Patent Publication Number: US-8109609-B2

Title: Ink ejecting device and method of manufacturing the same

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2008-0086801, filed on Sep. 3, 2008, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
     TECHNICAL FIELD 
     The present disclosure generally relates to an ink ejecting device and a method of manufacturing the same. 
     BACKGROUND OF RELATED ART 
     An inkjet image forming device forms images in predetermined colors by ejecting fine ink droplets from an inkjet head to a desired location on a printing medium. Generally speaking, inkjet heads may be classified in one of two types according to the mechanism being employed for ejecting ink droplets; a thermal type and a piezoelectric type. A thermal type inkjet head inkjet head produces ink bubbles using a thermal source, and ejects ink droplets as the bubbles expand. A piezoelectric type inkjet head, on the other hand, ejects ink droplets by applying pressure to the ink using deformation of a piezoelectric element. 
     In a thermal inkjet head inkjet head, when a pulse of electric current flows in a heater, e.g., formed of a resistive heating material, ink adjacent to the heater becomes instantaneously heated to a high temperature, which could be, e.g., approximately 300° C. by the heat produced by the heater, causing the ink to boil, and to produce ink bubbles. As the generated bubble(s) continue to expand and to thereby exert pressure to surrounding ink filled in an ink chamber, the ink close to a nozzle is ejected to the outside of the ink chamber as ink droplets. 
     The inkjet head may manufactured as a chip, and may have a structure in which a chamber layer and a nozzle layer are sequentially stacked on a substrate. The chamber layer includes a plurality of ink chambers that are to be filled with ink, whereas the nozzle layer includes a plurality of nozzles through which the ink is ejected from the ink chambers. Additionally, an ink feed hole for supplying ink to the ink chambers may be formed through the substrate. In an inkjet head having the above described structure, the ink feed hole formed through the substrate may present a structural weakness in, or, in some instances, deformation of the substrate. In practice, the inkjet head described above may be mounted on a base header, which may also include formed therein ink supply paths corresponding to the ink feed holes. The ink feed holes in the inkjet head substrate and/or the ink supply paths in the base header tend to reduce the mounting or adhesive surface area of the inkjet head and the base header. Misalignments of the ink feed holes and the corresponding ink supply paths may also occur. 
     SUMMARY OF THE DISCLOSURE 
     According to one aspect of the various embodiments of the disclosure, there is provided an ink ejecting device including an inkjet head having a substrate. The inkjet head may include an ink feed hole formed in the substrate, a plurality of via holes formed in a rear surface of the substrate, each of the plurality of via holes being connected to the ink feed hole, a chamber layer stacked on the substrate and a nozzle layer stacked on the chamber layer. The ink ejecting device may further include a base header on which the inkjet head is supported, the base header comprising a plurality of ink supply slots arranged to correspond to the plurality of via holes. 
     The ink base header may include a base plate in which the ink supply slots are formed and a body supporting the base plate thereon, the body including an ink supply path formed therein, the ink supply path being connected to the ink supply slots of the base plate. 
     The base plate may be attached to the rear surface of the substrate such that each of the plurality of ink supply slots is correspondingly connected to respective associated one of the plurality of via holes. 
     A portion of the rear surface of the substrate between the via holes may form at least one support beam. 
     Each of the plurality via holes may be wider than the ink feed hole. 
     The chamber layer may include one or more ink chambers formed therein for holding ink supplied by the ink feed hole. The nozzle layer may include one or more of nozzles formed therein, through which ink is ejected from the one or more ink chambers. 
     The ink chambers may be formed along both sides of the ink feed hole. The nozzles may be formed above the ink chambers. 
     The ink ejecting device may further comprise an insulation layer formed on the substrate, a plurality of heaters and a plurality of electrodes sequentially formed on the insulation layer and a passivation layer formed over, and covering, the heaters and the electrodes. 
     The ink ejecting device may further comprise an anti-cavitation layer formed on the passivation layer. 
     According to another aspect, a method of manufacturing an ink ejecting device may include forming a chamber layer having a plurality of ink chambers on a substrate, forming a plurality of via holes in a rear surface of the substrate, the plurality of via holes extending into the substrate at a predetermined depth, forming an ink feed hole in the substrate, the ink feed hole extending in the substrate to connect with each of the via holes and forming a nozzle layer on the chamber layer, the nozzle layer having a plurality of nozzles. 
     The method may further include attaching a base header to the rear surface of the substrate, the base header comprising a plurality of ink supply slots in corresponding arrangement with the plurality of via holes. 
     The base header may comprise a base plate in which the ink supply slots are formed and a body supporting the base plate thereon, the body including an ink supply path formed therein, the ink supply path being connected to the ink supply slots of the base plate. 
     The base plate may be attached to the rear surface of the substrate such that each of the plurality of ink supply slots is correspondingly connected to respective associated one of the plurality of via holes. 
     Each of the plurality of via holes may have a first width. The ink feed hole may have a second width. The first width may be greater than the second width. 
     The via holes may be formed by preparing an etching mask, on which a predetermined etching pattern is formed, on the bottom surface of substrate, and etching portions of the substrate exposed through the etching pattern to a predetermined depth. 
     The ink feed hole may be formed by etching the top surface of the substrate until the via holes are exposed. 
     The forming of the nozzle layer may include laminating a nozzle material layer formed of a photosensitive dry film on the chamber layer and forming the plurality of nozzles by patterning the nozzle material layer. 
     According to yet another aspect, an inkjet head may include a substrate having a top surface, bottom surface and a thickness, a chamber layer formed above the top surface of the substrate, an ink feed hole formed in the substrate and a plurality of recesses formed in the bottom surface of the substrate. The chamber layer may include one or more in chambers for receiving ink therein. The ink feed hole may define the ink supply path through which the ink received by one or more in chambers is supplied. Each of the plurality of recesses may define an access opening to the ink feed hole through which ink is to be supplied to the ink feed hole. The ink feed hole may extend in the substrate by a first depth less that the thickness of the substrate. Each of the plurality of recesses may extend from the bottom surface toward the top surface of the substrate by a second depth less than the first depth. At least a portion of the bottom surface of the substrate between two adjacent ones of the plurality of recesses may form a beam-like structure extending across the ink feed hole. 
     The plurality of recesses may each have a width across the bottom surface of the substrate that is wider the ink feed hole. 
     The ink feed hole may comprise a plurality of ink feed holes each corresponding to an associated subset of the plurality of recesses. A fist subset of the plurality of recesses associated with a first one of the plurality of ink feed holes may be in a staggered arrangement with respect to a second subset of the plurality of recesses associated with a second one of the plurality of ink feed holes adjacent the first one of the plurality of ink feed holes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of the present disclosure will become more apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is an exploded oblique view of an ink ejecting device according to an embodiment of the present disclosure; 
         FIG. 2  is a plan view showing an inkjet head shown in  FIG. 1 ; 
         FIG. 3  illustrates the portion A of  FIG. 2  in a closer detail; 
         FIG. 4  is an oblique view showing portions of the substrate shown in  FIG. 1 ; 
         FIG. 5  is a bottom view of the substrate shown in  FIG. 1 ; 
         FIG. 6  is a sectional view obtained along the line VI-VI′ of  FIG. 3 ; 
         FIG. 7  is a sectional view obtained along the line VII-VII′ of  FIG. 3 ; 
         FIG. 8  is an oblique view of the base header shown in  FIG. 1 ; and 
         FIGS. 9 through 14  illustrate a method of manufacturing an inkjet head according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS 
     Several embodiments will now be described more fully with reference to the accompanying drawings. In the drawings, like reference numerals denote like elements, and the sizes and thicknesses of layers and regions may be exaggerated for clarity. The various embodiments described can have many different forms and should not be construed as being limited to the embodiments specifically set forth herein. It will also be understood that when a layer is referred to as being “on” another layer or substrate, the layer can be disposed directly on the other layer or substrate, or there could be intervening layers between the layer and the other layers or substrate. 
     Referring to  FIG. 1 , the ink ejecting device according to an embodiment may include an inkjet head  100  and a base header  200  attached to the inkjet head  100 . The inkjet head  100  may have a structure in which a chamber layer  120  and a nozzle layer  130  are sequentially stacked on a substrate  110  in the order stated. A plurality of the inkjet heads  100  may be manufactured contemporaneously as a plurality of chips on a silicon wafer. 
       FIG. 2  is a plan view showing the inkjet head  100  shown in  FIG. 1 , the portion identified as “A” in  FIG. 2  being shown in more detail in  FIG. 3 .  FIG. 4  is an oblique view showing a portion of the substrate  110  of  FIG. 1 .  FIG. 5  is a bottom view of the substrate  110  of  FIG. 1 .  FIGS. 6 and 7  are sectional view obtained respectively along lines VI-VI′ and VII-VII′ as shown in  FIG. 3 . 
     Referring to  FIGS. 2 through 7 , the chamber layer  120  and the nozzle layer  130  may be sequentially stacked in that order on the substrate  110 , on which a plurality of material layers may be stacked. The substrate  110  may be a silicon substrate, for example. An insulation layer  112  may be formed on the substrate  110 . The insulation layer  112  may be formed of silicon oxide, for example. A plurality of heaters  114  for heating ink in ink chambers  122 , and for generating ink bubbles may be formed on the insulation layer  112 . The heaters  114  may be formed of resistive heating material, such as, e.g., tantalum-aluminium alloy, tantalum nitride, titanium nitride, tungsten silicide, or the like. A plurality of electrodes  116  may further be formed on the heaters  114  to apply electric current to the heaters  114 . The electrodes  116  may be formed of a material with sufficiently electric conductivity, such as, e.g., aluminium (Al), aluminium alloy, gold (Au), silver (Ag), or the like. 
     A passivation layer  118  may be formed on the heaters  114  and the electrodes  116  to protect the heaters  114  and the electrodes  116  from being oxidized and/or corroded by ink that may come into contact the heaters  114  and the electrodes  116 . The passivation layer  118  may be formed of silicon nitride or silicon oxide, for example. Furthermore, anti-cavitation layers  119  may be formed on the passivation layer  118  to protect the heater  114  from a cavitation force generated when bubbles disappear. The anti-cavitation layer  119  may be formed of tantalum (Ta), for example. 
     The chamber layer  120  may be disposed on the passivation layer  118 . The ink chambers  122  are formed in the chamber layer  120 . A plurality of restrictors  124  may further be formed in the chamber layer  120  as paths connecting the ink feed holes  11  and the ink chambers  122 . The chamber layer  120  may be formed of a photosensitive polymer, for example. The nozzle layer  130  may be stacked on the chamber layer  120 . A plurality of nozzles  132  through which ink is ejected are formed in the nozzle layer  130 . The nozzles  132  may be disposed above the ink chambers  122 . The nozzle layer  130  may also be formed of a photosensitive polymer, for example. In addition, a glue layer  121  for increasing adhesiveness between the chamber layer  120  and the passivation layer  118  may further be formed on the passivation layer  118 . The inkjet head  100  may also include bonding pads  140  for transmitting an electrical printing signal from an inkjet image forming device to each of the electrodes  116 . 
     At least one ink feed hole  111  for supplying ink to the ink chambers  122  is formed in the substrate  110 . The ink chambers  122  may be formed along the ink feed hole  111 , for example, on both sides of the ink feed hole  111 . While, in  FIGS. 1 and 2 , four ink feed holes  111  are illustrated for respectively supplying different color ink, for example, yellow ink, magenta ink, cyan ink, and black ink, it should be apparent that the number of ink feed holes  111  is not so limited, and that any number ink feed holes  111 , including, for example, a single ink feed hole  111  may be formed in the substrate  110 . 
     A plurality of via holes  111 ′ each having a predetermined depth may further be formed in the rear surface of the substrate  110  and below the respective one of the ink feed holes  111 , and to be in fluid communication with the respective ink feed holes  111 . The ink from the base header  200  ( FIG. 1 ) is supplied to the ink feed holes  111  via the via holes  111 ′. According to an embodiment, and as illustrated in, e.g.,  FIG. 6 , the width W of each of the via holes  111 ′ may be greater than the width W′ of the ink feed holes  111 . Thus, ink can be supplied to the ink feed holes  111  via the via holes  111 ′ efficiently. However, other alternative embodiments are also possible where the width W of each of the via holes  111 ′ may be equal to, or even less than, the width W′ of the ink feed holes  111 . Also, although  FIGS. 2 through 5  show an example where two via holes  111 ′ are formed below each of the ink feed holes  111 , the present disclosure is so limited. For example, three or more via holes  111 ′ may be formed below each of the ink feed holes  111 . 
     When the via holes  111 ′, connected to the respective ink feed hole  111 , are formed at the rear surface of the substrate  110 , a portion of the substrate  110  between the via holes  111 ′ may form at least one support beam  111   a . The support beam  111   a  may provide added mechanical strength for the substrate, and thus may mitigate the possible weakening of the substrate due to the formation of the feed holes  111 . Moreover, the support beams  111   a  may also provide additional surface area at the rear surface of the substrate with which the substrate may be adhesively attached to the base header  200 . 
     According to an embodiment, and as shown in  FIGS. 2 through 5 , a set of via holes  111 ′ corresponding to a predetermined ink feed hole  111  may be arranged in an alternating or staggered arrangement with respect to another set of via hole  111 ′ corresponding to an adjacent ink feed hole  111 . The ink supply slots  211  in the base plate  210  of the base header  200  may be configured to have the corresponding arrangement with the via holes  111 ′. 
     Referring to  FIG. 1 , the base header  200  is attached to a bottom surface of the inkjet head  100 .  FIG. 8  is an oblique view of the base header  200  shown in  FIG. 1 . 
     Referring to  FIG. 8 , the base header  200  includes a body  220  and a base plate  210  that is disposed on the body  220 , and which is to be attached to the rear surface of the substrate  110 . The ink supply slots  211  are arranged on the base plate  210  in a manner corresponding to the respective via holes  111 ′. That is, when the base plate  210  is attached to the rear surface of the substrate  110 , the ink supply slots  211  formed in the base plate  210  are correspondingly coincide with the via holes  111 ′ formed in the rear surface of the substrate  110 . The body  220  may further include ink supply paths  221  formed therein to correspond to one or more respective ink supply slots  210 . Thus, the ink supply paths  221  are in fluid communication with the respective corresponding to the ink feed holes  111  through the ink supply slots  211  and the via holes  111 ′. While for an illustrative purpose,  FIG. 8  shows four ink supply paths  221  formed corresponding to four ink feed holes  111 , the number and the shapes of the ink supply paths  221  may vary according to alternative embodiments. 
     In an ink ejecting device, according to one or more of the embodiments described above, ink of a predetermined color from an ink cartridge (not shown) may be supplied to a ink feed hole  111  via a ink supply path  221 , the ink supply slots  211  and the via holes  111 ′. 
     Hereinafter, a method of manufacturing an ink ejecting device according to an embodiment will be described.  FIGS. 9 through 14  are diagrams for describing a method of manufacturing the inkjet head  100  according to an embodiment. For the sake of brevity, a case where one ink feed hole is formed in a substrate will be described as an illustrative example. 
     Referring to  FIG. 9 , the substrate  110  is provided. The substrate  110  may be a silicon substrate, for example. Then the insulation layer  112  having a predetermined thickness is formed on the substrate  110 . The insulation layer  112  is for heat and electrical insulation between the substrate  110  and the heaters  114  as will be further described below, and may be formed of, for example, silicon oxide. Then, the heaters  114  for generating ink bubbles by heating the ink are formed on the insulation layer  112 . The heaters  114  may be formed by depositing resistive heating material, such as tantalum-aluminium alloy, tantalum nitride, titanium nitride, tungsten silicide, or the like, on the insulation layer  112 , and by patterning the deposited resistance heating elements as shown. Then, the electrodes  116  for applying electric current to the heaters  114  are formed on the heaters  114 . The electrodes  116  may be formed by depositing metals exhibiting sufficient electrical conductivity, such as aluminium (Al), aluminium alloy, gold (Au), silver (Ag), or the like, on the heaters  114  and patterning the deposited metals. Then, the passivation layer  118  may be formed on the insulation layer  112  to cover the heaters  114  and the electrodes  116  and prevent the heaters  114  and the electrodes  116  from being oxidized and/or corroded by ink that may otherwise come into contact with the heaters  114  and the electrodes  116 . The passivation layer  118  may be formed of silicon oxide or silicon nitride, for example. Furthermore, anti-cavitation layers  119  may further be formed on the passivation layer  118 . The anti-cavitation layers  119  are layers for protecting the heaters  114  from a cavitation force generated when bubbles expand and burst. The anti-cavitation layer  119  may be formed by depositing a material, e.g., tantalum, on the passivation layer  118  and patterning the deposited material. 
     Referring to  FIG. 10 , a chamber layer  120  is stacked on the passivation layer  118 . The chamber layer  120  may be formed by forming a photo-resist material, e.g., photosensitive polymer, on the passivation layer  118  to a predetermined thickness, and patterning the material to define the ink chambers  122  in the chamber layer  120 , above the heaters  114 , for containment of ink to be ejected. A plurality of restrictors  124 , which define the ink flow paths into the ink chambers  122  from the ink feed hole  111  (See, e.g.,  FIGS. 3 and 14 ), may further be formed in the chamber layer  120 . According to an embodiment, a glue layer  121  for increasing adhesiveness between the passivation layer  118  and the chamber layer  120  may be formed on the passivation layer  118  prior to the formation of the chamber layer  120 . According to an embodiment, after either the passivation layer  118  or the glue layer  121  is formed, one or more trenches (not shown) may additionally be formed by sequentially etching the passivation layer  118  and the insulation layer  112  above the location where the ink feed hole  111  is to be formed as will be further described below. 
     Referring to  FIG. 11 , the via hole  111 ′ is formed in the rear surface of the substrate  110  in a predetermined depth. Here, the via hole  111 ′ may be formed on the bottom surface of the substrate below the location where the ink feed hole  111  is to be formed. The via hole  111 ′ may be formed by providing an etching mask (not shown), on which a predetermined etching pattern is formed, on the rear surface of the substrate  110  and etching a portion of the substrate  110  exposed through the etching pattern to a predetermined depth. According to an embodiment, the width of the via hole  111 ′ may be greater than the width of the ink feed hole  111 . However, other alternative embodiments are also possible where the width of the via holes  111 ′ may equal or may be smaller than the width of the ink feed hole  111 . The remaining bottom portion of the substrate  110  between the via holes  111 ′ may thus form one or more support beams  110   a  (e.g., as shown in  FIG. 5 ). 
     Referring to  FIG. 12 , the ink feed hole  111  is formed in the substrate  110  above the via hole  111 ′ to connect to the via hole  111 ′. The ink feed hole  111  may be formed by, e.g., dry-etching the top surface of the substrate  110  until the via hole  111 ′ is exposed. 
     Referring to  FIG. 13 , a nozzle material layer  130 ′ is formed on the chamber layer  120 . The nozzle material layer  130 ′ may be formed by laminating a predetermined photosensitive dry film on the chamber layer  120 . Then, referring to  FIG. 14 , the nozzle layer  130  including the nozzles  132  is formed by patterning the nozzle material layer  130 ′ using a photolithography method. 
     Then, the base header  200  (shown in  FIG. 1 ) to be attached to the inkjet head  100  manufactured as described above is provided. The base header  200  may be manufactured by combining the base plate  210 , in which the ink supply slots  211  are formed, and the body  220 , in which an ink supply path  221  is formed, as, e.g., shown in  FIG. 8 . The ink supply slots  211  may be formed in a configuration that correspond to the via holes  111 ′ formed in the rear surface of the substrate  110 . The ink supply slots  211  may be formed to connect with the ink supply path  221 . 
     Then, the base header  200  is attached to the inkjet head  100  with an adhesive, thus completing the fabrication of an ink ejecting device according to an embodiment. The base plate  210  of the base header  220  is attached to the rear surface of the substrate  110  of the inkjet head  100  in such a manner the ink supply slots  211  are correspondingly connected to via holes  111 ′. 
     While the present disclosure has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the following claims.