METHOD OF ATTACHING PRINTHEAD INTEGRATED CIRCUITS TO AN INK MANIFOLD USING ADHESIVE FILM

Field of the Invention The present invention relates to printers and in particular inkj et printers.

Background of the Invention

The Applicant has developed a wide range of printers that employ pagewidth printheads instead of traditional reciprocating printhead designs. Pagewidth designs increase print speeds as the printhead does not traverse back and forth across the page to deposit a line of an image. The pagewidth printhead simply deposits the ink on the media as it moves past at high speeds. Such printheads have made it possible to perform full colour 1600dpi printing at speeds in the vicinity of 60 pages per minute, speeds previously unattainable with conventional inkjet printers.

Printing at these speeds consumes ink quickly and this gives rise to problems with supplying the printhead with enough mk. Not only are the flow rates higher but distributing the ink along the entire length of a pagewidth printhead is more complex than feeding ink to a relatively small reciprocating printhead.

Printhead integrated circuits are typically attached to an ink manifold using an adhesive film. It would be desirable to provide a film, which optimizes this attachment process so as to provide an printhead assembly exhibiting minimal ink leakages.

Summary of the Invention

In a first aspect the present invention provides a laminated film for attachment of one or more printhead integrated circuits to an ink supply manifold, said film having a plurality of mk supply holes defined therein, said laminated film comprising: a central polymeric film; a first adhesive layer for bonding a first side of said film to said ink supply manifold; and a second adhesive layer for bonding a second side of said film to said one or more printhead integrated circuits, said central polymeric film being sandwiched between said first and second adhesive layers, wherein a first melt temperature of said first adhesive layer is at least 10 ⁰ C less than a second melt temperature of said second adhesive layer.

Optionally, said first melt temperature is at least 20 ⁰ C less than said second melt temperature. RRE049 51 -PCT

Optionally, said central polymeric film is a polyiniide film.

Optionally, said first and second adhesive layers are epoxy films.

Optionally, a total thickness of said film is in the range of 40 to 200 microns.

Optionally, said central polymeric film has a thickness in the range of 20 to 100 microns.

Optionally, said first and second adhesive layers each have a thickness in the range of 10 to 50 microns.

Optionally, each ink supply hole has a length dimension in the range of 50 to 500 microns, and a width dimension in the range of 50 to 500 microns.

In a further aspect there is provided a film package comprising: the laminated film for attachment of one or more printhead integrated circuits to an ink supply manifold, said film having a plurality of ink supply holes defined therein, said laminated film comprising: a central polymeric film; a first adhesive layer for bonding a first side of said film to said ink supply manifold; and a second adhesive layer for bonding a second side of said film to said one or more printhead integrated circuits, said central polymeric film being sandwiched between said first and second adhesive layers, wherein a first melt temperature of said first adhesive layer is at least 10 ⁰ C less than a second melt temperature of said second adhesive layer. ; and first and second protective liners, each of said liners being removeably attached to a respective adhesive layer.

Optionally, each protective liner is a polyester film.

In another aspect the present invention provides a printhead assembly comprising: an ink manifold having a plurality of ink outlets defined in a manifold bonding surface; one or more printhead integrated circuits, each printhead integrated circuit having a plurality of ink inlets defined in a printhead bonding surface; and RRE049 51 -PCT

a laminated film sandwiched between said manifold bonding surface and said one or more prmthead bonding surfaces, said film having a plurality of ink supply holes defined therein, each ink supply hole being aligned with a respective ink outlet and an ink mlet, said laminated film comprising: a central polymeric film; a first adhesive layer bonded to said manifold bonding surface; and a second adhesive layer bonded to said one or more prmthead bonding surfaces, said central polymeric film being sandwiched between said first and second adhesive layers, wherein a first melt temperature of said first adhesive layer is at least 10 ⁰ C less than a second melt temperature of said second adhesive layer.

Optionally, each ink supply hole is substantially free of any adhesive.

Optionally, said first and second adhesive layers each have a uniform thickness along a longitudinal extent of said prmthead assembly.

Optionally, a first bonding surface of said first adhesive layer and a second bonding surface of said second adhesive layer are uniformly planar along a longitudinal extent of said prmthead assembly.

Optionally, the prmthead assembly comprising a plurality of prmthead integrated circuits butted end on end along a longitudinal extent of said ink supply manifold.

Optionally, said plurality of prmthead integrated circuits define a prmthead having a uniformly planar ink ejection face.

Optionally, said prmthead assembly exhibits a leakage rate of less than 5 mm' per mmute when charged with air at 10 kPa, said leakage rate being measured after soaking said prmthead assembly m ink at 90 ⁰ C for one week.

Optionally, a plurality of ink mlets are defined by an ink supply channel extending longitudinally along said prmthead bonding surface, and wherein a plurality of ink supply holes are aligned with one mk supply channel, each of said plurality of ink supply holes being spaced apart longitudinally along said mk supply channel.

Optionally, said ink supply manifold is an LCP molding.

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In another aspect there is provided a pagewidth printer comprising a stationary pπnthead assembly comprising: an ink manifold having a plurality of ink outlets defined m a manifold bonding surface; one or more pπnthead integrated circuits, each pπnthead integrated circuit having a plurality of ink inlets defined m a pnnthead bonding surface; and a laminated film sandwiched between said manifold bonding surface and said one or more pπnthead bonding surfaces, said film having a plurality of ink supply holes defined therein, each ink supply hole being aligned with a respective ink outlet and an ink inlet, said laminated film compπsmg: a central polymeπc film; a first adhesive layer bonded to said manifold bonding surface; and a second adhesive layer bonded to said one or more pπnthead bonding surfaces, said central polymeπc film being sandwiched between said first and second adhesive layers, wherein a first melt temperature of said first adhesive layer is at least 10 ⁰ C less than a second melt temperature of said second adhesive layer.

In a second aspect the present invention provides a method of attaching one or more pπnthead integrated circuits to an ink supply manifold, said method compπsmg the steps of:

(a) providing a laminated film having a plurality of ink supply holes defined therein, said laminated film compπsmg a central polymeπc film sandwiched between first and second adhesive layers, wherein a first melt temperature of said first adhesive layer is at least 1O ⁰ C less than a second melt temperature of said second adhesive layer; (b) aligning said film with said ink supply manifold such that each ink supply hole is aligned with a respective ink outlet defined m a manifold bonding surface of said ink supply manifold;

(b) bonding said first adhesive layer to said manifold bonding surface by applying heat and pressure to an opposite side of said film; (c) aligning said one or more pπnthead integrated circuits with said film such that each ink supply hole is aligned with an ink inlet defined in a pπnthead bonding surface of each pπnthead integrated circuit; and

(d) bonding said one or more pnnthead integrated circuits to said second adhesive layer.

Optionally, m step (b), said second adhesive layer is protected by a removeable protective liner.

Optionally, said protective liner is removed prior to step (c). RRE049 51 -PCT

Optionally, m step (b), said first adhesive layer reaches its melt temperature and said second adhesive layer does not reach its melt temperature.

Optionally, said first melt temperature is at least 20 ⁰ C less than said second melt temperature.

Optionally, m step (b), the applied heat corresponds to said first melt temperature.

Optionally, substantially no adhesive flows into said ink supply holes during at least step (b).

Optionally, step (c) comprises the step of optically locating a centroid of each ink supply hole, wherein said locating step is facilitated by the absence of adhesive from said ink supply holes.

Optionally, each ink supply hole has a length dimension m the range of 50 to 500 microns, and a width dimension m the range of 50 to 500 microns.

Optionally, said laminated film maintains its structural integrity after step (b), such that said second adhesive layer maintains a uniform thickness along its longitudinal extent.

Optionally, said laminated film maintains its structural integrity after step (b), such that a second bonding surface defined by said second adhesive layer maintains uniform planaπty along its longitudinal extent.

Optionally, step (d) comprises heating each pπnthead integrated circuit and positioning each heated prmthead integrated circuit on said second bonding surface.

Optionally, an adhesive bonding time m step (d) is less than 2 seconds by virtue of said uniform planaπty of said second bonding surface.

Optionally, a plurality of prmthead integrated circuits are individually aligned and bonded to said second adhesive layer, said plurality being positioned such that they butt together end on end along a longitudinal extent of said ink supply manifold.

Optionally, a plurality of ink inlets are defined by an ink supply channel extending longitudinally along said pπnthead bonding surface, and wherein a plurality of ink supply holes are aligned with

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one ink supply channel, each of said plurality of ink supply holes being spaced apart longitudinally along said ink supply channel.

Optionally, said central polymeric film is a polyimide film.

Optionally, said first and second adhesive layers are epoxy films.

Optionally, a total thickness of said laminated film is m the range of 40 to 200 microns.

Optionally, said central polymeric film has a thickness m the range of 20 to 100 microns.

Optionally, said first and second adhesive layers each have a thickness m the range of 10 to 50 microns.

In a third aspect the present invention provides a pπnthead assembly comprising: an ink manifold having a plurality of ink outlets defined m a manifold bonding surface; one or more pπnthead integrated circuits, each pπnthead integrated circuit having a plurality of ink inlets defined m a pnnthead bonding surface; and an adhesive film sandwiched between said manifold bonding surface and said one or more pπnthead bonding surfaces, said film having a plurality of ink supply holes defined therein, each ink supply hole being aligned with an ink outlet and an ink inlet, wherein said pnnthead assembly exhibits a leakage rate of less than 10 mnf per minute when charged with air at 10 kPa, said leakage rate being measured after soaking said pnnthead assembly m ink at 90 ⁰ C for one week.

Optionally, said leakage rate is less than 1 mm ³ per minute.

Optionally, said leakage rate is less than 0.2 mm ³ per mmute.

Optionally, each ink supply hole is substantially free of any adhesive.

Optionally, each ink supply hole has a length dimension m the range of 50 to 500 microns, and a width dimension m the range of 50 to 500 microns.

Optionally, a total thickness of said adhesive film is m the range of 40 to 200 microns.

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Optionally, said ink supply manifold is an LCP molding.

In a further aspect there is provided a printhead assembly comprising a plurality of printhead integrated circuits butted end on end along a longitudinal extent of said ink supply manifold.

Optionally, a plurality of ink inlets are defined by an ink supply channel extending longitudinally along said printhead bonding surface, and wherein a plurality of ink supply holes are aligned with one ink supply channel, each of said plurality of ink supply holes being spaced apart longitudinally along said ink supply channel.

Optionally, each printhead bonding surface has a plurality of ink supply channels defined therein, each ink supply channel defining a plurality of ink inlets.

Optionally, said adhesive film is a laminated film comprising: a central polymeric film; a first adhesive layer bonded to said manifold bonding surface; and a second adhesive layer bonded to said one or more printhead bonding surfaces, said central polymeric web being sandwiched between said first and second adhesive layers.

Optionally, a first melt temperature of said first adhesive layer is at least 10 ⁰ C less than a second melt temperature of said second adhesive layer.

Optionally, said first and second adhesive layers each have a uniform thickness along a longitudinal extent of said printhead assembly.

Optionally, a first bonding surface of said first adhesive layer and a second bonding surface of said second adhesive layer are uniformly planar along a longitudinal extent of said printhead assembly.

Optionally, said central polymeric film is a polyimide film.

Optionally, said first and second adhesive layers are epoxy films.

Optionally, said central polymeric film has a thickness in the range of 20 to 100 microns.

Optionally, said first and second adhesive layers each have a thickness in the range of 10 to 50 microns.

RRE049 51 -PCT

In another aspect there is provided the printhead assembly which is a pagewidth printhead assembly.

In a further aspect the present invention provides a pagewidth printer comprising a stationary printhead assembly comprising: an ink manifold having a plurality of ink outlets defined in a manifold bonding surface; one or more printhead integrated circuits, each printhead integrated circuit having a plurality of ink inlets defined in a printhead bonding surface; and an adhesive film sandwiched between said manifold bonding surface and said one or more printhead bonding surfaces, said film having a plurality of ink supply holes defined therein, each ink supply hole being aligned with an ink outlet and an ink inlet, wherein said printhead assembly exhibits a leakage rate of less than 10 mm ³ per minute when charged with air at 10 kPa, said leakage rate being measured after soaking said printhead assembly in ink at 90 ⁰ C for one week.

Brief Description of the Drawings

Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which:

Figure 1 is a front and side perspective of a printer embodying the present invention;

Figure 2 shows the printer of Figure 1 with the front face in the open position;

Figure 3 shows the printer of Figure 2 with the printhead cartridge removed; Figure 4 shows the printer of Figure 3 with the outer housing removed;

Figure 5 shows the printer of Figure 3 with the outer housing removed and printhead cartridge installed;

Figure 6 is a schematic representation of the printer's fluidic system;

Figure 7 is a top and front perspective of the printhead cartridge; Figure 8 is a top and front perspective of the printhead cartridge in its protective cover;

Figure 9 is a top and front perspective of the printhead cartridge removed from its protective cover;

Figure 10 is a bottom and front perspective of the printhead cartridge;

Figure 1 1 is a bottom and rear perspective of the printhead cartridge;

Figures 12A-F shows the elevations of all sides of the printhead cartridge: Figure 13 is an exploded perspective of the printhead cartridge;

Figure 14 is a transverse section through the ink inlet coupling of the printhead cartridge;

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Figure 15 is an exploded perspective of the ink inlet and filter assembly;

Figure 16 is a section view of the cartridge valve engaged with the printer valve;

Figure 17 is a perspective of the LCP molding and flex PCB;

Figure 18 is an enlargement of mset A shown m Figure 17; Figure 19 is an exploded bottom perspective of the LCP/flex PCB/pπnthead IC assembly;

Figure 20 is an exploded top perspective of the LCP/flex PCB/pπnthead IC assembly;

Figure 21 is an enlarged view of the underside of the LCP/flex PCB/pπnthead IC assembly;

Figure 22 shows the enlargement of Figure 21 with the pπnthead ICs and the flex PCB removed;

Figure 23 shows the enlargement of Figure 22 with the pπnthead IC attach film removed; Figure 24 shows the enlargement of Figure 23 with the LCP channel molding removed;

Figure 25 shows the pπnthead ICs with back channels and nozzles superimposed on the ink supply passages;

Figure 26 m an enlarged transverse perspective of the LCP/flex PCB/pπnthead IC assembly;

Figure 27 is a plan view of the LCP channel molding; Figures 28A and 28B are schematic section views of the LCP channel molding pπmmg without a weir;

Figures 29A, 29B and 29C are schematic section views of the LCP channel molding priming with a weir;

Figure 30 m an enlarged transverse perspective of the LCP molding with the position of the contact force and the reaction force;

Figure 31 shows a reel of the IC attachment film;

Figure 32 shows a section of the IC attach film between liners;

Figure 33A-C are partial sections showing vaπous stages of traditional laser-drilling of an attachment film; and Figures 34A-C are partial sections showing vaπous stages of double laser-drilling of an attachment film;

Figures 35A-D are longitudinal sections of a schematic pπnthead IC attachment process;

Figures 36A and 36B are photographs of ink supply holes m two different attachment films after a first bonding step; and Figures 37A and37B are longitudinal sections of a schematic pπnthead IC attachment process m accordance with the present indention.

Detailed Description of the Preferred Embodiments

OVERVIEW

Figure 1 shows a printer 2 embodying the present invention. The mam body 4 of the printer supports a media feed tray 14 at the back and a pivoting face 6 at the front. Figure 1 shows the pivoting face 6 closed such that the display screen 8 is its upπght viewing position. Control

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buttons 10 extend from the sides of the screen 8 for convenient operator input while viewing the screen. To print, a single sheet is drawn from the media stack 12 m the feed tray 14 and fed past the prmthead (concealed within the printer). The printed sheet 16 is delivered through the printed media outlet slot 18.

Figure 2 shows the pivoting front face 6 open to reveal the interior of the printer 2. Opening the front face of the printer exposes the prmthead cartridge 96 installed within. The prmthead cartridge 96 is secured m position by the cartridge engagement cams 20 that push it down to ensure that the ink coupling (described later) is fully engaged and the prmthead ICs (described later) are correctly positioned adjacent the paper feed path. The cams 20 are manually actuated by the release lever 24. The front face 6 will not close, and hence the printer will not operate, until the release lever 24 is pushed down to fully engage the cams. Closing the pivoting face 6 engages the printer contacts 22 with the cartridge contacts 104.

Figure 3 shows the printer 2 with the pivoting face 6 open and the pπnthead cartridge 96 removed. With the pivoting face 6 tilted forward, the user pulls the cartridge release lever 24 up to disengage the cams 20. This allows the handle 26 on the cartridge 96 to be gripped and pulled upwards. The upstream and downstream ink couplings 112A and 112B disengage from the printer conduits 142. This is described m greater detail below. To install a fresh cartridge, the process is reversed. New cartridges are shipped and sold m an unpπmed condition. So to ready the printer for printing, the active fluidics system (described below) uses a downstream pump to prime the cartridge and pπnthead with ink.

In Figure 4, the outer casing of the printer 2 has been removed to reveal the internals. A large ink tank 60 has separate reservoirs for all four different inks. The ink tank 60 is itself a replaceable cartridge that couples to the printer upstream of the shut off valve 66 (see Figure 6).

There is also a sump 92 for ink drawn out of the cartridge 96 by the pump 62. The printer fluidics system is described m detail with reference to Figure 6. Briefly, ink from the tank 60 flows through the upstream ink lines 84 to the shut off valves 66 and on to the printer conduits 142. As shown in Figure 5, when the cartridge 96 is installed, the pump 62 (driven by motor 196) can draw ink into the LCP molding 64 (see Figures 6 and 17 to 20) so that the prmthead ICs 68 (again, see

Figures 6 and 17 to 20) prime by capillary action. Excess ink drawn by the pump 62 is fed to a sump 92 housed with the ink tanks 60.

The total connector force between the cartridge contacts 104 and the printer contacts 22 is relatively high because of the number of contacts used. In the embodiment shown, the total contact force is 45 Newtons. This load is enough to flex and deform the cartridge. Turning briefly to RRE049 51 -PCT

Figure 30, the internal structure of the chassis molding 100 is shown. The bearing surface 28 shown in Figure 3 is schematically shown m Figure 30. The compressive load of the printer contacts on the cartridge contacts 104 is represented with arrows. The reaction force at the bearing surface 28 is likewise represented with arrows. To maintain the structural integrity of the cartridge 96, the chassis molding 100 has a structural member 30 that extends in the plane of the connector force. To keep the reaction force acting in the plane of the connector force, the chassis also has a contact rib 32 that bears against the bearing surface 28. This keeps the load on the structural member 30 completely compressive to maximize the stiffness of the cartridge and minimize any flex.

PRINT ENGINE PIPELINE

The print engine pipeline is a reference to the printer's processing of print data received from an external source and outputted to the printhead for printing. The print engine pipeline is described in detail in USSN 11/014769 (RRCOOlUS) filed December 20, 2004, the disclosure of which is incorporated herein by reference.

FLUIDIC SYSTEM

Traditionally printers have relied on the structure and components within the printhead, cartridge and ink lines to avoid fluidic problems. Some common fluidic problems are deprimed or dried nozzles, outgassing bubble artifacts and color mixing from cross contamination. Optimizing the design of the printer components to avoid these problems is a passive approach to fluidic control. Typically, the only active component used to correct these were the nozzle actuators themselves. However, this is often insufficient and or wastes a lot of ink in the attempt to correct the problem. The problem is exacerbated in pagewidth printheads because of the length and complexity of the ink conduits supplying the printhead ICs.

The Applicant has addressed this by developing an active fluidic system for the printer.

Several such systems are described in detail in USSN 11/677049 (Our Docket SBF006US) the contents of which are incorporated herein by reference. Figure 6 shows one of the single pump implementations of the active fluidic system which would be suitable for use with the printhead described in the present specification.

The fluidic architecture shown m Figure 6 is a single ink line for one color only. A color printer would have separate lines (and of course separate ink tanks 60) for each ink color. As RRE049 51 -PCT

shown in Figure 6, this architecture has a single pump 62 downstream of the LCP molding 64, and a shut off valve 66 upstream of the LCP molding. The LCP molding supports the printhead ICs 68 via the adhesive IC attach film 174 (see Figure 25). The shut off valve 66 isolates the ink in the ink tank 60 from the printhead ICs 66 whenever the printer is powered down. This prevents any color mixing at the printhead ICs 68 from reaching the ink tank 60 during periods of inactivity. These issues are discussed in more detail in the cross referenced specification USSN 11/677049 (our Docket SBF006US).

The ink tank 60 has a venting bubble point pressure regulator 72 for maintaining a relatively constant negative hydrostatic pressure in the ink at the nozzles. Bubble point pressure regulators within ink reservoirs are comprehensively described in co-pending USSN 11/640355 (Our Docket RMC007US) incorporated herein by reference. However, for the purposes of this description the regulator 72 is shown as a bubble outlet 74 submerged in the ink of the tank 60 and vented to atmosphere via sealed conduit 76 extending to an air inlet 78. As the printhead ICs 68 consume ink, the pressure in the tank 60 drops until the pressure difference at the bubble outlet 74 sucks air into the tank. This air forms a forms a bubble in the ink which rises to the tank's headspace. This pressure difference is the bubble point pressure and will depend on the diameter (or smallest dimension) of the bubble outlet 74 and the Laplace pressure of the ink meniscus at the outlet which is resisting the ingress of the air.

The bubble point regulator uses the bubble point pressure needed to generate a bubble at the submerged bubble outlet 74 to keep the hydrostatic pressure at the outlet substantially constant (there are slight fluctuations when the bulging meniscus of air forms a bubble and rises to the headspace in the ink tank). If the hydrostatic pressure at the outlet is at the bubble point, then the hydrostatic pressure profile in the ink tank is also known regardless of how much ink has been consumed from the tank. The pressure at the surface of the ink in the tank will decrease towards the bubble point pressure as the ink level drops to the outlet. Of course, once the outlet 74 is exposed, the head space vents to atmosphere and negative pressure is lost. The ink tank should be refilled, or replaced (if it is a cartridge) before the ink level reaches the bubble outlet 74.

The ink tank 60 can be a fixed reservoir that can be refilled, a replaceable cartridge or (as disclosed in RRCOOlUS incorporated by reference) a refillable cartridge. To guard against particulate fouling, the outlet 80 of the ink tank 60 has a coarse filter 82. The system also uses a fine filter at the coupling to the printhead cartridge. As filters have a finite life, replacing old filters by simply replacing the ink cartridge or the printhead cartridge is particularly convenient for the user. If the filters are separate consumable items, regular replacement relies on the user's diligence. RRE049 51 -PCT

When the bubble outlet 74 is at the bubble point pressure, and the shut off valve 66 is open, the hydrostatic pressure at the nozzles is also constant and less than atmospheric. However, if the shut off valve 66 has been closed for a period of time, outgassing bubbles may form in the LCP molding 64 or the printhead ICs 68 that change the pressure at the nozzles. Likewise, expansion and contraction of the bubbles from diurnal temperature variations can change the pressure in the ink line 84 downstream of the shut off valve 66. Similarly, the pressure in the ink tank can vary during periods of inactivity because of dissolved gases coming out of solution.

The downstream ink line 86 leading from the LCP 64 to the pump 62 can include an ink sensor 88 linked to an electronic controller 90 for the pump. The sensor 88 senses the presence or absence of ink in the downstream ink line 86. Alternatively, the system can dispense with the sensor 88, and the pump 62 can be configured so that it runs for an appropriate period of time for each of the various operations. This may adversely affect the operating costs because of increased ink wastage.

The pump 62 feeds into a sump 92 (when pumping in the forward direction). The sump 92 is physically positioned in the printer so that it is less elevated than the printhead ICs 68. This allows the column of ink in the downstream ink line 86 to "hang' from the LCP 64 during standby periods, thereby creating a negative hydrostatic pressure at the printhead ICs 68. A negative pressure at the nozzles draws the ink meniscus inwards and inhibits color mixing. Of course, the peristaltic pump 62 needs to be stopped in an open condition so that there is fluid communication between the LCP 64 and the ink outlet in the sump 92.

Pressure differences between the ink lines of different colors can occur during periods of inactivity. Furthermore, paper dust or other particulates on the nozzle plate can wick ink from one nozzle to another. Driven by the slight pressure differences between each ink line, color mixing can occur while the printer is inactive. The shut off valve 66 isolates the ink tank 60 from the nozzle of the printhead ICs 68 to prevent color mixing extending up to the ink tank 60. Once the ink in the tank has been contaminated with a different color, it is irretrievable and has to be replaced.

The capper 94 is a printhead maintenance station that seals the nozzles during standby periods to avoid dehydration of the printhead ICs 68 as well as shield the nozzle plate from paper dust and other particulates. The capper 94 is also configured to wipe the nozzle plate to remove dried ink and other contaminants. Dehydration of the printhead ICs 68 occurs when the ink solvent, typically water, evaporates and increases the viscosity of the ink. If the ink viscosity is too RRE049 51 -PCT

high, the ink ejection actuators fail to eject ink drops. Should the capper seal be compromised, dehydrated nozzles can be a problem when reactivating the printer after a power down or standby period.

The problems outlined above are not uncommon during the operative life of a printer and can be effectively corrected with the relatively simple fluidic architecture shown in Figure 6. It also allows the user to initially prime the printer, deprime the printer prior to moving it, or restore the printer to a known print ready state using simple trouble-shooting protocols. Several examples of these situations are described in detail in the above referenced USSN 11/677049 (Our Docket SBF006US).

PRINTHEAD CARTRIDGE

The printhead cartridge 96 is shown in Figures 7 to 16A. Figure 7 shows the cartridge 96 in its assembled and complete form. The bulk of the cartridge is encased in the cartridge chassis 100 and the chassis lid 102. A window in the chassis 100 exposes the cartridge contacts 104 that receive data from the print engine controller in the printer.

Figures 8 and 9 show the cartridge 96 with its snap on protective cover 98. The protective cover 98 prevents damaging contact with the electrical contacts 104 and the printhead ICs 68 (see Figure 10). The user can hold the top of the cartridge 96 and remove the protective cover 98 immediately prior to installation in the printer.

Figure 10 shows the underside and 'back' (with respect to the paper feed direction) of the printhead cartridge 96. The printhead contacts 104 are conductive pads on a flexible printed circuit board 108 that wraps around a curved support surface (discussed below in the description relating to the LCP moulding) to a line of wire bonds 110 at one side if the printhead ICs 68. On the other side of the printhead ICs 68 is a paper shield 106 to prevent direct contact with the media substrate.

Figure 11 shows the underside and the 'front' of the printhead cartridge 96. The front of the cartridge has two ink couplings 112A and 112B at either end. Each ink coupling has four cartridge valves 114. When the cartridge is installed in the printer, the ink couplings 112A and 112B engage complementary ink supply interfaces (described in more detail below). The ink supply interfaces have printer conduits 142 which engage and open the cartridge valves 114. One of the ink couplings 112A is the upstream ink coupling and the other is the downstream coupling 112B. The upstream coupling 112A establishes fluid communication between the printhead ICs

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68 and the ink supply 60 (see Figure 6) and the downstream coupling 112B connects to the sump 92 (refer Figure 6 again).

The various elevations of the printhead cartridge 96 are shown in Figure 12. The plan view of the cartridge 96 also shows the location of the section views shown in Figures 14, 15 and 16.

Figure 13 is an exploded perspective of the cartridge 96. The LCP molding 64 attaches to the underside of the cartridge chassis 100. In turn the flex PCB 108 attaches to the underside of the LCP molding 64 and wraps around one side to expose the printhead contacts 104. An inlet manifold and filter 116 and outlet manifold 118 attach to the top of the chassis 100. The inlet manifold and filter 116 connects to the LCP inlets 122 via elastomeric connectors 120. Likewise the LCP outlets 124 connect to the outlet manifold 118 via another set of elastomeric connectors 120. The chassis lid 102 encases the inlet and outlet manifolds in the chassis 100 from the top and the removable protective cover 98 snaps over the bottom to protect the contacts 104 and the printhead ICs (see Figure 11).

INLET AND FILTER MANIFOLD

Figure 14 is an enlarged section view taken along line 14-14 of Figure 12. It shows the fluid path through one of the cartridge valves 114 of the upstream coupling 112A to the LCP molding 64. The cartridge valve 114 has an elastomeric sleeve 126 that is biased into sealing engagement with a fixed valve member 128. The cartridge valve 114 is opened by the printer conduit 142 (see Figure 16) by compressing the elastomeric sleeve 126 such that it unseats from the fixed valve member 128 and allows ink to flow up to a roof channel 138 along the top of the inlet and filter manifold 116. The roof channel 138 leads to an upstream filter chamber 132 that has one wall defined by a filter membrane 130. Ink passes through the filter membrane 130 into the downstream filter chamber 134 and out to the LCP inlet 122. From there filtered ink flows along the LCP main channels 136 to feed into the printhead ICs (not shown).

Particular features and advantages of the inlet and filter manifold 116 will now be described with reference to Figure 15. The exploded perspective of Figure 15 best illustrates the compact design of the inlet and filter manifold 116. There are several aspects of the design that contribute to its compact form. Firstly, the cartridge valves are spaced close together. This is achieved by departing from the traditional configuration of self-sealing ink valves. Previous designs also used an elastomeric member biased into sealing engagement with a fixed member. However, the elastomeric member was either a solid shape that the ink would flow around, or in the form of a diaphragm if the ink flowed through it. RRE049 51 -PCT

In a cartridge coupling, it is highly convenient for the cartridge valves to automatically open upon installation. This is most easily and cheaply provided by a coupling m which one valve has an elastomeπc member which is engaged by a rigid member on the other valve. If the elastomeπc member is m a diaphragm form, it usually holds itself against the central rigid member under tension. This provides an effective seal and requires relatively low tolerances. However, it also requires the elastomer element to have a wide peripheral mounting. The width of the elastomer will be a trade-off between the desired coupling force, the integrity of the seal and the material properties of the elastomer used.

As best shown m Figure 16, the cartridge valves 114 of the present invention use elastomeπc sleeves 126 that seal against the fixed valve member 128 under residual compression. The valve 114 opens when the cartridge is installed m the printer and the conduit end 148 of the printer valve 142 further compresses the sleeve 126. The collar 146 unseals from the fixed valve member 128 to connect the LCP 64 into the pπnter fluidic system (see Figure 6) via the upstream and downstream ink coupling 112A and 112B. The sidewall of the sleeve is configured to bulge outwardly as collapsing inwardly can create a flow obstruction. As shown m Figure 16, the sleeve 126 has a line of relative weakness around its mid-section that promotes and directs the buckling process. This reduces the force necessary to engage the cartridge with the printer, and ensures that the sleeve buckles outwardly.

The coupling is configured for 'no-drip' disengagement of the cartridge from the printer. As the cartridge is pulled upwards from the pπnter the elastomeπc sleeve 126 pushes the collar 146 to seal against the fixed valve member 128. Once the sleeve 126 has sealed against the valve member 128 (thereby sealing the cartridge side of the coupling), the sealing collar 146 lifts together with the cartridge. This unseals the collar 146 from the end of the conduit 148. As the seal breaks an ink meniscus forms across the gap between the collar and the end of the conduit 148. The shape of the end of the fixed valve member 128 directs the meniscus to travel towards the middles of its bottom surface instead of pinning to a point. At the middle of the rounded bottom of the fixed valve member 128, the meniscus is driven to detach itself from the now almost hoπzontal bottom surface. To achieve the lowest possible energy state, the surface tension drives the detachment of the meniscus from the fixed valve member 128. The bias to minimize meniscus surface area is strong and so the detachment is complete with very little, if any, ink remaining on the cartndge valve 114. Any remaining ink is not enough a drop that can drip and stam prior to disposal of the cartridge.

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^" When a fresh cartridge is installed m the printer, the air m conduit 150 will be entrained into the ink flow 152 and ingested by the cartridge. In light of this, the mlet manifold and filter assembly have a high bubble tolerance. Referring back to Figure 15, the ink flows through the top of the fixed valve member 128 and into the roof channel 138. Being the most elevated point of the mlet manifold 116, the roof channels can trap the bubbles. However, bubbles may still flow into the filter inlets 158. In this case, the filter assembly itself is bubble tolerant.

Bubbles on the upstream side of the filter member 130 can affect the flow rate - they effectively reduce the wetted surface area on the dirty side of the filter membrane 130. The filter membranes have a long rectangular shape so even if an appreciable number of bubbles are drawn into the dirty side of the filter, the wetted surface area remains large enough to filter ink at the required flow rate. This is crucial for the high speed operation offered by the present invention.

^" While the bubbles m the upstream filter chamber 132 can not cross the filter membrane 130, bubbles from outgassmg may generate bubbles m the downstream filter chamber 134. The filter outlet 156 is positioned at the bottom of the downstream filter chamber 134 and diagonally opposite the mlet 158 m the upstream chamber 132 to minimize the effects of bubbles m either chamber on the flow rate.

The filters 130 for each color are vertically stacked closely side-by-side. The partition wall

162 partially defines the upstream filter chamber 132 on one side, and partially defines the downstream chamber 134 of the adjacent color on the other side. As the filter chambers are so thm (for compact design), the filter membrane 130 can be pushed against the opposing wall of the downstream filter chamber 134. This effectively reduces the surface are of the filter membrane 130. Hence it is detrimental to maximum flowrate. To prevent this, the opposing wall of the downstream chamber 134 has a series of spacer ribs 160 to keep the membrane 130 separated from the wall.

Positioning the filter mlet and outlet at diagonally opposed corners also helps to purge the system of air during the initial pπme of the system.

To reduce the πsk of particulate contamination of the pπnthead, the filter membrane 130 is welded to the downstream side of a first partition wall before the next partition wall 162 is welded to the first partition wall. In this way, any small pieces of filter membrane 130 that break off during the welding process, will be on the 'dirty' side of the filter 130.

LCP MOLDING/FLEX PCB/PRINTHEAD ICS

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The LCP molding 64, flex PCB 108 and printhead ICs 68 assembly are shown in Figures 17 to 33. Figure 17 is a perspective of the underside of the LCP molding 64 with the flex PCB and printhead ICs 68 attached. The LCP molding 64 is secured to the cartridge chassis 100 through coutersunk holes 166 and 168. Hole 168 is an obround hole to accommodate any miss match in coefficients of thermal expansion (CTE) without bending the LCP. The printhead ICs 68 are arranged end to end in a line down the longitudinal extent of the LCP molding 64. The flex PCB 108 is wire bonded at one edge to the printhead ICs 68. The flex PCB 108 also secures to the LCP molding at the printhead IC edge as well as at the cartridge contacts 104 edge. Securing the flex PCB at both edges keeps it tightly held to the curved support surface 170 (see Figure 19). This ensures that the flex PCB does not bend to a radius that is tighter than specified minimum, thereby reducing the risk that the conductive tracks through the flex PCB will fracture.

Figure 18 is an enlarged view of Inset A shown in Figure 17. It shows the line of wire bonding contacts 164 along the side if the flex PCB 108 and the line of printhead ICs 68.

Figure 19 is an exploded perspective of the LCP/flex/printhead IC assembly showing the underside of each component. Figure 20 is another exploded perspective, this time showing the topside of the components. The LCP molding 64 has an LCP channel molding 176 sealed to its underside. The printhead ICs 68 are attached to the underside of the channel molding 176 by adhesive IC attach film 174. On the topside of the LCP channel molding 176 are the LCP main channels 184. These are open to the ink inlet 122 and ink outlet 124 in the LCP molding 64. At the bottom of the LCP main channels 184 are a series of ink supply passages 182 leading to the printhead ICs 68. The adhesive IC attach film 174 has a series of laser drilled supply holes 186 so that the attachment side of each printhead IC 68 is in fluid communication with the ink supply passages 182. The features of the adhesive IC attach film are described in detail below with reference to Figure 31 to 33.

The LCP molding 64 has recesses 178 to accommodate electronic components 180 in the drive circuitry on the flex PCB 108. For optimal electrical efficiency and operation, the cartridge contacts 104 on the PCB 108 should be close to the printhead ICs 68. However, to keep the paper path adjacent the printhead straight instead of curved or angled, the cartridge contacts 104 need to be on the side of the cartridge 96. The conductive paths in the flex PCB are known as traces. As the flex PCB must bend around a corner, the traces can crack and break the connection. To combat this, the trace can be bifurcated prior to the bend and then reunited after the bend. If one branch of the bifurcated section cracks, the other branch maintains the connection. Unfortunately, splitting

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the trace into two and then joining it together again can give rise to electro-magnetic interference problems that create noise in the circuitry.

Making the traces wider is not an effective solution as wider traces are not significantly more crack resistant. Once the crack has initiated in the trace, it will propagate across the entire width relatively quickly and easily. Careful control of the bend radius is more effective at minimizing trace cracking, as is minimizing the number of traces that cross the bend in the flex PCB.

Pagewidth printheads present additional complications because of the large array of nozzles that must fire in a relatively short time. Firing many nozzles at once places a large current load on the system. This can generate high levels of inductance through the circuits which can cause voltage dips that are detrimental to operation. To avoid this, the flex PCB has a series of capacitors that discharge during a nozzle firing sequence to relieve the current load on the rest of the circuitry. Because of the need to keep a straight paper path past the printhead ICs, the capacitors are traditionally attached to the flex PCB near the contacts on the side of the cartridge. Unfortunately, they create additional traces that risk cracking in the bent section of the flex PCB.

This is addressed by mounting the capacitors 180 (see Figure 20) closely adjacent the printhead ICs 68 to reduce the chance of trace fracture. The paper path remains linear by recessing the capacitors and other components into the LCP molding 64. The relatively flat surface of the flex PCB 108 downstream of the printhead ICs 68 and the paper shield 172 mounted to the 'front' (with respect to the feed direction) of the cartridge 96 minimize the risk of paper jams.

Isolating the contacts from the rest of the components of the flex PCB minimizes the number of traces that extend through the bent section. This affords greater reliability as the chances of cracking reduce. Placing the circuit components next to the printhead IC means that the cartridge needs to be marginally wider and this is detrimental to compact design. However, the advantages provided by this configuration outweigh any drawbacks of a slightly wider cartridge. Firstly, the contacts can be larger as there are no traces from the components running in between and around the contacts. With larger contacts, the connection is more reliable and better able to cope with fabrication inaccuracies between the cartridge contacts and the printer-side contacts. This is particularly important in this case, as the mating contacts rely on users to accurately insert the cartridge.

Secondly, the edge of the flex PCB that wire bonds to the side of the printhead IC is not under residual stress and trying to peel away from the bend radius. The flex can be fixed to the RRE049 51 -PCT

support structure at the capacitors and other components so that the wire bonding to the printhead IC is easier to form during fabrication and less prone to cracking as it is not also being used to anchor the flex.

Thirdly, the capacitors are much closer to the nozzles of the printhead IC and so the electro-magnetic interference generated by the discharging capacitors is minimized.

Figure 21 is an enlargement of the underside of the printhead cartridge 96 showing the flex PCB 108 and the printhead ICs 68. The wire bonding contacts 164 of the flex PCB 108 run parallel to the contact pads of the printhead ICs 68 on the underside of the adhesive IC attach film 174. Figure 22 shows Figure 21 with the printhead ICs 68 and the flex PCB removed to reveal the supply holes 186. The holes are arranged in four longitudinal rows. Each row delivers ink of one particular color and each row aligns with a single channel in the back of each printhead IC.

Figure 23 shows the underside of the LCP channel molding 176 with the adhesive IC attach film 174 removed. This exposes the ink supply passages 182 that connect to the LCP main channels 184 (see Figure 20) formed in the other side of the channel molding 176. It will be appreciated that the adhesive IC attach film 174 partly defines the supply passages 182 when it is stuck in place. It will also be appreciated that the attach film must be accurately positioned, as the individual supply passages 182 must align with the supply holes 186 laser drilled through the film 174.

Figure 24 shows the underside of the LCP molding with the LCP channel molding removed. This exposes the array of blind cavities 200 that contain air when the cartridge is primed with ink in order to damp any pressure pulses. This is discussed in greater detail below.

PRINTHEAD IC ATTACH FILM Laser Ablated Film

Turning briefly to Figures 31 to 33, the adhesive IC attachment film is described in more detail. The film 174 may be laser drilled and wound onto a reel 198 for convenient incorporation in the printhead cartridge 96. For the purposes of handling and storage, the film 174 has two protective liners (typically PET liners) on either side. One is an existing liner 188B that is already attached to the film prior to laser drilling. The other is a replacement liner 192, which replaces an existing liner 188A, after the drilling operation.

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The section of the laser-drilled film 174 shown m Figure 32 has some of the existing liner 188B removed to expose the supply holes 186. The replacement liner 192 on the other side of the film replaces an existing liner 188A after the supply holes 186 have been laser drilled.

Figures 33A to 33C show in detail how the film 174 is manufactured by laser ablation.

Figure 33 A shows in detail the laminate structure of the film prior to laser-drilling. The central web 190 is typically a polyimide film and provides the strength for the laminate. The web 190 is sandwiched between first and second adhesive layers 194A and 194B, which are typically epoxy layers. The first adhesive layer 194A is for bonding to the LCP channel molding 176. The second adhesive layer 194B is for bonding to the printhead ICs 68. In accordance with the present invention, the first adhesive layer 194A has a melt temperature which is at least 10 ⁰ C less than the melt temperature of the second adhesive layer 194B. As described m more detail below, this difference in melt temperatures vastly improves control of the printhead IC attachment process and, consequently, improves the performance of the film 174 in use.

For the purposes of film storage and handling, each adhesive layer 194A and 194 B is covered with a respective lmer 188A and 188B. The central web 190 typically has a thickness of from 20 to 100 microns (usually about 50 microns). Each adhesive layer 194A and 194B typically has a thickness of from 10 to 50 microns (usually about 25 microns).

Referring to Figure 33B, laser-drilling is performed from the side of the film defined by the liner 188A. A hole 186 is drilled through the first liner 188A, the epoxy layers 194A and 194B and the central web 190. The hole 186 terminates somewhere in the liner 188B, and so the liner 188B may be thicker than the liner 188A (e g. liner 188A may be 10-20 microns thick; liner 188B may be 30-100 microns thick).

The foraminous liner 188A on the laser-entry side is then removed and replaced with a replacement liner 192, to provide the film package shown m Figure 33C. This film package is then wound onto a reel 198 (see Figure 31) for storage and handling prior to attachment. When the printhead cartridge is assembled, suitable lengths are drawn from the reel 198, the liners removed, and the film 174 adhered to the underside of the LCP channel molding 176 such that the holes 186 are in registration with the correct ink supply passages 182 (see Figure 25).

Laser drilling is a standard method for defining holes in polymer films. However, a problem with laser drilling is that it deposits a carbonaceous soot 197 in and around the drilling site (see Figures 33B and 33C). Soot around a protective liner may be easily dealt with, because this is usually replaced after laser drilling. However, soot 197 deposited in and around the actual supply RRE049 51 -PCT

holes 186 is potentially problematic. When the film is compressed between the LCP channel molding 176 and pπnthead ICs 68 during bonding, the soot may be dislodged. Any dislodged soot 197 represents a means by which particulates may enter the ink supply system and potentially block nozzles m the prmthead ICs 68. Moreover, the soot is surprisingly fast and cannot be removed by conventional ultrasonication and/or IPA washing techniques.

From analysis of laser-drilled films 174, it has been observed by the present Applicants that the soot 197 is generally present on the laser-entry side of the film 174 (i.e. the epoxy layer 194A and central web 190), but is usually absent from the laser-exit side of the film (i.e. the epoxy layer 194B).

Double-Pass Laser Ablated Film

The Applicant has found, surprisingly, that double-pass laser ablation of the ink supply holes 186 eliminates the majority of soot deposits 197, including those on the laser-entry side of the film. The starting point for double-pass laser ablation is the film shown m Figure 33 A.

In a first step, a first hole 185 is laser-drilled from the side of the film defined by the lmer 188A. The hole 185 is drilled through the lmer 188A, the epoxy layers 194A and 194B, and the central web 190. The hole 185 terminates somewhere m the lmer 188B. The first hole 185 has smaller dimensions than the intended ink supply hole 186. Typically each length and width dimension of the first hole 185 is about 10 microns smaller than the length and width dimensions of the intended ink supply hole 186. It will be seen from Figure 34A that the first hole 185 has soot 197 deposited on the first lmer 188A, the first epoxy layer 194A and the central web 190.

In a second step, the first hole 185 is reamed by further laser drilling so as to provide the ink supply hole 186 having the desired dimensions. The reaming process generates very little soot and the resulting ink supply hole 186 therefore has clean sidewalls as shown in Figure 34B.

Finally, and referring to Figure 34C, the first lmer 188A is replaced with a replacement lmer 192 to provide a film package, which is ready to be wound onto a reel 198 and used subsequently for attaching prmthead ICs 68 to the LCP channel molding 176. The second lmer 188B may also be replaced at this stage, if desired.

Comparing the films shown m Figures 33C and 34C, it will be appreciated that the double laser ablation method provides a film 174 having much cleaner ink supply holes 186 than simple

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laser ablation. Hence, the film is highly suitable for attachment of pπnthhead ICs 68 to the LCP channel molding 176, and does not contaminate ink with undesirable soot deposits.

PRINTHEAD IC ATTACHMENT PROCESS

Referring to Figures 19 and 20, it will be appreciated that the printhead IC attachment process is a critical stage of printhead fabrication. In the IC attachment process, a first adhesive surface of the laser-drilled film 174 is initially bonded to the underside of LCP channel molding 176, and then the printhead ICs 68 are subsequently bonded to an opposite second adhesive surface of the film 174. The film 174 has epoxy-adhesive layers 194A and 194B on each side, which melt and bond under the application of heat and pressure.

Since the LCP channel molding 176 has very poor thermal conductivity, application of heat during each of the bonding processes must be provided via the second surface of the film 174, which is not in contact with the LCP channel molding.

Control of the bonding processes is critical for optimal printhead performance, both in terms of the positioning of each printhead IC 68 and in terms of supply of ink to the printhead ICs. A typical sequence of printhead IC attachment steps, using a prior art film 174 (as described in US PublicationNo. 2007^0206056) is shown schematically in longitudinal section in Figures 35A-D.

Referring to Figure 35 A, the film 174 is initially aligned with LCP channel molding 176 so that ink supply holes 186 are in proper registration with ink outlets defined in a manifold bonding surface 175. The ink outlets take the form of ink supply passages 182, as described above. The first adhesive layer 194A faces the manifold bonding surface 175, whilst the opposite side of the film is protected with the protective liner 188B.

Referring to Figure 35B, bonding of the film 174 to the manifold bonding surface 175 proceeds by applying heat and pressure from a heating block 302. A silicone rubber pad 300 separates the heating block 302 from the film liner 188B so as to prevent any damage to the film 174 during bonding. During bonding, the first epoxy layer 194 A is heated to its melt temperature and bonds to the bonding surface 175 of the LCP channel molding 176.

As shown in Figure 35C, the liner 188B is then peeled from the film 174 to reveal the second epoxy layer 194B. Next, the printhead IC 68 is aligned with the film 174 ready for the second bonding step. Figure 35C illustrates several problems, which are typically manifest in the first bonding step. Since the epoxy layers 194A and 194B are identical in prior art films, both of these layers melt during the first bonding step. Melting of the second epoxy layer 194B is RRE049 51 -PCT

problematic for many reasons. Firstly, some of the epoxy adhesive 199 is squeezed out from the second epoxy layer 194B and lines the laser-drilled ink supply holes 186. This decreases the area of the ink supply holes 186, thereby increasing ink flow resistance m the completed pπnthead assembly. In some cases, ink supply holes 186 may become completely blocked during the bonding process, which is very undesirable.

Figure 36B shows an actual photograph of one of the ink supply holes 186 suffering from the epoxy "squeeze-out" problem. Outer perimeter walls 310 show the original dimensions of the laser drilled hole 186. The light-colored material 312 within the perimeter walls 310 is adhesive, which has squeezed into the ink supply hole 186 during bonding to the LCP channel molding 176. Finally, the central dark area defined by perimeter walls 314 shows the effective cross-sectional area of the ink supply hole 186 after bonding. In this example, the original laser-drilled ink supply hole 186 has dimensions of 400 microns x 130 microns. After bonding and epoxy "squeeze-out", these dimensions were reduced to 340 microns x 80 microns. Notwithstanding the significant problems of increased ink flow resistance, the blurred edges of the ink supply hole 186 are problematic for the second bonding step, because the pπnthead ICs 68 must be aligned accurately with the ink supply holes 186. In automated pπnthead fabrication, a specialized alignment device uses optical means to locate a centroid of each ink supply hole 186. Optical location of each centroid is made more difficult when edges of each ink supply hole 186 are blurred by squeezed- out epoxy. Consequently, alignment errors are more likely.

A second problem with the second epoxy layer 194B melting is that the film 174 loses some of its overall structural integrity. As a consequence, the film 174 tends to billow or sag into the ink supply passages 182 defined m the LCP channel molding 176. Figure 35C illustrates sagging portions 198 of the film 174 after the first bonding step. The present Applicant has coined the term "tenting" to describe this phenomenon. "Tenting" is particularly problematic, because the bonding surface 195 of the second adhesive layer 194B loses its planaπty. This loss of planaπty is further exacerbated by thickness variations m the second adhesive layer 194B, resulting from the epoxy "squeeze-out" problem. The combination of "tenting" and thickness variations m the second adhesive layer 194B reduces the contact area of its bonding surface 195, and leads to problems m the second bonding step.

In the second bonding step, shown m Figure 35 D, each pπnthead IC 68 is heated to about 25O ⁰ C and then positioned accurately on the second adhesive layer 194B. Accurate alignment of the pπnthead IC 68 with the film 174 ensures that the ink supply channel 218, m fluid communication with nozzles 69, is placed over its corresponding ink supply holes 186. One ink

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supply channel 218 is shown in longitudinal section in Figure 35D, although it will be appreciated (from Figure 25) that each printhead IC 68 may have several rows of ink supply channels.

As a result of epoxy "squeeze-out", the second adhesive layer 194B, having an original thickness of about 25 microns, may have its thickness reduced to 5 to 10 microns in some regions. Such significant thickness variations in the second adhesive layer 194B can lead to skewed printhead IC placement, in which one end of the printhead IC 68 is raised relative to the other end. This is clearly undesirable and affects print quality. A further problem with a non-planar bonding surface 195 is that relatively long bonding times of about 5 seconds are typically required, and each printhead IC 68 needs to be pressed relatively far into the second adhesive layer 194B.

The most significant problem associated with printhead assemblies where "tenting" occurs in the adhesive film 174 is that the seal provided by the film may be imperfect. The present Applicant has developed a leak test to determine the effectiveness of the seal provided by the film 174 in a printhead assembly. In this test, the printhead assembly is initially soaked in ink at 9O ⁰ C for one week. After ink soaking and flushing, one color channel of the printhead assembly is then charged with air at 10 kPa, and the rate of air leakage from this color channel is measured. Leakages may occur by transfer of air to other color channels in the printhead (via the film 174) or by direct losses of air to the atmosphere. In this test, a typical printhead assembly fabricated using the IC attachment film described in US Publication No. 2007/0206056 has a leakage rate of about 300 mm ³ per minute or greater.

In light of the above-mentioned problems, the present invention provides an improved printhead IC attachment process, where these problems are minimized. The improved IC attachment process follows essentially the same steps as those described above in connection with Figures 35A-D. However, the design of the film 174 reduces the problems associated with the first bonding step and, equally importantly, reduces the consequential problems associated with the second bonding step. In the present invention, the film 174 still comprises a central polymeric web 190 sandwiched between first and second adhesive layers 194A and 194B. (For convenience, corresponding parts of the film 174 have the same labels used in the preceding description). However, in contrast with previous film designs, the first and second epoxy layers 194A and 194B are differentiated in the film according to the present invention. In particular, the epoxy layer 194A has a melt temperature, which is at least 10 ⁰ C less than the melt temperature of the second epoxy layer 194B. Typically, the difference in melt temperatures is at least 2O ⁰ C or at least 30 ⁰ C. For example, the first epoxy layer 194A may have a melt temperature in the range of 80 to 130 ⁰ C, whilst the second epoxy layer may have a melt temperature in the range of 140 to 18O ⁰ C. The RRE049 51 -PCT

skilled person will readily be able to select adhesive films (e.g. epoxy films) meeting the criteria of the present invention. Suitable adhesive films for use in the laminate film 174 are Hitachi DF-XL9 epoxy film (having a melt temperature of about 120 ⁰ C) and Hitachi DF-470 epoxy film (having a melt temperature of about 160 ⁰ C).

With films according to the present invention, the first bonding step (illustrated by Figure 35B) can be controlled so that no melting of the second adhesive layer 194B occurs during bonding of the first adhesive layer 194A to the bonding surface 195 of the LCP channel molding 176. Typically, the temperature of the heating block 302 matches the melt temperature of the first adhesive layer 194A. Consequently, "squeeze-out" of the first adhesive layer is minimized or eliminated altogether. Furthermore, minimal or no "tenting" occurs during the bonding process.

Referring to Figure 37A, there is shown a bonded LCP/film assembly using the film 174 according to the present invention. In contrast with the assembly shown in Figure 35C, it can be seen that no "tenting" in the film 174 has occurred, and that the second adhesive layer 194B has uniform planarity and thickness. Figure 36A shows an actual photograph of one of the ink supply holes 186 after bonding to the LCP channel molding 176 using a film 174 according to the present invention. The definition of the ink supply hole 186 is dramatically improved compared to the ink supply hole shown in Figure 36B, and it can be seen that no epoxy "squeeze-out" has occurred. Consequently, there is no undesirable increase in ink flow resistance through the hole shown in Figure 36A, and optical location of the hole's centroid can be performed with minimal errors.

Moreover, with the problems associated with the first bonding step minimized, the consequential problems associated with the second bonding step are also minimized. As shown in Figure 37A, the second adhesive layer 194B has a planar bonding surface 195, and has minimal thickness variations. Accordingly, printhead IC placement and bonding is significantly improved, with the result that relatively short bonding times of about 1 second can be employed. The planar bonding surface 195 shown in Figure 37A also means that printhead ICs 68 do not need to be pressed far into the second adhesive layer 194B to provide sufficient bonding strength, and skewed printhead ICs 68 are less likely to result from the attachment process.

Referring to Figure 37B, the printhead assembly resulting from the improved printhead IC attachment process has excellent seals around each ink supply hole 186, largely as a result of the absence of "tenting" and epoxy "squeeze-out". In the Applicant's leak tests described above, the printhead assembly shown in Figure 37B (fabricated using the film 174 according to the present invention) exhibited a remarkable 3000-fold improvement compared to the printhead assembly shown in Figure 35D. After soaking in ink at 9O ⁰ C for one week, the measured leakage rate for the RRE049 51 -PCT

pnnthead assembly shown m Figure 37B was about 0.1 mm ³ per minute, when charged with air at 10 kPa. The leak tests demonstrate the significant advantages of the present invention when compared with the pnnthead assembly described m, for example, US Publication No. 2007/0206056.

ENHANCED INK SUPPLY TO PRINTHEAD IC ENDS

Figure 25 shows the pnnthead ICs 68, superimposed on the ink supply holes 186 through the adhesive IC attach film 174, which are m turn supenmposed on the mk supply passages 182 m the underside of the LCP channel molding 176. Adjacent pnnthead ICs 68 are positioned end to end on the bottom of the LCP channel molding 176 via the attach film 174. At the junction between adjacent prmthead ICs 68, one of the ICs 68 has a 'drop triangle' 206 portion of nozzles m rows that are laterally displaced from the corresponding row m the rest of the nozzle array 220. This allows the edge of the pnntmg from one pnnthead IC to be contiguous with the pnntmg from the adjacent prmthead IC. By displacing the drop triangle 206 of nozzles, the spacing (m a direction perpendicular to media feed) between adjacent nozzles remains unchanged regardless of whether the nozzles are on the same IC or either side of the junction on different ICs. This requires precise relative positioning of the adjacent pnnthead ICs 68, and the fiducial marks 204 are used to achieve this. The process can be time consuming but avoids artifacts m the printed image.

Unfortunately, some of the nozzles at the ends of a pnnthead IC 68 can be starved of ink relative to the bulk of the nozzles m the rest of the array 220. For example, the nozzles 222 can be supplied with ink from two ink supply holes. Ink supply hole 224 is the closest. However, if there is an obstruction or particularly heavy demand from nozzles to the left of the hole 224, the supply hole 226 is also proximate to the nozzles at 222, so there is little chance of these nozzles depnmmg from ink starvation.

In contrast, the nozzles 214 at the end of the prmthead IC 68 would only be m fluid communication with the mk supply hole 216 were it not for the ' additional ' ink supply hole 210 placed at the junction between the adjacent ICs 68. Having the additional mk supply hole 210 means that none of the nozzles are so remote from an mk supply hole that they risk mk starvation.

Ink supply holes 208 and 210 are both fed from a common mk supply passage 212. The mk supply passage 212 has the capacity to supply both holes as supply hole 208 only has nozzles to its left, and supply hole 210 only has nozzles to its right. Therefore, the total flowrate through supply passage 212 is roughly equivalent to a supply passage that feeds one hole only.

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Figure 25 also highlights the discrepancy between the number of channels

(colors) in the ink supply- four channels - and the five channels 218 in the printhead IC 68. The third and fourth channels 218 in the back of the prmthead IC 68 are fed from the same ink supply holes 186. These supply holes are somewhat enlarged to span two channels 218.

The reason for this is that the printhead IC 68 is fabricated for use in a wide range of printers and printhead configurations. These may have five color channels - CMYK and IR (infrared) - but other printers, such this design, may only be four channel printers, and others still may only be three channel (CC, MM and Y). In light of this, a single color channel may be fed to two of the printhead IC channels. The print engine controller (PEC) microprocessor can easily accommodate this into the print data sent to the prmthead IC. Furthermore, supplying the same color to two nozzle rows in the IC provides a degree of nozzle redundancy that can used for dead nozzle compensation.

PRESSURE PULSES

Sharp spikes in the ink pressure occur when the ink flowing to the printhead is stopped suddenly. This can happen at the end of a print job or a page. The Assignee's high speed, pagewidth printheads need a high flow rate of supply ink during operation. Therefore, the mass of ink in the ink line to the nozzles is relatively large and moving at an appreciable rate.

Abruptly ending a print job, or simply at the end of a printed page, requires this relatively high volume of ink that is flowing relatively quickly to come to an immediate stop. However, suddenly arresting the ink momentum gives rise to a shock wave in the ink line. The LCP molding 64 (see Figure 19) is particularly stiff and provides almost no flex as the column of ink in the line is brought to rest. Without any compliance m the ink line, the shock wave can exceed the Laplace pressure (the pressure provided by the surface tension of the ink at the nozzles openings to retain ink in the nozzle chambers) and flood the front surface of the printhead IC 68. If the nozzles flood, ink may not eject and artifacts appear in the printing.

Resonant pulses in the ink occur when the nozzle firing rate matches a resonant frequency of the ink line. Again, because of the stiff structure that define the ink line, a large proportion of nozzles for one color, firing simultaneously, can create a standing wave or resonant pulse in the ink line. This can result in nozzle flooding, or conversely nozzle deprime because of the sudden pressure drop after the spike, if the Laplace pressure is exceeded.

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To address this, the LCP molding 64 incorporates a pulse damper to remove pressure spikes from the ink line. The damper may be an enclosed volume of gas that can be compressed by the mk. Alternatively, the damper may be a compliant section of the ink line that can elastically flex and absorb pressure pulses.

To minimize design complexity and retain a compact form, the invention uses compressible volumes of gas to damp pressure pulses. Damping pressure pulses using gas compression can be achieved with small volumes of gas. This preserves a compact design while avoiding any nozzle flooding from transient spikes m the ink pressure.

As shown m Figures 24 and 26, the pulse damper is not a single volume of gas for compression by pulses m the ink. Rather the damper is an array of cavities 200 distributed along the length of the LCP molding 64. A pressure pulse moving through an elongate pπnthead, such as a pagewidth pπnthead, can be damped at any point m the ink flow line. However, the pulse will cause nozzle flooding as it passes the nozzles m the prmthead integrated circuit, regardless of whether it is subsequently dissipated at the damper. By incorporating a number of pulse dampers into the ink supply conduits immediately next to the nozzle array, any pressure spikes are damped at the site where they would otherwise cause detrimental flooding.

It can be seen m Figure 26, that the air damping cavities 200 are arranged m four rows.

Each row of cavities sits directly above the LCP mam channels 184 m the LCP channel molding 176. Any pressure pulses in the mk m the mam channels 184 act directly on the air m the cavities 200 and quickly dissipate.

PRINTHEAD PRIMING

Priming the cartridge will now be described with particular reference to the LCP channel molding 176 shown m Figure 27. The LCP channel molding 176 is pπmed with mk by suction applied to the mam channel outlets 232 from the pump of the fluidic system (see Figure 6). The mam channels 184 are filled with mk and then the mk supply passages 182 and prmthead ICs 68 self prime by capillary action.

The mam channels 184 are relatively long and thin. Furthermore the air cavities 200 must remain unpπmed if they are to damp pressure pulses m the mk. This can be problematic for the priming process which can easily fill cavities 200 by capillary action or the mam channel 184 can fail to fully pπme because of trapped air. To ensure that the LCP channel molding 176 fully primes, the mam channels 184 have a weir 228 at the downstream end prior to the outlet 232. To RRE049 51 -PCT

ensure that the air cavities 200 m the LCP molding 64 do not prime, they have openings with upstream edges shaped to direct the ink meniscus from traveling up the wall of the cavity.

These aspects of the cartridge are best described with reference Figures 28A, 28B and 29A to 29C. These figures schematically illustrate the priming process. Figures 28A and 28B show the problems that can occur if there is no weir m the mam channels, whereas Figures 29A to 29C show the function of the weir 228.

Figures 28A and 28B are schematic section views through one of the mam channels 184 of the LCP channel molding 176 and the line of air cavities 200 m the roof of the channel. Ink 238 is drawn through the inlet 230 and flows along the floor of the mam channel 184. It is important to note that the advancing meniscus has a steeper contact angle with the floor of the channel 184. This gives the leading portion of the ink flow 238 a slightly bulbous shape. When the mk reaches the end of the channel 184, the mk level rises and the bulbous front contacts the top of the channel before the rest of the ink flow. As shown m Figure 28B, the channel 184 has failed to fully prime, and the air is now trapped. This air pocket will remain and interfere with the operation of the prmthead. The mk damping characteristics are altered and the air can be an mk obstruction.

In Figure 29A to 29C, the channel 184 has a weir 228 at the downstream end. As shown m Figure 29A, the ink flow 238 pools behind the weir 228 and rises toward the top of the channel. The weir 228 has a sharp edge 240 at the top to act as a meniscus anchor point. The advancing meniscus pms to this anchor 240 so that the ink does not simply flow over the weir 228 as soon as the ink level is above the top edge.

As shown m Figure 29B, the bulging meniscus makes the ink πse until it has filled the channel 184 to the top. With the ink sealing the cavities 200 into separate air pockets, the bulging mk meniscus at the weir 228 breaks from the sharp top edge 240 and fills the end of the channel 184 and the mk outlet 232 (see Figure 29C). The sharp to edge 240 is precisely positioned so that the ink meniscus will bulge until the ink fills to the top of the channel 184, but does not allow the mk to bulge so much that it contacts part of the end air cavity 242. If the meniscus touches and pms to the interior of the end air cavity 242, it may prime with ink. Accordingly, the height of the weir and its position under the cavity is closely controlled. The curved downstream surface of the weir 228 ensures that there are no further anchor points that might allow the ink meniscus to bridge the gap to the cavity 242

Another mechanism that the LCP uses to keep the cavities 200 unpπmed is the shape of the upstream and downstream edges of the cavity openings. As shown m Figures 28A, 28B and 29A RRE049 51 -PCT

to 29C, all the upstream edges have a curved transition face 234 while the downstream edges

236 are sharp. An ink meniscus progressing along the roof of the channel 184 can pm to a sharp upstream edge and subsequently move upwards into the cavity by capillary action. A transition surface, and m particular a curved transition surface 234 at the upstream edge removes the strong anchor point that a sharp edge provides.

Similarly, the Applicant's work has found that a sharp downstream edge 236 will promote depπmmg if the cavity 200 has inadvertently filled with some mk. If the printer is bumped, jarred or tilted, or if the fluidic system has had to reverse flow for any reason, the cavities 200 may fully of partially prime. When the ink flows m its normal direction again, a sharp downstream edge 236 helps to draw the meniscus back to the natural anchor point (i.e. the sharp corner). In this way, management of the ink meniscus movement through the LCP channel molding 176 is a mechanism for correctly priming the cartridge.

The invention has been described here by way of example only. Skilled workers in this field will recognize many variations and modification which do not depart from the spirit and scope of the broad inventive concept. Accordingly, the embodiments described and shown in the accompanying figures are to be considered strictly illustrative and in no way restπctive on the invention.

RRE049 51 -PCT