Patent Publication Number: US-8540346-B2

Title: Patterned metallization on polyimide aperture plate for laser-ablated nozzel

Description:
FIELD OF THE EMBODIMENTS 
     The present teachings relate to the field of ink jet printing devices and, more particularly, to an ink jet print head and methods of making an ink jet print head. 
     BACKGROUND OF THE EMBODIMENTS 
     Fluid ink jet systems typically include one or more print heads having a plurality of ink jets from which drops of fluid are ejected toward a recording medium. The ink jets of a print head receive ink from an ink supply chamber (manifold) in the print head which, in turn, receives ink from a source such as an ink reservoir or an ink cartridge. Each ink jet includes a channel having one end in fluid communication with the ink supply manifold. The other end of the ink channel has an orifice or nozzle for ejecting drops of ink. The nozzles of the ink jets may be formed in an aperture plate that has openings corresponding to the nozzles of the ink jets. During operation, drop ejecting signals activate actuators to expel drops of fluid from the ink jet nozzles onto the recording medium. By selectively activating the actuators to eject ink drops as the recording medium and/or print head assembly are moved relative to one another, the deposited drops can be precisely patterned to form particular text and/or graphic images on the recording medium. 
     Ink jet print heads have been constructed using stainless steel aperture plates with nozzles which are etched chemically or formed mechanically. Reducing cost and improving the performance of ink jet print heads is an ongoing goal of design engineers. A print head having improved performance and lower cost than conventional print heads would be desirable. 
     SUMMARY OF THE EMBODIMENTS 
     The following presents a simplified summary in order to provide a basic understanding of some aspects of one or more embodiments of the present teachings. This summary is not an extensive overview, nor is it intended to identify key or critical elements of the present teachings nor to delineate the scope of the disclosure. Rather, its primary purpose is merely to present one or more concepts in simplified form as a prelude to the detailed description presented later. 
     In an embodiment of the present teachings, a method for forming a print head aperture plate can include covering a first layer having a first emissivity with a second layer having a second emissivity, wherein the first emissivity is higher than the second emissivity, patterning the second layer by removing at least a portion of the second layer from a nozzle location and leaving at least a portion of the first layer at the nozzle location and, after patterning the second layer, forming at least one nozzle through the first layer. 
     In another embodiment of the present teachings, a print head aperture plate can include a first layer having a first emissivity, a second layer over the first layer, the second layer having a second emissivity which is lower than the first emissivity, and at least one nozzle extending through the first layer, wherein the at least one nozzle has an edge and a first thickness of the second layer exposed at the at least one nozzle edge is less than a second thickness of the second layer at a location remote from the nozzle edge. 
     In another embodiment of the present teachings, a printer can include a print head aperture plate, comprising a first layer having a first emissivity, a second layer over the first layer, the second layer having a second emissivity which is lower than the first emissivity, at least one nozzle extending through the first layer, wherein the at least one nozzle has an edge, wherein a first thickness of the second layer exposed at the at least one nozzle edge is less than a second thickness of the second layer at a location remote from the nozzle edge. The printer can further include a jet stack subassembly comprising a plurality of piezoelectric elements, wherein the print head aperture plate is attached to the jet stack subassembly, a printed circuit board comprising a plurality of electrodes, wherein each of the plurality of electrodes is electrically coupled to one of the piezoelectric elements, a manifold attached to the printed circuit board, and an ink reservoir formed by a surface of the manifold and a surface of the printed circuit board. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present teachings and together with the description, serve to explain the principles of the disclosure. In the figures: 
         FIGS. 1-5  are cross sections, and  FIG. 6  is a plan view, depicting an in-process aperture plate in accordance with an embodiment of the present teachings; 
         FIG. 7  is a cross section depicting a print head in accordance with an embodiment of the present teachings; 
         FIG. 8  is a representation of a printing device formed in accordance with an embodiment of the present teachings; 
         FIGS. 9 and 10  are cross sections depicting an in-process aperture plate according to another embodiment of the present teachings; 
         FIGS. 11 and 12  are cross sections depicting an in-process aperture plate according to another embodiment of the present teachings; 
         FIGS. 13 and 14  are cross sections depicting an in-process aperture plate according to another embodiment of the present teachings; 
         FIGS. 15 and 16  are cross sections depicting an in-process aperture plate according to another embodiment of the present teachings; and 
         FIGS. 17-21  are cross sections depicting another embodiment of the present teachings. 
     
    
    
     It should be noted that some details of the FIGS. have been simplified and are drawn to facilitate understanding of the present teachings rather than to maintain strict structural accuracy, detail, and scale. 
     DESCRIPTION OF THE EMBODIMENTS 
     Reference will now be made in detail to the present exemplary embodiments of the present teachings, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     As used herein, the word “printer” encompasses any apparatus that performs a print outputting function for any purpose, such as a digital copier, bookmaking machine, facsimile machine, a multi-function machine, etc. The word “polymer” encompasses any one of a broad range of carbon-based compounds formed from long-chain molecules including thermoset polyimides, thermoplastics, resins, polycarbonates, and related compounds known to the art. 
     Stainless steel aperture plates are suitable for their intended purpose, but are expensive to manufacture due to the formation of apertures or nozzles using chemical or mechanical techniques. A polyimide aperture plate is less expensive to manufacture, for example because the nozzles can be laser etched, which reduces processing time and costs. However, polyimide has a much higher emissivity (0.95) than stainless steel (0.4), so radiative heat losses can be 137% higher with polyimide than stainless steel. For purposes of the present disclosure, “emissivity” is the relative ability of a material&#39;s surface to emit energy by radiation. An ink jet aperture plate with a low emissivity is generally more desirable, for example because a printing device with low emissive aperture plate uses less power than a printing device with an aperture plate having a higher emissivity. 
     An ink jet print head, a printer including the ink jet print head, and methods of forming the ink jet print head using a polyimide aperture plate is described in U.S. patent Ser. No. 12/905,561, titled “Metalized Polyimide Aperture Plate and Method for Preparing Same,” filed Oct. 15, 2010, which is incorporated herein by reference in its entirety. The ink jet print head of the aforementioned application can include an aperture plate with a first layer (for example, polyimide) having an emissivity and a second layer (for example, aluminum) having an emissivity, wherein the emissivity of the first layer is higher than the emissivity of the second layer. The emissivity of the described aperture plate (for example, polyimide and aluminum) is less than the emissivity of a polyimide aperture plate which omits the aluminum second layer, because the aluminum layer decreases the overall emissivity of the aperture plate. Furthermore, a low energy coating can be applied to the aluminum layer so that ink is more easily removed from the exterior of the aperture plate, for example through self-cleaning or removal using a wiper blade. A low energy coating adheres poorly to polyimide. 
     An embodiment of the present teachings is described with reference to  FIGS. 1-6 .  FIG. 1  depicts an in-process aperture plate assembly  10  including a first layer  12  having a first emissivity and a second layer  14  having a second emissivity, wherein the first emissivity is higher than the second emissivity. In an embodiment, the first layer can include polyimide and the second layer which covers the first layer can include aluminum. In another embodiment, the first layer can be polyimide, polycarbonate, polyester, polyetherketone, polyetherimide, polyethersulfone, polysulfone, liquid crystal polymer, and other polymers or combinations thereof, and the second layer can be aluminum, nickel, gold, silver, copper, chromium, titanium, a metal alloy, and other metals or combinations thereof. 
     Polyimide has good strength, good workability, and reasonable cost, and vacuum-deposited aluminum has a low emissivity value. For simplicity of explanation, the disclosure below is described with reference to a first layer of polyimide and a second layer of aluminum, but it will be realized that the first layer can include one or more other polymer and the second layer can include one or more other metal. 
     In an embodiment, the polyimide  12  can be any suitable thickness, for example between about 8 microns and about 75 microns, or between about 13 microns and about 50 microns, or between about 25 microns to about 38 microns thick. In a specific embodiment, the first layer  12  is about 25 microns thick. In an embodiment, the first layer can be a 1 mil thick DuPont™ Kapton® HN polyimide film. 
     In an embodiment, the second layer  14  can be any suitable thickness, for example between about 50 angstroms (Å) and about 1.0 micron, or between about 200 Å and about 5000 Å, or between about 300 Å and about 1000 Å thick. In embodiments, the second layer can be a sub-micron aluminum layer. In an embodiment, the second layer can be a 1.0 micron thick aluminum layer. The aluminum layer can be formed on the polyimide layer using any suitable process, for example physical vapor deposition (PVD), chemical vapor deposition (CVD), atomic layer deposition (ALD), sputtering, lamination, etc. 
       FIG. 1  further depicts a patterned mask  16  having openings  18  therein which expose the aluminum  14 . The patterned mask  16  can be a photosensitive layer such as photoresist which is patterned using conventional optical photolithography. The patterned mask can also be formed by spraying, stamping, spin coating, and can be a shadow mask or a dry film photoresist. The openings can be any desired shape, for example round, square, rectangular, oval, star-shaped, etc., and can overlap adjacent openings, for example as overlapping circles. In this embodiment, however, an area or width (or, in the case of a circular opening, a diameter) of each opening will be larger or wider than an area or width of a nozzle aperture (nozzle) which will subsequently be formed in the polyimide  12 . Additionally, an area or width of each opening can be larger or wider than a cross sectional area or width of a laser beam which is used to form nozzles during subsequent processing. Further, the area or width of the opening can be oversized to allow for alignment tolerance. Each opening  18  can be targeted to be centered on a location where the nozzle will subsequently be formed. In an embodiment, the openings  18  can be circular and have a diameter of between about 50 microns and about 700 microns, or between about 100 microns and about 400 microns, or between about 200 microns and about 300 microns. In terms of area, the openings  18  can be circular and have an area of between about 150 microns 2  and about 2200 microns 2 , or between about 315 microns 2  and about 1250 microns 2 , or between about 630 microns 2  and about 350 microns 2 . 
     Next, as depicted in  FIG. 2 , the aluminum is etched selective to the polyimide to remove the exposed aluminum  14  and to pattern the aluminum  14 , which forms openings in the aluminum  14 . Etching the aluminum  14  forms edges  20  of the aluminum  14 . A wet etch, a dry etch, or both, can be performed to remove the aluminum layer. For example, an aluminum layer which is 1.0 micron thick can be removed by plasma etching for a duration of less than one minute. To improve tolerances to alignment, each opening in the metal can have an ellipsis shape, wherein the long axis of the ellipse is oriented either parallel or perpendicular to the long axis of the aperture plate. The orientation to the aperture plate will depend on various factors related to mechanical alignment and stretching or shrinking of the polyimide during processing. Additionally, other patterning features can be stamped, etched (for example using a pattern in mask  16 ), or printed into the metal  14  to serve other functions. For example, identification codes, manufacturing codes, serial numbers, or other indicia, or alignment targets to aid the placement of the openings within the metal or nozzle placement during subsequent processing, can be stamped, etched, or printed into metal  14 . 
     After forming a structure similar to that depicted in  FIG. 2 , the patterned mask  16  is removed and an optional low energy coating  30  is applied to the aluminum  14  as depicted in  FIG. 3 . In this embodiment, the coating  30  encapsulates the exposed etched edges  20  of the aluminum, and also physically contacts the polyimide  12 . The coating can provide an anti-wetting agent for the completed aperture plate during use, and can improve jetting performance and assist in the removal of ink and other contaminants during print head maintenance. The coating can be applied as a liquid solution, such as Solvay Solexis Fluorolink® perfluoropolyether (PFPE), and then cured to remove volatile solvents to result in a solid coating. In another embodiment, the coating can be a vapor-phase deposited material such as a fluorinated diamond-like carbon (f-DLC) or a perfluoroalkoxy copolymer resin such as DuPont™ Teflon®. Other materials suitable for the coating include a fluoropolymer, a siloxane polymer, and polytetrafluoroethylene. 
     In embodiments, the coating  30  can have a thickness of between about 400 Å to about 2,000 Å, or from about 650 Å to about 1,350 Å, or from about 900 to about 1,150 Å thick. 
     In embodiments, the coating  30  can provide contact angle characteristics such that satellite droplets of UV gel ink and solid ink, for example 3 microliter drops of UV ink and 1 microliter drops of solid ink, landing on the aperture plate exhibit a contact angle of from about 35° to about 120°, in specific embodiments a contact angle greater than about 35° or greater than about 55° with coating  30 . 
     After forming a structure similar to that depicted in  FIG. 3 , nozzles can be formed through the polyimide  12  and, if present, the optional coating  30 . In an embodiment, the nozzles can be formed using one or more lasers  40  as depicted in  FIG. 4 , for example one or more excimer lasers, each outputting a laser beam  42 .  FIG. 5  depicts a completed aperture plate  50 , wherein laser ablation of the polyimide  12  and the coating  30  in  FIG. 4  forms nozzles  52  as depicted in  FIG. 5 . 
     The nozzles  52  can be circular and have a width (or, in the case of a circular opening, a diameter) of between about 25 microns and about 100 microns, or between about 30 microns and about 75 microns, or between about 35 microns or about 45 microns. In terms of area, the nozzles can be circular and have an area of between about 75 microns 2  and about 315 microns 2 , or between about 90 microns 2  and about 235 microns 2 , or between about 110 microns 2  or about 140 microns 2 . Nozzles  52  can be smaller than, and targeted to be concentric with, the openings in the aluminum layer  14 . Additionally, the nozzles can have shapes other than circular, such as square, rectangular, oval, and star shaped. 
     If the aluminum  14  was not patterned according to this embodiment, the formation of the nozzles  52  with a laser beam  42  at  FIG. 4  would rely on vaporization of the aluminum  14  by the laser beam  42  to provide a well-formed nozzle  52 . However, it has been found that in some instances the laser beam  42  does not sufficiently vaporize the aluminum  14 , but rather melts the aluminum  14 . As a result, the liquid aluminum  14  flows along the surface of the polyimide  12  due to surface tension. The liquid aluminum can then coalesce to form residual metal “flaps” around the perimeter of the nozzle  52 . These flaps can affect the roundness of the nozzle, can interfere with the flow of ink through the nozzle  52 , and may adversely affect the shape and trajectory of the projected ink during printing. With this embodiment, however, the laser beam  42  does not overlap the aluminum  14  during the formation of the nozzles  52  as depicted in  FIG. 4 . The thermal energy transferred to the aluminum  14  through the polyimide  12  and coating  30  during the formation of the nozzles is likely insufficient to melt the aluminum  14 . Even if the aluminum  14  is melted due to the conduction of heat through the polyimide  12  or the coating  30 , the aluminum  14  is encapsulated between the coating  30  and the polyimide  12 . In embodiments where the coating  30  is omitted, the aluminum is not encapsulated; however, a distance between the edge  20  of the aluminum  14  and the edge  54  of the nozzle  52  can be targeted according to the thickness of the aluminum to prevent any melted aluminum from flowing to the edge of the nozzle, or to ensure energy transfer from the laser beam  42  is insufficient to melt the aluminum  14 . 
     Additionally, covering the edge of the aluminum  14  with coating  30  to encapsulate the aluminum  14  prevents contact between the ink within the nozzle and the aluminum  14  during use. Thus any adverse chemical reaction between the ink and the metal  14  is prevented. Further, exposed aluminum at the nozzle edge is eliminated, which may decrease layer delamination at the nozzle edge. 
       FIG. 6  is a plan view of the  FIG. 5  structure depicting an array of nozzles  52  on a portion of an aperture plate  50 . A distance  60  between an edge  20  of the aluminum  14  and an edge  54  of the nozzle  52  can be targeted to prevent the formation of metal flaps at the edge  54  of the nozzle  52 . While  FIG. 6  depicts an exemplary 4×2 array of nozzles, it will be understood that aperture plate can include a larger array of nozzles, for example a 344×20 array. 
     As depicted in  FIGS. 5 and 6 , a first thickness of the aluminum  14  at the edge  54  of the nozzle is zero, and a second thickness of the aluminum  14  at a location remote from the edge  54  of the nozzle  52  is greater than zero. As depicted in  FIG. 6 , the openings  20  in the aluminum  14  are circular, the nozzles  52  are circular, and each opening  20  in the aluminum  14  encircles a nozzle  52 . In an embodiment, the circular nozzle  52  and the circular opening  20  in the aluminum  14  can be targeted to be concentric. 
     After forming the aperture plate  50 , it can be attached to a jet stack subassembly to form a jet stack  70  as depicted in  FIG. 7 . The jet stack can then be attached to a manifold  72  to form a print head  74 . The print head  74  can include various structures, including piezoelectric elements  76 , a printed circuit board  78 , electrodes  80 , and an ink reservoir  82  formed by a surface of the manifold and a surface of the printed circuit board. The formation and use of a print head is discussed in U.S. patent Ser. No. 13/011,409, titled “Polymer Layer Removal on PZT Arrays Using A Plasma Etch,” filed Jan. 21, 2011, which is incorporated herein by reference in its entirety. 
     The methods and structure described above thereby form an aperture plate  50  for an ink jet printer. In an embodiment, the aperture plate  50  can be used as part of an ink jet print head  74  as depicted in  FIG. 7 . 
       FIG. 8  depicts a printer  84  including one or more print heads  74  and ink  86  being ejected from one or more nozzles  52  ( FIG. 5 ) in accordance with an embodiment of the present teachings. The print head  74  is operated in accordance with digital instructions to create a desired image on a print medium  88  such as a paper sheet, plastic, etc. The print head  74  may move back and forth relative to the print medium  88  in a scanning motion to generate the printed image swath by swath. Alternately, the print head  74  may be held fixed and the print medium  88  moved relative to the print head, creating an image as wide as the print head  74  in a single pass. The print head  74  can be narrower than, or as wide as, the print medium  88 . 
     Adding a metal second layer to the first layer significantly reduces heat losses and radiative power loss, thereby decreasing power usage compared to printers using polyimide aperture plates. In the case of aluminum, the emissivity is expected to be less than 0.1, reducing radiative power losses by 75% compared to standard stainless steel and by 90% compared to raw polyimide. Furthermore, patterning the metal to provide an opening larger than the nozzles prior to forming the nozzles reduces or eliminates problems resulting from melted metal. While patterning the metal away from the location of the nozzle exposes the polyimide and may result in a slight increase in emissivity due to less metal surface area, the increase is expected to be less than 5%, and may be less than 2%. In general, an increase in emissivity may occur with increasing nozzle density. 
     Various alternate embodiments are contemplated. For example, in another embodiment, the  FIG. 2  structure can be formed, then the patterned mask  16  can be removed. Subsequently, laser formation of the nozzles  52  in the polyimide layer  12  as depicted in  FIG. 9  can be performed. In an embodiment, the  FIG. 9  structure forms a completed aperture plate. In another embodiment, a patterned coating  100  can be formed as depicted in  FIG. 10  using, for example, a plasma or electron beam process to deposit an anti-wetting layer such as a copolymer of Teflon and perfluoroalkoxyvinal ether (i.e., PFA Teflon) or fluorinated diamond-like carbon films (FDLC). 
       FIGS. 11 and 12  depict another embodiment of the present teachings. This embodiment can start with a structure similar to that depicted in  FIG. 2 , then the aluminum  14  is only partially etched to thin, but not completely etch through, the aluminum to result in the thinned aluminum  110  of  FIG. 11 . The partial etch of the aluminum  110  can be performed using a timed etch sufficient to only partially etch through the aluminum  110 . The etch duration will depend on the composition and starting thickness of the layer  110 , the width of opening  18 , and the type of etch and etchant. Thus the polyimide  12  is not exposed during the etch of the aluminum  110 . The process can then continue according to the embodiment of  FIGS. 3-5  to result in the  FIG. 12  structure which includes coating  30 . 
     In this embodiment, the aluminum  110  can be thinned from a starting thickness of between about 500 Å and about 5000 Å, to an ending thickness of between about 100 Å and about 300 Å. While the thickness of the aluminum  110  isn&#39;t completely removed, thinning the aluminum  110  can result in improved laser ablation so that the thinned portion of the aluminum  110  does not coalesce around the perimeter of the nozzle  52  upon melting. Additionally, only partially etching through the aluminum will result in metal up to the edge  122  of each nozzle  120  as depicted in  FIG. 12 . Thus the total surface area of the metal  110  is not decreased, which may result in improved emissivity of the completed structure over the embodiment of  FIG. 5 . This embodiment may be advantageous particularly in structures having a very high density of nozzles, which would have a higher percentage of metal removed than structures having a low nozzle density. 
     As depicted in  FIG. 12 , a first thickness of the aluminum  110  at the edge  122  of the nozzle  120  is less than a second thickness of the aluminum  110  at a location remote from the edge  122  of the nozzle  120 . In an embodiment, a thickness of the aluminum  110  exposed at the edge  122  of the nozzle  120  can be between about 100 Å and about 300 Å, and a thickness of the aluminum  110  at the location remote from the edge  122  of the nozzle  120  can be between about 500 Å and about 5000 Å. 
       FIGS. 13 and 14  depict another embodiment of the present teachings. This embodiment can start with a structure similar to that depicted in  FIG. 2 , then an etch of the structure is performed to etch through the complete thickness of the aluminum  14 , and to etch into the thickness of the polyimide  12  to result in the polyimide  130  of  FIG. 13 . The aluminum  14  and polyimide  12  can be etched using techniques known in the art. The process can then continue according to the embodiment of  FIGS. 3-5  to form the  FIG. 14  structure. 
     In this embodiment, the polyimide  130  can be thinned from a  FIG. 2  starting thickness of between about 25 microns and about 38 microns, to a  FIG. 13  an ending thickness in the location of the nozzle of between about 10 microns and about 25 microns. The polyimide  130  can have a thickness suitable for support, while thinning the polyimide in the nozzle location decreases the amount of polyimide which must be laser ablated, and may therefore simplify nozzle formation. 
     In an alternate method, a metal lift-off process can be used to form the second layer. As depicted in  FIG. 15 , a patterned mask  150  such as a patterned photoresist layer is formed on the polyimide  12  over future nozzle locations. The patterned mask  150  can be formed larger than the nozzle to leave additional distance such as distance  60  ( FIG. 6 ) between the edge of the nozzle and the edge of the metal. Additionally, the patterned mask  150  can be formed with a retrograde profile such that the directional (vertical) deposit of metal results in little or no metal material on mask sidewalls. After forming patterned mask  150 , a directional metal deposition is performed, such as by sputtering. This forms metal  152 A on the exposed polyimide  12  and metal  152 B on the top of the patterned mask  150 . A short optional metal etch can be used to clear any metal which forms on the vertically oriented sidewall of mask  150  which, if it forms at all, will form with a thickness which is less than the material on horizontally oriented surfaces. Subsequently, the patterned mask is etched away which leaves metal  152 A and frees metal  152 B, so metal  152 B can be removed as depicted in  FIG. 16 . Processing can be continued according to  FIGS. 3-5 , for example, to form a completed aperture plate. In another embodiment, the material which forms patterned layer  150  can be something other than photoresist, such as perfluoropolyether or other oil, which can be patterned using, for example, screen printing or flexography (flexo) printing. It will be understood that other materials may be thinner than the photoresist  150  depicted in  FIG. 15 , and may have any of a prograde, vertical, or retrograde profile. 
       FIGS. 17-21  depict another embodiment of the present teachings. This embodiment can result in a structure similar to that depicted in  FIG. 12 , but does not rely on a timed etch. This embodiment can provide improved process control and does not rely on a timed etch. 
     In this embodiment, a blanket first aluminum layer  170 , for example having a thickness of between about 100 Å and about 300 Å is formed over a polyimide layer  12 . Next, a patterned removable layer  172  is formed. The patterned removable layer  172  can include one or more materials such as a fluoropolymer, photoresist, etc. The patterned removable layer can be formed as a blanket layer and patterned using photolithography, or can be patterned using a screen printing process, for example. After forming the  FIG. 17  structure, a blanket conformal second aluminum layer  180  is formed over the first aluminum layer  170  and over the patterned removable layer as depicted in  FIG. 18 . At least a first portion  180 A of the second aluminum layer  180  overlies and physically contacts the patterned removable layer  172 , while at least a second portion  180 B of the second aluminum layer  180  overlies and physically contacts the first aluminum layer  170 , but does not overlie the patterned removable layer  172 . Next, the first portion  180 A of the second aluminum layer  180  is removed along with the patterned removable layer  172  as depicted in  FIG. 19 . The second portion  180 B of the second aluminum layer  180  adheres to the first aluminum layer  170 , and is not removed. 
     Next, an optional low energy coating  200  can be applied to the upper surface of the  FIG. 19  structure as depicted in  FIG. 20 . This coating can be similar to coating  30  as described above. 
     Subsequently, at least one nozzle  210 , for example a plurality of nozzles  210 , can be formed through the polyimide  12 , the first aluminum layer  170 , and the optional coating  200  as depicted in  FIG. 21 . The nozzles  210  can be formed according the to techniques described above. 
     In this embodiment, the thickness of layer  170  does not rely on a timed etch, but instead is formed as blanket layer to a suitable thickness The addition of layer  180  results in a thicker total aluminum including both the first aluminum layer  170  and the second aluminum layer  180  away from the nozzle  210 , but only layer  170  at the nozzle  210 . This embodiment leaves metal  170  up to the edge of the nozzle, such that the emissivity remains low due to the entire surface of the polyimide  12  being covered by aluminum. 
     Thus the methods above can be used to form an aperture plate, a print head, and a printing device. The aperture plate can have a decreased emissivity and decreased radiative power loss over a solid polyimide aperture plate, due to the formation of an overlying metal layer. Further, a low-energy coating will adhere better to the metal layer than to a polyimide surface, thereby improving the removal of ink during print head maintenance or self-cleaning. A low-energy coating can reduce ink drooling. Additionally, the metal according to some of the embodiments described above will not be exposed to ink during use, which can reduce or eliminate chemical interaction between the ink and the metal. Also, removing the metal from around the location of the nozzle prior to nozzle formation can eliminate metal flaps which may otherwise form around the edge of the nozzle due to melting of the metal during nozzle formation. In some embodiments, the metal is only partially etched to thin, but not remove, the metal in the area of the nozzle, which results in a complete metal surface so that emissivity is not increased, which can occur if metal is completely removed from an area which is larger than the nozzle opening. 
     Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the present teachings are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all sub-ranges subsumed therein. For example, a range of “less than 10” can include any and all sub-ranges between (and including) the minimum value of zero and the maximum value of 10, that is, any and all sub-ranges having a minimum value of equal to or greater than zero and a maximum value of equal to or less than 10, e.g., 1 to 5. In certain cases, the numerical values as stated for the parameter can take on negative values. In this case, the example value of range stated as “less than 10” can assume negative values, e.g. −1, −2, −3, −10, −20, −30, etc. 
     While the present teachings have been illustrated with respect to one or more implementations, alterations and/or modifications can be made to the illustrated examples without departing from the spirit and scope of the appended claims. In addition, while a particular feature of the disclosure may have been described with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular function. Furthermore, to the extent that the terms “including,” “includes,” “having,” “has,” “with,” or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.” The term “at least one of” is used to mean one or more of the listed items can be selected. Further, in the discussion and claims herein, the term “on” used with respect to two materials, one “on” the other, means at least some contact between the materials, while “over” means the materials are in proximity, but possibly with one or more additional intervening materials such that contact is possible but not required. Neither “on” nor “over” implies any directionality as used herein. The term “conformal” describes a coating material in which angles of the underlying material are preserved by the conformal material. The term “about” indicates that the value listed may be somewhat altered, as long as the alteration does not result in nonconformance of the process or structure to the illustrated embodiment. Finally, “exemplary” indicates the description is used as an example, rather than implying that it is an ideal. Other embodiments of the present teachings will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the present teachings being indicated by the following claims. 
     Terms of relative position as used in this application are defined based on a plane parallel to the conventional plane or working surface of a wafer or substrate, regardless of the orientation of the wafer or substrate. The term “horizontal” or “lateral” as used in this application is defined as a plane parallel to the conventional plane or working surface of a wafer or substrate, regardless of the orientation of the wafer or substrate. The term “vertical” refers to a direction perpendicular to the horizontal. Terms such as “on,” “side” (as in “sidewall”), “higher,” “lower,” “over,” “top,” and “under” are defined with respect to the conventional plane or working surface being on the top surface of the wafer or substrate, regardless of the orientation of the wafer or substrate.