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`AUSTRALIA
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`Patents Act 1990
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`Silverbrook Research Pty Ltd
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`PROVISIONAL SPECIFICATION
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`Invention Title:
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`Me1njet Four Color Modular Print Head Packaging
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`The invention is described in the following statement:
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`Memjet Four Color Modular Print Head Packaging
`Field of the Invention.
`This invention relates to a print head assembly. More particularly, the
`invention relates to a pagewidth ink jet print head assembly.
`Summary of the Invention.
`According to a first aspect of the invention there is provided a print
`head system which includes a plurality of print head assemblies aligned in
`end-to-end relationship~ each print head assembly including a plurality of
`print head modules, the print head modules being arranged in end-to-end
`relationship and being angled with respect to a longitudinal axis of the
`assembly such that print head chips of adjacent modules overlap in a
`direction transversely to a direction of movement of print media past the
`assemblies.
`The print head module at one end of each assembly may have a
`projecting portion which projects beyond an end of its assembly and the print
`head module at the other end has a recessed portion to receive the projecting
`portion of the print head module at said one end of an adjacent assembly.
`The print head module may comp1ise a microelec-tromechanical print
`head chip comprised of a number of ink jet nozzles, the nozzles of
`overlapping portions of adjacent modules to be used being digitally selected.
`The angle of the print head modules relative to the longitudinal axis of
`the assembly may be selected depending on a print pattern required. Each
`print head module may have approximately 1587 dots per inch (dpi). To
`simulate 1600 dpi printing the print heads may be angled at approximately '?
`to the longitudinal axis, more specifically 7.17°.
`Each assembly may include a chassis and an ink reservoir mounted on
`the chassis, the print head modules of the assembly being attached to the ink
`reservoir. Preferably, the modules are releasably attached to the ink
`reservoir.
`The assembly may include an ink supply system for supplying ink to
`the reservoirs of each assembly.
`The chassis may be a rigid chassis for imparting torsional rigidity to
`each assembly.
`The ink reservoir of each assembly may have ink inlet nozzles at one
`end and sealable air bleeding openings at an opposed end.
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`According to a second aspect of the invention there is provided a
`component for a print head module, the component including
`a print head chip;
`a flexible printed circuit board (PCB) on which the chip is
`5 mounted; and
`a carrier having fluid communication channels defined therein
`for supplying ink to the chip, the PCB being bonded to the carrier in a liquid
`tight manner so that th_e_PCB forms a wall of an ink supply chamber of the
`print head module.
`In this specification, the term "wall" is to be understood in a broad
`sense, unless the context clearly indicates otherwise, to include any part of a
`structure including its floor and roof or ceiling.
`The chip may be a microelectromechanical chip comprised of a
`number of nozzles.
`The flexible PCB may include a film member on which are arranged a
`plurality of electrically conductive pathways, contacts and connections for
`providing power and data signals to the chip. The film may be a Tape
`Automated Bond (TAB) film.
`The carrier, with the flexible PCB bonded thereto, may form a floor of
`the ink supply chamber.
`The carrier may be a rigid structure having flow paths defined therein.
`The carrier may comprise a frame from which a plurality of ribs extend to
`define a pair of opposed comb-like structures and a central, longitudinally
`extending channel between the structures in which the chip is received.
`The chip may be bonded sealingly to the flexible PCB on both sides of
`the PCB.
`According to a third aspect of the invention, there is provided a print
`head assembly which includes
`at least one print head module including a print head chip;
`a carrier for supporting the, or each, print head module in an
`operative position for printing on print media; and
`mating formations carried by the, or each, print head module and
`the carrier such that, when the, or each, print head module is mounted on
`the carrier, electrical contact is made between electrical contacts of the, or
`each, print head module and electrical contacts of the carrier.
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`The assembly may include a plurality of print head modules supported
`in end-to-end relationship on the carrier.
`Each print head module may include a cover molding defining a
`plurality of ink supply chambers for supplying ink to its associated chip.
`The cover molding may have a chamber-defining portion, a floor of
`which is defined by a micromolding sub-assembly which is secured to the
`chamber-defining portion in a fluid tight manner, the mating formation of
`each print head module_ being defined by a sidewall portion of the chamber(cid:173)
`defining portion which is angled with respect to the floor so that an included
`angle between the floor and the sidewall portion is an acute angle.
`The carrier may include an ink reservoir to which each print head
`module is releasably attached, the mating formation of the reservoir being
`defined by an angled wing portion extending from a roof of the reservoir and
`spaced from a reservoir-defining portion of the reservoir to define a slot in
`15 which the sidewall portion of the cover molding is slidably received, the
`angle of the wing corresponding with that of the sidewall portion to effect
`sliding contact between the electrical contacts of each print head module and
`the carrier when said print head module is attached to the carrier and vice
`versa.
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`The electrical contacts of each print head module may be defined by a
`flexible PCB wrapped about the sidewall and the electrical contacts of the
`carrier may be defined by a flexible PCB supported by the wing portion and
`busbars sandwiched, in use, between the sidewall portion and the wing
`portion.
`According to a fourth aspect of the invention there is provided an ink
`supply device for supplying ink to a print head chip, the device including a
`molding of a settable material, the molding being a two shot molding having
`a first part of a first material and a second part of a second material.
`The molding may be a precision injection molding.
`The first part may be of an elastomeric material and the second part
`may be of a rigid material. More particularly, the first part may comprise a
`plurality of collars of a hydrophobic, elastomeric compound which, in use,
`seal about ink supply nozzles of an ink reservoir and the second part may be
`a molding of an Acetal material.
`According to a fifth aspect of the invention, there is provided a power
`supply means for a print head assembly, the power supply means including
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`a first strip of an electrically conductive material, the first strip
`having a pair of spaced terminals projecting from a side edge thereof;
`a second strip of an electrically conductive material, the second
`strip having a single terminal projecting from a corresponding side edge
`thereof, the arrangement being such that, when the two strips are arranged
`side by side, the single terminal of the second strip is arranged between, and
`equidistantly from, the two terminals of the first strip; and
`a strip of insp.lating material arranged between the two strips.
`The first strip may be a positive power rail and the second strip is a
`negative power or earth rail.
`Power supply contacts may be arranged along those side edges of the
`strips having the terminals. The contacts may be in the form of resiliently
`flexible fingers.
`According to a sixth aspect of the invention there is provided a method
`of manufacturing a print head assembly which includes the steps of
`selecting a micromolding sub-assembly, the sub-assembly
`comprising a print head chip, a flexible printed circuit board (PCB) and a
`micromolding;
`attaching the micromolding sub-assembly to a cover molding to
`form a print module;
`forming an ink reservoir sub-assembly;
`attaching a plurality of the print head modules to the ink
`reservoir sub-assembly in end-to-end relationship; and
`charging ink into the reservoir sub-assembly and testing the
`completed assembly.
`The method may include forming the micromolding sub-assembly by
`applying the print head chip to the PCB, sealing the chip to the PCB,
`applying the PCB to a micromolding and sealing the PCB to the
`micromolding in a fluidtight manner.
`The method may further include testing the chip before applying it to
`the PCB.
`The method may include forming the ink reservoir sub-assembly by
`bonding an ink reservoir base molding and ink reservoir cover molding
`together, the cover molding having ink filling nozzles at one end and air
`bleeding openings at an opposed end.
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`The method may then include attaching the completed ink reservoir
`sub-assembly to a rigid chassis for inhibiting torsional displacement.
`The method may include attaching a flexible printed circuit board and
`a power supply means to the ink reservoir sub-assembly to make electrical
`contact with the PCB of each print head module when each print head
`module is mounted on the ink reservoir sub-assembly.
`The method may include, after charging ink into the reservoir of the
`ink reservoir sub-asse!I_ll?,ly, sealing the air bleeding openings.
`Finally, the method may include capping the print head chips prior to
`shipping the completed assemblies.
`BriefDescription of the Drawings.
`The invention is now described by way of example with reference to
`the accompanying drawings in which:
`Figure 1 shows a three dimensional view, from above, of a print head
`assembly, in accordance with the invention;
`Figure 2 shows a three dimensional view, from below, of the assembly;
`Figure 3 shows a three dimensional, exploded view of the assembly;
`Figure 4 shows a bottom view of the assembly;
`Figure 5 shows a three dimensional view, from below, of the assembly
`20 with parts omitted;
`Figure 6 shows, on an enlarged scale, an end view of the assembly;
`Figure 7 shows, on the enlarged scale, a sectional end view of the
`assembly:
`Figure 8 shows a three dimensional, exploded view of a print head
`25 module of the assembly;
`Figure 9 shows a bottom view of the module;
`Figure 10 shows a plan view of the module;
`Figure 11 shows a sectional end view of the module taken along line
`XI-XI in Figure 10;
`Figure 12 shows a three dimensional, exploded view of an ink reservoir
`of the assembly;
`Figure 13 shows a three dimensional view of a flexible printed circuit
`board of the assembly;
`Figure 14 shows a three dimensional, exploded view of a busbar
`arrangement of the assembly;
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`Figure 15 shows a three dimensional view of a multiple print head
`assembly configuration; and
`Figure 16 shows, on an enlarged scale, a sectional side view of the
`bonding of the print head chip to the TAB film.
`5 Detailed Description of the Drawings.
`A print head assembly, in accordance with the invention is designated
`generally by the reference numeral10. The assembly 10 uses a plurality of
`replaceable print head ~odules 12. The advantage of this arrangement is the
`ability to easily remove and replace any defective modules 12 in the
`assembly 10: ·This eliminates having to scrap an entire print head assembly
`10 if only one module 12 is defective.
`The assembly 10 comprises a chassis 14 on which an ink reservoir 16
`is secured. The print head modules 12 are, in turn, attached to the reservoir
`16.
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`Each print head module 12 is comprised of a microelectromechanical
`(Memjet) chip 18 (shown most clearly in Figure 8 of the drawings) bonded by
`adhesive 20 to a Tape Automated Bond (TAB) film 22, the TAB film 22 being
`electrically connected to the chip 18. The chip 18 and the TAB film 22 form
`a sub-assembly 24 which is attached to a micromolding 26. The
`20 micromolding 26 is, in turn, supported on a cover molding 28.
`Each module 12 forms a sealed unit with four independent ink
`chambers 30 defined in the cover molding 28, the ink chambers 30 supplying
`ink to the chip 18. Each print head module 12 is plugged into a reservoir
`molding 32 (shown most clearly in Figures 3 and 7 of the drawings) of the ink
`reservoir 16 that supplies the ink. Ten modules 12 butt together into the
`reservoir 16 to form a complete 8 inch print head assembly 10. The ink
`reservoirs 16 themselves are modular, so complete 8 inch print head arrays
`can be configured to form a print head assembly 10 of a desired width.
`The 8 inch modular print head assembly 10, according to the
`invention, is designed for a print speed and inkflow rate that allows up to 160
`pages per minute printing at 1600 dpi photographic quality. Additionally, a
`second print head assembly, of the same construction, can be mounted in a
`printer on the opposite side for double sided high speed printing.
`As described above, and as illustrated most clearly in Figure 8 of the
`drawings, at the heart of the print head assembly 10 is the :tviemjet chip 18.
`The TAB film 22 is bonded on to the chip 18 and is sealed with the adhesive
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`20 around all edges of the chip 18 on both sides. This forms the core Memjet
`print head chip sub-assembly 24.
`The sub-assembly 24 is bonded on to the micromolding 26. This
`molding 26 mates with the TAB film 22 which, together, form a floor 34
`(Figure 11) of the ink chambers 30 of the cover molding 28. The chambers
`30 open in a flared manner in a top 36 of the cover molding 28 to define
`filling funnels 38. A soft elastomeric, hydrophobic collar 40 is arranged
`above each funnel 38. ~he collars 40 sealingly engage with complementary
`filling formations or nozzles 42 (Figure 7) of the reservoir molding 32 of the
`ink reservoir-16 to duct ink to the chip 18.
`Snap details or clips 44 project from the top 36 of the cover molding 28
`to clip the cover molding 28 releasably to the ink reservoir 16.
`The TAB film 22 extends up an angled side wall46 of the cover
`molding 28 where it is also bonded in place. The side wall46 of the cover
`15 molding 28 provides the TAB film 22 with a suitable bearing surface for data
`and power contact pads 48 (Figure 8).
`The sub-assembly 24, the micromolding 26 and the cover molding 28
`together form the 1\!Iemjet print head module 12. A plurality of these print
`head modules 12 snap fit in angled, end-to-end relationship on to the ink
`reservoir 16. The reservoir 16 acts as a carrier for the modules 12 and
`provides ink ducts 52 (Figure 7) for four ink colors, Cyan, Magenta, Yellow
`and blacK (CNIYK). The four ink colors are channelled through the
`individual funnels 38 of the cover molding 28 into each print head module
`12.
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`The print head modul~s 12 butt up to one another in an overlapping,
`angled fashion as illustrated most clearly in Figures 2 and 4 of the drawings.
`This is to allow the Memjet chips 18 to diagonally overlap in order to
`produce continuous print head lengths from 0.8 inches to 72 inches (for wide
`format printers) and beyond.
`The :tvfemjet chip 18 is 21.0 mm long x 0.54 mm wide and 0.3 mm high.
`A protective silicon nozzle shield that is 0.3 mm high is bonded to the upper
`surface of the Memjet chip 18.
`Each Memjet nozzle includes a thermoelastic actuator that is attached
`to a moving nozzle assembly. The actuator has two structurally independent
`layers of titanium nitride (TiN) that are attached to an anchor on the silicon
`substrate at one end and a silicon nitride (nitride) lever arm/nozzle assembly
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`at the other end. The top TiN or "heater" layer forms an electrical circuit
`which is isolated from the ink by nitride. The moving nozzle is positioned
`over an ink supply channel that extends through the silicon substrate. The
`ink supply channel is fluidically sealed around the substrate holes periphery
`by a TiN sealing rim. Ink ejection is prevented between the TiN rim and the
`nitride nozzle assembly by the action of surface tension over a 1 micron gap.
`A 1 microsecond 3V, 27 rnA pulse (85 nanoJoules) is applied to the
`terminals of the heater l~yer, increasing the heater temperature by Joule
`heating. The transient thermal field causes an expansion of the heater layer
`that is structurally relieved by an "out of plane" deflection caused by the
`presence of the other TiN layer.
`Deflection at the actuator tip is amplified by the lever arm and forces
`the nozzle assembly towards the silicon ink supply channel. The nozzle
`assembly's movement combines with the inertia and viscous drag of the ink
`in the supply channel to generate a positive pressure field that causes the
`ejection of a droplet.
`1\llemjet actuation is caused by a transient thermal field. The passive
`TiN layer only heats up by thermal conduction after droplet ejection.
`Thermal energy dissipates by thermal conduction into the substrate and the
`ink, causing the actuator to return to the 'at rest' position. Thermal energy is
`dissipated away from the print head chip by ejected droplets. The drop
`ejection process takes around 5 microseconds. The nozzle refills and waste
`heat diffuses within 20 microseconds allowing a 50 KHz drop ejection rate.
`The Memjet chip 18 has 1600 nozzles per inch for each color. This
`allows true 1600 dpi color printing, resulting in full photographic image
`quality. A 21 mm CMYK chip 18 has 5280 nozzles. Each nozzle has a shift
`register, a transfer register, an enable gate, and a drive transistor. Sixteen
`data connections drive the chip 18.
`Some configurations of Memjet chips 18 require a nozzle shield. This
`nozzle shield is a micromachined silicon part which is wafer bonded to the
`front surface of the wafer. It protects the Memjet nozzles from foreign
`particles and contact with solid objects and allows the packaging operation to
`be high yield.
`The TAB film 22 is a standard single sided TAB film comprised of
`polyimide and copper layers. A slot accommodates the Memjet chip 18. The
`TAB film 22 includes gold plated contact pads 48 that connect with a flexible
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`printed circuit board (PCB) 54 (Figure 13) of the assembly 10 and bus bar
`contacts 56 (Figure 14) of bus bars 58 and 60 of the assembly 10 to get data
`and power respectively to the chip 18. Protruding bond wires are gold
`bumped, then bonded to bond pads of the Niemjet chip 18.
`The junction between the TAB film 22 and all the chip sidewalls has
`sealant applied to the front face in the first instance. The sub-assembly 24 is
`then turned over and sealant is applied to the rear junction. This is done to
`completely seal the chip 18 and the TAB film 22 together to protect electrical
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`contact because the TAB film 22 forms the floor 34 of the ink chambers 30 in
`the print head module 12.
`The flexible PCB 54 is a single sided component that supplies the TAB
`films 22 of each print head module 12 with data connections through
`contact pads, which interface with corresponding contacts 48 on each TAB
`film 22. The flex PCB 54 is mounted in abutting relationship with the TAB
`film 22 along the angled sidewall 46 of the cover molding 28. The flex PCB
`54 is maintained in electrical contact with the TAB film 22 of each print head
`module 12 by means of a pressure pad 62 (Figure 7) . The PCB 54 wraps
`underneath and along a correspondingly angled sidewall 64 of the ink
`reservoir molding 32 of the ink reservoir 16. The part of the PCB 54 against
`the sidewall 64 carries a 62 pin connector 66.
`The sidewall 64 of the ink reservoir molding 32 of the ink reservoir 16
`is angled to correspond with the sidewall 32 of the cover molding 16 so that,
`when the print head module 12 is mated to the ink reservoir 16, the contacts
`48 of the TAB film 22 wipe against those of the PCB 54. The angle also
`allows for easy removal of the module 12. The flex PCB 54 is 'sprung' by the
`action of the deformable pressure pad 62 which allows for positive pressure
`to be applied and maintained between the contacts of the flex PCB 54 and the
`TAB film 22.
`The micromolding 26 is a precision injection molding made of an
`30 Acetal type material. It accommodates the Memjet chip 18 (with the TAB
`film 22 already attached) and mates with the cover molding 28.
`Rib details 68 (Figure 8) in the underside of the micromolding 26
`provide support for the TAB film 22 when they are bonded together. The
`TAB film 22 forms the floor 34 of the print head module 12, as there is
`enough structural integrity due to the pitch of the ribs 68 to support a flexible
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`film. The edges of the TAB film 22 seal on the underside walls of the cover
`molding 28.
`The chip 18 is bonded on to 100 micron wide ribs 70 that run the
`length of the micromolding 26. A channel 72 is defined between the ribs 70
`for providing the final ink feed into the nozzles of the Memjet chip 18.
`The design of the micromolding 26 allows for a physical overlap of the
`Memjet chips 18 when they are butted in a line. Because the Memjet chips
`18 now form a continuo~s strip with a generous tolerance, they can be
`adjusted digitally to produce the required print pattern, rather than relying
`on very close tolerance moldings and exotic materials to perform the same
`function. The pitch of the modules 12 is 20.33 mm.
`The micromolding 26 fits inside the cover molding 28, the
`micromolding 26 bonding on to a set of vertical ribs 7 4 extending from the
`top 36 of the cover molding 28.
`The cover molding 28 is a two shot, precision injection molding that
`combines an injected hard plastic body (Acetal) with soft elastomeric
`features (synthetic rubber). This molding interfaces with the sub-assembly
`24 bonded to the micromolding 26. When bonded into place the base sub(cid:173)
`assembly, comprising the sub-assembly 24 and the micromolding 26, mates
`20 with the vertical ribs 74 of the cover molding 28 to form the sealed ink
`chambers 30.
`As indicated above, an opening of each chamber 30 is surrounded by
`one of the collars 40. These soft collars 40 are made of a hydrophobic,
`elastomeric compound that seals against the ink nozzles 42 of the ink
`reservoir 16. The snap fits 44 on the cover molding 28 locate the module 12
`with respect to the ink reservoir 16.
`The ink reservoir 16 comprises the ink reservoir molding 32 and a lid
`molding 76 (Figure 7). The molding 32 is a simple four chamber injection
`molding with the lid molding 76 that is bonded on top to form a sealed
`environment for each color ink. Ink supply pipes 78 (Figure 12) are arranged
`at one end of the lid molding 76 to communicate with ink channels 80
`defined in the reservoir molding 32. Labyrinthine, hydrophobic air holes 82
`are defined at an opposed end of the lid molding 76. The air holes 82 are
`included for bleeding the channels 80 during charging. These holes 82 are
`covered over with a self adhesive film 84 after charging.
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`The lid molding 76 has heat stakes 88, (pins that are designed to melt
`and hold the molding onto another part) which position and secure the ink
`reservoir 16 to the punched, sheet metal chassis 14. Additional heat stakes
`90 are arranged along the reservoir molding 32. These stakes are shown after
`deformation in Figure 1 of the drawings once the ink reservoir 16 has been
`secured to the chassis 14.
`Receiving formations 92 are defined along the sides of the reservoir
`molding 32 for releasabl_y receiving the clips 44 of the print head modules 12.
`As previously described, the sidewall 64 on the side of the reservoir
`10 molding 32 provides a mounting area for the flexible PCB 54 and data
`connector 66. The reservoir molding 32 also carries details for facilitating the
`accurate mounting of the V-and V + bus bars 58 and 60, respectively.
`The metal chassis 14 is a precision punched, folded and plated metal
`chassis used to mount the print head assembly 10 into various products. The
`ink reservoir 16 is heat staked to the chassis 14 via the heat stakes 88 and 90.
`The chassis 14 includes a return edge 94 for mechanical strength. The
`chassis 14 can be easily customized for print head mounting and any further
`part additions. It can also be extended in length to provide multiple arrays
`of print head assemblies 10 for wider format printers.
`Slots 97 are defined in the chassis 14 for enabling access to be gained
`to the clips 44 of the modules 12 to release the modules 12 from the ink
`reservoir 16 for enabling replacement of one or more of the modules 12.
`Thin finger strip metallic strip busbars 58 and 60 conduct V- and V+,
`respectively, to the TAB film 22 on each print head module 12. The two
`busbars 58 and 60 are separated by an insulating strip 96 (Figure 14). The
`flexible, finger-like contacts 56 are arranged along one side edge of each
`busbar 58, 60. The contacts 56 electrically engage the relevant contact pads
`48 of the TAB film 22 of each module 12 for providing power to the module
`12. The contacts 56 are separated by fine rib details on the underside of the
`ink reservoir molding 32.
`A busbar sub-assembly 98, comprising the busbars 58, 60 and the
`insulating strip 96 is mounted on the underside of the sidewall 64 of the
`reservoir molding 32 of the ink reservoir 16. The sub-assembly is held
`captive between that sidewall64 and the sidewall46 of the cover molding 28
`by the pressure pad 62.
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`A single spade connector 100 is fixed to a protrusion 102 on the busbar
`58 for ground. Two spade connectors 104 are mounted on corresponding
`protrusions 106 on the busbar 60 for power. The arrangement is such that,
`when the sub-assembly 98 is assembled, the spade connectors 104 are
`arranged on opposite sides of the spade connector 100. In this way, the
`likelihood of reversing polarity of the power supply to the assembly 10, when
`the assembly 10 is installed, is reduced. During print head module 12
`installation or replacem~nt, these are the first components to be disengaged,
`cutting power to the module 12.
`To assemble the print head assembly 10, a !viemjet chip 18 is dry tested
`in flight by a pick and place robot, which also dices the wafer and transports
`individual chips 18 to a TAB film bonding area. When a chip 18 has been
`accepted, a TAB film 22 is picked, bumped and applied to the chip 18.
`A slot in the TAB film 22 that accepts the chip 18 and has the adhesive
`20, which also functions as a sealant, applied to the upper and lower surfaces
`around the chip 18 on all sides. This operation forms a complete seal with
`the side walls of the chip 18. The connecting wires are potted during this
`process.
`The Memjet chip 18 and TAB film 22 sub-assembly 24 is transported to
`another machine containing a stock of micromoldings 26 for placing and
`bonding. Adhesive is applied to the underside of the fine ribs 70 in the
`channel 72 of the micromolding 26 and the mating side of the underside ribs
`68 that lie directly underneath the TAB film 22. The sub-assembly 24 is
`mated with the micromolding 26.
`The micromolding sub-assembly, comprising the micromolding 26 and
`the sub-assembly 24, is transported to a machine containing the cover
`moldings 28. When the micromolding sub-assembly and cover molding 28
`are bonded together, the TAB film 22 is sealed on to the underside walls of
`the cover molding 28 to form a sealed unit. The TAB film 22 further wraps
`around and is glued to the sidewall 46 of the cover molding 28.
`The chip 18, TAB film 22, micromolding 26 and cover molding 28
`assembly form a complete Memjet print head module 12 with four sealed
`independent ink chambers 30 and ink inlets 38.
`The ink reservoir molding 32 and the cover molding 76 are bonded
`together to form a complete sealed unit. The sealing film 84 is placed
`partially over the air outlet holes 82 so as not to completely seal the holes 82.
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`Upon completion of the charging of ink into the ink reservoir 16, the holes 82
`are sealed by the film 84. The ink reservoir 16 is then placed and heat staked
`on to the metal chassis 14.
`The full length flexible PCB 54 with a cushioned adhesive backing is
`bonded to the angled sidewall 64 of the ink reservoir 16. The flex PCB 54
`terminates in the data connector 66, which is mounted on an external surface
`of the sidewall 64 of the ink reservoir 16.
`Actuator V- and~+ connections are transmitted to each module 12 by
`the two identical metal finger strip busbars 58 and 60. The busbar sub-
`assembly 98. is mounted above the flex PCB 54 on the underside of the
`sidewall 64 of the ink reservoir molding 32. The busbars 58, 60 and the
`insulating strip 96 are located relative to the ink reservoir molding 32 via
`pins (not shown) projecting from the sidewall 64 of the ink reservoir molding
`32, the pins being received through locating holes 108 in the bus bars 58, 60
`and the insulating strip 96.
`The 1-'Iemjet print head modules 12 are clipped into the overhead ink
`reservoir molding 32. Accurate alignment of the module 12 to the reservoir
`molding 32 is not necessary, as a complete print head assembly 10 will
`undergo digital adjustment of each chip 18 during final QA testing.
`Each print head module's TAB film 22 interfaces with the flex PCB 54
`and busbars 58, 60 as it is clipped into the ink reservoir 16. To disengage a
`print head module 12 from the reservoir 16, a custom tool is inserted through
`the appropriate slots 97 in the metal chassis 14 from above. The tool'fingers'
`slide down the walls of the ink reservoir molding 32, where they contact the
`clips 44 of the cover molding 28. Further pressure acts to ramp the four clips
`44 out of engagement with the receiving formations 92 and disengage the
`print head module 12 from the ink reservoir 16.
`To charge the ink reservoir 16 with ink, hoses 110 (Figure 3) are
`attached to the pipes 78 and filtered ink from a supply is charged into each
`channel 80. The openings 82 at the other end of the ink reservoir cover
`molding 76 are used to bleed off air during priming. The openings 82 have
`tortuous ink paths that run across the surface, which connect through to the
`internal ink channels 80. These ink paths are partially sealed by the bonded
`transparent plastic film 84 during charging. The film 84 serves to indicate
`35 when inks are in the ink channels 80, so they can be fully capped off when
`charging has been completed.
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`15
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`For electrical connections and testing, power and data connections are
`made to the flexible PCB 54. Final testing then commences to calibrate the
`print head modules 12. Upon successful completion of the testing, the
`Memjet print head assembly 10 has a plastic sealing film applied over the
`underside that caps the print head modules 12 and, more particularly, their
`chips 18, until product installation.
`It is to be noted that there is an overlap between adjacent modules 12.
`Part of the testing procec:I:ure determines which nozzles of the overlapping
`portions of the adjacent chips 18 are to be used.
`As shown in Figure 15 of the drawings, the design of the modular
`Memjet print head assemblies 10 allows them to be butted together in an
`end-to-end configuration. It is therefore possible to build a multiple print
`head system 112 in, effectively, unlimited lengths. As long as each print
`head assembly 10 is fed with ink, then it is entirely possible to consider print
`head widths of several hundred feet. This means that the only width limit
`for a Memjet printer product is the maximum manufacturable size of the
`intended print media.
`Figure 15 shows how a multiple Memjet print head system 112 could
`be configured for wide format printers. Replaceable ink cartridges 114, one
`for each color, are inserted into an intermediate ink reservoir 116 that always
`has a supply of filtered ink. Hoses 118 exit from the underside of the
`reservoir 118 and connect up to the ink inlet pipes 78 of each print head
`assembly 10.
`It will be appreciate