JP2016215382A - Inkjet head, inkjet head manufacturing method and inkjet recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet head that can surely connect electrically an electrode at a head chip side and an electrode at a wiring substrate side without increasing pressure to be applied thereto when adhering the head chip to the wiring substrate, an inkjet head manufacturing method, and an inkjet recording device.SOLUTION: The inkjet head has: a head chip having an opening part of a channel and connection electrodes 15A and 15B, which are electrically connected to driving electrodes provided in the channel through the opening part, formed on the same surface; and a wiring substrate having wiring electrodes 33A and 33B corresponding to the connection electrodes 15A and 15B formed on a surface thereof, in which the head chip is adhered to the wiring substrate with an adhesive 5 containing a conductive particle 6 having protrusions 6a, so that the connection electrodes 15A and 15B are electrically connected to the wiring electrodes 33A and 33B.SELECTED DRAWING: Figure 7

Description

  The present invention relates to an ink jet head, a method for manufacturing an ink jet head, and an ink jet recording apparatus. More specifically, the head chip side electrode and the wiring substrate side can be obtained without increasing the pressure applied when the head chip and the wiring substrate are bonded. The present invention relates to an inkjet head capable of reliably performing electrical connection with the electrode, an inkjet head manufacturing method, and an inkjet recording apparatus.

  As an inkjet head, there is a shear mode type inkjet head. This ink-jet head has a head chip in which a partition wall defining a channel to which ink is supplied is a drive wall formed by a piezoelectric element, and a drive electrode is formed on the surface of the drive wall. Then, when a predetermined voltage is applied to the drive electrode, the drive wall is sheared to change the volume of the channel, and the ink generated in the channel is ejected from the nozzle using the pressure generated at that time. .

  A so-called harmonica type head chip is known as a head chip of such an ink jet head. This head chip has a hexahedral shape, and the channel is formed in a straight shape. For this reason, the drive electrode on the surface of the drive wall faces the channel and is not exposed to the outside, and a voltage cannot be directly applied to the drive electrode. Therefore, a device is devised to facilitate the application of voltage to the drive electrode by forming a connection electrode that is electrically connected to the drive electrode through the opening of the channel formed on the surface of the head chip on the same surface as the opening. It is taken.

  Conventionally, a wiring substrate on which a wiring electrode corresponding to the connection electrode is formed is bonded to the surface on which the opening of the head chip and the connection electrode are formed by using an adhesive containing conductive particles. An ink jet head is known in which a connection electrode and a wiring electrode are electrically connected (Patent Document 1).

JP 2014-128941 A

  Adhesion between the head chip and the wiring substrate is performed by applying a predetermined pressure. In particular, in the case of an electrode having an oxide film formed on the surface, since the connection resistance is larger than in the case where electrodes without an oxide film are electrically connected to each other, a higher pressure is applied, and the conductive particles between the electrodes Must be in direct contact with the electrode surface.

  In particular, the harmonica type head chip is characterized in that it can be easily lengthened. However, due to the lengthening, the head chip is particularly likely to warp and swell. For this reason, even when pressure is evenly applied and electrical connection is made, the pressure applied to each electrode may be biased. At this time, since the pressure applied to the conductive particles in the adhesive is also biased, a portion where the conductive particles interposed between the electrodes are sufficiently pressurized and a good electrical connection is made, and the electrode There is a possibility that a portion where electrical connection is insufficient due to insufficient pressurization of the conductive particles interposed therebetween. For this reason, when bonding the head chip and the wiring board, it is necessary to apply a higher pressure so that all the electrodes are electrically connected well.

  However, when bonding the head chip and the wiring board in this manner, applying a higher pressure may lead to damage to the head chip or the wiring board. In particular, the harmonica type head chip has a structure in which the pressure at the time of bonding is directly applied to the piezoelectric material. Therefore, excessive pressure may cause deterioration of the piezoelectric characteristics and may cause deterioration of the ejection characteristics of the inkjet head.

  Therefore, according to the present invention, the electrical connection between the electrode on the head chip side and the electrode on the wiring board side can be reliably performed without increasing the pressure applied when the head chip and the wiring board are bonded. It is an object to provide an inkjet head.

  Further, according to the present invention, the electrical connection between the electrode on the head chip side and the electrode on the wiring board side can be reliably performed without increasing the pressure applied when the head chip and the wiring board are bonded. It is an object to provide a method for manufacturing an inkjet head.

  Furthermore, according to the present invention, the electrical connection between the electrode on the head chip side and the electrode on the wiring board side can be reliably performed without increasing the pressure applied when the head chip and the wiring board are bonded. It is an object of the present invention to provide an inkjet recording apparatus that includes an inkjet head and can perform high-quality image recording.

  Other problems of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

1. A head chip in which an opening of a channel and a connection electrode electrically connected to a drive electrode provided in the channel through the opening are formed on the same surface;
In an inkjet head having a wiring substrate having a wiring electrode corresponding to the connection electrode formed on a surface thereof,
The connection electrode and the wiring electrode are electrically connected by bonding the head chip and the wiring board with an adhesive containing conductive particles having protrusions. Inkjet head.

  2. 2. The ink-jet head according to 1, wherein the conductive particles are core-shell particles having a shell made of a metal film having the protrusions formed on the surface of an organic core.

  3. 3. The ink jet head according to 2, wherein the conductive particles have a Young's modulus of the shell higher than that of the organic core.

  4). The shell of the conductive particles has a lower layer made of a metal having a higher Young's modulus than Au under the outermost layer made of Au, and the lower layer forms the protrusions. Or the inkjet head of 3.

  5. 5. The inkjet head according to any one of 1 to 4, wherein at least one of the connection electrode and the wiring electrode has an oxide film on the electrode surface.

  6). 6. The inkjet head as described in 5 above, wherein the height of the protrusion of the conductive particle is larger than the thickness of the oxide film.

  7). The inkjet head according to any one of 1 to 6, wherein the adhesive is a thermosetting adhesive.

  8). The inkjet head according to any one of 1 to 7, wherein the wiring board is arranged in parallel to a surface of the head chip on which the opening and the connection electrode are formed.

9. A head chip in which an opening of a channel and a connection electrode electrically connected to a drive electrode provided in the channel through the opening are formed on the same surface;
In a method of manufacturing an ink jet head having a wiring substrate having a wiring electrode corresponding to the connection electrode formed on a surface thereof,
After bonding the head chip and the wiring substrate through an adhesive containing conductive particles having protrusions, the adhesive is cured to electrically connect the connection electrode and the wiring electrode. A method for manufacturing an ink jet head, comprising: connecting to an ink jet head.

  10. 10. The method of manufacturing an ink-jet head according to 9, wherein the conductive particles are core-shell particles having a shell made of a metal film having the protrusions formed on the surface of an organic core.

  11. 11. The method of manufacturing an ink jet head according to 10, wherein the conductive particles have a Young's modulus of the shell higher than a Young's modulus of the organic core.

  12 The shell of the conductive particles has a lower layer made of a metal having a higher Young's modulus than Au under the outermost layer made of Au, and the lower layer forms the protrusions. Or the manufacturing method of the inkjet head of 11.

  13. At least one of the connection electrode and the wiring electrode has an oxide film on the electrode surface, The method of manufacturing an ink jet head according to any one of 9 to 12 above.

  14 14. The method for manufacturing an ink jet head according to 13, wherein the height of the protrusion of the conductive particle is larger than the thickness of the oxide film.

  15. 15. The method of manufacturing an ink jet head according to any one of 9 to 14, wherein the adhesive is a thermosetting adhesive.

  16. 16. The method of manufacturing an ink jet head according to any one of 9 to 15, wherein the wiring board is disposed in parallel with a surface of the head chip on which the opening and the connection electrode are formed.

17. Including the inkjet head according to any one of 1 to 8;
By applying a voltage to the drive electrode via the wiring electrode and the connection electrode of the inkjet head, ink in the channel is ejected from a nozzle provided in the channel, and an image is recorded on a recording medium. An ink jet recording apparatus.

  According to the present invention, the electrical connection between the electrode on the head chip side and the electrode on the wiring board side can be reliably performed without increasing the pressure applied when bonding the head chip and the wiring board. An ink jet head can be provided.

  In addition, according to the present invention, the electrical connection between the head chip side electrode and the wiring board side electrode can be reliably performed without increasing the pressure applied when the head chip and the wiring board are bonded. It is possible to provide a method for manufacturing an inkjet head capable of performing

  Furthermore, according to the present invention, the electrical connection between the electrode on the head chip side and the electrode on the wiring board side can be reliably performed without increasing the pressure applied when the head chip and the wiring board are bonded. It is possible to provide an ink jet recording apparatus that includes an ink jet head that can perform high quality image recording.

Schematic configuration diagram of an inkjet recording apparatus according to the present invention An exploded perspective view showing an example of an inkjet head Partial rear view of the head chip of the inkjet head shown in FIG. The figure which shows the joining state of the head chip and the wiring board Sectional drawing which follows the (v)-(v) line | wire of FIG. Conceptual diagram showing conductive particles partially cut away Sectional drawing which shows the state in which the connection electrode and the wiring electrode were electrically connected by the adhesive agent containing electroconductive particle Graph showing the distribution of the number of particles against the particle size of conductive particles Plan view showing a surface of a wiring board showing an example of a method of manufacturing an inkjet head Sectional drawing which shows the state which clamped the head chip and the wiring board with a pair of pressure plate Explanatory drawing of the state in which the base in the dummy channel is heated and expanded

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Inkjet recording device)
FIG. 1 is a schematic configuration diagram of an ink jet recording apparatus according to the present invention.

  In the inkjet recording apparatus 100, the recording medium P is sandwiched between the transport roller pair 101a of the transport mechanism 101, and is further transported in the Y direction (sub-scanning direction) by the transport roller 101b that is rotationally driven by the transport motor 101c. It has become.

  The inkjet head 10 is provided between the transport roller 101b and the transport roller pair 101a so as to face the recording surface PS of the recording medium P. The inkjet head 10 is mounted on the carriage 102 so that the nozzle surface side faces the recording surface PS of the recording medium P, and is electrically connected to a control device (not shown) via a flexible cable 103. The carriage 102 is illustrated in the drawing XX substantially orthogonal to the conveyance direction (sub-scanning direction) of the recording medium P along the guide rail 104 spanned across the width direction of the recording medium P by a driving unit (not illustrated). It is provided so as to be able to reciprocate along the 'direction (main scanning direction).

  The inkjet head 10 moves the recording surface PS of the recording medium P in the XX ′ direction in the drawing as the carriage 102 moves in the main scanning direction, and the channel (drive) provided in the inkjet head 10 during this movement process. The ink in the channel) is ejected from a nozzle provided in communication with the channel, and a desired inkjet image is recorded on the recording surface PS of the recording medium P.

(Inkjet head)
Next, the configuration of the inkjet head 10 will be described with reference to the drawings.

  2 is an exploded perspective view showing an example of the ink jet head, FIG. 3 is a partial rear view of the head chip of the ink jet head shown in FIG. 2, FIG. 4 is a view showing a bonding state of the head chip and the wiring board, and FIG. It is sectional drawing which follows the (v)-(v) line | wire of FIG.

  The inkjet head 10 includes a head chip 1, a nozzle plate 2 bonded to the front surface 1 a of the head chip 1, a wiring substrate 3 bonded to the rear surface 1 b of the head chip 1, and an FPC connected to the end 3 a of the wiring substrate 3. (Flexible substrate) 4 etc. are provided.

  The head chip 1 is formed of a hexahedron and has two channel rows of A rows and B rows. Here, the lower channel row shown in FIG. 3 is the A column, and the upper channel row is the B column. Each channel row is configured by alternately arranging drive channels 11A and 11B and dummy channels 12A and 12B. Partition walls between adjacent drive channels 11A or 11B and dummy channels 12A and 12B are drive walls 13A and 13B made of piezoelectric elements.

  The drive channels 11A and 11B and the dummy channels 12A and 12B are formed in a straight shape extending over the front surface 1a and the rear surface 1b of the head chip 1, and are opened on the front surface 1a and the rear surface 1b of the head chip 1, respectively. Reference numerals 11 a, 11 b, 12 a, and 12 b in FIG. 3 are channel openings disposed on the rear surface 1 b of the head chip 1. Drive electrodes 14 are formed on at least the surfaces of the drive walls 13A and 13B among the walls facing the drive channels 11A and 11B and the dummy channels 12A and 12B, respectively.

  The head chip 1 is an independent drive type head chip in which drive channels 11A and 11B and dummy channels 12A and 12B are alternately arranged in each channel row, and a drive signal of a predetermined voltage is applied to each drive electrode 14. Thus, the drive walls 13A and 13B sandwiched between the pair of drive electrodes 14 and 14 are subjected to shear deformation. As a result, a pressure change for ejection is applied to the ink supplied into the drive channels 11A and 11B, and the ink is ejected as ink droplets from the nozzles 21 of the nozzle plate 2 joined to the front surface 1a of the head chip 1.

  In the head chip 1 shown in the present embodiment, the surface on the side where the nozzles 21 are arranged and the ink is ejected is defined as “front surface”, and the surface on the opposite side is defined as “rear surface”. Further, the direction parallel to the front surface 1a or the rear surface 1b of the head chip 1 and away from the head chip 1 is defined as “side” of the head chip 1.

  The drive channel is a channel that ejects ink according to image data during image recording, and the dummy channel is a channel that does not always eject ink regardless of image data. Since the dummy channels 12A and 12B do not need to eject ink, the ink is not usually filled or the nozzle 21 is not formed on the nozzle plate 2. The nozzles 21 of the nozzle plate 2 shown in the present embodiment are opened only at positions corresponding to the drive channels 11A and 11B.

  Connection electrodes 15A and 15B are formed on the rear surface 1b of the head chip 1 so as to correspond to the drive channels 11A and 11B and the dummy channels 12A and 12B on a one-to-one basis. One end of each connection electrode 15A, 15B is electrically connected to each drive electrode 14 via the opening 11a, 11b of the corresponding drive channel 11A, 11B or the opening 12a, 12b of the dummy channel 12A, 12B. Yes.

  As shown in FIG. 3, the other ends of the connection electrodes 15A corresponding to the drive channels 11A and the dummy channels 12A in the A row are connected to one of the openings 11a and 12a of the channels 11A and 12A on the rear surface 1b of the head chip 1. It extends toward the edge 1c. The other ends of the connection electrodes 15B corresponding to the drive channels 11B and the dummy channels 12B in the B row extend from the openings 11b and 12b of the channels 11B and 12B toward the A row. It stops with a gap between. Accordingly, all of the connection electrodes 15A and 15B extend in the same direction from the openings 11a, 11b, 12a, and 12b.

  The wiring board 3 is bonded to the rear surface 1b of the head chip 1 via an adhesive 5 (see FIG. 5). The wiring substrate 3 is a flat substrate having an area larger than the area of the rear surface 1b of the head chip 1 from the viewpoint of securing an adhesion region 31 (shown by a one-dot chain line in FIG. 2) with the head chip 1. Preferably there is. That is, as shown in FIG. 2, the wiring board 3 has at least one end 3 a after being bonded to the head chip 1 extending outside the bonding region 31, and along the alignment direction of the channel rows of the head chip 1. It is preferable that it protrudes greatly to the side. Thereby, a large connection space with the FPC 4 can be secured by the projecting end portion 3a.

  The adhesion region 31 is a region where the surface of the wiring substrate 3 is covered by the rear surface 1b of the head chip 1, and is defined by a line that hangs down from the outer peripheral edge of the rear surface 1b of the head chip 1 to the wiring substrate 3.

  The material of the wiring board 3 can be an appropriate material such as glass, ceramics, silicon, or plastic. Among them, glass is preferable because it has moderate rigidity, is inexpensive, and can be easily processed.

  The wiring substrate 3 is bonded so as to cover the openings 11a, 11b, 12a, and 12b of all the channels disposed on the rear surface 1b of the head chip 1. Specifically, the wiring board 3 is arranged in parallel with the rear surface 1 b in which the openings 11 a, 11 b, 12 a, 12 b and the connection electrodes 15 A, 15 B in the head chip 1 are formed, and is bonded by the adhesive 5.

  In the bonding region 31 of the head chip 1 on the wiring board 3, through holes 32A and 32B for supplying ink to the drive channels 11A and 11B from the back side of the wiring board 3 are individually opened. The through holes 32A and 32B are formed only at positions corresponding to the drive channels 11A and 11B of the head chip 1. The through holes 32A and 32B are formed so that the opening on the head chip 1 side has the same shape as the openings 11a and 11b of the drive channels 11A and 11B.

  On the other hand, such a through hole is not formed in a portion of the wiring board 3 corresponding to the dummy channels 12A and 12B. For this reason, the dummy channels 12 </ b> A and 12 </ b> B are blocked by the wiring board 3.

  Wiring electrodes 33A and 33B are provided on the surface of the wiring substrate 3 that is to be bonded to the head chip 1 so as to correspond to the connection electrodes 15A and 15B arranged on the rear surface 1b of the head chip 1 on a one-to-one basis. Is formed. The wiring electrode 33A corresponds to each connection electrode 15A in the channel row of the A row, and the wiring electrode 33B corresponds to each connection electrode 15B in the channel row of the B row.

  As shown in FIG. 4, one end of the wiring electrode 33A reaches the vicinity of the corresponding drive channel 11A and the dummy channel 12A, overlaps with the corresponding connection electrode 15A, and the other end is to the side of the head chip 1. It extends toward the same end portion 3 a of the overhanging wiring board 3. Further, one end of the wiring electrode 33B reaches the vicinity of the corresponding drive channel 11B and the dummy channel 12B, and overlaps with the corresponding connection electrode 15B. The other end of the wiring electrode 33B passes between the adjacent drive channels 11A and 11A of the A-row channel row, straddles the A-row channel row, and faces the end portion 3a of the wiring board 3 in the same manner as the wiring electrode 33A. It extends. For this reason, the wiring electrodes 33A and 33B are arranged in parallel on the surface of the wiring substrate 3 protruding to the side of the head chip 1 from the inner side of the adhesion region 31 to the end portion 3a so as to alternate.

  The FPC 4 is an example of an external wiring member, and is connected to the end 3a of the wiring board 3 via, for example, an ACF (anisotropic conductive film) or the like, and is electrically connected to a drive circuit (not shown). . As a result, a drive signal of a predetermined voltage from the drive circuit is supplied to each channel 11A, 11B, 12A, 12B via the FPC 4, the wiring electrodes 33A, 33B of the wiring board 3, and the connection electrodes 15A, 15B of the head chip 1. The drive electrode 14 is applied.

(Adhesive containing conductive particles)
Examples of the adhesive 5 used for bonding the head chip 1 and the wiring board 3 include a room temperature curing adhesive that cures at room temperature, a thermosetting adhesive that cures by heating to cure, and an active energy such as ultraviolet rays. An active energy ray-curable adhesive that accelerates polymerization by irradiation and is cured can be used.

  In the present invention, the adhesive 5 is a conductive adhesive containing conductive particles 6 having protrusions. By bonding the head chip 1 and the wiring board 3 with the adhesive 5, the connection electrodes 15A and 15B on the rear surface 1b of the head chip 1 and the wiring electrodes 33A and 33B of the wiring board 3 corresponding thereto are connected. Electrically connected.

  FIG. 6 is a conceptual diagram showing the conductive particles 6 with a part cut away, and FIG. 7 is an electrical connection between the connection electrode 15A and the wiring electrode 33A (33B) by the adhesive 5 containing the conductive particles 6. It is sectional drawing which shows the state made.

  The conductive particle 6 has a plurality of protrusions 6a protruding from the surface. Therefore, when the head chip 1 and the wiring substrate 3 are bonded, the conductive particles 6 sandwiched between the connection electrodes 15A and 15B and the wiring electrodes 33A and 33B are separated from the electrodes 15A and 15B by the tips of the protrusions 6a. It contacts the surfaces of 33A and 33B. That is, the contact between the conductive particles 6 and the surfaces of the electrodes 15A, 15B, 33A, and 33B is close to point contact by the tips of the protrusions 6a, and when using spherical conductive particles that do not have the protrusions 6a. In comparison, the contact area is reduced.

  Thereby, the load at the time of pressure-bonding the head chip 1 and the wiring board 3 concentrates on the small contact area of the front-end | tip of each protrusion 6a. As a result, the pressure applied per unit area between the conductive particles 6 and the surfaces of the electrodes 15A, 15B, 33A, and 33B increases. Therefore, the conductive particles 6 can form a sufficient contact state with the surfaces of the electrodes 15A, 15B, 33A, and 33B, and the electrical connection between the connection electrodes 15A and 15B and the wiring electrodes 33A and 33B. Can be performed reliably.

  In particular, even when the head chip 1 or the wiring substrate 3 is warped or undulated, the surface of the conductive particles 6 and the electrodes 15A, 15B, 33A, 33B can be obtained without particularly increasing the pressure applied during pressure bonding. And the connection electrodes 15A, 15B and the wiring electrodes 33A, 33B can be reliably connected to each other.

  In addition, since each protrusion 6a of the conductive particle 6 pierces the surface of each electrode 15A, 15B, 33A, 33B by pressurization, the resistance between the connection electrode 15A, 15B and the wiring electrode 33A, 33B is reduced. The variation can be reduced, and the electrical connection state can be stabilized.

  Furthermore, since the conductive particles 6 having the protrusions 6 a on the surface are less likely to roll in the adhesive 5, there is an effect that the conductive particles 6 are less likely to aggregate between the head chip 1 and the wiring substrate 3. In particular, when a thermosetting adhesive is used as the adhesive 5, if heating is performed to a predetermined temperature for curing, the viscosity of the adhesive is temporarily reduced to easily flow, and accordingly, in the adhesive It is known that when the flow of the conductive particles is activated, the particles are easily aggregated. However, by using the conductive particles 6 having the protrusions 6a on the surface, the flow of the conductive particles 6 accompanying the decrease in the viscosity of the adhesive 5 during heating can be deactivated. Aggregation can be suppressed. Thereby, the short circuit between electrodes resulting from aggregation can be suppressed effectively.

  Such agglomeration due to the flow of the conductive particles 6 can occur even if it is not a thermosetting adhesive, but in particular, the thermosetting adhesive becomes easy to flow due to a decrease in the viscosity of the adhesive 5 due to heating, and the conductivity is increased. The rolling of the particles 6 is likely to occur. Therefore, in the present invention, it is preferable to use a thermosetting adhesive since the adhesive 5 has a remarkable effect of suppressing aggregation as described above. An epoxy adhesive is preferably used as the thermosetting adhesive, but is not particularly limited.

  In the present invention, when any one or both of the connection electrodes 15A and 15B and the wiring electrodes 33A and 33B are electrodes that form an oxide film on the surface, such as aluminum, the conductive particles 6 It is preferable to use an adhesive 5 containing An electrode having an oxide film on the surface generally has a high connection resistance. However, by using the conductive particles 6, the protrusions 6a can easily break through the oxide film and come into contact with the underlying metal surface. As a result, the conductive particles 6 can be brought into direct contact with the surfaces of the electrodes 15A, 15B, 33A, 33B and electrically connected without applying a particularly high pressure during pressure bonding, which is remarkable in the present invention. An effect is obtained.

  The conductive particles 6 used in the present invention are not particularly limited as long as the conductive particles 6 have protrusions 6a on the surface and have conductivity. However, as shown in FIG. It is preferable that the core-shell particle has a shell 62 made of a metal film on which is formed. When the conductive particles 6 are sandwiched between the electrodes at the time of pressure bonding, the organic core 61 is deformed and absorbs variations in pressure distribution. Therefore, the pressing pressure of the conductive particles 6 and the electrodes 15A, 15B, 33A, 33B is changed. It can be made uniform.

  The organic core 61 is not particularly limited, but resin particles whose main component monomer is divinylbenzene or the like can be used.

  On the other hand, the shell 62 is made of a metal film that covers the surface of the organic core 61. The specific metal which comprises the shell 62 is not specifically limited, For example, Ni, Au, etc. can be used. However, since the conductive particles 6 have the protrusions 6a on the surface of the shell 62, the shells are more than the Young's modulus of the organic core 61 from the viewpoint of stabilizing the electrical connection by the protrusions 6a sticking to the electrode surface. It is preferable that the Young's modulus of 62 is higher. Thereby, when the electroconductive particle 6 is pinched | interposed between electrodes at the time of pressure bonding, compared with the organic core 61, the processus | protrusion 6a becomes difficult to deform | transform. Therefore, since the protrusion 6a of the conductive particle 6 pierces the electrode surface while maintaining the protrusion shape, the electrical connection can be further stabilized.

  When the conductive particles 6 are core-shell particles, the shell 62 has a lower layer 622 made of a metal having a higher Young's modulus than Au under the outermost layer 621 made of Au, as shown in FIG. It is preferable that 622 forms the protrusion 6a. FIG. 6 shows a structure in which a lower layer 622 having protrusions 6a is formed by plating Ni (Young's modulus: 200 GPa) on the surface of the organic core 61, and Au (Young's modulus: 79GPa) is plated on the surface of this lower layer 622. Show.

  Since the outermost layer 621 is made of Au having high electrical conductivity, the connection electrodes 15A and 15B and the wiring electrodes 33A and 33B can be preferably electrically connected. Further, since Au is deformed to some extent during pressure bonding, it is possible to earn a contact area between the protrusion 6a and the surfaces of the electrodes 15A, 15B, 33A, 33B. On the other hand, the lower layer 622 having a high Young's modulus is less likely to deform than the outermost layer 621, and deformation of the protrusion 6a itself formed by the lower layer 622 is suppressed. For this reason, it is possible to ensure both good electrical connection between the electrodes by the protrusion 6a and suppression of deformation of the protrusion 6a at the time of pressure bonding, and a good contact state close to point contact can be formed. .

  The particle diameter of the conductive particles 6 is not particularly limited, but is preferably smaller than (thickness of the connection electrodes 15A and 15B) + (thickness of the wiring electrodes 33A and 33B), specifically 1 μm to 5 μm. A range is preferred. By setting it as this range, between the connection electrodes 15A and 15B and the wiring electrodes 33A and 33B can be preferably electrically connected.

  This particle size is an average particle size. The particle diameter has a distribution of the number of particles corresponding to the particle diameter as shown in FIG. When this distribution curve is a line object, the particle diameter at the peak of the number of particles is the average particle diameter. The particle diameter is the diameter up to the tip of the protrusion 6a and is measured by an electron micrograph.

  The protrusion height of the protrusion 6a is not particularly limited as long as it is within the range of the particle diameter. However, since the thickness of the oxide film formed on the electrode surface is approximately 5 nm to 10 nm, 6a is larger than the film thickness of this oxide film from the viewpoint that the connection resistance can be reduced by piercing the surface of each electrode 15A, 15B, 33A, 33B through the oxide film More specifically, it is preferably 15 nm or more. An upper limit of about 300 nm is appropriate.

  The shape of the protrusion 6a is not particularly limited as long as it protrudes from the surface of the conductive particle 6, but can form a contact state close to point contact with the surface of each electrode 15A, 15B, 33A, 33B, and pressurization From the viewpoint of effectively piercing the surface, a taper is preferred as it goes to the tip.

  The number of the protrusions 6a is not particularly limited, but from the viewpoint of being able to form a contact state close to point contact with the surface of each electrode 15A, 15B, 33A, 33B and effectively piercing the surface by pressing. It is preferable that the number per one is 20 to 200.

  A commercial item can be used for the electroconductive particle 6 which has such a processus | protrusion 6a.

  The content of the conductive particles 6 in the adhesive 5 is preferably 0.1% to 5% by volume mixing ratio (relative to the adhesive) from the viewpoint of dispersibility.

(Inkjet head manufacturing method)
Next, an example of a method for manufacturing the inkjet head 10 will be described with reference to FIGS.

  FIG. 9 is a plan view showing the surface of the wiring board 3 before being bonded to the head chip 1. First, on the surface of the wiring board 3 on which the through holes 32A and 32B and the wiring electrodes 33A and 33B are formed, a band is formed over the portion where the connection electrodes 15A and 15B of the head chip 1 and the wiring electrodes 33A and 33B overlap. Thus, the adhesive 5 containing the electroconductive particle 6 is apply | coated. Thereafter, the head chip 1 is positioned and bonded to the bonding region 31 and pressure bonded.

  FIG. 10 is a cross-sectional view showing a state in which the head chip 1 and the wiring substrate 3 are bonded and pressure bonded. The bonded head chip 1 and wiring board 3 are mounted between a pair of upper and lower pressure plates 7a and 7b, and a predetermined pressure is applied between the pressure plates 7a and 7b. Thereby, the adhesive 5 applied in a band shape flows between the head chip 1 and the wiring substrate 3 by a capillary force. In FIG. 10, the adhesive 5 is not shown.

  At this time, a part of the adhesive 5 reaching the dummy channels 12A and 12B passes through the wiring substrate 3 and enters the dummy channels 12A and 12B. This is because the openings 12a and 12b of the dummy channels 12A and 12B are closed by the wiring board 3. On the other hand, since the through holes 32A and 32B are formed in the drive channels 11A and 11B in the same shape as the openings 11a and 11b, the adhesive 5 enters the drive channels 11A and 11B along the wiring board 3. .

  Further, as shown in FIG. 7, a part of the conductive particles 6 in the adhesive 5 that has flowed along with the pressurization of the head chip 1 and the wiring substrate 3 are connected to the connection electrodes 15A and 15B and the wiring electrodes 33A, It is set as the state pinched | interposed between 33B. Thereafter, the conductive particles 6 are crushed along with the pressurization of the head chip 1 and the wiring board 3 by the pressure plates 7a and 7b, and the protrusions 6a on the surface become the surfaces of the electrodes 15A, 15B, 33A and 33B. Pierce. Thereby, the electrical connection between the connection electrodes 15A and 15B of the head chip 1 and the wiring electrodes 33A and 33B of the wiring board 3 can be reliably performed.

  At this time, contact between the conductive particles 6 and the surfaces of the electrodes 15A, 15B, 33A, and 33B is close to point contact by the tips of the protrusions 6a, and the contact area becomes small. The conductive particles 6 and the electrodes 15A, 15B, 15B, and the electrodes 15A, 15B, and the electrodes 15A, 15B, A sufficient contact state with the surfaces of 33A and 33B can be formed.

  A sheet-like sealing material 8 made of an elastic material is provided on the surface of the pressure plate 7a disposed on the front surface 1a side of the head chip 1 among the pressure plates 7a and 7b. When the pressure is applied, the sealing material 8 comes into contact with the front surface 1 a of the head chip 1. Generally, rubber can be used as the elastic material, and silicon rubber is particularly preferable.

  The reason for providing this sealing material 8 is as follows. In general, the head chip 1 is manufactured by fully cutting ceramics as a head chip material with a dicing blade or the like. At this time, traces at the time of cutting may remain as fine irregularities on the full cut surface (front surface 1a and rear surface 1b). In this state, it is difficult to seal the dummy channels 12A and 12B with only the flat pressure plate 7a. This problem can be improved by polishing the full-cut surface. However, by sandwiching the sealing material 8 as shown in the drawing, each opening of the front surface 1a of the head chip 1 can be effectively formed without performing the polishing work. Can be sealed.

  The openings 12a and 12b of the dummy channels 12A and 12B on the wiring board 3 side are in a sealed state by the adhesive 5 and the wiring board 3 that have flowed into the periphery thereof. For this reason, it is not always necessary to provide the sealing material 8 on the pressure plate 7b on the wiring board 3 side. The dummy channels 12A and 12B of the head chip 1 are sealed between the sealing material 8 of the pressure plate 7a and the wiring board 3, and the gas (air) is sealed inside.

  Next, by heating the head chip 1 and the wiring substrate 3 in this state, the gas sealed in the dummy channels 12A and 12B is expanded.

  When the adhesive 5 is a thermosetting adhesive, the heat at the time of heating can utilize the heat at the time of hardening this adhesive 5. When the adhesive 5 is not a thermosetting type, the adhesive 5 may be heated by an appropriate heating means such as an oven while being sandwiched between the pressure plates 7a and 7b. Here, the case where the adhesive 5 is a thermosetting adhesive and the above-described heating is performed using heat at the time of heat curing will be described with reference to FIG. FIG. 11 is an explanatory diagram of a state in which the base body in the dummy channels 12A and 12B is heated and expanded.

  When the gas in the dummy channels 12A and 12B expands due to the heating of the head chip 1, as shown in FIG. 11, the adhesive 5 that has entered the dummy channels 12A and 12B due to the expansion of the gas flows into the dummy channels 12A and 12B. It is extruded between the rear surface 1b of the head chip 1 and the wiring board 3 from the openings 12a and 12b. And by hardening the adhesive 5 in this state, it is avoided that the inside of the dummy channels 12A, 12B is blocked by the adhesive 5.

  The conductive particles 6 in the adhesive 5 that are not sandwiched between the connection electrodes 15A and 15B and the wiring electrodes 33A and 33B at the time of the heating expansion are easily flowable due to a decrease in viscosity due to heating. Try to flow with 5. However, since the conductive particles 6 have protrusions 6a on the surface and are difficult to roll, the flow of the conductive particles 6 is deactivated and aggregation is suppressed. Therefore, since the adhesive 5 is cured in a state where aggregation of the conductive particles 6 is suppressed, a short circuit between the electrodes is less likely to occur.

  In particular, like the inkjet head 10 shown in the present embodiment, the wiring substrate 3 is arranged in parallel with the rear surface 1b of the head chip 1 where the openings 11a, 11b, 12a, 12b and the connection electrodes 15A, 15B are formed. In the case of bonding, a region where the adhesive 5 flows between the head chip 1 and the wiring board 3 is widened. However, since the flow of the conductive particles 6 is deactivated by the protrusions 6a and aggregation is suppressed, a particularly remarkable effect is obtained in the present invention.

  The inkjet head 10 described above is an independent drive type in which the head chip 1 has the drive channels 11A and 11B and the dummy channels 12A and 12B, but is not limited to this. Therefore, the head chip 1 may be one in which all channels discharge ink. Further, the number of channel strings and the number of channels constituting the channel strings are not limited to those illustrated.

  The effects of the present invention are illustrated below by examples.

  A shear mode type head chip was manufactured using PZT as a driving wall material. On the rear surface of the head chip, a connection electrode that is electrically connected to an internal drive electrode through an opening of a channel disposed on the rear surface was formed as shown in FIG. The specifications of the head chip are as follows.

Number of channel columns: 2
Number of channels in one row: 512
Channel size: depth 360 μm x width 82 μm x length 3.0 mm
Connection electrode: Aluminum, 3μm thickness

  In the wiring substrate, through holes are formed in a transparent glass substrate only at positions corresponding to the channels of the head chip by blasting, and as shown in FIG. 4, the connection electrodes of the head chip have a one-to-one correspondence. A wiring electrode was formed. The wiring electrode was formed with aluminum to a thickness of 1 μm. An oxide film having a thickness of 5 to 10 nm was formed on the surface of the wiring electrode.

  The head chip and the wiring board were bonded together via a thermosetting adhesive (353ND manufactured by EPOTEK, final curing temperature: 100 ° C.). The adhesive was applied in a strip shape on the wiring board side as in FIG.

  Using adhesives containing conductive particles that do not have protrusions and those containing conductive particles that have protrusions, all are pressure-bonded at the same pressure to produce ink jet heads, respectively. did. The content of the conductive particles in the adhesive was common at a volume mixing ratio of 1% with respect to the adhesive. The particle diameter of each conductive particle and the protrusion height of the protrusion are as shown in Table 1.

(Evaluation method)
Connection resistance: In the obtained inkjet head, the conductive particles excluding the wiring resistance and the connection resistance between the conductive particles and the electrodes were measured with a digital multimeter and evaluated according to the following criteria. The results are shown in Table 1.
[Evaluation criteria]
○: Less than 1Ω △: 1Ω or more and less than 10Ω ×: 10Ω or more

Aggregation of conductive particles: The dispersion state of conductive particles in the adhesive before applying the adhesive to the wiring substrate and the dispersion state of conductive particles in the adhesive after bonding the head chip and the wiring substrate. The sample was observed under a microscope and evaluated according to the following criteria. The results are shown in Table 1.
[Evaluation criteria]
○: No aggregation of 10 or more conductive particles ×: Aggregation of 10 or more conductive particles * Initial state is ○

  As described above, in the inkjet heads (Nos. 2 to 6 and 8 to 12) prepared using the adhesive containing the conductive particles having protrusions on the surface, the conductive particles having no protrusions are used. Compared to the inkjet heads (Nos. 1 and 7) produced using the contained adhesive, both the connection resistance and the conductive aggregation were excellent.

1: Head chip 1a: Front surface 1b: Rear surface 1c: Edges 11A, 11B: Drive channels 11a, 11b, 12a, 12b: Openings 12A, 12B: Dummy channels 13A, 13B: Drive walls 14: Drive electrodes 15A, 15B: Connection electrode 2: Nozzle plate 21: Nozzle 3: Wiring substrate 3a: End 31: Adhesion region 32A, 32B: Through hole 33A, 33B: Wiring electrode 4: FPC
5: Adhesive 6: Conductive particles 6a: Protrusions 61: Organic core 62: Shell 621: Outermost layer 622: Lower layer 100: Inkjet recording apparatus 101: Conveying mechanism 101a: Conveying roller pair 101b: Conveying roller 101c: Conveying motor 102: Carriage 103: Flexible cable 104: Guide rail 10: Inkjet head P: Recording medium PS: Recording surface

Claims (17)

A head chip in which an opening of a channel and a connection electrode electrically connected to a drive electrode provided in the channel through the opening are formed on the same surface;
In an inkjet head having a wiring substrate having a wiring electrode corresponding to the connection electrode formed on a surface thereof,
The connection electrode and the wiring electrode are electrically connected by bonding the head chip and the wiring board with an adhesive containing conductive particles having protrusions. Inkjet head.   The inkjet head according to claim 1, wherein the conductive particles are core-shell particles having a shell made of a metal film having the protrusions formed on a surface of an organic core.   The inkjet head according to claim 2, wherein the conductive particles have a Young's modulus of the shell higher than that of the organic core.   The shell of the conductive particles has a lower layer made of a metal having a higher Young's modulus than Au under the outermost layer made of Au, and the lower layer forms the protrusions. The inkjet head according to 2 or 3.   The inkjet head according to claim 1, wherein at least one of the connection electrode and the wiring electrode has an oxide film on the electrode surface.   6. The ink jet head according to claim 5, wherein the height of the protrusion of the conductive particle is larger than the thickness of the oxide film.   The inkjet head according to claim 1, wherein the adhesive is a thermosetting adhesive.   The inkjet head according to claim 1, wherein the wiring board is arranged in parallel with a surface of the head chip on which the opening and the connection electrode are formed. A head chip in which an opening of a channel and a connection electrode electrically connected to a drive electrode provided in the channel through the opening are formed on the same surface;
In a method of manufacturing an ink jet head having a wiring substrate having a wiring electrode corresponding to the connection electrode formed on a surface thereof,
After bonding the head chip and the wiring substrate through an adhesive containing conductive particles having protrusions, the adhesive is cured to electrically connect the connection electrode and the wiring electrode. A method for manufacturing an ink jet head, comprising: connecting to an ink jet head.   10. The method of manufacturing an ink jet head according to claim 9, wherein the conductive particles are core-shell particles having a shell made of a metal film having the protrusions formed on a surface of an organic core.   The method of manufacturing an ink jet head according to claim 10, wherein the conductive particles have a Young's modulus of the shell higher than a Young's modulus of the organic core.   The shell of the conductive particles has a lower layer made of a metal having a higher Young's modulus than Au under the outermost layer made of Au, and the lower layer forms the protrusions. A method for producing an inkjet head according to 10 or 11.   The method of manufacturing an ink jet head according to claim 9, wherein at least one of the connection electrode and the wiring electrode has an oxide film on the electrode surface.   The method of manufacturing an ink jet head according to claim 13, wherein a height of the protrusion of the conductive particle is larger than a film thickness of the oxide film.   The method of manufacturing an ink jet head according to claim 9, wherein the adhesive is a thermosetting adhesive.   The method of manufacturing an ink jet head according to claim 9, wherein the wiring substrate is arranged in parallel with a surface of the head chip on which the opening and the connection electrode are formed. The inkjet head according to any one of claims 1 to 8,
By applying a voltage to the drive electrode via the wiring electrode and the connection electrode of the inkjet head, ink in the channel is ejected from a nozzle provided in the channel, and an image is recorded on a recording medium. An ink jet recording apparatus.

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