Method of manufacturing a micro-electromechanical fluid ejecting device

CROSS REFERENCES TO RELATED APPLICATIONS

[0001] The following Australian provisional patent applications are hereby incorporated by cross-reference. For the purposes of location and identification, US patent applications identified by their US patent application serial numbers (USSN) are listed alongside the Australian applications from which the US patent applications claim the right of priority.

1US PATENT/PATENT APPLICATIONAUSTRALIAN (CLAIMINGCROSS-REFERENCEDRIGHT OF PRIORITYAUSTRALIANFROM AUSTRALIANPROVISIONAL PATENTPROVISIONALDOCKETAPPLICATION NO.APPLICATION)NO.PO799109/113,060ART01PO850509/113,070ART02PO798809/113,073ART03PO9395 6,322,181ART04PO801709/112,747ART06PO801409/112,776ART07PO802509/112,750ART08PO803209/112,746ART09PO799909/112,743ART10PO799809/112,742ART11PO803109/112,741ART12PO8030 6,196,541ART13PO7997 6,195,150ART15PO797909/113,053ART16PO801509/112,738ART17PO797809/113,067ART18PO798209/113,063ART19PO798909/113,069ART20PO801909/112,744ART21PO7980 6,356,715ART22PO801809/112,777ART24PO793809/113,224ART25PO8016 6,366,693ART26PO802409/112,805ART27PO794009/113,072ART28PO793909/112,785ART29PO8501 6,137,500ART30PO850009/112,796ART31PO798709/113,071ART32PO802209/112,824ART33PO849709/113,090ART34PO802009/112,823ART38PO802309/113,222ART39PO850409/112,786ART42PO800009/113,051ART43PO797709/112,782ART44PO793409/113,056ART45PO799009/113,059ART46PO849909/113,091ART47PO8502 6,381,361ART48PO7981 6,317,192ART50PO798609/113,057ART51PO798309/113,054ART52PO802609/112,752ART53PO802709/112,759ART54PO802809/112,757ART56PO9394 6,357,135ART57PO939609/113,107ART58PO9397 6,271,931ART59PO9398 6,353,772ART60PO9399 6,106,147ART61PO940009/112,790ART62PO9401 6,304,291ART63PO940209/112,788ART64PO9403 6,305,770ART65PO9405 6,289,262ART66PP0959 6,315,200ART68PP1397 6,217,165ART69PP237009/112,781DOT01PP237109/113,052DOT02PO8003 6,350,023Fluid01PO8005 6,318,849Fluid02PO940409/113,101Fluid03PO8066 6,227,652IJ01PO8072 6,213,588IJ02PO8040 6,213,589IJ03PO8071 6,231,163IJ04PO8047 6,247,795IJ05PO8035 6,394,581IJ06PO8044 6,244,691IJ07PO8063 6,257,704IJ08PO8057 6,416,168IJ09PO8056 6,220,694IJ10PO8069 6,257,705IJ11PO8049 6,247,794IJ12PO8036 6,234,610IJ13PO8048 6,247,793IJ14PO8070 6,264,306IJ15PO8067 6,241,342IJ16PO8001 6,247,792IJ17PO8038 6,264,307IJ18PO8033 6,254,220IJ19PO8002 6,234,611IJ20PO8068 6,302,528IJ21PO8062 6,283,582IJ22PO8034 6,239,821IJ23PO8039 6,338,547IJ24PO8041 6,247,796IJ25PO800409/113,122IJ26PO8037 6,390,603IJ27PO8043 6,362,843IJ28PO8042 6,293,653IJ29PO8064 6,312,107IJ30PO9389 6,227,653IJ31PO9391 6,234,609IJ32PP0888 6,238,040IJ33PP0891 6,188,415IJ34PP0890 6,227,654IJ35PP0873 6,209,989IJ36PP0993 6,247,791IJ37PP0890 6,336,710IJ38PP1398 6,217,153IJ39PP2592 6,416,167IJ40PP2593 6,243,113IJ41PP3991 6,283,581IJ42PP3987 6,247,790IJ43PP3985 6,260,953IJ44PP3983 6,267,469IJ45PO7935 6,224,780IJM01PO7936 6,235,212IJM02PO7937 6,280,643IJM03PO8061 6,284,147IJM04PO8054 6,214,244IJM05PO8065 6,071,750IJM06PO8055 6,267,905IJM07PO8053 6,251,298IJM08PO8078 6,258,285IJM09PO7933 6,225,138IJM10PO7950 6,241,904IJM11PO794909/113,129IJM12PO806009/113,124IJM13PO8059 6,231,773IJM14PO8073 6,190,931IJM15PO8076 6,248,249IJM16PO807509/113,120IJM17PO8079 6,241,906IJM18PO805009/113,116IJM19PO8052 6,241,905IJM20PO794809/113,117IJM21PO7951 6,231,772IJM22PO8074 6,274,056IJM23PO794109/113,110IJM24PO8077 6,248,248IJM25PO805809/113,087IJM26PO805109/113,074IJM27PO8045 6,110,754IJM28PO795209/113,088IJM29PO804609/112,771IJM30PO9390 6,264,849IJM31PO9392 6,254,793IJM32PP0889 6,235,211IJM35PP088709/112,801IJM36PP0882 6,264,850IJM37PP0874 6,258,284IJM38PP139609/113,098IJM39PP3989 6,228,668IJM40PP2591 6,180,427IJM41PP3990 6,171,875IJM42PP3986 6,267,904IJM43PP3984 6,245,247IJM44PP398209/112,835IJM45PP0895 6,231,148IR01PP087009/113,106IR02PP086909/113,105IR04PP088709/113,104IR05PP0885 6,238,033IR06PP088409/112,766IR10PP0886 6,238,111IR12PP087109/113,086IR13PP087609/113,094IR14PP087709/112,760IR16PP0878 6,196,739IR17PP087909/112,774IR18PP0883 6,270,182IR19PP0880 6,152,619IR20PP088109/113,092IR21PO8006 6,087,638MEMS02PO800709/113,093MEMS03PO800809/113,062MEMS04PO8010 6,041,600MEMS05PO801109/113,082MEMS06PO7947 6,067,797MEMS07PO794409/113,080MEMS09PO7946 6,044,646MEMS10PO939309/113,065MEMS11PP087509/113,078MEMS12PP089409/113,075MEMS13

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.

FIELD OF THE INVENTION

[0003] The present invention relates to the field of inkjet printing and, in particular, discloses a method of manufacturing a micro-electromechanical fluid ejecting device.

BACKGROUND OF THE INVENTION

[0004] Many ink jet printing mechanisms are known. Unfortunately, in mass production techniques, the production of ink jet heads is quite difficult. For example, often, the orifice or nozzle plate is constructed separately from the ink supply and ink ejection mechanism and bonded to the mechanism at a later stage (Hewlett-Packard Journal, Vol. 36 no 5, pp 33-37 (1985)). The separate material processing steps required in handling such precision devices often add a substantial expense in manufacturing.

[0005] Additionally, side shooting ink jet technologies (U.S. Pat. No. 4,899,181) are often used but again, this limits the amount of mass production throughput given any particular capital investment.

[0006] Additionally, more esoteric techniques are also often utilized. These can include electroforming of nickel stage (Hewlett-Packard Journal, Vol. 36 no 5, pp 33-37 (1985)), electro-discharge machining, laser ablation (U.S. Pat. No. 5,208,604), micro-punching, etc.

[0007] The utilization of the above techniques is likely to add substantial expense to the mass production of ink jet print heads and therefore add substantially to their final cost.

[0008] It would therefore be desirable if an efficient system for the mass production of ink jet print heads could be developed.

SUMMARY OF THE INVENTION

[0009] In accordance with a first aspect of the present invention, there is provided a method of manufacturing a Dual Chamber Single Vertical Actuator Ink Jet Printer print head wherein an array of nozzles are formed on a substrate utilizing planar monolithic deposition, lithographic and etching processes. Preferably, multiple ink jet heads are formed simultaneously on a single planar substrate such as a silicon wafer.

[0010] The print heads can be formed utilizing standard vlsi/ulsi processing and can include integrated drive electronics formed on the same substrate. The drive electronics preferably being of a CMOS type. In the final construction, ink can be ejected from the substrate substantially normal to the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Notwithstanding any other forms which may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0012]
FIG. 1 shows a schematic side view of an ink jet nozzle of the invention in a quiescent state;

[0013]
FIG. 2 shows a schematic side view of the nozzle in an initial part of an ink ejection stage;

[0014]
FIG. 3 shows a schematic side view of the nozzle in a further part of an ink ejection stage;

[0015]
FIG. 4 shows a schematic side view of the nozzle in a final part of an ink ejection stage;

[0016]
FIG. 5 shows a schematic side view of the nozzle again in its quiescent state;

[0017]
FIG. 6 illustrates a side perspective view, of a single nozzle arrangement of the preferred embodiment.

[0018]
FIG. 7 illustrates a perspective view, partly in section of a single nozzle arrangement of the preferred embodiment;

[0019]
FIG. 8 shows a schematic side view of an initial stage in the manufacture of an ink jet nozzle of the invention with the deposition of a CMOS layer;

[0020]
FIG. 9 shows a step of an initial etch to form a nozzle chamber;

[0021]
FIG. 10 shows a step of depositing a first sacrificial layer;

[0022]
FIG. 11 shows a step of etching the first sacrificial layer;

[0023]
FIG. 12 shows a step of depositing a glass layer;

[0024]
FIG. 13 shows a step of etching the glass layer;

[0025]
FIG. 14 shows a step of depositing an actuator material layer;

[0026]
FIG. 15 shows a step of planarizing the actuating material layers;

[0027]
FIG. 16 shows a step of depositing a heater material layer;

[0028]
FIG. 17 shows a step of depositing a further glass layer;

[0029]
FIG. 18 shows a step of depositing a further heater material layer;

[0030]
FIG. 19 shows a step of planarizing the further heater material layer;

[0031]
FIG. 20 shows a step of depositing yet another glass layer;

[0032]
FIG. 21 shows a step of etching said another glass layer;

[0033]
FIG. 22 shows a step of etching the other glass layers;

[0034]
FIG. 23 shows a step of depositing a further sacrificial layer;

[0035]
FIG. 24 shows a step of forming a nozzle chamber;

[0036]
FIG. 25 shows a step of forming nozzle openings;

[0037]
FIG. 26 shows a step of back etching the substrate; and

[0038]
FIG. 27 shows a final step of etching the sacrificial layers;

[0039]
FIG. 28 illustrates a part of an array view of a portion of a printhead as constructed in accordance with the principles of the present invention;

[0040]
FIG. 29 provides a legend of the materials indicated in FIGS. 30 to 42; and

[0041]
FIG. 30 shows a sectional side view of an initial manufacturing step of an ink jet printhead nozzle showing a silicon wafer with a buried epitaxial layer and an electrical circuitry layer;

[0042]
FIG. 31 shows a step of etching the oxide layer;

[0043]
FIG. 32 shows a step of etching an exposed part of the silicon layer;

[0044]
FIG. 33 shows a step of depositing a second sacrificial layer;

[0045]
FIG. 34 shows a step of etching the first sacrificial layer;

[0046]
FIG. 35 shows a step of etching the second sacrificial layer;

[0047]
FIG. 36 shows the step of depositing a heater material layer;

[0048]
FIG. 37 shows a step of depositing a further heater material layer;

[0049]
FIG. 38 shows a step of etching a glass layer;

[0050]
FIG. 39 shows a step of depositing a further glass layer;

[0051]
FIG. 40 shows a step of etching the further glass layer;

[0052]
FIG. 41 shows a step of further etching the further glass layer;

[0053]
FIG. 42 shows a step of back etching through the silicon layer;

[0054]
FIG. 43 shows a step of etching the sacrificial layers; and

[0055]
FIG. 44 shows a step of filling the completed ink jet nozzle with ink.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

[0056] In the preferred embodiment, there is provided an inkjet printhead having an array of nozzles wherein the nozzles are grouped in pairs and each pair is provided with a single actuator which is actuated so as to move a paddle type mechanism to force the ejection of ink out of one or other of the nozzle pairs. The paired nozzles eject ink from a single nozzle chamber which is re-supplied by means of an ink supply channel. Further, the actuator of the preferred embodiment has unique characteristics so as to simplify the actuation process.

[0057] Turning initially to FIGS. 1 to 5, there will now be explained the principles of operation of the preferred embodiment. In the preferred embodiment, a single nozzle chamber 1 is utilized to supply ink to two ink ejection nozzles 2, 3. Ink is re-supplied to the nozzle chamber 1 via means of an ink supply channel 5. In its quiescent position, two ink menisci 6, 7 are formed around the ink ejection holes 2, 3. The arrangement of FIG. 1 being substantially axially symmetric around a central paddle 9 which is attached to an actuator mechanism.

[0058] When it is desired to eject ink out of one of the nozzles, say nozzle 3, the paddle 9 is actuated so that it begins to move as indicated in FIG. 2. The movement of paddle 9 in the direction 10 results in a general compression of the ink on the right hand side of the paddle 9. The compression of the ink results in the meniscus 7 growing as the ink is forced out of the nozzles 3. Further, the meniscus 6 undergoes an inversion as the ink is sucked back on the left hand side of the actuator 10 with additional ink 12 being sucked in from ink supply channel 5. The paddle actuator 9 eventually comes to rest and begins to return as illustrated in FIG. 3. The ink 13 within meniscus 7 has substantial forward momentum and continues away from the nozzle chamber whilst the paddle 9 causes ink to be sucked back into the nozzle chamber. Further, the surface tension on the meniscus 6 results in further in flow of the ink via the ink supply channel 5. The resolution of the forces at work in the resultant flows results in a general necking and subsequent breaking of the meniscus 7 as illustrated in FIG. 4 wherein a drop 14 is formed which continues onto the media or the like. The paddle 9 continues to return to its quiescent position.

[0059] Next, as illustrated in FIG. 5, the paddle 9 returns to its quiescent position and the nozzle chamber refills by means of surface tension effects acting on meniscuses 6, 7 with the arrangement of returning to that showing in FIG. 1. When required, the actuator 9 can be activated to eject ink out of the nozzle 2 in a symmetrical manner to that described with reference to FIGS. 1-5. Hence, a single actuator 9 is activated to provide for ejection out of multiple nozzles. The dual nozzle arrangement has a number of advantages including in that movement of actuator 9 does not result in a significant vacuum forming on the back surface of the actuator 9 as a result of its rapid movement. Rather, meniscus 6 acts to ease the vacuum and further acts as a “pump” for the pumping of ink into the nozzle chamber. Further, the nozzle chamber is provided with a lip 15 (FIG. 2) which assists in equalizing the increase in pressure around the ink ejection holes 3 which allows for the meniscus 7 to grow in an actually symmetric manner thereby allowing for straight break off of the drop 14.

[0060] Turning now to FIGS. 6 and 7, there is illustrated a suitable nozzle arrangement with FIG. 6 showing a single side perspective view and FIG. 7 showing a view, partly in section illustrating the nozzle chamber. The actuator 20 includes a pivot arm attached at the post 21. The pivot arm includes an internal core portion 22 which can be constructed from glass. On each side 23, 24 of the internal portion 22 is two separately control heater arms which can be constructed from an alloy of copper and nickel (45% copper and 55% nickel). The utilization of the glass core is advantageous in that it has a low coefficient thermal expansion and coefficient of thermal conductivity. Hence, any energy utilized in the heaters 23, 24 is substantially maintained in the heater structure and utilized to expand the heater structure and opposed to an expansion of the glass core 22. Structure or material chosen to form part of the heater structure preferably has a high “bend efficiency”. One form of definition of bend efficiency can be the Young's modulus times the coefficient of thermal expansion divided by the density and by the specific heat capacity.

[0061] The copper nickel alloy in addition to being conductive has a high coefficient of thermal expansion, a low specific heat and density in addition to a high Young's modulus. It is therefore a highly suitable material for construction of the heater element although other materials would also be suitable.

[0062] Each of the heater elements can comprise a conductive out and return trace with the traces being insulated from one and other along the length of the trace and conductively joined together at the far end of the trace. The current supply for the heater can come from a lower electrical layer via the pivot anchor 21. At one end of the actuator 20, there is provided a bifurcated portion 30 which has attached at one end thereof to leaf portions 31, 32.

[0063] To operate the actuator, one of the arms 23, 24 e.g. 23 is heated in air by passing current through it. The heating of the arm results in a general expansion of the arm. The expansion of the arm results in a general bending of the arm 20. The bending of the arm 20 further results in leaf portion 32 pulling on the paddle portion 9. The paddle 9 is pivoted around a fulcrum point by means of attachment to leaf portions 38, 39 which are generally thin to allow for minor flexing. The pivoting of the arm 9 causes ejection of ink from the nozzle hole 40. The heater is deactivated resulting in a return of the actuator 20 to its quiescent position and its corresponding return of the paddle 9 also to is quiescent position. Subsequently, to eject ink out of the other nozzle hole 41, the heater 24 can be activated with the paddle operating in a substantially symmetric manner.

[0064] It can therefore be seen that the actuator can be utilized to move the paddle 9 on demand so as to eject drops out of the ink ejection hole e.g. 40 with the ink refilling via an ink supply channel 44 located under the paddle 9.

[0065] The nozzle arrangement of the preferred embodiment can be formed on a silicon wafer utilizing standard semi-conductor fabrication processing steps and micro-electromechanical systems (MEMS) construction techniques.

[0066] For a general introduction to a micro-electro mechanical system (MEMS) reference is made to standard proceedings in this field including the proceeding of the SPIE (International Society for Optical Engineering) including volumes 2642 and 2882 which contain the proceedings of recent advances and conferences in this field.

[0067] Preferably, a large wafer of printheads is constructed at any one time with each printhead providing a predetermined pagewidth capabilities and a single printhead can in turn comprise multiple colors so as to provide for full color output as would be readily apparent to those skilled in the art.

[0068] Turning now to FIG. 8-FIG. 27 there will now be explained one form of fabrication of the preferred embodiment. The preferred embodiment can start as illustrated in FIG. 8 with a CMOS processed silicon wafer 50 which can include a standard CMOS layer 51 including of the relevant electrical circuitry etc. The processing steps can then be as follows:

[0069] 1. As illustrated in FIG. 9, a deep etch of the nozzle chamber 98 is performed to a depth of 25 micron;

[0070] 2. As illustrated in FIG. 10, a 27 micron layer of sacrificial material 52 such as aluminum is deposited;

[0071] 3. As illustrated in FIG. 11, the sacrificial material is etched to a depth of 26 micron using a glass stop so as to form cavities using a paddle and nozzle mask.

[0072] 4. As illustrated in FIG. 12, a 2 micron layer of low stress glass 53 is deposited.

[0073] 5. As illustrated in FIG. 13, the glass is etched to the aluminum layer utilizing a first heater via mask.

[0074] 6. As illustrated in FIG. 14, a 2-micron layer of 60% copper and 40% nickel is deposited 55 and planarized (FIG. 15) using chemical mechanical planarization (CMP).

[0075] 7. As illustrated in FIG. 16, a 0.1 micron layer of silicon nitride is deposited 56 and etched using a heater insulation mask.

[0076] 8. As illustrated in FIG. 17, a 2-micron layer of low stress glass 57 is deposited and etched using a second heater mask.

[0077] 9. As illustrated in FIG. 18, a 2-micron layer of 60% copper and 40% nickel 58 is deposited and planarized (FIG. 19) using chemical mechanical planarization.

[0078] 10. As illustrated in FIG. 20, a 1-micron layer of low stress glass 60 is deposited and etched (FIG. 21) using a nozzle wall mask.

[0079] 11. As illustrated in FIG. 22, the glass is etched down to the sacrificial layer using an actuator paddle wall mask.

[0080] 12. As illustrated in FIG. 23, a 5-micron layer of sacrificial material 62 is deposited and planarized using CMP.

[0081] 13. As illustrated in FIG. 24, a 3-micron layer of low stress glass 63 is deposited and etched using a nozzle rim mask.

[0082] 14. As illustrated in FIG. 25, the glass is etched down to the sacrificial layer using nozzle mask.

[0083] 15. As illustrated in FIG. 26, the wafer can be etched from the back using a deep silicon trench etcher such as the Silicon Technology Systems deep trench etcher.

[0084] 16. Finally, as illustrated in FIG. 27, the sacrificial layers are etched away releasing the ink jet structure.

[0085] Subsequently, the print head can be washed, mounted on an ink chamber, relevant electrical interconnections TAB bonded and the print head tested.

[0086] Turning now to FIG. 28, there is illustrated a portion 80 of a full color printhead which is divided into three series of nozzles 71, 72 and 73. Each series can supply a separate color via means of a corresponding ink supply channel. Each series is further subdivided into two sub rows e.g. 76, 77 with the relevant nozzles of each sub row being fired simultaneously with one sub row being fired a predetermined time after a second sub row such that a line of ink drops is formed on a page.

[0087] As illustrated in FIG. 28 the actuators are formed in a curved relationship with respect to the main nozzle access so as to provide for a more compact packing of the nozzles. Further, the block portion (21 of FIG. 6) is formed in the wall of an adjacent series with the block portion of the row 73 being formed in a separate guide rail 80 provided as an abutment surface for the TAB strip when it is abutted against the guide rail 80 so as to provide for an accurate registration of the tab strip with respect to the bond pads 81, 82 which are provided along the length of the printhead so as to provide for low impedance driving of the actuators.

[0088] The principles of the preferred embodiment can obviously be readily extended to other structures. For example, a fulcrum arrangement could be constructed which includes two arms which are pivoted around a thinned wall by means of their attachment to a cross bar. Each arm could be attached to the central cross bar by means of similarly leafed portions to that shown in FIG. 6 and FIG. 7. The distance between a first arm and the thinned wall can be L units whereas the distance between the second arm and wall can be NL units. Hence, when a translational movement is applied to the second arm for a distance of N×X units the first arm undergoes a corresponding movement of X units. The leafed portions allow for flexible movement of the arms whilst providing for full pulling strength when required.

[0089] It would be evident to those skilled in the art that the present invention can further be utilized in either mechanical arrangement requiring the application forces to induce movement in a structure.

[0090] One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps:

[0091] 1. Using a double sided polished wafer 50, complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process 51. Relevant features of the wafer at this step are shown in FIG. 30. For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle. FIG. 29 is a key to representations of various materials in these manufacturing diagrams, and those of other cross-referenced ink jet configurations.

[0092] 2. Etch oxide down to silicon or aluminum using Mask 1. This mask defines the ink inlet, the heater contact vias, and the edges of the print head chips. This step is shown in FIG. 31.

[0093] 3. Etch exposed silicon 51 to a depth of 20 microns. This step is shown in FIG. 32.

[0094] 4. Deposit a 1-micron conformal layer of a first sacrificial material 91.

[0095] 5. Deposit 20 microns of a second sacrificial material 92, and planarize down to the first sacrificial layer using CMP. This step is shown in FIG. 33.

[0096] 6. Etch the first sacrificial layer using Mask 2, defining the nozzle chamber wall 93, the paddle 9, and the actuator anchor point 21. This step is shown in FIG. 34.

[0097] 7. Etch the second sacrificial layer down to the first sacrificial layer using Mask 3. This mask defines the paddle 9. This step is shown in FIG. 35.

[0098] 8. Deposit a 1-micron conformal layer of PECVD glass 53.

[0099] 9. Etch the glass using Mask 4, which defines the lower layer of the actuator loop.

[0100] 10. Deposit 1 micron of heater material 55, for example titanium nitride (TiN) or titanium diboride (TiB2). Planarize using CMP. This step is shown in FIG. 36.

[0101] 11. Deposit 0.1 micron of silicon nitride 56.

[0102] 12. Deposit 1 micron of PECVD glass 57.

[0103] 13. Etch the glass using Mask 5, which defines the upper layer of the actuator loop.

[0104] 14. Etch the silicon nitride using Mask 6, which defines the vias connecting the upper layer of the actuator loop to the lower layer of the actuator loop.

[0105] 15. Deposit 1 micron of the same heater material 58 previously deposited. Planarize using CMP. This step is shown in FIG. 37.

[0106] 16. Deposit 1 micron of PECVD glass 60.

[0107] 17. Etch the glass down to the sacrificial layer using Mask 6. This mask defines the actuator and the nozzle chamber wall, with the exception of the nozzle chamber actuator slot. This step is shown in FIG. 38.

[0108] 18. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated.

[0109] 19. Deposit 4 microns of sacrificial material 62 and planarize down to glass using CMP.

[0110] 20. Deposit 3 microns of PECVD glass 63. This step is shown in FIG. 39.

[0111] 21. Etch to a depth of (approx.) 1 micron using Mask 7. This mask defines the nozzle rim 95. This step is shown in FIG. 40.

[0112] 22. Etch down to the sacrificial layer using Mask 8. This mask defines the roof of the nozzle chamber, and the nozzle 40, 41 itself. This step is shown in FIG. 41.

[0113] 23. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask 9. This mask defines the ink inlets 65 which are etched through the wafer. The wafer is also diced by this etch. This step is shown in FIG. 42.

[0114] 24. Etch both types of sacrificial material. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch. This step is shown in FIG. 43.

[0115] 25. Mount the print heads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink 96 to the ink inlets at the back of the wafer.

[0116] 26. Connect the print heads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper.

[0117] 27. Hydrophobize the front surface of the print heads.

[0118] 28. Fill the completed print heads with ink and test them. A filled nozzle is shown in FIG. 44.

[0119] The presently disclosed ink jet printing technology is potentially suited to a wide range of printing system including: color and monochrome office printers, short run digital printers, high speed digital printers, offset press supplemental printers, low cost scanning printers high speed pagewidth printers, notebook computers with in-built pagewidth printers, portable color and monochrome printers, color and monochrome copiers, color and monochrome facsimile machines, combined printer, facsimile and copying machines, label printers, large format plotters, photograph copiers, printers for digital photographic “minilabs”, video printers, PhotoCD printers, portable printers for PDAs, wallpaper printers, indoor sign printers, billboard printers, fabric printers, camera printers and fault tolerant commercial printer arrays.

[0120] It would be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.

[0121] Ink Jet Technologies

[0122] The embodiments of the invention use an ink jet printer type device. Of course many different devices could be used. However presently popular ink jet printing technologies are unlikely to be suitable.

[0123] The most significant problem with thermal ink jet is power consumption. This is approximately 100 times that required for high speed, and stems from the energy-inefficient means of drop ejection. This involves the rapid boiling of water to produce a vapor bubble which expels the ink. Water has a very high heat capacity, and must be superheated in thermal ink jet applications. This leads to an efficiency of around 0.02%, from electricity input to drop momentum (and increased surface area) out.

[0124] The most significant problem with piezoelectric ink jet is size and cost. Piezoelectric crystals have a very small deflection at reasonable drive voltages, and therefore require a large area for each nozzle. Also, each piezoelectric actuator must be connected to its drive circuit on a separate substrate. This is not a significant problem at the current limit of around 300 nozzles per print head, but is a major impediment to the fabrication of pagewidth print heads with 19,200 nozzles.

[0125] Ideally, the ink jet technologies used meet the stringent requirements of in-camera digital color printing and other high quality, high speed, low cost printing applications. To meet the requirements of digital photography, new ink jet technologies have been created. The target features include:

[0126] low power (less than 10 Watts)

[0127] High-resolution capability (1,600 dpi or more)

[0128] photographic quality output

[0129] low manufacturing cost

[0130] small size (pagewidth times minimum cross section)

[0131] high speed (<2 seconds per page).

[0132] All of these features can be met or exceeded by the ink jet systems described below with differing levels of difficulty. Forty-five different ink jet technologies have been developed by the Assignee to give a wide range of choices for high volume manufacture. These technologies form part of separate applications assigned to the present Assignee as set out in the table above under the heading Cross References to Related Applications.

[0133] The ink jet designs shown here are suitable for a wide range of digital printing systems, from battery powered one-time use digital cameras, through to desktop and network printers, and through to commercial printing systems

[0134] For ease of manufacture using standard process equipment, the print head is designed to be a monolithic 0.5-micron CMOS chip with MEMS post processing. For color photographic applications, the print head is 100 mm long, with a width which depends upon the ink jet type. The smallest print head designed is IJ38, which is 0.35 mm wide, giving a chip area of 35 square mm. The print heads each contain 19,200 nozzles plus data and control circuitry.

[0135] Ink is supplied to the back of the print head by injection molded plastic ink channels. The molding requires 50-micron features, which can be created using a lithographically micro machined insert in a standard injection-molding tool. Ink flows through holes etched through the wafer to the nozzle chambers fabricated on the front surface of the wafer. The print head is connected to the camera circuitry by tape automated bonding.

[0136] Tables of Drop-on-Demand Ink Jets

[0137] Eleven important characteristics of the fundamental operation of individual ink jet nozzles have been identified. These characteristics are largely orthogonal, and so can be elucidated as an eleven dimensional matrix. Most of the eleven axes of this matrix include entries developed by the present assignee.

[0138] The following tables form the axes of an eleven dimensional table of ink jet types.

[0139] Actuator mechanism (18 types)

[0140] Basic operation mode (7 types)

[0141] Auxiliary mechanism (8 types)

[0142] Actuator amplification or modification method (17 types)

[0143] Actuator motion (19 types)

[0144] Nozzle refill method (4 types)

[0145] Method of restricting back-flow through inlet (10 types)

[0146] Nozzle clearing method (9 types)

[0147] Nozzle plate construction (9 types)

[0148] Drop ejection direction (5 types)

[0149] Ink type (7 types)

[0150] The complete eleven dimensional table represented by these axes contains 36.9 billion possible configurations of ink jet nozzle. While not all of the possible combinations result in a viable ink jet technology, many million configurations are viable. It is clearly impractical to elucidate all of the possible configurations. Instead, certain ink jet types have been investigated in detail. These are designated IJ01 to IJ45 which matches the docket numbers in the table under the heading CROSS REFERENCES TO RELATED APPLICATIONS.

[0151] Other ink jet configurations can readily be derived from these forty-five examples by substituting alternative configurations along one or more of the 11 axes. Most of the IJ01 to IJ45 examples can be made into ink jet print heads with characteristics superior to any currently available ink jet technology.

[0152] Where there are prior art examples known to the inventor, one or more of these examples are listed in the examples column of the tables below. The IJ01 to IJ45 series are also listed in the examples column. In some cases, a printer may be listed more than once in a table, where it shares characteristics with more than one entry.

[0153] Suitable applications for the ink jet technologies include: Home printers, Office network printers, Short run digital printers, Commercial print systems, Fabric printers, Pocket printers, Internet WWW printers, Video printers, Medical imaging, Wide format printers, Notebook PC printers, Fax machines, Industrial printing systems, Photocopiers, Photographic minilabs etc.

[0154] The information associated with the aforementioned 11 dimensional matrix is set out in the following tables.

2DescriptionAdvantagesDisadvantagesExamplesACTUATOR MECHANISM(APPLIED ONLY TO SELECTED INK DROPS)ThermalAn electrothermal heaterLarge force generatedHigh powerCanon Bubblejet 1979 Endobubbleheats the ink to aboveSimple constructionInk carrier limited to wateret al GB patent 2,007,162boiling point, transferringNo moving partsLow efficiencyXerox heater-in-pit 1990significant heat to the aqueousFast operationHigh temperatures requiredHawkins et alink. A bubble nucleates andSmall chip area required forHigh mechanical stressU.S. Pat. No. 4,899,181quickly forms, expelling the ink.actuatorUnusual materials requiredHewlett-Packard TIJ 1982The efficiency of the process isLarge drive transistorsVaught et allow, with typically less thanCavitation causes actuatorU.S. Pat. No. 4,490,7280.05% of the electrical energyfailurebeing transformed into kineticKogation reduces bubbleenergy of the drop.formationLarge print heads are difficultto fabricatePiezoelectricA piezoelectric crystal such asLow power consumptionVery large area required forKyser et allead lanthanum zirconate (PZT)Many ink types can be usedactuatorU.S. Pat. No. 3,946,398is electrically activated, andFast operationDifficult to integrate withZoltan U.S. Pat. No. 3,683,212and either expands, shears, orHigh efficiencywith electronics1973 Stemmebends to apply pressure to theHigh voltage drive transistorsU.S. Pat. No. 3,747,120ink, ejecting drops.requiredEpson StylusFull pagewidth print headsTektroniximpractical due to actuator sizeIJ04Requires electrical poling inhigh field strengths duringmanufactureElectrostrictiveAn electric field is used toLow power consumptionLow maximum strain (approx.Seiko Epson, Usui et allactivate electrostriction inMany ink types can be used0.01%)JP 253401/96relaxor materials such as leadLow thermal expansionLarge area required for actuatorIJ04lanthanum zirconate titanateElectric field strength requireddue to low strain(PLZT) or lead magnesium(approx. 3.5 V/μm) can beResponse speed is marginalnobate (PMN).generated without difficulty(˜10 μs)Does not require electricalHigh voltage drive transistorspolingrequiredFull pagewidth print headsimpractical due to actuator sizeFerroelectricAn electric field is used toLow power consumptionDifficult to integrate withIJ04induce a phase transitionMany ink types can be usedelectronicsbetween the antiferroelectricFast operation (<1 μs)Unusual materials such as(AFE) and ferroelectric (FE)Relatively high longitudinalPLZSnT are requiredphase. Perovskite materials suchstrainActuators require a large areaas tin modified lead lanthanumHigh efficiencyzirconate titanate (PLZSnT)Electric field strength of aroundexhibit large strains of up to 1%3 V/μm can be readily providedassociated with the AFE to FEphase transitionElectrastaticConductive plates are separatedLow power consumptionDifficult to operate electrostaticIJ02, IJ04platesby a compressible or fluidMany ink types can be useddevices in an aqueous environ-dielectric (usually air). UponFast operationment application of a voltage, theThe electrostatic actuatorplates attract each other andwill normally need to bedisplace ink, causing dropseperated from the inkejection. The conductive platesVery large area required tomay be in a comb or honeycombachieve high forcesstructure, or stacked to increaseHigh voltage drive transistorsthe surface are and therefore themay be requiredforce.Full pagewidth print heads arenot competitive due to actuatorsizeElectrostaticA strong electric field is appliedLow current consumptionHigh voltage required1989 Saito et al,pull on inkto the ink, whereupon electro-Low temperatureMay be damaged by sparks dueU.S. Pat. No. 4,799,068static attraction accelerates theto air breakdown1989 Miura et al,ink towards the print medium.Required field strength increaseU.S. Pat. No. 4,810,954as the drop size decreasesTone-jetHigh voltage drive transistorsrequiredElectrostatic field attracts dustPermanentAn electromagnet directlyLow power consumptionComplex fabricationIJ07, IJ10magnetattracts a permanent magnet,Many ink types can be usedPermanent magnetic materialelectromagneticdisplacing ink and causing dropFast operationsuch as Neodymium Iron Boronejection. Rare earth magnetsHigh efficiency(NdFeB) required.with a field strength around 1Fast extension from singleHigh local currents requiredTesla can be used. Examplesnozzles to pagewidth print headsCopper metalization should beare: Samarium Cobalt (SaCo)used for long electromigrationand magnetic material in thelifetime and low resistivityneodymium iron boron familyPigmented inks are usually(NdFeB, NdDyFeBNb,infeasibleNdDyFeB, etc)Operating temperature limitedto the Curie temperature(around 540 K)Soft magneticA solenoid induced a magneticLow power consumptionComplex fabricationIJ01, IJ05, IJ08, IJ10, IJ12,corefield in a soft magnetic coreMany ink types can be usedMaterials not usually presentIJ14, IJ15, IJ17electromagneticor yoke fabricated from a ferrousFast operationin a CMOS fab such as NiFe,material such as electroplatedHigh efficiencyCoNiFe, or CoFe are requirediron alloys such as CoNiFe [1],Easy extension from singleHigh local currents requiredCoFe, or NiFe alloys. Typically,nozzles to pagewidth print headsCopper metallisation should bethe soft magnetic material is inused for long electromigrationtwo parts, which are normallylifetime and low resistivityheld apart by a spring. When theElectroplating is requiredsolenoid is actuated, the twoHigh saturation flux density isparts attract, displacing the ink.required (2.0-2.1 T is achievablewith CoNiFe [1])Lorenz forceThe Lorenz force acting on aLow power consumptionForce acts as a twisting motionIJ06, IJ11, IJ13, IJ16current carrying wire in aMany ink types can be usedTypically, only a quarter of themagnetic field is utilized. ThisFast operationsolenoid length provides forceallows the magnetic field to beHigh efficiencyin a useful directionsupplied externally to the printEasy extension from singleHigh local current requiredhead, for example with rarenozzles to pagewidth print headsCopper metallisation should beearth permanent magnets. Onlyused for long electro migrationthe current carrying wire needlifetime and low resistivitybe fabricated on the print head,Pigmented inks are usuallysimplifying materialsinfeasiblerequirements.Magneto-The actuator uses the giantMany ink types can be usedForce acts as a twisting motionFischenbeck,strictionmagnetostrictive effect ofFast operationUnusual material such asU.S. Pat. No. 4,032,929materials such as Terfenol-DEasy extention from singleTerfenol-D are requiredIJ25(an alloy of terbium, dysprosiumnozzles to pagewidth print headsHigh local currents requiredand iron developed at the NavalHigh force is availableCopper metallisation should beOrdnance Laboratory, henceused for long electro migrationTer-Fe-NOL). For bestlifetime and low resistivityefficiency, the actuator shouldPre-stressing may be requiredbe prestressed to approx. 8 MPa.Surface tensionInk under positive pressure isLow power consumptionRequires supplementary forceSilverbrook, EP 0771 658 A2reductionheld in a nozzle by surfaceSimple constructionto effect drop separationand related patent applicationstension. The surface tension ofNo unusual materials requiredRequires special ink surfactantsthe ink is reduced below thein fabricationSpeed may be limited bybubble threshold, causing theHigh efficiencysurfactant propertiesink to egress from the nozzle.Easy extension from singlenozzles to pagewidth print headsViscosityThe ink viscosity is locallySimple constructionRequires supplementary forceSilverbrook, EP 0771 658 A2reductionreduced to select which dropsNo unusual materials required into effect drop separationand related patent applicationsare to be ejected. A viscosityfabricationRequires special ink viscosityreduction can be achievedEasy extension from singlepropertieselectrothermally with most inks,nozzles to pagewidth print headsHigh speed is difficult to achievebut special inks can beRequires oscillating ink pressureengineered for a 100:1 viscosityA high temperature differencereduction.(typically 80 degrees) is requiredAcousticAn acoustic wave is generatedCan operate without a nozzleComplex drive circuitry1993 Hadimioglu et al,and focussed upon the dropplateComplex fabricationEUP 550,192ejection region.Low efficiency1993 Elrod et al, EUP 572,220Poor control of drop positionPoor control of drop volumeThermoelasticAn actuator which relies uponLow power consumptionEfficient aqueous operationIJ03, IJ09, IJ17, IJ18, IJ19,bend actuatordifferential thermal expansionMany ink types can be usedrequires a thermal insulator onIJ20, IJ21, IJ22, IJ23, IJ24,upon Joule heating is used.Simple planar fabricationthe hot sideIJ27, IJ28, IJ29, IJ30, IJ31,Small chip area required forCorrosion prevention can beIJ32, IJ33, IJ34, IJ35, IJ36,each actuatordifficultIJ37, IJ38, IJ39, IJ40, IJ41Fast operationPigmented inks may beHigh efficiencyinfeasible, as pigment particlesCMOS compatible voltages andmay jam the bend actuatorcurrentsStandard MEMS processes canbe usedEasy extension from singlenozzles to pagewidth print headsHigh CTEA material with a very highHigh force can be generatedRequires special material (e.g.IJ09, IJ17, IJ18, IJ20, IJ21,Thermoelasticcoefficient of thermal expansionThree methods of PTFEPTFE)IJ22, IJ23, IJ24, IJ27, IJ28,actuator(CTE) such as polytetrafluoro-deposition are under develop-Requires a PTFE depositionIJ29, IJ30, IJ31, IJ42, IJ43,ethylene (PTFE) is used. Asment: chemical vaporprocess, which is not yetIJ44high CTE materials are usuallydeposition (CVD), spin coating,standard in ULSI fabsnon-conductive, a heaterand evaporationPTFE deposition cannot befabricated from a conductivePTFE is a candidate for lowfollowed with high temperaturematerial is incorporated. Adielectric constant insulation(above 350° C.) processing50 μm long PTFE bend actuatorin ULSIPigmented inks may bewith polysilicon heater andVery low power consumptioninfeasible, as pigment particles15 mW power input can provideMany ink types can be usedmay jam the bend actuator180 μN force and 10 μmSimple planar fabricationdeflection. Actuator motionsSmall chip are required for eachinclude:actuatorBendFast operationPushHigh efficiencyBuckleCMOS compatable voltages andRotatecurrentsEast extension from singlenozzles to pagewidth print headsConductiveA polymer with a highHigh force can be generatedRequires special materialsIJ24polymercoefficient of thermal expansionVery low power consumptiondevelopment (High CTEthermoselastic(such as PTFE) is doped withMany inks can be usedconductive polymer)actuatorconducting substances toSimple planar fabricationRequires a PTFE depositionincrease its conductivity toSmall chip area required forprocess, which is not yetabout 3 orders of magnitudeeach actuatorstandard in ULSI fabsbelow that of copper. TheFast operationPTFE deposition cannot beconducting polymer expandsHigh efficiencyfollowed with high temperaturewhen resistively heated.CMOS compatible voltages and(above 350° C.) processingExamples of conducting dopantscurrentsEvaporation and CVDinclude:Easy extension from singledeposition techniques cannotCarbon nanotubesnozzles to pagewidth print headsbe usedMetal fibersPigmented inks may beConductive polymers such asinfeasible, as pigment particlesdoped polythiophenemay jam the bend actuatorCarbon granulesShape memoryA shape memory alloy such asHigh force is available (stressesFatigue limits maximum numberIJ26alloyTiNi (also known as Nitinol-of hundreds of MPa)of cyclesNickel Titanium alloy developedLarge strain is available (moreLow strain (1%) is required toat the Naval Ordnancethan 3%)extend fatigue resistanceLaboratory) is thermallyHigh corrosion resistanceCycle rate limited by heatswitched between its weakSimple constructionremovalmartensitic state and itsEasy extension from singleRequires unusual materialshigh stiffness austenic state.nozzles to pagewidth print heads(TiNi)The shape of the actuator inLow voltage operationThe latent heat of transformationits martensitic state ismust be provideddeformed relative to theHigh current operationaustenitic shape. The shapeRequires prestressing to distortchange causes ejection of athe martensitic statedrop.LinearLinear magnetic actuatorsLinear Magentic actuators canRequires unusual semiconductorIJ12Magneticinclude the Linear Inductionbe constructed with high thrust,materials such as soft magenticActuatorActuator (LIA), Linearlong travel, and high efficiencyalloys (e.g. CoNiFe)Permanent Magnet Synchronoususing planar semiconductorSome varieties also requireActuator (LPMSA), Linearfabrication techniquespermanent magnetic materialsReluctance SynchronousLong actuator travel is availablesuch as Neodymium iron boronActuator (LRSA), LinearMedium force is available(NdFeB)Switched Reluctance ActuatorLow voltage operationRequires complex multi-phase(LSRA), and the Linear Stepperdrive circuityActuator (LSA).High current operationBASIC OPERATION MODEActuatorThis is the simplest mode ofSimple operationDrop repetition rate is usuallyThermal ink jetdirectly pushesoperation: the actuator directlyNo external fields requiredlimited to around 10 kHz.Piezoelectric ink jetinksupplies sufficient kineticSatellite drops can be avoidedHowever, this is not funda-IJ01, IJ02, IJ03, IJ04, IJ05,energy to expel the drop. Theif drop velocity is less thanmental to the method, but isIJ06, IJ07, IJ09, IJ11, IJ12,drop must have a sufficient4 m/srelated to the refill methodIJ14, IJ16, IJ20, IJ22, IJ23,velocity to overcome the surfaceCan be efficient, dependingnormally usedIJ24, IJ25, IJ26, IJ27, IJ28,tension.upon the actuator usedAll of the drop kinetic energyIJ29, IJ30, IJ31, IJ32, IJ33,must be provided by theIJ34, IJ35, IJ36, IJ37, IJ38,actuatorIJ39, IJ40, IJ41, IJ42, IJ43,Satellite drops usually form ifIJ44drop velocity is greater than4.5 m/sProximityThe drops to be printed areVery simple print headRequires close proximitySilverbrook, EP 0771 658 A2selected by some manner (e.g.fabrication can be usedbetween the print head andand related patent applicationsthermally induced surfaceThe drop selection means doesthe print media or transfer rollertension reduction of pressurizednot need to provide the energyMay require two print headsink). Selected drops arerequired to separate the dropprinting alternate rows of theseparated from the ink in thefrom the nozzleimagenozzle by contact with theMonolithic color print heads areprint medium or a transferdifficultroller.ElectrostaticThe drops to be printed areVery simple print headRequires very high electrostaticSilverbrook, EP 0771 658 A2pull on inkselected by some manner (e.g.fabrication can be usedfieldand related patent applicationsthermally induced surfaceThe drop selection means doesElectrostatic field for smallTone-Jettension reduction of pressurizednot need to provide the energynozzle sizes is above airink). Selected drops arerequired to separate the dropbreakdownseparated from the ink in thefrom the nozzleElectrostatic field may attractnozzle by a strong electric field.dust.MagneticThe drops to be printed areVery simple print headRequires magnetic inkSilverbrook, EP 0771 658 A2pull on inkselected by some manner (e.g.fabrication can be usedInk colors other than black areand related patent applicationsthermally induced surfaceThe drop slection means doesdifficulttension reduction of pressurizednot need to provide the energyRequires very high magneticink). Selected drops arerequired to separate the dropfieldsseparated from the ink in thefrom the nozzlenozzle by a strong electric fieldacting on the magnetic ink.ShutterThe actuator moves a shutterHigh speed (>50 kHz) operationMoving parts are requiredIJ13, IJ17, IJ21to block ink flow to the nozzle.can be achieved due to reducedRequires ink pressure modulatorThe ink pressure is pulsed at arefill timeFriction and wear must bemultiple of the drop ejectionDrop timing can be veryconsideredfrequency.accurateStriction is possibleThe actuator energy can be verylowShuttered grillThe actuator moves a shutterActuators with small travel canMoving parts are requiredIJ08, IJ15, IJ18, IJ19to block ink flow through abe usedRequires ink pressure modulatorgrill to the nozzle. The shutterActuators with small force canFriction and wear must bemovement need only be equal tobe usedconsideredthe width of the grill holes.High speed (>50 kHz) operationStriction is possiblecan be achievedPulsedA pulsed magnetic field attractsExtremely low energy operationRequires an external pulsedIJ10magnetic pullan ‘ink pusher’ at the dropis possiblemagentic fieldon ink pusherejection frequency. An actuatorNo heat dissipation problemsRequires special materials forcontrols a catch, which preventsboth the actuator and the inkthe ink pusher from movingpusherwhen a drop is not to be ejected.Complex constructionAUXILLIARY MECHANISM (APPLIED TO ALL NOZZLES)NoneThe actuator directly fires theSimplicity of constructionDrop ejection energy must beMost ink jets, includingink drop, and there is noSimplicity of operationsupplied by individual nozzlepiezoelectric and thermalexternal field or otherSmall physical sizeactuatorbubble.mechanism required.IJ01, IJ02, IJ03, IJ04, IJ05,IJ07, IJ09, IJ11, IJ12, IJ14,IJ20, IJ22, IJ23, IJ24, IJ25,IJ26, IJ27, IJ28, IJ29, IJ30,IJ31, IJ32, IJ33, IJ34, IJ35,IJ36, IJ37, IJ38, IJ39, IJ40,IJ41, IJ42, IJ43, IJ44Oscillating inkThe ink pressure oscillates,Oscillating ink pressure canRequires external ink pressureSilverbrook, EP 0771 658 A2pressureproviding much of the dropprovide a refill pulse allowingoscillatorand related patent applications(includingejection energy. The actuatorhigher operating speedInk pressure phase andIJ08, IJ13, IJ15, IJ17, IJ18,acousticselects which drops are to beThe actuators may operate withamplitude must be carefullyIJ19, IJ21stimulation)fired by selectivity blockingmuch lower energycontrolledor enabling nozzles. The inkAcoustic lenses can be used toAcoustic reflections in the inkpressure oscillation may befocus the sound on the nozzleschamber must be designed forachieved by vibrating the printhead, or preferably by anactuator in the ink supply.MediaThe print head is placed inLow powerPrecision assembly requiredSilverbrook, EP 0771 658 A2proximityclose proximity to the printHigh accuracyPaper fibers may cause problemsand related patent applicationsmedium. Selected drops protrudeSimple print head constructionCannot print on rough substratesfrom the print head further thanunselected drops, and contact theprint medium. The drop soaksinto the medium fast enough tocause drop separation.Transfer rollerDrops are printed to a transferHigh accuracyBulkySilverbrook, EP 0771 658 A2roller instead of straight to theWide range of print substratesExpensiveand related patent applicationsprint medium. A transfer rollercan be usedComplex constructionTektronix hot melt piezoelectriccan also be used for proximityInk can be dried on the transferink jetdrop separation.rollerAny of the IJ seriesElectrostaticAn electric field is used toLow powerField strength required forSilverbrook, EP 0771 658 A2accelerate selected dropsSimple print head constructionseparation of small drops isand related patent applicationstowards the print medium.near or above air breakdownTone-JetDirectA magnetic field is used toLow powerRequires magnetic inkSilverbrook, EP 0771 658 A2magnetic fieldaccelerate selected drops ofSimple print head constructionRequires strong magnetic fieldand related patent applicationsmagnetic ink towards the printmedium.CrossThe print head is placed in aDoes not require magneticRequires external magnetIJ06, IJ16magnetic fieldconstant magnetic field. Thematerials to be integrated inCurrent densities may be high,Lorenz force in a currentthe print head manufacturingresulting in electromigrationcarrying wire is used to moveprocessproblemsthe actuator.PulsedA pulsed magnetic field is usedVery low power operation isComplex print head constructionIJ10magnetic fieldto cyclically attract a paddle,possibleMagnetic materials required inwhich pushes on the ink. ASmall print head sizeprint headsmall actuator moves a catch,which selectively preventsthe paddle from moving.ACTUATOR AMPLICATION OR MODIFICATION METHODNoneNo actuator mechanicalOperational simplicityMany actuator mechanisms haveThermal Bubble Ink jetamplification is used. Theinsufficient travel, orIJ01, IJ02, IJ06, IJ07, IJ16,actuator directly drives theinsufficient force, to efficientlyIJ25, IJ26drop ejection process.drive the drop ejection processDifferentialAn actuator material expandsProvides greater travel in aHigh stresses are involvedPiezoelectricexpansion bendmore on one side than on thereduced print head areaCare must be taken that theIJ03, IJ09, IJ17, IJ18, IJ19,actuatorother. The expansion may bematerials do not delaminateIJ20, IJ21, IJ22, IJ23, IJ24,thermal, piezoelectric,Residual bend resulting fromIJ27, IJ29, IJ30, IJ31, IJ32,magnetostrictive, or otherhigh temperature or high stressIJ33, IJ34, IJ35, IJ36, IJ37,mechanism. The bend actuatorduring formationIJ38, IJ39, IJ42, IJ43, IJ44converts a high force low travelactuator mechanism to hightravel, lower force mechanism.Transient bendA trilayer bend actuator whereVery good temperature stabilityHigh stresses are involvedIJ40, IJ41actuatorthe two outside layers areHigh speed, as a new drop canCare must be taken that theidentical. This cancels bendbe fired before heat dissipatesmaterials do no delaminatedue to ambient temperatures andCancels residual stress ofresidual stress. The actuatorformationonly responds to transientheating of one side or the other.Reverse springThe actuator loads a spring.Better coupling to the inkFabrication complexityIJ05, IJ11When the actuator is turned off,High stress in the springthe spring releases. This canreverse the force/distance curveof the actuator to make itcompatible with the force/timerequirements of the dropejection.Actuator stackA series of thin actuators areIncreased travelIncreased fabrication complexitySome piezoelectric ink jetsstacked. This can be appropriateReduced drive voltageIncreased possibility of shortIJ04where actuators require highcircuits due to pinholeselectric field strength, such aselectrostatic and piezelectricactuators.MultipleMultiple smaller actuators areIncreases the force availableActuator forces may not addIJ12, IJ13, IJ18, IJ20, IJ22,actuatorsused simultaneously to move thefrom an actuatorlinearly, reducing efficiencyIJ28, IJ42, IJ43ink. Each actuator need provideMultiple actuators can beonly a portion of the forcepositioned to control ink flowrequired.accuratelyLinear SpringA linear spring is used toMatches low travel actuator withRequires print head area for theIJ15transform a motion with smallhigher travel requirementsspringtravel and high force into aNon-contact method of motionlonger travel, lower forcetransformationmotion.Coiled actuatorA bend actuator is coiled toIncreases travelGenerally restricted to planarIJ17, IJ21, IJ34, IJ35provide greater travel in aReduces chip areaimplementations due to extremereduced chip area.Planar implementations arefabrication difficulty in otherrelatively easy to fabricate.orientations.Flexure bendA bend actuator has a smallSimple means of increasingCare must be taken not toIJ10, IJ19, IJ33actuatorregion near the fixture point,travel of a bend actuatorexceed the elastic limit in thewhich flexes much more readilyflexure areathan the remainder of theStess distribution is very unevenactuator. The actuator flexingDifficult to accurately modelis effectively converted fromwith finite element analysisan even coiling to an angularbend, resulting in greater travelof the actuator tip.CatchThe actuator controls a smallVery low actuator energyComplex constructionIJ10catch. The catch either enablesVery small actuator sizeRequires external forceor disables movement of an inkUnsuitable for pigmented inkspusher that is controlled in abulk manner.GearsGears can be used to increaseLow force, low travel actuatorsMoving parts are requiredIJ13travel at the expense of duration.can be usedSeveral actuator cycles areCircular gears, rack and pinion,Can be fabricated using standardrequiredratchets, and other gearingsurface MEMS processesMore complex drive electronicsmethods can be used.Complex constructionFriction, friction, and wear arepossibleBuckle plateA buckle plate can be used toVery fast movement achievableMust stay within elastic limitsS. Hirata et al. “An Ink-jetchange a slow actuator into aof the materials for long deviceHead Using Diaphragmfast motion. It can also convertlifeMicroactuator”, Proc. IEEEa high force, low travelHigh stresses involvedMEMS, Feb. 1996, pp 418-423.actuator into a high travel,Generally high powerIJ18, IJ27medium force motion.requirementTaperedA tapered magnetic pole canLinearizes the magnetic force/Complex constructionIJ14magnetic poleincrease travel at the expensedistance curveof forceLeverA lever and fulcrum is used toMatches low travel actuator withHigh stress around the fulcrumIJ32, IJ36, IJ37transform a motion with smallhigher travel requirementstravel and high force into aFulcrum area has no linearmotion with longer travel andmovement, and can be used forlower force. The lever can alsoa fluid sealreverse the direction of travel.Rotary impellerThe actuator is connected to aHigh mechanical advantageComplex constructionIJ28rotary impeller. A small angularThe ratio of force to travel ofUnsuitable for pigmented inksdeflection of the actuator resultsthe actuator can be matched toin a rotation of the impellerthe nozzle requirements byvanes, which push the inkvarying the number of impelleragainst stationary vanes and outvanesof the nozzle.Acoustic lensA refractive or diffractive (e.g.No moving partsLarge area required1993 Hadimioglu et al, EUPzone plate) acoustic lens is usedOnly relevant for acoustic550,192to concentrate sound waves.ink jets1993 Elrod et al, EUP 572,220SharpA sharp point is used toSimple constructionDifficult to fabricate usingTone-jetconductiveconcentrate an electrostatic field.standard VLSI processes for apointsurface ejecting ink-jetOnly relevant for electrostaticink jetsACTUATOR MOTIONVolumeThe volume of the actuatorSimple construction in theHigh energy is typicallyHewlett-Packard Thermalexpansionchanges, pushing the ink incase of thermal ink jetrequired to achieve volumeInk jetall directions.expansion. This leads toCanon Bubblejetthermal stress, cavitation,and kogation in thermal ink jetimplementationsLinear, normalThe actuator moves in aEfficient coupling to ink dropsHigh fabrication complexityIJ01, IJ02, IJ04, IJ07, IJ11,to chip surfacedirection normal to the printejected normal to the surfacemay be required to achieveIJ14head surface. The nozzle isperpendicular motiontypically in the line ofmovement.Parallel toThe actuator moves parallelSuitable for planar fabricationFabrication complexityIJ12, IJ13, IJ15, IJ33, IJ34,chip surfaceto the print head surface.FrictionIJ35, IJ36Drop ejection may still beStictionnormal to the surface.MembraneAn actuator with a high forceThe effective area of theFabrication complexity1982 Howkinspushbut small area is used to pushactuator becomes the membraneActuator sizeU.S. Pat. No. 4,459,601a stiff membrane that is inareaDifficulty of integration in acontact with the ink.VLSI processRotaryThe actuator causes the rotationRotary levers may be used toDevice complexityIJ05, IJ08, IJ13, IJ28of some element, such a grillincrease travelMay have friction at a pivotor impellerSmall chip area requirementspointBendThe actuator bends whenA very small change inRequires the actuator to be1970 Kyser et alenergized. This may be due todimensions can be convertedmade from at least two distinctU.S. Pat. No. 3,946,398differential thermal expansion,to a large motion.layers, or to have a thermal1973 Stemmepiezoelectric expansion,difference across the actuatorU.S. Pat. No. 3,737,120magnetostriction, or other formIJ03, IJ09, IJ10, IJ19, IJ23,of relative dimensional change.IJ24, IJ25, IJ29, IJ30, IJ31,IJ33, IJ34, IJ35SwivelThe actuator swivels around aAllows operation where the netInefficient coupling to the inkIJ06central pivot. This motion islinear force on the paddle is zeromotionsuitable where there areSmall chip area requirementsopposite forces applied toopposite sides of the paddle,e.g. Lorenz force.StraightenThe actuator is normally bent,Can be used with shape memoryRequires careful balance ofIJ26, IJ32and straightens when energized.alloys where the austenic phasestresses to ensure that theis planarquiescent bend is accurateDouble bendThe actuator bends in oneOne actuator can be used toDifficult to make the dropsIJ36, IJ37, IJ38direction when one element ispower two nozzles.ejected by both bend directionsenergized, and bends the otherReduce chip size.identical.way when another element isNot sensitive to ambientA small efficiency lossenergized.temperaturecompared to equivalent singlebend actuators.ShearEnergizing the actuator causesCan increase the effective travelNot readily applicable to other1985 Fishbecka shear motion in the actuatorof piezoelectric actuatorsactuator mechanismsU.S. Pat. No. 4,584,590material.RadialThe actuator squeezes an inkRelatively easy to fabricateHigh force required1970 Zoltanconstrictionreservoir, forcing ink from asingle nozzles from glass tubingInefficientU.S. Pat. No. 3,683,212constricted nozzle.as macroscopic structuresDifficult to integrate with VLSIprocessesCoil/uncoilA coiled actuator uncoils orEasy to fabricate as a planarDifficult to fabricate for non-IJ17, IJ21, IJ34, IJ35coils more tightly. The motionVLSI processplanar devicesof the actuator ejects the ink.Small area required, thereforePoor out-of-plane stiffnesslow costBowThe actuator bows (or buckles)Can increase the speed of travelMaximum travel is constrainedIJ16, IJ18, IJ27in the middle when energized.Mechanically rigidHigh force requiredPush-PullTwo actuators control a shutter.The structure is pinned at bothNot readily suitable for ink jetsIJ18One actuator pulls the shutter,ends, so has a high out-of-planewhich directly push the inkand the other pushes it.rigidityCurl inwardsA set of actuators curl inwardsGood fluid flow to the regionDesign complexityIJ20, IJ42to reduce the volume of inkbehind the actuator increasesthat they enclose.efficiencyCurl outwardsA set of actuators curl outwards,Relatively simple constructionRelatively large chip areaIJ43pressurizing ink in a chambersurrounding the actuators, andexpelling ink from a nozzlein the chamber.IrisMultiple vanes enclose a volumeHigh efficiencyHigh fabrication complexityIJ22of ink. These simultaneouslySmall chip areaNot suitable for pigmented inksrotate, reducing the volumebetween the vanes.AcousticThe actuator vibrates at a highThe actuator can be physicallyLarge area required for efficient1993 Hadimioglu et al,vibrationfrequency.distant from the inkoperation at useful frequenciesEUP 550,192Asoustic coupling and crosstalk1993 Elrod et al EUP 572,220Complex drive circuitryPoor control of drop volume andpositionNoneIn various ink jet designs theNo moving partsVarious other tradeoffs areSilverbrook, EP 0771 658 A2actuator does not move.required to eliminate movingand related patent applicationspartsTone-jetNOZZLE REFILL METHODSurface tensionThis is the normal way that inkFabrication simplicityLow speedThermal ink jetjets are refilled. After theOperational simplicitySurface tension force relativelyPiezoelectric ink jetactuator is energized, it typicallysmall compared to actuator forceIJ01-IJ07, IJ10-IJ14, IJ16,returns rapidly to its normalLong refill time usuallyIJ20, IJ22-IJ45position. This rapid return sucksdominates the total repetitionthe air through the nozzlerateopening. The ink surface tensionat the nozzle then exerts a smallforce restoring the meniscus toa minimum area. This forcerefills the nozzle.ShutteredInk to the nozzle chamber isHigh speedRequires common ink pressureIJ08, IJ13, IJ15, IJ17, IJ18,oscillating inkprovided at a pressure thatLow actuator energy, as theoscillatorIJ19, IJ21pressureoscillates at twice the dropactuator need only open or closeMay not be suitable forejection frequency. When a dropthe shutter, instead of ejectingpigmented inksis to be ejected, the shutterthe ink dropis opened for 3 half cycles:drop ejection, actuator return,and refill. The shutter is thenclosed to prevent the nozzlechamber emptying during thenext negative pressure cycle.Refill actuatorAfter the main actuator hasHigh speed, as the nozzle isRequires two indenpendentIJ09ejected a drop a second (refill)actively refilledactuators per nozzleactuator is energized. The refillactuator returns slowly, toprevent its return from emptyingthe chamber again.PositiveThe ink is held a slight positiveHigh refill rate, therefore aSurface spill must be preventedSilverbrook, EP 0771 658 A2ink pressurepressure. After the ink drop ishigh drop repetition rate isHighly hydrophobic print headand related patent applicationsejected, the nozzle chamber fillspossiblesurfaces are requiredAlternative for:, IJ01-IJ07,quickly as surface tension andIJ10-IJ14, IJ16, IJ20, IJ22-IJ45ink pressure both operate torefill the nozzle.METHOD OF RESTRICTING BACK-FLOW THROUGH INLETLong inletThe ink inlet channel to theDesigns simplicityRestricts refill rateThermal ink jetchannelnozzle chamber is made longOperational simplicityMay result in a relatively largePiezoelectric ink jetand relatively narrow, relying onReduces crosstalkchip areaIJ42, IJ43viscous drag to reduce inletOnly partially effectiveback-flow.PositveThe ink is under a positiveDrop selection and separationRequires a method (such as aSilverbrook, EP 0771 658 A2ink pressurepressure, so that in the quiescentforces can be reducednozzle rim or effectiveand related patent applicationsstate some of the ink dropFast refill timehydrophobizing, or both) toPossible operation of thealready protrudes from theprevent flooding of the ejectionfollowing: IJ01-IJ07, IJ09-IJ12,nozzle. This reduces thesurface of the print head.IJ14, IJ16, IJ20, IJ22, IJ23-IJ34pressure in the nozzle chamberIJ36-IJ41, IJ44which is required to eject acertain volume of ink. Thereduction in chamber pressureresults in a reduction in inkpushed out through the inlet.BaffleOne or more baffles are placedThe refill rate is not asDesign complexityHP Thermal Ink Jetin the inlet ink flow. When therestricted as the long inletMay increase fabricationTektronix piezoelectric ink jetactuator is energized, the rapidmethod.complexity (e.g. Tektronix hotink movement creates eddiesReduces crosstalkmelt piezoelectric print heads).which restrict the flow throughthe inlet. The slower refillprocess is unrestricted, anddoes not result in eddies.Flexible flapIn this method recently disclosedSignificantly reduces back-flowNot applicable to most ink jetCanonrestricts inletby Canon, the expandingfor edge-shooter thermal inkconfigurationsactuator (bubble) pushes onjet devicesIncreased fabrication complexityflexible flap that restricts theInelastic deformation of polymerinlet.flap results in creep overextended useInlet filterA filter is located between theAdditional advantage of inkRestricts refill rateIJ04, IJ12, IJ24, IJ27, IJ29,ink inlet and the nozzlefiltrationMay result in complexIJ30chamber. The filter has aInk filter may be fabricated withconstructionmultitude of small holes or slots,no additional process stepsrestricting ink flow. The filteralso removes particles whichmay block the nozzle.Small inletThe ink inlet channel to theDesign simplicityRestricts refill rateIJ02, IJ37, IJ44compared tonozzle chamber has a sub-May result in a relatively largenozzlestantially smaller cross sectionchip areathan that of the nozzle,Only partially effectiveresulting in easier ink egressout of the nozzle than out ofthe inlet.Inlet shutterA secondary actuator controlsIncreases speed of the ink-jetRequires separate refill actuatorIJ09the position of a shutter,print head operationand drive circuitclosing off the ink inlet whenthe main actuator is energized.The inlet isThe method avoids the problemBack-flow problem is eliminatedRequires careful design toIJ01, IJ03, IJ05, IJ06, IJ07,located behindof inlet back-flow by arrangingminimize the negative pressureIJ10, IJ11, IJ14, IJ16, IJ22,the ink-pushingthe ink-pushing surface ofbehind the paddleIJ23, IJ25, IJ28, IJ31, IJ32,surfacethe actuator between the inletIJ33, IJ34, IJ35, IJ36, IJ39,and the nozzle.IJ40, IJ41Part of theThe actuator and a wall of theSignificant reductions inSmall increases in fabricationIJ07, IJ20, IJ26, IJ38actuatorink chamber are arranged so thatback-flow can be achievedcomplexitymoves to shutthe motion of the actuator closesCompact designs possibleoff the inletoff the inlet.NozzleIn some configuaration of inkInk back-flow problem isNone related to ink back-flowSilverbrook, EP 0771 658 A2actuatorjet, there is no expansion oreliminatedon actuationand related patent applicationsdoes notmovement of an actuator whichValve-jetresult in inkmay cause ink back-flowTone-jetback-flowthrough the inlet.NOZZLE CLEARING METHODNormal nozzleAll of the nozzles are firedNo added complexity on theMay not be sufficient toMost ink jet systemsfiringperiodically, before the ink hasprint headdisplace dried inkIJ01, IJ02, IJ03, IJ04, IJ05,a chance to dry. When not in useIJ06, IJ07, IJ09, IJ10, IJ11,the nozzles are sealed (capped)IJ12, IJ14, IJ16, IJ20, IJ22,against air. The nozzle firingIJ23, IJ24, IJ25, IJ26, IJ27,is usually performed during aIJ28, IJ29, IJ30, IJ31, IJ32,special clearing cycle, after firstIJ33, IJ34, IJ36, IJ37, IJ38,moving the print head to aIJ39, IJ40, IJ41, IJ42, IJ43,cleaning station.IJ44, IJ45Extra powerIn systems which heat the ink,Can be highly effective if theRequires higher drive voltageSilverbrook, EP 0771 658 A2to ink heaterbut do not boil it under normalheater is adjacent to the nozzlefor clearingand related patent applicationssituations, nozzle clearing canMay require larger drivebe achieved by over-poweringtransistorsthe heater and boiling ink atthe nozzle.RapidThe actuator is fired in rapidDoes not require extra driveEffectiveness depends sub-May be used with: IJ01, IJ02,succession ofsuccession. In some config-circuits on the print headstantially upon the configurationIJ03, IJ04, IJ05, IJ06, IJ07,actuator pulsesurations, this may cause heatCan be readily controlled andof the ink jet nozzleIJ09, IJ10, IJ11, IJ14, IJ16,build-up at the nozzle whichinitiated by digital logicIJ20, IJ22, IJ23, IJ24, IJ25,boils the ink, clearing theIJ27, IJ28, IJ29, IJ30, IJ31,nozzle. In other situations,IJ32, IJ33, IJ34, IJ36, IJ37,it may cause sufficient vibrationsIJ38, IJ39, IJ40, IJ41, IJ42,to dislodge clogged nozzles.IJ43, IJ44, IJ45Extra power toWhere an actuator is notA simple solution whereNot suitable where there is aMay be used with: IJ03, IJ09,ink pushingnormally driven to the limit ofapplicablehard limit to actuator movementIJ16, IJ20, IJ23, IJ24, IJ25actuatorits motion, nozzle clearing mayIJ27, IJ29, IJ30, IJ31, IJ32be assisted by providing anIJ39, IJ40, IJ41, IJ42, IJ43enhanced drive signal to theIJ44, IJ45actuator.AcousticAn ultrasonic wave is applied toA high nozzle clearing capabilityhigh implementation cost ifIJ08, IJ13, IJ15, IJ17, IJ18,resonancethe ink chamber. This wave is ofcan be achievedsystem does not already includeIJ19, IJ21an appropriate amplitude andMay be implemented at very lowan acoustic actuatorfrequency to cause sufficientcost in systems which alreadyforce at the nozzle to clearinclude acoustic actuatorsblockages. This is easiest toacheive if the ultrasonic waveis at a resonant frequency ofthe ink cavity.Nozzle clearingA microfabricated plate isCan clear severely cloggedAccurate mechanical alignmentSilverbrook, EP 0771 658 A2platepushed against the nozzles. Thenozzlesis requiredand related patent applicationsplate has a post for everyMoving parts are requirednozzle. A post moves throughThere is risk of damage to theeach nozzle, displacing driednozzlesink.Accurate fabrication is requiredInk pressureThe pressure of the ink isMay be effective where otherRequires pressure pump or otherMay be used with all IJ seriespulsetemporarily increased so thatmethods cannot be usedpressure actuatorink jetsink streams from all of theExpensivenozzles. This may be used inWasteful of inkconjunction with acuatorenergizing. Print headA flexible ‘blade’ is wipedEffective for planar printDifficult to use if print headMany ink jet systemswiperacross the print head surface.head surfacessurface is non-planar or veryThe blade is usually fabricatedLow costfragilefrom a flexible polymer, e.g.Requires mechanical partsrubber or synthetic elastomer.Blade can wear out in highvolume print systemsSeparate inkA seperate heater is provided atCan be effective where otherFabrication complexityCan be used with many IJ seriesboiling heaterthe nozzle although the normalnozzle clearing methods cannotink jetsdrop ejection mechanism doesbe usednot require it. The heaters doCan be implemented at nonot require indiviual driveadditional cost in some ink jetcircuits, as many nozzles canconfigurationsbe cleared simultaneously, andno imaging is required.NOZZLE PLATE CONSTRUCTIONElectroformedA nozzle plate is seperatelyFabrication simplicityHigh temperatures and pressuresHewlett Packard Thermalformedfabricated from electrformedare required to bond nozzle plateInk jetnickel, and bonded to the printMinimum thickness constraintshead chip.Differential thermal expansionLaser ablatedIndividual nozzle holes areNo masks requiredEach hole must be individuallyCanon Bubblejetor drilledablated by an intense UV laserCan be quite fastformed1998 Sercel et al., SPIE,polymerin a nozzle plate, which isSome control over nozzle profileSpecial equipment requiredVol. 998 Excimer Beamtypically a polymer such ais possibleSlow where there are manyApplications, pp. 76-83polyimide or polysulphoneEquipment required is relativelythousands of nozzles per print1993 Watanabe et al.,low costheadU.S. Pat. No. 5,208,604May produce thin burrs at exitholesSiliconA seperate nozzle plate isHigh accuracy is attainableTwo part constructionK. Bean, IEEE Transactions onmicromachinedmicromachined from singleHigh costElectron Devices, Vol. ED-25,crysal silicon, and bonded toRequires precision alignmentNo. 10, 1978, pp 1185-1195the print head wafer.Nozzles may be clogged byXerox 1990 Hawkins et al.,adhesiveU.S. Pat. No. 4,899,181GlassFine glass capillaries areNo expensive equipmentVery small nozzle sizes are1970 Zoltancapillariesdrawn from glass tubing. Thisrequireddifficult to formU.S. Pat. No. 3,683,212method has been used forSimple to make single nozzlesNot suited for mass productionmaking individual nozzles, butis difficult to use for bulkmanufacturing of print headswith thousands of nozzles.Monolithic,The nozzle plate is depositedHigh accuracy (<1 μm)Requires sacrificial layer underSilverbrook, EP 0771 658 A2surfaceas a layer using standard VLSIMonolithicthe nozzle plate to form theand related patent applicationsmicromachineddeposition techniques. NozzlesLow costnozzle chamberIJ01, IJ02, IJ04, IJ11, IJ12,using VLSIare etched in the nozzle plateExisting processes can be usedSurface may be fragile to theIJ17, IJ18, IJ20, IJ22, IJ24,lithographicusing VLSI lithography andtouchIJ27, IJ28, IJ29, IJ30, IJ31,processesetchingIJ32, IJ33, IJ34, IJ36, IJ37,IJ38, IJ39, IJ40, IJ41, IJ42,IJ43, IJ44Monolithic,The nozzle plate is a buriedHigh accuracy (<1 μm)Requires long etch timesIJ03, IJ05, IJ06, IJ07, IJ08,etched throughetch stop in the wafer. NozzleMonolithicRequires a support waferIJ09, IJ10, IJ13, IJ14, IJ15,substratechambers are etched in the frontLow costIJ16, IJ19, IJ21, IJ23, IJ25,of the wafer, and the wafer isNo differential expansionIJ26thinned from the back side.Nozzles are then etched in theetch stop layer.No nozzle plateVarious methods have been triedNo nozzles to become cloggedDifficult to control drop positionRicoh 1995 Sekiya et alto eliminate the nozzles entirely,accuratelyU.S. Pat. No. 5,412,413to prevent nozzle clogging.Crosstalk problems1993 Hadimioglu et alThese include thermal bubbleEUP 550,192mechanisms and acoustic lens1993 Elrod et almechanismsEUP 572,220TroughEach drop ejector has a troughReduced manufacturingDrop firing direction is sensitiveIJ35through which a paddle moves.complexityto wicking.There is no nozzle plate.MonolithicNozzle slitThe elimination of nozzle holesNo nozzle to become cloggedDifficult to control drop position1989 Saito et alinstead ofand replacement by a slitaccuratelyU.S. Pat. No. 4,799,068individualencompassing many actuatorCrosstalk problemsnozzlespositions reduces nozzleclogging, but increases crosstalkdue to ink surface wavesDROP EJECTION DIRECTIONEdge (‘edgeInk flow is along the surfaceSimple constructionNozzles limited to edgeCanon Bubblejet 1979 Endoshooter’)of the chip, and ink drops areNo silicon etching requiredHigh resolution is difficultet al GB patent 2,007,162ejected from the chip edge.Good heat sinking via substrateFast color printing requiresXerox heater-in-pit 1990Mechanically strongone print head per colorHawkins et al U.S. Pat. No.Ease of chip handing4,899,181Tone-jetSurface (‘roofInk flow is along the surfaceNo bulk silicon etching requiredMaximum ink flow is severelyHewlett-Packard TIJ 1982shooter’)of the chip, and ink drops areSilicon can make an effectiverestrictedVaught et alejected from the chip surface,heat sinkU.S. Pat. No. 4,490,728normal to the plane of the chip.Mechanical strengthIJ02, IJ11, IJ12, IJ20, IJ22Through chip,Ink flow is through the chip,High ink flowRequires bulk silicon etchingSilverbrook, EP 0771 658 A2forwardand ink drops are ejected fromSuitable for pagewidth printand related patent applications(‘up shooter’)the front surface of the chip.headsIJ04, IJ17, IJ18, IJ24,High nozzle packing densityIJ27-IJ45therefore low manufacturing costThrough chip,Ink flow is through the chip,High ink flowRequires wafer thinningIJ01, IJ03, IJ05, IJ06, IJ07reverse (‘downand ink drops are ejected fromSuitable for pagewidth printRequires special handling duringIJ08, IJ09, IJ10, IJ13, IJ14shooter’)the rear surface of the chip.headsmanufacturingIJ15, IJ16, IJ19, IJ21, IJ23High nozzle packing densityIJ25, IJ26therefore low manufacturing costThroughInk flow is through the actuator,Suitable for piezolelectric printPagewidth print heads requireEpson Stylusactuatorwhich is not fabricated as partheadseveral thousand connections toTektronix hot melt piezoelectricof the same substrate as thedrive cicuitsink jetsdrive transistors.Cannot be manufactured instandard CMOS fabsComplex assembly requiredINK TYPEAqueous, dyeWater based ink which typicallyEnvironmentally friendlySlow dryingMost existing ink jetscontains: water, dye, surfactant,No odorCorrosiveAll IJ series in jetshumectant, and biocide.Bleeds on paperSilverbrook, EP 0771 658 A2Modern ink dyes have highMay strikethoughand related patent applicationswater-fastness, light fastnessCockles paperAqueous,Water based ink which typicallyEnvironmentally friendlySlow dryingIJ02, IJ04, IJ21, IJ26, IJ27,pigmentcontains: water, pigment,No odorCorrosiveIJ30surfactant, humectant, andReduced bleedPigment may clog nozzlesSilverbrook, EP 0771 658 A2biocide. Pigments have anReduced wickingpigment may clog actuatorand related patent applicationsadvantage in reduced bleed,Reduced strickthoughmechanismsPiezoelectric ink-jetswicking and strikethough.Cockles paperThermal ink jets(with significant restrictions)Methy EthylMEK is a highly volatile solventVery fast dryingOdorousAll IJ series ink jetsKetone (MEK)used for industrial printing onPrints on various substratesFlammabledifficult surfaces such assuch as metals and plasticsaluminum cans.AlcoholAlcohol based inks can be usedFast dryingSlight odorAll IJ Series ink jets(ethanol,where the printer must operateOperates as subfreezingFlammable2-butanol, andat temperatures below thetemperaturesothers)freezing point of water. AnReduced paper cockleexample of this is in-cameraLow costconsumer photographic printing.Phase changeThe ink is solid at roomNo drying time-ink instantlyHigh viscosityTektronix hot melt(hot melt)temperature, and is melted in thefreezes on the print mediumPrinted ink typically has apiezoelectric ink jetsprint head before jetting. HotAlmost any print medium can be‘waxy’ feel1989 Nowakmelt inks are usually wax based,usedPrinted pages may ‘block’U.S. Pat. No. 4,820,346with a melting point aroundNo paper cockle occursInk temperature may be aboveAll IJ series ink jets80° C. After jetting the inkNo wicking occursthe curie point of permenantfreezes almost instantly uponNo bleed occursmagnetscontacting the print mediumNo strikethrough occursInk heaters consume poweror a transfer roller.Long warm-up timeOilOil based inks are extensivelyHigh solubility medium forHigh viscosity: this is aAll IJ series ink jetsused in offset printing. Theysome dyessignificant limitation for usehave advantages in improvedDoes not cockle paperin ink jets, which usually requirecharacteristics on paperDoes not wick through papera low viscosity. Some short(especially no wicking orchain and multi-branched oilscockle). Oil soluble dies andhave a sufficiently low viscositypigments are required.Slow dryingMicroemulsionA microemulsion is a stable,Stops ink bleedViscosity higher than waterAll IJ series ink jetsself forming emulsion of oil,High dye solubilityCost is slightly higher thanwater, and surfactant. TheWater, oil, and amphiphilicwater based inkcharacteristic drop size is lesssoluble dies can be usedHigh surfactant concentrationthan 100 nm, and is determinedCan stabilize pigmentrequired (around 5%)by the preferred curvature ofsuspensionsthe surfactant.

Number	Date	Country	Kind
PP0872	Dec 1997	AU
PO7991	Jul 1997	AU

	Number	Date	Country
Parent	09112801	Jul 1998	US
Child	10302604	Nov 2002	US

Method of manufacturing a micro-electromechanical fluid ejecting device

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