.

  The electromechanical coupling coefficient k33 was measured using an impedance analyzer (manufactured by Hewlett-Packard Company, 4194A). Further, 10 samples were measured for each sample, and the average value was taken as the electromechanical coupling coefficient k33 of each sample.

  Regarding the driving time, three samples were measured for each sample, and the average value was defined as the number of driving cycles for each sample.

These measurement results are shown in Table 1. As is apparent from Table 1, the sample numbers 1 to 7 that are within the scope of the present invention have higher adhesion strength of the external electrodes and the number of drive cycles than the sample numbers 8 to 18 that are outside the scope of the present invention. 5.76 × 10 ⁸ times (equivalent to continuous driving for 800 hours) was achieved, and it was confirmed that there was no problem in actual use. Further, since the electromechanical coupling coefficient k33 showed the same value as the conventional sample numbers 17 and 18, it was confirmed that there is no problem in the electromechanical coupling coefficient by changing the glass frit.

On the other hand, Sample Nos. 8 to 11 and 14 to 18 which are out of the scope of the present invention have a low adhesion strength of the external electrodes and the number of driving cycles is less than 10 ⁸ times, which is a problem in actual use. It was. Sample Nos. 12 and 13 were not vitrified at the time of glass frit production, and various properties such as production of conductive paste and adhesion strength of external electrodes could not be measured.
[Experimental example 2]
Here, as Experimental Example 2, a single-plate piezoelectric electronic component including an external electrode formed using the conductive paste of the present invention was evaluated.
(4) Production of Glass Frit for Conductive Paste For Examples and Comparative Examples of the present invention, high purity boron oxide (B ₂ O ₃ ), silicon dioxide (SiO ₂ ) as a starting material for glass frit used for the conductive paste ₂ ), calcium oxide (CaO), bismuth oxide (Bi ₂ O ₃ ), barium oxide (BaO), lead oxide (PbO), zinc oxide (ZnO), aluminum oxide (Al ₂ O ₃ ), lithium oxide (Li ₂₎ Each powder of O) was prepared. Next, these powders were prepared so as to have respective composition ratios shown in Table 2 to obtain mixed powders.

  Next, as in (1) above, the mixed powder was placed in a crucible, then left in a heating furnace, and held at a maximum temperature of 1000 to 1600 ° C. for 60 minutes. After confirming that the mixed powder was completely melted, the crucible was taken out from the heating furnace, and the molten mixed powder was dropped into pure water to obtain a bead-shaped glass. The obtained bead-like glass was wet crushed for 16 hours using a ball mill, and then subjected to dehydration and drying treatment, thereby obtaining target glass frit Nos. 19 to 38. The obtained glass frit was confirmed to be amorphous by an X-ray diffraction method.

In Table 2, those marked with * are outside the scope of the present invention, and others are within the scope of the present invention.
(5) Preparation of conductive paste for evaluation Next, the spherical frit of 0.1 to 12.0% by weight of the glass frit of sample numbers 19 to 38 obtained in (4) and an average particle size of 2.0 μm was obtained. An organic vehicle containing 50.0 to 90.0% by weight and the balance containing ethyl cellulose and terpineol was mixed and kneaded using a three-roll mill to obtain a target conductive paste for evaluation.
(6) Preparation of piezoelectric electronic component for evaluation Next, using both metal masks on both main surfaces of a disk-shaped ceramic body having a diameter of 20 mm and a thickness of 10 mm, the main component of which is lead zirconate titanate, The conductive paste for evaluation obtained in (5) was printed to form a raw coating film having a diameter of 10 mm and a thickness of 400 μm. Next, it was dried in an oven at a temperature of 150 ° C. for 3 minutes. Next, a baking process was performed at 750 to 800 ° C. in an air atmosphere, and external electrodes were formed on both main surfaces of the ceramic body.

Next, an Sn-coated Cu wire having a wire diameter of 250 μm using Sn containing 3 wt% Ag and 0.5 wt% Cu as a main component (Sn-3Ag-0.5Cu solder). Was soldered to an external electrode on one main surface, and a lead wire was connected to the external electrode. Next, with respect to the external electrode on the other main surface to which no lead wire was connected, a metal vibration made of Cu having a length of 30 mm × width of 30 mm × thickness of 10 mm using a conductive adhesive mainly composed of epoxy resin. Fixed to the plate. Next, a voltage of 2.25 kV / mm was applied to the single-plate piezoelectric electronic component at room temperature and in an air atmosphere, and polarization treatment was performed to impart piezoelectric characteristics. Thereafter, it was washed with a hydrocarbon-based cleaning agent to obtain a target single plate type piezoelectric electronic component.
[Characteristic evaluation of single plate type piezoelectric electronic components]
The adhesion strength of the external electrode and the electromechanical coupling coefficient kp of the single-plate piezoelectric electronic component produced as described above were evaluated.

  Regarding the adhesion strength of the external electrodes, each sample was placed in a predetermined position of a tensile and compression tester (manufactured by Imada Seisakusho, SV-201), and the lead wire soldered to the external electrode of each sample was placed with a jig. The strength value when the lead wire was peeled off from the external electrode was measured. Further, 10 samples were measured for each sample, and the average value was taken as the adhesion strength of the external electrode of each sample.

  About the electromechanical coupling coefficient kp, it measured using the impedance analyzer (The Hewlett-Packard company make, 4194A). Further, 10 samples were measured for each sample, and the average value was used as the electromechanical coupling coefficient kp of each sample.

  These measurement results are shown in Table 2. As can be seen from Table 2, the sample numbers 19 to 25, 37 and 38 that are within the scope of the present invention have higher adhesion strength of the external electrodes than the sample numbers 26 to 36 that are outside the scope of the present invention. It was confirmed. In addition, since the electromechanical coupling coefficient kp showed the same value as the conventional sample numbers 35 and 36, it was confirmed that there is no problem in the electromechanical coupling coefficient by changing the glass frit.

  On the other hand, Sample Nos. 26 to 29 and 32 to 36, which are outside the scope of the present invention, resulted in problems in actual use due to the low adhesion strength of the external electrodes. Sample numbers 30 and 31 were not vitrified at the time of glass frit production, and various properties such as production of conductive paste and adhesion strength of external electrodes could not be measured.

By using the conductive paste according to the present invention, it is possible to reliably obtain a piezoelectric electronic component having external electrodes that are not broken by a minute expansion and contraction movement of the ceramic laminate while maintaining the bonding strength between the ceramic body and the external electrodes. It becomes possible.
Therefore, the present invention can be widely applied to the field of conductive paste used for manufacturing piezoelectric electronic components and the field of piezoelectric electronic components.

Claims (4)

A conductive paste comprising at least conductive powder made of Ag powder, glass frit, and an organic vehicle,
The glass frit is
The general _{formula: [xB 2 O 3 -ySiO 2} -zCaO]
(However, the unit of x, y, z is% by weight)
In the three-component composition diagram shown in FIG. 1 of the accompanying drawings, the composition range represented by (x, y, z) is A (75, 5, 20), B (15, 65, 20), C (15, 45, 40) and D (55, 5, 40) and one or more oxides selected from ZnO, Al ₂ O ₃ , and alkali metal oxides, and x + y + z = 100 And the alkali metal oxide is at least one selected from Li ₂ O, Na ₂ O, and K ₂ O and contains any of the oxides, the inclusion of the oxides in the glass frit The conductivity is in the range of 2 wt% ≦ ZnO ≦ 13 wt%, 1 wt% ≦ Al ₂ O ₃ ≦ 5 wt%, 3 wt% ≦ alkali metal oxide ≦ 25 wt% Sex paste. The conductive paste according to claim 1, further comprising 150% by volume or less of Bi ₂ O ₃ with respect to 100% by volume of the glass frit.   A piezoelectric electronic component comprising an electrode made of a sintered body in which the conductive paste according to claim 1 or 2 and a conductive reinforcing material are integrally sintered.   4. The piezoelectric electronic component according to claim 3, wherein the conductive reinforcing material is formed of a base metal material as a core material and a surface thereof is formed of a noble metal material, and is formed in a mesh shape in the electrode.

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