JP2005340302A - Multilayer ceramic element and its manufacturing process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer ceramic element in which electrical connection through a conductive member in a through hole is ensured during manufacturing and an internal electrode can be made thin. <P>SOLUTION: In the multilayer ceramic element 1, a melting point of a conductive member in a through hole is higher than that of the material of an internal electrode 2 or the like. Consequently, the shrinkage of the conductive member in a through hole becomes lower as compared with that of the internal electrode 2 at the time of calcination. Since the shrinkage of the conductive member is suppressed relatively at the time of calcination, a difference of shrinkage between a green sheet becoming a piezoelectric layer 3 and the conductive member in a through hole becomes small at the time of calcination. As a result, an electrical open circuit caused by the conductive member in a through hole is prevented. On the other hand, the internal electrode 2 is made thin because the shrinkage thereof is accelerated relatively at the time of calcination. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a multilayer ceramic element such as a multilayer piezoelectric element or a multilayer capacitor, and a manufacturing method thereof.

  As a conventional multilayer ceramic element, there is a multilayer piezoelectric element described in Patent Document 1, for example. In this stacked piezoelectric element, piezoelectric layers in which a plurality of individual electrodes are patterned and piezoelectric layers in which common electrodes are patterned are alternately stacked, and each individual electrode aligned in the stacking direction is They are connected by conductive members through through holes formed in the layers.

In such a piezoelectric element, a lead wire for connecting to a driving power source is soldered to each terminal electrode formed on the uppermost piezoelectric layer. Then, when a voltage is applied between the predetermined individual electrode and the common electrode via the lead wire, an active portion (a portion where distortion is generated by the piezoelectric effect) corresponding to the predetermined individual electrode in the piezoelectric layer. Is selectively displaced.
JP 2002-254634 A

  By the way, in the multilayer ceramic element such as the piezoelectric element as described above, the electrical connection by the conductive member in the through hole formed in the ceramic layer can be further ensured at the time of manufacture. It is desired. At the same time, from the viewpoint of miniaturization of the multilayer ceramic element, it is also desired that the internal electrodes such as individual electrodes are further reduced in thickness.

  Therefore, the present invention has been made in view of such circumstances, and is a multilayer ceramic that can ensure electrical connection by a conductive member in a through hole at the time of manufacture and can reduce the thickness of an internal electrode. An object is to provide an element and a method for manufacturing the element.

  As a result of intensive studies in order to achieve the above object, the inventors of the present invention cut the electrical connection by the conductive member in the through-hole in the production of the multilayer ceramic element, which becomes the ceramic layer. It was found that this was caused by a difference in shrinkage rate during firing between the ceramic body and the conductive member in the through hole. In other words, the shrinkage rate during firing is larger in the conductive member in the through hole than in the ceramic body that becomes the ceramic layer, so the conductive member is offset toward one end in the through hole during firing, The electrical connection by the conductive member in the through hole is broken due to separation. The present inventors have further studied based on this finding and have completed the present invention.

  That is, the multilayer ceramic element according to the present invention is a multilayer ceramic element formed by laminating a plurality of ceramic layers, and a ceramic layer adjacent to a conductive member disposed in a through hole formed in the ceramic layer. And the melting point of the material forming the conductive member is higher than the melting point of the material forming the internal electrode.

  In this multilayer ceramic element, since the melting point of the material forming the conductive member is higher than the melting point of the material forming the internal electrode, the shrinkage rate during firing is smaller in the conductive member than in the internal electrode. Thereby, since the shrinkage | contraction of the electrically conductive member at the time of baking is restrained relatively, the difference of the shrinkage | contraction rate at the time of the firing with the ceramic body used as a ceramic layer and the electrically conductive member in a through hole becomes small. As a result, it is possible to prevent the conductive member from moving to one end side in the through hole during the firing or being separated in the middle, and the electrical connection by the conductive member in the through hole being cut off. Is done. On the other hand, since the shrinkage of the internal electrode during firing is relatively promoted, the internal electrode is thinned by firing. Therefore, according to this multilayer ceramic element, it is possible to ensure electrical connection by the conductive member in the through hole during manufacturing and to reduce the thickness of the internal electrode.

  In the multilayer ceramic element according to the present invention, the conductive member and the internal electrode are made of a material containing at least one of silver element and gold element and palladium element, and the ratio of palladium element in the material forming the conductive member Is preferably higher than the ratio of palladium element in the material forming the internal electrode. Since the melting point of palladium element (Pd) is higher than the melting points of silver element (Ag) and gold element (Au), the ratio of Pd in the material forming the conductive member is larger than the ratio of Pd in the material forming the internal electrode. If it is made higher, the melting point of the material forming the conductive member can be made higher than the melting point of the material forming the internal electrode.

  In the multilayer ceramic element according to the present invention, the conductive member and the internal electrode are made of a material containing at least one of a silver element and a gold element and a platinum element, and the ratio of the platinum element in the material forming the conductive member Is preferably higher than the ratio of platinum element in the material forming the internal electrode. Since the melting point of platinum (Pt) is higher than that of silver element (Ag) or gold element (Au), the Pt ratio in the material forming the conductive member is higher than the Pt ratio in the material forming the internal electrode. If so, the melting point of the material forming the conductive member can be made higher than the melting point of the material forming the internal electrode.

  Furthermore, the method for manufacturing a multilayer ceramic element according to the present invention is a method for manufacturing a multilayer ceramic element in which a plurality of ceramic layers are stacked, and is formed in a through hole formed in a ceramic body to be a ceramic layer. Arranging a conductive member and forming an internal electrode on the surface of the ceramic body; and stacking a plurality of ceramic bodies on which the conductive member is arranged and having the internal electrode formed to form a ceramic laminate. The melting point of the material forming the conductive member is higher than the melting point of the material forming the internal electrode, and the melting point of the material forming the internal electrode is the temperature at which the ceramic laminate is fired. It is characterized by being higher.

  In this method for manufacturing a multilayer ceramic element, the melting point of the material forming the conductive member is higher than the melting point of the material forming the internal electrode, and the melting point of the material forming the internal electrode is higher than the temperature at which the ceramic laminate is fired. Since it is high, the shrinkage rate during firing is smaller for the conductive member than for the internal electrode. Therefore, according to this method for manufacturing a multilayer ceramic element, for the same reason as the above-mentioned multilayer ceramic element, the electrical connection by the conductive member in the through hole at the time of manufacturing is ensured, and the internal electrode is thinned. Is possible.

  According to the present invention, it is possible to ensure electrical connection by the conductive member in the through hole during manufacturing and to reduce the thickness of the internal electrode.

  Hereinafter, a laminated piezoelectric element and a manufacturing method thereof as preferred embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 1, a multilayer piezoelectric element (multilayer ceramic element) 1 includes a piezoelectric layer (ceramic layer) 3 on which individual electrodes (internal electrodes) 2 are formed and a common electrode (internal electrode) 4. The piezoelectric layers (ceramic layers) 5 are alternately stacked, and the piezoelectric layers (ceramic layers) 7 on which the terminal electrodes 17 and 18 are formed are stacked on the uppermost layer.

  Each of the piezoelectric layers 3, 5, and 7 is made of a material mainly composed of ceramics such as lead zirconate titanate, and is formed in a rectangular thin plate shape of, for example, “10 mm × 30 mm, thickness 30 μm”. The individual electrode 2 and the common electrode 4 are made of a conductive material containing Ag and Pd as main components, and are patterned by screen printing. The same applies to each electrode described below except for the terminal electrodes 17 and 18.

  As shown in FIG. 2, a plurality of rectangular individual electrodes 2 are formed on the upper surface of the second, fourth, sixth, and eighth piezoelectric layers 3a from the uppermost piezoelectric layer 7. Are arranged in a matrix. Each individual electrode 2 is arranged such that its longitudinal direction is orthogonal to the longitudinal direction of the piezoelectric layer 3a, and the individual electrodes 2 and 2 adjacent to each other are electrically isolated by taking a predetermined interval. And the influence by mutual vibration is prevented.

  Here, assuming that the longitudinal direction of the piezoelectric layer 3a is the row direction and the direction orthogonal to the longitudinal direction is the column direction, the individual electrodes 2 are arranged, for example, in 4 rows and 75 columns (in the drawing for the sake of clarity). 4 rows and 20 columns). As described above, since the plurality of individual electrodes 2 are arranged in a matrix shape, an efficient arrangement with respect to the piezoelectric layer 3a is possible, so that the area of the active portion contributing to vibration in the piezoelectric layer 3a is maintained. However, the stacked piezoelectric element 1 can be miniaturized or the individual electrodes 2 can be highly integrated.

  The individual electrodes 2 in the first and second rows are formed on the piezoelectric layer 3a immediately below the connection end 2a, with the end facing the first and second rows as the connection end 2a. The through-hole 13 is connected to a conductive member. Similarly, the individual electrodes 2 in the third row and the fourth row have end portions facing each other between the third and fourth rows as connection end portions 2a, and the piezoelectric layer 3a just below the connection end portion 2a. It is connected to the conductive member in the through hole 13 formed in.

  Furthermore, a relay electrode (internal electrode) 6 for electrically connecting the common electrodes 4 of the piezoelectric layer 5 positioned above and below is formed on the edge of the upper surface of the piezoelectric layer 3a. The relay electrode 6 is connected to a conductive member in the through hole 8 formed in the piezoelectric layer 3a immediately below.

  The individual electrodes 2 are arranged in a matrix on the upper surface of the lowermost piezoelectric layer 3b as in the second, fourth, sixth, and eighth piezoelectric layers 3a. . However, as shown in FIG. 3, the lowermost piezoelectric layer 3b is different from the piezoelectric layer 3a in that the relay electrode 6 and the through holes 8 and 13 are not formed.

  Further, as shown in FIG. 4, on the upper surface of the third, fifth, and seventh piezoelectric layers 5a counted from the uppermost piezoelectric layer 7, as shown in FIG. Then, the relay electrode (internal electrode) 16 is arranged so as to face each connection end 2a of the piezoelectric layer 3a in the thickness direction of the multilayer piezoelectric element 1, that is, the thickness direction of the piezoelectric layers 3 and 5. Is formed. Each relay electrode 16 is connected to a conductive member in a through hole 13 formed in the piezoelectric layer 5 immediately below.

  Further, a common electrode 4 is formed on the upper surface of the piezoelectric layer 5a. The common electrode 4 surrounds the set of the relay electrodes 16 in the first row and the second row and the set of the relay electrodes 16 in the third row and the fourth row with a predetermined interval, and in the stacking direction. As seen from FIG. 1, the individual electrodes 2 overlap the portions excluding the connection end 2a. As a result, the entire portion of the piezoelectric layers 3 and 5 facing the portion excluding the connection end 2a of each individual electrode 2 can be effectively used as an active portion that contributes to vibration. The common electrode 4 is formed at a predetermined interval from the outer peripheral portion of the piezoelectric layer 5a, and is a through hole formed in the piezoelectric layer 5 so as to face the relay electrode 6 of the piezoelectric layer 3a in the stacking direction. It is connected to the conductive member in 8.

  Note that the relay electrode 16 and the common electrode 4 are also formed on the upper surface of the ninth piezoelectric layer 5b in the same manner as the third, fifth, and seventh piezoelectric layers 5a. However, as shown in FIG. 5, the ninth piezoelectric layer 5b is different from the piezoelectric layer 5a in that the through hole 8 is not formed.

  Further, as shown in FIG. 6, a terminal electrode 17 is formed on the upper surface of the uppermost piezoelectric layer 7 so as to face the connection end portion 2a of each individual electrode 2 of the piezoelectric layer 3a in the stacking direction. A terminal electrode 18 is formed so as to face the relay electrode 6 of the piezoelectric layer 3a in the stacking direction. Each terminal electrode 17 is connected to a conductive member in a through hole 13 formed in the piezoelectric layer 7 immediately below it, and the terminal electrode 18 is electrically connected in a through hole 8 formed in the piezoelectric layer 7 immediately below it. Connected to the member.

  These terminal electrodes 17 and 18 are soldered with lead wires such as an FPC (flexible printed circuit board) in order to be connected to a driving power source. Therefore, in order to make it easy to put the solder when soldering the lead wire, the terminal electrodes 17 and 18 have good solder wettability on the base electrode layer made of a conductive material mainly composed of Ag and Pd. Therefore, a surface electrode layer made of a conductive material mainly composed of Ag is formed.

  By stacking the piezoelectric layers 3, 5, and 7 with the electrode pattern formed as described above, the five individual electrodes 2 are interposed with the relay electrodes 16 in the stacking direction with respect to the uppermost terminal electrodes 17. As shown in FIG. 7, the aligned electrodes 2, 16, and 17 are electrically connected by the conductive member 14 in the through hole 13. On the other hand, with respect to the uppermost terminal electrode 18, four common electrodes 4 are aligned in the stacking direction with the relay electrode 6 interposed, and the aligned electrodes 4, 6, 18 are conductive members in the through hole 8. 14 to be electrically connected.

  The conductive member 14 in the through holes 8 and 13 is made of a conductive material mainly composed of Ag and Pd. Further, the through holes 13 and 13 adjacent in the stacking direction are formed in the piezoelectric layers 3, 5 and 7 so that the central axes thereof are shifted from each other, and electrical connection by the conductive member 14 in the through hole 13 is ensured. It has become. The same applies to the through holes 8 and 8 adjacent in the stacking direction.

  When a voltage is applied between the predetermined terminal electrode 17 and the terminal electrode 18 by such electrical connection in the multilayer piezoelectric element 1, the individual electrode 2 and the common electrode 4 aligned under the predetermined terminal electrode 17 A voltage is applied during the period. As a result, in the piezoelectric layers 3 and 5, as shown in FIG. 7, an electric field E is generated in a portion sandwiched between the individual electrode 2 and the common electrode 4, and the portion is displaced as the active portion A. Therefore, by selecting the terminal electrode 17 to which the voltage is applied, among the active parts A corresponding to the individual electrodes 2 arranged in a matrix, the active parts A aligned under the selected terminal electrode 17 are arranged in the stacking direction. Can be displaced. Such a laminated piezoelectric element 1 is applied to a drive source of various devices that require minute displacement, such as valve control of a micropump.

  Next, a method for manufacturing the multilayer piezoelectric element 1 described above will be described. First, an element binder paste is prepared by mixing an organic binder, an organic solvent, or the like with a piezoelectric ceramic material mainly composed of lead zirconate titanate, and each element layer 3, 5, 7 is formed using the element paste. A green sheet (ceramic body) is formed. Then, through holes 8 and 13 are formed by irradiating laser light onto predetermined positions of the green sheets to be the piezoelectric layers 3, 5 and 7.

  Subsequently, using a conductive paste prepared by mixing an organic binder, an organic solvent, or the like with a metal material having a ratio of Pd: 20 with respect to Ag: 80, filling through-holes 8 and 13 is screen-printed. The conductive member 14 is disposed in the through holes 8 and 13.

  Then, using a conductive paste prepared by mixing an organic binder, an organic solvent, or the like with a metal material having a ratio of Pd: 15 with respect to Ag: 85, the green sheets to be the piezoelectric layers 3 and 5 are formed. On the other hand, screen printing is performed to form the internal electrodes 2, 4, 6, and 16. Further, using the same conductive paste, screen printing is performed on the green sheet to be the uppermost piezoelectric layer 7 to form the base electrode layers of the terminal electrodes 17 and 18.

  In the case where the conductive member 14 and the internal electrodes 2, 4, 6, 16 (hereinafter referred to as “internal electrode 2 etc.”) are made of a conductive material mainly composed of Ag and Pd, the internal electrode 2 etc. are formed. When the ratio of Pd in the conductive material is “a ratio of Pd: X with respect to Ag: (100−X)”, the ratio of Pd in the conductive material forming the conductive member 14 is “Ag: [100−X. (Ratio of Pd: (X + 3-30) to (X + 3-30)] ”(more preferably,“ Ratio of Pd: (X + 5-15) to Ag: [100- (X + 5-15)] ”) Is preferable.

  Then, the green sheet in which the electrode pattern was formed is laminated | stacked in the order mentioned above, and it presses in the lamination direction, and produces laminated body green. The laminate green is cut to a predetermined size, and the cut laminate green is degreased under conditions of 400 ° C. and 10 hours, and then fired under conditions of 1000 ° C. and 2 hours.

  Subsequently, a surface electrode layer made of a conductive material containing Ag as a main component is baked on the base electrode layer formed on the sintered sheet to be the piezoelectric layer 7 to form the terminal electrodes 17 and 18. In addition, you may use Au, Cu, etc. as a material of a surface electrode layer. Moreover, you may employ | adopt sputtering, an electroless plating method, etc. as a formation method of a surface electrode layer. Finally, a polarization process is performed to complete the multilayer piezoelectric element 1.

  As described above, in the multilayer piezoelectric element 1 and the manufacturing method thereof, the conductive member 14 and the internal electrode 2 are made of a conductive material mainly composed of Ag and Pd, and the conductive member 14 forms the conductive member 14. The ratio of Pd in the material (the ratio of Pd: 20 with respect to Ag: 80) is higher than the ratio of Pd in the conductive material forming the internal electrode 2 and the like (the ratio of Pd: 15 with respect to Ag: 85). ing. Thereby, the melting point of the conductive material forming the conductive member 14 becomes higher than the melting point of the conductive material forming the internal electrode 2 and the like. This is because the melting point of Pd is higher than the melting point of Ag.

  Thus, since the melting point of the conductive material forming the conductive member 14 is higher than the melting point of the conductive material forming the internal electrode 2 or the like, the shrinkage rate during firing is higher than that of the internal electrode 2 or the like. 14 is smaller.

  As a result, the shrinkage of the conductive member 14 at the time of firing is relatively suppressed, so that the green sheet to be the piezoelectric layers 3, 5, 7 and the conductive member 14 in the through holes 8, 13 are fired. The difference in shrinkage is reduced. As a result, the conductive member 14 is shifted to one end side in the through holes 8 and 13 at the time of firing or separated in the middle, so that the electrical connection by the conductive member 14 in the through holes 8 and 13 is established. It is prevented from being cut off. Therefore, the reliability of electrical connection by the conductive member 14 in the through holes 8 and 13 at the time of manufacture can be improved.

  On the other hand, since the shrinkage of the internal electrode 2 and the like during the firing is relatively promoted, the internal electrode 2 and the like are thinned by the firing. Such thinning of the internal electrode 2 and the like contributes to miniaturization of the multilayer piezoelectric element 1. Furthermore, the thinning of the individual electrode 2 and the common electrode 4 is particularly effective in improving the flexibility of displacement of the active part A in the stacking direction.

  The melting point of the conductive material forming the internal electrode 2 and the like is lower than the melting point of the conductive material forming the conductive member 14, but is higher than the temperature (1000 ° C.) at which the multilayer green body is fired. This is because the conductive material forming the internal electrode 2 and the like also contains Pd in addition to Ag.

  Next, evaluation results of the multilayer piezoelectric element of the example and the multilayer piezoelectric element of the comparative example will be described. The multilayer piezoelectric element of the example is manufactured by the method for manufacturing the multilayer piezoelectric element 1 described above. On the other hand, in the multilayered piezoelectric element of the comparative example, the ratio of Pd in the conductive material forming the conductive member in the through hole is Pd ratio in the conductive material forming the internal electrode (Pd: 15), which is different from the multilayer piezoelectric element of the embodiment.

  Evaluation was performed as follows. That is, the capacitance of 300 layers (between each terminal electrode on the individual electrode side and the terminal electrode on the common electrode side) was measured with an LCR meter for each of the produced laminated piezoelectric elements. A laminated piezoelectric element that could not obtain a predetermined capacitance value even at one location was regarded as a defective element, assuming that the electrical connection by the conductive member in the through hole was broken.

  As a result, in the multilayer piezoelectric element of the example, the generation of 100 defective elements was 0, whereas in the multilayer piezoelectric element of the comparative example, 100 defective elements were produced. Generation was 17 elements. Thereby, the effect of the multilayer piezoelectric element 1 and the manufacturing method thereof that can improve the reliability of the electrical connection by the conductive member in the through hole at the time of manufacture was demonstrated.

  The present invention is not limited to the embodiment described above. For example, the material forming the conductive member 14 and the internal electrode 2 is not limited to a conductive material mainly composed of Ag and Pd, and the melting point of the material forming the conductive member 14 forms the internal electrode 2 or the like. Any material may be used as long as it satisfies the condition that the melting point of the material is higher.

  As an example, the conductive member 14 and the internal electrode 2 are made of a material containing at least one of Ag and Au and Pd, and the ratio of Pd in the material forming the conductive member 14 forms the internal electrode 2 and the like. It may be higher than the ratio of Pd in the material. Further, the conductive member 14 and the internal electrode 2 and the like are made of a material containing at least one of Ag and Au and Pt, and the ratio of Pt in the material forming the conductive member 14 is the same as that in the material forming the internal electrode 2 and the like. It may be higher than the ratio of Pt. Also in these cases, since the melting points of Pd and Pt are higher than those of Ag and Au, the melting point of the material forming the conductive member 14 can be made higher than the melting point of the material forming the internal electrode 2 and the like.

  The present invention is not limited to the multilayer piezoelectric element 1 and the manufacturing method thereof, but can be applied to various multilayer ceramic elements in which a plurality of ceramic layers are stacked and the manufacturing method thereof. Examples of such multilayer ceramic elements include multilayer capacitors, inductors, thermistors such as NTC and PTC, and varistors.

1 is an exploded perspective view of a multilayer piezoelectric element as an embodiment of a multilayer ceramic element according to the present invention. FIG. 2 is a plan view of second, fourth, sixth, and eighth piezoelectric layers of the multilayer piezoelectric element shown in FIG. 1. FIG. 2 is a plan view of the lowermost piezoelectric layer of the multilayer piezoelectric element shown in FIG. 1. FIG. 2 is a plan view of third, fifth, and seventh piezoelectric layers of the multilayer piezoelectric element shown in FIG. 1. FIG. 2 is a plan view of a ninth piezoelectric layer of the multilayer piezoelectric element shown in FIG. 1. FIG. 2 is a plan view of the uppermost piezoelectric layer of the multilayer piezoelectric element shown in FIG. 1. FIG. 2 is an enlarged partial cross-sectional view perpendicular to the longitudinal direction of the multilayer piezoelectric element shown in FIG. 1.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Multilayer piezoelectric element (multilayer ceramic element), 2 ... Individual electrode (internal electrode), 3, 5, 7 ... Piezoelectric layer (ceramic layer), 4 ... Common electrode (internal electrode), 6, 16 ... Relay Electrodes (internal electrodes), 8, 13 through holes, 14 conductive members.

Claims (4)

A multilayer ceramic element formed by laminating a plurality of ceramic layers,
A conductive member disposed in a through-hole formed in the ceramic layer;
An internal electrode formed between the adjacent ceramic layers,
The multilayer ceramic element, wherein a melting point of a material forming the conductive member is higher than a melting point of a material forming the internal electrode. The conductive member and the internal electrode are made of a material containing at least one of silver element and gold element and palladium element,
The multilayer ceramic element according to claim 1, wherein a ratio of palladium element in a material forming the conductive member is higher than a ratio of palladium element in a material forming the internal electrode. The conductive member and the internal electrode are made of a material containing at least one of a silver element and a gold element and a platinum element,
The multilayer ceramic element according to claim 1, wherein a ratio of platinum element in a material forming the conductive member is higher than a ratio of platinum element in a material forming the internal electrode. A method for producing a multilayer ceramic element in which a plurality of ceramic layers are laminated,
Arranging a conductive member in a through hole formed in the ceramic body to be the ceramic layer, and forming an internal electrode on the surface of the ceramic body;
Laminating a plurality of the ceramic bodies on which the conductive members are disposed and the internal electrodes are formed, to form a ceramic laminate;
Firing the ceramic laminate,
The melting point of the material forming the conductive member is higher than the melting point of the material forming the internal electrode,
The method for manufacturing a multilayer ceramic element, wherein a melting point of a material forming the internal electrode is higher than a temperature at which the ceramic multilayer body is fired.

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