JP5146381B2 - Liquid ejection device - Google Patents

Description

  The present invention relates to a liquid ejection apparatus that includes an actuator that operates to eject liquid and a wiring board that supplies a drive signal to the actuator.

  An ink jet head which is an example of a liquid discharge apparatus includes a piezoelectric actuator formed by stacking piezoelectric sheets. In such an actuator, a plurality of electrodes for performing an operation of ejecting ink are provided, and electrode terminals electrically connected to the respective electrodes are provided on the surface of the actuator. In order to apply a predetermined potential to these electrode terminals, a wiring board is provided on the surface of the actuator. The wiring board has an insulating resin material on which a wiring group is formed, and the wiring terminals corresponding to the electrode terminals are exposed on the surface of the resin material, and conductive bumps installed on the electrode terminals The terminals are electrically connected to each other by contacting the wiring terminals. The wiring board extends outward from the actuator and is connected to a substrate outside the inkjet head.

  As a method for joining a wiring board and an actuator, for example, a so-called cover coat method shown in Patent Document 1 is known. In the cover coat method, a thermosetting adhesive is applied in an uncured state to the surface of the resin material from which the wiring terminals are exposed. When this wiring board is stacked on the actuator and thermocompression bonded with a bar heater or the like, the bump on the electrode terminal comes into contact with the wiring terminal so as to break through the adhesive. As a result, the adhesive adheres to the outer surface of the bump and surrounds the bump. Then, the adhesive is cured by heating the wiring board from the outer surface side. Thus, the wiring board is bonded to the bump via the adhesive, and further bonded to the actuator via the bump.

JP 2005-305847 A

  When bonding the wiring board to the actuator by thermocompression bonding, the resin material of the wiring board has a higher coefficient of thermal expansion than the actuator, so the resin material will thermally expand during heating and heat shrink in the opposite direction during subsequent cooling. To do. Due to this thermal stress, a tensile load acting in all directions in the plane direction acts on the joint portion composed of the bump and the adhesive, and the bump may be peeled off from the adhesive.

  In the case of a single joint, the tensile load acting on the joint is diverged to the surroundings, and the influence of the load on the joint is small. However, when there are a plurality of joints as in Patent Document 1, the resin material of the wiring board expands and contracts substantially radially from the center of the joint area with the actuator, and a large tensile load is generated particularly at the outer periphery of the joint area. May work. If there are other joints around a certain joint, it is considered that the tensile loads at each joint will cancel each other out. Therefore, it is considered that the tensile load acting on the joint is uneven and the bumps are easily peeled off from the adhesive. In particular, according to the joining method as disclosed in Patent Document 1, electrical connection between the electrode terminal and the wiring terminal is ensured by direct contact between the bump, the wiring terminal, and the electrode terminal. It becomes easy to generate a trouble.

  Further, in order to assemble the ink jet head with other components, or to connect the wiring board to the above-described external substrate, the portion pulled out from the piezoelectric actuator may be picked up. At this time, a tensile load acts on the bumps in a concentrated manner, and the adhesive may peel off from the outer surface of the bumps.

  In view of the above problems, the present invention aims to increase the bonding strength between the bump, the wiring board, and the actuator, thereby ensuring electrical connection between the wiring board side terminal and the actuator side terminal. Yes.

The present invention has been made in view of such circumstances, and a liquid ejection apparatus according to the present invention is for supplying an actuator that operates to eject liquid and a drive signal that drives the actuator to the actuator. It is interposed between a wiring board, a first terminal provided on the surface of the wiring board, and a second terminal provided on the surface of the actuator, and electrically connects the first and second terminals. A liquid ejecting apparatus including a first bump for bonding, and the wiring board overlaid on the actuator being joined to the actuator via the first bump, and disposed around the first bump. A second bump is further provided, and the second bump is disposed so as to partially overlap at least one of the first terminal and the second terminal in plan view, and the terminal is provided. It is provided with from the surface to bite into the outer edge of said terminals, to the surface of the actuator, terminal arrangement area for arranging a plurality of the second terminal is defined, the second bump, the terminal arrangement region The wiring board has a higher coefficient of thermal expansion than the actuator, and the wiring board is a step of heat-curing the first and second bumps. And the second bump corresponding to the second terminal disposed at the corner of the outer edge is based on the first bump corresponding to the second bump. The wiring board is arranged along the direction in which the circuit board is thermally deformed .

  By adopting such a configuration, even if the wiring board is pulled or thermal stress is generated at the time of joining, the second bump is provided to be engaged with the outer edge of the terminal. It is possible to receive an acting tensile load and protect the originally installed first bump. The second bump receiving the tensile load is engaged with the outer edge of at least one of the first terminal and the second terminal, and the bonding strength to these terminals is increased. For this reason, peeling is less likely to occur in the second bump. For this reason, it is possible to secure the state in which the first and second bumps are in contact with the first terminal and the second terminal, and to ensure electrical connection between the first terminal and the second terminal.

  According to the present invention, the bonding strength between the bump, the wiring board, and the actuator can be increased, and conduction between the first terminal and the second terminal can be ensured.

It is a disassembled perspective view of the inkjet head which concerns on embodiment of this invention. FIG. 2 is a partial cross-sectional view of the ink jet head shown by cutting along the line α-α in FIG. 1 in a state where the ink jet head, the wiring board, and the reinforcing plate of FIG. 1 are assembled. It is a bottom view of the wiring board shown in FIG. FIG. 2 is a partial cross-sectional view of the piezoelectric actuator and the wiring board shown cut along the line α-α in FIG. 1 in a state where the piezoelectric actuator and the wiring board shown in FIG. 1 are assembled. FIG. 2 is a schematic plan view of an ink jet head shown in an assembled state of the ink jet head shown in FIG. 1. 6A and 6B are views showing bumps arranged at corners of the terminal arrangement region shown in FIG. 5, where FIG. 6A is a partial plan view of the inkjet head showing the periphery of the bumps, and FIG. It is a fragmentary sectional view of the ink jet head shown cut along a line. It is a figure which shows the joining procedure of the wiring board using the bump and reinforcement bump shown in FIG. 6, and an inkjet head, (a) installs a bump and a reinforcement bump in an electrode terminal, and apply | coats an unhardened adhesive agent on a wiring board (B) shows a state where the wiring board is placed on the piezoelectric actuator and the reinforcing bumps are in contact with the wiring terminals. FIG. 7 is a partial plan view of an inkjet head showing an example of changing the arrangement of reinforcing bumps shown in FIG. 6.

  Embodiments of the present invention will be described below with reference to these drawings. FIG. 1 illustrates an ink jet head 1 mounted on an ink jet printer as an embodiment of a liquid ejection apparatus according to the present invention. Here, the direction in which ink is ejected from the inkjet head 1 is defined as the downward direction, the transport direction of the medium to be ejected is defined as the X direction, and the direction orthogonal to the transport direction is defined as the Y direction. The ink jet head 1 is formed by superposing a piezoelectric actuator 3 on a flow path unit 2 from above. The piezoelectric actuator 3 has an outer shape smaller than that of the flow path unit 2 and is arranged on the inner side of the outline of the flow path unit 2 in a plan view, and the upper surface of the flow path unit 2 is not covered with the piezoelectric actuator 3. Is formed. When the inkjet head 1 is mounted on an inkjet printer, the frame-like portion on the upper surface of the flow path unit 2 is bonded to the lower surface of the reinforcing plate 4 in order to ensure the rigidity of the inkjet head 1. At this time, the piezoelectric actuator 3 on the flow path unit 2 is disposed in the opening 5 formed in the central portion of the reinforcing plate 4.

  A flexible sheet-like wiring board 6 is overlaid on the piezoelectric actuator 3 from above. A plurality of electrode terminals 7 are formed on the upper surface of the piezoelectric actuator 3, and wiring terminals 36 (see FIG. 3) for applying a predetermined potential to the electrode terminals 7 are formed on the lower surface of the wiring substrate 6. The wiring board 6 is mechanically joined to the piezoelectric actuator 3 so that the wiring terminal 36 (see FIG. 3) is electrically connected to the electrode terminal 7. The wiring board 6 has a joint portion 8 that overlaps the piezoelectric actuator 3 and a pair of extension portions 9 and 10 extending from the joint portion 8. The extension portions 9 and 10 drive the piezoelectric actuator 3. Driving ICs 11 and 12 are mounted. The joint portion 8 is disposed in the opening 5 together with the piezoelectric actuator 3, and the extending portions 9 and 10 are pulled out from below the opening 5. The inkjet head 1 to which the reinforcing plate 4 is bonded is attached to a box-shaped head holder (not shown). The extending portions 9 and 10 of the wiring substrate 6 are bent with respect to the joint portion 8 (see FIG. 2) and are accommodated in a compact manner in the head holder.

  Four ink introduction ports 13 for introducing ink from the outside are opened in the frame-shaped portion on the upper surface of the flow path unit 2, and four through holes 14 communicating with the ink introduction ports 13 in the vertical direction are also opened in the reinforcing plate 4. doing. Reference numeral 15 denotes a filter. Further, a large number of pressure chamber holes 16 are opened on the upper surface of the flow path unit 2, and these pressure chamber holes 16 are closed on the lower surface of the piezoelectric actuator 3 as will be described later.

  FIG. 2 shows a partial cross-sectional view of the inkjet head 1. As shown in FIG. 2, the flow path unit 2 is a laminated body of a plurality of plates, and the ink introduction port 13 (see FIG. 1) and the pressure chamber hole 16 described above are opened on the upper surface, and ink is placed on the lower surface. A plurality of nozzles 17 for discharging are opened. An ink flow path 18 that guides ink from the ink inlet 13 (see FIG. 1) to each nozzle 17 is formed in the flow path unit 2 by the openings and grooves of the plates communicating with each other. The ink channel 18 includes a common ink chamber 19, a plurality of connection channels 20 branched from the common ink chamber 19, a plurality of pressure chambers 21 communicating with each connection channel 20, and a plurality of outflows communicating with each pressure chamber 21. The nozzles 17 are individually communicated with the lower ends of the respective outflow paths 22. The pressure chamber 21 is configured by closing the pressure chamber hole 16 on the lower surface of the piezoelectric actuator 3, and a plurality of rows aligned in the X direction are arranged in the Y direction. Therefore, the common ink chamber 19 also extends in the X direction, and a plurality of rows in which the nozzles 17, the outflow paths 22, and the connection flow paths 20 are also aligned in the X direction are arranged in the Y direction.

  The piezoelectric actuator 3 is formed by laminating a resin-made top sheet 29 on an upper surface of a laminate formed by laminating a plurality of piezoelectric sheets 23 to 28. A common electrode 30 common to the pressure chambers 21 is provided on the upper surfaces of the odd-numbered piezoelectric sheets 23, 25, 27 counted from the bottom, and the upper surfaces of the even-numbered piezoelectric sheets 24, 26 counted from the bottom. Are provided with individual electrodes 31 for each pressure chamber 21. Each individual electrode 31 is arranged so as to overlap with the corresponding pressure chamber 21 in plan view. Thereby, the common electrodes 30 and the individual electrodes 31 are alternately arranged above the pressure chambers 21.

  Referring to FIG. 1, the electrode terminal 7 formed on the upper surface of the piezoelectric actuator 3 (that is, the upper surface of the top sheet 29) is printed with an Ag—Pd material and is electrically connected to the common electrode 30. Common electrode terminal 32 and a plurality of individual electrode terminals 33 electrically connected to each individual electrode 31 are included. The common electrode terminal 32 extends in the Y direction at the edge of the top sheet 29 in the X direction, and the individual electrode terminal 33 is arranged so as to overlap the pressure chamber 21 (see FIG. 2) in plan view. A ground potential is supplied as a constant potential to the common electrode terminal 32 via the wiring substrate 6. The individual electrode terminal 33 is supplied with a ground potential during standby when ink ejection is not required, while wiring is performed when ink in the corresponding pressure chamber 21 (see FIG. 2) is ejected from the nozzle 17 (see FIG. 2). A drive signal is supplied from one of the drive ICs 11 and 12 (see FIG. 1) via the substrate 6. The drive signal is higher than the ground potential.

  Returning to FIG. 2, when a high potential based on the drive signal is applied to the individual electrode 31, the region sandwiched between the individual electrode 31 and the common electrode 30 is deformed, and the pressure chamber corresponding to the individual electrode 31 is deformed. The volume of 21 varies. A discharge pressure is applied to the ink in the pressure chamber 21 according to the volume fluctuation, and the ink is discharged downward from the nozzle 17 through the outflow path 22.

  As shown in FIG. 3, the wiring substrate 6 has a constant potential wiring (not shown) for supplying a ground potential as a constant potential to the common electrode 30 (see FIG. 2), and each individual electrode 31 (see FIG. 2). A plurality of individual wirings 35 for supplying drive signals to each other are provided, and one end of each individual wiring 35 is connected to one of the driving ICs 11 and 12. A wiring terminal 36 formed on the lower surface of the joint portion 8 of the wiring board 6 includes a constant potential wiring terminal 37 connected to the constant potential wiring 34 and an individual wiring terminal 38 connected to the other end of each individual wiring 35. And are included. The constant potential wiring terminal 37 extends in the Y direction at the X-direction edge of the joint, and the individual wiring terminals 38 are arranged in the same manner as the pressure chamber holes 16 (see FIG. 1). In addition, a plurality of input wirings (not shown) connected to the driving ICs 11 and 12 are disposed on the wiring substrate 6 on the side opposite to the individual wirings 35.

  As shown in FIG. 4, the wiring substrate 6 includes a strip-shaped substrate portion 39 on which wiring is formed on the surface, and a resist portion 40 that covers the surface of the substrate portion 39 on which the wiring is formed. The substrate portion 39 is made of polyimide and has insulating properties and flexibility. The resist portion 40 is partially cut out at the joint portion 8, and the wiring terminal 7 is exposed to the outside at the cut-out portion.

  The wiring board 6 is bonded to the piezoelectric actuator 3 using, for example, a so-called cover coat method. In other words, conductive bumps 41 are provided on the electrode terminals 7 of the piezoelectric actuator 3, and an uncured thermosetting adhesive 42 on the surface of the bonding portion 8 of the wiring board 6 where the wiring terminals 36 are exposed. The joint 8 is overlapped with the piezoelectric actuator 3 from above so that each wiring terminal 36 overlaps the corresponding electrode terminal 7 in plan view, and is thermocompression bonded with a bar heater (not shown) or the like. Then, the tip of the bump 41 comes into contact with the wiring terminal 36 so that the bump 41 breaks through the uncured adhesive 42, and the adhesive 42 adheres to the outer surface of the bump 41. Thereafter, the adhesive 42 is cured by heat applied to the joint 8. The wiring substrate 6 is bonded to the bump 41 and the piezoelectric actuator 3 via an adhesive 42 that is attached across the surface of the bonding portion 8 and the outer surface of the bump 41. The bump 41 is formed of a resin-made conductive adhesive material including a conductive material such as silver or solder, and the wiring terminal 36 and the electric terminal 7 are mechanically bonded via the adhesive 42 and are electrically connected. Conductive. The bump 41 is formed by printing or an inkjet method. In addition, although initially formed on the electrode terminal 7 has fluidity, its shape is maintained in a state having appropriate flexibility by thermosetting it to an appropriate hardness.

  As shown in FIG. 5, a terminal arrangement area A in which the electrode terminals 7 are arranged is defined on the upper surface of the piezoelectric actuator 3, and the bumps 41 are arranged on the contour line of the area A. The outline of the region A has a substantially rectangular shape along the outline of the piezoelectric actuator 3 in plan view.

  After the joining portion 8 is joined to the piezoelectric actuator 3, as described above, the extending portion 8 is bent with respect to the joining portion 8 (see arrow C in FIG. 5). At this time, since the extending portions 9 and 10 are drawn out in the X direction with respect to the joint portion 8, the bump 41 ′ on the line B extending in the Y direction out of the outline of the terminal arrangement region A extends. The load accompanying bending of the parts 9 and 10 acts. Therefore, in the portion where the bump 41 ′ is provided, the wiring board 6 is relatively easily peeled off from the piezoelectric actuator 3 as compared with other bumps not on the outline of the terminal arrangement area A.

  Further, the difference between the thermal expansion coefficient of the polyimide substrate portion 39 and the thermal expansion coefficient of the top sheet 29 which is a piezoelectric layer, the amount of heat transmitted from the bar heater to the wiring substrate 6 and the amount of heat transmitted to the top sheet 29 Based on the difference or the like, when the adhesive 42 (see FIG. 4) is cured, the thermal expansion amount of the wiring board 6 exceeds the thermal expansion amount of the top sheet 29. At this time, the joint portion 8 thermally expands radially from its central portion, and then thermally contracts in the opposite direction in the process of being cooled thereafter (see arrow D in FIG. 5). Therefore, a tensile load is applied to the bumps 41 in the plane direction. When other bumps 41 are arranged around a certain bump 41, it is considered that the respective tensile loads acting on these bumps cancel each other, but in the bumps arranged on the outline of the terminal formation region A, Since there are no other bumps outside the area A, the planar tensile load acting on the bumps is biased. In particular, in the bump 41 ″ arranged at the corner of the outline of the terminal arrangement region A, the influence of the thermal expansion / contraction of the wiring board 6 compared to other bumps arranged in the center of the terminal arrangement region A. Therefore, the wiring board 6 is relatively easily peeled off from the piezoelectric actuator 3 at this portion.

  6 shows a configuration around the bump 41 ″ arranged at the corner of the terminal arrangement region A. Here, each individual electrode terminal 33 is connected to the corresponding individual electrode 31 (see FIG. 2). A terminal main body 43 made of Ag-Pd in which a through hole for conduction is formed, and a land portion 44 having a rectangular shape in plan view made of Ag including a glass frit formed so as to protrude from the terminal main body 43. The bump 41 ″ is provided at the center of the land portion 44. The terminal main body portion 43 is formed at a position corresponding to the pressure chamber 21 and the piezoelectric layer serving as the active portion, and the land portion 44 is formed on the extension portion 43 a that extends from the terminal main body portion 43 to the side opposite to the pressure chamber 21. Is provided. As described above, since the joining point is located away from the pressure chamber 21 and the active part, the deformation of the active part is not hindered by the joining.

  Reinforcing bumps 45 are provided in the vicinity of the bumps 41 ″. The reinforcing bumps 45 are formed in the same manner as the bumps 41 and 41 ″ and have appropriate flexibility. And it is installed so that it may straddle on the land part 44 and the surface of the top sheet 29, and it overlaps with the land part 44 partially in planar view. Since the reinforcing bumps 45 are flexible like the bumps 41 and 41 ″, the reinforcing bumps 45 are brought into contact with the outer edge portions 46 of the land portions 44 as shown in FIG. 6B. At this time, since the adhesive 42 is flowing around the bump 41 ″ and is also in contact with the reinforcing bump 45, the bonding is performed in a state where the reinforcing bump 45 is engaged with the outer edge portion 46 of the land portion 44. By fixing with the agent 42, the bonding strength of the reinforcing bump 45 to the piezoelectric actuator 3 can be increased.

  Further, the reinforcing bump 45 is provided along the direction of thermal expansion / contraction of the wiring board 6 with reference to the bump 41 ″ disposed at the center of the land portion 44. In other words, FIG. ) Shows the direction of thermal expansion / contraction of the wiring board 6 with the bump 41 ″ as a reference for the sake of convenience, but the reinforcing bump 45 is disposed on the linear arrow B.

  FIG. 7A shows a state immediately after the bumps 41 ″ around the bump 41 ″. Before the wiring substrate 6 is overlaid on the piezoelectric actuator 3, the reinforcing bumps 45 together with the bumps 41 ″ of the piezoelectric actuator 3 are formed. Is formed. The reinforcing bump 45 partially overlaps the land portion 44, and the reinforcing bump 45 has a protruding height from the upper surface of the piezoelectric actuator 3 as compared with the bump 41 ″ installed at the center portion of the land portion 44. At this time, the bump 41 ″ and the reinforcing bump 45 are hardened to have an appropriate flexibility.

  Since the reinforcing bumps 45 are thus tall, in the process of superimposing the wiring board 6 on the piezoelectric actuator 3, the reinforcing bumps 45 first contact the individual wiring terminals 38 so as to penetrate the adhesive 42 (FIG. 7B). )reference). At this time, the adhesive 42 adheres to the outer surface of the reinforcing bump 45. When the wiring board 6 is further moved closer to the piezoelectric actuator 3 from this state, the central bump 41 ″ also contacts the individual wiring terminal 38 so as to break through the adhesive 42. In this process, the reinforcing bump 45 is further crushed. Therefore, the distance between the outer surface of the reinforcing bump 45 and the outer surface of the central bump 41 ″ is reduced. When the wiring board 6 is further brought closer to the piezoelectric actuator 3 side from this aspect and the central bump 41 ″ is also crushed, the operation of bringing the wiring board 6 closer to the piezoelectric actuator 3 side is finished (see FIG. 7B). As a result, the distance between the outer surface of the reinforcing bump 45 and the outer surface of the central bump 41 ″ is further reduced. Therefore, the adhesive 42 is provided between the outer surfaces of the bumps 45 and 41 ″. The adhesive 42 is bonded to the reinforcing bump 45 more than when only the bump 41 ″ is disposed. And the bonding strength to the bumps is improved. Further, the reinforcing bump 45 is provided so as to bite into the outer edge portion 47 of the individual wiring terminal 38. As a result, the bonding strength of the reinforcing bump 45 to the wiring board 6 can be increased. Note that the reinforcing bump 45 bites into the outer edge portion 47 in this way because the reinforcing bump 45 is partially connected to the individual wiring when the individual wiring terminal 38 is projected onto the piezoelectric actuator in plan view as shown in FIG. This is because they are arranged so as to overlap with the terminals 38.

  Thereafter, the adhesive 42 is cured by heating. At this time, since the reinforcing bump 45 is provided along the direction of thermal expansion of the wiring board 6 with respect to the central bump 41 ″, the central bump is caused by relative thermal expansion of the wiring board 6 with respect to the piezoelectric actuator 3. The load acting on 41 ″ is received by the reinforcing bump 45. Thereby, the influence of the thermal expansion that the central bump 41 ″ receives from the wiring board 6 can be alleviated, and the wiring board 6 can be made difficult to peel off from the piezoelectric actuator 3 in this portion. The effect when it occurs is the same as this, and the influence of thermal contraction that the central bump 41 ″ receives from the wiring board 6 can be reduced.

  The reinforcing bumps 45 are provided along the direction of thermal expansion / contraction based on the bumps 41 ″ arranged at the corners of the terminal arrangement area A (see FIG. 5). 7 may be provided on the inner side or the outer side of the upper surface, and only one reinforcing bump 45 is provided in the example of FIG. In this case, a higher reinforcing effect is expected. Further, since the reinforcing bumps 45 are formed of a resin material containing silver together with the bumps 41, an effect of increasing the number of conductive portions with respect to the terminals is also expected.

  Further, as shown in FIG. 5, reinforcing bumps 45 may be provided around the bumps 41 ′ arranged on the above-mentioned line B in the outline of the terminal arrangement region A. In this case, the reinforcing bump 45 is preferably arranged on the side where the extending portions 9 and 10 are provided with reference to the bump 41 ′. Thereby, the load accompanying the bending of the extension parts 9 and 10 can be received by the reinforcing bump 45, and the influence of the bending that the bump 41 ′ receives from the wiring board 6 can be reduced. Also in this case, the reinforcing bump 45 can be installed so as to be engaged with at least one of the outer edge portion of the wiring terminal and the outer edge portion of the electrode terminal, thereby joining the reinforcing bump 45 to the wiring terminal 7 and / or the piezoelectric actuator 3. Strength can be increased.

  Of course, the reinforcing bumps may be arranged close to the bumps arranged at the center of the land for the electrode terminals arranged inside the outline of the terminal arrangement region A.

  FIG. 8 shows a modification example of the arrangement of the reinforcing bumps 145. As shown in FIG. 8, a plurality of reinforcing bumps may be provided so as to surround the bump 41 arranged in the center of the land portion 44. By doing in this way, it is effective as a reinforcing structure because the bias can be compensated for in any direction in the outer edges and corners of the plurality of joints, regardless of the direction of the bias. These reinforcing bumps 145 are arranged at equal intervals along a virtual circle centering on the central portion of the central bump 41 in plan view.

  By providing a plurality of reinforcing bumps 145 in this manner, the effects of thermal expansion / shrinkage acting on the central bump 41 and the load associated with the bending of the extending portion are alleviated, and the central bump 41 is connected to the wiring board. The state in contact with the wiring terminal can be maintained well.

  As shown in FIG. 8, when a plurality of reinforcing bumps 145 are provided, some of them may not be arranged so as to bite into the end 46 of the land portion 44. In this way, the reinforcing bumps 145 that do not bite into the edge portion 46 of the land portion 44 may be arranged so as to bite into the edge portion of the wiring terminal in order to increase the bonding strength to the wiring terminal.

  In this embodiment, the reinforcing bumps are formed of a resin material including conductivity in consideration of conduction. However, the present invention is not limited to this, and the conductive material is used when specially provided for reinforcement. It may not be included, and a material having higher hardness may be used as long as it can be bitten into the land portion. Further, the shape of the land portion and the electrode, the number and arrangement of the reinforcing bumps, and the like can be appropriately modified.

  In the present embodiment, a so-called cover coat method is used for joining the piezoelectric actuator and the wiring member. In this cover coat method, the bonding action of the thermosetting resin is used when bonding the bump and the terminal. This is because the bump is cured by heating after formation by printing or an inkjet method, This is because the bonding action of the bumps is lost. Applying the cover coat method not only ensures the distance between the actuator and the wiring board, but also a brazing material in a fluidized state that is generated by joining with a conductive brazing material or a conductive adhesive. Further, since the adhesive does not protrude, the deformation of the active part of the actuator can be prevented from being hindered. However, it is not always necessary to use an adhesive as long as the distance between the actuator and the wiring board is secured by the bumps, and the present invention can be applied to other bonding methods. For example, if the bumps 41, 41 ″ and the reinforcing bumps 45 are cured to such an extent that the adhesive action remains after heating and the shape of the bumps is maintained, the adhesive acts by the adhesive action of the bumps themselves. Even in the joining method that does not use an adhesive as described above, the reinforcing bump 45 is installed so as to be bitten into the land portion 44, so that the present embodiment can be used. The same effect can be obtained.

  Although the embodiment according to the present invention has been described so far, the above configuration is merely an example, and can be appropriately changed within the scope of the present invention. As an example of the liquid ejection apparatus according to the present invention, an assembly including an inkjet head mounted on an inkjet printer and a wiring board electrically and mechanically connected to the inkjet head is illustrated. However, a liquid other than ink, for example, You may apply to the droplet discharge apparatus used for the apparatus which discharges a coloring liquid, manufactures the color filter of a liquid crystal display device, the apparatus which discharges a conductive liquid, and forms an electrical wiring.

  The present invention can increase the bonding strength between the bump, the wiring board, and the actuator, and can ensure the electrical connection between the terminal on the wiring board side and the terminal on the actuator side. It is beneficial to apply to an ink jet printer equipped with an assembly formed by bonding substrates.

A Terminal arrangement area 1 Inkjet head 2 Flow path unit 3 Piezoelectric actuator 6 Wiring board 7 Electrode terminal 8 Joint portion 9, 10 Extension portion 32 Common electrode terminal 33 Individual electrode terminal 36 Wiring terminal 37 Constant potential wiring terminal 38 Individual wiring terminal 41 41 ', 41 "Bump 42 Adhesive 43 Terminal body 44 Land 45, 145 Reinforcement bump 46 Outer edge 47 Outer edge

Claims (5)

An actuator that operates to discharge liquid;
A wiring board for supplying a drive signal for driving the actuator to the actuator;
A first intervening between a first terminal provided on the surface of the wiring board and a second terminal provided on the surface of the actuator to electrically connect the first and second terminals. With bumps,
A liquid ejection apparatus in which the wiring board overlaid on the actuator is joined to the actuator via the first bump,
A second bump disposed around the first bump;
The second bump, the are arranged to partially overlap with at least one in a plan view of the first terminal and the second terminal is provided from the surface to which the terminals are provided so as to bite an outer edge of the terminal ,
A terminal arrangement area for arranging a plurality of the second terminals is defined on the surface of the actuator,
The second bump is provided corresponding to the second terminal disposed at an outer edge of the terminal arrangement region;
The circuit board has a higher coefficient of thermal expansion than the actuator, and the circuit board is configured to be joined to the actuator through a process of heating and curing the first and second bumps.
The second bumps corresponding to the second terminals arranged at the corners of the outer edge are arranged along a direction in which the wiring board is thermally deformed with reference to the first bumps corresponding to the second bumps. and a liquid discharge apparatus characterized in that is.   2. The liquid ejection apparatus according to claim 1, wherein the second bump is taller than the first bump in a state before the wiring board is overlaid on the actuator. Liquid ejecting apparatus according to claim 1 or 2 more of the second bump is characterized by being provided so as to surround the first bump. The wiring board is bonded to the actuator by curing the adhesive applied on the surface on which the first terminals are formed while being adhered on the surfaces of the first bump and the second bump. apparatus according to any one of claims 1 to 3, characterized in that it is configured to be.   The first bump is provided on the second terminal in a state before the wiring board is overlaid on the actuator.
  The second bump is provided so as to bite into the outer edge of the second terminal from the surface of the actuator provided with the second terminal in a state before the wiring board is overlaid on the actuator. The liquid ejection device according to claim 1.

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