JP6171753B2 - Inkjet head and wiring board - Google Patents

Description

  The present invention relates to an ink-jet head and a wiring board, and more specifically, an ink-jet head and a wiring in which a head chip and a wiring board are joined with an adhesive containing conductive particles so as to make electrical connection between the electrodes. Regarding the substrate.

  As an inkjet head that records various images by discharging ink in a channel, there is a shear mode type inkjet head. In this case, a partition wall that partitions between a large number of juxtaposed channels is formed by a piezoelectric element to form a drive wall. Drive electrodes are formed on both sides of the drive wall. By applying a drive signal of a predetermined voltage to the pair of drive electrodes, the drive wall is subjected to shear deformation, and the pressure generated by the change in volume of the channel is used. Then, the ink in the channel is ejected from the nozzle.

  As a head chip used for such an ink jet head, there is a so-called harmonica type head chip. This head chip generally has a hexahedral shape, and has openings of channels serving as an ink outlet and an inlet on opposite front and rear surfaces, respectively, and has straight channels extending over both openings. In a head chip having such a straight channel, it is difficult to apply a voltage to each drive electrode because the drive electrodes on both sides of the drive wall are inside the channel and are not exposed to the outside.

  For this reason, conventionally, a connection electrode that is electrically connected to the drive electrode is individually formed on the rear surface of the head chip for each channel, and a wiring substrate in which wiring electrodes that are electrically connected to the connection electrode are arranged in parallel is provided on the head chip. A device has been devised to facilitate the application of voltage to the drive electrodes by bonding them to the rear surface so that each drive electrode is electrically drawn out of the head chip using a wiring board. The wiring board has through holes for supplying ink at positions corresponding to the respective channels, so that the ink in the manifold joined to the back side of the wiring board can be supplied into the respective channels through the through holes. (Patent Document 1).

  When the head chip and the wiring substrate are joined, the connection electrode and the wiring electrode overlap each other, whereby a gap corresponding to the sum of the thicknesses of both electrodes is formed between the head chip and the wiring substrate. The adhesive used for bonding exists in this gap, and flows in the gap by capillary force when in a low viscosity state immediately after bonding. The fluidized adhesive spreads over almost the entire area between the head chip and the wiring board, and is then cured to be bonded together.

  When the adhesive flows during the bonding, the conductive particles in the adhesive may agglomerate between the head chip and the wiring board. In particular, agglomeration of conductive particles is often observed around the opening of the channel, and this may cause short-circuiting of electrodes that are close to each other between the head chip and the wiring substrate.

  Therefore, the applicant of the present application is concerned with the short circuit occurring between the electrode on the head chip side and the electrode on the wiring board due to the aggregation of the conductive particles, the pitch between the channels, the arrangement of the wiring electrodes, the thickness of the wiring board, the Young's modulus, etc. A technique for preventing this problem by prescribing the condition is proposed (Patent Document 2).

Japanese Patent Laid-Open No. 2002-178509 (FIG. 18) JP 2012-16848 A

  The present inventors have confirmed that a short circuit between electrodes caused by aggregation of conductive particles in the adhesive occurs not only between the electrode on the head chip side and the electrode on the wiring board side, but also on the wiring board. It has been found that it may occur even between adjacent wiring electrodes arranged in parallel on the surface.

  That is, when bonding the head chip and the wiring substrate, a slightly larger amount of adhesive is usually applied to prevent the occurrence of adhesion failure. As a result, part of the adhesive that has flowed outward between the head chip and the wiring board protrudes to the outside of the head chip, and an adhesive fillet is formed on the outer periphery of the head chip. This adhesive fillet is formed across the side surface of the head chip and the surface of the wiring board. At this time, as the adhesive flowed, many conductive particles gathered in the adhesive fillet and agglomerated to cause a short circuit between the wiring electrodes passing under the adhesive fillet.

  In view of the above, the present invention provides an ink jet head in which the head chip and the wiring substrate are joined with an adhesive containing conductive particles, thereby electrically connecting the two electrodes. It is an object of the present invention to prevent a short circuit between wiring electrodes on a wiring board due to conductive particles.

  In addition, another object of the present invention is to use agglomerated conductive particles in an adhesive in a wiring board that performs electrical connection between both electrodes by bonding a head chip with an adhesive containing conductive particles. An object of the present invention is to prevent a short circuit between wiring electrodes on a wiring board.

  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 having a plurality of connection electrodes formed on the surface;
A plurality of wiring electrodes that are electrically connected to the connection electrodes and extend outside the bonding region with the head chip, and a wiring board arranged in parallel on the surface;
The adhesive that has flowed out between the head chip and the wiring board by bonding the wiring board to the surface of the head chip on which the connection electrodes are formed via an adhesive containing conductive particles. In an inkjet head in which an adhesive fillet is formed by
The inkjet head is characterized in that a first insulating film is formed on the wiring board so as to cover a portion passing through the adhesive fillet in the wiring electrode outside the bonding region.

  2. 2. The inkjet head according to claim 1, wherein the first insulating film has an extending portion formed so as to extend inside the bonding region.

  3. 3. The inkjet head according to claim 2, wherein the extending portion is formed so as to extend to the inside of the bonding region along the wiring electrode every other wiring electrode.

  4). When the particle diameter of the conductive particles is X, the thickness of the connection electrode is a, the thickness of the wiring electrode is b, and the thickness of the first insulating film is c1, c1 <a and X <a + b 4. The inkjet head as described in 3 above.

  5. The end portion of the head chip that is bonded to the extension portion via the adhesive so as to partially increase the distance between the head chip and the wiring board. The ink jet head according to 2, 3, or 4, wherein is recessed in a direction opposite to the wiring board.

  6). The wiring board has a portion with respect to the head chip such that the thickness of the portion where the extension portion is formed partially increases a distance between the wiring chip and the head chip. 5. The ink jet head according to 2, 3, or 4, wherein the ink jet head is recessed in an opposite direction.

7). The end portion of the head chip that is bonded to the extension portion via the adhesive so as to partially increase the distance between the head chip and the wiring board. Is recessed in the opposite direction to the wiring board,
The wiring board has a portion with respect to the head chip such that the thickness of the portion where the extension portion is formed partially increases a distance between the wiring chip and the head chip. 5. The ink jet head according to 2, 3, or 4, wherein the ink jet head is recessed in an opposite direction.

  8). When the particle diameter of the conductive particles is X, the thickness of the connection electrode is a, the thickness of the wiring electrode is b, and the thickness of the first insulating film is c1, c1 <a and X <a + b− 3. The inkjet head as described in 1 or 2 above, which is c1.

9. The material of the first insulating _film, the ink-jet head according to any one of 1 to 8, characterized in that either _{TiO 2, SiO 2, Al 2} O 3.

  10. 10. The inkjet head according to any one of 1 to 9, wherein the first insulating film is formed by CVD.

11. The head chip has a plurality of channel rows in which a plurality of channels are arranged in parallel,
The plurality of connection electrodes are arranged corresponding to the plurality of channels, respectively.
The wiring board is configured such that, among the plurality of wiring electrodes, the other end of the wiring electrode that is electrically connected to the connection electrode of any one of the channel rows straddles any other channel row. A second insulating film is formed on the inner side of the bonding region so as to cover the wiring electrode extending over the bonding region and straddling the channel row. The inkjet head according to any one of 10.

  12 12. The inkjet head according to 11, wherein the second insulating film is formed independently for each wiring electrode.

  13. A bonding area with the head chip and a plurality of wiring electrodes arranged in parallel so as to extend from the inside to the outside of the bonding area, and covering the wiring electrodes outside the bonding area and in the vicinity of the bonding area The wiring board used for the ink jet head according to any one of 1 to 12, wherein a first insulating film is formed.

  14 14. The wiring board according to 13, wherein the first insulating film has an extending portion formed so as to extend inside the bonding region.

  15. 15. The wiring board according to claim 14, wherein the extending portion is formed so as to extend along the wiring electrode to the inside of the bonding region every other wiring electrode.

  16. The wiring board has a portion with respect to the head chip such that the thickness of the portion where the extension portion is formed partially increases a distance between the wiring chip and the head chip. 16. The wiring board according to 14 or 15, wherein the wiring board is recessed in the opposite direction.

17. The material of the first insulating _film, a wiring board according to any one of the 13 to 16, characterized in that either _{TiO 2, SiO 2, Al 2} O 3.

  18. 18. The wiring board according to any one of 13 to 17, wherein the first insulating film is formed by CVD.

  According to the present invention, in the ink jet head in which the head chip and the wiring substrate are joined with an adhesive containing conductive particles to make an electrical connection between the electrodes, the aggregated conductive in the adhesive is obtained. It is possible to prevent a short circuit between the wiring electrodes on the wiring substrate due to the conductive particles.

  Further, according to the present invention, in the wiring board that performs electrical connection between the electrodes by bonding the head chip with the adhesive containing the conductive particles, the wiring board made of the aggregated conductive particles in the adhesive A short circuit between the upper wiring electrodes can be prevented.

1 is an exploded perspective view showing a first embodiment of an inkjet head according to the present invention. Partial rear view of the head chip in the inkjet head shown in FIG. View of the bonding state between the head chip and the wiring board as seen from the wiring board side The figure which shows a part of cross section cut | disconnected along the (iv)-(iv) line | wire of FIG. (A) is a sectional view taken along line (va)-(va) in FIG. 4, and (b) is a sectional view taken along line (vb)-(vb) in FIG. View of the bonding state between the head chip and the wiring board as seen from the wiring board side Sectional drawing which follows the (vii)-(vii) line in FIG. The partial top view of the wiring board which shows 3rd Embodiment of the inkjet head which concerns on this invention. The partial top view which expands and shows the edge part of the insulating film in FIG. Sectional drawing which shows 4th Embodiment of the inkjet head which concerns on this invention, and shows the cross section of the same site | part as Fig.5 (a) Sectional drawing which shows the other aspect of 4th Embodiment, and shows the cross section of the same site | part as Fig.5 (a) Sectional drawing which shows the further another aspect of 4th Embodiment, and shows the cross section of the same site | part as Fig.5 (a) The figure which showed 5th Embodiment of the inkjet head which concerns on this invention, and looked at the joining state of a head chip and a wiring board from the wiring board side. The figure which showed the other aspect of 5th Embodiment of the inkjet head which concerns on this invention, and looked at the joining state of a head chip and a wiring board from the wiring board side. Plan view of a wiring board showing an example of a manufacturing method of 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 where the gas in the dummy channel is heated and expanded

  Hereinafter, embodiments of the present invention will be described in detail.

(First embodiment)
FIG. 1 is an exploded perspective view showing a first embodiment of an ink jet head according to the present invention, FIG. 2 is a partial rear view of a head chip in the ink jet head, and FIG. 3 shows a bonding state between the head chip and the wiring board. FIG. 4 is a diagram showing a part of a cross section cut along line (iv)-(iv) in FIG. 3, and FIG. 5 (a) is a line (va)-(va) in FIG. (B) is sectional drawing which follows the (vb)-(vb) line | wire of FIG. 1 to 4, the adhesive existing between the head chip and the wiring board is not shown.

  In the figure, 1 is a head chip, 2 is a nozzle plate bonded to the front surface 1 a of the head chip 1, 3 is a wiring substrate bonded to the rear surface 1 b of the head chip 1, and 4 is connected to an end 3 a of the wiring substrate 3. FPC (flexible substrate).

  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. 2 is the A row, and the upper channel row is the B row. Each channel row is configured by alternately arranging drive channels 11A and 11B and dummy channels 12A and 12B. A partition wall between the adjacent drive channel 11A or 11B and the dummy channel 12A or 12B is a drive wall 13 made of a piezoelectric element.

  Each drive channel 11A, 11B and each dummy channel 12A, 12B are opened to the front surface 1a and the rear surface 1b of the head chip 1, respectively, and are formed in a straight shape extending over the front surface 1a and the rear surface 1b. A drive electrode 14 is formed on at least the surface of the drive wall 13 among the wall surfaces facing the drive channels 11A and 11B and the dummy channels 12A and 12B.

  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 driving wall 13 sandwiched between the pair of driving electrodes 14 and 14 is 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 present invention, in the head chip 1, the surface on the side where the nozzles 21 are arranged and the ink is ejected is defined as “front surface”, and the opposite surface is defined as “rear surface”. Further, a direction parallel to the front surface 1 a or the rear surface 1 b 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 in accordance with 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. In the nozzle plate 2 shown in the present embodiment, the nozzles 21 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 the drive electrode 14 in the corresponding drive channel 11A, 11B or dummy channel 12A, 12B.

  The other end of each connection electrode 15A corresponding to the drive channel 11A and the dummy channel 12A in the A row extends from the inside of each channel 11A, 12A toward one end edge 1c on the rear surface 1b of the head chip 1, and the end edge 1c. And about 200 μm apart. Further, the other end of each connection electrode 15B corresponding to the drive channel 11B and the dummy channel 12B in the B row extends toward the A row side from each of the channels 11B and 12B, and is 200 μm between the A row and the channel row. It stops at a certain interval. Accordingly, all of the connection electrodes 15A and 15B extend in the same direction from the respective channels 11A, 11B, 12A, and 12B.

  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, and is bonded to the rear surface 1b of the head chip 1 with an adhesive. At least one end portion 3a of the bonded wiring board 3 extends outside a bonding region 31 (shown by a one-dot chain line in FIG. 1) to which the head chip 1 is bonded. It protrudes greatly to the side along the line direction.

  The bonding region 31 is a region where the surface of the wiring substrate 3 is covered by the bonded 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 all the channels arranged on the rear surface 1b of the head chip 1, and in the bonding region 31 of the head chip 1 in the wiring substrate 3, the driving channel 11A of the head chip 1 is connected. , 11B, through-holes 32A, 32B for supplying ink to the drive channels 11A, 11B from the back side of the wiring board 3 are opened individually. Each through hole 32A, 32B is formed so that the opening on the head chip 1 side has the same shape as the opening on the rear surface 1b side of each drive channel 11A, 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 formed on the surface of the wiring board 3 that is a bonding surface with 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. 3, 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. In addition, 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, and the other end is the adjacent drive channel 11A in the channel row of the A column, 11A and across the channel row A, and extends toward the end portion 3a of the wiring board 3 like the wiring electrode 33A. For this reason, 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 inside of the bonding region 31 to the end portion 3a so as to alternate.

  An FPC 4, which is an example of an external wiring member, is connected to the end 3a of the wiring board 3 via, for example, an ACF (anisotropic conductive film) or the like, and electrically connected to a drive circuit (not shown). ing. 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.

  The adhesive used for joining the head chip 1 and the wiring board 3 is a conductive adhesive in which conductive particles are dispersed. As an adhesive, a normal temperature curable adhesive that cures at room temperature, a thermosetting adhesive that cures by heating to promote polymerization, an active energy ray curable adhesive that cures by accelerating polymerization by irradiation of active energy rays such as ultraviolet rays An adhesive or the like can be used.

  Among these, a thermosetting adhesive is preferable. When the thermosetting adhesive is heated to a predetermined temperature for curing after joining, the viscosity of the adhesive is temporarily reduced to easily flow, and the flow of the conductive particles in the adhesive accordingly. As a result, the agglomeration due to the conductive particles easily occurs in the adhesive fillet of the adhesive protruding from the head chip 1. For this reason, the effect of this invention is acquired notably. An epoxy adhesive is preferably used as the thermosetting adhesive, but is not particularly limited.

  Examples of the conductive particles include metal particles such as Au and Ni themselves, and those obtained by coating the surface of synthetic resin particles with a metal film such as Au and Ni by plating or the like, and any of them can be used in the present invention. .

  FIG. 5 is a cross-sectional view showing an adhesive fillet F formed by an adhesive protruding from between the head chip 1 and the wiring board 3 when the head chip 1 and the wiring board 3 are bonded to each other by an adhesive. ing. The adhesive fillet F is formed outside the bonding region 31 of the wiring substrate 3 along the outer peripheral edge of the head chip 1 so as to span the side surface of the head chip 1 and the surface of the wiring substrate 3. Reference numeral Fa in the drawing is an area where the adhesive fillet F is formed.

  The wiring electrodes 33 </ b> A and 33 </ b> B that have come out of the bonding region 31 extend under the adhesive fillet F to the end 3 a of the wiring substrate 3. An insulating film 34 (first insulating film) is formed on the surface of the wiring board 3. The insulating film 34 is formed so as to cover at least a portion passing through the adhesive fillet F in the wiring electrodes 33 </ b> A and 33 </ b> B outside the bonding region 31. As shown in FIG. 3, the edge 34 a on the bonding region 31 side of the insulating film 34 is formed linearly along the edge 31 a so as to contact the edge 31 a of the bonding region 31.

  Thus, the wiring electrodes 33A and 33B are in direct contact with the conductive particles P aggregated in the adhesive fillet F by covering the portion passing through the adhesive fillet F in the vicinity of the bonding region 31 with the insulating film 34. Is prevented. For this reason, short-circuit between the wiring electrodes 33A and 33B caused by the conductive particles P aggregated in the adhesive fillet F can be prevented.

  In the illustrated example, the insulating film 34 is formed so as to cover all the wiring electrodes 33A and 33B between the bonding region 31 and the end 3a except for the region where the FPC 4 is connected at the end 3a of the wiring substrate 3. The embodiment is shown. Therefore, the insulating film 34 covers the entire surface of the wiring electrodes 33A and 33B exposed between the head chip 1 and the FPC 4 and the space between the wiring electrodes 33A and 33B. In addition to preventing the wiring electrodes 33A and 33B from being short-circuited by the particles P, it is also possible to prevent the wiring electrodes 33A and 33B from being contaminated or from being short-circuited due to adhesion of ink or the like.

The insulating film 34 can be used as long as it can provide insulation on the wiring board 3. Specific examples of the material for the insulating film 34 include TiO ₂ , SiO ₂ , Al ₂ O _{3, and the} like.

  The insulating film 34 is preferably formed by CVD (Chemical Vapor Deposition). Since the wiring electrodes 33A and 33B protrude from the surface of the wiring substrate 3 with a predetermined thickness, when the conductive particles P aggregate, they easily come into contact with the side surfaces of the wiring electrodes 33A and 33B to cause a short circuit. Therefore, it is necessary to provide insulation not only on the upper surfaces of the wiring electrodes 33A and 33B but also on the side surfaces. According to CVD, since a uniform insulating film can be formed by wrapping around the side surfaces of the wiring electrodes 33A and 33B, occurrence of a short circuit can be effectively prevented.

  The particle diameter of the conductive particles P is the sum of the thickness of the connection electrodes 15A and 15B and the thickness of the wiring electrodes 33A and 33B so that the connection electrodes 15A and 15B and the wiring electrodes 33A and 33B can directly overlap each other. It must be smaller than the dimension. In addition, when the insulating film 34 is thickened, the conductive particles P in the adhesive that flows toward the outside of the bonding region 31 after the connection electrodes 15A and 15B and the wiring electrodes 33A and 33B overlap each other, There is also a possibility that the wiring electrodes 33A and 33B adjacent to each other inside the bonding region 31 may be short-circuited by being crushed by the portion 34a and not flowing out of the bonding region 31 but aggregating in the vicinity of the edge 34a outside the insulating film 34. is there. Therefore, when the thickness of the insulating film 34 is c1, the particle diameter of the conductive particles P is X, the thickness of the connection electrodes 15A and 15B is a, and the thickness of the wiring electrodes 33A and 33B is b, c1 <a and It is preferable that the condition X <a + b−c1 is satisfied. In addition, the particle diameter of the electroconductive particle P is an average particle diameter, and is prescribed | regulated by the equivalent volume sphere equivalent diameter.

  When the thickness of the insulating film 34 and the particle diameter of the conductive particles P satisfy the above conditions, the conductive particles in the adhesive that flow from the space between the head chip 1 and the wiring substrate 3 toward the outside of the bonding region 31 are obtained. P can flow out onto the insulating film 34 from between the adjacent wiring electrodes 33A and 33B over the edge 34a even after the connection electrodes 15A and 15B and the wiring electrodes 33A and 33B are completely overlapped. Therefore, aggregation of the conductive particles P in the vicinity of the edge 34a outside the insulating film 34 can be suppressed.

(Second Embodiment)
6 and 7 show a second embodiment of the inkjet head according to the present invention. 6 is a view of the bonding state between the head chip and the wiring board as viewed from the wiring board side, and FIG. 7 is a cross-sectional view taken along line (vii)-(vii) in FIG. Since the site | part of the same code | symbol as the inkjet head which concerns on 1st Embodiment has shown the site | part of the same structure, only the structure which is different here is demonstrated, The other description uses the description of 1st Embodiment, Description is omitted.

  In the present embodiment, the linear edge 34 a of the insulating film 34 extends in a straight line and straddles the edge 31 a of the junction region 31 to the connection electrode 15 </ b> A inside the junction region 31. As a result, the insulating film 34 has an extended portion 34 b that overlaps the bonding region 31.

  According to this, even if the aggregation of the conductive particles P occurs not only in the adhesive fillet F outside the joining region 31 but also in the vicinity of the adhesive fillet F inside the joining region 31, the wiring is extended by the extending portion 34 d. Since the short circuit between the electrodes 33A and 33B can be prevented, the short circuit prevention effect can be enhanced.

  The edge 34a of the insulating film 34 having the extended portion 34b is in a region from the edge 1c of the head chip 1 to the front of the connection electrode 15A so as not to overlap with the connection electrode 15A extending from the channel row A. In general, it may be formed so as to enter about 100 μm to 150 μm inside the bonding region 31.

  In the insulating film 34 according to the second embodiment, the extending portion 34b extends between the head chip 1 and the wiring substrate 3, and therefore the thickness c1 of the insulating film 34 is equal to the thickness a of the connection electrodes 15A and 15B. From the viewpoint of suppressing aggregation of the conductive particles P in the vicinity of the edge 34a outside the insulating film 34, at the same time, as in the first embodiment, the conductive particles need to be set to c1 <a. The relationship X <a + b−c1 is preferably satisfied in relation to the particle diameter X of P, the thickness a of the connection electrodes 15A and 15B, and the thickness b of the wiring electrodes 33A and 33B.

(Third embodiment)
8 and 9 show a third embodiment of the ink jet head according to the present invention. FIG. 8 is a partial plan view of the wiring board 3, and FIG. 9 is a partial plan view showing an enlarged edge portion of the insulating film in FIG. Since the site | part of the same code | symbol as the inkjet head which concerns on 1st Embodiment has shown the site | part of the same structure, only the structure which is different here is demonstrated, The other description uses the description of 1st Embodiment, Description is omitted.

  The insulating film 34 in the second embodiment shown in FIGS. 6 and 7 forms an extended portion 34 b that overlaps the joining region 31 by allowing the linear edge 34 a to enter the inside of the joining region 31. However, the extending portion 34b in the present embodiment extends from the edge portion 34a of the insulating film 34 so as to partially extend over the edge portion 31a of the bonding region 31 and protrude into the bonding region 31. Thus, it is formed in a comb-teeth shape.

  The extending part 34b is formed every other wiring electrode 33A, 33B arranged in parallel on the wiring board 3. Here, each extending part 34b is formed so as to cover the wiring electrode 33B of the wiring electrodes 33A and 33B. That is, each extending portion 34b covers the upper surface and the side surface of the wiring electrode 33B, and extends to the inside of the bonding region 31 along the wiring electrode 33B. However, it is not in contact with the wiring electrode 33A, and a slight gap is formed between the wiring electrode 33A so that the conductive particles P can pass therethrough.

  In this embodiment, the edge 34 a of the insulating film 34 is not in contact with the bonding region 31 of the head chip 1, and is slightly spaced from the edge 31 a of the bonding region 31. Accordingly, only each extending portion 34 b extends from the edge portion 34 a toward the inside of the bonding region 31 and straddles the edge portion 31 a of the bonding region 31. The distance between the edge 34 a of the insulating film 34 and the edge 31 a of the bonding region 31 is preferably about 10 times the particle diameter of the conductive particles P.

  According to such an insulating film 34, the conductive particles P flow toward the outside of the bonding region 31 in the adhesive between the head chip 1 and the wiring substrate 3 as indicated by arrows in FIG. 9. As a result, the fluid flows toward the outside of the joining region 31, but is not trapped and stagnated at the tip of the extending portion 34b, and the flow path passes through the gap between the extending portion 34b and the wiring electrode 33A. And flows out of the bonding region 31 and is received in the vicinity of the edge 34a of the insulating film 34. An adhesive fillet F is formed in the vicinity of the edge 34a (see FIG. 5), and a part of the conductive particles P aggregates in the adhesive fillet F.

  For this reason, even if the extending part 34b extends to the inside of the joining region 31, the conductive particles P are not trapped by the extending part 34b and aggregated inside the joining region 31. A short circuit between the wiring electrodes 33A and 33B on the inner side can be prevented. Further, as shown in FIG. 9, some of the conductive particles P in the adhesive fillet F that have flowed out of the bonding region 31 are not only insulated from the vicinity of the edge 34 a of the insulating film 34, but also insulated. Although it also aggregates on the extended portion 34b of the film 34 and the wiring electrode 33A, the extended portion 34b covers the upper surface and the side surface of the wiring electrode 33B, and thus the conductive particles in the adhesive fillet F are thus formed. Even if P aggregates on the extended portion 34b of the insulating film 34 or the wiring electrode 33A, the adjacent wiring electrodes 33A and 33B are not short-circuited.

  Further, when the rear surface 1b of the head chip 1 is not cut flat at the time of chip processing, the edge 1c of the head chip 1 may slightly protrude toward the wiring board 3 side. There is a possibility that the conductive particles P flowing toward the outside are wrinkled. In this case, if the extension part 34b which overlaps with the joining area | region 31 like a comb-like shape is formed like this embodiment, even if the electroconductive particle P crushed near the edge 1c of the head chip 1 will aggregate As described above, it is possible to prevent a short circuit between the adjacent wiring electrodes 33A and 33B.

  Also in the insulating film 34 of the present embodiment, since the comb-shaped extending portion 34b enters between the head chip 1 and the wiring substrate 3, the thickness c1 of the insulating film 34 is equal to the thickness a of the connection electrodes 15A and 15B. Therefore, it is necessary that c1 <a. However, the particle diameter X of the conductive particles P only needs to satisfy the condition of X <a + b in relation to the thickness a of the connection electrodes 15A and 15B and the thickness b of the wiring electrodes 33A and 33B. There is no need to consider the thickness. If this condition is satisfied, the conductive particles P can flow using the gap between the extending portion 34b of the insulating film 34 and the wiring electrode 33A as a flow path. This is because it is possible to prevent the adjacent wiring electrodes 33A and 33B from being short-circuited even if they are aggregated in the vicinity of the edge 34a of the insulating film 34.

  Further, since the particle diameter X of the conductive particles P does not need to consider the thickness of the insulating film 34, the particle diameter X can be increased accordingly. Since the reliability of the electrical connection is improved as the conductive particles P are larger, according to the present embodiment, the reliability of the electrical connection can be improved.

  Each comb-like extending portion 34b may also be located in the region from the edge 1c of the head chip 1 to the front of the connection electrode 15A so as not to overlap with the connection electrode 15A extending from the channel row A. In general, it may be formed so as to enter the bonding region 31 by about 100 μm to 150 μm.

  Here, each extending portion 34b is formed so as to protrude along the wiring electrode 33B, but instead, it may be formed so as to protrude along the wiring electrode 33A.

(Fourth embodiment)
FIG. 10 shows a fourth embodiment of the ink jet head according to the present invention, and is a cross-sectional view showing a cross section of the same portion as FIG. Since the parts having the same reference numerals as those of the ink jet heads according to the first and second embodiments indicate the parts having the same configuration, only the different structure will be described here, and the other description will be made in the first and second embodiments. The description is omitted and the description is omitted.

  The insulating film 34 in the present embodiment is common in that an extended portion 34b that overlaps the bonding region 31 is formed, as in the second embodiment shown in FIGS. The rear surface 1b forms a concave portion 16 with the end portion of the head chip 1 bonded to the extended portion 34b facing the extended portion 34b. The concave portion 16 is formed between the rear surface 1b and the wiring substrate 3. The difference is that the interval of is partially large. That is, the distance D between the rear surface 1b of the head chip 1 and the surface of the wiring board 3 in the recess 16 is related to the thickness a of the connection electrodes 15A and 15B and the thickness b of the wiring electrodes 33A and 33B, and D> a + b It has become. The extending part 34 b of the insulating film 34 is disposed in the recess 16.

  10, the thickness of the insulating film 34 is within the distance D between the rear surface 1b of the head chip 1 and the surface of the wiring board 3 in the recess 16, regardless of the thickness of the connection electrodes 15A and 15B. Since the film can be formed, this is a preferable embodiment from the viewpoint that the insulating film 34 can be thickened to improve the insulating property.

  The shape of the recess 16 is formed in a tapered shape that is notched obliquely so as to avoid interference with the insulating film 34, as shown in FIG. Also good.

  Further, when the insulating film 34 is made thicker in this way, instead of forming the recess 16 on the head chip 1 side as described above, an extension 34b is formed as shown in FIG. The thin part 35 is formed in the wiring board 3 by forming the wiring board 3 in a thin part so that the part of the wiring board 3 is recessed in the opposite direction to the head chip 1. However, the same effect can be obtained.

  In FIG. 12, the thin portion 35 is formed from the vicinity of the connection electrode 15 </ b> A of the head chip 1 to the end portion 3 a, but the thin portion 35 is bonded from a portion where the extending portion 34 b of the insulating film 34 is formed. What is necessary is just to be formed over the formation area Fa of the agent fillet F.

  Although not shown, in addition to forming the recess 16 on the rear surface 1b of the head chip 1 as shown in FIGS. 10 and 11, a thin portion 35 is formed on the surface of the wiring board 3 as shown in FIG. You may do it. The insulating film 34 can be made thicker.

  Also in the present embodiment, the particle diameter X of the conductive particles P only needs to satisfy the condition of X <a + b in relation to the thickness a of the connection electrodes 15A and 15B and the thickness b of the wiring electrodes 33A and 33B. There is no need to consider the thickness of the insulating film 34. Thereby, the reliability of the electrical connection of the electroconductive particle P can also be improved.

  In the present embodiment, the extending portion 34b of the insulating film 34 may be formed so that the linear edge portion 34a overlaps the bonding region 31 as shown in FIGS. Alternatively, as shown in FIGS. 8 and 9, the wiring electrodes 33 </ b> A and 33 </ b> B may be formed in a comb-like shape extending so as to protrude into the bonding region 31.

(Fifth embodiment)
FIG. 13 shows a fifth embodiment of an ink jet head according to the present invention, and is a view of a bonding state between a head chip and a wiring board as viewed from the wiring board side. Since the site | part of the same code | symbol as the inkjet head which concerns on 1st Embodiment has shown the site | part of the same structure, only the structure which is different here is demonstrated, The other description uses the description of 1st Embodiment, Description is omitted.

  In addition to the insulating film 34, another insulating film 36 (second insulating film) is formed on the wiring substrate 3 inside the bonding region 31. In the bonding region 31, the insulating film 36 passes between the drive channels 11A and 11A of the A column of the head chip 1 and straddles the channel column of the A column and the adjacent wiring electrode 33B. It is formed in a band shape so as to cover between 33B. One edge 36a of the insulating film 36 stops in front of the connection electrode 15B so as not to overlap with the connection electrode 15B of the B-row channel row, and the other edge 36b does not cover the wiring electrode 33A. Thus, it stops in front of the wiring electrode 33A. Accordingly, each through hole 32A is opened in the insulating film 36.

  Since the wiring electrodes 33B wired so as to straddle the channel rows in this manner are close to each other across the channel rows, when the aggregation of the conductive particles P occurs in the vicinity thereof, the neighboring wiring electrodes 33B, 33B There is a risk of causing a short circuit. However, by forming the insulating film 36 also in this part, such a short circuit between the wiring electrodes 33B and 33B can be prevented.

  Further, since the edge of the drive electrode 14 is exposed at the opening of the drive channel 11A and the dummy channel 12A opened on the rear surface 1b of the head chip 1, the wiring electrode 33B drives the drive channel 11A and the dummy channel 12A. A short circuit may occur due to the aggregated conductive particles P between the electrode 14 and the insulating film 36, so that the short circuit between the wiring electrode 33B and the drive electrode 14 can be prevented. Can be prevented.

  The insulating film 36 can be formed of the same material as the insulating film 34. In addition, since the insulating film 36 is formed in the bonding region 31, the thickness c2 of the insulating film 36 needs to be c2 <a in relation to the thickness a of the connection electrodes 15A and 15B. In order to avoid that some of the conductive particles P are wrinkled by the edges 36a and 36b of the 36, as in the case of the insulating film 34 in the first embodiment, the particle diameter X of the conductive particles P, the connection In relation to the thickness a of the electrodes 15A and 15B and the thickness b of the wiring electrodes 33A and 33B, it is preferable to satisfy the condition of X <a + b−c2 at the same time.

  Instead of forming the insulating film 36 in a strip shape along the A-column channel as described above, only the portion where the wiring electrode 33B straddles the A-channel channel row as shown in FIG. You may form so that it may cover separately. That is, the insulating film 36 is formed independently for each wiring electrode 33B. According to this, since a gap is formed between the insulating films 36 and 36, this gap can be used as a flow path for the adhesive and the conductive particles P. Therefore, in addition to the above effect, even if the insulating film 36 is formed thick, an effect that does not hinder the flow of the adhesive and the conductive particles P can be obtained.

  The insulating film 34 in the present embodiment may have a linearly extending portion 34b like the insulating film 34 in the second embodiment shown in FIGS. 6 and 7, or FIG. Like the insulating film 34 of 3rd Embodiment shown in FIG. 9, it may have the comb-tooth shaped extension part 34b. Further, in the present embodiment, as in the fourth embodiment, the head chip 1 may be formed with the recess 16 (FIGS. 10 and 11), and the wiring board 3 is formed with the thin portion 35. (FIG. 12).

(Other embodiments)
In the above description, the channel of the head chip 1 is exemplified by the drive channels 11A and 11B and the dummy channels 12A and 12B. However, all the channels may be drive channels that discharge ink.

  Further, the number of channel columns provided in the head chip 1 is not limited to two, and may be only one column or three or more columns. For example, an inkjet head having four channel rows can be configured by forming the inkjet head having the two channel rows described above symmetrically in FIGS. 2 and 3.

  Furthermore, in the above description, an inkjet head having a so-called harmonica type head chip 1 having a straight channel structure in which openings of the respective channels are arranged on the front surface 1a and the rear surface 1b is exemplified. An inkjet head having a head chip on the surface of which a plurality of connection electrodes corresponding to the respective channels are formed and bonding the wiring substrate to the surface on which the connection electrodes are formed with an adhesive containing conductive particles. What is necessary is just and it is not limited to what has a harmonica type head chip.

(Inkjet head manufacturing method)
Hereinafter, an example of a method for manufacturing an inkjet head will be described with reference to FIGS. Here, the inkjet head shown in the first embodiment will be described as an example, but the same can be done in other embodiments.

  FIG. 15 shows the surface of the wiring board 3. First, the connection electrodes 15A and 15B of the head chip 1 and the wiring electrodes 33A and 33B overlap the surface of the wiring substrate 3 on which the through holes 32A and 32B, the wiring electrodes 33A and 33B, and the insulating film 34 are formed. The adhesive 5 is applied so as to form a strip over the portion, and then the head chip 1 is positioned and bonded to the bonding region 31.

  Next, the dummy channels 12A and 12B opened in the front surface 1a located on the side opposite to the bonding surface of the head chip 1 with the wiring substrate 3 are sealed.

  FIG. 16 is a cross-sectional view showing a preferred method for forming this sealed state. The bonded head chip 1 and wiring board 3 are mounted between a pair of upper and lower pressure plates 6a and 6b, and a predetermined pressure is applied by being sandwiched between the pressure plates 6a and 6b. 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. 16, the adhesive 5 is not shown.

  At this time, part of the adhesive 5 that has reached the dummy channels 12A and 12B enters the dummy channels 12A and 12B through the wiring board 3. This is because the openings of the dummy channels 12 </ b> A and 12 </ b> B are blocked by the wiring board 3. On the other hand, since the drive channels 11A and 11B have through holes 32A and 32B having the same shape as the openings, the adhesive 5 travels along the wiring board 3 from the openings of the drive channels 11A and 11B to the inside. Hard to get in.

  A sheet-like sealing material 7 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 6a and 6b. The front surface 1a of the chip 1 is in contact with the front surface 1a. Generally, rubber can be used as the elastic material, and silicon rubber is particularly preferable.

  The reason for providing this sealing material 7 is as follows. In general, since the head chip 1 is manufactured by fully cutting ceramics with a dicing blade or the like, traces at the time of cutting may remain as fine irregularities on the full cut surfaces (front surface 1a and rear surface 1b). is there. In this state, it is difficult to seal the dummy channels 12A and 12B with only the flat pressure plate 6a. This problem can be improved by polishing the full-cut surface. However, even if the front surface 1a of the head chip 1 has an uneven shape by sandwiching a sealing material 7 made of an elastic material as shown in the drawing, it is bothered. The opening of the front surface 1a of the head chip 1 can be effectively sealed without performing a polishing operation.

  The openings of the dummy channels 12 </ b> A and 12 </ b> B 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 7 on the pressure plate 6b on the wiring board 3 side. The dummy channels 12A and 12B of the head chip 1 are sealed between the sealing material 7 of the pressure plate 6a and the wiring board 3, and gas (air) is sealed inside.

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

  When the adhesive 5 is a thermosetting adhesive, this heating can use heat at the time of heat curing. When the adhesive 5 is not a thermosetting type, it may be heated by an appropriate heating means such as an oven while being sandwiched between the pressure plates 6a and 6b. Here, the case where the adhesive 5 is of a thermosetting type and the above-described heating is performed using heat at the time of heat curing will be described.

  When the gas in the dummy channels 12A and 12B expands due to the heating of the head chip 1, as shown in FIG. 17, the adhesive 5 that has entered the dummy channels 12A and 12B due to the expansion of the gas is transferred to the dummy channels 12A and 12B. From the rear surface 1 b of the head chip 1 and the wiring substrate 3. Then, by curing the adhesive 5 in this state, the adhesive fillets 51 due to the adhesive 5 remaining in the openings of the dummy channels 12A and 12B are present independently at the four corners of the openings. As a result, the periphery of the openings of the dummy channels 12A and 12B is surrounded by the adhesive fillet 51 and sealed. At the same time, the inside of the dummy channels 12A and 12B is prevented from being blocked by the adhesive 5.

  As the adhesive 5 pushed out from the dummy channels 12A and 12B by the thermal expansion spreads between the head chip 1 and the wiring substrate 3, the adhesive 5 protruding from the head chip 1 causes the adhesive 5 to protrude as shown in FIG. An adhesive fillet F is formed on the surface. When the adhesive 5 is pushed out from the dummy channels 12A and 12B in this way, a large amount of the conductive particles P are easily carried to the adhesive fillet F by the flow caused by the extrusion, and the wiring electrodes 33A, The possibility of causing a short circuit between 33B is further increased. However, according to the present invention, it is possible to prevent the wiring electrodes 33A and 33B from being short-circuited by the conductive particles P aggregated in the adhesive fillet F by the insulating film 34. Effects can be obtained.

  The heating temperature and the heating time for expanding the gas need to appropriately expand the gas in the dummy channels 12A and 12B before reaching the adhesive curing temperature, and the viscosity of the adhesive 5 is not increased excessively. The temperature and the time must be such that the state can be maintained and the level does not flow after a certain amount of flow. Specific temperature and time are appropriately adjusted according to the type (curing temperature and viscosity) of the adhesive 5 used, the volume of the dummy channels 12A and 12B, the size and thermal conductivity of the head chip 1, and the like.

  After joining the head chip 1 and the wiring board 3 in this way, the nozzle plate 2 is joined to the front surface 1a of the head chip 1, and a manifold (not shown) is joined to the back side of the wiring board 3, By connecting the FPC 4 to the end 3a of the substrate 3, the ink jet head is completed.

  When a protective film such as a parylene film is formed on the surface of the drive electrode 13, the head chip 1 and the wiring substrate 3 can be bonded before the nozzle plate 2 is bonded. . When it is not necessary to form a protective film, the head chip 1 and the wiring board 3 after the nozzle plate 2 are bonded may be bonded. In this case, since the opening of the dummy channel 11b on the front surface 1a side of the head chip 1 is sealed by the nozzle plate 2, the sealing material 7 is not necessarily provided.

1: Head chip 1a: Front surface 1b: Rear surface 1c: Edge 11A, 11B: Drive channel 12A, 12B: Dummy channel 13: Drive wall 14: Drive electrode 15A, 15B: Connection electrode 16: Concavity 2: Nozzle plate 21: Nozzle 3: Wiring substrate 3a: End 31: Bonding region 31a: Edge 32A, 32B: Through hole 33A, 33B: Wiring electrode 34: Insulating film (first insulating film)
34a: Edge part 34b: Extension part 35: Thin part 36: Insulating film (second insulating film)
36a, 36b: Edge 4: FPC
5: Adhesive 51: Adhesive fillet 6a, 6b: Pressure plate 7: Seal material F: Adhesive fillet Fa: Formation area of adhesive fillet P: Conductive particles

Claims (18)

A head chip having a plurality of connection electrodes formed on the surface;
A plurality of wiring electrodes that are electrically connected to the connection electrodes and extend outside the bonding region with the head chip, and a wiring board arranged in parallel on the surface;
The adhesive that has flowed out between the head chip and the wiring board by bonding the wiring board to the surface of the head chip on which the connection electrodes are formed via an adhesive containing conductive particles. In an inkjet head in which an adhesive fillet is formed by
The inkjet head is characterized in that a first insulating film is formed on the wiring board so as to cover a portion passing through the adhesive fillet in the wiring electrode outside the bonding region.   The inkjet head according to claim 1, wherein the first insulating film has an extending portion formed so as to extend inside the bonding region.   The inkjet head according to claim 2, wherein the extending portion is formed so as to extend along the wiring electrode to the inside of the bonding region every other wiring electrode.   When the particle diameter of the conductive particles is X, the thickness of the connection electrode is a, the thickness of the wiring electrode is b, and the thickness of the first insulating film is c1, c1 <a and X <a + b The inkjet head according to claim 3, wherein the inkjet head is provided.   The end portion of the head chip that is bonded to the extension portion via the adhesive so as to partially increase the distance between the head chip and the wiring board. The ink jet head according to claim 2, wherein the ink jet head is recessed in a direction opposite to the wiring board.   The wiring board has a portion with respect to the head chip such that the thickness of the portion where the extension portion is formed partially increases a distance between the wiring chip and the head chip. 5. The ink jet head according to claim 2, wherein the ink jet head is recessed in the opposite direction. The end portion of the head chip that is bonded to the extension portion via the adhesive so as to partially increase the distance between the head chip and the wiring board. Is recessed in the opposite direction to the wiring board,
The wiring board has a portion with respect to the head chip such that the thickness of the portion where the extension portion is formed partially increases a distance between the wiring chip and the head chip. 5. The ink jet head according to claim 2, wherein the ink jet head is recessed in the opposite direction.   When the particle diameter of the conductive particles is X, the thickness of the connection electrode is a, the thickness of the wiring electrode is b, and the thickness of the first insulating film is c1, c1 <a and X <a + b− The inkjet head according to claim 1, wherein the inkjet head is c1. The inkjet head according to claim 1, wherein the material of the first insulating film is any one of TiO ₂ , SiO ₂ , and Al ₂ O ₃ .   The inkjet head according to claim 1, wherein the first insulating film is formed by CVD. The head chip has a plurality of channel rows in which a plurality of channels are arranged in parallel,
The plurality of connection electrodes are arranged corresponding to the plurality of channels, respectively.
The wiring board is configured such that, among the plurality of wiring electrodes, the other end of the wiring electrode that is electrically connected to the connection electrode of any one of the channel rows straddles any other channel row. The second insulating film is formed on the inner side of the bonding region so as to cover the wiring electrode extending outside the bonding region and straddling the channel row. The inkjet head in any one of -10.   The inkjet head according to claim 11, wherein the second insulating film is formed independently for each of the wiring electrodes.   A bonding area with the head chip and a plurality of wiring electrodes arranged in parallel so as to extend from the inside to the outside of the bonding area, and covering the wiring electrodes outside the bonding area and in the vicinity of the bonding area The wiring board used for the ink jet head according to claim 1, wherein a first insulating film is formed.   14. The wiring board according to claim 13, wherein the first insulating film has an extending portion formed so as to extend inside the bonding region.   The wiring board according to claim 14, wherein the extending portion is formed so as to extend along the wiring electrode to the inside of the bonding region every other wiring electrode.   The wiring board has a portion with respect to the head chip such that the thickness of the portion where the extension portion is formed partially increases a distance between the wiring chip and the head chip. The wiring board according to claim 14, wherein the wiring board is recessed in an opposite direction. 17. The wiring board according to claim 13, wherein the material of the first insulating film is any one of TiO ₂ , SiO ₂ , and Al ₂ O ₃ .   The wiring board according to claim 13, wherein the first insulating film is formed by CVD.

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