JP4334751B2 - Inkjet head and inkjet recording apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet head and an ink jet recording apparatus, and more particularly to an ink jet recording apparatus using an ink jet head.
[0002]
[Prior art]
The non-impact recording method is attracting attention for office use because it is so small that noise generation during recording can be ignored. Among them, the so-called inkjet recording method, which is capable of high-speed recording and can be recorded on plain paper without requiring a special fixing process, is an extremely powerful method, and various methods have been proposed or have already been commercialized. Has been practical. Such an ink jet recording method is a method in which a recording liquid droplet called a so-called ink is ejected and attached to a recording medium for recording, and a recording liquid droplet generation method and a droplet ejection are performed. Depending on the control method for controlling the direction, it is roughly divided into several methods. Among them, in recent years, as a method capable of high density and high integration using a silicon substrate, there is a technique described in Japanese Patent Laid-Open No. 4-52214 and a manufacturing method thereof as disclosed in Japanese Patent Laid-Open No. 3-293141. This is an electrostatic method in which a voltage is applied between the substrate and the electrodes of the diaphragm, and the diaphragm is deflected by electrostatic force to eject ink. As a method of forming the head, the silicon substrate is vibrated by etching with the liquid chamber. A method for forming a plate and attracting attention as a method capable of high density and high integration using a silicon substrate.
[0003]
Although not limited to such an electrostatic system, a head using a silicon wafer can be processed with high precision and fineness by application of a semiconductor process, so that the head can be mass-produced with a high yield and a low-cost small-sized head can be realized. It can be said that it is superior above. On the other hand, such an ink-jet head is usually driven by energization with a printed circuit board such as an FPC connected. However, as the size of the head is reduced, the bonding area of such a printed circuit board also becomes smaller. Ensuring bonding strength has become an important issue. In particular, in a thin head, there is a problem that the current-carrying medium such as solder and conductive adhesive protrudes. In order to solve the former problem, there has been proposed a method of reinforcing the periphery of a printed circuit board joint with an adhesive or a sealant as disclosed in JP-A-10-044441 (hereinafter referred to as Conventional Example 1). In order to solve the latter problem, a proposal for providing a slit in a conductor for the purpose of improving the solder joint strength of each conductor of a printed circuit board is disclosed in Japanese Patent Laid-Open No. 9-46031 (hereinafter referred to as Conventional Example 2). ).
[0004]
[Problems to be solved by the invention]
However, the method as in Conventional Example 1 can only reinforce the surroundings, and it is necessary to secure an area only for the adhesive and the sealant, which is not preferable for realizing a small head. Moreover, in the prior art example 2, sufficient effects cannot be obtained when using an anisotropic conductive paste or an anisotropic conductive film in which a bonding medium is disposed in addition to the conductor portion of the printed circuit board.
[0005]
The present invention has been made in view of such a problem, and reduces the protrusion of a bonding medium when bonding a printed circuit board such as an FPC to an inkjet head, and increases the bonding strength in a space-saving manner. It is an object to realize a head and an ink jet recording apparatus.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, a nozzle substrate on which nozzles for ejecting ink are formed, a liquid chamber communicating with the nozzles, and energy generation for ejecting ink from the nozzles by increasing the pressure in the liquid chamber According to the ink jet head according to the present invention, the printed circuit board includes the electrode substrate on which the means is formed and the printed circuit board for energizing the energy generating unit, and the printed circuit board and the electrode substrate are connected to each other by an electrical connection member. And a plurality of electrodes and a convex support member formed between the electrodes, and the support member is characterized by maintaining a distance between the printed circuit board and the electrode substrate. Therefore, when the printed circuit board and the electrode substrate are crimped and connected by the electrical connection member, the protrusion of the electrical connection member to the periphery can be reduced and the bonding strength can be increased.
[0007]
In addition, by forming the electrode disposed on the printed circuit board to be thicker than the convex support member , the protrusion of the electrical connection member to the periphery can be reduced, the bonding strength can be increased and the bonding quality can be improved. Can be stabilized.
[0008]
Furthermore, by forming the convex support member into a plurality of parts, it is possible to reduce the protrusion of the electrical connection member to the periphery and increase the bonding strength.
[0009]
Further, by forming the surface of the convex support member to be uneven, it is possible to reduce the protrusion of the electrical connection member to the periphery and increase the bonding strength.
[0011]
An ink jet recording apparatus according to the present invention includes the above ink jet head.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
According to the present invention, there are formed a nozzle substrate on which nozzles for ejecting ink are formed, a liquid chamber communicating with the nozzles, and energy generating means for increasing the pressure in the liquid chamber to eject ink from the nozzles. An ink-jet head having an electrode substrate and a printed circuit board for energizing the energy generating means, wherein the printed circuit board and the electrode substrate are connected to each other by an electrical connection member. The printed circuit board includes a plurality of electrodes and a gap between the electrodes. A convex support member formed, and the support member maintains a distance between the printed circuit board and the electrode substrate.
[0013]
【Example】
FIG. 1 is a schematic cross-sectional view showing the configuration of the ink jet recording apparatus of the present invention. As shown in the figure, the ink jet recording apparatus 101 includes four ink cartridges 102 each containing ink of each color of cyan C, magenta M, yellow Y, and black BK, and a plurality of nozzles 102. Recording paper is fed to the printing unit 107 from four ink jet heads 103 to which ink is supplied, a carriage 104 on which the ink cartridge 102 and the ink jet head 103 are mounted, and paper feed trays 105 a and 105 b that store recording paper and a manual feed table 106. A conveyance roller 108 for conveyance and a discharge roller 110 for discharging the printed recording paper to a discharge tray 109 are provided. When printing the image data sent from the host device on the recording paper, the inkjet head 103 is applied to the recording paper sent to the printing unit 107 by the transport roller 108 while scanning the carriage 104 along the carriage roller 111. Ink is ejected from the nozzles in accordance with the image data to record characters and images.
[0014]
Next, the ink jet head 1 used in the ink jet recording apparatus 101 of FIG. 1 is an external view of the ink jet head according to another invention, FIG. 2 is a view of FIG. As shown in FIG. 4, which is a cross-sectional view taken along the line BB ′, a liquid chamber substrate 11, a vibration plate substrate 12, an electrode substrate 13, a flexible printed wiring board (hereinafter abbreviated as FPC) 14 that is a printed substrate, Two rows of staggered nozzles 15, base 16 of FPC 14, electrode lead 17 of FPC 14, resist layer 18 of FPC 14, individual electrode 19, diaphragm 20 also serving as a common electrode, liquid chamber 21, electrode lead of FPC 14 17 and the individual electrodes 19 of the electrode substrate 13 are electrically connected, and include a conductive adhesive 22 such as solder, anisotropic conductive film, anisotropic conductive paste, or the like. ing. The common liquid chamber 23 is a liquid chamber that communicates with each liquid chamber 21 and supplies ink. The gap 24 is a gap between the individual electrode 19 and the diaphragm 20. The fluid resistance 25 is formed between the liquid chamber 21 and the common liquid chamber 23 and close to the liquid chamber substrate 11 and the diaphragm substrate 12. The electrode substrate 13 is made of a conductor or a semiconductor and includes a conductive substrate 26 and an insulating layer 27 formed thereon. The ink supply port 28 is a supply port that supplies ink from an ink tank (not shown) to the common liquid chamber 23 that communicates. Furthermore, by providing the liquid chambers 21 and the nozzles 15 in two rows in a staggered arrangement and doubling the nozzle pitch, it can be formed as a common ink supply port 28 for supplying ink to both, thereby effectively reducing the head area. Available. For the sake of simplicity, the ink supply means for the ink supply port is omitted.
[0015]
In addition, the liquid chamber substrate 11 is formed with a groove by a known method such as machining such as dicing or electroforming such as etching, and joined to the vibration plate substrate 12, whereby the nozzle 15, the liquid chamber 21, and the common liquid chamber 23. Can be formed. As the material of the liquid chamber substrate 11, a metal such as stainless steel, a semiconductor such as Si, and an insulating material such as glass are used. As a bonding method, a dry film may be used. A nozzle substrate (not shown) is bonded onto the liquid chamber substrate 11 with an adhesive. The discharge surface of the nozzle surface is subjected to water repellent treatment by a known method (plating, water repellent coating, etc.) in order to ensure water repellency with the ink.
[0016]
Furthermore, the diaphragm substrate 12 can accurately form a fine pattern with a desired thickness by a method such as etching a metal such as stainless steel or a semiconductor such as Si and electroforming Ni. The diaphragm substrate itself is preferable because it can be used as a common electrode. When an insulating material such as glass is used, the common electrode can be formed by depositing a metal such as Al, Cu, Cr, Ni, Au on the surface by a method such as vapor deposition or sputtering. The diaphragm substrate 12 has a recess having a diaphragm 20 formed on the bottom surface by a known method such as machining such as partial polishing or electroforming such as etching. Further, a part of the diaphragm substrate 12 extends to the individual electrode 19 side and serves as a common electrode pad for connection to the printed circuit board.
[0017]
The electrode substrate 13 is formed by etching a metal such as stainless steel or a semiconductor such as Si to form a gap 24 having a desired height, and the gap 24 is made of an insulating material such as resin or SiO _2. An insulating layer 27 is formed. On top of that, an electrode material such as Ni, Al, Ti / Pt, Cu or the like is formed as an individual electrode 19 to a desired thickness by a film forming technique such as sputtering, CVD, or vapor deposition, and then a photoresist is formed. By etching, an individual electrode can be formed only in the gap. Therefore, the electrode substrate 13 is made of a conductor or a semiconductor, and has a conductive substrate 26, an insulating layer 27 formed thereon, and a gap 24 with the diaphragm 20 on the insulating layer 27. A recess corresponding to this is formed, and an individual electrode 19 made of a conductive material is formed on the bottom surface thereof. In addition, on the surface of the electrode substrate 13, the individual electrode and the common electrode can be formed in substantially the same plane by extracting and fixing a part of the above-described common electrode in a region other than the individual electrode forming portion. Connection with a printed circuit board (head drive printed circuit board) described later becomes easy. The diaphragm substrate 12 and the electrode substrate 13 are bonded by bonding, anodic bonding, direct bonding, or the like according to the type of the material. In addition, an insulating layer made of SiO ₂ or a resist material may be formed on the individual electrode 19 except for the connection portion with the printed circuit board for the purpose of preventing the electrode from being damaged by a short circuit or discharge. .
[0018]
On the other hand, as the FPC 14 connected to the individual electrode 19, a plate-like printed board made of glass epoxy resin or phenol resin, or a film-like printed board (FPC) made of polyimide resin, PET resin or the like is used. On the FPC 14, an electrode lead 17 for applying a voltage to the individual electrode 19 is formed. As a method of electrically connecting the electrode lead 17 on the FPC 14, the individual electrode 19, and the electrode pad of the common electrode, for example, a method of thermocompression bonding with solder, a method of thermocompression bonding with an anisotropic conductive adhesive, or between electrodes The wire bonding method requires the height of the wire, and the wire part is sealed with resin to prevent mechanical damage to the wire and the connection between the wires. Since it has the fault that a sealing part becomes high for it to stop for that, it is unpreferable. A method of thermocompression bonding with solder, a method of thermocompression bonding with an anisotropic conductive adhesive, and a method of pressure-contacting between electrodes can be easily processed at low cost because a plurality of electrodes can be connected at a time. This is an excellent method in that the height for connection is low. Furthermore, among these, in the method of thermocompression bonding with solder or an anisotropic conductive film, the substrates are bonded to each other after the compression bonding, so that electrical connection and mechanical connection between the electrode substrate and the printed circuit board are performed simultaneously. Therefore, it is an excellent connection method in that it does not need to be reinforced separately so that the connection portion cannot be removed in the head assembly process or printing operation. In particular, the anisotropic conductive film is superior to solder in the selectivity of the electrode material, and can be used as a material for bonding a printed board to various ink jet heads.
[0019]
Such a connecting method of thermocompression bonding with solder or an anisotropic conductive film is performed in a process as shown in FIG. In this example, an FPC is used as the driving printed board, and an anisotropic conductive film is used for connection between the FPC and the electrode board. The anisotropic conductive film (anisotropic conductive film) 22 is obtained by dispersing conductive particles called fillers in a thermoplastic or thermosetting resin, sandwiched between electrodes, and heated. By applying pressure, the anisotropic conductive film 22 is crushed, the filler comes into contact with both electrodes, and conduction between the electrodes can be obtained. As shown in FIG. 5A, first, the anisotropic conductive film 22 is aligned with the electrode portion of the FPC 14 such as an FPC so as to be positioned on the end surface of the FPC, and then temporarily crimped, so that the FPC 14 such as the FPC. And the anisotropic conductive film 22 are adhered to each other. Thereafter, as shown in FIG. 5B, the protective film of the anisotropic conductive film 22 is removed, the electrode pad portion of the electrode substrate is aligned with the electrode lead of the FPC, and the (c) of FIG. ), The heated crimping head 51 is pressed against the electrode region and thermocompression bonded. At this time, since all the joints need to be in a uniform condition, a pressure-bonding head having as little temperature unevenness as possible and having no temperature fluctuation due to contact with the head or the like is used. In addition, since it is important that the pressure is applied uniformly, the pressure-bonding surface of the pressure-bonding head is finished with good flatness. However, if the electrode pattern pitch is reduced and the electrode width is reduced, it is difficult to ensure the bonding reliability only by the flatness of the crimping head. Therefore, a cushioning material such as silicone rubber or Teflon sheet is used between the crimping head and the printed circuit board. Bonding is performed and the bonding reliability is obtained. When joined by this method, depending on the joining conditions, the gap between the electrode leads 17 of the FPC which is the escape region of the anisotropic conductive film 22 is crushed by elastic deformation of the cushion material 61 as shown in FIG. As shown in FIG. 6B, the anisotropic conductive film 22 protrudes greatly around.
[0020]
Therefore, according to the first embodiment of the present invention, as shown in FIGS. 7A and 7B, dummy electrode leads 71 to which no drive signal is applied to the inkjet head between the electrode leads 17 are provided. The gap between the electrode substrate 13 and the base 16 of the FPC is maintained. Therefore, by providing the dummy electrode lead 71 in this way, deformation of the FPC by the cushion material 61 can be prevented, and as shown in FIG. 7B, the protrusion of the anisotropic conductive film 22 to the periphery is reduced. be able to. Moreover, since the contact area with the anisotropic conductive film 22 increases, the adhesive strength increases. Furthermore, as a method for increasing the contact area with the anisotropic conductive film 22 and increasing the adhesive strength, as a second embodiment, a dummy electrode lead 71 is divided in the longitudinal direction as shown in FIG. This method is also effective. Further, as a third embodiment, as shown in FIG. 9, a method of making the surface of the dummy electrode lead 71 uneven is also effective. In order to obtain the shape as shown in FIG. 9, a mask pattern with a narrow opening may be formed in the dummy electrode lead portion and etched. Since this narrow opening portion has a significantly lower etching efficiency than the wide opening portion, a saw-shaped pattern as shown in FIG. 9 can be formed. In this case, the height of the dummy electrode lead 71 can be made slightly lower than the height of the main electrode lead 17 to which a drive signal is applied to the inkjet head. By doing in this way, since the load by the crimping head 51 of FPC becomes easy to be applied to the main electrode lead 17, joint reliability improves. Further, as a fourth embodiment, the anisotropic conductive film 22 protrudes by forming recesses such as holes 81 and grooves 82 between the individual electrodes 19 on the surface of the electrode substrate 13 as shown in FIG. It can be reduced and the bonding strength can be increased. For example, as described above, when Si or glass is used for the electrode substrate 13 as described above, masking having an opening for forming a desired recess in the recess forming region is performed, followed by sand blasting or dry etching. Precise processing is possible.
[0021]
The electrostatic ink jet has been described as an example, but the present invention is also effective for miniaturization of ink jet heads of other printing methods such as a piezoelectric method and a bubble jet method.
[0022]
(Specific example 1)
Specific example 1 will be described below with reference to FIG. A borosilicate glass with a thickness of 1 [mm] was used as the electrode substrate 13, and a silicon substrate with a thickness of 200 [μm] was used as the diaphragm substrate 12. On the diaphragm substrate 12, a boron layer corresponding to the thickness of the diaphragm 20 was formed in advance on one surface of the silicon substrate, and the diaphragm 20 was formed by wet etching by using this boron layer as an etching stop layer. The electrode substrate 13 was formed by patterning a Ni electrode by sputtering in a groove formed by wet etching, and forming a SiO ₂ layer as an electrode protective film on the electrode by sputtering. Next, the electrode position of these substrates and the position of the diaphragm 20 are accurately positioned, and both are joined by anodic bonding, and the diaphragm 20 is disposed at 150 dpi and has a gap of about 0.7 [μm]. An electrostatic actuator was formed. Furthermore, in order to reduce the height of the liquid chamber 21 and increase the discharge efficiency, the upper surface of the diaphragm 20 was polished by about 100 [μm]. An FPC 14 as a printed circuit board was joined to the electrostatic actuator having such a configuration with an anisotropic conductive film 22. As the FPC 14, a polyimide film base material having a thickness of 12.5 [μm] and Cu having a thickness of 18 [μm] patterned using an adhesive having a thickness of 20 [μm] was used. The electrode pattern width was 40 [μm]. Further, as the anisotropic conductive film 22, a thermosetting film having a thickness of 18 [μm] was used. The anisotropic conductive film 22 was temporarily press-bonded to the end portion of the FPC 14 and then positioned and finally pressure-bonded with the electrode pad of the electrode substrate 13. The main pressure bonding was performed through silicone rubber having a thickness of about 200 [μm] as a cushioning material so that the applied pressure was uniform over the entire joint. When the capacitance of the electrostatic actuator was measured after the FPC 14 was joined, all the channels showed good capacitance values, and it was also confirmed that there was no connection failure of the FPC 14. Next, when a nozzle plate covering the contact portion of the FPC 14 was bonded to the vibration plate substrate 12 with an adhesive and filled with ink to perform ink ejection evaluation, satisfactory ejection could not be performed. When this head was disassembled and analyzed, it was found that ink leaked between the vibration plate substrate 12 and the nozzle plate and wetted the electrode pad portion. Furthermore, when the cause of the leak was pursued, the height of the anisotropic conductive film 22 that protruded from the end of the FPC was 100 [μm] or more, so that the nozzle plate could not be satisfactorily bonded to one side. I understood. Further, when the cause of the protrusion of the anisotropic conductive film 22 was pursued, it was found that the FPC 14 was depressed between the electrode leads 17 as shown in FIG. 6A, and the protrusion at that portion was particularly large. . Therefore, as shown in FIG. 7, a dummy electrode lead 71 having a width of about 30 [μm] is provided only in the vicinity of the junction region between the electrode lead 17 and the electrode substrate 13 as shown in FIG. As a result of evaluation, good injection characteristics could be obtained. Further, as a part of the joint quality evaluation, the joint strength was measured and the influence of the change of the FPC 14 was examined. As a result of the 90 degree peel test, it was about 68.6 [kPa] before the change, but after the change, it was about 78. It was 4 [kPa], and it was confirmed that the strength was also increased. Further, as a comparative experiment, it was confirmed that when the electrode pattern 17 was divided in the longitudinal direction as shown in FIG. 8 and the dummy pattern was divided in a dice shape, the strength was slightly improved.
[0023]
(Specific example 2)
Using the electrostatic actuator having the same configuration as that described in the specific example 1, the FPC 14 shown in FIGS. 6 and 7 was subjected to main pressure bonding without using silicone rubber as the cushion material 61. As a result, in both samples, the height of the protruding portion of the anisotropic conductive film 22 was 100 [μm] or less, which was satisfactory. It turned out to be. Therefore, as shown in FIG. 9, a dummy electrode lead 71 having a shape in which irregularities having a height of about 2 [μm] are formed on the surface and about 3 [μm] lower than the main electrode lead 17 that contributes to driving. When the FPC 14 having the same thickness was bonded under the same conditions, it was possible to bond well without generating a bonding failure channel. The protruding height of the anisotropic conductive film 22 was 100 [μm] or less, and the bonding strength was about 88.2 [kPa], confirming that it was good.
[0024]
(Specific example 3)
A hole having a size of about 25 [μm] and a depth of about 8 [μm] is obtained by sandblasting using abrasive grains having a particle size of 8 [μm] before the FPC 14 is bonded using the electrostatic actuator having the same configuration as in Example 1. A number 81 is provided around the individual electrode 19 as shown in FIG. When the FPC 14 shown in FIG. 6 was finally press-bonded to this actuator via the cushion material 61, the projecting height of the anisotropic conductive film 22 could be joined under the condition of 100 [μm] or less. Also, the bonding strength was about 83.3 [kPa], and a good bonding state could be obtained.
[0025]
In addition, this invention is not limited to the said Example, It cannot be overemphasized that various deformation | transformation and substitution are possible if it is description in a claim.
[0026]
【The invention's effect】
As described above, a nozzle substrate on which nozzles for ejecting ink are formed, a liquid chamber communicating with the nozzles, and energy generating means for increasing the pressure in the liquid chamber and ejecting ink from the nozzles are formed. According to the inkjet head according to the present invention, the printed circuit board includes a plurality of printed circuit boards, and a printed circuit board for energizing the energy generating means. It has an electrode and a convex support member formed between the electrodes, and the support member is characterized by maintaining a distance between the printed circuit board and the electrode substrate. Therefore, when the printed circuit board and the electrode substrate are crimped and connected by the electrical connection member, the protrusion of the electrical connection member to the periphery can be reduced and the bonding strength can be increased.
[0027]
In addition, by forming the electrode disposed on the printed circuit board to be thicker than the convex support member , the protrusion of the electrical connection member to the periphery can be reduced, the bonding strength can be increased and the bonding quality can be improved. Can be stabilized.
[0028]
Furthermore, by forming the convex support member into a plurality of parts, it is possible to reduce the protrusion of the electrical connection member to the periphery and increase the bonding strength.
[0029]
Further, by forming the surface of the convex support member to be uneven, it is possible to reduce the protrusion of the electrical connection member to the periphery and increase the bonding strength.
[0031]
An ink jet recording apparatus according to the present invention includes the above ink jet head.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing the configuration of an ink jet recording apparatus of the present invention.
FIG. 2 is an external view of an inkjet head according to another invention.
FIG. 3 is a view on arrow A in FIG. 2;
4 is a cross-sectional view taken along line BB ′ of FIG.
FIG. 5 is a process diagram when a printed circuit board is crimped and connected to individual electrodes.
FIG. 6 is a view showing a state in which an anisotropic conductive film protrudes during a conventional crimp connection.
FIG. 7 is a view showing a state in which an anisotropic conductive film protrudes at the time of crimping connection according to the first embodiment of the present invention.
FIG. 8 is a plan view of an FPC of an ink jet head according to a second embodiment of the present invention.
FIG. 9 is a cross-sectional view of an FPC of an ink jet head according to a third embodiment of the present invention.
FIG. 10 is a plan view of an electrode substrate of an ink jet head according to a fourth embodiment of the present invention.
[Explanation of symbols]
51; Crimp head, 61; Cushion material, 71; Electrode lead, 81; Hole,
82; groove.

Claims (5)

Nozzle substrate on which nozzles for discharging ink are formed, a liquid chamber communicating with the nozzles, and an electrode substrate on which energy generating means for increasing the pressure in the liquid chamber and discharging ink from the nozzles is formed And an inkjet head having a printed circuit board for energizing the energy generating means, wherein the printed circuit board and the electrode substrate are connected by crimping with an electrical connection member,
The printed circuit board includes a plurality of electrodes and a convex support member formed between the electrodes, and the support member maintains a distance between the printed circuit board and the electrode substrate. Inkjet head.   The ink-jet head according to claim 1, wherein the electrode is formed thicker than the convex support member.   The inkjet head according to claim 1, wherein the convex support member is divided into a plurality of parts.   The inkjet head according to claim 1, wherein a surface of the convex support member is formed to be uneven. An ink jet recording apparatus comprising the ink jet head according to claim 1 .

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