Abstract:
A printed wiring board  50  is assembled to a molded ink manifold  52 . A bonding board  50  has circuit contacts  54  aligned on a similar pitch as circuit contacts  56  on a die module  58 . A fluid seal material  64  is applied onto the die mold  58  on an ink inlet surface. During the same dispensing step, a series of microdots of conventional isotropic conductive adhesive  62  are dispensed upon the circuit contacts  56  of the die module  58 . The die module  58  is aligned brought into contact with the manifold  52 /wiring board  50  assembly. The bonds made by the fluid sealant  64  and the isotropic conductive adhesive  62  are cured simultaneously in an oven.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to the image rendering arts. It finds particular application in conjunction with thermal ink jet printheads, and will be described with particular reference thereto. However, it is to be appreciated that the present invention is also amenable to other like applications. 
     Typically, the manufacturing of thermal ink jet printheads involves numerous complicated steps both inside and outside of a clean room. Among the process steps are a plurality of precise adhesive placements and position alignments are performed in the clean room. More specifically, constituent components of the printhead assembly have adhesives applied, are aligned and pressed together, and the adhesives cured in a heater. Typically, each separate component is bonded and cured in a separate step. 
     More specifically to the prior art, U.S. Pat. No. 6,229,114 to Andrews, et al. describes the construction of a thermal ink jet printhead, and is herein incorporated by reference. First, in the clean room, a die bond epoxy is applied to the bottom side of a die module  1 . The die module  1  is then precisely aligned and assembled to a substrate  2 , in the case of Andrews, a heat sink. Next, the die bond is cured in an oven for approximately 45 minutes or longer. After the die bond is set, wire bonds  3  are applied between a printed wiring board  4  on said substrate  2  and an electrical contact portion of the die module  1 . An adhesion promoter is applied to the top surface of die module  1 . A tack fluid seal  5  is precisely located and applied to one surface of the ink manifold assembly  6 . The die module  1  and substrate  2  assembly and the manifold  6  an fluid seal  5  assembly are then precisely located to each other and are merged together and a UV adhesive is applied and cured The tack fluid seal is cured in an oven for approximately 45 minutes or longer. An encapsulation adhesive is then injected into the assembly to protect the wire bonds  3  from oxidation. A faceplate  7  is adhered to the operative surface of the printhead. 
     Once assembled, the printhead is subjected to an additional final cure, along with a series of integrity tests. 
     U.S. Pat. No. 4,601,777 to Hawkins, et al. describes an alternate method for constructing a thermal ink jet printhead, and is herein incorporated by reference. With reference to FIGS. 2 through 5 of the present application, aspects of existing manufacturing processes are illustrated. In FIG. 2, a daughter board  10  carries a thermal ink jet printhead  12 . A portion of daughter board electrodes  14  are carried entirely on the facing side of the daughter board  10 , and another portion of the electrodes  14  are carried partially on the reverse side of the daughter board  10 , switching sides at inversion points  15 . As seen in FIG. 3, daughter board electrodes  14  are connected to individual printhead electrodes  16 . The printhead electrodes  16  are carried upon a substrate  18 , as best seen in FIGS. 4 and 5. Wire bonds  20  are used to connect between each daughter board electrode  14  and its corresponding printhead electrode  16  counterpart. The wire bonds are installed with a standard wire bonding process as is known in the art. 
     Each printhead electrode  16  is connected to a heating element  22  (FIG.  5 ). A plurality of heating elements  22  are situated side by side along a front edge  24  of the substrate  18 . An etched manifold  26  is precision aligned with the substrate  18  such that etched grooves  28  in the manifold  26  align precisely with the heating elements  22 , defining ink jet channels between the manifold  26  and the substrate  18 . Internal pathways and capillaries within the manifold allow ink from a supply aperture  30  to flow into each of the ink jet channels. 
     The present invention is suited for applications wherein a heat sink substrate is not needed and thermal control of the printhead is accomplished through other means known in the art. The present invention contemplates a new and improved method and apparatus that replaces the wire bonds, and condenses other bonding steps with a single step or process, overcoming the above referenced problems, and others. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In accordance with one aspect of the present invention, a method of assembling an ink jet printhead is provided. A printed wiring board is attached to an ink jet manifold. A die module is simultaneously attached to the manifold and the printed wiring board. Adhesives used to bond the die module to the printed wiring board and the manifold are simultaneously cured. 
     In accordance with another aspect of the present invention, a method of constructing an ink jet cartridge is provided. A fluid seal is dispensed on a first portion of a die module. An isotropic conductive adhesive is dispensed on a second portion of the die module containing a series of bumped electrical contacts. A single component is aligned with the die module, the component including a first, ink jet manifold section and a second, printed wiring board section. The die module and single component are moved into engagement, whereby a fluid seal connection is made, and an electrical connection is made in a single processing step. 
     In accordance with another aspect of the present invention, a thermal ink jet cartridge is provided. The cartridge includes a manifold and a printed substrate attached to the manifold. A die module single component that includes the manifold and the substrate is attached to at least a printed daughter board, the die module being at least partially attached with a flip chip bumping process. 
     One advantage of the present invention resides in simplified construction of an ink jet printhead. 
     Another advantage of the present invention resides in a more robust electrical bond. 
     Another advantage resides in reduced manufacturing costs. 
     Still further advantages and benefits of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating preferred embodiments and are not to be construed as limiting the invention. 
     FIG. 1 is a prior art representation of a section view of a typical thermal ink jet printhead. 
     FIG. 2 is a prior art representation of a daughter board with a printhead attached thereupon, in accordance with the present invention; 
     FIG. 3 is a prior art representation of a close up view of an end ofthe daughter board of FIG. 2, with the printhead; 
     FIG. 4 is a prior art perspective view of the printhead and daughter board of FIGS. 2 and 3; 
     FIG. 5 is a prior art head-on cross-sectional view of the printhead and daughter board of FIGS. 2-4; 
     FIG. 6 is a head-on view of a print head and daughter board prior to assembly, in accordance with the present invention; 
     FIG. 7 is a top-down view of a printhead and daughter board in accordance with the present invention; 
     FIG. 8 is an exploded view of the printhead and daughter board of FIG. 7; 
     FIG. 9 is a perspective view of a printhead assembly prior to an engagement step, in accordance with the present invention; 
     FIG. 10 is an engaged view of the assembly of FIG.  9 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to FIG. 6, shown is a simplified diagram representing an embodiment for a manufacturing process which implements concepts of the present application. A printed wiring board portion, such as a daughter board  50  is provided with a manifold portion  52  as a single component. A possible board applicable to this embodiment is a single sided punched FR- 4  board. The daughter board  50  and the manifold portion  52  are attached using insert molding or staking in this embodiment. It is to be understood that other attachment means are also applicable to the present embodiment. A plurality of daughter board electrodes  54  are printed upon the daughter board portion  50 , the electrodes  54  corresponding to counterpart die module electrodes  56  carried on a die module  58 . The die module  58  also carries other typical components of a standard ink jet printhead, as are known in the art, including, but not limited to the heating elements, ink channels, an ink reservoir, etc. 
     The die module  58  is bonded to a component  53 , which includes the daughter board portion  50  and manifold portion  52  in a single connection step. It is to be understood that either the die module  58  can be brought into contact with the component  53  or vice versa, that is, the component  53  can be brought into contact with the die module  58 . Particularly, a connecting material such as, but not limited to, a gold (Au) bump  60  is applied to each electrode  56  on the die module  58 , preferably via an industry standard practice of wafer-level ball bonding. After the gold bumps are applied, an isotropic conductive adhesive (ICA)  62  is applied to each of the bumps  60 . In the present embodiment, the ICA  62  is applied in microdots to each of the gold bumps  60  as is typical in a flip chip bonding process. It is to be understood that other adhesives may also be used in other manners within the concepts of the present application. It is also to be understood that the gold bumps  60  and the ICA  62  can be applied to the contacts  54  of the daughter board  50  rather than the contacts  56  of the die module  58 . 
     In the same ICA dispensing step, a fluid seal adhesive  64  is applied to a surface of the die module  58 , more specifically, the surface that comes into contact with the manifold portion  52 . The fluid seal  64  can be a single component flexible epoxy with a low cure temperature, however, other materials such as silicones and the like are also applicable. It is to be understood that the fluid seal  62  can be applied to the manifold portion  52  instead of the die module, or can be applied to both surfaces. The fluid seal material may be applied as microdots or in any other appropriate manner. The die module undergoes a precision aligning step that precisely aligns the electrodes  54  of the daughter board portion  50  with the electrodes  56  of the die module  58 . The die module  58  is then simultaneously brought into contact with both the daughter board portion  50  and the manifold portion  52 , connecting the electrodes  54  and  56 . The manifold portion  52  can be designed so that it contains a full perimeter capping surface that is partially set back from the die module. Utilizing such a capping surface renders it unnecessary to assemble a separate face plate. Once the daughter board portion  50 , the manifold portion  52 , and the die module  58  are bonded together, the bonds are simultaneously cured in an oven, as is known in the art. It is to be understood that variances on the curing process are possible, such as local heaters set to different temperatures, local heaters heating for different amounts of time, microwave ovens, and the like. 
     In another embodiment, with reference to FIG. 7, a daughter board  70  carries a plurality of daughter board electrodes  72  on an upper surface thereof. A printhead substrate  74  carries an additional plurality of substrate electrodes  76 , also on an upper surface thereof. An ink jet manifold  78  is bonded to the upper surface of the substrate  74 . 
     With reference to FIG. 8, and with continuing reference to FIG. 7, the manifold  78  is precision aligned with the substrate  74 . Grooves in the manifold  78  are aligned precisely with resistive heating elements  80  at the end of each substrate electrode  76  defining ink jet channels when the manifold  78  is bonded to the substrate  74 . The substrate electrodes  76  pass through the substrate  74  at inversion points  82 . Underside contacts (not shown) provide an electrical connection between the substrate electrodes  76  and the daughter board electrodes  72 . The underside contacts are connected to the daughter board electrodes  72  using the solder ball bumping process as previously discussed. The gold bumps and the ICA microdots are applied to the underside contacts. In this application stage, the fluid seal microdots are also applied to an underside of the substrate  74 , the underside being opposite an upper side  84  of the substrate  74 . 
     Next, the manifold  78 /substrate  74  assembly is aligned with the daughter board  70  such that the underside contacts align with the daughter board electrodes  72 . The ICA and the fluid sealant are simultaneously bonded to the daughter board  70 . The bonds are cured in an oven as discussed previously. 
     In another embodiment, and with reference to FIG. 9, a component  90 , which includes a daughter board portion  92  and a manifold portion  94 , is bonded to a die module  96 . The aforementioned manifold portion  94 , daughter board portion  92 , and die module  96  can be constructed similarly to the components in FIGS. 4 and 5. The daughter board portion  92  carries a plurality of electrodes  98  that are in electronic communication with the printer. The die module  96  carries electrodes  100  that are in electrical communication with a plurality of heating elements  102  embedded on a surface of the die module  96 . Embedded electrical connections  103  are connected between the electrodes  100  and the heating elements. The heating elements  102  are evenly spaced along the surface of the die module  102 . Etched into the manifold  94  are a plurality of ink jet channels  104  that are spaced equally to the spacing ofthe heating elements  102 . It is to be understood that he electrodes  98  can be on the same horizontal level as the ink jet channels  104  and the electrodes  100  can be on the same horizontal level as the heating elements  102 . The present embodiment staggers the levels of these components to simplify an alignment process. 
     Microdots of fluid seal adhesive  106  are applied to the surface of the die module  96  that carries the heating elements  102 . In the same dispensing step, microdots of ICA are applied to the die module electrodes  100 , which were previously prepared for a solder bumping process, as described previously. It is to be understood that the fluid seal  106  and the ICA can be applied as set forth previously, or applied to the facing surfaces of the component  90 , or a combination of both. 
     A single precision alignment is performed. In this step, the electrodes  98 ,  100  are aligned and the heating elements  102  and the ink jet channels  104  are aligned. The component  90  is brought into physical contact with the die module  96 , as shown in FIG. 10 creating a bond therebetween. Alternately, the die module  96  can be moved to contact the component  90 . The electrodes  98 ,  100  are brought into electrical contact, and each ink jet channel  104  is positioned directly atop a heating clement  102 . The ICA and fluid seal bonds are then cured in an oven. 
     The invention has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.