JP2012124195A - Piezoelectric actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric actuator in which occurrence of migration for a first electrode from a lead-out part, to which a high potential may be imparted, is suppressed and to provide a manufacturing method therefor.SOLUTION: A plurality of individual electrodes 43 are arranged on the upper surface of a first piezoelectric layer 40 which is the uppermost layer of a piezoelectric actuator. A first common electrode 44 is arranged to face the individual electrodes 43 between the first piezoelectric layer 40 and a second piezoelectric layer 41 of an intermediate layer. The first common electrode 44 is led out to a first lead-out electrode 46 formed on the upper surface of a first piezoelectric layer 40 via a filler 65 in a through hole 37. The filler 65 in the through hole 37 is surrounded by the first lead-out electrode 46. The conductive material forming the individual electrodes 43 is Au, the conductive material forming the filler 65 is Ag, and Au is a material less likely to cause migration than Ag.

Description

  The present invention relates to a piezoelectric actuator.

  2. Description of the Related Art Conventionally, in various technical fields, piezoelectric actuators that drive an object using deformation (piezoelectric distortion) of a piezoelectric layer when an electric field acts on the piezoelectric layer have been used. For example, Patent Literature 1 discloses a piezoelectric actuator unit used in an ink jet head that ejects ink from a nozzle.

  The actuator unit of Patent Document 1 is a multi-layered arrangement of stacked piezoelectric elements, and two types of electrodes from each piezoelectric element are filled in the through holes on the upper surface of the insulating substrate. Pulled out with filler. One of the two types of electrodes is drawn to the upper surface of the substrate through a filler in a through hole formed in the substrate, and is an individual extraction electrode formed in the central region of the upper surface of the substrate. Connected to the end. The other electrode is pulled out to the upper surface of the substrate through a filler in a through hole formed in the substrate and connected to the end of the common electrode formed outside the central region on the upper surface of the substrate. ing. AgPd, AgPt, Au, or the like is used for each electrode such as the individual extraction electrode or the common electrode, and Ag is used for the filler in the through hole.

  A ground potential is always applied to the common electrode, and either a high driving potential or a ground potential is selectively applied to the individual extraction electrode. When the drive potential is applied to the individual extraction electrodes, an electric field is generated in the stacking direction of the piezoelectric layer portions sandwiched between the plurality of internal electrodes, and the plurality of piezoelectric layers extend in the stacking direction, and a ground potential is applied. And return to the original. Using the piezoelectric distortion of the piezoelectric element, ink in the liquid chamber unit connected to the piezoelectric element is ejected from the nozzle. In this way, different potentials are applied to the individual extraction electrode and the common electrode on the upper surface of the insulating substrate, thereby generating a potential difference.

JP 2001-71490 A (particularly FIG. 6)

  By the way, migration is known as a phenomenon in which a metal component moves on a non-metallic medium under the influence of an electric field. Generally, migration is performed when AgPd, AgPt, Au, Ag materials are compared. Most likely to occur. At this time, in Patent Document 1, the conductive material that is the filler in the through hole is a material that is more likely to migrate than the conductive material that forms each electrode such as the individual extraction electrode and the common electrode. Migration occurs from the filler in the through hole connected to the individual extraction electrode to which a high driving potential can be applied, to the common electrode having the ground potential via the surface of the insulating substrate.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a piezoelectric actuator that suppresses migration from a lead portion to which a high potential can be applied, and a method for manufacturing the same.

  The ink jet recording apparatus of the present invention includes a piezoelectric layer, a first electrode disposed on one surface of the piezoelectric layer, and a surface opposite to the first electrode on the other surface of the piezoelectric layer. A second electrode to which a higher potential than the electrode can be applied, and the piezoelectric layer is formed with a through hole, and by filling the through hole with a conductive filler, An extraction part is provided for drawing out the second electrode to one surface of the piezoelectric layer, and the filler forming the extraction part is a material different from the conductive material forming the first electrode, The conductive material forming the first electrode is a material that is less prone to migration than the filler, and surrounds an exposed portion of the one surface of the lead portion on the one surface of the piezoelectric layer, and The exposure Min and conduct, which is formed of the same conductive material as the first electrode, the migration blocking portion is provided.

  According to the piezoelectric actuator of the present invention, by enclosing the exposed portion of the lead-out portion with the migration prevention portion that is less likely to cause migration than the lead-out portion, a lower potential is applied from the lead-out portion to which a high potential can be applied. It is possible to suppress migration from occurring with respect to the first electrode.

  In addition, the lead portions of the first electrode and the second electrode are connected to a power source and electrically connected to a wiring member disposed so as to cover the one surface of the piezoelectric layer, thereby preventing the migration. It is preferable that a bump for electrically connecting the wiring member and the second electrode is formed on the portion.

  According to this, since the first electrode and the migration prevention part are formed of the same conductive material, the height of the first electrode and the migration prevention part is higher than that of the filler filled in the extraction part when the same formation method is used. It is almost the same. Since the bumps that are electrically connected to the second electrode are formed in the migration prevention portion having the same height as that of the first electrode, the bumps formed on the first electrode have the same height, and the wiring member is securely connected. Can be connected to.

  Furthermore, it is preferable that the conductive material forming the first electrode is a material in which migration is less likely to occur than the bump, and the bump is surrounded by the migration preventing portion.

  According to this, it is possible to suppress the migration from the bump to the first electrode by surrounding the bump that is electrically connected to the second electrode with the migration preventing portion that is less likely to cause the migration than the bump.

  A plurality of the first electrodes are provided, the second electrode is opposed to the plurality of first electrodes across the piezoelectric layer, and is a common electrode to which a predetermined positive potential is always applied, A plurality of the extraction portions are provided, the second electrode is drawn out to the one surface at a plurality of locations, and the exposed portions of the plurality of extraction portions are surrounded by one migration prevention portion. Is preferred.

  According to this, since the 2nd electrode is pulled out from a plurality of places by a plurality of extraction parts, the fall of the applied positive potential can be controlled. And by making several drawer | drawing-out parts conduct by one migration prevention part, it is not necessary to form the bump used for conduction | electrical_connection with a wiring member for every drawer | drawing-out part, for example.

  By surrounding the exposed part of the lead part with a migration preventing part that is less likely to cause migration than the lead part, migration from the lead part to which a high potential can be applied to the first electrode to which a lower potential is applied is performed. It can be suppressed from occurring.

It is a perspective view of the inkjet head of this embodiment. It is a top view of an inkjet head. It is the elements on larger scale of an inkjet head, (a) is a partial expanded plan view of FIG. 2, (b) is the sectional view on the AA line of (a), (c) is B of (a). FIG. FIG. 3 is a partially enlarged plan view of a left end portion of the piezoelectric actuator of FIG. 2, (a) is a plan view seen from the upper surface of a first piezoelectric layer (uppermost layer), and (b) is a second piezoelectric layer (intermediate layer). (C) is a plan view seen from the upper surface of the third piezoelectric layer (lowermost layer). It is CC sectional view taken on the line of Fig.4 (a). It is a figure explaining the manufacturing process of a piezoelectric actuator, (a) is a through-hole formation process, (b) is an internal electrode formation process, (c) is a baking process, (d) is extraction part formation. (E) is a surface electrode forming step. It is sectional drawing of the piezoelectric actuator explaining a conduction inspection process. 6 is a cross-sectional view of a piezoelectric actuator according to Modification 1. FIG. It is a figure explaining the manufacturing process of the piezoelectric actuator in the modification 1, (a) is an extraction | drawer part formation process, (b) is a filler inspection and defect determination process, (c) is an electrode formation process , (D) is a continuity inspection process. FIG. 10 is a cross-sectional view of a piezoelectric actuator according to Modification 2.

  Next, an embodiment of the present invention will be described. The present embodiment is an example in which the present invention is applied to a piezoelectric actuator of an ink jet head that records images, characters, and the like by ejecting ink onto recording paper.

  FIG. 1 is a perspective view of the ink jet head of the present embodiment. FIG. 2 is a plan view of the inkjet head. In the following description, the front side of the paper in FIGS. 1 and 2 is defined as the upper side, and the other side of the paper is defined as the lower side. The ink jet head 3 shown in FIGS. 1 and 2 opens on the lower surface with respect to a recording sheet (not shown) conveyed in a paper feeding direction orthogonal to the scanning direction while reciprocating in the scanning direction in the drawing. This is a so-called serial type ink jet head that ejects ink from a plurality of nozzles 15 (see FIG. 3).

  As shown in FIGS. 1 and 2, the inkjet head 3 includes a flow path unit 31 in which an ink flow path including a nozzle 15 and a pressure chamber 10 is formed, and a piezoelectric actuator 32 disposed on the upper surface of the flow path unit 31. And have. As shown in FIG. 1, a flexible wiring board 50 (FPC) that is connected to a power source (not shown) and has a driver IC 51 mounted thereon is bonded to the upper surface of the piezoelectric actuator 32.

  First, the flow path unit 31 will be described. As shown in FIGS. 1 and 2, four ink supply ports 9 for supplying four colors of ink (black, yellow, cyan, magenta) used in the inkjet head 3 are provided on the upper surface of the flow path unit 31. Is provided. An ink flow path connected to the ink supply port 9 is formed in the flow path unit 31.

  3 is a partially enlarged view of the inkjet head 3, (a) is a partially enlarged plan view of FIG. 2, (b) is a sectional view taken along line AA of (a), and (c) is ( It is BB sectional drawing of a). As shown in FIG. 3, the flow path unit 31 is composed of four plates 11 to 14 stacked on each other. The flow path unit 31 includes a manifold 16 connected to the ink supply port 9, and A plurality of pressure chambers 10 communicating with the manifold 16 and a plurality of nozzles 15 respectively communicating with the plurality of pressure chambers 10 are formed.

  The manifold 16 shown in FIG. 3B extends from the ink supply port 9 in the paper feeding direction (perpendicular to the paper surface in FIG. 3B). As shown in FIG. 3A, each of the plurality of pressure chambers 10 has a substantially elliptical planar shape whose longitudinal direction is the scanning direction. As shown in FIG. 2, the plurality of pressure chambers 10 are arranged along a manifold 16 extending in the paper feeding direction, thereby forming one pressure chamber row 8. Further, one pressure chamber group 7 is constituted by two pressure chamber rows 8 adjacent in the scanning direction, and the flow path unit 31 is provided with a total of five pressure chamber groups 7. Of the five pressure chamber groups 7, the two pressure chamber groups 7 located on the right side in FIG. 2 are black pressure chamber groups 7 to which black ink is supplied from the ink supply port 9. Also, the three pressure chamber groups 7 located on the left side in FIG. 2 are color pressure chamber groups 7 to which three color inks (yellow, magenta, cyan) are respectively supplied from three ink supply ports 9. is there.

  The plurality of nozzles 15 respectively communicating with the plurality of pressure chambers 10 are opened on the lower surface of the flow path unit 31 (the lower surface of the plate 14 positioned at the lowest layer). Although not shown, the plurality of nozzles 15 are also arranged in the same manner as the plurality of pressure chambers 10, and black ink corresponding to the two pressure chamber groups 7 is ejected on the right side in FIG. 2. 2 nozzle groups are arranged, and on the left side in FIG. 2, three nozzle groups for ejecting three color inks corresponding to the three pressure chamber groups 7 are arranged.

  As shown in FIG. 3 (b), a plurality of individual ink flow branches from the manifold 16 connected to the ink supply port 9 into the flow path unit 31 and reaches the nozzle 15 through the pressure chamber 10. A path 17 is formed.

  Next, the piezoelectric actuator 32 will be described. The piezoelectric actuator 32 includes three piezoelectric layers (first piezoelectric layer 40, second piezoelectric layer 41, and third piezoelectric layer 42), a plurality of individual electrodes 43, a first common electrode 44, and a second common electrode 45. Have. 4 is a partially enlarged plan view of the left end portion of the piezoelectric actuator 32 of FIG. 2, (a) is a plan view seen from the upper surface of the first piezoelectric layer 40 (uppermost layer), and (b) is the first view. It is the top view seen from the upper surface of the 2nd piezoelectric layer 41 (intermediate layer), (c) is the top view seen from the upper surface of the 3rd piezoelectric layer 42 (lowermost layer). FIG. 5 is a cross-sectional view taken along the line CC of FIG. 4A to 4C, hatched portions indicate regions where electrodes are formed and regions where lead portions are formed.

  The three piezoelectric layers 40 to 42 are each formed of a ferroelectric piezoelectric material mainly composed of lead zirconate titanate, which is a mixed crystal of lead titanate and lead zirconate, and are laminated to each other. In this state, the flow path unit 31 is disposed on the upper surface so as to cover the plurality of pressure chambers 10.

  The plurality of individual electrodes 43 are provided in regions on the upper surface of the uppermost first piezoelectric layer 40 facing the plurality of pressure chambers 10, respectively, and are arranged in a plane on the upper surface of the first piezoelectric layer 40. As shown in FIGS. 3A to 3C, each individual electrode 43 has substantially the same planar shape as the pressure chamber 10, and faces one pressure chamber 10 on the upper surface of the uppermost piezoelectric layer 40. It is provided for the entire area. Further, from each individual electrode 43, a contact portion 43a for connecting the individual electrode 43 to the FPC 50 (see FIG. 1) is drawn out to a region that does not face the pressure chamber 10. A bump 61 is disposed in the center on the contact portion 43a. The bump 61 has a diameter smaller than the diameter of the contact part 43a, is surrounded by electrodes forming the contact part 43a, and is connected to the FPC 50.

  The first common electrode 44 is disposed between the first piezoelectric layer 40 and the intermediate second piezoelectric layer 41. The first common electrode 44 includes a plurality of electrode portions 44a that respectively oppose the central portion of the plurality of pressure chambers 10 in the short direction (left-right direction in FIG. 3C). The electrode portion 44 a faces the individual electrode 43 with the first piezoelectric layer 40 interposed therebetween. Furthermore, as shown in FIG. 4B, the plurality of electrode portions 44a are electrically connected to each other.

  The second common electrode 45 is disposed between the second piezoelectric layer 41 and the lowermost third piezoelectric layer 42. The second common electrode 45 includes a plurality of electrode portions 45a that respectively oppose the lateral ends of the plurality of pressure chambers 10. The electrode portion 45a faces the individual electrode 43 with the first piezoelectric layer 40 and the second piezoelectric layer 41 interposed therebetween. Furthermore, as shown in FIG. 4C, the plurality of electrode portions 45a are electrically connected to each other.

  As shown in FIG. 4B, the upper surface of the upper left portion of the second piezoelectric layer 41 is electrically connected to the plurality of electrode portions 44a of the first common electrode 44, and has a large electrode area spread in a plane. A first conductive electrode portion 44b is formed. Further, as shown in FIG. 4A, a first extraction electrode 46 is formed on the upper surface of the first piezoelectric layer 40 so as to face the first conduction electrode portion 44b with the first piezoelectric layer 40 interposed therebetween. Yes. A plurality (three in this case) of bumps 62 are arranged on the first extraction electrode 46. The plurality of bumps 62 are surrounded by the first extraction electrode 46 and connected to the FPC 50.

  As shown in FIG. 5, a plurality (six in this case) of through holes 37 are formed in the portion where the first extraction electrode 46 of the first piezoelectric layer 40 is disposed. Are filled with a filler 65 made of a paste-like conductive material, and constitute a plurality of first extraction portions 68. The plurality of first lead portions 68 are arranged so as to be shifted in plan from the plurality of bumps 62, and the filler 65 in the through hole 37 is exposed from the upper surface of the first piezoelectric layer 40, and is one large first portion. One extraction electrode 46 is surrounded. As described above, the first conductive electrode portion 44 b of the first common electrode 44 and the first extraction electrode 46 are connected by the plurality of first extraction portions 68. Thus, by pulling out the first common electrode 44 from a plurality of locations by the plurality of first extraction portions 68, a voltage drop between the first extraction electrode 46 and the first common electrode 44 can be suppressed. .

  As shown in FIG. 4C, the upper surface of the lower left portion of the third piezoelectric layer 42 is electrically connected to the plurality of electrode portions 45a of the second common electrode 45, and has a large electrode area spread in a plane. A second conductive electrode portion 45b is formed. Further, as shown in FIG. 4A, on the upper surface of the first piezoelectric layer 40, a second extraction electrode facing the second conduction electrode portion 45b with the first piezoelectric layer 40 and the second piezoelectric layer 41 interposed therebetween. 47 is formed. A plurality (three in this case) of bumps 63 are arranged on the second extraction electrode 47. The plurality of bumps 63 are surrounded by the second extraction electrode 47 and connected to the FPC 50.

  As shown in FIGS. 2 and 4A, the width of the second extraction electrode 47 is narrower than the width of the first extraction electrode 46. Further, the contact part 43 a of the individual electrode 43 adjacent to the second extraction electrode 47 is formed larger than the contact part 43 a of the individual electrode 43 adjacent to the first extraction electrode 46.

  In addition, as shown in FIG. 5, a plurality (six in this case) of through holes 38 are formed in portions where the second extraction electrodes 47 of the first piezoelectric layer 40 and the second piezoelectric layer 41 are disposed. Each of the plurality of through holes 38 is filled with a filler 66 made of a paste-like conductive material, and constitutes a plurality of second lead portions 69. The plurality of second lead portions 69 are arranged so as to be shifted from the plurality of bumps 63 in a planar manner, and the filler 66 in the through hole 38 is exposed from the upper surface of the first piezoelectric layer 40 and is one large first. Two extraction electrodes 47 are surrounded. As described above, the second conductive electrode portion 45 b of the second common electrode 45 and the second extraction electrode 47 are connected by the plurality of second extraction portions 69.

  Also, the piezoelectric layer portion of the first piezoelectric layer 40 sandwiched between the individual electrode 43 and the electrode portion 44a of the first common electrode 44 (the portion facing the central portion of the pressure chamber 10 in FIG. 3C: first) The active portion 35) is previously polarized in the thickness direction. In addition, the piezoelectric layer portion of the first piezoelectric layer 40 and the second piezoelectric layer 41 sandwiched between the individual electrode 43 and the electrode portion 45a of the second common electrode 45 (the left and right end portions of the pressure chamber 10 in FIG. 3C). The portion opposite to the second active portion 36 is also polarized in the thickness direction in advance.

  As shown in FIG. 1, the FPC 50 is disposed on the upper surface of the piezoelectric actuator 32 (the upper surface of the first piezoelectric layer 40). The plurality of individual electrodes 43 positioned on the upper surface of the first piezoelectric layer 40 are connected to the FPC 50 via the bumps 61 on the contact portions 43a drawn out from each. The first common electrode 44 located between the first piezoelectric layer 40 and the second piezoelectric layer 41 is connected to the FPC 50 via the bumps 62 on the first extraction electrode 46 formed on the upper surface of the first piezoelectric layer 40. Connected. Further, the second common electrode 45 located between the second piezoelectric layer 41 and the third piezoelectric layer 42 is also connected to the FPC 50 via the bumps 63 on the second extraction electrode 47 formed on the upper surface of the first piezoelectric layer 40. Connected.

  As a result, the plurality of individual electrodes 43, the first common electrode 44, and the second common electrode 45 are each connected to the driver IC 51 mounted on the FPC 50. The potential of the individual electrode 43 is switched between a predetermined drive potential and a ground potential by the driver IC 51. The first common electrode 44 is always held at the driving potential, while the second common electrode 45 is always held at the ground potential.

  The operation of the piezoelectric actuator 32 described above during ink ejection will be described. In a standby state where ink is not ejected, the driver IC 51 applies a ground potential to each of the plurality of individual electrodes 43. Further, the driver IC 51 keeps the first common electrode 44 at a constant driving potential and the second common electrode 45 at a constant ground potential. Therefore, in the standby state, a voltage is applied between the individual electrode 43 and the first common electrode 44, and an electric field in the thickness direction acts on the first active portion 35 sandwiched between the electrodes 43 and 44. Since the direction of the electric field is parallel to the polarization direction of the first active portion 35, the first active portion 35 contracts in a plane direction perpendicular to the thickness direction. Thereby, the part facing the pressure chamber 10 of the piezoelectric layers 40 to 42 is in a state of being deformed so as to protrude toward the pressure chamber 10 side (the lower side in FIG. 3C). At this time, the volume of the pressure chamber 10 is smaller than that in the state where the piezoelectric layer 40 is not deformed.

  From this state, when the potential of a certain individual electrode 43 is switched from the ground potential to the predetermined drive potential by the driver IC 51, no voltage is applied between the individual electrode 43 and the first common electrode 44, and the driver IC 51 is deformed. The first active part 35 is restored. At the same time, since a voltage is applied between the individual electrode 43 and the second common electrode 45, an electric field in the thickness direction acts on the second active portion 36 sandwiched between the electrodes 43 and 45. Since the direction of the electric field is parallel to the polarization direction of the second active portion 36, the second active portion 36 contracts in a plane direction perpendicular to the thickness direction. As a result, the portion of the piezoelectric layers 40 to 42 facing the substantially central portion of the pressure chamber 10 is pulled upward, and the portion of the piezoelectric layers 40 to 42 facing the pressure chamber 10 is entirely opposite to the pressure chamber 10. By deforming so as to be convex (upper side in FIG. 3C), the volume of the pressure chamber 10 is increased.

  Thereafter, when the potential of the individual electrode 43 is returned to the ground potential again by the driver IC 51, no voltage is applied between the individual electrode 43 and the second common electrode 45, and the deformation of the second active portion 36 is restored. At the same time, the first active portion 35 contracts again in the surface direction, and the portion of the piezoelectric layers 40 to 42 facing the pressure chamber 10 is convex toward the pressure chamber 10 as a whole. At this time, since the volume of the pressure chamber 10 is greatly reduced, the pressure of the ink in the pressure chamber 10 is increased, and ink is ejected from the nozzle 15 communicating with the pressure chamber 10.

  Here, each electrode of the individual electrode 43, the first common electrode 44, the second common electrode 45, the first extraction electrode 46, and the second extraction electrode 47 is a conductive material having high adhesion to the piezoelectric layers 40 to 42. In this embodiment, Au is used. Moreover, since the fillers 65 and 66 in the through holes 37 and 38 require a large amount, a conductive material that is less expensive than Au is selected, and Ag is used in this embodiment. Furthermore, since the bumps 61 to 63 are also thick (height) and require a large amount, Ag is used in the present embodiment, like the fillers 65 and 66 in the through holes 37 and 38. In general, when Au and Ag are compared, it is said that Au is a material that is less prone to migration than Ag. The difference in the likelihood of migration is different from the order of the electrochemical column of ionization and is not clearly explained, but is in the order of Ag> Pb ≧ Cu> Sn> Au, and Fe, Pd, and Pt are generated. It is said that it is difficult. In addition, there has been reported an example in which the occurrence of migration can be delayed by alloying like Ag—Pd or Ag—Cu.

  By the way, when attention is paid to each conductive material arranged on the surface of the first piezoelectric layer 40, a driving potential higher than the ground potential is always applied to the first extraction electrode 46 and the first extraction portion 68. A drive potential higher than the ground potential can also be applied to the individual electrode 43. On the other hand, a ground potential is always applied to the second extraction electrode 47 and the second extraction portion 69. Then, on the surface of the first piezoelectric layer 40, migration may occur between the two conductive materials that are adjacent to each other and have a potential difference. Specifically, when a ground potential is applied to the individual electrode 43, a potential difference is generated between the first extraction electrode 46 and the first extraction portion 68 and the individual electrode 43. Further, when a driving potential is applied to the individual electrode 43, a potential difference is generated between the individual electrode 43, the second extraction electrode 47, and the second extraction portion 69.

  Therefore, in the present embodiment, the filler 65 made of Ag of the first lead portion 68 exposed from the surface of the first piezoelectric layer 40 to which a drive potential higher than the ground potential is always applied is first made of Au. Surrounded by the extraction electrode 46. As a result, a potential difference corresponding to the drive potential is generated between the filler 65 made of Ag, the ground potential, and the individual electrode 43 made of Au. Since the first extraction electrode 46 made of Au, which is less prone to migration than Ag, is disposed, it is possible to suppress migration from the filler 65 of the first extraction portion 68 to the individual electrode 43. .

  On the other hand, it is not necessary to surround the second extraction portion 69 of the second common electrode 45 to which the ground potential is always applied with the second extraction electrode 47 made of Au, but the second common electrode connected to the plurality of fillers 66. In 45, the second extraction electrode 47 allows the plurality of fillers 66 to be connected to each other so that variations in applied voltage do not occur.

  Further, in the above description, since the filler 65 in the through hole 37 is formed of Ag that easily causes migration, the filler 65 in the through hole 37 is replaced with the first extraction electrode 46 made of Au that is less likely to cause migration. , And the occurrence of migration was suppressed, but the same can be said for the bumps 61 to 63 formed of Ag.

  Specifically, a driving potential higher than the ground potential can be applied to the bump 61 connected to the contact portion 43a of the individual electrode 43. In addition, a driving potential higher than the ground potential is applied to the bump 62 connected to the first extraction electrode 46. On the other hand, a ground potential is applied to the bump 63 connected to the second extraction electrode 47. For this reason, when a driving potential is applied to the bump 61, a potential difference is generated between the bump 61 and the second extraction electrode 47. Further, when a ground potential is applied to the bump 61, a potential difference is generated between the bump 62 and the individual electrode 43.

  Therefore, in the present embodiment, the bump 61 made of Ag to which a drive potential higher than the ground potential is applied is surrounded by the individual electrode 43 made of Au, and the individual is close to the second extraction electrode 47 where migration is likely to occur. A contact portion 43 a is formed so as to surround the bump 61 of the electrode 43 larger than the other bumps 61. Similarly to the bump 61, the bump 62 made of Ag is surrounded by the first extraction electrode 46 made of Au. As a result, a driving potential is applied, and a driving potential is applied between the bump 61 made of Ag and a second extraction electrode 47 made of Au, to which a ground potential is applied, and migration is less likely to occur than Ag. The individual electrode 43 is arranged, and migration from the bump 61 to the second extraction electrode 47 can be suppressed. A drive potential is applied between the bump 62 made of Ag and a ground potential is applied to the individual electrode 43 made of Au and a first extraction electrode 46 made of Au is arranged. As a result, migration from the bump 62 to the individual electrode 43 can be suppressed.

  Further, since the various electrodes are formed of Au, which is the same conductive material, for example, when the same forming method such as screen printing is used, the fillers 65, 66 filled in the through holes 37, 38 and In comparison, the height tends to be almost the same. For example, when various electrodes are formed of Au and Ag, even if they are formed by the same screen printing, it is difficult to make them the same height due to differences in physical properties such as viscosity. The bumps 62 and 63 that are electrically connected to the common electrodes 44 and 45 are formed on the extraction electrodes 46 and 47 having the same height as the bump 61 formed on the individual electrode 43, so that the bump height is the same. The FPC 50 can be reliably connected.

  Here, when ink is ejected simultaneously from a large number of nozzles 15, the electrode portions 44 a of the common electrodes 44, 45 from the driver IC 51 are arranged so that a large current can easily flow through the first common electrode 44 and the second common electrode 45. The electrical resistance up to 45a is preferably as small as possible. Therefore, the extraction electrodes 46 and 47 are formed as solid electrodes having a large area. A plurality of lead portions 68 and 69 are formed. As described above, since a plurality of lead portions 68 and 69 are formed, a voltage drop at the lead portions 68 and 69 between the lead electrodes 46 and 47 and the common electrodes 44 and 45 can be suppressed. In addition, since the extraction electrodes 46 and 47 make the plurality of extraction portions 68 and 69 conductive, it is not necessary to form bumps for each of the extraction portions 68 and 69.

  Next, a method for manufacturing the piezoelectric actuator will be described. 6A and 6B are diagrams illustrating a manufacturing process of the piezoelectric actuator, in which FIG. 6A is a through hole forming process, FIG. 6B is an internal electrode forming process, FIG. 6C is a firing process, and FIG. Is a lead portion forming step, and (e) is a surface electrode forming step. FIG. 7 is a cross-sectional view of the piezoelectric actuator for explaining the conduction inspection step. Note that FIG. 6 shows a cross section of a portion D in FIG.

  First, after forming three green sheets to be the piezoelectric layers 40 to 42, as shown in FIG. 6A, through holes 37 and 38a are formed in the green sheet to be the first piezoelectric layer 40, and A through hole 38b is formed in the green sheet to be the second piezoelectric layer 41 (through hole forming step). Next, as shown in FIG. 6B, the first common electrode 44 is provided on one surface of the green sheet to be the first piezoelectric layer 40, and the second common is provided on one surface of the green sheet to be the second piezoelectric layer 41. The electrode 45 is formed by screen printing using Au as an electrode material (internal electrode forming step). At this time, electrodes are also formed on the inner peripheral surfaces in the vicinity of the openings of the through holes 37 and 38a.

  Then, as shown in FIG.6 (c), three green sheets are laminated | stacked and baked (baking process). At this time, the through hole 38a and the through hole 38b are overlapped to communicate with each other.

  Subsequently, as shown in FIG. 6D, the through holes 37 and 38 are filled with Ag as fillers 65 and 66 from the upper surface of the first piezoelectric layer 40 to form lead portions 68 and 69 (drawer). Part forming step). Thereafter, the conduction state of the fillers 65 and 66 in the through holes 37 and 38, that is, the electrical resistance of the fillers 65 and 66 and the common electrodes 44 and 45 is inspected (conduction inspection step). A method for inspecting the conduction state between the filler 65 in the through hole 37 and the first common electrode 44 will be specifically described, and a method for inspecting the conduction state between the filler 66 in the through hole 38 and the second common electrode 45 will be described. Since it is the same, the description is abbreviate | omitted.

  As shown in FIG. 7, using a tester 80 that measures the electrical resistance between the two probes 81a and 81b, one probe 81a of the tester 80 is filled in a certain through hole 37 (here, the through hole 37a). The exposed portion of the material 65 is brought into contact, and the other probe 81b is brought into contact with an exposed portion of the filler 65 in a through hole (here, the through hole 37b) different from the through hole 37. At this time, when it is determined that the electrical resistance between the two probes 81a and 81b is very small and conductive, the filler 65 connected to either probe 81a or 81b of the tester 80 is also the first common electrode 44. It is possible to detect that it is in a conductive state. Thereafter, one probe 81a is kept in contact with the exposed portion of the filler 65 in the same through hole 37a, and the other probe 81b is sequentially brought into contact with the exposed portion of the filler 65 in the remaining through hole 37. When it is determined that the electrical resistance between the two probes 81a and 81b is very large and insulated, the filler 65 in the through hole 37 in contact with the other probe 81b and the first common electrode 44 are insulated. It can be detected.

  On the other hand, when one probe 81a of the tester 80 is brought into contact with the exposed portion of the filler 65 in the through hole 37a and the other probe 81b is brought into contact with the exposed portion of the filler 65 in the through hole 37b, When it is determined that the electrical resistance between the probes 81a and 81b is very large and insulated, one probe 81a remains in contact with the exposed portion of the filler 65 in the same through-hole 37a while the other When the probe 81b is sequentially brought into contact with the exposed portion of the filler 65 in the remaining through-hole 37, when it is determined that the electrical resistance between the two probes 81a and 81b is very small and conductive, the other It is possible to detect that the filler 65 in the through hole 37 in contact with the first probe 81b is in conduction with the first common electrode 44.

  In the continuity inspection process as described above, among the plurality of through holes 37, the filler 65 in two or more through holes 37 is insulated from the first common electrode 44, or the plurality of through holes 38 Among these, when it is detected that the filler 66 in the two or more through holes 38 is insulated from the second common electrode 45, the piezoelectric actuator 32 in the middle of manufacture is determined to be defective (defect determination step).

  As shown in FIG. 6E, the individual electrodes 43 (not shown in FIG. 6E) and a plurality of lead portions are formed on the upper surface of the first piezoelectric layer 40 that has not been determined to be defective. Extraction electrodes 46 and 47 (connection portions) for connecting 68 and 69 to each other are formed by screen printing using Au as an electrode material (surface electrode formation step), and then the individual electrodes 43 and the extraction electrodes 46 and 47 are connected. Bumps 61 to 63 are formed on the upper surface using Ag as a material, and the piezoelectric actuator 32 is completed.

  According to the manufacturing method of the piezoelectric actuator 32 of the present embodiment, the inside of the piezoelectric layers 40 to 42 is sandwiched by inspecting the conductive state between the fillers 65 and 66 in the through holes 37 and 38 and the common electrodes 44 and 45. It is possible to inspect whether the common electrodes 44 and 45 are drawn out from the upper surface of the first piezoelectric layer 40.

  Also, if the continuity inspection process is performed after the extraction electrodes 46 and 47 are formed, the fillers 65 and 66 in the plurality of through holes 37 and 38 are electrically connected via the extraction electrodes 46 and 47. It becomes difficult to inspect the conduction state with the common electrodes 44 and 45 for each of the fillers 65 and 66 in the through holes 37 and 38. Therefore, by conducting a continuity inspection process before forming the extraction electrodes 46 and 47, it is possible to inspect the continuity state with the common electrodes 44 and 45 for each of the fillers 65 and 66 in the through holes 37 and 38. .

  Further, since the lead portions 68 and 69 are drawn out from the common electrodes 44 and 45 at a plurality of positions, the fillers 65 and 66 filled in some through holes 37 and 38 and the common electrodes 44 and 45 are insulated. Even if it is, the common electrodes 44 and 45 are drawn out to the upper surface of the first piezoelectric layer 40. Then, the conduction state with the common electrodes 44 and 45 is inspected for each of the fillers 65 and 66 in the through holes 37 and 38, and when the number of defects is 2 or more, the respective common electrodes are affected by the influence of the voltage drop. Since the potentials 44 and 45 vary, the piezoelectric actuator 32 is determined to be defective. In this way, by detecting the insulation number of the fillers 65 and 66 in the through holes 37 and 38 and determining the failure of the piezoelectric actuator 32 from the insulation number, the failure of the piezoelectric actuator 32 can be easily determined. Can do.

  The internal electrode forming step corresponds to the “second electrode forming step” in the present invention. Further, the surface electrode forming step corresponds to a step in which the “first electrode forming step” and the “connecting portion forming step” in the present invention are performed simultaneously.

  Next, modified examples in which various changes are made to the present embodiment will be described. However, those having the same configuration as that of the above-described embodiment are denoted by the same reference numerals and description thereof is omitted as appropriate.

  In the present embodiment, the width of the second extraction electrode 47 is narrower than the width of the first extraction electrode 46, but the widths of both extraction electrodes 46 and 47 may be the same. Further, the contact portion 43a of the individual electrode 43 adjacent to the second extraction electrode 47 is formed larger than the contact portion 43a of the individual electrode 43 adjacent to the first extraction electrode 46, but is not limited thereto. The contact portions 43a of all the individual electrodes 43 may be the same size.

  In the present embodiment, the bump 62 and the through hole 37 to which the driving potential is applied are surrounded by one large first extraction electrode 46, but may be independently surrounded by electrodes.

  In addition, the present embodiment is not limited to Ag or Au, and any conductive material can be used as long as the filler filled in the bumps and through holes is a conductive material that is more likely to migrate than the electrodes surrounding them. This effect can be achieved. Further, the filler filled in the bump and the through hole may not be the same conductive material.

  In this embodiment, the piezoelectric actuator 32 is provided with the first common electrode 44, the second common electrode 45, and the two common electrodes. For example, as shown in FIG. Thus, the present invention is also applied to a simple unimorph type piezoelectric actuator 106 in which both surfaces are sandwiched between an individual electrode 104 to which a drive potential and a ground potential are selectively applied and a common electrode 105 that is always maintained at the ground potential. Can be applied (Modification 1). At this time, the common electrode 105 is drawn out to the surface of the piezoelectric layer 103 on which the individual electrode 104 is formed via the filler 108 in the through hole 107.

  In this method of manufacturing the piezoelectric actuator, as shown in FIG. 9A, after the green sheet in which the through hole 107 is formed is fired, the through hole 107 is filled with a filler 108 to form a lead-out portion ( Drawer part formation process). After that, as shown in FIG. 9B, the probe 181a is brought into contact with the filler 108 exposed from the upper surface of the piezoelectric layer 103, and the probe 181b is brought into contact with the filler 108 exposed from the lower surface of the piezoelectric layer 103 to fill. The filling state of the material 108 is inspected (filler inspection step). When it is determined that the filling material 108 is not sufficiently filled in the through hole 107 and the electrical resistance between the probes 181a and 181b is not large, the piezoelectric actuator 106 is determined to be defective (defect determination step).

  Thereafter, as shown in FIG. 9C, the individual electrode 104 is formed on the upper surface of the piezoelectric layer 103 that has not been determined to be defective, and the common electrode 105 is connected to the lower surface of the piezoelectric layer 103 so as to be electrically connected to the filler 108. Is formed (electrode formation step). Thereafter, as shown in FIG. 9D, the continuity between the filler 108 exposed from the upper surface of the piezoelectric layer 103 and the common electrode 105 formed on the lower surface of the piezoelectric layer 103 is inspected (continuity inspection step). According to this manufacturing method, since the electrode is formed on the surface of the piezoelectric layer 103 after the defect determining step, the electrode material is not wasted without forming the electrode on the piezoelectric layer 103 determined to be defective.

  Further, for example, as shown in FIG. 10, a plurality of stacked piezoelectric layers 110 are provided, and an individual electrode 111 to which a driving potential and a ground potential are selectively applied between the plurality of piezoelectric layers 110. The present invention can also be applied to a so-called stacked actuator in which the common electrodes 112 that are always maintained at the ground potential are alternately arranged (Modification 2). At this time, the individual electrode 111 and the common electrode 112 are drawn on the upper surface of the uppermost piezoelectric layer 110. In this case, a plurality of lead portions of the common electrode 112 may be provided, and a connection portion that connects them to each other may be provided.

  Further, in the present embodiment, the plurality of lead portions 68 and 69 are drawn from the common electrodes 44 and 45 to the upper surface of the first piezoelectric layer 40, but may be drawn by one lead portion. In this case, taking the simple unimorph type piezoelectric actuator 106 described above as an example, a tester 80 as shown in FIG. 8 is used to connect one probe 81 a of the tester 80 to one of the fillers 108 in the through hole 107. The surface is brought into contact, and the other probe 81 b is brought into contact with the individual electrode 105 to inspect the conduction state between the filler 108 and the individual electrode 105. When the filling material 108 is insufficiently filled in the piezoelectric layer 103, the electrical resistance is very large, and it can be detected that the insulation is performed.

  Moreover, in this embodiment, although the internal electrode formation process and the surface electrode formation process were performed by the separate process, you may perform by the same process. That is, the individual electrode 43 and the extraction electrodes 46 and 47 may be formed in the same process as the formation of the common electrodes 44 and 45. Moreover, the continuity inspection process may be after the connection part formation process.

  In the present embodiment, the first common electrode 44 is formed on the lower surface of the first piezoelectric layer 40 in the internal electrode forming step. However, the second piezoelectric layer 41 is superimposed on the lower surface of the first piezoelectric layer 40. A first common electrode 44 may be formed on the upper surface of the first electrode. Further, the second common electrode 45 is formed on the lower surface of the second piezoelectric layer 41, but the second common electrode 45 is formed on the upper surface of the third piezoelectric layer 42 that is superimposed on the lower surface of the second piezoelectric layer 41. May be.

  As described above, in the embodiment described above and the modifications thereof, the present invention is applied to the piezoelectric actuator for an ink jet head that ejects ink onto recording paper and records an image and the like, and the manufacturing method thereof. Is not limited to such a piezoelectric actuator for an ink jet head, and can be applied to a piezoelectric actuator used for various applications and a method of manufacturing the same.

32 Piezoelectric actuators 37 and 38 Through holes 40 to 42 Piezoelectric layer 43 Individual electrode 44 First common electrode 45 Second common electrode 46 First extraction electrode 47 Second extraction electrode 65 and 66 Filler 68 First extraction portion 69 Second extraction Part

Claims (4)

A piezoelectric layer;
A first electrode disposed on one surface of the piezoelectric layer;
A second electrode disposed on the other surface of the piezoelectric layer so as to face the first electrode and capable of being applied with a higher potential than the first electrode,
A through hole is formed in the piezoelectric layer, and a lead-out portion is provided to draw the second electrode to one surface of the piezoelectric layer by filling the through hole with a conductive filler. And
The filler forming the lead portion is a material different from the conductive material forming the first electrode,
The conductive material forming the first electrode is a material that is less prone to migration than the filler,
In the one surface of the piezoelectric layer, a migration preventing portion that surrounds an exposed portion of the one surface of the lead portion and is electrically connected to the exposed portion and is formed of the same conductive material as the first electrode. A piezoelectric actuator is provided. The lead portions of the first electrode and the second electrode are connected to a power source and electrically connected to a wiring member disposed so as to cover the one surface of the piezoelectric layer,
2. The piezoelectric actuator according to claim 1, wherein a bump for electrically connecting the wiring member and the second electrode is formed in the migration preventing portion. The conductive material forming the first electrode is a material that is less prone to migration than the bump,
The piezoelectric actuator according to claim 2, wherein the bump is surrounded by the migration prevention unit. A plurality of the first electrodes are provided,
The second electrode is a common electrode that faces the plurality of first electrodes across the piezoelectric layer and is always given a predetermined positive potential,
A plurality of the lead portions are provided, and the second electrode is led out to the one surface at a plurality of locations;
The piezoelectric actuator according to any one of claims 1 to 3, wherein the exposed portions of a plurality of the extraction portions are surrounded by one migration prevention portion.

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