(12) United States Patent
`Silverbrook et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7,156,492 B2
`*Jan. 2, 2007
`
`US007l56492B2
`
`......................................... .. 347/49, 347/50
`(52) U.S. Cl.
`(58) Field of Classification Search .......... .. 347/ 12—13,
`347/20, 40, 42, 49—50, 63, 65, 67
`See application file for complete search history.
`
`(56)
`
`References Cited
`U . S. PAl'l:'N'l' D()C,UM1:'N'l'S
`
`NIODULAR PRINTHEAD ASSEMBLY WITH
`A CARRIER OF A METAL ALLOY
`
`Inventors: Kia Silverbrook, Bahnain (AU), Tobin
`Allen King, Balmain (AU)
`
`Assignee: Silvcrbrook Research Pty Ltd,
`Balmain (AU)
`
`Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`This patent is subject to a terminal dis-
`claimer.
`
`7/1985
`2/1999
`11/2000
`11/2001
`1/2002
`12/2002
`12/2003
`6/2006
`
`..
`
`Matsuda et al.
`Fuller et a1.
`.... ..
`Karita ct al.
`Raniaswami et al.
`Scheifelln et a1.
`Nakamura et al.
`Foote et al.
`.... ..
`Silvcrbrook ct a1.
`
`.
`
`..
`........ .. 347/49
`
`4,528,575 A
`5,869,595 A
`6,151,049 A
`6,315,384 B1
`6,341,845 B1
`6,488,355 B1
`6,655,786 B1
`7,066,573 B1*
`FOR 4 IGN PAT 4 N 1 DOCUMENTS
`W0 01/002172 A
`WO O1/042022 A
`
`11/450,440
`
`Jun. 12, 2006
`
`W0
`W0
`
`1/2001
`6/2001
`
`Prior Publication Data
`
`US 2006/0227185 A1
`
`Oct. 12, 2006
`
`Related U.S. Application Data
`
`Continuation of application No. 11/250,450, filed on
`Oct. 17, 2005, now Pat. No. 7,066,573, which is a
`continuation of application No. 10/728,922, filed on
`Dec. 8, 2003, now Pat. No. 6,997,545, which is a
`continuation of application No. 10/102,700, filed on
`Mar. 22, 2002, now Pat. No. 6,692,113.
`
`Foreign Application Priority Data
`(30)
`Mar. 27, 2001
`
`................................... .. PR3996
`
`(AU)
`
`(51)
`
`Int. Cl.
`B41] 2/I4
`B41] 2/16
`
`(2006.01)
`(2006.01)
`
`* cited by examiner
`
`Primary Exam1'ner—Jua11ita D. Stephens
`
`(57)
`
`ABSTRACT
`
`A modular printhead includes an elongate carrier. An elon-
`gate fluid transporter can be received in the carrier and
`defines a plurality of channels that can each transport a
`respective type of fluid. A plurality of printing modules is
`configured is mounted to the elongate ink transporter so that
`each printing module engages in fluid communication with
`each channel. A flexible printed circuit board (PCB) is
`located between the carrier and the fluid transporter. The
`PCB includes data connections to be interfaced to the
`printing modules.
`
`9 Claims, 19 Drawing Sheets
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`1
`MODULAR PRINTHEAD ASSEMBLY WITH
`A CARRIER OF A METAL ALLOY
`
`CROSS REFERENCE TO Rl:'LA1'EL)
`APPLICATION
`
`2
`second printhead assembly can be
`a
`Additionally,
`mounted on the opposite side of a paper feed path to enable
`double-sided l1igh- speed printing.
`
`OBJECTS OF THE INVENTION
`
`This is a Continuation Application of U.S. Ser. No.
`11/250,450 filed on Oct. 17, 2005, now U.S. Pat. No.
`7,066,573, which is a Continuation Application of US. Ser.
`No. 10/728,922 filed Dec. 8, 2003, now US. Pat. No.
`6,997,545 which is a Continuation Application of U.S. Ser.
`No. 10/102,700 filed on Mar. 22 2002, now U.S. Pat. No.
`6,692,113 all of wl1icl1 is herein incorporated by reference.
`
`CO—PENDING APPLICATIONS
`
`Various methods, systems and apparatus relating to the
`present invention are disclosed in the following co-pending
`applications filed by the applicant or assignee of the present
`invention: U.S. Ser. No. 09/575,141 (US. Pat. No. 6,428,
`133); U.S. Ser. No. 09/575,125 HIS. Pat. No. 6,526,658),
`U.S. Ser. No. 09/575,108 (U.S. Pat. No. 6,795,215), U.S.
`Ser. No. 09/575,109.
`The disclosures of these co-pending applications are
`incorporated herein by reference.
`
`BACKGROUND OF THE INVENTION
`
`The following invention relates to a printhead module
`assembly for a printer.
`More particularly, though not exclusively, the invention
`relates to a printhead module assembly for anA4 pagewidth
`drop on demand printer capable of printing up to 1600 dpi
`photographic quality at up to 160 pages per minute.
`The overall design of a printer in which the printhead
`module assembly can be utilized revolves around the use of
`replaceable printhead modules in an array approximately
`81/2 inches (21 cm) long. An advantage of such a system is
`the ability to easily remove and replace any defective
`modules in a printhead array. This would eliminate having to
`scrap an entire printhead if only one chip is defective.
`A printhead module in such a printer can be comprised of
`a “Memjet” chip, being a chip having mounted thereon a
`vast number of therino-actuators in micro-mechanics and
`r11icro-electromechanical systems (MEMS). Such actuators
`might be those as disclosed in US. Pat. No. 6,044,646 to the
`present applicant, however, might be other MEMS print
`chips.
`In a typical embodiment, eleven “Mcmjct” tiles can butt
`together in a metal charmel to form a complete 81/2 inch
`printhead assembly.
`The printhead, being the environment within which the
`printhead module assemblies of the present invention are to
`be situated, might typically have six ink chambers and be
`capable of printing four color process (CMYK) as well as
`infrared ink and fixative. An air pump would supply filtered
`air through a seventh chamber to the printhead, which could
`be used to keep foreign particles away from its ink nozzles.
`Each printhead module receives ink via an elastomeric
`extrusion that transfers the ink. Typically,
`the printhead
`assembly is suitable for printing A4 paper without the need
`for scamiing movement of the printhead across the paper
`width.
`
`The printheads themselves are modular, so printhead
`arrays can be configured to fonn printheads of arbitrary
`width.
`
`It is an objec of the present invention to provide an
`improved printhead module assembly.
`It is another object of the invention to provide a printhead
`assembly having improved modules therein.
`
`SUMMARY OF THE INVENTION
`
`there is
`
`According to a first aspect of the invention,
`provided a printhead assembly which comprises
`an elongate channel member having a floor and a pair of
`opposed side walls, the elongate channel member being
`of a metal having thermal expansion properties that are
`similar to thermal expansion properties of silicon; and
`at least one printhead module positioned in the support
`structure, along a length of the support structure, the, or
`each, printhead module comprising
`an elongate ink supply assembly that is positioned in
`the channel, the ink supply assembly being config-
`ured to receive a supply of ink and to provide a
`plurality of ink flow paths interposed between the
`supply of ink and a plurality of outlet openings
`defined by the ink supply assembly; and
`an elongate printhead chip that is mounted on the ink
`supply assembly to be fed with ink from the ink
`supply assembly.
`The elongate channel may be of a nickel iron alloy. In
`particular, the elongate channel may be a 36% nickel iron
`alloy.
`The printhead assembly may include a number of ink
`printhead modules positioned in the channel member such
`that the ink supply assemblies are positioned end-to-end in
`the channel member and the printhead chips define an array
`that spans a print medium, in use.
`The elongate ink supply assembly of each module may
`include an ink feed member that is positioned on the lloor of
`the channel member and defines a number of ink channels,
`extending longitudinally with respect to the channel member
`and in fluid communication with an ink supply and a
`, plurality of outlet openings in fluid communication with
`respective ink cl1a1mels from which ink can be fed.
`An ink delivery assembly may be positioned on each ink
`feed member. Each ink delivery assembly may define a
`mounting formation to permit
`the printhead chip to be
`mounted on the ink delivery system, a plurality of ink inlets
`that are ir1 fluid communication with the outlet openings of
`the ink feed member, a plurality of exit holes and tortuous
`ink flow pa hs from each ink inlet to a number of respective
`exit holes. Each printhead chip may incorporate a plurality
`of nozzle arrangements that extend along a length of the
`chip. The pri11tl1ead chip may be positioned so that the ink
`can be fed from the exit holes to the printhead chip.
`Each ink feed member may be in the form of an extrusion
`of an elastomeric material. The channels may extend lon-
`gitudinally in the extrusion and the outlet openings may be
`holes defined in a surface of the extrusion to be ir1 fluid
`communication with respective ink channels.
`Each ink delivery assembly may include a pair of micro-
`moldings that are positioned so that a lower micro-molding
`is interposed between an upper micro-molding and the ink
`feed member. The lower micro-molding may define a plu-
`rality of ink chambers ir1 fluid commtmication with respec-
`
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`tive outlet openings of the ink feed member, via the ink
`inlets. The upper micro—molding may define the exit holes in
`fluid communication witli the ink chambers.
`According to a second aspect of the invention, there is
`provided a printhead module for a printhead assembly
`incorporating a plurality of said modules positioned sub-
`stantially across a pagewidth in a drop on demand ink jet
`printer, co111prising:
`an upper micro—molding locating a print chip having a
`plurality of ink jet nozzles, the upper micro—molding
`having ink charmels delivering ink to said print chip,
`a lower micro—molding having inlets through wl1icl1 ink is
`received from a source of ink, and
`a mid—package film adhered between said upper and lower
`micro—moldings and having holes through which ink
`passes from the lower micro—molding to the upper
`n1icro-molding.
`Preferably the mid—package film is made of an inert
`polymer.
`Preferably the holes of the 1nid—package film are laser
`ablated.
`Preferably the mid—package film has an adhesive layer on
`opposed faces thereof, providing adhesion between the
`upper micro—molding, the mid—package film and the lower
`micro—molding.
`Preferably the up per 111icro-111oldi11g l1as an alignment pin
`passing through an aperture in the mid—package film and
`received within a recess in the lower micro—molding, the pin
`serving to align the upper micro—molding, the mid—package
`film and the lower micro—molding when they are bonded
`together.
`Preferably the inlets of the lower micro—molding are
`formed on an underside thereof.
`Preferably six said inlets are provided for individual inks.
`Preferably the lower micro—molding also includes a11 air
`inlet.
`Preferably the air inlet includes a slot extending across the
`lower micro—molding.
`Preferably the upper micro—molding includes exit holes
`corresponding to inlets on a backing layer of the print chip.
`Preferably the backing layer is made of silicon.
`Preferably the printhead module further comprises an
`elastomeric pad on an edge of the lower micro—molding.
`Preferably the upper and lower micro -moldings are made
`of Liquid Crystal Polymer (LCP).
`Preferably an upper surface of the upper micro—molding
`has a series of alternating air inlets and outlets cooperative
`with a capping device to redirect a [low of air through the
`upper inicro-molding.
`Preferably each printhead module has an elastomeric pad ,
`on an edge of its lower micro—molding, the elastomeric pads
`bearing against an imier surface of the charmel to positively
`locate the printhead modules within the channel.
`As used herein, the term “ink” is intended to mean any
`fluid which flows through the printhead to be delivered to
`print media. The fluid may be one of many different colored
`inks. infra-red ink, a fixative or the like.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`A preferred form of the present invention will now be
`described by way of example with reference to the accom-
`panying drawings wherein:
`FIG. 1 is a schematic overall View of a printhead;
`FIG. 2 is a schematic exploded view of the printhead of
`FIG. 1;
`FIG. 3 is a schematic exploded view of an i11k jet module;
`
`4
`FIG. 3a is a schematic exploded inverted illustration of
`the ink jet module of FIG. 3;
`FIG. 4 is a schematic illustration of an assembled ink jet
`module;
`FIG. 5 is a schematic inverted illustration of the module
`of FIG. 4;
`FIG. 6 is a schematic close—up illustration of the module
`of FIG. 4;
`FIG. 7 is a schematic illustration of a chip sub—assembly;
`FIG. 8a is a schematic side elevational view of the
`printhead of FIG. 1;
`FIG. 8b is a schematic plan view of the printhead of FIG.
`8a;
`FIG. 86 is a schematic side view (other side) of the
`printhead of FIG. 8a;
`FIG. 8d is a schematic inverted plan view of the printhead
`of FIG. 819;
`FIG. 9 is a schematic cross-sectional end elevational view
`
`V of the printhead of FIG. 1;
`FIG. 10 is a schematic illustration of tlie pri11tl1ead of FIG.
`1 in an uncapped configuration;
`FIG. 11 is a schematic illustration of the printhead of FIG.
`10 in a capped configuration;
`FIG. 12a is a schematic illustration of a capping device;
`FIG. 12b is a schematic illustration of the capping device
`of FIG. 12a, viewed from a different angle;
`FIG. 13 is a schematic illustration showing the loading of
`an ink jet module i11to a printhead;
`FIG. 14 is a schematic end elevational view of the
`printhead illustrating the printhead module loading method;
`FIG. 15 is a schematic cut-away illustration of the print-
`head assembly of FIG. 1;
`FIG. 16 is a schematic close—up illustration of a portion of
`the printhead of FIG. 15 showing greater detail in the area
`of the “Memjet” chip;
`FIG. 17 is a schematic illustration of the end portion of a
`metal channel and a printhead location molding;
`FIG. 18a is a schematic illustration of an end portion of
`an elastomeric ink delivery extrusion and a molded end cap;
`and
`FIG. 18b is a schematic illustration ofthe end cap of FIG.
`18a in an out-folded configuration.
`
`DETAILED DESCRIPTION OF TH:
`INVENTION
`
`In FIG. 1 of the accompanying drawings there is sche-
`matically depicted an overall View of a printhead assembly.
`FIG. 2 shows the core components of the assembly in an
`exploded configuration. The printhead assembly 10 of the
`preferred embodiment comprises eleven printhead modules
`11 situated along a metal “lnvar” channel 16. At the heart of
`each printhead module 11 is a “Memjet” chip 23 (FIG. 3).
`The particular chip chosen in the preferred embodiment
`being a six-color configuration.
`The “Memjet” printhead modules 11 are comprised of the
`“Memjet” chip 23, a fine pitch flex PCB 26 and two
`micro—moldings 28 and 34 sandwiching a mid—package film
`35. Each module 11 forms a sealed unit with independent ink
`chambers 63 (FIG. 9) which feed the chip 23. The modules
`11 plug directly onto a flexible elastomeric extrusion 15
`which carries air, ink and fixitive (see channels 49—55 in
`FIG. 15). The upper surface of the extrusion 15 has repeated
`patterns of holes 21 which align with ink inlets 32 (FIG. 3a)
`on the underside of each module 11. The extrusion 15 is
`bonded onto a flex PCB (flexible printed circuit board).
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`The fine pitch flex PCB 26 wraps down the side of each
`printhead module 11 and makes contact with the flex PCB 17
`(FIG. 9). The flex PCB 17 carries two busbars 19 (positive)
`and 20 (negative) for powering each module 11, as well as
`all data connections. The flcx PCB 17 is bonded onto the
`continuous metal “Invar” charmel 16. The metal chaimel 16
`serves to hold the modules 11 in place a11d is designed to
`l1ave a similar coeflicient of thermal expansion to that of
`silicon used in the modules.
`A capping device 12 is used to cover the “Memjet” chips
`23 when not in use. The capping device is typically made of
`spring steel with an onsert molded elastomeric pad 47 (FIG.
`12a). The pad 47 serves to duct air into the “Memjet” chip
`23 when uncappcd and cut 0
`air and cover a nozzle guard
`24 (FIG. 9) when capped. The capping device 12 is actuated
`by a camshaft 13 that typica y rotates throughout 180°.
`The overall thickness oftie “Memjet” chip is typically
`0.6 min which includes a 150-micron inlet backing layer 27
`and a nozzle guard 24 of 150—micron thickness. These
`elements are assembled at the wafer scale.
`The nozzle guard 24 allows filtered air into an 80-micron
`cavity 64 (FIG. 16) above the “Memjet” ink nozzles 62. The
`pressurized air flows through microdroplct holcs 45 in the
`nozzle guard 24 (with the ink during a priming operation)
`and serves to protect the delicate “Memjet" nozzles 62 by .
`repelling foreign particles.
`A silicon chip backing layer 27 ducts ink from the
`printhead module packaging directly into the rows of “Mem-
`jet” nozzles 62. The “Memjet” chip 23 is wire bonded 25
`from bond pads on the chip at 116 positions to the fine pitch
`flex PCB 26. The wire bonds are on a 120-micron pitch and
`are cut as they are bonded onto the fine pitch flex PCB pads
`(FIG. 3). The fine pitch flex PCB 26 carries data and power
`from the flex PCB 17 via a series of gold Contact pads 69
`along the edge of the flex PCB.
`The wire bonding operation between chip and fine pitch
`flcx PCB 26 may be done rcmotcly, bcforc transporting,
`placing and adhering the chip assembly into the printhead
`module assembly. Alternatively, the “Memjet” chips 23 can
`be adhered into the upper micro-molding 28 first and then
`the fine pitch flex PCB 26 can be adhered into place. The
`wire bonding operation could then take place in situ, with no
`danger of distorting the moldings 28 and 34. The upper
`micro-molding 28 can be made of a Liquid Crystal Polymer
`(LCP) blend. Since the crystal structure of the upper micro-
`molding 28 is minute, the heat distortion temperature (1 80°
`C.—260° C.),
`the continuous usage temperature (200°
`C.—240° C.) and soldering heat durability (260° C. for 10
`seconds to 310° C. for 10 seconds) are high, regardless ofthe
`relatively low melting point.
`Each printhead module 11 includes an upper micro-
`molding 28 and a lower micro-molding 34 separated by a
`mid—package film layer 35 shown in FIG. 3.
`The mid—package film layer 35 can be an inert polymer
`such as polyimidc, which has good chcmical rcsistancc and
`dimensional stability. The mid—package film layer 35 can
`have laser ablated holes 65 and can comprise a double-sided
`adhesive (ie. an adhesive layer on both faces) providing
`adhesion between the upper micro-molding, the mid—pack-
`age film layer and the lower micro-molding.
`The upper micro-molding 28 has a pair of alignment pins
`29 passing through corresponding apertures in the mid-
`package film layer 35 to be received within corresponding
`recesses 66 in the lower micro-molding 34. This serves to
`align the components when they are bonded together. Once
`bonded together, the upper and lower micro-moldings form
`a tortuous ink and air path in the complete “Memjet”
`
`‘
`
`6
`printhead module 11. In addition, an upper surface of the
`upper micro-molding 28 has a pair of opposed recesses 39
`which serve as robot pick-up points for picking and placing
`the micro-molding.
`There are armular ink inlcts 32 in the underside of the
`lower micro-molding 34. In a preferred embodiment, there
`are six such inlets 32 for various inks (black, yellow,
`magenta, cyan, fixitive and infrared). There is also provided
`an air inlet slot 67. The air inlet slot 67 extends across the
`lower micro-molding 34 to a secondary inlet which expels
`air through an exhaust hole 33, through an aligned hole 68
`in fine pitch flex PCB 26. This serves to repel the print media
`from the printhead during printing. The ink inlets 32 con-
`tinuc in thc undcrsurfacc of the upper micro-molding 28 as
`does a path from the air inlet slot 67. The ink inlets lead to
`200 micron exit holes also indicated at 32 in FIG. 3. These
`holes correspond to the inlets on the silicon backing layer 27
`of the “Memjet” chip 23.
`There is a pair of elastomeiic pads 36 on an edge of the
`lower 1nicro—1nolding 34. These serve to take up tolerance
`and positively located tl1e printhead modules 11 into the
`metal channel 16 when the modules are micro -placed during
`assembly.
`A preferred material for the “Memj et” micro-moldings is
`a LCP. This has suitable flow characteristics for the fine
`detail in tlie moldings and has a relatively low coefficient of
`thermal expansion.
`Robot picker details are included in the upper micro-
`inolding 28 to enable accurate placement of the printhead
`modules 11 during assembly.
`The upper surface of the upper micro-molding 28 as
`shown in FIG. 3 has a series of alternating air inlets and
`outlets 31. These act in con'unction with the capping device
`12 and are either sealed 0 " or grouped into air inlet/outlet
`chambers, depending upon tl1e position of tlie capping
`device 12. They connect air diverted from the inlet slot 67
`to the chip 23 depending u oon whether the unit is capped or
`uncapped.
`A capper cam detail 40 including a ramp for the capping
`device is shown at two locations in the upper surface of the
`upper micro-molding 28. This facilitates a desirable move-
`ment of the capping device 12 to cap or uncap the chip and
`the air chambers. That is, as the capping device is caused to
`move laterally across the print chip during a capping or
`, uncapping operation, the ramp of the capper cam detail 40
`serves to clastically distort and capping device as it is moved
`by operation of the camshaft 13 so as to prevent scraping of
`the device against the nozzle guard 24.
`The “Memjet” chip assembly 23 is picked and bonded
`into the upper micro-molding 28 on the printhead module
`11. The fine pitch flex PCB 26 is bonded and wrapped
`around the side of the assembled printhead module 11 as
`shown in FIG. 4. After this initial bonding operation, the
`chip 23 has more sealant or adhesive 46 applied to its long
`cdgcs. This serves to “pot” the bond wires 25 (FIG. 6), seal
`the “Memjet” chip 23 to the molding 28 and form a sealed
`gallery into which filtered air can flow and exhaust through
`tl1e nozzle guard 24.
`The flex PCB 17 carries all data and power connections
`from the main PCB (not shown) to each “Memj et” printhead
`module 11. The flex PCB 17 has a series of gold plated,
`domed contacts 69 (FIG. 2) which interface with contact
`pads 41, 42 and 43 that are located, together with section 44,
`on the finc pitch flcx PCB 26 of cach “Mcmjct” printhcad
`module 11.
`typically of 200
`Two copper busbar strips 19 and 20,
`micron thickness, are jigged and soldered into place on the
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`7
`flex PCB 17. The busbars 19 and 20 connect to a flex
`termination which also carries data.
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`US 7,156,492 B2
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`8
`The end cap 70 clamps onto the ink extrusion 15 by way
`of snap engagement
`tabs 77. Once assembled with the
`delivery hoses 78,
`ink and air can be received from ink
`reservoirs and an air pump, possibly with filtration means.
`Thc end cap 70 can bc cormcctcd to cithcr end of the
`extrusion, ie. at either end of the printhead.
`The plugs 74 are pushed into the channels of tlie extrusion
`15 and the plates 71 and 72 are folded over. Tl1e sr1ap
`engagement tabs 77 clamp the molding and prevent it from
`slipping off the extrusion. As the plates are snapped together,
`they form a sealed collar arrangement around the end of the
`extrusion. Instead of providing individual hoses 78 pushed
`onto the comiectors 76,
`the molding 70 might interface
`dircctly with an ink cartridge. A scaling pin arrangement can
`also be applied to this molding 70. For example, a perfo-
`rated, hollow metal pin with an elastomeric collar can be
`fitted to the top of tlie inlet connectors 76. This would allow
`the inlets to automatically seal with an ink cartridge when
`the cartridge is inserted. The air inlet and hose might be
`‘ smaller than the other inlets in order to avoid accidental
`charging of the airways with ink.
`The capping device 12 for the “Memjet” printhead would
`typically be formed of stainless spring stccl. An clastomcric
`seal or onsert molding 47 is attached to the capping device
`as shown in FIGS. 12a and 12b. The metal part from which
`tl1e capping device is r11ade is punched as a blank and then
`inserted into an injection molding tool ready for the elasto-
`meric onsert to be shot onto its underside. Small holes 79
`(FIG. 13b) are present on the upper surface of the metal
`capping device 12 and can be formed as burst holes. They
`serve to key the onsert molding 47 to the metal. After the
`molding 47 is applied, the blank is inserted into a press tool,
`where additional bending operations and forming of integral
`springs 48 takes place.
`The elastomeric onsert molding 47 l1as a series of rect-
`angular recesses or air chambers 56. These create chambers
`whcn uncappcd. Thc chambers 56 are positioned ovcr thc air
`inlet and exhaust holes 30 of the upper micro—molding 28 in
`the “Memjet” printhead module 11. These allow the air to
`flow from one inlet to the next outlet. When the capping
`device 12 is moved forward to the “home” capped position
`as depicted in FIG. 11, these airways 32 are sealed olf with
`a blank section of the onsert molding 47 cutting ofl airflow
`to tl1e “Menriet” chip 23. This prevents the filtered air from
`drying out and therefore blocking the delicate “Memjet”
`nozzlcs.
`Another function of the onsert molding 47 is to cover and
`clamp against the nozzle guard 24 on the “Memjet” chip 23.
`This protects against drying out, but primarily keeps foreign
`particles such as paper dust from entering the chip and
`damaging the nozzles. The chip is only exposed during a
`printing operation. when filtered air is also exiting along
`with the ink drops through the nozzle guard 24. This positive
`air pressure repels foreign particles during the printing
`process and thc capping dcvicc protccts thc chip in times of
`inactivity.
`The integral springs 48 bias tl1e capping device 12 away
`from tl1e side of the metal channel 16. Tl1e capping device
`12 applies a compressive force to the top of the printhead
`module 11 and the underside of the metal charmel 16. The
`lateral capping motion of the capping device 12 is govemed
`by an eccentric camshaft 13 mounted against the side of the
`capping device. It pushes the device 12 against the metal
`channel 16. During this movement, thc bosscs 57 bcncath
`the upper surface of the capping device 12 ride over the
`respective ramps 40 formed in the upper micro—molding 28.
`This action flexes the capping device and raises its top
`
`5
`
`The flex PCB 17 is approximately 340 mm in length and
`is formed from a 14 mm wide strip. It is bonded into the
`metal channel 16 during assembly and exits from one end of
`the printhead assembly only.
`The metal U-cl1am1el 16 ir1to which the main components
`are place is ofa special alloy called “Invar 36”. It is a 36%
`nickel iron alloy possessing a coe “icient of thermal expan-
`sion of 1/10”’ that of carbon steel a temperatures up to 400°
`F. The Invar is annealed for optimal dimensional stability.
`Additionally,
`the Invar is me <el plated to a 0.056%
`thickness of the wall section. This helps to further match it
`to the5coefficient of thermal expansion of silicon which is
`2><10 per ° C.
`The Invar channel 16 functions to capture the “Memjet”
`printhead modules 11 in a precise alignment relative to each
`other and to impart enough force on the modules 11 so as to
`form a seal between the ink inlets 32 on each printhead
`module and the outlet holes 21 that are laser ablated into the
`clastomcric ink dclivcry cxtrusion 15.
`The similar coefficient of thermal expansion of the Invar
`chamiel to the silicon chips allows similar relative move-
`ment during temperature changes. The elastomeric pads 36
`on one side of each printhead module 11 serve to “lubricate” '
`them within the channel 16 to take up any further lateral
`coefficient of thermal expansion tolerances without losing
`alignment. The Invar channel is a cold rolled, annealed and
`nickel plated strip. Apart from two bends that are required in
`its formation, the channel l1as two square cut-outs 80 at each
`end. These mate with snap fittings 81 on the printhead
`location moldings 14 (FIG. 17).
`The elastomeric ink delivery extrusion 15 is a non-
`hydrophobic, precision component. Its function is to trans-
`port ink and air to the “Memjet" printhead modules 11. The
`extrusion is bonded onto the top of the flex PCB 17 during
`assembly and it has two types of molded end caps. One of
`these cnd caps is shown at 70 in FIG. 18a.
`A series of patterned holes 21 are present on the upper
`surface of the extrusion 15. These are laser ablated into the
`upper surface. To this end, a mask is made and placed on the
`surface of the extrusion, which then has focused laser light
`applied to it. The holes 21 are evaporated from the upper
`surface, but the laser does not cut into the lower surface of 45
`extrusion 15 due to the focal length of the laser light.
`Eleven repeated patterns of the laser ablated holes 21
`form the ink and air outlcts 21 of thc cxtrusion 15. Thcsc
`in erface with the armular ring inlets 32 on the underside of
`the “Memj et” printhead module lower micro—molding 34. A
`di ‘erent pattern of larger holes (not shown but concealed
`beneath the upper plate 71 of end cap 70 in FIG. 18a) is
`ablated into one end of the extrusion 15. These mate with
`apertures 75 having armular ribs formed in the same way as
`those on the underside of each lower micro—molding 34
`described earlier. Ink and air delivery hoses 78 are connected
`to rcspcctivc connectors 76 that cxtcnd from thc uppcr platc
`71. Due to the inherent flexibility of the extrusion 15, it can
`contort into many ink connection mounting configurations
`without restricting ink and air flow. The molded end cap 70
`has a spine 73 from which the upper and lower plates are
`integrally hinged. The spine 73 includes a row of plugs 74
`that are received within the ends of the respective flow
`passages of the extrusion 15.
`The other end of the extrusion 15 is capped with simple
`plugs 18 which block the channels in a similar way as tl1e
`plugs 74 on spine 17.
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`US 7,156,492 B2
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`9
`surface to raise the onsert molding 47 as it is moved laterally
`into position onto the top of the nozzle guard 24.
`The camshaft 13, wl1icl1 is reversible, is l1eld ir1 position
`by two printhead location moldings 14. The camshaft 11 can
`have a flat surface built in one end or be otherwise provided 5
`with a spline or keyway to accept gear 22 or another type of
`motion controller.
`The “Memjet” chip and printhead module are assembled
`as follows:
`1. The “Memjet” chip 23 is dry tested in flight by a pick and
`place robot, which also dices the wafer and transports
`individual chips to a fine pitch flex PCB bonding area.
`. When accepted,
`the “Memjet” chip 23 is placed 530
`microns apart from the fine pitch flex PCB 26 and has
`wire bonds 25 applied between the bond pads on the chip
`and the conductive pads o11 the fine pitch flex PCB. This
`constitutes the “Memjet” chip assembly.
`3. An alternative to step 2 is to apply adhesive to the internal
`walls of the chip cavity in the upper micro—molding 28 of
`the printhead module and bond the chip into place first.
`The fir1e pitch flex PCB 26 can then be applied to the
`upper surface of the micro—molding and wrapped over the
`side. Wire bonds 25 are then applied between