JP3850298B2 - Ink jet head and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inkjet head of an inkjet printer and a method for manufacturing the inkjet head.
[0002]
[Prior art]
Conventionally, an electrical connection between an ink chamber electrode formed in an ink chamber of an ink jet head and an external circuit including a driving IC is such that the external connection electrode connected to the ink chamber electrode is extended outside the ink chamber. This is done by connecting the external connection electrode and the external circuit connection electrode.
[0003]
Specifically, as shown in FIG. 10, the conventional inkjet head includes an external connection electrode 122 extending from the ink chamber electrode 121 of the actuator 120 to the flat portion 200 of the actuator 120. Electrical connection is made by connecting to a bonding wire 150, a TAB (Tape Automated Bounding) lead 160, or a flexible substrate 170 conducted to a circuit (130).
[0004]
The electrical connection method between the ink chamber electrode 121 formed in the ink chamber of the ink jet head and an external circuit including the driving IC 130 includes the following specific methods.
[0005]
As shown in FIG. 10A, when the ink chamber electrode 121 and the driving IC 130 are electrically connected using the bonding wire 150 as the external connection electrode 122, the ink chamber electrode 121 is first extended. The external connection electrode 122 thus extended is extended to the flat portion 200 of the actuator 120.
[0006]
Next, Al wedge wire bonding technology and Au wire bonding technology are used. For example, heating ultrasonic waves are applied while pressing the bonding wire 150 using a bonding capillary in a direction perpendicular to the flat main surface on the ink chamber electrode 121. Thereby, the bonding wire 150 is metal-solid diffusion bonded to the main surface of the external connection electrode 122.
[0007]
Also, as shown in FIG. 10B, when the ink chamber electrode 121 and the driving IC 130 are electrically connected by outer lead bonding using the TAB lead 160, the ink chamber electrode 121 is first formed. The extended external connection electrode 122 is extended to the flat portion 200 on the actuator 120. Next, the outer lead (TAB lead 160) of the TAB device is aligned parallel to the flat main surface of the ink chamber electrode 121 extending on the flat portion 200 of the actuator 120.
[0008]
Furthermore, solder joining is performed by melting the solder supplied in advance to the outer lead surface from the direction perpendicular to the flat main surface of the ink chamber electrode 121 by using a lead pressing tool having a heating and pressing mechanism. It is also possible to perform electrical connection using ACF (anisotropic conductive film) or ACP (anisotropic conductive paste) instead of solder bonding.
[0009]
As shown in FIG. 10C, when the ink chamber electrode 121 and the driving IC 130 are electrically connected using the flexible substrate 170, similarly to the bonding using the TAB lead 160, Solder bonding is performed by ACF or ACP.
[0010]
Next, a method for extending the ink chamber electrode 121 as described above to the flat portion 200 on the actuator 120 will be described with reference to FIG. First, a dry film resist is laminated (laminated) on one surface of a piezoelectric element polarized in the thickness direction and cured.
[0011]
Next, by using a dicer dicing blade, the piezoelectric element is cut about half in the thickness direction to be a half size, whereby the ink chamber 125 is formed. Thus, it can be seen that when the dicing blade is raised, an R portion (curved surface portion) at the rear end of the ink chamber 125 is formed.
[0012]
Thereafter, only the dry film resist film is cut from the flat portion 200 on the upper surface of the piezoelectric element. After the ink chamber array is formed in this way, a metal that is an electrode material such as Al or Cu is perpendicular to the direction in which the ink chamber 125 extends and is oblique to the bottom surface of the ink chamber 125. Diagonally deposited.
[0013]
By performing this operation from the left and right directions when the direction in which the ink chamber 125 extends is the vertical direction, the metal electrodes are formed on the side surfaces of the ink chamber partition wall 129 facing each other. The dry film resist film and the metal film formed by the shadowing effect of each ink chamber partition wall 129 are formed to a depth of about ½ in the thickness direction of the ink chamber 125 and become the ink chamber electrode 121.
[0014]
Further, the metal film is formed by the same shadowing on the R portion at the rear end portion of the ink chamber 125 and the opening portion of the dry film resist film of the flat portion 200 on the main surface side of the piezoelectric substrate. At this time, when the metal film is obliquely deposited on the flat portion 200 on the upper surface of the piezoelectric element from the two left and right directions, the dry film is overlapped so that the two metal films formed by the oblique deposition performed from the two left and right directions overlap. The film thickness and opening width of the resist film are set.
[0015]
Therefore, in the flat part 200 as the projecting surface of the piezoelectric substrate, a metal film is formed over the entire opening. As a result, electrical connection between the metal films facing each other in the ink chamber 125 in the R portion is ensured. Thereafter, a cover having the ink supply holes 140 is adhered to complete the actuator 120.
[0016]
The actuator 120 formed in this way is driven in the share mode by applying voltages in opposite phases to the ink chamber electrodes 121 formed to face the ink chamber partition walls 129 forming the ink chamber 125. It is. That is, the ink chamber partition wall is deformed into a “<” shape or a mountain shape at the boundary between the region where the ink chamber electrode 121 of the ink chamber partition wall 129 is formed and the region where the ink chamber electrode 121 is not formed. The volume in the ink chamber 125 changes. Therefore, due to a change in ink pressure in the ink chamber 125 accompanying a change in volume in the ink chamber 125, ink droplets are ejected from the minute nozzles 30 arranged at the tip of the ink chamber 125 shown in FIG. .
[0017]
[Problems to be solved by the invention]
In the structure of the conventional inkjet head shown in FIGS. 10 and 11 as described above, the active area contributing to ink ejection is provided only at the front end side of the ink chamber 125 from the ink supply hole 140. The rear end side of the ink chamber 125 including the ink supply hole 140 is an area for supplying ink. Furthermore, the ink chamber electrode 121 portion formed on the R portion and the flat portion is electrically connected to an electrode that is connected to the driving IC 130 in the flat portion 200 as one electrode by connecting two electrodes facing each other in the ink chamber. This is a part for connection.
[0018]
In such an inkjet head configuration, there is a problem that a portion other than the active area (R portion + flat portion) that originally contributes to ink ejection is very large, and the material cost is high, so that an inexpensive inkjet head cannot be manufactured.
[0019]
Further, it is necessary to extend the external connection electrode 122 from the ink chamber 125 to the flat portion 200 along the surface of a piezoelectric substrate such as PZT having a high dielectric constant. Therefore, the distance between the external connection electrodes is increased, and the capacitance increases when the piezoelectric element is considered as a capacitor insulating film. As a result, when the actuator 120 is driven, the waveform of the drive voltage applied to the actuator is disturbed, and the voltage frequency is reduced. Therefore, the inkjet head has a problem that it is difficult to drive the actuator 120 at a high speed to perform high-speed printing.
[0020]
The disturbance of the waveform of the applied drive voltage can be improved by increasing the applied drive voltage. However, the amount of heat generated by driving the actuator 120 increases by increasing the applied drive voltage. The temperature of 120 increases. As a result, there is a problem that the ink viscosity changes and stable and highly accurate printing cannot be performed. Further, the driving IC 130 to which a high voltage is applied has a problem that the cost is increased. Furthermore, when the applied voltage becomes high, it becomes difficult to reduce the power consumed by the inkjet head.
[0021]
For this reason, in a portion other than the active area of the ink chamber electrode 121 of the actuator 120, a low dielectric constant such as a Si—N film is provided between the ink chamber partition wall 129 and the ink chamber electrode 121 constituting the piezoelectric substrate. By forming the film in advance, the capacitance in the portion other than the active area is set to a level at which it can be almost ignored.
[0022]
However, for PZT (lead zirconate titanate) having a low temperature Curie point of about 200 ° C., very expensive ECR-CVD is required for forming a low dielectric constant Si—N film by a low temperature process. (Electronic Cyclotron Resonance-Chemical Vapor Deposition) equipment is required. Therefore, there is a problem that the manufacturing cost increases and an inexpensive inkjet head cannot be manufactured.
[0023]
Further, in order to solve the above problems, the region for extending the ink supply hole 140 and the ink chamber electrode 121 as shown in FIG. 12 is not formed in the direction in which the ink chamber of the piezoelectric substrate extends. There is an inkjet head. As a structure for supplying ink, an ink supply hole 141 is provided at the rear end portion of the active area in the ink chamber of the piezoelectric substrate, and the ink chamber electrode 121 extends from the side on the ink supply side to the side on the ink discharge side. The electrode is provided in a letter shape, and electrical conduction is performed between a portion of the L-shaped electrode on the ink supply side and the electrode conducted to the driving IC 130. In this case, since there is no portion other than the active area in the ink chamber of the actuator 120, the material cost of the piezoelectric element constituting the piezoelectric substrate can be reduced, but there is still a problem that an extra capacitance is formed. Remain.
[0024]
Further, the ink chamber electrode 121 is bent at 90 ° from the ink supply side surface to the ink ejection side surface of the actuator 120, and the electrode for external connection is drawn out. In this case, it is impossible to form the ink chamber electrode using the oblique vapor deposition as shown in FIG. 11 in the electrode drawing process of the external connection electrode with respect to the upper surface of the actuator 120. Further, since it is necessary to deposit a metal film on the ink chamber electrode 121 and the side surface of the actuator 120 at the same time after the actuator 120 is cut into small pieces, the manufacturing process becomes complicated.
[0025]
Further, in order to reliably form the ink chamber electrode and the external connection electrode on the upper surface of the actuator 120 and the inner surface of the ink chamber in a state where the ink chamber electrode and the external connection electrode are electrically connected, at least the oblique deposition process shown in FIG. Need twice. Further, in order to electrically isolate the plurality of external connection electrodes 122 formed on the flat portion 200 of the piezoelectric substrate, dicing or YAG (Yttrium Aluminum Garnet) can be used even if resist patterning or patterning is not performed in advance. ) Since the electrode separation process by laser is required, the manufacturing process becomes very complicated. For this reason, there is a problem that the productivity is low and the production cost is increased due to a decrease in production yield.
[0026]
In addition, the external connection electrode can be formed by a plating technique other than the above-described oblique vapor deposition. However, like the oblique vapor deposition technique, a patterning process or an electrode separation process is required, and thus the process becomes complicated. There is.
[0027]
In addition, the bent portion of the electrode extending from the inner surface of the ink chamber to the upper surface of the actuator 120 has a high risk of being disconnected in a subsequent process or handling, and there is a problem that the yield is lowered, and environmental reliability is also improved. There is a problem of being inferior.
[0028]
The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an ink jet capable of realizing high-reliability high-speed printing while suppressing an increase in driving power without increasing manufacturing costs. It is to provide a head and a manufacturing method thereof.
[0029]
[Means for Solving the Problems]
  The ink jet head of the present invention includes both an ink chamber provided so as to extend from one end to the other end on the surface of the piezoelectric substrate, and an inner surface of the ink chamber.On each ofDrive electrode provided on theElectrokineticConnected to the pole and connected to the external electrode provided outside.TheAn external connection electrode, the external connection electrode at one end of the ink chamber,It is formed by cutting the piezoelectric substrate from one end to the other end after being embedded in the piezoelectric substrate so as to be exposed as both inner surfaces of the ink chamber. The drive electrode is formed so as to be in contact with the external connection electrode exposed on each of the inner side surfaces of the ink chamber.
[0030]
According to this configuration, since the external connection electrode is formed at one end of the ink chamber as a part of the material that forms the wall forming the ink chamber, the drive IC is directly connected to the external connection electrode. Thus, it is possible to connect the external electrode, and it is possible to manufacture a small inkjet head in which a portion other than the active area of the actuator is reduced. Thereby, since the material cost of the piezoelectric substrate is reduced, a low-cost inkjet head can be provided.
[0031]
In addition, since it is not necessary to draw the external connection electrode along the surface of the piezoelectric substrate, the increase in the capacitance caused by the drawn electrode is suppressed, thereby reducing the frequency of the voltage applied to the actuator. Therefore, high-speed printing can be performed. As a result, the drive voltage can be reduced, so that the withstand voltage of the drive IC can be lowered, so that the drive IC cost can be reduced and the drive power consumption for driving the actuator can be reduced. can do.
[0033]
  Also mentioned aboveAccording to the configuration, the drive electrode and the external connection electrode can be reliably connected to each other by forming the drive electrode on the exposed surface that is cut and has little dust and the like.
[0034]
In addition, when compared with the method described in the prior art, it is possible to suppress the occurrence of cracks in the external connection electrode due to the difference in thermal expansion coefficient between the piezoelectric substrate and the external connection electrode. Problems such as disconnection of the electrical connection between the electrode and the driving IC are reduced.
[0035]
The reason for this is that, in this configuration, it is possible to use a manufacturing method in which a groove is formed in one external connection electrode to relieve stress generated due to a difference in thermal expansion coefficient, and the external connection electrode and drive are used. This is because the electrical connection between the electrodes is performed at a portion unrelated to a portion where stress is generated due to a difference in thermal expansion coefficient. Therefore, according to the present configuration, the electrical connection between the drive electrode and the external connection electrode can be ensured and deterioration with time can be reduced.
[0036]
In the ink jet head of the present invention, more preferably, the external connection electrodes are exposed on both the inner surface of the ink chamber and the bottom surface of the ink chamber.
[0037]
According to this configuration, the pair of drive electrodes facing each other in the ink chamber are electrically integrated into one by the external connection electrode. As a result, the external electrode connected to the external drive IC only needs to be connected to a pair of drive electrodes. Therefore, by reducing the number of electrical connection points by half, it is possible to suppress a decrease in yield due to poor electrical connection. As a result, the manufacturing cost of the ink jet head is reduced, and the stability of electrical connection is improved.
[0038]
In the ink jet head of the present invention, the bottom surface of the ink chamber may be formed in a shape constituting an arc.
[0039]
According to the above configuration, when the ink chamber groove machining is performed using the dicing process, the ink chamber can be formed using the R shape of the outer periphery of the blade.
[0040]
In the inkjet head of the present invention, the external connection electrode may be made of a conductive resin, or the conductive resin may be a main component.
[0041]
According to this configuration, the conductive resin is embedded in advance in a part of the piezoelectric substrate serving as the actuator, and the embedded conductive resin is cut to form a wall that forms the ink chamber in the piezoelectric substrate. Thus, it can be made part of the wall forming the ink chamber. In this way, by using a conductive resin, it is possible to cure at a curing temperature below the Curie point of the piezoelectric substrate, thus reducing the possibility of impairing the electromechanical characteristics of the piezoelectric substrate when lowered after embedding. be able to.
[0042]
Further, since the conductive resin is easy to machine, a part of the conductive resin is cut when forming the wall forming the ink chamber, but the blade wear at that time is small. In addition, the external connection electrodes made of conductive resin are formed by filling the conductive resin and then curing the conductive resin, so that the degree of freedom of shape is high and mass production using a large area actuator substrate is possible. Suitable for performing.
[0043]
In the inkjet head of the present invention, the external connection electrode may be made of a solder paste, or the solder paste may be a main component.
[0044]
According to the above configuration, by using the solder paste, it is possible to obtain an external connection electrode having high mechanical strength and capable of reliable electrical connection by metal diffusion bonding. Also, the solder paste is embedded in advance in a part of the piezoelectric substrate that becomes the actuator, and the wall that forms the ink chamber is processed in the piezoelectric substrate, so that it can be made a part of the wall that forms the ink chamber. .
[0045]
In the ink jet head of the present invention, the external connection electrode is made of a free-cutting conductive material or has a free-cutting conductive material as a main component.
[0046]
Further, by using a free-cutting conductive material, it is possible to obtain an external connection electrode having high mechanical strength without impairing the characteristics of the actuator. Also, if a free-cutting conductive material such as a carbon block is used, the free-cutting conductive material is embedded in advance in a part of the piezoelectric substrate serving as an actuator, and the wall that forms the ink chamber is processed in the piezoelectric substrate. Thus, it is possible to easily form a part of the wall that forms the ink chamber.
[0047]
In the ink head according to the present invention, an end portion of the ink chamber on the side of the external connection electrode is filled with a nonconductive resin.
[0048]
According to this configuration, the mechanical strength of the external connection electrode and the ink chamber partition can be increased. Further, if the fillet is formed along the direction in which the ink chamber extends with the non-conductive resin filled in the ink chamber, it is possible to prevent air from being caught in the ink chamber. Furthermore, since the non-conductive resin is easy to control the thermal expansion coefficient by adding a silica agent, etc., if a non-conductive resin close to the thermal expansion coefficient of the piezoelectric substrate serving as the actuator is used, the non-conductive resin can be driven with Occurrence of peeling between the electrodes can also be suppressed.
[0049]
In the ink jet head of the present invention, the end portion of the ink chamber on the external connection electrode side is filled with a conductive resin.
[0050]
According to this configuration, the mechanical strength between the external connection electrode and the ink chamber partition can be increased. In addition, if the fillet is formed along the direction in which the ink chamber extends with the conductive resin filled in the ink chamber, it is possible to prevent air from being caught in the ink chamber. Furthermore, the conductive resin enables electrical connection between the drive electrodes facing each other, and in addition to electrically connecting the electrode connected to the external drive IC to the external connection electrode. It is also possible to electrically connect to a conductive resin filled in the ink chamber. Therefore, the reliability of the electrical connection between the external drive IC and the drive electrode of the inkjet head can be further enhanced.
[0053]
An ink jet head manufacturing method according to the present invention is an ink jet head manufacturing method including an ink chamber provided so as to extend from one end to the other end on a surface of a piezoelectric substrate. A step of forming, a step of embedding an external connection electrode material to be an external connection electrode connected to an external electrode provided outside the piezoelectric substrate in the counterbore, and a part of the external connection electrode material The electrode for external connection is cut to cut the groove for forming the ink chamber, and the drive electrode is in contact with the electrode for external connection and on the inner surface of the groove constituting the ink chamber. Forming a process.
[0054]
In this manufacturing method, an ink jet head capable of obtaining the same effect as the above-described ink jet head can be manufactured.
[0055]
In the ink jet head manufacturing method of the present invention, the counterbore is formed by sandblasting.
[0056]
According to this manufacturing method, since the counterbore hole is formed by sandblasting, a large amount of a large-area piezoelectric substrate can be processed at a time, and thus the manufacturing cost can be reduced. In addition, since the counterbore hole can be substantially hemispherical, the external connection electrode can be easily embedded.
[0057]
In the ink jet head manufacturing method of the present invention, the grooves constituting the ink chamber are cut by dicing in a direction perpendicular to the main surface of the piezoelectric substrate provided with counterbore holes.
[0058]
According to this manufacturing method, the dicing blade having a thickness of about the ink chamber groove rotated at high speed can be lowered vertically to the thickness direction of the piezoelectric substrate serving as the actuator to form the groove. As a result, it is possible to easily control the shape of the ink chamber, such as forming the one end of the ink chamber deeper and the other end shallower by utilizing the R shape of the blade.
[0059]
In addition, by performing such a manufacturing method, the load on the blade is small and the wear of the blade is suppressed, so that the manufacturing cost can be reduced and the height accuracy of the wall forming the ink chamber is improved. An ink jet device can be provided.
[0060]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an inkjet head according to an embodiment of the present invention and a manufacturing method thereof will be described in detail with reference to the drawings.
[0061]
(Constitution)
The configuration of the ink jet head according to the present embodiment will be described with reference to FIGS. FIG. 1 is a cross-sectional view of an inkjet head. In the drawing, the right side is the ink droplet ejection side (head front end side), and the left side is the external connection electrode side (head rear end side).
[0062]
The actuator 1 made of PZT (lead zirconate titanate) polarized in the thickness direction (vertical direction in FIG. 1) of the ink jet head according to the present embodiment has a plurality of grooves formed in the direction perpendicular to the paper surface. And an ink chamber 12 separated by an ink chamber partition wall 11. The depth of the groove of the ink chamber 12 is the deepest on the head front end surface side (right side in the figure), and gradually and gradually (R-shaped) in a curve as it goes to the head rear end side (left side in the figure). Accordingly, the height of the ink chamber partition wall 11 is also lowered accordingly.
[0063]
The cover 2 made of ceramic is gradually depressed from the end of the driving unit 100 on the head front end side (right side in the drawing) toward the end of the non-driving unit 101 on the head rear end side (left side in the drawing). In the driving unit 100, the surface of the cover 2 is bonded to the actuator 1 with an epoxy adhesive.
[0064]
In the ink jet head of the present embodiment, the top portion 13 of the ink chamber partition 11 and the side surface of the cover 2 are bonded, and the portion forming the ink chamber 20 surrounded by the four sides by the bonding is the driving portion 100 ( The other area is the non-driving part 101. In addition, when the II section of FIG. 1 is seen, the drive part 100 looks like a structure like FIG.
[0065]
In the non-driving portion 101, the top 13 of the ink chamber partition 11 is not bonded to the cover 2, and the ink chamber 12 is open on the upper side of the ink chamber partition 11. The space between the first ink chamber 12 and the ink chamber 12 serves as a first common ink chamber 20.
[0066]
A drive electrode 14 is formed from the drive portion 100 to the non-drive portion 101 at approximately the upper third of the side surface of the ink chamber partition wall 11. Further, the drive electrode 14 is electrically connected to the external connection electrode 15 at the head rear end (left side in the figure) of the actuator 1.
[0067]
A flexible substrate 4 connected to an external drive IC (not shown) is electrically connected to the external connection electrode 15 via an anisotropic conductive film 40. The flexible substrate 4, the actuator 1, and the head rear end surface of the cover 2 (left end surface in the drawing) are formed by plastic injection molding so as to close the first common ink chamber 20 opened toward the rear end surface side. A manifold 5 for constituting the second common ink chamber is bonded.
[0068]
Ink is supplied in the order of an ink tank (not shown), the manifold 5, the first common ink chamber 20, the ink chamber 12 of the non-driving portion 101, and the ink chamber 12 of the driving portion 100. The waveform of the drive voltage supplied by the external drive IC propagates in the order of the flexible substrate 4, the anisotropic conductive film 40, the external connection electrode 15, the drive electrode 14 of the non-drive portion 101, and the drive electrode 14 of the drive portion 100. Is done.
[0069]
Finally, a high-frequency voltage (potential difference) is applied between the electrodes provided on both sides of each ink chamber partition wall 11 of the driving portion 100 so that the ink chamber partition walls 11 are in opposite phases. Due to the deformation of the body in a shear mode, it deforms and vibrates into a "<" shape or an inverted "<" shape or a mountain shape, and the ink in the ink chamber 12 is opened to the nozzle plate 3 by the pressure vibration wave generated at that time. Are ejected as ink droplets from the nozzle holes 30.
[0070]
In the ink jet head of the present embodiment, the thickness of the actuator 1 in the polarization direction is 0.9 mm, the thickness of the cover 2 is 2 mm, and the height (ink chamber depth) of the ink chamber partition 11 at the head front end surface is 300 μm. The height of the ink chamber partition wall 11 at the rear end surface of the head is 50 μm. The width of the ink chamber 12 is 80 μm, and a plurality of ink chambers 12 are arranged in a direction perpendicular to the paper surface at a pitch of 170 μm.
[0071]
Next, the configuration of the head rear end of the ink jet head according to the present embodiment will be described.
[0072]
FIG. 3 is a perspective view of the rear end portion of the head. In the ink jet head of the present embodiment, the external connection electrode 15 is made of a conductive resin formed by curing a conductive adhesive containing a minute metal filler in an epoxy adhesive.
[0073]
The external connection electrode 15 made of a conductive resin has a substantially elliptical semicircular shape with the short side in the direction perpendicular to the groove (left and right in the figure) when viewed from the top side (arrow X direction) of the ink chamber partition wall 11. ing. On the other hand, when viewed from the head rear end face side (arrow Y direction), the ink chamber partition 11 has an almost elliptical semicircular shape with the height direction as the long side.
[0074]
The external connection electrodes 15 are embedded in the actuator 1 in the direction perpendicular to the grooves (left and right in the figure) at substantially the same pitch as the chopping pitch 51 of the ink chambers 12 and have the same number or more as the number of ink chambers 12. The external connection electrode 15 is electrically independent via the actuator 1.
[0075]
In the vicinity of the center of the external connection electrode 15, a shallow groove, which is the terminal portion of the ink chamber 12, is cut, and the shallow groove depth 52 is smaller than the thickness 53 of the external connection electrode 15 at the head rear end surface. . Accordingly, in the vicinity of the rear end of the head, the three sides of the ink chamber 12 which are shallow groove portions are constituted by the external connection electrodes 15.
[0076]
Since the depth 52 of the shallow groove is one sixth of the depth of the ink chamber 12 of the driving portion 100, the driving electrode 14 formed to a depth of about one third of the upper depth of the ink chamber partition wall 11 is the head. It is formed along the entire inner surface of the shallow groove at the rear end, and the drive electrode 14 and the external connection electrode 15 are electrically connected.
[0077]
At the rear end of the head, the ink chamber partition wall 11 is a piezoelectric material in which the conductive resin portion 15 b of the external connection electrode 15 adjacent to the conductive resin portion 15 a of one external connection electrode 15 serves as the base material portion 110 of the actuator 1. It has a sandwich structure in which elements are sandwiched, and adjacent external connection electrodes 15 are insulated from each other by piezoelectric elements by the base material portion 110 of the actuator 1.
[0078]
In other words, the drive electrodes 14 on both side surfaces in the individual ink chambers 12 are formed by forming the external connection electrodes 15 that are part of the ink chamber partition walls 11 in the shallow groove portion at the rear end of the head. It is electrically connected to each external connection electrode 15. Further, the drive electrodes 14 facing each other through the ink chamber 12 are connected so as to be electrically conducted from the external connection electrode 15.
[0079]
Next, the external connection electrodes 15 are patterned in the flexible substrate 4 at substantially the same pitch as the ink chamber cutting pitch 51 with respect to the exposed surfaces 16 of the individual external connection electrodes 15 on the rear end surface of the head. Each of the line electrodes 41 is connected via an anisotropic conductive film 40. The copper wire electrode 41 is an electrode that is electrically connected to an external drive IC 130 (not shown), and the external drive IC 130 and the drive electrode 14 of the inkjet head are electrically connected by the above configuration.
[0080]
In the ink jet head of the present embodiment, the ink chamber cutting pitch 51 is 170 μm, the shallow groove depth 52 is 50 μm, the maximum thickness 53 of the external connection electrode 15 is 100 μm, and the external connection electrode 15 in the direction perpendicular to the groove is used. The width 54 is 100 μm.
[0081]
(Production method)
A method for manufacturing the ink jet head of the present embodiment will be described in detail with reference to FIGS. FIG. 4 shows the structure of the actuator wafer before the ink chamber is formed. This actuator wafer 6 is a 0.9 mm thick PZT (lead zirconate titanate) substrate polarized in the thickness direction, and this substrate is then cut after the cover wafer is bonded, so that a plurality of inkjet heads are formed. It becomes a structural member.
[0082]
On the actuator wafer 6, external connection electrode portions 60 are regularly arranged at an approximately equal pitch with the ink chamber chopping pitch 51 in the X direction in the figure and at an interval of about twice the length of the inkjet head in the Y direction in the figure. Arranged and embedded, there is no step between the actuator wafer 6 and the external connection electrode portion 60, and the surface of the actuator wafer 6 and the surface of the external connection electrode portion 60 are a continuous plane. Yes.
[0083]
The external connection electrode portion 60 is embedded in the actuator wafer 6 in an elliptical hemisphere having a short side in the X direction in the drawing, and the exposed surface of one external connection electrode portion 60 on the actuator wafer 6 is embedded. The width is 100 μm in the X direction and 600 μm in the Y direction. Further, the external connection electrode 60 is buried deepest at the center point of the ellipse with respect to the thickness direction of the actuator wafer 6, and the maximum depth is 100 μm.
[0084]
The aforementioned actuator wafer 6 is manufactured by the following process. First, a first step of laminating a dry film resist film (DFR) on a PZT substrate polarized in the thickness direction is performed. The DFR film is a resist film for an exposure pattern having a thickness of about 15 to 30 μm. Further, the DRF film can be applied with a uniform film thickness by thermocompression bonding onto the substrate with a hot roller at 80 to 100 ° C.
[0085]
Next, a second step of patterning a portion to be the external connection electrode portion 60 into a DFR film is performed. In the ink jet head manufacturing method of the present embodiment, only the portion corresponding to the external connection electrode portion 60 is shielded with UV light by using a metal mask to expose the PZT substrate using a DFR film whose UV irradiation portion is altered. After that, the unmodified part of the DFR film is removed using a stripping solution. Thereby, a DRF film having a pattern in which only the DFR film in the vicinity of the position to be the external connection electrode portion 60 is selectively removed is formed.
[0086]
Next, a third step of forming a counterbore at a location to be the external connection electrode portion 60 by sandblasting is performed. In sandblasting, fine particles of alumina or SiC (diameter of several tens of μm) are sprayed at a high speed on the surface where the DFR film is applied to the surface, so that the portion without the DFR film of the actuator wafer 6 is countered. A depression is formed.
[0087]
In the ink jet head manufacturing method of the present embodiment, a counterbore with a maximum depth of 100 μm having an elliptical opening with a short side of 100 μm and a long side of 600 μm is formed on the actuator wafer 6 by sandblasting. The DFR film after completion of sandblasting is swelled and peeled using an organic solvent.
[0088]
Next, the 4th process of embedding the substance used as the electrode part 60 for external connection in the hollow of the hollow formed at the 3rd process is performed. In the ink jet head manufacturing method of the present embodiment, a conductive adhesive containing about 80% by weight Ag filler (diameter of several μm) in an epoxy adhesive is poured and then cured to form a conductive resin. The electrode part which consists of is formed.
[0089]
As a method of pouring the conductive adhesive containing Ag filler (diameter of several μm), it is poured by applying a single character on the XX line of FIG. 4 using a screen printing method or a dispenser. An easy method such as this can be considered. In addition, after apply | coating a conductive adhesive to one character, the unnecessary conductive adhesive which remained on the board | substrate surface is removed with a squeegee.
[0090]
Next, both sides or one side of the actuator wafer 6 is ground, unnecessary conductive resin adhering to portions other than this portion is removed, and the height of the surface of the external connection electrode portion 60 and the height of the surface of the actuator wafer 6 are determined. Match. The actuator wafer 6 shown in FIG. 4 is completed through the first to fourth steps.
[0091]
Next, the 5th-7th process of the manufacturing method of the inkjet head of this Embodiment is demonstrated using FIG. 5 and FIG. 5 and 6 show a part of the actuator wafer 6 after the seventh step.
[0092]
First, after the fourth step, a fifth step of applying DFR to the side of the actuator wafer 6 where the external connection electrode portion 60 is exposed is performed. In the fifth step, as in the first step, after the DFR is applied onto the wafer using a hot roller, the entire surface of the DFR is irradiated with ultraviolet rays to alter the DFR.
[0093]
Next, a sixth step of forming a groove to be the ink chamber 12 using a dicing device is performed. In the ink jet head manufacturing method according to the present embodiment, the blade rotating shaft is moved to the chopper processing position 61 (Y direction in FIG. 6) while rotating the dicing blade having the same thickness as the groove constituting the ink chamber at a high speed. At the center position between the adjacent external connection electrodes 60 and at the center position of each external connection electrode 60 in the X direction) from the wafer normal direction to the thickness direction. Then, after the actuator wafer 6 is cut by 300 μm in the depth direction at the chopper processing position 61, the dicing blade is raised in the normal direction of the actuator wafer 6. This operation is performed at a plurality of chopper machining positions on the actuator wafer 6, and the plurality of ink chambers 12 are cut into the actuator wafer 6.
[0094]
In the inkjet head manufacturing method of the present embodiment, chopper processing is performed using an electroformed blade having a diameter of 51 mm and a thickness of 75 μm at a blade rotation speed of 40000 rpm and a blade approach speed of 3 mm / s.
[0095]
By this chopper processing, the depth of the ink chamber 12 gradually decreases due to the R shape of the blade from the chopper processing position 61 in the ± Y direction, and the ink chamber depth at a location 4 mm away from the chopper processing position 61 is about. 50 μm. The ink chamber 12 and the ink chamber partition wall 11 are formed by this chopper processing, but the DFR film remains on the partition top portion 13 of the ink chamber partition wall 11.
[0096]
Next, the seventh step of forming the drive electrode 14 in the upper half of the side surface of the ink chamber partition wall 11 (about the maximum height) is performed. In the ink jet head manufacturing method of the present embodiment, the copper film was deposited twice from the directions of arrows 300 and 400 in the figure using a vacuum deposition apparatus.
[0097]
It is to be noted that by depositing a copper film from the oblique direction with respect to the main surface of the actuator wafer 6 in the direction in which the groove extends (perpendicular to the Y direction in FIG. 6), the adjacent ink chambers are formed. Using the shadowing effect of the partition wall 11, the drive electrode 14 is formed only between the upper half and the lower half of the ink chamber partition wall 11. Therefore, the width of the drive electrode 14 can be easily determined experimentally using the opening width of the groove of the ink chamber 12 and the vapor deposition incident angle as parameters.
[0098]
By this step, a copper film is also formed on the DFR film on the top 13 of the ink chamber partition wall 11. Next, the DFR is peeled off using an organic solvent, and at the same time, the copper film on the DFR on each wall top 13 is also peeled off.
[0099]
Next, the 8th and 9th process of the manufacturing method of the inkjet head of this Embodiment is demonstrated using FIG.
[0100]
After the seventh step, an eighth step of bonding the actuator wafer 6 and the cover wafer 7 is performed. The cover wafer 7 is formed by sand blasting in a portion where a cover recess 70 having a large area opening with a short side of about 5 mm and a long side of about 10 mm becomes the rear end of the head, and the cover recess 70 is the first common. It plays the role of the ink chamber 20.
[0101]
After alignment is performed so that the center position of the cover recess 70 of the cover wafer 7 is positioned at the center of the external connection electrode portion 60 of the actuator wafer 6, the cover wafer 7 and the actuator wafer 6 are bonded with an epoxy resin adhesive. Are bonded to produce a head chip wafer 8 as shown in FIG.
[0102]
Next, a ninth step of subdividing the head chip wafer 8 to manufacture head chips is performed. In the ink jet head manufacturing method of the present embodiment, the head chip wafer 8 is manufactured by cutting the head chip wafer 8 at the dicing line 80 in FIG. 7 using a dicing apparatus.
[0103]
(Another embodiment)
The feature of the ink jet head of the present embodiment is that "in connecting the ink chamber electrode to the external driving IC, the ink substrate and the driving electrode are not formed, but the external connecting electrode drawn out to the outside is not formed. A member that is an electrode for external connection is provided in advance.
[0104]
In the ink jet head of the present embodiment, an example is shown in which the ink chamber at the front end of the head is deep and the ink chamber at the rear end is shallow using the R shape of the dicing blade. However, such an ink chamber shape is not necessarily required. If the external connection electrode is provided so as to form the ink chamber partition wall, the external connection electrode and the external electrode can be electrically connected. For example, even if the ink chamber is formed using a parting groove having a constant depth, the ink chamber has the same characteristics as those of the ink jet head of the present embodiment described above. The same effect as that obtained can be obtained.
[0105]
In the ink jet head of the present embodiment, the height of the ink chamber 12 at the front end of the ink jet head is 300 μm, and the height of the ink chamber 12 at the rear end of the head is 50 μm. The present inventors have found that the height of the ink chamber 12 at the front end of the ink jet head is about twice the ink chamber cut pitch 51, and the width of the drive electrode 14 is 4 minutes of the height of the ink chamber 12 at the front end of the head. It has been found that the driving characteristics of the ink jet head are good in the range of 1 to 1/2. Further, the width of the drive electrode 14 is desirably a size between a half or more of the ink chamber cut pitch 51 and the same level as the ink chamber cut pitch 51.
[0106]
On the other hand, in the sandblasting process in which the recessed portion is formed in the actuator wafer 6, only the cutting to the same depth as the width of the recessed portion can be performed, and the insulating region between the adjacent external connection electrodes 15 can be formed. In consideration of the width, the width of the recess in the direction in which the external connection electrodes 15 are arranged is desirably 1/2 to 4/5 of the ink chamber cut pitch 51, and the depth of the external connection electrodes 15 Is preferably 1/2 to 4/5 of the ink chamber cutting pitch 51 at the maximum.
[0107]
By setting the depth of the ink chamber 12 at the rear end portion of the ink jet head to be half or less of the ink chamber cutting pitch 51, the external connection electrode 15 is not divided by the groove of the ink chamber 12. It becomes possible to electrically connect the drive electrodes 14 facing each other via the ink chamber 12.
[0108]
Further, by setting the depth of the ink chamber 12 to ¼ or less of the ink chamber cutting pitch 51 at the rear end portion of the ink jet head, the two drive electrodes 14 facing the ink chamber 12 can be Since it is vapor-deposited on the entire inner periphery of the groove at the rear end of the head and contacts the external connection electrode 15, the opposing drive electrodes 15 can be gathered together as one electrode. Further, since the exposed area of the external connection electrode 15 on the rear end face side of the inkjet head can be increased, the reliability of electrical connection between the drive electrode 14 and the external connection electrode 15 is increased.
[0109]
In addition, on the surface of the external connection electrode 15 that extends in the thickness direction of the piezoelectric substrate, it is possible to make contact with the copper wire electrode 41 that is electrically connected to the external drive IC. Therefore, the width of the copper wire electrode 41 that is electrically connected to the external driving IC can be reduced. In addition, short-circuiting between adjacent external connection electrodes 15 without strict alignment when connecting the copper wire electrode 41 electrically connected to the external connection electrode 15 and the external drive IC to the external connection electrode 15. The risk of this is reduced.
[0110]
In the ink jet head of the present embodiment, as the depth of the ink chamber 12 at the rear end of the ink jet head is shallower, the effect of reducing the risk of short-circuiting between adjacent external connection electrodes 15 is greater.
[0111]
In the ink jet head of the present embodiment, a conductive resin obtained by curing a conductive adhesive is used as the material of the external connection electrode 15, but the present invention is not limited to this.
[0112]
For example, a low-melting-point solder paste having a melting point of 200 ° C. or lower is poured into a hollow portion on the actuator wafer 6 instead of the conductive adhesive, and after cooling and hardening, unnecessary portions are removed by grinding, similarly to FIG. Actuator wafer 6 can be obtained. By using a solder paste as the external connection electrode 15, the drive electrode 14 is formed on a solder paste that is a metal material, so that electrical connection between the drive electrode 14 and the external connection electrode 15 is achieved. There is an advantage of improving the reliability.
[0113]
In addition, in the electrical connection between the external connection electrode 15 and the copper wire electrode 41 that is electrically connected to the external drive IC, the mechanical strength of the external connection electrode 15 is high and the copper wire electrode 41 is the external connection electrode. When contacting 15, the possibility that the external connection electrode 15 is damaged due to the contact is reduced. In addition, for example, electrical connection by an inexpensive and reliable metal diffusion bonding method such as wire bonding can be performed on the external connection electrode 15, so that the electrical connection between the external connection electrode 15 and the external electrode is improved.
[0114]
Further, a free-cutting conductive material such as carbon black may be used as the external connection electrode 15. For example, after forming a recessed portion on the channel wafer in the same manner as the ink jet head of the above-described embodiment, by bonding a carbon black having substantially the same shape as the recessed shape, and grinding unnecessary portions, A channel wafer similar to the inkjet head manufacturing method shown in FIG. 4 can be formed.
[0115]
Thus, by using a free-cutting conductive material as the material of the external connection electrode 15, it is not necessary to expose the actuator wafer to a high temperature process as compared with the case of using a conductive adhesive or solder paste. Therefore, it is possible to obtain the external connection electrode 15 having a high mechanical strength without impairing the characteristics of the actuator 1.
[0116]
Further, by using a free-cutting conductive material as the material of the external connection electrode 15, the grooves in the ink chamber 12 are cut as compared with the case where a conductive adhesive, solder paste, or the like is used for the external connection electrode. Since the blade friction in the process is reduced and the shape of the groove of the ink chamber 12 can be easily controlled, it is possible to obtain a high-performance inkjet head with little variation in ejection for each channel. Further, since the number of blade replacements may be small, the manufacturing cost can be reduced.
[0117]
In the ink jet head of the present embodiment, the drive electrode 14 is exposed in the groove at the rear end of the ink jet head, but the present invention is not necessarily limited thereto. The inventors have also manufactured an inkjet head in which a conductive resin or a non-conductive resin is embedded in a groove at the rear end of the inkjet head.
[0118]
In such an ink jet head, for example, after forming a groove in the ink chamber 12, a conductive adhesive or a non-conductive adhesive is applied to the external connection electrode 15 on the external connection electrode 15 in the X direction in FIG. It is applied and allowed to settle in the groove and then cured. Thereafter, unnecessary portions of the applied conductive resin can be ground, and the actuator wafer can be bonded and cut in the same manner as the ink jet head of the above-described embodiment.
[0119]
In addition, as shown in FIG. 8, when the resin to be poured is a non-conductive adhesive containing a non-conductive resin 90, an external connection electrode is applied onto the actuator wafer using a dispenser, and the actuator wafer and the cover are covered. It is also possible to apply an adhesive for bonding the wafer and bond the actuator wafer and the cover wafer simultaneously with the curing of the resin.
[0120]
By doing so, since the external connection electrode 15 is molded with the non-conductive resin 90 in the ink chamber 12 on the rear end surface of the head, the mechanical strength of the external connection electrode 15 is increased. Therefore, when the copper wire electrode 41 electrically connected to the external connection IC is brought into contact with the rear end surface side of the ink jet head of the external connection electrode 15, the possibility that the external connection electrode 15 is damaged is reduced. Increases nature.
[0121]
Further, by filling the rear end portion of the inkjet head with the non-conductive resin 90, the fillet having a gentle curve from the rear end portion to the front end portion of the inkjet head in the ink chamber 12 of the non-driving portion 101 is obtained. Is formed. When the non-conductive resin 90 is not filled, a rectangular space is generated by the copper wire electrode 41 connected to the groove of the ink chamber 12 at the rear end portion of the ink jet head and the external driving IC, and becomes an air reservoir. Although there is a possibility, filling the non-conductive resin 90 and forming the fillet in the direction in which the groove extends can prevent the air from being caught due to the air pool.
[0122]
The non-conductive resin 90 can be easily filled with a resin having a thermal expansion coefficient comparable to that of the actuator portion because the thermal expansion coefficient can be easily controlled by an additive such as silica. As a result, even in the case of long-term use, the occurrence of peeling due to the difference in thermal expansion coefficient between the external connection electrode and the actuator substrate is suppressed.
[0123]
On the other hand, as shown in FIG. 9, when the resin to be poured is the conductive resin 95, the degree of freedom is small compared to the non-conductive resin in terms of controlling the thermal expansion coefficient. In addition, since the cut surface of the conductive resin 95 is exposed, the exposed surface can be in contact with the copper wire electrode 41 that is electrically connected to the external driving IC. Therefore, the embedded conductive resin 95 serves as an auxiliary electrode of the external connection electrode 15 and can increase the contact area between the copper wire electrode 41 and the external connection IC as a whole. This increases the stability of the electrical connection.
[0124]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
[0125]
【The invention's effect】
According to the configuration of the ink-jet head of the present invention, it is possible to connect the electrode directly connected to the driving IC to the external connection electrode, and manufacture a small-sized ink-jet head with few portions other than the active area of the actuator. It becomes possible to do. Thereby, since material cost is reduced, a low-cost inkjet head can be provided.
[0126]
According to the method for manufacturing an ink jet head of the present invention, after forming holes with substantially the same pitch as the partition walls of the plurality of ink chambers at the locations where the plurality of grooves of the plurality of ink chambers are cut off on the piezoelectric substrate. An ink jet head that can obtain the same effect as that of the ink jet head described above can be easily manufactured by embedding a material to be an external connection electrode in the hole and cutting a plurality of grooves in the plurality of ink chambers. It becomes possible.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an inkjet head according to an embodiment.
FIG. 2 is a cross-sectional view taken along the line II of FIG.
FIG. 3 is a perspective view of a rear end portion of the inkjet head according to the embodiment.
4A and 4B are diagrams for explaining the actuator wafer before forming the ink chamber according to the embodiment, where FIG. 4A is a plan view of the actuator wafer, and FIG. 4B is a sectional view taken along line YY in FIG. is there.
FIG. 5 is a diagram for explaining a state of a channel wafer before forming ink chamber grooves.
FIG. 6 is a diagram for explaining a state of the channel wafer before forming ink chamber grooves.
FIG. 7 is a view for explaining a state of the head chip wafer before a cross section of the head chip.
FIG. 8 is a perspective view of a rear end portion of an inkjet head according to another embodiment.
FIG. 9 is a perspective view of a rear end portion of an ink jet head according to another embodiment.
FIG. 10 is a diagram for explaining the structure of a conventional inkjet head.
FIG. 11 is a diagram showing an electrode lead structure of an external connection electrode according to the prior art.
FIG. 12 is a diagram for explaining the structure of a conventional inkjet head.
[Explanation of symbols]
1 Actuator, 2 Cover, 3 Nozzle plate, 4 Flexible substrate, 5 Manifold, 6 Actuator wafer, 7 Cover wafer, 8 Head chip wafer, 11 Ink chamber partition, 12 Ink chamber, 13 Top of the ink chamber partition, 14 Drive electrode , 15 External connection electrode, 16 Exposed surface of connection electrode, 20 First common ink chamber, 30 Nozzle hole, 40 Anisotropic conductive film, 41 Copper wire electrode, 51 Ink chamber cut pitch, 52 Shallow groove depth 53, external electrode thickness, 54 external connection electrode width, 60 external connection electrode portion, 61 chopper machining position, 70 cover recess, 80 dicing line, 100 driving portion, 101 non-driving portion, 110 actuator base portion, 120 Actuator, 121 Ink chamber electrode, 122 External connection electrode, 13 0 Driving IC.

Claims (11)

An ink chamber provided to extend from one end to the other end on the surface of the piezoelectric substrate;
Drive electrodes provided on each of both inner surfaces of the ink chamber;
Is connected to該駆electrokinetic pole, and an external connection electrode connected to an external electrode provided externally,
The piezoelectric substrate from the one end to the other end after being embedded in the piezoelectric substrate so that the external connection electrode is exposed at both ends of the ink chamber as both inner surfaces of the ink chamber. Is formed by cutting
The ink jet head, wherein the drive electrode is formed so as to be in contact with the external connection electrode exposed on each of both inner side surfaces of the ink chamber . 2. The ink jet head according to claim 1 , wherein the external connection electrodes are exposed on both an inner surface of the ink chamber and a bottom surface of the ink chamber. The inkjet head according to claim 1 , wherein a bottom surface of the ink chamber is formed in a shape that forms an arc. 4. The inkjet head according to claim 1 , wherein each of the external connection electrodes is made of a conductive resin or contains a conductive resin as a main component. The ink jet head according to any one of claims 1 to 3 , wherein the external connection electrode is made of a solder paste or mainly composed of a solder paste. The inkjet head according to any one of claims 1 to 3 , wherein the external connection electrode is made of a free-cutting conductive material or a free-cutting conductive material as a main component. The inkjet head according to any one of claims 1 to 6 , wherein an end portion of the ink chamber on the side of the external connection electrode is filled with a nonconductive resin. The inkjet head according to claim 1 , wherein a conductive resin is filled in an end portion of the ink chamber on the side of the external connection electrode. A method of manufacturing an inkjet head comprising an ink chamber provided so as to extend from one end to the other end on the surface of a piezoelectric substrate,
Forming a counterbore in the piezoelectric substrate;
Embedding an external connection electrode material to be an external connection electrode connected to an external electrode provided outside the piezoelectric substrate in the counterbore,
Cutting a part of the electrode material for external connection to form the electrode for external connection, and cutting a groove for forming the ink chamber;
And a step of forming drive electrodes on both inner surfaces of the grooves constituting the ink chamber while contacting with the external connection electrode. The method for manufacturing an ink jet head according to claim 9 , wherein the counterbore is formed by sandblasting. A groove constituting the ink chamber, in a direction perpendicular to the main surface of the piezoelectric substrate on which the counterbore hole is provided, for switching time by performing the dicing process, as claimed in claim 9 or claim 10 A method for manufacturing an inkjet head.

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